How are ferrite magnets manufactured?

2nd March 2020

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	How are ferrite magnets manufactured?


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			Ferrite magnets are created from a combination of strontium carbonate and iron. To make these magnets, the manufacturers follow these steps:

			Step 1 – Calcination A powdered mixture of iron oxide and strontium carbonate is heated in an induction furnace to temperatures between 1000°C (1832°F) and 1350°C (2462°F) to create a metal oxide.



			Step 2 – Jet milling The metal compound is then ground down to a fine powder and mixed together thoroughly in a process called jet milling.

			Step 3 – Die pressing The powder is mixed with water and die pressed in a machine which places a total of 21000psi of pressure onto it. Whilst the powder is being die-pressed, it is exposed to a magnetic field to magnetise the ferromagnetic materials.

			Step 4 – Sintering The shaped metal is then placed into an electric oven, which heats the metal compound gradually from 250°C (482°F) to 900°C (1652°F).

			The magnets can take from 20 to 36 hours to be heated depending on the quality of the end magnet. A top quality magnet will take a lot longer in the oven than a low quality one, as a slower temperature rise will produce a greater magnetic force. For more information on sintering, see the Magnets glossary

			Step 5 – Machining After the magnets have been removed from the oven and left to cool, they are ground down to the correct size. To do this, an electrical discharge machine will take off millimetres of metal each time until the exact size of magnet is achieved.

			Step 6 – Coating The magnets are then coated to prevent them from oxidising. For more information on the types of platings and coatings, see the page: What are magnets coated with?