JPH11341749A - Method of annealing iron core in magnetic field - Google Patents

Abstract

PROBLEM TO BE SOLVED: To anneal an iron core easily in a magnetic field, by generating a magnetic field to be applied to an iron core by a coil, and also, heating the iron core by the heat generation from the coil or the application of high frequency magnetic field from the coil thereby annealing it. SOLUTION: E I iron cores 1 and 2 are ones being made of bidirectional electromagnetic steel plates, and currents are let flow to heating wires 3 and 4 so a to heat the E I iron cores 1 and 2. These heating wires 3 and 4 double as windings for magnetic field generation, and generate magnetic fluxes 5 and 6 at anealing, so they are annealed in the magnetic field. Currents are let flow to the heating wires 3 and 4 so as to anneal them for about two hours at about 800 deg.C. In this case, the currents being let flow to the heating wires 3 and 4 are rectangular pulses of 50 Hz in frequency, and the effective value of the currents is adjusted with the control of pulse width so as to adjust the temperature. Then, the quantity of heating is reduced, and they are cooled at the rate of about 100 deg.C/hour, by narrowing the pulse width, with the peak value of the pulse current constant. As compared with the case where they are annealed by usual annealing method, there is little difference in magnetic properties for the ones where the annealing in a magnetic field is applied, and the same effect can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic field annealing for improving the characteristics of a high performance iron core.

[0002]

2. Description of the Related Art Conventionally, as a method for improving characteristics of a magnetic material,
There is annealing in a magnetic field. However, practically, in addition to the annealing furnace, a winding and a power source are required, which leads to an increase in steps and an increase in cost, which is a problem.

[0003]

SUMMARY OF THE INVENTION The present invention provides a method for easily annealing a core in a magnetic field.

[0004]

The feature of the present invention is as follows.
It is as follows. (1) In a method of annealing a core in a magnetic field, in which a magnetic field is applied to the core while applying a magnetic field to the core, a magnetic field to be applied to the core is generated by a coil, and the core is heated by heat generation from the coil or application of a high-frequency magnetic field from the coil. Annealing in a magnetic field, characterized by performing annealing by magnetic field.

(2) The magnetic field annealing method according to (1), wherein the magnetic field applied to the iron core corresponds to a magnetic flux flow in a use state of the product.

(3) The magnetic field annealing method according to the above (1) or (2), wherein the annealing temperature is at least 100 ° C. lower than the Curie point of the iron core material.

(4) The magnetic field annealing method according to the above (1) or (2), wherein an iron core made of an electromagnetic steel sheet is used and the annealing temperature is 600 ° C. or more.

(5) The peak value of the current flowing through the winding is controlled so that the maximum value of the generated magnetic field is at least twice the coercive force of the iron core material at room temperature. The method according to (1), (2), (3) or (4), wherein the heating temperature of the iron core is controlled by changing the effective value of the current by changing the waveform. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A core is a motor, an actuator,
Used for energy conversion devices such as transformers, electric circuits such as inductors and reactors, used for control circuit elements, used for sensors, and used for generating magnetic flux or magnetic field. It is used to detect the physical quantity or chemical quantity to be detected by using the operation of the generated magnetic flux or magnetic field, or by using the magnetic phenomenon.

The iron core is a general soft magnetic material, and may be an amorphous magnetic material, an electromagnetic steel sheet or a laminate thereof, or may be a combination of a plurality of divided iron cores.

[0011] Electromagnetic steel is generally used as the iron core material.
It is a silicon steel sheet containing Si, a cold rolled steel sheet containing little or no Si, or an electromagnetic thick plate, and may be a plate-shaped, lump-shaped, or linear-shaped one. The method for producing the electromagnetic steel may be any method. The plate-shaped electromagnetic steel sheet may have any thickness, and includes a thin plate having a thickness of 0.2 mm or less other than the commonly used 0.35 mm and 0.5 mm. Non-oriented electrical steel sheet,
There are a grain-oriented electrical steel sheet, a bi-directional electrical steel sheet and the like, but an electrical steel sheet having any texture may be used.

