| 摘要 |
PURPOSE:To produce a high-tensile steel having excellent low-temp. toughness for large heat input welding by subjecting a molten steel to cooling and reheating under specific conditions then to hot rolling in the stage of casting continuously the molten steel contg. a specific ratio each of C, Ti and N. CONSTITUTION:The molten steel which contains 0.01-0.15wt% C, 0.005-0.015wt% Ti and <=0.006wt% N and in which the ratio Ti/N of Ti and N is >=1.0 and <=3.5 is prepd. Such molten steel is cooled at >=10 deg.C/min average cooling rate in the final solidifying part from the molten steel temp. in the stage of pouring up to 800 deg.C to produce a billet or steel ingot. The billet or ingot is reheated to >=900 deg.C and <=1,000 deg.C and is then subjected to hot rolling. The steel having the excellent low-temp. toughness at the joint formed by large heat input welding is thus obtd.
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