Examples, characteristics, and causes of steel pipe defects and defects

Surface indentation characteristics: The outer surface of the steel pipe is a spiral-shaped indentation.
cause:
1) The angle of the straightening machine roller is improperly adjusted and the reduction amount is too large.
2) The straightening roller is seriously worn, etc. Cause: The roller sticks to steel and other reasons.

Cause of cracks:
(1) The raw material itself has component segregation before conditioning;
(2) During the heat treatment process of steel pipes, excessive temperature stress will cause surface cracks in the steel pipes.

Causes of pockmarked (internal) surfaces:
(1) The mandrel is seriously worn and has not been replaced in time;
(2) The iron oxide scale in the punching blank has not been eliminated. The pitted surface (outer) features:

The surface of the steel pipe shows uneven pits.
cause:
1) The steel pipe stays in the furnace for too long or the heating time is too high, causing the iron oxide scale on the surface to be too thick, not clean, and rolled into the surface of the steel pipe.
2) The high-pressure water phosphorus removal equipment is not working properly and the phosphorus removal is not clean, etc.

Characteristics of internal scarring: The inner surface of the steel pipe shows scars, which generally do not take root and are easy to peel off.
cause:
1) Graphite lubricant contains impurities.
2) The iron ear at the rear end of the waste pipe is pressed into the inner wall of the steel pipe, etc.
3) Excessive inclusions in the tube blank or unreasonable rolling process can also cause it.