Cold-rolled seamless pipe is a cold-drawn or cold-rolled precision seamless steel pipe with high dimensional accuracy and good surface finish for mechanical structures and hydraulic equipment.

Seamless steel tubes are divided into two types: hot rolled and cold rolled （cold drawn) seamless steel tubes.

Cold rolled （cold drawn) seamless pipe is divided into general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe, other steel pipes, and also includes carbon thin-walled steel pipe and alloy thin-walled steel pipe. Stainless steel thin-walled steel pipe and special-shaped steel pipe. The outer diameter of the hot-rolled seamless pipe is generally larger than 32mm, the wall thickness is 2.5-75mm, the diameter of the cold-rolled seamless steel pipe can be 6mm, the wall thickness can be 0.25mm, the outer diameter of the thin-walled pipe can be 5mm, and the wall thickness is less than 0.25mm. Cold rolled has higher dimensional accuracy than hot rolled.

Hot-rolled seamless pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes.

The common used seamless pipe is made of low-alloy structural steel such as 16Mn, 5MnV, such as 10, 20, 30, 35, 45, etc., or alloy steel such as 40Cr, 30CrMnSi, 45Mn2, 40MnB, etc., which is hot rolled or cold rolled. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid conveying pipes. 45, 40Cr and other medium carbon steel seamless pipes are used to make mechanical parts, such as the force parts of automobiles and tractors. Generally, seamless steel pipes are required to ensure strength and flattening test. The hot rolled steel pipe is delivered in a hot rolled state or a heat treated state; the cold rolling is delivered in a heat treated state.

The main difference between hot rolled and cold rolled seamless pipes:

1. Cold-rolled steel allows partial buckling of the section, so that the bearing capacity of the bar after buckling can be fully utilized; and the hot-rolled steel does not allow local buckling of the section.

2. The causes of residual stresses in hot-rolled and cold-rolled steels are different, so the distribution on the cross-section is also very different. The residual stress distribution on the section of the cold-formed thin-walled steel is curved, while the residual stress distribution on the section of the hot-striped steel or welded steel is a film type.

3. The free torsional stiffness of hot-rolled steel is higher than that of cold-rolled steel, so the torsional properties of hot-rolled steel are better than those of cold-rolled steel.