Boiler tubes are metal tubes located inside a boiler that are used to heat water to produce steam.

The boiler tube is a type of seamless tube. The manufacturing method is the same as that of the seamless pipe, but there are strict requirements for the steel used in the manufacture of the steel pipe. According to the use of high and low temperature is divided into two types of general boiler tubes and high pressure boiler tubes.

The mechanical properties of the boiler tube are important indicators to ensure the final performance of the steel (mechanical properties), which depends on the chemical composition of the steel and the heat treatment system. In the steel pipe standard, according to different use requirements, tensile properties (tensile strength, yield strength or yield point, elongation), hardness and toughness index, as well as high and low temperature properties required by users are specified.

The general boiler tube use temperature is below 450 °C, and the domestic tube is mainly made of 10 or 20 carbon steel hot rolled tube or cold drawn tube.
High-pressure boiler tubes are often subjected to high temperature and high pressure conditions, and the tubes will oxidize and corrode under the action of high temperature flue gas and water vapor. Steel pipes are required to have high durability, high corrosion resistance and good structural stability.

How are boiler tubes manufactured?

Both medium and high pressure boiler tubes undergo the same initial manufacturing process, including fine drawing, surface brightening, hot rolling, cold drawing and thermal expansion. However, the following steps are taken to make high-pressure tubes stronger and more corrosion resistant.

Heat treatment involves the heating and cooling of the high-pressure boiler pipe, resulting in improved toughness, hardness and wear resistance. The different steps of heat treatment include quenching, tempering and annealing.

Quenching is done to increase the hardness of the high-pressure boiler tubes. The tubes are heated uniformly to the proper temperature and then quickly immersed in water or oil for instant cooling. It is then cooled in air or in a freezing zone.

Tempering is used to remove the brittleness of the pipe. Quenching may cause the pipe to be tapped or fractured.

Annealing removes the internal stresses in the pipe. In this process, seamless pipes are heated to a critical temperature and then slowly cooled in ash or lime.

Use of boiler tubes

General boiler tubes are mainly used to manufacture water-cooled wall pipes, boiling water pipes, superheated steam pipes, superheated steam pipes for locomotive boilers, large and small smoke pipes and arch brick pipes.
High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, air ducts, main steam tubes, etc. for high-pressure and ultra-high pressure boilers. The supply and demand trend of the high-pressure boiler tube industry is generally stable, but the supply and demand situation of each specific sub-sector will be further differentiated. Insiders pointed out that the most critical link is the use and promotion of new energy-saving insulation 20g high-pressure boiler tube equipment.

New energy-saving 20g high-pressure boiler tube products are gradually increasing in the market, for example, green environmental protection coatings, energy-saving and water-saving sanitary ware products, environmentally-friendly stone materials, environmentally-friendly external cement foam insulation boards, etc., energy-saving and environmental protection products in the vast market of 20g high-pressure boiler tube industry The prospects are optimistic.

Boiler pipe materials and standards

Standards and material for steel pipe is available at carbon, alloy, and stainless steel material.
Carbon steel: ASTM/ASME A/SA 106, ASTM A179, ASTM A192, ASTM/ASME A/SA 210, ASTM A333 Gr 1, 6,7 to Gr 9,
Alloy steel: ASTM/ASME A/SA 213 T1, T2, T5, T9, T11, T12, T22, T91, T92; ASTM A335 P1, P2, P5, P9, P11, P12, P22, P91, P92
Stainless Steel: ASTM A268, ASTM A213, TP304/L, TP316/L, 310S,309S,317,317L,321,321H, and duplex stainless steel material etc.
Common Sizes: OD from 6mm to 1240mm, thickness from 1mm to 50mm
Types: Straight boiler pipe, and U boiler steel pipe for tube exchanger bundle.
These standards specify the classification, size, shape, weight and allowable deviation, technical requirements, inspection and test, packaging, marking and quality certificate of seamless steel tubes for boiler.