JPH0736943B2 - High-permeability soft magnetic fiber and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-permeability soft magnetic fiber having extremely easy magnetization and a method for producing the same.

[Prior Art] A magnetic material such as silicon steel is used by stacking a plurality of thin materials after punching a thin material into a certain shape so as to be suitable for AC excitation. That is, the purpose is to reduce eddy current loss and hysteresis loss in AC excitation, and when a magnetic material is excited in a high frequency region, the magnetic material is further subdivided to reduce iron loss and magnetic permeability. It is necessary to improve the dynamic characteristics.

By the way, as technological innovation progresses, demands for miniaturization and weight reduction of electronic / electromagnetic devices are increasing more and more, and in order to meet such demands, improvement studies on small magnetic materials are being actively conducted.

As one method for downsizing or subdividing an electromagnetic device, it is conceivable to form a magnetic material into a fibrous shape. In order to enhance the magnetic characteristics of the fibrous magnetic material,
It is important to reduce defects such as crystal grain boundaries and impurities and internal strain so that the structure is easily magnetized. Moreover, in order to obtain a highly permeable soft magnetic fiber having anisotropy in the fiber axis direction,
It is necessary to align the easy axis of magnetization of the crystal with the fiber axis of the soft magnetic fiber.

[Problems to be Solved by the Invention] Under the circumstances as described above, the present invention facilitates magnetization by minimizing crystal grain boundaries and internal strain of a fibrous material made of a magnetic material, and facilitates magnetization. An object of the present invention is to provide a soft magnetic fiber having a very large relative magnetic permeability and a high level of magnetic permeability by providing structural characteristics in which the axis direction is aligned with the fiber axis direction, and a method for producing the same.

[Means for Solving Problems] The high-permeability soft magnetic fiber according to the present invention has a diameter of 100 μm or less and a relative magnetic permeability of 90,000 in a DC magnetized state.
The above is the gist, and such a high magnetic permeability soft magnetic fiber uses a magnetic material that is easily magnetized, and by melt spinning, the primary arm of the dendritic crystal is oriented in the fiber axis direction. It can be obtained by producing magnetic fibers having a dendritic structure with an angle within 20 degrees, preferably within 5 degrees, and having a diameter of 100 μm or less, and then performing heat treatment to reduce grain boundaries and internal strain as much as possible.

[Operations and Examples] As described above, the high magnetic permeability soft magnetic fiber of the present invention has a diameter of 10
It is very thin, 0 μm or less, and has a high level of relative magnetic permeability of 90,000 or more in a DC magnetized state. Here, the diameter of the fiber is set to 100 μm or less because, in the case of a large diameter fiber exceeding this value, sufficient directivity is not given to the fiber structure as will be described in detail later, and the high level of relative permeability as described above. This is because it cannot be secured. Further, the lower limit of the relative magnetic permeability in the direct-current magnetized state is set to 90,000 because if it is less than 90,000, the required characteristics as the high magnetic permeability soft magnetic fiber intended by the present invention cannot be satisfied.

There are various possible magnetic materials used in the present invention. Among them, Fe-Si alloys, Fe-Al alloys, and Fe-Si-Al alloys most effectively exhibit the characteristics of the present invention. Among these iron alloys, one containing one or more rare earth metals in an appropriate amount is also preferable. In addition, it is particularly preferable that the rare earth metal has an atomic number
It is selected from the lanthanum series of 57 to 71, specifically, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,
Lu, which may be contained alone or in combination of two or more. Among the above rare earth metals, Ce is particularly preferable. Further, in carrying out the present invention, it is possible to further mix other components depending on the use and required characteristics of the soft magnetic fiber.

By the way, as a method for producing a soft magnetic fiber having a high magnetic permeability as described above, a magnetic material is melt-spun and a primary arm of a dendrite is softly grown at an angle within 20 degrees with respect to the fiber axis direction. A method in which a magnetic fiber (see FIGS. 4 (a) and 4 (b)) is heat treated to remove internal strain, and dendrites disappear to homogenize the magnetic fiber can be used.

