| 摘要 |
PROBLEM TO BE SOLVED: To provide a detection method for a crack in a thermally affected part of a plated steel pipe capable of performing detection by a simple method surely, and in a feed-back mode. SOLUTION: Occurrence of a crack in the thermally affected part is detected by continuously measuring with a bead-width measuring sensor 7, 8, fluctuations in width of bead waste 5 produced when weld beads 3 after welding are cut with a bead cutting tool 4, and detecting the point of time when the pattern of the width fluctuations deviates from a preset width fluctuation pattern, when the pipe is made by heating a plated steel strip with a heating coil 1 and pressing it with a squeeze roll 2 after that, and welding end parts of the steel strip. COPYRIGHT: (C)2005,JPO&NCIPI
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