Vegetable and animal oils as a class of fluids have been used for hundreds of years, if not longer, as quenchants for hardening steel. However, when petroleum oils became available in the late 1800s and early 1900s, the use of these fluids as quenchants, in addition to their use in other industrial oil applications quickly diminished. This was primarily, but not exclusively, due to their generally very poor thermal-oxidative instability and the difficulty for formulating fluid analogs with varying viscosity properties. Interest in the use of renewable fluids, such as vegetable oils, has increased dramatically in recent years as alternatives to the use of relatively nonbiodegradable and toxic petroleum oils. However, the relatively poor thermal-oxidative stability has continued to be a significant reason for their general non-acceptance in the marketplace. Soybean oil is one of the most highly produced vegetable oils in Brazil. Currently, there are commercially produced epoxidized versions of soybean oil which are available. The objective of this paper is to discuss recently obtained results showing the dramatic improvement in thermal-oxidative stability of epoxidized soybean oils and to discuss their potential use and heat transfer properties as viable alternatives to petroleum oils for hardening steel.

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