Currently, the most common probe used for cooling curve analysis of quenchants is a 12.5 mm diameter x 60 mm Inconel 600 cylindrical with a Type K thermocouple inserted to into the geometric center. The time-temperature cooling curve is obtained at this position and is the basis for national and international standards including ASTM D6200, D6482, D6549, ISO 9950 and others. However, there would be much greater insight into the quenching process if a better profile were available of the uniformity and wetting kinematics of the quenching process. An alternative probe design that was proposed earlier by Prof. H.M. Tensi and his colleagues that utilized a cylindrical 15 mm diameter x 45 mm flat-bottom, Inconel 600 probe with four (4) thermocouples. One thermocouple was inserted to the geometric center of the probe at 22.5 mm from the bottom. The remaining three (3) thermocouples were located at 2 mm below the surface of the probe at 2 mm from the bottom; at 15 mm from the bottom; and 30 mm from the bottom. This probe was used to characterize the usual centerline cooling curve properties as well as rewetting properties of two vegetable oils, palm oil and canola oil, and a commercial fast and conventional petroleum oil quenchant. The probe construction, use and quenching characterization results will be reviewed in this paper.
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