JP6911596B2 - Unidirectional electromagnetic steel sheet with excellent film adhesion and its manufacturing method - Google Patents

Description

The present invention relates to a unidirectional electrical steel sheet used as an iron core material of a transformer and a method for producing the same, and in particular, a unidirectional electrical steel sheet having excellent adhesion of a tension-applying insulating film and a method for producing the same.

The unidirectional electromagnetic steel sheet is a silicon steel sheet containing 7% by mass or less of Si, which is composed of crystal grains highly oriented and accumulated in the {110} <001> direction (hereinafter, Goss direction), and is mainly used for transformers. Used as an iron core material. Highly oriented accumulation of Goss orientation in grain-oriented electrical steel sheets is realized by utilizing a grain growth phenomenon called secondary recrystallization.

One-way electrical steel sheets are required to have high magnetic flux density (represented by B8 value) and low iron loss ( _{represented by W 17/50} value) as magnetic characteristics, but recently, energy saving is required. From this point of view, there is an increasing demand for reduction of power loss, that is, reduction of iron loss.

In a unidirectional electrical steel sheet, the magnetic domain changes with the movement of the domain wall under an AC magnetic field. Smooth movement of the domain wall is effective in reducing iron loss, but when observing the movement of the magnetic domain, there are some magnetic domains that do not move.

In order to further reduce the iron loss of the unidirectional electromagnetic steel sheet, _{the interface of the forsterite (Mg 2} SiO ₄ ) -based film (hereinafter sometimes referred to as "glass film") on the surface of the steel sheet that hinders the movement of magnetic domains. It is important to eliminate the pinning effect due to unevenness. In order to eliminate this pinning effect, it is an effective means not to form a glass film on the surface of the steel sheet that hinders the movement of magnetic domains.

As a means for eliminating the pinning effect, for example, Patent Documents 1 to 5 describe Fe-based oxides (Fe ₂ SiO ₄ , FeO, etc.) in the oxide layer formed during decarburization annealing by controlling the dew point of decarburization annealing. ) Is not formed, and a substance such as alumina that does not react with silica is used as the annealing separator to achieve surface smoothing after finish annealing.

Further, when a unidirectional electromagnetic steel sheet is used as an iron core material for a transformer, it is essential to ensure the insulating property of the steel sheet, so an insulating film having tension is formed on the surface of the steel sheet. For example, the method disclosed in Patent Document 6 in which a coating liquid mainly composed of colloidal silica and phosphate is applied to the surface of a steel sheet and baked to form an insulating film has a large effect of applying tension to the steel sheet. In addition to ensuring insulation, it is effective in reducing iron loss.

As described above, forming an insulating film mainly composed of phosphate on the glass film formed in the finish annealing step is a general method for manufacturing electrical steel sheets.

When the above insulating film is formed on the glass film, considerable film adhesion can be obtained, but when the glass film is removed or when the glass film is not intentionally formed in the finish annealing step. The film adhesion is not sufficient.

When the glass film is removed, it is necessary to secure the required film tension only by the tension-imparting insulating film formed by applying the coating liquid, so that the film must be thickened inevitably. Further film adhesion is required.

Therefore, with the conventional film forming method, it is difficult to secure the film tension sufficient to bring out the effect of mirroring and also to secure the film adhesion, and it is possible to sufficiently reduce the iron loss. It wasn't done. Therefore, as a technique for ensuring the film adhesion of the tension-applying insulating film, a method of forming an oxide film on the surface of a finish-annealed unidirectional silicon steel sheet prior to forming the tension-applying insulating film is used. For example, it has been proposed in Patent Documents 7 to 10.

For example, the technique disclosed in Patent Document 8 is that a unidirectional silicon steel sheet that has been finish-annealed and prepared to be mirror-finished or close to a mirror surface is annealed at a specific atmosphere at each temperature to surface the steel sheet. This is a method in which an external oxide type oxide film is formed on the steel sheet, and the adhesion between the tension-imparting insulating film and the steel sheet is ensured by the oxide film.

The technique disclosed in Patent Document 9 applies an amorphous oxide base film on the surface of a finish-annealed unidirectional silicon steel sheet without an inorganic mineral film when the tension-applying insulating film is crystalline. This is a technique for preventing the oxidation of a steel sheet that occurs when the crystalline tension-imparting insulating film is formed.

The technique disclosed in Patent Document 10 further develops the technique disclosed in Patent Document 8 to obtain a film structure of a metal oxide film containing Al, Mn, Ti, Cr, and Si at the interface between the tension-imparting insulating film and the steel plate. It is a method of controlling and improving the adhesion of the insulating film. However, the adhesion between the metal oxide layer and the steel sheet, where stress sensitivity is the most problematic, is not controlled, and the technique disclosed in Patent Document 10 is insufficient as a technique for improving film adhesion. be.

Japanese Unexamined Patent Publication No. 07-278670 Japanese Unexamined Patent Publication No. 11-106827 Japanese Unexamined Patent Publication No. 11-118750 Japanese Unexamined Patent Publication No. 11-118750 Japanese Unexamined Patent Publication No. 2003-268450 Japanese Unexamined Patent Publication No. 48-0393338 Japanese Unexamined Patent Publication No. 60-131976 Japanese Unexamined Patent Publication No. 06-184762 Japanese Unexamined Patent Publication No. 07-278833 Japanese Unexamined Patent Publication No. 2002-348634

Iron and Steel, vol 99 (2013), 40.

In a unidirectional silicon steel sheet in which a tension-imparting insulating film is formed on the surface of the steel sheet, when the insulating film is formed on a glass film (forsterite-based film), the film adhesion of the insulating film is good, but When the formation of a glass film is intentionally suppressed, the glass film is removed by means such as grinding or pickling, and the surface of the steel sheet is flattened until it has a mirror gloss to form a tension-applying insulating film. The film adhesion of the insulating film is not sufficient, and it is difficult to achieve both film adhesion and magnetic stability.

Therefore, in the present invention, the formation of a glass film is intentionally suppressed, the glass film is removed by means such as grinding or pickling, and the surface of the steel sheet is flattened until it has a mirror gloss. A unidirectional electromagnetic steel sheet that solves this problem by forming a tension-applying insulating film with excellent film adhesion on the surface of a unidirectional electromagnetic steel sheet without impairing its magnetic properties and its stability. And its manufacturing method.

In order to solve the above problems, the present inventors have diligently studied a method for improving the film adhesion of the tension-applying insulating film. As a result, prior to the formation of the tension-applying insulating film, heat is formed in the step of forming an oxide film (hereinafter, sometimes referred to as "intermediate oxide film layer") on the surface of the finish-annealed unidirectional electromagnetic steel sheet. It was found that controlling the history and oxygen potential dramatically improves the film adhesion of the tension-applying insulating film.

Furthermore, the present inventors have diligently investigated the composition of the intermediate oxide film layer, which is considered to have the greatest effect on the film adhesion. As a result, an oxide of the intermediate oxide layer is an Si oxide (SiO _2), a SiO ₂ intermediate oxide layer, the interface between the SiO ₂ intermediate oxide layer and the steel plate, Al, Cu, Cr, It was found that one type or two or more types of Ca were concentrated.

When Al, Cr, Cu, and Ca are _{concentrated at the interface between the SiO 2} intermediate oxide film layer and the steel sheet, attractive electron-electron interaction occurs at the interface, and the steel sheet and the SiO ₂ intermediate oxide film layer adhere to each other. It is considered that the sex has improved.

