1. There are holes in seamless steel pipes, that is, there are round, long, elliptical, and various irregular holes inside the steel pipe, and they may also be aggregated into pieces, and the color is black or gray. The shape is most irregular, and the crystal grains are also very coarse. There are also some blisters. The so-called blisters refer to the presence of sand-like holes inside the tube. The reason for this situation is generally that air bubbles are mixed in the production process of the steel pipe.

2. Metal cracks refer to irregular-shaped cracks or lines on the metal surface, similar to the way the metal is torn. There are many reasons for this situation, mainly due to the insufficient heating temperature of the metal. The hard perforation operation causes the metal to tear. The solution is to control the temperature of the heating furnace.

3. Surface defects, some have pits, that is, there are certain pits and pits on the surface of the pipe body; there is also a phenomenon of metal scabs, which is generally caused by failure to deal with the surface of the steel pipe. The surface finish of the steel pipe is not good.

4. The size of the steel pipe is unqualified and exceeds the standard allowable error of the steel pipe, such as 10% of the outer diameter and wall thickness, which is caused by the inability to sizing during the rolling process. In this case, there is also the phenomenon of off-wall or eccentricity, and it is often easy to occur that one side is thick and the other is thin.