JPH05304016A - Low iron loss unidirectional electromagnetic steel plate - Google Patents

Abstract

PURPOSE:To reduce iron loss in a low magnetic field by a method wherein a magnetic domain fractionation treatment is conducted on a unidirectional electromagnetic steel plate containing specific weight of Si in the state wherein the quantity of oxide, when an insulating film is formed after finish annealing has been conducted, is specified. CONSTITUTION:The iron loss characteristics of a chemical polishing plate is better than a pickling plate before performance of a magnetic domain fractionation, but the iron loss of both plates is lowered when the magnetic domain fractonation treatment is conducted, and there is almost no difference of iron loss. This indicates that the effect of surface roughness inflicting on the iron loss of a unifirectional electromagnetic steel plate becomes small when the magnetic domain fractionation treatment is conducted. As a result, the amount of oxide present on the surface or on its vicinity of the unidirectional electromagnetic steel plate, containing Si of 2.0 to 4.5%, is decreased to 0.5g/m<2> or less per one side of the steel plate. As a result, a unidirectional electromagnetic steel plate, which displays excellent characteristics when used in a low magnetic field, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unidirectional electrical steel sheet with artificially subdivided magnetic domains and low iron loss, and more particularly to a unidirectional electrical steel sheet which exhibits excellent properties when used in a low magnetic field. It is a thing.

[0002]

2. Description of the Related Art A unidirectional electrical steel sheet is used as an iron core material for electric equipment and is required to have a small iron loss. Conventionally, many improvements have been made in order to reduce the iron loss value of the grain-oriented electrical steel sheet. As one of the technical means for reducing the iron loss value of the grain-oriented electrical steel sheet, for example, Japanese Patent Publication No.
As disclosed in JP-A-7-73724 or JP-B-61-49366, a laser beam is applied to the surface of the grain-oriented electrical steel sheet after finish annealing to introduce a minute strain,
As a result, a technique is known in which the magnetic domain is subdivided and the iron loss value is lowered.

This magnetic domain refining technique has a drawback in that the strain introduced into the steel sheet by stress relief annealing performed after the product is processed into an iron core disappears, so that the magnetic domain refining effect also disappears. Therefore, this magnetic domain refining technique is applied only to products that are not subjected to stress relief annealing after they have been processed into iron cores, for example products used for stacked iron cores. In order to make up for the above-mentioned drawbacks, a magnetic domain refining technique in which the effect of magnetic domain refining does not disappear even when stress-relief annealing is applied to an iron core is disclosed in, for example, Japanese Patent Publication No. 62-53579 or Japanese Patent Publication No.
It is disclosed in the publication.

Conventionally, a linear or dotted line minute strain is introduced into the surface of a grain-oriented electrical steel sheet, a linear or dotted line groove is formed, and further a linear or dotted line fine pattern is formed. After smoothing the surface of the steel plate (base iron) by chemical polishing, electrolytic polishing, etc. in order to further increase the iron loss reduction effect by forming grain (fine structure) areas (hereinafter referred to as magnetic domain refinement treatment) , The magnetic domain subdivision processing is performed, for example, in Japanese Patent Publication Sho 58
No. 14851.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a grain-oriented electrical steel sheet capable of maximizing the iron loss reducing effect by magnetic domain refining treatment.

[0006]

The subject matter of the present invention is as follows. (1) In a unidirectional electrical steel sheet containing Si: 2.0 to 4.5% by weight, the amount of oxide when the insulating film formed after finish annealing is removed is 0.
A unidirectional electrical steel sheet having a low iron loss, which is 5 g / m ² or less and is subjected to magnetic domain control processing (magnetic domain subdivision processing).

(2) Si: 2.0-4.5% by weight
In a unidirectional electrical steel sheet containing aluminum, the amount of oxide when the insulating coating formed after finish annealing is removed is 0.5 g / m ² or less per one side of the steel sheet, and the linear or dotted strain is applied to the steel sheet surface. A low-loss unidirectional electrical steel sheet having an introduction portion. (3) In a unidirectional electrical steel sheet containing Si: 2.0 to 4.5% by weight, the amount of oxide when the insulating coating formed after finish annealing is removed is 0.
A unidirectional electrical steel sheet having a low iron loss, which is 5 g / m ² or less and has a linear or dotted groove introduction portion on the surface of the steel sheet.

