Special-shaped seamless steel tube is the general name of seamless steel tube with other cross-sectional shapes except circular tube. According to the different cross-sectional shapes and sizes of steel pipes, they can be divided into special-shaped seamless steel pipes with equal wall thickness (code D), special-shaped seamless steel pipes with unequal wall thickness (code BD) and special-shaped seamless steel pipes with variable diameter (code BJ). Special-shaped seamless steel pipes are widely used in various structural parts, tools and mechanical parts. Compared with circular tubes, special-shaped tubes generally have larger moment of inertia and section modulus, and have greater bending and torsion resistance, which can greatly reduce structural weight and save steel. (1)GB3087-82 Seamless steel pipes for low-pressure and medium-pressure boilers. The test method of chemical composition conforms to GB222-84 and GB223 Chemical Analysis Methods of Steel and Alloy.
(2)GB53 10-95 Seamless Steel Pipe for High Pressure Boiler. The test method of chemical composition conforms to GB222-84 Chemical Analysis Method of Steel and Alloy and GB223 Chemical Analysis Method of Steel and Alloy.
(3) The chemical composition inspection of imported boiler steel pipes shall be carried out according to the relevant standards stipulated in the contract. (1) The grades of high-quality carbon structural steel are 20G, 20mg and 25MnG.
(2) alloy structural steel grades 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG,/kloc-0 12Cr3MoVSiTiB, etc.
(3) The commonly used rusted heat-resistant steel 1Cr 18Ni9,1Cr18ni1nb boiler tubes should be subjected to hydrostatic test one by one, and the flaring and flattening tests should be carried out. Steel pipes are delivered in heat treatment state.
In addition, there are certain requirements for the metallographic structure, grain size and decarburization layer of the finished steel pipe. (1)GB3087-82 Seamless steel pipes for low-pressure and medium-pressure boilers. According to GB/T228-87 for tensile test, GB/T24 1-90 for hydrostatic test, GB/T246-97 for flattening test, GB/T242-97 for flaring test and GB244-97 for cold bending test.
(2)GB53 10-95 Seamless Steel Pipe for High Pressure Boiler. Tensile test, hydrostatic test and flattening test are the same as those in GB3087-82. Impact test according to GB229-94, combustion test according to GB/T242-97, particle size test according to Yb/T 5148-93; Microstructure inspection shall be conducted according to GB 13298-9 1, decarburized layer inspection shall be conducted according to GB224-87, and ultrasonic inspection shall be conducted according to GB/T5777-96.
(3) The physical performance inspection and indexes of imported boiler tubes shall be carried out according to the relevant standards stipulated in the contract. (1) The main importers of boiler tubes are Japan and Germany. The frequently imported specifications are15914.2mm; 2734.0mm2 19. 1 10.0mm； 4 1975mm； 406.460mm, etc. The minimum specification is 3 1.84.5mm, and the length is generally between 5-8m. ..
(2) In the import claim case, ST45 seamless boiler tubes imported from mannesmann Steel Pipe Factory in Germany were found to have internal defects exceeding the factory regulations and German Iron and Steel Association standards by ultrasonic flaw detection.
(3) Alloy steel pipes imported from Germany mainly include 34CrMo4 and 12CrMoV. This kind of steel pipe has good high temperature performance and is often used as the steel pipe of high temperature boiler.
(4) There are many alloy pipes imported from Japan, with specifications of 426.438+02 mm5 ~ 8m；; 152 . 48 . 0mm 12m； 89. 1 10.0 mm6m； 10 1.6 10.0mm 12m； 1 14 . 38 . 0 mm6m； 127.08.0mm9m, etc. Japanese industrial standard JISG3458 is implemented, and the steel grade is STPA25. This kind of steel pipe is often used as a matching high temperature alloy pipe. (1) The main importers of high-pressure boiler tubes are Japan and Germany. The frequently imported specifications are15914.2mm; 2734.0mm2 19. 1 10.0mm； 4 1975mm； 406.460mm, etc. The minimum specification is 3 1.84.5mm, and the length is generally between 5-8m. ..
(2) In the import claim case, ST45 seamless boiler tubes imported from mannesmann Steel Pipe Factory in Germany were found to have internal defects exceeding the factory regulations and German Iron and Steel Association standards by ultrasonic flaw detection.
(3) Alloy steel pipes imported from Germany mainly include 34CrMo4 and 12CrMoV. This kind of steel pipe has good high temperature performance and is often used as the steel pipe of high temperature boiler.
(4) There are many alloy pipes imported from Japan, with specifications of 426.438+02 mm5 ~ 8m；; 152 . 48 . 0mm 12m； 89. 1 10.0 mm6m； 10 1.6 10.0mm 12m； 1 14 . 38 . 0 mm6m； 127.08.0mm9m, etc. Japanese industrial standard JISG3458 is implemented, and the steel grade is STPA25. This kind of steel pipe is often used as a matching high temperature alloy pipe. Boiler tube is a kind of seamless tube. The manufacturing method is the same as seamless pipe, but there are strict requirements on the steel grade used for manufacturing steel pipe. According to the service temperature, it can be divided into ordinary boiler tubes and high-pressure boiler tubes.
1, overview
(1) manufacturing method:
① Generally, the service temperature of boiler tubes is below 450℃, and domestic pipes mainly adopt 10 and 20 carbon steel heat pipes or cold-drawn pipes.
② High-pressure boiler tubes are often used under high temperature and high pressure. Under the action of high-temperature flue gas and steam, the tubes will be oxidized and corroded. Steel pipes are required to have high durable strength, high oxidation and corrosion resistance and good organizational stability.
(2) uses:
① General boiler tubes are mainly used to manufacture water wall tubes, boiling water tubes, superheated steam tubes, superheated steam tubes for locomotive boilers, large and small smoke tubes and arched brick tubes.
② High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, air ducts and main steam tubes of high-pressure and ultra-high-pressure boilers.