JPH05287462A - Superfine crystal alloy for transformer iron core and its production - Google Patents

Abstract

PURPOSE:To obtain an iron core material for transformer minimal in iron loss at a commercial frequency by rapidly cooling and solidifying a molten Fe-Zr-B-Cu alloy of specific composition and applying annealing to the resulting amorphous sheet at specific temp. CONSTITUTION:A molten Fe-Zr-B-Cu alloy having a composition represented by chemical formula Fe100-a-b-cZraBbCuc (where the symbols (a), (b), and (c) stand for, by atom, 2-6%, 4-16%, and 0.1-3%, respectively) is refined, in vacuum of <=10<-3>Torr or in an inert gas atmosphere of Ar, etc., in a vessel made of an oxide type refractory, such as MgO and CaO, having an affinity for O2 at >=1200 deg.C larger than the affinity of Zr for O2. Subsequently, this molten metal is rapidly cooled and solidified in the same atmosphere and the resulting amorphous alloy sheet is annealed at a temp. at which only the crystalline grain of alpha-Fe is precipitated, by which superfine crystalline grains having grain size, e.g. of <=50nm are uniformly precipitated. By this method, the alloy sheet for transformer iron core in which iron loss in 1.3T magnetic flux density at a commercial frequency of 50Hz, etc., is reduced to <=0.1w/kg and which has superior properties can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrafine crystal alloy for a transformer core and a method for producing the same, and particularly as a core for a transformer whose commercial frequency is 50 Hz.
An attempt is made to propose an Fe-based ultrafine crystal alloy having remarkable iron loss characteristics together with its advantageous manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a silicon steel sheet having a high saturation magnetic flux density and a relatively small iron loss has been used as a transformer core material used at a commercial frequency. However, although this silicon steel sheet has been gradually reduced in iron loss value due to technological progress, in recent years, when a material having more excellent iron loss characteristics is demanded due to the demand for energy saving, the iron loss characteristics are sufficiently reduced. It was not satisfactory, and there was also a disadvantage in terms of heat generation of the transformer.

Therefore, as a result of research and development on an Fe-based amorphous alloy ribbon produced by the single roll method, as described in JP-A-62-188748, etc.,
Some of which have a low iron loss value, which is about 1/3 that of silicon steel sheets at commercial frequencies, have been obtained, and some of them have been put into practical use. However, although this Fe-based amorphous alloy has a low iron loss, it has a large magnetostriction, and also has problems such as deterioration of magnetic properties due to vibration and deformation.

In recent years, by subjecting an amorphous alloy of an appropriate composition to a heat treatment to precipitate ultrafine crystals, not only the magnetostriction and aging which are problems of the above-mentioned amorphous alloy are suppressed, but also high frequency region. It has been found that compared with the amorphous alloy, the iron loss is remarkably reduced and the iron loss value is as low as that of the amorphous alloy even in the low frequency region of the commercial frequency. Examples of such materials include the materials described in JP-A-63-302504.

[0005]

[Problems to be Solved by the Invention] Japanese Patent Laid-Open No. 63-302504
The conventional ultrafine crystal material as described in Japanese Patent Publication is aimed at improving the magnetic characteristics especially at high frequencies, and therefore the iron loss value in the commercial frequency range is currently significantly different from that of amorphous alloys. There is no. Therefore,
There is a possibility that even better soft magnetic characteristics can be obtained in the commercial frequency range by devising the component system, manufacturing conditions, and the like. An object of the present invention is to newly develop an alloy ribbon for a transformer, which has a relatively high saturation magnetic flux density, a low magnetostriction, and a small change over time, and which has a lower iron loss than an amorphous alloy at a commercial frequency. To propose.

[0006]

The present invention has the chemical formula: Fe
_100-abc Zr _a B _b Cu _c , and a, b and c are a: 2 to 6 atom%, b: 4 to 16 atom% and c: 0.1
It is an ultrafine crystal alloy for a transformer iron core having a composition satisfying ~ 3 at%. It is advantageous that the ultrafine crystal alloy has an iron loss value of 0.1 W / kg or less at a commercial frequency of 50 Hz and a magnetic flux density of 1.3 T.

The method for producing an ultrafine crystal alloy of the present invention is represented by the chemical formula: Fe _100-abc Zr _a B _b Cu _c , and a, b and c are a: 2 to 6 atomic%, b: Molten metal prepared to have a composition satisfying 4 to 16 atomic% and c: 0.1 to 3 atomic% is rapidly solidified to produce an amorphous alloy ribbon, and then the amorphous alloy ribbon is annealed to obtain fine crystal grains. Is deposited.