The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) In mass%, C: 0.10% or less, Si: 0.80 to 7.00%, acid-soluble Al: 0.01 to 0.07%, N: 0.012% or less, Mn: 1. It contains .00% or less, S: 0.08% or less, is composed of the balance Fe and unavoidable impurities, has a tension-imparting insulating film on the surface of the steel sheet, and has the tension-applying insulating film and the surface of the steel sheet. In a unidirectional electromagnetic steel sheet having _{a SiO 2} intermediate oxide film layer having an average film thickness of 1.0 nm or more and 1.0 μm or less at the interface.
An interface-concentrated layer of metal element M (M: Al) is provided at the interface between the SiO _{2 intermediate oxide film layer and the steel sheet.}
The metal element M of the previous SL SiO ₂ intermediate oxide layer: time of the glow discharge optical emission spectrometry spectrum (M Al) differential curve f _M (t) is, film adhesion, characterized by satisfying the following formula (1) Unidirectional electromagnetic steel plate with excellent properties.

Tp: Time t (seconds) corresponding to the minimum value of the second-order time derivative curve of the glow discharge emission analysis spectrum of Si.
Tf: Time t (seconds) corresponding to 2 Tp-Ts, where Ts is the analysis start point of the glow discharge emission analysis spectrum of Si.

(2) The unidirectional electromagnetic steel sheet further contains, in terms of mass%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, and Ca: 0.001 to 0.05%. _{The time derivative curve f M} (t) of the glow discharge emission analysis spectrum of the metal element M (M: Cr, Cu, Ca) of the _{SiO 2} intermediate oxide film layer containing one kind or two or more kinds is the following formula (2). )-(4) The unidirectional electromagnetic steel plate having excellent film adhesion according to (1) above, which satisfies one or more of (4).

Tp: Time t (seconds) corresponding to the minimum value of the second-order time derivative curve of the glow discharge emission analysis spectrum of Si.
Tf: Time t (seconds) corresponding to 2 Tp-Ts, where Ts is the analysis start point of the glow discharge emission analysis spectrum of Si.

(3) The unidirectional electrical steel sheet is further characterized by containing one or two kinds of Sn: 0.01 to 0.20% and B: 0.001 to 0.010% in mass%. The unidirectional electromagnetic steel sheet having excellent film adhesion according to the above (1) or (2).

(4) A hot-rolling step of hot-rolling a steel piece having the component composition according to any one of (1) to (3) above to produce a hot-rolled steel sheet, a hot-rolled steel sheet annealing step of quenching a hot-rolled steel sheet, Pickling step of pickling the steel sheet after quenching, cold rolling process of cold rolling the steel sheet after pickling to produce cold rolled steel sheet, decarburizing anneal step of decarburizing the cold rolled steel sheet, decarburizing tempered steel sheet Finishing annealing step, finishing annealed steel sheet is annealed to form a SiO ₂ intermediate oxide film layer on the surface of the steel sheet, and an insulating film forming coating liquid is applied to the steel sheet after the oxide film is formed. The method for producing a unidirectional electromagnetic steel sheet having excellent film adhesion according to any one of (1) to (3) above, which comprises a step of forming an insulating film by baking and forming a tension-applying insulating film.
(I) _{Annealing in the oxide film forming step for forming the SiO 2} intermediate oxide film layer is performed at a temperature T1 (° C.) of 600 to 1400 ° C. for 5 to 1200 seconds and with an oxygen potential satisfying the following formula (5). , With subsequent cooling,
(Ii) The average cooling rate CR1 (° C./sec) in the temperature range of the temperature T2 (° C.) or higher and T1 (° C.) or lower defined by the following formula (6) is set to 50 ° C./sec or lower, and 40 ° C. or higher, the above. A method for producing a unidirectional electromagnetic steel plate having excellent film adhesion, wherein the average cooling rate in a temperature range below T2 (° C.) is set to an average cooling rate CR2 (° C./sec) satisfying the following formula (7). ..

P _H2O / P _H2 ≤ 5.65 ・ ・ ・ (5)
T2 = T1-100 ・ ・ ・ (6)
CR1> CR2 ・ ・ ・ (7)

(5) In _{the heating process of the oxide film forming step for forming the SiO 2} intermediate oxide film layer, the average heating rate HR1 (° C./sec) in the temperature range from room temperature to 600 ° C. or lower is set to 10 ° C./sec or more and 600 ° C. The unidirectional electromagnetic steel plate having excellent film adhesion according to (4) above, wherein the average heating rate HR2 (° C./sec) in the temperature range of T1 ° C. or lower is 50 ° C./sec or less. Production method.

According to the present invention, the formation of a glass film is intentionally suppressed, the glass film is removed by means such as grinding or pickling, and the surface of the steel sheet is flattened until it has a mirror gloss. A tension-applying insulating film having excellent film adhesion can be formed on the surface of the unidirectional electromagnetic steel sheet without impairing the magnetic properties and its stability.

It is a figure which shows the differential curve of the spectrum derived from Si obtained by the glow discharge emission analysis method (GDS).

The unidirectional electrical steel sheet (hereinafter sometimes referred to as “the electrical steel sheet of the present invention”) having excellent film adhesion of the present invention is
By mass%, C: 0.10% or less, Si: 0.80 to 7.00%, acid-soluble Al: 0.01 to 0.07%, N: 0.012% or less, Mn: 1.00% Hereinafter, S: contains 0.08% or less, is composed of the balance Fe and unavoidable impurities, has a tension-imparting insulating film on the surface of the steel sheet, and at the interface between the tension-applying insulating film and the surface of the steel sheet. In a unidirectional electromagnetic steel sheet having _{a SiO 2} intermediate oxide film layer having an average film thickness of 1.0 nm or more and 1.0 μm or less.
The _{time derivative curve f M} (t) of the glow discharge emission analysis spectrum of the metal element M (M: Al) of the _{SiO 2} intermediate oxide film layer satisfies the following formula (1).

Tp: Time t (seconds) corresponding to the minimum value of the second-order time derivative curve of the glow discharge emission analysis spectrum of Si.
Tf: Time t (seconds) corresponding to 2 Tp-Ts, where Ts is the analysis start point of the glow discharge emission analysis spectrum of Si.

Further, the electromagnetic steel plate of the present invention is one or two of Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, and Ca: 0.001 to 0.05% in terms of mass%. _{The time derivative curves f M} (t) of the glow discharge emission analysis spectrum of the metal element M (M: Cr, Cu, Ca) of the _{SiO 2} intermediate oxide film layer containing seeds or more are shown in the following formulas (2) to (2). It is characterized by satisfying one or more of 4).

Tp: Time t (seconds) corresponding to the minimum value of the second-order time derivative curve of the glow discharge emission analysis spectrum of Si.
Tf: Time t (seconds) corresponding to 2 Tp-Ts, where Ts is the analysis start point of the glow discharge emission analysis spectrum of Si.

Further, the electromagnetic steel sheet of the present invention is further characterized by containing one or two kinds of Sn: 0.01 to 0.20% and B: 0.001 to 0.010% in mass%.

