COLD-ROLLED STEEL SHEET & THE METHOD FOR ITS PRODUCING

摘要

A method for producing cold-rolled steel sheets which comprises the steps of: producing slabs containing 0.001 - 0.003 wt.% C, 0.004 wt.% or less N and 0.03 - 0.20 wt.% P, providing that P(wt.%) x N(wt.%)<4> wt.% is satisfied; hot-rolling the slabs into hot-rolled steel strips; cold-rolling the hot-rolled steel strips at 60 - 95% reduction ratio into cold-rolled steel strips; and annealing continuously the cold-rolled strips at temperature of recrystallization temperature to Ac3 transformation point temperature. The slabs further include 0.0005 - 0.0030 wt.% B. The hot-rolling is performed at finishing temperature ranging Ar3 transfromation point to Ar3 transformation + 100 DEG C, at coling temperature of 750 DEG C and less.