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Selection of pearlitic heat-resistant steel electrode
Selection of welding rod for Cr Mo pearlite heat-resistant steel
1. Understanding of heat-resistant steel:
The ability to maintain chemical stability (corrosion resistance, no peeling) at high temperatures is called thermal stability; Having sufficient strength at high temperatures is called thermal strength. The steel with thermal stability and thermal strength is called heat-resistant steel.
● Classification of heat-resistant steel:
(1) Low alloy heat-resistant steel:
The total content of alloy elements is less than 5%. The supply state is annealing, or normalizing+tempering. The structure is mainly pearlite+ferrite, so it is also called pearlite heat-resistant steel. The pearlitic heat-resistant steel with Cr and Mo as the main elements is called chromium molybdenum pearlitic heat-resistant steel.
■ For example: 12CrMo, 15CrMo, 12Cr1MoV, etc.
(2) Medium alloy heat-resistant steel:
The total content of alloy elements is 6-12%, mainly Cr, containing 0.5-1% Mo. The supply status is mainly annealing, or normalizing+tempering. It is also available in quenched and tempered state. The microstructure in the annealed state is ferrite+carbide; The structure under normalizing+tempering condition is ferrite+bainite. The structure of heat-resistant steel with total alloy element content more than 10% is martensite.
■ For example: 5Cr-0.5Mo, 7Cr-0.5Mo, 9Cr-1Mo-V, etc.
(3) High alloy heat-resistant steel:
The total content of alloy elements is more than 13%, mainly Cr or Cr Ni. The microstructure is composed of martensite, ferrite and austenite.
■ For example, 0Cr13Al (ferrite), 1Cr13 (martensite), 1Cr18Ni9Ti (austenite).
● High temperature performance of heat-resistant steel:
(1) Creep resistance.
Creep: plastic deformation of metal occurs slowly with the increase of time under the action of a certain temperature and stress.
(2) High temperature endurance strength: the ability of metal materials to resist fracture under high temperature and long-term stress.
(3) Creep brittleness (permanent plasticity of steel): brittleness tendency caused by combined action of temperature, stress and time.
(4) High temperature oxidation resistance.
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