Are all Rare Earth Magnetic Separators the Same?

By buntingeurope | 31 August 2016

2nd of 10 Magnetic Separator Myths

A client has a metal contamination problem and needs to install the most suitable magnetic separation.  The metal is small and so they believe that a Magnetic Separator with Rare Earth Magnets is what they need as this produces the strongest magnetic field.  So he picks up the phone and orders a Rare Earth Magnetic Separator and his problem is solved.

Or is it?

Bunting Europe at PRE 2015-2520

Unfortunately, the term ‘Rare Earth Magnet’ is pretty unspecific.  It’s the same as ordering a car instead of specifying a specific model like a Ford Mondeo or BMW 5 series.  This blog will help explain.

Rare Earth Magnets are strong permanent magnets made from alloys of rare earth elements such as Neodymium Iron Boron. Developed in the 1970s and ’80s, Rare Earth Magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets.  The magnetic field typically produced by rare-earth magnets can be in excess of 1.4 Tesla, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla. There are two types of Rare Earth Magnet:

The use of the different types of Rare Earth Magnets depends on the application and the following is a general guide:

  1. Neodynium Iron Boron (Nd2Fe14B) – Unfortunately, life is never that straight forward and there are two distinct types of Neodymium Magnet:
    • Sintered – These are produced using a high temperature process to produce a strong even and uniform bond of the material. This is the highest grade of Neodynium Iron Boron Rare Earth Magnet, producing surface fields of between 1 and 1.4 Tesla.  Due to the higher specification, these are higher in cost;
    • Bonded – These are weaker in terms of their magnetic properties. The materials are mixed and bonded using a synthetic resin or polymer.  However, due to the manufacturing process the magnetic strength is lower (0.6 to 0.7 Tesla) and they are physically weaker.  Bonded Neodynium Iron Boron is cheaper than sintered versions;
  2. Samarium Cobalt (SmCo5) – All Samarium Cobalt magnets are sintered and the magnetic fields produced range from 0.8 to 1.15 Tesla.  However, these magnets are significantly more expensive than Neodymium Iron Boron, but they are ideal for very high temperature applications.  Whereas standard Neodynium Iron Boron magnets are suitable for applications up to 80° C, Samarium Cobalt and high temperature Neodynmium Iron Boron magnets maintain their magnetic strength at higher temperatures;

In industry, the most common Rare Earth Magnets are Neodynium Iron Boron, but it is worth asking whether the magnets inside the Cartridge or Tube Magnet or Plate Magnet are sintered or bonded.  The vast majority of magnetic separators use the sintered Rare Earth Material as it is physically better and produces a higher magnetic field, but we recommend asking the question to ensure that what is supplied is true value for money and best suited for the application.

Other Magnetic Myths in this series published so far are:

Should you always use the strongest Magnet?

For more information or a site review by our trained sales engineers, please contact us on:

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