| 摘要 |
PURPOSE:To enhance the strength and the toughness of a rolled product, by a method wherein a steel piece with a specific composition subjected to hot molding rolling is again heated to an austenitizing temp. to be again subjected to hot rolling and the obtained rolled steel piece is subjected to tempering treatment. CONSTITUTION:A steel piece containing 0.02-0.15% C, 0.01-0.90% Si, 0.2-2.5% Mn, less than 0.025% P, less than 0.02% S, 0.001-0.01% N and 0.01-0.20% one or both of Nb and V and further containing one or more of Cu, Ni, Cr, Mo, Ti or B in a specific amount or containing one or more of Ca and Ce in a specific amount is heated to 1,200 deg.C or more to dissolve contained Nb, Al or V to form a solid solution and the treated steel is subjected to hot rolling to be processed into a steel plate, a steel pipe or die steel. Alternatively, the hot rolled steel may be further reheated to an austenitizing temp. to be subjected to hot rolling. The resulting steel is reheated on the way of cooling after hot rolling to be tempered at 400 deg.C-A1 point or below. |
