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.
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.
