Quenching performance of synthetic phosphate ester oils as determined by cooling curve analysis

Phosphate ester quench oils have been developed as an improvement over synthetic hydrocarbon or mineral oil fluids. Phosphate ester fluids are inherently fire resistant, and can be used to improve workplace safety as an alternative to aqueous quenchants. Phosphate esters are reactive with ferrous surfaces, and can be used to deposit protective films that significantly reduce wear, and provide corrosion inhibition. This paper reviews the cooling curve analysis data generated according to ISO 9950 on a series of phosphate ester fluids. The data indicates that phosphate esters will provide significantly faster cooling rates that mineral oils of similar viscosity. The speed and shape of the cooling curve is not directly related to fluid viscosity, but appears to be dependent on a combination of volatility, oxidative stability, viscosity, and viscosity index.