Rectangular tubes (such as a500 square tube and a500 rectangular tube) are a name for square tubes and rectangular tubes, that is, steel tubes with equal and unequal side lengths. It is made of strip steel after process treatment. Generally, the strip steel is unpacked, flattened, crimped, welded to form a round tube, and then rolled into a square tube from the round tube and then cut to the required length.

Welded steel pipe is a steel pipe made of steel plate or strip steel after being crimped and welded, generally with a length of 6 meters. The production process of welded steel pipe is simple, the production efficiency is high, there are many varieties and specifications, and the investment in equipment is small, but the general strength is lower than that of seamless steel pipe.

Welded steel pipes are generally formed by deforming steel strips or steel plates into round or square shapes under the action of external force, and then welding the seams on the surface to form welded steel pipes.The seamless steel pipe is mainly to perforate the solid tube billet or steel ingot to make a capillary pipe, and then process it through hot rolling, cold rolling, cold drawing, etc., and then form a seamless steel pipe. Since the seamless steel pipe contains a hollow section, this hollow section can be used as a pipe for conveying fluid.

Boiler steel pipe refers to a steel product with openings at both ends and a hollow section, and the ratio of its length to the surrounding area is large. According to the production method, it can be divided into seamless steel pipes and welded steel pipes. The specifications of boiler steel pipes are represented by external dimensions (such as outer diameter or side length) and wall thickness, and their size ranges from a small capillary tube to a large diameter tube with a diameter of several meters. Steel pipes can be used in pipelines, thermal equipment, machinery industry, petroleum geological exploration, containers, chemical industry and special purposes.

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.