Method for producing polycrystalline alumina abrasive grains

A method for producing polycrystalline alumina abrasive grains, the method comprising:

• a step of obtaining a liquid mixture of pseudo-boehmite, silica having an average particle diameter of 100 nm or less at 0.01 parts by mass or more and less than 3.0 parts by mass with respect to 100 parts by mass of a solid content of the pseudo-boehmite, and water of 400 to 630 parts by mass with respect to 100 parts by mass of the solid content of the pseudo-boehmite;
• a step of adding a deflocculant to the liquid mixture to obtain a sol;
• a step of adding alumina seeds having a median diameter (D50) of 700 nm or less at 0.01 to 5.0 parts by mass with respect to 100 parts by mass of the solid content of the pseudo-boehmite to the sol, to obtain a seed-containing sol;
• a step of drying the seed-containing sol to a moisture content of 15% by mass or less, crushing a residue, and then performing calcination at 550° C. or more and less than 1,200° C.;
• and
• a step of performing firing at 1,200 to 1,500° C., wherein the polycrystalline alumina abrasive grains have an alumina content is 95.0% by mass or more, a silica content of 0.05 to 3.30% by mass, a grain size of 0.100 to 0.400 um, and a Vickers hardness of 21.00 or more.