ATIG 용접에서 용입 특성과 이면비드 생성에 관한 연구

Abstract

TIG welding enables to produce high quality weldment. However it has some problems such as shallow penetration and large distortion due to low penetration aspect ratio after welding. In order to overcome those problems, there are many ongoing studies on ATIG welding, which use active flux. However, the problem of uneven backbead exists even with ATIG welding using active flux on STS butt welding. Therefore, it is necessary to develope ATIG welding process that enables to make even back bead in order to apply to a filed. In this study, first, the effect of arc length and shield gas on penetration aspect ratio and melting efficiency with BOP welding on STS 304 6t, on which active flux was spreaded, was investigated. Arc length was changed from 1mm to 3mm, and aspect ratio became higher as arc length was decreased in this range. 100% Ar gas, Ar-H₂ mixed gas, Ar-He mixed gas, and 100% He gas were used as shield gas in this study. When Ar-H₂ mixed gas, Ar-He mixed gas, and 100% He gas were applied, penetration and melting efficiency were both increased as compared with 100% Ar gas. Second, two pieces of STS 304 6t were prepared with I groove butt joint, 0mm root gap, and tack welded. This prepared specimen was spreaded with active flux and welded. Back bead profiles were investigated and compared between CW and pulse wave and between 100% Ar gas and mixed gas. Ar gas was used for back shielding. As a result, more even back bead profiles were made when pulse wave with mixed gas was used than when CW with 100% Ar gas.