Alnico is an alloy containing Aluminium (Al), Nickel (Ni), Cobalt (Co) hence its name Alnico. But Alnico actually contains more than just these three elements. It also contains Iron and Copper with some versions also containing Titanium and even Niobium. Alnico magnets were developed in the 1930’s and were the first “Real” performance permanent magnets. Alnico is produced by either a sintering method or, more commonly, a casting method. The as cast or as sintered shape is acceptable for many applications but surfaces may need to be ground for a smoother surface finish. The as cast look has darkened edges with a slightly rough texture; a machined face of an Alnico magnet has a bright silvery metallic surface and is usually extremely smooth as it is often precision ground.
The most commonly used Alnico is Alnico 5. But care should be used when using this terminology. There are 4 version of cast Alnico 5 plus a single version of sintered Alnico 5. Therefore a request for Alnico 5 could result in different performing magnets due to accidental interpretation of the grade requirement. There are 29 grades of Alnico. Alnico has many trade names used for naming the grades such as Columax, Alcomax 3SC, Alni, Hycomax, Ticonal, etc. China has given them names starting with the letters LNG followed by a number to try to give some clarity but this is not widely utilised. Most people still know Alnico under its more common grade names such as Alnico 5, Alnico 8, Alnico 9, Alnico 5DG, Alnico5-7, Alnico8HC, Alnico 6, Alnico 2, Alnico3, Alnico 500, Alnico 400, Alnico 600 and Alnico 700, etc.
|Grade||Equivalent MMPA Class||Remanence||Coercive Force||Max.energy product||Density||Rev. Temp. Coef.||Curie Temp.||Max. operating Temp.|
|Total||15 alnico magnets Aluminium (Al) Nickel (Ni) Cobalt (Co) magnets|
Alnico magnets are manufactured by a cast or sintered process. Production level cast Alnico magnets are produced by conventional foundry methods using resin bonded sand molds. The magnetic characteristics for some exotic grades of Alnico magnets are achieved during the casting operation and are due to the unique crystalline grain orientation developed during the process.
Sintered Alnico is a powdered metal and it is manufactured by compacting finely milled Alnico powder in a metallic mold. The resulting geometry is not fully dense and it must be sintered in a furnace to achieve a solid state.