JPH02133516A - Method for annealing thin amorphous alloy strip - Google Patents

Abstract

PURPOSE:To effectively prevent the deterioration of magnetic characteristics at the time of annealing by annealing the boron-contained iron-based thin amorphous alloy strip having an insulating film consisting of an oxide system on the surface while using a reduced-pressure inert gaseous atmosphere. CONSTITUTION:The boron-contained iron-based thin amorphous alloy strip having the insulating film consisting of an oxide system formed by an anodic oxidation on the surface is annealed to relieve stresses. The reduced-pressure inert gaseous atmosphere is used as the annealing environment at this time. The above-mentioned pressure reduction is preferably executed under 10<-4> to 100Torr. The deterioration in magnetic characteristics, such as iron loss, at the time of annealing is prevented in this way. An alloy contg. 7 to 16atomic% B, 4 to 14% Si, contg. further <=2% C at need, and consisting of the balance substantially Fe or an alloy contg. 7 to 16% B, 4 to 14% Si, 0.5 to 10% Mn or Ni, and further consisting of <=2% C and 65 to 85% Fe at need is adequate as the boron-contained iron-based alloy mentioned above.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a non-woven fabric having a surface coating suitable for use in magnetic materials such as iron cores used in electrical equipment such as power transformers and rotating machines. The present invention relates to a method of annealing a crystalline alloy ribbon, and is intended to advantageously prevent deterioration of core loss characteristics, which is particularly a concern during such annealing.

(Prior Art) Iron core materials used in electrical equipment such as transformers and rotating machines are required to have excellent excitation characteristics and iron loss characteristics.

For this reason, silicon steel sheets, especially grain-oriented silicon steel sheets, have been frequently used as materials satisfying these characteristics.

On the other hand, the boron-containing Fe-based amorphous alloy ribbon not only has low iron loss and excellent excitation characteristics, but also has a relatively high saturation magnetic flux density, so it satisfies the characteristics required as an iron core material. It has been known.

Furthermore, since the crystallization temperature is 500°C or higher, there is no problem in terms of heat resistance, and this has been confirmed in long-term demonstration tests using actual transformers.

In the liquid quenching method, which is a common manufacturing method for amorphous alloy ribbons, it is necessary to increase the solidification rate, so the thickness of the amorphous alloy ribbons obtained is extremely thin, usually 50 mm.
It is less than μm. Therefore, when producing an iron core for use in transformers, etc., it is necessary to wind and stack the iron core more times than silicon steel sheets.

If the interlayer insulation resistance generated in the laminated steel sheet is low as a result of winding or stacking, eddy currents will occur, causing increased iron loss. In order to reduce this eddy current loss, it is essential for silicon steel sheets to have a surface insulation coating.

In this regard, in the case of amorphous alloy ribbons, the electrical resistance of the alloy itself is high, and due to the moderate surface roughness, a certain degree of interlayer resistance can be obtained. It was sometimes thought that it was not necessary.

However, as the manufacturing technology for amorphous alloy strips has improved and the surface has become significantly smoother, the need for a surface insulating coating is reduced in the case of wide amorphous alloy strips. It became so. In addition, Fe-B-Si and Fe-B51-C alloys are used as amorphous alloys for transformer core materials, but these alloys do not have very good corrosion resistance, and can cause corrosion if left indoors. It had the disadvantage of rusting.

The surface coating is also considered necessary for imparting corrosion resistance.

Zokode JP-A-61-227194 and JP-A No. 63-8 (3
In No. 889, A1□03, ZrO□, and TaO were applied to the surface of the If quality alloy ribbon by anodizing.
We are proposing a method of applying an oxide-based insulating film such as □. In particular, by anodizing in an electrolyte containing sodium aluminate, a uniform film thickness can be achieved on the surface of the amorphous alloy ribbon.A! , 0. It is said that it is preferable to form this from the viewpoint of magnetic properties and corrosion resistance.

However, even if an amorphous alloy ribbon is simply electrolytically treated in an electrolytic solution containing sodium aluminate, the film formation rate is extremely slow, and an industrial threading rate cannot be ensured.

