JP2719978B2 - Amorphous alloy for high frequency magnetic core - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an amorphous soft magnetic alloy used in a high frequency band such as a mag amplifier (magnetic amplifier) or an inductance element of a switching power supply.

(Prior Art) Demands for miniaturization of power supplies for electronic computers, their peripheral devices, communication devices, etc. are increasing year by year. In order to reduce the size of the power supply, it is necessary to reduce the size of components used and increase the efficiency. In order to reduce the size of the magnetic portion, measures such as increasing the frequency and increasing the operating magnetic flux density may be taken. However, when the frequency and the operating magnetic flux density are increased, the loss increases, and as a result, the problem due to heat generation of the magnetic core increases. For this reason, a magnetic material with low loss at high frequency is required.

An amorphous alloy has attracted attention as a soft magnetic characteristic material with low loss at high frequencies. Amorphous alloys have higher electrical resistance than conventional soft magnetic metals, and can be easily manufactured from thin materials. That is, the higher the frequency, the more advantageous the amorphous alloy is. Above all, a Co-based amorphous alloy having almost zero magnetostriction has a small coercive force Hc and is already in practical use today as a core of a mag amplifier or a common mode choke.

All known zero magnetostrictive Co-based amorphous alloys are based on CoFeSiB alloy proposed by Kikuchi et al. And contain various auxiliary elements. The alloys described in JP-A-58-31053 and the alloys described in JP-B-63-28483 are typical examples. The former is CoFeSiB with Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, R
The thermal stability is improved by adding u, Hf, Ta, W, and Re. The latter is a square type annealed amorphous toroidal core of amorphous CoXSiB alloy in a magnetic field parallel to the circumferential direction. This is a method of manufacturing a core having a high ratio. Where X is Ti, V, Cr,
Mn, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W, Re, Fe, Y, Ce, Pr, Nd, Sm, Eu, G
One or more of d, Tb, and Dy. Practical components have various other property requirements. For example, it is required that the composition be hardly affected by the composition variation depending on the lot, that the range of annealing conditions is wide, that the deterioration in the core processing step is small, that the corrosion resistance be excellent, and the like. However, considering all of these additional factors, the alloys presented today are often unsatisfactory.

(Problems to be Solved by the Invention) The present invention not only satisfies the magnetic properties but also maintains a good balance of various properties required for practical components.
It is an object to provide a Co-based amorphous alloy and a high-frequency magnetic core.

(Means / Actions for Solving the Problems) The gist of the present invention is that the composition is Co _a Fe _b Mo _c Sn _d Si
soft magnetic properties at 100kHz or more high-frequency consisting of _e B _f is in the excellent high-frequency magnetic core amorphous alloy. Where a = 67
-71 (atomic%, the same applies hereinafter), b = 3-6, c = 1-3,
d = 0.05 to 1.0, e = 5 to 19, f = 7 to 16, and a +
b + c + d + e + f = 100.

The alloy of the present invention is characterized in that Mo and Sn are added in combination based on a conventionally known CoFeSiB alloy. Mo and
By adding Sn in combination, a new effect is added together with the improvement of the soft magnetic properties aimed at by the present invention. That is, not only can the loss or coercive force at high frequency be reduced as compared with the conventional composition, but also the practical characteristics which are insufficient with the conventional alloy can be improved. For example, expansion of annealing condition tolerance, reduction of distortion deterioration, improvement of corrosion resistance,
An increase in compositional freedom is achieved.

FIG. 1 compares the annealing temperature dependence of the magnetic properties of the Co-based amorphous alloy (b) to which Sn is not added and the Co-based amorphous alloy (a) of the present invention to which Sn is added. Sn as shown
In an alloy without addition of, the squareness ratio before resin coating (after annealing) changes sensitively depending on the annealing temperature, and the characteristic deterioration after resin coating (strain is added) is large. On the other hand, the alloy of the present invention exhibits excellent characteristics in a wide annealing temperature range with a wide squareness ratio before resin coating, and has little characteristic deterioration even after resin coating. As described above, the practical characteristics, which were not sufficient only by the addition of Mo, are further improved by the addition of Sn, and the production stability is further improved.

