Rare Earth (RE) magnets, such as samarium-cobalt, find use in Atomic Energy, Space and Defence industries for a variety of strategic and non-strategic applications. These exhibit superior quality in terms of performance ability, device miniaturization capability and stability at high operating temperatures. These are becoming increasingly indispensable components in high power motors, micro motors, alternators, couplers, bearings, and actuators etc. that cater to various non-strategic industries.
The requirement of Rare Earth Permanent Magnets (REPM) in the country is currently met by imports. Considering the dual uses of these and the fact that India is a non-signatory to Non-proliferation Treaty (NPT), the availability of the magnets has been scarce to the country. In view of the above, there is a dire need for making indigenous effort to produce REPM.
Indian Rare Earths Limited (IREL) has set up facilities for producing separated high pure RE oxides from mixed RE chlorides produced from its 10000 tons per annum monazite processing plant. The major RE’s used in production of REPM are Neodymium (Nd) and Samarium (Sm). IREL has facilities to produce Nd, Praseodymium (Pr) and Sm oxide.
Bhabha Atomic Research Centre (BARC) has developed a novel metallurgical process for making RE alloy powder using indigenous RE oxides prepared by IREL. The technology for converting the RE alloys to magnets is available with Defence Metallurgical Research Laboratory, Hyderabad. The magnets are then machined at BARC, magnetized and characterized for the required application.
RE alloys are industrially produced by melting pure RE metal and the alloying additions at high temperatures. However, high melting temperature, very high cost of pure RE metals and loss of RE at high temperature due to evaporation make the alloy product very expensive. Moreover, solid ingot requires further pulverization to yield powder, from which the magnets are made. All these processes are energy intensive. On the other hand, the process developed by BARC yields the alloy powders directly from inexpensive oxides at much lower temperature, thereby resulting in lower cost magnets made out of samarium available in Indian ore.
RE alloy powders thus prepared using BARC technology were converted to magnets by DMRL. Magnets of different shapes have been prepared and these have been found at par with imported magnets in terms of magnetic properties.
Based on the above mentioned indigenous efforts, IREL is considering to set up a plant for production of RE permanent magnets for use in the strategic sectors. BARC is now transferring the technology to IREL.