High Strength Low Alloy Steels (HSLA)
In respect to High Strength Low Alloy Steels (HSLA) for automotive applications (i.e., seats, suspensions, steering wheels, cross beam, etc.) the expertise gained by the CSM metallurgists is aimed at creating the microstructures that are best suitable to forming and guaranteeing the needed performance for the product. In this field proper, being involved in microstructures means, for CSM metallurgists, not only optimised new compositions, but also activities oriented to match the following criteria:
- to raise the quality standards of consolidated products;
- to introduce more efficient models for the control of both the austenite and the precipitates during the strip cooling;
- to revise chemical and process parameters in order to impose narrow manufacturing allowances for various mill & ROT configurations, and reduce both the number of the steel quality codes and the scattering of their features.
HR (ferrite-bainite), Dual Phase (ferrite-martensite), TRIP (bainite-retained austenite) and TWIP (high Mn, austenitic) steels
In the field of HR (ferrite-bainite), Dual Phase (ferrite-martensite), TRIP (bainite-retained austenite) and TWIP (high Mn, austenitic) steels metallurgy the technical offer of CSM mainly encompasses such alloy design capabilities as:
- Investigation of recrystallization and phase transformation by quench-deformation dilatometry devices, hot deformation simulators and pilot mills;
- Modelling of both austenite recrystallization during hot rolling and phase transformation on the ROT when using step cooling patterns;
- Identification of relationships between microstructural parameters and mechanical properties (YS, UTS, Y/T, El, uniform strain, work-hardening, etc.);
- Modelling of the effect of volume fraction, morphology and size of microstructural constituents on stress-strain curves.
This offer is also integrated by the process setting capability for several steel grade products (HR45 – HR60 and DP600 – DP 800) manufactured by means of both conventional and thin-medium slab routes, with either standard laminar cooling (LC) or combined with Ultra Fast Cooling (UFC + LC).
CSM metallurgists succeeded in developing a very lean chemical composition and the related thermo-mechanical treatment practice capable of maximizing the quality of the thin hot-rolled DP600 grade steel (1.5, 2.5 mm) and also in obtaining hot rolled DP600 1.2 mm thick strips, by means of an intercritical treatment carried out during the hot dip galvanizing phase of the process.