Investment Casting

The investment casting process, also called the lost wax process, was first used during the period 4000-3000BC.

The investment comes from a less familiar definition of invest i.e. to cover completely, which refers to the coating of refractory material around wax pattern.

It is a precision casting process capable of producing castings of high accuracy and intricate details, good surface finish and most complex features for all metals and alloys.

Figure:- Steps involved in investment casting

Steps involved in the process of investment casting are

Step-1 The pattern is made by injecting semisolid or liquid wax or plastic into a metal die in the shape of the pattern

Step-2 Several patterns are attached to a sprue to form pattern tree.

Step-3 Then this pattern tree is dipped into a slurry of refractory material consists of Sodium silicate & Ceramic particles. Then silica sand is sprinkled on pattern tree this process is called stuccoing.

Step-4 Full mould is formed by covering the coated tree with sufficient refractory material to make it rigid.

Step-5 Mould is held in an inverted position and heated to melt the wax and permit it to drip out the cavity (Temperature 363-448K) for an hour.

Step-6 The mould is preheated to an even higher temperature to burn out the wax residue.

Step-7 Now the molten metal has been poured into the mould and it solidifies.

Step-8 Mould is broken away from the finished casting and parts are separated from the sprue.

Disadvantage

Many processing steps are required steps are required.

Relatively expensive process.

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