ISSUE 1/2009

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Jaromir Roučka, Marek Kováč, Michal Jaroš and Ondřej Šikula, Brno, Czech Republic, Karel Hrbáček, Velká Bíteš, Czech Republic, Božena Podhorná, Prague, Czech Republic
Thermal process while pouring into ceramic shells and their numerical simulation

In the thermal regime of ceramic shell moulds made by the lost wax process the role of heat transfer by radiation and convection into the surrounding environment is significant while the portion of heat accumulated in the mould is less important. In ceramic shells the walls are mutually irradiated and there appear non-symmetrical heat flows in the direction of the axis of clusters and out of the clusters. Heat relations have up to now received little attention and only few verified thermo-physical parameters are available for numerical simulation. Experimental measuring enabled establishing the heat relations during casting and solidification of a model system of cylindrical castings of different diameters, which were placed on a ring gate. The casting material was the N155 alloy based on iron, nickel and cobalt. Thermocouples were used to measure the temperature waveforms in individual castings and in the walls of ceramic shells. The experimentally established data were used as significant temperatures in the subsequent numerical simulation of the thermal regime of the casting and solidification of the metal. The boundary conditions of heat transfer by radiation and convection were calculated using the FLUENT software. The actual thermo-physical and boundary conditions of the system were determined via inverse modelling by means of the ProCAST software. Using the CAFE module of the ProCast program the numerical simulation of the alloy structure in individual castings was performed; simulated structures were compared with the metallographically established structure.

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