Neodymium Iron Boron Magnets - General Information
Neodymium Iron Boron - Overview
Magnetic Yoke utilizing NdFeB magnets
Neodymium Iron Boron magnets were commercially introduced in the early 1980s. They are widely used today in many different applications. The cost of this magnet material (on a dollars per energy product basis) is comparable to that of Ferrite magnets. On a dollars per pound basis, the cost of Neo magnets is about 10 to 20 times that of Ferrite magnets.
Note that NdFeB magnets are covered by various patents (held by Neomax) and only licensed materials are allowed into the USA. There are a number of sources that do sell unlicensed products to those willing to purchase them. ITG does not sell unlicensed materials.
- Very high strength
- Relatively low cost (by weight about 20 times Ferrite magnets, by "Dollars per BHmax" about 1.5 times Ferrite magnets).
- Relatively easy to machine, compared to Alnico and SmCo magnets.
- Properties deteriorate rapidly at temperatures in excess of about 150°C (depending on grade and permeance coefficient magnet is operating at).
- Most grades of NdFeB magnets need to be protected against oxidation - by coating or plating the magnets.
- Density - 0.275 lbs per cubic inch
- Saturation magnetizing field required - about 35kOe
- Manufacturing methods - sintering (most common), injection molding, compression bonding, or calendaring.
- Shapes available - blocks, bars, discs, rings, arc segments, etc.
- Grades available - from about 3330 to 5311. (First 2 digits represent BHmax, and second two digits represent Intrinsic Coercivity, Hci.)
- Sizes - off tool the largest die pressed blocks are about 4" cube, while isostatically pressed blocks can be much longer in the orientation direction (up to 9 feet).
- Machining - Neodymium magnets should be machined by grinding using diamond wheels, However, of the hard magnet materials, Neo magnets are the least difficult to machine. We have successfully machined very small magnets - down to 0.012" diameter with a center hole of 0.003" diameter, 0.040" long.
Painting, coating, or plating is generally recommended for NdFeB, although recently certain grades have been made that exhibit higher resistance to oxidation. Plating NdFeB is a difficult process, and commercial plating houses unfamiliar with the specialized plating techniques required are unlikely to be able to achieve plating with good adhesion on Neo magnets. Nickel, Zinc, or Tin plating, plating provides good corrosion resistance for NdFeB magnets, though longer lead times or higher volumes may be required for these. We are also able to cadmium chromate or aluminum chromate plate NdFeB using ion vacuum deposition (IVD) techniques. A variety of organic coatings have also been successfully developed for NdFeB, exhibiting good corrosion resistance characteristics. For especially harsh environments, it may be advisable to use a combination of coating techniques, or to encapsulate the material in a sealed housing.
- NdFeB powder is very fine and when dry can ignite spontaneously - care must be taken in handling NdFeB powder.
- NdFeB magnets are very powerful - care must be taken in handling these magnets to avoid injuries.
- NdFeB magnets are susceptible to corrosion.