Development of Compound for Anisotropic Bonded Nd Magnets Using d-HDDR Magnet Powder

Bonded anisotropic Nd magnets with high-energy product (BH)_max of 20MGOe and freedom of shape design are effective in realizing motor size and weight reductions. The anisotropic powders were produced by d-HDDR treatment, grain boundary diffusion treatment with NdCuAl, and powder surface coating treatment. However, during the compression molding process, the molding pressure can induce the magnet powder grains to crack, which leads to degradation in magnetic performance, in particular the squareness ratio. A compound made of d-HDDR magnet powder coated with resin, fine SmFeN powder, and lubricant can produce molded blocks with a high density of 6.0 g/cm³ at a low molding pressure of 1 t/cm². In addition, by enabling molding at a low pressure, the loss of squareness of the magnet powder was reduced to 0.5%. From the above, through kneading and the addition of fine powder and lubricant, the surface treatment of d-HDDR magnet powder achieved high-density magnets at a low molding pressure and a compound capable of controlling the reduction in loss of squareness.