Rare earth-iron-boron permanent magnet.

摘要

An anisotropic sintered permanent magnet comprising 12 to 18 at % R, wherein R represents Pr, Nd, Dy, Tb and other rare earth element or elements contained as inevitable impurities provided that 0.8 </= (Pr + Nd + Dy + Tb)/R </= 1.0, 5 to 9.5 at % B, 2 to 5 at % Mo, 0.01 to 0.5 at % Cu, 0.1 to 3 at % A l , and balance being Fe, or Fe and Co substituting a part of Fe. B(x) and Mo(y) are (x -4.5 </= y </= (x - 3.0), and part of Fe may be replaced by Co to be 3 - 7 at % Co. Up to 90 at % of Mo may be replaced by V. The magnet is characterized by main tetragonal R2(Fe, Mo)14B or R2(Fe, Co, Mo)14B phase and boundary phase of (Fe, Mo)-B, or (Fe, Co, Mo)-B and Rm(Fe, Co, Mo)n where m/n = 1/2 to 3/1. B-rich phase Nd1 + epsilon Fe4 B4 disappears. Dy and/or Tb linearly increase iHc. High coercivity and maximum energy product are obtained: iHc >/= 15 kOe (or 21 kOe) and (BH)max >/= 20 MGOe (or 28 MGOe) with high corrosion resistance and high pulverizability of alloy.