The effect of recipe and production parameters on optimization of thermal conductivity and strength of refractory materials

This study analyzed the production of refractory raw materials at different pressures and thicknesses. The study focused on the raw materials used in the production process of SÖRMAŞ A.Ş. and magnesite based refractory bricks. Magnesite spinel refractory bricks are preferred in the cement industry. For this study, a total of nine different bricks were produced at pressures of 1400 kg/cm², 1500 kg/cm², and 1600 kg/cm², with thicknesses of 60 mm, 70 mm, and 80 mm. Chemical analysis was performed on the raw materials before production. After production, dimensional control, density, apparent porosity, water absorption, cold compressive strength, and thermal conductivity coefficient tests were conducted. Looking at the rates of change in width and length as a result of the investigations, a general negativity is observed. This negativity indicates shrinkage, meaning shrinkage, of the brick. The change in density shows a decrease depending on the width to length ratio due to the moisture released after firing. For balanced performance in terms of porosity, water absorption, and cold compression strength, a pressing pressure of 1500 kg/cm² and a thickness of 80 mm have been determined as optimal values. However, for applications where maximum mechanical strength is a priority, a pressing pressure of 1600 kg/cm² and a thickness of 80 mm are recommended. Looking at the thermal conductivity coefficient values, it has been observed that thermal conductivity values generally increase as pressure increases, according to experimental results. The sample with a pressure of 1600 kg/cm² and a thickness of 20 mm achieved the highest conductivity value (20,25 W/m.K). This value is a result of the effect of high density combined with low thickness. In contrast, the sample with a pressure of 1400 kg/cm² and a thickness of 30 mm measured the lowest conductivity value (16,037 W/m.K). This indicates that the combination of low pressing pressure and medium thickness creates more micro-pores and contact deficiencies within the material.