Steel pipe is a hollow long strip of steel, which is widely used as a pipeline for transporting fluids, such as oil, natural gas, water, gas, steam, etc. In addition, it is lighter in weight when bending and torsional strength are the same, so it is also widely used Used in the manufacture of mechanical parts and engineering structures. It is also commonly used to produce various conventional weapons, barrels, shells, etc.
Classification of steel pipes: steel pipes are divided into two categories: seamless steel pipes and welded steel pipes (seamed pipes). According to the cross-sectional shape, it can be divided into round tubes and special-shaped tubes. Round steel tubes are widely used, but there are also some square, rectangular, semicircular, hexagonal, equilateral triangle, octagonal and other special-shaped steel tubes.
For steel pipes under fluid pressure, a hydraulic test is required to check their pressure resistance and quality. It is qualified if no leakage, soaking or expansion occurs under the specified pressure. Some steel pipes also need to be crimped according to standards or requirements of the buyer , Flaring test, flattening test, etc.
Seamless steel pipe: seamless steel pipe is made of steel ingot or solid tube blank through perforation to make capillary tube, and then hot rolled, cold rolled or cold drawn. The specifications of seamless steel pipes are expressed in millimeters of outer diameter * wall thickness. There are two types of seamless steel pipes: 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 hot-rolled seamless 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. Rolling has higher dimensional accuracy than hot rolling.
Generally, seamless steel pipes are made by hot rolling or cold rolling of high-quality carbon structural steels such as 10, 20, 30, 35, 45, 16Mn, 5MnV and other low-alloy structural steels, or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other combined steels. 10, 20 and other low carbon steel seamless pipes are mainly used for fluid conveying pipelines. Seamless tubes 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 should be tested for strength and flattening. 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 work under high temperature and high pressure 1. 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 Structural steel steel grades are 20G, 20MnG, 25MnG; alloy structural steel steel grades are 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.; rusty heat-resistant steel is commonly used in 1Cr18Ni9, 1Cr18Ni11Nb high-pressure boiler tubes to ensure chemical composition and mechanical properties In addition, hydrostatic tests should be done one by one, and flaring and flattening tests should be done. 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 control; 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. Seamless steel pipes for oil drilling for geological drilling control are the main equipment for drilling, mainly including core outer pipes, core inner pipes, casings, drill pipes, 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 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 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 tubes for furnace tubes, heat exchanger tubes and pipelines used 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 condition. Stainless steel pipes: hot-rolled and cold-rolled stainless steel pipes of various stainless steels 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 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.
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Welded steel pipe: also called welded pipe, is made of steel plate or steel strip after bending and then welding. According to the weld form, it is divided into straight seam welded pipe and spiral welded pipe.
According to the application, it is divided into general welded pipe, galvanized welded pipe, oxygen blown welded pipe, wire casing, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welded thin-walled pipe, electric welded special-shaped pipe and spiral welded pipe.
