Quenching

The second step in the heat treatment process is called quenching. During this phase, the heated metal is cooled using either a gas or liquid medium. This allows the metal to be cooled at a faster rate than if it were left to cool naturally, thus retaining some of the physical alterations introduced by the initial heating stage. Once the metal has cooled, it should be tempered soon after quenching to relieve stresses in the metal due to the heating and quenching process.

Quenching too quickly can cause metals to crack, so providing the proper medium for the metal, as well as an adequate amount of the fluid, is important to obtain quality results. When quenching in liquid baths, it is important to use sufficient amounts of fluid in order to keep the liquid cool and effective. Approximately one gallon of oil or water per hour should be used for every pound of steel to be quenched. In general, the tool should be cooled in the quenching medium until it reaches 150 Fahrenheit, then allowed to cool to room temperature before placing it in the tempering oven.