JPH0680168B2 - Annealing method for iron-based amorphous alloy ribbon - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for annealing an iron-based amorphous alloy ribbon with an insulating coating suitable for use as a magnetic material such as an iron core material for a transformer, In particular, it is intended to advantageously prevent the deterioration of the iron loss characteristics, which has been a concern in the conventional annealing.

(Prior art) When a molten alloy such as Fe-B-Si system is rapidly quenched and solidified, the plate thickness becomes 30
An amorphous alloy ribbon having a thickness of about μm (hereinafter simply referred to as ribbon) can be produced. Such a ribbon has excellent soft magnetism,
In particular, it has an extremely low iron loss and is said to be a strong competing material for the grain-oriented silicon steel sheet, which is currently widely used as an iron core material.

Conventionally, such a ribbon has been used for an iron core of a transformer without forming an insulating film, but with the progress of ribbon manufacturing technology in recent years, its surface becomes smooth and the space factor is improved. In addition, the interlayer resistance is reduced, and eddy current loss tends to increase when the core is processed. Therefore, it has become indispensable to form an insulating film in order to reduce the eddy current loss and thus the total iron loss without lowering the space factor of the ribbon.

In addition, materials with good magnetic properties such as Fe-B-Si based amorphous alloys usually have a problem of corrosion resistance because they do not contain corrosion resistant components such as Cr. If left indoors for a month, red rust will occur. Occur. When such rusting occurs, not only the magnetic properties are deteriorated, but also the commercial value is significantly impaired. Therefore, the surface coating treatment can be said to be an effective means from the viewpoint of imparting corrosion resistance.

As a method for forming an insulating film on a ribbon, for example, Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 59-177377 proposes a method of forming a thin film by precipitating silica colloid from an alcohol solution of ethyl silicate. However, the use of an organic solvent has drawbacks such as not only being more expensive than a water solvent but also deteriorating the working environment.

Further, JP-A-59-20499 proposes a method for producing a chromium hydrate oxide film by an electrolytic method from an aqueous solution containing a trace amount of fluorine ions. This method is to remove the oxide thin film formed at the time of ultra-quenching due to the presence of fluorine ions, and to perform electrolysis uniformly,
It left a problem where complicated post-treatment such as fluorine ion treatment in waste water was essential.

Therefore, as a solution to the above problems, the inventors
Japanese Patent Application Laid-Open No. 62-56578 discloses a method of applying an aqueous treatment liquid containing a colloidal alumina hydrate as a main component, the pH of which is adjusted to 3.5 to 7, to the surface of an amorphous alloy ribbon and then performing low temperature baking. Proposed.

(Problems to be solved by the invention) However, the coated amorphous alloy ribbon obtained as described above, when annealed in an inert gas atmosphere, magnetic properties such as iron loss become unstable, It turned out that it was sometimes worse than the untreated material.

That is, when using an amorphous alloy ribbon as a transformer core, it is necessary to assemble it into a wound core or laminated core and then anneal it in a magnetic field to reduce internal stress and control magnetic domains. However, such annealing treatment caused a remarkable deterioration in magnetic properties.

As the magnetic field annealing conditions, an annealing temperature and an annealing time in a range where an amorphous alloy is not crystallized in an inert atmosphere such as N ₂ or Ar are usually adopted.

An object of the present invention is to propose an advantageous annealing method that does not cause deterioration of magnetic properties even when an amorphous alloy ribbon subjected to an insulating film treatment is annealed.

(Means for Solving the Problem) In order to solve the above problems, the inventors first conducted a detailed examination of the surface of the thin ribbon after annealing.

Fe-B surface-treated with colloidal alumina hydrate
-Si amorphous alloy ribbon was annealed at 400 ℃ in dry N ₂ atmosphere, and the ribbon surface was examined by thin film X-ray diffraction. As shown in Fig. 1b, α-Fe It was found that the crystallization of the above occurred. As a result of investigating the change in the amount of α-Fe due to the removal of the surface layer, it was found that this α-Fe was formed on the outermost surface of the amorphous alloy ribbon, and that the iron loss was recovered by removing the surface crystal layer. There was found.

