Measurement and Recording of Quenching Intensity in Workshop Conditions Based on Temperature Gradients

Abstract

The cooling characteristics of a liquid quenchant are usually determined by a laboratory test using a small cylindrical probe with one thermocouple in its geometrical center. The reasons why the results of the laboratory tests do not represent the real quenching intensity of quenching workpieces in workshop conditions are described. Instead, a new Liščić/Petrofer probe with a larger mass, having three thermocouples, is used for measurement and recording real quenching intensity during industrial practice. The working principle of this probe is the measurement of dynamic of heat extraction, which is best represented by the change of temperature gradients. The temperature gradient method and the Liščić/Petrofer probe are described using an example of quenching in mineral oil at room temperature, without agitation. Calculation of the heat-transfer coefficient, as well as distinctive characteristics of the cooling curves recorded and heat-transfer data calculated when using the Liščić/Petrofer probe is explained. For impartial analysis and use of results obtained by using the new probe, six characteristic criteria from the relevant diagrams are used. Based on selected tests with the new probe, the influence of quenchant temperature and agitation rate on the quenching intensity is shown in numerical form for mineral oil and for water. A series of 26 tests has proved that: (1) the results obtained by the new probe and method have provided information that is not obtainable from small laboratory probes; (2) the new method is sufficiently sensitive to clearly differentiate the results when changes of some quenching parameters (bath temperature or agitation rate) occur; and (3) the Liščić/Petrofer probe can be used for different kinds of liquid quenchants at different quenching conditions typically encountered in industrial practice.

Investigation of Transient Nucleate Boiling Processes and Their Practical Use in Heat Treating Industry

“…Transient nucleate boiling processes are not enough investigated yet. In heat treating industry, including big companies like DOW, are widely used only cooling curves and cooling rate data obtained by testing Inconel 600 probe [12][13][14][15]. These data can be used only for comparison reason to see how much new liquid quenchant differs from already existing, for example oil, and keep in shops cooling intensity of coolants at the same level.…”

Research on Maximizing Critical and Reducing Initial Heat Flux Densities to Eliminate Any Film Boiling and Minimize Distortion During Quenching

“…At a certain point in time, nucleate boiling instantaneously replaces film boiling. When boiling ceases, convection heat transfer occurs [1,2]. At the third type of heat-transfer mode some localized areas of the probe surface are covered by a vapor blanket, whereas at the same time other areas experience nucleate boiling.…”

“…At the third type of heat-transfer mode some localized areas of the probe surface are covered by a vapor blanket, whereas at the same time other areas experience nucleate boiling. At fourth type of heat-transfer mode the film boiling and nucleate boiling periodically replace each other during quenching [1,2]. For each type of nucleate boiling process its own specific boundary condition are used to solve correctly direct and inverse heat conductivity problems.…”

“…It is shown that critical heat flux densities are the main parameters in the first step of evaluating cooling capacity the different kinds of quenchants. Depending on a ratio between initial and the first critical heat flux, it could be four possible heat-transfer modes on their hot metal surface [1,2]. At the first type of heat-transfer mode full film boiling and nucleate boiling are present simultaneously on the probe surface.…”

Parallelized Particle Swarm Optimization to Estimate the Heat Transfer Coefficients of Palm Oil, Canola Oil, Conventional, and Accelerated Petroleum Oil Quenchants

“…Liščić has successfully utilized a larger cylindrical probe with a 50-mm diameter by 200-mm length to effectively characterize the heat transfer properties of quenching media under actual workshop conditions [16]. The TCs are positioned so that only radial heat flow is measured, which is a prerequisite for a 1-D heat transfer calculation.…”