Steel Times International September 2015 digital

Digital Edition - September 2015 No.1 – www.steeltimesint.com

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ELECTRIC STEELMAKING e TESTING & ANALYSIS e SPECIAL STEELS e HANDLING

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Reliable and Efficient.

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CONTENTS DIGITAL EDITION - SEPTEMBER 2015

Picture courtesy of Oerlikon Leybold Vacuum.

Digital Edition - September 2015 No.1 – www.steeltimesint.com

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2 Leader 5 Product news The latest technological innovations

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ELECTRIC STEELMAKING e TESTING & ANALYSIS e SPECIAL STEELS e HANDLING

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EDITORIAL Editor Matthew Moggridge Tel: +44 (0) 1737 855151 matthewmoggridge@quartzltd.com Consultant Editor Dr. Tim Smith PhD, CEng, MIM

Special steels 10 Higher standards demanded 15 Protectionism vs competitiveness

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Production Editor Annie Baker

SALES International Sales Manager Paul Rossage paulrossage@quartzltd.com Tel: +44 (0) 1737 855116

20 Sales Director Ken Clark kenclark@quartzltd.com Tel: +44 (0) 1737 855117

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Technology perspectives 17 Steel’s role in CO2 mitigation 20 Constant collaboration needed 22 Targets without technology?

25 Rolling Process and technologies to anneal current and future AHSS strips 29 Electric steelmaking Modernising and revamping an EAF

Advertisement Production Martin Lawrence

SUBSCRIPTION Elizabeth Barford Tel +44 (0) 1737 855028 Fax +44 (0) 1737 855034 Email subscriptions@quartzltd.com

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32 Handling Over and above 34 Electric steelmaking Gunning robots improve repairs

Steel Times International is published eight times a year and is available on subscription. Annual subscription: UK £173.00 Other countries: £247.00 2 years subscription: UK £311.00 Other countries: £445.00 ) Single copy (inc postage): £39.00 Email: steel@quartzltd.com Published by: Quartz Business Media Ltd, Quartz House, 20 Clarendon Road, Redhill, Surrey, RH1 1QX, England.

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Tel: +44 (0)1737 855000 Fax: +44 (0)1737 855034 www.steeltimesint.com Steel Times International (USPS No: 020-958) is published monthly except Feb,

38 Desulphurisation Improving hot metal desulphurisation performance 43 Testing and analysis High-speed archiving in hot strip mills

May, July, Dec by Quartz Business Media Ltd and distributed in the US by DSW, 75 Aberdeen Road, Emigsville, PA 17318-0437. Periodicals postage paid at Emigsville, PA. POSTMASTER send address changes to Steel Times International c/o PO Box 437, Emigsville, PA 17318-0437.

Printed in England by: Pensord, Tram Road, Pontlanfraith, Blackwood, Gwent NP12 2YA, UK ©Quartz Business Media Ltd 2015

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47 Vacuum degassing Pressure control during degassing 51 Perspectives Making the world safer and cleaner

ISSN1475-455X

www.steeltimesint.com

Contents sept.indd 1

Digital Edition - September 2015

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LEADER

If you want innovation, be prepared to pay for it

Matthew Moggridge Editor matthewmoggridge@quartzltd.com

Digital Edition - September 2015

Leader sept digital.indd 1

I never thought I’d be charged with the task of writing two leader articles in one month – let alone two magazines!

– but here I am, penning a few words to accompany this, our first ever digital edition of Steel Times International.

I must stress that the print edition of the magazine reigns supreme and always will, but we thought it might be a good idea to introduce a new editorial dimension and offer readers some additional technical articles, all fresh off the press, on top of those published in the print edition earlier this month.

In this issue, you will find articles on rolling, testing and analysis, handling, and electric steelmaking, not forgetting special steels, de-sulphurisation and vacuum de-gassing. There is also a healthy new products section replacing the conventional steel industry news, and a thought-provoking interview with a leading European technology provider and two prominent and influential steel industry associations.

In short, there’s plenty to say about steel processing technology and I felt it imperative that we produced a dedicated magazine that sets out to cover some of

the bases. My plan is to revisit the digital format one or twice next year and the focus will always be biased towards steel production techology in keeping with the long-established editorial remit of the Steel Times International brand.

Taking a closer look at some of the issues facing the steel industry in terms of production technology, Eurofer argues in this issue that the greatest test for the steel industry going forward is likely to be the need to secure continued and adequate financing for investment into the deployment of much-needed technologies for reducing CO2 emissions.

Alacero, the Latin American Steel Association, expects to see continued improvements and developments within the field of steel production technology, but argues that greater collaboration is needed between steelmakers and technology providers.

For technology providers, like Tenova, the real challenge is to cope with the lack of investment from the steel industry. As the company points out, “We are forced to provide the market with innovation and the highest technological standards, but the market is not willing, or able, to pay.”

www.steeltimesint.com

9/29/15 9:17 AM

SOLUTIONS LEADING THE WORLD IN LONG PRODUCTS STRAIGHTENING. Fives Bronx specializes in the latest long product straightening technology for the new, higher grades of rail, sections and round bar currently being processed globally.

Installations include the latest in computer-controlled, quick-change straightening technology that improve production capabilities, leading to less down time. Solutions include the complete integration of vertical and horizontal-axis machines along with ancillary equipment to maximize throughput.

Fives Bronx ... leading the world in Long Products Straightening. fivesbronx-sales@fivesgroup.com

Innovative technologies for the metals industry

Cold rolling ยง Strip processing ยง Chemical processes Thermal processes ยง Mechanical equipment Automation ยง Extractive metallurgy www.cmigroupe.com DE SIG N | ENGINEERING | COMMISS IO NING | TE C H NIC A L A S S IS TA NC E & TR A INING | A F T ER- S A L ES

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INNOVATIONS

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Fives finalises Indian furnaces contracts Fives Group has signed contracts to design and supply four new reheating furnaces this year in India: two for the Rourkela Steel Plant, and two others for another Indian steel plant on India’s western coast.

Primetals Technologies Japan, has entrusted the French steel production technology giant with the design and supply of two 300 tons/hr walking beam furnaces for reheating high quality steel slabs. They will serve a new 3Mt/yr hot strip mill installed at the Steel Authority of India Ltd’s (SAIL) Rourkela Steel Plant, located in the eastern state of Odisha. The mill is scheduled for commissioning in 2018 and will provide high quality coils for a proposed autosheet joint venture with ArcelorMittal.

Fives will supply its Stein Digit@l Furnace AT technology, equipped with the AdvanTek combustion system and controlled by the level 2 Virtuo® Edge-R package, which ensures optimum slab reheating with minimum environmental impact.

Fives claims that its AdvanTek burners provide ‘a unique feature of fuel flexibility allowing the customer to use available fuels most efficiently and easily switch between low calorific value mixed gas and heavy fuel oil.’

Stein Digit@l Furnace AT technology was awarded the Fives Engineered Sustainability brand for being best-in-class.

Further information, http://www.fivesgroup.com

Severstal hot dip galvanising contract awarded to CMI construction and white goods industries will be produced by April 2017.

The new lines are aiming for a high level of operational efficiency and eco-friendliness and feature the full spectrum of CMI’s process technologies: Multi-stage cleaning sections and ultra-low emission furnaces, claims CMI, adding that the HDG line also features a CMI-patented jet cooling system with energy recovery, Air-Knife and APC Blowstab low vibration cooling system, not forgetting an inline skin pass mill and tension leveller, chemical roll-coat post treatment and rotary exit shear. Other essential components of the CCL line are its four coaters – a chemcoater, a prime coater, and two finish coaters – as well as the latest generation of strip loopers, which guarantee smooth strip travel, says CMI. CMI claims that it can look back on many years of successful and trustful co-operation with Severstal. "As such this is the fourth galvanising line that the Severstal Group has entrusted to CMI Industry Metals over the past 10 years."

Further information, http://www.cmigroupe.com

PAO Severstal Russia has chosen CMI as the supplier of its new high-performance hot-dip galvanising line and colour coating line to be installed at its Cherepovets plant in Russia.

The Cherepovets Steel Mill is one of the world’s largest vertically integrated steel mills and part of the Russian Steel division of Severstal, a leading global steel and steel-related mining company.

CMI has been contracted to supply engineering, procurement and construction services for key production and processing equipment at the new coated steel plant.

In June, Severstal awarded CMI Industry Metals a contract for a hot-dip galvanising line (HDG) and a colour coating line (CCL) producing 400kt/yr and 200kt/yr respectively, and reaching process speeds of 180m/min and 120m/min.

According to CMI, "With this project the Russian steelmaker will not only significantly increase its output of higher added value products, but also its share of Russia’s apparent consumption."

Cherepovets, says CMI, is a strategically and economically important complex where galvanised and colour-coated strip destined for the

Oerlikon focused on reducing energy consumption Innovations in vacuum technology deliver an important contribution to productivity in heat treatment and furnace construction as well as in secondary metallurgy, claims Oerlikon.

According to the company, modern systems fulfil a number of requirements in order to save energy during the production of high-quality steel and guarantee the required vacuum level.

Where energy efficiency and robustness for heat treatment are concerned, Oerlikon argues that while, for a long time, emphasis has been placed on trouble-free operation and reliable production, improving energy efficiency was also top priority.

In a typical furnace operation, most vacuum pumps in the 600m3/h class require an operating pressure below 1 mbar and an output of approximately 10kW. The screw pumps of Oerlikon’s DRYVAC series consumed less energy due to optimised rotor design, an innovative drive concept and the inwww.steeltimesint.com

product pagesReadMM.indd 1

stallation of a perfectly adapted frequency converter.

Oerlikon claims that its DRYVAC DV650 sets new standards for energy consumption. The unit’s backing pumps consume 6.9kW at 1 mbar and are below that of a comparable rotary vane pump.

Additional energy savings are offered by the system’s built-in frequency converter and there is greater process control because many process steps do not require the full pumping speed, particularly when operating under rougher pressure ratios, such as during carburising.

The DV650’s dry compressing screw pumps, claims Oerlikon, have proven themselves even under rugged conditions and offer a higher degree of robustness and insensitivity towards dust, particles and vapours. Similar opportunities are offered by modern Roots pumps or with optimised operation of rotary vane pumps.

Further information, http://www.oerlikon.com Digital Edition - September 2015

9/29/15 9:24 AM

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INNOVATION

Hypertherm wins a coveted Communitas Award for leadership

SMS to supply turnkey pipe production facility

Larsen & Toubro and SMS Group, working as a consortium, have been awarded the contract to supply a turnkey LSAW (Longitudinal Submerged Arc Welded) pipe production facility for the Al Gharbia Pipe Company.

The plant will be built in Abu Dhabi within the Khalifa Industrial Zone Abu Dhabi (KIZAD) and will commence production in 2018.

SMS group will be responsible for the engineering and supply of process equipment while partner Larsen & Toubro will handle civil works and erection of the equipment.

Material grades up to X80 will be processed at a production capacity of 240kt/yr. The pipes will be suitable for use as offshore line pipes and onshore applications. The new line will be designed to make pipes up to 12.2 metres long with an outside diameter ranging from 18 to 56 inches. The maximum wall thickness will be 44.5 millimetres.

In addition to engineering, project planning, scheduling and co-ordination, SMS group will supply all key machinery and process equipment including workshops, laboratories and MES (Manufacturing Execution System) equipment. The production line will consist of an edge miller, a crimping press, a JCOE pipe forming press, tack welder, inside and outside welder, mechanical expander and a hydrostatic pipe tester.

The JCOE pipe forming process was developed

by SMS and offers a whole range of advantages

as the plant operator can change to other pipe dimensions quickly, allowing the economic production of even smaller batch sizes. All presses are equipped with variable speed pumps (VSPs) that provide an efficient hydraulic system with pressures up to 450 bar, reducing energy consumption by 30% compared with conventional hydraulic systems.

The SMS Shape automation system controls the forming process and improves performance as well as compensating for the influence of plate ‘inhomogeneity’ during the forming process. The end result is a guaranteed consistently high pipe quality.

Al Gharbia Pipe Company will manufacture high-grade large-diameter longitudinal welded steel pipes for the energy sector and is targeting markets in the Gulf.

With development and production of oil and gas forecasted to be ‘robust’ in these countries, demand is expected to grow.

Al Gharbia Pipe Company is a joint venture between investment company Senaat, JFE Steel and Marubeni-Itochu Steel (MISI). The company is leveraging JFE Steel’s technology for high-quality large-diameter longitudinal welded steel pipes, MISI’s sales capabilities and Senaat’s industrial footprint in Abu Dhabi.

Further information, http://www.sms-group.com

Netherlands-based Hypertherm, manufacturer of plasma, laser, and waterjet cutting systems, has won a Communitas Award for leadership excellence in the combined areas of community service and corporate social responsibility.

Communitas Awards recognise businesses, organisations and individuals that unselfishly give of themselves and their resources, and those that are changing how they do business to benefit their communities.

Judges found that Hypertherm demonstrated the spirit of communitas, a Latin word for people coming together for the good of a community, with work spanning multiple categories including volunteerism, philanthropy and ethical, sustainable business practices.

“Hypertherm is humbled to receive the Communitas Award and what it represents,” said Jenny Levy, vice president of corporate social responsibility for the company. “As an associate-owned company, we are committed toward a triple bottom line approach that places equal emphasis on people, planet, and profit.”

Hypertherm designs and manufactures advanced cutting products for use in a variety of industries.

Further information, http://www. hypertherm.com

Thermo Fisher plant awarded Swiss Industrial Excellence Award Thermo Fisher Scientific’s plant in Ecublens, Switzerland, has been awarded the 2015 Swiss Industrial Excellence Award, as chosen by an international jury of operations management professors from INSEAD and HEC Paris. The facility is also now a European Industrial Excellence Award finalist.

Thermo’s Ecublens plant manufacturers the company’s scientific laboratory analysers, including the ARL 9900, ARL iSpark, ARL 4460 and ARL PERFORM’X analysers, as well as the Laboratory Automation SMS solutions.

According to Thermo, the Ecublens facility was recognised for its high level of product quality, as well as its practical process improvement philosophy and strong customer satisfaction scores.

Additionally, auditors noted that the plant’s viDigital Edition - September 2015

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sion, mission, values and culture of continuous improvement were shared from senior leadership to employees on the factory floor.

Since 1995, the Industrial Excellence Award (IEA) competition has been a benchmark for European competitiveness in the industrial sector. The competition focuses on strategy deployment, recognising how organisations align distributed activities and knowledge to achieve common strategic goals. The eight finalists for the 2015 European Industrial Excellence Award will present to a panel of academic judges at the WirtschaftsWoche Industrial Excellence Conference and Award event on 29 September in Ludwigsburg, Germany, with the winner announced at a gala dinner that night.

Further information, http://www.thermoscientific.com www.steeltimesint.com

9/29/15 9:24 AM

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8

INNOVATION Magnetising coil

ct io n di re

As the flat sheet steel industry increases its share of high strength steel products, the growing complexity of the process and the increased quality requirement have led to the introduction of the latest Furnace Mathematical Model combined with EMG’s IMPOC, an online quality measuring device.

Drever’s Mathematical Model implemented at Segal integrates the latest self-adaptation technique, Advanced Transition Management technology and annealing process optimisation. It is designed to allow a synchronous automatic control of the annealing furnace and the process line speed.

EMG’s IMPOC is based on the magnetic ‘remanence’ principle for the non-destructive determination of the mechanical properties of ferromagnetic steel strips. A regression analysis of the IMPOC value with the results of the destructive tests and recorded data is the basis for modeling the online determination of both tensile strength and yield strength for different steel grades.

For every four metres of strip, the Furnace Mathematical Model monitors process history along with online-determined mechanical properties. Data analysis by SMS Siemag, obtained after several months of production, enabled the observation and explanation of the influence of different process settings and values (line speed, furnace temperature and steel grade) on the mechanical properties on a quantitative basis.

There are numerous benefits of combining the new Furnace Mathematical Model, the IMPOC device and the data analysis as follows: • The new Furnace Mathematical Model enables increased line production by up to 15 %.

Idler rollers

ru n

Hagen-based Hoesch Hohenlimburg, a German supplier of hot-rolled steel strip, which is mainly used for special applications in the cold-rolled and automotive industries, has recently upgraded the drive trains of the plant’s first two finishing stands (G11 and G12) with a view to boosting rolling force.

Hoesch Hohenlimburg, a subsidiary of ThyssenKrupp, awarded Danieli Transmission the contract to supply new gearboxes, safety couplings and oil-lubricated spindles in order to increase torque and power to the rolling stands.

According to Danieli, ‘one of the main challenges was to avoid making any change to the civil works and re-utilise the anchor bolts of the existing equipment’.

The project was completed on time over a ninemonth period.

Further information, http://www.danieli.com

EMG drives the optimisation of high strength steel

St rip

ThyssenKrupp takes on Danieli

Magnetising field sensor

Idler roller

Steel strip

• The new Furnace Mathematical Model leads to the optimisation of Dual Phase steel quality in general.

• The EMG IMPOC system enables a faster release procedure and online monitoring of steel quality.

• Data analysis indicates parameters along the production line that can be improved.

• All relevant data from the hot rolling stage will soon be utilised to enable direct optimisation of steel quality for the individual coil.

For the coming years SMS Siemag’s I-Furnace (Intelligent Furnace) concept ensures an efficient and resource saving production of high-quality steel strips.

This approach involves EMG’s IMPOC system, the Furnace Mathematical Model by Drever, SMS Siemag’s metallurgical model and data-driven models and opens up new avenues for annealing.

By introducing a combination of EMG’s IMPOC online quality measurement system and Drever’s Furnace Mathematical Model, it is possible to adjust the annealing peak metal temperature. One main benefit is the reduction of energy costs, plus increased line speed and productivity.

