JP2561573B2 - Amorphous ribbon saturable core - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous ribbon saturable magnetic core which operates in a high frequency band such as a mag amplifier (magnetic amplifier) used for a switching power supply.

[0002]

2. Description of the Related Art With the miniaturization of electronic computers, their peripheral devices, communication devices, etc., there is an increasing demand for miniaturization of power sources for supplying power to these devices. Currently, switching power supplies are mainly used for these power supplies, and miniaturization measures such as circuit integration and miniaturization of capacitors and magnetic parts by increasing the switching frequency are effective. However, if the switching frequency is increased, the magnetic core loss increases in the magnetic component, resulting in an increase in the space for the cooling fan and the heat dissipation plate for cooling the magnetic core. Therefore, there is a demand for a magnetic material with high frequency and low loss.

Amorphous alloys have been attracting attention as magnetic core materials with low loss at high frequencies. Amorphous alloys have a higher electric resistance than conventional soft magnetic metals, and a material with a thin plate thickness can be easily manufactured. Therefore, an increase in eddy current loss, which accounts for most of the core loss at high frequencies, is small. Above all,
The zero magnetostriction Co-based amorphous alloy has a small hysteresis loss, which is the rest of the magnetic core loss, so it has an excellent characteristic that the high-frequency loss is very small, and it has already been put to practical use as a saturable magnetic core such as a mag-amp or noise absorber Has been done.

Generally, two magnetic characteristics required for a saturable magnetic core are low iron loss and high squareness ratio (high ratio of residual magnetic flux density to saturated magnetic flux density). Since the zero magnetostrictive Co-based amorphous alloy can obtain a high squareness ratio by annealing in a magnetic field, it can be said that it is also an excellent material from this point of view. All of the zero magnetostrictive Co-based amorphous alloys known to date are based on the CoFeSiB alloy proposed by Kikuchi et al. And contain various auxiliary elements. The alloy described in JP-B-63-28483 is a typical example. This is a method of manufacturing a core having a high squareness ratio by annealing a toroidal core of an amorphous CoXSiB alloy ribbon in a magnetic field parallel to the circumferential direction. However, X is Ti, V, Cr, Mn, Ni, Zr, Nb, M
o, Ru, Hf, Ta, W, Re, Fe, Y, Ce, P
One or more of r, Nd, Sm, Eu, Gd, Tb and Dy.

The magnetic core currently put into practical use as a mag-amplifier uses an amorphous alloy ribbon having a thickness of about 20 μm and having the above composition, and is mainly used in a power supply with a switching frequency of 50 kHz or more in order to take advantage of low loss characteristics. in use. However, when it is used at a high frequency of 300 kHz or higher, heat generation due to an increase in loss is generally large depending on the operating magnetic flux density, and it is necessary to take measures to prevent a temperature rise by a cooling fan or a heat sink. In order to suppress the heat generation of the magnetic core, it is considered effective to reduce the eddy current loss by reducing the ribbon thickness. However, if the ribbon thickness is less than 15 μm, there is a problem that the squareness ratio decreases as the sheet thickness decreases. . For this reason,
It has been difficult to obtain an amorphous ribbon saturable magnetic core having a low iron loss and a high squareness ratio at such a high frequency.

[0006]

SUMMARY OF THE INVENTION The present invention is 300 kHz.
It is an object of the present invention to provide an amorphous ribbon saturable magnetic core that satisfies the requirements of low iron loss and high squareness ratio even at the above high frequencies.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is that a saturable magnetic core made of a Co-based amorphous alloy having a small magnetostriction has _a composition of Co _a Fe _b Mo _c Sn.
_d Si _e B is _f, and magnetostriction -0.1 × 10 ^-6 ~ -
An amorphous ribbon saturable magnetic core is characterized by using an amorphous alloy ribbon having a thickness of 15 μm or less in the range of 1 × 10 ⁻⁶ . Here, a = 67 to 72 (atomic%, the same applies hereinafter), b = 3 to 5, c = 1 to 3, d = 0.05 to 1.
0, e = 5 to 19, f = 7 to 16, and a + b + c + d
+ E + f = 100.

