JP2008127635A - Method for coating annealing-separation agent for grain-oriented magnetic steel sheets, and method for manufacturing grain-oriented magnetic steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for newly evaluating magnesia for annealing-separation agent when a grain-oriented magnetic steel sheet is manufactured, and to stably obtain the grain-oriented magnetic steel shhet excellent in not only a film characteristic, but magnetic characteristic, by using the magnesia satisfying the characteristic value evaluated with the above evaluating method. <P>SOLUTION: As the magnesia in the annealing-separation agent, a powdery material having impurities with the concentrations 0.01-0.04 mass% Cl, 0.25-0.70 mass% CaO, 0.05-0.15 mass% B, 0.05-0.50 mass% SO<SB>3</SB>and satisfying 50-90 sec in 40% of CAA(citiric acid activity), and further, 1.5-2.5 mass% of a hydrate quantity at 20°C for 30 min of a hydrate-test, and 3.0-5.0 mass% of the hydrate quantity at 20°C for 180 min of the hydrate-test, is used. The annealing-separation agent which is hydrated so that the hydrate quantity of the magnesia becomes 1.0-3.5 mass% after coating and drying by making the slurry-state to this powdery material with the adjustment of the hydrate temperature and the average hydrate time of the slurry, is coated and dried on the surface of this steel sheet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technology for producing a grain-oriented electrical steel sheet used for a core material of a transformer or other electrical equipment, more specifically, a method for applying an annealing separator for a grain-oriented electrical steel sheet and a method for producing a grain-oriented electrical steel sheet, In particular, by defining powder characteristics suitable as magnesia, the main component of the annealing separator used for forsterite film formation, and adjusting the amount of hydration after coating to a certain range, It is intended to advantageously improve the film properties and magnetic properties.

The grain-oriented electrical steel sheet is mainly used as an iron core material for transformers and other electric devices, and is required to have high magnetic flux density and small iron loss and magnetostriction as magnetic properties.
In order to obtain a grain-oriented electrical steel sheet having excellent magnetic properties, it is important to obtain a secondary recrystallized structure highly integrated in the {110} <001> orientation, the so-called Goss orientation. In order to effectively develop such secondary recrystallization, it is first necessary to disperse a precipitation dispersed phase called an inhibitor that suppresses the growth of primary recrystallized grains to a uniform and appropriate size. Yes.

  As such an inhibitor, those having low solubility in steel such as sulfides, Se compounds and nitrides represented by MnS, MnSe, AlN and BN are used, and the slab before hot rolling is used. A method in which the inhibitor is completely dissolved during heating and finely precipitated in the subsequent steps is employed.

Recently, as an important point of secondary recrystallization, in addition to the presence of inhibitors, the misorientation angle of adjacent grains in the primary recrystallization structure has been attracting attention. It is reported in Non-Patent Document 1 that a grain boundary (high energy grain boundary) having an angle of 20 to 45 ° plays an important role. Based on this, research on grain-oriented electrical steel sheets that do not use inhibitors has been actively conducted, and even if steel slabs do not contain inhibitor components, they can be produced industrially. Technology (inhibitorless method) has been developed.
"Acta Material 45 (1997) 1285"

However, in any case, as a method for producing a grain-oriented electrical steel sheet, the steel slab is subjected to hot-rolled sheet annealing as necessary after hot rolling, and then once or two or more times sandwiching the intermediate annealing. It is said that the final sheet thickness is obtained by cold rolling, and after decarburization and primary recrystallization annealing, an annealing separator mainly composed of magnesia is applied to the steel sheet, followed by final finishing annealing for the purpose of secondary recrystallization and purification. The process is common. The surface of the grain-oriented electrical steel sheet thus obtained is formed with an insulating film mainly composed of forsterite (Mg ₂ SiO ₄ ) except for special cases, a so-called forsterite film. It is normal.

This forsterite film is formed by a reaction between magnesia applied as an annealing separator and an oxide layer mainly composed of SiO ₂ (silica) formed on the steel sheet surface layer during decarburization and primary recrystallization annealing. This coating effectively improves iron loss and magnetostriction not only by electrical insulation of the surface but also by applying tensile stress to the steel sheet due to its low thermal expansibility.

  In general, grain-oriented electrical steel sheets are coated with a glassy insulating coating on the forsterite coating, but the forsterite coating also acts as a kind of binder that adheres the insulating coating to the steel part. is there. Note that this insulating coating is very thin and transparent, so the forsterite film determines the final appearance of the product. Therefore, the quality of the appearance greatly affects the product value. For example, a film having a film in which part of the iron is partially exposed is regarded as inappropriate as a product, and the effect of the film properties on the product yield is extremely large. Therefore, the formed forsterite film is required to have a uniform appearance and no defects, and to have excellent adhesion so that the film does not peel off in shearing, punching and bending processes. Furthermore, the surface must be smooth and have a high space factor when laminated as an iron core.

