Seamless steel pipes are made of a whole round steel perforated. Steel pipes with no welds on the surface are called seamless steel pipes. According to the production method, seamless steel pipes can be divided into hot-rolled seamless steel pipes, cold-rolled seamless steel pipes, cold-drawn seamless steel pipes, extruded seamless steel pipes, jacked pipes, etc. According to the cross-sectional shape, seamless steel pipes are divided into two types: round and special-shaped. Special-shaped pipes have various complex shapes such as square, oval, triangle, hexagon, melon-shaped, star-shaped, and finned pipes. The maximum diameter is 900mm and the minimum diameter is 4mm. According to different uses, there are thick-walled seamless steel pipes and thin-walled seamless steel pipes. Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemical industry, boiler pipes, bearing pipes, and high-precision structural steel pipes for automobiles, tractors, and aviation.

1. General-purpose seamless steel pipes are rolled from ordinary carbon structural steel, low alloy structural steel or alloy structural steel. They have the largest output and are mainly used as pipes or structural parts for transporting fluids.

2. Available in three categories according to different uses:

a. Supplied according to chemical composition and mechanical properties;

b. Supplied according to mechanical properties;

c. Supplied according to hydraulic pressure test. If the steel pipes supplied according to categories a and b are used to withstand liquid pressure, they must also undergo hydrostatic tests.

3. Special-purpose seamless pipes include seamless pipes for boilers, chemical and electric power, seamless steel pipes for geology, and seamless pipes for petroleum.

Seamless steel pipes have hollow sections 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 materials such as round steel, steel pipes are lighter in weight when the bending and torsional strength is the same, and they are an economical cross-section steel material.

It is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, bicycle frames, and steel scaffolding used in construction. Steel pipes can be used to make ring parts, which can improve material utilization, simplify manufacturing processes, and save materials and processing. Steel pipes have been widely used for manufacturing.