| 摘要 |
<p>PURPOSE:To provide an ultrahigh strength cold rolled steel sheet for an automobile excellent in bendability and shock resistance, having >=100kgf/mm<2> tensile strength and contg. soft layers in the surface layer parts. CONSTITUTION:This cold rolled steel sheet consists of 0.12-0.30% C, <=1.2 Si, 1-3% Mn, <=0.02% P, <=0.01% S, 0.01-0.06% sol. Al and the balance Fe with inevitable impurities, contains soft layers contg. <=0.1% C in the surface layer parts by 3-15vol.% per one side and has a combined structure consisting of <10vol.% retained austenite and a phase transformed at a low temp. and/or ferrite at the inner layer part.</p> |
