RU2792912C2 - Electrical steel sheet with oriented grain structure, steel sheet used for finish annealing, annealing separator, method for manufacturing electric steel sheet with oriented grain structure and method for manufacturing electric steel sheet for finished annealing steel plate - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to an annealing separator used in the process of finishing annealing in the production of a of electrical sheet steel with a grain-oriented structure. The annealing separator contains MgO as the main component, one or more elements selected from the group including Y, La and Ce, and one or more elements selected from the group including Ca, Sr and Ba. The proportions (%) of the contents of Mg, Y, La, Ce, Ca, Sr and Ba contained in the annealing separator, in relation to the content of MgO, satisfy the relationships: (1): (0.00562[Y]+0.00360[La]+0,00714[Ce])/0.0412[Mg]⋅100(%): from 0.20 to 1.60(%) and (2): (0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg]⋅100(%): from 0.20 to 1.80(%). The proportions (%) of the contents of Mg, Ca, Sr and Ba contained in the MgO raw material powder, in relation to the MgO content in the MgO raw material powder contained in the annealing separator, satisfy the relationship: (3): (0.0249[Ca']+0.0114[Sr']+0.0073[Ba'])/0.0412[Mg']⋅100(%): from 0.010 to 0.080(%). Therein the ratio (3) in relation to the ratio (2) is 0.200-0.020. The average particle size R1 of MgO is from 0.1 to 2.8 mcm, and the average particle size R2 of particles containing one or more elements selected from the group consisting of Ca, Sr and Ba in the annealing separator is from 0.2 to 3.0 mcm. The average particle size R1 and R2 satisfies the condition: (average particle size R2)/(average particle size R1) is from 0.5 to 3.0.

EFFECT: use of a calcined separator makes it possible to obtain a grain-oriented electrical steel sheet in which the fixing oxide layer and the surface oxide layer become suitable in shape, and it becomes possible to achieve both the shear and bending adhesion of the primary coating and the required steel loss characteristics.

2 cl, 4 dwg, 4 tbl, 1 ex

Description

FIELD OF TECHNOLOGY

[0001]

The present invention relates to a grain oriented electrical steel sheet, a finish annealing steel sheet, an annealing separator, a method for manufacturing a grain oriented electrical steel sheet, and a method for manufacturing a finish annealing steel sheet.

BACKGROUND OF THE INVENTION

[0002]

Grain-oriented electrical steel sheet is a steel sheet containing 0.5 to 7 mass% Si or so and having a crystal orientation controlled by {110}<001> orientation (Goss orientation). To control the orientation of the crystals, a phenomenon of catastrophic grain growth called secondary recrystallization is used.

[0003]

A method for manufacturing a grain-oriented electrical steel sheet is as follows: a slab is heated and hot-rolled to obtain a hot-rolled steel sheet. Hot rolled steel sheet is annealed according to needs. Hot rolled steel sheet is pickled. The pickled hot rolled steel sheet is cold rolled with a cold rolling reduction of 80% or more to produce a cold rolled steel sheet. The cold rolled steel sheet is subjected to decarburization annealing to cause primary recrystallization. Annealing-decarburized cold-rolled steel sheet is subjected to a finish annealing that causes secondary recrystallization. Through the above process, a grain-oriented electrical steel sheet is obtained.

[0004]

After the aforementioned decarburization annealing and before the finish annealing, an annealing separator containing MgO as a main component is applied to the surface of the cold rolled steel sheet. Generally, the method is to apply an aqueous slurry containing annealing separator components to a cold rolled steel sheet and dry it. Cold-rolled steel sheet coated with an annealing separator is wound into a roll, and then subjected to finishing annealing. During finish annealing, MgO from the annealing separator and SiO ₂ from the inner oxide layer formed on the surface of the cold-rolled steel sheet during the decarburization annealing react to form a primary coating on the surface of the steel sheet containing forsterite (Mg ₂ SiO ₄ ) as main component. After the formation of the primary coating, the primary coating, for example, is formed with an insulating coating (also called a "secondary coating"), consisting of colloidal silica and phosphate. Primary coating and insulation coating have lower coefficient of thermal expansion than the base steel sheet. For this reason, the primary coating, together with the insulating coating, applies tension to the base steel sheet in order to reduce steel (core) losses. In addition, the primary coating enhances the adhesion of the insulation coating to the base steel sheet. Therefore, it is preferable that the adhesion of the primary coating to the base steel sheet is higher.

[0005]

On the other hand, increasing the magnetic flux density and reducing the hysteresis loss are effective in reducing the steel loss in the grain-oriented electrical steel sheet.

[0006]

In order to increase the magnetic flux density of the grain-oriented electrical steel sheet, it is effective to control the crystal orientation of the base steel sheet according to the Goss orientation. A technique for improving integration into Goss orientation is provided in Patent Documents 1-3. In this patent literature, chemical elements that improve magnetic properties that enhance the effect of inhibitors (precipitated phases that inhibit the normal growth of crystal grains) (Cu, Sn, Sb, Bi, Te, Pb, Se, etc.) are contained in the main steel sheet. Due to this, the integration of the crystal orientations into the Goss orientation is improved, and the magnetic flux density of the grain-oriented electrical steel sheet can be improved.

[0007]

However, the interface of the base steel sheet and the primary coating is formed so that the free energy of the interface is as low as possible, making the interface between the base steel sheet and the primary coating flat. In particular, if the base steel sheet contains chemical elements to improve the magnetic properties, it is easier to make the interface flat. If the interface between the base steel sheet and the primary steel sheet becomes flatter, the fixing structures of the primary coating causing physical bonding strength between the primary coating and the primary steel sheet are lost, so the adhesion of the primary coating to the primary steel sheet is reduced. In particular, due to the compressive stress caused by the bending processes, peeling becomes easier and adhesion is markedly reduced.

[0008]

A technique for improving the adhesion of a primary coating to a steel sheet is described in Patent Documents 4 and 5.

[0009]

In Patent Document 4, slab components are made with a Ce content of 0.001 to 0.1 wt%, and the surface of a steel sheet is formed with a primary coating containing 0.01 to 1000 mg/m ² Ce. In Patent Document 5, a grain-oriented electrical steel sheet contains 1.8 to 7 mass% Si, has a primary coating containing forsterite as a main component, contains one or two elements of Ce, La, Pr, Nd in the primary coating. , Sc and Y with a density per side from 0.001 to 1000 mg/m ² and contains one or more elements of Sr, Ca and Ba with a density per side in a total amount of 0.01 to 100 mg/m ² .

[0010]

Patent Document 5 describes a manufacturing method including a series of processes for coating and drying an annealing cage on the surface of a base steel sheet that has been subjected to decarburization annealing and then finish annealing. Disclosed is a method for manufacturing a grain-oriented electrical steel sheet excellent in magnetic properties and primary coating adhesion, characterized in that an annealing separator containing MgO as a main component contains one or more oxides, hydroxides, sulfates or carbonates of Ce, La, Pr , Nd, Sc and Y with an average particle size of 0.1 to 25 μm in a total amount in terms of metal in the range from 0.01 to 14 wt.% in relation to MgO.

LIST OF QUOTATIONS

PATENT LITERATURE

[0011]

[PTL 1] Japanese Unexamined Patent Publication No. 6-88171

[PTL 2] Japanese Unexamined Patent Publication No. 8-269552

[PTL 3] Japanese Unexamined Patent Publication No. 2005-290446

[PTL 4] Japanese Unexamined Patent Publication No. 2008-127634

[PTL 5] Japanese Unexamined Patent Publication No. 2012-214902

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

[0012]

However, Patent Document 5 concerning Primary Coating Adhesion mentions the effect of reducing the peeling of the end surfaces caused by the shearing operation, but does not evaluate the peel resistance due to bending operations (bend operations by tens of mm or so) as being less applicable than operations shift. Peeling behavior due to shear and due to bending is different, therefore, in order to ensure the adhesion of the primary coating to the base steel sheet in the electrical steel sheet used in recent years for the high flexibility iron core manufacturing method, adhesion is necessary in which the primary coating does not peels off when bent under harsher conditions than before. Even in a material where there are no end face peel resistance problems, in some cases it is not always possible to obtain resistance to hard bending operations.

Further, in the process of cleaning the components of the steel sheet in the last stage of finishing annealing, nitrogen and other gases contained in the steel sheet are released. At this time, the primary coating slows down the passage of gas. At this time, if the rate of passage of gas through the primary coating becomes too slow, the gas pressure at the interface between the primary coating and the base iron becomes high, and the primary coating is sometimes blown away and destroyed. Due to this, exposed portions of the dot-shaped base material of a size that can be seen with the naked eye appear on the surface of the steel sheet. If these dot-shaped exposed portions of the base material appear with a certain number density over a wide range of the surface of the steel sheet, serious defects in insulation and appearance quality occur. The methods for improving Primary Coating adhesion mentioned above do not necessarily suppress pinholes, so an attempt has been made to control the shape of the Primary Coating without causing pinholes.

[0013]

With regard to Primary Coating adhesion, various studies have been carried out on end surface peeling in shearing operations and surface peeling in bending operations, but it cannot be said that optimal methods for manufacturing a steel sheet and manufacturing methods that are strictly different from each other have been proposed. The peeling behavior and mechanism due to shear and bending and high pressure gas generation are different, so when using the method of making iron rods that require bending operations, adhesion becomes necessary in which the primary coating does not peel off when performing more severe bending operations than before, and suppressing defects in the primary coating caused by outgassing from the steel sheet. If Y, La, Ce, Sr, Ca, and Ba are included in the annealing separator to form a primary coating containing Y, La, Ce, Sr, Ca, and Ba, technical problems arise, such as when there may be no problem with adhesion of the primary coating during shearing operations, but the adhesion of the primary coating during bending operations will be insufficient, or such as if the gas released from the steel sheet during finish annealing causes the destruction of the primary coating of the base steel sheet and the appearance of defects, and on the surface of the steel leaves show dotted shapes. For this reason, since the electrical steel sheet is free from insulation and appearance problems and is highly reliable, a material with Primary Coating adhesion in bending operations (hereinafter, simply referred to as "Coating Adhesion") and with few defects, if on dotted shapes appear on the base metal.

[0014]

It is an object of the present invention to provide a grain-oriented electrical steel sheet excellent in magnetic property and primary coating adhesion to a base steel sheet, having few defects when the base metal exhibits dotted shapes, and which is used for finish annealing of a steel sheet, to propose an annealing separator, a method for manufacturing a grain-oriented electrical steel sheet; and a method for manufacturing a steel sheet used for finishing annealing.

SOLUTION

[0015]

The present invention is characterized by controlling and determining the structure of an interface between a primary coating and a base steel sheet of a grain-oriented electrical steel sheet to define the structure of a primary coating.

In the present invention, based on the shape features schematically shown in FIG. 1, the Primary Coating is divided into two regions in the thickness direction, and patterns are defined in the respective regions. In the following explanation, in order to define these two regions, the surface side will be referred to as "surface oxide layer (1)", and the base steel sheet side will be referred to as "fixing oxide layer (2)". The surface oxide layer (1) is a region in the thickness direction where there is a part of the primary coating covering the surface of the base steel sheet relatively uniformly (hereinafter, this will sometimes be referred to as "surface oxides"). The anchor oxide layer (2) is a region in the thickness direction where portions of the Primary Coating penetrate into the base steel sheet are present, hereinafter they will sometimes be referred to as "fixing oxides"). The reference value H0 of the depth separating them will be explained later.

In this description, the structure of the interface will be determined by the morphological features of the primary coating from the side of the main steel sheet. Details will be explained later along with measurement methods.

Such interface structures between the primary coating and the base steel sheet, in particular the characteristic shapes, are generally sometimes referred to using the term "roots".

[0016]

The interface between the primary coating and the base steel sheet of the grain-oriented electrical steel sheet forms uneven shapes where fixing oxides penetrate into the inside of the base steel sheet. If the penetration depth of fixing oxides increases and the number density of the oxide particles (/µm ³ ) increases, then the adhesion of the primary coating to the base steel sheet increases due to the so-called "fixing effect"

[0017]

On the other hand, if the fixing oxides penetrate too much into the interior of the base steel sheet, they become factors preventing the growth of crystal grains of the steel sheet during secondary recrystallization or movement of the domain boundary during magnetization, and the magnetic properties deteriorate.

[0018]

In addition, the primary coating has the effect of imparting tension to the steel sheet and reducing steel loss. To increase the tension, the surface oxide layer (1) in the Primary Coating preferably has a high content of Mg ₂ SiO ₄ with a small linear expansion coefficient, while the surface oxide layer (1) is preferably thick.

[0019]

The authors investigated and studied the magnetic properties of a grain-oriented electrical steel sheet containing elements to improve the magnetic properties and adhesion of the primary coating formed using an annealing separator containing Y, La and Ce and Ca, Sr and Ba based on the above general assumptions. As a result, the authors obtained the following results.

Here, in the following explanation, one or more elements selected from the group consisting of Y, La and Ce will sometimes be collectively described as "elements of the Y group", and one or more elements selected from the group including Ca, Sr and Ba, will sometimes be described collectively as "elements of the Ca group".

[0020]

If the annealing separator contains Y-group elements and Ca-group elements to form the primary coating, even if the shear adhesion of the coating is sufficient, sometimes the adhesion of the coating in bending will be insufficient. In addition, if Y-group elements and Ca-group elements are added at the same time in large amounts to improve the bending adhesion of the coating, the steel loss and magnetic flux density sometimes decrease.

Further, lower, even if the surface area of the fixing oxide layer (2) is increased to control the shape of the Primary Coating to improve the adhesion of the coating, sometimes the Primary Coating is blown away by the gas released from the steel sheet during finishing annealing, and defects occur when the base metal point shapes appear.

Thereafter, if "adhesion" is simply mentioned, other than where clearly distinguished by coating shear adhesion and coating flexural adhesion, this will sometimes be used with the intention of indicating coating shear adhesion and flexural adhesion.

Further, below, when simply referring to "dot defects", this is sometimes used to refer to defects in which the Primary Coating is blown away by gas released from the steel sheet during finish annealing, and dot forms appear on the base steel sheet.

The authors additionally studied the influence of Y group elements and Ca group elements in the annealing separator and obtained the following results.

[0021]

If the annealing separator contains Y-group elements, then the anchoring oxide layer (2) becomes thicker. This improves shear adhesion of the coating.

