JP2002309378A - Separation agent for annealing and production method for grain oriented electromagnetic steel sheet glass coated - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grain oriented electromagnetic steel sheet which has an excellent glass coated and magnetic properties by using a high reactive separation agent for annealing, and which can control a bulk density, a fine particle distribution and the amount of Cl to be eluted into slurry by a produc tion method using a direct-fire rotary kiln. SOLUTION: The separation agent for annealing consists of a mixture of one or more kinds of MgO obtained from magnesium hydroxide by the reaction of bittern and/or seawater with slaked lime, and burnt by the direct-fire rotary kiln in the final stage of burning. The separation agent has a bulk density of 4 to 9 as a physical property, contains particles having a particle size of <=0.5 μm at least in >=5%, and fine particles having a particle size of <=1 μm in >=15%. The amount of Cl included in MgO is <350 ppm, and the ratio thereof to be eluted into water in a slurry control stage is >=70%. The production method for the grain oriented electromagnetic steel sheet uses the separation agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a process for forming a glass film in the final finish annealing of grain-oriented electrical steel sheet.
The present invention relates to an annealing separator for obtaining extremely excellent reactivity, and a method for producing a grain-oriented electrical steel sheet having an excellent glass coating using the same.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are usually made of Si: 2.5 to
A raw slab containing 4.5% is hot-rolled and subjected to one time of annealing and cold rolling of two or more times of annealing to obtain a final sheet thickness.
Next, decarburization, primary recrystallization, and formation of an oxide film mainly composed of SiO ₂ are performed in an H ₂ + N ₂ atmosphere by controlling the degree of oxidation.

As disclosed in JP-A-59-56522, Mn is 0.08 to 0.45% and S is 0.0
In the technology in which low-temperature slab heating is enabled by setting the temperature to 07% or less, a nitriding treatment is further performed after the decarburizing annealing. Thereafter, an annealing separator containing MgO as a main component is applied to the steel plate in the form of slurry, dried, wound around a coil, and subjected to final annealing. Thereafter, an insulating coating agent is applied, dried, baked and heat flattened to obtain a final product.

In this glass film forming reaction, MgO, which is the main component of the annealing separator, and SiO formed during decarburization annealing are used.
₂ Forsterite (Mg ₂
An SiO ₄ ) -based coating is formed. In the forsterite forming reaction, the properties of MgO have an extremely large effect along with the oxide film generated by the decarburizing annealing and the finish annealing conditions. It is also important to use an appropriate amount of an additive added to MgO as a reaction accelerator. By comprehensively optimizing these, the oxide film on the surface of the steel sheet is kept stable until the glass film is formed, the glass film is formed from a low temperature range, and non-uniform reactions such as additional oxidation are suppressed to achieve uniform glass. A coating can be formed.

Performing a uniform glass film formation reaction from a low temperature range in this way leads to stabilization of the inhibitor in steel up to a high temperature range, and together with an effect of improving the glass film,
The effect of improving magnetic properties is brought about. As a technique for improving the annealing separator MgO, for example, Japanese Patent Application Laid-Open No. 6-33138 discloses that as the MgO, the citric acid activity is 100 to 400 seconds at a reaction rate of 40% and 10% under a condition of a final reaction rate of 80%.
The hydration water content is 2.5% or less when stirred at a water temperature of 20 ° C. for 60 minutes, the average particle size is 2.5 μm or less, and the 325 mesh non-passing component is 5%
A technique for improving the glass film and magnetic properties of a material using AlN and Sb as inhibitors by using the following materials has been proposed.

Japanese Patent Application Laid-Open No. 11-269555 discloses that MgO is used as a main component and CAA 70% is 250 to 10%.
00 seconds, CAA 70% value / CAA 40% value is 1.5
~ 6.0, the particle diameter 20% value is 1.2 μm or less, B
An annealing separator having an ET value of 15 to 35 m ² has been proposed. JP-A-11-181525 discloses that as a MgO, a Mg element-containing raw material for producing MgO is calcined to obtain MgO, and this MgO is rehydrated to have a specific surface area of 4 to 15 m ² and a C-axis average diameter of crystallite. 50-12
And 00nm of Mg (OH) _2, the Mg (OH) ₂ to 40% CAA value obtained by re-sintering in a rotary kiln 40 to 100 seconds, a specific surface area of 12~35m ^2, Ig-L
MgO having an oss of 0.7 to 2.8% has been proposed.

