Process compatibility and damage performance of carbide-free bainite advanced high strength steel (AHSS) sheets

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Intense research efforts are being expended on developing advanced high strength steels (AHSS) for vehicle weight reduction (improved fuel economy/lower emissions) and crash resistance (improved passive safety). This has resulted in the development of a number of Third Generation (3G) steels. Although some of the newest 3G steels have demonstrated the required properties at the lab scale, the optimum thermomechanical processing requirements to commercially produce these grades are beyond current Canadian plant capabilities. Further, the high capital costs of upgrading production facilities may induce global steel manufacturers to concentrate production of these critical high value-added products in locations outside Canada. In order to mitigate this risk, McMaster University and CanmetMATERIALS will investigate the processing and performance of a specific class of bainitic steels that are suitable for processing on existing continuous galvanizing lines (CGL) at ArcelorMittal Dofasco's facilities in Hamilton, ON. The target performance is tensile strength of more than 1150MPa with total elongation approaching 20%, which significantly surpasses the properties of current AHSS commercial products made by steel plants in Canada (e.g. 780 and 980MPa grades). Further, ductility for improved forming response (e.g. stretch flangeability) is required to stamp complex autobody structural parts. The damage performance of the proposed CFB sheets has not been studied adequately and the interplay between microstructure-damage properties of this class of AHSS remains to be determined (knowledge gap). The main objectives of this research are twofold: (a) Tailor alloy composition and processing parameters of carbide-free bainitic AHSS sheets to the capabilities and limitations of existing facilities at ArcelorMittal Dofasco's Hamilton, ON, plant, and understand the microstructural factors controlling the strength and damage performance of carbide-free bainitic sheets. (b) Train a Ph.D. student with a unique opportunity to tackle the entire span of product development, ranging from alloy design to process optimization and product assessments while exposed to both pilot-scale facilities of CanmetMATERIALS and academic research environment of McMaster University.