Conference Papers

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Subject: search.filters.subject.Quench severity

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    Heat transfer during quenching and assessment of quench severity - A review
    (ASTM International, 2010) Prabhu, K.N.; Fernandes, P.
    In the heat treatment of steel, quenching is done to prevent ferrite or pearlite formation and allows formation of bainite and martensite. For a particular grade of steel, the effectiveness of quenching depends on the cooling characteristics of the quenching medium. The cooling rate is not a constant throughout the quenching process; instead it varies depending upon the various stages that occur during the quenching process. Knowledge of heat transfer during various stages of quenching and kinetics of wetting of the quench medium is fundamental to the understanding of the relationship between material, quench medium, microstructure, and properties. In this paper the characteristics of various quench media, the effect of process parameters on quenching, mechanisms of thermal transport, methods of assessing severity of quenching, and techniques of estimation of heat transfer coefficients are reviewed. An attempt is also made to highlight the importance of wetting kinetics of liquid media on quenching. Copyright © 2009 by ASTM International.
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    Effect of quench probe material and section size on cooling severity
    (2012) Ramesh, G.; Prabhu, K.N.
    In the present work simulation of heat transfer during quenching was carried out using finite difference heat transfer based SolidCast software. Simulation experiments were aimed to assess the effect of boundary heat transfer coefficient, quench probe material and its size on the cooling curve of the quench probe at geometric centre. Simulation results show that all these parameters had a significant effect on the simulated cooling curve of the probe. For a material, there is a critical diameter above which increase in cooling rate at the centre of the probe is negligible and this critical diameter depends on the thermal conductivity of the material used for quenching. A quenching system with a D/h ratio value of greater 0.000075m3K/W has no significant effect on the cooling rate at the centre of the probe. A simple quantitative model which correlates average cooling rate, probe material, section size and cooling severity of quench media was proposed. The results of the model is independent of characteristics of quench probe used in assessment of cooling severity and could be used effectively for selection of quenchants during heat treatment. Copyright © 2012 ASM International® All rights reserved.
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    Wetting kinetics and cooling performance of PAG polymer quenchants
    (Trans Tech Publications Ltd ttp@transtec.ch, 2015) Pai, A.; Nayak, U.; Pranesh Rao, K.M.; Prabhu, K.
    The present research work is aimed at the estimation of quench severity Polyalkylene Glycol (PAG) polymer quenchants having varying concentrations. An Inconel600 probe instrumented with thermocouples was used for this purpose. The thermal history at various locations in the probe was used as an input to the inverse heat conduction model. The inverse analysis yields spatially dependent heat flux transients. The quench severity was assessed using the Grossmann technique. The wetting kinematics of quenching was studied by cooling curve analysis. The severity of quenching as measured by the Grossmann’s technique was found to be higher for polymer quenchants. However, the heat flux transients estimated by the inverse technique and rewetting times measured form the cooling curve analysis suggested comparable and uniform heat transfer with polymer quenchants compared to water quenchants. © (2015) Trans Tech Publications, Switzerland.