| 摘要 |
PURPOSE:To improve straightening accuracy and to reduce straintening cost by heating a part of steel pipe, located at the position symmetric with respect to a weld-joining part, simultaneously with the start of welding or a little later than it. CONSTITUTION:Dollys 6 equipped with turning rolls 7 are provided, and a sheet pile 4 of steel pipe is mounted on the rolls 7 as well as a welding torch 8 is set. A heating burner 9 is attached to the opposite side of a joining part at a 0-3m distance back from the torch 8. Simultaneously with the starting of welding, the dollys 6 are moved in the arrow (a) direction to start the normal welding. When the dollys 6 moves to the other end of the welding part to finish the welding and heating, the sheet pile 4 is turned by 180 deg. and the dollys 6 are moved in the opposite direction to perform the normal welding and heating. In this way, as the expanding action, in the axial direction, of the position symmetric with respect to the joining part, is balanced, to improve the straightening accuracy. Thus, the need for a large space and straightening operators are eliminated to reduce the straightening cost.
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