In addition, if the annealing separator contains elements of the Ca group, the number density of the fixing oxide layer (2) of the formed primary coating is increased, and the shear adhesion of the coating is improved. In addition, as the total amount of the Ca group elements listed below in the primary coating, constituting the total content of the Ca group elements contained as impurities in the MgO raw material powder, and the amount obtained from the Ca group element compounds contained outside the powder of the Mg raw material in suitable ratios, the bending adhesion of the coating is improved and the deterioration of the magnetic properties is suppressed, and further pinholes are also suppressed. At the same time, in the primary coating, the surface oxide layer (1) becomes uniform in thickness and the Mg ₂ SiO ₄ phases increase, and furthermore, the fixing oxide layer (2) becomes longer in the longitudinal width direction in addition to the thickness direction. It is believed that the improvement in adhesion of the coating during bending is due to the fact that the thickness of the surface oxide layer (1) becomes uniform and the concentration of local stresses in areas of the surface oxide layer (1), which become thin in thickness, decreases during bending operations. In addition, the improvement in magnetic properties is believed to be due to the higher stress acting on the steel sheet due to the increase in the amount of Mg ₂ SiO ₄ phases in the surface oxide layer (1). In addition, by suppressing point defects, not only does the interface area of the fixing oxide layer (2) responsible for adhesion increase, but the oxides intertwine in shape, resulting in a structure with many gas diffusion paths. It is believed that the reason for this is the improvement in the gas permeability of the anchoring oxide layer (2).

In addition, it has been found that the primary coating having such excellent properties is characterized not only by the appearance of uneven shape at the interface, but also by the presence of Al in the vicinity of the interface of the primary coating. Next, the features of the annealing separator used to form such a primary coating were refined.

The interface between the base steel sheet and the primary coating takes on a complex three-dimensional shape having uneven shapes, such as shown in FIG. 1, so the authors experimented with setting the structural features of the three-dimensional phase interface. These activities are supposed to inherently quantize "three dimensional structures", but this has been difficult since they are three dimensional and complex structures. For this reason, the authors have experimented with projecting information related to interfacial structures onto a plane parallel to the surface of the steel sheet, as described below, and specifying interface features on the "plane". In addition, it was confirmed that the effect of the present invention can be evaluated and explained by quantitative statements based on "features on the projection plane".

[0022]

The salient features of the present invention resulting from these findings are as follows:

That is, when using an annealing separator containing MgO as the main component and where Y group elements and Ca group elements constitute a primary coating containing Mg ₂ SiO ₄ as a main component and containing Y group elements and Ca group elements, if the primary coating and the interface between the primary coating and the base steel sheet satisfies the features shown in the following items (1) to (8), then the fixing oxide layer (2) and the surface oxide layer (1) become suitable in shape, and it becomes possible to achieve both the adhesion of the primary coating in shear and bending, and the desired characteristics of losses in steel.

(1) The number density D3 of the number of areas of Al concentration is from 0.015 to 0.150/μm ² ,

(2) (Area S5 of regions consisting of anchoring oxide layer regions and Al concentration regions)/(Area S3 of Al concentration regions) ≥0.30,

(3) Distance H5 from the average value of the heights in the thickness direction of the regions consisting of the regions of the fixing oxide layer and the regions of Al concentration minus H0: 0.4 to 4.0 µm,

(4) (Total perimeter L5 of the regions consisting of the fixing oxide layer regions and the Al concentration regions)/(observed area S0): 0.020 to 0.500 μm/μm ² ,

(5) (Area S1 of fixing oxide layer areas)/(observed area S0) ≥0.15

(6) Total content of group Y elements: 0.1 to 6.0 mass%,

(7) Total content of Ca group elements: 0.1 to 6.0 mass%,

(8) Number density D4 of concentrated areas of Ca group elements: 0.005 to 2.000/ ^µm2

[0023]

In addition, the steel sheet used for finish annealing to produce a grain-oriented electrical steel sheet satisfies the following condition (9):

(9) Number density D42 of Ca-group elements in Ca-group element concentration regions of the annealing separator layer: 0.005 to 1.400/μm ³ .

[0024]

In addition, the primary coating and the annealing separator capable of forming the annealing separator layer satisfy the conditions (10) to (17).

(10) (0.00562[Y]+0.00360[La]+0.00712[Ce])/0.0412[Mg]*100(%): 0.20 to 1.60%,

(11) (1.40[Ca]+1.18 Sr+1.12 Ba)/1.66[Mg] •100%: 0.20 to 1.80%,

(12) (0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg] •100%: 0.010 to 0.080%,

(13) (12) (10)/(11): 0.020 to 0.200,

(14) R1 MgO average particle size: 0.1 to 2.8 µm,

(15) The average particle size R2 of particles containing elements of the Ca group in the areas of concentration of elements of the Ca group: from 0.2 to 3.0 μm,

(16) (average particle size R2)/(average particle size R1): 0.5 to 3.0.

[0025]

The essence of the present invention, obtained with these results, is as follows:

The grain-oriented electrical steel sheet of the present invention comprises a base steel sheet having a chemical composition containing, by mass%, C: 0.0050% or less, Si: 2.5-4.5%, Mn: 0.02 -0.20%, one or more elements selected from the group consisting of S and Se: total 0.005% or less, acid. sol. Al: 0.010% or less and N: 0.010% or less, and having other substances composed of Fe and impurities, and a primary coating formed on the surface of the base steel sheet and containing Mg ₂ SiO ₄ as the main component, where information about uneven shape of the surface of the primary coating in the direction from the side of the primary coating towards the main steel sheet in the direction of the thickness of the main steel sheet, as a positive projection on a plane parallel to the surface of the steel sheet, where the certain central value of the height of the surface of the primary coating is H0, the primary coating of the existing on the side of the base steel sheet from H0+0.2 µm, is referred to as "fixing the oxide layer area", and the base coating existing on the side of the primary coating from H0+0.2 µm is defined as the "surface area of the oxide layer", and according to the correlation diagram characteristic X-ray distribution, carrying information about the intensity of the component on the primary coating in the projection on a plane parallel to the surface of the steel sheet and uneven shape, and the maximum value of the characteristic X-ray intensity Al is determined, and the region where the intensity of the characteristic X-ray emission Al is 20% or more from the maximum value of the intensity of the characteristic X-ray radiation Al, is defined as the "Al concentration area", and the primary coating satisfies the conditions

(1) D3 number density of Al concentration areas: 0.015 to 0.150/μm ² ,

(2) (Area S5 of the regions, which is the region of the fixing oxide layer and is also the Al concentration region)/(Area S3 of the Al concentration regions) ≥0.30,

(3) Distance H5 from the average heights in the thickness direction of the regions that are the regions of the fixing oxide layer, as well as the region of Al concentration, minus H0: 0.4 to 4.0 µm,

(4) (Perimeter L5 of the regions that are the regions of the fixing oxide layer as well as the regions of Al concentration)/(observed area S0): 0.020 to 0.500 μm/μm ² ,

(5) (Area S1 of fixing oxide layer areas)/(observed area S0) ≥0.15

[0026]

In addition, the grain oriented electrical steel sheet is characterized in that the primary coating contains one or more elements selected from the group including Y, La and Ce, and one or more elements selected from the group including Ca, Sr and Ba, and when, in the correlation diagram of the characteristic X-ray intensity distribution and the uneven shape, the maximum values of the characteristic X-ray intensity Ca, Sr, and Ba, and the region where the characteristic X-ray intensity Ca is 20% or more of the maximum value of the characteristic X-ray intensity Ca, are identified, the region where the characteristic X-ray intensity - the Sr radiation intensity is 20% or more of the maximum value of the characteristic X-ray intensity Sr, and the region where the characteristic X-ray intensity Ba is 20% or more of the maximum value of the characteristic X-ray intensity Ba are together defined as "areas of concentration of elements of the Ca group", the primary coating satisfies the conditions

(6) The ratio of the total content of one or more elements selected from the group consisting of Y, La and Ce, to the content of Mg ₂ SiO ₄ in the primary coating: from 0.1 to 6.0%,

(7) The ratio of the total content of one or more elements selected from the group consisting of Ca, Sr and Ba to the content of Mg ₂ SiO ₄ in the primary coating: from 0.1 to 6.0%,

(8) Number density D4 of concentration areas of Ca group elements: 0.005 to 2.000/μm ² .

[0027]

In addition, the steel sheet used for finish annealing for producing grain-oriented electrical steel sheet contains a base steel sheet having a chemical composition containing, by mass%, C: 0.1% or less, Si: 2.5-4 .5%, Mn: 0.02-0.20%, one or more elements selected from the group consisting of S and Se: 0.005-0.07% total, acid. sol. Al: 0.005 to 0.050% and N: 0.003 to 0.0300% and having a balance of Fe and impurities, and an annealing separator layer deposited on the surface of the base steel sheet and containing MgO as the main component, where, when correlation of characteristic X-ray intensity distribution diagram and uneven shape, information related to the annealing separator on a plane parallel to the cross-section in the thickness direction of the base steel sheet is provided, the maximum values of the characteristic X-ray intensity of Ca, Sr and Ba are identified, and the region where the intensity of the characteristic X-ray of Ca is 20% or more of the maximum value of the characteristic X-ray intensity Ca, a region where the intensity of the characteristic X-ray Sr is 20% or more of the maximum value of the characteristic X-ray Sr, and a region where the intensity of the characteristic X-ray Ba is 20% or more from the maximum value of the characteristic X-ray intensity Ba, collectively referred to as "Ca group element concentration areas", the annealing separator layer is satisfied

(9) The number density D42 of particles containing one or more elements selected from the group consisting of Ca, Sr and Ba in concentration areas of Ca group elements present in a region of 0 to 3.0 µm from the surface of the base steel sheet: from 0.005 up to 1,400/µm ³ .

[0028]

The annealing separator according to the present invention is an annealing separator containing MgO as a main component, where the annealing separator contains one or more elements selected from the group including Y, La and Ce, and one or more elements selected from the group including Ca, Sr and Ba, and when determining the ratios (%) of the content of Mg, Y, La, Ce, Ca, Sr and Ba contained in the annealing separator, relative to the content of MgO, respectively [Mg], [Y], [La], [Ce ], [Ca], [Sr] and [Ba], satisfies the conditions

(10) (0.00562[Y]+0.00360[La]+0.00714[Ce])/0.0412[Mg]•100(%): 0.20 to 1.60(%) and

(11) (0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg]•100(%): 0.20 to 1.80(%), And

in determining the proportions (%) of the content of Mg, Ca, Sr and Ba contained in the MgO raw material powder, relative to the MgO content in the raw material powder contained in the annealing separator, as respectively [Mg'], [Ca'], [Sr'] and [Ba'] and satisfies the conditions

(12) (0.0249[Ca']+0.0114[Sr']+0.0073[Ba'])/0.0412[Mg']•100(%): 0.010 to 0.080(%), Besides

(13) ratio (0.0249[Ca']+0.0114[Sr']+0.0073[Ba'])/0.0412[Mg']•100% with respect to (0.0249[Ca] +0.0114[Sr]+0.0073[Ba])/0.0412[Mg]•100% is 0.200-0.020, in addition

(14) R1 MgO average particle size: 0.1 to 2.8 µm,

(15) average particle size R2 of particles containing one or more elements selected from the group consisting of Ca, Sr and Ba in the annealing separator: 0.2 to 3.0 µm, and

(16) (average particle size R2)/(average particle size R1): 0.5 to 3.0.

[0029]

The method for manufacturing a grain-oriented electrical steel sheet according to the present invention includes a process for hot rolling a slab containing, wt%: C: 0.1% or less, Si: 2.5-4.5%, Mn: 0.02- 0.20%, one or more elements selected from the group consisting of S and Se: total 0.005-0.07%, acid. sol. Al: 0.005 to 0.05% and N: 0.003 to 0.030% and having other substances composed of Fe and impurities to produce hot rolled steel sheet, cold rolling process of hot rolled steel sheet with cold rolling reduction of 80% or more to produce a cold-rolled steel sheet, a decarburization annealing process of a cold-rolled steel sheet for producing a decarburized annealed sheet, a process for coating the surface of the decarburized annealed sheet with an aqueous slurry and drying it, and a finishing annealing process for the steel sheet after the aqueous slurry has dried, where the aqueous slurry contains the aforementioned annealing separator.

[0030]

A method for manufacturing a steel sheet using finish annealing for manufacturing a grain-oriented electrical steel sheet includes a hot rolling process of a slab containing, by mass%, C: 0.1% or less, Si: 2.5-4.5%, Mn : 0.02-0.20%, one or more elements selected from the group consisting of S and Se: total 0.005-0.07%, acid. sol. Al: 0.005 to 0.05% and N: 0.003 to 0.030% and having other substances composed of Fe and impurities to produce hot rolled steel sheet, cold rolling process of hot rolled steel sheet with cold rolling reduction of 80% or more to produce a cold-rolled steel sheet, a cold-rolled steel sheet decarburization annealing process for producing a decarburized annealed sheet, and a process for coating the surface of the decarburized annealed sheet with an aqueous slurry and drying it, the aqueous slurry containing the above-mentioned annealing separator.

EFFECTS OF THE PRESENT INVENTION

[0031]

The grain-oriented electrical steel sheet according to the present invention has excellent magnetic properties and excellent adhesion of a primary coating to a base steel sheet. The method for producing a grain-oriented electrical steel sheet according to the present invention can produce the aforementioned grain-oriented electrical steel sheet. The annealing separator according to the present invention is used in the above production method. Due to this, the grain-oriented electrical steel sheet of the present invention can be obtained. The finish annealing steel sheet according to the present invention is for manufacturing the grain oriented electrical steel sheet according to the present invention. The method for producing a steel sheet using finish annealing according to the present invention can produce the above steel sheet using finish annealing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]

In FIG. 1 is a schematic representation of a 20 µm x 15 µm Primary Coating sample.

In FIG. 2 is a view for explaining the Gaussian filter applied to the primary cover height data acquired with a laser microscope.

In FIG. 3 is a schematic view showing the three-dimensional structure of the back surface and anchoring elements of a peelable Primary Coating.

In FIG. 4 is a view explaining the correlation of a characteristic X-ray intensity distribution diagram and an uneven shape.

DESCRIPTION OF OPTIONS FOR IMPLEMENTATION

[0033]

Details will be explained later, but in the present invention, in order to identify the interface structures of the primary coating and the base steel sheet of the grain oriented electrical steel sheet, the surface of the primary coating separated from the grain oriented electrical steel sheet from the side that is bonded to the base steel sheet is examined. , that is, the surface of the primary coating from the side forming the interface between the primary coating and the base steel sheet. This observed surface is analyzed with a scanning-type confocal laser microscope to obtain an irregular shape distribution at the interface (information about the interface in the depth direction). Next, the observed surface was analyzed using SEM-EDS. The concentration distributions of the various elements present in the primary coating were obtained from the characteristic X-ray intensities. Observations of this equipment are made in the direction vertical to the surface of the steel sheet from which the layer is removed, so the information obtained is information about the primary coating having a three-dimensional structure (uneven shapes and intensity of characteristic X-rays) projected onto a plane parallel to the surface of the steel sheet .

