Cold-rolled Tube Quality Defects and Their Prevention

Major quality defects of cold-rolled steel tubes include uneven wall thickness, out-of-tolerance outer diameters, surface cracks, wrinkles, and folds.

 

 

① Improving the wall thickness accuracy of the tube billet is crucial for ensuring uniform wall thickness of cold-rolled steel tubes.

 

② Ensuring the wall thickness accuracy of the tube billet, the quality of pickling, lubrication, and the surface finish of the tube rolling tools are crucial for improving the wall thickness accuracy of cold-rolled tubes. Over- or under-pickling of the tube billet should be avoided, as should the formation of roughness or residual iron oxide on the tube billet surface. Inspections of the cooling and surface quality of the tube rolling tools should be strengthened, and substandard mandrels and groove blocks should be promptly replaced.

 

③ Any measures to reduce rolling forces will help improve the outer diameter accuracy of steel pipes, including annealing the tube blank, reducing rolling deformation, improving the lubrication quality of the tube blank, and the surface finish of the rolling tools. Use high-strength and high-hardness materials for tube rolling tools, and strengthen the cooling and inspection of the tools. If tools are severely worn, they should be replaced promptly to prevent tube outer diameter deviations.

 

④ Surface cracks in steel pipes caused by uneven deformation of the metal during cold rolling. To prevent surface cracks in steel pipes during cold rolling, annealing the tube blank is necessary to eliminate work hardening and improve its plasticity.

 

⑤ The degree of rolling deformation is crucial to the occurrence of surface cracks in cold-rolled steel pipes. Appropriately reducing the deformation is a very effective method to reduce surface cracking in steel pipes.

 

⑥ Improving the surface finish of the rolling tools and the lubrication quality of the tube blank are proactive measures to prevent cracks in steel pipes.

 

⑦ Annealing heat treatment of the cold-rolled steel tubes billet to reduce the deformation resistance of the metal, reduce the deformation amount, improve the quality of tube rolling tools and lubrication quality, etc., are all beneficial to reducing the occurrence of steel tube rolling and scratch defects.