Large-diameter thick-walled seamless steel pipes are made from steel ingots or solid tube blanks that are perforated into capillary tubes, and then hot-rolled, cold-rolled, or cold-drawn. Large-diameter thick-walled seamless steel pipes play an important role in my country's steel pipe industry. According to incomplete statistics, there are more than 240 seamless steel pipe manufacturers in my country, more than 250 large-diameter thick-walled seamless steel pipe units, and an annual production capacity of about 4.5 million tons. In terms of caliber, those <φ76 account for 35%, and those <φ159-650 account for 25%. In terms of varieties, general-purpose pipes accounted for 1.9 million tons, accounting for 54%; oil pipes accounted for 760,000 tons, accounting for 5.7%; hydraulic props and precision pipes accounted for 150,000 tons, accounting for 4.3%; stainless steel pipes, bearing pipes, and automobile pipes totaled 50,000 tons. tons, accounting for 1.4%.
The raw material for large-diameter thick-walled seamless steel pipes is round tube blanks. The round tube blanks are cut by a cutting machine into billets with a length of about 1 meter and sent to the furnace for heating via a conveyor belt. The billet is fed into the furnace and heated to a temperature of approximately 1,200 degrees Celsius. The fuel is hydrogen or acetylene. Temperature control in the furnace is a key issue. After the round tube comes out of the furnace, it must be pierced through a pressure punching machine. Generally, the more common piercing machine is the tapered roller piercing machine. This type of piercing machine has high production efficiency, good product quality, large perforation diameter expansion, and can penetrate a variety of steel types. After perforation, the round tube blank is successively cross-rolled, continuously rolled, or extruded by three rollers. After extrusion, the pipe should be removed and calibrated. Sizing by high-speed rotary cone drill holes into the billet to form a tube. The inner diameter of the steel pipe is determined by the length of the outer diameter of the drill bit of the sizing machine. After the steel pipe is sized, it enters the cooling tower and is cooled by spraying water. After the steel pipe is cooled, it will be straightened. After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by the conveyor belt for internal flaw detection. If there are cracks, bubbles, and other problems inside the steel pipe, they will be detected. After the quality inspection of steel pipes, strict manual selection is required. After the quality inspection of the steel pipe, paint the serial number, specification, production batch number, etc. with paint. And hoisted into the warehouse by crane.
Specifications: The specifications of seamless steel pipes are expressed in millimeters of outer diameter * wall thickness.
Classification of large-diameter thick-walled seamless steel pipes: Seamless steel pipes are divided into two types: hot-rolled and cold-rolled (dial) seamless steel pipes. Hot-rolled seamless steel pipes are divided into general steel pipes, low and medium-pressure boiler steel pipes, high-pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes, and other steel pipes. In addition to general steel pipes, low and medium-pressure boiler steel pipes, high-pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other steel pipes, cold-rolled (dial) seamless steel pipes also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, Stainless thin-walled steel pipes, special-shaped steel pipes. The outer diameter of the hot-rolled seamless steel pipe is generally greater than 32mm, and the wall thickness is 2.5-75mm. The diameter of cold-rolled seamless steel pipe can reach 6mm, and the wall thickness can reach 0.25mm. The outer diameter of a thin-walled pipe can reach 5mm, and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.
Seamless steel pipes for general use: are made of high-quality carbon steel such as 10, 20, 30, 35, 45, 16Mn, 5MnV, and other low-alloy structural steels or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steels that are hot-rolled or cold-rolled. Seamless steel pipes made of low carbon steel such as 10 and 20 are mainly used for fluid conveying pipelines. Seamless steel pipes made of medium carbon steel such as 45 and 40Cr are used to manufacture mechanical parts, such as stressed parts of automobiles and tractors. Generally, seamless steel pipes are used to ensure strength and flattening tests. Hot-rolled steel pipes are delivered in a hot-rolled or heat-treated state; cold-rolled steel pipes are delivered in a heat-treated state.
Seamless steel pipes for low and medium pressure boilers: used to manufacture various low and medium pressure boilers, superheated steam pipes, boiling water pipes, water-cooled wall pipes and superheated steam pipes, large smoke pipes, small smoke pipes and arch brick pipes for locomotive boilers, etc. Hot-rolled or cold-rolled (dial) seamless steel pipes are made of high-quality carbon structural steel. It is mainly made of No. 10 and No. 20 steel. In addition to ensuring the chemical composition and mechanical properties, hydrostatic tests, crimping, flaring, and flattening tests are required. Hot rolling is delivered in a hot-rolled state, and cold rolling (dial) is delivered in a heat-treated state.