In the explanation of the interfaces in the Description, it should be noted in advance here that the explanation uses "objects on the projection plane". For example, "area" referring to interface structures is the area obtained on the projection plane. The areas of presence of elements are identified based on the intensity of the characteristic X-ray emission of the elements obtained on the projection plane.

However, it has been confirmed that these features obtained on the projection plane can well describe the features of the present invention. The use of information about the primary coating on the projection plane to explain the present invention, of course, does not lead to any loss of significance of the present invention.

In addition, in the present description, unless otherwise indicated, hereinafter, with respect to the numerical values of A and B, the expression "from A to B" means "A or more and B or less". In this expression, when only the numerical value of B is assigned to a unit, that unit is also applied to the numerical value of A. Hereinafter, in this description, "major component" means a component contained in 50% by mass or more in a certain substance, and preferably means 70% by weight or more, more preferably 90% by weight or more.

[0034]

The following will explain in detail the grain oriented electrical steel sheet according to the present invention and the manufacturing method of the grain oriented electrical steel sheet, the annealing cage used to manufacture the grain oriented electrical steel sheet, the finish annealed steel sheet used for manufacturing a grain-oriented electrical steel sheet, and a method for manufacturing a steel sheet used for finishing annealing. In this description, "%" in relation to the contents of elements will mean "mass %" unless otherwise indicated.

[0035]

A grain-oriented electrical steel sheet according to one aspect of the present invention is provided with a base steel sheet and a primary coating formed on the surface of the base steel sheet.

[0036]

Main steel sheet

The chemical composition of the base steel sheet constituting the aforementioned grain-oriented electrical steel sheet includes the following elements. Provided, however, that the distinguishing feature of the present invention lies in the primary coating. The main steel sheet need not be special. It should be noted that, as explained in the following manufacturing method, a base steel sheet is produced by cold rolling using a hot-rolled steel sheet having the following explained chemical composition. In addition, components are lost in the finish annealing process, so the chemical composition of the base steel sheet constituting the grain-oriented electrical steel sheet and the chemical composition of the hot-rolled steel sheet are significantly different.

[0037]

C: 0.0050% or less

Carbon (C) is an element effective for controlling the microstructure until the completion of the decarburization annealing in the manufacturing process, but if the C content exceeds 0.0050%, the magnetic properties of the grain oriented electrical steel sheet of the final product sheet fall. Therefore, the C content is 0.0050% or less. The C content is preferably as low as possible. However, even when the C content is reduced to less than 0.0001%, production costs only increase. The above effect is practically unchanged. Therefore, the preferred lower limit of the C content is 0.0001%.

[0038]

Si: 2.5 to 4.5%

Silicon (Si) increases the electrical resistance of steel to reduce eddy current losses. If the Si content is less than 2.5%, the above effect is not sufficiently achieved. On the other hand, if the Si content exceeds 4.5%, the cold workability of the steel falls. Therefore, the Si content is 2.5 to 4.5%. The preferred lower limit of the Si content is 2.6%, more preferably 2.8%. The preferred upper limit of the Si content is 4.0%, more preferably 3.8%.

[0039]

Mn: 0.02 to 0.20%

Manganese (Mn) binds with the further explained S and Se during the manufacturing process to form MnS and MnSe. These precipitated phases act as inhibitors (inhibitors of the normal growth of crystal grains) and cause secondary recrystallization in the steel. Mn also improves the hot workability of the steel. If the Mn content is less than 0.02%, the above effect is insufficient. On the other hand, if the Mn content exceeds 0.20%, secondary recrystallization does not occur, and the magnetic properties of the steel may fall. Therefore, the Mn content is 0.02 to 0.20%. The preferred lower limit of the Mn content is 0.03%, more preferably 0.04%. The preferred upper limit of the Mn content is 0.13%, more preferably 0.1%.

[0040]

One or more elements selected from the group consisting of S and Se: 0.005% total or less

The sulfur (S) and selenium (Se) contained are bound to Mn during production to form MnS and MnSe, which function as inhibitors. However, if the content of these elements exceeds only 0.005%, the magnetic properties drop due to the remaining inhibitors. In addition, due to the segregation of S and Se in the grain-oriented electrical steel sheet, surface defects sometimes occur. Therefore, in the grain-oriented electrical steel sheet, the total content of one or more elements selected from the group consisting of S and Se is 0.005% or less. The total content of S and Se in the grain-oriented electrical steel sheet is preferably as low as possible. However, even if the content of S and Se in the grain-oriented electrical steel sheet is reduced to less than 0.0001%, the production cost only increases. The above effect is practically unchanged. Therefore, the preferred lower limit of the total content of one or more elements selected from the group consisting of S and Se in the grain oriented electrical steel sheet is 0.0001%.

[0041]

Acid sol. Al: 0.010% or less

Aluminum (Al) bonds with N during the manufacturing process of the grain-oriented electrical steel sheet to form AlN, which functions as an inhibitor. However, if the acid content sol. Al in the grain-oriented electrical steel sheet is more than 0.010%, the above inhibitor remains in an excessive amount in the base steel sheet, so that the magnetic properties fall. Therefore, the acid content sol. Al is 0.010% or less. The preferred upper limit of acid content. sol. Al is 0.004%, more preferably 0.003%. Acid content. sol. Al is preferably as low as possible. However, even with a decrease in the content of acid. sol. Al in the grain-oriented electrical steel sheet is less than 0.0001%, the production cost simply rises. The above effect is practically unchanged. Therefore, the lower limit of acid content is preferable. sol. Al in the grain-oriented electrical steel sheet is 0.0001%. Note that in this Description, acid. sol. Al means "acid soluble Al". Therefore, the acid content sol. Al is the content of acid-soluble Al.

It should be noted that, as explained later, the Al characteristic of the primary coating of the present invention is obtained from a base steel sheet. For this reason, at first glance, the fact that the Al content in the base steel sheet is zero would seem to contradict the presence of Al in the Primary Coating, but what is concentrated in the Primary Coating is "Al that was contained in the Primary Steel Sheet". in the middle of production. In the grain oriented electrical steel sheet of the present invention, after Al is concentrated, according to the feature of the present invention, Al from the base steel sheet is removed from the system by high temperature heat treatment, also called "cleaning annealing", one process of finishing annealing. For this reason, the final base steel sheet containing no Al and the final primary coating having Al obtained from the present base steel sheet do not contradict each other.

[0042]

N: 0.010% or less

Nitrogen (N) bonds with Al during the production of grain-oriented electrical steel sheet to form AlN, which acts as an inhibitor. However, if the N content in the grain-oriented electrical steel sheet exceeds 0.010%, the above inhibitor remains excessively in the grain-oriented electrical steel sheet, so that the magnetic properties fall. Therefore, the N content is 0.010% or less. The preferred upper limit of the N content is 0.004%, more preferably 0.003%. The N content is preferably as low as possible. However, even if the total N content of the grain-oriented electrical steel sheet is reduced to less than 0.0001%, the production cost only increases. The above effect is practically unchanged. Therefore, the preferred lower limit of the N content in the grain-oriented electrical steel sheet is 0.0001%.

[0043]

The remainder of the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet of the present invention consists of Fe and impurities. Here, "impurities" means the following elements, which come from ore used as raw materials, scrap or production environment, etc. in the industrial production of the base steel sheet or remain in the steel without being completely removed by the cleaning annealing, and which are allowed in a content that does not adversely affect the operation of the grain-oriented electrical steel sheet of the present invention.

[0044]

Regarding impurities

As for copper (Cu), tin (Sn), antimony (Sb), bismuth (Bi), tellurium (Te) and lead (Pb), the part of Cu, Sn and Sb, Bi, Te and Pb in the main steel sheet is output out of the system by high temperature heat treatment, also known as "clean annealing" of a single finishing annealing process. These elements increase the orientation selectivity in finish annealing secondary recrystallization, showing an improvement in magnetic flux density, but if they remain in the base steel sheet after finish annealing is completed, they cause deterioration in steel loss in the form of simple impurities. Therefore, the total content of one or more elements selected from the group consisting of Cu, Sn and Sb, Bi, Te and Pb is 0.30% or less. As explained above, these elements are impurities, so the total content of these elements is preferably as low as possible.

[0045]

Primary Coating

The distinctive feature of the primary coating structure is the most important in the present invention. This distinguishing feature, as previously explained, also includes a limitation of the method of measurement. In the present invention, the interface information of the primary coating and the base steel sheet is projected onto a plane parallel to the surface of the steel sheet and determined on that plane (hence sometimes simply described as a "projection plane"). In order to get an idea of the distinguishing feature of Primary Coating, it is important to understand the measurement method, so the measurement method will be explained first.

[0046]

Method for measuring primary coverage, in particular interface structures

A grain-oriented electrical steel sheet with a primary coating formed on its surface is subjected to electrolysis by a constant potential in an electrolytic solution, so that only the base steel sheet begins to dissolve, then the primary coating is separated from the base steel sheet and used as an observation sample. Note that when electrolyzing to obtain a sample, the main steel sheet of the interface is selectively subjected to electrolysis, so it is not necessary to electrify the entire main steel sheet. A suitable amount of electrolysis can be set. The amount of electrolysis is, for example, 80 C per 1 cm ² area of the steel sheet (80 C/cm ² ). When separating the primary coating, there is a method of attaching the primary coating to the adhesive surface of a commercially available metal tape, etc., then removing the main steel sheet and observing what remains on the side of the tape, a method of using paraffin to wrap it, and then removing the paraffin and etc.

Thereafter, this separated Primary Coating will sometimes be referred to as the "Interface Observation Pattern", and the Primary Coating surface to be observed from the side deposited on the base steel sheet will sometimes be referred to as the "Observed Surface".

[0047]

Then, the interface observation pattern is observed by various types of observation equipment in a direction vertical to the surface of the cleaned steel sheet. (thickness direction of grain oriented electrical steel sheet). Accordingly, the data received from the equipment becomes the interface observation pattern information superimposed on the projection plane. Based on these projection data, the following explanation is given. That is, for example, the description "at the interface" is an explanation of the state of the data on the projection plane. Here, the direction in the thickness direction from the primary coating side to the base steel sheet side is defined as positive. The term "height" used below expresses the direction from the primary coating side to the base steel sheet side as upwards.

[0048]

With respect to the above observed surface of the interface observation specimen, an area of 20 μm • 15 μm or more is examined with a scanning-type confocal laser microscope (Model No. VK9710, manufactured by Keyence) to obtain data on the uneven shape of the interface on the projection plane. At this time, scan steps are performed at intervals of 0.1 µm or less. The acquired 30,000 pixels (200 pixels x 150 pixels) or more of jagged shape data are smoothed once by a 3 by 3 Gaussian filter of FIG. 2) once. In addition, the jagged shape data after smoothing was processed by automatic quadratic surface correction based on the centerline in the width direction and the centerline in the height direction to decompose the data on the projection plane and obtain the final 200×150 jagged shape distribution pattern.

In FIG. 3 is a schematic view showing the three-dimensional structure of the back surface of the peeled primary cover and the anchor members. H0 - the central value of the height of the surface of the primary coating. H1 is the average value of the heights of the fasteners present in positions greater than H0. These positions (H1 - H0) in the present invention are from 0.40 to 2.00 µm. Fig. 3 is projected onto a plane parallel to the surface of the steel sheet, and is a projection plane carrying information about the height distribution of the uneven shape.

The observed surface of the interface observation sample is analyzed for the characteristic X-ray intensity of Ca, Sr, Ba, and Al using SEM-EDS (Model No.: JSM-7900F, manufactured by JEOL). At this time, scanning steps are performed at a distance of 0.1 µm or less, and a characteristic X-ray intensity distribution diagram of 200×150 pixels is obtained on the projection plane. At this time, based on the resolution of the characteristic X-ray intensity distribution pattern, an area with a resolution of 200×150 pixels or more is superimposed on the uneven shape distribution pattern. That is, it is done so that each pixel of 200 x 150 pixels or more of the digital image area of the characteristic X-ray intensity distribution pattern corresponds to one or more points of the jagged shape distribution pattern height data in the corresponding area (preferably over all points). Below, this will be referred to as a correlation diagram of the intensity distribution of the characteristic X-ray radiation and the irregular shape. This schematic view is shown in Fig. 4. The method for identifying the shape of the coating using the information obtained from this figure will be explained next.

[0049]

From the correlation diagram of the characteristic X-ray intensity distribution and the irregular shape thus obtained, the following procedure is used to determine the regions A0-A5 described below.

In a schematic representation of the correlation of the characteristic X-ray intensity distribution diagram and the irregular shape shown in FIG. 4, the entire observation area within the outermost rectangle is labeled A0. Areas colored in dark gray are parts that exceed the center value H0 of the height of the uneven shape. The inner sides of the parts, shown in light gray lines, are areas (pinning oxide areas) of A1 still 0.2 µm higher than H0. The outer sides of the parts shown in light gray lines are the areas of the surface oxide layer A2. Al (aluminum) concentration areas are represented by A3 (shown as dots) and A5 (shown in black). In particular, A5 shows the areas of concentration of Al (aluminum) present inside the anchoring oxide regions (A1). Regions A4 (parts within dashed lines) show concentration regions of Ca group elements, described below.

[0050]

The area A0 is the observed area as a whole, that is, at least the area of 20 µm.times.15 µm or more. All pixels in the correlation diagram of the characteristic X-ray intensity and uneven shape correspond to this region A0. Below A0 will sometimes be referred to as the "observed area".

[0051]

The A1 regions and the A2 regions are classified based on the intensity of the characteristic X-ray emission and the uneven shape distribution correlation diagram.

In the present invention, the Primary Coating is classified into two types of regions in the thickness direction based on the position of H0 in the thickness direction of the steel sheet, that is, "fixing oxide layer (2)" and "surface oxide layer (1)" as described above. Areas A1 and areas A2 are areas with classifications located on the projection plane.

H0 is the central value of the surface height from the height data of the correlation diagram of the characteristic X-ray intensity distribution and the irregular shape. Here it is the arithmetic mean of two heights close to the center 200 x 150 pixels. In addition, the region with a height of H0+0.2 μm or more is the “fixing oxide layer (2)”, while what is seen on the projection plane is the “fixing oxide layer region” A1. In the same way, the area less than H0+0.2 µm is the "surface oxide layer (1)" and is the "surface oxide layer area" A2 on the projection plane.

[0052]

The A3 regions and the A4 regions are classified based on the correlation diagram of the characteristic X-ray intensity distribution and the irregular shape.

In the correlation diagram of the characteristic X-ray intensity distribution and the uneven shape, the maximum value of the characteristic X-ray intensity of Al (aluminum) is identified, and the region where the intensity of 20% or more of the maximum value of the characteristic X-ray intensity of Al is obtained is designated as A3. Hereinafter, the region A3 will be referred to as the "Al concentration region".