(4) Si: 2.0-4.5% by weight
In the unidirectional electrical steel sheet containing, the amount of oxide when the insulating coating formed after finish annealing is removed is 0.5 g / m ² or less per one side of the steel sheet, and the surface of the steel sheet is linear or dotted. A grain-oriented electrical steel sheet with low iron loss, which has a fine grain region having an orientation different from the Goss orientation ({110} <001> orientation).

(5) The unidirectional electrical steel sheet with low iron loss according to any one of the above items 1 to 4, which has an insulating coating containing phosphate and colloidal silica as main components. Hereinafter, the present invention will be described in detail. The inventors of the present invention have conducted a number of experiments to find out the surface condition of the grain-oriented electrical steel sheet that can maximize the iron loss reduction effect by the magnetic domain refinement treatment. Among them, it was newly found that the degree of inhibiting the iron loss reducing effect by the magnetic domain refining treatment is larger in the oxide remaining in the steel sheet than in the unevenness of the steel sheet surface.

The present inventors first investigated the influence of the unevenness of the steel sheet surface on the iron loss reduction effect of the magnetic domain refining treatment.
The result is shown in FIG. In FIG. 1, the pickled plate is obtained by pickling a secondary recrystallized grain-oriented electrical steel sheet and has a remarkable surface irregularity. The chemically polished plate is a plate obtained by pickling the pickled plate in a hydrofluoric acid-hydrogen peroxide aqueous solution to smooth the surface. As is clear from FIG. 1, before the magnetic domain refining treatment, the chemical polishing plate has better iron loss characteristics than the pickled plate (the iron loss value is low). In both cases, iron loss is reduced and there is almost no difference in iron loss. This indicates that the effect of surface irregularities on the core loss of the grain-oriented electrical steel sheet is reduced when the magnetic domain refinement treatment is performed.

On the other hand, the present inventors have made extensive studies on other factors that impede the iron loss reducing effect of the magnetic domain refining treatment. As a result, it was found that the amount of oxides existing near the surface of the steel sheet affects the iron loss. The present inventors
As a result of further research, it is possible to obtain a unidirectional electrical steel sheet with an extremely low iron loss value by reducing the amount of oxides existing on or near the surface of the steel sheet to 0.5 g / m ² or less per one side of the steel sheet. And succeeded in completing the present invention.

The present invention will be described in more detail below.
The present inventors measured the iron loss value of steel sheets with various oxide amounts in order to clarify the effect of the amount of oxide on the iron loss value of the product. First, as an experimental material, plate thickness:
A 0.23 mm finish annealed unidirectional electrical steel sheet was prepared. Normally, in a grain-oriented electrical steel sheet, MgO, which is the main component of the annealing separator, and SiO _{2 on the} surface of the steel sheet react during finish annealing to form an oxide mainly composed of Mg ₂ SiO ₄ (forsterite). ing. Therefore, the oxide on the surface of the steel sheet was removed by pickling with a mixed aqueous solution of hydrofluoric acid and sulfuric acid.
At this time, the amount of residual oxide was variously changed by changing the pickling time. After that, a treatment for forming an insulating film containing phosphate and colloidal silica as main components was performed.
Then, the surface of the steel sheet was irradiated with a laser beam to perform a magnetic domain subdivision process. For comparison, the iron loss value before magnetic domain refinement treatment was also measured.

The results are shown in FIG. As is clear from FIG. 2, when the magnetic domain refining treatment is not performed, the iron loss value is lower as the amount of oxide on the surface of the steel sheet is larger. This is because the effect of reducing iron loss due to the tension applied to the base metal by the oxide film (due to the difference in thermal expansion between the oxide film and the base iron) exceeds the effect of iron loss deterioration due to the unevenness of the oxide film-base iron interface. It is believed that there is. On the other hand, after removing the oxide generated on the steel sheet surface in the finish annealing step, forming an insulating coating containing phosphate and colloidal silica as the main components does not hinder the iron loss reduction effect by the magnetic domain refinement treatment. Not, rather, promote the effect.

