The article presents a novel method that allows measurement of thermal conductivity that is based on Stefan-Boltzmann law. The developed method can be used to determine thermal conductivity of ceramic investment casting molds. The methodology for conducting thermal conductivity tests of ceramic material samples is presented. Knowledge of the value of thermal capacity and thermal conductivity as a function of temperature enables computer simulations of the process of cooling and solidification of liquid metal in a mold.
Extremely intense development of civilization requires from foundry casting technologies very high quality and not expensive castings. In
the foundries, there are many treatments that allow increasing of the final properties of produced castings such as refining, modification,
heat treatment, etc. One of the methods of increasing the quality of the casting by removing inclusions from the liquid alloy is filtration.
The use of ceramic-carbon foam filters in filtration process is still analysed phenomenon that allows improving the final properties of
castings. A modern method of research, testing and synthesis of innovative chemical compositions allows improving the properties of such
filters. In the paper the evaluation of application properties of developed ceramic-carbon bonded foam filters is presented. The quality of
the foam filters is evaluated by Computer Tomography and foundry trials in pouring of liquid metal in test molds. Additionally computer
simulations were made to visualize the flow characteristics in the foam filter. The analysed filters are the result of the research work of
Foundry Research Institute and the Institute of Ceramics and Building Materials, Refractory Materials Department in Gliwice.
The results of testing the strength properties of experimental ceramic materials containing spending moulding sand after initial mechanical reclamation as a material for subsequent layers of the stucco composition were presented. Tests were carried out on spent moulding sands from various foundry technologies, i.e. sand with furfuryl resin and sand with hydrated sodium silicate. The spent, agglomerated moulding sand has undergone a crushing process. Next, the required granular fractions used for individual layers of the stucco material were separated. Ceramic samples, in which the spent moulding sand was a substitute for fresh silica sand in successive layers of the stucco composition, were prepared. As a reference material, identical ceramic samples were used but with all layers made from the fresh silica sand. Samples prepared in this way were used to determine the bending strength of ceramic materials in the temperature range from 20 to 900ºC. The obtained values of the bending strength have demonstrated that spent moulding sand can be used in investment casting with no adverse effect on the strength of ceramic materials.
Trials of cast steel filtration using two types of newly-developed foam filters in which carbon was the phase binding ceramic particles have
been conducted. In one of the filters the source of carbon was flake graphite and coal-tar pitch, while in the other one graphite was
replaced by a cheaper carbon precursor. The newly-developed filters are fired at 1000o
C, i.e. at a much lower temperature than the
currently applied ZrO2-based filters. During filtration trials the filters were subjected to the attack of a flowing metal stream having
a temperature of 1650°C for 30 seconds.
Characteristic of the filters’ properties before and after the filtration trial were done. It was found, that the surface reaction of the filter
walls with molten metal, which resulted in local changes of the microstructure and phase composition, did not affect on expected filter
lifetime and filtration did not cause secondary contamination of cast steel.
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