Welding method for forming chromium oxide passivated film at welded portion, welding apparatus, and process apparatus

摘要

The invention has as an object thereof to provide a welding method which is capable of forming an oxide passivated film, which is corrosion resistant, non-catalytic, and has an extremely small amount of released gasses, chiefly on the welded portion or in the vicinity thereof during the welding process. During the welding process, a gas in which 800 ppm DIFFERENCE 2.5% of moisture is contained in an inert gas is caused to flow, and a passivated film having chromium oxide as a chief component thereof is formed on the surface of the welded portion. The welding method comprises a welding process and a passivation process; in the passivation process, a gas in which 1000 ppm DIFFERENCE 2.5% of moisture is contained in an inert gas is employed. The apparatus is provided with a system for generating moisture, a system for supplying an inert gas or a mixed gas in which hydrogen is added to an inert gas as a back shield gas, a system for supplying a back shield gas comprising an inert gas containing moisture, and a mechanism for supplying these gasses to the portion to be welded via switching of both systems.