Quenchant Characterization using the TENSI Probe

Currently, the most common probe used for cooling curve analysis of quenchants is a 12.5 mm dia 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, 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 for international standardization by the IFHTSE (International Federation for Heat Treatment and Surface Engineering) Quenching & Cooling Committee. This 15 mm dia x 45 mm cylindrical Inconel 600 probe four (4) 1.5 mm diameter holes drilled along the Z-axis. The thermocouple tips were flat and were tightly pressed to the bottom of the holes. The locations of the tips of the thermocouples are shown in Figure 1. One 1.5 mm diameter Type K thermocouple was inserted to the center of the probe. The other three holes were located 2 mm below the surface of the probe but at different distances from the bottom. Thermocouple number 1 was located 2 mm from the bottom and 2 mm from the cylindrical surface. Thermocouple number 2 was located 15 mm from the bottom and 2 mm from the cylindrical surface. Thermocouple number 3 was located 30 mm from the bottom and 2 mm from the cylindrical surface. The thermocouple at the center was located 22.5 mm from the bottom.