Rebonded fusion-cast azs refractory grain

Abstract

Fired refractory articles are made of a shaped refractory composition predominantly comprising grain of fusion-cast AZS refractory having: (i) a three-phase microstructure of interlocking crystals of corundum (alpha alumina) phase and baddeleyite (zirconia) phase with intercrystalline glassy phase therebetween, the glassy phase being about 15-30 vol.% of the AZS refractory, and (ii) an oxide analysis consisting of 35-60 wt.% Al.sub.2 O.sub.3 plus Cr.sub.2 O.sub.3 with Cr.sub.2 O.sub.3 .ltoreq. 60 wt.% of Al.sub.2 O.sub.3 plus Cr.sub.2 O.sub.3, 25-50 wt.% ZrO.sub.2, 10-18 wt.% SiO.sub.2, 0.8-1.8 wt.% Na.sub.2 O plus K.sub.2 O, and up to 0.7 wt.% other ingredients (e.g. impurities). Refractory composition consists of: (A) 25-60 wt.% fusion-cast AZS refractory coarse grain being at least 89 wt.% -6+20 Tyler mesh, (B) 0-38 wt.% fusion-cast AZS refractory medium grain being at least 73 wt.% -10+35 Tyler mesh, and (C) 30-50 wt.% at least one component selected from the group consisting of: (1) 0-50 wt.% fusion-cast AZS refractory fine grain being at least 60 wt.% -35+325 Tyler mesh and (2) 0-30 wt.% at least one constituent selected from the group consisting of: (a) alumina being at least 90 wt.% -325 Tyler mesh, at least 98.5 wt.% Al.sub.2 O.sub.3 and not more than 0.5 wt.% Na.sub.2 O, and (b) -325 Tyler mesh chromic oxide being at least 95 wt.% Cr.sub.2 O.sub.3, and (D) 0-7 wt.% colloidal silica.