Production method of boiler seamless steel pipe: Boiler seamless steel pipe is a type of seamless steel pipe. The manufacturing method is the same as that of seamless steel pipes, but there are strict requirements for the type of steel used in manufacturing steel pipes. According to the operating temperature, it is divided into two types: general boiler tubes and high-pressure boiler tubes. The mechanical properties of steel are important indicators to ensure the final performance (mechanical properties) of steel. It depends on the chemical composition and heat treatment system of the steel. In steel pipe standards, tensile properties (tensile strength, yield strength or yield point, elongation), hardness, toughness, and high and low-temperature properties required by users are specified according to different use requirements.
1 Overview
(1) Manufacturing method:
① Generally, the operating temperature of boiler tubes is below 450°C. Domestic tubes are mainly made of No. 10 and No. 20 carbon steel hot-rolled pipes or cold-drawn pipes.
② High-pressure boiler tubes are often exposed to high temperatures and high-pressure conditions when used. Under the action of high-temperature flue gas and water vapor, the tubes will oxidize and corrode. Steel pipes are required to have high lasting strength, high resistance to oxidation and corrosion, and good structural stability.
(2)Use:
①General 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 arch brick tubes, etc.
② High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, air guide tubes, main steam pipes, etc. for high-pressure and ultra-high-pressure boilers.
Boiler seamless steel pipe uses
①General 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 arch brick tubes, etc.
② Boiler seamless steel pipes are mainly used to manufacture superheater tubes, reheater tubes, air guide tubes, main steam pipes, etc. for high-pressure and ultra-high-pressure boilers.
2. Type
Boiler seamless steel tubes are divided into general boiler tubes and high-pressure boiler tubes according to their high-temperature performance. Regardless of general boiler tubes or high-pressure boiler tubes, they can be divided into various steel tubes according to their application requirements.
3. Specifications and appearance quality
(1) GB3087-82 “Seamless Steel Tubes for Low and Medium Pressure Boilers”. There are 43 types of steel pipe specifications for boilers with various structures, with an outer diameter of 10 to 426 mm. There are 29 types in total with a wall thickness of 1.5~26mm. However, the outer diameter and wall thickness of superheated steam pipes, large smoke pipes, small smoke pipes, and arch brick pipes used in locomotive boilers are otherwise regulated.
(2) GB5310-95 “Seamless Steel Tubes for High-Pressure Boilers” has an outer diameter of 22-530mm and a wall thickness of 20-70mm. Cold-drawn (cold-rolled) tubes have an outer diameter of 10-108mm and a wall thickness of 2.0-13.0mm.
(3) GB3087-82 “Seamless Steel Tubes for Low and Medium Pressure Boilers” and GB5310-95 “Seamless Steel Tubes for High-Pressure Boilers”. Appearance quality: Cracks, folds, rolling folds, scars, delamination, and hairlines are not allowed on the inner and outer surfaces of steel pipes. These defects should be completely removed. The cleaning depth shall not exceed the negative deviation of the nominal wall thickness, and the actual wall thickness of the cleaning place shall not be less than the minimum value allowed by the wall thickness.
4. Chemical composition inspection
(1) GB3087-82 “Seamless Steel Tubes for Low and Medium Pressure Boilers”. The chemical composition test method is by the relevant parts in GB222-84 and GB223 “Chemical Analysis Methods of Iron, Steel and Alloy”.
(2) GB5310-95 “Seamless Steel Tubes for High-Pressure Boilers” regulations. The chemical composition test method is by relevant parts in GB222-84 and “Chemical Analysis Methods of Iron and Steel and Alloys”, and GB223 “Chemical Analysis Methods of Iron, Steel and Alloys”.
(3) The chemical composition inspection of imported boiler steel pipes shall be carried out by the relevant standards stipulated in the contract.
5. Boiler seamless steel pipe adopts steel grade
(1) The steel grades of high-quality carbon structural steel are 20G, 20MnG, and 25MnG.
(2) Alloy structural steel Steel grades 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.
(3) 1Cr18Ni9 and 1Cr18Ni11Nb boiler tubes commonly used in rusty and heat-resistant steels should not only ensure the chemical composition and mechanical properties, but also need to do a hydraulic test one by one, and do flaring and flattening tests. 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.
Post time: Sep-07-2023