In the method for producing a unidirectional electromagnetic steel sheet having excellent film adhesion of the present invention (hereinafter, may be referred to as "the method for producing the present invention"), a steel piece having a component composition of the electromagnetic steel sheet of the present invention is hot-rolled and hot-rolled. Hot-rolled process for manufacturing steel sheets, hot-rolled sheet annealing process for tempering hot-rolled steel sheets, pickling process for pickling steel sheets after shrinking, cold rolling of steel sheets after pickling for cold rolling to manufacture cold-rolled steel sheets Rolling process, decarburizing and annealing process of decarburizing cold-rolled steel sheet, finishing annealing process of finishing and annealing of decarburized and annealed steel sheet, _{oxide film that forms a SiO 2} intermediate oxide film layer on the surface of steel sheet by annealing the finished annealed steel sheet. In the manufacturing method for manufacturing an electromagnetic steel sheet of the present invention, which comprises a step of forming an insulating film, which comprises a step of applying a coating liquid for forming an insulating film to a steel sheet after forming an oxide film and baking the steel sheet to form a tension-applying insulating film.
(I) _{Annealing in the oxide film forming step for forming the SiO 2} intermediate oxide film layer is performed at a temperature T1 (° C.) of 600 to 1400 ° C. for 5 to 1200 seconds and with an oxygen potential satisfying the following formula (5). , With subsequent cooling,
(Ii) The average cooling rate CR1 (° C./sec) in the temperature range of the temperature T2 (° C.) or higher and T1 (° C.) or lower defined by the following formula (6) is set to 50 ° C./sec or lower, and 40 ° C. or higher, the above. The average cooling rate in the temperature range below T2 (° C.) is set to the average cooling rate CR2 (° C./sec) satisfying the following formula (7).

P _H2O / P _H2 ≤ 5.65 ・ ・ ・ (5)
T2 = T1-100 ・ ・ ・ (6)
CR1> CR2 ・ ・ ・ (7)

Further, in the production method of the present invention, in _{the heating process of the oxide film forming step of forming the SiO 2} intermediate oxide film layer, the average heating rate HR1 (° C./sec) in the temperature range from room temperature to 600 ° C. or lower is set to 10 ° C./sec. As described above, the average heating rate HR2 (° C./sec) in the temperature range of more than 600 ° C. and T1 ° C. or lower is set to 50 ° C./sec or less.

Hereinafter, the electromagnetic steel sheet of the present invention and the manufacturing method of the present invention will be described.

<Ingredient composition>
First, the reason for limiting the component composition of the electromagnetic steel sheet of the present invention will be described. Hereinafter,% related to the component composition means mass%.

C: 0.10% or less When C exceeds 0.10%, the steel undergoes phase transformation during secondary recrystallization annealing, secondary recrystallization does not proceed sufficiently, and good magnetic flux density and iron loss characteristics are obtained. Therefore, C is set to 0.10% or less. From the viewpoint of improving iron loss characteristics, 0.08% or less is preferable.

Although the lower limit includes 0%, since the detection limit of C is about 0.0001%, 0.0001% is a substantial lower limit on a practical steel sheet.

Si: 0.80 to 7.00%
If Si is less than 0.80%, the steel undergoes phase transformation during secondary recrystallization annealing, secondary recrystallization does not proceed sufficiently, and good magnetic flux density and iron loss characteristics cannot be obtained. Is 0.80% or more. It is preferably 2.50% or more, more preferably 3.00% or more.

On the other hand, if Si exceeds 7.00%, the steel sheet becomes brittle and the plate-passability in the manufacturing process is significantly deteriorated. Therefore, Si is set to 7.00% or less. It is preferably 4.00% or less, more preferably 3.75% or less.

Acid-soluble Al: 0.01-0.07%
In the electromagnetic steel sheet of the present invention, acid-soluble Al (sol.Al) is an essential element from the viewpoint of improving film adhesion. That is, acid-soluble Al is _{an element that is concentrated at the interface between the SiO 2} intermediate oxide film layer and the steel sheet to form a concentrated layer, and the film adhesion is remarkably improved.

If the acid-soluble Al is less than 0.01%, the concentrated layer is not formed, so that the film adhesion is not improved, AlN functioning as an inhibitor is not sufficiently produced, and secondary recrystallization is not possible. The acid-soluble Al is set to 0.01% or more because it becomes sufficient and the iron loss property is not improved. It is preferably 0.02% or more.

On the other hand, when the acid-soluble Al exceeds 0.07%, the steel sheet becomes brittle, and in particular, the electromagnetic steel sheet of the present invention having a large amount of Si becomes embrittled significantly. Therefore, the acid-soluble Al is set to 0.07% or less. It is preferably 0.05% or less.

N: 0.012% or less If N exceeds 0.012%, blister (vacancy) will occur in the steel sheet during cold spreading, and the strength of the steel sheet will increase, resulting in deterioration of sheet permeability during manufacturing. , N is 0.012% or less. It is preferably 0.010% or less, more preferably 0.009% or less.

On the other hand, in order to combine with Al to form AlN that functions as an inhibitor, N is preferably 0.004% or more. More preferably, it is 0.006% or more.

Mn: 1.00% or less When Mn exceeds 1.00%, the steel undergoes phase transformation during secondary recrystallization annealing, secondary recrystallization does not proceed sufficiently, and good magnetic flux density and iron loss characteristics are obtained. Therefore, Mn is set to 1.00% or less. It is preferably 0.50% or less, more preferably 0.20% or less.

MnS can be utilized as an inhibitor during secondary recrystallization, but when AlN is utilized as an inhibitor, MnS is not essential, so the lower limit of Mn includes 0%. When MnS is used as an inhibitor, Mn is 0.02% or more. It is preferably 0.05% or more, more preferably 0.07% or more.

S: 0.08% or less If S exceeds 0.08%, hot brittleness causes extremely difficult hot rolling, so S is 0.08% or less. It is preferably 0.04% or less, more preferably 0.03% or less.

When AlN is used as an inhibitor, MnS is not essential, so the lower limit includes 0%, but when MnS is used as an inhibitor during secondary recrystallization, S is preferably 0.005% or more.

Further, a part of S may be replaced with Se or Sb. In that case, a value converted by Seq = S + 0.406Se or Seq = S + 0.406Sb is used.

In addition to the above elements, the electrical steel sheet of the present invention may contain one or more of the following elements in order to improve the characteristics of the electrical steel sheet of the present invention.

Cr: 0.01 to 0.50%
Cr is an _{element that is concentrated at the interface between the SiO 2} intermediate oxide film layer and the steel sheet to form a concentrated layer, which contributes to the improvement of film adhesion. If it is less than 0.01%, the effect of improving the film adhesion cannot be sufficiently obtained, so Cr is set to 0.01% or more. It is preferably 0.03% or more, more preferably 0.05% or more.

On the other hand, if it exceeds 0.50%, Cr may combine with Si and O and _{inhibit the formation of the SiO 2} intermediate oxide layer, so Cr is set to 0.50% or less. It is preferably 0.30% or less, more preferably 0.20% or less.

Cu: 0.01-0.50%
Like Al and Cr, Cu is an _{element that is concentrated at the interface between the SiO 2} intermediate oxide film layer and the steel sheet to form a concentrated layer, which contributes to the improvement of film adhesion. If it is less than 0.01%, the effect of improving the film adhesion cannot be sufficiently obtained, so the Cu content is set to 0.01% or more. It is preferably 0.03% or more, more preferably 0.05% or more.

On the other hand, if it exceeds 0.50%, the steel sheet becomes brittle during hot rolling, so the Cu content is set to 0.50% or less. It is preferably 0.20% or less, more preferably 0.10% or less.

Ca: 0.001-0.05%
Like Al, Cr, and Cu, Ca is an _{element that is concentrated at the interface between the SiO 2} intermediate oxide film layer and the steel sheet to form a concentrated layer, which contributes to the improvement of film adhesion. If it is less than 0.001%, the effect of improving the film adhesion cannot be sufficiently obtained, so Ca is set to 0.001% or more. It is preferably 0.005% or more, more preferably 0.010 or more.