High-pressure boiler steel pipes: mainly used to manufacture high-quality carbon structural steel, alloy structural steel, and stainless heat-resistant steel seamless steel pipes for steam boiler pipes of high pressure and above. These boiler pipes often work under high temperatures and pressure. The pipe will also undergo oxidation and corrosion under the action of high-temperature flue gas and water vapor. Therefore, the steel pipe is required to have high lasting strength, high oxidation resistance, and good organizational stability. The steel grades used are: high-quality carbon structure Steel grades include 20G, 20MnG, 25MnG; alloy structural steel grades 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.; rusty and heat-resistant steel commonly used 1Cr18Ni9, 1Cr18Ni11Nb high-pressure boiler tubes in addition to ensuring chemical composition and mechanical properties, It is necessary to do hydrostatic test one by one, and to do flaring and flattening tests. Steel pipes are delivered in a heat-treated state. In addition, there are certain requirements for the microstructure, grain size, and decarburization layer of the finished steel pipe.
Seamless steel pipes for geological drilling and oil drilling: To explore the underground rock structure, groundwater, oil, natural gas, and mineral resources, drilling rigs are used to drill wells. The exploitation of oil and natural gas is inseparable from well drilling. Seamless steel pipes for geological drilling and oil drilling are the main equipment for drilling, mainly including outer core pipes, inner core pipes, casings, drill pipes, etc. Since drilling pipes have to go deep into the stratum of several thousand meters, the working conditions are extremely complex. The drill pipes are subjected to stresses such as tension, pressure, bending, torsion, and uneven impact loads, as well as mud and rock wear. Therefore, pipes are required to It must have sufficient strength, hardness, wear resistance, and impact toughness. The steel used for steel pipes is represented by "DZ" (the Chinese pinyin prefix for geology) plus a number one to represent the steel yield point. Commonly used steel grades include DZ45 45MnB and 50Mn; DZ50’s 40Mn2, 40Mn2Si; DZ55’s 40Mn2Mo, 40MnVB; DZ60’s 40MnMoB, DZ65’s 27MnMoVB. Steel pipes are delivered in a heat-treated state.
Petroleum cracking tubes: seamless steel tubes for furnace tubes, heat exchanger tubes, and pipelines in petroleum refineries. Commonly used are high-quality carbon steel (10, 20), alloy steel (12CrMo, 15CrMo), heat-resistant steel (12Cr2Mo, 15Cr5Mo), stainless steel (1Cr18Ni9, 1Cr18Ni9Ti). In addition to verifying the chemical composition and various mechanical properties of steel pipes, steel pipes must also ensure water pressure, flattening, flaring, and other tests, as well as surface quality and non-destructive testing. Steel pipes are delivered in the heat-treated condition. Stainless steel pipes: Hot-rolled and cold-rolled stainless steel pipes made of various stainless steels are widely used in petroleum and chemical equipment pipelines and stainless steel structural parts for various purposes. In addition to ensuring the chemical composition and mechanical properties, any steel pipe is used to withstand fluid pressure To ensure that the hydrostatic test is qualified. All kinds of special steel pipes shall be guaranteed according to the regulations.
Large-diameter thick-walled seamless steel pipe executive standard
1. Seamless steel pipe for structure: GB8162-2008
2. Ground seam steel pipe for conveying fluid: GB8163-2008
3. Seamless steel pipe for boiler: GB3087-2008
4. High-pressure seamless steel pipe for boilers: GB5310-2008 (ST45.8-ⅲ type)
5. High-pressure seamless steel pipes for fertilizer equipment: GB6479-1999
6. Seamless steel pipe for geological drilling: YB235-70
7. Seamless steel pipe for oil drilling: YB528-65
8. Seamless steel pipe for petroleum cracking: GB9948-88
9. Special seamless steel pipe for oil drill collars: YB691-70
10. Seamless steel pipe for automobile half shaft: GB3088-1999
11. Seamless steel pipe for ships: GB5312-1999
12. Cold drawn and cold rolled precision seamless steel pipe: GB3639-1999
13. Various alloy pipes 16Mn, 27SiMn, 15CrMo, 35CrMo, 12CrMov, 20G, 40Cr, 12Cr1MoV, 15CrMo. In addition, there are GB/T17396-1998 (hot-rolled seamless steel pipes for hydraulic props), GB3093-1986 (high pressure for diesel engines) Seamless steel pipe), GB/T3639-1983 (cold drawn or cold rolled precision seamless steel pipe), GB/T3094-1986 (cold drawn seamless steel pipe special-shaped steel pipe), GB/T8713-1988 (precision inner diameter for hydraulic and pneumatic cylinders) Seamless steel pipe), GB13296-1991 (stainless steel seamless steel pipe for boilers and heat exchangers), GB/T14975-1994 (stainless steel seamless steel pipe for structural use), GB/T14976-1994 (stainless steel seamless steel pipe for fluid transportation) GB/ T5035-1993 (seamless steel pipe for automobile half-shaft casing), API SPEC5CT-1999 (casing and oil pipe specification), etc.
