JP2017101292A - Production method of grain oriented electrical steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a grain oriented electrical steel sheet by which a grain oriented electrical steel sheet excellent in film adhesion property is obtained.SOLUTION: Cr of 0.07 to 0.35 g/mis contained in a forsterite base film of finish-annealed sheet of the grain oriented electrical steel sheet, and coating liquid is applied including at least one kind of phosphate and silica selected by a group comprising Mg, Al, Ca, Sr, Fe, Cu, Mn and Zn so that P/MX is within a range of 1.002 to 1.035, where X is an ion valency of a metal element M of the phosphate, and P/M is a molar ratio of the phosphor element P and the metal element M in the formed coating, and flat annealing is performed to form coating on the base film, in the production method of the grain oriented electrical steel sheet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet.

  In general, in a grain-oriented electrical steel sheet, a coating is provided on the surface in order to provide insulation, workability, rust prevention, and the like. Such a film is composed of a base film (forsterite film) mainly composed of forsterite formed during final finish annealing, and a phosphate-based topcoat film (coating) formed thereon.

  These coatings are formed at high temperature and have a low coefficient of thermal expansion, so the effect of reducing the iron loss by applying tension to the steel sheet due to the difference in thermal expansion coefficient between the steel sheet and the coating when lowered to room temperature. There is. In addition, it is necessary to satisfy all of the many required characteristics such as corrosion resistance, insulation, and voltage resistance.

  In order to satisfy such various characteristics, various coatings have been proposed conventionally. For example, Patent Document 1 proposes a coating mainly composed of magnesium phosphate, colloidal silica, and chromic anhydride, and Patent Document 2 discloses a coating mainly composed of aluminum phosphate, colloidal silica, and chromic anhydride. Has been proposed.

Japanese Examined Patent Publication No. 56-52117 Japanese Patent Publication No.53-28375 Japanese Patent No. 4635347 Japanese Patent No. 4731625 Japanese Patent No. 5104128

By the way, when a grain-oriented electrical steel sheet is used as a core of a transformer for a wound core, an EI core, or the like, strain relief annealing at about 800 ° C. is performed in order to remove strain introduced during processing. . At this time, depending on the user, annealing is often performed by changing the atmosphere of strain relief annealing to a highly reactive atmosphere such as air or DX gas.
However, when annealing is performed in such an atmosphere, the film may be damaged and the film adhesion may deteriorate. In particular, the coating in the vicinity of the end face of the slit steel plate is easy to peel off, and if peeled off, the steel plate becomes conductive when the transformer is used, which may lead to a serious trouble that the core may melt in some cases.

  As a countermeasure for preventing such deterioration of film adhesion after strain relief annealing, for example, in Patent Document 3, a coating solution containing an organometallic compound having a metal bonding group is applied on a steel sheet and baked. A technique for specifying the oxygen partial pressure of the atmosphere at the time of application is disclosed, and Patent Document 4 discloses aluminum phosphate, zinc phosphate, cobalt hydroxide, strontium hydroxide, polyester resin emulsion, epoxy resin emulsion, silicic acid. A technique of applying a coating solution containing aluminum and titanium chelates is disclosed.

However, the technique disclosed in Patent Document 3 is a technique in which a coating is formed directly on a steel sheet on which a forsterite base film is not formed, and is different from a steel sheet with forsterite that has been mainly used conventionally. In addition, since an expensive silane coupling agent is used, there is a difficulty in industrial mass production.
The technique disclosed in Patent Document 4 is a technique mainly formed on a non-oriented electrical steel sheet, and is different from a directional electrical steel sheet with a forsterite film. In addition, since a large amount of the organic resin emulsion is used, there has been a problem that the carbon characteristics enter the steel by the strain relief annealing and the magnetic properties deteriorate.

  This invention is made | formed in view of the above point, and it aims at providing the manufacturing method of the grain-oriented electrical steel plate from which the grain-oriented electrical steel plate excellent in film adhesiveness is obtained.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors include a specific amount of Cr in the forsterite undercoat and specify the ratio of the phosphorus element to the metal element in the coating. Thus, the present inventors have found that the film adhesion is excellent and completed the present invention.

