Heat resistant steel alloys introduction
Heat-resistant alloy steel, mainly refers to the high temperature oxidation resistance and the strength does not reduce a lot of alloy steel. Heat-resistant steel, including anti-oxidation steel and two types of hot strong steel. Antioxidant steel generally requires good chemical stability,But the bear of load is low. Hot high-strength steel requires a higher temperature strength and the corresponding oxidation resistance. Heat-resistant steel commonly used in the manufacture of boilers, steam turbines, power machinery, industrial furnaces and aviation, petrochemical and other industrial sectors working in high temperature parts. In addition to these components require high temperature strength and high temperature oxidation corrosion, and according to different purposes also requires sufficient toughness, good workability and weldability, and a certain degree of organizational stability.
Correct use of heat-resistant steel
1. According to the different environmental media, select the applicable heat-resistant steel.
2. Precautions in use
a. Try to form a stable and dense protective oxide film - pre-oxidation treatment
Heat-resistant steel surface with a stable and dense protective oxide film is the normal use of equipment prerequisites.Therefore, the electric heating equipment before the official opening, the power heated to high enough temperature, heat long enough to form the ideal oxide film.Normal use can not replace the pre-oxidation process.Pre-oxidation should be carried out in an empty furnace.Pre-oxidation temperature should be higher than the normal temperature of 50 ℃ (can not exceed the maximum allowable temperature of the material),Holding time 4 to 6 hours.If the equipment is suspended for a long time, it should be pre-oxidized before it can be reused.
b. Equipment temperature does not exceed the maximum allowable temperature of the material.
c. Equipment heating must be uniform, but not too hot. When using a rod-shaped heating element, the heating element should be at a sufficient distance from the heated equipment.
d. Welding parts must be in accordance with the correct welding process welding.Try to avoid and reduce hydrogen corrosion and intergranular corrosion of base metal around the weld.
e. To ensure the service life of heat-resistant steel and the normal use of equipment, the correct material selection is to ensure that clear-phase environment is the premise.Various parameters of the gas phase environment is a direct factor in determining and affecting the oxidation of heat-resistant steel.
① chemical composition of the gas is a single oxygen or a mixture of two or more gases.
② The total pressure of the gas phase and the partial pressure of the reaction gas components, and the pressure change.
③ Gas flow status and flow rate.
④ Whether the flowing gas contains particles that react easily with the surface of the heat-resistant steel.
⑤ Ambient temperature is constant or alternating.
⑥ External force is constant or alternating.
f. During the normal heating process of the workpiece, the same material test piece is placed in the equipment, and the evaluation of the heat-resistant steel equipment is replaced by the observation and evaluation result of the test piece.
g. Heat-resistant steel equipment try to avoid the rapid heat in the heating process.
pressure valves for general machinery.