La Metallurgia Italiana - Giugno 2018

La

Metallurgia Italiana

International Journal of the Italian Association for Metallurgy

n. 6 Giugno 2018 Organo ufficiale dell’Associazione Italiana di Metallurgia.

Rivista fondata nel 1909

Innovative. Reliable. Precise. www.soloswiss.it

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La Metallurgia Italiana

La

Metallurgia Italiana

International Journal of the Italian Association for Metallurgy

n. 6 Giugno 2018 Organo ufficiale dell’Associazione Italiana di Metallurgia.

Rivista fondata nel 1909

International Journal of the Italian Association for Metallurgy Organo ufficiale dell’Associazione Italiana di Metallurgia.

House organ of AIM Italian Association for Metallurgy.

Innovative. Reliable. Precise. www.soloswiss.it

Rivista fondata nel 1909

Linea completamente automatica di forni a campana in atmosfera protettiva SOLO Swiss Profitherm Italia, Febbraio 2018

Direttore responsabile/Chief editor: Mario Cusolito Direttore vicario/Deputy director: Gianangelo Camona Comitato scientifico/Editorial panel: Livio Battezzati, Christian Bernhard, Massimiliano Bestetti, Wolfgang Bleck, Franco Bonollo, Bruno Buchmayr, Enrique Mariano Castrodeza, Emanuela Cerri, Lorella Ceschini, Mario Conserva, Vladislav Deev, Augusto Di Gianfrancesco, Bernd Kleimt, Carlo Mapelli, Jean Denis Mithieux, Marco Ormellese, Massimo Pellizzari, Giorgio Poli, Pedro Dolabella Portella, Barbara Previtali, Evgeny S. Prusov, Emilio Ramous, Roberto Roberti, Dieter Senk, Du Sichen, Karl-Hermann Tacke, Stefano Trasatti

n. 6 Giugno 2018 Anno 110 - ISSN 0026-0843

Drawing / Trafilatura Defects, their source and detection in wire drawn products C. Mapelli, S. Barella, A. Gruttadauria, D. Mombelli, A. F. Ciuffini, M. Cusolito 5 Development of new tests to assess sulfide stress corrosion cracking of line pipes M. Cabrini, S. Lorenzi, T. Pastore, D. Pesenti Bucella, G. Pellegrini, A. Paggi, E. Paravicini Bagliani, P. Darcis 11

Segreteria di redazione/Editorial secretary: Valeria Scarano

Muffle tubes: choose the right material for longer service life A. Spaghetti 22

Comitato di redazione/Editorial committee: Federica Bassani, Gianangelo Camona, Mario Cusolito, Ottavio Lecis, Carlo Mapelli, Valeria Scarano

Surpassing steel performance by creating a very fine grained microstructure M.I. Lembke, L. Oberli, G. Olschewski, R. Dotti - Steeltec AG, Switzerland 31

Direzione e redazione/Editorial and executive office: AIM - Via F. Turati 8 - 20121 Milano tel. 02 76 02 11 32 - fax 02 76 02 05 51 met@aimnet.it - www.aimnet.it

siderweb LA COMMUNITY DELL’ACCIAIO

Gestione editoriale e pubblicità Publisher and marketing office: Siderweb spa Via Don Milani, 5 - 25020 Flero (BS) tel. 030 25 400 06 - fax 030 25 400 41 commerciale@siderweb.com - www.siderweb.com La riproduzione degli articoli e delle illustrazioni è permessa solo citando la fonte e previa autorizzazione della Direzione della rivista.

Reproduction in whole or in part of articles and images is permitted only upon receipt of required permission and provided that the source is cited.

Reg. Trib. Milano n. 499 del 18/9/1948.

Sped. in abb. Post. - D.L.353/2003 (conv. L. 27/02/2004 n. 46) art. 1, comma 1, DCB UD Siderweb spa è iscritta al Roc con il num. 26116 Stampa/Printed by: Poligrafiche San Marco sas - Cormòns (GO)

Attualità industriale / Industry news Hot-rolled steels for special purposes: high carbon wire-rod for cold-drawing a cura di: N. Bolognani, A. Parimbelli - Caleotto S.p.A 38 Pulizia in linea del filo metallico su impianti di trafilatura ad alta velocita’: innovazione, ecologia e performance a cura di: G. Orlando - Decapaggio-Passivazione Consulting R. Giovanardi, L. Trombi - Università di Modena e Reggio Emilia 44 Continuous annealing by resistance heating furnace of stainless steels wire drawn a cura di: R. Nemfardi, R. Bedini, G. Zucchelli, D. Bonora - Eure Inox, Italy C. Mapelli, S. Barella, A. Gruttadauria, D. Mombelli - Politecnico di Milano, Italy 48 Scenari / Experts’ Corner Intervista a Gianluca Roda a cura di: Mario Cusolito

52

Materie prime, metalli e acciaio attualità e prospettive 201 a cura di: Achille Fornasini Partner & Chief Analyst siderweb

54

Trafilerie: la fotografia del settore italiano a cura di: Stefano Ferrari Responsabile Ufficio Studi siderweb

61

Atti e notizie / Aim news Resoconto ICS 2018

66

AIM – UNSIDER Norme pubblicate e progetti in inchiesta (aggiornamento 31 maggio 2018)

69

l’editoriale La Metallurgia Italiana Cari Lettori,

la trafilatura a freddo di leghe metalliche è un passaggio fondamentale per ottenere prodotti di alta qualità caratterizzati da una buona finitura superficiale e prestazioni affidabili.

Il ciclo termo-meccanico che coinvolge la trafilatura a freddo mira ad ottenere

Ing. Sandro Fraccia

superfici lisce, leghe temprate, una buona lavorabilità, un severo controllo delle tolleranze geometriche e delle caratteristiche microstrutturali (ad esempio la dimensione del grano).

Con questo incontro internazionale, che ho avuto il piacere di presiedere, l’Associazione Italiana di Metallurgia ha inteso condividere la conoscenza sui processi di fabbricazione dei prodotti trafilati, sulla progettazione, sull’ottimizzazione ed il controllo di questi processi oltre che sulla gestione e la logistica.

L’evento è stato organizzato con grande apprezzamento da parte degli oltre 100 partecipanti nella splendida sede di Sant’Agostino dell’Università di Bergamo alla fine del novembre 2017.

Visto l’alto profilo tecnico dei lavori presentati, il Comitato Editoriale della rivista ha ritenuto di dedicare il numero di giugno 2018 al tema Trafilatura, così da poter dare ulteriore visibilità ai migliori lavori presentati a Bergamo e pubblicarne di nuovi.

Nel corso del Workshop ha trovato spazio anche un’interessante sezione riguardante la situazione attuale del mercato coordinata da Siderweb.

Buona lettura

4

La Metallurgia Italiana - n. 6 2018

Trafilatura Defects, their source and detection in wire drawn products C. Mapelli, S. Barella, A. Gruttadauria, D. Mombelli, A. F. Ciuffini, M. Cusolito

Wire drawn products are very susceptible to defects. At the end of the process, this product can have a very small resistant section, and, for this reason, even small defects can lead to the wire failure or scrap. Moreover, the wire finishing must be very high to match aesthetic criteria and to improve the fatigue life. Flaws can originate in each part of the process, and in this paper some examples of defects in wire drawn products caused by melting, casting practice and metallurgical sources are reported.

KEYWORDS: WIRE DRAWING – DEFECTS – LIQUID STEEL – CASTING

INTRODUCTION In wiredrawing, the cross section of a long rod or wire is reduced or changed by pulling it through a die called draw die. During the process some defects can arise, and they can be classified as surface and internal defects. Moreover, because they undergo non-uniform deformation during drawing, cold drawn products are usually featured by the residual stresses. They cause the component to warp. Internal defects due to the wiredrawing process are usually represented by cracks caused by the tensile hydrostatic stress in the centerline and they can be avoided using a right die design and reducing the non-metallic inclusion fraction in the steel. The so-called seams are surface defects that can be originated during cold drawing and they are constituted by longitudinal scratches or folds in the material. Several other surface defects (such as scratches and die marks) also can be caused by improper selection of the process parameters, i.e. poor lubrication or poor die condition [1].

However, many defects spring up during the process or during the subsequent forming operations, due to defects already existing inside the raw material. Some examples of this flaws are scabs, laminations, slivers, seams, embedded scale and laps [2].

These problems can be attributed to different sources: melting and casting practice, metallurgical sources, heating and rolling practices [3]. For example, scabs are associated to melting and casting practice. Scabs are irregularly shaped, flattened protrusions caused by splash, boiling or other problems from teeming, casting or conditioning [4]. Non-metallic inclusions are originated from a metallurgical source: they are produced during the steel secondary metallurgy. Some residual inclusions, like alumina or silica, proximal to the surface, give rise to seams and slivers. These two types of flaws can be also originated by another metallurgical source: the high concentration of Cu, Zn or Sn in the steel. These chemical elements are considered as detrimental because they can cause many cracks to form on the La Metallurgia Italiana - n. 6 2018

surface during mechanical working at high temperatures such as hot rolling. This phenomenon has been known as surface hot shortness: selective oxidation of Fe at the steel/scale interface occurs while portions of steel featured by Cu, Zn and Sn form during the heating and melt at low temperature [5,6]. Actually, the phases enriched by Cu, Zn and Sn are featured by a low melting point, so they tend to liquefy at the austenite grain boundaries and under stress during hot rolling such phases cause cracks on the steel surface. The concentration of Cu, Sn e Zn is continuously increasing in scraps and this problem can only worsen in the future [7]. Embedded scale can be due to an excessive scale formation during the heating operations. Finally, laps can be ascribed to pass overfilling during the rolling: the

C. Mapelli, S. Barella, A. Gruttadauria, D. Mombelli, A. F. Ciuffini Politecnico di Milano, Italy

M. Cusolito Associazione Italiana di Metallurgia

5

Drawing roll pass is not adequately filled, and part of the section falls over in the roll pass [2].

The previous list is not exhaustive, but just a brief overview of the blemishes that can be detected in drawn products. These defects can be found during non-destructive tests. Usually, a rotating-type ultrasonic unit is used, in the form of a phasedarray, to detects internal defects but this method is not jet sufficiently reliable for surface flaws [8]. However, a flawless product cannot be ensured neither in the billet before the rolling and wire drawing nor in the wire. Thus, this kind of defects

results in failure during the deformation process or in service.

In the following, some examples of defects in wire drawn products examined during the PoliMi Lab activities are reported.

In particular, the focus has been on defects caused by melting, casting practice and metallurgical sources.

Example 1 On several wire rods, after the first pass of drawing, some defects were detected after visual examination. These defects appear like slivers (Figure 1).

Fig. 1 – Slivers detected on the wire after the drawing Some metallographic sections were obtained, and the samples were analyzed by means of SEM-EDS.

In Figure 2 the micrographies are reported and also the points in which the chemical composition is measured.

Fig. 2 – SEM-EDS analysis on the metallographic sample: (a) at low magnification and (b) at higher magnification. In A, B and C chemical analysis was performed (Table 1).

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La Metallurgia Italiana - n. 6 2018

Trafilatura Tab. 1 – Chemical composition in A, B and C in Figure 2 % by weight

C

O

Ca

Mn

Fe

Cu

Fig.2 A

30,68

20,50

0,52

-

45,44

2,86

Fig.2 B

8,04

13,86

-

-

78,10

-

Fig.2 C

12,78

15,31

0,71

-

69,74

1,47

Figure 2 shows long inclusions under the surface of the wire.

The inclusions, using the BSE probe, appear oxidized. The EDS analysis suggest that this defect is mainly iron oxide but, in some points, a high concentration of copper was detected.

This flaw is due to a hot shortness phenomenon: the high concentration of copper creates a liquid film between the grain and some cracks are formed. The defect origin is probably related to the deformation processes prior to the wire drawing (i.e. hot

rolling) as a consequence of the high oxidation level featuring the observed crack.

Example 2 On several wire rods, at the end of the drawing process, some defects were detected after visual examination. These defects appear like laminations (Figure 3) pointing out the typical shape similar to the tool chipping.

Fig. 3 – Laminations on wire drawn products (diameter 7mm).

In order to understand the origin of the observed defects a metallographic section normal to the wire axis has been analyzed.

La Metallurgia Italiana - n. 6 2018

Optical and electronical microscopy were used to understand the defect genesis.

7

Drawing

a

b

c Fig. 4 – OM of the defects

d

Figure 4 shows many flaws in the sub-cortical zone of the sample: there are some cracks (Fig.4-a), some non-metallic inclusions (b) and a huge number of porosities proximal to the cracks. All these factors could have given a contribute to the lamination formation. Sub-superficial cracks are often oxidized and, during the drawing process, they tend to open. Moreover,

deformable inclusions tend to align and because of their poor ductility (if compared to the matrix) they tend to break under the high stress and strain generated by the process.

The SEM-EDS analyses shows a relevant cracks oxidation and the chemical composition of the nonmetallic inclusions (Table 2).

Tab. 2 – Non-metallic inclusion chemical composition (Fig.4-b) % by weight

O

Si

Ca

Mn

Fe

Inclusion (fig. 4-b)

20,83

29,33

2,04

44,24

3,56

These inclusions can be originated by the re-oxidation of the steel in the tundish or in the mold during the continuous casting process. This phenomenon creates the Si and Mn oxides and promotes the gas formation inside the molten metal.

Example 3 8

On several wire rods, at the begining of the drawing process, some defects were detected after visual examination. This defects can lead to failure or scarp at the endo of the drawing.

These defects appear like seams (Figure 5).

La Metallurgia Italiana - n. 6 2018

Trafilatura

Fig. 5 – Seams on a wire before the wire drawing Also in this case, the flaw analysis was performed by means of

OM and SEM.

a

b

Fig. 6 – Micrographic investigation on transversal section of the wire in Figure 5: (a) optical microscopy and (b) SEM-EDS analysis.

Figure 6-a shows some non-metallic inclusions featured by a particular curvature. This “hook” is peculiar of lubricant entrapment due to pronounced oscillation marks arisen during

the continuous casting. SEM-EDS supports this hypothesis because of the detected chemical composition (Table 3).

Tab. 3 – Local chemical composition: figure 6-b point A % by weight

O

Na

Al

Si

Cl

K

Ca

Fe

Mo

Fig.6 A

35,64

12,15

2,81

15,58

12,78

5,09

1,91

8,99

5,05

La Metallurgia Italiana - n. 6 2018

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Drawing As a matter of fact, this chemical composition is typical of the powder used in the mold during the continuous casting. The lubricant viscosity, the oscillation frequency and the mold stroke have to be taken into account for the formation of such a defect [9].

Conclusion In this paper a brief overview about the defects revealed on the wiredrawn products was presented.

Defects can have many origins, but a high-quality rod can help

for decreasing the failure during and after the wiredrawing.

During the steel production, many metallurgical defects can arise, and they cause the final defects or the product failure.

Some defects can be detected by NDT but, unfortunately, a complete control on the whole production is not sustainable.

For this reason, a good metallurgical practice, in all the parts of the steelmaking process, can decrease the defect formation (in particular the sub-surficial zone) and give rise to a contained failure and waste of the final wiredrawn products.

REFERENCES [1]

S. Kalpakjian, S.R. Schmid, Manufacturing Engineering and Technology, Pearson, 2014.

[2]

V. AA., ASM Handbook. Volume 17, Nondestructive Evaluation and Quality Control, Metals Park, Ohio : ASM International, c1989., n.d.

[3]

S. Mummidisetty, ASSESSMENT OF SURFACE DEFECTS IN WIRE RODS USED FOR MAKING ELECTROPLATED WIRE, 2004.

[4]

V. AA, Detection, Classification, and Elimination of Rod and Bar Surface Defects, 1986.

[5]

K. Shibata, S.-J. Seo, M. Kaga, H. Uchino, A. Sanauma, K. Asakura, C. Nagasaki, Mater. Trans. 43 (2002) 292–300.

[6]

L. Yin, S. Sridhar, Met. Mater. Trans B 42 (2011) 1031–1043.

[7]

K. Noro, M. Takeuchi, Y. Mizukami, ISIJ Int. 37 (1997) 198–206.

[8]

V. AA., Le Prove Non Distruttive Presentate dall’AIM, 2013.

[9]

H.J. Shin, G.G. Lee, W.-Y. Choi, S.-M. Kang, J.-H. Park, S.-H. Kim, B. Thomas, AISTech Assoc. Iron Steel Technol. 2 (2004) 15–17.

