Abstract: Provided are a method for producing an alumina sintered compact satisfying the following (1) and (2), which comprises mixing and sintering an ilmenite powder and an alumina powder; the alumina sintered compact obtained according to the production method; and an abrasive grain and a grain stone. (1) The total amount of the TiO2-equivalent content of the titanium compound, the Fe2O3-equivalent content of the iron compound and the alumina content is at least 98% by mass; (2) The total amount of the TiO2-equivalent content of the titanium compound and the Fe2O3-equivalent content of the iron compound is from 5 to 13% by mass.

Abstract: Provided are an alumina sintered compact containing a titanium compound and an iron compound, wherein the total amount of the TiO2-equivalent content of the titanium compound, the Fe2O3-equivalent content of the iron compound and the alumina content is at least 98% by mass, the total amount of the TiO2-equivalent content of the titanium compound and the Fe2O3-equivalent content of the iron compound is from 5 to 13% by mass, and the ratio by mass of the TiO2-equivalent content of the titanium compound to the Fe2O3-equivalent content of the iron compound (TiO2/Fe2O3) is from 0.85/1.15 to 1.15/0.85; and an abrasive grain and a grain stone using the alumina sintered compact.

Abstract: Provided are an alumina sintered compact containing a titanium compound and an iron compound, wherein FeTiAlO5 grains exist in the grain boundary of the alumina grains and the mean grain size of the FeTiAlO5 grains is from 3.4 to 7.0 ?m; and an abrasive grain and a grain stone using the alumina sintered compact.

Abstract: Provided are an alumina sintered compact containing a titanium compound and an iron compound, wherein the total amount of the TiO2-equivalent content of the titanium compound, the Fe2O3-equivalent content of the iron compound and the alumina content is at least 98% by mass, the total amount of the TiO2-equivalent content of the titanium compound and the Fe2O3-equivalent content of the iron compound is from 5 to 13% by mass, and the ratio by mass of the TiO2-equivalent content of the titanium compound to the Fe2O3-equivalent content of the iron compound (TiO2/Fe2O3) is from 0.85/1.15 to 1.15/0.85; and an abrasive grain and a grain stone using the alumina sintered compact.

Abstract: Provided are an alumina sintered compact containing a titanium compound and an iron compound, wherein FeTiAlO5 grains exist in the grain boundary of the alumina grains and the mean grain size of the FeTiAlO5 grains is from 3.4 to 7.0 ?m; and an abrasive grain and a grain stone using the alumina sintered compact.

Abstract: Provided are a method for producing an alumina sintered compact satisfying the following (1) and (2), which comprises mixing and sintering an ilmenite powder and an alumina powder; the alumina sintered compact obtained according to the production method; and an abrasive grain and a grain stone. (1) The total amount of the TiO2-equivalent content of the titanium compound, the Fe2O3-equivalent content of the iron compound and the alumina content is at least 98% by mass; (2) The total amount of the TiO2-equivalent content of the titanium compound and the Fe2O3-equivalent content of the iron compound is from 5 to 13% by mass.

Abstract: A roundish fused alumina particles having a mean particle size of 5 to 4,000 ?m and a roundness of 0.85 or more, and a producing method thereof are provided. The method comprises removing edges of fused alumina particles by making the fused alumina particles collide with each other.

Abstract: A roundish fused alumina particles having a mean particle size of 5 to 4,000 ?m and a roundness of 0.85 or more, and a producing method thereof are provided. The method comprises removing edges of fused alumina particles by making the fused alumina particles collide with each other.

Abstract: The invention provides a dry grinding system including grinding means for dry-grinding a material to be ground; first classification means for classifying a ground product obtained through the grinding means, into fine powder having a relatively small average particle size and coarse powder having a relatively large average particle size; second classification means for further classifying the coarse powder obtained through the first classification means, into find powder having a relatively small average particle size and coarse powder having a relatively large average particle size; and returning means for returning to the grinding means the coarse powder obtained through the second classification means. The invention enables production of a powder product having a desired average particle size at high efficiency.

Abstract: A roundish fused alumina particles having a mean particle size of 5 to 4,000 ?m and a roundness of 0.85 or more, and a producing method thereof are provided. The method comprises removing edges of fused alumina particles by making the fused alumina particles collide with each other.

Abstract: The invention provides a dry grinding system including grinding means for dry-grinding a material to be ground; first classification means for classifying a ground product obtained through the grinding means, into fine powder having a relatively small average particle size and coarse powder having a relatively large average particle size; second classification means for further classifying the coarse powder obtained through the first classification means, into find powder having a relatively small average particle size and coarse powder having a relatively large average particle size; and returning means for returning to the grinding means the coarse powder obtained through the second classification means. The invention enables production of a powder product having a desired average particle size at high efficiency.

Abstract: The invention provides a dry grinding system including grinding means for dry-grinding a material to be ground; first classification means for classifying a ground product obtained through the grinding means, into fine powder having a relatively small average particle size and coarse powder having a relatively large average particle size; second classification means for further classifying the coarse powder obtained through the first classification means, into fine powder having a relatively small average particle size and coarse powder having a relatively large average particle size; and returning means for returning to the grinding means the coarse powder obtained through the second classification means. The invention enables production of a powder product having a desired average particle size at high efficiency.

Abstract: The invention provides a dry grinding system including grinding means for dry-grinding a material to be ground; first classification means for classifying a ground product obtained through the grinding means, into fine powder having a relatively small average particle size and coarse powder having a relatively large average particle size; second classification means for further classifying the coarse powder obtained through the first classification means, into fine powder having a relatively small average particle size and coarse powder having a relatively large average particle size; and returning means for returning to the grinding means the coarse powder obtained through the second classification means. The invention enables production of a powder product having a desired average particle size at high efficiency.