JP3537339B2 - Grain-oriented electrical steel sheet having excellent film properties and magnetic properties and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet mainly used as an iron core for transformers and other electric equipment, and a method for producing the same. In particular, the present invention provides a grain-oriented electrical steel sheet having excellent film properties and magnetic properties by controlling the rate of temperature rise and atmosphere in decarburization annealing, and a method for producing the same.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet used as a magnetic iron core in many electric devices usually contains 2.0 to 7% of Si, and the crystal structure of the product is highly integrated in the {110} <001> direction. Steel sheet As the product properties of grain-oriented electrical steel sheets, iron loss (represented by W17 / 50 (1.7T, power loss under 50 Hz excitation condition)) is low, and magnetic flux density (B
₈ (represented by a magnetic flux density at 800 A / m) is required to be high. In particular, recently, from the viewpoint of global environmental conservation and energy saving, iron core materials with low power loss,
That is, a grain-oriented electrical steel sheet having a low iron loss is required.
Also, increasing the crystal grain structure of the product {110} <001> and integrated in orientation B ₈ is effective in reducing iron loss by increasing the excitation characteristics. For this reason, technology development for improving iron loss and magnetic flux density of grain-oriented electrical steel sheets has been repeated.

A general method of manufacturing a grain-oriented electrical steel sheet is as follows. A silicon steel slab containing 2 to 7% or less of Si is hot-rolled and finished to a final sheet thickness by one or two cold-rolling steps including intermediate annealing. After that, decarburization, formation of a subscale mainly composed of SiO ₂ , and primary recrystallization are performed by annealing in a wet hydrogen atmosphere (decarburization annealing). Subsequently, an annealing separator mainly composed of MgO is suspended in water to form a slurry, applied and dried, wound around a coil, and subjected to final finish annealing. Due to this final annealing, secondary recrystallization occurs, and the crystal grain structure of the steel sheet accumulates in the {110} <001> direction. At the same time, MgO in the annealing separator and SiO ₂ in the subscale react on the steel sheet surface to form an annealed film mainly composed of forsterite (Mg ₂ SiO ₄ ). When AlN was used as an inhibitor for secondary recrystallization, this annealed film was MgAl ₂ O
Also contains ₄ . For this annealed film, a glass film, which is a common name in the following, will be used. The directional silicon steel sheet after the finish annealing is coated with an insulating coating as necessary.

One of the typical techniques for reducing iron loss is a so-called magnetic domain refining process. For example, Japanese Unexamined Patent Publication (Kokai) No. 58-26405 discloses a method in which a steel beam after finish annealing is irradiated with a laser beam to give a local minute strain as a material for a core of a pile. For a wound iron core, Japanese Patent Application Laid-Open No. 62-8617 discloses a method in which the magnetic domain refining effect is not lost even by strain relief annealing after processing a silicon steel sheet into an iron core.

One of the typical techniques for improving magnetic flux density is a manufacturing method disclosed in Japanese Patent Publication No. 40-15644. This is a manufacturing method in which AlN and MnS function as inhibitors and the rolling reduction in the final cold-rolling step is a strong rolling exceeding 80%. According to this method, the grain orientation is accumulated in the {110} <001> orientation by secondary recrystallization occurring at the time of final finish annealing, and B ₈ has a high magnetic flux density of 1.87 T or more. Is obtained. Although this manufacturing method can reduce iron loss to some extent, the secondary recrystallized grain size is 10 m.
m, and when the so-called magnetic domain segmentation treatment was not performed, a sufficiently low iron loss value expected from a high magnetic flux density was not obtained.

[0006] On the other hand, Japanese Patent Publication No. 6-51187 discloses a method of reducing the secondary recrystallized grain size and reducing iron loss without impairing the degree of orientation accumulation of the secondary recrystallized grain structure. . In this method, in the annealing for primary recrystallization (usually decarburizing annealing), the temperature is raised at a rate of 140 ° C./sec or more.
It is heated to a temperature of 75 ° C. or higher, subsequently decarburized, and then subjected to secondary recrystallization by ordinary final finish annealing. By increasing the rate of temperature rise in the primary recrystallization annealing, the secondary recrystallized grain size becomes smaller.

However, simply increasing the rate of temperature increase in the primary recrystallization annealing or decarburization annealing does not provide a low iron loss. In order to actually exert the metallurgical iron loss reduction effect of a high degree of orientation accumulation and a small secondary recrystallized grain size, it is necessary to apply a tensile stress to the steel sheet. The glass coating mainly composed of forsterite and spinel generated by the final finish annealing has a smaller coefficient of thermal expansion than the steel sheet, and greatly contributes to the reduction of iron loss. Therefore, it is necessary to form a good glass film. However, changing the heating rate changes the properties of the subscale generated by decarburization annealing, impairs the formation of the glass film, and the effect of the film on imparting tension to the steel sheet becomes insufficient, resulting in secondary recrystallization. The effect of improving iron loss by reducing the particle size decreases.

[0008] Good formation of a glass film is not only necessary for reducing iron loss, but also important in a transformer manufacturing process. In particular, in the case of a wound transformer, a bending process is applied to the grain-oriented electrical steel sheet in the manufacturing process, and at that time, the glass film may peel off. Therefore, the glass film is required to have excellent film adhesion. A change in the rate of temperature increase in the primary recrystallization annealing or the decarburization annealing deteriorates the adhesion of the glass film.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for increasing the temperature of primary recrystallization annealing or decarburizing annealing,
It discloses a method for improving the formation of a glass film. As a result, an object is to provide a grain-oriented electrical steel sheet which is superior to conventional grain-oriented electrical steel sheets in both film properties (coating adhesion) and magnetic properties (iron loss properties).

[0010]

Means for Solving the Problems In order to obtain a grain-oriented electrical steel sheet having both excellent film properties (film adhesion properties) and magnetic properties (iron loss properties), the inventors of the present invention carried out a decarburizing annealing process in which the temperature was raised. A test was conducted in which the final finish annealing was performed after various changes in the heating rate, atmosphere, and atmosphere during the soaking process of decarburization annealing. The relationship between the decarburizing annealing conditions and the film adhesion and iron loss characteristics of the product after final finish annealing was investigated, and the following findings were obtained.

