| 摘要 |
PURPOSE: To continuously obtain a permanent magnet alloy powder for bond magnet having stable magnetic characteristic by adjusting the pressure in a rapid cooling vessel according to the molten metal surface level in a molten metal storing vessel. CONSTITUTION: A raw material 20 blended into the composition of R-Fe-B base magnet is melted in a melting furnace 3 and stored into a molten metal storing vessel 4. The molten metal 21 in the molten metal storing vessel 4 is dropped on a water-cooling roll 7 rotated at high speed to obtain a rapid cooling strip 22 having amorphous structure or ultra-fine crystal structure of <=1nm average crystal grain diameter by rapid cooling solidification. At the time of tapping this molten metal, the molten metal tapping rate is kept constant by adjusting the pressures in a rapid cooling vessel 2 and a melting vessel 1 according to the molten metal surface level in the molten metal storing vessel 4. After cutting off the obtd. rapid cooling strip 22 into the rapid cooling flakes 23 with a cut-off machine 10, the flakes are pressed into 2-3g/cm<3> apparent sp.gr. with a compressor 11. Further, the pressed flakes are crushed into 3-50μm average powder grain diameter, separately with a crusher, and successively, heat treatment is executed at 600-800 deg.C in inert gas to obtain the magnet alloy powder of fine crystal having 1-30nm average crystal grain diameter. |
