Question 5
(a) Explain the following qualities of moulding sand as used in sand casting:
- compatibility;
- permeability;
- refractoriness.
(b) List three mechanical properties of ferrous metals.
(c) (i) What is coolant?
(ii) State two functions of coolant.
Observation
Most of the candidates could not explain the listed qualities of moulding sand. Parts (b) and (c) were well attempted by the candidates. The expected responses are as given below:
- Compatibility
It is the property of moulding sand that makes it adhere together without breaking during moulding.
- Permeability
It is a property of sand which allows gases to pass through the sand during pouring of the molten metal.
- Refractoriness
It is the property which enables sand to resist high temperature of the molten metal without breakdown or fusing.