Cooling Rate is a measure of how quickly a casting is cooling down, in °C per minute, measured at each point in the casting as that point hits the Niyama Point on the cooling curve.
Cooling Rate can be an indication of material quality. Areas of the casting that cool rapidly generally have a more favorable grain structure, with less deposition of partially-soluble compounds at the grain boundaries. Therefore, these areas tend to have better material properties such as strength, elongation and hardness. Those areas of the casting that cool more slowly generally tend to have poorer material properties.
The plot above shows the areas of the casting with the lowest cooling rates.
It is possible to correlate cooling rates with material properties. One useful method for this plot is to find out what minimum cooling rate is required to achieve, for example, a given hardness. Then, plot cooling rate, using this minimum value as a boundary. Your plot, then, will only highlight those areas with cooling rates below your established minimum.