According to the findings obtained by the study of the present inventors, when the magnetic loss is reduced by reducing the iron loss of the product by applying the magnetic domain refining treatment, the iron loss reducing effect is improved. It will be noticeable. In particular, by setting the amount of oxide per one surface of the steel sheet to 0.5 g / m ² or less, a product having a low iron loss value can be obtained. The present inventors obtained the above-mentioned knowledge by the following experiment. That is, an experiment was conducted in which Al ₂ O ₃ was applied to a steel sheet as an annealing separator and the amount of oxide remaining on the surface of the steel sheet after finish annealing was changed by adjusting the partial pressure of water vapor in the finish annealing step.

The results obtained are shown in FIG. As is clear from FIG. 3, when the magnetic domain refining treatment is not performed, the iron oxide characteristics are better (the iron loss value is lower) as the amount of oxide in the steel sheet increases. However, when the magnetic domain refinement treatment is performed, the iron loss reduction effect becomes more remarkable when the amount of oxides remaining in the steel sheet is smaller. In particular, the amount of oxide remaining on the steel sheet is 0.5.
The iron loss reducing effect is remarkable in the range of g / m ² or less. As described above, the oxide remaining in the steel sheet after finish annealing inhibits the iron loss reduction effect from the magnetic domain refinement treatment.

In order to reduce the amount of oxides remaining in the steel sheet after finish annealing to 0.5 g / m ² or less per side of the steel sheet, for example, a) the composition and dew point of the atmosphere during decarburization annealing,
Three important factors are b) the type and properties of the annealing separator, and c) the composition and dew point of the atmosphere in the finish annealing. The atmosphere in the decarburization annealing is usually a mixed gas of hydrogen and nitrogen, but it is important to control the mixing ratio and dew point at this time so that the steel sheet will not be overoxidized. Further, as the annealing separator, it is necessary to use one that is difficult to react with silica on the surface of the steel sheet after decarburization annealing. When an annealing separating agent containing MgO as a main component is used, it is desirable to use one having a low hydration amount. Alternatively, the use of an alumina-based annealing separator that does not react with silica to generate forsterite can reduce the amount of oxides remaining in the steel sheet after finish annealing. Further, the atmosphere during finish annealing should be as low as possible in an oxidizing atmosphere so as to prevent additional oxidation of the steel sheet during finish annealing. When the annealing separator is applied to the steel sheet after decarburization annealing, the electrostatic coating method is most effective.
The present inventors have used these methods in combination to determine the amount of oxides remaining in the steel sheet after finish annealing to 0.5 g per one side of the steel sheet.
/ M ² or less.

However, in the present invention, the amount of oxide remaining in the steel sheet after finish annealing is 0.5 g / m ² per one side of the steel sheet.
It goes without saying that the following means are not limited to the above method. For example, the steel sheet after finish annealing is pickled, and the amount of oxides remaining in the steel sheet is 0.5 per one side of the steel sheet.
You may make it g / m < ² > or less. When subjecting a steel sheet to a magnetic domain refinement treatment, a method of introducing a linear or dotted strain into the steel sheet, a method of introducing a linear or dotted groove into the steel sheet, a linear or dotted fine crystal A method of forming a grain area or the like can be adopted.

