GMAW 초층 이면비드 용접에서 단차와 갭변동 극복을 위한 아크력 제어에 관한 연구

Abstract

It is important to form stable back bead formation on manufacture of pipe or tank in field of shipbuilding or plant industry. In most industry, manual TIG welding is preferred for formation of stable back bead in root weld of butt joint. However, manual TIG welding has low productivity as compared with GMAW, also it has unstable bead quality which depend on skilled workers. So it is necessary to develop process of root pass welding by using automation GMAW that have stable back bead formation and high productivity. In this study, design of U-groove with 3mm root face was applied to extend tolerance of misalignment in condition of standard 1.5mm gap and arc force of GMAW was considered for groove with thick root face for stable back bead formation. Consequently, effect of arc force was verified by experiment for current, voltage and welding speed variation in water cooled copper plate. Arc force condition was established by control of current, voltage and welding speed in butt joint welding of 3t plate. From the result of oscillation width variation on pipe U-groove welding, back bead height increases with decrease in oscillation width. Arc impulse was defined by effect of oscillation width variation. If width of gap is narrower than 1.5mm, larger arc impulse is needed for back bead formation. Otherwise if width of gap is wider than 1.5mm, the lower arc impulse is needed for back bead formation.