JP2007239009A - Method for manufacturing grain-oriented silicon steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the film characteristics of an inhibitorless grain-oriented silicon steel sheet. <P>SOLUTION: When manufacturing the grain-oriented silicon steel sheet by using a steel slab having a composition containing, by mass%, 0.01-0.10% C, 1.0-5.0 % Si, ≤0.5% Mn, and 0.01-0.2% Cr, and <50 ppm S, Se. and O respectively, <100 ppm sol.Al and <60 ppm N and the balance Fe and inevitable impurities as a raw material, the Cr concentration on the surface is adjusted in such a manner that the Cr concentration on the extreme surface of the steel sheet prior to primary recrystallization annealing becomes 0.5 to 0.8 times the Cr concentration in ferrite. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet, and in particular, intends to obtain a grain-oriented electrical steel sheet having excellent coating properties at a low cost.

  Oriented electrical steel sheet is a soft magnetic material used as an iron core material for transformers and generators, and has a crystal structure in which the <001> orientation, which is the easy axis of iron, is highly aligned with the rolling direction of the steel sheet. is there. Such a texture preferentially grows crystal grains of (110) [001] orientation, so-called Goss orientation, preferentially during final finish annealing during the production process of grain-oriented electrical steel sheet, Formed through secondary recrystallization.

Conventionally, such a grain-oriented electrical steel sheet heats a steel slab containing Si in an amount of 4.5 mass% or less and containing an inhibitor component such as MnS, MnSe, or AlN to 1300 ° C. or higher to temporarily fix the inhibitor component. After being melted, it is hot-rolled and, if necessary, hot-rolled sheet annealing is performed, and then the final thickness is obtained by one or more cold rollings sandwiching intermediate annealing, followed by primary in a wet hydrogen atmosphere. After recrystallization annealing, primary recrystallization and decarburization are performed, and after applying an annealing separator mainly composed of magnesia (MgO), secondary recrystallization and inhibitor components are purified at 1200 ° C for about 5 hours. Has been manufactured by performing final finish annealing (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).
U.S. Pat. No. 1,965,559 Japanese Patent Publication No. 40-15611 Japanese Patent Publication No.51-13469

In the conventional grain-oriented electrical steel sheet described above, precipitates (inhibitor components) such as MnS, MnSe, and AlN are contained in the slab stage, and these inhibitor components are once solid-dissolved by high-temperature slab heating exceeding 1300 ° C. In this step, a step of causing secondary recrystallization by finely dispersing and precipitating was employed.
Thus, in the conventional manufacturing process of grain-oriented electrical steel sheets, slab heating at a high temperature exceeding 1300 ° C. was indispensable, and the manufacturing cost had to be extremely high. That is, in the conventional grain-oriented electrical steel sheet in which the inhibitor component is contained in the slab, high-temperature slab heating is required in the production process, and thus it has not been possible to meet the recent demand for production cost reduction.

By the way, recently, the inventors have found that the essence of secondary recrystallization of Goss-oriented grains is the control of the primary recrystallization structure, and the presence or absence of the inhibitor component is indirectly controlled by secondary recrystallization through the control of the primary recrystallization structure. It was elucidated that it is acting and is not directly related to the expression of secondary recrystallization itself (for example, Patent Document 4).
JP 2000-129356 A

  As a result, the addition of the inhibitor component, and hence slab heating at a high temperature for dissolving it, is no longer necessary, and a grain-oriented electrical steel sheet can be produced at a low cost.

  However, as the manufacturing technology of grain-oriented electrical steel sheets not containing the inhibitor component described above has been put into practical use, a new problem has arisen in that the coating is inferior to the conventional one. This is thought to be because the trace content in the steel is different from that of the conventional steel, and thus a unique film forming behavior is exhibited, and the film form becomes poor under the conventional manufacturing conditions.

