Patent ID: 7722726

Claim:
A method for producing alloy flakes for a rare earth sintered magnet, said alloy flakes having a structure containing an R-rich region and dendrites of an R 2 Fe 14 B phase with a dendrite content of not less than 80 vol %, said method comprising the steps of: (A) preparing an alloy melt of a composition consisting of: at least one element R selected from the group consisting of rare earth metal elements including yttrium, boron, and at least one element M selected from the group consisting of transition metals, silicon, carbon, and mixtures thereof, with iron being essential, (B) supplying and solidifying said alloy melt prepared in step (A) on a cooling roll under such conditions as to generate an alloy structure having an R-rich region and dendrites of an R 2 Fe 14 B phase with a dendrite content of not less than 80 vol %, and an average size of crystal grains including said R-rich region and said dendrites of the R 2 Fe 14 B phase of not smaller than 40 μm, wherein said cooling roll has on its roll surface a plurality of linear nucleation inhibiting portions for inhibiting formation of dendrites of a R 2 Fe 14 B phase and chill crystals, and a plurality of nucleating portions for formation of said dendrites, and wherein said nucleation inhibiting portions have a region with a width of more than 100 μm.