What is the term for immersing a metal part in a cooling medium?

The term for immersing a metal part in a cooling medium is known as quenching. This process is commonly used in metallurgy to rapidly cool heated metal, often following a heat treatment process. When a metal is heated to high temperatures, its structure changes, and quenching helps to lock in that structure by rapidly reducing the temperature.

This rapid cooling can significantly increase the hardness of the metal by transforming its internal structure, which is critical in processes like steelmaking or the production of various alloyed metals. Quenching can involve the use of water, oil, or air as the cooling medium, depending on the material and the desired properties after treatment.

In contrast, chilling refers to a more general term for lowering temperatures without the specific intent of achieving a structural change through rapid cooling. Hardening involves the overall process of making a metal hard, which includes steps beyond just quenching. Tempering, on the other hand, is a subsequent heat treatment process that follows quenching and typically involves reheating the metal to alleviate internal stresses and reduce brittleness.