That is, the present invention provides the following [1] to [3].
[1] 0.07 to 0.35 g / m ^{2 of} Cr is contained in the forsterite undercoat of the finish annealed sheet of grain-oriented electrical steel sheet, and Mg, Al, Ca, Sr, At least one phosphate selected from the group consisting of Fe, Cu, Mn, and Zn and silica, where the ion value of the metal element M of the phosphate is X, and the phosphorus element P in the coating formed When the molar ratio with the metal element M is P / M, the coating solution contained so that P / MX is in the range of 1.002 to 1.035 is applied, and planarization annealing is performed. A method for producing a grain-oriented electrical steel sheet, wherein a coating is formed on an undercoat.
[2] The direction according to [1], wherein the coating liquid further contains chromic anhydride or at least one dichromate selected from the group consisting of Mg, Al, Ca, Fe, and Mn. Method for producing an electrical steel sheet.
[3] The method for producing a grain-oriented electrical steel sheet according to [1], wherein the coating liquid further contains a compound containing at least one selected from the group consisting of Sb, Mn, Ti, Fe, and Sn.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the grain-oriented electrical steel plate from which the grain-oriented electrical steel plate excellent in film adhesiveness is obtained can be provided.

FIG. 1 is a graph showing the influence of the amount of Cr in the undercoat and the P / MX of the coating on the bending adhesion after strain relief annealing. FIG. 2 shows an analysis result obtained by analyzing a cross section of a steel sheet having poor bending adhesion after strain relief annealing using EPMA, FIG. 2 (a) is a secondary electron image, and FIG. 2 (b). Is an Mg mapping image, and FIG. 2C is a P mapping image.

[Knowledge obtained by the present inventors]
As a result of intensive studies on various methods for improving the film adhesion after strain relief annealing, the present inventors have included a specific amount of Cr in the forsterite undercoating and a phosphorus element in the coating. It was newly found out that excellent film adhesion can be obtained by specifying the ratio of the metal element to the metal element. The following describes the experiments that led to this finding.

Directional silicon steel slabs with different Cr concentrations in the materials shown in Table 2 below (components other than Cr are C: 0.04 mass%, Si: 3.4 mass%, Mn: 0.07 mass%) Al: 0.006% by mass, P: 0.04% by mass, S: 0.003% by mass, N: 0.004% by mass, Sb: 0.03% by mass, and the balance inevitable impurities) It carried out to finish annealing by a conventional method. As a result, a finish-annealed sheet of grain-oriented electrical steel sheet having a forsterite base coating was obtained. Next, this was sheared to a size of 300 mm × 100 mm, and pickled with phosphoric acid. Thereafter, a coating liquid described in Patent Document 5 in which 100 parts by mass of magnesium phosphate, 100 parts by mass of colloidal silica, and 50 parts by mass of titanium lactate as a titanium compound were mixed at a dry mass of 10 g / d on both sides. It was applied as a m ^2.
At this time, when manufacturing the magnesium phosphate used as a raw material, the ratio P / 2Mg described later was variously changed by changing the ratio of phosphoric acid and magnesia in order to change the ratio of phosphorus and magnesium. .
Thereafter, planarization annealing at 800 ° C. was performed in a dry N ₂ atmosphere, and a coating was formed on the base film to obtain a product plate.

Separately, the base film of the finish annealing plate is removed by pickling, and the samples before and after (with or without the base film) are each acid-dissolved, and then the Cr concentration is chemically analyzed using atomic absorption spectrometry. From the measured value, the amount of Cr contained in the undercoat was determined in terms of basis weight.
In addition, the coating on the product plate is dissolved with alkali, and the concentrations of phosphorus element P and magnesium element Mg in the solution are measured by chemical analysis using an absorptiometer and Mg is an atomic absorption spectrometer. The P / Mg molar ratio P / Mg was calculated, and based on this, the ratio P / 2Mg was determined (2 is the ionic value of Mg).

  In this ratio P / 2Mg, the ionic value (valence) of the metal element M of the phosphate used in the coating solution is X, and the molar ratio of the phosphorus element P to the metal element M in the coating is P / M. This corresponds to the ratio P / MX in the case.

