Effects of particle size distribution on the properties of alumina-zirconia-graphite refractory

Alumina-Zirconia-Graphite (AZG) refractory is one of the most important ref ractory for AISI 304 stainless steel strip casting, especially used as slid e gates or nozzles. A suitable particle size distribution desired by simple R (c/m) values, weight of coarse Al2O3 (500-1000 mu m)/weight of medium Al 2O3 (61-125 pm), is important for controlling the apparent porosity, which affects the thermal shock resistance and erosion resistance as well. The si ze modulus, R (c/m), has been shown to be a useful parameter for the evalua tion of particle packing, as controlled by the particle size distribution, on various properties of the Alumina-Zirconia-Graphite refractory. The lowe st apparent porosity (5%) and highest bulk density (3.5 g/cm(3)) were obtai ned at R (c/m) value of 6.0. The relation of bulk density (D) with R(c/m) c an be represented by D= -0.040R(2) (c/m) +0.351R(c/m) +2.741 for R(c/m) 0.4 to 3.7, and D=-0.006R(2)(c/m) +0.086R(c/m) +3.272 for R(c/m) 3.7 to 13, re spectively. The average pore size ((P) over bar(s),) with R(c/m) value is e xpressed as,(P) over bar(s)=0.035R(2) (c/m) - 0.554R(2)(c/m) + 7.138. The a verage pore size (P) of AZG: refractory decreased from 6.5 pm to 3.1 pm, as the R(c/m) increased from 0.4 to 6.0. The number of air exposure cycles fo r the thermal shock resistance (R-st) were 14-17, and the relation of therm al shock resistance with R (c/m) is correlated by R-st =0.160R(2)(c/m) -1.3 71R(c/m) +16.860 for R(c/m) 0.4 to 3.7, and R-st= -0.007R(2)(c/m) +0.277R(c /m) + 13.082 for R (c/m) 3.7 to 13, respectively. The thermal shock resista nce decreased gradually as the R (c/m) value was increased from 0.4 to 3.7. The effect of apparent porosity (P,) on the erosion fraction (E-r) is expr essed by E-r= 0.233Po + 1.204.