> A Range of Applications of Permanent Magnets
Hard ferrites magnets have three major applications: acoustics (rings), motors (segments) and holding instruments (including magnet separators). The largest share goes to acoustics, followed by motors and holding instruments. Within these categories, applications of hard ferrites vary in different countries. Holding instruments refer to applications that make use of the tractive and/or repelling force of the magnet—i.e., the attraction between a magnet and a soft magnetic material, such as a piece of iron or steel, or the attraction or repulsion between two magnets—to do mechanical work. The applications in this category include magnetic separators, magnetic holding devices (such as magnetic latches), magnetic torque drives and magnetic bearing device, among others. The sidebar shows 15 major application areas for NdFeB permanent magnets.
Samarium magnets is combined with cobalt to create a permanent magnet with the highest resistance to demagnetization of any known material. Because of its ability to take continuous temperatures above 250°C, it is essential in both aerospace and military applications. Precision-guided munitions use SmCo permanent magnet motors to direct the flight control surfaces (fins). SmCo can be used as part of stealth technology in helicopters to create white noise to cancel or hide the sound of the rotor blades. These permanent magnets are also used as part of aircraft electrical systems, and to move flight control surfaces of aircraft, including flaps, rudder and ailerons. Samarium is used in both missile and radar systems’ traveling wave tubes (TWTs). SmCo magnets are used in defense radar systems, as well as in several types of electronic counter-measure equipment, such as the tail warning function.
Although there is serious competition from other types of magnets, such as ferrite and RE magnets, alnico magnets is still widely used for meters (e.g., watt-hour meter, voltmeter, ampere meter, mileage meter), acoustic devices, motors, and sensors in automobiles and motorcycles, due to its excellent thermal stability. The biggest application for produced alnico is the watt-hour meter. Its absolute output tonnage has increased slightly, although its output percentage has significantly decreased. Alnico magnets are also used in communications, aerospace and defense, industrial and consumer products, meters, and instrumentation.
The historical intention for developing bonded neo was to compete with hard ferrites (non-bonded), which are the most-used magnet material in the world (by weight). Today, because of the flexibility offered in making different shapes and sizes, bonded magnets find a wide range of applications.
With the increase in the cost of producing bonded ferrite magnets, the industry has shifted from developed countries to developing countries, including China, just as has happened for other types of magnets. The use of bonded magnets in each country is different. Therefore, the direction in which the industry develops in each country is also different.