Effect of superheat,mold, and casting materials on the metal/mold interfacial heat transfer during solidification in graphite-lined permanent molds |
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Authors: | K Narayan Prabhu K M Suresha |
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Affiliation: | (1) Department of Metallurgical & Materials Engineering, National Institute of Technology Kamataka, Surathkal, P.O. Srinivasnagar, 575 025, India |
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Abstract: | Heat transfer during the solidification of an Al-Cu-Si alloy (LM4) and commercial pure tin in single steel, graphite, and
graphite-lined metallic (composite) molds was investigated. Experiments were carried out at three different superheats. In
the case of composite molds, the effect of the thickness of the graphite lining and the outer wall on heat transfer was studied.
Temperatures at known locations inside the mold and casting were used to solve the Fourier heat conduction equation inversely
to yield the casting/mold interfacial heat flux transients. Increased melt superheats and higher thermal conductivity of the
mold material led to an increase in the peak heat flux at the metal/mold interface. Factorial experiments indicated that the
mold material had a significant effect on the peak heat flux at the 5% level of significance. The ratio of graphite lining
to outer steel wall and superheat had a significant effect on the peak heat flux in significance range varying between 5 and
25%. A heat flux model was proposed to estimate the maximum heat flux transients at different superheat levels of 25 to 75
°C for any metal/mold combinations having a thermal diffusivity ratio (α
R) varying between 0.25 and 6.96. The heat flow models could be used to estimate interfacial heat flux transients from the
thermophysical properties of the mold and cast materials and the melt superheat. Metallographic analysis indicated finer microstructures
for castings poured at increased melt superheats and cast in high-thermal diffusivity molds. |
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Keywords: | composite mold graphite lining interfacial heat flux superheat thermal diffusivity |
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