| 摘要 |
PROBLEM TO BE SOLVED: To propose a structural component having an excellent impact strength property. SOLUTION: A steel raw material composed of a composition containing 0.40 to 0.50 mass% C,≤0.05 mass% Si, 0.50 to 1.2 mass% Mn,≤0.20 mass% P, 0.002 to 0.008 mass% S, 0.30 to 0.50 mass% Mo, 0.02 to 0.05 mass% Al,≤1.0 mass% Cu, 0.015 to 0.030 mass% Ti, and 0.0015 to 0.0030 mass% B, and the balance Fe and inevitable impurities is heated to a temperature area of 900 to 1,050°C and is then subjected to bar steel rolling at a finishing temperature of≥880°C to produce the bar steel with 15 to 30% of an area rate of a bainite phase. The bar steel is molded to a desired shape by forging in a temperature area including ordinary temperature and is thereafter subjected to induction hardening. COPYRIGHT: (C)2009,JPO&INPIT
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