Classification of small diameter seamless steel pipe:

The specification of seamless steel pipe is usually expressed by outer diameter * wall thickness (unit: mm). According to the production method, seamless steel pipe can be divided into hot-rolled seamless steel pipe and cold-rolled (DIAL) seamless steel pipe.

Hot rolled seamless steel 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, geological steel pipe and other steel pipes.

Cold rolled (drawn) seamless steel pipe includes not only general steel pipe, low and medium pressure boiler steel pipe, high-pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe and other steel pipes, but also precision steel pipe, carbon thin-walled steel pipe, alloy thin-walled steel pipe, stainless steel thin-walled steel pipe, special-shaped steel pipe, etc.

The outer diameter of hot-rolled seamless pipe is generally greater than 32mm and the wall thickness is mm. The outer diameter of cold-rolled seamless steel pipe can be up to 6mm and the wall thickness can be up to 0.25mm. The outer diameter of thin-walled pipe can be up to 5mm and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling. In pipeline engineering, when the diameter exceeds 57mm, hot-rolled pipe is often used, and cold drawn (rolled) pipe is often used when the diameter is less than 57mm.