| 摘要 |
PURPOSE:To build a building etc. economically by manufacturing a steel pipe having projections by pressing a pressing part and pressing fittings against a steel plate using a steel plate having projections as a material. CONSTITUTION:A material steel plate 1 is carried under a mandrel bar 2. After positioning, the steel plate 1 is pressed by the pressing part 3 of a lower cylinder 4 against the mandrel bar 2. Pressing fittings 5 of left and right rotating arms 12 are put a little inside from both ends of the steel plate 1. Current is applied to electromagnetic coils of pressing fittings 5 to make the pressing fittings 5 electromagnets to prevent detaching of the fittings 5 from the steel plate 1. Then, rotating arms 12 are rotated to bend the steel plate 1 to A2 position, and both ends of the steel plate 1 are enclosed by the pressing part 3 of an upper cylinder 16, and pushed down to form the steel plate. After this, butted parts of the steel plate 1 are tack welded. Then, the steel pipe is pulled out from the mandrel bar 2 and the seam is welded regularly. |
