| 摘要 |
PROBLEM TO BE SOLVED: To provide a non-heat-treated steel which can be applied to fracture- splittable, low-ductility parts such as connecting rods for automobile engines, while retaining strength and a low cost comparable to those of a conventional non-heat-treated steel for automobiles. SOLUTION: The non-heat-treated steel for machine structural use showing excellent machinability and fracture splittability comprises, by mass, 0.35-0.60% C, 0.50-1.30% Si, 0.05-1.00% Mn, 0.05-0.40% S, 0.005-0.035% Al, 0.03-0.30% V, 0.0030-0.0250% N and the balance being Fe and unavoidable impurities, wherein an atomic ratio of Mn/S is 0.6-1.4, and contains≥5,000 fine sulfide particles essentially comprising MnS per 1 mm<SP>2</SP>. COPYRIGHT: (C)2004,JPO
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