The steel sheet thus obtained is subjected to strain relief annealing in a DX gas atmosphere (dew point: 10 ° C., CO: 1%, H ₂ : 1%, CO ₂ : 12%, balance nitrogen) at 850 ° C. × 3 hr, and is bent and adhered. Sex was evaluated. The bending adhesion was obtained by winding a steel plate around a round bar having a different diameter every 10 mm, and obtaining the maximum diameter (unit: mm) at which the film did not peel off. The results are shown in the graph of FIG.
In the graph of FIG. 1, “◯” is plotted when the maximum diameter at which the coating is not peeled is 40 mm or less, “Δ” is plotted when 50 to 60 mm, and “X” is plotted when 70 mm or more. . If it is "(circle)", it can be evaluated as what is excellent in film adhesiveness.

  From the graph shown in FIG. 1, the film adhesion after strain relief annealing in the DX gas atmosphere is improved by keeping the amount of Cr in the undercoat and P / MX (P / 2Mg) within a specific range. I understand that.

In order to investigate this cause, the steel sheet (the amount of Cr in the undercoat = 0.05 g / m ² , P / MX (P / 2Mg) = 1.045) in which the film adhesion after strain relief annealing was poor was used. The cross section was analyzed using EPMA (electron beam microanalyzer). The analysis results at this time are shown in FIGS. 2 (a) to 2 (c).

2A is a secondary electron image, FIG. 2B is an Mg mapping image, and FIG. 2C is a P mapping image. For example, referring to FIG. 2 (b), which is an Mg mapping image, it can be seen from the intensity of Mg that the film is a two-layer film consisting of an upper layer and a lower layer. That is, the lower layer is an undercoat mainly composed of forsterite. In the upper layer, Mg derived from magnesium phosphate used for coating appears.
Moreover, when FIG.2 (c) which is a P mapping image is seen, P is concentrated in the coating part of the upper layer of Mg mapping, However, A part is concentrated to the interface of a base film and a ground iron. I understand that. Since phosphorus is hardly contained in the undercoat before the coating is formed, it is considered that the phosphorus concentration is that the phosphorus in the coating has passed through the undercoat and has reached the base iron interface.

  From the above, about the result that the film adhesion after strain relief annealing is improved by increasing the Cr amount in the base film and keeping the ratio of phosphorus and metal of the phosphate in the coating within a certain range. The present inventors considered as follows.

  First, in the case of a normal coating, the metal of the phosphate and silica react and crosslink, but a part of the non-crosslinked phosphoric acid exists. When strain relief annealing is performed in a strong oxidizing atmosphere such as a humid atmosphere or an oxygen-containing atmosphere, such non-crosslinked phosphoric acid content increases. This diffuses during annealing and penetrates to the interface between the ground iron and the underlying coating, where it reacts with iron to form a compound. As a result, the anchor effect due to the complicated interface shape between the base coating and the ground iron disappears and the coating peels off. However, when Cr is present in the undercoating film, Cr is concentrated in the undercoating film and shuts out the intrusion of phosphorus into the coating base metal interface. As a result, the adhesion of the film is maintained without losing the anchor effect.

  At this time, it is important not only to make Cr exist in the base film but also to keep P / MX within a predetermined range in the coating (coating liquid). When this is too high, non-crosslinked phosphoric acid increases.

However, it has been newly clarified that adhesion deterioration occurs even if P / MX is too low. This is considered to be because the stability of the raw material phosphate solution is impaired by lowering P / MX.
In general, when forming a phosphate coating, an aqueous solution of a primary phosphate such as primary magnesium phosphate or primary aluminum phosphate and silica such as colloidal silica are mixed and applied, At this time, if P / MX is too low, the aqueous solution of the primary phosphate becomes unstable, and it becomes easy to gel or solidify. This is entrained when applying the coating liquid, resulting in fine protrusions. When the layers are laminated in such a state and subjected to strain relief annealing, a very slight gap is generated between the steel plates due to the protrusions. When the gas during annealing flows through the gap, the coating is more easily exposed to the atmospheric gas. As a result, the non-crosslinked phosphoric acid content increases and adversely affects the adhesion.

  From the above points, by keeping the amount of Cr in the undercoat and the P / MX of the coating within an appropriate range, deterioration of the coating adhesion can be prevented even in a highly oxidative strain relief annealing atmosphere.

  Next, the manufacturing method of the grain-oriented electrical steel sheet according to the present invention will be described again.

