| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel excellent in fatigue crack propagating characteristic, suitable to a steel material used for welding to a large structural material which receives variable loading, such as ship, bridge, ocean structure. SOLUTION: The steel composed by mass% of 0.05-0.2% C, 0.05-0.7% Si, 0.05-2.5% Mn,≤0.03% P,≤0.02% S, 0.005-0.1% Al, 0.005-0.03% Ti and if necessary, adding one or more kinds of Cu, Ni, Cr, Mo, Nb, V, B, Ca, Mg, REM and the balance Fe with inevitable impurities, is cooled to Ar<SB>1</SB>transformation point or lower after solution-treatment, and after again heating to 1,000-1,350°C, hot-rolling is applied and if necessary, accelerating-cooling and further, tempering are performed. COPYRIGHT: (C)2007,JPO&INPIT
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