How Are Neodymium Magnets Made?

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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, NdFeB magnets are the strongest permanent magnets available in 2009.

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