| 摘要 |
PROBLEM TO BE SOLVED: To avoid the stress corrosion crack of the joint part of tubes which is caused by a residual tensile stress field. SOLUTION: By tacking and fixing the tip part of an existing tube 4 and that of a new tube 5 by full periphery welding of several passes from the inside surface of the tubes, the cladding layer 7 of welding on the existing tube side is successively formed in the direction separating from the new tube 5 by the full periphery welding on an inside surface near the joint part of the existing tube 4, and a welded joint 6 connecting the tip parts of both tubes 4, 5 is formed by the full periphery welding from the inside surface of the tubes. By forming successively the cladding layers 8, 9 of the welding of a joint part on the inside surface of the joint part of both tubes 4, 5 from the start edge of the forming of the cladding layer 7 of the welding on the above mentioned existing tube side toward the new tube 5 so that adjacent welding beads are lapped by the full periphery welding and by changing the start position of the welding for each pass, a residual compressive stress field is uniformly generated on the whole periphery of the outside surface of the joint part of both tubes 4, 5.
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