| 摘要 |
PURPOSE:To manufacture steel products with high strength and superior characteristics of stopping the propagation of brittle cracks by subjecting a steel contg. specified amounts of C, Si, Mn, Nb, S, V, Cu, Cr, Mo and Ti to rolling, hardening and tempering under specified conditions. CONSTITUTION:A steel contg. 0.04-0.18% C, 0.01-0.90% Si, 0.30-2.00% Mn, 0.008-0.060% Nb, 0.012-0.020% S, 1 or >=2 kinds of metals selected from 0.01- 0.10% V, 0.05-0.50% Cu, 0.05-1.0% Cr, 0.05-0.50% Mo and 0.005-0.050% Ti, and inevitable impurities or further contg. 0.20-2.00% Ni is heated to >=1,200 deg.C and hot-worked. The hot worked steel is cooled to a temp. below the Ar1 transformation point, austenitized again, cooled to a temp. close to ordinary temp. at a higher rate than air cooling rate, and tempered by heating to 400 deg.C- the Ac1 transformation point to convert most of the structure into a fine ferrite structure. |