On the other hand, if it exceeds 0.05%, fine CaS is generated in the steel and the magnetic characteristics deteriorate, so the Ca is set to 0.05% or less. It is preferably 0.04% or less, more preferably 0.03% or less.

Sn: 0.01 to 0.20%
Sn is an _{element that does not concentrate at the interface between the SiO 2} intermediate oxide film layer and the steel sheet, but contributes to the improvement of film adhesion. The mechanism for improving the film adhesion of Sn is not clear, but as a result of investigating the smoothness of the steel sheet after secondary recrystallization, it was found that the smoothness of the steel sheet was improved. It is considered that this contributes to the formation of the interface between _{the SiO 2} intermediate oxide film layer and the steel sheet, which has few unevenness defects.

If it is less than 0.01%, the effect of smoothing the surface of the steel sheet cannot be sufficiently obtained, so Sn is set to 0.01% or more. It is preferably 0.02% or more, more preferably 0.03% or more.

On the other hand, if it exceeds 0.20%, the secondary recrystallization becomes unstable and the magnetic characteristics deteriorate, so Sn is set to 0.20% or less. It is preferably 0.15% or less, more preferably 0.10% or less.

B: 0.001 to 0.010%
Similar to Al, Cr, Cu, and Ca, B is _{concentrated at the interface between the SiO 2} intermediate oxide film layer and the steel sheet to form a concentrated layer (the present inventors confirmed the concentrated layer by GDS). , An element that contributes to the improvement of film adhesion. If it is less than 0.001%, the effect of improving the film adhesion cannot be sufficiently obtained, so B is set to 0.001% or more. It is preferably 0.002% or more, more preferably 0.003% or more.

On the other hand, if it exceeds 0.010%, the strength of the steel sheet increases and the passability in cold rolling deteriorates, so B is set to 0.010% or less. It is preferably 0.008% or less, more preferably 0.006% or less.

The rest of the component composition of the electrical steel sheet of the present invention is Fe and unavoidable impurities, but the improvement of magnetic properties, the improvement of properties required for structural members such as strength, corrosion resistance, and fatigue properties, and the improvement of castability and plate-passability. , Mo, W, In, Sn, Bi, Sb, Ag, Te, Ce, V, Co, Ni, Se, Re, Os, Nb, Zr, Hf, for the purpose of improving productivity by using scrap, etc. One or more of Ta, Pb, Y, La and the like may be contained in a total amount of 5.00% or less, preferably 3.00% or less, and more preferably 1.00% or less.

<SiO ₂ intermediate oxide film layer>
_{Next, the SiO 2} intermediate oxide film layer, which plays an important role in improving the film adhesion, will be described. Since the electromagnetic steel sheet of the present invention is manufactured by removing the glass film by grinding, pickling, etc., or intentionally preventing the formation of the glass film, the film adhesion of the tension-applying insulating film is sufficiently ensured. _{Therefore, a SiO 2} intermediate oxide film layer having a required thickness is formed at the interface between the tension-applying insulating film and the steel sheet.

Average film thickness of the SiO ₂ intermediate oxide film layer: 1.0 nm or more, 1.0 μm or less If _{the average film thickness of the SiO 2} intermediate oxide film layer is less than 1.0 nm, sufficient film adhesion cannot be ensured. Therefore, _{the average thickness of the SiO 2} intermediate oxide film layer is set to 1.0 nm or more. It is preferably 5.0 nm or more, more preferably 9.0 nm or more.

On the other hand, if it exceeds 1.0 μm, _{cracks that are the starting points of fracture occur inside the SiO 2} intermediate oxide film layer, and the film adhesion deteriorates. Therefore, _{the average film thickness of the SiO 2} intermediate oxide film layer is 1. It shall be 0 μm or less. It is preferably 0.7 μm (= 700 nm) or less, more preferably 0.4 μm (= 400 nm) or less.

The thickness of the SiO ₂ intermediate oxide film layer is measured by observing the sample cross section with a transmission electron microscope (TEM) or a scanning electron microscope (SEM).

The fact that the compound constituting the intermediate oxide film layer is "SiO ₂ " can be confirmed by elemental analysis by TEM or energy dispersive spectroscopy (EDS) associated with SEM. Since the chemical bond ratio of Si and O is not always 2, the characteristics of the electromagnetic steel sheet of the present invention are impaired even if the ratio is SiOx (x is an arbitrary number) as a result of analysis of the stoichiometric ratio. I can't.

Specifically, in _{the EDS spectrum of the SiO 2} intermediate oxide film layer, Si-Kα rays are detected at the position of energy 1.8 ± 0.3 kev on the horizontal axis, and at the same time, the position of 0.5 ± 0.3 kev. _{The presence of "SiO 2} " can be confirmed by detecting OKα rays. The element can be identified by using Lα line or Kγ line in addition to Kα line.

However, since the EDS spectrum of Si may include a spectrum derived from Si in the steel sheet, to be precise, the cross section of the steel sheet is analyzed with an electron probe microanalyzer (EPMA), and whether Si is derived from the steel sheet. , SiO ₂ Determine whether it is derived from the intermediate oxide film layer.

Moreover, the a SiO ₂ intermediate oxide layer was measured with Fourier transform infrared spectroscopy (FTIR), confirming that the peak derived from SiO ₂ is present in the wave number 1250 (cm ^-1) is, SiO ₂ intermediate oxide It is preferable for identifying the compound constituting the membrane layer.

However, since FTIR is a method for selectively analyzing the compound on the outermost surface of the sample, the analysis is performed on (a) a sample in which a tension-imparting insulating film does not exist, or (b) tension is applied to the surface of the steel sheet. For a sample having a sex insulating film, perform this after completely removing the tension-applying insulating film by alkaline cleaning or the like.

Infrared spectroscopy (IR) includes a reflection method and an absorption method. In the absorption method, information on the outermost surface of the sample and information on the inside of the steel plate are superimposed, so that _{the compound constituting the SiO 2} intermediate oxide film layer is formed. The reflection method is preferred for identifying.

Further, in the absorption method, the wave number derived from the _{SiO 2} intermediate oxide film layer does not become ^{1250 (cm -1} ), and the peak shifts depending on the formation state of _{SiO 2.} However, it is not sufficient to secure the film adhesion only by controlling the average film thickness of _{the SiO 2 intermediate oxide film layer to 1.0 nm or more and 1.0 μm or less.}

By controlling the thickness of the SiO ₂ intermediate oxide layer, it can be ensured film adhesion tensioning insulating film and SiO ₂ intermediate oxide layers, SiO ₂ interface of the intermediate oxide layer and the steel sheet Since it is an interface between a metal and an oxide, that is, an interface between dissimilar atoms and a weak interatomic interaction, peeling _{often occurs from the interface between the SiO 2} intermediate oxide film layer and the steel plate. ..

Accordingly, when Al is concentrated on the interface between the SiO ₂ intermediate oxide layer and the steel plate, attraction electronic interactions between the SiO ₂ intermediate oxide layer and the steel plate acts is believed that improved film adhesion. For example, since the interaction between C and Fe is attractive, it is known that when C segregates at the grain boundaries, the grain boundary strength increases. On the premise of this, in the electromagnetic steel sheet of the present invention, it can be considered that Al also caused an attractive electron-electron interaction between _{SiO 2 and Fe.}

Although it is difficult to directly detect the degree of electron-electron interaction by experiment, the concentration mode of Al concentrated at the interface between _{the SiO 2 intermediate oxide film layer and the steel plate exposes the SiO 2} intermediate oxide film layer. It is possible to analyze the surface of the steel plate in the state of being in a state by the glow discharge emission analysis method (GDS).