Further information, http://www.emg-automation.com

Couplings cut vibration and torque amplification on table roller drives, says Renold Table rollers in steel mills are effectively heavy-duty conveyors that move steel around the plant from one process to the next. They are absolutely critical to production as failure to any part of this conveying system would result in the loss of ability to move product around the mill and could halt the production process.

Shock loading, vibration and torque amplification are common operating conditions on table rollers and the driveline must be designed to withstand this. When a shock load occurs, such as when a billet of steel hits the rolls, the impact passes down the drive train transmitting the torque to the driving motor.

A key factor in peak torques and torque amplification is backlash, which acts like a hammer blow to the system as the torque from the shock load accelerates over the backlash gaps and abruptly decelerates to the operating speed transmitting dynamic torque along the driveline.

The problem can be cured, claims Renold HiTec, by fitting rubber-in-compression couplings.

With metal-to-metal contact eliminated, drive is through pre-compressed rubber elements that dampen vibration, eliminate backlash, and ensure that the natural frequency of the drive train does Digital Edition - September 2015

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not coincide with running speed. Rubber-in-compression type flexible couplings are comprised of two round, metal sections fitting one inside the other with what looks a bit like paddles projecting inwards from the outer section and outwards from the inner.

Rubber blocks are placed in the spaces in-between the paddles, and, as the outer section is turned by the motor, it drives the inner section through the rubber blocks. As this happens the rubber is compressed, and hence the term rubber-in-compression.

Renold claims that its engineers rely upon soft-

ware to measure and determine true torque loads and vibration frequencies.

Couplings can be tuned with different types of rubber blocks to alter natural frequency and avoid damaging resonant frequencies.

Rubber-in-compression couplings are maintenance-free and the rubber blocks provide 10 years of service before needing replacement.

They are also used on other steel mill applications including rolling mill drives, ladle cranes, hoists, pilgar mills, pickling lines and edger drives.

Further information, http://www.renold.com www.steeltimesint.com

9/29/15 9:24 AM

SINTERING AND PELLETIZING INNOVATIONS BASED ON DECADES OF EXPERIENCE Outotec offers leading technology solutions and services for the processing of iron ores and other ferroalloys materials across the entire value chain from ore to metal.

Our innovative technologies are based on decades of experience and continuous R&D. Globally we have delivered more than 400 sintering plants and 65 pelletizing plants for a wide range of ore types. Our technologies ensure high performance and quality, low life cycle cost, and reduced energy consumption and emissions.

Read more at www.outotec.com

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SPECIAL STEELS

Higher standards demanded Whether you produce or sell a power or distribution transformer outside of the country in which you are located, you are competing in a global market – not just for the finished transformer, but more importantly, for the materials used to produce them. Ben Ehmcke* reports

Who would have thought in January 2014 that a majority of US power and distribution transformer manufacturers would be making the decision to outsource their core manufacturing, that the International Trade Commission would deny the petitions against imported grain oriented electrical steel (GOES) and that foreign mills would be in the position that they no longer needed the US market?

What has changed?

There are three basic categories of factors that are going to effect the future of all transformer manufacturers: 1) global socio-economic; 2) efficiency standards; and 3) political protectionism.

Socio-economic factors What are the global socio-economics that are driving this change?

• Global population in 2012 was 7 billion, and is increasing at a rate of one billion every 12 years.

• In 2014 there were 1.5 billion people in India that did not have electricity.

• An estimated third of India’s population has no electricity.

• An additional one third of the population in India is without access to reliable electrical supplies.

• From January through August 2014 over 93,000 distribution transformers in India exploded.

• 70% of all distribution transformers in India are at least 50% overloaded.

• The average life span of a distribution transformer in India is seven years as compared to the US at 30+ years.

• Major population growth areas are: India, Malaysia, Africa, Central and South America.

• Environmental concerns • Electric vehicles • 150,000 registered in California during the first nine months of 2014.

• Move to PV and wind power.

• Increased emphasis on buried

distribution and transmission lines.

• Global transformer market growth by 2019 • Power transformer market is worth $28 billion • Distribution transformer market is worth $20 billion Data from India is typical of that from any of the emerging countries. Not only are these developing regions spending billions to build and/or upgrade power grids, they are also requiring that the transformers perform to the highest standards in developed countries.

Efficiency standards Since the mid-1990s there has been increased global pressure to increase efficiency standards for power and distribution transformers, with Canada and Japan leading the way. In 2010 the US

implemented the current standard which requires higher GOES grades and designs needing up to 20% additional material.

Stricter standards In 2014 Japan had implemented stricter standards with increased need for amorphous metal. The EU finalised its 2020 transformer standard that required all transformers to be at least 99.5% efficient, which will require GOES of MOH085 and better or amorphous metal.

The US Department of Energy, mandated by a Federal Court ruling, issued the 2016 Distribution Transformer Efficiency Standard for both liquid immersed and dry-type transformers. Again this pushes demand for better grades of GOES. For those companies in the US, don’t be surprised that shortly after January 1, 2016 we hear the cry for the US to adopt the 2020 European Union standard.

* Ehmcke Consulting LLC. Email: behmcke@theimpactpaper.com Digital Edition - September 2015

SPECIAL STEELS GOES EhmckeReadMM.indd 1

www.steeltimesint.com

9/29/15 9:25 AM

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SPE6_Mise en page 1 09/09/2015 14:41 Page 1

SPECIAL STEELS

Political protectionism • Sixteen mills capable of producing GOES, but not all able to produce better grades.

• Only seven known amorphous metal facilities, mostly in Asia.

• US and European mills cannot provide enough for their own markets.

• US mills move to block the import of GOES. • By late 2014 the International Trade Commission rules against the US mills.

• European Union started its investigation into imported GOES in late 2014 in spite of the ITC rulings in the US case.

As predicted in The Demise of American Made Electrical Steel published last year.

The US International Trade Commission has taken the next step to try and block the import of GOES. In January this year the ITC added import codes for both GOES cores and laminations.

What changed?

With the global transformer market calling for materials of an MOH090 and better or amorphous, the Asian mills now find themselves in the position that their

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SPECIAL STEELS GOES EhmckeReadMM.indd 2

domestic markets will consume their total output of the better grades and are no longer dependent on the US market. US mills are losing their foreign markets for the poorer GOES grades.

Tempel, Summit, JFE, Cogent, National Materials, Hammond Power Systems and others have all invested in either building or expanding core making facilities in both Canada and Mexico; and this has been driven by US transformer manufacturers committing to outsource the GOES core process.

There are two reasons for this change: First, the need to reduce internal costs; and second, to gain access to better GOES grades at the best price. Core manufacturing incurs some of the highest fixed and variable costs in any transformer plant. Foreign core manufacturers have access to the better grades of GOES and would not be subject to the possible duties and tariffs imposed in the US. While the ITC reversed the GOES rulings, the transformer companies have not changed their plans to buy foreign cores.

Of the 16 mills in the world capable of making GOES, 40% of global production is of the poorer grades. Hitachi has two amorphous plants in Japan, and Metglas

13

in the US, while China has at least five amorphous plants in production and a possible three additional plants in some phase of development.

Unless the GOES mills can vastly

improve their product mix to the better grades, transformer manufacturers can expect to find the better grades of GOES on allocation by the end of 2015. Order books for the grades with the lower losses are already sold out through the first half of 2015 and the mills expect to close their books, for these grades, for 2015 sometime in May. t

Digital Edition - September 2015

9/29/15 9:25 AM

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SPECIAL STEELS

15

Protectionism versus competitiveness The EU’s proposed anti-dumping measures concerning non-EU imports of certain grain-oriented flat-rolled products of grain-oriented electrical steel (GOES) are protecting a few companies, to the detriment of an entire EU industry.*

GOES is a highly specialised product – accounting for only 0.016% of global steel production, it is one of the most expensive types of steel. It is the core material in power and distribution transformers and makes up a substantial percentage of overall production costs. An essential product for the transmission and distribution industry, which employs over 200,000 people in the EU, it is now at the centre of a dispute between its producers and users in Europe.

Just over a year ago, in August 2014, the European Commission announced the initiation of an anti-dumping proceeding into EU imports of GOES from China, Japan, the Republic of Korea, Russia and the USA. The complaint was lodged by the European Steel Association (EUROFER), on behalf of four EU GOES producers, and has been fiercely contested by non-EU producers, but also the EU’s transformer industry – which is going to receive the biggest hit from the proposed measures.

The EU has historically been the largest transformer producer in the world – and a leader in technology and innovation in the industry. It supplies power and distribution transformers to Europe and the rest of the world for applications such as power generation, wind and solar power generation, transmission and distribution, commercial and residential usage, railway applications, and oil and gas applications.

Non-EU GOES producers targeted by the EU have all disputed the antidumping allegations and provided various explanations or justifications for exemptions from the measures. However, their underlying message, confirmed

by GOES users in the EU, is that the measures would lead to a decline in EU competitiveness and, in the long-term, be to the detriment of the EU specialised steel industry overall.

In May 2015, the European Commission imposed provisional anti-dumping measures – pending the conclusion of the investigation this autumn. The measures are already having a detrimental impact on GOES users in the EU. The rates

imposed on imports of GOES from the five non-EU countries, which range from 21.6% to 35.9%, have led to sharp price increases of at least 25-35%, which are being passed onto GOES users.

Such substantial price increases on the essential raw material for transformers will have considerable repercussions on companies’ entire production lines, leading to a significant increase in the

manufacturing industries overall.

The European steel industry already faces weakening demand, and decreasing competitiveness from high energy costs and more efficient foreign competition.

Trade measures, such as anti-dumping duties, which would drive out downstream industries, is not the right way to address these challenges. As T&D Europe – the European Association of the Electricity

price of transformers manufactured in the EU and, in turn, the ability of EU companies to compete with products from outside the EU. A sustained decline in EU competitiveness would inevitably lead to a decreased market share for EU transformer producers, who would be pushed to relocate production to third countries. In addition to job losses, in the long-term, the decline or relocation of the EU’s transformer industry will have an impact on the European steel and

Transmission and Distribution Equipment and Services Industry, has pointed out, the anti-dumping measures would have a disproportionate impact on the EU transformer industry, which directly employs 30,000 people within the EU. This is 10 times more than the EU GOES industry employs (only around 2,700).

EcoDesign Another argument against the measures relates to the EU’s new EcoDesign

*Article based on information provided by T&D Europe – www.tdeurope.eu www.steeltimesint.com

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SPECIAL STEELS

regulation, which sets higher standards for electrical appliances by requiring enhanced efficiency in transformers.

Meeting the new requirements will heavily

depend on the EU transformer industry’s access to the highest quality GOES for their production. The regulation came into force in July 2015 and will further drive up demand for high permeability GOES (HiB) and domain-refined GOES (DR) necessary for the production of more efficient transformers. However, according to T&D Europe, EU producers would not be able to supply even half of the EU’s demand.

European transformer manufacturers will, therefore, be forced to purchase GOES carrying anti-dumping duties. This would further drive up price levels of highly efficient transformers and make the EU transformer industry less competitive.

ABB, Siemens and other transformer manufacturers have confirmed that the duties on imports would make it more difficult and costly for producers to meet the EU’s new regulations.

The EU’s case has been further criticised by specialised service centres, which import lower grade conventional GOES (second and third choice products) and effectively “recycle” them by cutting and transforming them for further resale. In Italy alone, there are over 50 companies within the transformer supply chain and where many of these centres

are located. The Italian federation of electronic equipment has fiercely opposed the measures and has called upon the Italian government not to back measures that would protect a limited number of European companies, to the detriment of the entire transformer industry.

More importantly, specialised steel products, such as GOES, may only make up a small fraction of global steel production, but are the driving force behind many industries. It is, therefore, rather alarming that the European Commission appears to overlook the interests of those other industries and adopts anti-dumping measures that would be to the detriment of over 30,000 people.

For the EU’s transformer industry to grow and maintain a leading global role in innovation, it’s essential that manufacturers are guaranteed access to the highest quality and technologically most advanced materials for their production. EU GOES producers must continue to innovate and adapt to the growing market. Protecting them through anti-dumping measures may provide short-term relief, but will not incentivise innovation and will damage EU competitiveness overall.

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TECHNOLOGY PERSPECTIVES

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Steel’s role in CO2 mitigation

According to EUROFER’s Charles de Lusignan*, the greatest test for the steel industry going forward is likely to be in securing continued and adequate financing for investment into the deployment of much needed technologies for CO2 reduction.

1. “You cannot have targets without technology” said Gordon Moffat, former director-general of EUROFER, explaining how the technology doesn’t exist yet to enable steelmakers in Europe to meet EU carbon reduction targets.

What is your view?

The European Steel Association, EUROFER, is supportive of the need to reduce the carbon and energy intensity of its product. This is why the steel industry has worked so hard to reduce these factors, succeeding in doing so by over 50% since 1960 while broadening the range of steel grades available. However, Mr Moffat’s statement still stands. Policy makers, particularly EU policy makers, need to treat the world as it is, not legislate for the world as they’d like it to be. If targets are to succeed, they need to be technically and economically feasible, and supported with means to incentivise investment into the research and development that could produce results.

The large-scale technologies of the kind needed to commercially produce steel at the CO2 reduction levels sought by the EU for ETS sectors of 43% between 2005-

2030 – and by 80-95% by 2050 – are not yet available. While in the coming decades technology may be developed that will achieve the CO2 reductions sought, policy should not be based on ifs and maybes if it is to be coherent. Rather, the policy should support innovation in order to encourage progress on meeting regulatory targets. The industry is ready to work with policy makers to assess economically feasible measures for improvement, but encourages the use of tools to incentivise the industry’s efforts to reduce emissions.

2. If currently the technology simply isn’t there to meet carbon reduction targets in Europe, what is the situation globally?

Presently, Europe’s competitor regions do not face the same regulatory burden, particularly as regards CO2. Europe’s environmental legislation is the most stringent in the world, and this has a direct effect on the costs of the industry.

A recent CEPS study (http://www.ceps.eu/ system/files/steel-cum-cost-imp_en.pdf) on the matter concluded that regulatory costs probably account for a third of total production costs.

3. When it comes to emissions reduction technology in steelmaking, how ‘cutting edge’ is the equipment of the present day?

Fundamentally, industrial steel production produces CO2 as well as a number of other by-products, which for the most part, are put back into production or used as basic resources in other sectors.

Steelmaking is CO2 and energy intensive.

It requires coke, which is a product of coal, and is implicitly carbon rich. Still, the European steel industry is at the forefront of carbon efficiency worldwide. As a result, present processes and technologies are rapidly approaching the limit of their thermodynamic efficiency, even in the best performing facilities.

4. We often hear talk about ‘plant efficiency’ – should processing equipment manufacturers be proud of their achievements to date and will we ever reach a time when a steel plant has reached peak efficiency?

Emissions per tonne of steel produced have been reduced by 50% since 1960, and by 25% since 1990 – a significant

*Charles de Lusignan, communications manager, EUROFER. http://www.eurofer.org www.steeltimesint.com

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TECHNOLOGY PERSPECTIVES

achievement [Source: BCG Steel’s contribution to a low carbon Europe 2050]. As a result of this progress, the best facilities are approaching the limits of their thermodynamic efficiency potential, at least with best available techniques.

Under EU ETS as it is currently in force, even best performing plants face costs related to their CO2 emissions, because the number of allocations is about 10% below the technically feasible level. This is the ‘benchmark’ level, which, according to the current arrangements, is at a level lower than the best performing plants can presently achieve. This makes it very hard to invest in further reduction, while making the sector as a whole uncompetitive relative to third country industries.

In the meantime, work is being conducted to further relatively decouple the production of steel from its CO2 emissions. There are a number of projects underway. One, for instance, is the further investment being distributed via the Ultra Low Carbon Technologies (ULCOS) programme, which is financing a couple of promising technological avenues.

5. In your opinion, are there any particular steelmakers that shine in respect of reducing emissions and being ultra efficient?

The measurement of best performing plants is, in and of itself, problematic.

Certain steelmakers, particularly of highergrade and speciality steels, are ‘less efficient’ in the sense that for a given tonne of steel their process will use more energy and produce more CO2. However, higher grades of steel simply require more processing, which implicitly raises their CO2 intensity. For the quality and utility of steel produced, many EU-based steelmakers are at the pinnacle of production efficiency.

However, for the purposes of the EU ETS benchmark, these steelmakers are relatively penalised because it does not take into account the wide range of metal types that make up the European steel sector, nor the efficiency of their products’ later lifecycles.

6. What, in your opinion, are the major challenges facing steel production technology providers over the next decade?

The greatest test is likely to be in securing continued adequate financing for investment into the deployment of much needed technologies for CO2 reduction.

As even best performers will face costs for CO2 credits, this will have the effect of reducing their available capital for investment. The industry is already looking at a situation in which the future EU ETS will result in negative profitability in terms of EBITDA, meaning that the industry will be losing money just to stand still. It is Digital Edition - September 2015

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understandably hard to invest in emissions reduction technology if facing losses on production.

7. How optimistic are you feeling generally towards the future development of steel production technology?

There are a number of innovations across all areas of the steel industry production chain. These are in the process technologies, in equipment, process management (digitalisation, smart management) and in material innovation (new steel grades). Steel is already at the forefront of the ‘smart’ manufacturing trend.

Global steel demand in 2050 is expected to be 1.7 times the demand of 2010.

[Source: Allwood, Sustainable Materials: With Both Eyes Open]. This implicitly means that demand for advanced steel production technology is both strong now, and likely to rise in the future.

The Research Fund for Coal and Steel (RFCS), as well as Horizon 2020, are both contributing to that goal in Europe.

The EU is already a world leader in the development of steel processing technology (Best Available Techniques

reference documents; Ultra Low Carbon Steel Making). The need for continued, relative decoupling of the energy and carbon intensity of steel production and processing, ensure that Europe is well placed to fulfil this role as well as contributing to a circular economy.

