Seamless steel pipe is a long steel bar with a hol

Steel pipes have a hollow cross section, and are widely used as pipelines for transporting fluids, such as pipelines for transporting oil, natural gas, coal gas, water, and certain solid materials. Compared with solid steel such as round steel, steel pipe is lighter in weight when the flexural and torsional strength is the same. It is an economic cross-section steel and is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, and bicycles. Frame and steel scaffolding used in construction. 

The use of steel pipes to manufacture ring parts can improve material utilization, simplify the manufacturing process, save materials and processing hours, such as rolling bearing rings, jack sleeves, etc. At present, steel pipes have been widely used for manufacturing. Steel pipes are also indispensable materials for various conventional weapons, and the barrels and barrels are all made of steel pipes. 

Steel pipes can be divided into round pipes and shaped pipes according to different cross-sectional shapes. 
Since the circle area is the largest under the condition of equal circumference, more fluid can be transported with a round tube. 
In addition, when the circular cross-section is subjected to internal or external radial pressure, the force is relatively uniform. Therefore, most steel tubes are round tubes.

However, the round tube also has certain limitations. For example, under the condition of flat bending, the round tube is not as strong as the square and rectangular tube. Some agricultural machinery skeletons and steel-wood furniture are commonly used. 
According to different applications, other shaped steel tubes with other cross-sectional shapes are required.