In this article, a method to model the heat flux during quenching has been developed to bring out the effect of initial soaking temperature. Quench probes with a diameter of 20 mm and a length of 50 mm were prepared from 304 L stainless steel. These probes were quenched from different initial soaking temperatures ranging from 400 °Cto 950 °C in water. Time-temperature data were recorded during the quenching. The heat flux and temperature at the quenched surface were estimated based on the inverse heat-conduction method. The computation results showed that the peak in the heat flux increased with an increase in the initial soaking temperature of the probes. The heat flux was dependent on the initial soaking temperature. A model for the surface heat flux was proposed as a function of dimensionless parameters. The model could be used to compute the heat flux at different surface temperatures and was specified as a boundary condition to simulate the quenching for the particular material-quenchant combination. The model was verified by running a direct quenching simulation with heat fluxes computed at different surface temperatures using the proposed model as a boundary condition in ANSYS, a commercial finite element program. © The Minerals, Metals & Materials Society and ASM International 2009.

T. Sasi Prasanna Kumar

304L stainless steel

Dimensionless parameters

DIRECT-QUENCHING

FINITE ELEMENT PROGRAMS

mathematical modeling

QUENCHANTS

Quenched surfaces

SOAKING TEMPERATURE

Surface heat fluxes

Surface temperatures

TIME-TEMPERATURE

Atmospheric temperature

Boundary conditions

finite element method

Probes

Quenching

Stainless steel

Surface Properties

Heat flux

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IIT Madras

Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science

A serial algorithm for the inverse heat conduction problem (IHCP) has been developed to estimate the individual flux components, one by one, at the unknown boundary, based on the function specification method. The sensitivity coefficient defined in this algorithm brings out the influence of the heat flux components independent of each other. The objective function minimizes the difference in the measured temperature and the contribution of the individual flux component to the thermal field at the sensor location. The serial algorithm developed here could be used with data from both overspecified and underspecified sensors with respect to the number of flux components. The method was tested for delineating independent heat fluxes at the boundary of a two-dimensional solid for both space- and time-varying heat fluxes. Simulated thermal histories obtained from direct solution were used as inputs for the inverse problem for characterizing the new algorithm. Three types of analyses were done on the results of the IHCP, focused on (1) the convergence of error in estimated temperatures at the different sensor locations, (2) overall error in estimated temperatures for the whole domain, and (3) the total heat energy transferred across the boundary. It is shown that the optimum configuration of independent unknown fluxes is given by the one with minimum energy estimates across the boundary, for both cases.

Numerical Heat Transfer, Part B: Fundamentals

A serial solution for the 2-D inverse heat conduction problem for estimating multiple heat flux components

Most of the research work pertaining to metal-mold heat transfer in casting solidification either assumes no spatial variation in the air gap formation or limits the study to only those experimental systems in which air gap formation is uniform. However, in gravity die-casting, filling effects induce variation in thermal field in the mold and casting regions. In this paper, we show that this thermal field variation greatly influences the time of air gap initiation along a vertical mold wall, which subsequently leads to the spatial variation of air gap and in turn, the heat flux at the metal-mold interface. In order to study the spatial variation of heat flux at the metal-mold interface, an experimental setup that involved mold filling was devised. A Serial-IHCP (inverse heat conduction problem) algorithm was used to estimate the multiple heat flux transients along the metal-mold interface. The analysis indicates that the fluxes at different mold segments (bottom, middle, and top) of the metal-mold interface reaches the peak value at different time steps, which shows that the initiation of air gap differs along the mold wall. The experimental and numerical results show that the heat transfer in the mold is two-dimensional during the entire period of phase change, which is initially caused by the filling effects and further enhanced by the spatial variation of the air gap at the metal-mold interface. © 2007 Elsevier Ltd. All rights reserved.

International Journal of Heat and Mass Transfer

Spatial variation of heat flux at the metal-mold interface due to mold filling effects in gravity die-casting

Metallurgical and Materials Transactions B

Effect of Sample Start Temperature during Transient Boiling Water Heat Transfer

Materials Science and Engineering: A

FEM simulation of quenching process and experimental verification of simulation results

It is of engineering importance to accurately predict the surface cooling characteristics in bath quenching of metals and alloys. In this investigation, the surface cooling characteristics in quenching of Wolfson probe are estimated with reasonable accuracy by solving an inverse heat conduction problem. Regularization method is used for smoothening the input temperature measurements at probe center, for superior inversion estimates. The reverse pool-boiling curve is captured on bath quenching characteristic, plotted as cooling velocity versus surface temperature. The prime advantage is the bypassing of convection coefficients, which are uncertain in pool boiling.

Experimental Heat Transfer

Cooling characteristics during bath quenching of test probe using inverse heat transfer

Mathematical modeling of surface heat flux during quenching

Journal	Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
ISSN	10735615
Open Access	No