Effects of Particle Size Distribution on the Properties of Alumina-Zirconia-Graphite Refractory.

Abstract

Alumina-Zirconia-Graphite (AZG) refractory is one of the most important refractory for AISI 304 stainless steel strip casting, especially used as slide gates or nozzles. A suitable particle size distribution desired by simple R(c/m) values, weight of coarse Al2O3 (500-1000μm)/weight of medium Al2O3 (61-125μm), is important for controlling the apparent porosity, which affects the thermal shock resistance and erosion resistance as well. The size modulus, R(c/m), has been shown to be a useful parameter for the evaluation of particle packing, as controlled by the particle size distribution, on various properties of the Alumina-Zirconia-Graphite refractory. The lowest apparent porosity (5%) and highest bulk density (3.5g/cm3) were obtained at R(c/m) value of 6.0. The relation of bulk density (D) with R(c/m) can be represented by D=-0.040R2 (c/m)+0.351R(c/m)+2.741 for R(c/m) 0.4 to 3.7, and D=-0.006R2(c/m)+0.080R(c/m)+3.272 for R(c/m) 3.7 to 13, respectively. The average pore size (Ps) with R(c/m) value is expressed as Ps=0.035R2(c/m)-0.554R2(c/m)+7.138. The average pore size (Ps) of AZG refractory decreased from 6.5μm to 3.1μm, as the R(c/m) increased from 0.4 to 6.0. The number of air exposure cycles for the thermal shock resistance (Rst) were 14-17, and the relation of thermal shock resistance with R(c/m) is correlated by Rst=0.160R2(c/m) -1.371R(c/m)+16.860 for R(c/m) 0.4 to 3.7, and Rst=0.007R2(c/m)+0.277R(c/m)+13.082 for R(c/m) 3.7 to 13, respectively. The thermal shock resistance decreased gradually as the R(c/m) value was increased from 0.4 to 3.7. The effect of apparent porosity (Po) on the erosion fraction (Er) is expressed by Er=0.233 Po+1.204.