In addition to the method of improving the subscale formed by decarburization annealing and the method of improving various additives such as MgO and auxiliary agents used as the main agent of the annealing separator, there are patents as a conventional way of improving the coating film. Although various means such as a desiliconized layer generated by intermediate annealing and a method of controlling the residual scale to be within a predetermined range as seen in documents 5 to 9 have been solved, sufficient film properties are still obtained. It is not done.
JP-A-7-188757 JP-A-9-143562 JP-A-10-199536 Japanese Patent Laid-Open No. 11-140546 Japanese Patent Laid-Open No. 10-8133

  The present invention relates to an improvement in manufacturing technology of grain-oriented electrical steel sheets that do not contain the inhibitor component described above (hereinafter referred to as inhibitor-less grain-oriented electrical steel sheets), and is advantageous for producing grain-oriented electrical steel sheets having excellent coating properties. The purpose is to propose a method.

As a result of intensive studies on the method for improving the coating on the inhibitorless grain-oriented electrical steel sheet, the inventors have found that the coating characteristics are improved by subtle changes in the element concentration distribution on the steel sheet surface before the primary recrystallization annealing. Found a new change.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
(1) In mass%,
C: 0.01-0.10%,
Si: 1.0-5.0%
Mn: 0.5% or less and
Cr: 0.01% or more and 0.2% or less, and each of S, Se and O is less than 50 ppm,
Steel slab with sol.Al less than 100ppm and N less than 60ppm with the balance being Fe and inevitable impurities, hot-rolled and then hot-rolled sheet annealed, followed by one or intermediate annealing In the manufacturing method of the grain-oriented electrical steel sheet, which is subjected to cold rolling at least twice and finished to the final sheet thickness, followed by primary recrystallization annealing and then secondary recrystallization annealing.
A method for producing a grain-oriented electrical steel sheet, comprising adjusting the Cr concentration on the surface so that the Cr concentration on the outermost surface of the steel plate before primary recrystallization annealing is 0.5 to 0.8 times the Cr concentration in the ground iron.
Here, the Cr concentration in the outermost surface of the steel sheet and the iron core part is the Cr peak intensity at the outermost surface when the surface is analyzed in the depth direction by GDS, and the Cr peak at the sputtering time: 100 to 150 seconds. It shall be defined by the average value of intensity.

(2) In the above (1), the steel sheet is further mass%, Ni: 0.01 to 1.50%, Sn: 0.01 to 0.50%, Sb: 0.005 to 0.50%, P: 0.005 to 0.50%, Te: 0.003 to 1.50. %, Bi: 0.003-1.50%, Pb: 0.003-1.50%, and Cu: 0.01-0.3%.

  According to the present invention, when producing an inhibitorless grain-oriented electrical steel sheet, the coating film characteristics can be remarkably improved by adjusting the Cr concentration on the outermost surface of the steel sheet before primary recrystallization annealing appropriately.

Hereinafter, the experimental results that led to the present invention will be described. Unless otherwise specified, “%” in relation to ingredients means mass%.
Contains C: 0.03%, Si: 3.0%, Mn: 0.10%, S: 40ppm, Se: 2ppm, Cr: 0.01%, 0: 10ppm, N: 25ppm and sol.Al: 20ppm, the balance being Fe and inevitable Steel slab with a composition of mechanical impurities is hot rolled into a hot rolled sheet with a thickness of 2.0 mm, then annealed at 1000 ° C. for 1 minute, then concentration: 5%, temperature: 80 ° C. The surface scale was removed by pickling using 2 ml of hydrochloric acid under two conditions of 60 seconds or 150 seconds. After that, cold rolling to 0.27mm thickness, decarburization and primary recrystallization annealing at 850 ℃ for 100 seconds, and after applying annealing separator, secondary recrystallization annealing at 1200 ℃ for 10h Was given. Next, after removing the residual annealing separation agent, an insulating coating treatment solution was applied, and annealing was performed at 850 ° C. for 30 seconds in combination with baking and heat flattening treatment to obtain a final product.

The film adhesion of the product thus obtained was evaluated by the minimum bending diameter at which the sample was wound around a cylindrical rod and the film did not peel off.
As a result, it was found that when the pickling time was short, the peeled diameter was as good as 20 mmφ, but when the pickling time was long, it was significantly deteriorated to 50 mmφ.

