Quenching is the rapid cooling of a metal part following heat treatment. The purpose is to lock in the hardened microstructure created by heating and prevent it from reverting as the part cools.<\/p>\n\n\n\n
When steel is heated to a specific temperature, its internal grain structure transforms into a phase called austenite. Quenching that part rapidly converts austenite into a harder phase. For most steels, that phase is martensite.<\/p>\n\n\n\n
But quenching is a balancing act. Cool too slowly and the part won’t reach the desired hardness. Cool too quickly and the rapid contraction of the metal can cause distortion or cracking, particularly in thicker parts or higher-carbon steels.<\/p>\n\n\n\n
After quenching, most parts go through tempering, a secondary heat process that reduces the brittleness martensitic steel tends to develop. Quenching and tempering together form one of the most common processing sequences in commercial heat treating.<\/p>\n\n\n\n