Abstract: An alumina-zirconia sintered body comprising 92 to 35% by weight of aluminum oxide and 8 to 65% by weight of zirconium oxide having mainly tetragonal system, and 0.2 to 5 parts by weight of silicon oxide per 100 parts by weight of the total of aluminum oxide and zirconium oxide, and having a relative density of 95% or more, has improved wear resistance and suitable for use in an impact grinder.

Abstract: An alumina-zirconia sintered body comprising 92 to 35% by weight of aluminum oxide and 8 to 65% by weight of zirconium oxide having mainly tetragonal system, and 0.2 to 5 parts by weight of silicon oxide per 100 parts by weight of the total of aluminum oxide and zirconium oxide, and having a relative density of 95% or more, has improved wear resistance and suitable for use in an impact grinder.

Abstract: A first rotor disk (21) and a second rotor disk (22) having a plurality of crushing pins (30) mounted so as to form rows along the circumference are opposed to each other and rotatably supported within casings (14, 15). The first and second rotor disks (21, 22) are rotated to crush materials to be crushed which are charged into the casings (14, 15). The crushing pins (30) are mounted on the first and second rotor disks (21, 22) in a cantilever manner. Escape spaces are provided on the first and second rotor disks (21, 22) so as to face to the extreme ends of the crushing pins (30).