Precision casting process molding process
1. Gravity casting: sand casting, hard mold casting.The molten metal is poured into the cavity by the metal's own gravity.
2. Pressure casting: low pressure casting, high pressure casting.The molten metal is instantaneously pressed into the casting cavity by additional pressure.
The casting process usually includes
(1) casting (make liquid metal into a solid casting container) preparation, casting according to the material can be divided into sand mold, metal mold, ceramic mold, clay mold, graphite mold, according to the number of times can be divided into one-time type, semi-permanent type and permanent type, casting preparation is the main factor affecting the quality of the casting;
(2) melting and pouring of casting metals, casting metals (casting alloys) mainly have all kinds of cast iron, cast steel and cast non-ferrous metals and alloys;
(3) casting treatment and inspection, casting treatment including removal of core and casting surface foreign bodies, the removal of the riser, shovel grinding burr and seam and other convex objects, as well as heat treatment, plastic, rust prevention and rough processing.
The casting process can be divided into three basic parts: metal preparation, mold preparation and casting treatment.Casting metal refers to the metal material used in casting production for casting. It is an alloy with a metal element as the main component and other metal or non-metallic elements added. It is traditionally called casting alloy and mainly consists of cast iron, cast steel and cast non-ferrous alloy.
Metal smelting involves not only pure melting, but also the process of smelting, so that the metal poured into the mold meets the expected requirements in terms of temperature, chemical composition and purity.For this reason, in the melting process for the purpose of quality control of all kinds of inspection and testing, liquid metal can be allowed to pour after reaching the specified indicators.Sometimes, in order to meet the higher requirements, the liquid metal after the furnace outside the treatment, such as desulfurization, vacuum degassing, furnace refining, inoculation or metamorphic treatment.Common equipment for smelting metals are cupola, arc furnace, induction furnace, resistance furnace, furnace and so on.
Advantages: 1. It can produce parts with complex shapes, especially the blank with complex inner cavity; 2.
2, wide adaptability, industrial commonly used metal materials can be cast, a few grams to several hundred tons;
3. Wide source of raw materials and low price, such as scrap steel, scrap parts and chips;
4, the shape and size of the casting is very close to the parts, reducing the amount of cutting, which is non-cutting processing;
5, widely used, agricultural machinery in 40% to 70%, 70% to 80% of the weight of machine tools are castings.
Disadvantages: 1. Mechanical properties are not as good as forgings, such as large structure and many defects;
2, sand casting, single, small batch production, labor intensity of workers;
3, casting quality is not stable, the process is many, the influence factors are complex, easy to produce many defects.
Casting defects have an important influence on casting quality. Therefore, in order to select casting alloy and casting method, we should start from casting quality, and combine the formation and prevention of main casting defects.