The 20G high pressure boiler tube is a type of boiler tube and belongs to the category of seamless steel tubes. The manufacturing method is the same as that for seamless pipes, but there are strict requirements for the steel grades used in the manufacture of steel pipes. 20G high-pressure boiler tubes are often used under high temperature and high pressure conditions. The tubes are subject to oxidation and corrosion under the effect of high-temperature flue gas and water vapor. The steel pipe is required to have high endurance strength, high oxidation corrosion resistance, and good organization stability. The 20G high pressure boiler tube is mainly used to manufacture superheater tubes, reheater tubes, air tubes, and main steam tubes for high pressure and ultrahigh pressure boilers. Low and medium pressure boiler tubes GB3087-1999, 20G high pressure boiler tubes GB5310-1999 are used to manufacture superheated steam tubes, boiling water tubes and superheated steam tubes for boilers of various structures, large smoke tubes, small smoke tubes and arch bricks. High-quality carbon structural steel for hot-rolled and cold drawn (rolled) seamless steel tubes. Seamless steel pipe for structural use (GB/T8162-1999) is a seamless steel pipe for general structure and mechanical structure. Specifications and appearance quality: GB5310-95 "seamless steel tubes for high-pressure boilers" The outer diameter of hot-rolled tubes is 22-530mm, and the wall thickness is 20-70mm. Cold-drawn (cold-rolled) tubes have an outer diameter of 10 to 108 mm and a wall thickness of 2.0 to 13.0 mm. Shaped seamless steel tubes are the general term for seamless steel tubes of other cross-sectional shapes than circular tubes. According to the different shapes and sizes of steel pipe sections, they can be divided into equal-wall thickness special-shaped seamless steel pipes (code D), unequal wall thickness profiled seamless steel pipes (codenamed BD) and variable-diameter special-shaped seamless steel pipes (coded as BJ). Shaped seamless steel tubes are widely used in various structural parts, tools and mechanical parts. Compared with round tubes, shaped tubes generally have larger moments of inertia and section modulus, and have greater resistance to bending and torsion, which can greatly reduce the structural weight and save steel. 4. Chemical composition inspection (1) GB3087-82 "Seamless steel tubes for low and medium pressure boilers" provisions. The chemical composition test method is based on the relevant parts of GB222-84 and GB223 "Methods for chemical analysis of steel and alloys". (2) GB5310-95 "High-pressure boiler seamless steel pipe" provisions. Chemical composition test method According to the relevant parts of GB222-84 and "Chemical Analysis Method for Steel and Alloys" and GB223 "Method for Chemical Analysis of Steel and Alloys". (3) Inspection of the chemical composition of imported boiler pipes shall be carried out in accordance with the relevant standards stipulated in the contract. 5. Boiler pipe using steel (1) high-quality carbon structural steel steel 20G, 20MnG, 25MnG. (2) Alloy structural steel grades 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, P11 12Cr3MoVSiTiB, etc. (3) The rust-resistant heat-resistant steel commonly used 1Cr18Ni9, 1Cr18Ni11Nb boiler tubes in addition to ensure chemical composition and mechanical properties, to do the hydrostatic pressure test by root, to be flaring, flattening test. The steel pipe is delivered in a heat-treated state. In addition, there are certain requirements on the microstructure, grain size, and decarburization layer of the finished steel pipe. 6. Physical performance inspection (1) GB3087-82 "Seamless steel tubes for low and medium pressure boilers" provisions. Tensile test according to GB/T 228-87, hydraulic test according to GB/T241-90, flattening test according to GB/T246-97, flaring test according to GB/T242-97, cold bending test according to GB244-97. (2) GB5310-95 "High-pressure boiler seamless steel pipe" provisions. Tensile test, hydrostatic test and flattening test are the same as GB3087-82; impact test according to GB229-94; flaring test according to GB/T242-97; grain size test according to YB/T5148-93; GB13298-91, decarburization layer inspection according to GB224-87, ultrasonic inspection according to GB/T5777-96. (3) The inspection of physical properties of the imported boiler tubes and the indicators are carried out according to the relevant standards stipulated in the contract. 7. Major import and export conditions (1) The main importers of 20G high pressure boiler tubes are Japan and Germany. Frequently imported specifications are 15914.2mm, 2734.0mm, 219.110.0mm, 41975mm, 406.460mm and so on. The smallest size is 31.84.5mm, and the length is generally from 5 to 8m. (2) In the case of import claims, the ST45 seamless boiler tubes imported from the Mannesmann Steel Pipe Plant in Germany were surveyed by ultrasonic flaw detection and found that the internal defects of a few steel tubes exceeded the specifications of the plant and the standards of the German Steel Association. (3) Alloy steel pipes imported from Germany, mainly including 34CrMo4 and 12CrMoV. This kind of steel pipe has good high temperature performance and is commonly used as high temperature boiler steel pipe. (4) There are many alloy tubes imported from Japan. The specifications are 426.012mm5 to 8m; 152.48.0mm12m; 89.110.0mm6m; 101.610.0mm12m; 114.38.0mm6m; 127.08.0mm9m. The Japanese Industrial Standard JIS G3458 steel No. is STPA25. This type of steel pipe is commonly used as a supporting high-temperature alloy pipe.