That is, the essence of the present invention is to add a composite of Mo and Sn based on a conventionally known CoFeSiB alloy, and to set the magnetostriction in the range of -0.1 × 10 ^-6 to -1 × 10 ^-6 . By doing so, it is possible to obtain a saturable magnetic core having a high squareness ratio while using a thin amorphous alloy ribbon of 15 μm or less. The present invention will be described in more detail below.

In general, it is known that thinning the thin ribbon is effective for reducing the eddy current loss, which accounts for most of the iron loss of the amorphous thin ribbon magnetic core. However, the present inventors have encountered a phenomenon in which, in the conventional magnetic core, when the ribbon is thinned to a certain plate thickness or less, the squareness decreases as the plate thickness decreases. A specific example thereof is shown in FIG. This figure shows that the composition is (CoFe) ₇₂ Mo.
The coercive force Hc and the squareness of the saturable magnetic core prepared by winding a ribbon of magnetostriction of 0.2 × 10 ⁻⁶ with ₂ (SiB) ₂₆ and annealing in a circumferential magnetic field when the ribbon thickness is changed. It shows the measurement results of the ratio. From this figure, it is understood that the coercive force Hc, which is an index of iron loss, decreases almost proportionally to the ribbon thickness, and that thinning is effective in reducing iron loss. However, 1
If the thickness is 5 μm or less, the squareness ratio decreases, so that it is not possible to simultaneously achieve low iron loss and high squareness ratio. The cause of this decrease in the squareness ratio is not clear, but it is presumed that the stress effect due to the thin oxide layer or the partially crystallized layer on the surface or the effect of the surface unevenness becomes remarkable as the plate thickness becomes thinner. Therefore, the inventors of the present invention have conducted various studies for the purpose of simultaneously achieving a low iron loss and a high squareness ratio, and as a result, it is possible to solve the above-mentioned problems by selecting an alloy composition and optimizing magnetostriction. Therefore, the present invention has been completed.

Next, the reasons for limiting the alloy composition of the present invention will be described. Sn is an essential element for imparting high polygonal properties in thin materials, which is the object of the present invention, and is 0.05 to 1.
The range was limited to 0% (atomic%, the same applies hereinafter). The reason is that if it is less than 0.05%, the effect of Sn, which is the object of the present invention, does not remarkably appear, and if it is added in excess of 1.0%, no significant effect is observed. The effect brought about by the addition of Sn seems to be due to the surface modification action of Sn. The basis for this is the phenomenon found by the present inventors that Si is abnormally concentrated on the surface of the Sn-doped amorphous alloy ribbon as shown in FIG. That is, it is presumed that the abnormal surface segregation of Si changes the state of the ribbon surface, and suppresses the reduction of the squareness ratio due to the influence of the surface portion in the range of magnetostriction described later.

Mo is an element having the effect of improving the thermal stability and amorphous forming ability of the amorphous alloy and improving the magnetic characteristics at high frequencies, and its range is limited to 1 to 3%. If it is less than 1%, the above addition effect is insufficient, so the lower limit is 1%, and if it exceeds 3%, the saturation magnetic flux density decreases, so the upper limit was made 3%. The composition range of the four elements Co, Fe, Si and B was determined so as to satisfy the following conditions in consideration of the amounts of Sn and Mo to be added. The first condition is magnetostriction-
0.1 × 10 ⁻⁶ to −1 × 10 ⁻⁶ , the second condition is a saturation magnetic flux density of 0.45 T or more, and the third condition is AC magnetic field at 100 kHz after annealing in a magnetic field applied in the circumferential direction of the magnetic core. Squareness ratio Br / when using a thin strip with characteristics of 10 μm
Bm> 0.95, coercive force Hc <12 A / m, preferably squareness ratio Br / Bm> 0.97, coercive force Hc <10 A / m
(Br = residual magnetic flux density, Bm = magnetic flux density at maximum applied magnetic field). In the present invention, Co is 67 to 72
%, Fe 3 to 5%, Si 5 to 19%, and B 7 to 16%. If Co and Fe deviate from the specified ranges, the conditions for magnetostriction and saturation magnetic flux density will not be satisfied. Also,
If Si and B deviate from the specified range, it becomes difficult to form an amorphous alloy and the predetermined AC magnetic characteristics are not satisfied.

