Neodymium-iron-boron (Nd-Fe-B) magnets have revolutionised the field of permanent magnets and become an indispensable component of modern technology. The strongest variety, “Sintered NdFeB magnets”, was developed by Japanese inventor and materials scientist Masato Sagawa. Before the 1980s, the preferred material for high-performance permanent magnets was an expensive combination of samarium and cobalt. Motivated by the lower cost of iron and its magnetic properties, Sagawa experimented with various elements to develop a new type of magnet. Using a sintering process that bonds the powdered components through a combination of heat and pressure, while keeping the fine microstructure, he eventually found the key by inserting boron into a neodymium and iron crystal lattice. This gave his magnets high coercivity, a resistance to demagnetisation, along with unparalleled strength. Nd-Fe-B magnets’ superior properties have led to their widespread adoption across industries, and they account for around 95% of all permanent magnets on the market today by value, with the sintered variety being the strongest among them. Sagawa developed an idea for Nd-Fe-B magnet in his spare time while working as a researcher at Fujitsu from 1972 to 1982. Recognising its potential, Sagawa resigned from his position, patented the magnet, and joined Sumitomo Metal Industries in 1982, where Nd-Fe-B magnet was commercialized.
According to the different production processes, Neodymium Magnets can be divided into three types: sintered NdFeB magnets, bonded NdFeB magnets, and hot-pressed NdFeB magnets.Since the beginning of the 21st century, although the development of the sintered NdFeB industry in developed countries such as Japan, the United States, and Europe has slowed down, due to the extraordinary development of China's sintered NdFeB industry, the global rare earth permanent magnet industry has maintained a rapid growth trend. In 2017, China's output of sintered NdFeB finished products was 104,000 tons, an increase of 8.8% over the previous year; the global output was about 120,000 tons, and China accounted for 87% of the global share.
Mine to Magnet
AREPL aims to master the production process of "Mine to Magnet." The process can be understood in the following points:
Mining: This process is not done by AREPL, but raw materials are procured from IREL (Indian Rare Earths Limited). According to the Government of India, only selected companies have the license to mine these raw materials. IREL specialises in mining, separation and extraction of rare earths in the form of their oxides in a series of steps, ensuring a stable and high-quality supply of raw materials essential for start-up's production process.
Raw Material (Oxide or Fluoride Form) to NdPr Metal: The raw materials in the form of oxides are processed to extract NdPr (Neodymium-Praseodymium) metal through advanced techniques. This involves refining and purifying the raw materials to obtain high-purity NdPr metal, which is a crucial component for high-performance magnets. The process includes steps to ensure the removal of impurities and achieve the desired purity levels.
Metal to Alloy Powder (NdFeB Powders): The NdPr metal is then converted into NdFeB (Neodymium-Iron-Boron) alloy powder. This involves melting the NdPr metal along with iron and boron to form an alloy. The molten alloy is rapidly cooled to produce fine NdFeB powders. These powders are critical for producing magnets with high energy density and excellent magnetic properties. Advanced techniques like strip casting are used to produce uniform and high-quality alloy powders.
Alloy Powders to Magnet Blocks: The alloy powders are processed to form magnet blocks through a series of steps, including pressing and sintering. In the pressing stage, the alloy powders are compacted into the desired shape using presses. The compacted powders are then subjected to high-temperature sintering, which involves heating them in a controlled atmosphere to bond the particles together, resulting in dense and solid magnet blocks with superior magnetic properties.
Cutting Operations on Magnet Blocks for Manufacturing Sintered NdFeB Magnets:
The magnet blocks undergo precise cutting operations to manufacture sintered NdFeB magnets. This involves slicing, grinding and shaping the blocks into the required dimensions and geometries. Advanced machining techniques, such as wire EDM (Electrical Discharge Machining) and precision grinding, are used to ensure the final magnets meet the stringent quality and performance standards required for high-tech applications.
Each stage involves various technologies and techniques to ensure efficiency and quality.
Though India produces Nd-Pr oxide required for the production of Nd-Fe-B permanent magnets, and the production facility for making magnets and the end-use market of windmills, EVs, etc., the intermediate supply chain of production of metal and alloy is absent. A tripartite agreement has been signed between IREL, BARC, and AREPL on 14th July 2021 for the development and production of Nd-Pr using Indian Rare Earth resources under incubation mode.
