| 摘要 |
PROBLEM TO BE SOLVED: To remove the retention of a liquid state cooling medium W1 caused by evaporation, to effectively cool a smoothing tool 2 for an inside bead B, and to smooth the inside bead B in stable condition for a long time. SOLUTION: After the both ends, in the width direction, of metallic belt continuously formed in cylindrical shape are welded, and when a supporting body 4 attached with the smoothing tool 2 at the end is inserted into the inside of a welded pipe P from a non-welded part side and the bead inside the surface is smoothed, the inside space 5 of the smoothing tool 2 is connected to the inside hollow part 6 of the supporting body 4, the liquid state cooling medium W1 is fed to the inside space 5 of the smoothing tool 2 through a supply pipe 12 arranged under the inside space 5 and the inside hollow part 6, and the liquid state cooling medium W2 used for cooling the smoothing tool 2 is discharged out of the system through the inside space 5 of the smoothing tool 2 and the inside hollow part 6 of the supporting body 6.
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