Where advancing steel production technologies are concerned, it is important to respect the long-term sustainability of the industry, meaning that investment costs need to be recuperated over the normal business cycle.

Legislation needs to be designed in order to accommodate the requirement for long planning and investment cycles that can, and do, exceed the length of the usual political mandate. Long-term thinking is vital in this regard.

Steel is part of the wider range of solutions to ensure enhanced sustainability, a circular economy and the mitigation of climate change, via its many applications.

Steel has a central role in CO2 mitigation, as in its capacity as a 100% recyclable, ‘permanent’ material; it can be used, for instance, in the generation of renewable energy, in efficient power generation and transformation, and in weight reduction in transport. t www.steeltimesint.com

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TECHNOLOGY PERSPECTIVES

Constant collaboration needed The Latin American Steel Association (Alacero) expects to see continued improvements and developments within the field of steel production technology, but argues that constant collaboration is needed between the steel industry and the technology providers. Steel, says Rafael Rubio* has always been a dynamic industrial sector with current cutting-edge technologies including compact strip production lines, twin rolls casting and horizontal belt casting technologies – all of which are associated with hot rolling. There have also been great advances made in the development of third generation advanced high strength steels 1. “You cannot have targets without technology” said Gordon Moffat, former director-general of EUROFER, explaining how the technology doesn’t exist yet to enable steelmakers in Europe to meet EU carbon reduction targets.

What is your view?

Gordon Moffat´s comment is correct.

The steel industry has made a significant reduction of its emissions since the 1970s.

Since 1975, the amount of energy required to produce a ton of crude steel has been reduced by 50%, lowering the need for fossil fuels, one of the chief causes of carbon emissions. But we are far from being ready to reduce carbon emissions to the levels that some governments are setting.

Beyond the current limit, only breakthrough technologies can bring in further improvements in efficiency to the steel industry.

These kind of developments require

significant public-private collaboration and involvement in R&D. Currently, some of these technologies are just in early pilot plant phases and because of their high investment requirements, will need special funding programs to be implemented on an industrial scale.

Improvements in efficiency require the constant and collaborative work of equipment manufacturers and the steel industry.

2. If currently the technology simply isn’t there to meet carbon reduction targets in Europe, what is the situation globally?

Globally the situation is far behind what is under consideration in Europe, except for South Korea and Japan, as these countries seem to be on a par with Europe. New technologies will demand huge investment in R&D and extensive dedication, and will require investigating the actual applicability of such innovations.

3. When it comes to emissions reduction technology in steelmaking, how ‘cutting edge’ is today’s equipment?

Where CO2 emissions reductions are concerned, the main opportunities are related to plants that do not utilise gases from the basic oxygen furnace (BOF) to produce energy, and to the use of Variable Frequency Drivers (VFD) to reduce electrical energy consumption during the idle time of the steel production process.

Other marginal improvements are still possible. However, it is expected that all these developments will not generate more than 10% improvements in plant efficiency and the consequent reduction of CO2 emissions.

4. In your opinion, are there any particular steelmakers that shine in respect of reducing emissions and being ultra-efficient?

Because of their efficient manufacturing

*General director, Alacero. http://www.alacero.org Digital Edition - September 2015

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management, several Latin American steel production plants are considered benchmarks within the global corporations they belong to, on attributes such as energy generation from the BF and BOF gases and process yields.

Members of Alacero are actively involved in worldsteel´s benchmarking programmes. Among them, it is worth mentioning the Energy Management Project because of its direct relationship with the emission reduction efforts of the industry.

Alacero also develops its own initiatives with its member companies. For instance, benchmarking programs related to process yields of the main production lines, or establishing the best regional practices in environmental control.

Alacero and most of its members have been recognised by worldsteel as “Climate Action Members” because of their involvement and co-operation with global activities on climate change risk reduction.

5. What, in your opinion, are the major challenges facing steel production technology providers over the next decade?

There are two groups of challenges.

The first is related to current production routes and includes improvement in environmental control and emission reduction, energy re-use and the integration of process control systems and simulation.

The second refers to breakthrough technologies. Up until now, steel companies have carried most of the burden of these developments.

However, the co-operation of technology suppliers is needed, allocating resources in order to advance from laboratory to pilot phases and finally to the industrial scale.

Both challenges required significant financial resources. In some regions of the world, like Europe and the United States, this is possible through joint efforts between private companies and governments. In other regions, this is not possible.

6. In which area of steel production are we seeing the most innovation?

A good part of the innovation efforts go to steel shop technologies and relations between steel shops and upstream and downstream processes, particularly those for integration with the hot rolling mill. In a sense, innovations are related to the use of energy and how to make more efficient use of this input.

Current cutting-edge technologies we could mention include compact strip production lines, twin rolls casting and horizontal belt casting technologies, all of them associated with hot rolling. www.steeltimesint.com

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7. What, if any, are the stumbling blocks one might associate with the development of smart manufacturing?

Smart manufacturing must be aligned with the characteristics of each industry.

Up to continuous casting, steel production behaves like a typical process industry. Beyond this stage, the mechanical aspects of production become more important.

Therefore, different smart manufacturing approaches should be applied on each phase of the steel production process.

During reduction and steelmaking, the use of complex methods to integrate physical systems and information technology could enhance steel production and make it more cost-effective and environmental friendly.

The adoption of such systems addresses real situations that cannot be solved only on the basis of metallurgical and thermodynamics rules.

The first stumbling block is the assessment of the real improvement that a smart manufacturing approach will provide.

The second is to find people who can design operator-friendly algorithms.

Fortunately, in Latin America, there is a young generation attracted by mathematics, science and information technology.

Downstream – from continuous casting – the interaction between the different processing lines and the optimum set of parameters for rolling is subject to continuous improvement.

Advanced sensors and sophisticated process control systems find wide applications in all stages of steel production and are important components of smart manufacturing.

8. What is your view of the global steel market and the market for steel processing technology?

Currently, global installed overcapacity – concentrated mainly in China – along with growing unfair trade practices are distorting the international market.

The arrival of subsidised and dumped steel products in Latin America (especially from China) are damaging local industry by eroding margins and discouraging investment. The situation is restraining the development of the Latin American steel industry.

Currently, only those projects already in progress are being completed. However, even these are showing delays because of the difficult financial position of Latin American steelmakers.

9. Where in the world is the steel industry experiencing the most growth in terms of steel

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processing technology?

As most global steel production comes from plants in the Northern hemisphere, most of the technology centres are located in Europe, Japan and Korea.

These are the regions where steel processing technologies are growing faster. However, it is worth highlighting that Latin America has mothered some relevant advances too.

For instance, the use of biomass (charcoal from planted forests) and natural gas in the reduction and steelmaking processes.

10. It is argued that modernisation of existing steel plants will be far more common than the development of brand new facilities. How will this determine the future direction and development of steel manufacturing technology globally?

As commented above, currently there are no new greenfield projects under development in Latin America. However, in many plants, diverse projects concerning environmental control and equipment improvement along the production process are taking place.

One goal of these initiatives is to keep up with the increasingly challenging requests of the steel consuming sectors. These requirements will define the developments of steel production technologies in our region.

11. How optimistic are you feeling generally towards the future development of steel production technology?

The steel industry has always been a dynamic sector. Consequently, we expect to see continued improvements and developments for the current productive routes, such as some already on-going initiatives including Salzgitter’s BSC (belt strip casting) and CEM (compact endless casting and rolling mill, from POSCO and SMS Group).

Another important area of development is related to the production of third generation advanced high strength steels (AHSS).

Also, significant progress has been made in process control of coating lines, considering that the microstructures of such steel require appropriate heating and high cooling conditions, implemented in different parts of the lines.

Finally, hot press coated steel is also improving and broadening its applications for the automotive industry.

However, when it comes to breakthrough technologies related to carbon emission reduction, we tend to be cautious about the feasibility of their adoption in the short and medium terms. t Digital Edition - September 2015

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TECHNOLOGY PERSPECTIVES

Targets without technology? Why not?

What is the current state of the steel processing equipment and technology market? Is it true that the technology simply doesn’t exist to meet stringent carbon reduction targets, particularly in Europe?

Italian steel processing technology provider Tenova* begs to differ and argues that it already has the technology in its portfolio to enable the steel industry to meet emissions targets. It is more a matter of funding power and commercial interests and definitely not a question of technological availability 1. “You cannot have targets without technology” said Gordon Moffat, former director-general of EUROFER, explaining how the technology doesn’t exist yet to enable steelmakers in Europe to meet EU carbon reduction targets.

What is your view?

“You cannot have targets without technology” – to give a provocative answer: “Of course you can!”.

However, from a steel producer’s perspective, we need to face the reality of high standards and ambitious targets driven by society, governmental and non-governmental organisations. It is our responsibility to support sustainable economic growth, which includes all levels: ecological, social and economic.

These influences will increase; they won’t go away, so we need to understand the dynamics with regard to technological progress when considering our economic efficiency calculation in future. At Tenova, we are not afraid of targets, because we are prepared. We already have technology available in our portfolio (such as DRI) and there will be further advancements in terms of resource efficiency. At present it is more a matter of funding power and commercial interests, not a question of technological availability.

In the past decades our industry standard has already improved considerably. Over the last 30 years, CO2 emissions have halved and while this is a good start, it is not enough. Research estimates that currently only 10% of our industry’s investment is related to environmental protection and this demonstrates that there is still plenty of potential for investment in new technology – some of which is already available or being developed in partnership with the market.

2. If currently the technology simply isn’t there to meet carbon reduction targets in Europe, what is the situation globally?

It is not “simply” a matter of missing technology. With DRI technology – technically – it would be possible to get very close to carbon reduction targets.

But from an economic standpoint, DRI production is only viable in countries with access to natural gas deposits. At the moment this restricts the implementation of the technology to specific regions in the world.

3. When it comes to emissions reduction technology in steelmaking, how ‘cutting edge’ is the equipment of the present day?

A lot of improvement has been undertaken in this sector. Tenova – and others – have focused their research and development, besides production efficiency and safety, on emissions reduction.

Tenova’s FlexyTech Regenerative Flameless Burners or its iRecovery technology are very good examples.

4. We often hear talk about ‘plant efficiency’ – should processing equipment manufacturers be proud of their achievements to date and will we ever reach a time when a steel plant has reached peak efficiency?

Yes – processing equipment manufacturers introduced various promising innovations, concepts and products to the market over recent years. But plant efficiency is not achieved by selective optimisation or single product upgrades. It needs a holistic approach and the synchronisation of different process steps and plant equipment. This is the key to efficient steelmaking and thus plant efficiency.

The market currently lacks the willingness to invest in the latest technologies and cutting edge products even in the case of a perfect return on investment scenario.

5.

What, in your opinion, are

*www.tenova.com Digital Edition - September 2015

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TECHNOLOGY PERSPECTIVES

the major challenges facing steel production technology providers over the next decade?

The real challenge is to cope with the lack of investment. We are forced to provide the market with innovation and the highest technological standards, but the market is not willing, or able, to pay. The market asks for “high tech” but compares the price with “low cost” suppliers.

We see a good opportunity for longterm focused companies such as Tenova.

Being part of an international industrial corporation (Techint Group) with a strong entrepreneurial tradition in the steelmaking industry (Tenaris and Ternium are sister companies), we have the interest and insight to remain a technology leader in our field.

6. In which area of steel production are we seeing the most innovation in terms of technology?

For us a key-driver and trendsetter for the steel industry is the automotive sector.

This sector is continuously asking for “new” and “premium” steel quality or, in other words, is asking for continuous innovation.

Generally speaking we see two drivers for innovation: In the primary area of steel production, environmental impact and topics like resource and cost efficiency are driving innovation.

In the secondary part, the material characteristics of steel are continuously challenged to become better and more competitive with other materials (such as aluminium). Improvements in coating, annealing, galvanising or heat treating technologies will play important roles.

7. What is your view on digitalisation and smart manufacturing? We hear a lot about the ‘factory of the future’ and ‘industry 4.0’ but what is the steel industry doing globally in this arena?

The steel industry is still in the very early stages of digital transformation. Everybody talks about it and we see a lot of ideas and first applications, but it is more “patchwork” than “integrated strategy”.

Clearly there is a future for the “smart” approach entering the steel production environment to improve plant efficiency and quality aspects.

It will be interesting to see how the “culture” of the steel making industry will be influenced by standardisation and digitalisation.

At the moment “safety” is a main area of application. Robots, or high performance communication tools, which can manage “Big Data” in real time will significantly change the industrial environment and will help protect people engaged in crucial www.steeltimesint.com

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production steps on the shop floor and around the plant to increase efficiencies.

8. What, if any, are the stumbling blocks one might associate with the development of smart manufacturing in the steel industry?

In addition to the “cultural change” required in an industry that still has an artisanal attitude, we see two main aspects that might be challenging the paradigm shift in the industry.

First, opponents of digitalisation may raise network security as an important argument. If everything in a plant is standardised, automated and remotely managed, a loss of control or the fear of system outages is always present.

Secondly, but more obvious, the digital transformation of the steel industry will

go hand-in-hand with the investment capability of manufacturers.

It will very much depend on how quickly a clear business case for a “steel industry 4.0” will be valid and what investments will have the highest priority for the manufacturers.

9. What is your view of the global steel market and the market for steel processing technology?

Where in the world is the steel industry experiencing the most growth in terms of steel processing technology?

Short-term we see more consolidation and a continuing emphasis on a return on investment coupled with longer decisionmaking processes.

We also get signals that the market requires investment in new equipment in

23

order to remain competitive and ensure compliance with demand for “greener” production. This is getting more and more important in China and the USA where environmental protection has become part of the political agenda.

We focus on anything concerning efficiency, flexibility and quality, as we see these leading themes as mandatory requirements for all dimensions of a sustainable business.

10. It is argued that modernisation of existing steel plants will be far more common than the development of brand new facilities. How will this determine the future direction and development of steel manufacturing technology globally?

Steel is and remains one of the most important basic materials for industrial societies.

Currently, the worldwide installed capacity meets the needs of global society based on an annual economic growth rate of 2% for the next five to eight years without the need for additional facilities.

However, a large proportion of existing plants are more or less at the end of their life-cycles, but investment reserves are small and this is a major challenge for steel producers and technology suppliers as investment in steel plant modernisation will become more modular, while also having an holistic approach in mind.

Any technology investment that brings an additional immediate benefit or shortterm return-on-investment will stand a better chance of being established in the market. t Digital Edition - September 2015

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ROLLING

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Process and technologies to anneal current and future AHSS strips The production of advanced high-strength steel (AHSS) grades in a continuous annealing line requires strict cooling control to limit strength deviation within the coil in order to improve homogeneity and formability. Fives has developed ‘Wet Flash Cooling’ to reach the required AHSS characteristics. This paper was presented by Eric Magadoux* during the Rolling – Cold Sheet Rolling and Annealing session at the METEC and 2nd ESTAD Congress in June 2015 in Düsseldorf, Germany WATER quench technology has been used on certain continuous annealing lines for more than 30 years now to produce high strength steel (HSS) grades. Market demand for HSS is accelerating today and various advanced high strength steel (AHSS) grades have been developed for which yield strength and other properties are also considered to ensure formability.

The production of AHSS grades in a continuous annealing line requires strict cooling control to limit strength deviation within the coil to improve homogeneity and formability. To reach the required AHSS characteristics, Fives has developed Wet Flash Cooling to offer a more flexible control of the strip cooling cycle, including initial and final strip temperatures and modulation of the cooling rate.

This technology has been successfully operating in a large capacity industrial continuous annealing line at a major steel plant for four years following start-up in 2009.

is required, which means significantly increasing the cooling rate of the annealing cycle.

A higher cooling rate can be achieved by using a higher H2 content in the gas cooling section. This technology allows

a cooling rate up to 200°C/s/mm thick, which is suitable for most DP grades. For AHSS of the highest tensile strength a lean composition with low C is preferred, in

AHSS grade characteristics Demand for AHSS is increasing, especially in the automotive market.

Numerous steel grades have been developed for this particular requirement1.

The production of the highest strength grades, which are based on martensite formation, has to comply with cooling speed requirements as per the CCT diagram. If the cooling speed is too low, the steel grade has to be enriched by a higher content of certain additional elements, such as silicon or molybdenum, to avoid the formation of upper phases, such as pearlite and bainite instead of martensite. However these additions compromise weldability and formability.

On future lines, therefore, a way of decreasing these additional elements * Eric Magadoux, research and development engineer, Fives Stein (France) eric.magadoux@fivesgroup.com www.steeltimesint.com

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Fig 1: The typical annealing cycle with WQ process

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Fig 2: Sketch of the test rig 1. Collector with nozzles 2. Pressure gauge 3. Test plate 4. Motor with rope 5. Girder 6. Trolley with position sensor and datalogger for recording temperatures and position of test plate 7. Heater 8. Water tank 9. Pump 10. Control valve

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order to avoid mainly welds embrittlement and internal fracture, and to improve hole expansion behaviour.

Current processes To obtain ultra-high cooling rates water quench processes have been developed and applied in industrial annealing lines for more than 30 years. With the aim of improving the mechanical behaviour of the steel, a tempering treatment can also be performed after the water quench (WQ). A typical annealing cycle sketch is represented in Fig 1. It should be noted that this tempering treatment requires high capacity induction reheating after WQ cooling.

However, the WQ process must comply with several requirements: 1. A high strip cooling rate, up to 1000°C/s (the cooling rate usually expected by steelmakers is approximately 400°C/s).

2. Accurate control of the cooling rate and good strip thermal homogeneity, during the whole process is required to achieve good crosswise mechanical properties and good strip flatness.

3. Flexibility in strip temperature choice, for both the start and finish of WQ cooling.

The Fives process is based on “film boiling” conditions, in order to comply with these requirements.