Further, as a technique for improving a glass film forming reaction by an additive to an annealing separating agent, for example, Japanese Patent Application Laid-Open No. Hei 8-1
No. 65521 discloses that the present inventors, as a glass coating of a low-temperature slab heating material using AlN as an inhibitor and a technology for improving magnetic properties, use one, two or more halogen compounds per 100 parts by mass of MgO as F, Cl, Br. , I
The slurry containing 0.015 to 0.120 parts by mass is applied, and the region of 850 to 1100 ° C. in the finish annealing is 12 ° C. /
There has been proposed a technique of increasing the temperature below Hr.

As described above, it has been attempted to improve the quality of the grain-oriented electrical steel sheet by improving the MgO properties and the reaction accelerator, thereby improving the glass film forming reaction. However, in finish annealing by coil annealing, particularly in a large coil, there is a problem that the quality of the glass coating varies due to a material component, an oxide film forming condition, a non-uniform temperature in the coil, a difference in air permeability of atmosphere gas, and the like. For this reason, further improvement of the annealing separator is desired.

[0009]

The object of the present invention is to improve the properties and additives of MgO in the prior art by changing the composition of steel and decarburizing annealing. In order to solve the problem that a film cannot be obtained, the annealing separator is improved. That is, the present invention
By improving the bulk specific gravity, particle size, activity distribution, impurities, etc. of the annealing separator, it is excellent in coatability and adhesion, low hydration, high reactivity, a new annealing separator, and glass coating using it An object of the present invention is to provide a method for producing an excellent grain-oriented electrical steel sheet.

[0010]

SUMMARY OF THE INVENTION The present invention relates to an annealing separator MgO having excellent reactivity and a method for producing a grain-oriented electrical steel sheet for forming an excellent glass coating using the same. Make a summary. (1) Magnesium hydroxide is obtained using bitterness and / or seawater as a starting agent, and the final stage of firing comprises one or a mixture of two or more MgOs fired by a direct-fire rotary kiln, and has a bulk specific gravity of 4 -9, containing at least 5% or more of particles having a particle size of 0.5 μm or less and 15% or more of particles having a particle size of 1 μm or less as particles in water measured by a laser diffraction type particle size meter, and the Cl content in MgO is 3
An annealing separator comprising less than 50 ppm and a rate of elution into water of 70% or more in a slurry adjusting step. (2) The activity distribution is characterized by having a CAA 40% value of 45 seconds or more, and an activity of T20 value ≤ 300 seconds as measured using a PH stat at 0.1 N HCl at 20 ° C. The annealing separator according to the above (1). (3) C: 0.03 to 0.100%, Si: 2.5 to
An electromagnetic steel slab containing 4.5% and a normal inhibitor component is hot-rolled, and annealed sheet annealing is performed or not, and a final thickness is obtained by cold rolling once or twice or more with and without annealing, and decarburization annealing. A method for producing a grain-oriented electrical steel sheet having an excellent glass coating, comprising applying the annealing separating agent according to claim 1 or 2 as a slurry, performing final annealing, performing insulating coating treatment, and performing heat flattening. (4) The method for producing a grain-oriented electrical steel sheet having an excellent glass coating according to (3), wherein a Cl compound is added to the slurry so that the total amount of aqueous Cl becomes 300 to 600 ppm. (5) A grain-oriented electrical steel sheet having an excellent glass coating as described in (3) or (4) above, wherein 1 to 7 parts by mass of a Ti compound is added as Ti to 100 parts by mass of MgO as an annealing separator slurry. Manufacturing method. (6) The amount of the annealing separator applied to the surface of the steel sheet is MgO, 4.5 to 10 g / m ² per one side of the steel sheet, and the amount of water adhering to the surface of the steel sheet after drying is 0.054 to 0.250 g.
/ M ² and then, the finish annealing Atsushi Nobori process 750 ° C. after PH ₂ O
Manufacturing method (3) to (5) oriented electrical steel sheet excellent in any of the glass coating, characterized in that the annealing / PH ₂ as 0.01 or less. (7) The method for producing a grain-oriented electrical steel sheet having an excellent glass coating according to any one of (3) to (6), wherein nitriding is performed after decarburizing annealing to finish annealing.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have determined the bulk specific gravity of MgO applied to a grain-oriented electrical steel sheet after decarburizing annealing, the composition conditions of fine particles, the particle activity, the elution conditions of contained impurities in a slurry, and the like. By comprehensively examining and improving these, we succeeded in obtaining an excellent glass coating over the entire surface of the coil with low hydration.

