JPH1136018A - Manufacture of grain oriented silicon steel sheet having extremely excellent glass film and magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method of manufacturing a grain oriented silicon steel sheet, for obtaining a uniform glass film and excellent magnetic properties by using a separation agent at annealing, having excellent reactivity and adhesion to steel sheet, in the course of film formation. SOLUTION: A hot rolled plate, having a composition containing, by weight, 0.03-0.100% C and 2.5-4.5% Si, is annealed if necessary and is then cold-rolled once or cold-rolled twice, while annealed between cold rolling stages, to final sheet thickness. The resultant sheet is subjected, in succession, to decarburizing annealing, to nitriding or sulfurizing treatment for inhibitor formation, to application of a separation agent at annealing, to finish annealing, to insulating film treatment, and to heat flattening, by which the grain oriented silicon steel sheet is manufactured. At this time, a separation agent at annealing, prepared by adding 0.1-5.0 pts.wt. of one or >=2 kinds selected from the hydroxides of Ca, Mg, Ba, and Al and having <=3 μm average grain size and 0.05-0.5 pts.wt. of one or >=2 kinds among the sulfates, chlorides, oxychlorides, and oxides of Sb and/or Bi to 100 pts.wt. of MgO, is applied to the steel sheet after decarburizing annealing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet mainly used as an iron core of a transformer or other electric equipment. In particular, the present invention relates to a method for producing a grain-oriented electrical steel sheet for obtaining an extremely uniform glass film and excellent magnetic properties by using an annealing separator having excellent reactivity and adhesion to a steel sheet in a film forming process.

[0002]

2. Description of the Related Art Oriented electrical steel sheets are usually C: 0.03 to 0.03.
A material slab containing 0.100%, Si; 2.5 to 4.5% is hot-rolled, and the final sheet thickness is obtained by annealing and cold rolling once or twice or more with intermediate annealing. Then H ₂ or N
₂ + H controls the oxidation degree perform decarburization annealing in a ₂ atmosphere,
Decarburization, primary recrystallization, and oxide film formation processing mainly composed of SiO ₂ are performed. In the technology of enabling low-temperature slab heating by reducing Mn to 0.08 to 0.45% and S; 0.007% or less as disclosed in JP-A-59-56522, stripping is performed after decarburizing annealing. A nitriding process is performed during running.

[0003] After that, an annealing separator containing MgO as a main component is applied to a steel plate in the form of slurry, dried, wound around a coil, and subjected to final finish annealing. Thereafter, a tension imparting type insulating film agent is applied, dried, baked and heat flattened to obtain a final product. In this grain-oriented electrical steel sheet, (110) <001> crystals having a <001> axis grow preferentially by secondary recrystallization at a high temperature, and the growth is caused by AlN, MnS or the like dispersed as an inhibitor in the steel. (11) to erode other crystals that are
0) <001> crystals are considered to grow preferentially. Therefore, in order to produce an excellent grain-oriented electrical steel sheet, it is important to control the state of dispersion of the inhibitor in the steel and its decomposition. In particular, in the process of forming the glass film in the final finish annealing, a decarbonated film, an annealing separator,
The effect of finish annealing conditions is significant.

In this glass film forming reaction, Mg
In a pure system, the reaction between O and SiO ₂ does not occur unless the temperature is as high as about 1600 ° C. Therefore, the properties (components, state of formation) of the oxide film generated in the decarburization step, impurities, particle size, surface state, activity, etc. of MgO, which is the main component of the annealing separator, and addition as a reaction accelerator In addition to the agent, the balance between the heat cycle and the atmosphere gas conditions in the finish annealing is particularly important. As a result, the oxide film surface components are kept stable until the glass film formation time, and a uniform glass film is formed from a low temperature. At the same time, the inhibitor is kept stable up to a high temperature range and good magnetic properties are obtained.

