| 摘要 |
PURPOSE:To improve the quality of a weld zone and the yield of a product by controlling the welding electric power according to the wall thickness of a blank pipe, the feeding speed of the same, etc., based on the relation of the optimum welding heat input amount found in advance and various characteristics. CONSTITUTION:The relation of the wall thickness of a blank pipe 3 and the rolling reduction force by a squeezing roll 1 is inputted in a controller in advance and based on this, the roll gap of the squeezing roll 1 is controlled at a optimum value by a driving means 6 according to the wall thickness of the blank pipe 3. The welding electric power is controlled so as to make the welding state optimum from the relation of the feeding speed of the blank pipe and optimum heat input amount which were found in advance and that of the wall thickness and feeding speed of the blank pipe and the optimum heating width of the weld zone. In this way the quality can be improved.
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