| 摘要 |
PROBLEM TO BE SOLVED: To protect a protection layer, such as a powder coating on the inside face of a tube from adverse effects due to welding heat, when welding is made to form an insertion projection part on the outer circumferential face of an insertion port of the tube. SOLUTION: The inside of the insertion port 7 is closed by means of a partition member 21, in the deeper position beyond the mounting positions for an insertion ring 14 and an insertion ring 15 on the outer circumferential face 7a of the insertion port 7. An end face 22 of the insertion port 7 is closed, by means of a plug member 23 having a water supply port 29 and a water discharge port 30, and via the water supply port 29 and the water discharge port 30, and cooling water is supplied into the inside of the insertion port 7 between the plug member 23 and the partition member 21, from the outside of the insertion port 7 for cooling the powder coating part 12 of the insertion port 7.
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