JPH0135065B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-loss amorphous alloy used in magnetic cores of electromagnetic devices, and particularly relates to a low-loss amorphous alloy suitable for high-frequency magnetic cores such as switching regulators. Conventionally, crystalline materials such as permalloy and ferrite have been used as magnetic cores used in high frequency applications such as switching regulators. However, permalloy has a drawback of high iron loss at high frequencies due to its low resistivity. Furthermore, although ferrite has a small loss at high frequencies, its magnetic flux density is as small as 5000G at most, so when used with a high operating magnetic flux density, it approaches saturation and increases iron loss. Transformers used at high frequencies, such as power transformers used in switching regulators, are desired to be made smaller and therefore require an increase in operating magnetic flux density, but in this case the iron loss of ferrite increases. has become a big problem in practice. Amorphous magnetic alloys without a crystalline structure, which have recently attracted attention, are known to exhibit excellent soft magnetic properties such as high magnetic permeability and low coercive force. These amorphous magnetic alloys are based on Fe, Co, and Ni, and include P, C, B, Si, Al, Ge, etc. as amorphous elements (metalloids), but these are universally compatible with high frequencies. This does not mean that iron loss is small. for example
Fe-based amorphous alloys exhibit very small iron loss of ~1/4 of silicon steel at low frequencies of 50 to 60 Hz.
At high frequencies of 10 to 50 kHz, it exhibited a significantly large iron loss, making it unsuitable for high frequency applications such as switching regulators. In view of the above points, the present invention relates to a high-frequency magnetic core used in a state of high magnetic flux density, and an object of the present invention is to provide a high-frequency magnetic core using a low-loss amorphous alloy with low iron loss. . The present invention is a high-frequency magnetic core using a low-loss amorphous alloy consisting of (Fe _1-a Ni _a ) _100-xy Si _x B _y (atomic ratio) where (0.2a0.7 1x20 5y9.5), Especially B is 5y7, Ni is 0.3a
By setting it to 0.45, it is possible to further reduce iron loss at high frequencies. The reasons for limiting the compositional components of the low-loss amorphous alloy in the present invention are as follows. Ni has the effect of reducing iron loss at high frequencies, but if it is less than 0.2 atomic percent, the effect is not so great.
If it exceeds 0.7 atomic %, the Curie point will become extremely small and the magnetic flux density will become less than 5000G, making it impractical, so it was set in the above range. More preferably, by setting Ni to 0.3a0.45, it is possible to obtain an even higher magnetic flux density and a smaller core loss. Further, the reason why B is set to 5 to 9.5 atomic % is that outside this range, it becomes difficult to produce an amorphous alloy, and furthermore, the effect of reducing iron loss becomes less noticeable. In particular, if B is set to 5y7, the iron loss will be significantly reduced, and it is preferable for practical purposes to set it within this range. Si is an element that has the effect of promoting amorphization and reducing iron loss, but if it is less than 1 atomic %, it has no particular effect, and if it exceeds 20 atomic %, it may actually hinder the creation of an amorphous alloy. This range was chosen because it would be difficult. Hereinafter, the present invention will be explained in detail based on Examples. Example 1 (Fe _0.6 Ni _0.4 ) ₈₀ Si ₁₄ B ₆ amorphous alloy was produced using a rolling quenching method. That is, the molten alloy is jetted between two high-speed rotating rolls from a quartz tube nozzle under argon gas pressure, and is rapidly cooled to a thickness of 2 mm in width and thickness.
A ribbon sample of 30 μm and 10 m in length was prepared. A length of 140cm was cut from this sample, wound around an alumina bobbin with a diameter of 20φ, and after heat treatment at 400°C for 30 minutes, both the primary and secondary coils were wound 70 times and iron loss was measured using a Wattmeter. The saturation magnetization was also measured using a sample vibrating magnetometer. Magnetic flux density Bm=3kG
Table 1 shows the iron loss at high frequencies of 10kHz and 20kHz, together with the saturation magnetization. For comparison, Table 1 also shows the results for Mn--Zn ferrite, which has been conventionally used for switching power supplies. As can be seen from the table, the amorphous alloy of the present invention has a larger magnetic flux density than ferrite and exhibits smaller core loss than ferrite. Example 2 Amorphous alloys shown in Table 1 were produced using the same method as in Example 1, and core loss was evaluated. It can be seen that the amorphous alloy of the present invention exhibits small iron loss.

[Table] Example 3 (Fe _0.55 Ni _0.45 ) ₇₈ Si _22-y B _y Amorphous alloy Example 1
It was manufactured using the same method as above, and the iron loss was measured.
Figure 1 shows the dependence of iron loss on the amount of B at Bm = 3kG and frequency of 20kHz. As can be seen from the figure, the core loss is particularly small when B is 5 to 9.5 at%. As described above, the amorphous alloy of the present invention has a higher magnetic flux density than ferrite, and is also superior to ferrite in core loss especially at high frequencies. Therefore, it is possible to miniaturize high frequency transformers, etc., and is industrially useful. .

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the iron loss of the amorphous alloy according to the present invention.

Claims (1)

[Claims] 1 (Fe _1-a Ni _a ) _100-xy Si _x B _y (atomic ratio), characterized by consisting of [0.2≦a≦0.7 1≦x≦20 5≦y≦9.5] A high-frequency magnetic core using a low-loss amorphous alloy. 2 In claim 1, B is 5≦y
A magnetic core for high frequency, characterized in that ≦7. 3 In claim 1 or 2,
A magnetic core for high frequency use, characterized in that Ni is 0.3≦a≦0.45.