[0005] In the process of forming the glass film, the annealing separator M
When gO is applied to a steel sheet, the state of contact and adhesion to the surface of the steel sheet after drying is important together with the state of dispersion of particles in the slurry and the degree of progress of hydration. Usually this M
gO is suspended in water using a stirrer together with a small amount of an additive to be added as a reaction accelerator if necessary, and is applied to a steel sheet as a slurry. Compounds such as oxides, sulfides, borates and the like have been used as additives for lowering the melting point for forming forsterite.

As an improvement technique of such an annealing separator, there is, for example, Japanese Patent Application Laid-Open No. Sho 62-156226.
For this, a method has been proposed in which a MgO outermost surface layer fired at a high temperature forms a hydrated layer in a gas phase and is activated. Japanese Patent Publication No. Sho 63-3022 discloses a technique for improving a glass film and magnetic properties by an additive to an annealing separator.
0.05 to 2.0 parts by weight of antimony sulfate based on 0 part by weight, and 5 to 20% by weight of chlorine of one or more of chlorides of Sb, Sr, Ti, and Zr added to the antimony sulfate as chlorine. By using an annealing separator, a grain-oriented electrical steel sheet having excellent magnetic properties and film properties can be obtained. JP-A-3-120376 discloses a similar chloride addition method in which a metal chloride selected from Mg, Ca, Na, and K is added to MgO without adding antimony sulfate and sodium metaborate. The effect of improving the magnetic characteristics can be obtained.

As described above, the glass film forming reaction has been improved by improving the properties of MgO and the additives as a reaction accelerator in forming the glass film. However, in coil annealing, there are differences in the uneven heating of the coil when heating the coil, the displacement of the hydrated water in each part of the coil, the difference in the permeability of atmospheric gas, and the adhesion of the annealing separator to the steel sheet. A large impact. For this reason, depending on the steel composition, decarburizing annealing conditions, and final finishing annealing conditions, the glass film characteristics and magnetic characteristics may become unstable. This is not yet a sufficient technique, and further improvement is desired.

[0008]

SUMMARY OF THE INVENTION In particular, the present invention is to uniformly form a glass coating on the entire surface of a coil in the production of grain-oriented electrical steel sheet in which an inhibitor is formed by nitriding annealing or sulfurizing treatment after decarburizing annealing. And stabilization of the magnetic characteristics. That is, by improving the additive of the annealing separator, the coatability, adhesion and reactivity on the oxide film of the steel sheet are enhanced, and an excellent glass film formation is obtained. Accordingly, it is an object to suppress the non-uniform additional oxidation in the coil, obtain a uniform glass film over the entire surface of the coil, keep the inhibitor stable, and at the same time obtain an excellent effect of improving the magnetic properties.

[0009]

Means for Solving the Problems In the production of grain-oriented electrical steel sheets based on the step of forming an inhibitor by nitriding treatment or sulfurizing treatment after decarburizing annealing,
One or more hydroxides selected from Ca, Mg, Ba, and Al and one or two of sulfates, chlorides, oxychlorides, and oxides of Sb and / or Bi as MgO as an annealing separator. It has been found that by adding more than one kind at the same time, a grain-oriented electrical steel sheet having excellent magnetic film properties and excellent magnetic properties over the entire surface of the coil can be obtained. Further, the amount of Fe—O formed in the decarburization annealing step at this time and Sb and / or
Alternatively, the addition amount of the Bi compound is maintained in a constant relationship, and the temperature is increased from 350 to 850 ° C. in the final annealing.
By maintaining a soaking temperature of 40 hours, a more excellent glass film and improved magnetic properties were successfully obtained.

