| 摘要 |
PURPOSE:To obtain a high tensile steel having good quality, high yield point and high tensile strength by subjecting the billet of the high tensile strength consisting of a specific compsn. to controlled hot rolling and quick cooling then to reheating to a low temp. region and holding the steel in said region for a specified period. CONSTITUTION:The steel consisting of 0.04-015wt% C, 0.01-0.35% Si, 0.50-1.50% Mn, <=0.010% P, <=0.002% S, 0.005-0.015% Ti, 0.01-0.07% Al, 0.0015-0.0050% N and the balance Fe and inevitable impurities is melted. The billet thereof is heated to (Ac3+100)-1,100 deg.C and is subjected to hot rolling at <=40% draft in an (Ar3+100)-Ar3 temp. region, then to quick cooling down to <=250 deg.C at >=3 deg.C/sec speed. The steel is thereafter reheated without stagnating the same for >=120min at <100 deg.C and is held at 250-500 deg.C. The steel is cooled after >=3hr of the stagnation time at >=100 deg.C is assured, by which the high tensile steel having the desired characteristics is obtd.
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