After the forming strength rise heat treatment talent and the high tension cold rolling steel sheet and its production mannered null mass which are superior in

摘要

PROBLEM TO BE SOLVED: To provide a high strength cold rolled steel sheet which has excellent heat treatability to increase its strength after forming, and has excellent deep drawability, and to provide a production method therefor.;SOLUTION: A steel stock having a composition containing 0.0050% C, 0.005 to 0.03% Al, 0.005 to 0.040% N, 0.005 to 0.050% Nb, 0.0003 to 0.0015% B and 0.01 to 0.5% V, and also in the conditions wherein the contents (mass%) of C, Al, N, Nb and V satisfy 0≤{V/51+Nb/93-C/12} and 0.5≤{V/51+Nb/93-C/12+Al/27}/(N/14)≤3.0 is subjected to hot rolling at a heating temperature, and a finishing temperature in finish rolling of ≥800°C, and is coiled. The steel is thereafter subjected to cold rolling at a draft of 60 to 95%, and is next subjected to recrystallization annealing at ≥700°C. Thus, the cold rolled steel sheet having heat treatability to increase its strength after forming satisfying ≥500 MPa ΔTS, and having deep drawability satisfying an r value of ≥1.2 is obtained.;COPYRIGHT: (C)2003,JPO