Development programme Current quenching technologies reach adequate performance with regard to

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the expected cooling rate, even for thick strip (typical strip thickness for these grades is approx 1.5mm). However, not all technologies are satisfactory where temperature flexibility is concerned, especially the ability to stop the cooling at any strip temperature with good crosswise temperature homogeneity. Consequently Fives performed a development programme with this aim in mind. An extensive R&D study was carried out, including: • Numerical calculations; • Test rig to characterise the heat transfer performance of the nozzles, to investigate the uniformity of cooling and flexibility of operation; • Equipment design in order to operate in vertical arrangements and for all steel grades; • Industrial operation.

Cooling rate In this study, various geometrical nozzle arrangements were tested in order to optimise the cooling nozzle mesh. The

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objective was to characterise and improve the heat transfer co-efficient according to several parameters. An experimental test rig was developed, including heating and cooling for a steel sample (Fig 2).

The test rig was composed of: • a test plate, equipped with thermocouples • a vertical trolley supporting the steel plate, capable of moving upwards and downwards • the plate heating device • the cooling system.

Before the cooling test, the steel plate was moved upward to be heated to 900°C. The cooling system was then switched on and the steel plate moved downwards at a constant speed of 180 mpm. This fullscale test, therefore, was representative of industrial conditions and led to a spraying geometry that was then installed in the industrial line.

Fives continued to refine its design, leading to a second and more efficient nozzle arrangement. In this second geometry 2

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geometry the nozzle’s mesh was tighter, and the strip closer to the nozzles (100mm instead of 250mm for the first geometry). The main improvement in cooling performance is due to the smaller distance between strip and nozzles without interaction between the spraying jets.

It is well known that the heat exchange co-efficient of this type of technology is better when the strip is cold, below Leidenfrost temperature (typically 400600°C depending on the configuration).

Fig 3 clearly shows the influence of the final strip temperature on the global cooling rate (initial temperature is 900°C).

The results are summarised below (Fig 4), and show the influence of water pressure on the average cooling rate.

The geometry n°1 achieves its optimum performance at approximately 5 bars. The geometry n°2 is more efficient at every pressure. At 12 bars the average cooling rate from 900°C to 200°C is approximately 1500°C/s.

In the industrial design, the nozzles are fed with both water and nitrogen.

Nitrogen, of course, is replaced by air in the test rig. The strip cooling rate is controlled by the water pressure (Fig 4), the gas flow rate being adjusted accordingly.

Water pressure can be controlled separately in each group of nozzles (or even in each nozzle) and also in transversal direction, in order to control the cooling rate during the whole cooling time. It is www.steeltimesint.com

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also possible to switch off some groups of nozzles to change the cooling pattern.

Cooling cycle flexibility With conventional water quench processes the final strip temperature is close to the water temperature (in any case below Mf).

This requires a further reheating of the strip to proceed with tempering.

The Wet Flash Cooling process allows total control of the cooling slope, i.e. initial and final strip temperature and cooling rate. This enables the production, for example, of TRIP steels but also Q&P grades2. With Q&P grades, a partial transformation from austenite to martensite is required by cooling the steel to a pre-determined quench temperature, followed by a partitioning step at a suitable temperature, at which carbon migrates from over-saturated martensite to austenite. An example of an annealing cycle is shown (Fig 5).

Thanks to the controllability of the cooling rate, it seems clear that this process is well-suited to produce the desired structure. As compared with dry jet cooling technology, in which the cooling rate is controlled by the H2 content in the blowing atmosphere, Wet Flash Cooling® offers a wider process window (Fig 6).

Industrial application This developed concept has been proven over four years of industrial operation on an annealing line in a major steel plant. A

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typical sketch of the cooling pass is shown in Fig 7. The pass line configuration can be vertical, upward or downward. The water flow rate used to feed the spraying nozzles is quite low (Fig 8), especially when compared with other technologies3.

Industrial operation confirmed a good crosswise thermal homogeneity of the strip.

Conclusions Wet Flash Cooling is an efficient tool to produce all steel qualities on an annealing line, from CQ to martensitic grades. The nozzle design and the mesh geometry allow total flexibility of the cooling pattern. The ability to stop the cooling at any strip temperature is, of course, of prime interest when producing specific grades such as Q&P. t References 1. B. Mintz, Hot dip galvanizing of transformation induced plasticity and other inter-critically annealed steels, International Materials Reviews, 2001, Vol 46, No 4, p 169.

2. B C De Cooman, J G Speer, Quench and partitioning steel: a new AHSS concept for automotive anti-intrusion applications, steel research int. 77 (2006) No 9-10, p 634.

3. D. Bourquegneau, A. Fouarge, V. Lhoist, J. Crahay, P. Klinkenberg, P. Simon, Production d’aciers à haute résistance par un dispositif de refroidissement à turbulence controlée, La Revue de Métallurgie-CIT, Juillet-Août 2003, p 697.

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ELECTRIC STEELMAKING

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Modernising and revamping an EAF Modernising and revamping an electric arc furnace will maintain or increase its asset value and boost productivity, claims Primetals Technologies, but bearing in mind corresponding activities and the need to provide long-term, ongoing feedback on all aspects of the plant, means that service partners must acquire a deep understanding of customer operations and processes. By Patrik Zipp* and Jens Apfel* A high performance conventional heat load operation using an electric arc furnace can be ultra-productive if existing transformer capacity is fully utilised in conjunction with a rigid electrode lifting system and associated process knowledge.

The electric transmission path to the arc must be designed for maximum power input. Alternatively, a more powerful transformer with a suitably high-current system up to the electrodes can be installed. Cycle times during power-off and power-on times may be reduced with faster single movements with new hydraulic settings.

The latest modernisation developments for maximum electric power input enables: • Increased productivity • Lower conversion costs • The ability to operate with a symmetrical power input • Limited refractory wear • Improved plant availability and life time with heavy duty components In the real world, steel producers face multiple challenges. Rising raw material and energy prices and stricter environmental regulations present major obstacles for the electric steelmaking industry. In this highly competitive and globalised market, steelmakers constantly need to find new ways to optimise their cost structures and decrease their conversion costs.

Consumption figures can be reduced with continuous improvements in technology, equipment and system maintenance.

Enhancements in plant availability and utilisation boost productivity and improve quality and consistency. Steelmakers strive to achieve maximum improvements with minimum investment in order to attain high plant performance and production efficiency. All of these requirements are met by adopting a strategy of continuous modernisation over the entire lifecycle of a steel plant. Combining modernisations with commensurate services extends the

Fig 1: Plant lifecycle

lifecycle of the plant and ensures flexible and competitive operation.

Primetals Technologies does not only build metallurgical mills and plants, but services and modernises the installed base in order to ensure a long and extended service life. We provide our services at the early stages of a project and are present during the commissioning phase to ensure a smooth start-up. Spare parts are defined and managed to account for equipment wear and ensure subsequent high levels of plant uptime. This is where the lifecycle begins. The plant must be fine-tuned with additional technical assistance and training in order to reach efficiency and performance levels. This assistance is best provided by the OEM during operation as well as during scheduled plant shutdowns. The subsequent inspections, both on- and off-site, serve as a basis for recommendations of ongoing process improvement. If problems are identified, the OEM continuously improves and redesigns the corresponding components.

If significant modifications are required, plant components are modernised and revamped. Throughout a long-term partnership, the manufacturer offers multi-dimensional on-site technical and technological support with engineering and process expertise.

The steps described below constitute the typical lifecycle loop of a plant, which is repeated several times. The benefit of such a procedure is continual or increasing asset value that enables the plant operator

to deliver consistent product quality and improve profitability.

A typical estimate of EAF service and modernisation expenses is about 1.5 times the original investment cost during the lifecycle. The following typical expenses are generally incurred over the entire lifecycle of an EAF. Watercooled panels make up the largest share of the spare parts budget, accounting for approximately half of the €8 million spent during the 10-year service life of an EAF. Personnel costs amount to roughly €100,000 per annum, corresponding to €1 million in a decade. On average there is one major revamp package over the 10-year period and that costs roughly €2–3 million. There are also three smaller revamp cycles that cost between €0.5–1.0 million each. In total, this amounts to approximately €5 million in a decade of which approximately 20% (€1 million) is required for erection, commissioning and tuning. This short calculation summarises the important service and modernisation expenses incurred during the service life of an EAF. It also underscores the need to invest in continuous improvement to steadily decrease the conversion cost and boost productivity.

Modernising the electrical power input system Energy consumption and input strongly influence the productivity and conversion costs of an EAF operation. One way of boosting productivity is to increase

* Patrik Zipp, Jens Apfel, Primetals Technologies Germany GmbH, Reithallenstr. 1, 77731 Willstaett-Legelshurst, Germany.

Phone: +49 7852-41241, Mail: patrik.zipp@primetals.com www.steeltimesint.com

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ELECTRIC STEELMAKING

Fig 2: Copper cladded current conducting electrode arms

power levels during the power-on phase.

This is achieved by fully utilising existing transformer capacity and assuring that the entire electric transmission path to the arc is suited to the maximum power input. An alternative would be to install a more powerful transformer with a suitable high-current system up to the electrode. Productivity can also be improved by reducing the power-off time and thus upgrading EAF movements and reducing delays. A hydraulic system revamp with gantry modification – such as EAF equipment tuning and process optimisation – can lead to further increases in productivity.

Example: 150 t, 110 MVA AC EAF in Finland Key facts • New electrode lifting system implemented in existing gantry • New hydraulic system • New current conducting electrode arms Key results • Symmetrical power input (reactance un-symmetry from 17% to 5%) • better melting operation • constant tap weight Lower conversion costs Plant availability and reliability are the primary factors that determine conversion costs. Ideally, steel plant staff and the technology provider’s service department co-operate on establishing an ongoing feedback process concerning plant problems and jointly develop solutions.

Initial activities focus on optimised spareparts management and identifying specific components that need to be re-engineered to suit the specific requirements of the plant operator. These solutions are then implemented on-site and the results monitored. In general, the solutions discussed are small modifications and revamps that produce maximum shortDigital Edition - September 2015

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Fig 3: EAF 150t at Outokumpu Stainless

term effect.

The next factor in reducing conversion costs is boosting productivity, but first existing productivity must be determined.

This is achieved by conducting a factfinding mission on-site. The number of tons produced hourly defines EAF productivity. Increasing the tapping weight while maintaining the same cycle time can also influence productivity. Other influencing factors are electrical power input, power-on time during every cycle, and improvements to the EAF’s mode of operation. Energy consumption is another influential parameter.

Using higher electrical power levels during the power-on phase will further boost productivity and requires the full utilisation of existing transformer capacity combined with a revision of the entire electrical transmission path to the arc or the installation of more powerful transformers.

EAF using larger scrap buckets and a correspondingly optimised EAF geometry.

The tapping weight can be increased by using higher and bigger shells and a bottom shell with higher capacity.

Additional improvements can be implemented by including new design features with additional technologies such as injection tools and cooling blocks in the shell. The deployment of an additional injection system using a chemical energy medium is another way to increase total energy input and improve the efficiency of the thermal and metallurgical processes.

Bolstering productivity Reducing power-off time, upgrading EAF movements and reducing delays will also bolster productivity. Revamping the hydraulic system with a gantry modification, for example, as well as finetuning EAF equipment and optimising the process can yield further increases in productivity. In order to reduce poweroff time and increase productivity, however, the steel producer requires technical assistance for fine tuning and process optimisation, the end result being a reduction in operational delays and maintenance, faster diagnosis of problems and shorter reaction times, not to mention speedy replacement of spare parts and efficient handling using trained operators for synchronised operation and the application of a standard mode of operation.

Customer-tailored solutions It takes close and continuous co-operation between a plant operator and a service provider to identify which of the above measures will yield maximum gains for a given process and production situation. It is also helpful if this co-operation extends over the entire service life of the EAF so that the service partner has a detailed understanding of the customer’s specific operational and maintenance aspects.

The service provider needs to hold a wide range of skills spanning equipment design, service and maintenance management and technological competence all the way to process control. This expertise is necessary to offer the multi-dimensional solutions required to preserve asset value over the entire service life of the EAF. Problems with the plant have to be resolved with tailor-made technological upgrade solutions that are implemented in short installation times and fit into scheduled plant shutdowns. The supplied components and systems need to be designed for reliability, low maintenance, safety and environmentally friendly operation. In case of emergencies, fast response and short delivery times for the service provider are of vital importance.

Using larger scrap buckets A further promising modification is to better utilise fed energy by charging the

Service support Besides having a long track record as an equipment manufacturer, Primetals www.steeltimesint.com

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ELECTRIC STEELMAKING

Fig 4: RCB Temp; contact free temperature

Technologies also provides services and is capable of covering all aspects of system operation across the entire lifecycle of a plant. The company’s service support goes beyond spare parts and emergency service: its specialists provide plant operator training and equipment performance analysis, and develop customised upgrade and revamp packages that can easily be installed in regular service breaks. In recent years, Primetals has built a reputation for competent process support and highly efficient upgrading and revamping projects for all aspects of a plant, from electrical and mechanical up to plant erection and all the necessary project execution steps.

Ancillary process solutions Primetals has also developed a number of innovative solutions for specific aspects of EAF operation.

Precise, reliable and predictable acquisition of temperature data, for example, is important to ensure consistently high product quality as well as safe working conditions.

RCB technology Steelmaking is about knowing the exact liquid steel temperature at any given time.

Until now, this has been accomplished through time-consuming and dangerous manual cartridge taking. However, with its supersonic oxygen injection technology based on Refining Combined Burner technology, RCB Temp offers a new approach. The burner preheats scrap during power-on time, accelerates the melting process and injects a supersonic oxygen stream during the refining phase.

As soon as the defined homogenisation level is reached, the system switches to temperature mode and measures the temperature at short intervals in a contactfree procedure. Compared with manual sampling this allows for a quicker and easier decision as though tapping the EAF. This results in shorter tap-to-tap times and www.steeltimesint.com

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Fig 5: EAF at Swiss Steel, modernised in 2013 with a new furnace gantry, roof, tilting platform, hydraulic system and ladle car

higher productivity, and precludes any risks for the plant operator. Additionally, it reduces operating costs by eliminating expensive cartridges.

LiquiRob for EAF Another solution is the LiquiRob for EAF, a robot-aided automatic measuring and sampling system optimised for the rough environment of EAFs, converters, secondary metallurgical plants and casters.

The system gives the plant operator the needed flexibility and reliability to ensure uninterrupted, fail-safe and controlled EAF steel production and it replaces mechanical manipulators, performs fully automatic temperature and sample measurement cycles, and takes care of automatic cartridge replacement and thus eliminates manual work in hazardous areas.

Flexibility of raw material choice Other EAF-specific modernisation solutions target process optimisation and help to boost productivity while decreasing energy consumption: A DC EAF revamp including Fin-Type anode modernisation extends EAF service life by offering faster exchange times and improved safety, since no cooling water is underneath the EAF. In steel plants where hot metal is available, more flexibility of raw material choice offers economical advantages.

The implementation of an EAF hot-metal charging turret with tilting ladle and launder offers increased flexibility for material input.

AC EAF modernisation At Swiss Steel, the main goals of modernisation were to shorten process times and cut conversion costs. Production capacity rose to 650kt/yr of steel and simultaneously improved operating safety while reducing maintenance costs.

• Tap-to-tap time reduced from 55 to 52 minutes • Idle times reduced by approximately

50 hours per year Swiss Steel AG has signed the FAC for an electric arc furnace modernised by Primetals Technologies. The production capacity has been increased to 650kt/yr by reducing power-off times considerably.

Energy consumption has been reduced accordingly.

Shaft furnace modernisation Primetals modernised the finger-shaft electric arc furnace at Natsteel in Singapore, increased productivity and decreased energy consumption. The new furnace is equipped with a FAST (Furnace Advanced Slag-free Tapping) system, renewed furnace shaft and lower shell, and a state-of-the-art automation system.

In order to further increase furnace productivity and reduce the specific energy requirement, Primetals installed new mechanical equipment based on the EAF Quantum solution platform especially developed for electric arc furnaces, and new automation equipment.

The main feature of the furnace modernisation was the FAST system, as well as a new anode. The lower shell of the furnace has been adapted, and, going forward, the plan is to automate the plugging of the tap hole. The FAST system helped to reduce the tap-to-tap time and increase productivity by around 6% and reducing specific energy input by some 5kWh. Conclusion When investing in an EAF it is important to take into account the expenses likely to be incurred for service, maintenance and modernisation in the overall lifecycle cost calculation. There is wide scope for EAF modernisation and revamping to help maintain or even increase the asset value of the furnace. The corresponding activities extend over a long period of time and require that a service partner gains a deep understanding of the customer’s operation and processes. t Digital Edition - September 2015

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HANDLING

When California Steel Industries, constructed a new furnace in its hot strip rolling mill, plant engineers knew that accessing the associated large components for maintenance was not going to be easy.

CALIFORNIA Steel Industries is located 50 miles east of Los Angeles near Fontana, California, and has been operating here since 1984. It has an annual operating capacity of 2.5Mt. The company’s engineering group needed to develop a way of moving oversized motors and fans out of the bay where the new furnace was located and into the next bay where maintenance could be safely performed. They wanted to install a new overhead crane to access the furnace and its components. But overhead space in this nearly 60-year old building was limited. The company contacted three crane suppliers requesting a bid.

“We asked them to give us some sort of crane in order to remove the motors from their current location and take them to where another crane could access them,” said mechanical engineer Joe Speigl. “Without crane access they would be very difficult to move, and, therefore, not maintainable. The problem we faced was two-fold. First, there was no access to bring in a new crane. Second, there were beams in the way of any traditional method of installing either crane runways or the crane itself.”

