Low, medium and high pressure seamless boiler tubes

Keywords: boiler tubes, boiler seamless tube
Boiler seamless tube is a kind of boiler tube, which belongs to the category of seamless steel tube. The manufacturing method is the same as that of seamless tubes, but there are strict requirements on the steel grades used to manufacture steel pipes.

Boiler seamless tubes are often used in high temperature and high pressure conditions, and the pipes will be oxidized and corroded under the action of high temperature flue gas and water vapor. The steel pipe is required to have high lasting strength, high oxidation corrosion resistance, and good organizational stability. High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, gas guide tubes, main steam tubes, etc. of high-pressure and ultra-high-pressure boilers. Boiler seamless steel tubes are divided into general boiler tubes (low and medium pressure) and high pressure boiler tubes according to the high temperature performance they are subjected to.

Classified by usage conditions:

1. Seamless steel tubes for steam (GB/T8163-2008). Mainly used in the manufacture of steam turbine generator sets and nuclear power equipment in industry.
2. Seamless steel tubes for low and medium pressure boilers (B3087-2008). Mainly used in power plants and nuclear power plants for heating, steel pipes for superheaters, etc.
3. Seamless steel tubes for pressure cookers (GB5310-2008). It is mainly used for high temperature and high pressure pipelines in power plants and nuclear power plants to transport fluids and other media.
4. Special seamless steel pipe for fertilizer equipment (GB6479-2000). It is mainly used in the pipeline for conveying high temperature flue gas on fertilizer equipment.

Specifications and appearance quality:


GB5310-95 "Seamless Steel Tubes for High Pressure Boilers" has an outer diameter of 22 to 530mm and a wall thickness of 20 to 70mm. The outer diameter of the cold drawn (cold rolled) tube is 10-108mm, and the wall thickness is 2.0-13.0mm. The inner and outer surfaces of the steel pipe are not allowed to have cracks, folds, folds, scars, delaminations and hairlines. 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 at the cleaning place shall not be less than the minimum allowable wall thickness.
Calculation method of theoretical weight of boiler seamless management: (outer diameter - wall thickness) * wall thickness * 0.02466

Boiler seamless steel tube 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) The commonly used 1Cr18Ni9 and 1Cr18Ni11Nb boiler tubes with rust and heat-resistant steels should be subjected to hydrostatic tests, flaring and flattening tests one by one in addition to ensuring chemical composition and mechanical properties. Steel pipes are delivered in heat-treated condition.
In addition, there are certain requirements for the microstructure, grain size and decarburization layer of the finished steel pipe.

Manufacturing method:
① Generally, the use temperature of seamless boiler tubes is below 450 °C, and domestic tubes are mainly made of No. 10 and No. 20 carbon steel hot-rolled tubes or cold-drawn tubes.
② High-pressure boiler tubes are often used in high temperature and high pressure conditions, and 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 lasting strength, high oxidation corrosion resistance, and good organizational stability.

Boiler tube use:
①General boiler seamless 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 and arch brick pipes, etc.
②High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, gas guide tubes, main steam tubes, etc. of high-pressure and ultra-high-pressure boilers.