Conference Papers
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/28506
Browse
3 results
Search Results
Item Severity of quenching and kinetics of wetting of nanofluids and vegetable oils(ASTM International, 2010) Jagannath, V.; Prabhu, K.N.In the present work, the suitability of vegetable oil blends with mineral oil and alumina based nanofluids as quench media for industrial heat treatment was investigated. Sunflower oil, palm oil, and mineral oil were used for preparing the blends. Alumina based nanofluids of varying concentrations ranging from 0.01-4 % were used. The size of alumina particles was about 50 nm. The severity of quenching and heat transfer coefficients were estimated during quenching of copper probes. Heat transfer coefficients were estimated using a lumped heat capacitance model. The static contact angle was measured on copper substrates having a surface texture similar to the probes used for estimation of heat transfer coefficients. A dynamic contact angle analyzer was used for this purpose. The measured contact angles of nanofluids on copper were high compared to oils, indicating poor wetting by quench media that are polar in nature. Wetting characteristics had a significant effect on heat transfer coefficients estimated during quenching. Copyright © 2009 by ASTM International.Item 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.Item 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.