As an important part of steel products, steel pipes are divided into two categories, namely seamless steel pipes (round billets) and welded steel pipes (boards and strips) because of their different manufacturing processes and the shape of the pipe blanks used.
(1) Seamless Steel Tubes Because of their different manufacturing processes, they are divided into hot rolled (extrusion) seamless steel tubes and cold drawn (rolled) seamless steel tubes. Cold drawn (rolled) tube is divided into two kinds of round tube and shaped tube. a. Process Overview Hot-Rolled (Extruded Seamless Steel Pipe): Round Billet → Heating → Perforated → Three-Roll Rolling, Continuous Rolling or Extrusion → Stripping → Sizing (or Reducing) → Cooling → Blanking Tube → Straightening → Hydrostatic test (or flaw detection) → marking → storage. Cold drawn (rolled) seamless steel tube: round tube blank → heating → piercing → start → annealing → pickling → oil coating (copper plating) → multi-pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → Hydrostatic test (flaw detection) → mark → storage. b. Seamless steel tubes, due to their different uses, are divided into the following varieties: GB/T8162-1999 (structural seamless steel tubes). Mainly used for general structure and mechanical structure. The representative material (brand): carbon steel 20,45 steel; alloy steel Q345, 20Cr, 40Cr, 20CrMo, 30-35CrMo, 42CrMo and so on. GB/T8163-1999 (transport fluid seamless steel pipe). It is mainly used for conveying fluid pipelines in engineering and large-scale equipment. Representative material (brand) is 20, Q345 and so on. GB3087-1999 (Seamless steel tubes for low and medium pressure boilers). Mainly used for industrial boilers and domestic boilers to transport low and medium pressure fluids. Representative materials for the 10,20 steel. GB5310-1995 (high pressure boiler seamless steel tubes). Mainly used in power station and nuclear power plant boilers on high temperature, high pressure conveying fluid headers and pipes. Representative materials are 20G, 12Cr1MoVG, 15CrMoG and so on. GB5312-1999 (Carbon and carbon-manganese steel seamless steel tubes for ships). Mainly used for ship boiler and superheater I, II pressure pipe. Representative materials for the 360,410,460 steel grade. GB1479-2000 (seamless steel pipe for high pressure fertilizer equipment). It is mainly used for conveying high-temperature and high-pressure fluid pipes on chemical fertilizer equipment. Representative materials are 20, 16Mn, 12CrMo, 12Cr2Mo and so on. GB9948-1988 (petroleum cracking seamless steel pipe). It is mainly used in boilers, heat exchangers and pipelines for transporting fluids in petroleum smelters. Its representative material is 20, 12CrMo, 1Cr5Mo, 1Cr19Ni11Nb and so on. GB18248-2000 (Seamless steel tubes for gas cylinders). Mainly used for the production of various gas, hydraulic cylinders. Its representative material is 37Mn, 34Mn2V, 35CrMo and so on. GB/T17396-1998 (Hot-rolled seamless steel tubes for hydraulic props). It is mainly used for making coal mine hydraulic supports and cylinders, columns, and other hydraulic cylinders and columns. Its representative material is 20, 45, 27SiMn and so on. GB3093-1986 (high pressure seamless steel tubes for diesel engines). Mainly used for diesel engine injection system high pressure oil pipe. The steel pipe is generally a cold-drawn pipe, and its representative material is 20A. GB/T3639-1983 (cold drawn or cold rolled precision seamless steel tubes). Mainly used for mechanical structure, carbon pressure equipment, requiring high dimensional accuracy, good surface finish steel pipe. Its representative material 20, 45 steel and so on. GB/T3094-1986 (cold drawn seamless steel pipe shaped steel pipe). It is mainly used for making various structural parts and parts. Its material is high-quality carbon structural steel and low-alloy structural steel. GB/T8713-1988 (precision inner diameter seamless steel tubes for hydraulic and pneumatic cylinders). It is mainly used for making cold drawn or cold rolled seamless steel tubes with precision inner diameter dimensions for hydraulic and pneumatic cylinders. Its representative material is 20, 45 steel and so on. GB13296-1991 (boiler, heat exchanger stainless steel seamless steel pipe). It is mainly used for boilers, superheaters, heat exchangers, condensers, and catalytic tubes in chemical companies. Used high temperature, high pressure, corrosion resistant steel pipe. Its representative material