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La Metallurgia Italiana - n. 6 2018

Trafilatura Development of new tests to assess sulfide stress corrosion cracking of line pipes M. Cabrini, S. Lorenzi, T. Pastore, D. Pesenti Bucella, G. Pellegrini, A. Paggi, E. Paravicini Bagliani, P. Darcis Semi-scale tests were performed with the aim of evaluating the influence on the resistance against SSCC of as-produced inner surface of steel pipes. The activity includes the design of tests on specimens sampled by preserving the inner surface of pipe and preliminary tests, which covers four samples taken from a commercial pipe. Two of the specimens were tested in as-produced surface conditions; the other two were heat treated in order to achieve 24 HRC hardness. Such value is above the minimum limit reported in ANSI/NACE MR0175/ISO15156-1, i.e. 22 HRC. The tests were performed in NACE solution saturated with H2S at 25°C and 1 bar.

KEYWORDS: SSCC - LINE - PIPE STEELS - SEMI-SCALE TESTS

Introduction Sulphide Stress Corrosion Cracking (SSCC) is an Environmental Assisted Cracking phenomenon typical of Oil & Gas Industry. The term Environmentally Assisted Cracking (EAC) means the phenomenon that takes place due to the synergistic action of the environment on a susceptible material under tensile loading[1–7].

EAC causes the formation of cracks that propagate under the combined action of stress and environment, with a risk of rupture in structural components even at loads lower than the tensile yield strength.

In Oil & Gas Industry, H2S is often present in production fluid generally associated with high pressure of CO2. It can affect both the risk of sweet generalized corrosion and environmental cracking. The iron sulfide corrosion products formed on carbon steel (mainly mackinawite) are poorly soluble. Small amounts of H2S in mixture with CO2 can stabilize the scale of carbonate, and thus their formation on the surface can slow down the dissolution rate of steel [8–10]. However, the mixed scale of iron sulfide and carbonate is conductive and can act as an effective cathodic area, changing the corrosion morphology from uniform to localized attack. As far as SSCC is concerned, H2S increases the concentration of adsorbed hydrogen on the metal surface (Hads) and promotes its entry into the metal. In the presence of external stresses, Sulphide Stress Corrosion Cracking (SSCC) can take place on high strength steels. Its insurgence mainly depends on the H2S partial pressure, pH and tensile strength of steels. ANSI/ NACE MR0175/ISO15156-1:2015 gives requirements and recommendations for the selection and qualification of carbon and low-alloy steels, corrosion-resistant alloys, and other alloys for service in equipment used in oil and natural gas production and natural gas treatment plants in H2S-containing environments. A La Metallurgia Italiana - n. 6 2018

limit hardness value of 22 HRC is recommended for carbon steels for sour service, but it is common practice to evaluate the SSCC resistance of materials for Oil & Gas industry by means of experimental tests.

The assessment of SSCC susceptibility of steel for pipelines is generally carried out according to NACE TM0177 by means of constant load tests on specimens sampled from components of large thickness, which show certain variability of microstructure and properties over the depth and between the external surface - subject to high cooling rates during production - and the

M. Cabrini, S. Lorenzi, T. Pastore D. Pesenti Bucella University of Bergamo, Department of Engineering and Applied Sciences, viale Marconi 5, 24044, Dalmine (Italy); CSGI - Consorzio per lo Sviluppo dei Sistemi a Grande Interfase, via della Lastruccia 3, 50019, Sesto Fiorentino, Italy; Consorzio INSTM Via G. Giusti, 9, 50121 Firenze (ITALY)

G. Pellegrini University of Bergamo, Department of Management, Information and Production Engineering, viale Marconi 5, 24044, Dalmine (Italy)

A. Paggi, E. Paravicini Bagliani, P. Darcis TenarisDalmine, Dalmine S.p.A., Italy

11

Drawing inner one. Furthermore, surface variations of alloy chemical composition - promoted by decarburation or preferential oxidations of alloying elements, during high temperature manufacturing should be taken into account.

In addition, an oxide layer generally forms during production, which could significantly affect the electrochemical behavior of steel and hydrogen permeation kinetics [11]. The presence of hot mill scale on the metal surface increases the corrosion potential, and in some cases can stimulate the initiation of the stress corrosion cracks [12]. Koh et al reported that cracks nucleate predominantly at nonmetallic inclusions and propagate through the steel matrix in a quasi-cleavage manner regardless of the test materials’ compositions [13]. The presence of a multi-layered corrosion film consisting of iron oxides (Fe2O3 and Fe3O4) and iron sulphides (pyrrhotite, mackinawite and pyrite) was found in the correspondence of the internal surface of a failed pipeline, near the crack nucleation [14]. Residual elements, such as copper, nickel and tin, which are more noble than iron, are usually accumulated at the scale–substrate interface [15,16].

Due to this fact, it is advisable to develop easy and reliable techniques to highlight the material behavior directly on as-produced surfaces, as it can be useful to assess the actual behavior of the material in areas in direct contact with the environment. Anodic reaction of iron dissolution takes place due to hydrogen sulfide chemiadsorption on the steel surface and oxidation according to the mechanism shown by several authors, followed by the formation of mackinawite scale or its dissolution[8,17–19]. Iron sulphide (mackinawite or other complex sulphides) can re-precipitate only once Fe2+ e HS- ions in contact with the steel surface reach supersaturation conditions. According to such mechanism, in presence of corrosion products scale on steel causes the modification of the corrosion[20] and SSCC behaviour of steel.

In view of this, the experimental activity is mainly oriented to the evaluation of the geometries of pipe samples taken directly by production by preserving the inner surface, the evaluation of suitable loading scheme and design of the loading device for bending tests to achieve uniform load and deformation condition on the inner surface of the specimen. The design of the testing procedure has been performed by numerical simulations.

Experimental validation of the results has been also carried out.

Preliminary tests have been carried out with the proposed methodology for examining the behavior of four samples of an experimental steel production. Two of the specimens were tested in as-received conditions and the other two were heat treated

12

in order to achieve a hardness value of 24 HRC, to some extent above the limit reported in NACE MR 0175-12.

Development of the test methodology The design of the methodology on pipe samples started from the evaluation of the specimen size and the loading scheme to achieve even distribution of stresses along a large area of the internal surface. Among possibilities, four point bending is the most reliable loading scheme, which grant homogeneous stress distribution along the inner surface due to constant bending moment. Actually, the curved geometry of the steel pipe specimens causes a certain inhomogeneity. Starting from this consideration, three different loading schemes were evaluated and the results were compared to four point bending: three points bending, three points bending with prismatic support and tie-rod system.

For the analysis, the material behavior of API 5L X65 steel was modeled by considering elastic modulus of 206000 MPa and yield strength of 448 MPa. The maximum tensile strength in the at the inner surface of the pipe segment was equal to the eighty percent of the yield strength. The specimen width was considered equal to twice the thickness to ensure a plane strain conditions.

In view of this assumption, two-dimensional FEM model was considered.

FEM simulations Simulations were performed for the three point bending (3PB) tests at different thickness, distance between the lower supports (span) and shape of the die (pin or prismatic) (Fig. 1). Further simulations were carried out for the four point bending (4PB) loading scheme at the same span - equal to 80 mm - between the upper die. Two different distances between the lower dies were chosen, i.e. 150 mm and 180 mm. In order to limit the forces necessary for specimen loading, the specimens’ sizes were decreased from cross section size of 17x34 mm to 10x20 mm.

The 3PB loading showed the sharpest decrease of stresses moving away from the loading symmetry axis, whilst the more homogeneous stresses distribution along the inner surface was found for 4PB specimens, as expected. Tab. 1 shows the values of force and the stroke on the punch for the different loading conditions. The highest forces on the punch were calculated for 4PB loading condition. The distribution of stresses calculated by numerical simulation for the simulations with 150 mm span and for the 3PB/pin is shown in Fig. 2 and Fig. 3.

La Metallurgia Italiana - n. 6 2018

Trafilatura

Fig. 1 – Loading devices for three point bending tests (3PB) and four points bending tests (4PB). Specimens with a thickness of 17 mm and a width of 34 mm Tab. 1 – Results of the FEM simulations Span (mm)

Load element

Upper pin stroke (mm)

Fy (kN)

Gauge length° (mm)

17

150

Pin*

0.83

13

7.8

3PB

17

180

Pin*

1.68

8.8

10

3PB

17

150

Prism**

0.87

12.9

8.3

4PB

17

150-80

Pin*

1.06

18.6

24.2

4PB

17

180-80

Pin*

1.78

10.8

29.9

3PB

16

150

Pin*

0.88

11.9

7.6

3PB

10

150

Pin*

1.38

2.9

6.5

4PB

10

150-80

Pin*

1.48

4.2

13.2

Laoding Devices

Thickness (mm)

3PB

* Pin Ø20 mm ** Prism 20x10 mm ° Length in which σ > 95% σmax La Metallurgia Italiana - n. 6 2018

13

Drawing

Fig. 2 – Stress distribution for the 3PB load scheme, on the specimen 10 mm thick

Fig. 3 – Stress distribution for the 4PB load scheme, on the specimen 10 mm thick

A loading system based on the application of tie-rod device placed in correspondence of the inner surface of the specimen was devised to overcome several limits deriving from the application of traditional loading schemes. The designed device is far more compact compared to traditional 4 point and 3 point ben-

14

ding devices and it permits to further reduce the dimensions of the loading device and the surfaces extension in contact with the testing solution. Fig. 4 and Fig. 5 show the design and the assembly of the loading device.

La Metallurgia Italiana - n. 6 2018

Trafilatura

Fig. 4 – Loading device assembled before the test

Fig. 5 – Construction drawings and loading scheme of the tie rod system at the intrados

La Metallurgia Italiana - n. 6 2018

15

Drawing Fig. 6 compares the stress distribution along the tensioned zones in correspondence of the inner zones of the specimen for the three loading schemes. The results refer to the simulations performed in the case of the specimen with reduced thickness (10 mm). As expected, the stresses decrease very rapidly moving away from the load axis for the 3PB scheme, whilst they are quite homogeneous for the 4PB configuration. The tie rod system allows the achievement of homogeneous tensile load at distances up to 15 mm from the symmetry axis. Under such loading case, it is possible to attain homogeneous stress di-

stribution over a curved surface under an arc of about 30 mm.

The loading device is definitely more compact compared to the others, and it is than possible to study the behavior of different conditions in the same autoclave thus accomplishing the limitation on the ratio between exposed surface to solution volume. The tie rod system ca be a reliable alternative loading device to assess the SSCC susceptibility of pipe steels with their own natural oxide scale deriving directly from the production process.

Fig. 6 – Trend of stress in the intrados area, for the tie rod system

Experimental validation The validation of the numerical results has been performed on pipe sections taken from an experimental heat. The tests have been carried out on four specimens taken from a pipe preserving the as-produced internal surface (Fig. 7). The specimens have 20mmx10 mm cross section. Firstly, circular segments were obtained by external turning of the pipe and subsequent longitudinal cutting. The specimens were then mounted in a numerical controlled milling machine equipped with measure-

16

ments transducers. The position of the actual axis of the pipe was obtained by numerical interpolation based on seven control points taken with the measuring device. The milling path was then programmed to achieve circular segments by external contouring up to a final thickness of the specimen of 10 mm, constant over the whole length of the specimen (Fig. 8). Subsequently, the 20x10 mm cross section specimens were cut and drilled to achieve the positioning of the pins at 150 mm span.

La Metallurgia Italiana - n. 6 2018

Trafilatura

Fig. 7 – Pipe segments extracted and milled preserving the as-produced internal surface

Fig. 8 – Pipe segments after external contouring by means of peripheral milling

The hardness of the steel considered in the experimentation was 207 HV1, below the limit of 22 HRC specified by NACE MR0175/ISO 15156 for sour environments. In order to variate steel hardness, two specimens were austenitized at 920 °C for 10 minutes, followed by water quenching and tempered at 580 °C for 30 minutes. After quenching, the hardness rises up to 32 HRC (330 HV1) and decreases to 24 HRC (266 HV1) after the subsequent tempering.

Loading calibration procedure The correlation between load and deformation at the inner and outer surface of the specimen was obtained experimentally by

La Metallurgia Italiana - n. 6 2018

using an INSTRON tensile testing machine. For this purpose, loading and unloading ramps were carried out up to 8000 N. Clip gage was applied in correspondence of the most strained zones (Fig. 9). Fig. 10 shows the loading curves. The curves can be used to fix the target value to achieve at the most strained zone of the inner surface of the specimens. The value of deformation at 80% of the yield strength was taken into account for specimens loading. Practically, 0.1% of deformation measured by the clip gage at the outer surface permits to achieve about 0.20% deformation at the inner surface.

17

Drawing

Fig. 9 – Loading and unloading ramps with an INSTRON tensile testing machine

Fig. 10 – Loading ramps for the calibration of specimen loading. Correlation between deformation along the inner surface and outer surface

18

La Metallurgia Italiana - n. 6 2018

Trafilatura Specimen loading After the calibration procedure, the loading of specimens for long-term exposure tests in sour environment was carried out by rotating the threaded sleeve, which increases its length. The device is equipped with right and left-handed threads to act as tie rod system being extended. The deformation at the inner surface is estimated by measuring the deformation at the outer surface by means of clip gage, in analogy to the calibration

procedure. The loading procedure was stopped once the target deformation was reached (Fig. 11). During tests, the specimens was loaded at a compression deformation equal to -0.10% at outer surface, corresponding to a tensile stress at the inner surface equal to the 80% of the nominal tensile yield strength.

Fig. 11 – Assembly for the specimen loading by means of the tie rod system Experimental testing Preliminary tests were performed in Type A NACE solution (0.5% by weight of CH3COOH and 5% by weight of NaCl, dissolved in distilled water) according to the NACE Standard TM0177-2016, deaerated with N2 for 24 hours before the test at a temperature of 25 °C and saturated with pure H2S at 1 bar. The nitrogen flow was then maintained for further 8 hours, before H2S bubbling. The test duration was equal to 720 hours.

The flow of H2S was constantly maintained during test. At the end of the exposure, the solution was purged with N2 for at least 24 hours and the specimens were then taken out from

the testing chamber.

The specimens were washed with water by using non-metallic soft brush, and then they were degreased in acetone and dried at air (Fig. 12). Finally, the specimens were observed under an optical microscope up to 50x to detect the presence of SSCC cracks. No cracks were observed effect at the optical microscope denoting no relevant effect internal surface produced by manufacturing process adopted for the experimental heat considered for testing. However, further testing should be planned in order to assess conditions representative of production.

Fig. 12 – Aspect of the specimens: a) recovered at the end of the test and b) after washing La Metallurgia Italiana - n. 6 2018

19

Drawing Conclusions New methodology has been proposed for assessing the behaviour of line pipe steel to SSCC steel respect directly on as produced internal surfaces, based on the adoption of tie-rod bending test which permit to fill the gap in literature regarding such topic. Numerical simulation were performed to evaluate the best loading scheme allowing the achievement of constant loading condition on the inner surface of pipe segments obtai-

ned directly from production pipes. The system with a central tie rod was adopted in order to achieve uniform distribution of stresses along the inner surface of the pipe segment by using compact device. The suitability of the system have been demonstrated by experimental validation of the numerical results.

Experimental test in sour environment have been also carried out on pipe segments obtained from an experimental heat.

REFERENCES [1]

Cabrini, M.; Lorenzi, S.; Pellegrini, S.; Pastore, T. Environmentally assisted cracking and hydrogen diffusion in traditional and high-strength pipeline steels. Corros. Rev. 2015, 33, doi:10.1515/corrrev-2015-0051.

[2]

Cabrini, M.; D’Urso, G.; Pastore, T. Evaluation of the resistance to hydrogen embrittlement by the slow bending test; 2008; ISBN 9780080446356.

[3]

Cabrini, M.; Pastore, T. Hydrogen diffusion and EAC of pipeline steels under cathodic protection. In Fracture of Nano and Engineering Materials and Structures - Proceedings of the 16th European Conference of Fracture; 2006; pp. 1005–1006.

[4]

Cabrini, M.; Lorenzi, S.; Marcassoli, P.; Pastore, T. Hydrogen embrittlement behavior of HSLA line pipe steel under cathodic protection. Corros. Rev. 2011, 29, 261–274, doi:10.1515/CORRREV.2011.009.

[5]

Cabrini, M.; Migliardi, L.; Pastore, T.; Spinelli, C. Effect of cathodic potential and strain rate on hydrogen embrittlement of HSLA steels. In Hydrogen Effects on Material Behaviour and Corrosion Deformation Interactions - Proc. of the International Conference on Hydrogen Effects on Material Behaviour and Corrosion Deformation Interactions; 2003; pp. 979–988.

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Trafilatura [6]

Barsanti, L.; Bolzoni, F. M.; Cabrini, M.; Pastore, T.; Spinelli, C. Hydrogen-embrittlement resistance of X100 steels for longdistance high-pressure pipelines; 2008; ISBN 9780080446356.