In the electromagnetic steel sheet of the present invention, Al is _{concentrated at the interface between the SiO 2} intermediate oxide film layer and the steel sheet to form a concentrated layer, so that _{the depth position of the SiO 2} intermediate oxide film layer and the depth of the Al concentrated layer The positional relationship is important. The existing position of the SiO ₂ intermediate oxide film layer can be analyzed from the GDS spectrum derived from Si (hereinafter, _{may be referred to as “F Si} (t)”).

In the analysis, the obtained spectrum may be smoothed by using peak analysis software or the like. Further, from the viewpoint of improving the accuracy of peak analysis, the measurement time interval Δt is preferably small, preferably 0.05 seconds or less.

Hereinafter, t is a time (second) corresponding to the depth position of the sample, and is a variable when the GDS spectrum is used as a function of time.

_{When the SiO 2} intermediate oxide film layer is present on the surface of the sample collected from the steel plate, in the region corresponding to the surface of the sample, in the Si-derived GDS spectrum, (A) the peak rising position from the background and (B) the peak The apex position and (C) the peak end position to the background can be observed.

Here, t corresponding to the peak rising position is Ts, t corresponding to the peak apex position is Tp, and t corresponding to the peak end position is Tf. The SiO ₂ intermediate oxide film layer corresponds to the outermost surface of the measurement sample. That is, assuming that t of the measurement start point of the GDS spectrum corresponds to the peak rising position, the measurement start point of the GDS may be defined as Ts. Further, the peaks are symmetrical according to the normal distribution and can be defined as Tf = 2Tp−Ts.

Since the measurement time interval Δt of the GDS spectrum is as small as 0.05 seconds or less, Ts ≈ 0 may be approximated and Tf = 2 × Tp may be set. In any case, in determining Tf, it is necessary to determine Tp. The method for determining Tp will be described below.

FIG. 1 shows the differential curve of the spectrum derived from Si obtained by the glow discharge emission analysis method (GDS).

Tp corresponds to the peak apex position of the Si-derived GDS spectrum. To determine the peak apex position, F _Si (t) is second-order differentiated over time, and t corresponds to the minimum value of ^{the second-order differential curve (see "d 2} F (t) / dt ^{2" in FIG. 1).} Just find. However, this minimum value is limited to those found in the range of t = 0 seconds or more and Δt × 100 seconds or less. This is because the SiO ₂ intermediate oxide film layer exists only on the sample surface and does not exist inside the steel sheet, so that t has a relatively small value.

Further, _{in the curve f Si} (t) (= dF _{Si (t) / dt) obtained by first-ordering F Si} (t) with respect to time (see “dF (t) / dt” in FIG. 1), t = In the range of Ts _{to Tp, if f Si} (t) ≥ 0, it is more decisive that Tp corresponds to the peak apex position.

The derivative may be obtained as the method for deriving the differential curve, or f (t _n ) = [F (t _n ) −F (t _n-1 )] / [t _n −t _{n-” by the difference method. 1} ] may be approximated. Here, the nth measurement point (time) is t _n, and the spectral intensity at that time is F (t _n ).

When the peak derived from Si is unclear, it can be analyzed from the GDS spectrum derived from Fe [hereinafter, F _Fe (t)]. In this case, in _{the first-order differential curve of F Fe} (t) (hereinafter referred to as f _Fe (t)), when t corresponding to the maximum value is Tf, the Tp is Tp = 0.5. Although it is shown as × (Tf + Ts), it may be approximated to Ts≈0 and Tp = 0.5 × Tf. This is because the maximum value of _{f Fe} (t) corresponds to the interface between _{SiO 2 and the base iron.}

However, this maximum value is limited to those found in the range of t = 0 seconds or more and Δt × 100 seconds or less. This is because the SiO ₂ intermediate oxide film layer exists only on the surface of the sample and does not exist inside the steel sheet, so that t has a relatively small value.

In the electromagnetic steel sheet of the present invention, Al needs to be concentrated at t = Tf, which is the position of the interface between _{the SiO 2 intermediate oxide film layer and the steel sheet, for the purpose of improving the film adhesion.} However, it is impossible to keep Al only at the position of t = Tf, and in reality, it is distributed over the range of t = Tp to Tf starting from t = Tf. This region is hereinafter referred to as an interfacial concentrated layer.

In addition to Al, it has been confirmed that Cr, Cu, and Ca also contribute to the improvement of film adhesion by forming an interface-concentrated layer. That is, in the electromagnetic steel sheet of the present invention, the metal element M (M = Al, Cr, Cu, Ca) is an interface-enriched layer in the range of t = Tp to Tf corresponding to the interface between _{the SiO 2 intermediate oxide film layer and the steel sheet.} Is forming.

The presence of the interface concentrated layer may be confirmed using GDS spectra derived from the metal element M (hereinafter sometimes referred to as "F _M (t)".). Specifically, integrating the time derivative curve f _M (t) of F _M (t) (the integral range: t = Tp~Tf) were time, if the integrated value is greater than 0, the metal element M, the surfactant thickening It can be judged that it exists as a layer.

Since the metal element M is uniformly distributed inside the steel sheet _{, the integrated value of f M} (t) inside the steel sheet is 0 or a value as close to 0 as possible.

Further, t in the measurement of GDS is not continuous, and f _M (t) is a collection of discontinuous points in t = Tp to Tf. Therefore, _{each point of f M} (t) is connected by a straight line and approximated as a continuous function for integration. It should be noted that the integrated value using Σ may be used.

From the above discussion, _{it is necessary to satisfy the following formula (1) in order for Al to be concentrated at the interface between the SiO 2} intermediate oxide film layer and the steel sheet and to exist as a concentrated layer.

Further, by satisfying one or more of the following formulas (2) to (4), the film adhesion is further improved.

In the electromagnetic steel sheet of the present invention, the metal element M (Al, Cr, Cu, Ca) can also be detected by chemical analysis. The steel plate portion of the sample in the state before the tension-imparting insulating film is formed or in the state where the tension-applying insulating film is removed is dissolved by the iodine-methanol method _{to extract the SiO 2} intermediate oxide film layer. Next, the extracted SiO ₂ intermediate oxide film layer is chemically analyzed using ICP or the like. As a result, the metal element M that has penetrated into the _{SiO 2 intermediate oxide film layer can be captured.}

The metal element M (Al, Cr, Cu, Ca) may be present in the SiO ₂ intermediate oxide film layer in a mass% of 0.05% or more and 2.00% or less in total. If it is less than 0.05%, the film adhesion is not improved, so that the total of the metal elements M is preferably 0.05% or more. More preferably, it is 0.10% or more.

On the other hand, if it exceeds 2.00%, the crystal lattice _{of SiO 2 is disturbed due to the influence of segregation, many lattice defects are introduced at the interface between the SiO 2} intermediate oxide film layer and the steel sheet, and the film adhesion deteriorates. The total of the metal elements M is preferably 2.00% or less. More preferably, it is 1.50% or less.

For verification of the effect of improving film adhesion by GDS or chemical analysis, the steel _{sheet sample in the state after forming the SiO 2} intermediate oxide film layer on the steel sheet surface and before forming the tension-applying insulating film is most suitable. However, for steel sheet samples with a tension-applying insulating film formed on the surface, only the tension-applying insulating film is completely removed by pickling or ultrasonic cleaning with alcohol, water, etc. after alkaline cleaning. And use it for analysis.

