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In this paper, we present comparative investigations. We examined two kinds of ceramic materials used to produce bricks for isothermal cleading of the riser heads of middle and large steel castings. The ceramic materials were characterised by a low specific density (No. 1 − ρ = 0.854 g/cm³; No. 2 − ρ = 0.712 g/cm³). Thermal conductivity tests at a transient heat flow were performed by analysing the heating process of samples taken from the tested ceramic bricks, placed in a special mould in which metal was poured, and by recording the cooling process of the casting. The method proposed in this paper for the determination of samples’ thermo-physical properties is based on measuring the temperature field of the casting–sample system by means of thermocouples situated in various measuring points; it allows the direct investigation of cooling and solidification processes of metals in sand moulds. The heating process of the ceramic samples was analysed by measuring the temperature in five points situated at various distances from the heating surface (casting–sample surface). A large difference in the heating rates of samples of different materials was revealed in our comparative investigations, which indirectly indicated the materials’ heat abstraction ability from the casting surface. The ceramic material characterised by a lower density much slowly conducted heat and, therefore, appeared to be a better material for insulation cleading. At the depth of 40.0 mm, we measured differences in the heating degree corresponding to more than 190 °C. The aim of this comparative study was the evaluation of the suitability of porous insulating materials as cleading of riser heads used in the production of large steel castings.

Keywords: riser heads; insulation cleading; porous ceramic bricks