| 摘要 |
PURPOSE:To manufacture fine grain rolled steel stock having a superior mechanical property similar to that after normalizing without requiring normalizing after rolling, by applying hot rolling and heat treatment under specified conditions to low or medium carbon steel or alloy steel contg. specified small quantities of Al and N. CONSTITUTION:Steel slab of low and medium carbon steel or alloy steel contg. by weight 0.10-0.60% C, 0.10-0.35% Si, 0.30-1.80% Mn, 0.010-0.045% Al, 0.007-0.020% N, (Al/N weight ratio >1.6) of further 0.015-0.10% Nb or singly or composedly one kind or more among <1.5% Cr, <0.3% Mo, 0.050-0.30% V is heated to 750-950 deg.C and hot rolled. In this case, the plate is cooled to Ms point - 850 deg.C from 850-1,000 deg.C before finish rolling, and finish rolling is ended at 700-850 deg.C. Steel stock contg. fine AlN, having uniform and fine ferrite and pearlite structure and superior mechanical property can be manufacture without requiring normalizing after rolling.
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