[Method of manufacturing grain-oriented electrical steel sheet]
In the method for producing a grain-oriented electrical steel sheet according to the present invention, 0.07 to 0.35 g / m ^{2 of} Cr is contained in the forsterite base coating of the finish annealed plate of the grain-oriented electrical steel, and the upper layer of the base coating is included. And at least one phosphate selected from the group consisting of Mg, Al, Ca, Sr, Fe, Cu, Mn and Zn, and silica, where the ion value of the metal element M of the phosphate is X, A coating solution containing P / MX in the range of 1.002 to 1.035 when the molar ratio of the phosphorus element P to the metal element M in the coating is P / M. This is a method for producing a grain-oriented electrical steel sheet in which flattening annealing is performed to form a coating on the undercoat.

  In the present invention, for example, silicon-containing steel is used as a material. The silicon-containing steel is not particularly limited as long as it is a directional silicon steel material. This is hot-rolled by a known method, finished to the final plate thickness by one or more annealings and cold rolling, and then subjected to primary recrystallization annealing, and an annealing separator is applied and final finishing annealing is performed. As a result, a base coating mainly composed of forsterite is formed.

It is one of the features of the present invention that an appropriate amount of Cr is contained in the undercoat.
Examples of a method for containing Cr in the undercoat include, for example, a method in which Cr is added in advance in the steel output component; and an electrodeposition treatment of Cr at any stage before the undercoat is formed after the steel is extracted. Or by forming a coating film containing a Cr compound and then concentrating the underlying coating layer by annealing at the time of forming the underlying coating; a method of adding a Cr compound in the annealing separator; Can be mentioned. Either method is applicable. Moreover, the Cr compound to be used is not particularly limited, and various Cr compounds can be used.
The amount of Cr in the undercoat is 0.07 to 0.35 g / m ² in terms of the weight per unit area of both sides. If it is less than 0.07 g / m ² , the effect of film adhesion cannot be obtained. If it is more than 0.35 g / m ² , the undercoat becomes thick, and it partially peels off, resulting in a film defect, and the film adhesion is also deteriorated as a whole.

  After forming the base film in this manner, preferably, the unreacted annealing separator is removed by washing with water or light pickling, and then the coating liquid is applied.

  The coating liquid contains at least a phosphate and silica.

The metal species of the phosphate is not particularly limited as long as it is at least one selected from the group consisting of Mg, Al, Ca, Sr, Fe, Cu, Mn, and Zn.
A phosphate may be used individually by 1 type and may use 2 or more types together.
As the phosphate, primary phosphate (heavy phosphate) is preferably used from the viewpoint of availability.

As the silica, colloidal silica is usually used. The average particle size of the colloidal silica is preferably 5 to 200 nm, more preferably 10 to 100 nm. The average particle diameter of colloidal silica can be measured by the BET method (converted from the specific surface area by the adsorption method). It is also possible to substitute an average value actually measured from an electron micrograph.
Moreover, the content of silica is preferably 50 to 150 parts by mass with respect to 100 parts by mass of phosphate in terms of solid content. If the silica content is too small, the effect of reducing iron loss by applying tension to the steel sheet of the coating may be low, and if it is too high, fine cracks may be generated on the surface and the corrosion resistance may be inferior. If it is inside, the effect of reducing iron loss and corrosion resistance will be good.

In the present invention, the ion valence (valence) of the metal element M of the phosphate in the coating solution is X, and the molar ratio of the phosphorus element P and the metal element M in the coating to be formed is P / M. In this case, the ratio represented by P / MX is set in the range of 1.002 to 1.035.
When this ratio is lower than 1.002, the stability of the coating liquid is impaired and the film adhesion is deteriorated. On the other hand, if it is higher than 1.035, the non-crosslinked phosphoric acid content increases in the coating to be formed, and the film adhesion is also deteriorated.

  In addition, as above-mentioned, multiple types of phosphate can be used for a coating liquid. In this case, for example, when the molar ratio of P, Mg, and Al is 5: 1: 1, P / MX = P / (2Mg + 3Al) = 5 / (1 × 2 + 1 × 3) = 1 .

  The method for adjusting the ratio P / MX is not particularly limited. For example, a method of changing the ratio of phosphoric acid and metal ions of the raw material when producing the primary phosphate; phosphoric acid and metal in the coating solution And a method of adding an ionic compound later.

