Casting is one of the most important and common methods of manufacturing workpieces and machine parts. Casting receive workpieces of different configurations, the size and weight of various metals I alloys — cast iron, steel, aluminum, copper, magnesium, etc. alloys. Casting — it the most simple and cheap, and sometimes the only way of obtaining products.

The casting process is, that molten metal is poured into a prepared mold, the cavity which in size and configuration conforms to the shape and size of future harvesting. After cooling and solidification of the billet (or detail) extracted form. The products of the foundry is called casting.

Molds can be a one-off (for the manufacture of a single casting) and permanent (repeated use).

To obtain high-quality castings casting alloys must have certain properties: good liquid fluidity, low shrinkage, small liquidation (the heterogeneity of the chemical composition of the alloy structure and on the thickness of the casting).

Depending on, in what form (permanent or one-time) filled with metal and how is the fill, there go the other molding. Currently up to 60% iron and steel castings obtained by casting in. sand forms. To produce castings of high dimensional accuracy, good surface quality and best patterns of metal use special methods of casting (mold, under pressure, centrifugal method, investment casting, etc.).

The process produce castings of single sand-clay forms includes a number of long-running operations, associated with the preparation of the molding and
core mixtures, manufacture of pattern equipment, rods, drying them, moulding etc. Despite the fact, currently time-consuming operations; this method is mechanized and automated, it still remains a relatively low-productivity and labour-intensive method of casting.

So casting in sand forms used mainly, in single and pilot production, and in those cases, when the product is in other ways impossible or difficult. Enterprises, producing castings in bulk quantity, created automatic and semi-automatic production lines. The disadvantage of casting in sand-clay molds is also low dimensional accuracy and poor surface quality of castings, what causes the necessity for subsequent machining. And this leads to loss of metal in the chip and extends
technological cycle of manufacturing the product.

 

 

Gravity die casting one of the most common ways to produce castings in permanent metal forms. The moulds are made of cast iron, steel, aluminum. By construction, the molds are fixed and detachable. The most widely split molds, consisting of two parts with a horizontal or a vertical parting plane. To increase productivity when molding the mold used in multi-machine carousel, at a certain position which is consistently one of the operations.

Benefits of shell mold casting compared to casting in sandy-argillaceous forms are: higher dimensional accuracy and surface quality of castings; the best mechanical properties, due to high cooling rate of the casting and more subtle patterns; better performance.

Injection molding a high — performance method of obtaining castings of high dimensional accuracy of non-ferrous alloys (aluminum, zinc, copper, magnesium).

The method consists in filling a metal mold with molten metal under pressure of the piston. Are casting machines for casting under pressure — semi-automatic. Used piston machine with hot and cold (horizontal or vertical) the pressing chamber.

Piston machine with a hot pressing chamber is used for making small castings of magnesium I zinc alloys. Machines with a cold pressing chamber is used mainly for casting of body parts from aluminium and copper alloys.

Centrifugal casting — productive method of manufacturing castings, having the surface of bodies of rotation, with Central hole — pipes, bushings, etc., as well as parts of castings by. The method consists in filling the molten metal rotating shape. Under the action of centrifugal force the liquid metal is discarded to the walls of the mold and hardens.

The result is a compact structure of casting without shrinkage cavities. Non-metallic inclusions are collected on the inner side of the casting and is removed during further machining.

Iron castings, steel and non-ferrous metals and alloys produced centrifugal machines centrifugal casting with a horizontal and a vertical axis of rotation. Shaped castings of small height are getting on machines with vertical axis of rotation. On machines with a horizontal axis of rotation are made of cast iron and steel pipes, sleeves and other parts with hole.

Advantages of centrifugal casting are: high performance, efficiency (is not required costs for the preparation of the molding mixture, manufacturing of rods, etc.) and the quality of the castings.

The casting is used to produce castings of high dimensional accuracy and surface quality from any casting alloys. With its help it is possible to obtain products of complex configuration with a thin section
mi. However, the process of this casting method has a high complexity and high cost of the materials used.

Technological process of investment casting involves the following operations: manufacturer model — model casting of free-cutting alloy (aluminum); the manufacture of molds for metal standard, in which the model is compressed from easily fusible materials (paraffin, stearin, polystyrene, wax, etc); the manufacture of the shell by repeatedly applying the model of refractory composition — ceramic slurry with quartz sand with subsequent drying
(treatment with hot air)at a temperature of 150-200°C to remove fusible models; calcining the obtained mold in a furnace at 800-850 “With; die casting. Cleaning the casting residue from the ceramic coating produced by leaching with subsequent rinsing in hot water. The high cost of castings, received this
method, allows you to use this method only for the manufacture of particularly complex configuration of hard and refractory materials in bulk or
large-scale production.

Shell casting is used in mass and large-scale manufacture for the manufacture of shaped castings made of steel, iron, aluminum and copper alloys. The essence of the method lies in the fact, what on the surface is preheated to 200 °C metal model, attached to the molding plate, fill the moldable mixture (quartz sand and 6 — 7% bakelite is a synthetic resin), then, all together, annealed at t = 300 °C for 1-2 min. The resin melts and hardens irreversibly, forming a sand-resin shell thickness 5-8 mm. The shell-mold collect, fasten and hammer liquid metal. These moulds are made for single, two and four-way machines with semi-automatic or automatic control. The shell molding provides high dimensional accuracy of castings, minor surface roughness, high quality metal structure. To select the casting method when receiving the workpieces it is necessary to consider all the factors, affecting technical and economic indices of the process.