Co-precipitation-reduction-diffusion process for the preparation of neodymium-iron-boron permanent magnetic alloys

• Main Authors: SHEN; PANWEN, ZHANG; SHOUMIN, ZHOU; YONGQIA, HU; XUYING
• Format: Patent
• Language: English
• Published: 18.04.2000
• Edition: 7
• Subjects: ALLOYS; BASIC ELECTRIC ELEMENTS; CASTING; CHEMISTRY; ELECTRICITY; FERROUS OR NON-FERROUS ALLOYS; INDUCTANCES; MAGNETS; MAKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; METALLURGY; PERFORMING OPERATIONS; POWDER METALLURGY; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES; TRANSFORMERS; TRANSPORTING; TREATMENT OF ALLOYS OR NON-FERROUS METALS; WORKING METALLIC POWDER

The present invention relates to the preparation of Nd-Fe-B permanent magnetic alloys and more particularly to a process of preparing Nd-Fe-B permanent magnetic alloys with neodymium, iron and boron as their basic constituents, wherein ammonium hydroxide (concentrated ammonia water) and ammonium carbonate are used as the precipitant, and neodymium salts, ferrous salts and soluble boron compounds as the starting materials for alloy elements such as neodymium, iron and boron, in addition, machining surplus or wastes of Nd-Fe-B alloys can also be used as raw materials so as to avoid the use of expensive rare earth metal. The process of the present invention comprises the steps of co-precipitation, hydrogen pre-reduction, calcium reduction-diffusion, rinsing, drying and powder manufacturing etc. and is capable of significantly reducing the costs compared with any of the existing processes. The invention has the ability to directly introduce non-metallic element boron into the alloys, to solve the problem concerning solid-phase side-reactions during hydrogen pre-reduction, and to avoid neodymium run-off and oxidation of alloy elements during rinsing procedure so as to ensure the rinsing cleanliness, whereby alloys are obtained with purity above 99% and calcium content of 0.01-0.05 wt %.