| 摘要 |
PROBLEM TO BE SOLVED: To provide steel parts which have both of high strength and such a machinability as to enable mass production, and achieves great weight saving for the underbody parts of automobiles. SOLUTION: The steel for the parts comprises, by weight ratio, 0.06-0.20% C, 0.03-1.00% Si, 1.00-3.00% Mn, 0.030% or less P, 0.04-0.30% S, 0.50-2.00% Cr, 0.05-1.00% Mo, 0.001-0.060% Al, 0.30-1.00% V, 0.0080-0.0200% N, 0.0005-0.0100% Ca, 0.0005-0.0100% Mg and the balance Fe with impure elements; and has a structure comprising ferrite pearlite or martensite of 30% or less (including 0%) by area rate. The method for manufacturing the steel parts comprises hot forging the steel, and aging it at a temperature of 550 to 700°C. COPYRIGHT: (C)2004,JPO
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