Examples of the melt spinning method include a glass coating spinning method, a water spinning method, and a rotating liquid spinning method. Among them, particularly preferred is a spinning solution as disclosed in JP-A-55-64948. Medium spinning method. 1 and 2 are a schematic front view and a partial cross-sectional side view illustrating the method, and FIG.
By rotating at high speed, the cooling liquid layer 8 is formed on the inner peripheral surface side. Then, toward the liquid surface 9 of the liquid layer 8,
The molten magnetic material is ejected from the ejection nozzle 2 on the lower surface of the crucible 1, and the magnetic material is made into a thin wire 4 and rapidly cooled and solidified, and wound around the inner peripheral wall of the rotary drum 6. In the figure, 3 is a heater for melting the magnetic material, 5 is an inert gas for ejecting the molten magnetic material, 7 is a motor, and 10 is a belt. If the peripheral velocity of the rotating cooling liquid layer is set to be substantially the same as or slightly higher than the ejection velocity of the molten magnetic material from the ejection nozzle 2, magnetic fibers having good cross-sectional uniformity can be easily obtained. . The cooling liquid used here may be a pure liquid, a solution, an emulsion or the like, but water is most preferable in terms of cost and cooling efficiency. The rotating drum may be horizontal or vertical, but the surface velocity of the cooling liquid layer in the drum is 300 to 900 m / mi.
n, the penetration angle of the molten magnetic material into the cooling liquid layer is 40 to 8
0 °, the distance between the jet nozzle 2 and the liquid surface 9 of the cooling liquid layer 8 is
0.5 to 10 mm is suitable for each. In this case, it should be noted that the diameter of the jet nozzle 2 should be 100μ.
The diameter of the spun magnetic fiber must be 100 μm or less. However, when the diameter of the jet nozzle 2 exceeds 100 μm, the growth direction of the dendrite primary arms with respect to the fiber axis direction is not aligned within 20 degrees in the internal structure, and the heat treatment as described below is performed to crystallize. Even if grain boundaries and internal strain are reduced as much as possible, the above-mentioned soft magnetic fiber having high magnetic permeability cannot be obtained. The reason why the above-mentioned structure is formed by setting the diameter of the fiber to 100 μm or less, the details of the mechanism are not clear, but from the observation result of the internal structure and the crystal orientation of the obtained fiber, the following is obtained. You can think like. That is, the cooling rate in the cooling liquid layer changes due to the difference in the thickness of the jet flow of the molten magnetic material, and the crystal growth and growth conditions change, so that the crystal growth direction is aligned with the fiber axis direction. It is presumed that the orientation of the primary arm was maintained even after the dendrites disappeared, which had a favorable effect on the orientation of the crystals.

The heat treatment should be appropriately determined according to the type of magnetic material so that the internal strain is eliminated and the dendrites formed during fish coagulation are substantially eliminated, and the purpose of homogenization can be achieved. As a standard, the temperature is lower than [solidus temperature of the magnetic material −10 ° C.] and [1 / the melting point of the magnetic material] so that the fibers can be homogenized in a short time without melting.
3] It is better to do it in the temperature range above. Further, it is desirable that the heat treatment is performed in a vacuum or in an atmosphere of an inert gas such as argon in order to prevent the fiber surface from being oxidized.

For example, Fe-5.7 wt% Si alloy is used as the magnetic material, and the diameter of the jet nozzle (corresponding to the diameter of the spun fiber) at the time of spinning in the rotating liquid as described above is 150 μm or 95
After the magnetic fiber was set to μm and heat-treated at 1000 ° C. for 1 hour, the DC magnetization curve at room temperature when a DC magnetic field was applied in the fiber axis direction was examined. Specific maximum magnetic permeability of fiber is 53,00
The value is as low as 0, whereas the diameter is 95 μm.
The specific maximum magnetic permeability of the small-diameter magnetic fiber was 121,000, which was more than doubled. In addition, Fig. 3 shows that the magnetic fibers spun in the same manner as above using the same materials as above
Shows the magnetic permeability of the relative magnetic permeability (vertical axis) (horizontal axis) of the magnetic fiber heat-treated for 2 hours at 95 μm in diameter as compared with the thick magnetic fiber in 150 μm in diameter. , Shows a large relative permeability in each frequency band.