[7]

Cabrini, M.; Lorenzi, S.; Marcassoli, P.; Pastore, T. Effect of hydrogen diffusion on environmental assisted cracking of pipeline steels under cathodic protection | Effetto della diffusione dell’idrogeno sui fenomeni di environmental assisted cracking di acciai per pipeline in condizioni di protezione catodi. Metall. Ital. 2008, 100.

[8]

Sun, W.; Nesic, S. A Mechanistic Model of H2S Corrosion of Mild Steel. NACE Int. - Corros. Conf. Expo 2007, No.07655.

[9]

Smith, S. N.; Pacheco, J. L. Prediction of corrosion in slightly sour enviroments. In Corrosion; 2002; p. Paper no. 2241.

[10]

Smith, J. S.; Miller, J. D. A. Nature of Sulphides and their Corrosive Effect on Ferrous Metals: A Review. Br. Corros. J. 1975, 10, 136–143, doi:10.1179/000705975798320701.

[11]

Hyodo, T.; Iino, M.; Ikeda, A.; Kimura, M.; Shimizu, M. The hydrogen permeation and hydrogen-induced cracking behaviour of line pipe in dynamic full scale tests. Corros. Sci. 1987, 27, 1077–1098, doi:10.1016/0010-938X(87)90100-4.

[12]

Cabrini, M.; Lorenzi, S.; Pastore, T.; Bucella, D. P. Effect of hot mill scale on hydrogen embrittlement of high strength steels for pre-stressed concrete structures. Metals (Basel). 2018, 8, doi:10.3390/met8030158.

[13]

Koh, S. U.; Yang, B. Y.; Kim, K. Y. Effect of alloying elements on the susceptibility to sulfide stress cracking of line pipe steels.

Corrosion 2004, 60, 262–274, doi:10.5006/1.3287730

[14] Azevedo, C. R. F. Failure analysis of a crude oil pipeline. Eng. Fail. Anal. 2007, 14, 978–994, doi:10.1016/j.engfailanal.2006.12.001.

[15]

Grabke, H. J.; Leroy, V.; Viefhaus, H. Segregation on the Surface of Steels in Heat Treatment and Oxidatio. ISIJ Int. 1995, 35, 95–113, doi:10.2355/isijinternational.35.95.

[16]

Chen, R. Y.; Yuen, W. Y. D. Review of the high-temperature oxidation of iron and carbon steels in air or oxygen. Oxid. Met. 2003, 59, 433–468.

[17}

Bai, P.; Zhao, H.; Zheng, S.; Chen, C. Initiation and developmental stages of steel corrosion in wet H2S environments. Corros.

Sci. 2015, 93, 109–119, doi:10.1016/j.corsci.2015.01.024.

[18] Zheng, Y.; Brown, B.; Nešić, S. Electrochemical study and modeling of H2S corrosion of mild steel. Corrosion 2014, 70, doi:10.5006/0937.

[19]

Veloz, M. a.; González, I. Electrochemical study of carbon steel corrosion in buffered acetic acid solutions with chlorides and H2S. Electrochim. Acta 2002, 48, 135–144, doi:10.1016/S0013-4686(02)00549-2.

[20]

Choi, Y.-S.; Nesic, S.; Ling, S. Effect of H2S on the CO2 corrosion of carbon steel in acidic solutions. Electrochim. Acta 2011, 56, 1752–1760, doi:10.1016/j.electacta.2010.08.049.

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21

Drawing Muffle tubes: choose the right material for longer service life A. Spaghetti

Muffle tubes can be mostly used in wire drawing mills muffle furnaces and bundy tube production, or can be found in such applications as razor blade production and tube annealing furnaces.

They are used to shield a product from the environment of the furnace during heat treatment, and create conditions for a more even temperature distribution. In most cases, protective shielding gas is fed into the muffle tube – this can be hydrogen, nitrogen, cracked ammonia or endogas.

Some of these gases are very aggressive and will shorten the life of the tubes significantly. In the annealing furnaces, the temperature is usually between 800 to 1120°C (1472 to 2048 °F), aggressive conditions which often result in a short service life.

If premature failures happen, we recommend careful analysis of the process, which may result in the selection of a more suitable material optimized for your special conditions.

As the value of lost production (and time spent with unplanned maintenance) is so high, a better grade of tube material can have significant economic returns. Our technical and sales teams see this first-hand, working closely with customers to find cost effective solutions to their corrosion issues.

KEYWORDS: MUFFLE – CARBURIZATION – HOT CORROSION – NITRIDATION – SHIELDING GAS – FURNACE – TUBES

Introduction Sandvik muffle tubes are characterized by long service life and contribute to reduced maintenance costs .

Muffle tubes can be mostly used in wire drawing mills muffle furnaces and bundy tube production, or can be found in such applications as razor blade production and tube annealing furnaces (fig.1).

They are used to shield a product from the environment of the furnace during heat treatment and create conditions for a more even temperature distribution. In most cases, protective shielding gas is fed into the muffle tube – this can be hydrogen, nitrogen, cracked ammonia or endogas.

Some of these gases are very aggressive and will shorten the life of the tubes significantly. In the annealing furnaces, the temperature is usually between 800 to 1120°C (1472 to 2048 °F), aggressive conditions which often result in a short service life.

22

Alessandra Spaghetti Sandvik Materials Technology, Italy

La Metallurgia Italiana - n. 6 2018

Trafilatura

Fig. 1 – Where muffle tubes can be found.

Drawing During the drawing operation the cross section of a long rod or wire is reduced or changed by pulling it through a die called «draw die». This can also be applied to small diameter stock up to reach wire size down to 0,03 mm.

Drawing is a cold working process and thanks to this it is possible to achieve a final product (wire) with: • Close dimensional control • Good surface finish • Improved mechanical properties such as strength and hardness • Adaptability to economical batch or mass production Prior to drawing, the beginning stock must be properly prepared and this can be done through three steps: (1) Annealing (2) Cleaning (3) Pointing The purpose of annealing is to increase the ductility of the stock to accept deformation during drawing.

As previously mentioned, annealing is sometimes needed between steps in continuous drawing. Cleaning of the stock is required to prevent damage of the work surface and draw die. It involves removal of surface contaminants (e.g., scale and rust) by means of chemical pickling or shot blasting. In some cases,

prelubrication of the work surface is accomplished subsequent to cleaning. Pointing involves the reduction in diameter of the starting end of the stock so that it can be inserted through the draw die to start the process. This is usually accomplished by swaging, rolling, or turning. The pointed end of the stock is then gripped by the carriage jaws or other device to initiate the drawing process.

Various other surface defects (such as scratches and die marks) also can result from improper selection of the process parameters, poor lubrication, or poor die condition. Because they undergo non-uniform deformation during drawing, cold-drawn products usually have residual stresses.

Tube annealing Annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It consists in heating a material to above its recrystallization temperature – maintaining a suitable temperature – cooling (air, water, oil, salt).

In steel, there is a decarburization mechanism that can be described as three distinct events: the reaction at the steel surface, the interstitial diffusion of carbon atoms and the dissolution of carbides within the steel (fig. 2).

Fig. 2 – Decarburizaton mechanism steps

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23

Drawing The three stages of the annealing process that proceed as the temperature of the material is increased are: recovery, recrystal-

lization, and grain growth (fig 3).

Fig. 3 – Annealing: a three stages process.

The first stage is recovery, and it results in softening of the metal through removal of primarily linear defects called dislocations and the internal stresses they cause. Recovery occurs at the lower temperature stage of all annealing processes and before the appearance of new strain-free grains. The grain size and shape do not change. The second stage is recrystallization, where new strain-free grains nucleate and grow to replace those deformed by internal stresses. If annealing is allowed to continue once recrystallization has completed, then grain growth (the third stage) occurs. In grain growth, the microstructure starts to coarsen and may cause the metal to lose a substantial part of its original strength. This can however be regained with hardening.

The high temperature of annealing may result in oxidation of the metal’s surface, resulting in scale. If scale must be avoided, annealing is carried out in a special atmosphere, such as with endothermic gas (a mixture of carbon monoxide, hydrogen gas, and nitrogen gas). Annealing is also carried out in forming gas, a mixture of hydrogen and nitrogen (fig. 4). Continuous annealing furnaces are designed for years of trouble-free service in the processing of wire, rod, strand, strip and tube products.

These furnaces are ideally suited for copper, copper alloy, nickel, nickel chrome, titanium, stainless steel and refractory metals. Different temperature ranges are offered to cover a wide variety of applications.

Fig. 4 – How to avoid scaling.

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Trafilatura Bundy tubes Bundy tube, sometimes called Bundy pipe, is type of doublewalled low-carbon steel tube manufactured by rolling a copper coated steel strip through 720 degrees and resistance brazing the overlapped seam in a process called Bundywelding. It may be zinc- or terne- coated for corrosion protection. It is used in automotive hydraulic brake lines in cars manufactured in the USA since the 1930s.

Razor blades Blade manufacturing processes involve mixing and melting of the components in the steel. This mixture undergoes a process known as annealing, which makes the blades stronger. The steel is heated to temperatures of 1,967-2,048°F (1,075-1,120°C), then quenched in water to a temperature between -76- -112° F (-60- -80° C) to harden it. The next step is to temper the steel at a temperature of (482-752°F (250- 400°C).

Muffle tubes product range Sandvik muffle tube is used in a wide range of industrial applications where a muffle furnace (check) of some type is used as part of the production process. In this case temperatures are up

to 1200°C so the key word is heat resistance. When it comes to Sandvik’s muffle tube range, some of the key elements are superior heat resistance, excellent corrosion resistance, good material consistency from batch to batch and full traceability.

And Sandvik has a strong track record of delivering to some of the most demanding industries and customers in the world.

Some of the key benefits include: • Premium quality and consistency • Superior proven heat resistance • Outstanding corrosion resistance • Long lifetime of tube reduces maintenance costs • Full traceability from batch to batch • Strong Sandvik reference list All stainless steel materials have protective oxide layers on their surface called Cr2O3 (Chromium Oxide). At room temperature, this protective layer provides a sufficient barrier for diffusion of the gases and protect the tubes to corrode. Unfortunately, when it comes to temperatures higher than 500°C a diffusion mechanism starts with the gases into the metal structure which they start bonding with some of the beneficial elements of the grade (fig. 5).

Fig. 5 – Diffusion mechanism.

Oxygen, carbon and nitrogen compounds tend to bond with chromium though depleting the protective Cr oxide layer. On the other sulfur is easily joinable to Nickel and that is why in case of sulfidation risk it is preferable to use a material very

La Metallurgia Italiana - n. 6 2018

poor or with a lack of Nickel, like a ferritic grade.

Sandvik can produce different types of high temperature resistance alloys that can withstand to all kinds of shielding gases and environments up to 1200°C as per table below (tab. 1)

25

Drawing Tab. 1 – High temperature corrosion resistance materials.

Muffle tube materials (other grades can be supplied upon request) Sandvik grade (UNS)

Max. operating temp. °C (°F)

Typical enviroments

Sandvik 253 MA* UNS S30815

1100°C (2010°F)

For oxidizing and sulfidizing conditions

Sandvik 353 MA* UNS S35315

1150°C (2100°F)

For oxidizing, carburizing and nitriding conditions as well as in endothermic gas or environments contaning hydrogen gas (H2)

Sandvik 4C54 UNS S44600

800°C (1470°F)

For oxidizing, sulfdizing conditions as well as for environments contaning hydrogen gas (H2)

SanicroTM 61 UNS N06601

1150°C (2100°F)

For oxidizing, nitridig conditions

SanicroTM 31HT UNS N0881/N08810

1100°C (2010°F)

For carburizing and nitridig conditions

*253 MA and 353 MA are tradmarks owned by Outokumpu Stainless

Material selection When choosing a material which is able to resist a high temperature corrosive atmosphere, three factors need to be considered (fig. 6):

- - -

Corrosion resistance Structure stability Creep strength

Fig. 6 – Properties to consider in the high temperature world

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Trafilatura Corrosion resistance to different environments The table below shows a comparison of some grades at different and most common atmospheres.

Tab. 2 – Comparsion between some grades at different atmospheres

A comparison between Sandvik high-temperature materials with TP 304H Sandvik grade

In air

Oxidizing sulfur

Reducing sulfur

Carburizing

Nitriding

304H

0

0

0

0

0

321H

0

0

0

0

0

347H

0

0

0

0

0

316H

0

0

0

0

0

309

++

++

+

+

++(**)

0

310H*

+++

++

253 MA*

++++

+++

353 MA*

++++

+

Sanicro 31HT*

++

Sanicro 61

++++

TM

TM

++

++

+++

++(**)

0

++++

++++

+

0

+++

+++

0

-

+

++

Sanicro 70

+++

0

-

+

++++

4C54*

++++

+++

++++

-

-

2C48

+++

+++

+++

-

-

TM

* Sandvik stock standard ** In low oxygen potential (<100ppm O2), nitriding may occur *** In low dew point (<20°C), severe nitriding may occur 0 = reference value + = superior to – = inferior to

The main atmosphere used in muffle furnaces are: - Hydrogen up to 1250°C - Nitrogen up to 1150°C - Cracked ammonia up to 1100°C - Endogas up to 1150°C - Air up to 1250°C With each of them it is important to carefully select the best grade in order to fulfill the requested performances.

Sandvik Sanicro 31HT is often used in environments with cracked ammonia, which is the most aggressive environment in this application. It causes rapid nitriding of the tube material, which leads to a loss of the mechanical strength. By selecting an alloy with higher nickel content, it is possible to extend the service life. In this environment, Sandvik Sanicro 61 offers much longer service life.

Sandvik Sanicro 31HT is a highly suitable material where pure nitrogen or a gas mixture of nitrogen and hydrogen is used.

Nitrogen is a less severe environment than cracked ammonia.

The endogas will cause a rapid carburization, which also reduces the muffle tube’s mechanical strength. In these conditions, Sandvik 353 MA is the most cost-effective material. For seveLa Metallurgia Italiana - n. 6 2018

rely carburizing conditions, Kanthal APM or APMT is a better choice than Sandvik 353 MA. Hydrogen is a less aggressive environment. In these conditions, the most cost-effective material is Sandvik 253 MA, followed by Sandvik Sanicro 31HT. Sandvik 4C54 is a cost effective choice for annealing of carbon steel as it is done in a lower temperature range. Certain operational conditions will shorten the service life. Residuals, such as hydrocarbons, soap or drawing powder can increase the risk of corrosion. Frequent temperature cycling will also shorten the service life. If premature failures happen, a careful analysis of the process is recommended, which may result in the selection of a more suitable material optimized for any special conditions.

The figure below (fig. 7) shows the recommended operating temperatures in air for some of the main grades.

Structural stability These materials are made to work at high temperature so there are some ranges that should be avoided since they can encounter in the precipitation/formation of some harmful intermetallic and fragile phases as shown in figure 8.

27

Drawing

Fig. 7 â&#x20AC;&#x201C; Recommended operating temperature in air

Fig. 8 â&#x20AC;&#x201C; ranges of temperature to avoid due to precipitation of intermetallic phases

For example the Sanicro 31HT can form gamma prime phase while all the others form the well known brittle sigma phase.

4C54, a ferritic grade, can also have issues due to the pheno-

28

mena of the 475°C-embrittlement.

The formation of these phases happen with different velocities based on the material as shown in the TTT diagram in figure 9.

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Trafilatura

Fig. 9 – TT Diagram showing 1% sigma phase formation curves.

Within the precipitation ranges for the different phases it is important to consider that 1% sigma phase is precipitated at 800°C for 353MA after 7000 h, for 253MA after 2000 h, and for 310 and 309 after less than 200 h. 4C54 precipitates 1% sigma phase at 650°C after less than 200 h.

From fig. 9 the mechanism and the different kinetics are even clearer.

Creep strength Creep strength is important in case there is the risk of deformation of the material at high temperature.

As can be seen the ferrtic grade is the less resistant to creep while SAN31HT and the MA grades seem to have better performances.

Fig. 10 – Creep rupture strength.

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Drawing Summary and conclusions Muffle furnaces are most often used in wire drawing mills and in bundy tube production, but they can also be found in other applications such as razor blade production and tube annealing. They are used to shield a product from the environment of the furnace during heat treatment, and to create conditions for a more even temperature distribution. In most cases, some protective gas is fed into the muffle tube. This shielding gas can be hydrogen, nitrogen, cracked ammonia or endogas (CO + H2). Some of these gases are very aggressive and will shorten the life of the muffle tubes significantly.

In some annealing furnaces, the temperature can reach above 1,200°C, but temperatures between 800 and 1,120°C are most common. These high temperatures often result in a short service life, leading to frequent stoppages for maintenance and muffle tube replacements. As the value of lost production is high, the decision to select a better grade (tube material) will pay off in the long run.

