Cold-rolled pipe quality defects and the prevention

The main quality defects of cold-rolled steel pipes include: uneven wall thickness, out-of-tolerance outer diameter, surface cracks, wrinkles, roll folds, etc.

① Improving the wall thickness accuracy of the tube blank is an important condition to ensure uniform wall thickness of cold-rolled steel pipes.

② Ensuring the wall thickness accuracy and pickling quality of the tube blank, the lubrication quality and the surface finish of the tube rolling tool are important guarantees for improving the wall thickness accuracy of the cold rolled tube. Over-pickling or under-pickling of the tube blank should be prevented, and the surface of the tube blank should be prevented from being over-pickled or under-pickled. If pitting or residual iron oxide scale is produced, strengthen the cooling of pipe rolling tools and inspection of tool surface quality, and promptly replace unqualified mandrel rods and rolling groove blocks.

③ All measures to reduce the rolling force are conducive to improving the outer diameter accuracy of the steel pipe, including annealing the tube blank, reducing the amount of rolling deformation, improving the lubrication quality of the tube blank and the surface finish of the tube rolling tool, etc., using Use materials with high strength and hardness to make pipe rolling tools, and strengthen the cooling and inspection of pipe rolling tools. Once the pipe rolling tools are found to be severely worn, they should be replaced in time to prevent the outer diameter of the steel pipe from exceeding the tolerance.

④ Cracks on the surface of steel pipes produced during the cold rolling process are caused by uneven deformation of the metal. In order to prevent surface cracks in the steel pipe during cold rolling, the tube blank should be annealed when necessary to eliminate work hardening of the metal and improve the plasticity of the metal.

⑤ The amount of rolling deformation has a crucial impact on the surface cracks of cold-rolled steel pipes. Appropriate reduction of the deformation is a very effective method to reduce the surface cracks of steel pipes.

⑥ Improving the surface finish of pipe rolling tools and the lubrication quality of pipe blanks are active measures to prevent cracks in steel pipes.

⑦ By annealing and heat treating the tube blank to reduce the deformation resistance of the metal, reduce the amount of deformation, and improve the quality of the tube rolling tools and lubrication quality, etc., it is beneficial to reduce the occurrence of steel pipe rolling folding and scratch defects.