  In addition to the above-described function, magnesia also has a function of affecting the magnetic properties by changing the decomposition / growth behavior of precipitates in the steel sheet and the growth behavior of crystal grains. For example, if too much moisture is brought into the slurry when magnesia is slurried, the steel sheet is oxidized and the magnetic properties are deteriorated, or point-like defects are generated in the coating. Furthermore, it is also known that the primary recrystallization behavior changes when impurities contained in magnesia penetrate into steel during annealing. Therefore, the quality of the impurity components and the powder characteristics of the annealing separator is an important factor that affects the coating characteristics and magnetic characteristics of the grain-oriented electrical steel sheet.

For this reason, various methods have been proposed for improving the quality of magnesia for annealing separators.
For example, Patent Document 1 discloses a method for forming a good forsterite film by specifying the impurity concentration, hydration amount, and sieving ability of magnesia fired at high temperature in a muffle furnace.
Japanese Examined Patent Publication No. 54-14566

Patent Document 2 discloses a technique for forming a good film by keeping the impurity concentration, specific surface area, particle size, and citric acid activity distribution of CaO, SO ₃ , B, etc. within a predetermined range. .
Japanese Patent Publication No.57-45472

Patent Document 3 discloses a BET specific surface area in which magnesium hydroxide having a BET specific surface area of 30 m ² / g or less is calcined and subsequently moisture-absorbed so that the number of OH groups per surface area: 100 ² is in the range of 15-30. There magnesium oxide 15 to 30 m ² / g: and 70～90Wt%, magnesium oxide having a BET specific surface area of 1 to 10 m ² / g: and 10 to 30 wt% by using MgO whose components, adhesion of the steel plate Methods have been disclosed for improving film properties and magnetic properties by increasing force.
Japanese Patent Publication No.57-8188

Patent Document 4 discloses a method for improving magnetic characteristics by using MgO having a MgO particle diameter of 0.08 to 0.18 μm measured from the expansion of the diffraction line width of X-ray diffraction.
JP 58-193373 A

  Furthermore, as described above, magnesia is applied to the steel sheet in the form of a slurry, but magnesia reacts with water to produce magnesium hydroxide, which becomes moisture brought into the steel sheet, and if it is too much, the forsterite film Adversely affects the formation and magnetic properties. It is known that the influence of this brought-in water is very large, and various methods for reducing the influence have been proposed.

For example, Patent Document 5 discloses a method for improving a forsterite film and iron loss by using an annealing separator obtained by adding TiO ₂ and A1 ₂ S ₃ or ZnS to MgO having a hydrated water content of 1 to 4%. Is disclosed.
Japanese Patent Laid-Open No. 53-15205

In Patent Document 6, MgO is fired at a high temperature of 1300 ° C. or higher to be inactivated, and when this is made into a slurry, the ignition loss rate at a temperature of 450 ° C. or higher is set to 2.0 to 10% by hydration in warm water. Thus, a technique for forming a good forsterite film is disclosed.
Japanese Patent Publication No. 60-33896

Patent Document 7 proposes a method of reducing hydration moisture by applying magnesia and then drying by heating at a heating rate of 80 ° C./s or more.
Japanese Patent No. 2634847

Patent Document 8 specifies the distribution of N ₂ gas adsorption isotherm and water vapor adsorption isotherm in addition to impurity concentration such as CaO, SO ₃ , B, particle size, hydration amount, citric acid activity (CAA 40%) A technique for improving the film properties and the magnetic properties by setting the above range is disclosed. Patent Document 9 discloses a technique for improving film properties and magnetic properties by controlling the pore volume within a specific range.
However, the N ₂ gas adsorption isotherm and pore volume are both indices that focus on the hydration of magnesia and the release process of water, and although effective to some extent, there are problems with measurement accuracy and ease of measurement. there were.
Japanese Patent No. 3695008 Japanese Patent No. 3707144

Further, Patent Document 10 discloses a technique in which a hydration amount curve at a temperature of 20 ° C. and a hydration time of 80 minutes or less satisfies a region surrounded by FIG. 1 in the document. Yes. However, although there is a description that the amount of moisture brought into the steel sheet is greatly influenced by the activity of MgO, the residence time when slurryed, the slurry water temperature, the stirring speed during slurry mixing, etc., Since the amount of hydration after coating and drying on a steel sheet is not specified, the effect of improving magnetic and film properties was insufficient. In addition, there is a problem that a sufficient effect cannot be obtained because the range of the prescribed MgO hydration amount is wide.
Japanese Patent Laid-Open No. 10-88241

