Magnetic Particle Inspection Level 1 Practice Exam

What type of defect results from the cooling of metal during casting?

1. Withdrawal marks

2. Clinker

3. Hot tears

4. Surface indentations

The correct answer is: Hot tears

Hot tears are a type of defect that occurs during the cooling phase of metal casting, and they result from the shrinkage of metal as it solidifies. As molten metal is poured into a mold and begins to cool, it goes through a transformation from liquid to solid, and this process can create internal stresses. If the metal contracts in a way that causes it to become constrained or unable to continue to shrink freely, cracks may form. These cracks are referred to as hot tears and typically appear on the surface of the casting. The characteristic nature of these defects is important to recognize, as they can compromise the structural integrity of the finished product. Unlike surface indentations, withdrawal marks, or clinker, which stem from other issues related to mold design, pouring practices, or substandard materials, hot tears are specifically linked to the thermal stresses encountered during the cooling phase. Understanding this defect helps inspectors and engineers find ways to mitigate its occurrence, such as optimizing cooling rates and mold designs.