Sandvik Sanicro 31HT is often used in environments with cracked ammonia, which is the most aggressive environment in this application. It causes rapid nitriding of the tube material, which leads to a loss of the mechanical strength. By selecting

an alloy with higher nickel content, you can extend the service life. In this environment, Sandvik Sanicro 61 offers much longer service life.

Sandvik Sanicro 31HT is recommended as a suitable material where pure nitrogen or a gas mixture of nitrogen and hydrogen is used. Nitrogen is a less severe environment than cracked ammonia. The endogas will cause a rapid carburization, which also reduces the muffle tube’s mechanical strength. In these conditions, Sandvik 353 MA is the most cost-effective material.

For severely carburizing conditions, Kanthal APM or APMT is a better choice than Sandvik 353 MA. Hydrogen is a less aggressive environment. In these conditions, the most cost-effective material is Sandvik 253 MA, followed by Sandvik Sanicro 31HT. Sandvik 4C54 is a cost-effective choice for annealing of carbon steel as it is carried out in a lower temperature range.

Certain operational conditions will shorten the service life. Residuals, such as hydrocarbons, soap or drawing powder, can increase the risk of corrosion. Frequent temperature cycling will also shorten the service life. If premature failures happen, we recommend a careful analysis of the process, which may result in the selection of a more suitable material optimized for your special conditions.

REFERENCES [1]

- http://uomustansiriyah.edu.iq/media/lectures/5/5_2016_04_18!11_56_42_AM.pdf

[2]

- http://www.sut.ac.th/engineering/Metal/pdf/MetForm/05_Drawing%20of%20rod-wire%20and%20tubes.pdf

[3]

- S-130-ENG. 09.2011 – Sandvik Materials Technology

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Trafilatura Surpassing steel performance by creating a very fine grained structure M.I.Lembke, L. Oberli, G. Olschewski, R. Dotti

Facing overcapacity and global competition steel part production costs must be continuously lowered. To be able to fulfil these upcoming needs new steel concepts are designed and innovative production technologies are developed. Through its systematic development of the thermochemical processing, Steeltec is now able to treat almost any conventional standard steel and significantly improve its properties. An ultrafine grain size is achieved by carefully controlled combination of heat and mechanical force, producing steel properties that could otherwise only be achieved by high alloy concentrations or by complex and costly additional processing stages. The possibilities of this technology are presented on the bar steel product 7MnB8. After austenising and a single extreme deformation step the ductile-to-brittle transition temperature can be shifted significantly to lower temperatures for 7MnB8. The observed temperature shift is due to the ultrafine microstructure attained after processing. The fine grain size in hot-rolled and air-cooled 7MnB8 bar resulted in the 27 J criteria to be fulfilled at temperatures as low as –101°C. Additionally, crack free cold bending is possible at room temperature using a version of the 7MnB8 providing high strength and high toughness.

KEYWORDS: BAR STEEL – GRAIN SIZE – IMPACT STRENGTH – DEFORMATION – LOW TEMPERATURES

Introduction In the past bright bar drawn steels from Steeltec have been developed to enhance the properties strength and toughness using dislocation strengthening, microalloying elements and bainitic steel grades.

ture, deformation and cooling [3]. For low-alloy carbon steels it is desirable to achieve a high degree of deformation in one or a small number of rolling steps in order to impede recovery

Fig. 1 – Methods to improve material properties

The markets slow acceptance for new steel grades and compositions, plus the ongoing need for further quality improvements, was incentive to apply a new method of improving the properties by modifying the process.

Grain-boundary strengthening, as expressed by the Hall-Petch relation, is a fundamental mechanism for strengthening materials. Steeltec’s new long bar manufacturing process achieves a considerable reduction in grain size and thus enables the material properties of conventional steels to acquire previously unobtainable values [1,2].

The technology combines a high-reduction forming stage with a single-bar heat treatment line. This allows the production of an ultrafine microstructure, due to precise control of temperaLa Metallurgia Italiana - n. 6 2018

M.I. Lembke, L. Oberli, G. Olschewski, R. Dotti Steeltec AG, Switzerland

31

Drawing [4]. The benefits of applying ultrafine grain steels produced by multipass warm calibre rolling for the mechanical properties of steel have been published e.g. Murty and Torizuka [5].

Steel bars produced using this technology are an alternative to higher alloyed QT-steel grades, as this new technology significantly boosts the performance of low-alloy steel grades.

Experimental For the experiments a microalloyed low carbon steel, of type C-Mn-B was used. The chemical composition is shown in Table 1. The material, which was produced by a conventional rolling process, had a yield strength of ~530 MPa and a tensile strength of ~690 MPa. Its elongation at fracture was ~19% and the ductile-to-brittle transition temperature was in the range of 30–40 °C.

Tab. 1 – Material prior treatment, chemical composition in weight %, Rp0.2 and Rm in MPa, A5 in %

7MnB8

C

Si

Mn

P

S

B

Rp0.2

Rm

A5

0.07

0.20

1.90

0.01

0.01

0.0025

530

690

19

Results and discussion The aim of this study was to determine how the new manufacturing process changes the structure and mechanical properties of the steel. The first area investigated was the influence of austenising temperature on the impact strength.

The first step involved measuring the austenite grain size at different temperatures. This is shown exemplary on the steel grade 7MnB8. A grain size of approximately 11 μm was found in the temperature range 950 °C to 1150 °C. At higher temperatures, grain growth started to occur.

The austenising temperature range 950–1100 °C was used for the production line trials. The bars were heated to the desired temperature by inductive heating, whilst monitoring the temperature optically. The bars were then cooled to < 800 °C before forming. The deformation was achieved in one step [3].

After deformation, the bars were cooled in still air. The degree of deformation selected was  ≥ 0.3. A marked increase in impact strength was observed with decreasing austenising tem-

perature.

The degree of deformation, needed to achieve the desired impact strength was defined by searching for the minimum degree of deformation needed to achieve the desired impact strength and the maximum degree of deformation that does not harm the material. As quality criteria a minimum of 27 J was aimed for. For 7MnB8 the deformation degrees were altered between 0.3 to 0.6. Fig.2 presents the results achieved using an austenising temperature of < 1000 °C and a temperature before forming of < 800 °C. The marked influence of increasing deformation on the impact transition temperature (ITT) of steel was published by Pickering in 1975 who stated, that continuing heavy-rolling reductions to very low temperatures can produce a further improvement in strength and ITT, due to additional refining of the grain size and formation of a very fine polygonised sub-structure [6].

Fig. 2 – Impact strength curves for different degrees of deformation

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Trafilatura For the 7MnB8 steel grade examined here, the impact transition temperature shifted to approximately -120 °C when the material underwent austenisation < 1000 °C and a forming temperatures < 800°C was used. The impact strength of bars that had been rolled on the new processing line showed a distinct upper shelf in comparison with material from a conventional rolling process. For the deformation range studied and with air cooling, the upper shelf (ductile fracture)

was at approximately 160 J. The decrease in the impact strength curve starts at around - 20°C. The greater the degree of deformation imparted to the material, the lower the temperature at which the ductile-to-brittle transition (ITT) occurs. Even under severe plastic deformation, with a degree of deformation of 0.6, no material defects in the form of microcracks were revealed by microscopic inspection.

Fig. 3 – Microstructure of 7MnB8 after conventional rolling and after the high deformation process, degree of deformation of 0.6 and air cooling The shift of the ITT is thought to be caused by increasing grain refinement, see Fig. 3.

The conventional rolled material can exhibit a structure composed of both ferrite and pearlite. A structure of ferrite and pearlite was observed under the light microscope for the 7MnB8 after the high deformation process step.

The superior mechanical properties of the steel produced on the new processing line are related to the microstructure, which contains most probably increasing amounts of polygonal ferrite with increasing degree of deformation. Starting from the conventional rolled material, the surface area of the austenite grain boundary area increases during deformation, due to pancaking [7]. As a result of the enhanced defect density along the grain boundaries of the deformed grains, polygonisation can

begin and may well also increase the number of nucleation sites inside the grain. This will accelerate the ferrite transformation. It is also possible that the strain induced by the deformation causes intra-granular ferrite nucleation that will further contribute to grain refinement [7].

In addition to the improved impact strength, we also studied the mechanical strength achievable in the austenitisation temperature range 900–1100 °C. The tensile strength and the yield strength showed a relatively small change of about 50 MPa to 100 MPa. The elongation varied by approximately 5%. Tests were therefore performed that included an increased amount of water cooling after the deformation stage ( = 0.6), an austenitisation temperature of < 1000 °C and a temperature before forming < 800 °C.

Fig. 4 – Processing line for the heat treatment and deformation step La Metallurgia Italiana - n. 6 2018

33

Drawing The production process can use various cooling elements in close proximity after the deformation step, see Fig. 4. The cooling step is an additional element, with which the process parameters can be altered. A variation of mechanical properties achie-

vable using a technology with a severe plastic deformation step combined with a single-bar heat treatment line, due to different process parameters is shown in Tab. 2 for the 7MnB8.

Tab. 2 – Various mechanical properties achievable with different process parameters for 7MnB8 in comparison to 42CrMoS4

1.5519

Material Condition

Rp0.2 [MPa]

Rm [MPa]

A5 [%]

AV,RT [J]

T27 [°C]

Hot rolled

≥400

690-750

≥15

<30

20

moderate strength, extreme low temperature toughness

425

700

22

≥150

-101

high strength, higher low temperature toughness

625

800

20

≥150

-101

extreme strength, high low temperature toughness

825

1000

13

≥100

-50

42CrMoS4 +QT

≥750

1000-1200

≥11

≥35

Due to the additional cooling step the structure of the 7MnB8 changed and the grain size could no longer be determined under the light microscope. An analysis was performed under the scanning electron microscope. The sample used had a yield strength of 644 MPa, a tensile strength of 809 MPa and an impact strength at room temperature of 215 J. The sample exhibited a granular bainitic structure. The bainitic microstructure was characterised on the basis of the unified terminology introduced by Zajac et al. [8].

Misorientation maps produced by electron backscattered diffraction (EBSD) from the near surface region and from the core zone were used to gain information of the boundaries and the

orientation of the grains. The EBSD maps contain the diffraction data from an area of roughly 15 μm2. By measuring the orientation of the adjacent grains, the grain boundary crystallography was determined. A step size of ~0.07 μm was used.

For statistical purposes, any boundary exceeding 15° was considered a boundary. The EBSD analysis revealed a high amount of boundaries > 15°.

The conventional rolling mill material displays an average ferrite grain size of approximately 13.8 μm [9]. After forming with a deformation degree of 0.6, the grain size was considerably reduced to below 5 μm.

Fig. 5 – SEM and EBSD images of 7MnB8 with a Rp0.2 = 644 MPa, Rm = 809 MPa and Av,RT = 215 J 34

La Metallurgia Italiana - n. 6 2018

Trafilatura The conventional rolled steel grade 7MnB8 has been used for cold heading applications [10]. To see if further forming after high deformation of the 7MnB8 was possible, a 18 mm bar with a yield strength of 990 MPa, a tensile strength of 1100 MPa and an elongation at rupture of 13 % was used for cold

bending. The bending radius was 10 mm. The strength level was similar to a 42CrMoS4, see Tab. 2. Samples after cold bending up to 150° were metallographically investigated and no cracks were visible. This positive result is thought to be related to the fine grain size.

Fig. 6 – Bending test of a 18 mm bar of 7MnB8 with Rp0.2 = 990 MPa, Rm = 1100 MPa and A5 = 13% Conclusions . A production process was introduced that enables to adjust the mechanical properties within a wide range after austenising and a single extreme deformation step . The adjustment of the process parameters step by step was investigated for the steel grade 7MnB8 .The high degrees of deformation enables a very small average grain size to be achieved. An average grain size < 5 μm was observed .The impact transition temperature can be shifted considerably to lower temperatures

La Metallurgia Italiana - n. 6 2018

.The notch impact energy for a version of the high deformed 7MnB8 is ≥ 150 J at room temperature .Good formability even at high strength Acknowledgments We would like to thank Dr. F. Jakob for insights into material behaviour at high degrees of deformation, Prof. B. Masek from the University of West Bohemia, Pilsen (Czech Republic), Prof.

R. Kuziak from IMZ, Gliwice (Poland) and Prof. F. Caballero from CENIM, Madrid (Spain).

35

Drawing REFERENCES [1]

R.W.K Honeycombe, H.K.D.H. Bhadeshia. ‘Steels Microstructure and Properties’ Elsevier 2003

[2]

http://www.xtp-technology.com/ : access 16.01.2017

[3]

A. Borowikow. ‘Graduierte Kornfeinung durch thermomechanische Behandlung’ HTM Journal of Heat Treatment and Materials, 67, 2012, A12–A13 p.

[4]

H.-J. Eckstein, F. Jakob. ‘Mikrolegieren von Stahl‘, VEB Verlag für Grundstoffindustrie, Leipzig 1984, 97–116 p.

[5]

S.V.S. Narayana Murty, S. Torizuka. Material Science Forum; 2010, Vols 633-634; 211–221 p.

[6]

F.B. Pickering. New York: Micro Alloying; 1975, 9–31 p.

[7]

E. Pereloma, D.V. Edmonds. ‘phase transformation of steels’ Vol. 2, Woodhead publishing (2012), 191-198 p.

[8]

S. Zajac, J. Komenda, P. Morris, P. Dierickx, S. Matera and F. Penalba Diaz. ‘Quantitative structure–property relationship for complex bainitic microstructures’, Technical Steel Research report no. EUR 21245EN, European Commission, Luxembourg, 2005.

[9]

F.G. Caballero, H. Roelofs, St.Hasler, C. Capdevila, J. Chao, J. Cornide and C. Garcia-Mateo. ‘Influence of bainite morphology on impact toughness of continuously cooled cementite free bainitic steels’ Materials Science and Technology Vol. 28, Nr.1 (2012), 95-102 p.

[10]

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S. Hasler, H. Roelofs, U. Urlau, J. Kruse. Salzburg: SCT2011 ; 2011, 307-314 p.

La Metallurgia Italiana - n. 6 2018

Le manifestazioni AIM AIM meetings and events 2018

MATERIALI METALLICI E PROCESSI PRODUTTIVI

LA PREVENZIONE E LA GESTIONE DELLE

INNOVATIVI PER L'AEROSPAZIO

MALATTIE PROFESSIONALI

Convegno - Centri ML, MFM e MP

GdS - Centro AS

Napoli, 19-20 luglio

Brescia, 25 ottobre

METALLURGY SUMMER SCHOOL - 2a edizione

LA PRODUZIONE DI GETTI PER APPLICAZIONI

COMET

STRUTTURALI. ASPETTI METALLURGICI E DI PROCESSO

Bertinoro (FC), 22-25 luglio

GdS - Centro P Travagliato (BS) c/o IDRA, 9 novembre

37° CONVEGNO NAZIONALE AIM Convegno – SEGR

UTENSILI DIAMANTATI

Bologna, 12-14 settembre

GdS - Centro MP Vicenza, 15 novembre

EOSC 2018 - 8TH EUROPEAN OXYGEN STEELMAKING CONFERENCE

FAILURE ANALYSIS

Convegno Internazionale

Corso - Centro CCP

Taranto, 10-12 ottobre

20-21-28-29 novembre

TRATTAMENTI TERMICI DEGLI ACCIAI PER STAMPI

CLEAN TECH - 4TH EUROPEAN CONFERENCE ON CLEAN

A CALDO E A FREDDO PER IL SETTORE AUTOMOTIVE

TEHNOLOGIES IN THE STEEL INDUSTRY

GdS - Centro TTM

Convegno Internazionale

Ivrea c/o Confindustria Canavese, 11 ottobre

Bergamo, 28-29 novembre

GLI ACCIAI INOSSIDABILI - 10a EDIZIONE

RIVESTIMENTI - 1° modulo Rivestimenti PVD e CVD

Corso - SEGR

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Milano, 17-18-24-25 ottobre/7-8-14-15 novembre

Roma, novembre

Per ulteriori informazioni rivolgersi alla Segreteria AIM e-mail: info@aimnet.it oppure visitare il sito internet www.aimnet.it

La Metallurgia Italiana - n. 6 2018

37

Industry news Hot-rolled steels for special purposes: high carbon wire-rod for cold-drawing a cura di: N. Bolognani, A. Parimbelli This work investigates the effects of different cooling conditions after hot rolling in the Stelmor transport line on the mechanical properties of a commercial high carbon steel rod. By activating and deactivating the fans in the Stelmor system and by making structural modification to the Stelmor conveyor rollers, an optimal patented air process is performed on a commercial high carbon steel. The cooling curves of three different characteristic points (side, intermediate and center) of the rings are measured. These data are used to evaluate the global heat transfer coefficients that characterize the Stelmor system. The distribution of the rings on the conveyor is also analyzed. The wire rods produced under different cooling conditions are analyzed by tensile tests. The optimum cooling conditions required for high strength and ductility are then evaluated.

