| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve a problem that a conventional technique has difficulty to obtain an electric resistance welded tube excellent both in out-of-roundness and buckling resistance. Ž<P>SOLUTION: In the manufacturing method of the electric resistance welded tube, roll-forming is applied while a band steel is passed through, with the abutted both ends in the width direction resistance-welded to form a tube and, after heat treatment on a resistance welded zone, the tube is straightened. In straightening the tube, rotary straightening machines are used, wherein the minimum diameter of the concave-surface rolls of the machine is set equal to or larger than the outer diameter of the tube. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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