As a method of introducing linear or dotted strain into the steel sheet, an insulating film is formed after finish annealing as disclosed in, for example, Japanese Patent Publication No. 57-73724 and Japanese Patent Publication No. 61-49366. A method of irradiating the treated steel plate with a laser beam can be adopted. The linear or dotted strain introduced into the steel sheet is 45 in the rolling direction of the steel sheet.
Width 10 to 100μ so as to extend in the direction of ~ 90 °
When the m is less than 5 μm and the distance is 1 to 15 mm, the iron loss reducing effect is large. When the strain introduced into the steel sheet is a dotted line or a broken line, it is desirable that the distance between the points in the direction in which the dotted or broken strain extends be 0.1 mm or less. When introducing a linear or dotted groove into a steel plate,
Although the step of forming the groove may be before the finish annealing, it is necessary that the groove exists in the steps of the final product. Examples of means for forming a linear or dotted fine crystal grain region include, for example, Japanese Patent Publication Nos. 62-53579 and 63.
As disclosed in Japanese Patent No. 44804/1992, a large strain is introduced by a roll in which a tooth profile is engraved on a steel plate after finish annealing, and then heated to a temperature range of 550 ° C. or higher (stress relieving annealing may be substituted. Yes, it is possible to adopt a method of forming a fine grain region. The means for forming the linear or dotted fine crystal grain region is not limited to this, but the fine crystal grain size is 200 μm or less, and the linear or dotted fine crystal grain region is a steel plate. 45-90 ° to the rolling direction of
The effect of reducing the iron loss of the product is great when it extends in the direction of.
The fine grain area may be linear or dotted,
It is desirable that the distance between the dots in the direction in which the dotted or broken fine grain regions extend is 0.1 mm or less. Although the step of forming the linear or dotted fine crystal grain regions may be before the finish annealing, it is necessary that the fine crystal grain regions exist in the final product stage.

Next, in the present invention, the Si content is set to 2.
The reason for limiting the content to 0 to 4.5% will be described. If the Si content is less than 2.0%, the γ phase is generated in the finish annealing stage,
Disables secondary recrystallization. On the other hand, the Si content is 4.5
%, The steel sheet becomes brittle, cold rolling becomes extremely difficult, and smooth production is hindered.

[0020]

EXAMPLES Examples of the present invention will be described below. Example 1 C: 0.054%, Si: 3.30%, Mn: 0.14
%, S: 0.007%, acid-soluble A1: 0.030%,
N: 0.0075%, Cr: 0.10%, Sn: 0.0
5%, 115% steel ingot consisting of balance Fe and unavoidable impurities
After heating to 0 ° C., it was hot-rolled to a plate thickness of 1.6 mm.

The hot-rolled sheet was annealed at 1100 ° C., pickled and cold-rolled to a thickness of 0.16 mm. After this, 830 ℃,
Decarburization annealing was performed in a mixed gas atmosphere of hydrogen 25%, nitrogen 75%, and dew point 45 ° C. Next, as an annealing separator, Al ₂
Applying a O ₃ on the surface of the steel sheet, 1200 in a 100% hydrogen
Finish annealing was performed at 20 ° C. for 20 hours.

Next, using a tooth profile roll, a broken line-shaped groove having a depth of 3.5 μm, a width of 25 μm and an interval of 6 mm in the rolling direction was formed in a direction of 75 ° with respect to the rolling direction of the steel sheet. afterwards,
An insulating film mainly composed of phosphate and colloidal silica was formed. As a comparative example, the same process up to the cold rolling process was performed. After decarburizing and annealing in a mixed gas atmosphere of hydrogen 75%, nitrogen 25%, and dew point 55 ° C., the steel sheet surface was MgO 95%, TiO ₂ 5
%, An annealing separator having a blending composition of 100% was applied, finish annealing was carried out at 1200 ° C. for 20 hours in 100% hydrogen, and then an insulating coating containing phosphate and colloidal silica as a main component was formed. ..

The magnetic characteristics are shown in Table 1.

[0024]

[Table 1]

It can be seen from Table 1 that the present invention is superior to the comparative example, and iron loss can be further reduced by forming an insulating coating film containing phosphate and colloidal silica as main components. Example 2 C: 0.056%, Si: 3.36%, Mn: 0.09
%, S: 0.007%, acid-soluble Al: 0.029%,
N: 0.0078%, Cr: 0.08%, Sn: 0.0
4%, steel ingot consisting of balance Fe and unavoidable impurities 115
After heating to 0 ° C., it was hot-rolled to a plate thickness of 1.4 mm.