Further, in the correlation diagram of the characteristic X-ray intensity and the irregular shape, the characteristic X-ray intensities of Ca, Sr, and Ba and the area combining the area where the characteristic X-ray intensity Ca is obtained, which is 20% or more of the maximum value of the characteristic X-ray intensity Ca, the region where the characteristic X-ray intensity Sr of 20% or more of the maximum characteristic X-ray intensity Sr is obtained, and the region where the characteristic X-ray intensity Ba of 20% or more of the maximum characteristic X-ray intensity value of 20% or more of the maximum characteristic X-ray intensity is obtained is denoted as A4. That is, region A4 is a region where the characteristic X-ray intensity of any element Ca, Sr and Ba becomes an intensity of 20% or more of the maximum value of the characteristic X-ray intensity of that element. Below, the region A4 will be referred to as the "region of concentration of elements of the Ca group".

[0053]

In addition, a region present in the region A1 of the fixing oxide layer and consisting of the region A3, the Al (aluminum) concentration region, is referred to as A5. Hereinafter, the region A5 will be referred to as the "Al (aluminum) anchoring region".

[0054]

Further, in the above regions, the quantitative densities of the number of regions (/μm ² ), the total area of the regions (μm ² ), and the position of the regions in the thickness direction (height (μm)) are determined. Space is needed in areas A0, A1, A3 and A5. Their total areas are designated as S0, S1, S3 and S5.

Area quantity densities are needed in A3 and A4. The quantitative densities of the regions A3 and A4 are respectively D3 and D4. When determining quantity densities, an area where pixels continue up and down or left and right in pixel units is considered one area. In addition, areas consisting of four or more pixels are identified and their number is counted. Note that the area of one pixel is, as explained above, the scan step of 0.1 µm at the time of measurement (more specifically 0.092 µm), so the area of the area becomes 0.1 µm x 0.1 km (more specifically 0.092 µm x 0.092 µm) •number of areas.

Needless to say, but, for example, D3 is, for areas A3, the value of the total number of areas measured when considering areas where pixels continue in units of pixels as separate areas divided by the area of the observed area A0 (i.e., the entire observed area S0). D4 is also calculated in a similar way.

The position of the regions in the thickness direction are required in the regions A5. The position of area A5 is designated as H5. Note that this position is identified based on the H0 interface between the surface oxide layer (1) and the anchoring oxide layer (2). In particular, this is the value of the average height for all pixels in the area A5 minus H0. The region A5 is the region where the height in the X-ray characteristic intensity correlation diagram and the irregular shape is at the position H0+0.2 µm or more, so the average value of the pixel heights of the region A5 is always H0+0.2 µm or more. As a result, H5 becomes 0.2 µm or more.

[0055]

Distinctive feature of the primary coating / Distribution of Al inside the fixing oxide layer

The primary coating characterizing the present invention will be explained below. The primary coating of the present invention contains Mg ₂ SiO ₄ as the main component, but there is a major difference in the distribution of Al near the interface between the primary coating and the base steel sheet. This feature can be mainly identified in the “fixing oxide layer (2)”, so the feature related to the fixing oxide layer (2) will be explained first, and then the characteristic of the primary coating as a whole.

With regard to the above D3 number density of concentrated areas A3 near the interface, the present invention is characterized by D3: 0.015 to 0.150/μm ² . If D3 is outside this range, the effect of improving the bending adhesion of the coating cannot be obtained.

In addition, the ratio of the perimeter L5 of the regions consisting of the anchoring oxide layer region in Al concentrated regions, that is, the regions consisting of the region of the anchoring oxide layer A1 and regions, the concentration of Al (aluminum) A3 (Al anchoring regions A5), to the observed region, L5/S0 is characterized by being in the range from 0.020 to 0.500 µm/µm ² . If this ratio becomes less than 0.02 μm/μm ² , the effect of improving the bending adhesion of the coating cannot be obtained. In addition, if more than 0.500 μm/μm ² , the steel loss property deteriorates. Here, the perimeter L5 is the sum of the perimeters of the Al A5 anchoring area, while the perimeter of the Al A5 anchoring area is the perimeter of successive pixels forming one Al A5 anchoring area.

In addition, with regard to the position of H5 in the thickness direction of the Al A5 fastening region, H5 has a value of 0.4 to 4.0 μm. If this value becomes less than 0.4 µm, it is impossible to obtain the effect of improving the bending adhesion of the coating. In addition, if the distance exceeds 4.0 μm, the fixing oxides are stretched too much in the thickness direction, so the perimeter is reduced, and the outgassing property is no longer improved and pinholes are generated.

[0056]

The reason why the Al distribution above affects bendability is not clear, but it is thought to be due to:

Al is an element with a strong tendency to form oxides, so during finish annealing on the surface of the steel sheet, Al is selectively oxidized and Al diffuses from inside the base steel sheet to the surface. At this time, the amount of Mg ₂ SiO ₄ decreases on the surface of the oxides resulting from the reaction of the annealing separator, when a part of MgAl ₂ O ₄ is replaced, the linear expansion coefficient increases, and the magnetic properties deteriorate. In addition, the surface oxide layer (1) mainly composed of Mg ₂ SiO ₄ becomes uneven in thickness. To avoid this, Al can be oxidized inside the steel sheet to prevent it from reaching the surface oxide layer (1). That is, it is believed that the present invention can achieve both an improvement in the magnetic properties and an improvement in the bending adhesion of the coating by providing a structure in which Al oxides are formed at the front end positions of the fixing oxides deeply penetrating into the base steel sheet.

The set value expressing this state is H5. In the present invention, H5 is 0.4 µm or more. That is, it is considered that the above structure is achieved by forming the Al anchoring regions at positions inside the steel sheet separated from H0 by 0.4 µm or more (the front end sides of the anchoring oxides), and providing the perimeters L5 of the Al anchoring regions to an observed area of 0.02 microns or more.

In addition, the statement that such Al A5 pinning regions are present at the front ends of the pinning oxides means, therefore, that D3 becomes a suitable range of values. That is, if the density of the number of Al pinning regions A5 is small, D3 becomes low. In addition, even if there is a temporary situation where the Al pinning areas become excessively high in density, since the distance between adjacent Al pinning areas A5 becomes smaller, they will eventually merge together with the growth of the primary coating, and finally D3 will be difficult to become excessively high in value.

In addition, if the above-mentioned appropriate Al A5 anchoring regions are formed, Al diffusing from the inside of the steel sheet no longer reaches the surface oxide layer (1), so S5/S3 inevitably becomes a high value.

Note that in the present invention, the state of Al in the Al concentration regions of A3 is not prescribed at all, but considering the fact that the main component of the primary coating is Mg ₂ SiO ₄ , it is appropriate to think that Al in A3 is present as an oxide.

[0057]

Distinctive feature of the primary coating / Presence of areas of the fixing oxide layer

In the primary coating of the present invention, it cannot be said that the shape of the fixing oxide layer (2) has remarkable features in terms of external shape, but the above characteristic distribution of Al uses the phenomena in the front end regions of the fixing oxide layer (2), so if the fixing oxides themselves oxides are absent, the formation of a characteristic distribution of Al also becomes difficult.

For this reason, the presence of anchoring oxides and the area ratio of the regions of the anchoring oxide layer on the projection plane are prescribed. It should be noted that the numerical range of this position itself is one of the limits observed even in a grain-oriented electrical steel sheet excellent in coating adhesion under a general shear operation, but it can also be said to be important as an essential condition for obtaining a characteristic Al distribution. .

In the present invention, it is necessary that (the area S1 of the fixing oxide layer regions)/(the observed region S0) ≧0.15. This value of less than 0.15 means that even if each individual anchoring oxide is formed over a large area, the number density of the number of anchoring oxides is extremely small, or even if the number density is a certain value, the area of each individual anchoring oxide is small. In any case, it expresses a state in which the interval between anchoring oxides becomes relatively wide. Details will be explained later, but in such a situation, it becomes difficult to form the above Al distribution characteristic.

[0058]

Distinctive Feature of Primary Coating/Composition of Primary Coating and Distribution of Ca Group Elements

The primary coating of the present invention contains forsterite (Mg ₂ SiO ₄ ) as the main component. More specifically, the primary coating contains from 50 to 95 wt.% Mg ₂ SiO ₄ . The remainder is mainly the commonly known MgAl ₂ O ₄ and other oxides or MnS or alkaline earth metal sulfides.

[0059]

In addition, the primary coating of the present invention contains elements of the Y group of only 0.1 to 6.00 wt.% and elements of the Ca group of only 0.1 to 6.00 wt.% in relation to the content of Mg ₂ SiO ₄ in the primary coating.

[0060]

Details will be explained later, but in order to realize the aforementioned distribution of Al oxides, it is preferable to use an annealing separator containing Y-group elements. In this case, the Y-group elements also remain in the primary coating after finishing annealing. If the total content of Y-group elements in the Primary Coating is less than 0.1 mass%, it cannot be said that the Y-group content of the annealing separator is sufficient and the bending adhesion of the coating is improved. If more than 6.0 wt.%, the thickness of the fixing oxide layer (2) becomes too large, and the oxides prevent the movement of the domain boundary during magnetization, so the negative effect on the magnetic properties becomes noticeable.

In the same way, in order to realize the aforementioned distribution of Al oxides, it is preferable to use an annealing separator containing elements of the Ca group. In this case, elements of the Ca group also remain in the primary coating after finishing annealing. When the total content of Ca group elements in the primary coating is less than 0.1 wt.%, it cannot be said that the content of Ca group elements in the annealing separator is sufficient. It is impossible to increase the adhesion of the coating during bending. At more than 6.0 wt.%, the quantitative density of the anchoring oxide layer (2) becomes too high, and the adjacent anchoring oxides combine and form solid particles, whereby the quantitative density of the anchoring oxide particles falls. In addition, it is not possible to obtain a characteristic distribution of Al and improve the flexural adhesion of the coating.

[0061]

The content of Mg ₂ SiO ₄ in the Primary Coating is obtained by using the Primary Coating separated from the electrical steel sheet by the above method as a sample and quantifying Mg in the sample by inductive coupling plasma mass spectrometry (ICP-MS). The product of the obtained quantized value (wt.%) and the molecular weight of Mg ₂ SiO ₄ , divided by two atomic weights of Mg, is the content of Mg ₂ SiO ₄ .

Further, in the same way, Ca, Ba and Sr, as well as La, Y and Ce are quantitatively analyzed by a method similar to the above. The obtained content (wt%) is calculated in the same manner as above to calculate the content of these elements. The total amount of the obtained concentrations of Ca, Ba and Sr is defined as the "content of the elements of the Ca group", and the total amount of the concentrations of La, Y and Ce obtained is defined as the "content of the elements of the Y group".

[0062]

Further, in the primary coating of the present invention, the number density of Ca D4 group element concentration areas on the projection plane is preferably 0.005/μm ² or more. The details will be explained later, but the Ca-group elements that the annealing separator contains are believed to play an important role in controlling the number density of anchoring oxides during the formation of the primary coating. The number density D4 of the Ca group elements concentrated in the A4 regions of the Primary Coating described herein is believed to express the state that the Ca group elements acting to form anchoring oxides during Primary Coating formation remain in the Primary Coating. If D4 becomes high, the Ca-group elements evenly enter the anchor oxides, so the D3 number density of the Al-based oxides becomes higher, and the penetration of the anchor oxides into the core steel material increases.

If D4 becomes less than 0.005/μm ² , the number density of the fixing oxide particles cannot be sufficiently obtained and the adhesion is not improved. Not only that, the above characteristic distribution of Al cannot be obtained.

The upper limit is not particularly set, but if D4 is too high, then the frequency of formation of the anchoring oxide particles formed in this connection also becomes excessively high, and the adjacent anchoring oxides combine and form integral particles, so the formation of the characteristic distribution of Al is disturbed, as explained above. . For this reason, D4 is preferably 2000/μm ² or less.

[0063]

Preparation method

One example of a method for manufacturing a grain-oriented electrical steel sheet according to the present invention will be explained.

One example of a method for producing a grain-oriented electrical steel sheet is a steelmaking process, a hot rolling process, a hot-rolled sheet annealing process, a cold rolling process, a decarburization annealing process, a finish annealing process, an alignment annealing process, a coating sintering process, and a wall control process. domain. These processes will be explained below. Please note that the processing conditions of the following processes do not differ from the general ranges and do not need to be special. In the method of the present invention, the characterizing feature is the surface condition of the steel sheet containing the annealing separator in the steel sheet before finishing annealing to control the primary coating structure.

[0064]

steelmaking process

In the steelmaking process, molten steel is produced in a converter or other conventional method, and a known refining process and a casting process are performed to produce a slab having the following chemical composition. Note that the slab chemistry is removed to a certain extent from the steel components in the finishing annealing explained below. In particular, S, Al, N, etc. acting as inhibitors are removed to a large extent. For this reason, the chemical composition of the slab described here is different from the chemical composition of the steel sheet of the final product.

[0065]

C: 0.1% mass or less

If the C content exceeds 0.1 mass%, the time required for decarburization annealing increases. In this case, production costs rise and productivity falls. Therefore, the content of C in the slab is 0.1 mass% or less. The preferred upper limit of the C content in the slab is 0.092% by weight, more preferably 0.085% by weight. In addition, if the C content is lower than 0.005 wt%, the dispersion state of MnS, MnSe, AlN and other precipitated phases, as well as the particle structure of the steel sheet after decarburization annealing, will not become uniform, and the degree of integration into the Goss orientation after secondary recrystallization may deteriorate. . Therefore, the lower limit of the C content in the slab is 0.005 mass%. The preferred lower limit of the C content in the slab is 0.02 mass%, more preferably 0.04 mass%.

[0066]

Si: 2.5 to 4.5 wt%,

As explained in the section on the chemical composition of the grain-oriented electrical steel sheet of the finished product, Si increases the electrical resistance of the steel, but if it is excessive, the cold workability decreases. If the content of S in the slab is 2.5-4.5% by mass, the content of Si in the grain-oriented electrical steel sheet becomes 2.5-4.5% by mass after the finish annealing process. The preferred upper limit of the Si content in the slab is 4.0%, more preferably 3.8 mass%. The preferred lower limit of the Si content in the slab is 2.6 mass%, more preferably 2.8 mass%.

[0067]

Mn: 0.02 to 0.20 wt%

As explained in the section on the chemical composition of the grain oriented electrical steel sheet of the finished product, during the manufacturing process, Mn binds with S and Se to form precipitates that act as inhibitors. Mn further enhances the hot workability of the steel. If the Mn content of the slab is 0.02 to 0.20%, the Mn content of the grain-oriented electrical steel sheet after the finish annealing process becomes 0.05 to 0.20 wt%. The preferred upper limit of the Mn content in the slab is 0.13%, more preferably 0.10%. The preferred lower limit of the Mn content in the slab is 0.03%, more preferably 0.04%.

