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

　　Cold rolled (dialed) seamless steel pipes include general steel pipes, low and medium pressure boiler pipes, high pressure boiler pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes and other steel pipes. They also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, stainless thin-walled steel pipes and profiled steel pipes.

　　The outer diameter of hot-rolled seamless pipe is generally larger than 32 mm, the wall thickness is 2.5-75 mm, the diameter of cold-rolled seamless pipe can reach 6 mm, the wall thickness can reach 0.25 mm, the outer diameter of thin-walled pipe can reach 5 mm, the wall thickness is less than 0.25 mm, and the dimension precision of cold-rolled seamless pipe is higher than that of hot-rolled pipe.

　　ASTM A53 Sch140 Round ERW Seamless Steel Pipes are generally made by hot rolling or cold rolling of high quality carbon-bonded steel 16Mn, 5MnV or low alloy structural steel 40Cr, 30CrMnSi, 45Mn2, 40MnB, etc. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid transmission pipelines. Seamless tubes made of medium carbon steel, such as 45, 40Cr, are used to manufacture mechanical parts, such as stress parts of automobiles and tractors. Generally, seamless steel tube should be used to ensure strength and flattening test. Hot-rolled steel pipes are delivered in hot-rolled or heat-treated state; cold-rolled steel pipes are delivered in hot-rolled or heat-treated state.

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