2, cast steel (cast steel) Casting steel. Cast a kind of alloy. Cast steel is divided into cast carbon steel, cast low alloy steel and special steel casting 3 categories. ①cast carbon steel. Cast steel with carbon as the main alloying element and with a few other elements. Less than 0.2% of carbon for the casting of low carbon steel, carbon 0.2% to 0.5% for the casting of medium carbon steel, carbon greater than 0.5% for the casting of high carbon steel. As the carbon content increases, the strength of the cast carbon steel increases and the hardness increases. Cast carbon steel with high strength, ductility and toughness, low cost, used in heavy machinery for the manufacture of large load bearing parts, such as rolling mill chassis, hydraulic press base, etc .; in railway vehicles used to create large force And bear the impact of parts such as bolsters, side frames, wheels and coupler and so on. ② casting low alloy steel. Cast steel containing manganese, chromium, copper and other alloying elements. The total amount of alloying elements is generally less than 5%, with greater impact toughness, and can be obtained by heat treatment better mechanical properties. Casting low alloy steel than carbon steel has excellent performance, can reduce the quality of parts, improve service life. ③ casting special steel. To meet the special needs of the refining of alloy steel, a wide variety, usually containing one or more of the high amount of alloying elements in order to obtain a special performance. For example, high manganese steel containing 11% ~ 14% manganese can be impact-resistant and wear-resistant, and is mainly used for wear-resistant parts of mining machinery and construction machinery. Various stainless steels containing chromium or chrome-nickel as the main alloying elements are used for corrosion- ℃ above the working conditions of high temperature parts, such as chemical valves, pumps, containers or large-capacity power station turbine casing. 2.1 stainless steel AISI304 (stainless steel aisi 304) before the introduction of stainless steel 304, it is necessary to make a comprehensive introduction to stainless steel.According to the composition can be divided into Cr series (400 series), Cr-Ni series (300 series), Cr-Mn-Ni (200 series) and precipitation hardening system (600 series). 2.3 Monel welding grade. Has good resistance to all common organic acids and salt water corrosion. Also has a high resistance to corrosion of most alkaline solution Heat resistance, temperature up to +400 degrees Celsius Mainly for the valve containing hydrogen fluoride medium, mainly for the transport of alkali, salt solution, food and many inorganic acids, especially sulfuric acid And hydrofluoric acid pipes and fittings. In addition, this type of valve can also be used for steam and sea water pipes. Has a tough, corrosion-resistant properties, widely used in chemical and other industrial LWR nuclear power plant important structural materials,