Oil Quench Hardening

Oil quench hardening is a common process for hardening tool steels. The process is ideal for achieving the required strength and hardness properties on many alloys with a reduced risk of distortion compared to water or polymer quench processes.


ThermTech runs most oil hardening processes in our batch-type internal quench atmosphere furnaces, which are ideal for process and lot control. All furnaces are certified to meet the temperature uniformity and accuracy requirements of AMS 2750, and our largest furnace capable of performing oil quench hardening has internal working dimensions of 36”W x 72”L x 42”H and can handle weights of up to 7000 pounds.  Alternatively, we also offer vacuum oil hardening, which can result in a bright surface finish after hardening (depending on the tempering temperature employed).


The process of oil quench hardening for tool steel and dies is performed by first fully austenitizing the steel in the temperature range of 1500°F – 1650°F depending on the steel grade. It is held at this temperature for a time determined by the part’s cross-section.

The entire austenitizing process is carried out either under a protective carbon-controlled atmosphere or under vacuum; this protects the surface quality of the parts at high temperature.  Once soaked at the austenitizing temperature for the appropriate amount of time, the load is quenched in agitated oil to produce a fully hardened martensitic microstructure. From this point, the parts are tempered down to the specified hardness range to improve toughness while reducing overall strength.
In cases where parts are especially distortion sensitive, ThermTech will customize the oil quench process to minimize or eliminate these problems completely while still achieving the required material properties.  If distortion is a major concern, please have a look at our marquench hardening or  austempering services.


Please be aware that lower final hardness ranges that require tempering above 900°F will result in temper oxide formation on most steel grades. Because of this, ThermTech offers blasting services suitable for removing that oxide formation from tool steels as well as improving the surface finish of such products.
ThermTech offers oil hardening processes for several grades of tool steel. The most common tool steel grades that are processed using oil quenching include:

  • Oil hardening S-5 steel
  • Oil hardening 52100 steel
  • Oil hardening O-1 steel
  • Oil hardening O-6 steel

For heavier cross-section parts or for components made from lower alloy grades, we recommend our polymer quench process or our water quench hardening process, and be sure to ask about salt quenching for distortion sensitive parts.
Please be aware that in cases where tool steel components are particularly sensitive to distortion either due to part geometry or specification, ThermTech offers a variety of straightening services to mitigate distortion after hardening.

For large volumes of tool and/or die products, or to learn more about how our oil hardening process can benefit them please contact our sales staff for a formal quote today!