JPS61121406A - Demagnetizing method of permanent magnet - Google Patents

Abstract

PURPOSE:To make a residual flux in a magnet very small and to treat a large quantity of magnet in a short time with a small demagnetizing device by demagnetizing in alternating current through heating a mangan-aluminium- carbonaceneous alloy magnet into a specific temperature. CONSTITUTION:An oscilation circuit is formed out of a Slidak 1 for voltage adjustment, a diode 2 for rectification, a condenser 3 and a coil 5, and is provided with a bidirectional thyristor 4. A heated magnet 6 is put into a cylinder of the coil 5. This mangan-aluminium-carbonaceneous alloy magnet 6 is heated into 160 deg.C-300 deg.C, and demagnetized in alternating current. By using this damagnetizing method, with a small demagnetizing device, a residual flux in the magnet is made very small and a large quantity of ma-gnet can be treated without discoloration in a short time.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for demagnetizing a permanent magnet.

Conventional Structures and Problems Conventionally, there have been various methods for demagnetizing permanent magnets, including heating the magnet to a temperature above one cubit. In the case of manganese-aluminum-carbon alloy magnets, it is possible to demagnetize them by heating them to 350°C to 450°C, but when processing large quantities, it takes 6 hours to heat and cool, and the magnet surface may discolor. This required surface polishing, which resulted in high work costs.

Other demagnetization methods include using an attenuating alternating current magnetic field, but manganese-aluminum-carbon i-based alloy magnets
Because the coercive force is large, a large peak magnetic field is required, that is, a large demagnetizing device is required.Furthermore, due to the electric discharge property, the magnitude of the demagnetizing magnetic field at the center and outer part of the magnet is reduced due to the influence of eddy currents. However, it is difficult to uniformly demagnetize the entire
1.

Purpose of the Invention The present invention eliminates these conventional drawbacks, and uses a small demagnetizing device to reduce the residual magnetic flux within the magnet, and can process a large amount of magnets in a short time, and also eliminates surface discoloration. This provides a demagnetization method that does not cause demagnetization.

Structure of the Invention To achieve this objective, the EiA of the present invention heats a manganese-aluminum-carbon alloy magnet to 160°C to 300°C and demagnetizes it with alternating current. residual magnetic flux? Very small, maf? :
, a large amount of magnets can be processed in a short time.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a demagnetizing device used in the present invention. In Fig. 1, 1 is a slider for voltage adjustment, 2 is a diode for rectification, 3 is a capacitor for fully charging electricity, and together with the coil 6, it forms a complete resonant circuit, 4 is a bidirectional thyristor, 5 Outer diameter φ60, inner diameter φ10 KM + length 6
0 rrun coil, inner diameter φ10 min & length 5
A heated magnet 6 is placed in a cylindrical shape with a diameter of 0 mm.

FIG. 2 shows the waveform of the attenuating alternating current magnetic field inside the coil.

In FIG. 2, 7 is the peak value of the alternating magnetic field.

The results of the examples are shown in Table 1.

Table 1 When the method of the present invention is applied to reduce the residual magnetic flux density within the magnet to approximately 20 G or less (a level that does not cause any practical problems), the heating temperature of the magnet will be thermally demagnetized (s5oC to 4oC) as shown in Table 1.
It becomes possible to reduce the temperature to about % or less of the time (oc). Therefore, not only can the time required for heating and cooling the magnet be significantly shortened, but also an inexpensive heating device can be used. In addition, since the magnet has a low temperature (3ooC or less), surface discoloration does not occur, and post-processing polishing is not required.

Furthermore, the peak value of the demagnetizing magnetic field i12. It is possible to reduce the power from o000e to (5oO~2.0Q00e), which is common as a power supply.
o Hz Mano can also use a 60Hz power supply.

Furthermore, the residual magnetic flux density inside the magnet is approximately 50G in the conventional method.
However, if the method of the present invention is applied, the demagnetization effect can be improved to 15G or less, which is sufficient for practical use.

By using the demagnetizing method of the present invention as described above,
A small demagnetizing device reduces the residual magnetic flux inside the magnet to a very low level.
Furthermore, it becomes possible to process a large amount of magnets in a short period of time without discoloration, which is extremely advantageous in practice.

[Brief explanation of the drawing]

Figure 1 is a groove bottom view showing the demagnetizing device used in the present invention, Figure 2 is a groove bottom view showing the demagnetizing device used in the present invention.
The figure is a waveform diagram of the alternating current magnetic field of the demagnetizing coil. 5... Demagnetizing coil, 6... Magnet. Figure 1, Figure 2! ! ! I

Claims (1)

[Claims] Manganese-aluminum-carbon alloy magnet from 160℃
A method for demagnetizing a permanent magnet, characterized by heating it to 300°C and demagnetizing it with alternating current.