In addition, after pickling or ultrasonic cleaning with alcohol, water, etc., annealing at 800 ° C. or higher and 1100 ° C. or lower for 1 hour or more and 5 hours or less in an atmosphere of 100% hydrogen for the purpose of further surface cleaning. It may be carried out and subjected to analysis. Since SiO ₂ is a stable compound, SiO ₂ is reduced by the _{above annealing, and the SiO 2} intermediate oxide film layer does not disappear.

The electromagnetic steel sheet of the present invention is hot-rolled, hot-rolled sheet annealed, cold-rolled, primary recrystallized annealed, and secondly formed by melting and continuously casting steel pieces in a converter in the same manner as in the production of ordinary electromagnetic steel sheets. It is manufactured by performing next recrystallization annealing, annealing _{to form a SiO 2} intermediate oxide film layer, and annealing to form an insulating film.

The hot rolling may be direct hot rolling or continuous hot rolling, and the heating temperature of the steel piece is not limited. The cold rolling may be cold rolling or warm rolling twice or more, and the rolling reduction is not limited. The secondary recrystallization annealing may be either batch annealing in a box-shaped furnace or continuous line annealing, and does not depend on the annealing method.

The annealing separator may be any one containing an oxide such as alumina, magnesia, or silica, and it does not depend on the type.

When producing an excellent grain-oriented electrical steel sheet film adhesion, the formation of the SiO ₂ intermediate oxide layer, and generates a SiO ₂ intermediate oxide layer, the metal element M (Al, Cr, Cu, Ca) It is important to adopt heat treatment conditions that thicken the interface between the SiO _{2 intermediate oxide film layer and the steel plate.} That is, it is important to secure a concentration time at which Al, Cr, Cu, and Ca are _{concentrated at the interface between the SiO 2 intermediate oxide film layer and the steel sheet.}

In the electromagnetic steel sheet of the present invention, the SiO ₂ intermediate oxide film layer is formed by annealing the steel sheet after secondary recrystallization at a temperature T1 (° C.) of 600 ° C. or higher and 1400 ° C. or lower for 5 to 1200 seconds.

If the annealing temperature is less than 600 ° C., SiO ₂ is not formed and the SiO ₂ intermediate oxide film layer is not formed. Therefore, the annealing temperature is set to 600 ° C. or higher. On the other hand, if the annealing temperature exceeds 1400 ° C., the steel sheet may melt, so the annealing temperature is set to 1400 ° C. or lower. Preferably, it is 700 to 1150 ° C., which is the precipitation temperature of _{SiO 2.}

The _{annealing time is set to 5 seconds or more in order to grow the SiO 2} intermediate oxide film layer and secure the layer thickness necessary for ensuring excellent film adhesion. It is preferably 20 seconds or more. The annealing time may be long from the viewpoint of ensuring excellent film adhesion, but from the viewpoint of productivity, the upper limit is 1200 seconds. It is preferably 1000 seconds or less.

The annealing atmosphere is an annealing atmosphere that produces externally oxidized silica (SiO ₂ intermediate oxide film layer) and avoids the formation of lower oxides such as firelite, wustite, and magnetite. Therefore, the oxygen potential P _H2O / P _H2 of the annealing atmosphere, the oxygen potential which satisfies the following equation (5).
P _H2O / P _H2 ≤ 5.65 ・ ・ ・ (5)

The lower the oxygen potential P _H2O / P _{H2, the} easier it is to form externally oxidized silica (SiO ₂ intermediate oxide film layer), and the effect of the present invention is likely to be exhibited. However, the oxygen potential P _H2O / P _{H 2} is 3.0. Since it is difficult to control it to less than × 10 ^{-4 , industrially, about 3.0 × 10 -4} is a practical lower limit.

On the other hand, when the oxygen potential P _H2O / P _H2 exceeds 5.65, lower oxides such as firelite, wustite, and magnetite are generated, so the oxygen potential P _H2O / P _H2 is set to 5.65 or less. It is preferably 2.25 or less.

In order to effectively concentrate the metal element M (Al, Cr, Cu, Ca) at _{the interface between the SiO 2} intermediate oxide film layer and the steel sheet, it is necessary to secure the segregation temperature of the metal element M. Therefore, _{in cooling after annealing to form the SiO 2} intermediate oxide film layer, the temperature range of T2 (° C.) or higher and T1 (° C.) or lower defined by the following formula (6), which is the segregation temperature range, is set to 50 ° C. Cool at an average cooling rate of CR1 (° C./sec) of / sec or less.

Cooling at an average cooling rate of 50 ° C./sec or less does not deteriorate the characteristics of the electromagnetic steel plate of the present invention, but CR1 is preferably 0.1 ° C./sec or more from the viewpoint of productivity. If the cooling rate is increased after cooling to T2 (° C), thermal strain is introduced and the film adhesion and magnetic characteristics deteriorate. Therefore, the average cooling rate CR2 in the temperature range of 40 ° C to T2 (° C) is as follows. Let the average cooling rate satisfy the formula (7).
T2 = T1-100 ・ ・ ・ (6)
CR1> CR2 ・ ・ ・ (7)

In annealing atmosphere having an oxygen potential P _H2O / P _H2 satisfying the above expression (5), after forming a SiO ₂ intermediate oxide layer on the surface of the steel sheet, once cooled to room temperature, then, T2 ° C. or higher, the T1 ° C. or less After reheating to a temperature range and holding for 10 seconds or more, the temperature range above room temperature and below T2 ° C. may be cooled at an average cooling rate of CR3: 30 ° C./sec or less.

_{In forming a SiO 2} intermediate oxide film having excellent film adhesion, the heating rate for heating the steel sheet is also important. Oxides other than SiO ₂ not only reduce the adhesion of the tension-imparting insulating film, but also hinder the surface smoothness of the steel sheet, resulting in a decrease in iron loss characteristics. Therefore, oxides _{other than SiO 2} are generated as much as possible. It is necessary to adopt a heating rate that does not.

As described in Non-Patent Document 1, SiO ₂ is not as stable as other Fe-based oxides, so it is preferable to adopt a thermal history in which Fe-based oxides are not generated during heating. Specifically, by setting the average heating rate HR1 in the temperature range from room temperature to 500 ° C. to 10 ° C./sec or more, _{the formation of Fe X} O can be avoided. The faster the heating rate in this temperature range is, the more preferable it is. However, for industrial reasons, the upper limit of the average heating rate HR1 is preferably 200 ° C./sec.

The formation temperature range of SiO ₂ is 600 ° C. or higher and T1 ° C. or lower. Therefore, in order _{to generate more SiO 2} , the average heating rate HR 2 in this temperature range is set to 50 ° C./sec or less. However, if the heating rate is slow, _{Fe 2} SiO ₄ , which is thermally more stable than _{SiO 2} , is produced, so the average heating rate HR 2 is preferably 5 ° C./sec or more.

Further, since _{the generation driving force of SiO 2} increases as the heating rate increases up to 600 ° C., it is preferable to increase the heating rate from room temperature to 600 ° C. and lengthen the stay period at the subsequent generation temperature. Therefore, it is preferable that the average heating rate satisfies the following formula (8) in terms of ensuring film adhesion.
HR1 <HR2 ・ ・ ・ (8)

Hereinafter, the technical contents of the present invention will be further described with reference to examples of the present invention. The conditions in the examples shown below are one condition example adopted for confirming the feasibility and effect of the present invention, and the present invention is not limited to this one condition example. Further, the present invention can adopt various conditions as long as the gist of the present invention is not deviated and the object of the present invention is achieved.

