MEASUREMENT OF THE EFFECTIVE THERMAL-CONDUCTIVITIES OF MOLDING SANDS AT HIGH-TEMPERATURES

It is well known that the effective thermal conductivity of bonded mol ding sands depends on the volume fraction, thermal conductivity and ar rangement of the components e.g., sand particles, bonding medium and a ir. The arrangement of components is known to be affected by particle size distribution, average size and shape. In this study, an experimen tal system using the line-heat-source method was designed and effectiv e thermal conductivities of molding sands at temperatures up to 750 de grees C were measured. The effects of binder content, initial moisture content, dry density and temperature were also investigated for four selected sand types : silica, olivine, zircon and chromite sands. The effect of dry density on the effective thermal conductivity of bentoni te-bonded molding sands turned out to be more significant than the eff ect of either binder content or initial moisture content. The minimum effective thermal conductivity for bentonite bonded silica sand occurr ed at about 500 degrees C The effective thermal conductivity of silica sands bonded with western bentonite was found to be higher than that of silica sands bonded with southern bentonite up to 750 degrees C.