KEYWORDS: AIR PATENTING - HIGH CARBON STEEL - STELMOR - MECHANICAL CHARACTERISTICS UNIFORMITY

N. Bolognani, A. Parimbelli Department of process engineering and quality management of Caleotto S.p.A., Via Arlenico 22, 23900 Lecco, Italy Drafted on April 2018

INTRODUCTION The introduction of controlled forced air cooling of rod has brought about significant improvement in tensile properties of high carbon steel wire rods. The present study is focused on the final step of the rolling mill process, which is the cooling of the wire rod through the Stelmor system. This system is characterized by the shaping of the wire rod into rings and their disposition on the conveyor. The cooling is performed through the action of the fans and can be carried out in different ways in function of the produced steel grade. The microstructure thereby achievable in plain high carbon steel grades in some cases provides a better quality to that of patenting process.

It has been shown that the final properties of the hot rolled rods are influenced by the reheating temperature of the billet, the rate of deformation, the temperature of deformation, the finishing temperature and the rate of cooling after rolling.

Among the above parameters, the last one can be considered the one that has the greatest consequences on the finished tensile properties of the rod. It is known that in the continuous 38

cooling conditions, the more the cooling rate is increased below the A1 and A3 temperature, the transformation temperature is decreased, and it produces finer pearlite lamellae. It is therefore clear that the uniformity and the fineness of the microstructures can offer a considerable improvement compared to the as rolled rods with non-uniform microstructures.

So, obviously, a completely pearlitic structure offers a better ductility of perlite plus proeutectoid ferrite structure.

The global heat transfer coefficient, that characterize cooling potential of the Stelmor system, are estimated from the temperature detected directly on the Stelmor system.

Mechanical tests are then performed on the studied material, varying the sampling position on the rod.

The alloy chosen for this study is a C82D2+Cr grade steel (table 1) on 10 mm round wire rod.

La Metallurgia Italiana - n. 6 2018

Attualità industriale Tab. 1 – Chemical Composition of C82D2+Cr steel

Element

C

Mn

Si

Cr

Weight percent

0.82

0.23

0,75

0.28

2. Experimental procedures The Stelmor system consists of several water cooling boxes that cool the wire immediately after the last rolling stand and allow the correct temperature to be reached to start the co-

oling treatment in the air, which is 850 °C. Fig.1 shows the Stelmor system used in this research. This has sixteen fans adjustable in power beneath the cooling conveyor system, which allow to obtain the optimal cooling process.

Fig. 1 - Schematic diagram of the Stelmor system

2.2. Applied cooling conditions In this research, the following cooling conditions were applied to C82 steel wire rod, of chemical composition shown in Table 1.

2.2.1. Condition A The laying head temperature (i.e. the start cooling temperature) was set to 850 °C and twelve fans were turned on at the maximum power. In this cooling condition, it was found that the temperature profile along a loop is very different, so the final mechanical properties will be different.

2.2.2. Condition B The laying head temperature was set to 850 °C and twelve fans were turned on at the maximum power. In this condition was made a structural modification to the false rolls of the conveying system to bring greater quantity of air towards the lateral area. Thanks to this, it was noticed an excellent improvement in homogeneity of the temperature in the three characteristic points and so in mechanical characteristics.

La Metallurgia Italiana - n. 6 2018

2.2.3. Condition C The laying head temperature was set to 850 °C and fourteen fans were turned on at the maximum power. Thanks to the two extra fans it is noted that the phase transformation of the lateral area takes place always just a moment later the central area (in this condition the false rolls of the B condition were installed on the Stelmor system).

2.3. Temperature detection The scope of this study is to track the temperature profile of the wire rod in three different positions of the transversal section of the conveyor. These three characteristic points of the laid rings are: - Side: represents the external point of the ring on the conveyor, that are the ones in proximity of the refractory wall - Center: represents the point in correspondence of the central axis of the conveyor - Intermediate: represents the point between the previous, where the selected distance is at R/2 form the side, with R being the ring radius.

The temperature, for each of these points, was taken at diffe-

39

Industry news rent distances, starting from the laying head, following a well-defined procedure.

2.4. Heat transfer coefficient Firstly, the energy balance between the rod and the surroundings was studied:

In addition to the classical terms present in the formula, h is the global heat transfer coefficient [W/m2K] and Q expresses the generated heat flux, due to the phase transformation [W].

form the tensile tests: each ring was divided in eight parts (figure 2) measuring 430 mm each. The ring was so composed by two, four and two samples corresponding respectively to central, intermediate and side sections.

2.5. Mechanical tests From different data conditions, some rings were taken to per-

Fig. 2 - Schematic diagram of the loop 3. Results 3.1. Temperature detection In the following graphs it can be seen the three different conditions expressed by time-temperature cooling curves.

Fig. 4 - Temperature of the three characteristic points in A, B and C conditions 40

La Metallurgia Italiana - n. 6 2018

Attualità industriale In B condition, by making structural modifications to the false-rolls of the cooling conveyor, homogenization of the cooling temperatures has been achieved. In C condition, thanks to the two extra fans it is possible to notice the complete transformation phase of the material in all three points (side, intermediate, center): a second phase transformation on the lateral part of the loop is appreciable.

3.2. Heat transfer coefficient

where X represents the fraction of transformed pearlite (0≤X≤1).

By re-elaborating the above formula and using the tempera-

tures measured on the Stelmor it is possible to estimate the global heat transfer coefficient:

It is well known that the transformation heat (Q), from Pearlite to Austenite, it is equal to about 77’000 [J/kg]. It is possible to write the balance as:

Fig. 3 - Heat transfer coefficient at difference distance from the laying-head

Obtained the values of h in different sections of the carpet of the three characteristic regions, it was tried to correlate them with some significant parameters of the production process by imposing a multilinear regression. In the case under study were considered: the instantaneous temperature of the

wire T [°C]; the value of ψ(x) which is parameter that expresses the relationship between the free volume on the carpet and that occupied by the loops; the ratio between the power of the fans and the speed of the conveyors. The relationship that correlates these is the following:

The ψ(x) ratio is obtained from the geometrical analysis of the wire rod that flows on the conveyor in the three characteristic regions: side, intermediate and center. The following graphs (figure 3) shows the trend of the ψ(x) value

with the points on the axis of the abscissas 10, 250 and 550 that correspond respectively to the position of the side, center and intermediate.

La Metallurgia Italiana - n. 6 2018

41

Industry news

Fig. 4 - Schematic diagram of the value of Ď&#x2C6;(x)

Thanks to a multilinear regression it was possible to calculate the values of the heat exchange coefficient hi in the sections of the Stelmor where the fans are running. The result

of this study is a function that describes the cooling curve of the wire rod that runs on the Stelmor system:

3.3. Mechanical tests Tensile test specimens were made by cutting 430 mm lengths from the rod of each condition. Tensile tests were

carried out at room temperature using an Instron machine.

The results are presented in Table 2:

Condition

UTS (MPa)

Total deviation (MPa)

ce A nt

1261

60,3

B

1219

38,8

C

1232

33,5

Conclusions By studying the peculiar geometry of the wire rod, it was possible to estimate the arrangement of the wire along the Stelmor system as the parameters of the cooling process vary. It has been shown that this arrangement determines a marked difference in terms of mass density between the lateral area, where the overlap of the loops is greater, and the central one of the conveyor, characterized by more empty spaces.

42

An uneven mass distribution therefore generates different cooling in various areas of the cross section of the Stelmor. This statement is corroborated by the results obtained from the thermal analysis of the material on the mat.

Comparing the temperature profiles of conditions A and B (condition in which false shaped rollers were inserted to direct a greater amount of cooling air into the side of the carpet), a decrease in the difference between the curves in all the sections was observed: it is therefore possible to La Metallurgia Italiana - n. 6 2018

Attualità industriale confirm that the insertion of new shaped rollers has allowed to homogenize the cooling conditions of the entire loop.

Following the temperature measurements it was then possible to calculate the values if the heat exchange coefficient, exploiting the modeling with concentrated parameters and introducing the heat of microstructural transformation. All the coefficients obtained are consistent with what is present in literature, thus confirming the validity of the method.

The correlation between the global heat exchange coefficients and some significant parameters of the production process was also found: the wire temperature, the ψ(x) ratio between the volume not occupied by the loops and total volume, the fans power and the conveyor speed.

Finally, a mechanical analysis, consisting of a tensile test, was performed on the samples taken from the coils produced in

the three different conditions.

The analysis was consistent with the thermal analysis: the samples produced in condition B showed a more homogeneous breaking load distribution to those in condition A, confirming that a more uniform cooling contributes to obtain a lower dispersion of the load values breaking; in C condition, due to the activation of two further fans with respect to condition B, a slight improvement in the homogeneity of the mechanical characteristics and an increase in their average value are noted.

Acknowledgments The authors would like to thank the University Politecnico di Milano – Lecco campus for the support given to carry out this work.

REFERENCES [1] Ishant J., Shaumik K., Satish K., Saurabh K., An approach to heat transfer analysis of wire loops over the Stelmor

conveyor to predict the microstructural and mechanical attributes of steel rods; 3:2016 [2] Chung-Jen Fang, Yi-Ying Lin, A novel temperature diagnostic system for Stelmor air-cooling of wire rods, China

steel technical report, no. 25, pp 66-72, 2012 [3] Jalil A. A., Gage C. H., Fournier K., Apparatus for cooling hot rolled steel rod, EP 0178799, 04:1986 [4] Lindermann A., Schmindt J., ACMOD-2D – A heat transfer model for the simulation of the cooling of the wire,

Journal of Materials Processing Technology, 2005 [5] Nicodemi W., Metallurgia principi generali, 2000 [6] Kazeminezhad M., Karimi Taheri A., The effect of controlled cooling after hot rolling on the mechanical properties

of a commercial high carbon steel wire rod, 04:2003 [7] Bowering RE, The microstructure and mechanical properties of rolled wire rods controlled cooled on a moving

conveyor, mechanical working and steel processing Gordon and Breach, 1968

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43

Industry news Pulizia in linea del filo metallico su impianti di trafilatura ad alta velocità: innovazione, ecologia e performance a cura di: G. Orlando Nei processi di trafilatura il filo metallico subisce una sequenza di passaggi forzati attraverso matrici (filiere), di diametro decrescente, che ne riducono progressivamente la sezione fino al valore desiderato. Per assicurare il passaggio attraverso le filiere, riducendo quanto più possibile l’attrito, è necessaria una lubrificazione, ottenuta tramite l’utilizzo di diverse sostanze chimiche: si passa da emulsioni acqua/olio per lubrificazione liquida, a stearati di sodio e/o calcio o polimeri per lubrificazione solida. Tali lubrificanti devono formare un film sottile, omogeneo e ben adeso al filo, ma devono poter essere rimossi al termine dei processi di riduzione di sezione se si desidera ottenere un filo superficialmente pulito e pronto per eventuali successivi trattamenti galvanici, termici o di rivestimento superficiale di vario genere. In questo articolo verrà analizzata una tecnica innovativa per la pulizia del filo, in linea con l’impianto di trafilatura, applicabile sia a monte del processo (pulizia/decapaggio della vergella) sia a valle (pulizia finale prebobinatura).

La tecnica in esame, basata su un processo elettrochimico, può essere integrata su linee già esistenti e va a sostituire le vasche chimiche o ad ultrasuoni di pulizia post-trafilatura, facendo uso di elettroliti a minor impatto ambientale rispetto ai tradizionali liquidi per sgrassaggio acido e alcalino.

G. Orlando Decapaggio-Passivazione Consulting, Viale Verdi 18, 41121 Modena R. Giovanardi, L. Trombi Università di Modena e Reggio Emilia, Dipartimento di Ingegneria ‘Enzo Ferrari’, Via Vivarelli 10, 41125 Modena

Il processo di pulizia elettrochimica L’impianto di pulizia elettrochimica è costituito da 4 stadi tra loro indipendenti e modulari, sia mono sia multifilo, per offrire la massima flessibilità ed efficacia: 1° stadio - trattamento elettrochimico contactless: in questo step avviene la pulizia vera e propria del filo, grazie ad un processo elettrochimico, diverso dai tradizionali sistemi elettrolitici; rispetto a questi ultimi, le potenze in gioco sono nettamente inferiori grazie all’innovativo sistema di distribuzione della corrente ed agli elettroliti ecologici sviluppati e messi a punto per ogni tipologia di lavorazione e di materiale. Attraverso l’applicazione di un’opportuna differenza di potenziale, si ha un’istantanea reazione elettrochimica che converte le sostanze organiche presenti sulla superficie agevolandone la dissoluzione nell’elettrolita.

44

Inoltre risulta particolarmente efficace su qualsiasi tipologia di profilo: è possibile trattare con egual risultato fili tondi così come profili di diversa sezione.

2° stadio – risciacquo ad alta pressione in ricircolo: in questo stadio il sottile velo di elettrolita rimasto sul filo viene rimosso tramite una serie di ugelli ad alta pressione e bassa portata.

Lavorando in ricircolo l’elettrolita, seppur ecologico, viene asportato senza diventare refluo diretto.

3° stadio – risciacquo ad alta pressione a circuito aperto: in questo stadio il filo, già pulito dal precedente, viene ulteriormente sciacquato da un getto ad alta pressione e bassissima portata, garantendo un refluo minimo e di facile gestione, rispetto alle centinaia di litri di refluo inquinato degli impianti di pulizia tradizionali, basati su acidi forti o La Metallurgia Italiana - n. 6 2018

Attualità industriale soda caustica.

4° stadio – asciugatura ad aria (calda) in controcorrente: in questo stadio si effettua l’asciugatura del filo, per garantire l’assenza di umidità superficiale in uscita dal trattamento.

I sistemi attualmente sul mercato possono operare fino a velocità di 15 m/s e fanno uso di elettroliti non pericolosi, sia dal punto di vista dell’operatore che di emissioni e smaltimento.

Fig. 1 - aspetto di filo inox per saldatura Ø1.2 mm prima e dopo il processo di pulizia elettrochimica

Efficacia del processo Per valutare l’efficacia del processo sono stati analizzati alcuni spezzoni di filo in acciaio inox (AISI308), raccolti prima e dopo il processo di pulizia elettrochimica, mediante microscopia elettronica a scansione (SEM) abbinata a spettrometria per dispersione di energia (EDS). In Figura 2 sono mostrate le micrografie acquisite sulla superficie del filo prima (immagini in alto) e dopo (immagini in basso) il trattamento

La Metallurgia Italiana - n. 6 2018

di pulizia elettrochimica; il detector BSE utilizzato permette di mettere in contrasto le zone del materiale con elementi chimici a basso peso atomico (scure) rispetto alle zone del materiale con elementi chimici ad alto peso atomico (Fe, Cr e Ni presenti nell’acciaio, zone chiare). In questo modo è possibile identificare i lubrificanti ancora presenti sul filo come accumuli di materiale scuro (vedi immagini in alto in Figura 2).

45

Industry news

Fig. 2 - micrografie SEM acquisite su filo prima (immagini in alto) e dopo (immagini in basso) il trattamento di pulizia elettrochimica; detector BSE, ingrandimento 1000x.

Osservando ad ingrandimenti maggiori una zona caratterizzata da accumulo di prodotti scuri del filo prima della pulizia (Figura 3) è possibile notare come le sostanze applicate come lubrificanti solidi si siano accumulate, durante il processo di trafilatura, nelle cavità superficiali del materiale.

46

Eseguendo unâ&#x20AC;&#x2122;analisi EDS puntuale sulle sostanze scure di Figura 3 sono stati rilevati elevati tenori di carbonio e sodio, costituenti dei tipici lubrificanti solidi quali stearato di sodio.

La Metallurgia Italiana - n. 6 2018

Attualità industriale

Fig. 3 - micrografia SEM acquisita su filo prima del trattamento di pulizia elettrochimica, con risultati dell’analisi EDS relativi al punto indicato dalla freccia rossa; detector BSE, ingrandimento 8000x.

E’ possibile concludere che il trattamento di pulizia elettrochimica rappresenta una valida soluzione per la rimozione dei lubrificanti applicati nei processi di trafilatura, consentendo un’efficace rimozione delle sostanze residue e garantendo l’impiego di elettroliti ecologici e non pericolosi per l’operatore e per l’ambiente, con notevoli vantaggi in termini di processo, di stoccaggio e di smaltimento; infine il

La Metallurgia Italiana - n. 6 2018

processo può essere implementato per consentire l’applicazione di ulteriori trattamenti superficiali al filo (ad esempio la deposizione di rame che offre, rispetto ai tradizionali processi chimici ed elettrolitici, una migliore adesione e maggiore lucentezza del metallo applicato).

