TITANIUM WELDED PIPE FOR FRETTING FATIGUE RESISTANT MEMBER, AND METHOD FOR MANUFACTURING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a titanium welded pipe for a fretting fatigue member which can improve fatigue properties while maintaining formability of welded parts and can suppress the occurrence of fretting fatigue that occurs on the surface of a base metal, and to provide a method for manufacturing the same.SOLUTION: The titanium welded pipe for the fretting fatigue resistant member has a higher nitrogen concentration by 0.003 to 0.030% by mass in the interior portion of the welded part than that in the interior part of the base metal, and has titanium nitride on the surface of the base metal on which a surface layer remains being unremoved after cold rolling. The method for manufacturing the titanium welded pipe includes: heating a titanium sheet or strip which is used in pipe-making and has the surface layer remaining unremoved after cold rolling, in a nitrogen gas atmosphere for nitriding heat treatment to perform predetermined nitriding; forming the sheet or strip into a tubular shape; shielding the abutted portion with an argon gas; and performing welding without use of a hot charge. The welded pipe may be heated in a nitrogen gas atmosphere or an oxidation atmosphere for light nitriding or light oxidation.