  In the knowledge about the relationship between the conventional cold rolling process and the film characteristics, for example, as described in Patent Document 5, the desiliconized layer generated by the intermediate annealing affects the film, or described in Patent Document 7 As has been known, it has been known that the scale produced by the intermediate annealing has an adverse effect on the coating.

Therefore, these points were confirmed by analyzing the depth direction with GDS.
That is, the Si concentration as an evaluation component of the desiliconization layer and the O concentration as an evaluation component of the descaling layer were measured for the sample before the primary recrystallization annealing treated under the above two conditions.
The obtained results are shown in FIGS. 1 (a) and 1 (b).

  As apparent from FIGS. 1 (a) and 1 (b), almost no change in the desiliconized layer was observed by changing the pickling time. In this experiment, it is considered that the desiliconization layer produced by hot-rolled sheet annealing has become thin enough to cause no problem because it is rolled at a high pressure reduction rate after hot-rolled sheet annealing. Further, with respect to the descaling layer, the longer the pickling time should be, the less the result, but the result is different from the conventional one that the film deteriorates nevertheless.

Therefore, the conventional findings cannot explain the experimental results, so the profiles of other elements were also investigated.
As a result, as shown in FIGS. 2 (a) and 2 (b), Cr is affected by the pickling time, and although Cr tends to decrease in concentration at the outermost surface, It was observed that the decrease was small.
From the above results, it was considered that the Cr concentration on the outermost surface had an effect on the quality of the coating film. Next, an experiment was conducted to confirm this.

  A steel slab having the same composition as described above is hot-rolled into a hot-rolled sheet having a thickness of 2.0 mm, and then subjected to hot-rolled sheet annealing at 1000 ° C. for 1 minute, and then using sulfuric acid with a concentration of 7%. The surface scale was removed by pickling under various conditions of temperature: 40 to 90 ° C. and time: 10 to 150 seconds. After that, cold rolled to a thickness of 0.27mm, decarburized and primary recrystallized annealing at 850 ℃ for 100 seconds, then applied with an annealing separator, and subjected to secondary recrystallization annealing at 1200 ℃ for 10h. did. Then, after removing the residual annealing separator, an insulating coating treatment solution was applied, and annealing was performed at 850 ° C. for 30 seconds in combination with baking and heat flattening treatment to obtain a final product. At the same time, the steel sheet before the primary recrystallization annealing was analyzed in the depth direction by GDS to measure the Cr concentration on the outermost surface.

FIG. 3 shows the results of examining the relationship between the Cr concentration on the outermost surface and the film adhesion of the product. In the figure, the horizontal axis represents the ratio between the Cr concentration on the outermost surface and the concentration on the ground iron part.
As is clear from the figure, it is understood that excellent film adhesion can be obtained when the Cr farming degree on the outermost surface satisfies the range of 0.5 to 0.8 times the Cr concentration in the ground iron.

The reason why the above results were obtained has not yet been clearly clarified, but the inventors consider as follows.
That is, it is known that the influence of Cr on the coating film develops the anchor of the forsterite film after finish annealing by forming spinel in the subscale formed after the primary recrystallization annealing. Therefore, it is considered that the Cr is intentionally added to exist in the steel, and by utilizing this Cr, the form of the forsterite coating is optimized and good coating properties can be obtained. All of these Cr effects mainly act on the interface between the subscale and forsterite coating and the ground iron within a few μm from the surface of the steel sheet. An appropriate amount of Cr concentration can be achieved in this depth region. It is important to have.
On the other hand, in the steel plate outermost layer, Cr has an action of promoting oxidation, but in a system not containing an inhibitor like this time, there is no element having an effect of suppressing oxidation such as S and Al. As a result, a subscale having a low additional oxidation resistance is formed in which the film thickness is thicker than that of the conventional steel and the oxide is developed in a dendrite shape. In the case of such a subscale, the obtained forsterite film has a thick and flat structure, but when it is peeled off, film defects are likely to occur.
Therefore, in order to suppress such oxidation to the inside, it is effective to reduce the Cr concentration on the outermost surface.

