IMPROVEMENT OF RESISTANCE OF WELD ZONE OF AUSTENITIC STAINLESS STEEL TO HIGH-TEMPERATURE SALT DAMAGE AND CORROSION CRACKING

摘要

PURPOSE:To entirely eliminate the high-temp. salt damage and corrosion cracking generated in a weld bond part by subjecting a welded pipe and welding member to annealing in a prescribed temp. range in an inert atmosphere and reducing atmosphere, and then cooling the above with an inert gas and reducing gas. CONSTITUTION:The welded pipe and/or welding member is subjected to the annealing in the =900 deg.C and =1250 deg.C range in the inert atmosphere and/or reducing atmosphere and is then cooled by the inert gas and/or reducing gas. For example, the thin sheet of an austenitic stainless steel is slit to a prescribed 1 width and is made into a tube by welding. The welded tube is produced by TIG welding under a gaseous Ar or gaseous Ar+H2 shield. After the tube is cut to a prescribed length, the tube is made into the flexible tube by liquid- pressure bulging. A buldged peak part 2 and a weld zone 3 are provided to the stock tube 1. The work after the bulging is subjected to 1100 deg.CX3 minutes annealing in gaseous H2+N2 and while the H2 is substd. with Ar, the tube is cooled. While the high-temp. salt damage and corrosion cracking gas is concentrically generated in the weld bond part in the as-buldged state, the tube formed by annealing in the reducing gas is entirely free from the high temp. salt damage and corrosion cracking.