According to this, the coatability and adhesion to the steel sheet of MgO, which cannot be realized by the prior art, can be obtained, the temperature of the glass film can be reduced, and a uniform glass film can be formed. As a result, in coil annealing, uniformity and stability of the glass coating are obtained, and a reduction in the coating defect rate is achieved. In addition, an improvement in the glass film forming reaction leads to an improvement in magnetic properties.

In the present invention, the bulk specific gravity, fine particle distribution and activity distribution of MgO used as the main component of the annealing separator used as the main component of the annealing separator, the amount of Cl contained in MgO and the It is characterized by its solubility in the slurry and the amount of Cl added according to this solubility and controlled to a constant amount. By properly controlling these, MgO
The wettability, adhesion, and hydration of the product are properly maintained, and a product having an excellent glass coating can be obtained.

First, the method for measuring the bulk specific gravity described in the present invention will be described. The bulk specific gravity in the present invention is a constant mass (10
g) MgO was weighed and dropped from a fixed height (5 cm) into a graduated cylinder-shaped volume measuring device having a funnel-shaped sample dropping part, and the volume was measured. The volume (cc) / mass (g) ). The particle size measuring method used in the present invention is based on a commercially available laser diffraction type particle size measuring method, and is measured using water as a MgO dispersion solvent. In this measurement, the slurry is subjected to an ultrasonic dispersion treatment for the purpose of minimizing the dispersion due to aggregation during the preparation of the slurry, and then the measurement is performed.

Next, the CAA value is based on a normal citric acid activity test, and is an index representing the hydratability of MgO. When 2 g of MgO powder is added to 100 ml of 0.4N citric acid aqueous solution, the CAA value is 30%. The time required for the pH to reach 8 at ° C is a numerical value expressed in seconds. An important activity evaluation test PH stat value in the present invention is a commercially available P value.
Measure using an H-stat meter. First, a 200 cc beaker was set in a thermostat at 20 ° C., 100 ml of deionized water was added, 40 mg of a weighed sample was charged, and the mixture was stirred and dispersed with a magnetic stirrer for 30 seconds.
Soak the set of H meter electrode and syringe and immediately
Start the H-stat and recorder. T from recorder
5, T10 and T20 are obtained. Here, T5 is 0.1N
-Means the time when the HCl consumption reaches 1.0 ml.
T20 defined in the present invention corresponds to 4.0 ml.

Next, a description will be given of the reasons for limiting the conditions specified in the present invention. The raw material in the magnesium hydroxide production stage applied to the production of MgO according to the present invention is Mg (Mg) obtained by a reaction with Ca (OH) ₂ or the like using either MgCl ₂ from bitter and Mg ion raw material from seawater. O
H) It is obtained by mixing one or more of MgO obtained by firing ₂ . When two or more kinds are mixed, MgO having the physical property values of the present invention may be adjusted in any of the bitter / seawater stage, the stage after the reaction with Ca (OH) _2, and the stage after calcination. .

Here, as the firing conditions in the present invention, firing at least in the final stage is limited to a direct-fired rotary kiln fired product. In the case of rotary kiln firing, there is a method of firing with a rotary kiln of a direct fire type or an inter-heating type. The reason for limiting to the direct fire type in the present invention is that
In order to satisfy the conditions such as purity, activity distribution, and particle size, the fired product in a direct fire furnace is stable and good. That is, since the inter-heating furnace fired product has low firing efficiency at the time of firing, in order to obtain the desired purity, it must necessarily be fired at a high temperature and for a long time. There is a problem that cannot be avoided.

