How Are Neodymium Magnets Made?

By Ma Wen Jie

Neodymium Manufacturing Processes

There are two ways to manufacture neodymium magnets. The first, and most common, is a sintering process that creates stronger magnets. The second is a bonding process that facilitates the forming of the magnets into unusual shapes, but results in slightly weaker magnets.

Sintered Neodymium Magnets

Sintered neodymium magnets are produced by Sumitomo Special Metals. Sintering is a process of heating a powdered neodymium, iron, and boron mix in a sintering furnace. Because of their composition, neodymium magnets are sometimes called NIB or NeFeB magnets. A sintering furnace keeps powdered metallurgical materials below their melting point. The heat and pressure in the furnace cause the powdered materials to adhere to each other. Once a sintered neodymium magnet has been created, it is highly reactive to air and oxidization and usually must be coated to keep air from interacting with the magnet. An estimated 50,000 to 55,000 tons of finished neodymium magnets are produced each year, with 90% being sintered neodymium magnets.

Bonded Neodymium Magnets

Bonded neodymium magnets are made by making thin ribbons out of melted NeFeB alloy. The alloy ribbon is then pulverized into a powder and mixed with a polymer that is then injected into a mold to make the magnets. Bonded neodymium magnets aren't as strong as sintered magnets, but offer an advantage in cost and flexibility of shape.

Magnetizing Finished Neodymium Magnets

Regardless of how the composite rare earth magnets are manufactured, both types of magnets are placed in a very strong electromagnetic field to magnetize the rare earth elements. Once magnetized, NIB magnets are the strongest permanent magnets available in 2009.

What is Neodymium?

Neodymium (Nd) is a rare earth metallic element located at 60 on the periodic table of elements. Of all the rare earth elements, Nd is more prone to reacting and combining with other elements and quickly oxidizes by combining with oxygen in the air.

History of Neodymium Magnets

Neodymium magnets were simultaneously developed in 1982 by the China Academy of Sciences, Sumitomo Special Metals and the General Motors Corporation as a response to the high-material costs for earlier strong permanent rare earth magnets. Although all three organizations developed NIB magnet technology, their manufacturing technologies differed. Sumitomo developed sintered NIB magnets while General Motors developed powdered bonded NIB magnets. GM subsequently sold the neodymium magnet division, Magnequench, to a Chinese consortium headed by Archibald Cox Jr. along with San Huan New Material and China National Nonferrous Metals Import and Export Company (CNNMIEC). In 2005, Magnequench merged with the Canadian company AMR. Control of the merged company remained with scientists closely associated with the China Academy of Sciences.