The present invention has the following features as an annealing separator having excellent reactivity, a decarburizing annealing oxide film condition balanced with the annealing separating agent, and a heating condition at the time of raising the temperature in final finishing annealing. (1) By weight%, C: 0.03 to 0.100%, Si;
Anneal the hot-rolled sheet containing 2.5-4.5% as needed, and make it the final sheet thickness by one or two cold-rolling steps including annealing, decarburize annealing, and inhibit by nitriding or sulfurizing treatment. , An annealing separator is applied, finish annealing is performed, and an insulating film treatment and heat flattening are performed. In the method for producing a grain-oriented electrical steel sheet, MgO: 100 parts by weight is added on the steel sheet after the decarburizing annealing. On the other hand, 0.1 to 5.0 parts by weight of one or more hydroxides selected from Ca, Mg, Ba, and Al having an average particle diameter of 3 μm or less and Sb and / or B
a glass coating characterized by adding 0.05 to 0.5 part by weight of one or more of sulfates, chlorides, oxychlorides and oxides of i, and a grain-oriented electrical steel sheet having extremely excellent magnetic properties Manufacturing method. (2) The Sb compound is added in the range shown by the following formula according to the amount of Fe-O on the steel sheet surface after the decarburizing annealing, and the glass film according to (1) and the magnetic properties are extremely excellent. Manufacturing method of grain-oriented electrical steel sheet.

-0.2x + 0.1≤H≤-1.2x +
0.5 (0.025 ≦ x ≦ 0.30) H: MgO: Sb and / or Bi per 100 parts by weight
Compound Total amount (parts by weight) x: Fe-O content in the oxide film (g / m ²⁾ Fe-O: total amount of Fe oxide in the oxide (g / m
² ) (3) When the temperature in the finish annealing is 400
The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein the soaking is performed at a temperature of 5 to 40 hours at a temperature of from 5 to 850 ° C.

As a result, the adhesion of the annealing separator to the oxide film on the surface of the steel sheet and the coatability of the MgO particles, which cannot be realized by the prior art, are improved, whereby the uniformity and stability of glass film formation in coil annealing are improved. Technology was successfully developed. That is, according to the present invention, it is possible to obtain a grain-oriented electrical steel sheet whose glass film and magnetic properties are good over the entire surface of the coil under a wide range of finish annealing conditions more effectively than conventional MgO or a reaction promoting additive.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In applying the present invention, as a starting material, C: 0.03 to 0.100 as% by weight.
%, Si: 2.5 to 4.5% orientated magnetic steel sheet slab is heated to 1280 ° C. or less, then hot-rolled,
Cold rolling is performed twice or more times with or without annealing to obtain a final sheet thickness, and then the degree of oxidation of the atmosphere gas is adjusted at 800 to 900 ° C. to perform decarburizing annealing to oxidize the steel sheet surface with SiO ₂ as a main component. Form a film. Thereafter, an inhibitor is formed by performing a nitriding treatment or a sulfurizing treatment on the same line or another line. One or two or more hydroxides selected from Ca, Mg, Ba, and Al having a particle diameter of 3 μm or less with respect to 100 parts by weight of MgO on this steel sheet.
0 parts by weight and at least one of sulfate, chloride, oxychloride and oxide of Sb and / or Bi 0.05 to 0.5
A part by weight of the annealing separator added at the same time is dispersed in water to form a slurry, which is applied to a steel sheet with a coating roll or the like,
After drying, it is wound on a coil. At this time, in addition to the additive of the present invention, a boron compound, a sulfur compound, a nitrogen compound, an oxide, and the like are used as an annealing separator in addition to the additive of the present invention for the purpose of promoting the reaction of the glass film, adjusting the atmosphere between the plates, or reinforcing the inhibitor. It is added together depending on the processing conditions. When applying the annealing separator of the present invention, the addition amount of the Sb and / or Bi compound is added in a range indicated by a certain formula between the addition amount of the oxide film Fe—O formed by the decarburization annealing, and More stable and good glass film and magnetic properties can be obtained.

[0014] The coil thus treated is subjected to final finishing annealing in a batch or continuous furnace.
At a temperature of 50 to 1200 ° C., a high-temperature and long-time treatment such as 20 hours is performed, and a glass film is formed, and secondary recrystallization and purification are performed. Thereafter, as a heat cycle at the time of raising the temperature of the finish annealing, preferably, the soaking is maintained at a stage of a furnace temperature of 400 to 850 ° C. After forming the glass film, the coil is washed and removed in a continuous line with an excess of annealed separating agent, and after light pickling, an insulating film is applied.Then, heat baking, shape correction, and strain flattening are performed. Product.