[0068]

One or more elements selected from the group consisting of S and Se: 0.005% to 0.070% total

Sulfur (S) and selenium (Se) bind to Mn during the manufacturing process to form MnS and MnSe. MnS and MnSe function as inhibitors necessary to suppress the growth of crystal grains during secondary recrystallization. If the total content of one or more elements selected from the group consisting of S and Se is less than 0.005% by mass, the above effect is difficult to obtain. On the other hand, if the total content of one or more elements selected from the group consisting of S and Se exceeds 0.070 mass%, then secondary recrystallization does not occur during production, and the magnetic properties of the steel fall. Therefore, in the slab, the total content of one or more elements selected from the group consisting of S and Se is from 0.005 to 0.070%. A preferred lower limit for the total content of one or more elements selected from the group consisting of S and Se is 0.008%, more preferably 0.016%. The preferred upper limit for the total content of one or more elements selected from the group consisting of S and Se is 0.060%, more preferably 0.050%.

[0069]

sour sol. Al: 0.005 to 0.050 wt%

Aluminum (Al) bonds with N during production to form AlN. AlN acts as an inhibitor. If the acid content sol. Al in the slab is less than 0.005%, the above effect is not obtained. On the other hand, if the acid content sol. Al in the slab is more than 0.050 wt.%, AlN coarsens. In this case, AlN becomes difficult to function as an inhibitor, and sometimes secondary recrystallization is not caused. Therefore, the acid content sol. Al in the slab is from 0.005 to 0.050%. The preferred upper limit of acid content. sol. The Al in the slab is 0.040%, more preferably 0.035%. The preferred lower limit of acid content. sol. The Al in the slab is 0.010%, more preferably 0.015%.

[0070]

N: 0.0030 to 0.0300% by weight

During the manufacturing process, nitrogen (N) binds to Al to form AlN, which functions as an inhibitor. If the N content of the slab is less than 0.0030 mass%, the above effect is not achieved. On the other hand, if the N content of the slab exceeds 0.0300 mass%, AlN becomes coarser. In this case, AlN becomes difficult to function as an inhibitor, and sometimes secondary recrystallization is not caused. Therefore, the N content in the slab is 0.0030 to 0.0300%. The preferred upper limit of the N content in the slab is 0.0200 wt%, more preferably 0.0150%. The preferred lower limit of the N content in the slab is 0.0040%, more preferably 0.0060%.

[0071]

The remainder of the chemical composition in the slab of the present invention consists of iron and impurities. Here, "impurities" means elements that come from ore used as raw materials, scrap or production environment, etc. in the industrial production of the slab, and which are allowed to be present in a range that does not adversely affect the slab of the present embodiment.

[0072]

Regarding additional items

The slab according to the present invention may further contain, instead of a portion of Fe, one or more elements selected from the group consisting of Cu, Sn and Sb, totaling 0.60 mass% or less. All of these elements are optional.

[0073]

One or more elements selected from the group consisting of Cu, Sn and Sb: a total of 0 to 0.60 wt.% copper (Cu), tin (Sn) and antimony (Sb) are optional elements and should not be included. If so, Cu, Sn, and Sb increase the magnetic flux density of the grain-oriented electrical steel sheet. If Cu, Sn and Sb are present at least in a small amount, then the above effect is achieved to a certain extent. However, if the content of Cu, Sn and Sb exceeds only 0.6%, it becomes difficult to form an inner oxide layer during decarburization annealing. In this case, during the finish annealing, the formation of the primary coating is delayed, which proceeds with the reaction of the MgO of the annealing separator and the SiO ₂ of the inner oxide layer. As a result, the adhesion of the resulting primary coating decreases. In addition, Cu, Sn and Sb easily remain as impurity elements after cleaning annealing. As a result, the magnetic properties deteriorate. Therefore, the content of one or more elements selected from the group consisting of Cu, Sn and Sb is only 0 to 0.6 wt%. A preferred lower limit for the total content of one or more elements selected from the group consisting of Cu, Sn and Sb is 0.005% by weight, more preferably 0.007% by weight. The preferred upper limit for the total content of one or more elements selected from the group consisting of Cu, Sn and Sb is 0.50 wt%, more preferably 0.45 wt%.

[0074]

The slab according to the present invention may further contain, instead of a portion of Fe, one or more elements selected from the group consisting of Bi, Te and Pb, in total 0.030 mass% or less. All of these elements are optional.

[0075]

One or more elements selected from the group consisting of Bi, Te and Pb: 0 to 0.030% total

Bismuth (Bi), tellurium (Te), and lead (Pb) are optional elements, but are elements to be considered in the present invention from the following point of view.

These elements increase the magnetic flux density of the grain oriented electrical steel sheet. The preferred lower limit value for the total content of one or more elements selected from the group consisting of Bi, Te and Pb for this is 0.0005 wt.%, more preferably 0.001 wt.%.

On the other hand, if these elements segregate to the surface during finishing annealing, the fixing oxide layer (2) will not become thicker and the adhesion of the coating to the primary coating will decrease. For this reason, despite the effect of increasing the magnetic flux density, the number of elements had to be limited to 0.005 mass% or so or less in order to ensure adhesion of the coating. The effect of the present invention becomes especially effective by changing the structure of anchoring oxides to improve coating adhesion, and therefore becomes especially effective when using a manufacturing method containing these elements. In the case of the present invention, excellent coating adhesion becomes provided by these elements even in an amount of 0.010 mass% or more, more preferably 0.015 mass% or more. Meanwhile, if these elements are excessively added, the decrease in adhesion cannot be avoided even by carrying out the present invention, so the upper limit is 0.030 wt%. The preferred upper limit is 0.020%, while the more preferred upper limit is 0.015%.

[0076]

hot rolling process

The slab having the above chemical composition is heated. The heating temperature of the slab is, for example, 1280 to 1350° C. or less. The heated slab is hot rolled to produce hot rolled steel sheet. Hot rolled steel sheet can be annealed as needed. The annealing conditions of the hot-rolled steel sheet are, for example, 900 to 1100° C. for 3 to 5 minutes.

[0077]

cold rolling process

In the cold rolling process, the hot rolled steel sheet is cold rolled to produce a cold rolled steel sheet.

[0078]

The prepared hot-rolled steel sheet is subjected to cold rolling to produce a cold-rolled steel sheet of a base steel sheet. Cold rolling may be performed only once, or may be performed several times. When performing cold rolling, several times after performing cold rolling, process annealing is carried out to soften the steel, and then cold rolling is carried out. By performing cold rolling once or several times, a cold-rolled steel sheet having a finished product thickness (finished product thickness) is produced.

[0079]

The cold rolling reduction in one or more cold rolling passes is 80% or more. Here, the cold rolling reduction (%) is defined as follows:

Cold rolling reduction (%)=1-(thickness of cold rolled steel sheet after finishing cold rolling)/(thickness of hot rolled steel sheet before start of initial cold rolling)•100%

[0080]

Note that the preferred upper limit of cold rolling reduction is 95%. In addition, before cold rolling the hot-rolled steel sheet, the hot-rolled steel sheet may be heat treated or pickled.

[0081]

Decarburizing Annealing Method

The cold rolled steel sheet produced by the cold rolling process is decarburized and nitrided as needed. The decarburization annealing is carried out in a known hydrogen-nitrogen humid atmosphere. Due to the decarburization annealing, the C concentration in the grain-oriented electrical steel sheet is reduced to 50 ppm or less, which can suppress deterioration due to magnetic aging. In the process of decarburization annealing, primary recrystallization occurs in the structure of the steel sheet, and the working stress caused by cold rolling is relieved. In addition, in the decarburization annealing process, a part of the surface layer of the base steel sheet is formed with an inner oxide layer whose main component is SiO ₂ . The SiO ₂ formed here reacts with MgO in an aqueous slurry containing an annealing separator to be applied later during the finish annealing to form the shape controlled primary coating of the present invention. The annealing temperature of the decarburization annealing process is known, for example, 750 to 950°C. The holding time at this annealing temperature is, for example, 1 to 5 minutes.

[0082]

Method for forming an annealing separator layer

In the present invention, "annealing separator" means a substance formed to give the function of preventing sticking during finish annealing to the sheet surface after decarburization annealing where finish annealing is to be performed. In addition, the annealing separator layer formed on the surface of the sheet after the decarburization annealing is referred to as the "annealing separator layer".

In this process, an aqueous slurry containing compounds forming an annealing separator, etc. is obtained. An aqueous slurry is prepared by adding later explained elements forming an annealing separator, etc., as compounds, etc. to pure water. and mixing. This slurry is applied to the surface of the above sheet after decarburization annealing by a roller coater, a spray gun, etc. The steel sheet to which the slurry is applied is placed in an oven maintained at a temperature of 400 to 1000°C and held for 10 to 90 seconds to thereby dry the slurry on the surface. Note that at this time, the temperature of the steel sheet itself only rises to 400°C or so (no change in the crystal structure such as recrystallization occurs). What remains on the surface of the steel sheet at this point in time is the annealing separator of the present invention. The state of this annealing separator deposited on the surface of the steel sheet before finishing annealing is referred to as the "annealing separator layer".

Basically, finally, the annealing separator covering the surface of the steel sheet before finishing annealing can be considered to be obtained by simply mixing various compounds, etc. used as raw materials.

[0083]

Finishing annealing process

The annealing separator is dried and then finished annealed. In the finish annealing, the annealing temperature is 1150 to 1250°C, and the base steel sheet (cold rolled steel sheet) is held. The holding time is, for example, 15 to 30 hours. The atmosphere of the finish annealing furnace is a known atmosphere. Please note that in the final process of the finishing annealing process, in particular, part of S, Al, N and other elements that function as inhibitors are removed from the system. This process is sometimes referred to as "cleaning (annealing)".

[0084]

In the grain-oriented electrical steel sheet produced by the above process, a primary coating containing Mg ₂ SiO ₄ as a main component is formed on the surface. At this time, by using the annealing separator described below, the interface structure of the base steel sheet and the primary coating satisfies the present invention, and the adhesion of the coating is improved.

[0085]

It should be noted that due to the decarburization annealing process and the finish annealing process, the elements of the chemical composition of the hot-rolled steel sheet are removed to a certain extent from the steel components. In particular, S, Al, N, etc. acting as inhibitors are removed to a large extent. For this reason, compared with the chemical composition of the hot-rolled steel sheet, the content of elements in the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet becomes lower, as explained above. By using a hot-rolled steel sheet of the aforementioned chemical composition to operate the above manufacturing method, a grain-oriented electrical steel sheet having a base steel sheet of the aforementioned chemical composition can be produced.

[0086]

Method for forming an insulating coating

In one example of the method for manufacturing a grain-oriented electrical steel sheet according to the present invention, a further insulating coating forming process may be performed after the finish annealing process. In the process of forming the insulating coating, the surface of the grain-oriented electrical steel sheet is coated with an insulating coating material mainly composed of colloidal silica and phosphate after the temperature is lowered in the finish annealing process, and then fired. As a result, the primary coating is formed with the insulating coating of the tension coating.

[0087]

Processing Method for Grinding Magnetic Domains

In addition, the grain-oriented electrical steel sheet of the present invention can be subjected to a known magnetic domain refinement treatment after cold rolling, after decarburization annealing, after finishing annealing, after forming an insulating coating, and so on. In the magnetic domain refining process, the surface of a grain-oriented electrical steel sheet is irradiated with a laser beam having a magnetic domain refining effect, or formed with grooves on the surface. In this case, a grain-oriented electrical steel sheet with excellent magnetic properties can be produced.

[0088]

Annealing separator

The annealing separator of the present invention contains magnesium oxide (MgO) as a main component and further contains one or more elements selected from the group including Y, La and Ce (elements of the Y group), and one or more elements selected from the group including Ca, Sr and Ba (elements of the Ca group).

[0089]

Y, La and Ce

In the annealing separator, the ratios of the contents of Y, La, Ce and Mg relative to the content of MgO in the annealing separator are expressed in % and are denoted as [Y], [La], [Ce] and [Mg]. The annealing separator contains these elements, satisfying the following formula:

(0.00562[Y]+0.00360[La]+0.00712[Ce])/0.0412[Mg]•100(%): 0.20 to 1.60(%)

Here, the coefficients in the above formula are the coefficients for finding the concentration ratios and are calculated as follows, assuming that the Y, La, Ce, and Mg atoms present in the annealing separator are respectively composed of the stable oxides Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ and MgO:

Y factor: 1/atomic weight Y/2=1/88.9/2=0.00562

Coefficient La: 1/atomic weight La/2=1/138.9/2=0.00360

Ce coefficient: 1/atomic weight Ce=1/140.1=0.00714

Mg coefficient: 1/atomic weight Mg=1/24.3=0.0412

[0090]

(0.00562[Y]+0.00360[La]+0.00714[Ce])/0.0412[Mg]•100% is the proportion (percentage) of the content obtained by converting the Y group elements in the annealing separator to stable oxides of the elements and their summation and the main constituent MgO in the annealing separator. In other words, we can say that this is an indicator showing the magnitude of the influence of the elements of the Y group on Mg in oxides. Below (0.00562[Y]+0.00360[La]+0.00714[Ce])/0.0412[Mg]•100% will be referred to as "CY".

[0091]

Note that the Y group elements must be contained as compounds containing oxygen, or as compounds changing to compounds containing oxygen by finishing annealing oxidation.

The compounds of group Y elements are, for example, oxides or hydroxides, carbonates, sulfates, etc., which are partially or completely converted into oxides by the later explained firing treatment (drying treatment) and finishing annealing treatment.

[0092]

In the annealing separator where the compound of the Y group elements is added, the roots for the primary coating develop due to the oxygen evolution effect explained later. As a result, the adhesion of the primary coating to the base steel sheet is increased. If CY is less than 0.20%, the above effect is not sufficiently secured. On the other hand, if the CY exceeds 1.60%, the primer roots develop excessively and the magnetic properties drop. Thus, CY is between 0.20 and 1.60%. The preferred lower limit of CY is 0.40%, more preferably 0.50%. The preferred upper limit is 1.40%, more preferably 1.30%.

[0093]

The reason why controlling the content of Y-group elements improves adhesion is not entirely clear, but it is believed to be due to the following: i.e., Y-group elements containing oxygen release oxygen during finish annealing, maintain a partial pressure of oxygen between the steel sheets of the coil during finishing annealing and increase the fixing oxide layer (2) of the primary coating. Below will be explained in detail the relationship between the release of oxygen and the development of the anchoring oxide layer (2).