Fe treated with colloidal alumina hydrate in this way
It was found that when the -B-Si amorphous alloy ribbon is annealed in an inert gas atmosphere, surface crystallization into α-Fe occurs, which leads to iron loss deterioration. As a result of earnest studies on the relationship between the surface crystallization and the insulating coating, the following new findings were obtained.

That is, when water is contained in the annealing atmosphere during annealing, B in the vicinity of the surface of the Fe-B-Si alloy ribbon is selectively oxidized, so that a low B region is formed in the surface layer and the crystallization temperature is increased. It is significantly reduced, resulting in surface crystallization of α-Fe. Generally, in the annealing of amorphous alloys, the water content in the atmosphere is reduced, but if a large amount of bound water is contained in the insulating coating, the water content is released during heating, resulting in a water-rich atmosphere, As a result, surface crystallization may occur due to the same mechanism as described above.

Then, when the thermal behavior of the colloidal alumina hydrate was investigated, it was found that the release of bound water occurred in the temperature range of 200 to 400 ° C. as shown in FIG. That is, most of the adhered water is desorbed in the low temperature baking process after the surface treatment liquid is applied, but the structured water is released at 200 to 400 ° C.
It turned out to be progressing in.

This temperature range almost overlaps with the temperature range of magnetic field annealing performed to reduce the iron loss of the Fe-B-Si amorphous alloy and improve the magnetic permeability. Therefore, when the amorphous alloy ribbon surface-treated with the colloidal alumina hydrate is subjected to the annealing in the atmosphere, the ribbon surface is exposed to the atmosphere containing a large amount of released moisture as it is heated. This is Fig. 1 (b).
Of Fe-B-Si amorphous alloy ribbon surface-treated with colloidal alumina hydrate as shown in Fig. 4 in dry N ₂ atmosphere.
It is considered to be the cause of the α-Fe surface crystallization that occurs when annealed at 00 ℃.

Therefore, in the present invention, in order to prevent boron from being selectively oxidized on the alloy surface layer by the moisture released from the insulating coating during the heating process and causing surface crystallization, the annealing treatment is performed under reduced pressure. We decided to actively exclude the water released by the annealing atmosphere.

That is, according to the present invention, an iron-based amorphous alloy ribbon with an alumina insulating coating obtained by applying an aqueous treatment liquid containing a colloidal alumina hydrate as a main component on the surface and then baking the same is annealed in a reduced pressure atmosphere. This is a method of annealing an iron-based amorphous alloy ribbon.

Fe-based amorphous alloys suitable for applying the present invention include Fe
-B-Si system, Fe-B-Si-C system, Fe-Mn-B-Si system, Fe-Ni-B-Si system
There is a system.

The experimental results which are the basis of the present invention will be described below.

A molten alloy of Fe ₇₈ B ₁₀ Si ₁₂ composition (atomic%) was rapidly solidified by a single roll method to produce an amorphous alloy ribbon having a width of 50 mm and a thickness of 25 μm. Next, a colloidal alumina hydrate (alumina sol-200 manufactured by Nissan Chemical Industries, Ltd.) aqueous treatment solution was applied, and baked at 200 ° C. for 3 minutes. The film thickness of the dry surface coating thus obtained was 0.1 μm, and the space factor was 83.5%, which was the same as that of the untreated ribbon.

Next, this amorphous alloy ribbon with an insulating coating was used as a toroidal core with a diameter of 6 cm, and then a magnetic field of 200 A / m was applied for about 10 ^-2 To
Annealing was performed for 2 hours at 360 ° C in a vacuum of rr, and after cooling as it was, iron loss was examined.
Hz, the iron loss W _13/50 at 1.3T was 0.11W / kg. The ribbon surface after this annealing was examined by thin film X-ray diffraction.
As shown in FIG. 1 (a), only the halo pattern was observed and surface crystallization did not occur.

Thus, the iron loss of the Fe-B-Si amorphous alloy ribbon treated with colloidal alumina hydrate with excellent film-forming property is deteriorated by annealing at 300-450 ℃ under reduced pressure. There is nothing to do, and the ribbon can be annealed.

If the depressurization degree of the annealing atmosphere is 100 Torr or less, the adverse effect of the water discharged from the insulating film can be eliminated. In this sense, there is no lower limit of working pressure, but it is difficult to industrially set it below 10 ^-4 Torr, so 10
^A practical range is ^{-4 to} 100 Torr.

