The influence of quenchant composition on the cooling rate

Adequate selection of quenching media decreases the risk of tensile stresses, and also of cracking and workpiece distortion. High-performance quenching oils must have very high oxidation and thermal resistance and low sludge formation, must be non-staining and have a high flash point and acceptable heat-transfer characteristics. The quenching media contain a base oil and different types of additives according to application requirements. Mineral oils, synthetic and natural oils, used separately or in combination, may be used as base oils. Mineral base oils are widely used because of their advantages with respect to stability in comparison to natural oils, or lower prices in comparison to synthetic oils. There are numerous compounds available for use but, besides their functional properties, the environmental and safety requirements have to be considered in the selection of components. Based on that, barium additives must be replaced with less harmful compounds. Petroleum derivatives should be replaced with renewable base stocks that are biodegradable, which is a general trend in lubricant development. By changing the composition of quenching oils, base oils and additives, heat transfer characteristics are also changed. In this study, the results of investigation into physical and chemical properties and also cooling characteristics of new quenching oils with different compositions are presented. Cooling curves for different compositions have been evaluated according to the ISO 9950 standard.