The earliest material used in boilers and heating furnaces is low carbon steel, the temperature used is generally about 200 ° C, and the pressure is only 0.8MPa. Until the boiler is used with low carbon steel, such as 20g, the use temperature does not exceed 450℃, and the working pressure does not exceed 6MPa. With the continuous increase of the use temperature of various power plants, the working pressure has increased rapidly, and the use temperature of modern heat-resistant steel has reached 700 ° C, and the use environment has become more complex and harsh. The temperature range of heat-resistant steel is 200 ~ 1300℃, the working pressure is several mpa to tens of mpa, and the working environment is developed from a simple oxidation atmosphere to a vulcanized atmosphere, a mixed atmosphere and a more complex environment such as molten salt and liquid metal.
