Thermal conductivities of molten iron, cobalt, and nickel by laser flash method
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10/30/03
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Thermal Conductivities of Molten Iron, Cobalt, and Nickel by Laser Flash Method TSUYOSHI NISHI, HIROYUKI SHIBATA, HIROMICHI OHTA, and YOSHIO WASEDA New attempts were made for the measurement of thermal diffusivity of molten iron, cobalt, and nickel at temperatures close to 1900 K by a laser flash method. A simple but useful sample cell system was developed to keep the molten metal shape uniform for a given thickness. It is also necessary to consider the effect of not only the radiative heat loss but also the conductive heat loss at the interface between the molten metal sample and the sample cell material under the present experimental conditions. The conductive heat loss was found, through computational simulation, to be negligibly small for the present laser flash measurements. Thermal conductivity values of molten iron, cobalt, and nickel were calculated by combining the present thermal diffusivity data with specific heat and density, and the resulting values are given in the following equations (unit: W m1 K1)
Fe 2.15 102 (T 1818) 33.3 Co 2.79 102 (T 1768) 30.4 Ni 2.30 102 (T 1728) 53.0
I. INTRODUCTION
THERMAL diffusivity and conductivity values of molten metals at elevated temperatures are required to elucidate the metal production processes, such as continuous casting, welding, and refining by developing computer simulation models. For this purpose, thermal diffusivity[1] and conductivity[2] of molten metals, compiled in the TPRC (Thermophysical Properties Research Center, Purdue University) Data Series have been widely used in the past. However, almost all values in the TPRC Data Series for molten metals are estimated by extrapolation from the values of respective metals in the solid states at high temperature. This frequently induces differences between the simulated results and experimental data. The main purpose of this work is to provide sufficiently reliable values of thermal diffusivity and conductivity for molten iron, cobalt, and nickel at temperatures above 1700 K by developing a novel sample cell system for a laser flash method. The contribution from the conductive heat loss at interface between the molten metal sample and the sample cell material to the thermal diffusivity measurements in the present experimental condition has been accounted for. II. EXPERIMENTAL Chemical compositions of the iron, cobalt, and nickel samples used in this study are summarized in Table I. The samples were heated to 1900 K with a tungsten mesh heater under vacuum of less than 2 103 Pa and thermal diffusivity values of molten metals were measured by a laser flash tech-
TSUYOSHI NISHI, Graduate Student, Department of Materials Processing, and HIROYUKI SHIBATA, Research Associate, and YOSHIO WASEDA, Professor, Institute of Multidisciplinary Research for Advanced Materials, are with Tohoku University, Sendai 980-8577, Japan. Contact e-mail: [email protected] HIROMICHI OHTA, Associate Professor, is with the Department of Materials Science, Ib
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