About Neodymium Magnets
Neodymium Magnets from Magnet Montreal are made from an alloy containing, amongst others, the elements Neodymium, Iron and Boron (NdFeB). The NdFeB magnets are the strongest type of magnet commercially available and are manufactured in a wide range of shapes, sizes and grades.
NdFeB magnets are anisotropic sintered magnets – the alloy is jet milled to a fine powder and is then compacted in the presence of a magnetic field to give it a preferred direction of magnetisation (making it anisotropic in performance). NdFeB magnets are then sintered to fuse the powder together before final machining and magnetising produces the completed super strength Neodymium magnet.
Neodymium magnets are also known as Neo Magnets, Neodymium Iron Boron magnets, Neodymium-Iron-Boron magnets, NdBFe magnets, NdFeB magnets, NIB magnets, Super Strength magnets and Rare Earth magnets. NdFeB is called a Rare Earth magnet because the Neodymium is a Rare Earth element, having a value of 60 on the Periodic Table. Note that there’s nothing rare about Rare Earth magnets – the required elements are readily available and the NdFeB magnets are produced in several hundreds of tonnes each year.
The greater force exerted by rare earth magnets creates hazards that are not seen with other types of magnet. Neodymium magnets larger than a few centimetres are strong enough to cause injuries to body parts pinched between two magnets, or a magnet and a metal surface, even causing broken bones. Magnets allowed to get too near to one another can strike each other with enough force to chip and shatter the brittle material, and the flying chips can cause injuries. There have even been cases where young children who have swallowed several magnets have had a fold of the digestive tract pinched between the magnets, causing injury or death. The stronger magnetic fields can be hazardous also, and can erase magnetic media such as hard disks and credit cards, and magnetize the shadow masks of CRT type monitors at a significant distance.
History and manufacturing techniques
In 1982, General Motors Corporation and Sumitomo Special Metals discovered the NdFeB compound. The effort was principally driven by the high material cost of the SmCo permanent magnets, which had been developed earlier. General Motors focused on the development of melt-spun nanocrystalline NdFeB magnets, while Sumitomo developed full density sintered NdFeB magnets. General Motors Corporation commercialized its inventions of isotropic Neo powder, bonded Neo magnets and the related production processes by founding Magnequench in 1986. Magnequench is now part of the Neo Materials Technology Inc. and supplies melt spun NdFeB powder to bonded magnet manufacturers. The Sumitomo facility has become part of the Hitachi Corporation and currently manufactures and licenses other companies to produce sintered NdFeB magnets.
Sintered NdFeB tends to be vulnerable to corrosion. In particular, corrosion along grain boundaries may cause deterioration of a sintered magnet. This problem is addressed in many commercial products by providing a protective coating. Nickel plating or two layered copper nickel plating is used as a standard method, although plating with other metals or polymer and lacquer protective coatings are also in use.