HIGH-STRENGTH HOT-ROLLED STEEL SHEET HAVING SUPERIOR SUITABILITY TO STRETCH FLANGING AND FERRITE-BAINITE STRUCTURE AND ITS MANUFACTURE

摘要

PURPOSE:To improve the workability, especially the suitability to stretch flanging by adding prescribed percentages of C, Si, Mn, P, S and Al and forming a prescribed mixed structure. CONSTITUTION:A steel contg., by weight, 0.03-0.3% C, =1.2% Si, 0.7-1.7% Mn, =0.03% P, =0.015% S and 0.01-0.06% Al or further contg. 0.0005-0.005% B is refined. The steel is hot rolled and cooled to form a mixed structure consisting of ferrite and 50-60% by area of bainite.