1. What is a boiler tube?
Boiler tube refers to a steel with open ends and a hollow section, and its length is larger than that of the periphery. According to the production method, it can be divided into seamless steel pipe and welded steel pipe. Wall thickness means a wide range of dimensions, from capillary tubes with a small diameter to large-diameter tubes with a diameter of several meters. Steel pipes can be used for pipelines, thermal equipment, machinery industry, petroleum geological exploration, containers, chemical industry and special purposes.
Boiler tubes are divided into general boiler tubes and high-pressure boiler tubes according to the high temperature performance they bear, and can be divided into various steel tubes according to their different requirements.
3. Production method of boiler tube
The boiler tube is a kind of seamless tube. The manufacturing method is the same as that of seamless steel pipes
, but there are strict requirements on the steel grades used in the manufacture of steel pipes. According to the operating temperature, it can be divided into general boiler tubes and high-pressure boiler tubes.
The mechanical properties of the boiler tube is an important index to ensure the final use performance (mechanical properties) of the steel, and it depends on the chemical composition of the steel and the heat treatment system. In the steel pipe standard, according to different application requirements, the tensile properties (tensile strength, yield strength or yield point, elongation), hardness, toughness indexes, and high and low temperature properties required by users are specified.
①Generally, the temperature of boiler tubes is below 350℃. Domestic tubes are mainly made of No. 10 and No. 20 carbon steel hot-rolled tubes or cold-drawn tubes.
②High-pressure boiler tubes are often in high temperature and high pressure conditions when they are used. The tubes will be oxidized and corroded under the action of high temperature flue gas and water vapor. The steel pipe is required to have high enduring strength, high oxidation and corrosion resistance, and good organizational stability.
4. Purpose of boiler tube
①General boiler tubes are mainly used to make water wall tubes, boiling water tubes, superheated steam tubes, superheated steam tubes for locomotive boilers, large and small smoke tubes and arched brick tubes.
②High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, air guide tubes, main steam tubes, etc. of high-pressure and ultra-high-pressure boilers.
The supply and demand trend of the high-pressure boiler tube industry is generally stable, but the supply and demand situation of each specific sub-industry will be further divided. Insiders pointed out that the most critical link is the use and promotion of new energy-saving insulation 20g high-pressure boiler tube equipment.
New energy-saving 20g high-pressure boiler tube products are gradually increasing in the market, such as green paint, energy-saving water-saving sanitary products, environmentally friendly stone, environmentally friendly external cement foam insulation board, etc. Energy-saving and environmentally friendly products are in the broad market of 20g high pressure boiler tube The prospects in China are promising.
5. Use steel grade
(1) The grades of high-quality carbon structural steel are 20G, 20MnG, and 25MnG.
(2) Alloy structural steel grades 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.
(3) In addition to ensuring chemical composition and mechanical properties, 1Cr18Ni9 and 1Cr18Ni11Nb boiler tubes commonly used in rusty and heat-resistant steel must be subjected to hydrostatic tests, as well as flaring and flattening tests. 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.
6. Main import and export situation
(1) The main import countries of boiler tubes are Japan and Germany. The frequently imported specifications are 15914.2mm; 2734.0mm; 219.110.0mm; 41975mm; 406.460mm, etc. The smallest specification is 31.84.5mm, and the length generally ranges from 5 to 8m.
(2) In the case of import claims, the ST45 seamless boiler tube imported by Mannesmann Steel Pipe Factory in Germany was inspected by ultrasonic flaw detection and found that a small number of internal defects of the steel pipe exceeded the factory's regulations and the standards of the German Iron and Steel Association.
(3) The 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 steel pipe for high temperature boiler.
(4) There are many alloy pipes imported from Japan, with specifications of 426.012mm5~8m; 152.48.0mm12m; 89.110.0mm6m; 101.610.0mm12m; 114.38.0mm6m; 127.08.0mm9m and so on. Implementation of Japanese Industrial Standards JISG3458 steel grade is STPA25. This kind of steel pipe is often used as a matching high-temperature alloy pipe.
According to GB2102-88, there are three types of steel pipe packaging: strapping, boxing, oil-coated strapping or oil-coated box.
Tips: ERW steel pipe is formed by rolling strip and welding the seam, with tighter dimensional tolerances and less weight. The weld seam is heat treated after welding that no untempered martensite remains, and the weld flash can be removed from both inner and outer surfaces.
ASTM A53 ERW pipe is a typical carbon steel pipe. It is largely used to convey fluids at low / medium pressures such as oil, gas, steam, water, air and also for mechanical applications.