According to California Steel’s mechanical engineers Chau Pham and Joe Speigl, Konecranes was the only company that returned a bid. The other two vendors declined, telling California Steel that the job was too difficult. “We appreciated their positive approach,” said Pham. “The other two vendors said it couldn’t be done.”

“It was a relief that Konecranes did not decline, but personally I was sceptical that they would be able to get a crane into this location,” said Speigl.

Unaware of this dire forecast, Konecranes’ John Browne began work on a quote based on what California Steel’s engineers had asked for, which was a five-ton, 55-foot span, top-running single girder crane on a 65-foot long runway oriented east/west across the building.

When Browne received the order, he and his installation partner Kim Ramsey of Ramsey Machine Services made a site visit

Over and above to review the customer’s application and verify dimensions.

“We quickly realised the difficulties of getting a crane into the building, and felt that we could offer a better crane for the job,” said Browne.

They recommended rotating the crane 90 degrees and going with an underrunning five-ton CXT model instead of a top-running design. Based on that premise, they were able to specify a much better solution. They saw a way to take the load closer to the destination bay where maintenance was performed. The idea was to extend the runway past the congestion with a 10-foot cantilever that would enable operators to put the load down in an accessible area where an existing cab-driven crane could pick it up and move it into the maintenance bay.

“The earlier idea would not have gotten the components out of that bay and into the adjacent bay,” said Ramsey. “Initially they were thinking they could move the components away from the furnace with the crane, and then put them onto carts and roll them through a pit to a place where they could access the load with the overhead crane in the next bay. It was possible to do it that way, but it wasn’t efficient.”

Konecranes waited until a planned shutdown late in 2013 to install the crane and runway, an operation that took nearly a week.

“The challenge was the distance that had to be covered from where we could set up the mobile crane and installation equipment,” Ramsey explained. “We had to reach through beams and ductwork to put 80 feet of runway and crane girders

in place. Access was very tough,” he said.

“What the Konecranes team came up with was doing it in two lifts, temporarily supporting the beam in between the lifts,” said California Steel’s Joe Speigl. “Once they described it, the procedure seemed simple. They lifted the whole beam, moved it over, and then set it down. Then they moved it halfway into position and temporarily supported it. Finally, they moved the crane into a second location and then re-rigged the beam to make the final lift into position. It was the only way to do it with a single mobile crane, which is all that would fit. One crane in either location was all they had to work with. Temporarily supporting the girder while they moved the mobile crane was how they got it done. It wasn’t an obvious solution, but it worked.”

There was a significant usage differential in the initial configuration requested by California Steel and the solution that they ultimately bought.

The new solution gave them substantially more hook coverage of the area. “Compared to what we were looking at initially, this crane fits their needs much better,” said Ramsey.

Konecranes has load-tested the crane and demonstrated the efficiency of the cantilever set-up, but according to Speigl, the crane has not yet been needed to perform the function it was designed for, as the furnace is just five years old and the components for which the crane is designed to move have not yet required maintenance.

“I’m sure that when we do need the crane that it will be a valuable asset,” he said. t

*Further information, http://www.konecranes.com Digital Edition - September 2015

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Gunning robots improve repairs The hot gunning repair of aggregates – converter, ladle, EAF, RH-snorkels and so on – is a cost-saving alternative to shutting down and renewing the complete lining. It also increases the service life of a furnace, leading to savings of reheating energy. Quick repair also reduces the number of circulating aggregates, says Christian Wolf* THE use of gunning manipulators is necessary to improve working conditions for the operators. They further allow for a more well-directed repair of the corresponding positions. When compared with manual gunning, higher gunning capacities considerably reduce repair time and heat loss of the aggregates. In short, the steel plant saves money on refractory and has less downtime. Moreover, there is a reduced risk of accident. In the melt shops, however, gunning robots have to be customised for optimum performance.

Ladles A typical refractory consumption for ladles is 0.2kg/tonne of steel at the bottom and side wall and 0.4 kg/tonne of steel in the slag zone. When checking the lining it is often found that only the slag zone needs to be repaired. At plants with secondary metallurgy the slag zone wears out quicker. Sometimes the top of the lining (the lip ring) is damaged because slag removal using a break-out machine has been too forceful.

The ladle can be put back into operation very quickly after gunning repair of the slag zone alone has been carried out.

There is no need for replacing refractory, which is still good to go, and there is no loss of time or energy to heat up and dry a new lining.

The most convenient location for a hot repair is the tilting stand where the slide gate is repaired. It is possible to use a manual gunning lance, but this can be physically stressful in hot working areas (Fig. 1).

When using a gunning robot the gunning repair is:• quicker, because of higher gunning rates • more efficient, because of the welldirected jet • easier, because of no physical stress for the worker Depending on plant layout Velco has developed two different solutions for this task. Version one is a fixed installation consisting of a rotating lance that can move in and out and runs on a beam structure. The robot shown has been in operation at a German steel shop since 1987. For each repair stand one robot is required. (Fig. 2 and Fig. 3).

Version two is a gunning lance, which is mounted on an electric trolley that can

Fig 1: Manual gunning of ladle

drive from its parking position to one or more repair locations. Fig. 4 shows a manipulator for the repair of laying ladles (liquid content approximately 150 tonnes) at Voestalpine Stahl in Linz, Austria. The manipulator is driven in front of the laying ladle and is operated by a radio remote control. The robot is fed by a pressure vessel gunning machine with a high pressure water pump and an electronic water adjustment.

At Outokumpu in Tornio, Finland, Velco has installed a fully automatic gunning system for standing ladles located in a specially erected hall. The ladles are transported via rail into the gunning hall. In total four gunning positions and different programs for automatic gunning of bottom, sidewall and spout are available.

The programs can be started individually or sequentially without interrupting the gunning process. Two different gunning materials are used: a material for the repair of the permanent lining and a light material for the wearing layer. The operator selects the gunning position, the gunning program and the type of material and then the gunning process is carried out automatically.

When changing the gunning material, it is not necessary to exchange the gunning equipment. Furthermore, the operator can take over the manual gunning control using a joystick and can gun individually at Fig 2: Stationary ladle gunning installation

* Managing director, Velco GmbH, Velbert, Germany. Email: cwolf@velco.de Digital Edition - September 2015

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ELECTRIC STEELMAKING

35

Fig 4: Mobile lance trolley for ladle gunning

Fig 3: Gunning of slag zone

selected spots.

This installation considerably reduces working strain and dust exposure for the operator. The necessary gunning time could be reduced, as the gunning robot works at a higher gunning capacity and enables faster change between the two different materials. Fig 5 and Fig. 6 Electric arc furnaces In the past 25 years Velco has supplied 15 gunning robots for EAF operations.

However, due to the different melt shop layouts, no robot is alike. Moreover, the operating principles of the plants are different. A few have the ability to exchange the complete furnace vessel.

These plants do minor hot gunning and replace the complete lining every two weeks. Because most plants have to keep the lower vessel in place, the exchange of the lining increases down time dramatically. Hot gunning keeps the furnace running.

Typically, when using hand lancing, a 6m to 8m long pipe is introduced through the slag door. The gunning rate is only 60 to 80 kg/min. Handling the pipe is hard work and not all areas at the furnace are

accessible.

Fig. 7 shows the gunning manipulator HYTOP at Deutsche Edelstahlwerke, a stainless steel plant in Siegen, Germany, for the repair of a 140 tonne EAF. When the gunning nozzle is driven into the requested working position, the furnace cover has to be turned away in order to create an entry point. Gunned zones are the slag line, the tapping spout and the door area (Fig.8). The robot is fed by three gunning machines, which can run three different material grades. The operator starts the gunning machine and controls the repair by means of joysticks using a radio remote control. Alternatively pre-set gunning programs can be run where the

Fig 5: Ladle gunning robot

operator pre-selects positions via a touch panel (Fig.9) and the robot automatically repairs the selected locations.

In Germany at BSW in Kehl, the melt shop layout was so tight that no place could be found to locate a gunning robot adjacent to the furnace. The plant operates two independent furnaces, each 100 tonnes, within a distance of only 50m. Here the task was to build a robot that could be used for both furnaces. The robot, known as PNEUTOP, is moved via overhead crane into the furnace and is parked in a support frame located between both furnaces. The robot is fed by a pressure vessel gunning machine (Fig.10) and both are controlled by one radio remote control.

The robot is well balanced; the gunning head is nearly as stable as the fixed arm design. When co-ordinated properly the crane movement of the robot does not influence the charging of the other furnace. BSW typically guns two to three tonnes of refractory per repair. Using a higher gunning rate of 125-150 kg/min, the downtime could be reduced compared to hand lancing (Fig. 11).

A stainless steel producer in Italy has two 110-tonne EAFs on the same meltshop

Fig. 6: Automatic ladle gunning

Fig. 7: HYTOP

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ELECTRIC STEELMAKING

Fig 8: Slag door gunning repair

Fig 9: Zone selection for automatic gunning

Fig 10: PNEUTOP and gunning machine

floor and requested a mobile gunning robot mounted on a self-driven carriage.

Velco decided to modify a commercial diesel-driven telescopic loader.

The MobiGUN parks on the meltshop deck and can access both furnaces. The gunning head is attached to the boom and is air-cooled by an onboard compressor.

For driving, the boom is retracted and the gunning head folded in. For gunning, the boom is expanded and the gunning head lowered from the top to the furnace.

All movements of the gunning lance, the water regulation and the start/stop of the gunning machine can be activated with a single radio remote control (Fig. 12).

The MobiGUN needs only two connections: one to the gunning material hose and a second to the works water line.

RH-degassers The high quality requirements of the automotive industry increase demand for vacuum degassed melts. Snorkel lifetime, therefore, is an important factor if the RH-degasser is to be used extensively. Due to the reaction with steel and slag the snorkel wears out internally and externally and the outside lining is often damaged Digital Edition - September 2015

electric steelmaking velcoReadMM.indd 3

by slag removal using scrapers or debricking machines. Keeping the system safe in order to avoid break-outs of hot metal is of primary importance. However, service time is limited as the steel plant’s sequences take priority. An unplanned exchange of snorkels should be avoided.

Outside gunning is commonplace, but the workplace is exposed to heat and

the operator likes to stay away from the snorkel, so gunning is not always well directed and has high rebound losses (Fig.13).

Some steel plants have a service car with an attached platform for hand gunning. Nevertheless, inside gunning is not possible because of the danger of hot steel or slag dripping from the RH-vessel.

Where outside repair is concerned, using a gunning robot is beneficial because the gunning is better directed and the physical stress on workers is reduced (Fig. 14). A robot is essential for the inside repair of the RH snorkel (Fig. 15). If gunning is performed well, the consumption is in the range of 0.5kg/tonne steel. Typically gunning takes place after six to eight treatments.

For inspection and documentation of the wear pattern it is possible to attach a camera to the robot (Fig.16). Instead of the gunning lance, a water-cooled camera is driven into the snorkel. A video can be made of the snorkel or the lower vessel area. Using the robot’s positioning encoders the area in the video can be exactly determined (Fig.17). The video can be stored and the wear can

Fig 11: Crane moved robot PNEUTOP

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ELECTRIC STEELMAKING

Fig 12: MobiGUN on meltshop deck

be documented to determine optimum lifetime. The inspected areas can be precisely repaired with the robot.

Typical robots have a lance for inside repair and a rotating base to reach the second snorkel. When inside and outside repair is requested, most robots have two

Fig 14: Outside gunning of RH snorkel

37

Fig 13: High material loss at manual gunning

gunning lances based on a frame that can rotate 180 degrees (Fig 18). One lance can repair the inside of snorkel A while the other is doing the outside repair of snorkel B. When finished, the main base rotates, so snorkel A is repaired on the outside and B on the inside.

Fig 15: Inside gunning of RH snorkel

If the snorkels are placed in the moving direction of the service car, it is possible to simplify the robot design by moving the service car to reach the other snorkel. This requires precise positioning of the service car – which is not always installed. t

Fig 16: Water cooled inspection camera

Fig 17 (left): Inside picture of RH-snorkel taken with inspection camera

Fig 18: Gunning robot with two lances for inside and outside repair

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DE-SULPHURISATION

How to improve hot metal de-sulphurisation performance The implementation of Multiple Linear Regression analysis to better determine the exact amount of de-sulphurising agent to add to blast furnace hot metal has resulted in an average saving of 5.3% of addition for CaD, with results dependent on the aim S-level. By Sunil Kumar* and Yakov Gordon*

THERE are several ways to improve the cost performance of hot metal desulphurisation (De-S). These include development of new De-S compounds, improvement of slag raking operation, lance design and so on. Another way to reduce cost is to improve the on-line model employed to estimate the amount of De-S compound to be added for a given operating condition. This study was undertaken with the main aim of reducing the consumption of De-S compounds on the basis of simple (yet, effective) statistical analysis of historical data, and well supported by the fundamentals of metallurgical process analysis. On this basis, an improved statistical regression model was developed and implemented on-line after successful performance in plant trials.

Process engineering A number of analytical techniques are Basic steps 1

employed for process engineering and development of on-line process models.

These include metallurgical and empirical formulations, simulation techniques, genetic programming, artificial neural networks and statistical regression analysis[5-9].

In this work, statistical regression analysis was adopted to develop quantitative variable relationships (linear and nonlinear) to build a model for the De-S process, to predict process parameters.

Statistical techniques are used to develop one or more equations relating one (or more) dependent variable(s) to one (or more) independent variable(s). This is commonly referred to as the Multiple Linear Regression (MLR) Technique.

Since this technique can handle more than one independent variable, it is extremely popular with process engineers looking for quick solutions for in-plant implementation.

The primary step in the MLR analysis is the determination of unknown parameters and in its simplest form, the MLR model can be described as: Y = b0+b1X1+b2X2 + ... + bnXn+ε

[1]

where, Y output (dependent) variable X1, X2, X3,…, Xn input (independent) variables b1, b2, b3, … bn etc: coefficients of the equation b0 constant in the equation Error term (difference between the actual and predicted value of Y).

ε

The co-efficients of the MLR model are determined through the least square method which basically minimises the sum of squares of residuals (difference between observed actual output value

Comments Objective definition

This is the identification phase of a dependent variable which is to be optimised.

The response of the dependent variable to variations in the independent variable is studied.

2

Measurement system analysis

This includes the study of sampling technique, measurement equipment and methods like GR & R (Gauge R&R) studies etc.

This may not be required, if level II Automation systems exist.

3

Data collection

This phase involves collection of data of both dependent and independent variables. Appropriate measures are necessary to ensure accuracy of data.

4

Scatter diagram

This is a visual representation (eg simple x-y graphs) of the relationship between 1-2 independent variables (generally on x-axis) and a dependent variable (generally on y-axis). The scatter diagram shows how a dependent variable responds to change in an independent variable.

5

Development of MLR model

by

The model is generally developed using a commercial software like SPSS, Statistica, Minitab, Systat or SAS etc. The equations generated are solved

by Differential Calculus/Matrix algebra. The linear equation is of the form as shown earlier in the paper.

Table 1: Basic steps adopted in MLR analysis

* The authors are with Hatch Ltd, 2800 Speakman Drive, Mississauga, ON, Canada L5K 2R7 e-mail skumar@hatch.ca; igordon@hatch.ca Digital Edition - September 2015

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DE-SULPHURISATION

AIM Sulphur %

%

% Heats with

% Heats with

Opportunity for

Opportunity for improving

of Heats

DS Out S

DS Out S

improving consumption

strike rate

within

of De-S compound

AIM + 0.003

AIM+/-0.003

0.005

17

82

82

Limited scope for optimisation

Improvement needed

0.010

5

96

65

Scope exists for optimisation

Strike rate is already high

0.015

35

100

21

Large scope for optimisation

Strike rate is already high

0.020

25

100

0

Large scope for optimisation

Strike rate is already high

Table 2: Summary of initial analysis of De-S process data No.

De-S Process variables

1

Input hot metal sulphur content (at the start of De-S Process)

2

Input hot metal temperature (at the start of De-S Process)

3

Weight of hot metal (in ladle for De-S)

4

Co-injection ratio = Weight of CaC2 injected/weight of Mg injected

5

Final hot metal sulphur content (after the De-S Process)

6

Aim hot metal sulphur (entered by operator in the system, depending on steel grade to be produced)

7

Carbide injection rate

8

Magnesium injection rate

9

Amount of calcium carbide injected

10

Amount of magnesium injected

11

Injection time

Table 3: Variables in De-S process considered in the development of the new MLR model

and corresponding predicted/fitted output value).

In the current work, the MLR technique was selected to develop a new or modified on-line model for the De-S process. The basic steps in MLR analysis are presented in Table 1.

For the MLR technique, the value of a statistical parameter, R2, indicates variability in data accounted for by the model. The higher the value of R2, the higher is the accuracy of prediction of the model. The regression model is applicable for the region for which the model is developed and it is not advisable to extrapolate. The model that is developed may not be valid in future, if there is a change in the process with respect to input variables and other operating strategy/ conditions. Thus, frequent, regular finetuning of model, based on recent (current) data, is necessary.

Existing on-line model In the existing on-line model, a single equation is employed to calculate the amount of de-sulphurisation additions of CAD and MAG for a given input and aim conditions, as follows: Sp MAG = [1 / (a*COINJ + a2)]* (FACTOR) [2] Factor = b1*ln(Si/Sa) – b2*((ln(Si*1000))2 – (ln (Sa*1000))2) + b3*(Si–Sa) + b4.