(1) The glass film structure of a product excellent in both characteristics has characteristics different from those of a conventional grain-oriented electrical steel sheet.
That is, Al and Fe in glow discharge emission analysis
In the profile (1), the discharge time at which Al shows a peak is 1.5 times or more the discharge time at which the emission intensity of Fe becomes half the value of the bulk. (2) In the profiles of Al and Fe in the glow discharge emission analysis, the discharge time at which Al shows a peak is:
In the case where the emission time of Fe is twice or more of the discharge time when the emission intensity of the Fe becomes 1/2 of the bulk value, both characteristics are further excellent.

The glass film having the feature (1) is
The temperature range of at least 650 ° C. or higher in the temperature raising stage of the decarburizing annealing step is heated to 800 ° C. or higher at a temperature rising rate of 100 ° C./s or higher, and the atmosphere in this temperature range is defined as (a) or (b) below. (A) 10 ^-6 to 10 in volume fraction
An inert gas containing oxygen of ^-2 ; (b) the constituents of the atmosphere are H ₂ O and H ₂ , or H ₂ O and an inert gas, or H ₂ O and H ₂ and an inert gas; _The partial pressure of ₂ O is 10 ^{−4 to} 6 × 10 ⁻¹ , while the constituent components of the atmosphere during soaking in decarburizing annealing are H ₂ and H ₂ O or H ₂ and H _2.
O and an inert gas, and a ratio PH ₂ O / PH ₂ of the H ₂ O partial pressure to the H ₂ partial pressure is set to 0.15 to 0.65. The inert gas referred to in the present invention is N ₂ , A
It indicates gas species such as r and He that are neutral to the oxidation-reduction reaction.

The glass film having the feature (2) is
The temperature range of at least 650 ° C. or higher in the temperature raising stage of the decarburizing annealing step is heated to 800 ° C. or higher at a temperature raising rate of 100 ° C./s or higher, and the atmosphere in this temperature range is defined by the following (c) or (d). (C) 10 ^-6 to 10 in volume fraction
^-3 , an inert gas containing oxygen, (d) an atmosphere containing H ₂ O and H ₂ , or H ₂ O and an inert gas, or H ₂ O and H ₂ and an inert gas; _The partial pressure of ₂ O is 10 ^-4 to 1 × 10 ^-1 . On the other hand, the constituent components of the atmosphere during soaking in decarburization annealing are H ₂ and H ₂ O or H ₂ and H _2.
O and an inert gas, and a ratio PH ₂ O / PH ₂ of the H ₂ O partial pressure to the H ₂ partial pressure is set to 0.15 to 0.65.

The present invention is based on these findings, and the gist thereof is as follows. (1) By weight%, C: 0.005% or less, Si: 2.0
To 7.0%, the balance being Fe and unavoidable impurities, and an annealed film made of oxides of Mg, Si, and Al was formed on the surface, and the amount of the annealed film formed was 1 per one side of the steel sheet. ５5 g / m ² , the profile of Al and Fe in the glow discharge optical emission analysis satisfies the following formula, and the rate y at which film peeling does not occur when bending 20 mm in diameter.
A grain-oriented electrical steel sheet having excellent film properties and magnetic properties, characterized in that (%) satisfies the following equation and iron loss property W satisfies the following equation.

[0015] t (Al _p) a discharge time of emission intensity exhibits a peak of Al, t a (Fe _1/2) as the discharge time indicating the half of the emission intensity of the bulk value of Fe, t (Al _p ) / T (Fe _1/2 ) ≧ 1.5 where d is the plate thickness (mm), y (%) ≧ −122.45d + 112.55... W (W / kg) ≦ 2.37d + 0.280 (2) ) The profile of Al and Fe in the glow discharge emission analysis satisfies the following formula, the rate y (%) at which film peeling does not occur when bending 20 mm in diameter satisfies the following formula, and the iron loss characteristic W satisfies the following formula. (1) A grain-oriented electrical steel sheet having excellent film properties and magnetic properties as described in (1).

[0016] t (Al _p) a discharge time of emission intensity exhibits a peak of Al, t a (Fe _1/2) as the discharge time indicating the half of the emission intensity of the bulk value of Fe, t (Al _p ) / T (Fe _1/2 ) ≧ 2.0, where d is the plate thickness (mm), y (%) ≧ −122.45d + 122.55 W (W / kg) ≦ 2.37d + 0.260 (3) ) The grain-oriented electrical steel sheet according to (1) or (2), further comprising a magnetic domain refining treatment, wherein the grain-oriented electrical steel sheet has excellent film properties and magnetic properties.

(4) By weight%, C: 0.10% or less, S
i: 2.0 to 7.0%, Al: 400 ppm or less
And further contains a known inhibitor, with the balance being Fe and
Slabs consisting of unavoidable impurities
And rolling to the final product thickness to form a strip
And a step of decarburizing annealing and a step of final finishing annealing,
Coating and baking an insulating coating.
In the production method, at least the heating stage of the decarburization annealing process
Temperature rise rate of 100 ° C / s or more over temperature range of 650 ° C or more
To 800 ° C or higher, and immerse the atmosphere in this temperature range.
10 in integration rate^-6-10^-2Inert gas containing oxygen
On the other hand, the constituent components of the atmosphere during soaking in decarburization annealing
H _TwoAnd H_TwoO or H_TwoAnd H_TwoO and inert gas
And H_TwoO partial pressure H_TwoRatio PH to partial pressure_TwoO / P
H_Two0.15 to 0.65
(1) Grain-oriented electrical steel with excellent coating and magnetic properties
Plate manufacturing method.

