| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material having a structure consisting mainly of a hard phase and having excellent resistance to fatigue crack propagation and to provide its manufacturing method. SOLUTION: In the steel material, structure is composed mainly of bainite/ martensite, and a half value breadth of the X-ray diffraction intensity from a (200) face is≥0.20°. The steel contains 0.01-0.15% C, 0.03-0.6% Si, 0.5-2.0% Mn, 0.005-0.1% sol.Al, 0.0005-0.008% N and also 4.0-6.0 Ft (3Mn+Cu+1.5Cr+1.8 Ni+1.5Mo). The steel may further contain≤0.0030% B and have 3.5-5.5% Ft. One or more elements selected among Cu, Ni, Cr, Mo, Nb, Ti and V may be contained. The steel is manufactured by quenching after hot rolling. COPYRIGHT: (C)2004,JPO
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