A METHOD OF PRODUCING ULTRA HIGH STRENGTH STEEL WITH MINIMAL DUCTILITY FROM FERRITE-BAINITE STARTING DUAL PHASE STEEL

摘要

This invention relates to a method of producing an ultra high strength steel with minimal ductility from ferrite-bainite dual phase steel comprising the steps of: producing C-Mn-Si based steel having composition in weight % of C - 0.1-0.3, Mn - 1.1 - 1.7, Si - 0.2 - 0.6, S - ≤ 0.015, P - ≤ 0.02, Ti - ≤ 0.01, V - 0.1 - 0.3, Cr - 0.05 - 0.1, 1 in an air induction furnace, forging a bloom of said steel at 900-1100°C with different amount of deformation at each stroke to achieve a homogenized structure and conveying the same to hot rolling mill, and hot rolling the bloom at just above Ar3 temperature and normalising to obtain slab of ferrite-bainite steel slab, cold rolling the said hot rolled slab to 20-85 % deformation and annealing the cold reduced steel sheet / strip at 200-700°C for 20 - 60 minutes to result ultra high strength steel with minimal ductility.