(5) By weight%, C: 0.10% or less, S
i: 2.0 to 7.0%, Al: not more than 400 ppm, further contains a known inhibitor, and the remainder is treated with a usual method of a slab consisting of Fe and unavoidable impurities, until the final product thickness. A step of rolling into a strip, a step of decarburizing annealing, and a step of final finishing annealing,
Coating and baking an insulating coating, wherein the temperature range of at least 650 ° C. or higher in the temperature raising step of the decarburizing annealing step is increased to 800 ° C. or higher at a temperature raising rate of 100 ° C./s or higher. After heating, the components of the atmosphere in this temperature range are H ₂ O and an inert gas, or H ₂ O and H ₂ ,
Alternatively, H ₂ O, an inert gas and H ₂ are used, and the H ₂ O partial pressure is 10 ^{−4 to} 6 × 10 ⁻¹ . On the other hand, the constituent components of the atmosphere during the soaking of the decarburizing annealing are H ₂ and H ₂ O. Or H ₂ and H
The film characteristics according to (1), wherein ₂ O and an inert gas are used, and the ratio PH ₂ O / PH ₂ of the H ₂ O partial pressure to the H ₂ partial pressure is 0.15 to 0.65. A method for producing grain-oriented electrical steel sheets with excellent magnetic properties.

(6) By weight%, C: 0.10% or less, S
i: 2.0 to 7.0%, Al: not more than 400 ppm, further contains a known inhibitor, and the remainder is treated with a usual method of a slab consisting of Fe and unavoidable impurities, until the final product thickness. A step of rolling into a strip, a step of decarburizing annealing, and a step of final finishing annealing,
Coating and baking an insulating coating, wherein the temperature range of at least 650 ° C. or higher in the temperature raising step of the decarburizing annealing step is increased to 800 ° C. or higher at a temperature raising rate of 100 ° C./s or higher. Heating and atmosphere in this temperature range)
Inert gas containing 10 ^-6 to 10 ^-3 oxygen in volume fraction, while the constituent components of the atmosphere at the time of soaking in decarburizing annealing are H ₂ and H ₂ O or H ₂ and H ₂ O and H ₂ O. The ratio PH ₂ O / P of the H ₂ O partial pressure to the H ₂ partial pressure as an active gas
Of H _2, characterized in that a 0.15 to 0.65 (2) film characteristics and production method excellent grain-oriented electrical steel sheet on the magnetic properties described.

(7) By weight%, C: 0.10% or less, S
i: 2.0 to 7.0%, Al: 400 ppm or less
And further contains a known inhibitor, with the balance being Fe and
Slabs consisting of unavoidable impurities
And rolling to the final product thickness to form a strip
And a step of decarburizing annealing and a step of final finishing annealing,
Coating and baking an insulating coating.
In the production method, at least the heating stage of the decarburization annealing process
Temperature rise rate of 100 ° C / s or more over temperature range of 650 ° C or more
To 800 ° C. or higher and the atmosphere in this temperature range
The component is H_TwoO and inert gas or H_TwoO and H_Two,
Or H_TwoAnd H_TwoO and an inert gas, and H_TwoO minutes
Pressure 10^-Four~ 1 × 10^-1On the other hand, during the decarburization annealing
The constituent components of the atmosphere _TwoAnd H_TwoO or H_TwoWhen
H_TwoO and an inert gas, and H_TwoO partial pressure H_TwoTo partial pressure
Ratio PH to_TwoO / PH_Two0.15 to 0.65
Excellent in film characteristics and magnetic characteristics described in (2)
Method for manufacturing oriented magnetic steel sheets.

(8) The rapid heating of the decarburizing annealing is performed by energizing heating using an energizing roll.
(7) The method for producing a grain-oriented electrical steel sheet having excellent film properties and magnetic properties according to any one of (7). (9) The method for producing a grain-oriented electrical steel sheet having excellent film properties and magnetic properties according to any one of (4) to (8), further comprising performing a magnetic domain refining treatment.

Next, the present invention will be described in detail. Figure
1 、 final finish firing of grain oriented 0.23mm-oriented electrical steel sheet
Steel plate after dulling, that is, before applying insulation coating, or
Is glow discharge light emission from a steel plate with the insulation coating removed.
This is the analysis result by spectroscopy (GDS).
It reflects the structure. Fig. 1 (a) shows a normal product
1 (b) and (c) show the results of GDS measurement
5 is a GDS measurement result of a product according to the invention. FIG. 1 (a),
In (b) and (c), t (Al_p) Is for Al
The discharge time, t (Fe _1/2) Is the emission intensity of Fe
Is the discharge time at which the value of the bulk becomes 1/2. Also figure
1 (b) is t (Al_p) / T (Fe_1/2) Is 1.5 or more
Fig. 1 (c) shows the case where the value is 2.0 or more.
It is.

As described above, t (Al _p ) / t (Fe
_1/2 ) can vary depending on the manufacturing method. Therefore, 0.23
mm of grain-oriented electrical steel sheet, the film adhesion and t
FIG. 2 shows the result of investigating the relationship of (Al _p ) / t (Fe _1/2 ). The adhesion of the film is evaluated by a ratio (%) at which film peeling does not occur in a 20 mm diameter curvature bending. t
The larger the (Al _p ) / t (Fe _1/2 ), the more difficult it is for the film to peel off, indicating that the adhesion of the film is improved.

FIG. 3A shows the correlation between the thickness of the obtained steel sheet and the adhesion of the glass film. Adhesion of film is 20mm
The evaluation is made based on the ratio (%) at which no film is formed when the film is bent at the curvature of the diameter. That is, 130 manufactured under the same conditions
Approximately six test pieces were collected for each coil from the product coil before and after, and the frequency of occurrence of film peeling is shown. FIG.
1A, FIG. 1B, FIG. 1C
Respectively correspond to the test piece group showing the GDS profile described in. In the present invention, the adhesiveness is improved at all plate thicknesses as compared with conventional products. In particular, the adhesion is remarkably improved.

