Cast and Sintered Alnico (Al-Ni-Co) Magnets

Cast and sintered Alnico (Al-Ni-Co) magnets, known as Alcomax and Hycomax, are composed of aluminum, nickel, and cobalt. These magnets, developed in the 1930s, are made using traditional foundry casting or sintering techniques. Alnico magnets find use in a variety of applications, including triggering proximity switches like reeds and Hall effects, instrumentation, high-temperature “pot” magnets, holding magnets, horseshoe designs for lifting, entry door locks, non-destructive testing (NDT), magnetic fluid seals, and ferrous separation such as sump plugs.

Alnico magnets boast the best temperature coefficient among permanent magnets (0.02% per degree centigrade), ideal for applications requiring a consistent field across a broad temperature range (-270°C to +500°C).

Their high nickel content grants Alnico magnets stability against corrosion and oxidation, and they also conduct electricity well. However, due to their coarse-grained, hard, and brittle nature, they are not suitable for drilling or conventional machining and should not be used as structural components.

Alcomax, a low coercive force material, should ideally be magnetized post-assembly. Improper handling or exposure to other magnetic fields can impact its effectiveness. In open circuit applications, rod magnets should have a magnetic length about five times their diameter for optimal performance. For instance, a 5mm diameter rod magnet should ideally be 25mm in magnetic length.

The Cobalt content in Alnico magnets contributes to their cost, making them relatively more expensive than other options.

Various Alnico grades are available, each with specific magnetic properties. These include Isotropic Cast or Sintered Alnico 3 and 2, Anisotropic Cast or Sintered Alnico 5 (Alcomax 3), 6, 8 (Hycomax 3), and Anisotropic Cast Alnico 4, 5DG, 5-7, 8HE, 8HC, and 9.

For detailed information and magnetic properties of each grade, please refer to our Data Sheet.