In the present invention, when the iron core is annealed in a magnetic field, the winding for generating the magnetic field is a heat generating means for annealing the iron core. The method of heating the iron core by the winding includes a case where the winding itself is a heating element and a case where high frequency heating is performed by the winding. As the heating element, any heating element may be used, such as a nichrome wire, a Kanthal wire, or a silicon knit. When high-frequency heating is used, a high-frequency magnetic field is generated by a winding, and heat generated by iron loss generated in an iron core is used. The magnetic field used in the magnetic field annealing may be not only a direct current but also an alternating magnetic field or a rotating magnetic field.

The magnetic field used for the annealing in the magnetic field preferably corresponds to the magnetic flux flow when the iron core is actually used. The annealing temperature was set at 10 from the Curie point as shown in Example 2.
If the temperature is lower than 0 ° C., the effect is great. The annealing temperature can be increased as long as recrystallization or the like does not adversely affect the magnetic properties of the iron core. In the iron core made of the magnetic steel sheet, the annealing temperature is preferably 600 ° C. or more as in the third embodiment. It is preferable that a magnetic field is applied during cooling, but it is not always necessary to maintain the magnetic field at a certain level or more in a low temperature range where there is no annealing effect in a magnetic field.

In the present invention, both heating and application of a magnetic field are performed by a current flowing through a winding. The current is periodically maintained at a predetermined value or more, and the waveform of the current is controlled. It is preferable to control the heating temperature. Here, the predetermined value is the minimum current value necessary for annealing in a magnetic field, and the maximum value of the magnetic field generated by energizing the winding is at least twice the coercive force of the iron core material at room temperature. Is the minimum current value that can maintain the value of. Note that the coercive force of the iron core material refers to a value when excited so that the maximum magnetic field of excitation / coercive force> 10. As described above, annealing in a magnetic field while applying a magnetic field that is at least twice the coercive force of the iron core material is not performed sufficiently even when a magnetic field less than that is applied. This is because a desired magnetic flux density cannot be obtained in the magnetic field direction.

In order to control the heating temperature by controlling the current waveform, a current-type pulse width modulation method (PWM method) may be used. When the resistance heating value of the winding is controlled by using the PWM method, the heating can be increased even if the magnitude of the peak current is constant by increasing the modulation duty, and the magnitude of the peak current can be increased by decreasing the modulation duty. Even if the temperature is constant, the heating can be weakened and the cooling process can be controlled. On the other hand, if the cycle of the current is too short, eddy current loss occurs in the iron core, making it difficult for the magnetic flux to flow through the iron core.Therefore, the cycle of the peak value should be longer than the time at which the magnetic flux can respond at room temperature. If the length is too long, the effect of annealing in a magnetic field is reduced. Therefore, it is necessary to set the range so that the effect of annealing in a magnetic field can be maintained. There is also a method of using a high-frequency current having a short peak value cycle after sufficiently increasing the peak current value to sufficiently secure the annealing effect in a magnetic field.

[0016]

Embodiment 1 FIG. 1 shows an embodiment in which an EI iron core is annealed in a magnetic field. The EI cores 1 and 2 are made of a bi-directional electrical steel sheet.
Heat the iron cores 1 and 2. These windings 3 and 4 also serve as magnetic field generating windings, and generate magnetic fluxes 5 and 6 at the time of annealing, so that they are annealed in a magnetic field. Apply current to the heating wires 3 and 4
Anneal at 00 ° C. for 2 hours. In this case, the current flowing through the heating wires 3 and 4 was a rectangular pulse having a frequency of 50 Hz, and the effective value of the current was adjusted by pulse width control to adjust the temperature. afterwards,
The peak value of the pulse current was constant, the amount of heating was reduced by narrowing the pulse width, and cooling was performed at 100 ° C./hour. Compared to the case of annealing by the conventional annealing method (a method in which a magnetic field generating winding is separately applied), the one subjected to the magnetic field annealing of the present invention has almost no difference in magnetic properties, and the same effect is obtained. .

