Corning Glass Works

Robert N McNally

Jack A Brothers

Robert C Doman

Dense fused cast product and fused grain product of material whose microstructure consists essentially of at least 70 volume % chrome-containing corundum solid solution crystal phase, at least about 5 volume % oxidic secondary crystal phases mainly comprising chrome-containing alkaline earth hexaluminate solid solution, and less than 10 volume % metal phase. Analytical composition of material, by weight, consists essentially of at least 90% Al.sub.2 O.sub.3 +Cr.sub.2 O.sub.3, 20-60% Cr.sub.2 O.sub.3, 1-4% MO where M is Ca, Ba, Sr, Mg, Fe and mixtures thereof, 0.4-3.5% CaO, BaO, SrO and mixtures thereof, not greater than 3% MgO, not greater than 3.5% FeO, &lt;5% SiO.sub.2, up to 0.5% fluorine, &lt;1.5% R.sub.2 O wherein R is Li, Na, K, Rb, Cs and mixtures thereof, up to 2% TiO.sub.2 and up to 3% ZrO.sub.2. Resistant to corrosion by soda-lime and borosilicate glasses. Notable electrical resistivity with SiO.sub.2 &lt;1% by weight.

Fused refractory

Fused abrasive grain consists essentially of: (1) crystalline phases of corundum and zirconia, with an average crystallite size smaller than 300 microns and at least in part being an eutectic matrix and (2) analytically by weight, about 44 to 91% (preferably 44 to 80%) Al.sub.2 O.sub.3, about 5 to 50% (preferably 17.6 to 50%) ZrO.sub.2 to 0.1 to 12% (preferably 0.2 to 5%) R.sub.2 O.sub.3 wherein R is at least one metal selected from vanadium, chromium, manganese and cobalt, the percentage of R.sub.2 O.sub.3 is based on all R metal content calculated as R.sub.2 O.sub.3, and the balance, if any, being incidental impurities not exceeding 2%. The R metal content is present as oxide in solid solution within the corundum, as random particles of aluminate phase and/or as small particles of the R metal scattered throughout the grain, depending upon the relative oxidizing-reducing ambient conditions during melting. Melted raw material is formed, directly or indirectly, into grain of appropriate particle sizes for use in abrasive articles such as grinding wheels, coated abrasive products and the like.

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Corning, NY, United States of America

Robert N McNally