Production process of heat-resistant steel

Production process of heat-resistant steel
Heat resistant steel is an alloy steel with high strength and good chemical stability at high temperature.
Heat resistant steels include oxidation resistant steels and heat strength steels. Oxidation resistant steels generally require better chemical stability, but bear lower load; High temperature strength and corresponding oxidation resistance are required for heat strength steels. Heat resistant steel is often used to manufacture parts and components working under high temperature in industrial sectors such as boilers, steam turbines, power machinery, industrial furnaces, aviation, petrochemical, etc. In addition to high temperature strength and resistance to high temperature oxidation corrosion, these components also require sufficient toughness, good machinability, weldability, and certain structural stability according to different applications. Heat resistant cast steel is mostly used as cast, and corresponding heat treatment is also adopted according to the type of heat resistant steel.

The following is a brief introduction to the production process of heat-resistant steel:
Smelting: Heat resistant steel is generally smelted in electric arc furnace or induction furnace, and vacuum refining and off furnace refining are often used for those with high quality requirements.
Casting: some high alloy heat-resistant steels are difficult to process and deform. It is not only cheaper to produce castings than rolled products, but also the castings have higher lasting strength. Therefore, heat-resistant cast steels account for a large proportion of heat-resistant steels. In addition to sand casting, the casting process can also be used to obtain products with smooth surface and accurate size. Centrifugal casting is often used for the high-temperature furnace tubes used for the cracking of synthetic ammonia and ethylene.
Heat treatment: pearlitic heat strength steel is usually used after normalizing or quenching and tempering; Martensitic heat-resistant steel is quenched and tempered to stabilize the structure and obtain good comprehensive mechanical properties and high temperature strength.
Ferritic steels cannot be strengthened by heat treatment. In order to eliminate the internal stress caused by cold plastic deformation processing and welding, it can be annealed at 650~830 ℃, and then cooled quickly after annealing, so as to quickly pass the 475 ℃ brittle temperature range; Austenitic oxidation resistant steels are mostly treated by high temperature solution heat treatment to obtain good cold deformation. Austenitic heat strength steel is first treated by high temperature solution treatment, and then aged at 60~100 ℃ higher than the service temperature to stabilize the structure and precipitate two phases to strengthen the matrix.