Definition And Classification Of Seamless Carbon Steel Pipe
1. Definition of seamless carbon steel pipe
Seamless carbon steel pipes are made of steel ingots or solid tube billets through perforation to make capillary tubes, and then made by hot rolling, cold rolling or cold drawing. Seamless carbon steel pipe has an important position in my country’s steel pipe industry.
2. Classification of seamless carbon steel pipes
Classification of seamless carbon 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.
Cold-rolled (dial) 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, and other steel pipes, as well as carbon thin-walled steel pipes, alloy thin-walled steel pipes, Stainless thin-walled steel pipes, special-shaped steel pipes. The outer diameter of hot-rolled seamless pipe is generally greater than 32mm, and the wall thickness is 2.5-75mm. The diameter of cold-rolled seamless pipe can be up to 6mm and the wall thickness can be up to 0.25mm. The outer diameter of thin-walled pipe can be up to 5mm and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.
General seamless carbon steel pipe: It is made of 10, 20, 30, 35, 45 and other high-quality carbon steels such as 16Mn, 5MnV and other low-alloy structural steels or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steels by hot rolling or cold rolling. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid transportation pipelines. Seamless 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 must be used for strength and flattening tests. Hot-rolled steel pipes are delivered in hot-rolled state or heat-treated state; cold-rolled steel pipes are delivered in 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 arched brick pipes. Use high-quality carbon structural steel hot-rolled or cold-rolled (dial) seamless steel pipe. It is mainly made of No. 10 and No. 20 steel. In addition to ensuring the chemical composition and mechanical properties, a hydraulic test, such as crimping, flaring, and flattening, is to be done. Hot-rolled products are delivered in a hot-rolled state, and cold-rolled products are delivered in a heat-treated state.
High-pressure boiler steel pipes: High-quality carbon structural steel, alloy structural steel and stainless heat-resistant steel seamless steel pipes mainly used to manufacture high-pressure and above steam boiler pipes. These boiler pipes are often working under high temperature and high pressure. The pipe will be oxidized and corroded 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 structural stability. The steel grades used are: high-quality carbon structure Steel grades are 20G, 20MnG, 25MnG; alloy structural steel grades 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.; rusty heat-resistant steel commonly used 1Cr18Ni9, 1Cr18Ni11Nb high pressure boiler tube in addition to ensuring chemical composition and mechanical properties , It is necessary to do a hydraulic test one by one, and do a flaring and flattening test. The steel pipe is delivered in a heat-treated state. In addition, there are also certain requirements for the microstructure, grain size, and decarburized layer of the finished steel pipe.
Seamless steel pipes for geological drilling and oil drilling: use drilling rigs to drill wells for the exploration of underground rock structure, groundwater, oil, natural gas and mineral resources. Petroleum and natural gas exploitation is even more inseparable from well drilling. Seamless steel pipes for geological drilling are the main equipment for drilling, including core outer tubes, core inner tubes, casings, and drill pipes. Because drilling pipes need to be deep into the formation depth of several kilometers, the working conditions are extremely complicated. The drill pipe is subjected to stresses such as tension, compression, bending, torsion, and uneven impact load, and is also subject to mud and rock wear. Therefore, pipe materials are required It 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 representing the yield point of steel. Commonly used steel grades are 45MnB and 50Mn of DZ45; 40Mn2, 40Mn2Si of DZ50; 40Mn2Mo, 40MnVB of DZ55; 40MnMoB of DZ60, 27MnMoVB of DZ65. The steel pipes are delivered in a heat-treated state.
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