The forming process of thin-walled welded steel pipe

1. Downhill forming method

Downhill shaping of welded steel pipe equipment can significantly reduce edge extension.

2. Increase the elongation in the middle of the billet

During the forming process, the reduction of the opening hole pattern is increased, so that the gap between the upper and lower rolls is slightly smaller than the thickness of the billet. The middle part of the billet is micro-calendered to make the extension of the middle part slightly larger to reduce the relative extension of the edge. If the middle extension is greater than the edge extension, the outlet is bent upwards, and if the middle extension is smaller than the edge extension, downward bending occurs. The central extension increases the deformer of the forming machine, which increases the power consumption, causes serious wear of the rollers, and easily damages the equipment. When the tube blank slides relative to the roll surface, roll marks and scratches are easily generated.

3. Increase the length of the deformation belt

If possible, increase the number of frames involved in the deformation, i.e. increase the length of the deformation zone and reduce the deformation between two adjacent frames. Since the side extension is proportional to the square of the frame height, the side extension can be significantly reduced.

4. Increase the diameter of the roller

Increasing the roll diameter means increasing the length of the deformation zone of the frame. The edge extension is inversely proportional to the length of the deformation zone of the weld bead. Where possible, increase the roll diameter as much as possible to reduce edge extension.

5. Reduce the distance between racks

When the distance between the frames is large, the cumulative edge extension of each frame must be compressed and absorbed by the last frames, which can easily cause swelling. Shortening the inter-frame distance essentially increases the number of frames that can be compressed and absorbed at any time, improving shaping conditions. However, the distance between the frames cannot be too small, and there must be enough room for manipulation.