Alnico magnets

Star Trace Alnico magnets are made primarily from aluminium, nickel, cobalt, copper, iron and sometimes titanium. They can be either cast or sintered.

Sintered Alnico

Sintered alnico is made from a powdered mixture of ingredients that are pressed into a die under tons of pressure, sintered in a hydrogen atmosphere and then cooled either within a magnetic field or without (anisotropic Vs Isotropic).

Cast Alnico

Cast Alnico melted and poured into a mold. Once solidified, the material is rough ground and then heat-treated and cooled, sometimes in a magnetic field. When treated in the presence of a magnetic field, the magnet is called anisotropic. This orients the material to take on maximum magnetization and allows a higher gauss level. A cast magnet that is not heat-treated in a magnetic field is called Isotropic. After heat treatment and cooling, the material can be ground to specific tolerances and then magnetized.

  • Alnico magnets

Attributes of both Cast and Sintered Alnico

  • Very temperature stable great for high heat applications
  • Maximum working temperature 525o C - 550o C
  • May be ground to size
  • Does not lend itself to conventional machining (Hard and Brittle)
  • High residual induction and energy product compared to Ferrite material
  • Low coercive force compared to Ferrite and rae earth materials (more subject to demagnetization)
  • Most common grades of Alnico are 5 and 8

Applications of Alnico Magnets

Magnetos, Separators, sensors, electron tubes, traveling wave tubes, radar, holding magnets, coin acceptors, clutches and bearings, motors, distributors, relays, controls, generators, receivers, telephones, microphones, bell ringers, guitar pickups, loudspeakers, security systems, cow magnets.

Visual imperfections such as cracks, porosity, voids, surface finish, etc., (commonly found in sintered ceramic magnets) do not constitute cause for rejection.

Magnetizing and Handling

Magnetizing is done after the magnet has been machined to the correct tolerances. Care should be taken when handling alnico material since it is brittle and chip or break if dropped on a hard surface. Also, because it has a low resistance to demagnetization, it will lose power if it is stored improperly (poles repelling each other). For best results, store magnetized alnico so that pieces are attracting each other, or with a steel keeper.


Alnico is a very hard and brittle material and does not lend itself to conventional machining. The STAR TRACE Employs Experienced Machinists and the proper equipment to grind alnico to its require Ship.

Alnico Magnet Materials Specification

Anisotropic Alnico Density Maximun Energy Product BH(max) Residual Imduction BR Coercive Force Hc Intrinsic Coercive Force Hci Maximum Operating Temperature Curie Temperature
g/cm3 MGO Gauss Oersteds Oersteds Co Co
Alnico 5(Cast) 7.3 5.5 12800 640 640 525 860
Alnico 8(Cast) 7.3 5.3 8200 1650 1890 550 860
Alnico 5(Sintered) 6.9 3.9 10900 620 630 525 860
Alnico 5(Sintered) 7.0 4.0 7400 7500 1690 550 860
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