Question

What is Freezing Range? Describe the significances of Freezing Range of a material in casting.

Answer 1

Freezing range:

Freezing range of a material is defined as a region between the liquidus temperature and solidus temperature. For an instance, the solidification of the material being cast occurs over a range of temperature, if a casting metal or an alloy does not have a specific melting point.

The material transforms from all liquid to all solid in this temperature range which is regarded as 'freezing range'.

The significance of Freezing range in casting:

1. Casting microstructure is severely affected by the freezing range, especially size and shape of the grain

2. The metals or alloys with short freezing range behave like the pure metal

3. The thermal gradient inside the casting and the cooling rate influences the effective freezing range

4. In the casting 'freezing range' decides the feeding distance which is usually calculated from short and long freezing alloy

5. The freezing range also influence the type of cavities formed in the casting therefore relevant freezing range should have been considered while developing the casting process

6. The development of directional solidification largely depends on the freezing range

7. It is difficult to achieve 'absolute soundness' in casting alloy with an extremely long freezing range under normal foundry conditions