In addition, according to the objective, other various components can be mix | blended with a coating liquid, Even in that case, the effect which contained Cr in the base film is not impaired. For example, the technique disclosed in Patent Document 1 or 2 or the technique such as the chromeless coating disclosed in Patent Document 5 can be applied particularly preferably.
The coating liquid can further contain chromic anhydride or at least one dichromate selected from the group consisting of Mg, Al, Ca, Fe and Mn. By using the coating liquid containing these, the corrosion resistance of the grain-oriented electrical steel sheet obtained can be made favorable.
The content of chromic anhydride or dichromate in the coating solution is preferably 10 to 50 parts by mass with respect to 100 parts by mass of phosphate in terms of solid content (dry solids ratio). If this content is too low, the effect of improving the corrosion resistance may be reduced, and if it is too high, film formation may be difficult and the hygroscopicity may be easily deteriorated. The effect of corrosion resistance is sufficiently obtained, and the hygroscopicity is also excellent.

Moreover, the coating liquid which does not contain the Cr compound (chromium compound) developed from the viewpoint of avoiding hexavalent chromium harmful to the human body as much as possible in the production process as well as the product can be used. In that case, it is preferable to further contain a compound containing at least one selected from the group consisting of Sb, Mn, Ti, Fe and Sn instead of the Cr compound.
The said compound may be used individually by 1 type, and may use 2 or more types together.
If the compounding amount of the compound is too small, the effect is insufficient, and if it is too large, the film formability may be inferior. For example, in terms of solid content, 10 to 50 parts per 100 parts by mass of phosphate. About mass parts.

  Further, it is possible to improve heat resistance by further adding inorganic mineral particles such as silica powder and alumina powder. Content of an inorganic mineral particle is about 0.1-10 mass parts with respect to 100 mass parts of phosphates in conversion of solid content, for example.

If the coating weight is too small, the tension effect may be reduced and the magnetic properties may be deteriorated. If the coating weight is too large, the space factor may be reduced. Therefore, the total amount on both sides is 5 to 15 g / m ² . It is preferable to do.

This coating solution is applied and dried as necessary, and then flattening annealing is performed also for baking.
It does not specifically limit as a coating method, A conventionally well-known method can be used.
Drying includes, for example, charging a steel plate coated with a coating solution into a drying furnace and drying at 150 to 450 ° C. for 0.25 to 2 minutes, but is not limited thereto. Absent.

As conditions for flattening annealing, if the annealing temperature is too low, the coating may not be sufficiently formed and the corrosion resistance and magnetic properties may be inferior, and if it is too high, the steel plate may be deformed and the magnetic properties may be easily deteriorated. The annealing temperature is preferably in the temperature range of 750 to 900 ° C.
As the annealing atmosphere, any of N ₂ , Ar, H _{2 and the} like can be used, but it is preferable that N ₂ is mainly used from the viewpoint of cost and safety.
Although annealing time is not specifically limited, For example, it shall be 3 to 120 seconds.

  By satisfying the above various conditions, it is possible to obtain a grain oriented electrical steel sheet having good film adhesion after strain relief annealing in an oxidizing atmosphere.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.

[Experimental Example 1]
As shown in Table 2 below, a silicon steel slab containing Cr in an amount of less than 0.01% by mass to 0.2% by mass (components other than Cr are C: 0.04% by mass, Si: 3. 4 mass%, Mn: 0.07 mass%, Al: 0.006 mass%, P: 0.04 mass%, S: 0.003 mass%, N: 0.004 mass%, Sb: 0.03 mass% %, The remaining inevitable impurities) were subjected to finish annealing by a conventional method to produce a finish annealed sheet of a grain-oriented electrical steel sheet having a thickness of 0.23 mm. After this, the unreacted separating agent was removed, and this was pickled with phosphoric acid. A coating liquid having a component composition of 1 to 10 is applied and dried (300 ° C., 1 minute) so that both sides are 10 g / m ² after drying, and flattening annealing (800 ° C., 20 seconds, combined with baking) N ₂ 100% atmosphere) to form a coating.
As colloidal silica, AT-30 manufactured by ADEKA (average particle size: 10 nm) was used.

