ステンレス鋼溶接ヒューム中の六価クロム低減技術

摘要

ステンレス鋼の溶接においてフラックス入りワイヤによる溶接（以下，FCAWという）は，その優れた溶接作業性と高能率性などから化学工業などの幅広い業稀で使用されているが，他の溶接方法と比較して溶接ヒュームの発生量が多く，作業環境への負荷となっている。溶接ヒュームは，溶接アークによって発生した金属蒸気が大気中で冷却されて凝固した酸化物である。%It is well known that the fumes generated in welding stainless steel contain hazardous Hexavalent Chromium, Cr(Ⅵ). This report focuses on fundamental studies that were conducted to investigate Cr(Ⅵ) in fumes generated in flux-cored arc welding (FCAW). Analysis by Electron Spectroscopy for Chemical Analysis (ESCA) revealed that the Cr(Ⅵ) spectrum corresponds to alkaline metal compounds. The higher content of alkaline metal in flux-cored wire can be a cause of the increase in Cr(Ⅵ), and fluoride was found to be effective in reducing Cr(Ⅵ) in fumes. Based on this knowledge, the ingredients in 308L, 309L and 316L type flux-cored wires are formulated in an optimum composition and their Cr(Ⅵ) generation rates are reduced by approximately 80％ compared to conventional wires in the market. Cr(Ⅵ) exposure assessment carried out in the welding workplace revealed that the generation rate of Cr(Ⅵ) from flux-cored wire is the most influential factor in controlling Cr(Ⅵ) in the atmosphere.