(Example) Example 1 An alumina sol-200 aqueous treatment solution (alumina concentration 1%) having a pH of 5.5 was dried to a thickness of 0.2 µm on the surface of a ribbon having a width of 5 cm and a thickness of 28 µm, which had a composition of Fe ₇₈ B ₁₀ Si _12. So that
Then, a baking treatment was performed at 250 ° C. for 1 minute.

Next, it was annealed in a magnetic field at 370 ° C. for 1 hour under a reduced pressure of 1 to 3 Torr and cooled as it was.

The space factor of the ribbon with an insulating film thus obtained is 84.0.
%, And iron loss W _13/50 was 0.09W / kg.

The surface layer was examined by thin film X-ray diffraction, but no crystalline substance was detected.

Example 2 A ribbon having an alumina insulating coating was produced by performing the same treatment as in Example 1 except that the thickness of the insulating coating was 0.4 μm.

Then, it was annealed in a magnetic field at 370 ° C. for 1 hour under a reduced pressure of 10 ⁻³ Torr.

The space factor of the ribbon with an insulating film thus obtained is 83.8.
% And iron loss W _13/50 is 0.10 W / kg, and more its surface layer was detected alpha-Fe crystals.

Example 3 The same process as in Example 1 was carried out except that the alloy composition was Fe ₇₇ Mn ₁ B ₁₂ Si ₁₀ (atomic%).

Iron loss W of the obtained ribbon with insulating coating after annealing in a magnetic field
_13/50 was 0.11W / kg. No crystalline substance was detected in the surface layer by thin film X-ray diffraction.

Example 4 The same process as in Example 1 was carried out except that the alloy composition was Fe ₇₅ Mn ₂ Ni ₂ B ₁₂ Si ₉ (atomic%).

Iron loss W of the obtained ribbon with insulating coating after annealing in a magnetic field
_13/50 was 0.13 W / kg. No crystalline substance was detected in the surface layer.

Comparative Example 1 An amorphous alloy ribbon coated with an alumina insulating film was magnetically annealed in a dry Ar gas stream in the same manner as in Example 2 (370
When subjected to 200A / m for 1 hour at ℃, the space factor is 83.8%.
And was good, but the iron loss W _13/50 was degraded to 0.26 W / kg.

Also, when the ribbon surface was examined by thin film X-ray diffraction,
-The surface crystallization of Fe was confirmed.

Comparative Example 2 The ribbon produced in Example 1 was subjected to magnetic field annealing at 370 ° C. for 1 hour in a dry Ar gas stream without forming an insulating film, and the space factor was 84.0%, W _{13 / 50} was 0.16 W / kg. No α-Fe crystal was detected in the surface layer.

(Effect of the Invention) Thus, according to the present invention, the insulating coating can be effectively formed on the surface of the iron-based amorphous alloy ribbon having the alumina insulating coating without deteriorating the iron loss characteristics. .

[Brief description of drawings]

Fig. 1 a and b are thin films obtained by annealing Fe-B-Si amorphous alloy ribbons surface-treated with colloidal alumina hydrate in vacuum at 10 ^-2 Torr and in dry N ₂ atmosphere. X-ray diffraction spectrum, FIG. 2 is a diagram showing the results of differential thermal analysis of colloidal alumina hydrate.

Claims (4)

[Claims] 1. An iron-based amorphous alloy ribbon with an alumina insulating coating obtained by applying an aqueous treatment liquid containing a colloidal alumina hydrate as a main component on the surface and then baking it is annealed in an atmosphere under reduced pressure. A method for annealing an iron-based amorphous alloy ribbon, which is characterized in that: 2. The method according to claim 1, wherein the degree of reduced pressure is 10 ^{−4 to} 100 Torr. 3. An Fe-based amorphous alloy containing B: 7 to 16 atomic% and Si: 4 to 14 atomic%, the balance being a Fe-B-Si based alloy having a substantially Fe composition. A method as claimed in claim 1 or claim 2. 4. An iron-based amorphous alloy comprising B: 7 to 16 atom%, Si: 4 to 14 atom%, one or two of Mn and Ni: 0.5 to 10 atom%, Fe: 65 to 85 atom%. The method according to claim 1 or 2, which is an Fe- (Mn, Ni) -B-Si alloy.