On the other hand, JP-A-63-109194 and JP-A-63-1030
According to the multi-stage anodization in an electrolytic solution containing sodium aluminate and tartaric acid, which was proposed in the 98-Ru publication, the film formation rate was increased and an oxide surface film was easily obtained.

(Problem to be solved by the invention) When the coated amorphous alloy ribbon obtained by anodizing as described above is annealed in an inert gas atmosphere, magnetic properties such as iron loss become unstable. It was found that the material was sometimes even worse than untreated material.

In other words, when an amorphous alloy ribbon is used as a transformer core, it is necessary to assemble it into a normal wound core or a laminated core and then apply magnetic field annealing to relieve internal stress and control magnetic domains. However, such annealing treatment caused significant deterioration of magnetic properties.

Note that such magnetic field annealing conditions are usually Nz or A
An annealing temperature and annealing time are used in an inert atmosphere such as R and within a range in which the amorphous alloy ribbon does not crystallize. Since N gas has low activity in an environment for annealing an amorphous alloy ribbon, it can be used in the same manner as a static gas, and will hereinafter be collectively referred to as an inert gas.

The purpose of this invention is to propose an advantageous annealing method that does not cause deterioration of magnetic properties even when an amorphous alloy ribbon that has been anodized with an insulating film is subjected to annealing, especially strain relief annealing. be.

(Means for Solving the Problem) In this invention, a surface coating treatment method is adopted as a surface coating treatment method for forming a coating with a uniform thickness on the surface of an amorphous alloy ribbon. and; An AhO:l film was formed by anodization in an electrolyte containing roolitic acid.

However, Fe-B5 with such an AlzOi coating
When a 1-series amorphous alloy ribbon was annealed at 400"C in a dry-activated (N2) gas atmosphere, the iron properties deteriorated, and at the same time α-Fe crystallization occurred on the ribbon surface. Furthermore, it was found that the α-Fe crystals were formed on the outermost surface of the amorphous alloy ribbon, and that the core loss characteristics were recovered by removing this surface crystal layer.

The inventors conducted extensive studies on the cause of core loss deterioration due to annealing of an amorphous alloy ribbon having such an anodized coating, and as a result, they obtained the following new knowledge.

First, it was found that the Al2O3 film formed on the surface of the amorphous alloy ribbon by anodization is a hydrated oxide and has an extremely high water content. Therefore, if a large amount of water is contained in the surface coating, it is thought that the amount of water vapor in the annealing atmosphere will increase due to dehydration during the annealing process.

In the boron-containing iron-based amorphous alloy ribbon, when there is moisture in the atmosphere, boron in the alloy is selectively oxidized during the annealing process, and the amount of boron near the alloy surface is reduced. As a result, the crystallization temperature near the surface of the ribbon decreases markedly, so it is thought that surface crystallization progresses due to annealing, and the iron loss deteriorates.

FIG. 1 shows the infrared reflection spectrum of the Al2O:l coating formed on the surface of three amorphous alloy bands by anodization. As is clear from the figure, the surface coating contains a large amount of bound water alloy. While heat-treating the amorphous alloy ribbon having such a surface coating, infrared irradiation, ■
When I investigated the change in the spectrum, I found that it was 250-400'
It has also been found that moisture is released in the temperature range of 71'rU.

This temperature range is the same as the temperature range of magnetic field annealing performed to lower the iron I member of the Fe-B-3i amorphous alloy. King is almost always duplicated. Therefore, when an amorphous alloy ribbon with an alumina anodized coating is annealed in a dryene active atmosphere, the ribbon surface 1! You will be exposed to an atmosphere containing a large amount of moisture. This means that F
This is thought to be the cause of α-Fc surface crystallization that occurs when an e-B-Si-based amorphous alloy ribbon is annealed in a dry N2 atmosphere.

Therefore, in this invention, in order to prevent boron from being selectively oxidized in the alloy surface layer due to moisture released from the insulating coating during the heat treatment process, and surface crystallization occurs, the annealing treatment is carried out under reduced pressure. By carrying out the process in an active gas atmosphere, it was decided that the released water would be eliminated from the Vl sludge. In other words, even if moisture contained in the insulating film is released during the heating process, it will be discharged outside the system, so that selective oxidation of boron will not occur. Therefore, since a low boron region is not formed, α-1
? c Surface crystallization does not occur and there is no deterioration in iron loss.

