In the production process of precision castings, cooling is a very important step, so how to do cooling well?

When the thin-walled part of the casting undergoes a solid phase change, the thick-walled part is still in a plastic state. If the specific volume of the new phase is greater than that of the old phase during the phase change, the thin-walled part will expand and the thick-walled part will be plastically stretched during the phase change. Therefore, only a small tensile stress is generated inside the casting, which gradually disappears over time. In this case, if the casting continues to cool, the thick-walled part will undergo a phase change and increase its volume. Because it is already in an elastic state, the thin-walled part will be elastically stretched by the inner layer to form a tensile stress. The thick-walled part is elastically compressed by the outer layer to form a compressive stress. In this case, the residual phase transformation stress and the residual thermal stress have opposite signs and can cancel each other out.

When the thin-walled part of the casting undergoes a solid phase change, the thick-walled part is already in an elastic state. If the new relative capacity is greater than the old relative capacity, the thick-walled part will be elastically stretched to form a tensile stress, while the thin-walled part will be elastically contracted to form a temporary compressive stress. At this time, the sign of the phase change stress is the same as the sign of the thermal stress, that is, the stress is superimposed. When the casting continues to cool until the thick wall part changes, the specific capacity increases and expands, so that the phase change stress formed in the previous part disappears.
Therefore, to do a good job of cooling precision castings, these details must be done well.