本发明介绍的制造方法是:使带钢向下方弯捲并呈螺旋状送进,然后连续地将其外缝先后焊两次,内缝焊一次。由图1可见,开卷后的带钢1由送料辊2和2′送入,并被倾斜辊3、压辊4和成形轴5强制迴转,以形成螺旋管状。倾斜辊3、压辊4和成形轴5坚固地支持在焊管装置的本体上。首先,带钢1的右边缘11与已形成管的 The manufacturing method described in the present invention is to make the strip coil curl downward and feed it in a spiral shape, and then continuously weld the outer seam thereof twice successively and weld seam once. It can be seen from Fig. 1 that the unwound strip 1 is fed by the feed rolls 2 and 2 ’and forcedly rotated by the bevel roll 3, the pressure roll 4 and the forming shaft 5 to form a spiral tube shape. The skew roller 3, the pressure roller 4 and the forming shaft 5 are firmly supported on the body of the pipe welding apparatus. First of all, the right edge 11 of the strip 1 is formed with the tube