Although the characteristics of grain-oriented electrical steel sheets have been improved and stabilized by the above technologies, it is difficult to say that sufficient effects are still being obtained, and product defects often occur due to differences in the production lots of magnesia. Yes, it can be said that the effect of changes in powder properties of magnesia on product properties has not yet been fully elucidated.
So far, as an index for evaluating magnesia, impurities such as CaO, Cl, B, and SO ₃ , citric acid activity, BET specific surface area and particle size distribution, and powders such as N ₂ gas adsorption isotherm and pore volume Properties have been used.
However, it is difficult to accurately determine the applicability of MgO based on these characteristics, and the influence of each powder characteristic on the product characteristics may be different from the tendency that has been said. Therefore, it has been strongly desired to find a more appropriate evaluation index for magnesia.

The present invention was developed in view of the above circumstances, and presents a new evaluation method for annealing separator magnesia during the production of grain-oriented electrical steel sheets, and magnesia satisfying the characteristic values evaluated by this evaluation method. By using it in an appropriate slurry state, the object is to stably obtain a grain-oriented electrical steel sheet having excellent coating properties and consequently magnetic properties.
That is, the present invention provides an advantageous application of an annealing separator for grain-oriented electrical steel sheets mainly composed of magnesia having a predetermined powder property in order to stably obtain a grain-oriented electrical steel sheet having excellent coating properties and magnetic properties. It aims at proposing a method with the manufacturing method of a grain-oriented electrical steel sheet.

The elucidation process of the present invention will be described below.
Now, in order to achieve the above object, the inventors have conducted various studies on magnesia conditions optimal for film formation.
As a result, Cl concentration impurity 0.01~0.04mass%, CaO concentration 0.25~0.70mass%, B concentration 0.05~0.15mass%, SO ₃ concentration 0.05~0.50mass%, at CAA40% 50 to 90 seconds Select a powder, then conduct hydration test at 20 ° C, 30 minutes and 20 ° C, 180 minutes, the former hydration amount is 1.5-2.5mass% and the latter hydration amount is 3.0-5.0mass% It was found that the frequency with which a good forsterite film is obtained is improved by using magnesia.

  Furthermore, in an actual production line, the annealing separator slurry is used by applying a certain amount and consuming a new amount, and adding it to the remaining slurry. Therefore, although the hydration temperature can be controlled to be constant, it is difficult to make the hydration time constant, so it is extremely difficult to make the amount of hydration constant over the entire coil length. This is because the amount of hydration of magnesia increases as the hydration temperature increases or the hydration time increases. The reason for this is that the increase in the amount of hydration is caused by the progress of hydration and part of magnesia becomes magnesium hydroxide. However, by controlling the hydration temperature and the average hydration time, it is possible to make the hydration amount within a certain range, for example, about 2.5 ± 0.3%.

  In Japanese Examined Patent Publication No. 61-47887, non-hydrated magnesium oxide calcined at 1100 ° C. or higher: 50 to 99 wt%, magnesium hydroxide 1 to 50 wt% and aluminum compound 0.1 to 0.5 wt% are blended. Has proposed a technique using an annealing separator adsorbed on the above non-hydrated magnesium oxide, but this technique does not change the amount of hydration at all even if the working (hydration) time is as long as 24 hours. It can be seen from FIG. 3 in the publication. However, investigations leading to the present invention have revealed that it is difficult to obtain a good forsterite film with magnesia in which the hydration amount does not change at all with respect to the hydration time. The reason for this is considered that magnesia, in which the hydration amount hardly changes even when the hydration time is increased, has a low forsterite film forming ability (reactivity) during finish annealing.

  In the actual production line, the present invention is the same as Japanese Patent Publication No. 61-47887 in that attention is paid to the necessity of making the amount of hydration almost constant. However, as magnesia, magnesia with different hydration amounts at 20 ° C, 30 minutes and 20 ° C, 180 minutes, as well as impurity concentration, etc. is used, considering the consumption of magnesia and the mixing pitch of the new slurry, etc. By controlling the hydration temperature and the average hydration time of the powder, it is a novel feature of the present invention that the amount of hydration of magnesia after the powder is applied in a slurry and applied and dried is within a certain range. is there.

That is, the gist configuration of the present invention is as follows.
1. Application method of annealing separator for grain-oriented electrical steel sheet comprising applying and drying annealing separator mainly composed of magnesia to decarburized annealing sheet for grain-oriented electrical steel sheet having oxide film containing SiO ₂ on steel sheet surface layer In
As magnesia in the annealing separator, Cl concentration impurity 0.01~0.04mass%, CaO concentration 0.25~0.70mass%, B concentration 0.05~0.15mass%, SO ₃ concentration 0.05~0.50mass%, CAA40% Satisfying 50 to 90 seconds, hydration amount by hydration test at 20 ° C for 30 minutes is 1.5 to 2.5 mass%, and hydration amount by hydration test at 20 ° C for 180 minutes is 3.0 to 5.0 mass% Using the powder that is
By adjusting the hydration temperature and the average hydration time of the slurry, water was applied so that the amount of hydration of magnesia after the slurry was applied in slurry form with water and dried was 1.0 mass% to 3.5 mass%. A method for applying an annealing separator for grain-oriented electrical steel sheets, wherein the annealed separator is applied to the surface of the steel sheet and dried.