As the insulating film agent, 130 to 200 parts by weight of one or more of phosphates such as Al, Mg, Ca, etc. is added to 100 parts by weight of colloidal silica, and chromic acid, chromate, One or more of the chromates are C
to use those as and rO ₃ was blended 12 to 40 parts by weight is advantageous in terms of the tensioning and the film performance. To further improve the iron loss characteristics after this, laser, tooth roll, etching, local plating, etc., control the spacing, width and depth in a line, a point in a direction substantially perpendicular to the rolling direction, and strain, Grooves, plating layers, and the like are formed, and magnetic domain subdivision processing is performed.

Next, the reasons for limitation of the present invention will be described. First, as a steel plate material to be applied, C: 0.03 to
A slab containing 0.100% and Si: 2.5 to 4.5% is hot-rolled, cold-rolled, decarburized and annealed, and a steel sheet subjected to nitriding treatment or sulfurizing treatment is used. The nitriding treatment and the sulfurizing treatment are not particularly limited. In the case of the nitriding treatment, for example, N ₂ + H ₂ + NH at a furnace temperature of 700 to 850 ° C.
_In the atmosphere of ₃ , the concentration of NH ₃ is changed to obtain a predetermined nitriding amount. A nitriding amount of 150 to 300 ppm is a preferable condition for achieving both secondary recrystallization and glass coating. When nitriding or sulfurizing treatment is performed after such decarburizing annealing, a reduction action of iron-based oxide (firelite) in an oxide film formed on the surface of the steel sheet occurs, and in the formation of the glass film, The reactivity decreases. For this reason, the additive of the annealing separator of the present invention exerts an extremely large effect. First, in the present invention, one or two or more hydroxides selected from Ca, Mg, Ba, and Al of fine particles having an average particle diameter of 3 μm or less with respect to 100 parts by weight of MgO. One or more of sulfates, chlorides, oxychlorides and oxides of Sb and / or Bi together with 0 parts by weight
It is characterized in that parts by weight are added simultaneously. Ca, M
The fine particle hydroxides of g, Ba and Al are covered as fine particles on the surface of MgO as a main component and other additives or on the oxide film on the surface of the steel plate, thereby increasing the reaction area in the formation of glass. The hydroxide layer is made of MgO
Acts as a binder between additives and other particles, creating strong adhesion. As a result, peeling or lifting of the annealing separating agent from the steel plate surface during transportation and handling of the coating coil is suppressed. For this reason, in the MgO reaction between the steel sheet oxide layer and the MgO layer, a uniform reactivity improving effect is produced in the coil state. When the mixing ratio of these hydroxides is less than 0.1 part by weight with respect to 100 parts by weight of MgO, the effect of improving the glass film by sufficiently improving the adhesion and the covering property is not observed. If the added amount exceeds 5.0 parts by weight, decomposed water resulting from excess hydroxide is generated. For this reason, gas marks, scales, and pinhole-shaped metallic luster, which are peculiar to the peroxidation phenomenon, occur, and the glass film is not uniform in the longitudinal direction and the width direction of the coil. In this case, when the particle diameter of the hydroxide is 3 μm or less, the glass film and the effect of improving magnetism can be stably obtained. This is because in the case of fine particles of 3 microns or less, the effect of improving the adhesion between the particle coating of MgO or other additives by the hydroxide and the oxide layer of the steel sheet can be stably obtained. Thereby, a stable glass film forming effect can be realized. As the Sb and / or Bi compound added simultaneously with this hydroxide, one or more of sulfates, chlorides, oxychlorides and oxides may be 0.05 to 0.5 parts by weight per 100 parts by weight of MgO. It is added in parts by weight. All of these have a large low melting point effect, and together with the effect of covering with a fine hydroxide, bring about an extremely uniform and stable reactivity improving effect of forming a glass film. As a result, additional oxidation that is likely to occur at the coil outer peripheral portion or the edge portion in a high temperature region is suppressed, and the glass film is made uniform. If the addition amount is less than 0.05 part by weight,
Even with b and / or Bi compounds, the effect of improving reactivity is not sufficient. On the other hand, if it exceeds 0.5 parts by weight, the effect of lowering the melting point is too strong due to the synergistic effect with the hydroxide added and blended at the same time, and a film defect similar to the peroxide phenomenon occurs. As a result, the inhibitor is deteriorated during the temperature rise process of the finish annealing, and the magnetic properties are also deteriorated, which is not preferable. Next, in the present invention in which the hydroxide of the present invention and the Sb and / or Bi compound are added together, the Fe—O
By simultaneously controlling the formation amount, a glass film formation reaction improving effect can be stably obtained. This is because Fe—O in the oxide film (surface) has an effect of lowering the melting point in the reaction between MgO and SiO ₂ , so that the hydroxide and Sb and / or
Alternatively, by performing the addition balanced with the addition amount of the Bi compound, a more stable and excellent improvement effect can be obtained. At this time, the relationship between the Sb and / Bi compounds and Fe-O in the oxide film is -0.2x + 0.1≤H≤-1.2x + 0.5 (0.0
25 ≦ x ≦ 0.30) H: Sb and / or Bi per 100 parts by weight of MgO
Total amount of compound added (parts by weight) x: Fe-O amount in oxide film (g / m ² ) Fe-O: Total amount of Fe oxide in oxide (g / m ² )
² ) It is better to control the relationship. When Fe—O in the oxide is controlled in such a range, a product having an extremely good glass film and magnetic properties can be stably obtained in coil annealing.

