Seamless boiler pipe refers to the steel with openings at both ends and hollow section, whose length is larger than that of the surrounding steel. According to the production method, it can be divided into seamless steel pipe and welded steel pipe. The specification of steel pipe is expressed by the overall dimension (such as outer diameter or side length) and wall thickness, and its size range is very wide, from the capillary with small straight diameter to the large-diameter pipe with a diameter of several meters. Steel pipe can be used for pipeline, thermal equipment, mechanical industry, petroleum geological exploration, container, chemical industry and special purpose.
A method of producing seamless tubes
Boiler tube is a kind of seamless tube. The manufacturing method is the same as that of seamless pipe, but there are strict requirements for the steel grades used for manufacturing steel pipes. According to the temperature, it can be divided into two types: general boiler pipe and high-pressure boiler pipe.
The mechanical property of steel is an important index to ensure the final use performance (mechanical property), which depends on the chemical composition and heat treatment system of steel. In the steel pipe standard, according to different requirements, the tensile properties (tensile strength, yield strength or yield point, elongation), hardness and toughness indexes, as well as the high and low temperature properties required by users are specified.
Classification of steel pipe: steel pipe is divided into seamless steel pipe and welded steel pipe (seamed pipe). According to the section shape, it can be divided into circular pipe and special-shaped pipe. Circular steel pipe is widely used, but there are also some square, rectangular, semicircle, hexagon, equilateral triangle, octagon and other special-shaped steel pipes. Hydraulic pressure test shall be carried out for the steel pipes bearing fluid pressure to check their pressure resistance and quality. If there is no leakage, wetting or expansion under the specified pressure, it is qualified. Some steel pipes shall be subject to crimping test, expanding test, flattening test, etc. according to the standards or the requirements of the demander.
(1) manufacturing method:
① generally, the use temperature of boiler tubes is below 350 ℃, and the domestic tubes are mainly made of No.10 and No.20 carbon steel hot-rolled tubes or cold drawn tubes.
② the high-pressure boiler pipe is often in high temperature and high pressure conditions when it is used. Under the action of high temperature flue gas and water vapor, the pipe will be oxidized and corroded. The steel pipe is required to have high endurance strength, high oxidation resistance and corrosion resistance, and good structure stability.
① general boiler pipes are mainly used to manufacture water wall pipes, boiling water pipes, superheated steam pipes, superheated steam pipes for locomotive boilers, large and small smoke pipes, arch brick pipes, etc.
② high pressure boiler pipe is mainly used to manufacture superheater pipe, reheater pipe, air pipe, main steam pipe, etc. of high pressure and ultra-high pressure boiler.
Seamless furnace pipe adopts steel grade
(1) high quality carbon structural steel grades are 20g, 20mng and 25mng.
(2) alloy structural steel grades: 15mog, 20mog, 12crmog, 15CrMoG, 12CR2MOG, 12crmovg, 12Cr3MoVSiTiB, etc.
(3) in addition to ensuring the chemical composition and mechanical properties, the common boiler pipes of 1Cr18Ni9 and 1cr18ni11nb with rust and heat-resistant steel shall be subject to hydraulic test one by one, and the expansion and flattening tests shall be conducted. Steel pipes shall be delivered in heat treatment state.
The boiler pipe is divided into general boiler pipe and high pressure boiler pipe according to the high temperature performance. No matter the general boiler pipe or high-pressure boiler pipe are different according to their use requirements, they can be divided into various steel pipes.
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