In addition, although the patent documents 5-9 mentioned above have shown the technique which specifies the surface layer residual scale amount and intermediate thickness after intermediate annealing, about the influence which the surface state of hot-rolled sheet annealing has on a film There has never been any knowledge. That is, since the cold rolling reduction ratio after intermediate annealing is relatively low, it was known that the scale and desiliconization layer produced by intermediate annealing had an effect even before decarburization annealing. Since the cold rolling reduction ratio is high, even if there is a desiliconized layer or residual scale, it has been considered that it is thinned to a negligible extent after cold rolling and does not affect the formation of subscales.
However, in this experiment, the scale produced by hot-rolled sheet annealing or hot-rolling remains before decarburization annealing, affecting the formation of subscales, and the film thickness depends on the pickling conditions after hot-rolled sheet annealing. For the first time, it was clarified that the quality of the changes in the quality.

Hereinafter, with respect to the method for producing a grain-oriented electrical steel sheet according to the present invention, requirements for obtaining the effect of the present invention, its range and action will be described.
First, the reason why the component composition of the steel slab is limited to the above range in the present invention will be described.
C: 0.01-0.10%
C is an element that not only effectively contributes to improving the hot-rolled structure using transformation, but is also useful for the generation of goth-oriented crystal grains, and needs to be contained in an amount of 0.01% or more. If the content exceeds 50%, the effect becomes too strong and the texture deteriorates, so C is limited to a range of 0.01 to 0.10%.

Si: 1.0-5.0%
Si is an element necessary not only to increase the electric resistance and decrease the iron loss, but also to stabilize the α phase of iron and enable high-temperature heat treatment, and requires at least 1.0%. If it exceeds 5.0%, cold rolling becomes difficult, so Si is limited to a range of 1.0 to 5.0.

Mn: 0.5% or less
Mn has the effect of improving the hot workability during production. For this purpose, it is preferable to contain at least 0.01% of Mn, but when it exceeds 0.5%, the primary recrystallized texture deteriorates and the secondary is highly accumulated in the Goss orientation. Since no recrystallized grains were obtained and the magnetic properties deteriorated, the upper limit was made 0.5%.

Cr: 0.01% or more and 0.2% or less In the present invention, Cr is contained as an element involved in film formation. However, if the content is less than 0.01%, the effect of improving the film is poor. Since this causes a decrease, Cr is limited to the range of 0.01% to 0.2%.

In the present invention, since an inhibitor is not used, it is not necessary to contain each element such as S, Se, O, sol. Therefore, it was limited to the following ranges, respectively.
S, Se, O: less than 50 ppm each When S, Se, O is contained in an amount of 50 ppm or more, secondary recrystallization becomes difficult and magnetic properties deteriorate. Therefore, these elements were reduced to less than 50 ppm.

sol.Al: less than 100ppm
If Al is present in excess, secondary recrystallization becomes difficult. In particular, when sol.Al is 100 ppm or more, secondary recrystallization hardly occurs and magnetic properties are deteriorated, so sol.Al must be suppressed to less than 100 ppm.

N: less than 60 ppm Also, when N is contained in an amount of 60 ppm or more, secondary recrystallization is similarly difficult and the magnetic properties are deteriorated. Therefore, the N content is limited to less than 60 ppm.

As described above, the essential component and the suppressing component have been described. In addition, in the present invention, the following elements can be appropriately contained from the viewpoint of improving the texture by improving the texture.
Ni: 0.01-1.50%
Ni is an element useful for improving the magnetic properties by improving the hot-rolled sheet structure. However, if the content is less than 0.01%, the amount of improvement in magnetic properties is small. On the other hand, if it exceeds 1.50%, secondary recrystallization becomes unstable and the magnetic properties deteriorate, so Ni is contained in the range of 0.01 to 1.50%. It is preferable.

