Quenching

In <a href="/facts/Materials_science/N5HrXRYW">materials science</a>, quenching is the rapid <a href="/facts/Conduction_(heat)/5vRktgcS">cooling</a> of a workpiece in water, gas, oil, polymer, air, or other fluids to obtain certain <a href="/facts/Material_properties/Cg2LVoQe">material properties</a>. A type of <a href="/facts/Heat_treating/xR2tVyTU">heat treating</a>, quenching prevents undesired low-temperature processes, such as <a href="/facts/Phase_(matter)/NkHXDdN3">phase</a> transformations, from occurring. It does this by reducing the <a href="/facts/Window_of_opportunity/fSx8z7Ik">window of time</a> during which these undesired reactions are both thermodynamically favorable and kinetically accessible; for instance, quenching can reduce the crystal grain size of both metallic and plastic materials, increasing their hardness.
In <a href="/facts/Metallurgy/1SANyxX4">metallurgy</a>, quenching is most commonly used to <a href="/facts/Hardening_(metallurgy)/Cepsv5RL">harden</a> <a href="/facts/Steel/aN6qWo4H">steel</a> by inducing a <a href="/facts/Martensite/xpSt9mna">martensite</a> transformation, where the steel must be rapidly cooled through its <a href="/facts/Eutectoid/UFbecnqo">eutectoid</a> point, the temperature at which <a href="/facts/Austenite/Fzp52xYc">austenite</a> becomes unstable. Rapid cooling prevents the formation of <a href="/facts/Cementite/BvMdo027">cementite</a> structure, instead forcibly dissolving carbon atoms in the ferrite lattice. In steel alloyed with metals such as <a href="/facts/Nickel/KwMCHYRP">nickel</a> and <a href="/facts/Manganese/j9ELd1TL">manganese</a>, the eutectoid temperature becomes much lower, but the kinetic barriers to phase transformation remain the same. This allows quenching to start at a lower temperature, making the process much easier. <a href="/facts/High-speed_steel/6m6SCmof">High-speed steel</a> also has added <a href="/facts/Tungsten/WYwbNDYX">tungsten</a>, which serves to raise kinetic barriers, which, among other effects, gives material properties (hardness and abrasion resistance) as though the workpiece had been cooled more rapidly than it really has. Even cooling such alloys slowly in the air has most of the desired effects of quenching; high-speed steel weakens much less from heat cycling due to high-speed cutting.
Extremely rapid cooling can prevent the formation of all crystal structures, resulting in <a href="/facts/Amorphous_metal/5YrugEP4">amorphous metal</a> or "metallic glass".

Quenching open-in-new

Quenching