PRODUCTION OF COLD ROLLED STEEL SHEET FOR DEEP DRAWING HAVING EXCELLENT RIDGING RESISTANCE AND CHEMICAL CONVERTIBILITY

摘要

PURPOSE:To obtain a cold rolled steel sheet which is improved in deep drawability and chemical convertibility without generating a ridging defect by subjecting a low-carbon steel which is controlled in the content of Ti in association with C, N and S and is added with adequate ratios of Nb and B to hot rolling at a specified finishing temp. by using a lubricating oil and to cold rolling, then subjecting the steel to recrystallization annealing. CONSTITUTION:The low-carbon steel which contains =0.005wt% C, =0.005% N and =0.007% S, contains 0.01-0.05% Ti, satisfies 2=Ti/(C+N+S)=5 and contains 0.001-0.02% Nb, and 0.001-0.002% B is cast. Such ingot is hot rolled in at least one pass by using the lubricating oil at the finishing temp. specified to 600-800 deg.C. The steel is in succession thereof cold rolled at 50-95% draft and is subjected to the recrystallization annealing. The cold rolled steel sheet having the excellent deep drawability and chemical convertibility is obtd. by the above-mentioned method without having the possibility of generating the ridging defect.