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Industry news Continuous annealing by resistance heating furnace of stainless steels wire drawn edited by: R. Nemfardi, R. Bedini, G. Zucchelli, D. Bonora - Eure Inox, Italy, C. Mapelli, S. Barella, A. Gruttadauria, D. Mombelli - Politecnico di Milano, Italy

Introduction Cold working is an operation often performed on metals.

Wire drawing belongs to this kind of processes and, during this operation the materials undergo a hardening work and the microstructure experiences significant changes. This is due to the deformation energy retained by the metal in the form of defects (i.e. vacancies, dislocation).

This change in microstructure leads to transformations in physical and mechanical properties of the material. In particular, the mechanical resistance increases but the deformability decreases. In order to perform further cold working process, an annealing treatment is necessary to avoid the wire break [1].

The annealing promotes the recrystallization phenomenon.

Recrystallization will take place if the diffusion phenomena are promoted, for instance at high temperature the activation energy is enough to trigger this phenomenon [3].

Recrystallization starts with the material recovery in which

annihilation and rearrangement of defects take place. After that the nucleation and growth of free defects grains begins (recrystallization) [4, 5]. In the first stage of the process only physical properties, i.e resistivity, and residual stresses have been recovered, during the second stage the mechanical properties, i.e. hardness, decrease and the ductility have improved. However, after recrystallization is completed much attention must be payed to avoid the metals grain growth.

This fact increases the grain size and consequently gives rise to an excessive mechanical resistance decrease [6].

In the industrial practice two main processes are available to perform annealing: batch and continuous [7]. In the former, the wire is wound and in the latter the wire is unwound. For this reason, in batch annealing the process can last one or more days while, due to the higher heating and cooling rates, in the continuous annealing the process lasts some minutes. In Figure 1, an example of these thermal are reported.

Fig. 1 - Thermal cycles of batch annealing (a) and continuous annealing (b) suitable for a eutectic steel [2].

48

La Metallurgia Italiana - n. 6 2018

AttualitĂ industriale These two processes lead to different microstructural features, and for this reason the processes must be studied in detail to obtain the right combination of parameters to optimize the grain size and the final microstructure.

In this work the continuous annealing of stainless steels wire drawn has been studied. In particular, the aim of this work is to understand the effect of the continuous heat treatment on the material grain size and the consequent drawability of the wire.

Experimental Eure Inox continuous annealing is performed in different steps. In the first steps the stainless steel is degreased, then the cold drawn wire is annealed in the continuous resistance furnace. At the end of the furnace the air cooling guarantees a fine microstructure and finally the coating process (using salt) facilitates the further drawing operation, avoiding the appearance of defects during the reduction of section. The thermal cycle during the whole process is reported in Figure 2.

Fig. 2 - Sketch of the thermal cycle during the Eure Inox continuous annealing.

The analyzed stainless steels are 1.4567 (AISI 304Cu) and 1.4016 (AISI 430), the chemical

compositions are reported in Table 1.

Tab. 1 - Analyzed steel chemical composition (wt.%)

Cmax

Mnmax

Pmax

Smax

Simax

Cr

Ni

Mo

Others

c1.4567

0,04

2,00

0,045

0,03

1,00

17-19

8,5-10,5

-

N<0,11 Cu=3-4

1.4016

0,08

1,00

0,04

0,03

1,00

16-18

-

-

-

These different steels undergo different processes due to the different mechanical behavior that turns out in different work hardening.

The grain size of these steels was measured after different steps of the process. The ASTM E112 standard was used to determine the grain size.

The chemical etching was performed using oxalic acid at 10%.

Results and discussion In Figure 3 the microstructure of a wiredrawn and annealed wire of 1.4567 steel is reported. This wire in wiredrawn from 5,50 to 5 mm in diameter and then annealed in the La Metallurgia Italiana - n. 6 2018

continuous furnace (speed 3,5 m/min) at T/Tm 0,8. The grain size of the work hardened material is about GN 4 and many mechanical twins can be detected. After the annealing, the grain size increases (GN 1) and this points out the goodness of the annealing process. Moreover, the twins disappeared testifying the material recrystallization. In addiction, some hardness tests were performed on the materials in the two different conditions: the wiredrawn material shows 93HRB instead the annealed material is softer, and the hardness decreases to 80HRB. The wire feed rate is slow and, consequently, the residence time in the furnace is high, allowing the material recrystallization.

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Industry news

Fig. 3 - 1.4567 steel grades: wire drawing from Ă&#x2DC;5,50 to Ă&#x2DC;5,00 mm (a) and soaked in continuous furnace at T/Tm=0,8 v=3,5 m/min (b) The same material was subsequently drawn at 3,78 mm in diameter and then annealed and skinpassed.

The annealing temperature was T/Tm 0,80 and the annea-

ling speed was 9 m/min. In figure 4 the microstructure and the grain size near the surface and the core are reported.

Fig. 4 - 1.4567 steel grades annealed at T/Tm>0.80 (9 m/min) and skinpassed to Ă&#x2DC;3,70 mm: (a) surface, (b) core.

As the wire feed rate increases, the grain size of the annealed materials decreases. In particular at the core the recrystallization is reduced and the steel is not completely restored.

This suggest a strict control on the annealing speed in relation to the final properties required.

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Finally, the continuos annealing effect was studied on a ferritic grade. As reported in Figure 5, the carbides distribution is uniform both at the sample core and at the surface. Also this high wire speed (19m/min) allows to obtain a homogeneous microstructure

La Metallurgia Italiana - n. 6 2018

Attualità industriale

Fig. 5 - 1.4016 steel grades annealed at T/Tm=0,65 (19 m/min) Ø2.90 mm annealed and skinpassed to Ø2.50 mm: (a) surface, (b) core Conclusions In this paper the continuous annealing of stainless steel has been investigated. During the continuous annealing the wire speed in the furnace influences the final grain size and consequently the final mechanical properties and the deformation. After a preliminary analysis, having taken into account only energetic parameters, the use of electrical furnace could prove to be disadvantageous; in fact the elec-

tricity costs are ten times higher than the natural gas ones.

But a more in-depth analysis related to the metallurgical features of the final products better shows a uniform microstructure and homogeneous mechanical properties: the hardness set point is reached with an accuracy of 2.8%.

In conclusion, a better temperature control and homogeneity in the resistance furnace allow to obtain very high-quality products to satisfy the market increasing demands.

REFERENCES [1] F.C. Campbell, Elements of Metallurgy and Engineering Alloys, ASM International, Ohio, 2008 [2] G.E. Totten, Steel Heat Treatment, metallurgy and technologies, Taylor and Francis, Portland, 2006 [3] Amandeep Singh Wadhwa, Er. Harvinder Singh Dhaliwal, A Textbook of Engineering Material and Metallurgy,

Firewall Media, 2008, p. 367 [4] F.J. Humphreys and M. Hatherly, Recrystallization and Related Annealing Phenomena (Second

Edition), Elsevier, Oxford, 2004, Pages 169-267 [5] Eric J. Mittemeijer, Fundamentals of Materials Science: The Microstructure–Property Relationship Using Metals

as Model Systems, Springer Science & Business Media, 2010, pages 463-483 [6] Lorraine F. Francis, Materials Processing: A Unified Approach to Processing of Metals, Ceramics and Polymers,

Academic Press, 2015, p. 267 [7] D. T. Llewellyn, Steels: Metallurgy and Applications, Elsevier, 2013, pages 19-23

La Metallurgia Italiana - n. 6 2018

51

Experts’ corner Intervista a Gianluca Roda “Nel distretto lecchese delle trafilerie negli anni ‘50, la prima idea vincente di mio padre fu di installare un impianto di laminazione a caldo, introducendo sul mercato italiano gli acciai legati al piombo. La seconda idea che ha consentito alla nostra realtà di espandersi sui mercati internazionali, fu l’avvio di una peculiare rete commerciale, un modello di efficienza distributiva che soprattutto ai suoi esordi non aveva eguali, basato sullo sviluppo diretto all’estero di filiali commerciali”.

C

osì esordisce Gianluca Roda, figlio del fondatore Giuseppe Roda e presidente del gruppo Rodacciai divenuto recentemente Rodasteel Corporation.

Realtà che nel 2016 ha compiuto 60 anni e alla quale è stata intitolata la via che porta alla sede centrale di Bosisio Parini. L’impianto di laminazione, invece, dalla vecchia sede di Pusiano si è spostato a Sirone, mentre un altro storico polo produttivo - Olarra Aceros Inoxidables, acciaieria che conta 450 addetti e produce circa 90mila tonnellate di acciaio inox di qualità - è situato in Spagna.

Nel 2017 il gruppo ha venduto oltre 345 mila tonnellate di acciaio e fatturato circa 530 milioni di euro: “Realizziamo 6 famiglie di acciai differenti coprendo tutte le esigenze del mercato e sul finito a freddo siamo i più forti d’Europa. Il nostro giro d’affari è generato per il 53% dal mercato interno italiano e per il 47% dall’estero, il che può sorprendere, dato che in molti, specie negli ultimi anni, hanno puntato sui mercati stranieri. Noi

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invece abbiamo creduto nel Bel Paese, sviluppando ancora di più il fatturato in Italia”.

Tradizionali punti di forza di Rodacciai sono il marchio trainante perché riconosciuto dai mercati, la diversificazione della gamma produttiva e, come accennato, la rete distributiva capillare che consente di fornire un tempestivo servizio al cliente. Inoltre il laminatoio consente la lavorazione degli acciai necessari alla successiva fase del processo produttivo, realizzando acciai in formati unici sul mercato, nel segno di un’ampia flessibilità produttiva, e rendendo più veloce l’evasione degli ordini, oltre a garantire l’eccellenza qualitativa. Questo è Rodacciai oggi.

Ma, facendo un passo indietro, dopo la scomparsa del fondatore Giuseppe Roda nel 2007, la seconda generazione rappresentata da Gianluca Roda, negli anni a ridosso della crisi ha dovuto affrontare un processo di “rigenerazione” e riorganizzazione aziendale molto profondo, a tratti traumatico per le risorse che lavo-

ravano in azienda da decenni. Processo che si può ritenere oggi giunto ad un definitivo compimento.

Racconta il presidente: “In quegli anni ho dovuto affrontare un mercato totalmente mutato, in cui le regole che conoscevamo nell’ambito dell’acciaio erano saltate. Occorreva mutare sia l’organizzazione interna, sia l’aspetto gestionale.

Operazione a tratti dolorosa, soprattutto per alcuni dipendenti che si sono trovati il mondo rovesciato, all’improvviso”. Oltre a inserire in azienda i principi della Toyota Academy e della lean production e a lavorare sull’evoluzione culturale del team per effettuare cambiamenti proficui sulle tre macro aree della supply chain, operations e sales, alla fine del 2014 l’impresa ha ultimato il processo degli esodi agevolati per 60 risorse della vecchia guardia, rimpiazzandole con giovani talenti, formati successivamente e gradatamente in seno alla Rodacciai, nell’academy aziendale.

“Oggi i dipendenti sono 600 tra Bosisio Parini e Sirone, ai quali dedichiamo 140

La Metallurgia Italiana - n. 6 2018

Scenari giornate di formazione su base annua, sia su argomenti tecnici (ambientali e di sicurezza), sia su tematiche gestionali e organizzative. Abbiamo scelto di cambiare per restare competitivi, coinvolgendo tutte le risorse nelle attività di miglioramento dei principali processi aziendali, anche attraverso l’adozione di evoluti applicativi IT”, spiega Roda.

Il gruppo, che sin dal 1990 vanta la certificazione di sistema ISO 9001 seguito da una serie di ulteriori certificazioni di prodotto e specifiche per l’impiego in determinati mercati - ha imboccato la

La Metallurgia Italiana - n. 6 2018

via di uno sviluppo basato su un’attenta politica di contenimento dei costi, sull’analisi del dato e il puntuale monitoraggio delle performance aziendali, come pure sull’esame delle fluttuazioni rispetto alle attese. “Rodacciai, dopo 60 anni, è giovane ed è pronta a conquistare nuovi orizzonti. Grazie a questa considerevole operazione di rinnovamento, oggi l’impresa vanta prospettive di crescita come nel suo passato migliore”.

Con la visione tipica del capitano d’industria, Gianluca Roda ha concluso un cambio generazionale sopraggiunto in

un periodo critico, quello della crisi del 2008/09, impostando il gruppo per l’avvenire e dando continuità a un’impresa storica. “La via intitolata a mio padre l’anno scorso indica proprio la volontà della mia famiglia di perseguire questo percorso di sfide e nuovi obiettivi”. Un cammino già intrapreso dalla terza generazione: i figli del presidente, Andrea e Giorgio che si occupano rispettivamente delle aree commerciale e operations - sono già inseriti in azienda. Dunque... avanti tutta!

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Experts’ corner Materie prime, metalli e acciaio attualità e prospettive 2018 a cura di: Achille Fornasini Partner & Chief Analyst siderweb

Achille Fornasini Partner & Chief Analyst siderweb. Responsabile del Laboratorio di Dinamiche dei Sistemi e dei Mercati finanziari presso il Dipartimento di Economia e Management dell’Università degli studi di Brescia, dove insegna Analisi Tecnica dei Mercati finanziari.

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a rinnovata forza del dollaro, che dai livelli dello scorso febbraio si è apprezzato di oltre il 6% sull’euro, sta rallentando i rialzi dei prezzi di tutte le materie prime quotate in dollari. Si consideri al riguardo la figura 1 comprendente, distinte per colore e aggiornate a fine aprile 2018, le medie mensili di quattro indici generali

54

rappresentanti altrettanti panieri di materie prime basilari elaborati dal Fondo Monetario Internazionale in base a dati forniti dalla Banca Mondiale. Come evidenziato nel riquadro rosso, nel 2016 si individua l’anno della svolta sia dell’insieme energetico (petrolio, gas naturale e carbone), sia dei metalli ferrosi e non ferrosi. Sebbene i valori correnti degli

indici siano ancora lontani dai rispettivi massimi storici, raggiunti rispettivamente nel 2008 e nel 2011, dal mese di gennaio 2016 le due dinamiche si sono orientate al rialzo e, dopo un biennio di riscossa impetuosa, nei primi cinque mesi del 2018 si nota un loro rallentamento.

La Metallurgia Italiana - n. 6 2018

Scenari Del tutto diverso l’andamento degli altri due indici, tendenti a fluttuare lateralmente: a spiegare la dinamica delle due coppie di valori sono i diversi equilibri sottesi alle classiche forze della domanda e dell’offerta riferite ai relativi mercati. Mentre i raccolti a livello mondiale di beni alimentari (mais, frumento, ecc.) e agro-industriali (cotone, gomma, ecc.) si sono finora dimostrati sufficienti a far fronte alle rispettive richieste, l’indice

energetico ha risentito soprattutto della forzosa contrazione dell’offerta organizzata dall’Opec al fine di sostenere i prezzi del greggio. Il comportamento dell’indice dei metalli esprime invece le ricadute di una domanda di materiali basilari in continuo aumento, frutto della solida ripresa economica a livello planetario, a fronte di un’offerta ridottasi a causa degli effetti dei mancati investimenti minerari conseguenti al tracollo

dei prezzi verificatosi nel quinquennio 2011-2015.

L’evidenza grafica e i dati percentuali confermano la persistenza di una domanda di metalli industriali che l’offerta non riesce a soddisfare: lo prova lo stato degli stock presenti complessivamente nei magazzini ufficiali della borsa londinese, che dall’inizio del 2016 a tutto

il mese di maggio 2018 consolidano un calo del 48,8%. Un esito che attesta il diffuso interesse al ritiro dei materiali fisici sia a pronti che a termine.

Nel biennio 2016-2017 lo zinco guida il rialzo la pattuglia dei metalli industriali, che nel primi cinque mesi di quest’anno

tende invece a frenare il recupero dai minimi assoluti con l’unica eccezione del prezzo del nickel che, come si vedrà nel prosieguo, si muove in controtendenza, trainato al rialzo da una domanda aggiuntiva alla tradizionale destinazione verso le produzioni inox.

Metalli non ferrosi e ferrosi Focalizzando l’analisi sui metalli, si consideri dapprima la figura 2, che illustra l’andamento della curva che sintetizza la media settimanale dei prezzi dei sei principali non ferrosi quotati al London Metal Exchange dei quali la tabella 1 sintetizza le performance.

