Alnico magnetic properties change little with the temperature changes, is still widely used in instrumentation, motors and other requirements of high temperature stability of permanent magnetic devices, especially for torpedos, missiles, aircraft and other weapons and satellites Used in spacecraft. The residual flux density of this material is high up to 1.35T, but their intrinsic coercivity is very low, usually less than 160kA / m, its demagnetization curve is a non-linear change, and Alnico The return line and the demagnetization curve do not coincide, so special attention must be paid to the particularity of the design and manufacturing of the magnetic circuit of the device, and the permanent magnet must be magnetically processed in advance. According to Alnico permanent magnet material with low coercive force, it is strictly forbidden to contact with any ferromagnetic material in the process of using, so as to avoid local irreversible demagnetization or distortion of magnetic flux density distribution. In addition, in order to strengthen its anti-demagnetization capacity, Alnico permanent magnetic pole surface is often designed to grow a long column or long bar. In addition, AlNiCo permanent magnetic materials, low mechanical strength, high hardness, brittle, poor workability, it can not be designed as a structural member, processing can only be a small amount of grinding or EDM, can not be used forging And other machining.