| 摘要 |
PURPOSE: A steel material with superior toughness of a heat-affected zone for high heat input welding is provided to cut down on manufacturing costs by reducing the composition of titanium and nitrogen and secure stability in electro-gas welding even under a high heat input condition. CONSTITUTION: A steel material with superior toughness of a heat-affected zone for high heat input welding comprises C of 0.05-0.12weight%, Si of 0.18-0.22weight%, P of 0.012weight% or less, Mn of 1.0-1.6weight%, S of 0.002-0.006weight%, Al of 0.015-0.060weight%, Ti of 0.004-0.015weight%, N of 0.001-0.006weight%, Nb of 0.005weight% or less, B of 0.0005-0.0015weight%, and iron and inevitable impurities of the remaining amount, where Ti and N satisfy Ti/N<=7.0. The micro-structure of the steel material includes austenite with a grain size of 250μm or greater. |
