High-strength cold-rolled steel strip and molten zinc-plated high- strength cold-rolled steel strip having good formability and method of producing such strips

摘要

A high-strength cold-rolled steel strip or a molten zinc- plated high- strength cold-rolled steel strip which have a low yield strength, containing, by weight, of 0.0005-0.01% C, not more than 0.8% Si, more than 0.5% but not more than 3.0% Mn, 0.01-0.12%: P. 0.0010-0.015% S, 0.01- 0.1% Al, 0.0005-0.0060% N, not less than 0.0001% but less than 0. 005-0.1% the content of Nb being made to satisfy Nb ≧93/12 (C-0.0015), or instead of 0.005-0.1% Nb, 0.0005-0.1% Ti and 0.003-0.1% Nb, the content of Nb and the content of Ti being made satisfy, Ti≧3.42N, and the balance Fe and incidental impurities is provided. Another steel strip or molten zinc-plated strip is provided that contains 0.2-3.0% Cr but does not require B, and includes both Ti and Nb. The method of producing such is also provided.