2. A series of steel sheets with the final thickness are decarburized and annealed, an oxide film containing SiO ₂ is formed on the surface of the steel sheet, and then an annealing separator containing magnesia is applied and dried, followed by final finish annealing. In the method for producing a grain-oriented electrical steel sheet comprising the steps of:
As magnesia in the annealing separator, Cl concentration impurity 0.01~0.04mass%, CaO concentration 0.25~0.70mass%, B concentration 0.05~0.15mass%, SO ₃ concentration 0.05~0.50mass%, CAA40% Satisfying 50 to 90 seconds, hydration amount by hydration test at 20 ° C for 30 minutes is 1.5 to 2.5 mass%, and hydration amount by hydration test at 20 ° C for 180 minutes is 3.0 to 5.0 mass% Using the powder that is
By adjusting the hydration temperature and the average hydration time of the slurry, water was applied so that the amount of hydration of magnesia after the slurry was applied in slurry form with water and dried was 1.0 mass% to 3.5 mass%. A method for producing a grain-oriented electrical steel sheet, characterized in that a annealed annealing separator is applied to a steel sheet surface and dried.

  Use magnesia for annealing separator that satisfies the powder characteristics specified in the present invention, and in the actual production line, apply the powder in slurry form with water at the hydration temperature and average hydration time of the slurry. -By controlling the hydration amount of magnesia after drying within a certain range, a grain-oriented electrical steel sheet having excellent coating properties and magnetic properties can be obtained.

Hereinafter, the experimental results on which the present invention is based will be described. In addition, unless otherwise indicated, "%" display regarding the component composition of a steel plate shall mean mass% (mass%).
(Experiment 1)
C: 0.065%, Si: 3.34%, acid-soluble Al: 0.026%, N: 0.0087%, Mn: 0.074%, Se: 0.018%, Sb: 0.04% and Cu: 0.10%, the balance being Fe and inevitable Fifteen silicon steel slabs with an impurity composition were heated at 1400 ° C. for 30 minutes and hot-rolled to a thickness of 2.2 mm. Then, after normal annealing at 1000 ° C. for 45 seconds, it was cold-rolled to a thickness of 1.5 mm. After intermediate annealing at 1100 ° C. for 45 seconds, the final cold-rolled sheet thickness was 0.22 mm by the second cold rolling. At this time, the final cold rolling was performed such that the steel plate temperature immediately after the rolling roll exit side was 180 to 250 ° C. for at least one pass. Then, after decarburization and primary recrystallization annealing at a temperature of 850 ° C. in H ₂ —H ₂ 0-N ₂ , an annealing separator containing magnesia is applied and dried, and then final finish annealing is performed. went.

At this time, 15 kinds of powders (No. 1 to 15) having powder characteristics shown in Table 1 were used as magnesia. In Table 1, CAA40 (s) was measured using the method disclosed in JP-B-57-45472 (measurement at 0.4N citric acid at 30 ° C). Further, 8 parts by mass of TiO ₂ , ₂ parts by mass of Sr (OH) ₂ .8H ₂ 0, and 2 parts by mass of SnO ₂ were added to 100 parts by mass of each magnesia to obtain an annealing separator.
After that, as final finish annealing, heating was performed from 850 ° C. to 1150 ° C. at a rate of temperature increase of 15 ° C./h, followed by purification annealing at 1200 ° C. for 5 hours. Then, after removing the unreacted separating agent, an insulating coating mainly composed of magnesium phosphate, colloidal silica and chromic acid was applied to obtain a product plate.

The results of examining the magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ), film defect occurrence rate, and film adhesion of the _grain- oriented electrical steel sheet thus obtained are also shown in Table 1.
The film defect occurrence rate was evaluated using a laser type surface inspection apparatus, and the film adhesion was determined by winding test pieces around round bars having various diameters at intervals of 5 mm as the film bend adhesion. The minimum diameter that does not peel was evaluated.