It is considered that the effect of the addition of Sn is mainly due to the surface modification of Sn. As the basis, as shown in Fig.
There is a phenomenon found by the present inventor himself that Si is abnormally concentrated in the surface layer of the Sn-added amorphous alloy ribbon. That is,
It is considered that the high-frequency loss is reduced because the abnormal surface segregation of Si increases the insulation resistance of the ribbon surface and suppresses the increase in interlayer eddy current loss. The improvement of the corrosion resistance can be similarly explained. Although the annealing latitude and the composition freedom are not clear, it is also assumed that the surface layer is involved.

As described above, the present invention has been completed through the process of investigating the relationship between the abnormal behavior and characteristics of Sn.

Next, the reason for limiting the alloy composition of the present invention will be described.

Sn is an essential element for imparting excellent practical characteristics aimed at by the present invention, and is 0.05 to 1.0% (atomic%, the same applies hereinafter).
Specified in the range. The reason is that if it is less than 0.05%, the effect of Sn intended by the present invention is not remarkably exhibited, and if it exceeds 1.0%, no remarkable effect is observed.

Mo is an element that enhances the thermal stability and amorphous forming ability of an amorphous alloy and has the effect of improving magnetic characteristics at high frequencies by coexisting with Sn. The range of Mo is limited to 1 to 3%. If it is less than 1%, the effect of addition is insufficient, so that the lower limit is 1%. If it exceeds 3%, the saturation magnetic flux density is reduced, so the upper limit is 3%.

The composition ranges of Co, Fe, Si, and B4 elements were determined so as to satisfy the following conditions in consideration of the amounts of Sn and Mo added. The first condition is that the magnetostriction is 10 ^-6 or less, and the second condition is that the saturation magnetic flux density is 0.5T.
As described above, the third condition is that the AC magnetic characteristics at 100 kHz after annealing in a magnetic field applied in the circumferential direction of the core have a squareness ratio Br / Bm> 0.90 and a coercive force Hc <300 mOe, preferably Br / Bm
> 0.95, coercive force Hc <200 mOe (Br = residual magnetic flux density,
Bm = magnetic flux density at the maximum applied magnetic field). The magnetic permeability at 100 kHz after annealing in a magnetic field applied in the perpendicular direction is at least 20,000. As composition conditions satisfying these conditions, in the present invention, Co is 67 to 71%, Fe3 to 6%.
%, 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. On the other hand, if Si and B are out of the specified range, it becomes difficult to form an amorphous alloy and the predetermined AC magnetic characteristics cannot be satisfied.

Next, embodiments of the present invention will be described. First, a raw material or a mother alloy blended so as to be in the above-described composition range is melted, and an amorphous continuous ribbon is formed by a usual liquid quenching method. The nozzle used at this time can be a single slit nozzle, a multi-slit nozzle, or a wrapped multi-hole nozzle. The atmosphere for casting may be any of air, inert gas, and vacuum. The manufacturing method of the amorphous ribbon described above is not particularly limited, and other methods can be adopted.

The amorphous alloy ribbon is annealed after being formed into a wound core having a predetermined size. Usually, before being formed into a core, the amorphous ribbon is subjected to some coating for interlayer insulation. However, in the alloy of the present invention, a high-resistance surface film is already formed in the quenched state, so that an insulating coating is unnecessary. Annealing is performed in a magnetic field parallel to the circumferential direction of the core when a high squareness ratio is required. A magnetic field strength of 10 times the coercive force of the alloy is sufficient. Annealing temperature is Tx-120 ° C to Tx-20 ° C, where Tx is the crystallization start temperature of the alloy.
The range and time are suitably from 30 to 120 minutes. When a high magnetic permeability is required, a magnetic field is applied at right angles to the circumferential direction of the core. The annealing temperature and time may be almost the same as in the case of the high squareness ratio. Further, in order to achieve high magnetic permeability, a method of annealing at a temperature equal to or higher than the Curie temperature and then cooling with water may be employed.