The heat cycle at the time of raising the temperature in the finish annealing is as follows.
Performing soaking at a temperature of 40 Hr gives better results than with the annealing separator of the present invention. Naturally, in the coil state, the temperature rises rapidly in the outer peripheral portion and the edge portion, and the decomposition of hydrated water occurs at different timings in each portion of the coil. H ₂ O generated by the decomposition of hydrated water increases the degree of oxidation between the steel sheets, and in the case of coil annealing, causes unevenness in the degree of oxidation between the coil sheets. However, on the other hand, if the dew point between plates can be maintained properly, the decomposition of Fe—O in the oxide film is suppressed until the glass film is formed, and the decrease in reactivity is suppressed. Improving performance is important. In the annealing separator of the present invention, since the effect of improving the adhesion of the minute amount of hydroxide added in combination to the oxide film on the steel sheet and the effect of lowering the melting point of the Sb and / or Bi compound are large, the water content of the combined addition is small. Film formation is achieved with little need for For this reason, it is advantageous to sufficiently remove hydrated water from between the coils before forming the glass film. As a condition at this time, if the furnace temperature is less than 400 ° C., dehydration of the outer peripheral portion of the coil does not sufficiently occur, and the rate of bringing in moisture to a high temperature range is undesirably increased. On the other hand, if it exceeds 850 ° C., it is a temperature at which glass film formation and oxidation of the steel sheet already occur in this temperature range. Therefore, the coil is rapidly heated with a large amount of undecomposed water up to this temperature range or with a large temperature difference in the coil, which is likely to cause a peroxide-like film defect, which is limited. The holding time is 5 to 40 hours in the above temperature range. If it is less than 5 hours, the decomposition of water will be insufficient, and the problem of glass coating and magnetic deterioration due to excessive oxidation will occur. On the other hand, if it exceeds 40 Hr, the decomposition of water occurs sufficiently, but at the same time, the surface layer of the oxide film is reduced,
The amount of Fe-O is extremely low, and even if the annealing separator of the present invention is used, it is disadvantageous for the film formation, so that it is limited.