[3] COINJ = Sp. CAD / Sp. MAG [4] Sp. CAD = COINJ* Sp. MAG [5] Where: a1, a2: coefficients / constants b1, b2, b3, b4: coefficients / constants Sp MAG: specific consumption of MAG (in kg / tonne hot metal) Sp CAD: specific consumption of www.steeltimesint.com

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CAD (in kg / tonne hot metal) Si, S-initial: input hot metal sulphur level before De-S treatment (in %) Sf, S-achieved actual sulphur level achieved after De-S treatment (in %) Sa, S-aim: target sulphur level to be achieved after De-S treatment (in %) COINJ: co-injection ratio (= amount of CAD / amount of MAG) Although a single equation is used to calculate the amount of De-S compound to be added, the mathematical form of the equation is quite complex. For example, the term FACTOR is a logarithmic function of the ratio of S-initial and S-aim, logarithmic function of the square of S-initial and S-aim, and also, the difference between S-initial and S-aim. Thus, the impact of S-initial and S-aim is not very easy to assess.

Historical data was collected for one year during which De-S compound to be added for a given operating condition, was estimated based on the existing model.

The result of data analysis is presented in Table 2 which shows the performance of the existing model and the potential for improvement – reducing consumption of De-S compound and/or improving the strike rate (ie percentage of heats in which S-achieved is <= [S-aim + 0.003]).

It is evident that there is scope for optimisation of De-S consumption for ~60% of the heats (having S-aim >0.010%S) where De-S output sulphur level is significantly lower than S-aim.

It is noted in Table 2 that the strike rate in ~18% of heats (with S-aim of 0.005%) also needs improvement. It was concluded from the analysis of historical data that

39

application of a single equation in the existing on-line model, to cover the entire range of input and aim conditions, is not effective. Thus, there was a need to adopt a multi-equation approach using MLR. Scope and objectives The main focus of the current work was to improve the performance of the De-S process by overcoming the limitations of the existing on-line model.

The main objectives were: • Analyse operating data to understand the behaviour of the De-S process for different aim sulphur levels; • Optimise (minimise) De-S compound consumption.

The development of a new MLR model was based on analysis of historical operating data over the one-year period.

In this work, it was decided to adopt a co-injection factor range of 6.0-10.0. In addition, the impacts of factors such as blast furnace slag, efficiency of slag raking and so on were not considered due to non-availability of reliable data.

Methodology The following were the major steps adopted in the current work: • Collection of historical data for analysis; • Identification and assessment of pertinent factors influencing performance of De-S process; • MLR analysis to determine significance of each parameter (relative to each other) with respect to variability in performance of De-S process; • Development of statistical correlations between dependent and independent variables on the basis of heats exhibiting ‘good’ performance. (heats where S-achieved is <= [S-aim + 0.003%]); • Refine the model formulation further by testing the model using data from a new data set corresponding to a recent month (that is not included in the historical data collected); • Conduct plant trials with new model formulation and analyse its performance.

Development of new MLR models The key variables considered in the new MLR model are presented in Table 3.

Out of these parameters, only the following three were found to be Digital Edition - September 2015

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DE-SULPHURISATION

1.00

1.00 R2 = ~10%

0.75

Specific magnesium consumption, kg/thm

Specific magnesium consumption, kg/thm

R2 = ~65%

0.50

0.25

0.00 0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.75

0.50

0.25

0.00 0

HM initial sulphur (%)

Fig 1: Scatter diagram of specific magnesium (MAG) consumption versus S-initial

4

10 12 8 Co-injection ratio

6

14

16

18

20

Fig 2: Scatter diagram of specific magnesium (MAG) consumption versus co-injection ratio 0.60

1.00 R2 = ~5% 0.75

0.50

0.25

0.00 0.000

Old model

0.55 Specific MAG consumption, kg/thm

Specific magnesium consumption, kg/thm

2

0.005

0.010

0.015

0.020

New model

0.50 0.45 0.40 0.35 0.30 0.25

Co-injection ratio =7 S-aim=0.015%

0.20

0.025

0.040

0.050

HM sulphur level after desulphurisation (%)

Coefficient

Coefficient

Coefficient

Coefficient

R2 (in%)

content (%)

A

B

C

D

(in %)

0.003 - 0.006

4.298

-0.030

-17.731

0.449

74.000

0.007-0.010

4.251

-0.023

-11.817

0.396

67.000

>0.010

4.216

-0.019

-2.270

0.222

95.000

Table 3: Variables in De-S process considered in the development of the MLR model

Specific

MAG

consumption

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was

0.080

0.090

0.100

Fig 4:Specific magnesium (MAG) consumption for Old Model and New MLR Model for different S-initial

Aim sulphur

The MLR analysis revealed the following correlations between specific MAG consumption and the other parameters: - R2 of 60–70% between specific MAG and S-initial; - R2 of 8–10% between specific MAG and co-injection ratio; - R2 of 3–5% between specific MAG and S-aim; - Poor correlation was noted with hot metal temperature (operating range of 1250-1350°C) and also, the other parameters.

0.070 S-intial (%)

Fig 3: Scatter diagram of specific magnesium (MAG) consumption versus S-achieved after desulphurisation

statistically significant and considered for formulation of the new MLR model. In order of priority these were: • S-initial (input sulphur level before De-S treatment); • Co-injection ratio; • S-aim (target sulphur level).

0.060

considered as the output variable, Y. For model formulation, data for good heats (heats where final S-achieved was <= [S-aim + 0.003%]) was first filtered out. Next, statistical co-relations were developed linking consumption of De-S compound to significant operating parameters. The scatter diagrams presented in Figs 1 to 3, show correlations between the input variables and the output variable.

As shown in the scatter diagram in Fig 1, there is a high degree of positive correlation between specific MAG consumption and initial S level.

With respect to the other two scatter diagrams, there is only a moderate degree of negative correlation between specific MAG and co-injection ratio (Fig 2), and a very low degree of negative correlation between specific MAG and S-achieved level (Fig 3).

The new equation developed in this

work is of the following general form: Sp.MAG = [A * Si + B * COINJ + C * Sa + D] [6] Sp.CAD = Sp.MAG * COINJ [7] MAG = (HM Wt) * Sp.MAG [8] CAD = (HM Wt) * Sp.Carbide [9] where, A, B, C, D: coefficients / constants Sp.MAG: specific MAG (Magnesium) consumption (in kg/t hot metal); Sp.CAD: specific CAD (Carbide) consumption (in kg/t hot metal); MAG: MAG (Magnesium) consumption (in kg/heat); CAD: CAD (Carbide) consumption (in kg/heat); HM Wt: weight of hot metal in ladle (tonne hot metal/heat); Si, S-initial: input hot metal sulphur level before De-S treatment (in %); Sf, S-achieved: actual sulphur level achieved after De-S treatment (in %); Sa, S-aim: target sulphur level to be achieved after De-S treatment (in %); COINJ: co-injection ratio (= amount of CAD/amount of MAG).

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DE-SULPHURISATION

0.60

0.60 Old model New model

0.50 0.45 0.40 0.35 0.30 0.25

New model

0.50 0.45 0.40 0.35 0.30 0.25

S-initial = 0.070%

Co-injection ratio =7

0.20 0.002

0.004

0.006

0.008

0.010

0.012 0.014 S-aim (%)

0.016

0.018

S-aim = 0.015%

0.20

HM initial sulphur = 0.070%

0.020 0.022

5.5

0.60 New model

0.55 Specific carbide consumption, (kg/ton)

Old model New model – fitted line

3.8

Old model – fitted line

3.4 3.0 2.6 2.2 1.8 1.4 0.040

0.050

0.060

0.070

6.5

0.080

0.090

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8.0

8.5

9.0

9.5

10.0

10.5

0.100

0.50

Old model New model – fitted line Old model – fitted line

0.45 0.40 0.35 0.30 0.25 0.20 0.040

0.050

0.060

0.070

0.080

0.090

0.100

Hot metal initial sulphur (%)

Fig 7: Specific CAD consumption for old model and new MLR model for plant trials

Sensitivity analysis The specific magnesium (MAG) consumption estimated by the new model is presented in Fig 4.

It is evident from the figure that specific MAG consumption estimated by the new MLR model, is lower than that estimated by the existing (old) model, for the same co-injection ratio and S-aim level.

The divergence between the two model estimations increases with increase in S-initial level (slopes of the two lines are different). This difference has a direct bearing on reduction in De-S compound consumption, which is seen to increase with increases in S-initial level.

The specific MAG consumption estimated by the new MLR model (as a function of S-aim level), shows a different

7.5

New model

Hot metal initial sulphur (%)

values of coefficients A, B, C and constant D for the three ranges of aim sulphur level, are tabulated in Table 3.

This empirical formula is applicable for co-injection ratio in the range 6 to 10 and S-input (before De-S) in the range of 0.040% to 0.100%. These two conditions cover over 90% of the heats treated at the De-S unit in the melt shop.

7.0

Fig 6: Specific magnesium (MAG) consumption for old model and new MLR model for different co-injection ratios

4.6 4.2

6.0

Co-injection ratio

Fig 5: Specific magnesium (MAG) consumption for old model and new MLR model for different S-aim

Specific carbide consumption, (kg/ton)

Old model

0.55 Specific MAG consumption, kg/thm

Specific MAG consumption, kg/thm

0.55

Fig 8: Specific MAG consumption for old model and new MLR model for plant trials

pattern as compared to the same obtained from the existing (old) model (Fig 5).

While both models exhibit a reducing trend in specific MAG consumption with increasing S-aim, the new MLR model has a kink at S-aim of 0.007% and at 0.010% S. The reason for this trend is that the equations in the new MLR model are different for different bands of S-aim. This was derived on the basis of MLR modeling approach. The MLR model prediction is found to be slightly higher than that of the existing (older) model in the S-aim range 0.007 to 0.010% S. It should be mentioned that the number of data points in this band (S-aim 0.007-0.010% S) is limited (only ~5%). This is a limitation of the MLR approach since unusual behaviour of few data points can abnormally skew the model. This would not be a cause of concern here since the bulk of heats in the melt shop have essentially three S-aim levels (0.005%, 0.015% or 0.020%).

The MLR model provides, on an average basis, savings in specific MAG consumption of ~0.018kg/t of hot metal and savings in specific CAD consumption of ~0.126 kg/t of hot metal for various co-injection ratios.

Fig 6 suggests the possibility of operating in a particular band of coinjection ratio to optimise the cost of De-S compounds further.

Plant trials A trial was conducted to test the performance of the new MLR model with respect to optimising consumption of De-S compounds and reducing process variability. Since it was not possible to change the existing on-line equations (for calculating De-S compound to be added for various conditions) in the Level 1 system during the trial period, a lookup table was created for the operators, adopting the calculations of the new MLR model.

Plant trials were conducted for a period of two weeks and operators employed the new MLR model calculation in 60 heats.

The results presented in Table 4 revealed the following benefits: - Average CAD consumption was lower by ~0.20 kg/t; - Average MAG consumption was lower by ~0.03 kg/t.

The scatter diagrams in Figs 7 and 8 show the actual data points as well as trend lines Digital Edition - September 2015

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DE-SULPHURISATION

3.7

Carbide consumption, (kg/t)

0.080

Trend of carbide consumption (kg/tcs thru De-S) Trend of HM input sulphur (%)

0.075

3.5

0.070

3.3

0.065

3.1

0.060

2.9

0.055 Before project

HM initial sulphur (%)

3.9

Fig 9: Trend of CAD consumption and HM S-initial for De-S heats

References

After project 0.050

2.7 1

2

3

4

5

6

7

8

9

10

11

12

Months

MLR modelling approach to reduce De-S compound consumption in the melt shop.

On-line implementation of MLR On the basis of the encouraging results obtained during plant trials, the new MLR model was implemented on-line.

Changes were first made at Level–1 system, and regular use of the model started for estimating the addition of De-S compound. Average CAD consumption was ~3.35kg/t during the three months before the start of the project. After

S th pec en e g ial gi lo ise ne ba d er l s tag in te s g el an in , m d du e la st tal be ry s ls an f d or

for the new and existing models. The trend lines and data points of the old model lie above that of the new model, indicating a reduction in consumptions of MAG and CAD in the trial heats. Since estimation of the new MLR model was followed in some (but not all) heats during the trial period, the cost savings are only indicative and pertain to those where predictions of the new equations were followed by the De-S operators.

The trials’ results satisfactorily demonstrated the potential of the new

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project implementation, this decreased to ~3.17kg/t. It is interesting to note that the average S-initial (before De-S) was ~0.066% before project implementation, while it was at a higher level ~0.075% during the trial period. Even with the increase in blast furnace hot metal sulphur level, a decreasing trend was noted in De-S compound consumption (Fig 9).

1.

S M Mehra, Sunil Kumar and Ashok Kumar: Economics of Steelmaking with External De-sulphurisation – Experience of Tata Steel and Jamipol, Proceedings of Asia Steel International Conference, Jamshedpur, India, Indian Institute of Metals, 2003.

2.

M R Beauregard, R J Mikulak and B A Olson : ‘A Practical Guide to Statistical Quality Improvement – Opening up the Statistical Toolbox,’ New York, Van Nostrand Reinhold.

3.

S L Quinn and V Vaculik : Improving the De-sulfurisation Process using Adaptive Multivariate Statistical Modelling,’ Journal of AISE Steel Technology, October, 2002.

4.

F W Breyfogle III: Communication from Smarter Solutions Inc, Austin, TX. 5.

‘Implementing Six Sigma – Smarter Solutions using Statistical Methods,’ New York, John Wiley & Sons Inc.

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TESTING & ANALYSIS

43

High-speed archiving in hot strip mills Consumers of flat sheet steel demand the highest quality from their suppliers. If there are any questions regarding the final quality of the supplied product, modern data archiving allows producers to review recorded process parameters and trace any dimensional abnormalities upstream to the hot strip mill, which is one of the harshest environments for process instrumentation and sensors. However, as material speed and temperature increases, so does the importance of the measurement values.

By C Burnett*, J Davey** and D Berg*** THE versatility and strength of steel has resulted in its use in a wide variety of applications throughout the manufacturing world. In 2014, over 1.6 billion tons of crude steel were produced1 and steel producers were challenged to differentiate their products in a market where conditions are less than ideal.

World-class companies rely on consistent mill processes to efficiently produce the highest quality steel. Optimising mill operations requires analysing volumes of data from a number of process variables.

Process variables in the hot strip mill There are many derivatives of the modern hot strip mill2, from multi-stand to reversing Steckel mills to direct casting, but the end goal is to produce a coil with uniform mechanical and dimensional properties from head-to-tail and edgeto-edge. Advanced process control algorithms use hundreds of variables, from various sensors and drives, to maximise the prime quality yield from each ton of steel rolled. Starting with the mechanical properties of the steel grade, strip tensions and temperatures are measured between every stand, pressure transducers measure reduction force and laser-based velocimeters provide line speeds that monitor mass flow for use in feed-back and feed-forward control loops. At the end of the mill, prior to the strip coiler, a state-of-the-art, simultaneous profile gauge is used to validate that the strip produced meets the tight dimensional tolerances demanded in the market place.

While each sensor contributes to the overall strip quality, the operator and mill computer are responsible for digesting those inputs and producing the desired product. The profile gauge has the ultimate responsibility for validating, and therefore ensuring, that the specifications

are achieved. In the past, if coil quality was questioned, the chart recording of the gauge output might be the only archived data to review. However, today, with high speed data archiving, all of the previously Simultaneous Profile

Profile Pair

Fig 1: Measurement data from two single-point style x-ray thickness gauges arranged in a Profile Pair compared to Thermo Scientific SIPRO

mentioned variables and measurements can be recorded and reviewed by quality assurance, process engineers and plant management. Each discipline is able to mine the data for information critical to their areas of responsibility.

Simultaneous Profile Gauge (SIPRO) In the last two decades, the evolution and miniaturisation of the integrated circuit has made high-speed radiation sensor arrays compact enough to fit into a robust frame for use in a hot strip mill. In the past larger ion chamber or scintillator/Photomultiplier-based detectors only provided a single measurement point averaged over several hundred square millimetres. The modern detector arrays can provide over 500 independent measurements providing a quantum leap in the percentage of strip area measured.

When these detectors are positioned below two x-ray sources arranged in such X-Ray source 1

TEMPERATURE PROFILE

X-Ray source 2

Fig 2: Dimensional measurements available from the stereoscopic SIPRO gauge

STRIP POSITION

Hot strip movement

Detector array WIDTH CONTOUR FLATNESS

THICKNESS PROFILE

CROWN & WEDGE

EDGE DROP

RIDGES & GROOVES

CENTERLINE THICKNESS

*C.Burnett , Thermo Fisher Scientific, 200 Research Drive, Wilmington, MA 01887 USA; **J. Davey, Thermo Fisher Scientific, Highnam Business Centre, Highnam, Gloucester,GL2 8DN UK; ***D. Berg, G. Schoeppner Thermo Fisher Scientific, Frauenauracher Str 96, Erlangen, Germany, D-91056 www.steeltimesint.com

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TESTING & ANALYSIS

– accurate horizontal and vertical positions are known (see Fig. 3) At this stage, because of the assumption that the strip is not perfectly flat, the vertical positions of points on the strip between the edges are not known. Initially however, the vertical position of each point can be estimated from the “trendline” – an imaginary line between the edges of the strip.

It is possible to make a calculation of the contour using these points. If the thickness of a point on the strip is measured from two directions, there will be a difference in measured thickness which is dependent upon the gradient of the strip. The gradient can be calculated from the two thickness values as shown in the vector diagram (Fig.4). R1 is the results from the vectors t1 and t2 and its direction is the gradient of the strip. The directions of t1 and t2 are calculated from the positions of the detectors where they are measured relative to the sources. These directions are fixed from the outset, since there is no movement of either source or detectors.

This method of measurement assumes that both strip surfaces are parallel – i.e. the thickness does not change. Additionally it assumes that the gradient of the strip is not changing. In both cases the distance between the detector elements is very important. When detector elements are 25mm or further apart, there will be an error in the gradient; and it is, therefore, essential that the transverse measurement resolution is as small as possible so that the effects of changes – in thickness or gradient – are minimised.