<Example 1>
The silicon steel having the composition shown in Table 1 is heated to 1000 to 1400 ° C. and subjected to hot rolling to obtain a hot-rolled steel sheet having a thickness of 2.3 to 2.8 mm, and the hot-rolled steel sheet is annealed at 900 to 1200 ° C. After that, one cold rolling or a plurality of cold rollings sandwiching intermediate quenching were performed to obtain a cold-rolled steel sheet having a final plate thickness of 0.23 mm.

The cold-rolled steel sheet of the final sheet thickness 0.23 mm, subjected to decarburization annealing and nitriding annealing, then applying an annealing separator, and finish-annealed at 1200 ° C., then final annealed sheet, the oxygen potential P _{H2 O} Annealing was carried out in an atmosphere of / _PH2 = 0.9 under the conditions of 1200 ° C. × 400 seconds _{to form a SiO 2} intermediate oxide film layer on the surface of the steel sheet.

The average cooling rate CR1 in the temperature range of 1100 ° C. or higher and 1200 ° C. or lower was set to 20 ° C./sec, and the average cooling rate CR2 of 40 ° C. or higher and lower than 1100 ° C. was set to 7 ° C./sec.

Then, a coating liquid for forming an insulating film was applied to the surface of the steel sheet and baked to form a tension-imparting insulating film, and the film adhesion of the insulating film was evaluated and the magnetic characteristics (magnetic flux density) were evaluated.

The film adhesion of the tension-imparting insulating film was evaluated by the film residual area ratio when the evaluation sample was wound around a cylinder having a diameter of 20 mm and bent by 180 °. The evaluation is VG (very excellent) when the film remaining area ratio is 95% or more without peeling from the steel sheet, G (excellent) when 90% or more and less than 95%, and 80% or more and less than 90%. F (effective) and less than 80% were B (ineffective).

The magnetic properties were evaluated according to JIS C 2550. The magnetic flux density was evaluated using B8. B8 is a magnetic flux density at a magnetic field strength of 800 A / m, and serves as a criterion for determining the quality of secondary recrystallization. B8 = 1.89T or more was judged to be secondary recrystallization.

For some samples, after the SiO ₂ intermediate oxide film layer was formed, the tension-imparting insulating film was not formed, and the film was used for _{the film thickness investigation of the SiO 2} intermediate oxide film layer and the investigation of the interface-concentrating element. .. The _{film thickness of the SiO 2} intermediate oxide film layer was identified by TEM observation according to the method described in Patent Document 10. Interfacial enrichment elements were investigated by GDS. The GDS measurement time was 100 seconds and the time interval was 0.02 seconds. Table 2 shows a series of evaluation results.

B1 to B7 are examples of the invention, and all of them show good film adhesion. On the other hand, b1 to b8 are comparative examples. In b3, b5, and b6, steel a3, steel a5, and steel a6 each contained a large amount of Si, Al, and N, so that embrittlement at room temperature was remarkable and cold rolling was impossible. In b8, the steel a8 contained a large amount of S, embrittlement during heat was remarkable, and hot rolling was impossible. Therefore, none of b3, b5, b6, and b8 has reached the evaluation of film adhesion.

None of b1, b2, b4, and b7 was secondary recrystallized because the additive element of steel was outside the scope of the present invention. The samples that did not undergo secondary recrystallization had poor film adhesion. It is considered that when the secondary recrystallization was not performed, the crystal grain size of the steel sheet was fine, the surface unevenness was severe, and the SiO ₂ intermediate oxide film layer could not be properly grown.

<Example 2>
The silicon steel having the composition shown in Table 1 is heated to 1000 to 1400 ° C. and subjected to hot rolling to obtain a hot-rolled steel sheet having a thickness of 2.3 to 2.8 mm, and the hot-rolled steel sheet is annealed at 900 to 1200 ° C. After that, one cold rolling or a plurality of cold rollings sandwiching intermediate quenching were performed to obtain a cold-rolled steel sheet having a final plate thickness of 0.23 mm.

The cold-rolled steel sheet of the final sheet thickness 0.23 mm, subjected to decarburization annealing and nitriding annealing, then applying an annealing separator, and finish-annealed at 1200 ° C., then final annealed sheet, the oxygen potential P _{H2 O} Annealing was carried out under the conditions of / _PH2 = 0.005 and 1100 ° C. × 200 seconds _{to form a SiO 2} intermediate oxide film layer on the surface of the steel sheet.

The average cooling rate CR1 in the temperature range of 900 ° C. or higher and 1100 ° C. or lower was set to 15 ° C./sec, and the average cooling rate CR2 in the temperature range of 40 ° C. or higher and lower than 1000 ° C. was set to 7 ° C./sec.

Then, a coating liquid for forming an insulating film was applied to the surface of the steel sheet and baked to form a tension-applying insulating film, and the adhesion of the insulating film was evaluated and the magnetic characteristics (magnetic flux density) were evaluated.

Table 3 shows the evaluation results of the film thickness of the SiO ₂ intermediate oxide film layer, the degree of concentration of the interface-concentrating element by GDS analysis, and the film adhesion. The measurement and evaluation were carried out according to the measurement and evaluation of Example 1. _{Further, in the column of "Eths that concentrate on the interface between the SiO 2} intermediate oxide film layer / steel sheet" in Table 3, the elements whose concentration was confirmed by the GDS spectrum are described.

C1 to C8 are examples of the invention. In C1 to C4, concentration of any one of Cr, Cu, and Ca has been confirmed, showing good film adhesion. Concentration of Cr, Cu, and Ca was confirmed in C5 and C6, and the film adhesion was even better than that of C1 to C4.

In C7, the concentration of Cr cannot be confirmed, but in addition to the concentration of Cu and Ca, the concentration of Sn and B shows the same film adhesion as that of C5. In C8, in addition to the concentration of Cr, Cu, and Ca, the concentration of Sn and B is added, so that the film adhesion is further improved.

<Example 3>
The silicon steel having the composition shown in Table 1 is heated to 1000 to 1400 ° C. and subjected to hot rolling to obtain a hot-rolled steel sheet having a thickness of 2.3 to 2.8 mm, and the hot-rolled steel sheet is annealed at 900 to 1200 ° C. After that, one cold rolling or a plurality of cold rollings sandwiching intermediate quenching were performed to obtain a cold-rolled steel sheet having a final plate thickness of 0.23 mm.

A cold-rolled steel sheet having a final thickness of 0.23 mm is subjected to decarburization annealing and nitriding annealing, then an annealing separator is applied and finish annealing is performed at 1200 ° C., and then the finish annealed sheet is shown in Table 4. _{Annealing was carried out under the conditions to form a SiO 2} intermediate oxide film layer on the surface of the steel sheet. Then, a coating liquid for forming an insulating film was applied to the surface of the steel sheet and baked to form a tension-applying insulating film, and the film adhesion of the insulating film was evaluated and the magnetic characteristics (magnetic flux density) were evaluated.

Table 4 shows the evaluation results of the film thickness of the SiO ₂ intermediate oxide film layer, the degree of concentration of the interface-concentrating element by the GDS spectrum, and the film adhesion. The measurement and evaluation were carried out according to the measurement and evaluation of Example 1.

D1 to D9 are examples of the invention. In particular, D7 and D8 show extremely good film adhesion because the annealing temperature and oxygen potential at the time of forming the _{SiO 2 intermediate oxide film layer are within the preferable ranges.}

On the other hand, d1 to d4 are comparative examples. In d1 to d3, the annealing temperature for forming the SiO ₂ intermediate oxide layer, annealing time, and, either oxygen potential, it is beyond the scope of the present invention, SiO ₂ intermediate oxide layer is formed Therefore, the film adhesion could not be ensured. Further, in d1 to d3, since _{the peak derived from SiO 2} could not be observed by GDS, Tp and Tf could not be defined.

