Remember the only important criteria for a quench are:
1) Safety: Flammability, toxicity etc
2) The speed of quench. Faster is harder unless it is too fast then it may break the steel
3) Uniformity of quench. If the steel is cooled non-uniformly it may fracture the part. Circulate the quench or move the steel around in the quench liquid to assist in uniformity of quench.
Many factors determine these criteria. As an example a thick gear only will be a slower quench than ATF fluid. This is due to ATF being less viscous and will move around more readily in the quench process, exposing the steel to fresh unheated oil than if the quenchant were heavy gear oil.
Remember: Brine is faster, water but more uniform. Items that fracture in a water quench may survive a brine quench.
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