[0018] For this reason, the activity of MgO is extremely reduced when trying to obtain the same active particles from the same raw material as compared with direct firing. In particular, the single firing method is limited because MgO having high reactivity that satisfies the bulk specific gravity, particle size condition and activation condition of the present invention cannot be obtained. As the physical property value condition of MgO used in the present invention, first, the bulk specific gravity is 4 to 9. Bulk specific gravity, including particle size, firing conditions and shape,
It depends on the MgO production conditions and is important for obtaining a uniform coating film, reactivity, etc. in the coating process.

The present inventors have pursued the effect of the bulk specific gravity in the on-site production. As a result, if the bulk specific gravity is less than 4, the stability of the slurry is reduced, and a uniform coating film cannot be obtained. It has been found that the adhesion is remarkably reduced, and the stability of the coating film and, consequently, the glass film forming property are greatly affected. When the bulk specific gravity is more than 9, the viscosity of the slurry becomes too high, and not only is it difficult to control the slurry and control the wettability, but also it is necessary to suppress the hydration in the slurry adjustment step and the coating line. Limited because of difficulty.

When the bulk specific gravity is 4 to 9, a good coating state and good adhesion can be obtained under ordinary slurry water mixing conditions and coating and drying conditions. Also, the glass film forming reaction shows a considerable correlation. When the bulk specific gravity is less than 4, the reaction tends to be poor, and when the specific gravity exceeds 9, a peroxide-like defect occurs, and a stable glass film is hardly obtained. Next, what is important in the present invention is the conditions for forming the fine particles. As for the ratio of fine particles, particles having a particle size of 0.5 μm or less
% And at least 15% of particles having a size of 1 μm or less. The present inventors changed the manufacturing conditions in the MgO manufacturing stage, and studied the effects of the fine particle composition conditions. As a result, in the case of MgO in which the condition of the fine particles is controlled within the above range, the wettability of the slurry and the adhesion after drying are improved.
It was found that the glass film was extremely good in forming properties, a uniform and good glass film was formed in a large coil, and the effect of improving the magnetic properties was extremely large.

As the fine particle distribution, compatibility of 0.5% or less and 5% or more and 1 μm or less and 15% or more is important. Under the condition that even if 1% or less and 15% or more are satisfied, 0.5% or less and 5% or more are not satisfied. However, the reactivity is lower than the former, which is not sufficient. Further, those having a small amount of fine particles that do not satisfy any of them are not preferable because the reactivity is extremely poor. This is presumably because, in the early stage of the glass film formation reaction, fine particles having an important role in the reactivity selectively act.

Next, as the MgO of the present invention, the Cl content is 3
It is important that the content of Cl is less than 50 ppm and the proportion of Cl dissolved in the slurry accounts for 70% or more. The present inventors have found that the role of Cl in MgO, as described in the prior art, has a glass film forming reaction promoting effect due to the effect of lowering the melting point of MgO in the presence of an appropriate amount. ing.

However, depending on the MgO production conditions, Cl
Is uniformly distributed in the central part of the MgO particles and the whole particles, so that the elution ratio at the time of preparing the slurry is in a relatively small range. The eluted Cl covers the vicinity of the surface of the particles in the coating and drying step, so that the reaction between MgO and SiO ₂ is efficiently promoted. On the other hand, Cl taken in the particles does not contribute to the reaction in the low temperature region in the early stage of the formation of the glass film in the finish annealing, and is released between the steel sheets in the high temperature region, which may have a bad influence on the film. .

[0024] The present inventors have proposed that Mg under various manufacturing conditions.
As a result of investigating the influence of the elution degree of Cl on O, when the dissolution ratio of Cl in the water slurry is 70% or more, a sufficient reaction promoting effect is obtained and there is no adverse effect. The solubility of Cl can be known by filtering MgO in a water slurry and analyzing the residue and the filtrate separately. The reason why the Cl content is set to 350 ppm is that the Cl content of 350 ppm or more is rather excessive in reaction depending on the steel composition and processing conditions, and a coating defect similar to excessive oxidation is likely to appear. This is to facilitate adjustment of the Cl amount according to the application conditions.

