COLD ROLLED DEAD-SOFT STEEL SHEET EXCELLENT IN FORMABILITY AFTER HIGH DENSITY ENERGY BEAM WELDING AND SURFACE TREATED STEEL SHEET USING THIS COLD ROLLED STEEL SHEET AS STARTING SHEET

摘要

PURPOSE: To produce a cold rolled dead-soft steel sheet, showing superior formability at the time of press forming after high density energy beam welding, and also a steel sheet prepared by using the cold rolled steel sheet as a starting sheet and properly applying continuous annealing, temper rolling, and surface treatment to it. ;CONSTITUTION: A steel sheet, having a composition which consists of, by weight, 0.0005-0.005% C, 0.005-1% Si, 0.05-2.5% Mn, 0.005-0.1% P, ≤0.01-0.1% sol.Al, ≤0.005% N, 0.005-0.15% Ti, 0-0.003% B, and the balance Fe other than inevitable impurities and in which the value of f(C, Si, Mn, P, B) is regulated to 2.6-12.5, is obtained. This f(C, Si, Mn, P, B) is defined by the following equations: f(C, Si, Mn, P, B)=100[%C]+[%Si]+2[%Mn]+50[%P]+9000[%B] when B≤0.0005%; f(C, Si, Mn, P, B)=100[%C]+[%Si]+2[%Mn]+50[%P] +1000([%B]-0.0005)+4.5 when B0.0005%.;COPYRIGHT: (C)1995,JPO