Criteria for evaluating the cooling capacity of quenching media

Abstract

Numerous criteria have been suggested for evaluating the cooling capacity of quenching media. Although the cooling capacity of a medium can hardly be evaluated by a single number, such data can be helpful in the initial stage of choosing the medium for quenching a specific part. Various criteria for evaluating the cooling capacity of polymer quenching media have been analyzed within the developed international standard based on ISO 9950 (for industrial quenchants). Those that can be calculated from results of tests of a medium by means ofa Wolfson gauge, recommended by the ISO 9950 standard, have been chosen. The aim of the present work consists in determining the correlation between the criteria suggested by various researchers for various domestic and foreign quenching |iquids on a polymer base.Over ten criteria for evaluating the cooling capacity of quenching media are described in [1]. Analyzing these criteria, we established that many of them cannot be obtained for this or that reason from results of the test envisaged by ISO 9950 [2] (cooling a Wolfson gauge, i.e., a cylinder of Inconel-600 alloy with a therrnocouple in the geometric center, in the studied medium). Far from all of the criteria can be used as a universal means for describing all quenching media or at least a large number of them.For example, the V-criterion suggested by the author of [3] is recommended only for evaluating the quenching capacity of oils. Moreover, in order to calculate Vthe characteristic temperatures must be determined graphically, which is quite subjective. Therefore, it is impossible to treat V as a unique characteristic of the cooling capacity.The same defects are inherent in the "hardening power" (liP) characteristic of a cooling medium suggested in [4].In the evluating of the uniformity of quenching by the method of [5] and calculating the quenching factor (QFA) suggested in [6] results of Wolfson gauge tests envisaged by ISO 9950 are not used.The method of Liscic [7] is based on the use of results of quenchant tests by means of a special gauge of the gradient type. This requires quenching of a specimen of the studied steel, which makes the method rather laborious. In addition, it is not connected with the test envisaged by ISO 9950.The authors of [8] have developed the QTA method, which makes it possible to predict the hardness after quenching by the heat flow from the cooled part. But this method is recommended for quenching a specific steel and does not envisage the use of results of a Wolfson gauge measurement.The author of [9] has derived a number of regression relationships for several quenching media that relate the maximum cooling rate and the cooling rate at 300~ to the concentration of the polymer in the solution and the rate of flow of the liquid. It is obvious that similar relationships can be obtained for other media but this requires much experimental work.The other criteria described in [1] have similar disadvantages.From the standpoint of the applicability of the parameters envisaged by ISO 9950 to calcu...

Comparison of Industrial Quenching Oils

“…Area under the cooling curve at certain temperatures (the amount of heat removed in the nose region of the Continuous cooling transformation curve). This is based on [4,5].…”