What is Alnico?
Alnico is an acronym referring to aluminum (Al), nickel (Ni) and cobalt (Co). These elements are combined with iron, copper and sometimes titanium to create permanent magnets that are excellent for high-temperature use and offer good corrosion resistance. Before the development of rare earth magnets in the 1970s, they were the strongest type of magnet.
Adams stocks a variety of shapes, sizes, and grades of Alnico magnets. Alnico 5 is the grade most widely used, but we also offer Alnico 2, 5, 5-7, 7, 8 and 9. Adams provides in-house cutting and grinding to meet your application requirements. We also provide magnetic circuit design assistance to enable you to choose the proper material and the appropriate size magnet to perform the task you require.
Grinding and Tolerances
Alnico is hard and brittle (45-55 Rockwell C), and is not suitable for drilling, tapping or conventional machining operations. Holes are usually rough cast during the foundry process and magnets are cast close to their final size and then finish machined to closer tolerances if necessary. Adams provides in-house cutting and grinding to meet your application requirements.
The most efficient utilization of Alnico magnets requires that they be magnetized after the magnet is assembled in the final magnetic circuit. Shipping the alnico magnets before magnetizing them also eliminates the need for special packaging and prevents contamination by potential contact with ferrous materials.
Temperature Constraints and Demagnetization
Alnico has the best temperature coefficient of any but the most advanced commercial magnet material, providing for excellent stability over a wide temperature range. A properly designed circuit using Alnico magnets will have a stable flux output during temperature fluctuations.
Other Design Considerations
Because Alnico is hard and brittle and not suitable for drilling, tapping or conventional machining operations, it is not usually used as a structural component in product design. We recommend selecting simple shapes when possible, fitting into slots rather than holes. Cross sections of less than .125″ (3.18 mm) should be avoided. Finishing increases cost, so if your application can use “as cast” or “as sintered” then cost will be lower.
For holding applications requiring mounting, or to protect the magnet, alnico assemblies such as rotors or magnetron magnets may be supplied with aluminum housings. Alnico may be painted for aesthetic reasons, like the ever popular red horseshoe magnet.
Alnico Magnet Manufacturing Methods
Most alnico magnets are manufactured using typical foundry casting techniques, where the molten alloy is poured into sand molds. Very small magnets, usually one ounce or less, are produced using press and sinter techniques. Sintered Alnico magnets have features which make them particularly effective in very small precision devices. Sintering magnets with small holes and intricate shapes is possible. Sintered magnets are available in both isotropic and anisotropic form, with a broad range of unit properties. Their magnetic properties are similar but often slightly lower than cast magnets of equivalent grade.
Alnico magnets, cast and sintered, are finished ground using abrasive grinding to produce the final shape and tolerance. Once ground the material is a shiny metallic finish. These materials are brittle and cannot be machined or drilled.
Adams Stock Products Catalog
In addition to a listing of some stock magnets, our catalog includes information about our fabrication capabilities, available in Elmhurst, IL and Carlsbad, CA. You will also find neodymium holding assemblies, a MAGbond Magnetic Media System overview, and high energy wide-format magnetic sheet (40″ wide and still printable!). If you’d prefer to receive a hard copy of this catalog, let us know.
Adams Hard Magnet Materials Catalog
(7MB) This PDF catalog features a magnet materials overview, chart of materials properties and demagnetization curves for Neodymium, Samarium Cobalt, Ceramic (Ferrite) and Alnico materials offered by Adams. New in 2020, we’ve added more curves, and a coatings chart to assist with corrosion protection decisions.
Chart of Material Properties
Displays each permanent magnet material along with its Maximum Energy Product: Bhmax, Residual Flux Density: Br Gauss, Coercive Force: Hc Oersteds, Intrinsic Coercive Force: Hci Oersteds and Maximum Operating Temperature: C / F.
Breakaway Force of a Magnet
Explains the test methods used to determine how much force it takes to pull a magnet directly away from the surface it is attached to.
Standard Specifications for Permanent Magnet Materials
Defines thermal and mechanical characteristics and properties of commercially available permanent magnet materials including Alnico, Ceramic, Rare Earth (Samarium cobalt and neodymium) and Iron-Chromium-Cobalt. Includes a Glossary of Terms and Magnetic Quantities (Symbols, Units and Conversion Factors).
Alnico Magnets Stock Selection
Adams offers a wide selection of Alnico magnet products. Click on your desired product type for stock product specifications.
We stock Alnico rod magnets in Grade 5. We can supply grade 8 upon request. We will grind them to your specifications.
Alnico bar magnets offer excellent temperature stability, high residual induction, and relatively high energies.
Our rotor magnets are made of Alnico 5 material and supplied un-magnetized (magnetization provided after assembly).
Adams supplies Alnico Cow Magnets in Alnico Grade 5. Other types are available upon request.
Alnico channel magnets can be used for holding applications and also for removal of tramp iron from chutes.
Each button magnet includes a metal keeper for storage and to help retain magnetic strength.
Alnico horseshoe magnets provide a compact, high power magnetic source, and are used for traction, lifting, sorting, clamping and retrieval.