It is not clear why the above-mentioned correlation exists between the Al and Fe profiles in GDS and the glass film adhesion. It is presumed that the profile-like feature probably represents the structure of the glass film and the interface with the iron base. FIG. 3B shows the thickness dependence of the obtained iron loss characteristics. In FIG. 3B, FIG.
1 (b) and 1 (c) respectively correspond to the test piece groups showing the GDS profiles. In the present invention, the iron loss value is reduced at all plate thicknesses as compared with conventional products. In particular, the improvement in iron loss is remarkable.

The good iron loss characteristics of the product of the present invention were obtained by controlling the temperature rise rate of decarburization annealing to 100 ° C./sec or more and controlling the atmosphere during the temperature rise. Two points have an effect. One is the metallurgical effect. The second factor is the effect of improving the film itself. The metallurgical effect of the heating rate of decarburization annealing is
This can be interpreted with reference to, for example, US Pat.

First, (11) in the primary recrystallization texture
0) By preferentially growing the grains in the secondary recrystallization annealing, a secondary recrystallized structure in which {110} <001>, which is a desirable crystal structure, is dominant is obtained. That is, the (110) grains in the primary recrystallization texture are nuclei for obtaining a good secondary recrystallization texture. Therefore, as the number increases, the number of secondary recrystallized grains increases, and the secondary recrystallized grain size becomes smaller. On the other hand, (11) in the primary recrystallization texture
1) The grains promote the growth of (110) grains in the secondary recrystallization and have a function of stabilizing the secondary recrystallization. Therefore, it is important to enrich the (110) grains in the primary recrystallization texture in order to make the secondary recrystallized grain size smaller, but it is also necessary to take care not to reduce (111) at that time.

The influence of the heating rate on the nucleation of the primary recrystallization is large and has a significant effect on the primary recrystallization texture. When the heating rate increases, (110) increases while (111) decreases. The effect of increasing (110) is 10
The effect is remarkable at a heating rate of 0 ° C./sec or more,
A sufficient amount of (110) can be obtained by securing a temperature of 800 ° C. or higher at a temperature rising rate of 0 ° C./second or higher. The decrease in (111) due to an increase in the rate of temperature rise can be recovered by cooling immediately after heating. This effect becomes more pronounced as the cooling rate increases. In the case of energizing heating, the steel sheet between the pair of rolls is heated using two pairs of energizing rolls.
It is possible to perform cooling at 10 to 40 ° C at a cooling rate of ° C / sec. Therefore, in the electric heating method, both effects of rapid heating and rapid cooling can be obtained.

On the other hand, the effect on the film and the atmosphere dependency when the temperature rise rate of the decarburizing annealing is increased are based on completely new knowledge of the inventors. This finding was obtained using equipment that can independently control the warming zone and the atmosphere in the solitary tropics. The operation and effect will be described below. During the heating process, an initial oxide film is formed. The nature of the initial oxide film has a significant effect on subscale formation during the subsequent soaking process. Generally, oxidation of a Si-containing iron alloy occurs at 650 ° C. or higher, and therefore, in forming an initial oxide film, a temperature rise rate of 650 ° C. or higher and an atmosphere are important.

The present inventors have found that when a heating rate of 100 ° C./sec or more is employed, the obtained decarburized annealed oxide film and the base film obtained therefrom can be obtained even if the conditions for soaking are exactly the same as in the prior art. It has been found that the properties of the glass film formed on the film are completely different. In addition, it has been found that, when a heating rate of 100 ° C./sec or more is adopted, it is necessary to change the way of controlling the atmosphere during the heating.

Before describing the atmosphere control method at the time of temperature rise when the rapid temperature rise was adopted, which was found by the inventors, the concept of the conventional atmosphere adjustment for decarburization annealing will be described. The purpose of decarburization annealing is three points: formation of subscale, decarburization, and primary recrystallization necessary for a glass film formed by final finish annealing. The influence of the atmosphere is the former two points.
In order to form a good glass film by the final finish annealing, the main component of the subscale at the time of decarburizing annealing must be SiO ₂ and the generation of harmful FeO must be prevented. This is achieved by making the atmosphere weakly oxidizable. Specifically, the annealing atmosphere is a mixed atmosphere of H ₂ O and H ₂ and the partial pressure ratio is made 0.65 or less. On the other hand, SiO ₂ in subscale too lowered oxidizing atmosphere
And the decarburization is inhibited. So, usually,
The lower limit of the partial pressure ratio of H ₂ O to H ₂ is set to about 0.15. That is, the atmosphere design is described by an equilibrium parameter called H ₂ O and H ₂ partial pressure ratio. The above is the atmosphere design method at the time of soaking in the decarburizing annealing. However, when the heating rate at the time of heating is 50 ° C./sec or less as in the conventional case, the atmosphere design of the heating zone is also H ₂ O And H ₂ partial pressure ratio.

On the other hand, the inventors have found that when the rate of temperature rise is 100 ° C./sec or more, it is necessary to change the concept of the atmosphere during temperature rise. For example, H ₂
Even in the case of a mixed atmosphere of O and H ₂ , the final result is reflected not by the partial pressure ratio but by the absolute partial pressure of H ₂ O and the mixed atmosphere of N _{2 and} O _2. It has been found that good results can be obtained even in an atmosphere having high performance. This suggests that the oxidation reaction does not proceed equilibrium at a rapid heating rate. The detailed examination results are shown below.