Detector elements, therefore, with a high cross-strip resolution ensure that the effects of changing thickness and gradient are insignificant, and allow the strip to be located very precisely in space. It is, therefore, possible to evaluate the height (and hence flatness) at any point across the strip. The true strip end-points are calculated from the stereoscopic views, and the contour is calculated from one end of the strip to the other. This allows

590 580 570

ne ndli

560

Tre

)

uess

ial g

(init

550 540 530 520

Actual contour

510 500 -800

-600

-400

490

-200

0

200

400

600

800

Fig 3: Contour measurement with trendline overlaid

a way as to provide a stereoscopic view of the full strip width, the Thermo Scientific SIPRO gauge is capable of providing not just a high-resolution thickness profile, but a flatness value as well.3 The individual detector pixels are positioned every 6mm across the lower arm of the stainless steel C-frame. When translated up to the level of the roller table, the resulting measurements are provided at a resolution of 5mm of strip width. This high resolution provides mill operators information on ridges and grooves that are missed with lower resolution sensors.

The two x-ray sources of the SIPRO are positioned above the strip and arranged to view it from different angles. A unique rotating shutter design exposes the hot strip to one source at a time. Data from the detector array is collected every five milliseconds and is synchronised with the rotation of the shutter. At a strip speed of 15 m/s, this five-millisecond update equates to a measurement value every 75mm of strip length. Profile systems based on scanning or oscillating sensors require much more time and are 200 to 2000 times slower.

The positioning and synchronised data collection from the different sources also provide information on the physical position of the strip in space. If the strip

bounces above the roll table surface, the profile thickness, width and all other measurements are not degraded.

Flatness measurement The measurement of flatness is essentially a two-stage process. First the contour is measured and then a history of the contour in the process direction is built up and the flatness calculated.

The contour calculation itself follows a number of stages: 1. Select a series of points across the strip – for which it is necessary to “locate” the strip.

2. Calculate the transverse gradient at these points.

3. Integrate the gradient to give a relative height profile (contour).

4. If necessary carry out further iterations The flatness calculation stages include: 1. Collecting height data along a set of “threads”.

2. For each thread, calculate the length of the thread and the horizontal distance between ends.

3. Calculate the flatness.

Locating the strip The locations of the edges of the strip are calculated from the stereo thickness view

Beam from source 2

Beams from source 2

R1

Beams from source 1

R2

Beam from source 1 t4

t1 R1

Strip t2

t1

t2

t3

t4

Detectors Detectors

Fig 4: Calculating the gradient from a stereo thickness view of the strip. The view is along the process direction

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Fig 5: Potential errors when calculating gradient from stereo thickness measurements. R1 is in error because the thickness is changing. R2 is in error because the two views do not intersect at the strip

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TESTING & ANALYSIS

45

X-Ray source X-Ray source Hot strip

X-Ray source

Hot strip

Hot strip

GAUGE COMPUTER

GAUGE COMPUTER

Detector area

Detector area

GAUGE COMPUTER

Supervisor PC

Supervisor PC

Supervisor PC

ibaRackline + ibaPDA-V6-Unlimited

ibaRackline + ibaPDA-V6-2048

XMDarchive

iba-files

PDA Fiber-Optic hub

Fig 6: Data archiving using gauge computer

Fig 7: Data archiving using Ethernet link to ibaPDA Archiving computer

us to relate the data to any point on the strip (for example, the centre). Although the contour data is primarily a step in the flatness calculation, it can potentially be used to detect non-flatness features, such as tunnelling.

The operator will want to examine the flatness at a number of pre-determined points across the strip. These points extend in the process direction along ribbons or threads and can be configurable.

Each time the contour is evaluated the heights are calculated for each of them.

For each thread, the height data is built up over time and can be related to the longitudinal position on the strip. The latter is calculated from the velocity of the strip and the time since the head of the strip was detected.

The flatness along each thread can be calculated in two ways:

Fourier transform has drawbacks. It can only detect discrete wavelengths, leading to resolution problems. If there is more than one component in the wave, the analysis can be difficult. There is an upper limit to the wavelengths that can be detected, dependent upon the number of measurements that are taken (and hence the time spent taking them). Finally, a relatively large number of points are required for an effective analysis, leading to a long delay before results are given.

The first method involves calculating length differential directly. This avoids many of the problems associated with the Fourier method. However, there are still challenges. There is the possibility of noise in the height measurement, partly due to thickness noise and partly due to height variation related to the steel not being perfectly flat. Appropriate smoothing is required to avoid any erroneous ‘out-offlatness’ (noise in the height data would always involve an increase in the flatness measurement). There are a number of methods which may be suitable for this kind of smoothing, and these are under investigation.

1) Calculate the actual longitudinal length of the strip along the thread. This is the length of the thread if it was cut out along the length of the strip and allowed to lay flat S I = ∆L x105 = -1 x105 Equation 1 L L

( )

(

)

2) Calculate the amplitude and wavelength of a “wave” in the strip.

(πλa)

I=

.

2

x105

Equation 2

In the second method, the amplitude and wavelength can be calculated using Fourier analysis. Fourier transforms are good at filtering out unwanted noise and non-cyclic changes. The discrete www.steeltimesint.com

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Data archiving architecture The SIPRO system collects and calculates hundreds of measurement values every five milliseconds. Over the short 45- to 90-second time frame required to roll a single hot strip, over one million analog data points can be collected including: • Thickness measured from source A • Thickness measured from source B • Temperature measured from scanning pyrometer • Width

PDA Fiber-Optic hub

Fig 8: Data archiving using Fiber-optic link to ibaPDA Archiving computer

• Crown and wedge • Flatness • Location of any grooves or ridges The system’s diagnostics monitor dozens of internal analog and digital sensors related to gauge operation, interface commands and overall health.

This volume of data creates storage challenges for over 25MB of disk space required per coil. The first and easiest approach is to select key parameters to record and set the system to record a filtered signal that averages over a longer time frame. However, when smaller defects occur at high speed, high-resolution data storage is needed to analyse the abnormalities.

There are three common hardware arrangements to consider for data storage on the SIPRO system.

1) The first is to store the data files directly on the gauge computer.

This arrangement is compact, but limits access and review of data unless it is transferred on a regular basis to a server or another storage location. The gauge computer converts the data collected directly to an iba .dat file for easy display through iba PDA software. In order to have manageable file sizes, the profile data is archived every 200 milliseconds (ms).

2) The second method of data archiving transfers the data from the SupervisorPC to a dedicated ibaRackline Archiving PC with ibaPDA V6-2048 module. Data transfer is handled via traditional TCP/IP which has the benefit of widespread use in other applications, and off-the-shelf hardware availability.

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TESTING & ANALYSIS

Fig 9: iba Analyzer software display of 3-D profile data from SIPRO

Fig 10: photo of 40mm void detected by SIPRO in hot strip mill running at 10 m/s

Additionally, the archiving PC can be physically located farther away from the harsh mill environment and connected to a mill-wide server for regular backup and storage. Profile data along with temperature and shape information can be stored at intervals of 200ms, with 10ms rates for key parameters such as centre line thickness. The one limitation is that only 4096 bytes are allowed per interface.

3) The third arrangement for data storage uses reflective memory (RFM) between the Supervisor PC and Archiving PC. This configuration requires the use of a fibre-optic connection in place of the Ethernet link.

The RFM arrangement allows for highspeed data storage. Specialised hardware components are required for this architecture. The GE PCIE-556RC provides the reflective memory interface between the gauge and storage computer. An iba storage computer needs to be licensed for an unlimited number of variables. All Digital Edition - September 2015

measurement analysis thermoReadMM.indd 4

profile data and key parameters can be sent at a rate of 40ms and the flatness and diagnostic data can be recorded every 100 ms. The diagnostic data allows process engineers to view individual source views to verify the location of any defects in space.

Regardless of the data archiving arrangement, profile data can be stored on a coil-by-coil, shift-by-shift, or daily basis.

The reflective memory arrangement can also be used to integrate the gauge data into the mill’s own process control archiving. This allows gauge parameters to be charted alongside mill control parameters Coil reports and analysis of archived data Using the flexible tools of the iba Analyzer software, process and quality engineers can create PDO templates and import data from any stored file. Data files can be converted to coil reports with statistical data and quality information.

Two and three dimensional profiles can be viewed and analysed for variations and dimensions that are out of specification.

The zoom feature can help determine exact defect locations in the strip and the ability to compare multiple coils can reveal system-wide maintenance needs.

The future development of high-speed analysis of individual source views – at a rate of 5ms for a full profile – has proven extremely promising in terms of identifying small defects in the hot mill that can result in major quality concerns downstream.

Currently, high volume storage of data at the 5ms rate is only possible with internal storage of .dat files that can be evaluated post-production. In Fig. 10, a void in the steel of approximately 40mm in diameter was captured in the profile data. The strip speed was approximately 10m/s so the defect was only measured by the gauge for 15ms. The void resulted in an increase in the x-ray signal and thanks to the stereoscopic view of the SIPRO, its position within the strip was identified. The defect was addressed before the coil was further processed and this saved the producer’s reputation as well as lost production time in the cold mill.

Conclusion The quality of the steel produced in a modern hot strip mill has a direct impact on the success of a steel producer’s business.

A high speed simultaneous profile gauge is an essential component of the mill as it provides not only critical dimensional information in real time for profile and shape control, but also the ability to identify defects before they impact upon downstream processes. The archiving of millions of process data points from the profile gauge requires the alignment of data handling hardware with the needs and expectations of process and quality engineers. When properly configured, the profile archiving system becomes an invaluable tool to maintaining dimensional quality in the hot strip mill.

Further information, http://www.thermoscientific.com t Acknowledgments Thanks to iba-AG in Fürth, Germany.

References [1] www.WorldSteel.org/statistics 2014 Crude Steel Production data by country, Feb 2015.

[2] Conventional Hot Mill Applications, W. Filipczyk, TMEIC Corporation, AIST Process Systems Training Conference, Mobile Alabama 2015.

[3] Hot Strip Steel Flatness Measurement using Simultaneous Thickness Profiles, C. Burnett, P. Kelly, Thermo Fisher Scientific, CONAC 2014. www.steeltimesint.com

9/29/15 9:31 AM

47

VACUUM DEGASSING

Pressure control during degassing During degassing, it is necessary to be able to rapidly slow the pump-down speed as reactions commence to avoid over-flow of the vessel. This paper reviews the methods appropriate for various degassing and oxygen lance decarburisation systems and concludes that multiple small mechanical pumps provide the greatest control, and that systems are often over-specified regarding capacity.

By Wilhelm Burgmann* STEELMAKERS who wish to improve quality by vacuum treatment during secondary metallurgy often have only a rough idea regarding the kind of vacuum pump to be selected, the required suction capacity, the pump down time and the essential selection criteria.

For all kinds of vacuum pumps – Steam Ejector Vacuum Pumps (SVP) or dry operating Mechanical Vacuum Pumps (MVP) – much information has been presented in recent literature[1-5] such that the choice of suction capacity can be made according to the kind of vacuum process used and the metallurgical possibilities of the RH- or VD-process.

There is a general tendency to over-size suction capacity based on the argument that the cost of a steam ejector is roughly the same for medium and high suction capacities and also that steam to supply the energy of a SVP is nearly no cost, and that a reserve in capacity has to be made. Such a reserve should be made to safeguard against any reduction in pump performance by: • ejector clogging by dust, • erosion by water droplets contained in unsaturated steam, • seasonal climatic changes • unknown pressure drops between pump and reaction vessel.

In contrast, MVP- systems do not need oversizing resulting from decreasing pump Make

Type

Typical motor

performance. They are built-up in modules and offer both redundancy and expansion possibilities, while capacity losses by gas coolers, cyclone, filter, suction pipe and valves have been investigated and measured[6].

Sense and nonsense With the beginning of vacuum technology for steel degassing in the 1950s, MVPs were rather small and had low suction capacity. The criterion for rapid pump down had been established as relevant to pump performance. But in this respect it is necessary to distinguish between two different vacuum degassing processes, the RH- and the VD-processes.

RH-plants have rather small volumes, operate without any active slag and have a very large vessel freeboard so they are able to cope with vigorous degassing reactions. It has been reported that rapid pump-down to a low pressure of 1hPa in RH-plants is beneficial for obtaining low carbon contents[7].The limits of such a procedure are metal splashing, but the RH-process offers an elegant way of mastering the intensity of reactions by modulating the melt circulation rate by adjusting the argon flow rate.

VD-plants, whether treatment is in a ladle, converter or tank, operate under the constraint of restricted freeboard and have to consider an active slag. Therefore rapid pump-down to low pressures cannot

be achieved without risk. VD tanks have rather large volumes and require quick removal of plant air.

To understand the need for quick pump-down the different steps of the degassing processes to which the pump performances have to be adapted need to be considered: • Typically, a vacuum treatment cycle starts with the pressure achieving equilibrium between a section of plant already evacuated, such as a cyclone, cooler, filter and the pumps themselves, and the section of plant that is at atmospheric pressure – the vessel and part of the suction duct. On connecting these two sections the total plant pressure drops to 500-700hPa within a few seconds.

• The first duty of any pump system is then to lower the pressure as quickly as possible until a value where vigorous reactions start, ie ~300hPa for unkilled melts or 100hPa for fully killed melts covered by an active slag.

• In the next step the pump-down rate ∆p/δt must be greatly reduced in order to permit the slag to degas and the melt to be liberated from excessive amounts of H, N and volatile metallic elements such as Zn and to boil off using the dissolved oxygen or to react with lance-injected oxygen as in the VD-OB, VOD or RHO-processes.

At a constant pumping rate the pressure decreases continuously in parallel to the decreasing gas load.

Number of high

Installed power

Installed power

Total moment of inertia

volume pumps

of complete pump set

for high volume stages

for all high volume pumps and comparison with lowest (%)

OLV

WH7000

18.5kW 2pB5

72

2200kW

1332kW

70kgm²

100%

AERZEN

17.15.HV

30kW 4pB5

30

2400kW

900kW

360kgm²

520%

AERZEN

18.17 HV

37.5kW 4pB3

18

2175kW

675kW

590kgm²

840%

EDWARDS

HV 40 K

30kW 4pB5

20

1450kW

600kW

660kgm²

940%

AERZEN

19.19 HV

55kW 4pB3

12

2160kW

660kW

980kgm²

1400%

AERZEN

20.21 HV

75kW 6pB3

6

1950kW

450kW

1340kgm²

1900%

Table 1 Moment of inertia of various high volume stage vacuum pumps installed for a capacity of about 500,000m³/h at 2 to 0.67hPa

*Consultant in vacuum metallurgy, Strasbourg, France Dr.Ing.Wilhelm Burgmann, 34 rue de Chambord, F -67000 Strasbourg Tel 0033 388 311 409 Mobile: 0033 680 58 27 27 – e-mail: wburgmann@burgmann-net.de www.steeltimesint.com

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VACUUM DEGASSING

Mode 1 Reducing the rotational speed of MVP or steam flow of SVP, delayed engagement of pump stages or delayed acceleration of low pressure pump stages.

Variable speed drives as hydraulic couplings or frequency converters are in use.

These means have a limited effect unless used in combination with other modes.

Mode 2 Shut-off of some pumps that operate in parallel in the low pressure stage.

Needs isolation valves for all considered pumps. Does not deliver a “smooth” regulation.

Mode 3 Shut-off of complete modules or independent lines.

In case several independent units are installed in parallel. Does not deliver a “smooth” regulation.

Mode 4 Throttling the gas flow via the main valve or its by-pass valve Requires expensive valve positioner or several parallel valves to cover a wide flow range.

High noise level. Increased wear of valve sealing.

Smooth re-opening required.

Mode 5 Injection of inert gas at the reaction vessel.

Energy and inert gas consuming.

Frequently done with permanent melt surface observation, but lacking precision of control.

Mode 6 Adjusting the argon flow rate for stirring or circulation.

Only effective for RH-circulation plants, but insufficient and dangerous for VD-plants for which Argon stirring is important in order to avoid over-saturation of any element at the bath surface.

Mode 7 Recycling off-gas by injecting part of it at the low pressure suction side of the pump system.

Frequently used in SVP and easily installed in MVP. Slightly energy consuming as all ballasting modes.

Picture courtesy of Oerlikon-Leybold-Vacuum, Cologne, Germany

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• At the end of oxygen blowing or after 3-5 minutes of boiling off, pumpdown should continue again to about 5hPa using the pump capacity to its full extent.

• At that pressure, all degassing reactions become very intensive and all pump sets that are oversized with respect to the vessel or ladle freeboard and the ladle covering system must be reduced again to avoid over spilling.

• Only at about 1 to 2hPa, depending on the pump size, the argon flow rate and the method by which the argon is injected, can the full capacity of the pump be used.

Frequently, a rapid pump-down to 1hPa or less is requested by the customer and agreed by the pump supplier in a blank test without the effect of the melt being considered. This is meaningless for the evaluation of pump performance, as a fast pump-down cannot be realised in practise in a loaded degasser. Once charged with a heat, a pump set offering rapid pumpdown is not necessarily powerful enough at low pressures.

According to the above process analysis, in no case can rapid pump-down features shown in an empty vessel be used to indicate operational practice. This includes argon-stirred melts: • in any concentration of dissolved gases (H, N) and volatile metals (Zn, Cd, Mg), • whether unkilled or fully Al-killed, or • whether covered with slag or not.

Steelmakers have an interest in overcoming any idle time during pumpdown as the melt is cooling, particularly if the melt size is small. But it is as inappropriate to extrapolate the blank test results to operational practice as it is for a pump supplier to guarantee rapid pumpdown under operational conditions.

In both SVP or MVP systems, the pumpdown speed is mainly determined by the high pressure pump stages, ie water ring pumps (WRP) and boosting ejectors for SVP or WRPs, endless screws and direct exhausting Roots pumps for MVP systems.

The suction capacity of the low-pressure high-volume pump stages has only a minor effect on the blank test pumpdown time.

