Carbon steel pipes are categorized into hot-rolled and cold-rolled (drawn) steel pipes.
Hot-rolled carbon steel pipes are classified into general steel pipes, low- and medium-pressure boiler pipes, high-pressure boiler pipes, alloy steel pipes, stainless steel pipes, oil cracking pipes, geological steel pipes, and other steel pipes.
Cold-rolled (drawn) carbon steel pipes, in addition to general steel pipes, low- and medium-pressure boiler pipes, high-pressure boiler pipes, alloy steel pipes, stainless steel pipes, oil cracking pipes, and other steel pipes, also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, stainless thin-walled steel pipes, and special-shaped steel pipes. Hot-rolled seamless pipes generally have an outer diameter greater than 32mm and a wall thickness of 2.5-75mm. Cold-rolled seamless pipes can have an outer diameter of up to 6mm and a wall thickness of up to 0.25mm. Thin-walled pipes can have an outer diameter of up to 5mm and a wall thickness of less than 0.25mm. Cold-rolling offers higher dimensional accuracy than hot-rolling.
General carbon steel pipes are made by hot rolling or cold rolling of high-quality carbon steels such as 10, 20, 30, 35, and 45, low-alloy structural steels such as 16Mn and 5MnV, or alloy steels such as 40Cr, 30CrMnSi, 45Mn2, and 40MnB. Seamless pipes made of low-carbon steels such as 10 and 20 are mainly used for fluid transportation pipelines. Seamless pipes made of medium-carbon steels such as 45 and 40Cr are used to manufacture mechanical parts, such as load-bearing parts of automobiles and tractors. Generally, carbon steel pipes must ensure strength and flattening tests. Hot-rolled steel pipes are delivered in hot-rolled or heat-treated state; cold-rolled steel pipes are delivered in heat-treated state .
