Abstract
Fe-Al-C permanent magnet alloy, the products of which have been produced since 1947 under the commercial name of MT magnets, is the unique magnet alloy which possesses comparatively high coercive force of 200 Oersteds containing none of rare metals. In this report, there will be dealt with the results of experiments relative to industrial aspects which are believed necessary to be known by customers, with special emphasis on those basic magnetic properties and experimental data on demagnetization in additions to industrial applications.
The essential magnetic properties are listed in Table 1. The residual induction of MT magnet is nearly equal to one of MK or NKS magnet and the coercive force is nearly equal to one of high Co steel. The stability of magnetic induction over extended period of time is very important in case of electrical instruments or meters. The magnetic aging may be due either to structural change and thermal fluctuation or to external demagnetizing influences such as stray field, mechanical shock, heating or change of reluctance. Effects of various demagnetizing factors on the magnetic stability were investigated accordingly.
In all cases this magnetic change can be related to time and external actions in a logarithmic form. Magnetic aging will be stabilized by means of the previous demagnetizing of alternative field and heating. Thermal coefficient of this alloy for the watt-hour meter is -4.0×10-4/°C and is considerably larger than one of chrome steel.
The application of this magnet to industrial fleld is now being expanded. Among its applications, some are now developed to commercial production with great success. The representative examples of industrial uses are mentioned. By the performance tests of MT and Cr steel for watt-hour meters, it was proved that MT is more stable against demagnetization and maintains higher magnetic flux even with its less weight.