2011-2015

2016

2017

2018 (31 maggio)

Rame (US$/ton)

-51,7%

+16,9%

+30,1%

-4,6%

Alluminio (US$/ton)

-38,7%

+13,6%

+30,8%

+1,9%

Nickel (US$/ton)

-65,3%

+15,5%

+22,5%

+23,9%

Zinco (US$/ton)

-34,2%

+60,2%

+29,1%

-6,3%

Piombo (US$/ton)

-30,3%

+10,1%

+25,7%

-1,9%

Stagno (US$/ton)

-44,9%

+44,5%

-5,8%

+4,6%

La Metallurgia Italiana - n. 6 2018

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Experts’ corner Filiere dell’acciaio Passando alla siderurgia, si osservi la figura 3 dedicata all’evoluzione dei prezzi

medi settimanali del minerale di ferro (curva marrone riferita alla scala di destra) e del carbone da coke (curva nera

riferita alla scala di sinistra).

Dopo l’ininterrotta discesa dei prezzi culminata a fine 2015, le due curve risalgono la china in modo diverso: mentre i prezzi del minerale di ferro australiano per consegna al porto cinese di Qingdao si sviluppano al rialzo in modo abbastanza equilibrato fino al mese di marzo 2017, i valori del coking coal, nello stesso periodo, esprimono un’altissima volatilità. La prima anomalia dinamica del carbone è culminata a inizio dicembre 2016, quando si esaurì la corsa all’accaparramento innescata da ingiustificati timori di un deficit d’offerta; la seconda

fibrillazione risale invece ad un anno orsono, quando le quotazioni si impennarono a causa dei blocchi ferroviari conseguenti agli uragani abbattutisi sul Nordest australiano, che complicavano il trasporto di carbone dal Queensland ai porti di esportazione verso la Cina.

Esauritisi i due strappi del carbone, dal mese di giugno 2017 i due movimenti si mostrano orientati moderatamente al rialzo in quasi perfetta sincronia ciclica con le quotazioni del minerale a delineare la direzione. Le performance dei due elementi basilari della filiera dell’acciaio

al carbonio sono sintetizzate nella tabella 2, che evidenzia come l’anno 2017 sia connotato da una variabilità decisamente minore dell’anno precedente e i primi cinque mesi del 2018 si chiudano in negativo.

Le prospettive delineate dagli indicatori posti a piè di grafico segnalano la persistenza dell’arretramento dei prezzi del minerale, che farà da zavorra anche al carbone da coke.

2011-2015

2016

2017

2018 (31 maggio)

Minerale di ferro (US$/ton)

-75,1%

+87,4%

-6,6%

-12,7%

Carbone metallurgico (US$/ton)

-67,8%

+153,7%

-0,9%

-6,9%

A completamento dell’analisi relativa alla filiera del ciclo integrale dell’acciaio, proponiamo la figura 4, che illustra l’an-

56

damento dei prezzi medi settimanali dei coils a caldo rilevati quotidianamente in Cina e in Turchia: si noti innanzitutto

come la curva dei valori cinesi anticipi regolarmente gli analoghi movimenti definiti dalle quotazioni turche.

La Metallurgia Italiana - n. 6 2018

Scenari

Dopo le due potenti ondate rialziste del 2016, seguono un 2017 connotato da dinamiche ascendenti meno violente e i primi cinque mesi del 2018 in fase di-

scordante: mentre i prezzi cinesi tendono a muoversi lateralmente tra i massimi e i minimi di marzo, i valori europei flettono con decisione volgendosi al ribasso

(tabella 3). Gli indicatori tecnici prospettano l’arresto del trend ascendente iniziato nel 2016 e l’avvio di un generale ripiegamento.

2011-2015

2016

2017

2018 (31 maggio)

Coils a caldo – FOB Shanghai (US$/ton)

-59,0%

+87,7%

+14,4%

+3,1%

Coils a caldo – FOB Black Sea (US$/ton)

-58,8%

+94,1%

+13,1%

-2,7%

Rottame e prodotti lunghi L’analisi dei prezzi in campo elettrosiderurgico si avvale della figura 5 che propone le dinamiche del rottame quo-

La Metallurgia Italiana - n. 6 2018

tato in Turchia (curva azzurra riferita alla scala di destra) e della media dei prezzi di quattro categorie di rottame - demolizioni, frantumato, torniture e lamierino

- quotate in Italia rilevate da Siderweb (curva nera riferita alla scala di sinistra).

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Experts’ corner Si noti l’alta concordanza evolutiva delle due curve, le cui fasi cicliche, sia ascendenti che declinanti, sono regolarmente anticipate dai movimenti espressi dai prezzi rilevati in Turchia. Dagli inizi del 2016 le due dinamiche si muovono fluttuando al rialzo fino al mese di gennaio 2018, quando si osserva una correzione

un andamento sostanzialmente laterale di entrambe le curve, connotate da una progressiva perdita di volatilità e di direzionalità: con il conforto degli indicatori tecnici si profila la persistenza del consolidamento destinato a rallentare ulteriormente il trend rialzista di fondo.

2011-2015

2016

2017

2018 (31 maggio)

Rottame – FOB Turchia (€UR/ton)

-57,5%

+72,6%

+18,6%

-4,3%

Rottame – Media nazionale (€UR/ton)

-48,3%

+29,5%

+29,3%

+0,7%

La tabella 5 è dedicata alle performance dei principali prodotti lunghi, i cui prezzi sono rilevati settimanalmente da Siderweb: dopo i ribassi generalizzati

del quinquennio 2011-2015, i due anni successivi sono caratterizzati da rialzi di entità omogenea, con l’eccezione dei laminati mercantili che, durante l’intero

periodo esaminato, evidenziano una variabilità sensibilmente inferiore a quella degli altri prodotti da forno elettrico.

2011-2015

2016

2017

2018 (31 maggio)

Tondo per cemento armato (€UR/ton)

-34,1%

+16,5%

+31,0%

-8,5%

Vergella da trafila (€UR/ton)

-36,8%

+24,0%

+23,8%

+3,6%

Vergella da rete (€UR/ton)

-35,3%

+24,4%

+25,0%

+3,2%

Travi (€UR/ton)

-24,6%

+9,0%

+17,3%

-0,5%

Laminati mercantili (€UR/ton)

-15,8%

+1,7%

+18,0%

-0,5%

Al rialzo dei prezzi delle produzioni tipiche dell’elettrosiderurgia hanno concorso non solo gli aumenti del rottame e dei costi energetici, ma anche i forti rialzi che hanno investito le quotazioni degli elementi di lega indispensabili per conferire caratteristiche specifiche agli acciai (tabella 6). Nel biennio 20162017, infatti, si archiviano performance straordinarie dei prezzi delle ferroleghe, le cui prospettive appaiono ora meno

58

e l’avvio di un moto laterale dei prezzi turchi, seguito a ruota dalla media dei prezzi nazionali. Le performance racchiuse nella tabella 4 evidenziano la maggiore variabilità dei prezzi turchi fino a tutto il 2016, dopodiché si assiste ad una normalizzazione degli esiti. I primi cinque mesi del 2018 evidenziano

pimpanti del recente passato: dopo i forti aumenti ci si attendono blande derive ribassiste nel quadro di un assestamento generalizzato delle quotazioni.

Nel 2017 hanno inoltre preso corpo anomali rincari sia degli elettrodi in grafite per i forni ad arco, sia dei materiali refrattari a causa della chiusura di molti impianti cinesi conseguenti a denunce di inquinamento ambientale. Ancorché l’emergenza provocata dall’improvvi-

sa forte contrazione dell’offerta di tali elementi sia parzialmente rientrata, il riposizionamento al rialzo dei prezzi appare ormai un dato di fatto. In definitiva, in funzione dell’orientamento assunto dalle componenti di costo tipiche della produzione elettrosiderurgica, i prossimi mesi saranno caratterizzati da prezzi stabilmente elevati, sebbene in moderata flessione, di tutte le produzioni lunghe.

La Metallurgia Italiana - n. 6 2018

Scenari 2016

2017

2018 (31 maggio)

Ferro-manganese (US$/ton)

+105,3%

-14,3%

-4,5%

Ferro-cromo (US$/ton)

+6,9%

+25,9%

+4,7%

Ferro-silicio (US$/ton)

+18,3%

+50,0%

-9,1%

Ferro-tungsteno (US$/ton)

+21,6%

+42,0%

+7,4%

Ferro-titanio (US$/ton)

-12,2%

+72,3%

-5,3%

Ferro-molibdeno (US$/ton)

+33,3%

+45,5%

+12,7%

Ferro-vanadio (US$/ton)

+77,8%

+87,5%

+50,0%

Il comparto inox Concludiamo la nostra analisi, proponendo la figura 6 dedicata all’andamento delle medie settimanali dei prezzi del

nickel quotati al London Metal Exchange (curva nera riferita alla scala di destra) a confronto con la dinamica dei prezzi del rottame inox (più precisamente i co-

siddetti “cascami nuovi”) rilevati settimanalmente da Siderweb (curva azzurra riferita alla scala di sinistra).

Come si può osservare, le due evoluzioni sono abbastanza concordanti con la dinamica del nickel che sembra orientare sistematicamente quella del rottame.

Dopo il lustro ribassista si nota non solo la lenta rimonta del non ferroso, che trascina al rialzo il rottame, ma anche l’ac-

celerazione rialzista dei prezzi sospinta dal continuo calo delle scorte ufficiali: una condizione che lascia presagire la continuazione della fase ascendente dei prezzi. L’unico fattore in grado di rallentarne la marcia è il contestuale rafforzamento del biglietto verde. L’effetto di

tale dinamica, unitamente alle evoluzioni del Cromo e del Molibdeno, continuerà a ripercuotersi sulle tipiche produzioni inox rappresentate nella figura 7, le cui performance sono precisate nella tabella 7.

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Experts’ corner

60

2011-2015

2016

2017

2018 (31 maggio)

Lamiera a freddo Serie 304 (€UR/ton)

-26,1%

+13,9%

+0,3%

=

Lamiera a freddo Serie 316 (€UR/ton)

-28,6%

+9,5%

+0,6%

+2,1%

Lamiera a freddo Serie 430 (€UR/ton)

-8,7%

+7,0%

+2,1%

-1,5%

La Metallurgia Italiana - n. 6 2018

Scenari Trafilerie: la fotografia del settore italiano a cura di: Stefano Ferrari Responsabile Ufficio Studi siderweb

Stefano Ferrari Stefano Ferrari, nato nel 1980, dopo la laurea in Consumi, Distribuzione Commerciale e Comunicazione d’Impresa ottenuta all’Università IULM di Milano, nel 2005 inizia la propria collaborazione con Siderweb Spa. Dopo cinque anni come giornalista, nel 2009 diventa direttore responsabile di Siderweb, la community dell’acciaio italiana. Nel 2013 e 2015 si occupa dell’ufficio stampa di Made in Steel, la principale manifestazione fieristica della filiera dell’acciaio dell’Europa meridionale, mentre da gennaio 2014 è impiegato nell’Ufficio Studi siderweb.

Il comparto della trafilatura in Italia conta circa 200 aziende, che impiegano poco più di 5.000 lavoratori, generando un fatturato di circa 2,2 miliardi di euro nel 2016 (ultimi dati disponibili), in leggero calo rispetto al 2015. Il fat-

turato per dipendente è pari a 420.000 euro. L’export del settore è pari a circa il 27,3% del fatturato, ma il dato sarebbe ancora più elevato se si riuscisse a quantificare il valore del riexport: molte aziende infatti vendono prodotti trafilati

ad industrie italiane che li trasformano in beni che sono successivamente venduti sui mercati esteri. Il valore aggiunto del comparto è pari a poco più del 21% del fatturato, mentre il valore aggiunto per dipendente sfiora i 90.000 euro.

Le imprese piccole dominano il mercato Prendendo in considerazione la dimensione media delle imprese, notiamo che il 41% delle trafilerie italiane conta meno di 10 dipendenti, il 22% tra 10 e

19, il 19% tra 20 e 49, mentre solo il 5% ha un numero di occupati superiore a 100. Se applicassimo la definizione europea di piccole imprese (ovvero quelle fino a 49 dipendenti), esse sono l’82% del totale e le PMI, ovvero le imprese

fino a 250 dipendenti, sono il 99% del totale. Se dividiamo il numero di dipendenti per il numero di aziende otteniamo 28,5 dipendenti medi per azienda, un numero molto contenuto.

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Experts’ corner

Lombardia capitale Dal punto di vista geografico, oltre il 60% delle trafilerie nazionali è sito in Lombardia, la regione che vanta anche circa il 70% degli impiegati nel comparto. Segue il Veneto, con circa il 10% delle aziende e degli occupati, poi Emi-

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lia Romagna, Piemonte e Campania. La maggior parte delle aziende è sita al nord. Fa eccezione nella top 5 solo la Campania.

Entrando maggiormente nel dettaglio, si rileva che Lecco è la vera a propria capitale italiana della trafileria: nella provin-

cia hanno sede circa un quinto del totale delle aziende italiane del comparto ed un quarto degli occupati. Le altre province nelle quali la trafilatura è presente in modo sostanziale sono Milano (13% delle aziende, 15% degli occupati), Brescia (12% e 14%) e Bergamo.

La Metallurgia Italiana - n. 6 2018

Scenari Un settore solido Prendendo in considerazione le performance economico-finanziarie del settore delle trafilerie in Italia (i dati sono estratti dallo studio di siderweb Bilanci d’Acciaio e si riferiscono all’esercizio 2016), si nota che il 72% delle aziende analizzate ha un fatturato compreso tra 0 e 25 milioni di euro, il 20% tra i 25 ed i 50 milioni di euro e l’8% più di 50 milioni di euro. Le imprese di maggiori dimensioni, pur essendo numericamente esigue, generano il 39,5% del fatturato totale del comparto. Nell’ultimo triennio queste società sono cresciute più della media. Il valore aggiunto creato dalle grandi imprese, però, è percentualmente inferiore, fermandosi al 34,9% (contro il 39,5% del fatturato). In questo particolare frangente il comparto leader è quello delle medie imprese con il 35,1% (contro il 32% del fatturato). L’ebitda, inoltre, è ancora inferiore per le grandi imprese, pari a solo il 33% del totale.

Anche nell’utile le protagoniste sono le medie imprese, con un 43% del totale, in aumento rispetto al 2014.

Passando dal conto economico allo stato patrimoniale, si nota che, in termini di solidità, la situazione è in termini generali discreta, anche se le grandi imprese fanno registrare i valori più elevati per il rapporto di indebitamento complessivo ed il rapporto di indebitamento finanziario. Per le imprese medio piccole, invece, i rapporti di indebitamento sono inferiori e l’evoluzione vede un miglioramento dei valori tra il 2014 ed il 2016.

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Mercati: il commercio estero di vergella, barre e trafilati Da importatore netto ad esportatore netto. Questo è quanto è avvenuto nel comparto italiano della vergella, uno dei prodotti maggiormente impiegati dalle trafilerie, dove si notiamo due diversi trend tra il 2008 ed il 2016. Mentre per la vergella in acciaio inossidabile ci sono state variazioni di poco conto, che hanno mantenuto il Paese importatore netto di materiale per circa 30-40.000 tonnellate annue, per la vergella in acciaio al carbonio l’Italia è passata da importatore netto per circa 250-300.000 tonnellate annue nel quadriennio 2008-2011 ad esportatore netto del prodotto, fino ad un massimo di +225.000 tonnellate nel 2016. Per quanto concerne la vergella di acciai legati, la dipendenza dell’Italia dell’estero è scesa in modo costante, nonostante alcune oscillazioni, ed oggi è di circa 150.000-200.000 tonnellate annue.

Per quanto concerne le barre, l’importexport italiano si sta spostando in maniera lenta ma progressiva verso la maggiore qualità e specializzazione: le esportazioni nette di barre in acciaio al carbonio sono scese da 900.000 a 700.000 tonnellate tra il 2008 ed il 2016, mentre quelle di barre in acciaio inox sono salite da 146.000 a 170.00 tonnellate e quelle di barre in acciaio speciali a 80.000 tonnellate.

Il prodotto delle trafilerie, ovvero i trafilati, invece mostrano una spiccata tendenza all’export dell’Italia. In termine

di valore economico, le importazioni di prodotti trafilati in Italia sono strutturalmente più basse delle esportazioni di circa 200 milioni di euro annui, un valore più o meno costante dal 2011 ad oggi. Dal punto di vista dei volumi, invece, si nota una netta progressione dell’export italiano, che è passato dalle circa 300.000 tonnellate del 2009 ad oltre 500.000 tonnellate nel 2016, con un processo di crescita pressoché continuo e costante. Per quanto riguarda le importazioni, il dato è sostanzialmente stabile e si attesta tra le 150.000 e le 200.000 tonnellate annue.