Next, the reason for limiting the magnetostriction will be described. Figure 3
Composition is (CoFe)₇₂Mo₂Sn_0.2(SiB)_25.8Of
For gold, the balance between Co and Fe is changed, and the magnetostriction is different.
Amorphous alloy ribbon with a plate thickness of about 10 μm
It is the result of processing and measuring the squareness ratio. Revealed from this figure
As you can see, when the magnetostriction is positive, the angle is negative when it is negative.
The phenomenon that the form ratio is reduced is reduced. From this, magnetostriction
The upper limit of −0.1 × 10^-6And Also, -1 x 10^-6
On the negative side, the coercive force Hc increases and the iron loss increases.
Lower limit -1 x 10 ^-6And

Next, embodiments of the present invention will be described. First, a raw material or a mother alloy compounded so as to have the above composition range is melted, and an amorphous continuous ribbon is formed by an ordinary liquid quenching method. The nozzle used at this time is preferably a single slit nozzle suitable for manufacturing thin materials. The atmosphere for casting may be air, inert gas, or vacuum. The method for producing the amorphous ribbon described above is not particularly limited, and other methods can be adopted.

The amorphous ribbon is formed into a wound magnetic core having a predetermined size and then annealed in a circumferential magnetic field. A magnetic field strength of 10 times the coercive force of the alloy is sufficient. When the crystallization start temperature of the alloy is Tx, the annealing temperature is Tx-
Range of 120 ° C to Tx-20 ° C, holding time 30 to 1
20 minutes is appropriate.

[0015]

Example A ribbon having the chemical composition shown in Table 1 was produced by a single roll quenching method. The width of the ribbon is 5 mm and the thickness is about 10
It is 20 μm. It was confirmed by X-ray diffractometry that the produced ribbon was amorphous. Magnetostriction was measured by the three-terminal capacitance method. These thin strips each have an inner diameter of 12 m
m after forming into a wound magnetic core with an outer diameter of 18 mm, then about 400 A
Annealing was performed in an Ar stream while applying a DC magnetic field of / m. Regarding the annealing conditions, the holding time was fixed to 1 hour, and the temperature was changed in the range of 400 to 480 ° C. The annealed magnetic core was coated with resin, and then the AC magnetic characteristics were measured. Table 1 shows the magnetic characteristics at each optimum annealing temperature. As is clear from this table, the magnetic core according to the present invention has a high squareness ratio regardless of the plate thickness. On the other hand, in the case of the comparative material, the squareness ratio decreases at 15 μm or less, and it can be seen that the target characteristics cannot be satisfied.

[0016]

[Table 1]

[0017]

The amorphous ribbon saturable magnetic core according to the present invention comprises:
Both the requirements of low iron loss and high squareness can be satisfied even at high frequencies. Therefore, when used in a mag amplifier or the like in a switching power supply of 300 kHz or more, heat generation in the magnetic core is smaller than that of a conventional power supply, the power supply can be downsized and the cooling method can be simplified, and its industrial value is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a ribbon thickness, a coercive force Hc, and a squareness ratio Br / Bm of a conventional wound magnetic core made of an amorphous alloy ribbon having a composition without addition of Sn.

FIG. 2 was analyzed by glow discharge emission spectrometry (GDS),
Figure comparing the element concentrations in the depth direction of the ribbon (however,
(A) is an amorphous alloy containing Sn of the present invention, (b) is an amorphous alloy containing no Sn).

FIG. 3 is a diagram showing the magnetostriction dependence of the squareness ratio of the magnetic core of the present invention (prepared from an amorphous alloy ribbon having a composition containing Sn).

Claims (1)

(57) [Claims] 1. A saturable magnetic core made of a Co-based amorphous alloy having a small magnetostriction has _a composition of Co _a Fe _b Mo _c Sn _d.
Si _e B _f and has magnetostriction of −0.1 × 10 ⁻⁶ to −1.
An amorphous ribbon saturable magnetic core comprising an amorphous alloy ribbon having a thickness of 15 μm or less in the range of × 10 ⁻⁶ .
Here, a = 67 to 72 (atomic%, the same applies hereinafter), b = 3
-5, c = 1-3, d = 0.05-1.0, e = 5-1
9, f = 7 to 16, and a + b + c + d + e + f = 10
0.