As is clear from Table 1, in the comparison from No. 1 to No. 13, except for No. 2 where CaO and SO ₃ concentrations are high, the hydration amount in a hydration test at 20 ° C. for 30 minutes is 1.5 to 2.5. When magnesia with a hydration amount of 3.0 to 5.0 wt% (No. 7 to 13) is used at wt% and 20 ° C for 180 minutes (No. 7 to 13), the occurrence rate of film defects is reduced and good A film could be obtained. Also, good magnetic properties were obtained. On the other hand, even if the above hydration amount range is satisfied, No. 2 with high CaO and SO ₃ concentrations increases the film defect occurrence rate, and No. 1, ₃ to 6 does not satisfy the above hydration amount range. Then, the film defect occurrence rate was further increased and the adhesion was also deteriorated.
However, Nos. 14 and 15 were coated even though the hydration amount satisfied the above range, and the amounts of Cl, CaO, B and SO ₃ and CAA40 values were equivalent to those of Nos. 7 to 13. The properties and magnetic properties were not good.

In order to investigate this cause, the operating conditions of each line and the passage date were examined. As a result, magnesia No.14 and 15 was applied at a date and time different from that of magnesia No.1-13. It turned out that it was a hot day with high temperatures.
Usually, the hydration temperature of magnesia slurry is set to 20 ° C, but it seems that the hydration of magnesia is likely to proceed due to the high temperature of piping and steel sheets on hot days. Therefore, when No. 14 and 15 magnesia were applied, the amount of hydration after the actual application and drying was high, and it was assumed that good film and magnetic properties could not be obtained due to the effect. It was.

  Therefore, in order to verify the above estimation, the average hydration determined by the blending pitch of the new liquid slurry in consideration of the annealing separator slurry consumption determined by the line speed, the plate width of the steel sheet, the application amount of the annealing separator, etc. By controlling the time and hydration temperature of the slurry, the amount of magnesia hydration was varied within a certain range, and the effect of the amount of hydration after coating and drying on the coating properties and magnetic properties of grain-oriented electrical steel sheets was investigated. did.

(Experiment 2)
C: 0.073%, Si: 3.41%, acid-soluble Al: 0.023%, N: 0.0080%, Mn: 0.067%, Se: 0.02%, Sb: 0.037% and Cu: 0.08%, the balance being Fe and inevitable Ten silicon steel slabs with an impurity composition were heated at 1430 ° C. for 30 minutes and hot-rolled to a thickness of 2.4 mm. Then, after normal annealing at 1000 ° C. for 60 seconds, it was cold-rolled to 1.6 mm thickness, and after intermediate annealing at 1100 ° C. for 30 seconds, the final cold-rolled sheet thickness was 0.22 mm by the second cold rolling. At this time, the final cold rolling was performed such that the steel plate temperature immediately after the rolling roll exit side was 180 to 250 ° C. for at least one pass. Then, after decarburization and primary recrystallization annealing at a temperature of 850 ° C. in H ₂ —H ₂ 0-N ₂ , an annealing separator containing magnesia is applied and dried, and then final finish annealing is performed. went.

At this time, two types of powders (symbols A and B) having powder characteristics shown in Table 2 were used as magnesia. At that time, CAA40 (s) was measured using the method disclosed in the above-mentioned JP-B-57-45472. Each magnesia: 10 parts by weight of TiO ₂ per 100 parts by _{mass, Sr (OH) 2 · 8H} 2 0 to 3 parts by weight, and the annealing separator is added 4 parts by weight of Sn0 _2.
Furthermore, by controlling the hydration temperature and average hydration time of the slurry, the amount of hydration of magnesia after applying and drying the annealing separator slurry was made to be within a certain range shown in Table 3.

  After that, as final finish annealing, heating was performed from 850 ° C. to 1150 ° C. at a rate of temperature increase of 15 ° C./h, followed by purification annealing at 1200 ° C. for 5 hours. Then, after removing the unreacted separating agent, an insulating coating mainly composed of magnesium phosphate, colloidal silica and chromic acid was applied to obtain a product plate.

Table 3 shows the results of examining the magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ), film defect occurrence rate, and film adhesion of the _grain- oriented electrical steel sheet thus obtained.
The film defect occurrence rate was evaluated using a laser type surface inspection apparatus, and the film adhesion was determined by winding test pieces around round bars having various diameters at intervals of 5 mm as the film bend adhesion. The minimum diameter that does not peel was evaluated.

  As is clear from Table 3, by adjusting the hydration temperature and average hydration time of the slurry, the amount of hydration of magnesia after coating and drying was controlled in the range of 1.0 mass% to 3.5 mass%. In some cases, good film properties and magnetic properties could be obtained.

