TANDEM ELECTRO GAS ARC WELDING METHOD

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PURPOSE : A tandem electro gas arc welding method for controlling constituents of the weld metal to prevent drop of impact toughness of a weld metal due to nitrogen contained in the weld metal and high heat input applied during welding when performing tandem electro gas arc welding of ultra-thick steel products is provided. CONSTITUTION : In a tandem electro gas arc welding for performing high heat input welding of the welding part using a face side electrode(40) and a root side electrode(50) in the state that a welding part(11) of steel products(10) is sheltered from the atmosphere by a shielding gas, a tandem electro gas arc welding method comprises controlling constituents of the weld metal such that a weld metal(18) composing the welding part of the steel products contains a composite oxynitride comprising Ti, Si, Al and Mn as basic components and at least one component of Zr, Mg, Ca and rare earth metal elements. The steel products include ultra-thick steel products with a thickness of 60 mm or more. The tandem electro gas arc welding has a welding heat input of 500 kJ/cm or more. The weld metal comprises 0.0010 to 0.0080 wt.%% of B. The weld metal comprises 0.005 to 0.015 wt.%% of N. © KIPO 2007