Cold-rolled steel sheet for deep drawing and method of producing the same

Abstract

A cold-rolled steel sheet suitable for deep drawing has a composition containing up to about 0.005 wt % of C, up to about 0.1 wt % of Si, up to about 1.0 wt % of Mn, up to about 0.1 wt % of P, up to about 0.05 wt % of S, about 0.01 to 0.10 wt % of Al, up to about 0.005 wt % of N, one, two or more elements selected from the group consisting of about 0.01 to 0.15 wt % of Ti, about 0.001 to 0.05 wt % of Nb and about 0.0001 to 0.0020 wt % of B, and the balance substantially Fe and incidental impurities. The steel sheet exhibits a Lankford value (r-value) of about r.gtoreq.2.8 and also exhibits the difference (r.sub.max -r.sub.min) between the maximum value r.sub.max and the minimum value r.sub.min satisfying the condition of (r.sub.max -r.sub.min).ltoreq.about 0.5. The steel sheet is produced by a process having the steps of: conducting hot-rolling on the steel material of the above-described composition; conducting a primary cold rolling at a rolling reduction not smaller than about 30%; conducting intermediate annealing at a temperature ranging between the recrystallization temperature and about 920.degree.; conducting secondary cold rolling at a rolling reduction not smaller than about 30% so as to provide a total rolling reduction not smaller than about 78%; and conducting final annealing at a temperature which is between the recrystallization temperature and about 920.degree. C.