It is will known that most of tool steels are quenched in oil to prevent cracking and distortion which appears when quenching in water due to non-uniform cooling caused by formation of insulating vapor blanket "film boiling".

but according to some literature 1 using 14% brine solution or 1% polymr solution eliminate this vapor blanket so we can expecting more uniform cooling compared to water quenching.

according to another literature 2 the probability of quench crack formation at first increases to the maximum value, and then decreases to zero. enter image description here

increasing cooling rate is possible by using strongly circulated brine quenching bath, and using brine eliminate vapor blanket which ensure uniform cooling.

so, can we excepting maximum hardening depth, minimal cracking and distortion and eliminated fire hazard by quenching high alloy tool steels by quenching in circulated brine instead of oil ?

  • $\begingroup$ Interesting point! I might guess that brine could result in scale formation, causing dimensioning or tolerance issues, or surface quality issues, and adding a cleaning step. Additionally, I imagine brine results in a more expensive to maintain recirculating system, since the pipes, bath, valves and pumps all need to be resistant to attack by hot brine. That doesn't mean it is infeasible, just some thoughts. $\endgroup$
    – wwarriner
    Dec 23, 2018 at 16:52
  • $\begingroup$ In another side agitated brine have quenching severity H=5 compared to oil which have only H=0.2-0.3 , which means hardening depth can increased 4 folds !! that so interesting. I think agitation can be provided by propeller-type agitators, so the corrosion issues will be minimized. $\endgroup$
    – anameen
    Dec 23, 2018 at 22:39
  • $\begingroup$ I have a feeling/vauge memory that boiling (without forming a film) gives you the most uniform results, as the temperaute of the quenching media is kept constant. You also have to consider the size of your part. Quenching a thick section at a fast rate, will give you a greater temperature difference between the core and the surface and you may get cracking from thermal stresses. Also there are more factors to consider with regards to how much you want to harden it, as you will lose ductilty while increasing hardness/strength and may find you have other issues. $\endgroup$
    – Kagekiba
    Jan 3, 2019 at 11:49
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    $\begingroup$ "high alloy tool steel" is too broad a category for aspecific answer. There are many 13 Cr type tool steels which are often air quenched . And HSS types that have retained austenite after a hot oil quench and reach full hardness only after tempering., etc. $\endgroup$ May 22, 2019 at 16:01

2 Answers 2


The quench all depends on the grade of steel that you are working with. Each steel is specially formulated to be used for a specific type of application. As others have stated you need to narrow down your material then investigate from that point. I don't know how anyone could answer this vague of a question with any accuracy.

The following list gives a brief description what each Grade of tool steel is:

  • A Series: Air Hardening, Cold Work Tool Steel, Air Quench Only
  • D Series: High Carbon, High Chromium, Cold Work Tool Steels, All D grade except D3 are quenched in either air or salt bath
  • L Series:Low Alloy Special Purpose Tool Steels, Use many different methods to quench including molten salt baths for some
  • P Series: Mold Steels, most use oil or brine to quench.
  • H Series: Hot Work Tool Steels, Molton Salt Bath, Atmosphere or Vacuum to quench.
  • T Series: Tungsten High-Speed Tool Steels, these are quenched in air, oil or molten salt.
  • M Series: Molybdenum High-Speed Tool Steels, these are quenched in air, oil or molten salt.

Most of these materials are tested by time and usage for decades and most heat treat companies have perfected the processes they use to ensure a good finished product.

Every type of steel will react different to one specific heat treatment. This why there are so many methods. Each method is used for a specific purpose. So to answer your question broadly, no brine cannot be used for all types of tool steel and still have a good product. Some will crack some will distort. each type of steel needs to be quenched so the steel can accurately cool down at a specific rate to get the desired end result for each type of steel.A brine bath will not do this for all tool steels.


I would say it really depends on the tool steel being used. I read that its recommended for water hardening steels to be quenched in a brine solution opposed to straight water, so perhaps there's some validity to the statement. Whether or not you can quench an oil hardening steel in water/brine, id imagine water quenching an O type steel would "shock" the part too much, promoting cracking of thin sections and brittleness. I also wouldn't try and quench an air hardening material in a liquid for the same reasons.

  • $\begingroup$ It also depends on the size and shape of the part. I cracked an O-1 ( Ketos ?) in warm oil from 1525 F ; small part , 2" long X 1/2" wide X 1/4 " . But when quenched from 1650 F ( greater shock) they did not crack because of retained austenite; double temper gave full hardness. $\endgroup$ Mar 8, 2020 at 1:41

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