Alnico magnets and their different uses

Alnico magnets were the strongest permanent magnets that existed until the introduction of rare earth magnets and, although somewhat displaced, Alnico magnets are still commonly used in various industries for specific jobs such as high temperature handling equipment and sensor manufacturing, among others.

Alnico magnets have long life, excellent temperature stability, high residual induction and relatively high energies due to their composition, a combination of aluminium (al), nickel (ni) and cobalt (co).

This development and introduction of Alnico meant that expensive electromagnets could be replaced with these permanent magnets in essential devices such as motors and generators.  But despite not having the prominence of years ago, Alnico magnets still perform better than their successors in specific situations and, therefore, are still used for many applications that require a very high temperature concentration such as;

  • Electric motor.

  • Microphones.

  • Engineering applications.

  • Aerospace applications.

  • Military applications.

  • Commonly used for various types of sensors.

In addition, Alnico magnets are widely used in rotary machinery, meters, instruments, detection devices and retention applications, to name a few.

It should be noted that Alnico is hard and brittle. Therefore, machining or drilling cannot be done by ordinary methods. Holes are usually drilled in the foundry, magnets are molded near the final size and then machined to closer tolerances.

Likewise, Alnico magnets have high magnetic resistance and low resistance to demagnetization and remagnetization.

Main elements of the Alnico     Percentage in weight
Aluminium (Al)     6% - 13%
Nickel (Ni)     13% 26%
Cobalt (Co)     0% - 42%
Copper (Cu)     2% - 6%
Titanium (ti)     0% -9%
Niobium (Nb)     0% -3%
Iron (Fe)    Balance (e.g. 30% -40%)

Advantages of Alnico magnets

  • Excellent temperature stability up to 1,000F.

  • High residual induction.

  • Alnico's corrosion resistance is considered excellent and no surface treatments are required.

  • Past Alnico magnets can be produced in relatively complex shapes.

Disadvantages of Alnico magnets

  • They can be demagnetized more easily than other magnetic materials.

  • They are relatively expensive, as they contain nickel and cobalt.

  • Alnico clot magnets often have cast pores and voids, which can be problematic for appearance and magnetic flux.

Their uses are based on their strength

Unlike, for example, ferrite magnets, Alnico magnets are generally stronger and are electrically conductive, while they are less fragile than most rare earth magnets and can produce a strong magnetic field. In addition, Alnico magnets can operate at the highest temperatures of any magnetic material and maintain their magnetism even when they are red-hot.

How is this possible? Because of its composition. Alnico magnets are manufactured by casting or sintering processes. Under the first mode of manufacture, a molten metal alloy is poured into a mold and then passed through several heat cycles. The final product is a magnet with a dark grey exterior, with a rough surface, but the machined magnet surfaces have a glossy appearance.

In the second way, they are manufactured by compacting fine Alnico powder in a press and then sintering the compacted powder into a solid magnet.

The typical composition of the Alnico alloy is:

If you are interested in learning more about Alnico magnets, at IMA we have a wide variety of them and help you choose the right model for your needs. If you have any questions, ask us.

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