Steel pipes made of a single piece of metal without seams on the surface are called seamless pipes.  According to the production method, seamless tube is divided into hot rolled pipe, cold rolled pipe, cold drawn pipe, kneading pipe, pipe jacking, etc.  According to the section shape, seamless pipe is divided into round and special-shaped, special-shaped pipe has square, oval, triangle, hexagonal, melon seed, star, winged pipe complex shape.  The maximum diameter is 650mm and the minimum diameter is 0.3mm.  Different according to use, there are thick wall pipe and thin wall pipe.  Seamless pipe is mainly used as petroleum geology drilling pipe, petrochemical cracking pipe, boiler pipe, bearing pipe and car, tractor, aviation high-precision structural steel pipe.  

Seamless works in a wide range of ways.  The general use of seamless pipe by general carbon structural steel, low alloy structural steel or alloy structural steel rolling, production is the most, mainly used for transporting fluid pipeline or structural parts.  According to the use of different types of supply: a, according to the chemical composition and mechanical properties of supply;  B. Supply according to mechanical properties;  C. Supply according to water pressure test.  The steel pipes supplied according to class A and B, if used to withstand liquid pressure, shall also be subjected to hydrostatic test.  The seamless pipe of special use has boiler with seamless pipe, chemical power with, geology with seamless pipe and oil with a variety of seamless pipe.  

 
Seamless pipe has a hollow section, many used for transporting fluid pipelines, such as transporting oil, natural gas, gas, water and some solid material pipelines.  Compared with solid steel such as round steel, steel pipe has the same bending and torsional strength and lighter weight, so it is a kind of economic section steel.  And widely used in the production of structural parts and mechanical parts, such as oil drill pipe, car drive shaft, bicycle frame and construction of steel scaffolding and other steel pipe production ring parts, can improve the utilization rate of data, simplify the production process, save data and processing time.  

 
The mechanical properties of steel, which depend on the chemical composition of steel and the heat treatment criteria, are important objectives to ensure the ultimate performance of steel.  In the steel pipe specification, according to different application requirements, the tensile properties (tensile strength, yield strength or yield point, elongation) and hardness, tolerance targets, as well as high and low temperature properties required by users.