The inventors consider the reason why such a result is obtained as follows.
Conventionally, citric acid activity (CAA) is generally used as a method for evaluating the reactivity of magnesia for an annealing separator, that is, a film forming ability. In this method, an evaluation method using values at various reaction stages such as CAA40, CAA70, and CAA80 and their ratios has been proposed. In addition, methods using a BET specific surface area, an N ₂ gas adsorption isotherm, a water vapor adsorption isotherm, and the like have been proposed. However, since magnesia for annealing separator is slurried with water and used, the degree of time change in the amount of hydration in the hydration test is the closest to the process conditions than the conventional method, and the reactivity is improved. It is thought that it was because of the evaluation.
In addition to the powder holding properties of magnesia, the amount of hydration and moisture actually brought into the coiled steel sheet greatly affects the coating properties and magnetic properties, so the amount of magnesia hydration after coating is possible. Control as strictly as possible is considered to greatly contribute to the improvement and stabilization of the film characteristics and magnetic characteristics.

Now, as for the component composition of the grain-oriented electrical steel sheet targeted in the present invention, any conventionally known grain-oriented electrical steel sheet is suitable.
For example, the preferable range of C is 0.01% or more and 0.10% or less. That is, if the amount of C is less than 0.01%, a good primary recrystallization structure cannot be obtained. On the other hand, if it exceeds 0.10%, the decarburization load during decarburization annealing increases and productivity decreases.
Si is preferably in the range of 2.0% to 4.0%. In other words, Si is a useful component for increasing the electrical resistance of the product and reducing eddy current loss. However, if the content is not less than 2.0%, the crystal orientation is impaired by α-γ transformation during final finish annealing. On the other hand, if it exceeds 4.0%, there is a problem in cold-rollability.

  In addition to the above C and Si, an inhibitor constituent element is added. As the inhibitor, AlN, MnS, MnSe and the like are well known, and any of these may be used. For example, when MnS and / or MnSe is used, Mn: 0.05 to 0.20% and Se and / or S: 0.01 to 0.03% are preferable ranges. That is, if the Mn amount is less than 0.05%, or the S or Se alone or the total amount is less than 0.01%, the inhibitor function is insufficient, while the Mn amount exceeds 0.20% and the Se and S amounts are 0.03%. If it exceeds 50%, the temperature required for slab heating becomes too high, which is not practical. Moreover, when using AlN for an inhibitor, Al: 0.01-0.04% and N: 0.0050-0.012% are a suitable range. If the amount exceeds these upper limits, the AlN is coarsened and loses its restraining force. On the other hand, if the lower limit is not reached, the AlN amount is insufficient.

Further, Sb or Sn can be added as an auxiliary inhibitor for improving the magnetic properties. If the content of Sb is less than 0.005%, the effect of addition is poor. On the other hand, if it exceeds 0.10%, the decarburization property becomes very poor, so 0.005 to 0.10% is a suitable range. On the other hand, if Sn content is less than 0.03%, the effect of addition is poor. On the other hand, if it exceeds 0.30%, it becomes difficult to obtain a good primary recrystallized structure, so 0.03 to 0.30% is a suitable range.
Furthermore, Cu is an element effective for improving and stabilizing magnetic properties. However, if the content is less than 0.05%, the effect of addition is poor, while if it exceeds 0.20%, pickling and brittleness during hot rolling deteriorate, so 0.05 to 0.20% is a suitable range.

In addition to the elements described above, Mo, Cr, Ni, P, Bi, etc. can be added alone or in combination as a component for improving magnetic properties or film properties.
When the content of Mo is less than 0.005%, the effect of addition is poor. On the other hand, when the content exceeds 0.10%, decarburization deteriorates, so 0.005 to 0.10% is a preferable range.
When Cr content is less than 0.04%, the effect of addition is poor. On the other hand, when it exceeds 0.30%, it becomes difficult to obtain a good primary recrystallized structure, so 0.04 to 0.30% is a preferable range.
When Ni content is less than 0.03%, the effect of addition is poor. On the other hand, when Ni content exceeds 0.50%, the hot strength decreases, so 0.03 to 0.50% is a preferable range.
If the P content is less than 0.008%, the effect of addition is poor. On the other hand, if it exceeds 0.40%, it is difficult to obtain a good primary recrystallized structure, so 0.008 to 0.40% is a preferred range.
If the content of Bi is less than 0.005%, the effect of addition is poor. On the other hand, if it exceeds 0.20%, it becomes difficult to obtain a good primary recrystallized structure, so 0.005 to 0.20% is a suitable range.

Next, preferred production conditions for the grain-oriented electrical steel sheet of the present invention will be described.
The molten steel adjusted to the above components is cast by a continuous steel casting method or an ingot-making method by a steel making method conventionally used, and a slab is produced with a lump process interposed as necessary. Further, a thin cast piece having a thickness of 100 mm or less may be directly produced using a direct casting method.
Next, the slab is heated according to a normal method, and then hot rolled to form a hot rolled coil.