Sn: 0.01-0.50%
Sn is an element that improves and stabilizes magnetic properties. However, if the content is less than 0.01%, the effect of addition is poor. On the other hand, if it exceeds 0.50%, a good primary recrystallized structure cannot be obtained. , Sn content is preferably in the range of 0.01 to 0.50%.

Sb: 0.005-0.50%
Sb is a useful element that suppresses nitriding and oxidation of the steel sheet during final finish annealing, promotes secondary recrystallization of crystal grains having a good crystal orientation, and improves magnetic properties. For that purpose, it is desirable to make it contain 0.005% or more. On the other hand, if the Sb content exceeds 0.50%, the cold rollability deteriorates, so Sb is desirably contained at an upper limit of 0.50%.

P: 0.005-0.50%
P has a function of improving the magnetic flux density by improving the texture after cold rolling and recrystallization by grain boundary segregation. However, if the content is less than 0.005%, a sufficient effect cannot be obtained. On the other hand, if the content exceeds 0.50%, a good primary recrystallized structure cannot be obtained. Therefore, the P content is preferably in the range of 0.005 to 0.50%.

Te: 0.003-1.50%, Bi: 0.003-1.50%, Pb: 0.003-1.50%
Te, Bi, and Pb each have a function of segregating at the grain boundary to improve the primary recrystallization structure. For this purpose, it is desirable to contain 0.003% or more. On the other hand, if each content exceeds 1.50%, the hot workability is impaired, so it is desirable to contain 1.50% as the upper limit.

Cu: 0.01-0.3%
Cu is a useful element that suppresses nitriding and oxidation of the steel sheet during final finish annealing, promotes secondary recrystallization of crystal grains having a good crystal orientation, and improves magnetic properties. For that purpose, it is desirable to make it contain 0.01% or more. On the other hand, if Cu is contained in excess of 0.3%, the hot rollability deteriorates, so it is desirable to contain Cu with 0.3% as the upper limit.

Next, the manufacturing method of this invention is demonstrated.
The slab adjusted to the above suitable component composition range is produced by a normal ingot-making method and a continuous casting method. Further, a thin cast piece having a thickness of 100 mm or less may be manufactured by a direct casting method.
Next, after heating a slab, it is set as a hot rolled sheet by hot rolling.
Next, after performing hot-rolled sheet annealing, it is finished to the final sheet thickness by one or more cold rolling processes including intermediate annealing. Here, the hot-rolled sheet annealing is preferably performed at 800 to 1100 ° C. for about 1 to 120 seconds. This hot plate annealing works to homogenize the magnetic properties in the longitudinal direction of the coil, but there is no effect at less than 800 ° C or less than 1 second, while at 1100 ° C or more than 120 seconds the particle size becomes too large. The subsequent cold rolling property is impaired.

  Next, primary recrystallization annealing is performed. In the present invention, the surface Cr concentration is adjusted so that the Cr concentration on the outermost surface of the steel sheet before this primary recrystallization annealing is 0.5 to 0.8 times the Cr concentration in the ground iron. It is important to do. Here, if the Cr concentration on the surface is higher than 0.8 times that of the ground iron, oxidation of the steel sheet surface will progress excessively during the primary recrystallization annealing, resulting in film deterioration, while the surface Cr concentration is If it is lower than 0.5 times, oxidation of the steel sheet surface is suppressed too much during the primary recrystallization annealing, resulting in a thin film, which also causes film deterioration.

  In the present invention, as a method of adjusting the Cr concentration on the surface of the steel sheet, a chemical grinding method by removing the scale after the hot-rolled sheet annealing by pickling using phosphoric acid, hydrochloric acid, nitric acid, sulfuric acid, or a mixed acid thereof. Alternatively, it can be performed by a mechanical grinding method using shot blasting, air blasting, a grinder grindstone, a baffle or a belt sander, or a method using a combination thereof. As a result of Cr being diffused and oxidized on the surface by hot-rolled sheet annealing, a Cr removal layer is formed, but polishing is performed to such an extent that the oxide is removed while the Cr removal layer is not removed.