Here, the container for holding the molten metal used when preparing the molten metal is
The affinity for oxygen at 1200 ° C or higher is made of an oxide refractory or a complex oxide of an element having an affinity for Zr and oxygen or higher, and the annealing temperature is a temperature at which only α-Fe crystal grains are precipitated. Advantageously, the step of preparing the molten metal, the step of producing the amorphous alloy ribbon and the step of annealing the amorphous alloy ribbon are performed in a vacuum or an inert gas atmosphere.

[0009]

[Function] According to the present invention, by limiting the component composition range of the ultrafine crystal alloy as described above, an ultrafine crystal alloy having a grain size of about 20 nm can be obtained, which results in a relatively high saturation magnetic flux density. It has low magnetostriction, little change over time, and a magnetic flux density of 1.3 T at a commercial frequency of 50 Hz, which is lower than that of amorphous alloys, that is, a low iron loss value of 0.1 W / kg or less.

In the present invention, Cu is an essential component, and its content c is in the range of 0.1 to 3 atom%. If the Cu content is less than 0.1 at%, there is almost no iron loss effect due to the addition of Cu, while if it is more than 3 at%, there is a disadvantage that the alloy is already apt to become brittle at the time of producing the ribbon. A particularly preferable Cu content is 0.5 to 2 atomic%, and in this range, an alloy having a particularly low iron loss can be obtained.

Further, Zr has a function of refining the crystal grains precipitated by complex addition with Cu. Zr content a is 2
Is limited to 6 atom%. If the Zr content is less than 2 atomic%, there is no sufficient iron loss reducing effect, while if it exceeds 6 atomic%, the saturation magnetic flux density decreases, making it unsuitable as a transformer material for commercial frequencies. A more preferable Zr content is 3 to 6 atomic%.

B is a component useful for facilitating the formation of an amorphous alloy during the production of the ribbon and for refining the crystal grains during annealing. The content b of B is limited to 4 to 16 atom%. If it is out of this range, it becomes difficult to form an amorphous alloy, which is not preferable. More preferable B content is
It is 6 to 10 atom%.

The alloy of the present invention comprises the steps of obtaining an amorphous alloy having the above composition by a liquid quenching method such as a single roll method,
It is obtained by a heat treatment step of heating and annealing this to form ultrafine crystal grains. The crystal grains formed by such heat treatment are mainly composed of α-Fe solid solution, and the ultrafine crystal grains having a grain size of 50 nm or less are almost evenly distributed, and this shows excellent soft magnetism. is there. In the case of an alloy exhibiting particularly excellent soft magnetism, the crystal grain size is often about 20 nm, and therefore, a suitable crystal grain size is about 20 nm ± 10 nm. The crystal grains are α-Fe solid solution. The structure of the alloy is mainly amorphous except for the ultrafine crystal grains, and the ratio of the ultrafine crystal grains in the structure is 60 to 100.
% Is preferable.

In producing the ultrafine crystal alloy of the present invention, it is preferable that the following conditions (1) to (4) are satisfied in order to produce an alloy sample having a particularly low iron loss value. Use an oxide refractory or a complex oxide of an element having an affinity for oxygen at 1200 ° C. or higher and an affinity for Zr and oxygen at or above 1200 ° C. in a molten metal holding container for melting the alloy. Annealing is performed at a temperature at which only the α-Fe phase precipitates. Perform melting, ribbon production and annealing in a vacuum or inert gas atmosphere.

Among the alloy components, and are intended to prevent the oxidation of Zr, which has a particularly strong affinity with oxygen. The presence of non-metallic inclusions caused by the oxidation of Zr in the alloy at a melting point of 1200 ° C or higher, which is the melting point of the present alloy, significantly deteriorates the soft magnetic properties. The refractory material may be MgO, CaO or Zr.
There are O _{2 and the} like, and two or more of these may be used. Further, it is desirable that these refractories have high purity with the impurity components suppressed as much as possible.

Further, as the vacuum atmosphere, specifically,
As a reduced pressure atmosphere of 10 ⁻³ torr or less and an inert gas atmosphere, an atmosphere of Ar, He, N ₂ or the like or a mixed gas thereof is preferable.

The reason is that only the α-Fe phase is a phase capable of forming ultrafine crystals. The optimum crystal structure can be obtained in the present invention by setting the annealing to a temperature at which only the α-Fe phase is precipitated. Among the crystallization temperatures from the amorphous phase in the alloy sample of the present invention, the crystallization temperature of the α-Fe phase is the lowest. Therefore, it is extremely easy to set the annealing temperature for crystallizing only this phase. The annealing temperature is about 480 to 530 ° C., and the annealing time is about 1 to 3 hours, although it depends on the component composition. If the annealing temperature is higher than the temperature at which only the α-Fe phase precipitates, it will be coarse.
It is gratifying that the crystal grains of the Fe-based compound will precipitate and the magnetic properties will deteriorate.

