A lot of people say "cooling" when referring to the solidification part of sand casting. However, there are actually two cooling stages separated by the actual solidification stage. The first cooling is the liquid cooling to the freezing temperature, then after the part has fully solidified/frozen, the part is still hot and continues to cool until it is at room temperature. This is illustrated in the graph below.
Solidification takes time, the metal inside of the mold cavity does not solidify all at once, as we can see in the video below. Solidification starts as soon as the metal is poured, the walls of the mold chill the metal, solidifying the outside of the part, then the metal crystallizes inwards until it is a solid piece of metal.
Solidification takes time, the metal inside of the mold cavity does not solidify all at once, as we can see in the video below. Solidification starts as soon as the metal is poured, the walls of the mold chill the metal, solidifying the outside of the part, then the metal crystallizes inwards until it is a solid piece of metal.
The metals used in sand casting also affect how solidification occurs. Pure metals have a melting point, which is equal to their freezing point, and solidification happens at that constant temperature. Alloys don't freeze at a particular temperature, but rather over a temperature range.