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HOME技術情報三菱重工技報 第32巻 第6号 生産技術特集全姿勢対応狭開先MAG溶接法の開発

三菱重工技報
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全姿勢対応狭開先MAG溶接法の開発

All Position Narrow‐Gap MAG Welding for Heavy Wall Structures

波多野 怜・飯島史郎・馬渕洋三郎・筌口泰宏・河野隆之

Satoru Hatano, Shiro Iijima, Youzaburou Mabuchi, Yasuhiro Ukeguchi, Takayuki Kawano
狭開先溶接は従来のV又はX開先溶接に比較し,溶接金属量が少ないため,溶接作 業量が少なく,積層が単純で自動化しやすい点で優れている。しかし,本溶接法は 板厚が厚くなると開先壁面に溶接欠陥が発生しやすいため,従来の技術では溶接性 の良い下向き姿勢以外では実機適用が困難であった。当社では溶接トーチを180 °反復回転し,溶接ワイヤー先端のアークの動きを狭い開先内で自由に制御し,上 向き,立向き及び横向きの全姿勢に対応できる溶接法を開発した。この溶接法は既 に工場及び現地の配管溶接並びに厚肉の大型圧力容器に適用し,溶接能率の向上及 び信頼性向上面で大いに貢献している。 (著者抄録)

Narrow-gap arc welding is known to be an advantageous welding method compared to welds with V type grooves or X type grooves. This is because the welding time can be greatly reduced due to less deposited metal and also due to its capability of automatic, unmanned operation by the simple one pass-one layer method. However, it can also be said that narrow-gap arc welding is a more difficult method because better techniques will be required to control the arc position in deeper groove and to prevent weld defects. In recent years, many welding methods with arc oscillation without oscillating the torch have been developed. Heavy wall welding joints with high reliability can be achieved by these methods. Most of these methods utilize flat position welding and there are very few cases with other positions. This paper describes an all position narrow-gap MAG welding process for extra heavy wall structures of approximately 100 mm. By this process, narrow-gap overhead, vertical and horizontal welding has been made possible by curving the wire at the tip of the torch and rotating the torch to be left and right for 180 degrees with fine control of weld metal flow by delicate adjustments of the oscillation I. E. rotation of the torch. This process has already been applied to all position narrow-gap welding of boiler pipes and large size pressure vessels with high efficiency and quality.