METHOD FOR PRODUCTION OF POWDER FILLER FOR COMPOSITE HARD MAGNETIC MATERIAL Russian patent published in 1994 - IPC

FIELD: production of ferritic powder filler for composite permanent magnets. SUBSTANCE: ferritic powder produced by crushing anisotropic magnets is heat treated at temperature of 750-1000 C and then treated by mixing in solution of mineral acid for 0.5-1.5 h. Powder-to-acid solution ratio for mixing is taken within 1:(1-6) by mass. After treatment with acid, powder is washed with water and dried to obtain powder with range of particle dimensions within 20-150 microns with 60-70% of particles of spheroidal shape. Powder particles possess single-axis magnetic anisotropy. Composite material based on powder of strontium ferrite with its content up to 92% possesses melt yield of 20-30 g/10 min that makes it possible to process it by extrusion or casting at pressure. Produced composite magnets feature residual induction Br= 2800-2820 Gs, coercive force of H=3550-3820 Oe and energy of 1.7-1.8 MGs Oe. EFFECT: higher homogeneity of granulometric composition and spheroid powder particles and improved casting properties of composite material with preserved magnetic properties. 1 tbl