Abstract: 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.about.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.about.2.5% of moisture is contained in an inert gas is employed.

Abstract: It is a metal oxidation treatment apparatus for carrying out the inactivation treatment of metal tubes used especially in a super high purity gas piping system and an apparatus of super high vacuum.The support part of a support member is made as a tubular form member, and a tapered part is provided on the outer periphery thereof, and further, since a spring is mounted to be displaceable, even if fluctuation is present in the internal diameter of stainless steel tubes, it is possible to let the stainless tubes easily be supported on the support part. Also, even fluctuation of the length is present in the stainless steel tubes, the support member is always pushed to the stainless steel tubes. Oxidative gas diffusing out of the tube to be treated to the outside thereof can be released to the outside of the oxidation treatment furnace without letting it contact to the tube to be treated.