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 steel includes oxidation resistant steel and hot strength steel: oxidation resistant steel generally requires better chemical stability, but bears lower load; High temperature strength and corresponding oxidation resistance are required for hot strength steel. Heat resistant steel is often used in the manufacture of boiler, steam turbine, power machinery, industrial furnace, aviation, petrochemical and other industrial sectors working at high temperature parts. In addition to high-temperature strength and high-temperature oxidation corrosion resistance, these parts also require sufficient toughness, good machinability and weldability, as well as certain structural stability according to different applications. Heat resistant cast steel is mostly used in as cast state, and corresponding heat treatment is adopted according to the type of heat resistant steel. Here is a brief introduction to the production process of heat-resistant steel

Smelting: heat resistant steel is usually smelted in electric arc furnace or induction furnace, and vacuum refining and out of furnace refining process are often adopted for those with high quality requirements.

Casting: some high alloy heat-resistant steels are difficult to process and deform. It is not only more cost-effective to produce castings than rolled products, but also has higher endurance strength, so heat-resistant cast steel accounts for a large proportion of heat-resistant steels. In addition to sand casting, precision casting can also be used to obtain products with smooth surface and accurate size. Centrifugal casting is often used for high temperature furnace tubes for ammonia and ethylene cracking.

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.

Ferrite steel cannot be strengthened by heat treatment. In order to eliminate the internal stress caused by cold plastic deformation processing and welding, annealing treatment can be carried out at 650-830 ℃ and then cooling rapidly to pass through the brittle temperature range of 475 ℃; High temperature solid solution heat treatment is mostly used for Austenitic oxidation resistant steel to obtain good cold deformability. The austenitic hot strength steel is first treated with high temperature solid solution treatment, and then aged at 60 ~ 100 ℃ higher than the service temperature to stabilize the structure and precipitate the second phase to strengthen the matrix.