Conference Papers

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Subject: search.filters.subject.Quenching

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    Inverse modeling of heat transfer with application to solidification and quenching
    (2002) Prabhu, K.N.; Ashish, A.A.
    The inverse modeling of heat transfer involves the estimation of boundary conditions from the knowledge of thermal history inside a heat conducting body. Inverse analysis is extremely useful in modeling of contact heat transfer at interfaces of engineering surface during materials processing. In the present work, the one-dimensional transient heat conduction equation was inversely modeled in both cartesian as well as cylindrical coordinates. The model is capable of estimating heat flux transients, chill surface temperature, and total heat flow from the source to the sink for an input of thermal history inside the sink. The methodology was adopted to solve boundary heat transfer problems inversely during solidification and quenching. The response of the inverse solution to measured sensor data was studied by carrying out numerical experiments involving the use of varying grid size and time steps, future temperatures, and regularization techniques.
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    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.
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    Assessment of wetting kinematics and cooling performance of select vegetable oils and mineral-vegetable oil blend quench media
    (Trans Tech Publications Ltd ttp@transtec.ch, 2015) Pranesh Rao, K.M.; Prabhu, K.
    Quench hardening is a process where an alloy is heated to solutionizing temperature and held for a definite period, and then rapidly cooled in a quenching medium. Selection of quenchant that can yield desired properties is essential as it governs heat extraction process during quenching. In the present work, the cooling performance of vegetable oil and mineral-vegetable oil blend quench media was assessed. The vegetable oils used in this work were olive oil, canola oil and rice bran oil. The mineral-vegetable oil blends were prepared by blending 10 and 20 vol. % of rice bran and canola oil in mineral oil. Inconel probe of 12.5mm diameter and 60mm height, instrumented with thermocouples were used to characterize quenchants. The probe was heated to 850°C and quenched in the oil medium. The cooling curves at different locations in the probe were used to study wetting kinematics. Inverse modelling technique was used to estimate spatially dependent metal-quenchant interfacial heat flux. It was found that the vegetable oils exhibited very short vapour blanket stage compared to mineral oil and blends. Faster wetting kinematics obtained with blends resulted in uniform heat transfer compared to that of mineral oil. The temperature distribution in the probe quenched in vegetable oils and blends was more uniform compared to that in mineral oil. It is expected that the parts quenched in vegetable oils and blends would lead to better hardness distribution compared to mineral oils. © (2015) Trans Tech Publications, Switzerland.
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    Heat transfer during immersion quenching in MWCNT nanofluids
    (Trans Tech Publications Ltd ttp@transtec.ch, 2015) Nayak, U.; Prabhu, K.
    Quench heat treatment consists of rapid cooling of steel alloys after austenetization by subjecting them to cooling in a suitable cooling medium. At the heart of quench treatment is the transient heat transfer that occurs between the metal surface and the quenchant at their interface. This governs the quality of the component as it influences phase transformation, residual quench stresses and mechanical properties developed. In the present research work, spatially dependent transient heat flux in the axial direction was estimated using cooling curve analyses coupled with inverse heat conduction technique. A standard Inconel 600 probe instrumented with multiple thermocouples and heated to 865°C was quenched in distilled water (DW) and DW based multi walled carbon nanotubes (MWCNT) quench media. For evaluating the cooling performance, nanoquenchants with concentrations of 0.01, 0.1 and 1.0g/lt. were prepared. The cooling rate curve calculated from the measured temperature at the geometric center of the probe and the estimation of spatially dependent heat fluxes showed that the heat extraction during quenching with MWCNT nanoquenchant (0.1g/lt.) was higher than the other quenchants. The measured values of thermal conductivity and viscosities of quenchants did not show any significant variation. © (2015) Trans Tech Publications, Switzerland.
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    Estimation of Heat Flux Transient During Quench Hardening of Varying Diameter Steel Probes Using IHCP-Phase Transformation Coupled Model
    (ASM International, 2023) Samuel, A.; Nayak, U.V.; Pranesh Rao, K.M.P.; Prabhu, K.N.
    The phase transformation model is coupled with the inverse heat conduction problem (IHCP) to estimate the steel/quenchant interfacial heat flux. Cylindrical steel probes having section thicknesses 25 and 50mm, respectively, and lengths 30mm were made from medium and high carbon steels (AISI 1045 and 52100). The probes were quenched in mineral, neem, and sunflower oils. The cooling curves at the centre and near the surface of steel probes were recorded. The near-surface cooling curve was used as a reference temperature data in the IHCP algorithm for the estimation of surface heat flux, whereas the cooling curve at the centre was used as the boundary condition of the axisymmetric model of the probe. The effect of phase transformation on the metal/quenchant interfacial heat flux was indicated by a kink and rise of heat flux. The increase in the section thickness of the probe from 25 to 50mm decreased the magnitude of the heat flux. Increasing section thickness increases the phase transformation, increasing the resistance to heat flow at the metal/quenchant interface. © © 2023 ASM International®