The temperature in the soaking area in the primary recrystallization annealing is preferably 750 to 950 ° C. If the temperature exceeds 950 ° C, the primary recrystallized grains grow too much, resulting in secondary recrystallization failure.On the other hand, if the temperature is lower than 750 ° C, the primary recrystallized grains do not progress and the orientation of the secondary recrystallized grains is not good. Causes stability. The soaking time is preferably 20 to 240 s. If it is less than 20 s, primary recrystallization failure occurs, and if it exceeds 240 s, primary recrystallization grain growth proceeds and both cause deterioration of magnetic characteristics. Furthermore, the atmospheric oxidizing P (H ₂ O) / P (H ₂ ) during annealing is preferably 0.15 to 0.75. If it is less than 0.15, a good oxide film cannot be obtained and the film deteriorates, and if it exceeds 0.75, a peroxide film mainly composed of FeO is formed and the film also deteriorates.

After the primary recrystallization annealing, an annealing separator is applied. At least 50% or more of magnesia is used as the main component of the sinter separating agent. The additives of the annealing separating agent, as known additives, TiO ₂ and, Mg, Sr, Sb, Cu, sulfates such as Zn, Li, borates such as Na, other hydroxides, chlorides, etc. Various compounds are used, and these can also be used in the present invention. The addition amount of these compounds is preferably about 0.5 to 15 parts by mass with respect to 100 parts by mass of magnesia. In addition, the application amount and hydration amount of the annealing separator may be about 5 to 15 g / m ² (both sides) and about 0.5 to 5% as usual.

After the annealing separator is applied, final finish annealing is performed, but there is no particular limitation on this, and any known method may be followed.
After final finish annealing, if necessary, a tension-imparting coating or an insulating coating is baked on the surface of the steel sheet, followed by flattening annealing to obtain a product.
Also, for the purpose of reducing iron loss due to magnetic domain subdivision, the steel plate after flattening annealing is subjected to a plasma jet or laser irradiation in a linear manner, a process of providing a dent in a linear shape by a protruding roll, or etching after the final cold rolling It is also possible to perform a process for forming a groove substantially perpendicular to the rolling direction.
Furthermore, it is also effective for reducing iron loss to combine techniques for forming a tension film by a known method such as a sol-gel method or TiN deposition after final finish annealing.

Example 1
C: 0.06%, Si: 3.35%, Mn: 0.07% and Cr: 0.01%, S is suppressed to 30ppm, Se is 1ppm, O is 10ppm, Al is 50ppm and N is suppressed to 35ppm, the balance is Fe Silicon steel slab (steel grade A) and C: 0.06%, Si: 3.25%, Mn: 0.06%, Cr: 0.07% and Cu: 0.01%, and S: 20 ppm, Se Is controlled to 2ppm, O is 12ppm, Al is 20ppm and N is 29ppm, and the balance is Fe and silicon steel slab (steel grade B) with inevitable impurities, respectively. After heating and holding for 60 minutes, a hot-rolled sheet having a thickness of 2.0 mm was formed by hot rolling, followed by annealing at 1000 ° C. for 1 minute.
Next, after removing the scale under various conditions shown in Table 1, it was cold rolled to a final thickness of 0.30 mm, and then the atmosphere was oxidized with P (H ₂ O) / P (H ₂ ) = 0.40. After decarburizing and annealing at 850 ° C. for 100 seconds in the inside, an annealing separator having a composition of MgO: 100 parts by mass, TiO ₂ : 2 parts by mass, and strontium hydroxide: 3 parts by mass was applied in a coating amount per both sides of the steel sheet. After 14 g / m ^{2 was} applied, it was wound around a coil and subjected to final finish annealing.

Then, after removing the unreacted annealing separating agent by washing with water, an insulating tension coating liquid containing magnesium phosphate containing colloidal silica as a main component was applied, and a product was obtained after flattening annealing.
Table 2 shows the results of investigation on the appearance, bending adhesion, magnetic flux density B ₈ and iron loss W _17/50 of the product thus obtained.
The bending adhesion was evaluated based on the minimum bending diameter at which the sample was wound around a cylindrical rod and the coating did not peel off. Further, the magnetic flux density B ₈ and the iron loss W _17/50 were measured by the Epstein test method.

