Heat Treating of Tool Steels – Quenching

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The quenching operation is extremely important in setting up the proper microstructure of the steel.  There are many mediums that can be used to quench steel such as oil, air, salt and steam to name a few.
The purpose of quenching is to transform austenite to martensite, or in simpler words, create a martensitic structure (larger volume) and stop the cooking process.  The goal of an optimal quench cycle is to achieve as much transformation as possible to martensite with no or very little austenite (retained austenite) left in the steel.
Note: if the material is still non-magnetic after quenching, the cooling rate was too slow (no transformation has taken place) and your datums have probably shrunk.
The material should be transferred to tempering immediately after tempering and while the steel is between 90f and 120f.  Allowing it to fully cool to room temperature could result in the build-up of an excessive amount of quench stresses, which could cause cracking.

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