HIGH STRENGTH COLD ROLLED STEEL SHEET FOR DEEP DRAWING, EXCELLENT IN SURFACE CHARACTERISTIC AFTER PRESS FORMING

摘要

PROBLEM TO BE SOLVED: To provide a high strength cold rolled steel sheet for deep drawing, excellent in surface characteristic, while increasing strength by the addition of P and preventing the occurrence of surface ruggednss after press working. ;SOLUTION: This steel sheet has a composition consisting of, by weight, ≤0.08% C, ≤1.0% Si, 0.1-2.5% Mn, 0.04-0.15% P, ≤0.02% S, 0.01-0.1% sol.Al. ≤0.01% N, and the balance Fe with inevitable impurities or further containing one or ≥2 kinds among 0.005-0.1% Ti, 0.005-0.1% Nb, 0.005-0.1% V, 0.01-2% Cr, and ≤0.005% B. Further, when the degree of segregation of P in one part is represented by (α) and [α=(concentration of P in the part)/(average concentration of P in the steel)] is satisfied, the value of the ratio between the maximum value αMAX and minimum value αMIN of the degree of segregation in the cross section of the steel sheet, αMAX/αMIN, is regulated to ≤4.;COPYRIGHT: (C)1999,JPO