General welded pipe: general welded pipe is used to transport low-pressure fluid. Made of Q195A, Q215A, Q235A steel. It can also be manufactured from other mild steels that are easy to weld. Steel pipes are subject to water pressure, bending, flattening and other tests, and have certain requirements for surface quality. Usually, the delivery length is 4-10m, and it is often required to deliver in fixed length (or double length). The specification of the welded pipe is indicated by the nominal diameter (millimeter or inch). The nominal diameter is different from the actual one. The welded pipe has two types of ordinary steel pipe and thickened steel pipe according to the specified wall thickness. 6-17 is the size of welded steel pipe. Table 6-17 Welded steel pipes for low-pressure fluid transmission (according to GB/T3092-93) Nominal diameter and outer diameter Ordinary steel pipe Thickened steel pipe mm in Nominal size mm Allowable deviation Wall thickness theoretical weight kg/m Wall thickness theoretical weight kg/m Nominal size mm allowable deviation % nominal size mm allowable deviation % 6 1/8 10.0 +0.50mm -0.50mm 2.00 +12 -15 0.39 2.50 +12 -15 0.46 8 1/4 13.5 2.25 0.62 2.75 0.73 10 3/8 17.0 2.25 0. 82 2.75 0.97 15 1/2 21.3 2.75 1.26 3.25 1.45 20 3/4 26.8 2.75 1.63 3.50 2.01 25 1 33.5 3.25 2.42 4.00 2.91 32 11/4 42.3 3.25 3.13 4.00 3.78 40 11/2 48.0 3.50 3.84 4.25 4.58 50 2 60.0 +1% -1% 3.50 4.88 4.50 6.16 65 21/2 75.5 3.75 6.64 4.50 7.88 80 3 88.5 4.00 8.34 4.75 9.81 100 4 114.0 4.00 10.85 5.00 13.44 1 25 5 140.0 4.00 13.42 5.50 18.24 150 6 165.0 4.50 17.81 5.50 21.63
With the improvement of welded steel pipe technology and the ease of processing, welded pipes now replace some seamless pipes, and welded steel pipes have been able to produce more than 219mm (8 inches). the
Galvanized steel pipe: In order to improve the corrosion resistance of the steel pipe, the general steel pipe (black pipe) is galvanized. There are two types of galvanized steel pipes: hot-dip galvanizing and electric steel zinc. The hot-dip galvanizing layer is thicker and the cost of electric galvanizing is low.
Oxygen-blowing welded pipe: It is used as a pipe for oxygen-blowing in steelmaking. Generally, small-diameter welded steel pipes are used, and the specifications range from 3/8 inch to 2 inch. Made of 08, 10, 15, 20 or Q195-Q235 steel strip. In order to prevent corrosion, some are aluminized.
Wire casing: It is also an ordinary carbon steel electric-welded steel pipe, which is used in concrete and various structural power distribution projects. The commonly used nominal diameter is from 13-76mm. The wall of the wire casing is relatively thin, and it is mostly used after coating or galvanizing, and a cold bending test is required.
Metric welded pipe: The specifications are in the form of seamless pipes, welded steel pipes expressed by outer diameter * wall thickness mm, welded with ordinary carbon steel, high-quality carbon steel or ordinary low-alloy steel with hot or cold strips, or after welding with hot spots Then it is made by cold drawing method.
Metric welded pipes are divided into ordinary and thin-walled pipes, which are generally used as structural parts, such as transmission shafts, or conveying fluids, and thin-walled pipes are used to produce furniture, lamps, etc. The strength and bending test of steel pipes must be guaranteed.
Roller tube: used for belt conveyor roller electric welded steel pipe, generally made of Q215, Q235A, B steel and 20 steel, with a diameter of 63.5-219.0mm. There are certain requirements for the bending degree of the pipe, the end surface should be perpendicular to the center line, and the ellipticity, and the water pressure and flattening tests are generally carried out. Transformer tubes: Used to manufacture transformer cooling tubes and other heat exchangers. They are made of ordinary carbon steel and require flattening, flaring, bending, and hydraulic tests.
Steel pipes are delivered in fixed lengths or double lengths, and there are certain requirements for the bending degree of steel pipes. Special-shaped pipes: square pipes, rectangular pipes, hat-shaped pipes, hollow plastic steel doors and windows steel pipes welded by ordinary carbon-bonded structural steel and 16Mn steel strips, mainly used as agricultural machinery components, steel windows and doors, etc.
Welded thin-walled tube: mainly used to make furniture, toys, lamps, etc. In recent years, thin-walled tubes made of stainless steel strips have been widely used in high-end furniture, decoration, fences, etc. Spiral welded pipe: It is made by rolling low-carbon carbon structural steel or low-alloy structural steel strip into a tube blank according to a certain helical angle (called forming angle), and then welding the pipe seam. It can be made with narrower Strip steel produces large diameter steel pipes. Spiral welded pipes are mainly used for oil and natural gas transmission pipelines, and their specifications are expressed by outer diameter * wall thickness. Spiral welded pipes have single-side welding and double-side welding. The welded pipes should ensure that the hydraulic test, the tensile strength of the weld and the cold bending performance must meet the regulations.
