| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a laser welded steel pipe, which solves the problem that undercut and underfill tend to occur in laser welding and by which the laser welded steel pipe of which the welded portions are of high quality is stably manufactured at a high yield rate. <P>SOLUTION: In the method for manufacturing the laser welded steel pipe, a steel sheet is shaped into a cylindrical open pipe by means of forming rolls and the edge 2 of the cylindrical open pipe is irradiated with laser beams from the outer surface of the cylindrical open pipe while the edge 2 of the cylindrical open pipe is subjected to pressure by squeeze rolls, so that the edge 2 is welded. Two or more of laser beams 3-1, 3-2, 3-3 and 3-4, which are transmitted with the use of different fibers and of which the spot diameter in just focus is larger than 0.3 mm, are classified into preceding laser beams and following laser beams. The preceding laser beams are made to precede the following beams in the direction of a weld line, and laser beam welding is performed, with the center-to-center distance in the steel sheet between the preceding laser beams and the following beams being 1 mm or longer and with the preceding laser beams and the following beams being arrayed in the direction of the weld line. <P>COPYRIGHT: (C)2012,JPO&INPIT |