  As shown in the table, according to the present invention, any steel sheet that has been appropriately adjusted for the Cr concentration on the outermost surface of the steel sheet before the primary recrystallization annealing can be obtained with excellent coating properties as well as excellent magnetic properties. It was.

Example 2
Silicon steel slabs with various composition shown in Table 3 were charged into a gas heating furnace, heated to 1210 ° C, held for 60 minutes, hot rolled into a hot rolled sheet of 2.0 mm thickness, and 1000 Hot-rolled sheet annealing was performed at 1 ° C. for 1 minute.
Next, after removing the scale under the condition shown in No. 5 in Table 1, it was finished to a final thickness of 0.30 mm by cold rolling, and then the oxidation property was P (H ₂ O) / P (H ₂ ) = 0.46. After decarburizing and annealing in an atmosphere at 850 ° C. for 120 seconds, an annealing separator having a composition of MgO: 100 parts by mass, TiO ₂ : 2 parts by mass, and magnesium sulfate: 3 parts by mass is applied to both sides of the steel sheet. After applying 13 g / m ² , it was wound around a coil and subjected to final finish annealing.

Then, after removing the unreacted annealing separating agent by washing with water, an insulating tension coating liquid containing magnesium phosphate containing colloidal silica as a main component was applied, and a product was obtained after flattening annealing.
The results of investigations on the appearance, bending adhesion, magnetic flux density B ₈ and iron loss W _17/50 of the product thus obtained are also shown in Table 3.
The bending adhesion was evaluated based on the minimum bending diameter at which the sample was wound around a cylindrical rod and the coating did not peel off. Further, the magnetic flux density B ₈ and the iron loss W _17/50 were measured by the Epstein test method.

  As shown in the table, both the composition composition range of the present invention and the Cr concentration on the outermost surface of the steel sheet before the primary recrystallization annealing were appropriately adjusted were excellent not only in magnetic properties but also in coating properties. The product has been obtained.

It is a figure which shows the depth direction analysis result when Si and O in the steel plate before the primary recrystallization annealing at the time of descaling by changing pickling time are measured. It is a figure which shows the depth direction analysis result when carrying out GDS measurement of Cr in the steel plate before the primary recrystallization annealing when descaling processing is performed by changing the pickling time. It is a figure which shows the relationship between Cr density | concentration ratio of the iron-base part of the outermost surface of the steel plate before primary recrystallization annealing, and film adhesiveness.

Claims (2)

% By mass
C: 0.01-0.10%,
Si: 1.0-5.0%
Mn: 0.5% or less and
Cr: 0.01% or more and 0.2% or less, and each of S, Se and O is less than 50 ppm,
Steel slab with sol.Al less than 100ppm and N less than 60ppm with the balance being Fe and inevitable impurities, hot-rolled and then hot-rolled sheet annealed, followed by one or intermediate annealing In the manufacturing method of the grain-oriented electrical steel sheet, which is subjected to cold rolling at least twice and finished to the final sheet thickness, followed by primary recrystallization annealing and then secondary recrystallization annealing.
A method for producing a grain-oriented electrical steel sheet, comprising adjusting the Cr concentration on the surface so that the Cr concentration on the outermost surface of the steel plate before primary recrystallization annealing is 0.5 to 0.8 times the Cr concentration in the ground iron. 2. The steel sheet according to claim 1, further comprising, in mass%, Ni: 0.01 to 1.50%, Sn: 0.01 to 0.50%, Sb: 0.005 to 0.50%, P: 0.005 to 0.50%, Te: 0.003 to 1.50%, Bi: A method for producing a grain-oriented electrical steel sheet, comprising one or more selected from 0.003 to 1.50%, Pb: 0.003 to 1.50%, and Cu: 0.01 to 0.3%.

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