Known as Rare Earth magnets, Neodymium Iron Boron magnets are alloys of the Lanthanide group of elements. NdFeB magnets offer the highest energy product per unit mass, and highest energy product per unit cost of any current permanent magnet material. Energy Products range from 30 to 55 MGOe, with recommended operating temperatures from 60º - 220ºC, and the temperature coefficient of residual induction ranges from -0.09 to -0.13%/°C.
BJA Magnetics prepares its anisotropic powders by either casting an alloy melt into a mold, or strip casting. Strip Casting offers the advantage of better chemical stability. Subsequently, the ingot from the mold or the flakes from Strip Casting are pulverized to a uniform grain/particle size. The best method for obtaining the desired grain size is by HDDR. The HDDR [hydrogenation-decomposition-desorption-recombination] process yields a more homogenous particle size with a minimum of α-Fe, and Nd-rich phases. Anisotropic Nd-Fe-B, HDDR powders prepared from strip cast alloys are used for the HAST [Highly Accelerated Stress Test] grades of NdFeB Magnets, including N, H, SH, UH, EH, and BJA Magnetics exclusive “W” grades for Wind Power applications.
When you purchase your NdFeB magnets from BJA Magnetics, you receive the following benefits:
Improved Corrosion Resistance – The HAST protocol used on uncoated neodymium iron boron magnets can qualitatively reflect the service life of the magnet. This test exposes the magnet to 130°C, 95% RH, at 2 ATM for 20 days. The magnet is massed before and after the test. Our magnets measure a weight loss of less than 3 mg/cm2. Competitors’ magnets can loose 10 times this much or more.
Batch to batch uniformity – The BHmax of our magnets has a Cpk greater than 1.6.
High Maximum Working Temperature – Our AH series of NdFeB magnets have working temperatures up to 230°C.
Excellent Adhesion of Plating to Magnet – Our magnets develop up to 2,175 psi attractive force between the plating and the magnet.
Excellent Corrosion Resistance – BJA Magnetics offers a number of coatings including, Nickel, Epoxy, Zinc, Tin, Phosphate, Parylene, Hybrid Coatings, Aluminum Spray coating, and IVD-Aluminum [Ion Vapor Deposition of Aluminum].
Low Surface Tension – Adhesives require a properly prepared surface for bonding. Good wet-ability is one of the keys to good bonding. The shear strength for our Ni Plated magnets is 50% greater than competitive magnets.
Surface Treatments: The corrosion resistance [sensitivity to oxidation] of NdFeB magnets is far better than it was just a few years ago due to changes in chemical composition. BJA Magnetics still recommends coating or plating for most applications. Plating NdFeB is a difficult process, and commercial plating houses are unlikely to be able to achieve plating with good adhesion. Nickel, Zinc, or Tin plating provides good corrosion resistance for NdFeB magnets.
We are able to Cadmium Chromate or Aluminum Chromate plate NdFeB using vacuum deposition techniques. A variety of organic coatings have also been successfully developed for NdFeB, exhibiting good corrosion resistance characteristics. The latest advance in coating technology is Ion Vapor Deposition of Aluminum, typically referred to as “IVD Aluminum”. For especially harsh environments, it may be advisable to use a combination of coating techniques, or to encapsulate the material in a sealed housing.
Organic Coatings – Epoxies, and urethanes are not hermetic (do not seal against moisture, or oxygen), but do slow the reaction with the magnet.
Nickel: Electrolytic nickel provides a hermetic seal, but is prone to corrosion in salt, and acidic conditions. Electroless (chemical) nickel offers improved coating into crevices, internal threads, ID holes, but is less protective of the magnet.
Zinc plating is sacrificial, releasing particulates. By itself, the performance is marginal, so conversion coatings are often used in conjunction with zinc.
Aluminum IVD is a malleable coating that requires bead blasting, and conversion coatings to provide a good seal against the elements.
Conversion Coatings – provides short-term protection only, but are used in conjunction with other coatings to enhance performance.
Combination Coatings – typically nickel plating plus an organic overcoat; offers improved resistance to salt spray plus protection from moisture and oxygen.
Common Applications for Neodymium Iron Boron Magnets:
- Holding systems requiring very high holding forces
- High field yoke magnets
- High performance stepper, DC, servo, linear, and voice coil motors
- Magnetic bearings
- Magnetic couplings
- Halbach arrays
- Magnetic separation
- Magnetic resonance
- Sensor for Reed Switches, and Hall Effect devices
- Vacuum deposition
- Charged particle beam guidance
- Particle accelerators