The inventors set the heating rate of the decarburizing annealing to 100
In the case where the temperature was set to not less than ° C., various atmospheres were used at the time of raising the temperature and at the time of soaking, and the adhesion of the glass film formed by the final finish annealing was examined. The target was a grain-oriented electrical steel sheet having a thickness of 0.23 mm. Fig. 4 shows the results.
Shown in FIG. 4A shows a case where the atmosphere at the time of raising the temperature of decarburization is a mixed atmosphere of an inert gas and O ₂ . As shown in the figure, when the oxygen partial pressure at the time of temperature rise is less than 10 ^-6 and the PH ₂ O / PH ₂ at the time of soaking is less than 0.15, the residual carbon amount after the decarburization annealing is reduced. Therefore, the iron loss value of the final product is extremely deteriorated. O ₂ partial pressure at the time of temperature rise is 10 ^-2
And PH ₂ O / PH ₂ at the time of soaking is 0.
If it exceeds 65, F is added to the subscale after decarburizing annealing.
The glass film generated by the final finish annealing containing eO is not formed well. On the other hand, the O ₂ partial pressure at the time of temperature rise is 10 ⁻⁶ to 10 ⁻² , and the PH ₂ O / PH ₂
Is 0.15 to 0.65, the adhesion of the glass film generated by the final finish annealing is improved as compared with the normal production method in which the temperature rise rate of the decarburizing annealing is set to less than 100 ° C./sec. Is done. In addition, when the structure of the glass film in this case was analyzed by GDS, in the profiles of Al and Fe, the discharge time at which Al peaked was one of the discharge times at which the emission intensity of Fe was の of the bulk value. .5 times or more. In particular, the O ₂ partial pressure at the time of temperature rise is 10 ⁻⁶ to 1
0 ^-3 and then, and 0.15 to the PH ₂ O / PH ₂ during soaking
When it is set to 0.65, the heating rate of the decarburization annealing is set to 100
The adhesion of the glass film is remarkably improved as compared with a normal production method at a temperature of less than ° C./sec. Further, when the structure of the glass film in this case was analyzed by GDS, in the profiles of Al and Fe, the discharge time at which Al exhibited a peak was two times the discharge time at which the emission intensity of Fe was １ ／ of the bulk value. More than doubled.

FIG. 4 (b) shows that the atmosphere at the time of decarburization heating is H _2.
O and H ₂ , or H ₂ O and an inert gas, or H ₂
This is the case where O, H ₂ and an inert gas are used. As shown in the figure, when the H ₂ O partial pressure at the time of temperature rise is less than 10 ⁻⁴ and PH ₂ O / PH ₂ at the time of soaking is less than 0.15, the residual carbon after decarburization annealing is reduced. The amount is not less than 0.005%, and the iron loss value of the final product is extremely deteriorated. When the H ₂ O partial pressure at the time of temperature rise exceeds 0.6, and PH ₂ O / PH ₂ at the time of soaking
Exceeds 0.65, FeO is contained in the subscale after decarburizing annealing, and a glass film generated by final finishing annealing is not formed satisfactorily. On the other hand, H
₂ O partial pressure is set to 10 ^{-4 to} 6 × 10 ^-1 , and PH at the time of soaking
_{When 2} O / PH ₂ is set to 0.15 to 0.65, the glass film generated in the final finish annealing is compared with the normal production method in which the temperature rise rate of the decarburizing annealing is set to less than 100 ° C./sec. Is improved. In addition, when the structure of the glass film in this case was analyzed by GDS, in the profiles of Al and Fe, the discharge time at which Al peaked was one of the discharge times at which the emission intensity of Fe was の of the bulk value. .5 times or more. In particular, H ₂ O
The partial pressure is set to 10 ^-4 to 10 ^-1 and PH ₂ O / P at the time of soaking.
When of H ₂ and 0.15 to 0.65, compared with heating rate of the decarburization annealing to the usual production method below 100 ° C. / sec, adhesion glass coating film is remarkably improved You. In addition, the structure of the glass film in that case was analyzed by GDS.
The discharge time at which Al exhibited a peak was twice or more the discharge time at which the emission intensity of Fe became half the value of the bulk.

It is surprising from the above results that the atmosphere during the decarburization heating process is almost always equilibrium harmful F
It is in the eO generation area. However, the state of formation of the glass film after the final finish annealing is extremely good, and no change in the color tone indicating that FeO is generated is observed on the surface of the steel sheet after the decarburizing annealing. Therefore, when the temperature rising rate of the decarburizing annealing is set to 100 ° C./sec, which is higher than the conventional rate, it can be said that the formation of the oxide film in the temperature rising process has a very strong non-equilibrium aspect.

As described above, in the present invention, the rate of temperature rise is set to be higher than that in the conventional decarburization annealing, and the atmosphere during the temperature rise process uses the absolute partial pressure of O ₂ or H ₂ O. Thus, a grain-oriented electrical steel sheet having excellent film properties and magnetic properties can be manufactured. In the present invention, as the heating equipment used in the temperature raising process of the decarburizing annealing, an induction heating device, an energization heating device including two pairs of energization rolls, or the like can be employed. As described above, the electric heating device is more preferable because in addition to the primary recrystallization texture improvement effect by rapid heating, the primary recrystallization texture improvement effect by rapid cooling can be obtained.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a grain-oriented electrical steel sheet of the present invention will be described. The grain-oriented electrical steel sheet of the present invention has C: 0.
005% by weight or less, Si: 2.0 to 7.0% by weight. If C exceeds 0.005%, the magnetic characteristics deteriorate due to magnetic aging. Si is required to be 2% or more in order to reduce iron loss, but if added excessively, it is easily cracked during cold rolling, and is made 7.0% or less.

The grain-oriented electrical steel sheet of the present invention has a glass coating mainly composed of forsterite or spinel on its surface, and the coating amount is 1 to 4 g / m ² per one side of the steel sheet.
It is. When the glass coating amount exceeds 4 g / m ² , the space factor deteriorates. On the other hand, the coating amount is 1 g / m
^If it is less than ² , the applied tension to the steel sheet is small and the effect of reducing iron loss is small, so it was set to 1 g / m ² or more.

The greatest feature of the grain-oriented electrical steel sheet of the present invention is that
It is in the structure of the glass film. That is, in the profiles of Al and Fe in the glow discharge emission analysis, the discharge time at which Al has a peak is set to be 1.5 times or more the discharge time at which the emission intensity of Fe becomes １ ／ of the bulk value. When this index exceeds 1.5 times, excellent adhesion of the glass film is obtained as compared with the conventional grain-oriented electrical steel sheet. That is, assuming that t is a plate thickness (mm), a probability y (%) of which film peeling does not occur when bending 20 mm in diameter is y (%) ≧ −12.
2.45t + 112.55 can be achieved.

