A seamless pipe is a tube that does not have any welding seam. Seamless pipes are derived from solid steel that is in sheet or bar form and is formed into a solid round shape known as “billets” which are then heated and cast over a form such as a piercing rod to create a hollow tube or shell.A seamless tube may also be known as a seamless pipe.

Characteristics of seamless steel pipe

High precision can do small batch production.
Smaller diameter.
Weldability strong, high compression capability.
Steel pipe superior performance, relatively dense metal.
Steel Cross area is more complex.
High precision cold drawn products, good surface quality.
Classification of Seamless Steel Pipe

According to the manufacturing process, seamless pipe can be divided into hot-rolled seamless steel tubes and cold-drawn seamless steel pipe two kinds. Cold drawn tube is also divided into circular pipe and shaped pipe. 

Hot-rolled seamless steel pipe

Hot rolled is relative to the cold-rolled, cold rolling is below the recrystallization temperature of the rolling, and hot rolled is carried out at above the recrystallization temperature of the rolling.

Advantages Hot-rolled seamless steel pipe

hot rollded seamless steel pipe can damage the cast microstructure of the steel ingot, refinement of the crystal grains of the steel, and eliminate the defects of the microstructure, so that the the steel organization compacting, improve the mechanical properties. This improvement is reflected in the rolling direction, so that the steel is no longer to a certain extent isotropic; pouring the formation of bubbles, cracks, and osteoporosis, under high temperature and pressure can also be welded together.

Advantages and disadvantages of cold rolled seamless pipes

Advantages

1. The speed of molding and the productivity are high. The coating will not be damaged. The sections can be made in various shapes so as to adapt to different conditions. Cold rolled processes can make steel have great plastic deformation so as to increase the yield point of steel.
2. Cold rolled processes can destroy the casting structure of steel ingots, refine the grain of steel products and eliminate the defects of microstructure so as to make the structure of steel products compact and improve the mechanical property of steel products. This kind of improvement reflects mainly along the rolling direction, which makes steel products not isotropic bodies any longer to some extent. Bubbles, cracks and shrinkage formed in casting can be repaired under the effects of high temperatures and pressure.
Disadvantages
1. The section of cold rolled steel is the open section generally, which has relatively low free torsion stiffness. The steel is twisted easily when it is bent; flexural-torsional buckling showed up easily when steel is pressed. The torsion resistance is relatively poor.
2. The wall of the cold rolled steel pipe is relatively thin. The corners connecting plates are not thickened. The bearing ability of the partial concentrated load is weak.