What Material Are Boiler Tubes Made Of ?

What is a boiler?

A boiler is a closed device used to heat a fluid (usually water). It does not actually vaporize the gas. The heated or vaporized fluid leaves the boiler and is used for different processes or heating applications such as water heating, central heating and power generation, relying on boiler tubes, cooking and sanitary facilities.

What materials are boiler tubes made of? What type of tubes are used in boilers?

Boiler tubes are seamless pipes(ASTM A179) made of carbon steel (or alloy) or traditional wrought iron. They are widely used in steam boilers, power generation, fossil fuel plants, industrial processing plants, power plants, etc. Boiler tubes can be medium-pressure boiler tubes or high-pressure boiler tubes.

The main function of boiler tubes is to transport steam or other media and withstand harsh environments such as high temperature, high pressure, and water vapor corrosion. Boiler tubes are both seamless tubes and electric resistance welded tubes. Seamless tubes are more popular because of their high pressure and temperature resistance. Its specifications are usually expressed in terms of outer diameter or side length and wall thickness, and the size range is very wide, from capillaries with extremely small diameters to large-diameter tubes with diameters of several meters.

Material classification of boiler tubes

High-quality carbon structural steel: such as 20G, 20MnG, 25MnG, etc. This type of steel is usually used in the manufacture of general boiler tubes, and the use temperature is below 350℃.

Alloy structural steel: such as 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc. These alloy steels are suitable for the manufacture of high-pressure boiler tubes, and are often in high temperature and high pressure conditions when used.

Stainless steel: Stainless steel is also used in boiler tubes, such as the stainless steel seamless steel tubes for boilers and heat exchangers specified in GB/T 13296-2013.

Rust-resistant heat-resistant steel: such as 1Cr18Ni9, 1Cr18Ni11Nb, etc. In addition to ensuring the chemical composition and mechanical properties, this type of steel also needs to be tested for water pressure, expansion and flattening one by one.

The manufacturing method of boiler tubes is the same as that of seamless tubes, but there are strict requirements on the type of steel used to manufacture steel tubes. Boiler tubes are divided into general boiler tubes and high-pressure boiler tubes according to the use temperature. General boiler tubes are mainly used for water-cooled wall tubes, boiling water tubes, superheated steam tubes, etc., while high-pressure boiler tubes are used for key components such as superheater tubes, reheater tubes, gas guide tubes, and main steam tubes of high-pressure and ultra-high-pressure boilers. In the production process of boiler tubes, heat treatment is a key process, which has an important impact on the intrinsic quality and surface quality of steel tubes.