[0018]

【Example】

<Example 1> 0.05% by weight of C, 3.4% by weight of Si
5%, Mn: 0.10%, acid-soluble Al: 0.030%,
S: 0.0067%, N: 0.0070%, Sn: 0.
A material comprising 040% and the balance of Fe and unavoidable impurities was hot-rolled to 2.0 mm, annealed at 1120 ° C. for 2 minutes, pickled, and cold-rolled to a final thickness of 0.225 mm. Then 83
N ₂ 25% + H ₂ 75% at 90 ° C. for 90 seconds, dew point (D.
P) Decarburization annealing in an atmosphere of 68 ° C, and subsequently 750 ° C
For 30 seconds in N ₂ 25% + H ₂ 75% + NH ₃ so that the N content in the steel was 210 ppm. At this time, the Fe-based oxide amount of the steel sheet was 0.1 g / m ² . An annealing separator containing a hydroxide and a Sb, Bi compound having the composition shown in Table 1 was applied to the surface of the steel sheet, dried, and then dried at 1200 ° C.
At a final temperature of 20 hours. afterwards,
100 ml of 20% colloidal silica + 50% Al phosphate
An insulating coating agent consisting of 50 ml + 5 g of CrO ₃ was applied so that the weight after baking was 4 g / m ² , and baking was performed at 850 ° C.

[0019]

[Table 1]

Table 2 shows the results of the state of adhesion of the annealing separator to the steel sheet, the properties of the glass film, and the magnetic properties in this test.

[0021]

[Table 2]

As a result of this test, when the annealing separator of the present invention was used, the adhesion of the annealing separator to the steel sheet was good, and especially when 2 parts by weight of hydroxide was added, the adhesion was high. An excellent tendency was observed, and the glass film formation state after finish annealing was uniform and formed a glossy glass film. Also, in the case of the present invention, excellent results were obtained in both the magnetic flux density and the iron loss value in the case of the present invention.

On the other hand, when the hydroxide of the comparative material was not added, the adhesion to the steel sheet was poor, and when the Sb and / or Bi compound was not added, the magnetic properties tended to be considerably inferior. In addition, the stability of each of the glass films was poor, and the formation state was poor especially when no Sb or Bi compound was added. <Example 2> In weight%, C: 0.058%, Si: 3.3
5%, Mn: 0.12%, Al: 0.028%, S:
0.0070%, N: 0.0072%, Sn: 0.03
%, The balance being Fe and unavoidable impurities, the grain-oriented electrical steel sheet material was treated in the same manner as in Example 1 to obtain a final sheet thickness of 0.2.
It was 25 mm. This steel sheet was placed in a continuous annealing furnace at 845 ° C. for 90 seconds in an atmosphere of N ₂ 25% + H ₂ 75%. After decarburizing annealing by changing P, 25% of N ₂ + 75% of H ₂ +
The NH ₃ concentration was adjusted with NH ₃ atmosphere, the amount in the steel N 22
The nitriding treatment was performed so as to be 0 ppm.

As shown in Table 3, an annealing separator containing an Sb and / or Bi compound and a hydroxide was applied to a steel sheet having different Fe—O in the oxide film, dried, and dried at a temperature of 1200 ° C. A final finish annealing of 20 hours was performed. After that, an insulating film treatment was performed in the same manner as in Example 1 to obtain a product. Table 4 shows the results of the glass film and magnetic properties in this test.

[0025]

[Table 3]

[0026]

[Table 4]

As a result of this test, those using the annealing separator of the present invention exhibited excellent adhesion to a steel sheet, and all showed good glass film and magnetic properties as in Example 1. In particular, the amount of Fe oxide in the oxide film after nitriding annealing is set to 0.05 to 0.2.
In the case of 5 g / m ² , more excellent glass film and magnetic properties were obtained. On the other hand, in the case of 0.70 parts by weight of Bi oxychloride, which is outside the scope of the present invention, a scale-like and uneven coating was obtained, and the magnetic properties were also poor. When the particle size of the hydroxide is as large as 5 μm as in Comparative Example 2, the adhesion of the annealing separator to the steel sheet is poor, the film is slightly thin, the unevenness is locally generated, and the magnetic properties are slightly improved. Inferior results. <Example 3> Example 2 After performing decarburizing annealing-nitriding annealing-annealing separator applying treatment in the same manner as in the condition of the present invention 2, a 20-ton coil was finalized under the conditions shown in FIGS. Finish annealing was performed. Thereafter, baking of an insulating film and heat flattening were performed. Table 5 shows the magnetic characteristics of the film formation at each part of the coil at this time.

