What type of defect usually develops due to rapid temperature changes in metal casting?

Shrinkage cracks are a type of defect that typically occurs in metal casting as a result of rapid temperature changes. During the casting process, as molten metal cools and solidifies, it undergoes contraction. If the metal cools too quickly due to sudden temperature changes, this can lead to uneven cooling rates throughout the material. The areas that cool more rapidly will contract at different rates compared to the areas that cool slowly, creating internal stresses.

When these stresses exceed the material's strength, they can lead to cracks forming in the casting, particularly in the areas where the material has solidified but is still under stress. These cracks are particularly problematic as they can compromise the structural integrity of the finished product.

In contrast, while weld porosity relates to a defect formed when gas bubbles are trapped in the weld area, laps indicate a surface defect where metal fails to properly fuse together, and core shifts involve misalignment of the core during the casting process, these issues are not primarily influenced by rapid temperature changes in the same way that shrinkage cracks are. This emphasizes the significance of temperature control in metal casting to prevent such defects.