HIGH STRENGTH COLD ROLLED STEEL SHEET WITH EXCELLENT STRETCH FLANGEABILITY AND MANUFACTURING METHOD THE SAME

摘要

A high strength cold rolled steel sheet with excellent stretch flangeability, which is an aspect of the present invention comprises 0.065-0.075 wt% of C; 0.1-0.3 wt% of Si; 1.7-2.0 wt% of Mn; 0.01-0.03 wt% of Al; 0.01-0.02 wt% of P; equal to or less than 0.006 wt% of S; 0.15-0.35 wt% of Cr; 0.03-0.07 wt% of Mo; and the rest of Fe and inevitable impurities. The refined structure of the manufactured steel sheet comprises 11-20% of Martensite; 15-25% of Bainite; and the rest of Ferrite with respect to the whole area.