In d4, although the SiO ₂ intermediate oxide film layer could be formed, the cooling rate was high, and the time for Al _{to concentrate at the interface between the SiO 2} intermediate oxide film layer and the steel sheet could not be secured, so the film adhesion was evaluated. Was B (no effect).

<Example 4>
The silicon steel having the composition shown in Table 1 is heated to 1000 to 1400 ° C. and subjected to hot rolling to obtain a hot-rolled steel sheet having a thickness of 2.3 to 2.8 mm, and the hot-rolled steel sheet is annealed at 900 to 1200 ° C. After that, one cold rolling or a plurality of cold rollings sandwiching intermediate quenching were performed to obtain a cold-rolled steel sheet having a final plate thickness of 0.23 mm.

A cold-rolled steel sheet having a final thickness of 0.23 mm is subjected to decarburization annealing and nitriding annealing, then an annealing separator is applied, and finish annealing is performed at 1200 ° C., and then the finish annealed sheet is shown in Table 5. _{Annealing was carried out under the conditions to form a SiO 2} intermediate oxide film layer on the surface of the steel sheet. Then, a coating liquid for forming an insulating film was applied to the steel sheet and baked to form a tension-imparting insulating film, and the film adhesion of the insulating film was evaluated and the magnetic characteristics (magnetic flux density) were evaluated.

Table 5 shows the evaluation results of the film thickness of the SiO ₂ intermediate oxide film layer, the degree of concentration of the interface-concentrating element by the GDS spectrum, and the film adhesion. The measurement and evaluation were carried out according to the measurement and evaluation of Example 1.

E1 to E5 are examples of inventions. In particular, E5 satisfies the condition of HR1 <HR2, and the evaluation of film adhesion is VG. E1 to E3 satisfy the condition of HR1 <HR2, but since HR1 or HR2 is close to the upper and lower limits of the enclosure of the present invention, the film adhesion is slightly inferior to that of E5, and the evaluation is G. ..

In E4, although _{the annealing temperature, annealing time, oxygen potential, and cooling rate at the time of forming the SiO 2} intermediate oxide film layer are all within the range of the present invention, the conditions of HR1 <HR2 are not satisfied. The evaluation of film adhesion was F.

As described above, according to the present invention, the formation of a glass film is intentionally suppressed, the glass film is removed by means such as grinding or pickling, and the surface of the steel sheet is flattened until it has a mirror gloss. A tension-applying insulating film having excellent film adhesion can be formed on the surface of the finish-annealed unidirectional electromagnetic steel sheet without impairing the magnetic properties and its stability. Therefore, the present invention is highly applicable in the electromagnetic steel sheet manufacturing industry and the electromagnetic steel sheet utilization industry.

Claims (5)

By mass%, C: 0.10% or less, Si: 0.80 to 7.00%, acid-soluble Al: 0.01 to 0.07%, N: 0.012% or less, Mn: 1.00% Hereinafter, S: contains 0.08% or less, is composed of the balance Fe and unavoidable impurities, has a tension-imparting insulating film on the surface of the steel sheet, and at the interface between the tension-applying insulating film and the surface of the steel sheet. In a unidirectional electromagnetic steel sheet having _{a SiO 2} intermediate oxide film layer having an average film thickness of 1.0 nm or more and 1.0 μm or less.
An interface-concentrated layer of metal element M (M: Al) is provided at the interface between the SiO _{2 intermediate oxide film layer and the steel sheet.}
The metal element M of the previous SL SiO ₂ intermediate oxide layer: time of the glow discharge optical emission spectrometry spectrum (M Al) differential curve f _M (t) is, film adhesion, characterized by satisfying the following formula (1) Unidirectional electromagnetic steel plate with excellent properties.

Tp: Time t (seconds) corresponding to the minimum value of the second-order time derivative curve of the glow discharge emission analysis spectrum of Si.
Tf: Time t (seconds) corresponding to 2 Tp-Ts, where Ts is the analysis start point of the glow discharge emission analysis spectrum of Si. The unidirectional electromagnetic steel sheet further comprises one or two of Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, and Ca: 0.001 to 0.05% in terms of mass%. _{The time derivative curves f M} (t) of the glow discharge emission analysis spectrum of the metal element M (M: Cr, Cu, Ca) of the _{SiO 2} intermediate oxide film layer containing seeds or more are shown in the following formulas (2) to (2). The unidirectional electromagnetic steel plate having excellent film adhesion according to claim 1, which satisfies one or more of 4).

Tp: Time t (seconds) corresponding to the minimum value of the second-order time derivative curve of the glow discharge emission analysis spectrum of Si.
Tf: Time t (seconds) corresponding to 2 Tp-Ts, where Ts is the analysis start point of the glow discharge emission analysis spectrum of Si. The claim that the grain-oriented electrical steel sheet further contains one or two kinds of Sn: 0.01 to 0.20% and B: 0.001 to 0.010% in mass%. The unidirectional electromagnetic steel sheet having excellent film adhesion according to 1 or 2. A hot-rolling step of hot-rolling a steel piece having the component composition according to any one of claims 1 to 3 to produce a hot-rolled steel sheet, a hot-rolled steel sheet annealing step of quenching a hot-rolled steel sheet, and a steel sheet after annealing. Pickling step of pickling, cold rolling process of cold rolling steel sheet after pickling to manufacture cold rolled steel sheet, decarburization annealing step of decarburizing and quenching cold rolled steel sheet, finishing annealing of decarburized and tempered steel sheet Finishing annealing step, an oxide film forming step of annealing a finished annealed steel sheet to _{form a SiO 2} intermediate oxide film layer on the surface of the steel sheet, applying a coating liquid for forming an insulating film to the steel sheet after forming the oxide film, baking, and tensioning. The method for producing a unidirectional electromagnetic steel sheet having excellent film adhesion according to any one of claims 1 to 3, which comprises an insulating film forming step for forming an imparting insulating film.
(I) _{Annealing in the oxide film forming step for forming the SiO 2} intermediate oxide film layer is performed at a temperature T1 (° C.) of 600 to 1400 ° C. for 5 to 1200 seconds and with an oxygen potential satisfying the following formula (5). , With subsequent cooling,
(Ii) The average cooling rate CR1 (° C./sec) in the temperature range of the temperature T2 (° C.) or higher and T1 (° C.) or lower defined by the following formula (6) is set to 50 ° C./sec or lower, and 40 ° C. or higher, the above. A method for producing a unidirectional electromagnetic steel plate having excellent film adhesion, wherein the average cooling rate in a temperature range below T2 (° C.) is set to an average cooling rate CR2 (° C./sec) satisfying the following formula (7). ..
P _H2O / P _H2 ≤ 5.65 ・ ・ ・ (5)
T2 = T1-100 ・ ・ ・ (6)
CR1> CR2 ・ ・ ・ (7) In _{the heating process of the oxide film forming step for forming the SiO 2} intermediate oxide film layer, the average heating rate HR1 (° C./sec) in the temperature range from room temperature to 600 ° C. or lower is set to 10 ° C./sec or more, and exceeds 600 ° C. The method for producing a unidirectional electromagnetic steel plate having excellent film adhesion according to claim 4, wherein the average heating rate HR2 (° C./sec) in a temperature range of T1 ° C. or lower is 50 ° C./sec or less.

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