  At this time, for the steel sheet after the finish annealing, the base film is removed by pickling, the samples before and after (with or without the base film) are acid-dissolved, and then the Cr concentration is chemically analyzed using atomic absorption spectrometry. Then, the amount of Cr contained in the undercoat was determined from the measured value in terms of basis weight. The results are shown in Table 2 below.

Further, the coating of the steel plate after the flattening annealing is dissolved with an alkali, and the concentration of the metal element M such as phosphorus element P and magnesium in the solution, P is an absorptiometer, and M is a chemical using an atomic absorption analyzer. The molar ratio P / M of P and M in the coating was calculated by analysis, and based on this, the ratio P / MX was obtained (X is the ionic value of M). The values of P / MX are shown in Table 1 and Table 2 below.
In addition, the value of P / MX was adjusted by changing various mixing ratios of metal ions and phosphorus during the manufacturing process of the raw material primary phosphate.

Next, the obtained steel sheet is subjected to strain relief annealing (850 ° C., 3 hours) in a DX gas atmosphere (dew point: 10 ° C., CO: 1%, H ₂ : 1%, CO ₂ : 12%, remaining nitrogen). After that, the bending adhesion was evaluated. The bending adhesion was obtained by winding a steel plate around a round bar having a different diameter every 10 mm, and obtaining the maximum diameter (unit: mm) at which the film did not peel off. The results at this time are shown in Table 2 below.
If the maximum diameter at which the coating did not peel is 40 mm or less, it can be evaluated as having excellent coating adhesion.

  From the results shown in Table 2 above, it can be seen that coating adhesion after strain relief annealing is good by keeping the amount of Cr in the base coating and the P / MX of the coating within an appropriate range.

[Experiment 2]
C: 0.04 mass%, Si: 3.4 mass%, Mn: 0.07 mass%, Al: 0.006 mass%, P: 0.04 mass%, S: 0.003 mass%, N: 0.004% by mass, Sb: 0.03% by mass, Cr: <0.01% by mass, steel ingot of the remaining inevitable impurities is used to perform decarburization annealing in a conventional manner, and then MgO: 100 parts by mass On the other hand, the slurry of the annealing separator added with the Cr compound shown in the following Table 3 in the addition amount shown in the following Table 3 was applied, dried, and finish-annealed. Then, after removing the unreacted separating agent and pickling with phosphoric acid, No. 1 shown in Table 1 above was obtained. A coating solution having a component composition of 10 to 24 was applied and dried in the same manner as in Experimental Example 1, and was subjected to flattening annealing also serving as baking to form a coating.
In addition, it carried out similarly to Experimental example 1, and calculated | required by converting the Cr amount in a base film into a fabric weight. Further, P / MX was determined in the same manner as in Experimental Example 1.
Next, the obtained steel sheet is subjected to strain relief annealing (850 ° C., 3 hours) in a DX gas atmosphere (dew point: 10 ° C., CO: 1%, H ₂ : 1%, CO ₂ : 12%, balance nitrogen). Thereafter, the bending adhesion was evaluated in the same manner as in Experimental Example 1. The results are shown in Table 3 below. If the maximum diameter at which the coating did not peel is 40 mm or less, it can be evaluated as having excellent coating adhesion.

  From the results shown in Table 3 above, it can be seen that even if the Cr compound is added to the annealing separator to increase the amount of Cr in the base coating, the coating adhesion after strain relief annealing is good.

Claims (3)

The Cr in the base coat finish annealed sheet forsterite of oriented electrical steel sheet 0.07~0.35g / m ² is contained, the upper layer of the underlying film, Mg, Al, Ca, Sr , Fe, Cu , Mn and Zn, and at least one phosphate selected from the group consisting of silica and silica, where the ion value of the metal element M of the phosphate is X, the phosphorus element P and the metal element M in the coating formed The coating solution containing P / MX in the range of 1.002 to 1.035 is applied, and planarization annealing is performed on the base film. A method of manufacturing a grain-oriented electrical steel sheet in which a coating is formed.   The grain-oriented electrical steel sheet according to claim 1, wherein the coating liquid further contains chromic anhydride or at least one dichromate selected from the group consisting of Mg, Al, Ca, Fe and Mn. Production method.   The method for manufacturing a grain-oriented electrical steel sheet according to claim 1, wherein the coating liquid further contains a compound containing at least one selected from the group consisting of Sb, Mn, Ti, Fe and Sn.