Classification of quality defects of seamless steel pipes

a. Serious defects of seamless steel pipes: cracks, internal folds, external folds, rolling, delamination, scarring, concave, convex hulls, etc.

b. General defects of seamless steel pipes: pits, blue lines, scratches, bumps, slight inner and outer straights, roll marks, etc.

Causes of defects in seamless steel pipes:

① Due to surface defects or internal defects of the tube blank.
② In the production process, such as incorrect design of rolling process parameters, unsmooth die surface, poor lubrication conditions, and unreasonable pass design and adjustment.
③ In the process of heating, rolling, heat treatment and straightening of the tube blank, if the heating temperature is not properly controlled, the deformation is uneven, the heating and cooling speed is unreasonable or the straightening deformation is too large, resulting in excessive damage. Residual stress may also lead to surface cracks in seamless steel pipes.