| 摘要 |
PURPOSE:To eliminate the generation of recess of a steel sheet and damages and rotation defect of a roll, by providing a cylindrical roll, having an axis in the direction of a pipe axis, only to a roll, positioning at the edge part of a steel sheet, among forming rolls arranged in a single row at the inside and in double rows at the outside of the steel sheet to be formed into a pipe. CONSTITUTION:A steel sheet 5 is forced into between pyramid shaped single row of rolls 2 and double rows of rolls 2 and 4 to be formed into a spiral shaped sheet, and it is welled at the seam-parts to be formed into a steel pipe 1. Cylindrical edge part rolls 7, of which roll axes are set parallelly to the axis of pipe 1, are set at both the ends of the row 3 of rolls and a the right (welding side) and of the running direction of the sheet 5 of the row 4 of rolls. Other rolls of the roll axes 3 and 4 are conventional disc-type rolls 9 and are arranged approximately in the direction of a forming angle. In this case, the rolls 7 are set to advnace the rotation slightly to the left direction in order to prevent the sheet 5 from moving to the right direction by the thrust due to the cylinder forming action of the rolls 7. Further, a spiral pipe of larger dia. and of small dia. with heavier wall thickness as compared with usual spiral pipes are obtained. |