The fixing oxide layer is composed of MgO in the annealing separator and Mg ₂ SiO ₄ formed by reaction with SiO ₂ inside the base steel sheet. That is, in order to obtain an anchoring structure with noticeable uneven shapes, it is necessary that the oxides inside the steel sheet, that is, SiO ₂ , inherently have noticeable uneven shapes. SiO ₂ having such interfaces has a high interfacial energy, so it is unstable during finishing annealing performed at a high temperature. For this reason, during the finish annealing, the SiO ₂ formed inside the base steel sheet breaks down and diffuses as SiO ₂ in the base steel sheet, thereby becoming flat. In addition, finish annealing is carried out in a hydrogen atmosphere, so that the supply of oxygen to the inside of the base steel sheet is small. In addition, Al-based oxides, which are more stable oxides than SiO ₂ , are generated, whereby the oxygen in the base steel sheet decreases and SiO ₂ becomes more and more unstable. As a result, SiO ₂ present inside the base steel sheet at a depth deeper than where Al-based oxides are formed is significantly destroyed. The SiO ₂ becomes progressively flatter due to diffusion after destruction, and the anchoring oxide layer (2) of the Primary Coating also becomes flatter.

Here, the oxygen-containing Y-group elements contained in the annealing separator release oxygen, whereby the oxygen partial pressure between coil steel sheets during finish annealing becomes higher. Due to the higher oxygen partial pressure between the steel sheets, oxygen is supplied to the base steel sheet, and the smoothing of internal SiO ₂ oxides is slowed down. The delay in the smoothing of the SiO ₂ during the finish annealing means the formation of Mg ₂ SiO ₄ with noticeable irregular shapes. Mg ₂ SiO ₄ is more stable than SiO ₂ . There is a slight change in shape due to subsequent finishing annealing. As a result, uneven shapes of the fixing oxide layer (2) of the primary coating become noticeable.

[0094]

Ca, Sr and Ba

In the present invention, the total content of Ca group elements contained in the annealing separator, the total content of Ca group elements contained as impurities in the MgO raw material powder contained in the annealing separator, and the ratio of these contents are specified.

In the annealing separator, the ratio of the content of Ca, Sr, Ba and Mg relative to the content of MgO in the annealing separator is expressed in % and is designated as [Ca], [Sr], [Ba] and [Mg]. The annealing separator contains these elements, satisfying the following formula:

(0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg]*100(%) = 0.20 to 1.80(%)

In addition, the contents of Ca, Sr, Ba and Mg contained in the MgO raw material powder, relative to the MgO content of the MgO raw material powder contained in the annealing separator, are referred to as [Ca'], [Sr'], [Ba'] and [Mg']. The annealing separator contains these elements, satisfying the following formula:

(0.0249[Ca’]+0.0114[Sr’]+0.0073[Ba’])/0.0412[Mg’]•100(%): 0.010 to 0.080(%)

In addition, the total content of Ca group elements contained in the annealing separator and the total content of Ca group elements in the MgO raw material powder contained in the annealing separator satisfies the relationship (total content of Ca group elements in the MgO raw material powder contained in the annealing separator)/( total content of elements of the Ca group contained in the annealing separator): 0.020-0.200.

Here, the coefficients in the above formula are coefficients calculated assuming that the Ca, Ba, Sr, and Mg atoms present in the annealing separator or MgO raw material powder, respectively, are composed of stable oxides of CaO, BaO, SrO, and MgO, and can be calculated as follows using coefficients calculated from the respective quantitative ratios:

Coefficient Ca: 1/atomic weight Ca=1/40.1=0.0249

Sr coefficient: 1/atomic weight Sr=1/87.6=0.0114

Coefficient Ba: 1/atomic weight Ba=1/137.3=0.0073

Mg coefficient: 1/atomic weight Mg=1/24.3=0.0412

[0095]

(0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg]•100 (%) is the ratio (percentage) of the content obtained by converting Ca group elements in annealing separator into stable oxides of elements and their summation with the main component MgO in an annealing separator. In other words, we can say that this is an indicator showing the magnitude of the influence of elements of the Ca group on the Mg content in oxides. Below, the total quantitative ratio of Ca group elements contained in the annealing separator (0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg]•100 (%) will be called " CC", and the total quantitative ratio of elements of the Ca group contained as impurities in the MgO raw material powder contained in the annealing separator (0.0249[Ca']+0.0114[Sr']+0.0073[Ba'])/ 0.0412[Mg']•100 (%), will be referred to as "CC'".

The Ca group elements are, for example, oxides or hydroxides, carbonates, sulfates, etc., which are partially or completely converted into oxides by the roasting treatment (drying treatment) and finish annealing treatment that will be explained later.

[0096]

The Ca group elements are believed to diffuse into the Primary Coating during finish annealing, reaching the Primary Coating interface at the side of the base steel sheet and reacting with the SiO ₂ present in the surface area of the base steel sheet, becoming the starting points for forming the Primary Coating to to facilitate the formation of anchoring oxides, that is, to increase the density of the number of regions of the anchoring oxide layer.

The reason why such an action is shown is not clear, but it is believed that it is as follows.

The base steel sheet is oxidized by decarburization annealing. In the region of the surface layer, SiO ₂ is formed. The growth of the anchoring oxides, part of the primary coating, mainly composed of Mg ₂ SiO ₄ , to the inside of the base steel sheet, that is, the phenomenon of increasing the thickness of the anchoring oxide layer (2), occurs due to Mg contained as the main element of the annealing separator, diffusing to SiO ₂ inside the base steel sheet and forming Mg ₂ SiO ₄ . At the same time, Al concentration regions characterizing the present invention are believed to be formed by Al diffusing from inside the steel sheet, reacting with Mg ₂ SiO ₄ , and concentrating in this region. That is, the more Mg ₂ SiO ₄ is generated inside the base steel sheet, the more Al concentration areas are formed inside the base steel sheet.

The Ca group elements have an action similar to Mg and form composite oxides of Ca group element oxides and Si oxides. It is believed that if composite oxides react with Al, then Al is forced to concentrate in the reaction regions. In addition, when comparing the diffusion rates of Mg and Ca group elements in SiO ₂ , the Ca group elements diffuse faster. If the Ca group elements are present in the annealing separator, the composite oxides of SiO ₂ and the Ca group elements are formed in the area inside the base metal sheet earlier than the Mg ₂ SiO ₄ of the composite oxide of SiO ₂ and Mg, and the fixing rate of the oxides passing through the inside of the steel sheet , increases. At the same time, the annealing separator containing elements of the Ca group not only increases the thickness of the fixing oxide layer (2), but also increases the concentration of Al in it, that is, H5. For this reason, the Ca group elements already become oxides or oxygen-containing compounds before the preparation of the aqueous suspension or after the drying process and must diffuse into the annealing separator.

In addition, if the elements of the Ca group are contained in the MgO raw material powder as impurities, the reactivity of the MgO raw material powder with SiO ₂ increases. Along with this, in the last period of annealing, they function as relatively stable sources of elements of the Ca group. By supplying sources of Ca group elements to the Primary Coating, the oxides of the Primary Coating can be stabilized. In this case, the unstable SiO ₂ may be replaced by CaMgSi ₂ O ₆ or another stable oxide coating at any early period. In addition, CaMgSi ₂ O ₆ is stabilized as a source of Ca group elements without restricting the Mg supply path. As a result, CaMgSi ₂ O ₆ can retain its shape until Mg ₂ SiO ₄ is replaced. However, if the impurity elements of the Ca group in MgO become excessively large, then the amount of Ca supply becomes excessive compared to Mg, the supply of Mg group elements to form CaMgSi ₂ O ₆ , necessary to maintain the complex shape of the primary coating, decreases compared to the Ca group elements , and the formation of the more stable MgSi ₂ O ₄ is retarded, whereby, due to the heat effect of annealing, the Primary Coating changes shape and it becomes impossible to maintain the intricately woven shape of the Primary Coating to prevent pinholes. As a result, point defects increase. In addition, even if the impurity elements of the Ca group in MgO are excessively small, in the same way, even if the additives containing the Ca group elements added to the raw material powder other than MgO provide a sufficient amount of the Ca group elements, the supply of Mg is relatively reduced, in as a result, the formation of more stable MgSi ₂ O ₄ slows down and, for a similar reason, point defects increase. Since the overall ratio of the Ca group elements in the annealing separator is balanced in the amounts of Mg and Ca, there are CC=0.20-1.80 and CC'=0.010-0.080. CC'/CC=0.020-0.200.

[0097]

If the CC is less than 0.20, then the above effect cannot be sufficiently obtained. On the other hand, if the CC exceeds 1.80, the fixing oxide layer becomes excessively thick, and the magnetic property sometimes drops. If the CC is 0.20 to 1.80, then the drop in magnetic property can be suppressed while the adhesion of the Primary Coating to the base steel sheet can be improved.

In addition, if CC' is less than 0.010 or greater than 0.080, or if CC'/CC is less than 0.020 or greater than 0.200, then pinholes will occur. For this reason, the CC' range of the present invention is 0.010 to 0.080, and the CC'/CC range is 0.020 to 0.200.

[0098]

Additional components of the annealing separator

The annealing separator may further contain, if necessary, Ti, Zr and Hf. Thereafter, one or more elements selected from the group consisting of Ti, Zr and Hf will sometimes be described as "elements of the Ti group".

The proportion of the content of Ti, Zr, Hf and Mg relative to the content of MgO in the annealing separator is expressed as % by mass and is denoted as [Ti], [Zr], [Hf] and [Mg]. The annealing separator contains these elements in exactly the quantities that satisfy the following formula:

(0.0209[Ti]+0.0110[Zr]+0.0056[Hf])/0.0412[Mg]•100(%)≤5.0(%)

Here, the coefficients in the above formula are coefficients calculated considering that the Ti, Zr and Hf present in the annealing separator are respectively composed of stable oxides TiO ₂ , ZrO ₂ , HfO ₂ and MgO, and can be calculated as follows using coefficients calculated according to the corresponding quantitative ratios:

Ti coefficient: 1/atomic weight Ti=1/47.9=0.0209

Zr coefficient: 1/atomic weight Zr=1/91.2=0.0110

Hf coefficient: 1/atomic weight Hf=1/178.5=0.0056

Mg coefficient: 1/atomic weight Mg=1/24.3=0.0412

[0099]

(0.0209[Ti]+0.0110[Zr]+0.0056[Hf])/0.0412[Mg]•100 (%) is the ratio (in percent) of the content obtained by converting Ti group elements to annealing separator into stable oxides of elements and their summation with the main constituent substance MgO in the annealing separator. In other words, we can say that this is an indicator showing the magnitude of the influence of elements of the Ti group on Mg in oxides. Below (0.0209[Ti]+0.0110[Zr]+0.0056[Hf])/0.0412[Mg]•100(%) will be referred to as "CT". The elements of the Ti group may be included individually or as alloys or compounds. Such compounds are, for example, sulfates, carbonates, hydroxides, etc.

[0100]

In the finish annealing, the Ti group elements promote the reaction of MgO in the annealing separator and the SiO ₂ of the surface layer of the base steel sheet formed by the decarburization annealing and promote the formation of Mg ₂ SiO ₄ . On the other hand, if CT exceeds 5.0, this effect saturates, so 5.0 is the upper limit.

[0101]

In addition, the annealing separator may also contain elements with known effects in ranges that do not interfere with the effect of the present invention.

[0102]

The values of the above CY, CC and CT are determined by the content of the elements of the group and the content of Mg in the annealing separator.

[0103]

Diffusion of elements in the annealing separator

The annealing separator of the present invention contains various of the above elements, but they are present not only in the form of metals alone, but also in a mixed state in the form of various types of compounds.

The present invention contains several provisions regarding this mixed state.

[0104]

In the annealing separator of the present invention, the average particle size of MgO is 0.1 to 2.8 µm. Below, the average particle size of MgO will be referred to as R1.

If R1 is less than 0.1 µm, then MgO becomes too active, the coil sheets stick together after finishing annealing, and the properties of the annealing separator deteriorate.

If R1 exceeds 2.8 µm, then MgO becomes too inert and the formation of the primary coating is delayed. For this reason, R1 is between 0.1 and 2.8 µm.

R1 and R2 are measured as follows. That is, the raw material powder is measured by a laser diffraction/scattering method based on JIS Z8825 (2013) using a laser diffraction/scattering type particle size distribution measuring device to obtain a volume-based particle size distribution. In addition, this is converted to a particle size distribution based on the number of particles, and finally, for each element, an average particle size based on the number of particles is determined.

[0105]

The annealing separator of the present invention has an average particle size containing elements of the Ca group, from 0.2 to 3.0 μm. Below, the average size of particles containing elements of the Ca group will be referred to as R2.

If R2 is less than 0.2 µm, then Ca becomes too active, and the supply amount of Ca group elements to the Primary Coating during formation becomes too large compared to the supply amount of Mg. For this reason, the reaction of Mg and Si slows down, so the formation of Mg ₂ SiO ₄ , on the contrary, slows down, and the adhesion of the primary coating deteriorates.

If R2 exceeds 3.0 µm, then MgO and SiO ₂ are no longer in contact with each other, so the formation of Mg ₂ SiO ₄ slows down and the adhesion of the primary coating deteriorates.

The R2 measurement method will be explained later.

[0106]

It should be noted that R1 and R2 prescribed in the present invention are values calculated based on the number of particles.

As a rule, the average particle size is often determined on the basis of weight. Based on weight, in a powder with uneven particle sizes, the proportion of particles in a certain particle size range is expressed as a fraction of the total weight. This average particle size based on weight cannot be representative of the measured object particles as a whole in the particle size distribution. For example, if the ratio of large particles, which are extremely rare in frequency of occurrence, does not change much because the ratio of large particles by weight is generally large, then the resulting average particle size fluctuates greatly.

On the other hand, the average particle size based on the number of particles described in the present invention is based on the number of particles present, classified by size, so if the number of particles of certain sizes does not change much, the overall average particle size will not fluctuate much. That is, the size becomes a value reflecting the size of particles with a high frequency of presence. In other words, this value has a strong correlation with the number of particles per unit volume.

The effect of the present invention is realized, as explained below, by controlling the particle size with a high frequency of existence. The principles of the invention should be based on an average particle size based on the number of particles and not on weight.

[0107]

In addition, the annealing separator of the present invention has an R2 to R1 ratio, that is, R2/R1, in the range of 0.5 to 3.0.

If R2/R1 becomes less than 0.5, the area ratio (S1/S0) of the Al bonding regions of the primary coating formed falls, and the adhesion of the coating deteriorates. Preferably, it is 0.6 or more, more preferably 0.8 or more.

On the other hand, even if R2/R1 exceeds 3.0, the area ratio (S1/S0) of the anchoring oxides of the primary coating formed falls, and the adhesion of the coating deteriorates. Preferably it is 2.6 or less, more preferably 2.2 or less.

