The casting parts made by steel are steel castings. Steel castings have similar performance with the iron castings, but have good strength than cast iron.
There are three types of steel castings, main divided into carbon steel castings, low alloy steel castings and special alloy steel castings.
1. carbon steel casting
The main element of carbon steel is carbon and has few other elements. Less than 0.2% carbon for casting low carbon steel, carbon 0.2% to 0.5% for the casting of carbon steel, carbon 0.5% for the casting of high carbon steel. With the increase of carbon content, increasing the strength of cast steel, and the hardness increased. Carbon cast steel has good physical properties such as high strength, ductility and toughness, and has low cost. So carbon steel castings have wide uses in the heavy machinery under heavy load, such as the rolling mill frame, hydraulic press base, etc. In the railway vehicle, carbon steel castings are used to produce large force and absorb the shocks of the parts such as bolster, side frame, wheels and coupler and so on.
2. low-alloy steel casting
Low alloy steel casting has manganese, chromium, copper and other alloying elements. Alloying elements are generally less than 5% of the total. Low alloy steel castings have great toughness, and have better mechanical properties after suitable heat treatment. Low alloy steel castings have better performance in application, and can improve service lifetime.
3. special alloy steel casting
The special alloy cast steel is refining to meet the special needs, usually containing one or more of the high amount of alloying elements in order to obtain a particular performance. For example, manganese 11% - 14% has better impact and wear ability, used for mining machinery and engineering machinery wear parts. Chrome or chrome-nickel stainless steel has good anti-corrosion or performance in the working condition upper than 650 centigrade, can been used for chemical valve, pump, container or high-capacity power station turbine housing and so on.
The heat treatment of steel castings
All steel castings need heat treatment after production. It is because steel castings after casting process normally have air pores, cracks, shrinkage, coarse grains, uneven organization and residual stress and other casting defects. So, the strength of steel castings, in particular the ductility and toughness, will be greatly reduced. For grain refinement, even within the organization and to eliminate stress, cast steel must be normalized or annealed. After normalizing the steel, its mechanical properties will be highly improved.
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