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How are alnico magnets manufactured?

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Alnico deep pot magnet Alnico magnets are made from a combination of aluminium, nickel, cobalt, iron and copper. To create these magnets, manufacturers usually follow these steps:
Strip casting alnico

Step 1 – Strip casting

First, a combination of aluminium, nickel, cobalt, iron and copper are ground up and melted in a large oven at 14426.7°C (26000°F).

Wonkee Donkee says "Strip casting is the name given to heating up a group of different metals until they are molten and then cooling them down together into a solid"
Ball milling making magnet powder

Step 2 – Milling

The metal compound is ground down to a fine powder and mixed together thoroughly in a ball mill.

Die pressing machine steps

Step 3 – Die pressing

The powder is then weighed and put in a die pressure machine which places a total of 21000psi of pressure onto it. The die is usually the shape of the final magnet, so should not need any further shaping.

PSI is the amount of pressure there is Per Square Inch, inside the machine.

Time

Step 4 – Sintering

The shaped metal is placed into an electric oven. The oven heats the metal compound gradually from 250°C (482°F) to 900°C (1652°F).

Extremely hot thermometer 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 information on sintering, see the Magnets glossary

Cooling

Step 5 – Cooling

After heating, the magnets are removed from the oven and left to cool.

Zinc plated disc magnet

Step 6 – Coating

The magnets are then coated. For more information on the types of coatings, see our page: What are magnets coated with?

Magnetising

Step 7 – Magnetising

Finally, the mixture is magnetised. A magnetising machine envelops the magnet in a high strength magnetic field by sending 2400 volts electrical current through the magnet to create a permanent alnico magnet.

For information on permanent magnets, see the Magnets glossary