AlNiCo permanent magnet material is developed successfully in the 1930s, it is the first developed in history of a permanent magnet material, is an alloy composed of aluminum, nickel, cobalt, iron and other trace metal elements. Before the discovery of rare earth permanent magnet materials in the 1970s, AlNiCo alloy was the strongest permanent magnet materials. But with the advent of ferrite permanent magnet and rare earth permanent magnet, AlNiCo permanent magnet was gradually replaced in many applications, and its proportion showed a declining trend.
Classification of AlNiCo
AlNiCo permanent magnet material has low mechanical strength, high hardness, crisp quality and poor machinability, so it can not be designed as structural parts. It can only carry out a small amount of grinding or electric discharge machining during processing, and can not use forging and other mechanical processing.
AlNiCo is mainly produced by casting method. 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 AlNiCo” is as follows: batching → smelting → casting → heat treatment → performance testing → mechanical processing → inspection → packaging
The production process of “Sintered AlNiCo” is as follows: batching → powder making → pressing → sintering → heat treatment → performance testing → machining → inspection → packaging
Casting AlNiCo can be processed into different sizes and shapes; Sintered AlNiCo is mainly small size products, the size tolerance of the blank produced is better than that of cast products, magnetic properties are slightly lower than cast products, but the machinability is better.
Properties and applications of AlNiCo magnets
AlNiCo magnet has the advantages of high remanence (up to 1.35T), low coercivity (usually less than 160kA/m) and nonlinear demagnetization curve, so AlNiCo magnet is easy to be magnetized, but also easy to demagnetize. Special attention should be paid to its particularity in the design and manufacture of magnetic circuit of devices, and the magnet must be stabilized in advance. It is strictly prohibited to contact with any ferromagnetic material during use, so as not to cause local irreversible demagnetization or distortion of flux density distribution.
Among permanent magnet materials, casting AlNiCo permanent magnet has the lowest reversible temperature coefficient. AlNiCo magnet has good temperature stability and aging stability, and is suitable for making instruments, motors, electroacoustic devices, magnetic machinery, etc.