This invention is based on the above knowledge.

That is, the present invention proposes to use a high-pressure inert gas atmosphere as an annealing environment when annealing a J-containing boron-iron-based amorphous alloy ribbon having an oxide-based insulating film formed on the surface by anodizing. This is a characteristic method for annealing amorphous alloy ribbon.

Boron-containing iron-based amorphous alloys to which this invention is applied include Fe-B-Si, Fe-B-3i-C,
Fe-(Mn, Ni)-B-3i system, Be-(Mri
, -B-3i-C system of Ni, etc.

(for production) The experiments that formed the basis of this invention will be explained below.

The molten alloy with Feeo B + zSie composition (atomic %) was injected from a slit-shaped pouring nozzle directly onto a cooling roll made of a warm alloy that rotates at high speed, and was rapidly solidified.
An amorphous alloy ribbon with a width of m was produced.

Next, an electrolytic treatment was performed using an aqueous solution containing 3 wt% sodium aluminate and 1 wt% tartaric acid as an electrolyte at a liquid temperature of 40° C. and a current density of 10 A/dm with the amorphous alloy ribbon side as the anode. However, after 2 seconds of electrolysis, an alumina film with an average thickness of about 70,708 μm was formed.

The amorphous alloy ribbon with the surface coating coated in this way was subjected to magnetic field annealing at 380°C for 11 hours in a vacuum of approximately 10" Torr, and its magnetic properties were measured.
The iron 1 member at Hz and 1.3 T was 0.09 W/kg, and the magnetic flux density at 100 Δ/m was 1.42 T. The surface of this annealed ribbon was examined by thin film X-ray diffraction, but only a halo pattern was observed, and no surface crystallization occurred.

In this way, by performing annealing at 300 to 450°C in a reduced pressure inert gas atmosphere, the iron loss of the Fe-B-Si amorphous alloy ribbon treated with the alumina anodic oxide film can be degraded. The ribbon can be annealed without the need for annealing.

Here, if the degree of pressure reduction in the annealing atmosphere is 100 Torr or less, it is possible to eliminate the negative effects caused by water released from the insulating coating. In this sense, it is difficult to reduce the pressure below 10-' Torr, so the
A range of r is practical.

Also, Fe-B-Si system, Fe-B-Si-C system, Fe-
(Mn, Ni B-Si system, and Fe-(Mn, Ni
The -B-Si-C based boron-containing iron-based amorphous alloy contains 7 to 16 at% and 4 to 14 at% of B and Si, respectively, in order to increase the crystallization temperature and reduce iron loss. It is preferable that MnNi be contained in one type or in total of 0.5 to 1 in order to suppress a decrease in magnetic flux density and reduce iron loss.
It is preferable to contain 0 atomic %. When Mn and Ni are contained, it is desirable that Fe be in the range of 65 to 85 at %.

CS is an element that is normally contained in iron that can be used industrially, but it is the object of the present invention (as a d-type material, it is an element contained in Fe-based amorphous alloys used in -C). It is desirable that the content is 2 at% or less.
This is because, if it exceeds, iron 1n deteriorates and the ability to form an amorphous state also decreases.

(Example) Implementation-Example-1- FetaB Width 5c resulting in 1osi+zm composition (atomic %)
m, amorphous formation ability with a plate thickness of 28 μm):) is used as an anode,
Electrolytic treatment was performed in an aqueous solution containing 34% sodium aluminate and 1 wt% tartaric acid. At this time, electrolysis: 7 nights, the temperature was 40°C, and the electric density was 10^/d.
m 2, after 2 seconds of electrolysis the average film]T
An alumina coating of 0.0871 m thick was formed.

Next, magnetic field annealing was performed at 370° C. for 11 hours under a reduced pressure of 1 to 3 Torr, followed by cooling. Iron 1, an amorphous alloy ribbon with an insulating coating prepared in this way,
tlW+:+zs. was 0.11 W/kg. The surface layer was examined by thin film X-ray diffraction, but no crystalline material was detected.

