Abstract: A ceramic filter for filtering molten metals includes aggregate particles consisting of fused alumina and/or sintered alumina, and a binder material, wherein the binder is present in an amount of 10 to 22 parts, by weight, per 100 parts of the aggregate particles. The binder material consists of 15 to 25%, by weight, of Al.sub.2 O.sub.3, 35 to 52% of B.sub.2 O.sub.3, not less than 7% and less than 15% of Sio.sub.2, and the balance of MgO. The ceramic filter may be prepared by kneading 100 parts of aggregate particles consisting essentially of either or both of fused alumina and sintered alumina, 10 to 22 parts of the foregoing binder material, an appropriate amount of an organic binder and an appropriate amount of water; molding the resulting mixture; drying the molded mixture; and then firing the same at a temperature ranging from 1150 to 1300.degree. C.

Abstract: A filter for the filtration of molten aluminum is obtained by binding 100 parts by weight of aggregate particles with 10 to 20 parts by weight of an inorganic binding material, said aggregate particles being composed of at least one alumina selected from the group consisting of fused alumina and sintered alumina and said inorganic binding material having a raw material composition comprising 25 wt. % to 35 wt. % of SiO.sub.2, 30 to 40 wt. % of B.sub.2 O.sub.3, 20 to 35 wt. % of Al.sub.2 O.sub.3 and the balance being MgO. A filter according to the invention has a crystallinity of from 10% to 25% with the proviso that in the powder X-ray diffraction, the crystallinity is expressed in terms of a percentage of a peak height of 9Al.sub.2 O.sub.3 .multidot.2B.sub.2 O.sub.3 appearing at 2.theta.=16.5.degree. to a peak height of .alpha.-Al.sub.2 O.sub.3 appearing at 2.theta.=43.4.degree.. Needle crystals of 9Al.sub.2 O.sub.3 .multidot.2B.sub.2 O.sub.