Oil Quench Hardening

ThermTech is proud to offer oil quench hardening for steel castings. The process is typically employed on castings made from many low to medium- alloy steel grades with carbon in excess of .40%, or those with higher amounts of total alloy content.


All oil quench hardening processes are ran out of internal quench batch-type furnaces with fully automated quench transfer for optimum process and lot control.  Our largest furnace capable of performing oil hardening has internal working dimensions of 36”W x 72”L x 42”H.  All ThermTech furnaces are certified to AMS 2750, ensuring optimal temperature uniformity during the hardening process.


The process begins by 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 commensurate with the part cross section, and then quenched in oil usually between 120-160F. Oil hardening is always performed under a controlled protective atmosphere in the austenitizing furnace, including during the quench transfer.

Once fully heated or “soaked” the load is quenched in a strongly agitated oil tank to produce a fully hardened martensitic microstructure commensurate with the steel grade and section thickness of the casting. ThermTech uses industry-leading quench oil technology to provide the fastest possible quench rate in oil, translating to superior casting properties and performance.

From this fully hardened state, the parts are tempered down to the specified hardness range to improve ductility while reducing overall strength.  


In cases where parts are especially distortion sensitive but still require the superior depth of hardness provided by oil quenching, ThermTech will customize an oil quench process to best minimize or eliminate distortion problems while still achieving the required material properties. In cases where distortion is a primary concern, please consider other process our other available methods such as marquenching or austempering.

ThermTech offers oil hardening processes for castings made from a wide variety of steel grades. Some of the most common oil quenching processes we perform are:

  • Oil Quenching 4140 Steel

  • Oil Quenching 4340 Steel

  • Oil Quenching 4150 Steel

  • Oil Quenching 5160 Steel

Please be aware that lower final hardness ranges that require tempering temperatures above 900°F may result in temper oxide formation on most steel grades. ThermTech offers a variety of blasting services for castings to remove any oxide formation and improve the surface finish. For bright finish requirements, ThermTech is also proud to offer vacuum hardening of castings using either gas or oil quench hardening.

Contact a sales representative today to learn more about the benefits of our oil hardening process!