Where are shrinkage cracks typically found in a casting?

Shrinkage cracks in a casting are primarily found at abrupt changes in thickness. This is because as the molten metal cools and solidifies, it contracts. Areas of varying thickness cool at different rates, leading to unequal contraction. This differential cooling can create high-stress zones, especially at points where the thickness suddenly changes. These stresses can exceed the tensile strength of the material, resulting in shrinkage cracks forming at these locations.

Other potential locations for cracks, such as edges or weld areas, are influenced by different factors like thermal stress, but they are not directly correlated with the fundamental behavior of metal contraction during the solidification process as seen with abrupt changes in thickness. Understanding the mechanics of solidification helps in identifying and mitigating potential defects in casting design.