Disaster - Umeboshi J2 Processing was carried out in the same manner as in Example 1, except that the alloy composition was changed to FetJnlB +zSi+o. The resulting amorphous alloy ribbon with an insulating coating had an iron yield 3/So of 0.
It was 10 pairs/kg. Furthermore, no crystalline substance was detected in the surface layer by thin film X-ray diffraction.

The process was carried out in the same manner as in Example 1, except that the two U-neck inlay alloys had a composition of Fe7sMnzSizB +zSio. The resultant amorphous alloy ribbon with an insulating coating was easily beaten 1W1i after annealing in a magnetic field.
/s. was 0.12←/'kg. Furthermore, no crystalline substance was detected in the surface layer by thin film X-ray diffraction.

Example 1 An amorphous alloy thin film with a t'A coating was prepared in the same manner as in Example 1 except that the alloy composition was changed to Fe, tMn+B+zSiqC+.

Next, air: Magnetic field baking at 380°C for 21 hours in a 1.L
Ai! Around the time of i, 1iJnW+:+/so is 0.0
It was 9W/kg-. Furthermore, no crystalline substance was detected in the surface layer by thin film X-ray diffraction.

For comparison, an amorphous alloy ribbon having the same alloy composition as in Example 2 was subjected to electric treatment in the same manner as in Example 1, and the obtained amorphous alloy ribbon with an insulating coating was treated in a dry Ar gas stream. Magnetic field annealing (37
0'C 11 hours, 20008/m), the steel was 1 member W + 3/S. deteriorated to 0.29W/kg. In addition, when the surface of the ribbon was examined by X-ray diffraction, surface crystallization of α-Fe was found to be 611 L'2.

(Effects of the Invention) According to the present invention, an amorphous alloy ribbon coated with an insulating film by anodization can be annealed without causing deterioration of core loss characteristics.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the infrared reflection spectrum of an A12011 coating formed on the surface of an amorphous alloy ribbon by anodization. Figure 1

Claims (1)

[Claims] 1. A reduced pressure inert gas atmosphere is used as the annealing environment when annealing the boron-containing iron-based amorphous alloy ribbon having an oxide insulating film formed on the surface by anodizing. Annealing method for amorphous alloy ribbon. 2. Reduced pressure inert gas atmosphere is 10^-^4 to 10
The method of annealing an amorphous alloy ribbon according to claim 1, wherein the annealing temperature is 0 Torr. 3. The boron-containing iron-based amorphous alloy contains B: 7 to 16 atom%, Si: 4 to 14 atom%, and the balance is substantially Fe-B-
A method for annealing an amorphous alloy ribbon according to claim 1 or 2, wherein the amorphous alloy ribbon is a Si-based alloy. 4. The boron-containing iron-based amorphous alloy contains: B: 7 to 16 atomic %, Si: 4 to 14 atomic %, and C: 2 atomic % or less, and the remainder is Fe- B-
A method for annealing an amorphous alloy ribbon according to claim 1 or 2, wherein the amorphous alloy ribbon is a Si-C alloy. 5. The boron-containing iron-based amorphous alloy contains: B: 7 to 16 at%, Si: 4 to 14 at%, total of one or two of Mn and Ni: 0.5 to 10 at%
The method of annealing an amorphous alloy ribbon according to claim 1 or 2, wherein the amorphous alloy ribbon is an Fe-(Mn, Ni)-B-Si alloy consisting of 65 to 85 at% of Fe. 6. The boron-containing iron-based amorphous alloy has the following characteristics: B: 7 to 16 atomic %, Si: 4 to 14 atomic %, C: 2 atomic % or less, total of one or two of Mn and Ni: 0.5 to 16 atomic %. 10 atomic%
The method of annealing an amorphous alloy ribbon according to claim 1 or 2, wherein the amorphous alloy ribbon is an Fe-(Mn, Ni)-B-Si-C alloy consisting of 65 to 85 atomic % of Fe.