Thin-walled seamless steel pipes are made of steel ingots or solid tube blanks that are perforated into capillary tubes and then made by hot rolling, cold rolling, or cold drawing. Thin-walled seamless steel pipes play an important role in my country's steel pipe industry. Thin-walled seamless steel pipe According to incomplete statistics, there are more than 240 seamless steel pipe manufacturers in my country, more than 250 seamless steel pipe units, and an annual production capacity of about 4.5 million tons. In terms of caliber, <φ76 accounts for 35%, and <φ159-650 accounts for 25%. In terms of varieties, general-purpose pipes are 1.9 million tons, accounting for 54%; petroleum pipes are 760,000 tons, accounting for 5.7%; hydraulic props and precision pipes are 150,000 tons, accounting for 4.3%; stainless steel pipes, bearing pipes, and automotive pipes total 50,000 tons, accounting for 1.4%.
The raw material of the thin-walled seamless steel pipe is a round tube billet. The round tube billet should be cut by a cutting machine into a billet with a length of about 1 meter and sent to the furnace for heating by a conveyor belt. Billet is fed into the furnace to heat, the temperature is about 1200 degrees Celsius. The fuel is hydrogen or acetylene. The temperature control in the furnace is a key issue. After the round tube is out of the furnace, it must be pierced through a pressure piercer. Generally, the more common piercer is the cone roll piercer. This kind of piercer has high production efficiency, good product quality, large perforation diameter expansion, and can wear a variety of steel types. After piercing, the round tube billet is successively cross-rolled, continuously rolled, or extruded by three rolls. After extrusion, the tube should be taken off for sizing. 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 thin-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 steel 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.
General seamless steel pipe: It is made by hot rolling or cold rolling of high-quality carbon structural steel such as 10, 20, 30, 35, 45, 16Mn, 5MnV, and another low alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steel. 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 wall pipes, and superheated steam pipes for locomotive boilers, large smoke pipes, small smoke pipes, and arch brick pipes, 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 pipe: mainly used to manufacture high-quality carbon structural steel, alloy structural steel, and stainless heat-resistant steel seamless steel pipe for steam boiler pipes with high pressure and above pressure. These boiler pipes often work under high temperatures and high pressure. The pipe will also be oxidized and corroded under the action of high-temperature flue gas and water vapor. Therefore, the steel pipe is required to have high durable strength, high oxidation resistance, and good structural stability. The steel grades used are: high-quality carbon structure Steel grades 20G, 20MnG, and 25MnG; alloy structural steel grades are 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.; 1Cr18Ni9 and 1Cr18Ni11Nb high-pressure boiler tubes are commonly used in rusty heat-resistant steel 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: use drilling rigs to drill wells to find out the structure of underground rock formations, groundwater, oil, natural gas, and mineral resources. The exploitation of oil and natural gas is inseparable from well drilling. The seamless steel pipe for oil drilling used in geological drilling is the main equipment for drilling, mainly including core outer pipe, core inner pipe, casing, drill pipe, etc. Since the drilling pipe has to work deep into the formation depth of several thousand meters, the working conditions are extremely complicated. The drill pipe is subjected to stresses such as tension, compression, bending, torsion, and unbalanced impact loads, and is also subject to mud and rock wear. Therefore, pipes are required must have sufficient strength, hardness, wear resistance, and impact toughness. The steel used for steel pipes is represented by "DZ" (geological Chinese pinyin prefix) plus a number one to represent the yield point of the steel. The commonly used steel grades are 45MnB and 50Mn of DZ45; 40Mn2, 40Mn2Si of DZ50; 40Mn2Mo, 40MnVB of DZ55; 40MnMoB of DZ60, 27MnMoVB of DZ65. 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 high-quality carbon steel (10, 20), alloy steel (12CrMo, 15CrMo), heat-resistant steel (12Cr2Mo, 15Cr5Mo), stainless steel (1Cr18Ni9, 1Cr18Ni9Ti) manufacturing. In addition to the chemical composition and various mechanical properties of the steel pipe, it is also necessary to ensure the water pressure, flattening, flaring, and other tests, as well as surface quality and non-destructive testing. Steel pipes are delivered in heat-treated conditions. Stainless steel pipes: Hot-rolled and cold-rolled stainless steel pipes of various stainless sheets of steel are widely used in petroleum, chemical equipment pipelines, and stainless steel structural parts for various purposes. In addition to ensuring chemical composition and mechanical properties, steel pipes are 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.
Implementation standards for thin-walled seamless steel pipes
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 boiler: GB5310-2008 (ST45.8-Ⅲ type)
5. High-pressure seamless steel pipes for chemical 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 collar: YB691-70
10. Seamless steel pipes for automobile half shafts: GB3088-1999
11. Seamless steel pipes for ships: GB5312-1999
12. Cold-drawn and cold-rolled precision seamless steel pipe: GB3639-1999
13. Various alloy tubes 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 seamless steel pipes for diesel engines), GB/T3639-1983 (cold-drawn or cold-rolled precision seamless steel pipes), GB /T3094-1986 (cold-drawn seamless steel pipe with special-shaped steel pipe), GB/T8713-1988 (precision inner diameter seamless steel pipe for hydraulic and pneumatic cylinders), GB13296-1991 (stainless steel seamless steel pipe for boilers and heat exchangers), GB/T14975 -1994 (stainless steel seamless steel pipes for structural use), GB/T14976-1994 (stainless steel seamless steel pipes for fluid transportation) GB/T5035-1993 (seamless steel pipes for automobile axle shaft casings), API SPEC5CT-1999 (casing and oil pipes specifications), etc.