[0028]

[Table 5]

As a result of this test, in the case of the finish annealing condition-A in which the uniform annealing is not maintained during the finish annealing temperature raising process, a film defect occurs at the outermost and innermost edges of the coil, and the magnetic properties are inferior in this portion. It was observed. On the other hand, when the soaking is performed at 550 ° C. and 750 ° C. at the time of raising the temperature as in the annealing conditions B and C, a good glass film is formed over the entire length of the coil, and the magnetic properties are also very stable and good. Results were obtained.

[0030]

According to the present invention, in the coil annealing, the adhesion of the annealing separator to the steel sheet is improved by the added fine-particle hydroxide, and a uniform and strong coating film is formed. Further, the synergic effect of the S and / or Bi compounds added at the same time significantly enhances the glass film forming reaction, and provides excellent glass film and magnetic properties. Further, the present invention provides a manufacturing technique of a grain-oriented electrical steel sheet that can obtain more excellent glass coating and magnetic properties by improving the surface oxide after the nitriding treatment and the conditions of the final finish annealing.

[Brief description of the drawings]

FIG. 1 is an analysis of Fe—O (as FeO) in an oxide film of a steel sheet after nitriding annealing when adding Ca, Mg, Ba, and Al hydroxides and Sb and / or Bi to the annealing separator in the present invention. FIG. 3 is a diagram showing an optimal range with the amount.

FIG. 2 is a view showing an annealing cycle when adding a hydroxide, Sb, and a Bi compound to an annealing separator in Example 3 of the present invention.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 1/16 H01F 1/16 B (72) Inventor Osamu Tanaka 59 Nippon Steel Plant Design, 46 Ohara Nakahara, Tobata-ku, Kitakyushu, Fukuoka Prefecture Inside the corporation

Claims (3)

[Claims] C: 0.03 to 0.100% by weight
%, Si: 2.5 to 4.5% hot rolled sheet is annealed as required, and cold rolled once or twice with annealing to obtain a final sheet thickness, decarburized annealing, nitriding or immersion. In a method for producing a grain-oriented electrical steel sheet, comprising forming an inhibitor by sulfuric acid treatment, applying an annealing separator, performing finish annealing, and performing insulation coating treatment and heat flattening, the method includes the step of forming MgO on the steel sheet after the decarburizing annealing. : Average particle diameter 3 μm with respect to 100 parts by weight
0.1 to 5.0 parts by weight of one or more of the following hydroxides selected from Ca, Mg, Ba, Al and Sb and / or
Or one of Bi sulfate, chloride, oxychloride and oxide
A method for producing a grain coating and a grain-oriented electrical steel sheet having extremely excellent magnetic properties, characterized by adding 0.05 to 0.5 part by weight of a seed or two or more kinds. 2. The glass film according to claim 1, wherein the Sb compound is added in a range represented by the following formula according to the amount of Fe—O on the surface of the steel sheet after the decarburizing annealing. An excellent method for producing grain-oriented electrical steel sheets. −0.2x + 0.1 ≦ H ≦ −1.2x + 0.5 (0.0
25 ≦ x ≦ 0.30) H: MgO: Sb and / or Bi per 100 parts by weight
Compound Total amount (parts by weight) x: Fe-O content in the oxide film (g / m ²⁾ Fe-O: total amount of Fe oxide in the oxide (g / m
² ) 3. The glass coating according to claim 1 or 2, wherein the soaking is performed at a furnace temperature of 400 ° C. to 850 ° C. at a temperature of 400 to 850 ° C. during the final annealing. An excellent method for producing grain-oriented electrical steel sheets.