Need for pressure control The target to remove dissolved gases from a melt quickly and completely leads to the collateral problem of keeping the melt inside the reaction vessel.

Degassing reactions occur suddenly resulting in much splashing and, in the presence of an active slag, also in slag Table 2: Possibilities of pressure control during vacuum degassing

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VACUUM DEGASSING

Process Deoxidation Metallurgical gas load

VD

Tank degassing

Al killed

at start

0.18 Sm³/t

120 ppm ∆ (H+N+O+C)

Argon flow rate (5 litres/min/t)

66 Sm³/h

( 80 kg/h DAE20)

Nitrogen flow rate

10 Sm³/h

( 12 kg/h DAE20)

Air leak rate

21 Sm³/h

( 25 kg/h DAE20)

Peak flow of metallurgical gases

36 Sm³/h

( 43 kg/h DAE20)

Peak gas load at 100 hPa

4650 m³/h

(550 kg/h DAE20)

Gas load at end pressure

105 Sm³/h

(125 kg/h DAE20)

Pump set configuration

4 x (8-2-3)

Oerlikon-Leybold-Vacuum

Pump capacity at 0.67hPa

233’000 m³/h

( 186 kg/h DAE20)

Pump capacity at 100hPa

32’600 m³/h

( 3880 kg/h DAE20)

Primary pump capacity

13’800 m³/h

(16600 kg/h DAE20)

575 m³

Pre-evacuated: 245m³

Plant volume Suction duct diameter

1.6 m

Length incl. bows: 50m

Filter surface

800 m²

Filter volume: 2 x 45m³

Total pressure loss at 0.67hPa

0.11 hPa

(16 % of 0.67hPa)

Effective pump capacity at vessel

200’000 m³/h

Installed motor power

1100 kW

Peak power absorption

720 kW

Time to reach 550hPa

8 sec

Time to reach 100hPa

173 sec

Time to reach 0.67hPa

300 sec

At end pressure: 400kW

in blind test

Table 3: Characteristic data of a 220t VD - plant with MVP

foaming and over-spill.

In RH-plants the gas load can be moderated by reducing the argon flow and thus the circulation rate. In VD-plants the sudden appearance of degassing reactions at the bath surface can be moderated by intensive stirring during pump-down but a very short response time is required to moderate the reactions by the resulting increase in pressure.

One way out of this dilemma is to adapt the pump-down curves to the pump capacity and to the gas load resulting from the plant volume, leaks, argon, metallurgical gases and vapours.

The pressure drop rate ∆p/δt is reduced in the medium and sometimes also in the low pressure range.

It is not necessary, and because of the sudden start of degassing reactions, also very difficult, to hold the pressure constant or to hold the pumping speed constant via a control loop.

Even at a constant pumping speed, the gas mass load decreases continuously owing to the decreasing gas content or to the decreasing oxygen yield to CO in oxygen blowing processes.

However, the rate of pressure drop should be reduced significantly and without delay, before full suction capacity is engaged again and reached quickly. The response time of the pumps is, therefore, an essential criterion.

Mechanical pumps with the lowest moment of inertia and the highest ratio of motor power to inertia are the best for rapid reduction of pressure and acceleration of rotational speed for restart of the pumps. These critical features are compared in Table 1 for a volume flow of 500,000m³/h at 0.67hPa, common for all pump type arrangements. The comparison is made for the pumps engaged in the www.steeltimesint.com

OerlikonReadMM.indd 3

high volume flow stage at <30hPa. Table 1 demonstrates the advantage of a high number of small pumps and the handicap of large pumps when a frequency modulation of pumping speed is required as is the case for all vacuum degassing and decarburising processes. The smaller pumps do not need any ‘brake’ resistance in the frequency converter.

The larger pumps need higher motor power to cope with the moment of inertia of the pumps. However this will increase the total inertia of pump plus motor.

Because of this handicap in motor sizing, the larger pumps cannot reach a pressure of 1hPa quickly when engaged at 30hPa. There are different means to reduce the pressure drop rate ∆p/δt as listed in Table 2.

Large VD-melts As a case study, the various pressure control modes are investigated for a large vacuum degassing plant with the characteristic data shown in Table 3.

Pump-down in a blind test with plant air and any air leaks as the only gas ballast reached 0.67hPa within 4.5 minutes, but this pressure could only be reached during an uncontrolled and unhindered pumpdown with the melt, its slag, and argon and nitrogen flow in place within 12.5 minutes. During such an uncontrolled operation, the melt could not be contained in the ladle without heavy over-spilling.

This is demonstrated in Fig 1. At 100hPa when the first heavy degassing reactions are expected to occur; the total gas load is 4700m³/h while the pump capacity is 33,000m³/h. As a consequence of this difference the continuing evacuation of air from the plant leads to falling pressure and even more violent degassing reactions.

In an attempt to master the vigorous

49

degassing reactions the pumping speed was reduced by 50% in the critical pressure range. Fig 2 shows that the time to reach 0.67hPa has increased slightly, but that this reduced pumping speed is insufficient to reach the level of gas load at 100hPa. Already the primary pumps alone have a higher capacity than would be needed for the gas load.

One is, therefore, tempted to block a complete module for some minutes (Mode 3 in Table 1). However, this would only be possible if several modules or independent lines operate in parallel.

Ballasting by recycling of off-gas (Mode 7 in Table 2) as shown in Fig 3 is preferable.

Such ballasting by recycling of off-gas requires a valve and a by-pass pipe and increases energy consumption marginally.

A simple shut-off valve could be used if this pressure control is combined with frequency modulation of the pump motor.

A simple and cheap way has been successfully tried by throttling the gas flow via a valve (Modes 4 or 5 in Table 2 ).This requires smooth valve positioning.

Fig 3 does not show clearly the pumpdown delay. Therefore, in Fig 4 the same volume flow is plotted over the treatment time. In this case the pumps are ballasted with recycled off-gas during a period of 2.5 minutes at 100hPa. Below 5hPa the pump capacity is reduced slightly by lowering the motor frequency by 13% for about a further eight minutes.

Flow control at low pressure depends upon the overcapacity of the pump with respect to the gas load, the argon flow rate, the vessel freeboard and gas constraint by a lid or heat shield on the ladle. In other words, a plant with no overcapacity, a large freeboard and an argon flow adapted to the ladle lid does not need flow control at low pressure.

In the oxygen blowing processes (VOD, VD-OB, RHO) pressure control is very simple since the pumping speed automatically adapts to the gas load generated by decarburisation. Only in the case where the suction capacity is too high and consequently the vacuum pressure would drop too much, a slight flow reduction by frequency control should be made. See Fig 5.

Conclusions The various tasks of a vacuum pump set which include rapid pump-down, controlled pump-down, short response time while modulating the pumping speed and a low end pressure, often lead to over-sizing of the suction capacity in certain pressure ranges.

The requirement of a short pump-down time to the lowest pressure is neither justified nor useful for the evaluation of the pump set. For tank or ladle degasser Digital Edition - September 2015

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systems a short pump-down time cannot be realised operationally as this would cause over-spilling of the ladle.

The aim to reach the shortest pumpdown time realised for empty systems only increases investment costs to more or bigger pumps.

Establishing a constant pressure via a control loop is not easy since the response time must be extremely short as degassing reactions start suddenly and are intensive.

However, at a given pumping speed and argon flow rate the gas load is lowered continuously due to the decreasing content of dissolved gases thus making any pressure control loop unnecessary.

In processes using oxygen injection the pumping speed is automatically adapted to the gas load. Gas load is lowered continuously due to decreasing oxygen Digital Edition - September 2015

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Fig 4: Variation of volume flow with treatment time showing the cumulated gas loads with a ballast control at 100hPa and with a frequency control at < 5hPa Fig 5: Variation of volume flow with treatment time at the vacuum pump and at the reaction vessel and the cumulated gas loads during the VOD-process

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0,1

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yield.

To master the metallurgical reactions there are several possibilities for temporary reduction of the pressure fall rate.

Generally, off-gas recycling to the suction side of the high volume pump stage can be applied to all systems and processes. This permits a marked and rapid temporary reduction of pump-down speed as well as a rapid return to full suction capacity afterwards.

Beside the systematic reduction of the drop in pressure in VD plants beginning at a pressure that ranges from 350hPA to 70hPa, depending upon the degree of deoxidation, a frequency-controlled reduction of suction capacity at pressures as low as 5 to 2hPa is recommended depending upon the degree of oversizing of the suction capacity. This control

mode is increasingly efficient with smaller pumps as these have a lower moment of inertia. t References

[1] Bruce S, V.Cheetham, Recent Developments and Experiences in Modern Dry Mechanical Vacuum Pump Systems for Secondary Steel Processing: 9th EAF conf Krakow / Poland,19./21.5. (2008) [2] Zöllig U, T.Dreifert, Latest generation mechanical vacuum technology for secondary metallurgy: MPT International 3 (2011) pp.98103 [3] Dorstewitz F, D.Tembergen, Kriterien zur Auswahl des Vakuumpumpsystems für pfannenmetallurgische: Anlagen Stahl und Eisen 133 (2013), No 5, pp 33-44 [4] Burgmann, W Latest development in mechanical vacuum pumps for steel degassing, Steel Times International 7/8 (2013) pp.24-30, & La Metallurgia Italiana 5 (2013) pp.60-64, & JISRI vol25, No 5, (2013) pp.1-7 [5] Burgmann, W, T.Gustafson, J.Davené, Selection of vacuum pump systems for steel degassing: Metall ResTechnology 111 (2014) pp.119-128 [6] Burgmann, W, J Davené, J Laffitte, Off-gas preparation for vacuum pumps: La Metallurgia Italiana 11/12 (2013) pp.11-19 [7] Pluschkell W, Metallurgische Reaktionskinetik zur Einstellung niedrigster Gehalte an C,P,S und N im Stahl Stahl und Eisen 110 (1990) No 5, pp 61-70 www.steeltimesint.com

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PERSPECTIVES: LANZATECH

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Making the world safer and cleaner Lanzatech’s Jennifer Holmgren* believes that maintaining the status quo and not doing anything to challenge the current global climate and energy trajectory is concerning. He says we have an opportunity today to make a difference and while it may take time and perseverance we must pull out all the stops to make the world a safer and cleaner place for future generations

1. How are things going at Lanzatech? Is the steel industry keeping you busy?

Things are going well at LT. We have just announced financial approval from the board of one of our partners, China Steel, in Taiwan to build the first commercial unit that will capture steel mill off-gases from the flue stacks and convert it to fuels and chemicals. Our biological carbon capture platform has gained a lot of interest over recent years.

The steel industry has been a great partner for LT and has helped us articulate the potential that the technology can have on their operations today and in the future. It is a testament to these forward thinking players that we find ourselves so busy today.

2. In which sector of the steel industry does Lanzatech mostly conduct its business?

LanzaTech deals with that section of steel making wherein iron ore is reduced to crude steel 3. Where in the world are you busiest at present?

We are very much a global company and as we scale up our process using industrial waste gases, we find that there is significant interest across Asia for our carbon recycling platform. There is a lot of steel in China and they are acutely aware of the need to find ways to reduce their carbon footprint and source alternative clean energy and so we do a significant amount of work there.

4. Can you discuss any major steel contracts you are currently working on?

Unfortunately we cannot go into details, but we are partnered with multiple steel producers globally and the next 18-24 months will be significant as we begin to scale our technology commercially.

5. “Aluminium will always outperform steel on a weight basis; and on the stiffness issue alone it will carry the day,” said Alcoa’s chief technology officer Ray Kilmer speaking about aluminium usage within the global automotive industry. Where do you stand on the aluminium versus steel argument?

We cannot comment on the specific merits of one metal over the other. Both play a significant role in the global economy.

6. It is always claimed that aluminium is the ‘greener’ metal when compared to steel. What’s your view?

Our view is that any industry can institute measures to lower the carbon footprint of its operations. We have greater familiarity with the steel sector, who we know are receptive to the LanzaTech technology as it not only enables an improvement of their environmental footprint but, more importantly, adds value to their carbon emissions by converting them to fuels and chemicals.

7. “…any hint of doubt when it comes to predictions of climate doom is evidence of greed, stupidity, moral turpitude or psychological derangement.” This is a quote from Bret Stephens writing in The Wall Street Journal.

Do you sympathise with his view?

Inaction – be it through apathy or denial – is our biggest threat today. What we must concentrate on is developing and supporting all technologies and innovations that are available to us to present options that don’t need to be defended. Solutions in the clean energy space that just make sense economically and environmentally so that the naysayers – whether they have the issues mentioned above or not – will have no reason not to

embrace them.

8. In fact, talking of ‘green issues’ and emissions control, how is the steel industry performing in this respect?

A lot of players in the steel industry have been working very hard to reduce emissions and pollutants and increase efficiency in their processes. For example, heat integration has been of interest and water management is increasingly a concern. In addition, emission sources are mapped and monitored. International standards for the calculation of carbon dioxide emissions have been around for a number of years. LCA data for key products is available and we have seen strong interest globally from steel mills to develop processes to reduce their carbon footprint using new technologies such as ours.

9. In your dealings with steel producers, are you finding that they are looking to companies like Lanzatech to offer them solutions in terms of energy efficiency and sustainability? If so, what can you offer them?

LanzaTech’s biological fermentation process has ~60% superior energy conversion efficiency, about double the efficiency of power generation with the additional benefit that the off-gas carbon is captured in useful liquid products, rather than used for energy, which could be provided by other cleaner means, such as solar, hydro or wind. In addition the technology reduces pollutants and particulate matter compared to untreated emissions from combustion of these gases.

So we offer them the chance to reduce their carbon footprint and pollutants while generating additional revenue from production of low carbon useful products.

LanzaTech’s carbon recycling platform presents a new way of thinking about

* CEO, Lanzatech. Further information, http://www.lanzatech.com www.steeltimesint.com

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PERSPECTIVES: LANZATECH

energy sources and how we treat waste.

When we consider the reality of climate change, a two-degree carbon budget will require countries to leave 80 % of coal, 50 % of gas and 33 % of global oil untouched.

LanzaTech offers a pathway for the steel industry to maximise existing resources, helping to keep fossil commodities underground.

10. How quickly has the steel industry responded to ‘green politics’ in terms of making the production process more environmentally friendly and are they succeeding or fighting a losing battle?

By virtue of the various steel companies

that LanzaTech is currently engaged with, we do believe that the steel industry is very receptive to technologies that enable greening while providing a positive ‘value added’ proposition.

11. Where does Lanzatech lead the field in terms of steel production technology?

LanzaTech is the only company to have scaled a biological gas fermentation process using steel mill off gases. The field of gas fermentation is relatively new and LanzaTech has over 40,000 hours of onstream data from operating steel plant demonstration units globally. In China we operated two facilities, the first with Baosteel and a second with Shougang.

We also successfully operated a facility in Taiwan with China Steel. The process was initially scaled in 2008 with a pilot plant in New Zealand with Bluescope Steel.

Each of these facilities helped LanzaTech’s technology get to where it is today on its pathway to commercial scale.

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12. How do you view Lanzatech’s development over the short-tomedium term in relation to the global steel industry?

We do believe that in the next five years, several LanzaTech process units will be either operational or being installed in steel mills across geographies. The recent press release on China Steel Corporation’s (Taiwan) decision to construct a facility producing up to 100,000 metric tons/yr of ethanol is the first of many more to come.

So LanzaTech’s initial commercial success using steel mill waste gases for fuel and chemical production is inextricably linked to the global steel industry.

13. The Chinese still rely heavily upon Western steel production

technology. What is Lanzatech’s experience of the Chinese steel industry LanzaTech has partners and investors from the steel industry in China who have shown tremendous commitment to sustainable growth. Our first two demonstration scale plants were commissioned in Chinese steel mills, the first with Baosteel and the second with Shougang. The major steel players are very conscious of producing steel at the lowest price and lowest carbon footprint.

14. Adrian Bodea of MTAG once asked, “Which breakthrough technologies will have a revolutionary impact and will it be something that is ‘one size fits all’ or a number of different technologies? What’s your view?

Successful strategies in the technology space should be adaptable to the market.

Depending on one feedstock or one product market is risky. If you have a

strong technology that can be adaptable to a variety of markets and geographies you will have a much greater impact than those that are focused on one. Those that can meet these challenges will be the revolutionary ones that can grow significantly globally.

15. Where do you see most innovation in terms of production technologies – primary, secondary or more downstream?

Technological innovation is the corner stone of many industries, not just steel. We believe that innovation is key in helping us meet our current energy and climate challenges and this could be throughout each step of the production process.

16. How optimistic are you for the global steel industry and what challenges face global producers in the short-to-medium term?

Steel, like oil, is an integral part of the global economy. The first adopters of innovative technological solutions derive the most benefit. Innovation will enable this industry to overcome challenges related to environmental performance as well as generating value-added products to increase the bottom line.

Nippon Steel is an example of an integrated steel company that has managed to integrate its steel and chemicals sector and increase its product offering in the global market. LanzaTech’s platform offers the steel sector opportunities to expand its product portfolio while reducing its carbon footprint.

With technologies such as this available today in the sector, the outlook for the steel industry as a whole should remain positive.

17. Lanzatech is based in the USA, but what’s happening steel-wise in the country?

LanzaTech is headquartered in the USA, but our customers are global. Our base here in the USA is driven primarily by the fact that the infrastructure and resources needed for our own growth is best enabled by being based here.

18. Apart from strong coffee, what keeps you awake at night?

Calls to inaction when it comes to dealing with our global climate and pollution problems. Maintaining the status quo and not doing anything to challenge our current climate and energy trajectory is concerning. We have an opportunity today to make a difference and though it may take time and perseverance we MUST keep at it to make this world a safer and cleaner place for future generations. t www.steeltimesint.com

9/29/15 10:27 AM

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