During the smelting and rolling (forging) process of carbon steel pipes, steel is lacking due to reasons such as equipment, technology and operation. It mainly includes scars, cracks, shrinkage cavity residues, delamination, white spots, segregation, non-metallic inclusions, loose and banded tissues, etc.

High carbon steel pipe is a seamless steel pipe with high carbon content, the carbon content is from 0.60% to 1.70%. It is made of steel ingot or solid tube blank by perforation, and then hot rolled, cold rolled or cold drawn, and can be quenched and tempered.

The flange connection of the seamless pipe is to fix two pipes, pipe fittings or equipment on a flange respectively. Then add flange pads between the two flanges, and finally tighten the two flanges with bolts to make them tightly combined. A detachable joint. The connection between stationary pipelines and rotating or reciprocating equipment can be realized.

Stainless steel pipe is a hollow elongated round steel material, which is widely used in petroleum, chemical, medical, food, light industry, mechanical instrumentation and other industrial pipelines and mechanical structural components. In addition, when the bending and torsional strength are the same, the weight is lighter, so it is also widely used in the manufacture of mechanical parts and engineering structures, and is also commonly used as furniture and kitchen utensils.

Seamless steel pipes or welded steel pipes with a ratio of outer diameter to wall thickness of less than 20 are called thick-walled steel pipes. It is mainly used as octg pipe, petroleum geological drilling pipe, cracking pipe for petrochemical industry, boiler pipe, bearing pipe, high-precision structural pipe for automobile, tractor and aviation, etc.

The thick-walled square tube is a hollow square cross-section light-duty thick-walled steel tube, also known as steel cold-formed profile. It is a section steel with a square cross-section shape and size made of Q235 hot-rolled or cold-rolled strip or coil as the base material, which is cold-bent and then high-frequency welded. In addition to the thickened wall thickness of the hot-rolled extra-thick-walled square tube, its corner size and edge straightness have reached or even exceeded the level of the resistance-welded cold-formed square tube.