  After the above-described hot rolling, hot-rolled sheet annealing is performed as necessary, and then a cold-rolled sheet having a final thickness is obtained by one or more cold rolling or two or more cold rollings sandwiching intermediate annealing. The cold rolling may be performed at room temperature, or may be performed at a temperature higher than room temperature, for example, about 150 to 300 ° C. for rolling. Moreover, you may perform the aging treatment in the range of 150-300 degreeC in the middle of cold rolling once or several times.

The steel sheet having such a final thickness is subjected to decarburization (primary recrystallization) annealing in a wet hydrogen atmosphere. It is desirable to reduce the residual C amount to 0.004% or less by this decarburization annealing. At that time, it is important to form an oxide film containing silica (SiO ₂ ) on the surface layer of the steel sheet. In addition, you may perform the process which nitrides about 30-200 ppm steel plate following such decarburization annealing.

Thereafter, an annealing separator containing magnesia as a main agent is applied in a slurry state on the steel plate surface subjected to the decarburization annealing, and then dried. Here, in order to obtain good film characteristics, the magnesia powder characteristics are as follows: impurity Cl concentration is 0.01 to 0.04%, Ca concentration is 0.25 to 0.70%, B concentration is 0.05 to 0.15%, and SO ₃ concentration is Select powder with 0.05-0.50% and CAA40% value of 50-90 seconds, and further hydrated by 1.5-2.5 mass% at 20 ° C for 30 minutes and water at 20 ° C for 180 minutes It is important to use a powder having a hydration amount of 3.0 to 5.0 mass% according to the sum test.

Furthermore, it is necessary to actually hydrate the powder so that the amount of hydration of magnesia after it is slurryed with water, applied to a steel sheet, and dried is 1.0 mass% to 3.5 mass%. . Here, the amount of hydration in the actual line needs to be adjusted by the hydration temperature and average hydration time of the slurry. That is, in the production line, the annealing separator slurry is used by applying a certain amount and consuming it, and then adding a new amount almost commensurate with the consumption amount and adding it to the remaining slurry. Therefore, although the hydration temperature can be controlled to be constant, it is difficult to make the hydration time constant, so it is extremely difficult to make the amount of hydration constant over the entire coil length. This is because the amount of hydration of magnesia increases as the hydration temperature increases or the hydration time increases.
However, by controlling the hydration temperature and the average hydration time, the amount of hydration can be adjusted to a certain range, for example, a range of 2.5 ± 0.3%.

Here, the average hydration time can be determined, for example, as follows.
As an example, as shown in FIG. 1, when preparing a slurry, let us consider a case where 1/3 of the tank capacity for storing the slurry is prepared at a time. In this figure, the amount of 1/3 is blended every 30 minutes until the start of slurry application. The average hydration time at the start of application (a ₁ ) is
a ₁ = 1/3 x 1.5hr + 1/3 x 1hr + 1/3 x 0.5hr = 1hr
It becomes. And 1/3 of the amount is consumed every 1 hour of application to the steel plate, and if 1/3 of the amount is added and added each time,
a ₂ = 2/3 (remaining) × (1 + 1) hr ^* + 1/3 × 0hr = 1.33hr
(* Average hydration time at the start of application: 1 hr + 1 hr until addition)
It becomes. Similarly, during the second addition,
a ₃ = 2/3 × (1.33 + 1) + 1/3 × 0hr = 1.56hr
It becomes. Therefore, the average hydration time an _{+ 1} at the time of the nth addition in this example is
a _{n + 1} = 2/3 (a _n +1)
It is expressed by the recurrence formula. Here, since a ₁ = 1,
a _{n + 1} = 2− (2/3) ⁿ
The average hydration time in this example can be determined by the general formula:

  In addition, in order to control the hydration moisture content of magnesia after using the magnesia having the above-mentioned powder characteristics and applying and drying the powder in a slurry state to the range of 1.0 mass% to 3.5 mass% The hydration temperature of the slurry is set to 5 to 22 ° C. to control the above average hydration time. The average hydration time is determined by the blending amount per slurry, the blending interval of the new liquid slurry, and the consumption per unit time of the slurry. Therefore, in consideration of these factors, the average hydration time may be controlled so that the amount of hydration of magnesia after coating and drying is within the above range, and preferably this average hydration time is 20%. It should be in the range of ~ 90 minutes.

Further, as the auxiliary agent in the annealing separator used for improving the magnetic properties and film properties, conventionally known ones can be used, but in general, TiO ₂ , SnO ₂ , MoO ₃ , WO ₃ , CuO, oxides such as _{MnO, MgSO 4 · 7H 2 O} , SrSO 4, sulfides such as _{SnSO 4, Sr (0H) 2} · 8H 2 0 or hydroxides such as LiOH, Na ₂ B ₄ 0 B-based compounds such as ₇ and Sb-based compounds such as Sb ₂ 0 ₃ and Sb ₂ (SO ₄ ) ₃ are known. When these compounds are added, the addition amount is preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of magnesia, and one or two or more can be added individually or in combination. However, the total addition amount is desirably 20 parts by mass or less with respect to 100 parts by mass of magnesia.