Next, the activity of the MgO of the present invention is evaluated by CAA conventionally used as a method for measuring the activity and the PH stat method newly proposed in the present invention. The present inventors have conducted extensive experiments and studies on the reactivity of the MgO activity and the glass film, and as a result, compared with the conventional CAA,
It was found that the activity evaluation using a stat was more excellent as a method for evaluating the reactivity of forming a glass film. That is, CAA
It has been found that, when the PH stat value is controlled under the condition that the activity is constant, it is possible to control more excellent glass film forming conditions.

First, desirable activation conditions for MgO used in the present invention are: CAA 40% value ≧ 45 seconds;
The H stat value is T20 ≦ 300 seconds. CAA
If the value is less than 45 seconds, the change over time of MgO itself is fast, and it is difficult to obtain stable quality. In addition, it is difficult to suppress the hydration of the slurry, and moisture is introduced between the coils, which is limited.

Next, as the PH stat value, T20 ≦ 3
Must be limited to 00 seconds. The present inventors have proposed that Mg
As a result of various studies on the activity evaluation method of O, even if the impurities and the CAA value which is the conventional activity evaluation method are the same, there is a difference in the glass reactivity, so the activity evaluation technique was examined. As a result, it was found that a finer difference in activity distribution can be found by using the PH stat method, and a more accurate difference in activity can be found.

The values such as T5 and T10 are also important for knowing the influence of the glass film formation on the initial reaction, but it has been found that the T20 value can be represented in the overall evaluation of the reactivity. In MgO controlled to the activity distribution as in the present invention,
An extremely excellent glass coating and improved magnetic properties can be obtained. If these conditions are not satisfied, the glass coating will be poorly formed and will be limited.

Next, conditions for producing a grain-oriented electrical steel sheet using the annealing separator of the present invention will be described. First, as a steel plate material to be applied, C: 0.03 to 0.100%, S
i: A slab containing 2.5 to 4.5% and a usual inhibitor component is used. C has a content of 0.03
%, The secondary recrystallization becomes unstable. Further, even when the secondary recrystallization is performed, the variation in the magnetic properties of the product is increased, which is limited. On the other hand, when the content is too large, more than 0.100%, formation of an oxide film in decarburizing annealing becomes disadvantageous, and annealing time becomes longer, thereby hindering productivity.

If the content of Si is less than 2.5%, it is difficult to obtain a product having a low iron loss. On the other hand, if the content of Si exceeds 4.5%, cracks and fractures occur frequently during cold rolling, making stable cold rolling work difficult. As the inhibitor component, any inhibitor such as MnS and AlN may be used. Further, a method of forming an inhibitor by subjecting a steel sheet to nitriding treatment after decarburizing annealing to finish annealing may be used.

The grain-oriented electrical steel sheet of the present invention may contain other steel components in addition to the above, but the present invention does not particularly limit the types and amounts of these components. In the production of a grain-oriented electrical steel sheet according to the present invention, the slab adjusted to the steel component is hot-rolled after slab heating, and cold-rolled one or more times to sandwich the annealing to a final sheet thickness, and then At 800 to 900 ° C., the degree of oxidation of the atmosphere gas is adjusted and decarburization annealing is performed to form an oxide film mainly composed of SiO ₂ on the surface of the steel sheet. The annealed separating agent of the present invention is applied as a slurry on a steel sheet subjected to the decarburizing annealing with a coating roll or the like, dried and wound into a coil.

The thus treated coil is subjected to final finishing annealing in a batch furnace in the state of the coil for 1 hour.
Long-time annealing for about 20 hours is performed in a temperature range of 100 to 1200 ° C. In this annealing step, glass film formation, secondary recrystallization, and purification treatment are performed. Then, after removing the excess annealing separating agent by water washing and light pickling, an insulating coating agent is applied, and heat flattening is performed by performing baking, coil shape correction, and strain relief annealing to obtain a final product.

When the annealing separator is used as a slurry, a Cl compound is used as a reaction accelerator, and the amount of aqueous Cl is 30%.
It is preferable to add so as to be 0 to 600 ppm.
If the amount of water-soluble Cl is less than 300 ppm, the effect of promoting the reactivity at the time of forming the glass film is weak and not sufficient. On the other hand, 600
If the content exceeds ppm, corrosion effects due to excess chlorine occur, and in particular, coating defects such as discoloration and scale are likely to occur near the center of the coil and at the edges. As the Cl compound, H
Cl, MgCl ₂ , CaCl _{2 and the} like are preferable.

