Chills

Chills are used to improve the directional solidification with faster heat conduction by metallic chills; solidification is initiated and accelerated at desired locations. The thinner section of a casting solidifies earlier in comparison to thicker section, which results in distortion, internal stress set up, crack etc. Chills increase the solidification rate in thicker section and equal the solidification rate in thinner section. There are of two types of chills: internal and external chills.

Internal Chills: They are located within the mould cavity and form a part of the casting. They are usually in the form of thin wires and are hung in the mould by inserting their one end into the sand.

External Chills: They are embedded in the mould such that they are flush with the mould walls and form a part of it. Their exposed surface is given the desired shape so that it confirms to the shape of mould wall and hence of the casting.

Chills are metallic objects of high heat capacity and high thermal conductivity which are placed in the mould/mould cavity to increase the cooling rate of castings or to promote directional solidification. These are cleaned of scale/oxide to avoid any reaction with hot metal.