The rapid heating in the temperature rising process of the decarburizing annealing has an effect of reducing the secondary recrystallized grain size. The improvement in the adhesion of the glass coating improves the application of tension to the steel sheet by the glass coating, and effectively exerts the iron-reducing ability of a potential product obtained by secondary recrystallization and refinement. As a result, assuming that t is a plate thickness (mm), iron loss characteristics W (W / kg)
≦ 2.37t + 0.280 This is a grain-oriented electrical steel sheet having good magnetic properties.

Further, in glow discharge emission analysis, Al
In the profile of Fe and Fe, the grain-oriented electrical steel sheet in which the discharge time at which Al shows a peak is 2.0 times or more the discharge time at which the emission intensity of Fe becomes の of the bulk value,
The adhesion of the glass film is further improved. That is, assuming that t is a plate thickness (mm), a probability y (%) that film peeling does not occur when bending 20 mm in diameter is y (%) ≧ −122.45 t + 12.
2.55 can be achieved. As a result, the iron loss characteristics are further improved, and W (W / kg) ≦ 2.37t + 0.2
A grain-oriented electrical steel sheet having good magnetic properties of 60 is obtained.

Next, a method of manufacturing a grain-oriented electrical steel sheet according to the present invention will be described. The grain-oriented electrical steel sheet of the present invention,
% By weight, C: 0.10% or less, Si: 2.0 to 7.0
%, Al: not more than 400 ppm and a usual inhibitor component, the remainder being a slab consisting of Fe and unavoidable impurities as a starting material. C is necessary for texture control in the intermediate step, but if it exceeds 0.10%, the time required for decarburization annealing becomes long, which is economically disadvantageous.
0%.

Si is required to be 2% or more in order to reduce iron loss, but if added excessively, it is easily cracked during cold rolling.
7.0% or less. Acid soluble Al is added because it utilizes AlN as an inhibitor to achieve good secondary recrystallization. The addition amount is set to 400 ppm or less from the viewpoint of obtaining a proper dispersion state of AlN. The amount of N added is not particularly limited in the present invention, but is preferably 0.003 to 0.02% in order to optimize AlN.

The addition of other precipitates and elements in addition to AlN as inhibitors generally gives good results with regard to secondary recrystallization. MnS or (Mn, Fe)
When S is used, Mn and S are added. In order to obtain an appropriate dispersion state of these sulfides in flight, the amount of S added is desirably 0.001 to 0.05%.
Note that Se may be added instead of S, or S and Se may be added simultaneously.

In addition, Cu, Sn, Sb, Cr, P,
Since elements such as Bi and Mo have the effect of strengthening the inhibitor, these elements are added in an amount not exceeding 1.0%.
More than one kind may be added. First, a molten steel containing the above components is used as a slab, which is hot-rolled to obtain a hot-rolled strip. After subjecting the hot-rolled strip to hot-rolled sheet annealing as necessary, a strip having a final product thickness is obtained by cold rolling once or twice or more including intermediate annealing.

When two or more cold rollings including intermediate annealing are employed, preferred conditions for hot-rolled sheet annealing, reduction ratio distribution, and intermediate annealing are as follows. The first rolling is performed at a rolling reduction of 5 to 60%, and hot-rolled sheet annealing and intermediate annealing are performed at 95%.
The temperature is 0 to 1200 ° C. for 30 seconds to 30 minutes, and the final draft is 85% or more. In cold rolling, a desired rolling reduction or plate thickness is obtained by a plurality of rolling passes.
Performing the holding at least once at 100 ° C. or more for about 30 seconds during the rolling pass is effective for improving the magnetic properties.

The strip rolled to the final product thickness as described above is subjected to decarburization annealing. The feature of the production method of the present invention lies in this decarburization annealing step. First, in the temperature rising process of decarburization annealing, a temperature range of at least 650 ° C.
The strip is heated to a temperature of 800 ° C. or higher with a temperature increase rate of 0 ° C./sec or higher. In order to achieve such a high heating rate, it is preferable to employ induction heating or energization heating as a heating method for the heating zone.

More importantly in the present invention, the above
It is a temperate atmosphere. The atmosphere in the temperature rising zone is O_TwoTo
Containing inert gas or H_TwoH containing O_Two, Inert gas
Or a mixed gas thereof. O_TwoTo
If the atmosphere contains_TwoThe partial pressure of 10^-6-10^-2of
Set to a range. H_TwoIn the case of an atmosphere containing O, H _Two
O partial pressure 10^-Four~ 6 × 10^-1Set to the range.

On the other hand, a tropical atmosphere is a normal
Similar to charcoal annealing. That is, H _TwoAnd H_TwoO, maybe
Is H_TwoAnd H_TwoO and inert gas mixed atmosphere, PH_Two
O / PH_TwoIs set to 0.15 to 0.65. PH_TwoO
/ PH_TwoIs less than 0.15, poor decarburization occurs and
Insufficient scale formation produces final finish annealing
The slippery glass film becomes thinner. On the other hand, exceeds 0.65
And FeO mixed into the sub-scale, resulting in poor glass film
Become

When the heating rate and the atmosphere in the heating zone for decarburizing annealing are set as described above, a grain-oriented electrical steel sheet having excellent film properties and magnetic properties can be obtained. The glass coating structure has characteristics different from those of conventional grain-oriented electrical steel sheets. That is, in the profiles of Al and Fe in the glow discharge emission analysis, the discharge time at which Al peaks is 1.5 times or more the discharge time at which the luminescence intensity of Fe becomes の of the bulk value. .

