A large amount of metal materials are used in thermal power plant boilers. With the development of power generation technology, large-capacity and high-parameter thermal power units have been put into the power grid in recent years. Now supercritical (ultracritical) units have become the main models in China’s power production market. One of the most effective ways to improve the efficiency of thermal power plants is to increase the parameters of boiler steam temperature and pressure. The main difficulty encountered in improving steam parameters is the problem of metal materials.
Boiler steel plate is one of the most critical materials in boiler manufacturing. It mainly refers to the hot-rolled special carbon steel and low-alloy heat-resistant steel medium and thick steel plates used to manufacture important parts such as boiler shells, drums, header end covers, and supports in boilers. Boiler steel plates often work under medium and high temperature and high pressure. In addition to bearing high temperature and pressure, they are also subject to impact, fatigue loads, and corrosion by water and gas, and the working conditions are poor. If a destructive accident occurs during the use of the boiler, it will cause serious losses.
Therefore, boiler steel plates must have good physical properties, mechanical properties and machinability, and strict regulations should be given in the technical terms of material standards to meet their safety in use.
1.Classification by material
Based on the material, boiler steel plates can be divided into two categories: special carbon steel plates and low-alloy heat-resistant steel plates.
① The materials used for boiler steel plates have strict control over the chemical composition, especially harmful elements such as phosphorus and sulfur and residual elements such as chromium, nickel, and copper;
② Good deoxidation and removal of non-metallic inclusions should also be carried out during smelting to ensure good plasticity and toughness;
③ The organizational structure requires uniformity and the grain size is controlled within a certain range (usually the grain size is expected to be between 3 and 7 levels);
④ There are also strict requirements for surface quality and internal defects;
⑤ In addition, the mechanical properties at room temperature and high temperature must be guaranteed.
2.Classification by use environment
According to different working conditions, boiler steel plates can be divided into two categories: steel plates for manufacturing room temperature and medium temperature pressure-bearing components and steel plates for manufacturing high temperature pressure-bearing components.
3.Main features of boiler steel plates:
Since boiler steel plates are important products with strict safety and reliability requirements and high manufacturing technology difficulty, the materials must have the following main features:
(1) The material has a high yield strength performance within a certain temperature range (normal temperature and high temperature);
(2) The material has sufficient toughness and will not cause brittle failure accidents during manufacturing or use;
(3) The material has a small strain aging sensitivity, especially in the corresponding working temperature range, a certain value of aging impact energy must be guaranteed;
(4) The material has a low notch sensitivity, which can prevent the steel from cracking during welding, opening, and local stress concentration areas;
(5) The material has good welding performance;
(6) The material has a good microstructure, and white spots and cracks are not allowed to exist.
