10.10: Summary

There are 4 main ways of casting metals; sand casting, die casting, continuous casting and investment casting. Each has advantages and disadvantages, and is suited for producing different components or using different materials.
The Biot number predicts how a casting will solidify, and is equal to

\[\frac{h}{K / L}\]
where: h = heat transfer coefficient
L = length of the casting
K = thermal conductivity

Commonly 3 zones form as the casting solidifies;

• Chill zone – small crystals form on mould wall.
• Columnar zone – larger grains growing in optimum crystallographic orientations.
• Equiaxed zone – small grains that solidified early but detached and moved back into the liquid.

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