- Except for the superheater, reheater and header whose wall temperature exceeds the allowable use temperature of carbon steel, and the main steam pipe, which is made of heat-resistant alloy steel, the remaining heating surfaces of the boiler, such as water-cooled wall, economizer, air preheater, convection tube, low-temperature section superheater reheater, steam drum and downcomer, are almost all made of 20 steel.
- 20 steel is a steel with a higher carbon content among low-carbon steels. It not only has high tensile strength, but also has good toughness and plasticity, and can be bent at room temperature. 20 steel has good oxygen cutting and welding performance. Generally, no measures are required before welding. As long as the wall thickness does not exceed 30mm or the rigidity of the workpiece is not large, no heat treatment is required after welding, and a good performance welded joint can be obtained. Therefore, the use of 20 steel brings great convenience to the manufacture, installation and maintenance of boilers.
- Although the tensile strength of steel increases with the increase of carbon content, the increase is not large, and the toughness and plasticity of steel decrease. When the carbon content of steel exceeds 0.25%, the welding performance is poor. Therefore, although the use of high carbon steel can improve the tensile strength, reduce the wall thickness of the heating surface, header or drum, and save a small amount of steel, the poor machining and welding performance at room temperature brings many difficulties to the manufacture, installation and maintenance of boilers. Weighing the pros and cons, the advantages of using 20 steel far outweigh the disadvantages, so 20 steel is widely used in boilers to manufacture various boiler parts.