Causes of cracking of cold drawn seamless steel pipes

Material defects:

If the steel pipe material itself has defects, such as inclusions, microcracks or segregation, these defects may become stress concentration points during the cold drawing process, leading to cracking.

Insufficient lubrication:

During the cold drawing process, if the lubricant is used improperly or the lubrication is insufficient, the friction between the steel pipe surface and the mold will increase, increasing the risk of cracking.

Cold work hardening:

The steel pipe material will harden during the cold drawing process. If the degree of hardening is too high, the plasticity of the material will be reduced, which may easily cause cracking.

Drawing speed is too fast:

If the drawing speed is too fast, the internal stress of the steel pipe will not have time to be redistributed, which may cause excessive local stress and cause cracking.

Improper mold design:

Improper mold design, such as improper mold angle, shape or size, may cause uneven stress on the steel pipe during the drawing process, increasing the risk of cracking.

Improper heat treatment:

Improper heat treatment process of steel pipes before cold drawing, such as insufficient annealing, may also lead to uneven internal structure of the material, affect the plasticity of the steel pipe, and increase the risk of cracking.

Internal stress:

Steel pipes may generate internal stress during manufacturing, transportation or storage. If these stresses are not effectively released before cold drawing, they may also become the cause of cracking.

Corrosion:

If there is corrosion on the surface of the steel pipe, the organizational structure of the corroded part will change, resulting in a decrease in material performance and easy cracking during the cold drawing process.

Temperature influence:

Improper temperature control of the steel pipe during the cold drawing process. If the temperature is too low, the plasticity of the material will be reduced, which may also lead to cracking.

Improper operation:

Unskilled operators or operating errors, such as excessive or uneven pulling force, may also cause the steel pipe to crack.

In order to avoid cracking of cold-drawn seamless steel pipes, comprehensive consideration and control must be carried out from material selection, mold design, lubrication, heat treatment, operation control and other aspects. At the same time, it is also very important to conduct regular quality inspections of steel pipes to promptly detect and deal with potential cracking risks.