The hot rolled sheet was annealed at 1100 ° C., pickled and cold rolled to a thickness of 0.14 mm. After that, decarburization annealing is performed in a mixed gas atmosphere of 820 ° C., hydrogen 25%, nitrogen 75%, and dew point 45 ° C., and MgO as an annealing separator is applied to the surface of the steel sheet. Finish annealing was performed for a period of time, followed by pickling to reduce oxides.

Next, after forming an insulating film containing phosphate and colloidal silica as main components, a laser beam is irradiated to the steel plate in a direction of 75 ° with respect to the rolling direction, and the depth is 3 μm.
m, a width of 80 μm, and a strain of 10 mm in the rolling direction were formed in a dotted line shape. As a comparative example, the same process up to the cold rolling process was performed, and after decarburization annealing in a mixed gas atmosphere of 75% hydrogen, 25% nitrogen and 55 ° C dew point, 95% MgO and TiO ₂ were applied to the steel plate surface.
An annealing separator having a composition of 5% was applied, finish annealing was performed at 1200 ° C. for 20 hours in 100% hydrogen, and then an insulating coating film containing phosphate and colloidal silica as a main component was formed. did.

The magnetic characteristics are shown in Table 2.

[0029]

[Table 2]

It can be seen from Table 2 that the present invention is superior to the comparative example, and iron loss can be further reduced by forming an insulating coating film containing phosphate and colloidal silica as main components. As described above, according to the present invention, by setting the amount of oxide before the insulating coating forming step to 0.5 g / m ² or less per one side of the steel sheet, the iron loss reducing effect by the magnetic domain refining treatment is maximized. Become.

[0031]

INDUSTRIAL APPLICABILITY The present invention can remarkably improve the iron loss of the grain-oriented electrical steel sheet, and can greatly contribute to the effective use of energy.

[Brief description of drawings]

FIG. 1 is a diagram showing iron loss values of a pickled plate and a chemically polished plate before and after magnetic domain subdivision processing.

FIG. 2 is a diagram showing a relationship between an oxide amount and an iron loss value when the oxide amount is changed by a pickling method.

FIG. 3 is a diagram showing a relationship between an oxide amount and an iron loss value when Al ₂ O ₃ is used as an annealing separator.

Front page continuation (72) Inventor Takeo Nagashima 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Technical Development Division (72) Inventor Katsuro Kuroki 1-1, Hibatacho, Tobata-ku, Kitakyushu, Fukuoka Japan Steelworks Yawata Works

Claims (5)

[Claims] 1. In a unidirectional electrical steel sheet containing Si: 2.0 to 4.5% by weight, the amount of oxide when the insulating coating formed after finish annealing is removed is 0.5 g per one side of the steel sheet. / M ² or less and a magnetic domain control treatment (magnetic domain subdivision treatment) is applied, a low iron loss unidirectional electrical steel sheet. 2. In a unidirectional electrical steel sheet containing Si: 2.0 to 4.5% by weight, when the insulating film formed after finish annealing is removed, the amount of oxide is 0.5 g per one side of the steel sheet. / M ² or less, and a unidirectional electrical steel sheet with low iron loss, which has a linear or dotted line strain introduction portion on the steel sheet surface. 3. A unidirectional electrical steel sheet containing Si: 2.0 to 4.5% by weight, wherein the amount of oxide when the insulating coating formed after finish annealing is removed is 0.5 g per one side of the steel sheet. / M ² or less, and a unidirectional electrical steel sheet with low iron loss, which has a linear or dotted groove introduction portion on the surface of the steel sheet. 4. In a unidirectional electrical steel sheet containing Si: 2.0 to 4.5% by weight, the amount of oxide when the insulating coating formed after finish annealing is removed is 0.5 g per one side of the steel sheet. / M ² or less, and has a low iron loss characterized by having a fine grain region on the surface of the steel sheet which is linear or dotted and has an orientation different from the Goss orientation ({110} <001> orientation). Grain-oriented electrical steel sheet. 5. The grain-oriented electrical steel sheet with low iron loss according to claim 1, which has an insulating coating containing phosphate and colloidal silica as main components.