The metal materials used for thermal power equipment in thermal power plants mainly include carbon steel, alloy steel, copper and copper alloys, and titanium.
Metallic materials for boilers should have high corrosion resistance, good plasticity, excellent weldability and sufficiently high mechanical strength. For equipment with a temperature higher than 400~450℃, it must have creep resistance. Generally, low-pressure boiler steel pipes (steam temperature <450℃) mainly use No. 10 and No. 20 high-quality carbon steels, and medium and high-pressure boilers (steam temperature> 450℃) water wall pipes and gas-saving pipes use No. 20 steel; steam temperature is higher For subcritical and above pressure boilers, water wall tubes and economizer tubes are made of high-quality carbon steel 20G, 20MnG, 25MnG, etc.; other tubes are mostly made of alloy steel. The alloy steels used in boiler tubes include low-alloy pearlite heat-resistant steel, martensitic heat-resistant steel and austenitic heat-resistant steel, of which low-alloy pearlite heat-resistant steel is the most used.
The superheater tube with wall temperature ≤500℃ generally adopts No. 20 steel; the superheater tube with wall temperature of 500~550℃ adopts 15CrMo; the superheater tube with wall temperature of 550~580℃ adopts 12CrlMoV, 12MoVWBSiRe; the wall temperature is 600~ The 620℃ superheater tube adopts 12Cr2MowViB and 12Cr3MoVSiTiB. In foreign countries, the superheater tube whose wall temperature exceeds 600℃ uses Cr12% martensitic heat-resistant steel and 1Cr18Ni9Ti and other Cr-Ni austenitic stainless steels. The steam temperature of supercritical and ultra-supercritical units exceeds 600℃, so the requirements for the material and process of the superheater tube are higher.
Low and medium pressure boiler drums generally use high-quality carbon steel 20G, 22G, high pressure or ultra-high pressure and above pressure boiler drums use ordinary low alloy steel, such as 14MnMoVg, 18MnMoNbg.
Turbine blade materials should have sufficient mechanical properties at room temperature and high temperature, good vibration resistance, high structural stability, good corrosion resistance and cold and hot processing performance. Blade steel is mainly chromium stainless steel 1Cr3, 2Cr13 and reinforced stainless steel 1Cr11MoV, 1Cr12WMoV, 2Cr12WMoVNbB, etc.
The materials of the main shaft and impeller of the steam turbine are required to have good comprehensive mechanical properties and a certain degree of resistance to steam corrosion. For impellers and spindles operating at high temperatures, it is also required to have sufficiently high creep limit, enduring strength, enduring plasticity and structural stability, as well as good process properties such as hardenability and weldability. The materials of the spindle and impeller are mainly medium Carbon steel and medium carbon alloy steel, such as No. 35 steel, 34CrMo, 35CrMoV, 20CrWMoV, etc.
Due to the different temperature and pressure of the cylinder, partition and other static parts, gray cast iron, high-strength heat-resistant cast iron, cast steel or low-alloy heat-resistant steel can be selected.
The pipes used in heaters and condensers require good heat transfer performance, certain strength and good corrosion resistance. Copper alloy pipes, stainless steel pipes and titanium pipes are commonly used. Copper alloy pipe materials include brass H68A, HSn70-1A, HA177-2A, cupronickel B10 and B30, etc., and stainless steel materials include TP304, TP316, TP317, etc. Steel pipes are mostly used for high-pressure heaters.