[0018]

[Examples] Various mother alloys having the composition ranges shown in Table 1 were prepared, and these were respectively melted in a crucible of MgO refractory having a purity of 98% in an Ar atmosphere, and then by a single roll method in an Ar atmosphere. It was rapidly solidified to produce an amorphous alloy ribbon with a width of 10 mm and a thickness of 20 μm. 1 of these amorphous ribbons
Annealing was performed for 1 hour at various temperatures in the range of 400 to 600 ° C. in a vacuum of 10 ⁻⁵ Torr.

[0019]

[Table 1] Alloy composition: Fe _100-abc Zr _a B _b Cu _c where a: 0 to 10 atom% b: 0 to 20 atom% c: 0 to 5 atom%

The iron loss value at a frequency of 50 Hz and a magnetic flux density of 1.3 T was measured for each of the annealed samples. The annealing temperature at the time of producing the sample showing the lowest iron loss value in each composition was taken as the optimum annealing temperature in that composition. FIG. 1 shows the relationship between the iron loss value and the content of the constituent elements at the optimum annealing temperature of each composition. According to this, the content of Zr is 4
It can be seen that the lowest iron loss value is obtained at ~ 6 atom%. As for the B content and the Cu content, as shown in FIGS. 2 and 3, respectively, it was found that the optimum values were 7 to 9 atom% and 0.5 to 2 atom%, respectively. Also, when Agnesia material is used for the molten metal holding container, it is about 70
It showed a low iron loss value (0.07 W / kg).

FIG. 4 shows the state of heat generation due to crystallization in the differential thermal analysis, and FIG. 5 shows the relationship between the annealing temperature and the iron loss value. In FIG. 4, among the plurality of exothermic peaks in the differential thermal analysis, the lowest temperature peak corresponds to the crystallization temperature T _X1 of α-Fe, and the higher temperature peak is the crystallization temperature T of the Fe-based compound. Corresponds to _X2 . As is clear from FIG. 5, by setting the annealing temperature to a temperature slightly higher than the crystallization temperature T _X1 of α-Fe and obviously lower than the crystallization temperature T _X2 of the Fe-based compound, the lowest iron loss can be obtained. Indicates a value. In addition, in the component composition shown in FIG. 5, it was T _X1 : 480 ° C. and T _X2 : 570 ° C.

The iron loss value at a frequency of 50 Hz and a magnetic flux density of 1.3 T of the sample having the lowest iron loss value and the annealing temperature was 0.07 W / kg. This value is an excellent value of about 70% of the iron loss value of a typical amorphous alloy.

[0023]

The alloy of the present invention has a relatively high saturation magnetic flux density, a low magnetostriction and a small change over time, and has a significantly lower iron loss than the amorphous alloy in the low frequency region, and is excellent as a low frequency transformer material. ing.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of Zr amount on iron loss value.

FIG. 2 is a graph showing the effect of the amount of B on the iron loss value.

FIG. 3 is a graph showing the effect of Cu amount on the iron loss value.

FIG. 4 is a graph showing crystallization of an amorphous alloy by differential thermal analysis.

FIG. 5 is a graph showing the influence of the crystallization temperature on the iron loss value.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C22C 45/02 A H01F 1/153

Claims (6)

[Claims] 1. A chemical formula: Fe _100-abc Zr _a B _b Cu _c , wherein a, b and c are a: 2 to 6 atom%, b: 4 to 16 atom% and c: 0.1 to 3 Ultra-fine crystal alloy for transformer iron core with composition satisfying atomic%. 2. The ultrafine crystal alloy for a transformer iron core according to claim 1, which has an iron loss value of 0.1 W / kg or less at a commercial frequency of 50 Hz and a magnetic flux density of 1.3 T. 3. A chemical formula: Fe _100-abc Zr _a B _b Cu _c , wherein a, b and c are a: 2 to 6 atom%, b: 4 to 16 atom% and c: 0.1 to 3 Molten metal prepared to have a composition satisfying atomic% is rapidly solidified to produce an amorphous alloy ribbon, and then this amorphous alloy ribbon is annealed to precipitate fine crystal grains. Manufacturing method of ultrafine crystal alloy. 4. The molten metal holding container used when preparing the molten metal is made of an oxide refractory or a complex oxide of an element having an affinity for oxygen at 1200 ° C. or higher that is equal to or higher than the affinity for Zr and oxygen. Item 4. A method for producing an ultrafine crystal alloy for a transformer core according to Item 3. 5. The method for producing an ultrafine crystal alloy for a transformer iron core according to claim 3, wherein the annealing temperature is a temperature at which only α-Fe crystal grains are precipitated. 6. The method of claim 3, wherein the step of preparing the molten metal, the step of preparing the amorphous alloy ribbon and the step of annealing the amorphous alloy ribbon are performed in a vacuum or an inert gas atmosphere.
A method for producing an ultrafine crystal alloy for a transformer iron core according to the description.