The advantage of P11 alloy steel pipe is that it can be 100% recycled, in line with the strategy of environmental protection, energy saving and resource conservation, and the policy encourages the expansion of the application field of alloy pipe P11.

At present, the consumption of P11 alloy steel pipes in China accounts for only half of the total amount of developed steel, and the expansion of the use of P11 alloy steel pipes provides a broader space for the development of the industry. According to the research of the P11 alloy steel pipe branch of China Special Steel Association, the average annual growth of China’s high-pressure P11 alloy steel pipe long products can reach 10-12% in the future.

1. Seamless steel pipe

Due to its different manufacturing processes, it is divided into two types: hot-rolled (extruded) seamless steel pipe and cold-drawn (rolled) seamless steel pipe. Cold-drawn (rolled) pipes are divided into two types: round tubes and special-shaped tubes.

a． Process overview

Hot rolled (extruded seamless steel pipe): Round pipe billet → heated → perforated→ three-roll oblique rolling, continuous rolling or extrusion → de-sizing→ sizing (or reducing diameter) → cooling → billet pipe → straightening→ hydrostatic test (or flaw detection) → marking → storage.

Cold-drawn (rolled) seamless steel pipe: round round pipe billet→ heating→perforating→ heading→ annealing→ pickling→ oiling (copper plating), →multi-pass cold-drawn (cold-rolled) →billet pipe→ heat treatment→ straightening→ hydrostatic test (flaw detection) → marking → storage.

b. Seamless steel pipe, due to its different uses, is divided into the following varieties:

GB/T8162-2008 (seamless steel pipe for structure). It is mainly used for general structure and mechanical structure. Its representative material (grade): carbon steel 20, 45 steel; Alloy steel Q345, 20Cr, 40Cr, 20CrMo, 30-35CrMo, 42CrMo, etc.

GB/T8163-2008 (seamless steel pipe for transporting fluids). It is mainly used to transport fluid pipelines on engineering and large-scale equipment. Representative materials (grades) are 20, Q345, etc.

GB3087-2008 (seamless steel pipe for low and medium pressure boilers). It is mainly used in pipelines for transporting low and medium pressure fluids in industrial boilers and domestic boilers. The representative material is 10 and 20 gauge steel.

GB5310-2008 (seamless steel pipe for high pressure boiler). It is mainly used for high-temperature and high-pressure conveying fluid headers and pipelines on boilers in power stations and nuclear power plants. Representative materials are 20G, 12Cr1MoVG, 15CrMoG, etc.

GB5312-1999 (carbon steel and carbon manganese steel seamless steel pipe for ships). Mainly used in ship boilers and superheaters with I and II pressure resistant tubes. Representative materials are 360, 410, 460 steel grade, etc.

GB6479-2000 (seamless steel pipe for high-pressure fertilizer equipment). It is mainly used in the pipeline of high temperature and high pressure fluid transportation on fertilizer equipment. Representative materials are 20, 16Mn, 12CrMo, 12Cr2Mo, etc.

GB9948-2006 (seamless steel pipe for petroleum cracking). Mainly used in boilers, heat exchangers and their conveying fluid pipelines in petroleum refineries. Its representative materials are 20, 12CrMo, 1Cr5Mo, 1Cr19Ni11Nb, etc.

GB18248-2000 (seamless steel pipe for gas cylinder). It is mainly used to make various gas and hydraulic gas cylinders. Its representative materials are 37Mn, 34Mn2V, 35CrMo, etc.

GB/T17396-1998 (hot-rolled seamless steel pipe for hydraulic pillar). It is mainly used to make coal mine hydraulic supports, cylinders, columns, and other hydraulic cylinders and columns. Its representative materials are 20, 45, 27SiMn, etc.

GB3093-1986 (high-pressure seamless steel pipe for diesel engine). It is mainly used for high-pressure oil pipes in diesel engine injection systems. Its steel pipe is generally cold-drawn pipe, and its representative material is 20A.

GB/T3639-1983 (cold-drawn or cold-rolled precision seamless steel pipe). Mainly used for mechanical structure, carbon compression equipment, high dimensional accuracy, good surface finish of steel pipe. Its representative materials are 20, 45 steel, etc.

GB/T3094-1986 (cold-drawn seamless steel pipe special-shaped steel pipe). It is mainly used to make various structural parts and parts, and its materials are high-quality carbon structural steel and low-alloy structural steel.

GB/T8713-1988 (precision inner diameter seamless steel pipe for hydraulic and pneumatic cylinders). It is mainly used to make cold-drawn or cold-rolled seamless steel pipes with precise inner diameter dimensions for hydraulic and pneumatic cylinder barrels. Its representative materials are 20, 45 steel, etc.

GB13296-1991 (stainless steel seamless steel pipe for boiler and heat exchanger). Mainly used in boilers, superheaters, heat exchangers, condensers, catalytic tubes, etc. in chemical enterprises. High temperature, high pressure, corrosion resistant steel pipe. Its representative materials are 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr18Ni12Mo2Ti, etc.

GB/T14975-1994 (stainless steel seamless steel pipe for structure). It is mainly used for general structure (hotel, restaurant decoration) and chemical enterprise mechanical structure for atmospheric and acid corrosion resistant and certain strength steel pipe. Its representative materials are 0-3Cr13, 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr18Ni12Mo2Ti, etc.

GB/T14976-1994 (stainless steel seamless steel pipe for fluid transportation). It is mainly used in pipelines to transport corrosive media. Representative materials are 0Cr13, 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr17Ni12Mo2, 0Cr18Ni12Mo2Ti, etc.

YB/T5035-1993 (seamless steel pipe for automobile half-shaft casing). It is mainly used to make high-quality carbon structural steel and alloy structural steel hot-rolled seamless steel pipe for automobile half-shaft casing and drive axle shell shaft tube. Its representative materials are 45, 45Mn2, 40Cr, 20CrNi3A, etc.