COLD ROLLED STEEL SHEET HAVING EXTREMELY SUPERIOR DEEP DRAWABILITY AND BULGING PROPERTY AND ITS PRODUCTION

摘要

PURPOSE: To produce a cold rolled steel sheet having superior deep drawability and bulging deformability by preparing a steel which has a specific composition having respectively specified C, S, N, Ti, and Nb contents and where the inplane mean value of Lankford value and the work hardening index in the prescribed tensile strain region are specified, respectively. ;CONSTITUTION: The cold rolled steel sheet having a composition which consists of, by weight, ≤0.0030% C, ≤0.05% Si, 0.05-0.50% Mn, ≤0.02% P, =0.02% S, 0.03-0.06% Sol. Al, ≤0.0040% N, 0.005-0.0015% Nb, 0.04-0.14% Ti, and the balance Fe with inevitable impurities and where (Ti*/-[C]) satisfying equations I,II {where [%C], [%Ti], and [%S] represent C content (%), Ti content (%), and S content (%), respectively} and inequality III {where [%Nb] represents Nb content(%)} is regulated to ≥7 is produced. In this cold rolled steel sheet, the inplane mean value (means-r) of Lankford value defined by equation IV {where [r₀] means r-value in a steel sheet rolling direction} and the work hardening index evaluated in the region of 10-20% tensile strain are regulated to ≥2.8 and ≥0.26, respectively.;COPYRIGHT: (C)1993,JPO&Japio