METHOD AND STRUCTURE FOR WELDING CLAD STEEL TUBE

摘要

Provided is a method for welding a clad steel tube (4), the purpose of the method being to improve the corrosion resistance of a portion where friction stir welding (FSW) is started when the welding is performed by friction stir welding from a clad layer side, the welding method comprising a step for circumferentially welding the abutting portions of the ends of the clad steel tube by friction stir welding from the inner side of the clad steel tube in which a clad layer (6) is laminated on the inner periphery of a carbon steel layer (5), wherein an FSW end position (PE) is made to overlap an FSW start position (PS) (by a lap margin (N)), a tool hole (12) formed at the FSW end position is filled in (to form a plugged welded portion (22)) by arc welding using a highly corrosion-resistant welding material (21), and the area (the area from (P1) to (P2)) from the mixed area of the carbon steel layer (5) and the clad layer (6) at the FSW start position (PS) up to the end position where the tool hole (12) is filled in is covered by a padding welding bead (13) formed by arc welding using the highly corrosion-resistant welding material (21) from the inner side of the clad steel tube (4).