Effect of process parameters on the properties of alumina-zirconia-graphite (AZG) refractories (part 2) - Baking temperature and time

Alumina- zirconia- graphite (AZG) materials are important refractories for AISI 304 stainless steel strip casting, which is especially used as slide g ates and nozzles. AZG refractories were obtained through a baking technique using fused Al2O3, partially stabilized ZrO2 and flake graphite as startin g materials with Al, Si, and SiC powders as additives. A particle size dist ribution was according to the Furnas model for coarse Al2O3 (500-1000 mum/m edium Al2O3 (61-125 mum/fine Al2O3 (< 44 mum in which the contents of coars e, medium and fine Al2O3 powders were varied with the constant amount of ot her fine particles in the matrix. The bulk density reached the values 3.29, 3.19 and 3.13 g.cm(-3) when baked at 200 degreesC for 2, 2 and 2.5 h, resp ectively. The apparent porosity decreased from 7.6 to 6.3% upon increasing the baking time at 160 degreesC from 0.5 to 2.5 h, and then gradually incre ased from 6.3 to 6.6% as the baking time increased from 2.5 to 3.0 h. The m odulus of rupture was < 80 MPa when the baking time was 1.5 h for all sampl es formed at 150 MPa and baked at 200 degreesC. On the other hand, the modu lus of rupture increased sharply and attained a maximum value > 120 MPa for a baking time of 3.0 h. The erosion fraction (E-r) increased with increasi ng apparent porosity (P-o) and could be expressed E-r = 0.30P(o) -0.27.