Introduction to seamless boiler tubes

Seamless boiler tubes are a type of boiler tube that falls under the category of seamless steel tubes. Their manufacturing process is similar to that of other seamless tubes, but the steel grades used to produce these tubes must meet strict criteria.

Boiler seamless tubes are often utilized in high-temperature and high-pressure environments. Under the influence of high-temperature flue gases and water vapor, these pipes can become oxidized and corroded. Therefore, they must possess high strength, excellent resistance to oxidation and corrosion, and stable structure. High-pressure boiler tubes are primarily used in the construction of superheater tubes, reheater tubes, air guide tubes, and main steam tubes for high-pressure and ultra-high-pressure boilers. Based on their high-temperature performance, boiler seamless steel tubes are classified into general boiler tubes (low and medium pressure) and high-pressure boiler tubes.

Classification by Usage Conditions:

- Seamless Steel Tubes for Steam (GB/T8163-2008)

Primarily used in the manufacture of steam turbine generator sets and nuclear power equipment.

- Seamless Steel Tubes for Low and Medium Pressure Boilers (B3087-2008)

Used in power plants and nuclear power plants for heating and superheater steel pipes.

- Seamless Steel Tubes for Pressure Cookers (GB5310-2008)

Used for high-temperature and high-pressure pipelines in power plants and nuclear power plants to transport fluids and other media.

- Special Seamless Steel Pipe for Fertilizer Equipment (GB6479-2000)

Used in pipelines for conveying high-temperature flue gases in fertilizer equipment.

Specifications and Appearance Quality:

According to GB5310-95 "Seamless Steel Tubes for High-Pressure Boilers," these tubes have an outer diameter of 22 to 530 mm and a wall thickness of 20 to 70 mm. The outer diameter of cold-drawn (cold-rolled) tubes ranges from 10 to 108 mm, with a wall thickness of 2.0 to 13.0 mm. The steel pipes must be free from cracks, folds, scars, delaminations, and hairlines, which should be completely removed if present. The cleaning depth must not exceed the negative deviation of the nominal wall thickness, and the actual wall thickness at the cleaned areas must meet the minimum allowable wall thickness.

The theoretical weight of boiler seamless tubes can be calculated using the formula: (outer diameter−wall thickness)×wall thickness×0.02466(\text{outer diameter} - \text{wall thickness}) \times \text{wall thickness} \times 0.02466(outer diameter−wall thickness)×wall thickness×0.02466.

Steel Grades Used in Boiler Seamless Tubes:

- High-Quality Carbon Structural Steel Grades:

20G, 20MnG, 25MnG

- Alloy Structural Steel Grades:

15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB

- Commonly Used Rust and Heat-Resistant Steels:

1Cr18Ni9, 1Cr18Ni11Nb

These boiler tubes must undergo hydrostatic tests, flaring, and flattening tests in addition to meeting chemical composition and mechanical property requirements. The steel pipes are delivered in a heat-treated condition, with specific requirements for the microstructure, grain size, and decarburization layer of the finished steel pipe.

Manufacturing Methods:

- General Use Seamless Boiler Tubes:

Typically used at temperatures below 450°C and are primarily made from No. 10 and No. 20 carbon steel, either hot-rolled or cold-drawn.

- High-Pressure Boiler Tubes:

Used in high-temperature and high-pressure conditions, requiring tubes that resist oxidation and corrosion and maintain high strength and structural stability.

Applications of Boiler Tubes:

- General Boiler Seamless Pipes:

Used in manufacturing water wall pipes, boiling water pipes, superheated steam pipes for locomotive boilers, large and small smoke pipes, and arch brick pipes.

- High-Pressure Boiler Tubes:

Used in manufacturing superheater tubes, reheater tubes, gas guide tubes, and main steam tubes for high-pressure and ultra-high-pressure boilers.