| 摘要 |
PURPOSE:To enable seam welding to be carried out nicely without sacrificing welding speed by seam welding under the specific initial welding pressure for the upward slope of a circular arc of a member and seam welding with increased welding pressure at the top of the circular arc for the downward slope of the circular arc of the member. CONSTITUTION:The upward slope of a circular arc is seam welded under the specific initial welding pressure P, set by a pressurizing means 16 as shown in the pressurization curve 1, the position is detected at the top of the circular arc and the pressurizing force is changed by switching an air circuit. Then, the downward slope of the circular arc is seam welded by increasing the pressure so as to substantially copensate reduced pressure. In this instance, the initial welding pressure P, which is to become substantial welding pressure at the top-most vertex B is set to the lowest limit, or in its vicinity, of the proper welding pressure range 12, and the substantial at starting welding point A and the substantial welding pressure at the top-most vertex B after pressure increase are respectively set to the upper limit, or in its vicinity, of the proper welding force range 12. By this method, reduction of welding strength in the vicinity of the starting climb, welding burns and spattering in the vicinity of the descending terminal are avoided, thus enabling a good seam welding to be carried out.
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