The pipe blank was scratched by the welding machine in the pipe welding unit.
Published Time:
2020-07-06
Scratches in the guiding section generally occur on both sides of the tube blank. If the guiding structure with the guide sleeve is improperly adjusted, frictional scratches will also appear on the upper and lower surfaces of the tube blank. These scratches are characterized by a relatively large and continuous wound area. This is mainly because the height of the guide sleeve is incorrect, or the bearings of the upper and lower guide rollers are damaged, resulting in poor control of the tube blank and friction with the guide sleeve. In addition, scratches on both sides of the tube blank can also be caused when the guide roller deviates too far from the rolling center line, or when the axial difference between the guide sleeve and the guide roller is too large.
Scratches on the billet appearing on the welding machine of the welded pipe unit are mainly caused by two parts: the guiding mechanism and the extrusion welding mechanism.
1.1 Scratches of the guiding mechanism
Scratches in the guiding area generally occur on both sides of the billet. If the guiding structure with the guide sleeve is not adjusted properly, frictional scratches will also appear on the upper and lower surfaces of the billet. The characteristics of this type of scratch are a relatively large wound surface and strong continuity. This is mainly because the height position of the guide sleeve is incorrect, or the bearings of the upper and lower guide rollers are damaged, and the billet cannot be well controlled, causing friction with the guide sleeve. In addition, when the guide roller deviates too much from the rolling center line, or when the axial difference between the guide sleeve and the guide roller is too large, scratches on both sides of the billet will also occur.
1.2 Scratches of the extrusion welding mechanism
Scratches caused by the extrusion rollers mainly occur at the bottom of the billet. The reasons are roughly as follows:
1.1. Mismatched die: The weld extrusion structure has two-roller, three-roller, and four-roller types. As long as the combined die is mismatched, it is easy to cause scratches on the billet surface, especially in the two-roller structure. There are many factors that cause the die to be mismatched. Taking the two-roller structure as an example, such as bearing damage; axial movement of the roller; different die sizes; different height positions of the two rollers; shaft bending; and unstable assembly, etc.
1.2. Height matching: The lower edge of the extrusion roller die should be consistent with the height of the rolling line, while the height of the guide roller is determined by the billet wall thickness. If the height of the guide roller is reduced to a certain limit, the edge fillet of the extrusion roller die will cause scratches at the bottom of the billet, especially when the R fillet of the extrusion roller die is sharpened, scratches are more likely to occur.
1.3. Insufficient extrusion pressure on the extrusion roller: Especially for the two-roller extrusion roller device, when the upper extrusion pressure is insufficient, the roller shaft will tilt upwards under the tension of the billet, causing the edge R fillet of the die to protrude, thus causing scratches at the bottom of the billet. When the R fillet of the extrusion roller die is sharpened, it will aggravate the occurrence of scratches.
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