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Advantages of casting process

Low cost: Casting is usually found to be the cheapest method of metal shaping.

Dimensional accuracy: Castings can be made to fairly close dimensional tolerances by choosing the

proper type of molding and casting process. Tolerances as close as 0.1 mm can be achieved depending

on the cast metal, the casting process, and the shape and size of the casting. The surface finish can also

be controlled and may vary from 5 microns to 50 microns.

Versatility in production: metal casting is adaptable to all types of production. It is suitable for jobbing

work as for mass production. For example, a large number of parts require for the automotive industry,

agricultural implements, home appliances, construction, and transportation are all produced by casting

process.

Metallurgical advantages

Fibrous structure: Wrought metals have a fibrous structure, mainly due to a stringer-like arrangement ofthe inclusions of non-metallic impurities. In cast metals, the inclusions are more or less randomly

distributed during the solidification process. When wrought metals are worked, the inclusions are strung

out in the direction of working, and so the fibrous nature results in marked directional properties. Cast

alloys do not usually exhibit any fibering or directionality of properties except under unfavorable

conditions of solidification.

Grain size: Although mechanical working of wrought metals causes breaking up of coarse grain, and

promotes fine grain size, many castings have grain sizes not very different from those of the former.

Most non-ferrous alloys retain the grain size attained during freezing of the casting. Subsequent heat

treatment of castings can also help in improving the grain size.

Density: The density of cast alloys is usually identical to that of wrought alloys of the same chemical

composition and heat treatment, when both are fully sound.

Today, it is becoming increasingly difficult to cope with the growing demand for various types of castings

as required for automobiles, scooters, tractors, earth-moving machinery, and railways. Sophisticated

castings needed for aeronautics, atomic energy, defence, and space research pose yet another challenge

in terms of stringent requirements of quality. The problem is more or less similar in all developing

countries.

To achieve self-reliance, the foundry industry has to accept the challenge and quickly learn the

new technology, methods and know how already available in is use elsewhere. It is also possible,

through a sharper awareness and greater appreciation of the need for improved materials and more

efficient methods, to increase production with the existing level of inputs in terms of equipment and

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manpower. Adequate means of quality control at all levels of production, steps to keep the wastage of

materials and unproductive efforts at the minimum through proper organization and coordination, and

the use of enlightened human relations can go a long way in enhancing production and productivity in

foundries.

The casting process is basically one of introducing molten metal into a cavity in the mold,

previously shaped as desired, and allowing it to solidify. The mold is usually prepared in sand; an object

similar in shape and size to the casting required, which is called a pattern, embedded in the sand. The

pattern is thus an exact facsimile of the articles to be cast.