Rimanendo sulle importazioni, la Cina ha guadagnato via via terreno nel corso degli anni, risultando il maggior fornitore per i clienti italiani nel 2016 con il 16% circa dei volumi, seguita dalla Germania (13%), dall’Austria (11%), dalla Repubblica Ceca (10%) e dalla Spagna (7%). Sul versante dell’export, invece, i prodotti trafilati italiani trovano mercato soprattutto in Europa con la Svizzera, nazione che si trova ai confini delle province italiane dove c’è il maggior numero di trafilerie, che è il maggior cliente delle trafilerie italiane con circa il 19% dei volumi. Segue la Germania con il 18%, la Francia con il 13% e l’Austria con il 6%.

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Experts’ corner

Un settore vivo ma con qualche criticità da risolvere Concludendo e riassumendo quanto visto, si rileva che il comparto italiano della trafila vede una presenza numerosa di imprese, che però mediamente sono piccole e concentrate in pochi distretti nel nord del Paese, in particolare in Lombar-

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dia. Le esportazioni di prodotti trafilati sono elevate ed in crescita, risultando superiori alle importazioni, ma sono per prodotti dal valore unitario in calo ed inferiore a quello delle importazioni. Sul versante della fornitura, l’Italia è esportatrice netta sia di vergella sia di barre, ma con una dipendenza dall’estero per i

prodotti a più elevata qualità. Sarà quella della qualità quindi la direzione nella quale il comparto dovrà lavorare con maggiore impegno nei prossimi anni, al fine di proseguire la strada dello sviluppo imboccata negli scorsi anni.

La Metallurgia Italiana - n. 6 2018

Aim news Calendario degli eventi internazionali International events calendar

Trafilatura QUOTE SOCIALI AIM 2018 (ANNO SOLARE) Benemeriti (quota minima) 1.750,00 €

July 15-19, Columbus, USA, International Conference on Strenght of Materials (ICSMA 18) July 15-21, Paris, France International Conference on Composites or Nano Engineering (ICCE-26) July 23-24, Santa Barbara, USA, Diversity in the Minerals, and Materials Professions 3 (DMMM3) August 13-15, Austin, USA, Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference August 16-18, Qingdao, China, 7th International Conference on Modelling and Simulation of Metallurgical Processes in Steelmaking (SteelSim)

Sostenitori (quota minima)

750,00 €

Ordinari (solo persona)

70,00 €

Seniores

25,00 €

Juniores

15,00 €

La quota dà diritto di ricevere la rivista dell’Associazione, La Metallurgia Italiana (distribuita in formato digitale). Ai Soci viene riservato un prezzo speciale per la partecipazione alle manifestazioni AIM e per l’acquisto delle

Semptember 5-8, Las Vegas, USA, MEI2018 (Mining Expo International)

pubblicazioni edite da AIM.

September 9-13, Oxford, United Kingdom, Eurosuperalloys 2018

Per ulteriori informazioni, iscrizioni, rinnovi:

September 11-14, Graz, Austria, 15th International Forgemaster Meeting (IFM) September 12-14, Xi’ An, China, 25TH IFHTSE September 13-14, Aachen, Germany, Metallurgie im Wandel 4.0 September 26-28, Darmstadt, Germany, Materials Science and Engineering

AIM, Via F. Turati 8 20121 Milano Tel.: 02 76021132/76397770, fax: 02 76020551 e-mail: amm.aim@aimnet.it www.aimnet.it

October 10-12, Taranto, Italy, 8th European Oxygen Steelmaking Conference (EOSC 2018) October 14-18, Seattle, USA, Furnace Tapping 2018 Conference October 16-19, Stockholm, Sweden, 3rd Ingot Casting, Rolling and Forging Conference, ICRF 2018 November 28-29, Bergamo, Italy, 4th European Conference on Clean Tech Technologies in the Steel Indutry (CLEAN TECH 4)

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Aim Drawing news Resoconto ICS 2018 Si è tenuto a Venezia, presso l’NH Laguna Palace, in data 1315 giugno il Congresso Internazionale ICS 2018, dedicato alla Scienza e alla Tecnologia nella produzione siderurgica. Il convegno, giunto alla sua settima edizione dopo quelle in Giappone (1996 e 2008), Regno Unito (2001), Stati Uniti (2005), Germania (2012), Cina (2015), è approdato per la prima volta in Italia da AIM.

L’evento, che ha visto come autorevoli chairman il Prof. Carlo Mapelli (Past-President AIM), il prof. Dong-Joon Min (Yonsei University, Korea), il prof. Johannes Schenk (Montanuniversitaet Leoben, Austria) e il prof. Dieter Senk (RWTH Aachen University, Germany) ha accolto ben 400 iscritti, provenienti da oltre 30 paesi.

Prof. Dong-Joon Min (Yonsei University, Korea), Prof. Johannes Schenk (Montanuniversitaet Leoben, Austria), Prof. Carlo Mapelli (PastPresident AIM)

L’elevato numero di memorie pervenute ha consentito di sviluppare il Congresso in cinque sessioni di lavoro giornaliere.

In particolare, le presentazioni erano suddivise in 13 macro sessioni: • Continuous Casting - Fluid Flow & Solidification • Continuous Casting - Mold Fluxes • Continuous Casting - Slab Quality Control • EAF Steelmaking • Electro Slag Remelting • Hot Metal Pretreatment • Industry 4.0 & Automation • Non-metallic inclusions

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• Oxygen Steelmaking • Process Fundamentals • Products & Technology • Secondary Refining • Sustainability & Environment, Recycling & Use of by-Products Nell’ambito del Congresso Internazionale si è svolta anche la XXVI edizione del Convegno Nazionale Trattamenti Termici e Metallografia con ottima partecipazione non solo da parte dei tecnici, ma anche dell’imprenditoria del comparto. In occasione della Cerimonia d’apertura del Convegno, sono stati assegnati due riconoscimenti. Il primo, il Premio Elio Gianotti 2018, è

La Metallurgia Italiana - n. 6 2018

AttiTrafilatura e notizie stato conferito dal nipote di Elio Gianotti all’ing. Andrea Francesco Ciuffini per la memoria “Ottimizzazione del trattamento termico di ricottura in un processo di trafilatura a freddo della lega di titanio Ti-6Al-4V ELI”; il secondo, un riconoscimento alla carriera, è stato conferito dal prof. Mapelli e dal dott. Petta,

Presidente del Centro di Studio AIM Trattamenti Termici e Metallografia, al dott. Antonio Bavaro “Per il notevole impegno e la grande passione generosamente profusi nell’organizzazione di Corsi e Giornate di Studio di alto profilo tecnico nell'ambito dei Trattamenti Termici e della Metallografia”.

Federico Gianotti premia l’Ing. Andrea Francesco Ciuffini

Il Congresso ICS 2018 ha anche ospitato un workshop internazionale organizzato da EIT Raw Materials dedicato alla produzione siderurgica.

Uno dei punti focali dell’evento è stata la mostra, animata dalle oltre 20 aziende sponsor dell’evento, che hanno saputo cogliere quest’importante opportunità di visibilità per i propri prodotti e tecnologie.

La Metallurgia Italiana - n. 6 2018

La sera del 14 giugno i numerosi partecipanti sono stati accompagnati in una visita guidata della laguna di Venezia a bordo di tre barche panoramiche con approdo in San Marco, dopo di che è stata loro offerta la cena di gala nel prestigioso salone del ridotto del Palazzo Dandolo – Hotel Monaco e Gran Canal.

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Aim Drawing news

Cena di gala a Palazzo Dandolo – Hotel Monaco e Gran Canal

La incantevole città di Venezia ha rappresentato il palcoscenico ideale per l’ICS 2018: la cornice dell’ NH Laguna Palace Hotel ha consentito ai partecipanti non solo di seguire con facilità le sessioni scientifiche ma anche, nei momenti di pausa, di approfondire la conoscenza personale e di scambiare pareri e impres-

sioni circa l’evoluzione della tecnologia. Il contesto logistico, ampie sale riunioni e ampi spazi comuni, l’area espositiva, il clima primaverile e piazza San Marco hanno facilitato l’aggregazione e gli scambi di conoscenze.

Foto di gruppo dei partecipanti

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La Metallurgia Italiana - n. 6 2018

AttiTrafilatura e notizie AIM – UNSIDER

Norme pubblicate e progetti in inchiesta (aggiornamento 31 maggio 2018)

Norme pubblicate e progetti allo studio Elenco Norme UNSIDER pubblicate da UNI nel mese di maggio 2018 UNI EN 1092-1:2018 Flange e loro giunzioni - Flange circolari per tubazioni, valvole, raccordi e accessori designate mediante PN Parte 1: Flange di acciaio UNI EN ISO 4885:2018 Materiali ferrosi - Trattamenti termici – Vocabolario UNI EN ISO 3183:2018 Industrie del petrolio e del gas naturale - Tubi di acciaio per i sistemi di trasporto per mezzo di condotte UNI EN ISO 7500-1:2018 Materiali metallici - Taratura e verifica delle macchine di prova statica uniassiale - Parte 1: Macchine di prova a trazione/compressione – Taratura e verifica del sistema di misurazione della forza UNI EN ISO 6507-4:2018 Materiali metallici - Prova di durezza Vickers - Parte 4: Prospetti dei valori di durezza

per i sistemi di trasporto per mezzo di condotte UNI EN ISO 6507-4:2006 Materiali metallici - Prova di durezza Vickers - Parte 4: Prospetto dei valori di durezza Norme UNSIDER pubblicate da CEN e ISO nel mese di maggio 2018 EN ISO 10426-1:2009/AC:2018 Petroleum and natural gas industries - Cements and materials for well cementing - Part 1: Specification - Technical Corrigendum 2 (ISO 10426-1:2009/Cor 2:2012) EN 1011-8:2018 Welding - Recommendations for welding of metallic materials - Part 8: Welding of cast irons EN ISO 6892-2:2018 Metallic materials - Tensile testing - Part 2: Method of test at elevated temperature (ISO 6892-2:2018) EN ISO 4829-1:2018 Steel and cast iron - Determination of total silicon contents - Reduced molybdosilicate spectrophotometric method - Part 1: Silicon contents between 0,05 % and 1,0 % (ISO 4829-1:2018)

Norme UNSIDER ritirate da UNI nel mese di maggio 2018

ISO 19203:2018 Hot-dip galvanized and zinc-aluminium coated high tensile steel wire for bridge cables -- Specifications

UNI EN ISO 4885:2017 Materiali ferrosi - Trattamenti termici – Vocabolario

ISO 17832:2018 Non-parallel steel wire and cords for tyre reinforcement

UNI EN ISO 7500-1:2016 Materiali metallici - Taratura e verifica delle macchine di prova statica uniassiale - Parte 1: Macchine di prova a trazione/compressione – Taratura e verifica del sistema di misurazione delle forze

ISO 10855-1:2018 Offshore containers and associated lifting sets -- Part 1: Design, manufacture and marking of offshore containers

EC 1-2015 UNI EN 1092-1:2013 Flange e loro giunzioni - Flange circolari per tubazioni, valvole, raccordi e accessori designate mediante PN Parte 1: Flange di acciaio UNI EN 1092-1:2013 Flange e loro giunzioni - Flange circolari per tubazioni, valvole, raccordi e accessori designate mediante PN Parte 1: Flange di acciaio UNI EN ISO 3183:2012 Industrie del petrolio e del gas naturale - Tubi di acciaio La Metallurgia Italiana - n. 6 2018

ISO 10855-2:2018 Offshore containers and associated lifting sets -- Part 2: Design, manufacture and marking of lifting sets ISO 10855-3:2018 Offshore containers and associated lifting sets -- Part 3: Periodic inspection, examination and testing ISO 9443:2018 Surface quality classes for hot-rolled bars and wire rod ISO 1083:2018 Spheroidal graphite cast irons -- Classification La Metallurgia Italiana - n. 6 2018 69

Aim Drawing news Progetti UNSIDER messi allo studio dal CEN (Stage 10.99) – maggio 2018

Progetti UNSIDER al voto FprEN e ISO/FDIS – giugno 2018

prEN ISO 13679 rev Petroleum and natural gas industries - Procedures for testing casing and tubing connections

FprEN – progetti di norma europei

EN 10222-2:2017/prA1 Steel forgings for pressure purposes - Part 2: Ferritic and martensitic steels with specified elevated temperatures properties Progetti UNSIDER in inchiesta prEN e ISO/DIS – giugno 2018 prEN – progetti di norma europei prEN ISO 19902 Petroleum and natural gas industries - Fixed steel offshore structures (ISO/DIS 19902:2018) prEN 17248 District heating and district cooling pipe systems - Terms and definitions prEN 253 District heating pipes - Bonded single pipe systems for directly buried hot water networks - Factory made pipe assembly of steel service pipe, polyurethane thermal insulation and a casing of polyethylene prEN 1562 Founding - Malleable cast irons EN 13480-6:2017/prA1 Metallic industrial piping - Part 6: Additional requirements for buried piping prEN ISO 7438 Metallic materials - Bend test (ISO/DIS 7438:2018)

FprEN ISO 204 Metallic materials - Uniaxial creep testing in tension Method of test (ISO/FDIS 204:2018) FprCEN/TR 10261 Iron and steel - European standards for the determination of chemical composition ISO/FDIS – progetti di norma internazionali ISO/FDIS 18632 Alloyed steels -- Determination of manganese -- Potentiometric or visual titration method ISO/FDIS 15835-3 Steels for the reinforcement of concrete -- Reinforcement couplers for mechanical splices of bars -- Part 3: Conformity assessment scheme ISO/FDIS 12108 Metallic materials -- Fatigue testing -- Fatigue crack growth method ISO/FDIS 4978 Steel sheet and strip for welded gas cylinders ISO/FDIS 4954 Steels for cold heading and cold extruding ISO/FDIS 204 Metallic materials -- Uniaxial creep testing in tension -Method of test

EN 10216-2:2013/prA1 Seamless steel tubes for pressure purposes - Technical delivery conditions - Part 2: Non-alloy and alloy steel tubes with specified elevated temperature properties ISO/DIS – progetti di norma internazionali ISO/DIS 7438 Metallic materials -- Bend test ISO/DIS 19902 Petroleum and natural gas industries -- Fixed steel offshore structures ISO/DIS 6930 High yield strength steel plates and wide flats for cold forming -- Delivery conditions

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Materiali metallici e processi produttivi innovativi per l’aerospazio convegno organizzato dai centri di studio metalli leggeri metallurgia fisica e scienza dei materiali metallurgia delle polveri e tecnologie additive della

e da

CON LA COLLABORAZIONE DI

Napoli 19-20 luglio 2018 Tematiche del Convegno: >> l’utilizzo tecnologico dei materiali metallici con particolare enfasi su alluminio e titanio, definendone le proprietà e le caratteristiche, in relazione ai requirements propri del settore aerospaziale; >> l’aspetto economico dei processi produttivi per Additive Manufacturing (AM); >> l’analisi e lo studio delle proprietà delle polveri al fine di ottimizzare i processi di formatura per AM; >> i problemi legati alla risoluzione/definizione consentita dai processi produttivi per AM; >> lo studio delle caratteristiche meccaniche dei pezzi prodotti per AM; >> i trattamenti superficiali dei materiali metallici; >> i criteri di progettazione delle macchine per la produzione di AM. Al Convegno saranno presenti le imprese che, a vario titolo, sono coinvolte nei processi produttivi di componenti per l’aerospazio, quelle che utilizzano l’AM, i fornitori di trattamenti superficiali ed i ricercatori della comunità scientifica nazionale, che hanno sviluppato significative conoscenze nel settore.

SPONSOR DELL’EVENTO Segreteria organizzativa Via F. Turati, 8 · 20121 Milano Tel. 02-76021132 / 02-76397770 E-mail: info@aimnet.it · www.aimnet.it

8th European Oxygen Steelmaking Conference Taranto . Italy 10-12 October 2018 Organised by

2018

With the support of

Exhibition & Sponsorship opportunities As an integral element of the event, EOSC 2018 will feature a table top Exhibition that will enable excellent exposure for company products, technologies, innovative solutions or services. At this opportunity the Organizers will set an area strategically located. This area will be a focal point of the Conference, so that enough time will be available to guarantee a perfectly targeted potential customerâ&#x20AC;&#x2122;s environment.

Companies will be able to reinforce their participation and enhance their corporate identification by taking advantage of the benefits offered to them as Sponsor of the Conference.

Companies interested in exhibiting and/or sponsoring the event may contact the Organising Secretariat: aim@aimnet.it

CONTACTS

AIM - Associazione Italiana di Metallurgia Via Filippo Turati 8, 20121 Milan - Italy Tel. +39 02 76021132 Fax +39 02 76020551 E-mail: aim@aimnet.it

www.aimnet.it/eosc2018