Seamless steel pipes are divided into hot rolled and cold rolled (rolled) seamless steel pipes.
Hot rolled seamless
Steel Pipe is divided into general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe,
alloy steel pipe,
Stainless Steel Pipe, petroleum cracking pipe, geological steel pipe and other steel pipes.
In addition to ordinary steel tubes, low and medium pressure boiler steel tubes, high pressure boiler steel tubes, alloy steel tubes, stainless steel tubes, petroleum cracking tubes, and other steel tubes, cold rolled (rolled) seamless steel tubes also include carbon thin-walled steel tubes, alloy thin-walled steel tubes, stainless thin-walled steel tubes, and special-shaped steel tubes. 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 reach 6mm, the wall thickness can reach 0.25mm, the outer diameter of thin-walled pipe can reach 5mm, and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.
Generally, seamless steel pipes are hot-rolled or cold-rolled with carbon bonded steel 16Mn, 5MnV and other low alloy structural steels such as 10, 20, 30, 35, 45, or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steels. 10. 20 and other low carbon steel seamless pipes are mainly used for fluid transmission pipelines. Seamless pipes made of medium carbon steel such as 45, 40Cr are used to manufacture mechanical parts, such as stressed parts of automobiles and tractors. Generally, the strength and flattening test of seamless steel pipe shall be ensured. Hot rolled steel pipes shall be delivered in hot rolling state or heat treatment state; Cold rolling shall be delivered in heat treatment state.
Seamless steel tubes for low and medium pressure boilers
It is 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. Seamless steel tubes shall be hot-rolled or cold-rolled with carbon structural steel. It is mainly made of 10 # and 20 # steel. In addition to ensuring chemical composition and mechanical properties, hydrostatic test, crimping, flaring, flattening and other tests shall be conducted. Hot rolling shall be delivered in hot rolling state, and cold rolling (rolling) shall be delivered in heat treatment state.
High pressure boiler steel pipe
It is mainly used to manufacture carbon structural steel, alloy structural steel and stainless heat-resistant seamless steel pipes for steam boiler pipes with high pressure and above. These boiler pipes often work under high temperature and high pressure, and the pipes will be oxidized and corroded under the action of high-temperature flue gas and water steam. Therefore, steel pipes are required to have high endurance strength, high oxidation resistance and good organizational stability, The adopted steel grades are: carbon structural steel grades are 20G, 20MnG and 25MnG; Alloy structural steel grades 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc; In addition to ensuring the chemical composition and mechanical properties, the common 1Cr18Ni9 and 1Cr18Ni11Nb high-pressure boiler tubes made of rusty and heat-resistant steel shall be subject to hydrostatic test, flaring and flattening test one by one. Steel pipes shall be delivered in heat treatment state. In addition, there are also certain requirements for the microstructure, grain size and decarburization layer of the finished steel pipe.
Seamless steel pipe for geological drilling and oil drilling
In order to explore the underground rock structure, groundwater, oil, natural gas and mineral resources, drilling rigs are used to drill wells. Oil and natural gas exploitation can not be separated from well drilling. Seamless steel pipes for oil drilling for geological drilling are the main drilling equipment, mainly including outer core pipes, inner core pipes, casings, drill pipes, etc. As the drilling pipe needs to work at a depth of several thousand meters, the working conditions are extremely complex, and the drill pipe is subject to tensile, compressive, bending, torsional and unbalanced impact loads, as well as mud and rock wear. Therefore, the pipe must have sufficient strength, hardness, wear resistance and impact toughness. The steel pipe is represented by "DZ" (Chinese phonetic prefix for geology) plus a number representing the steel yield point, Common steel grades are 45MnB and 50Mn of DZ45; 40Mn2 and 40Mn2Si of DZ50; 40Mn2Mo and 40MnVB of DZ55; 40MnMoB of DZ60, 27MnMoVB of DZ65. The steel pipes are delivered in heat treatment state.
Petroleum cracking tube
Seamless tubes for furnace tubes, heat exchanger tubes and pipes used in petroleum refineries. Commonly used carbon steel (10, 20), alloy steel (12CrMo, 15CrMo), heat-resistant steel (12Cr2Mo, 15Cr5Mo) and stainless steel (1Cr18Ni9, 1Cr18Ni9Ti). In addition to the chemical composition and various mechanical properties of steel pipes, water pressure, flattening, flaring and other tests, as well as surface quality and nondestructive inspection shall be guaranteed. The steel pipe shall be delivered in the heat treatment state. Stainless steel pipe: hot-rolled and cold-rolled stainless steel pipes are widely used in petroleum and chemical equipment and pipes and stainless steel structural parts for various purposes. In addition to ensuring chemical composition and mechanical properties, all steel pipes used to withstand fluid pressure shall be qualified in hydrostatic test. Various special steel pipes shall be guaranteed according to the specified conditions.