Further, if a Ti compound is further added to the slurry, it is effective in improving the reactivity of forming a glass film. A preferable addition amount is 1 to 7 parts by mass as Ti with respect to 100 parts by mass of MgO. If the amount is less than 1 part by mass, the reactivity improving effect is not sufficient. On the other hand, if it exceeds 7 parts by mass, the reaction becomes excessive depending on the components of the material and the conditions for forming the decarbonated film, and defects on the scale and discoloration of the edge portion, which are peculiar to the excessive reaction, easily occur. When the amount is 1 to 7 parts by mass, an appropriate effect of improving the reactivity can be obtained, and the magnetic properties can be kept sound.

Further, in addition to the additives of the present invention, a boron compound, a sulfur compound, and the like are added to the slurry for the purpose of promoting the reaction of the glass coating, adjusting the atmosphere between plates, or strengthening the inhibitor.
Nitrogen compounds and oxides may be added in combination depending on the steel components and processing conditions. The conditions for applying the annealing separator to the steel sheet are as follows: the coating amount is MgO, and 4.5 to 4.5
10 g / m ² and the amount of water adhering to the surface after drying is 0.1 g
It is preferable to control the slurry adjustment conditions and the drying conditions so as to make the amount of the mixture between 054 and 0.250 g / m ² .

If the coating amount of MgO is less than 4.5 g / m ^2, it is difficult to form a glass film stably, and there is a case where seizure of an edge portion occurs during coil annealing, which is limited. On the other hand, if it exceeds 10 g, it becomes difficult to adjust the amount of water brought in between the steel sheets. If the amount of water adhering is less than 0.054 g / m ^{2, the} space between the coil plates becomes too dry, and the oxide layer formed during the decarburizing annealing is reduced in the course of the finish annealing heating, which may result in poor formation of the glass film. is there. Also, 0.250
On the other hand, when the amount exceeds g / m ² , the amount of water which is decomposed in the course of increasing the temperature of the adhering water increases.

In the application of the present invention, the finish annealing is performed in an N ₂ + H ₂ atmosphere at the time of raising the temperature, and the PH ₂ O / P after 750 ° C.
When H ₂ is 0.01 or less, the glass coating is more effectively improved. If the value exceeds 0.01, excessive oxidation defects called scales and scales on the outer periphery and edge of the coil are likely to occur.

[0038]

EXAMPLES (Example 1) C by mass; 0.075%, S
i; 2.28%, Mn: 0.068%, acid-soluble Al0.
028%, S: 0.024%, N: 0.0078%, S
n: 0.12%, Cu: 0.08%, a material consisting of the balance Fe and unavoidable impurities was hot-rolled to a thickness of 2.3 mm,
After annealing at 120 ° C. for 2 minutes, pickling is performed and the final sheet thickness is 0.225.
mm.

Next, 225 ° C. × 110 seconds, N ₂ 25
% + H ₂ 75%, continuous decarburization annealing at DP 70 ° C.
On the surface of this decarburized plate, bitumen was used as a starting material,
H) ₂ was adjusted, the firing conditions were changed, and as shown in Table 1, 4 parts by mass of TiO ₂ and 0.3 parts by mass of Na ₂ B ₄ O ₇ were added to 100 parts by mass of MgO whose bulk specific gravity and particle size distribution were changed. Part was added at a rate of 6.5 g / m ² per one side of the steel sheet, dried, wound on a coil, and then dried.
Final finish annealing at 20 ° C. × 20 hours was performed.

Then, 20% colloidal silica 100 m
An insulating coating agent consisting of l + 50% Al phosphate 50 ml + CrO ₃ 5 kg was baked at a rate of 4.5 g / m ² in terms of mass after baking, and heat flattening and baking were performed in a continuous furnace at a plate temperature of 850 ° C. The results are shown in Table 1.

