| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacturing an electric-seam welded steel pipe which is suitable for producing a small lot and many kinds, can lighten a mill load and is further excellent in being processed, having nice surface texture without seizure cracking and a line of equipments. SOLUTION: In the method of manufacturing the electric-seam welded steel pipe by repeating each step of roll forming a hoop, seam welding an open pipe obtained and roll reducing the pipe obtained, the pipe after being seam welded whose bead is cleared is subsequently heated as a whole to roll reduce at a temperature region of a transformation point 400 deg.C-Ac3. Further, on request one or more than two of the following are applied: bead rolling before heating the pipe whose bead is cleared, seam annealing before heating the pipe whose bead is cleared, seam cooling before heating the pipe whose bead is cleared, keeping warm or heating after roll reducing and chamfering at the width end of the hoop before roll forming.
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