[0108]

The reason why the adhesion of the coating is improved with the above R1, R2 and R2/R1 is not clear, but it is believed to be the following:

In general, the smaller the powder, the easier it is for it to aggregate. When mixing powdered compounds with very different particle sizes, fine compounds aggregate. Considering the mixed state of MgO and Ca group elements, if the Ca group element compounds are excessively fine and R2/R1 becomes less than 0.5, the Ca group element compounds aggregate. When such a mixture is applied to the surface of the base steel sheet in the state of contact with the base steel sheet, areas where only Ca group elements are in contact with the base steel sheet will be present as areas of considerable size. When the primary coating is formed by finishing annealing in this state, in areas where only the Ca group elements are in contact with the base steel sheet, Mg supply becomes slow, so the formation of the primary coating becomes slow and the adhesion of the coating becomes poor.

In the same way, if R2/R1 exceeds 3.0, the diffusion of the Ca group elements with respect to MgO becomes more rarefied, so the supply of Ca is slowed down, and the coating adhesion of the formed primary coating becomes poor.

This results in Ca-group element compounds between MgO and the steel sheet, and prevents Mg from being supplied to the base steel sheet. That is, the regions where MgO does not contact with the base steel sheet are simply voids if the Ca group element compounds are not present in relatively thin states, but if the Ca group element compounds are relatively thin, then the areas change to areas preventing Mg from being supplied to the base steel. sheet. As a result, in areas where MgO contacts the base steel sheet and areas where it does not, there is a noticeable difference in the supply of Mg to the base steel sheet, and the primary coating becomes uneven in development. For this reason, the number density of anchoring oxides becomes excessive and becomes an inhibitory factor in magnetic properties.

In the same way, even when adding Ca group elements with a particle size much larger than the MgO particle size, the range to which Ca group elements can be supplied is reduced, so that eventually the supply of Ca group elements becomes one-sided, and in places where they are supplied excessively, the primer base density becomes excessively high.

On the other hand, if R2/R1 is in a suitable range, the number density of Ca group element compounds dispersed in the annealing separator layer near the steel sheet increases, so compared to making the Ca group element compounds finer and adding them to large quantities, the supply of Ca, Sr and Ba to the base steel sheet becomes uniform, and as a result, the number density of the fixing oxides can be uniform.

[0109]

Annealing separator layer

The present invention provides for the structure of the annealing cage in the state applied to the surface of the steel sheet just before finishing annealing after the above-mentioned annealing cage layer forming process is completed.

In the annealing separator layer of the present invention, the number density of particles containing Ca group elements in Ca group concentration regions present in a region of 0 to 3.0 μm from the surface of the base steel sheet is 0.003 to 1.400/μm ² . Below, this "number density of particles containing elements of the Ca group in the areas of concentration of the Ca group" will be called D42. By adjusting D42 within the above range, the Primary Coating adhesion after finishing annealing is improved.

[0110]

The reason why Primary Coating adhesion is improved if D42 is in the above range is not entirely clear, but is believed to be as follows: it is believed, as explained above, that the Ca group elements contained in the annealing separator diffuse into the Primary Coating, formed during finish annealing to the side of the base steel sheet and form composite oxides with Al supplied from the base steel sheet side of primary coating, that is, from the side of the base metal at the front ends of the anchor oxides, thereby acting to fix Al at the front ends of the anchor oxides. . To make this effect more noticeable, the position of the presence of the Ca group elements in the annealing separator layer is important. It becomes convenient to have Ca group element concentration regions on the side of the base steel sheet, that is, a region of 0 to 3.0 µm from the surface of the base steel sheet. In addition, as explained above, the contact with the base steel sheet should not have a local slope. It is believed that the appropriate diffusion state of the elements in the annealing separator correlates with the number density of the Ca group concentration regions in the formed primary coating.

[0111]

D42 can be found in the following way.

The annealing separator layer of the surface of the steel sheet using finishing annealing after drying is analyzed by EDS-SEM on the cross section obtained by processing each steel sheet using finishing annealing with CP treatment to obtain the characteristic X-ray intensity of Ca group elements. That is, the obtained characteristic X-ray intensity distribution diagram is a distribution diagram in which the information contained in the annealing separator is projected onto a plane parallel to the cross section of the steel sheet used for finish annealing in the thickness direction. The intensity distribution diagram of the characteristic X-ray emission of the Ca group elements was obtained in the field of view, where the boundary between the surface of the steel sheet and the annealing separator layer becomes extremely parallel to the upper and lower ends of the observed area, and, in addition, the annealing separator layer does not protrude outward from under the bottom and bottom ends of the observed region. Hereinafter, the direction of the observed width of the surface of the steel sheet and the annealing separator layer and the direction perpendicular to the direction of the observed width will be referred to as the direction of the observed height. The scanning steps of the characteristic X-ray intensity distribution diagram are performed in the same way in the observed width direction and the observed height direction, and have a length of 0.1 μm or less. Further, the observed width direction is made at least 20 µm long or more. That is, the characteristic X-ray intensity distribution pattern is split into at least 200 pixels in the observed width direction. Here, in the intensity distribution of the characteristic X-ray emission of the obtained elements of the Ca group, the corresponding intensities of the characteristic X-ray emission Ca, Sr, and Ba and the area in which the intensity of the characteristic X-ray emission Ca, which is 20% or more of the maximum intensity value of the characteristic X-ray emission Ca, the area, where the obtained characteristic X-ray intensity Sr is 20% or more of the maximum value of the characteristic X-ray intensity Sr, and the area where the characteristic X-ray intensity Ba is obtained, which is 20% or more of the maximum value of the characteristic X-ray intensity Ba, collectively referred to as as "areas of concentration of elements of the Ca group". In addition, an area in which pixels of such a concentrated area of a group element Ca extend up and down or left and right in units of pixels is considered one area, and an area consisting of four or more pixels is considered a particle. In addition, the coordinates of the center of gravity of each element of the Ca group, concentrated in the area of the observed area, is obtained by image analysis. Thereafter, the number N1 of particles with centers of gravity present at a height of 3 μm from the surface of the base steel sheet in the thickness direction was counted. The average value R2 of the equivalent diameters of the circles of particles containing elements of the Ca group is calculated in the areas of concentration of elements of the Ca group (√((area of 1 pixel)•(the number of pixels of successive units)•4/π)). From the obtained N1, R2 obtained as explained above, and the length Lm of the observation area in the observation direction (the length of the observation area in the direction perpendicular to the cross-sectional thickness direction (the length of the observation area in the width direction of the steel sheet using finish annealing)), you can get D42=N1/(3•L•R2)(/μm ³ ).

[0112]

It should be noted that the average particle size (e.g., R1) of the compounds dispersed in the annealing separator bed is understood to be substantially the same as the average particle size obtained from the particle size distribution of only the raw material powder added during preparation as an aqueous suspension. Accordingly, the average particle sizes of the compounds can be found from the average particle sizes of the raw material powders using methods similar to the method for calculating R1. The method of adjusting the particle sizes of the compounds containing the elements in the raw material powder to suitable ranges is not to be limited. A powder having a target particle size distribution can be made by adjusting the firing conditions and classification, etc. It will not be difficult for a specialist who knows the technique of making powder from raw materials.

[0113]

By using such Ca group compound powder and MgO powder as the raw material for the aqueous suspension, the density of the number of Ca group concentration areas can be appropriately controlled in areas from 0 to 3.0 µm from the surface of the base steel sheet in the annealing separator layer.

EXAMPLES

[0114]

In the following, the modes of the present invention will be more specifically explained by examples. These examples are only illustrations to confirm the effects of the present invention and do not limit the present invention.

The present invention relates to an annealing separator, which plays an important role in forming the primary coating and coating the steel sheet before finishing annealing, and to the primary coating formed by it. The main steel sheet need not be special. For this reason, in the examples, the steel sheet was produced under constant conditions (hot rolling, cold rolling, annealing conditions, etc.) not directly related to the effects of the invention. First, the general conditions in examples as a whole will be explained, then in examples 1 and 2, the results of the study of the effects of the invention by changing the conditions relating to the primary coating will be explained.

[0115]

Grain-Oriented Electrical Steel Sheet Production

Molten steel having each of the chemical compositions listed in Table 1 was produced in a vacuum melting furnace. The resulting molten steel was used to make a slab by continuous casting.

[0116]

[Table 1]

Molten Steel No. C Si Mn S Se S+Se Acid Rust. Al N Cu sn Sb Cu+Sn+Sb Bi Te Pb Bi+Te+Pb 1 0.077 3.3 0.074 0.028 - 0.028 0.030 0.0080 - - - 0.00 - - - 0.000 2 0.078 3.3 0.075 - 0.044 0.044 0.029 0.0080 - - - 0.00 - - - 0.000 3 0.108 3.3 0.074 0.025 - 0.025 0.030 0.0077 - - - 0.00 - - - 0.000 4 0.078 2.2 0.074 0.028 - 0.028 0.030 0.0080 - - - 0.00 - - - 0.000 5 0.077 4.8 0.074 0.025 - 0.025 0.030 0.0078 - - - 0.00 - - - 0.000 6 0.078 3.3 0.018 - 0.032 0.032 0.029 0.0080 - - - 0.00 - - - 0.000 7 0.078 3.3 0.240 0.027 - 0.027 0.030 0.0080 - - - 0.00 - - - 0.000 8 0.078 3.3 0.076 0.002 - 0.002 0.030 0.0080 - - - 0.00 - - - 0.000 9 0.078 3.3 0.075 0.002 0.002 0.004 0.030 0.0080 - - - 0.00 - - - 0.000 10 0.077 3.3 0.074 - 0.003 0.003 0.030 0.0080 - - - 0.00 - - - 0.000 eleven 0.077 3.3 0.076 - 0.065 0.065 0.030 0.0080 - - - 0.00 - - - 0.000 12 0.078 3.3 0.077 0.035 0.030 0.065 0.030 0.0080 - - - 0.00 - - - 0.000 13 0.077 3.3 0.076 0.062 - 0.062 0.029 0.0080 - - - 0.00 - - - 0.000 14 0.078 3.3 0.075 0.028 0.010 0.038 0.004 0.0080 - - - 0.00 - - - 0.000 15 0.078 3.3 0.074 0.020 0.015 0.035 0.060 0.0080 - - - 0.00 - - - 0.000 16 0.078 3.3 0.077 0.020 0.013 0.033 0.029 0.0020 - - - 0.00 - - - 0.000 17 0.076 3.3 0.074 0.015 0.020 0.035 0.029 0.0330 - - - 0.00 - - - 0.000 18 0.078 3.3 0.074 0.021 0.011 0.032 0.030 0.0080 0.10 - - 0.10 - - - 0.000 19 0.078 3.3 0.074 0.019 0.015 0.034 0.030 0.0080 0.62 - - 0.62 - - - 0.000 20 0.078 3.3 0.075 0.027 - 0.027 0.031 0.0079 0.10 0.07 - 0.17 - - - 0.000 21 0.078 3.3 0.077 0.028 - 0.028 0.030 0.0080 0.10 - 0.07 0.17 - - - 0.000 22 0.078 3.3 0.075 0.024 0.008 0.032 0.030 0.0080 0.10 0.20 0.02 0.32 - - - 0.000 23 0.076 3.3 0.075 0.025 - 0.025 0.030 0.0080 0.16 0.46 - 0.62 - - - 0.000 24 0.078 3.3 0.075 0.026 0.010 0.036 0.030 0.0080 0.10 0.08 - 0.18 0.003 - - 0.003 25 0.078 3.3 0.080 0.025 - 0.025 0.030 0.0080 0.10 0.08 - 0.18 0.006 0.005 - 0.011 26 0.077 3.3 0.075 0.028 0.015 0.025 0.030 0.0080 - 0.08 0.05 0.13 - - 0.003 0.003 27 0.078 3.3 0.075 0.028 0.01 0.038 0.030 0.0080 0.10 0.08 - 0.18 0.010 0.016 0.005 0.031

[0117]

Each slab in Table 1 heated at 1350° C. was hot rolled to produce a hot-rolled steel sheet with a thickness of 2.3 mm. In Molten Steel No. 5, the Si content of the molten steel was too high, so cracks occurred during hot rolling, and a hot-rolled steel sheet could not be produced.

[0118]

The obtained hot-rolled steel sheet was annealed, then the hot-rolled steel sheet was pickled. Annealing of hot rolled products was carried out at a temperature of 1100°C for 5 minutes.

[0119]

The hot-rolled steel sheet after pickling was subjected to cold rolling to produce a cold-rolled steel sheet with a thickness of 0.22 mm. The cold rolling reduction was 90.4%.

[0120]

The cold-rolled steel sheet was annealed by primary recrystallization annealing, which also served as a decarburization annealing. The annealing temperature of the primary recrystallization annealing ranged from 750 to 950°C. The holding time at the annealing temperature was 2 minutes.

[0121]

The cold-rolled steel sheet after the primary recrystallization annealing was coated on its front and back surfaces with an aqueous slurry prepared by mixing the annealing separator components from Table 2 with pure water.

[0122]

[0123]

The annealed decarburized steel sheet coated with an aqueous slurry on its surface was held in an oven at 900° C. for 10 seconds to dry the aqueous slurry.

The sample was taken from the steel sheet obtained by this method, and was measured for the number density D42 containing one or more elements selected from the group including Ca, Sr and Ba, in the concentration areas of Ca group elements present in the range from 0 to 3 .0 µm from the surface of the base steel sheet. This value is shown in table 2.

[0124]

In addition, the sample was subjected to finishing annealing, keeping it at a temperature of 1200°C for 20 hours. Through the above process, a grain-oriented electrical steel sheet having a base steel sheet and a primary coating was produced.

In Molten Steel No. 3, the C content was too high, the amount of iron loss after secondary recrystallization deteriorated significantly, and the result was outside the scope of the present invention. In molten steel No. 4, the Si content was too low and secondary recrystallization did not occur, so the value of the magnetic flux density B8 deteriorated significantly, and the result was outside the scope of the present invention.

In molten steel No. 6-17, the content of Mn, S, Se, acid. sol. Al or N was outside the range of a suitable amount to form inclusions necessary to cause secondary recrystallization, and secondary recrystallization did not occur, so the B8 magnetic flux density value deteriorated significantly, and the result was out of the scope of the present invention.

In molten steel No. 19, the Cu content was too high, the coating adhesion became extremely poor, and the result was outside the scope of the present invention.

In molten steel No. 23, the content of Sn was too high, the adhesion of the coating became poor, and the result was outside the scope of the present invention.

In molten steel No. 27, the total content of Bi, Te and Pb was too large, the adhesion of the coating became poor, and the result was beyond the scope of the present invention.

[0125]

In the above production, as well as in the general grain-oriented electrical steel sheet, decarburization annealing and finishing annealing (cleaning annealing) were carried out. Due to this, the composition of the base steel sheet becomes different from the original slab. The chemical composition of the base steel sheet of the produced grain oriented electrical steel sheet is shown in Table 3.