In order to further improve the film properties and magnetic properties, it is necessary to use O ₂ or H ₂ O
May be set more strictly. That is, when the atmosphere containing O ₂ sets the partial pressure of O ₂ in the range of 10 ^-6 to 10 ^-3. When the atmosphere containing of H ₂ O is, H ₂
The O partial pressure is set in the range of 10 ^-4 to 1 × 10 ^-1 . In the glass film of the grain-oriented electrical steel sheet obtained under the above conditions, in the profiles of Al and Fe in the glow discharge emission analysis, the discharge time at which Al peaks, the emission intensity of Fe is の of the bulk value. 2.0 times or more of the discharge time.

Incidentally, the amount of residual carbon after the decarburizing annealing needs to be 50 ppm or less as in the ordinary case. AlN
When only the inhibitor is used, the steel plate may be nitrided by annealing in an ammonia-containing atmosphere after the decarburizing annealing, and the inhibitor may be formed at this stage.
After decarburizing annealing, an annealing separator mainly composed of MgO is applied to the steel sheet and dried, and a final finish annealing at 1100 ° C. or higher is performed for the purpose of forming a glass film, secondary recrystallization, and purification. In many cases, after the final annealing, an additional insulating film is applied on the glass film. In particular, an insulating film obtained by baking a coating solution mainly composed of a phosphate and colloidal silica has a large applied tension to a steel sheet, and is effective for further improving iron loss.

Further, if the grain-oriented electrical steel sheet is subjected to a so-called magnetic domain refining treatment by laser irradiation, groove formation, or the like, an extremely low iron loss value can be obtained. This will be described in an embodiment.

[0054]

<Example 1> 3.25% by weight of Si,
0.078% C, 0.08% Mn, 0.01% P, 0.1%
03% S, 0.03% Al, 0.09% N, 0.08%
Molten steel containing Cu and 0.1% Sn was cast and hot-rolled after slab heating to obtain a hot-rolled sheet having a thickness of 2.3 mm. Subsequently, annealing was performed at 1100 ° C. for 3 minutes, and after pickling, cold rolling was performed to a thickness of 0.22 mm. During cold rolling, 220 ° C
For 5 minutes.

The rolled strip was divided into A to J, and coils A and B were subjected to ordinary decarburization annealing (conventional method). The coils C to J were subjected to rapid heating treatment of decarburizing annealing by electric heating. Table 1 shows the heating rate, the heating zone, and the atmosphere setting conditions for the solitary zone. Then, after applying MgO and performing final finish annealing in a hydrogen atmosphere at 1200 ° C. for 24 hours, an insulating film mainly composed of colloidal silica and phosphate was formed to obtain a product.

The properties obtained are shown in Table 1. The coils C to F satisfying the conditions of the present invention are grain-oriented electrical steel sheets having excellent film properties and magnetic properties. In particular, C to D satisfying the most preferable conditions show more excellent film properties and magnetic properties.

[0057]

[Table 1]

<Example 2> Of the coils obtained in Example 1, B, C, F and H were further subjected to a magnetic domain refining process.
That is, using a toothed roll, grooves having a depth of 15 μm and a width of 90 μm were formed at intervals of 5 mm in a direction at an angle of 12 ° with the direction perpendicular to the sheet passing direction (direction C). As shown in Table 2, the iron loss characteristics of each coil are very low.

[0059]

[Table 2]

[0060]

According to the present invention, a grain-oriented electrical steel sheet having excellent film properties and extremely good magnetic properties can be provided, and a method for producing the grain-oriented electrical steel sheet can be provided.

[Brief description of the drawings]

FIG. 1 (a) is a view showing Al and Fe profiles of a conventional grain-oriented electrical steel sheet by glow discharge emission spectroscopy. (B) The figure which shows the profile of Al and Fe in the glow discharge emission spectroscopy of the grain-oriented electrical steel sheet of Claim 1 of this invention. (C) The figure which shows the profile of Al and Fe in the glow discharge emission spectroscopy of the grain-oriented electrical steel sheet of Claim 2 of this invention.

FIG. 2 is a diagram showing a relationship between t (Al _p ) / t (Fe _1/2 ) and film adhesion of a grain-oriented electrical steel sheet.

FIG. 3 (a) is a diagram showing a correlation between a plate thickness and film adhesion. (B) The figure which shows the correlation of plate thickness and iron loss.

[FIG. 4] (a) The atmosphere in the heating zone of decarburization annealing is inert gas
And O_TwoOf the temperature rise zone_TwoAnd uniform tropical PH
_TwoO / PH_TwoThe figure which shows the relationship between a film property. (B) The atmosphere in the heating zone of the decarburization annealing is H_TwoO and inert gas
Or H_TwoO and H _TwoOr H_TwoO and inert gas
And H_TwoOf the temperature rise zone_TwoO and tropics
PH_TwoO / PH_TwoThe figure which shows the relationship between a film property.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kenji Kosuge No. 1 Fujimachi, Hirohata-ku, Himeji-shi, Hyogo Nippon Steel Corporation Hirohata Works (56) References JP-A-8-269561 (JP, A JP-A-7-316656 (JP, A) JP-A-7-278668 (JP, A) JP-A-7-113120 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 303 C21D 8/12 C22C 38/06 H01F 1/16

Claims (9)