(Example) Hereinafter, an example will be described.

Example 1 Chemical composition (Co _68.5 FE _3.5 Si ₁₈ B ₈ Mo ₂ ) _100-x Sn _x alloy (x
= 0.1,0.2,0.5,1.0) were produced by a single roll quenching method. The width of the ribbon is 5 mm and the thickness is 15 to 20 μm.
The produced ribbon was confirmed to be amorphous by X-ray diffraction.

The ribbons each inner diameter 14 mm, was molded into a toroidal core having an outer diameter of 21 mm, and annealed in an N ₂ stream while applying a DC magnetic field of about 10e. The annealing conditions were such that the retention time was fixed at 1 hour, and the temperature was varied as a parameter in the range of 400 to 480 ° C. Magnetic properties were measured before and after resin coating to evaluate the practical properties of the annealed core. That is, the magnetic properties were measured for each of the core after the annealing, which was directly wound in a resin case, and the core which was wound after the core was coated with the resin.

Table 1 shows the magnetic properties of the alloy of the present invention under the optimum annealing conditions. Also, it does not belong to the present invention for comparison
Table 1 also shows the characteristics of the alloy containing no predetermined amount of Sn. First
As is clear from the table, the alloy of the present invention has excellent magnetic properties (square ratio> 0.95, coercive force> 200 mO) before resin coating.
As shown in e), it can be seen that there is almost no deterioration of the characteristics even after the resin coating. On the other hand, the composition without addition of Sn and the composition in which Sn is not in the range specified in the present invention have insufficient properties before resin coating or have a large deterioration after resin coating even if the properties before coating are good ( Squareness ratio <0.90 or coercive force> 300 mOe) It can be seen that the target characteristics cannot be achieved.

In addition, it can be seen that the alloy of the present invention has stable characteristics over a wide range of annealing temperatures, and also has high degree of freedom (margin) of annealing conditions in characteristics after resin coating.

Example 2 Annealing was performed while applying a magnetic field perpendicular to the circumferential direction of a toroidal core formed from an amorphous ribbon having the same composition as in Example 1. The magnetic permeability before resin coating and the magnetic permeability after resin coating are shown in Table 2. As is evident from Table 2, the alloy of the present invention not only has excellent magnetic permeability before resin coating, but also has smaller property deterioration after resin coating than the comparative alloy.

(Effect of the Invention) The Sn-added Co-based zero magnetostrictive amorphous alloy of the present invention exhibits excellent soft magnetic properties and has extremely small deterioration in properties even after resin coating. Also, the degree of freedom of the annealing conditions is wide. As described above, the Co-based amorphous alloy in which Sn and Mo coexist has significantly improved practical characteristics as compared with the conventional Co-based amorphous alloy.

[Brief description of the drawings]

FIG. 1 is a diagram comparing the annealing temperature dependence of the magnetic properties (square ratio) of the Sn-added amorphous alloy (a) of the present invention and the conventional Sn-free amorphous alloy (b). FIG. 2 is a diagram comparing element concentrations in the surface depth direction analyzed by glow discharge emission spectroscopy (GDS) (where (a) is an amorphous alloy containing Sn of the present invention, and (b) is a Sn alloy). Alloy containing no).

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshio Yamada 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture New Nippon Steel Corporation 1st Technical Research Institute (72) Inventor Satoshi Yamashita 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Nippon Steel Corporation 1st Technical Research Institute (72) Inventor Hideo Hagiwara 1618 Ida Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Nippon Steel Corporation 1st Technical Research Institute (56) References JP-A-63-232383 JP, A) JP-A-51-65395 (JP, A)

Claims (1)

(57) [Claims] 100kHz to 1. A composition consisting of _{Co a Fe b Mo c Sn d} Si e B f
An amorphous alloy for a high-frequency magnetic core having excellent soft magnetic properties at the above high frequencies. Here, a = 67-71 (atomic%, the same applies hereinafter), b = 3-6, c = 1-3, d = 0.05-1.0, e =
5-19, f = 7-16, and a + b + c + d + e + f =
It is 100.