[0126]

[Table 3]

Steel sheet no. C Si Mn S Se S+Se Acid Rust. Al N Cu sn Sb Bi Te Pb 1 0.0005 3.3 0.073 0.001 <0.0005 0.001 0.001 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 2 0.0005 3.3 0.075 <0.0005 0.001 0.001 0.001 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 3 0.0180 3.3 0.073 0.001 <0.0005 0.001 0.001 0.002 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 4 0.0005 2.0 0.074 0.001 <0.0005 0.001 0.001 0.002 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 6 0.0005 3.3 0.017 <0.0005 0.001 0.001 0.001 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 7 0.0005 3.3 0.238 0.001 <0.0005 0.001 0.001 0.002 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 8 0.0005 3.3 0.076 0.001 <0.0005 0.001 0.002 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 9 0.0005 3.3 0.075 0.001 0.001 0.002 0.002 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 10 0.0005 3.3 0.072 <0.0005 0.001 0.001 0.001 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 eleven 0.0005 3.3 0.076 <0.0005 0.003 0.003 0.001 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 12 0.0005 3.3 0.077 0.001 0.001 0.002 0.001 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 13 0.0005 3.3 0.074 0.003 <0.0005 0.003 0.001 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 14 0.0005 3.3 0.075 0.001 0.001 0.002 0.001 0.001 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 15 0.0005 3.3 0.074 0.001 0.001 0.002 0.002 0.003 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 16 0.0005 3.3 0.076 0.001 0.001 0.002 0.001 0.002 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 17 0.0005 3.3 0.074 0.001 0.001 0.002 0.001 0.002 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 18 0.0005 3.3 0.073 0.001 0.001 0.002 0.001 0.003 0.08 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 19 0.0005 3.3 0.074 0.001 0.001 0.002 0.001 0.003 0.051 <0.0005 <0.0005 <0.0005 <0.0005 <0.0005 20 0.0005 3.3 0.075 0.001 <0.0005 0.001 0.002 0.003 0.07 0.03 <0.0005 <0.0005 <0.0005 <0.0005 21 0.0005 3.3 0.077 0.001 <0.0005 0.001 0.001 0.003 0.08 <0.0005 0.04 <0.0005 <0.0005 <0.0005 22 0.0005 3.3 0.074 0.001 0.001 0.002 0.001 0.003 0.07 0.11 0.08 <0.0005 <0.0005 <0.0005 23 0.0005 3.3 0.075 0.001 <0.0005 0.001 0.001 0.002 0.09 0.42 <0.0005 <0.0005 <0.0005 <0.0005 24 0.0005 3.3 0.075 0.001 0.001 0.002 0.001 0.003 0.05 0.08 <0.0005 0.002 <0.0005 <0.0005 25 0.0005 3.3 0.080 0.001 <0.0005 0.001 0.001 0.002 0.07 0.07 <0.0005 0.002 0.002 <0.0005 26 0.0005 3.3 0.074 0.001 0.001 0.002 0.001 0.002 <0.0005 0.07 0.04 <0.0005 <0.0005 0.001 27 0.0005 3.3 0.075 0.001 0.001 0.002 0.001 0.003 0.07 0.07 <0.0005 0.002 0.003 0.001

[0127]

Property evaluation

In molten steel Nos. 1, 2, 16, 18, 19, 20, 21, 22, 24, 25, 26, and 27 with steel sheet components of the present invention, the magnetic properties of the produced grain oriented electrical steel sheet and adhesion primary coverage. The magnetic properties of the produced grain oriented electrical steel sheet and the adhesion of the primary coating were evaluated as Test No. 1-52.

[0128]

Magnetic properties

From each of the grain oriented electrical steel sheet that passed the numbered tests, a sample was taken in the rolling direction with a length of 300 mm and a width of 60 mm. The sample was subjected to a magnetic field of 800 A/m to determine the magnetic flux density B8. Next, an insulating coating mainly composed of colloidal silica and phosphate was cured by drying (sintering), then the loss in W17/50 steel was measured during excitation at a maximum magnetic flux density of 1.7 T and a frequency of 50 Hz. A grain-oriented electrical steel sheet having a magnetic flux density B8 of 1.92 T or more and W17/50 of 0.75 W/kg or less was considered excellent in magnetic properties.

[0129]

Adhesion

A rolling direction sample 60 mm long and 15 mm wide was taken from each of the grain oriented electrical steel sheets in a numbered test. The specimen was subjected to a bend test with a curvature of 10 mm. The bending test was carried out using a cylindrical mandrel bending test machine with it mounted on the specimen so that the axial direction of the cylinder corresponds to the width direction of the specimen. Examined the surface of the sample after the bend test and determined the total area of the areas in which the primary coating remained without peeling. The following formula was used to determine the remaining percentage of primary coverage.

Residual Primary Coating = Total Area of Areas where Primary Coating Remains Without Peeling / Sample Surface Area •100%

The remaining percentage of the primary coating of 90% or more was recognized as excellent adhesion of the coating.

Point Defects

A sample in the rolling direction 1 m long and 1 m wide was taken from the grain oriented electrical steel sheet of each numbered test and visually examined to determine the frequency NP of occurrence of pinhole defects (pore number density). The point defects were suppressed if the number of point defects per 1 m ² was 5 or less.

[0130]

Primary Coating Structure

A sample in the rolling direction, 300 mm long and 60 mm wide, was taken from each numbered test anisotropic steel sheet and electrolyzed at a constant potential in an electrolytic solution so that only the base steel sheet began to dissolve. The Primary Coating was peeled off and the structure and composition of the Primary Coating were examined. The peeling method and measurement methods used were in accordance with the aforementioned means. As an electrolytic solution, a non-aqueous solvent based on 10% acetylacetone - 1% methanol of tetramethylammonium chloride was used. The amount of electrolysis was 80 C/cm ² . Finally, the following values were obtained.

(1) Number density D3 of concentrated Al regions

(2) Area S5 of regions consisting of pinning oxide layer regions and Al concentration regions

(3) Area S3 of all concentrated areas

(4) Distance H5 of regions consisting of anchor oxide layer regions and concentrated Al regions from the reference value H0 of the interface between the surface oxide layer and the anchor oxide layer

(5) Total content of group Y elements

(6) Total content of elements of the Ca group

(7) Density of the number D4 of concentrated regions of the Ca group

(8) Area S1 of the regions of the fixing oxide layer

(9) Observed region S0

[0131]

Annealing separator layer

A sample was cut from a steel sheet in the state before the final annealing and after the drying of the aqueous slurry. The annealing separator layer was examined according to the above method.

(10) Numerical density D42 of Ca concentration regions in the annealing separator layer was obtained

[0132]

Annealing separator

The raw material powder of the aqueous slurry annealing separator was measured according to the above means, and the following values were obtained:

(11) Total quantitative ratio of CY elements of group Y (0.00562[Y]+0.00360[La]+0.00714[Ce])/0.0412[Mg]•100(%)

(12) CC content of Ca CC group elements (0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg]•100(%)

(13) Average particle size R1 MgO

(14) Average particle size R2 of an element of the Ca group containing particles

Further, only MgO of the annealing separator was separated and the following values were obtained:

(16) Number of CC’ elements of the Ca impurity group in MgO (0.0249[Ca’]+0.0114[Sr’]+0.0073[Ba’])/0.0412•100(%)

(17) CC’/CC ratio (16)/(12) of impurities in MgO in the total amount of Ca group elements in the annealing separator

Note that RCa, RSr and RBa are respectively the averages of the equivalent circle diameters Ca, Sr and Ba

[0133]

Example 1

An aqueous slurry to be applied to a steel sheet after decarburization annealing was prepared by mixing compounds containing MgO, Y group elements and compounds containing Ca group elements with water to obtain a group element content such as shown in Table 2. At this time, the types of compounds and ratios of the existence of groups of elements (CY, CC).

[0134]

The results are shown in Table 4. If the remaining percentage of the Primary Coating is 90% or more, the adhesion of the Primary Coating to the base steel sheet is said to be excellent. It is known that the satisfaction of the provisions of the present invention leads to good properties. Further, if the magnetic flux density B8 is 1.92 or more and the frequency number of pinholes is 5/m ² or less, then the presence of a pinhole inhibition effect was judged. It is known that the implementation of the provisions of the present invention leads to the inhibition of point defects. Referring to Table 4, in Test Nos. 35-51, the chemistry was appropriate and the conditions in the annealing separator (CC, CC', CC'/CC, CY, R1, R2, R2/R1) were appropriate. As a result, the area ratio S1/S0 of the fixing oxide layer became 0.15 or more, the area ratio S5/S3 of the Al fixing regions A5 became 0.30 or more, the distance H5 became 0.4 or more, the number density D3 of Al concentration regions became 0.020 or more, and the results were within the scope of the present invention. As a result, in each of the grain-oriented electrical steel sheets in these numbered tests, the magnetic flux density B8 was 1.93 T or more, and excellent magnetic properties were obtained. In addition, the remaining percentage of the primary coating was 90% or more, the occurrence of pinholes was 5/m ² or less, and excellent properties of the primary coating were demonstrated.

[0135]

On the other hand, in tests No. 1-3, the total ratio of CC elements of the Ca group was too small, the primary coating did not develop in shape, S1/S0 became less than 0.18, S5/S3 became less than 0.30, and D3 became less 0.005. As a result, the remaining primary coating rates were 82%, 84%, and 76%, respectively, and the adhesion of the coating became poor.

[0136]

In tests Nos. 4-6, the total CC ratio of the Ca group elements was too high, the shape of the primary coating developed too much, and D3 exceeded 0.150/μm ² . As a result, the loss in steel W17/50 was more than 0.75, and the magnetic properties became poor.

[0137]

In tests no. 7-9, the total quantitative ratio of CC' elements of the Ca group in MgO was too low. In addition, in Test Nos. 13-15, the CC'/CC ratio was too low, so that the Primary Coating was not sufficiently developed in shape, and L5/S0 became less than 0.020 µm/µm ² . As a result, 5/m ² or more pinholes occurred, the pinholes became worse, the remaining proportion of the primary coating fell below 90%, and the adhesion became poor.

[0138]

In tests nos. 10-12, the total quantitative ratio of CC' elements of the Ca group in MgO was too high. In addition, in Test Nos. 16-18, the CC'/CC ratio was too high, so the shape of the primary coating developed too much, and L5/S0 was more than 0.500 µm/µm ² . As a result, the loss in steel W17/50 was more than 0.75, and the magnetic properties became poor.

[0139]

In tests #19-21, the total CY ratio of group Y elements was too low, so the primary coating was underdeveloped in shape, and H5 fell below 0.4. As a result, the remaining proportion of the primary coating became 90% or less, and the adhesion became poor.

[0140]

In tests #22-24, the total CY ratio of group Y elements was too high, so the primary coating developed too much in shape, and H5 exceeded 4.0. As a result, the magnetic flux density became 1.93 T or less.

[0141]

In test no. 25, the average particle size R1, based on the amount of MgO, was too small, so the sheets stuck together during finish annealing.

[0142]

In Test No. 26, R1 was too high and the supply of Mg to the Primary Coating was slow. As a result, S1/S0, S5/S3, L5/S0 and H5 were below the control values. As a result, the remaining percentage of the primary coating was 42%, and the adhesion of the coating was poor.

[0143]

In tests nos. 27, 29 and 31, R2 was too low, the intake of Ca and Mg group elements became uneven, and S1/S0 became less than 0.15. As a result, the remaining percentage of the primary coating was less than 90%, and the adhesion of the coating was poor.

[0144]

In tests nos. 28, 30 and 32, R2 was too high, the intake of elements of the Ca and Mg groups became uneven, S1/S0 became less than 0.15, and D3 became less than 0.015. As a result, the remaining percentage of the primary coating was less than 90%, and the adhesion of the coating was poor.

[0145]

In test #33, R1 and R2 were within range, but R2/R1 was greater than 3.0. As a result, the remaining percentage of the primary coating was less than 90%, and the adhesion of the coating was poor.

[0146]

In test #34, R1 and R2 were in range, but R2/R1 fell below 0.3. As a result, 5/m ² or more pinholes occurred, the pinholes became worse, the remaining percentage of the primary coating fell below 90%, and the adhesion of the coating became poor.

[0147]

In Test No. 52, the conditions of the annealing separator were within limits, but the content of Bi, Te, and Pb in the molten steel components exceeded 0.03%. As a result, the remaining percentage of the primary coating was less than 90%, and the adhesion of the coating was poor.

[0148]

[0149]

The embodiments of the present invention have been explained above. However, the embodiments described above are merely illustrative for the operation of the present invention. Therefore, the present invention is not limited to the above-described embodiments, and can be developed by appropriate modification of the above-described embodiments to the extent not deviating from its spirit.

LIST OF SYMBOLS

[0150]

1. surface oxide layer

2. fixing the oxide layer

3. deepest anchoring position

A0. the entire observed area

A1. anchoring the oxide region

A2. area of the surface oxide layer

A3. concentration area of Al (aluminum)

A4. area of concentration of elements of the Ca group

A5. Al concentration region (aluminum) present in the oxide pinning region

Claims (15)

1. An annealing separator containing MgO as the main component, where the annealing separator contains one or more elements selected from the group including Y, La and Ce, and one or more elements selected from the group including Ca, Sr and Ba, when determining the proportions (%) of the contents of Mg, Y, La, Ce, Ca, Sr and Ba contained in the annealing separator, in relation to the content of MgO, as respectively [Mg], [Y], [La], [Ce], [Ca], [Sr] and [Ba], is satisfied (0.00562[Y]+0.00360[La]+0.00714[Ce])/0.0412[Mg]⋅100(%): 0.20 to 1.60(%), and (0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg]⋅100(%): 0.20 to 1.80(%), and when determining the proportions (%) of the contents of Mg, Ca, Sr and Ba contained in the MgO raw material powder, in relation to the MgO content in the MgO raw material powder contained in the annealing separator, as respectively [Mg'], [Ca'], [Sr '] and [Ba'], is satisfied (0.0249[Ca']+0.0114[Sr']+0.0073[Ba'])/0.0412[Mg']⋅100(%): 0.010 to 0.080(%), in addition, the ratio (0.0249[Ca']+0.0114[Sr']+0.0073[Ba'])/0.0412[Mg']⋅100 towards (0.0249[Ca]+0.0114[Sr]+0.0073[Ba])/0.0412[Mg]⋅100 is 0.200-0.020, and average particle size R1 MgO: 0.1 to 2.8 µm, average particle size R2 of particles containing one or more elements selected from the group consisting of Ca, Sr and Ba in the annealing separator: 0.2 to 3.0 µm, and (average particle size R2)/(average particle size R1): 0.5 to 3.0. 2. The annealing separator according to claim 1, further comprising one or more elements selected from the group consisting of Ti, Zr and Hf.

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