is 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr18Ni12Mo2Ti and so on. GB/T14975-1994 (stainless steel seamless pipe for structural use). Mainly used for general structure (hotel, hotel decoration) and mechanical structure of the chemical industry with atmospheric, acid corrosion and a certain degree of strength of the steel pipe. Its representative material is 0-3Cr13, 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr18Ni12Mo2Ti and so on. GB/T14976-1994 (stainless steel seamless pipe for fluid transport). Mainly used for conveying corrosive media. Representative materials are 0Cr13, 0Cr18Ni9, 1Cr18Ni9Ti, 0Cr17Ni12Mo2, 0Cr18Ni12Mo2Ti and so on. YB/T5035-1993 (Seamless steel tubes for automotive axle sleeves). It is mainly used for the production of high-quality carbon structural steel and alloy structural steel hot-rolled seamless steel tubes used for automobile axle bushings and drive axle axle tubes. Its representative material is 45, 45Mn2, 40Cr, 20CrNi3A and so on. API SPEC5CT-1999 (Specifications for Casings and Tubings) is the one developed and published by the American Petroleum Institute (API) and used throughout the world. Among them: Casing: The surface of the pipe extends into the well and is used as a pipe lined with the well wall. The pipes are connected by couplings. The main materials are steel grades such as J55, N80, P110, and steel grades such as C90 and T95 which are resistant to hydrogen sulfide corrosion. Its low grade (J55, N80) can be welded steel pipe. Tubing: A tube inserted from the surface of the earth into the casing up to the oil layer. The tubes are connected by couplings or integrally connected. Its role is that the pumping unit transports the oil from the oil layer to the ground through the oil pipe. The main material is J55, N80, P110, and C90, T95 and other steel grades that are resistant to hydrogen sulfide corrosion. Its low grade (J55, N80) can be welded steel pipe. API SPEC 5L-2000 (Line Pipeline Specification), developed and published by the American Petroleum Institute, is common throughout the world. Line pipe: It is the oil, gas or water from the shaft to the oil and gas industry. The line pipe includes two kinds of seamless and welded pipe. The pipe end has a flat end, a threaded end and a socket end; the connection mode is a terminal welding, a coupling connection, a socket connection, and the like. The main material of the tube is B, X42, X56, X65, X70 and other steel grades.
(2) Welded steel pipe Welded steel pipe is made of steel plate or strip steel. Because of its different welding processes, it is divided into furnace pipe, electric welding (resistance welding) pipe and automatic arc welding pipe. Because of its different welding methods, it is divided into two types: straight seam welded pipe and spiral welded pipe. Because of the shape of its end is divided into round welded pipe and shaped (square, flat, etc.) welded pipe. Welded pipes are divided into the following categories due to their different materials and uses: GB/T3091-1993 (galvanized welded steel pipe for low pressure fluid delivery). Mainly used to transport water, gas, air, oil and heating water or steam and other general low pressure fluid and other uses. It stands for Q235A grade steel. GB/T3092-1993 (Galvanized Welded Steel Pipe for Low Pressure Fluid Transport). Mainly used to transport water, gas, air, oil and heating water or steam and other general low pressure fluids and other uses. Its representative material is: Q235A grade steel. GB/T14291-1992 (mine fluid transport welded steel pipe). Mainly used for mine pressure wind, drainage, axial discharge gas with straight seam welded steel pipe. Its representative material Q235A, B grade steel. GB/T14980-1994 (large diameter welded steel pipe for low pressure fluid delivery). Mainly used for conveying water, sewage, gas, air, heating steam and other low-pressure fluids and other uses. It stands for Q235A grade steel. GB/T12770-1991 (stainless steel welded pipe for mechanical structures). Mainly used for machinery, automobiles, bicycles, furniture, hotel and restaurant decoration and other mechanical parts and structural parts. Its representative material 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb and so on. GB/T12771-1991 (stainless steel welded pipe for fluid transport). It is mainly used for conveying low-pressure corrosive media. Representative materials are 0Cr13, 0Cr19Ni9, 00Cr19Ni11, 00Cr17, 0Cr18Ni11Nb, 0017Cr17Ni14Mo2 and so on.