Alnico permanent magnet material was successfully developed in the 1930s. It is the earliest permanent magnet material developed in history. It is an aluminum, nickel, cobalt, iron, and other trace metal elements alloy. Before the discovery of rare earth permanent magnet materials in the 1970s, Alnico alloy was the strongest permanent magnet material. Still, with the advent of ferrite permanent magnets and rare earth permanent magnets, Alnico permanent magnets have been gradually replaced in many applications, and their proportion has been declining.
Classification of Alnico:
Alnico permanent magnet materials have low mechanical strength, high hardness, brittleness, and poor machinability. Therefore, they cannot be designed as structural parts. Only a small amount of grinding or electric spark machining can be performed during processing. Forging and other mechanical processing cannot be used.
Alnico is mainly produced by casting. In addition, sintered magnets corresponding to cast magnets can also be made by powder metallurgy, but the performance is slightly lower. The production process of cast aluminum nickel cobalt [Cast AINiCo]: ingredients - smelting - casting - heat treatment - performance testing - machining - inspection - packaging
The production process of sintered aluminum nickel cobalt: ingredients - powder making - pressing - sintering - heat treatment - performance testing - machining - inspection - packaging
Cast aluminum nickel cobalt can be processed into different sizes and shapes; sintered aluminum nickel cobalt is mainly small-sized products, and the rough dimensional tolerance of the products produced is better than that of cast products, and the magnetic properties are slightly lower than those of cast products, but the machinability is better.
Performance and application of AlNiCo magnets
The advantages of AlNiCo magnets are high remanence (up to 1.35T), and the disadvantages are very low coercive force (usually less than 160KAm) and a nonlinear demagnetization curve. Therefore, AlNiCo magnets are easily magnetized and demagnetized. Special attention should be paid to their particularity when designing and manufacturing the magnetic circuit of the device. The magnet must be stabilized in advance. During use, it is strictly prohibited to contact with any ferromagnetic material to avoid local irreversible demagnetization or distortion of the magnetic flux density distribution.
Among permanent magnetic materials, cast AlNiCo permanent magnets have the lowest reversible temperature coefficient. AlNiCo magnets have good temperature stability and aging stability and are suitable for making instruments, motors, electroacoustic devices, magnetic machinery, etc.