[0041]

[Table 1]

As a result of this test, MgO having a composition ratio of bulk specific gravity and fine particle diameter of the present invention formed a very uniform coating film curtain at the time of coating, and a coating film having excellent adhesion was obtained. Further, the glass film after the finish annealing formed a uniform and good gloss glass film, and the result that the magnetic properties were also excellent was obtained. On the other hand, when the bulk specific gravity of the comparative example was too small, uneven coating occurred, the adhesion of the coating film was poor, the glass coating tended to be slightly thin, and the magnetism was poor.

When the bulk specific gravity is large, striped spots are generated on the coating film, and the adhesion is relatively good. However, the glass coating is inferior in appearance in which marbling and scale-like spots are scattered. It became a film. Also in this case, the magnetism was considerably poor. Further, in Comparative Examples 3 and 4 in which the particle ratio of the particle diameter of 0.5 μm did not satisfy the present invention, the results were that the glass coating was slightly thin and the magnetic properties were slightly inferior.

Example 2 C: 0.058% by mass, S
i; 3.30%, Mn; 0.11%, Al; 0.028
%, S: 0.0070%, N: 0.0074%. Sn;
A grain-oriented electrical steel sheet material containing 0.05% and the balance Fe and unavoidable impurities was treated in the same manner as in Example 1 to a final sheet thickness of 0.225 mm.

This steel sheet was placed in a continuous annealing furnace at 845 ° C. × 11.
0 _{seconds, N 2 25% + H 2} 75%, decarburization annealing in an atmosphere of DP 68 ° C., subsequently 750 ° C. × 30 seconds, N ₂
25% + H ₂ 75% + NH ₃ atmosphere in steel sheet nitrogen amount 215
The starting material was annealed to become ppm. On this steel plate,
Mg (OH) ₂ was prepared using seawater as a starting material, calcined in a direct-fired rotary kiln and an inter-heating rotary kiln, and 4 parts by mass of TiO ₂ with respect to 100 parts by mass of MgO having the activity shown in Table ₂ . 0.3 parts by mass of Na ₂ B ₄ O ₇ and water-soluble Cl according to the amount of Cl eluted from MgO.
Using HCl as a compound, the total amount of eluted Cl was 42
The slurry was adjusted to 5 ppm, applied, dried, and then subjected to finish annealing at 1200 ° C. × 20 hr and baking of the insulating coating agent in the same manner as in Example 1. Mg at this time
Table 3 shows the results of the application of O, the formation of the glass film, and the magnetic properties.

[0046]

[Table 2]

[0047]

[Table 3]

As a result of this test, when using MgO of the direct fire type rotary kiln firing satisfying CAA, PH stat value, bulk specific gravity, 1 μm or less% of the present invention, uniform and good coating film was obtained at the slurry coating and baking stage. Was obtained, the adhesion was good, and the glass coating after the finish annealing and the magnetic properties were good. On the other hand, even with direct firing sintering,
The bulk specific gravity is smaller than the invention example, the comparative example having a small elution Cl ratio, or the comparative example fired by an inter-heating rotary kiln, the glass coating and the magnetic properties are poor, especially the inter-heating kiln fired product is The result was considerably inferior to the present invention.

(Example 3) Table 4 shows the amount of adhering water and the amount of adhering water on the steel sheet surface using the MgO of Inventive Example 2 in Example 1 for the decarburized annealed steel sheet treated in the same manner as in Example 1. As described above, the slurry is adjusted and the drying conditions are adjusted, and the coating is performed.
Change the PH ₂ O / PH ₂ above 1200 ° C to 1200 ° C x 20
Finish annealing of Hr was performed. The temperature rise rate in this finish annealing was 15 ° C./Hr, and the temperature rise atmosphere gas was N ₂ 2.
The atmosphere gas after reaching 5% + H ₂ 75% and 1200 ° C. is H ₂ 1
Annealing was performed at 00%.

Next, an insulating film treatment was performed in the same manner as in Examples 1 and 2, and a glass film formation and magnetic properties were examined. The results are shown in Table 5.

