Cold-rolled high-strength steels offer keeps growing

Following the successful introduction and positive customer feedback of ArcelorMittal HC500LA and S550GD HyPer® cold-rolled high-strength steel grades, industry manufacturers are asking for ever better performing steel products: lighter, thinner, more reliable and sustainable products to build strong and long-lasting structures more economically. At the same time, market interest is shifting more towards coated grades for applications that require additional corrosion resistance, such as housing and solar frames, roofing and cladding.

MEETING MARKET NEEDS

There is huge potential in the construction market for high-strength low-alloyed coldrolled steel grades – both bare and coated, which could extend the cold-rolled product offer above 500MPa. OCAS is developing an extended family of ever-stronger yet ductile cold-rolled microalloyed high-strength steel grades by using robust and flexible metallurgical concepts. In collaboration with different ArcelorMittal cold-rolling-annealing and galvanising lines across Europe, the OCAS lab concepts have been industrially realised and high-strength steels with yield strength ranging up to 700MPa (coated) and 850MPa (bare) are now industrially feasible. These new cold-rolled grades have a tightly controlled chemical composition and microstructure that allow reliable performance. The high level of yield strength is a result of the addition of micro-alloying elements, contributing to fine carbide precipitations, substitutional and interstitial strengthening, and grain refinement. These grades are perfectly suited for cold-forming, such as bending, tubing, rollforming. They provide a very high strength while maintaining excellent formability. Such grades allow thickness and weight reduction and provide a smart solution for sustainable development: environmentallyfriendly, light, durable, and cost-effective. These grades have already found their way to the manufacturing of automotive

components, such as seat frame structures, pedal systems, and windscreen wipers. Other typical applications are in mechanical engineering, racks, poles, tubes, transportation (trucks, wagons, and chassis), and industrial or agricultural equipment. In addition, the use of advanced high-strength low-alloy steels has a positive environmental impact by reducing the carbon footprint for the life cycle of a structure.

OUTLOOK

OCAS is currently optimising the metallurgical route for the coated grades for various galvanising lines. Each galvanising line is different in terms of parameters that influence the microstructure, and thus, the in-use properties. This adds a new layer of challenges to this development. The aim is to offer sufficient flexibility to the galvanising plants, combined with a rational cold-rolled product offer worldwide.

Customers need steels that are everstronger, yet thinner and more corrosionresistant, and that allow weight reduction – all without compromising on formability. OCAS’s metallurgical solutions are making this a reality.

Arunim Ray