Embodiment 2 FIG. 2 shows an embodiment in which a wound iron core is annealed in a magnetic field. The iron core 11 is made of an iron-based amorphous magnetic material Fe
_{It is made of 80.5} B ₇ Si ₁₂ C _0.5 (Curie temperature 410 ° C).
Heat to 75 ° C. The reference numeral 12 also serves as a magnetic field generating winding and generates a magnetic field during annealing, so that it is annealed in a magnetic field. In this case, a power supply for supplying a current to the heating wire 12 is adjusted by current-type pulse width control at a carrier frequency of 1 kHz. After that, the peak value of the pulse current is constant, and the pulse width is narrowed to reduce the amount of heating, and 100 ° C /
Cooled in time. Magnetic properties comparable to conventional magnetic field annealing were obtained.

Table 1 shows the results obtained when the temperature was lower than the Curie temperature by 100 ° C. and higher than the Curie temperature in addition to the annealing temperature of 375 ° C. Temperature 3 which is 100 ℃ lower than Curie temperature
It can be seen that even at 10 ° C., both the magnetic flux density and the iron loss are improved.

Next, Table 2 shows the results of annealing in a magnetic field performed by changing the effective value of the applied magnetic field. Applied magnetic field is 40
Annealing in a magnetic field of 0 A / m and 1200 A / m was performed by the method of the present invention, and the others were comparative examples. In the comparative example, annealing was performed without a magnetic field using a heating furnace as in the related art, or annealing in a magnetic field was performed using a heating furnace and applying a magnetic field using a normal magnetic field application winding as in the related art.

[0020]

[Table 1]

[0021]

[Table 2] Example 3 E made of non-oriented electrical steel sheet 50A700
The iron core was annealed in a magnetic field by the method of the present invention. The method was the same as in Example 1, except that the annealing temperature was changed. With respect to the iron loss value in the case of no annealing, the iron loss is 0.9 times at 600 ° C., 0.75 times at 700 ° C., and 0.65 times at 750 ° C.
In the case of non-oriented electrical steel sheet, the temperature of magnetic field annealing is 600 ° C.
It can be seen that the above is effective.

[0022]

The magnetic field annealing according to the present invention is a heating wire used for heating, and a magnetic field for annealing in the magnetic field is also generated at the same time, so that no separate winding for generating a magnetic field is provided. A power supply for heating and a power supply for generating a magnetic field can be shared. Therefore, it does not require an annealing furnace and is very economical.

[Brief description of the drawings]

FIG. 1 shows an embodiment in which an EI core is annealed in a magnetic field.

FIG. 2 shows an embodiment in which a wound core is annealed in a magnetic field.

[Explanation of symbols]

 1, 2, 11: Iron core 3, 4, 12: Heating wire and magnetic field generating winding 5, 6: Magnetic flux

Claims (5)

[Claims] In a method for annealing a core in a magnetic field, wherein the magnetic field is applied to the core by applying a magnetic field to the core, a magnetic field to be applied to the core is generated by a coil, and the core is heated by the coil or by applying a high-frequency magnetic field from the coil. A method for annealing in a magnetic field, comprising annealing by heating. 2. The magnetic field applied to an iron core corresponds to a magnetic flux flow in a use state of a product.
The described annealing method in a magnetic field. 3. The annealing temperature is set at 1 from the Curie point of the iron core material.
3. The method for annealing in a magnetic field according to claim 1, wherein the temperature is lower by at least 00.degree. 4. The method for annealing in a magnetic field according to claim 1, wherein an annealing temperature is set to 600 ° C. or more using an iron core made of an electromagnetic steel sheet. 5. A method for controlling a peak value of a current flowing through a winding so that a maximum value of a generated magnetic field is equal to or more than twice a coercive force of an iron core material at room temperature. 5. The magnetic field annealing method according to claim 1, wherein the heating temperature of the iron core is controlled by changing the waveform to change the effective value of the current.