Six Common Defects in Cold Forming Of Square And Rectangular Tubes

The cold roll forming process is a very complicated process. If the design is not reasonable, various deformation defects will appear during the debugging process. Once these faults are found, they must be solved properly, otherwise, the cold bending forming process of square and rectangular tubes will be further damaged. Below we will introduce six common defects in the cold bending of square and rectangular tubes:

(1) Pocket wave

The generation of pocket waves is mainly due to the non-uniform stress of transverse stretching generated by the pipe during the bending process, while the strain of the sheet material along the thickness direction is relatively small. Shrinkage deformation occurs. The repeated action of this elastic deformation will also form surface cracks.

(2) Longitudinal bending

There are many reasons for longitudinal bending. One of the most important reasons is that the edge of the section is subjected to tension when the side is bent, trying to elongate the entire section longitudinally, but the tension is not enough to elongate the entire rigid section. , causing the front end of the square tube to bend upward or downward, and thick plates are more prone to longitudinal bending than thin plates. At present, because the equipment has a straightening device to make up for the correction, it is not taken seriously by many people.

(3) Crack

The main cold-bending defect of a square rectangular tube is a cold-bending crack, which is determined by its own material properties.

(4) Edge waves

The generation of edge waves is mainly a combination of two effects: the first one is the same as the previous bag-shaped wave in the same mechanism; the second is that the material at the edge is first stretched and sheared to lengthen under the action of external force, and then stretched again. The plastic deformation caused by compression and shearing results in edge waves.

(5) Cross-section burrs

Burrs can be caused by blunt cutting blades, excessive gaps, blunt saw blades, and improper installation. The irregular welding system will also make it easier to leave burrs when cutting.

(6) Dimensional fluctuations

The reason for the large dimensional fluctuations in the cold bending of rectangular tubes is mainly due to improper operation when adjusting the rolls, or too fast compaction speed.