(57) [Claims] 1% by weight of C: 0.005% or less, Si: 2.0 to 7.0%, the balance being Fe and unavoidable impurities, and oxidation of Mg, Si, Al on the surface. An annealed film made of a material is formed, the amount of the annealed film formed is 1 to 5 g / m ² per one surface of the steel sheet, and the profile of Al and Fe in glow discharge emission analysis satisfies the following formula. A grain-oriented electrical steel sheet having excellent film properties and magnetic properties, characterized in that the rate y (%) at which film peeling does not occur satisfies the following equation and the iron loss property W satisfies the following equation. t (Al _p) a discharge time of emission intensity exhibits a peak of Al, t a (Fe _1/2) as the discharge time indicating the half light emission intensity of the bulk of the value of _{Fe, t (Al p) /} t (Fe _1/2 ) ≧ 1.5 where d is the plate thickness (mm), y (%) ≧ −122.45d + 112.55... W (W / kg) ≦ 2.37d + 0.280 2. The profile of Al and Fe in glow discharge emission spectroscopy satisfies the following formula, the rate y (%) at which film peeling does not occur when bending 20 mm in diameter satisfies the following formula, and the iron loss characteristic W satisfies the following formula. The grain-oriented electrical steel sheet according to claim 1, which is excellent in film properties and magnetic properties. t (Al _p) a discharge time of emission intensity exhibits a peak of Al, t a (Fe _1/2) as the discharge time indicating the half light emission intensity of the bulk of the value of _{Fe, t (Al p) /} t (Fe _1/2 ) ≧ 2.0 where d is the plate thickness (mm), y (%) ≧ −122.45d + 122.55 W (W / kg) ≦ 2.37d + 0.260 3. The grain-oriented electrical steel sheet according to claim 1, wherein the grain-oriented electrical steel sheet is further subjected to a magnetic domain refining treatment. 4. A composition containing, by weight, C: 0.10% or less, Si: 2.0 to 7.0%, and Al: 400 ppm or less, further containing a known inhibitor, with the balance being Fe and unavoidable. A process of processing a slab made of impurities by a usual method, rolling it to a final product thickness to form a strip, and a process of decarburizing annealing,
In a method for manufacturing a grain-oriented electrical steel sheet including a step of final finish annealing and a step of applying and baking an insulating coating, a temperature range of at least 650 ° C. or more in a temperature rising step of a decarburizing annealing step is increased by 100 ° C./s or more. Heated at a temperature rate of 800 ° C. or higher,
The atmosphere in this temperature range is an inert gas containing oxygen in a volume fraction of 10 ^-6 to 10 ^-2 , while the components of the atmosphere at the time of soaking in the decarburizing annealing are H ₂ and H ₂ O, Alternatively, H ₂ and H ₂ O and an inert gas are used, and H ₂ O partial pressure H ₂
The ratio PH ₂ O / PH ₂ to the partial pressure is 0.15 to 0.65
The method for producing a grain-oriented electrical steel sheet having excellent film properties and magnetic properties according to claim 1. 5. In% by weight, C: 0.10% or less, Si: 2.0-7.0%, Al: 400 ppm or less.
Inhibitors, the balance being Fe and unavoidable impurities
Slab is processed in the usual way and pressed to the final product thickness.
A process of extending into a strip, a process of decarburizing annealing,
Final finishing annealing process and insulation coating application baking process
In the production method of grain-oriented electrical steel sheet including
The temperature range of at least 650 ° C. or higher in the heating stage of the blunt process
Heating to 800 ° C. or more at a rate of 100 ° C./s or more,
The constituents of the atmosphere in this temperature range are H_TwoO and inert gas
Or H_TwoO and H_TwoOr H_TwoO and inert gas
And H_TwoAnd H_TwoO partial pressure is 10^-Four~ 6 × 10^-1,
On the other hand, the constituent components of the atmosphere during the soaking of the decarburizing annealing are H
_TwoAnd H_TwoO or H_TwoAnd H_TwoO and inert gas,
And H_TwoO partial pressure H_TwoRatio PH to partial pressure_TwoO / PH_Two
Is set to 0.15 to 0.65.
Manufacture of grain-oriented electrical steel sheets with excellent described film properties and magnetic properties
Construction method. 6. In% by weight, C: 0.10% or less, Si: 2.0 to 7.0%, Al: 400 ppm or less, further containing a known inhibitor, the balance being Fe and inevitable A process of processing a slab made of impurities by a usual method, rolling it to a final product thickness to form a strip, and a process of decarburizing annealing,
In a method for manufacturing a grain-oriented electrical steel sheet including a step of final finish annealing and a step of applying and baking an insulating coating, a temperature range of at least 650 ° C. or more in a temperature rising step of a decarburizing annealing step is increased by 100 ° C./s or more. Heated at a temperature rate of 800 ° C. or higher,
And the atmosphere in this temperature range is 10 ^-6 to 10 ^{-3 in} volume fraction.
Inert gas containing oxygen, while components of the atmosphere during soaking in decarburizing annealing are H ₂ and H ₂ O or H ₂
Coating of H ₂ and O and an inert gas, and claim 2, wherein the ratio PH ₂ O / PH ₂ to H ₂ partial pressure of H ₂ O partial pressure, characterized in that a 0.15 to 0.65 A method for producing grain-oriented electrical steel sheets with excellent properties and magnetic properties. 7. In weight percent, C: 0.10% or less, Si: 2.0-7.0%, Al: 400 ppm or less.
Inhibitors, the balance being Fe and unavoidable impurities
Slab is processed in the usual way and pressed to the final product thickness.
A process of extending into a strip, a process of decarburizing annealing,
Final finishing annealing process and insulation coating application baking process
In the production method of grain-oriented electrical steel sheet including
The temperature range of at least 650 ° C. or higher in the heating stage of the blunt process
Heating to 800 ° C. or more at a rate of 100 ° C./s or more,
The constituents of the atmosphere in this temperature range are H_TwoO and inert gas
Or H_TwoO and H_TwoOr H_TwoAnd H_TwoO and not
Activated gas and H_TwoO partial pressure is 10^-Four~ 1 × 10^-1,
On the other hand, the constituent components of the atmosphere during the soaking of the decarburizing annealing are H
_TwoAnd H_TwoO or H_TwoAnd H_TwoO and inert gas,
And H_TwoO partial pressure H_TwoRatio PH to partial pressure_TwoO / PH_Two
Is 0.15 to 0.65.
Manufacture of grain-oriented electrical steel sheets with excellent described film properties and magnetic properties
Construction method. 8. The directionality excellent in film characteristics and magnetic characteristics according to claim 4, wherein the rapid heating of the decarburizing annealing is performed by electric heating using an electric roll. Manufacturing method of electrical steel sheet. 9. The method for producing a grain-oriented electrical steel sheet having excellent film properties and magnetic properties according to claim 4, wherein the electrical steel sheet is further subjected to a magnetic domain refining treatment. .