In order to elucidate the reason why the soft magnetic properties are remarkably improved by reducing the diameter of the magnetic fiber, the internal structure of the fiber was examined, and the following facts were confirmed. That is, in the large diameter magnetic fibers having a diameter of more than 100 μm, there are many magnetic fibers in which the primary arm growth direction of the dendrites exceeds 20 ° with respect to the fiber axis direction before heat treatment.
The growth direction of the primary arms of the dendrites in the magnetic fibers having a diameter of 100 μm or less was all within 20 ° with respect to the fiber axis direction. After further heat treating these to reduce the crystal grain boundaries and internal strain, the crystal orientation of the heat treated fiber was examined by the etch pit method. The crystal orientation of the heat treated fiber reflects the structure before heat treatment. There are many specific crystal orientations that exceed 20 degrees with respect to the fiber axis direction, whereas in thin magnetic fibers, the specific crystal orientation is within 20 degrees with respect to the fiber axis direction. It was confirmed that they were even. It is known that the direction of easy magnetization has a certain relationship with the crystal orientation. For small-diameter magnetic fibers with a diameter of 100 μm or less, the direction of the fiber axis is as described above.
The dendrite primary arms before heat treatment aligned at an angle of 20 degrees or less are effectively reflected even after the reduction of grain boundaries and internal strain, resulting in a magnetic fiber with easy magnetization and extremely strong anisotropy, It is considered that these had a favorable effect on the improvement of magnetic permeability.

In addition, the fact that the number of crystal grain boundaries is extremely small means that the toughness and flexibility are excellent, and it is a material that is extremely easy to handle including secondary processing.

The high-permeability soft magnetic fiber thus obtained can be used as a small soft magnetic material as it is,
It is also possible to bundle a large number of the fibers coated with an insulating film by an appropriate method and use them as a soft magnetic material having excellent high frequency characteristics.

For example, when the soft magnetic material is applied to the magnetic core of a magnetic amplifier, a magnetic amplifier having an excellent performance with a very small time constant can be manufactured.

[Advantages of the Invention] The present invention is configured as described above, has a small diameter, has very few crystal grain boundaries and internal strains that obstruct magnetization, and has high magnetic permeability,
It has become possible to provide a soft magnetic fiber that satisfies both the required characteristics of low coercive force and a manufacturing method thereof. And this high permeability soft magnetic fiber is useful as a small soft magnetic material or as a magnetic core material for various transformers and magnetic amplifiers with very small eddy current loss and hysteresis loss. Expected to be widely used.

[Brief description of drawings]

FIGS. 1 and 2 are views for explaining a spinning in-liquid spinning method. FIG. 1 is a schematic front view, FIG. 2 is a partial cross-sectional side view, and FIG. 3 is a soft magnetic fiber obtained in an example. 4 is a graph showing the relationship between the relative magnetic permeability at room temperature and the excitation frequency. 4 (a) and 4 (b) are explanatory views of a soft magnetic fiber having a dendritic tissue in which the angle formed by the primary arm and the fiber axis is 20 degrees or less. 1: crucible 2: jet nozzle 3: heater, 4: fine wire 5: inert gas, 6: rotating drum 7: motor, 8: cooling liquid 9: cooling liquid level, 10: belt

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-51-138517 (JP, A) JP-A-61-123448 (JP, A) JP-A-55-64948 (JP, A)

Claims (2)

[Claims] 1. A magnetic fiber having a dendritic structure with a diameter of 100 μm or less and a primary arm of the dendritic crystal grown at an angle within 20 degrees with respect to the fiber axis direction, is subjected to heat treatment to remove internal strain and to be dendritic A high-permeability soft magnetic fiber characterized by having a tissue disappeared and having a relative magnetic permeability of 90,000 or more in a DC magnetized state. 2. A magnetic material is melt-spun to obtain a magnetic fiber having a dendritic structure having a diameter of 100 μm or less and a primary arm of dendrite growing at an angle within 20 ° with respect to the fiber axis direction. A method for producing a high-permeability soft magnetic fiber, characterized in that the internal strain of the fiber is removed by heat treatment and the dendritic structure is eliminated so that the relative magnetic permeability in a direct current magnetized state is 90,000 or more.