[0051]

[Table 4]

[0052]

[Table 5]

As a result of this test, the adhesion amount of the annealing separating agent on the steel sheet surface was 5.5 to 7.5 g / m ² , and the attached moisture amount was 0.11.
In the case of 0 to 0.150, the finish annealing temperature is raised (700 ° C.
~) Under the condition of PH ₂ O / PH ₂ ≦ 0.008,
An extremely excellent glass film was formed, and the magnetic properties were also excellent. However, when the amount of adhesion is too small or too large as in Invention Examples 1 and 7, or when the moisture content of the steel sheet is not appropriate, the coating level tends to be inferior. (° C.) is highly oxidizable, the coating and the magnetic property level tend to be inferior even when the annealing separator of the present invention is used.

[0054]

According to the present invention, a glass coating can be formed by using a MgO whose bulk specific gravity, particle size distribution, and amount of chlorine in MgO and elution amount into a slurry are controlled by direct firing type rotary kiln firing. Improved reactivity,
A grain-oriented electrical steel sheet having extremely excellent coating properties and magnetic properties can be obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/02 C22C 38/02 (72) Inventor Akio Oguri 1-1 Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (72) Inventor Tsuyoshi Hamaya 1-1, Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture Nippon Steel Corporation Yawata Works (72) Inventor Takeshi Kimura Kitakyushu-shi, Fukuoka Prefecture Inside the Yawata Works, Nippon Steel Co., Ltd. 1-1, Tobata-cho, Tobata-ku (72) Inventor Haru Tanaka 59-46 Nakahara, Ohata, Tobata-ku, Kitakyushu, Fukuoka F-term (reference) 4K026 AA03 AA22 BA02 BB05 BB10 CA16 CA18 DA15 DA16 EA17 EB11 4K033 AA02 BA00 FA00 FA12 HA01 HA03 JA04 LA00 LA01 LA04 MA00 MA03 PA04 PA07 RA04 SA02 SA03 SA04 TA01 TA02 TA03 UA02

Claims (7)

[Claims] Claims: 1. A magnesium hydroxide is obtained from bitter and / or seawater as a starting agent, and the final stage of firing comprises one or a mixture of two or more MgOs fired by a direct-fired rotary kiln. Specific gravity of 4-9, the particle size in water measured by a laser diffraction type particle size analyzer is 0.
5% or less of particles is at least 5% or more, and particle size is 1μ
m and less than 15% of the particles
An annealed separating agent, wherein the amount of l is less than 350 ppm, and the rate of elution into water is 70% or more during the slurry preparation step. 2. The activity distribution is as follows: CAA 40% value: 45 seconds or more;
The annealing separator according to claim 1, wherein the agent has an activity of T20 value ≤ 300 seconds at an activity measured at 0 ° C. 3. C: 0.03 to 0.100%, Si:
Electromagnetic steel slabs containing 2.5-4.5% and normal inhibitor components are hot rolled and annealed, with or without annealing, to achieve a final thickness by one or two or more cold rollings with annealing. A method for producing a grain-oriented electrical steel sheet having an excellent glass coating, comprising decarburizing annealing, applying the annealing separating agent according to claim 1 or 2 as a slurry, performing final annealing, and performing insulating coating treatment and heat flattening. . 4. A Cl compound is added to the slurry,
The method for producing a grain-oriented electrical steel sheet having an excellent glass coating according to claim 3, wherein the total amount of the grains is 300 to 600 ppm. 5. An MgO 1 as an annealing separator slurry.
5. The method for producing a grain-oriented electrical steel sheet having an excellent glass coating according to claim 3, wherein 1 to 7 parts by mass of a Ti compound is added as Ti with respect to 00 parts by mass. 6. 6. The amount of the annealing separator applied to the surface of the steel sheet is set to Mg.
O is set to 4.5 to 10 g / m ² per one side of the steel sheet, and the amount of water adhering to the steel sheet surface after drying is 0.054 to 0.5 g / m ² .
And 250 g / m ^2, the glass film according to any one of claims 3 to 5 the PH ₂ O / PH ₂ of the finish annealing Atsushi Nobori process 750 ° C. after characterized by annealing as 0.01 or less An excellent method for producing grain-oriented electrical steel sheets. 7. The method for producing a grain-oriented electrical steel sheet having an excellent glass coating according to claim 3, wherein the nitriding treatment is performed after the decarburizing annealing to the finish annealing.