欧美午夜精品久久久久免费视_中国性孕妇孕交tv_日韩人妻无码精品久久免费一_欧美深夜福利_伊人网五月天_办公室挺进少妇双腿间小说

Smelting, heat-resistant steel is usually smelted in electric arc furnace or induction furnace. Vacuum refining and secondary refining are often used for those with high quality requirements. Casting, some high alloy heat-resistant steel is difficult to process and deform. The production of castings is not only more cost-effective than rolled products, but also has higher endurance strength, so heat-resistant cast steel accounts for a large proportion in heat-resistant steel. In addition to sand casting, precision casting can also be used to obtain products with smooth surface and accurate size. Centrifugal casting method is often used for high temperature furnace tubes used in ammonia and ethylene cracking. Heat treatment Pearlite Heat-resistant 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 cooled rapidly to pass through the brittle temperature range of 475 ℃. High temperature solution heat treatment is usually used in austenitic oxidation resistant steels to obtain good cold deformation. The austenite heat-resistant steel is first treated with high temperature 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. Heat resistant cast steel is mostly used in as cast state, and some are heat treated according to the type of heat-resistant steel. It is commonly used in the manufacture of high-temperature parts and components in aviation machinery, boiler and chemical industry. 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 steel has been produced in China since 1952. After that, some new low-alloy heat-resistant steels were developed, so that the working temperature of Pearlite Heat-resistant Steels was raised to 600-620 ℃. In addition, some new low chromium nickel anti-oxidation steels were developed. Some stainless steels have the characteristics of heat-resistant steel, which can be used either as stainless acid resistant steel or as heat-resistant steel.