How are neodymium magnets made?

Neodymium is a metal which is ferromagnetic meaning that like iron it can be magnetized to become a magnet.

Neodymium magnets are made by a sophisticated process that includes some very high-tech metallurgical methods comprising powder metallurgy and advanced process metallurgy.

Composition of neodymium magnets

Neodymium magnets are made from an alloy of neodymium, iron and boron to form the Nd₂Fe₁₄B structure.  The exact ingredients depend on the strength and on the grade of magnet being manufactured.

The strength of neodymium magnets is the result of several factors.  Like other magnets, the neodymium magnet alloy is composed of microcrystalline grains which are aligned in a powerful magnetic filed during the manufacturing process so their magnetic axes all point in the same direction.  It then gives the compound a very high coercivity (resistance to being demagnetized).

To increase the coercivity of the alloy and their resistance to demagnetisation and corrosion we can also add dyprosium.  Dyprosium is the element that has the highest magnetic strength of all elements.

The magnetic energy value of a neodymium magnet is about 18 times greater than ceramic magnets by volume and 12 times by mass. 

How are magnets made?

In practice, the magnetic properties of neodymium magnets depend on the allow composition, microstructure and manufacturing technique employed.

Here are the main manufacturing process steps:

Melting

Sintered neodymium magnets are prepared by the raw materials being heated melted in a vacuum induction furnace to form the alloy material.  Then it is cast into a mold and cooled to form ingots.

Milling

Jet milling turns the resulting material into a powder with a very small particle size.  The average particule size is 3 micrometers.  One micrometer being one-millionth of a meter.  The smallest particles we can see with our eyes are those larger than 50 micrometers.

Pressing

The powder enters a mould and is pressed between plates while under a strong magnetic field forming a block of material.  The magnetic field orients the grains so that the magnetic domains remain aligned in the designed direction.  

Sintering

The material is compressed at elevated temperatures until its particles adhere to each other.

Cutting, machining and grinding.

At this stage the sintered magnets are cut to the desired shape.  Due to all of the prior steps, the neodymium magnet have had a lot of value added.  In this process waste is kept to a minimal by design.  Waste material is reused and recycled.

Coating

Since unplated neodymium magnets are prone to corrosion, and will quickly lose their magnetic properties in the presence of moisture, it is imperative to add a coating.

The baseline treatment is nickel-copper-nickel (Ni-Cu-Ni) electroplate, which protects the magnet from corrosion.

Other coatings with greater protection then Ni-Cu-Ni can be offered.  For example, Aluminum-Zinc coating offers much greater protection than Ni-Cu-Ni.  Epoxy coating is very good for intense environments.  Rubber or PTFE coating is also available on large quanitities.

Testing

Testing and evaluation are performed at almost every process step.  Rigourous testing insures only top-quality products are shipped to the customers. 

Magnetizing

At this point, the magnets have a preferred direction of magnetization, but they are not magnetized.  The material is placed inside an electric coil which is energized to produce a very strong magnetic field.

In conclusion

Making a neodymium is not simple.  It takes several steps to achieve a high quality magnet.

As you may have noticed, it is not easy to machine a neodymium magnet and we don't not recommend trying to machine them.

Neodymium magnets are very strong but also very brittle and can break under impact.  Please handle them with care.

If you are looking for a special shape or application please contact our sales representative in order to obtain assistance.

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