Further, the annealing separator is preferably applied in a range of about 4 to 10 g / m ² per one side of the steel sheet. This is because if the coating amount is less than 4 g / m ^2, the formation of forsterite becomes insufficient. On the other hand, if it exceeds 10 g / m ² , the forsterite film is excessively formed and becomes thick. Because it invites.

Subsequently, final finish annealing consisting of secondary recrystallization annealing and purification annealing is performed by a conventionally known method.
Thereafter, a phosphate-based insulating coating, preferably an insulating coating that imparts tension, is applied to the steel sheet surface to obtain a product. The type of insulating coating is not particularly limited, and any conventionally known insulating coating is suitable. For example, a coating solution containing phosphate-chromic acid-colloidal silica described in JP-A-50-79442 and JP-A-48-39338 is applied to a steel plate and baked at about 800 ° C. The method is preferred.
Furthermore, performing a known magnetic domain refinement treatment after the final cold rolling, after the final finish annealing, or after forming the insulating coating is effective in further reducing iron loss.

Example 1
Contains C: 0.072%, Si: 3.41%, Mn: 0.072%, Se: 0.019%, acid-soluble Al: 0.024%, N: 83ppm, Cu: 0.10%, Sb: 0.041% and Ni: 0.2%, the balance Slabs for grain-oriented electrical steel sheets having a composition of Fe and unavoidable impurities were heated at 1420 ° C. for 30 minutes, and then hot-rolled to form a hot-rolled sheet having a thickness of 2.2 mm. Then, after hot-rolled sheet annealing at 1000 ° C. for l minute, the sheet thickness is 1.6 mm by the first cold rolling, and after intermediate annealing at 1100 ° C. for 1 minute, the final sheet thickness is 0.22 by the second cold rolling. Finished to mm. At this time, the second cold rolling was performed so that the steel plate temperature immediately after the exit side of the rolling roll was 150 to 250 ° C. for at least two passes.

Next, after degreasing the cold-rolled sheet to clean the surface, decarburization and primary recrystallization annealing at 840 ° C for 2 minutes in an H ₂ --H ₂ 0-N ₂ atmosphere was performed on the steel sheet surface layer. After forming an oxide layer containing silica (SiO ₂ ), magnesia: An annealing separator containing 10 parts by mass of TiO ₂ and 3 parts by mass of Sr (0H) ₂ · 8H ₂ 0 is added to 100 parts by mass of water. The slurry was applied as a slurry. Table 4 shows the hydration amount after coating and drying, which was controlled by changing the powder characteristics of the magnesia used at this time and the hydration temperature and average hydration time of the slurry.
Then, after retentive annealing at 850 ° C for 20 hours in a nitrogen atmosphere, secondary recrystallization annealing was performed to raise the temperature to 1150 ° C at a rate of 15 ° C / h in an atmosphere of nitrogen: 25% and hydrogen: 75%. After the application, final finish annealing was performed in a hydrogen atmosphere at 1200 ° C. for 5 hours, and then an insulating coating containing magnesium phosphate, chromic acid and colloidal silica as the main components was applied.

Table 4 shows the results of examining the magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ), coating appearance and coating adhesion of each product plate thus obtained.
The appearance of the film was evaluated as the film defect occurrence rate, and the film adhesion was evaluated as the bending adhesion of the film by wrapping a test piece around a round bar having various diameters at intervals of 5 mm and the minimum diameter at which the film did not peel off.

  As is apparent from Table 4, all of the inventive examples produced under the conditions according to the present invention have good magnetic properties and coating properties.

Example 2
Contains C: 0.039%, Si: 3.36%, Mn: 0.068%, Se: 0.020%, Cu: 0.12%, Sb: 0.025%, Mo: 0.012%, with the balance being Fe and inevitable impurities The slab for grain-oriented electrical steel sheet was heated at 1410 ° C. for 30 minutes and then hot-rolled to obtain a hot-rolled sheet having a thickness of 2.5 mm. Then, after hot-rolled sheet annealing at 1000 ° C. for 1 minute, the sheet thickness is 0.6 mm by the first cold rolling, and after final annealing at 1000 ° C. for 1 minute, the final sheet thickness is 0.22 by the second cold rolling. Finished to mm.

Next, after degreasing the cold-rolled sheet to clean the surface, decarburization and primary recrystallization annealing at 820 ° C for 2 minutes in an H ₂ --H ₂ 0-N ₂ atmosphere is performed on the steel sheet surface layer. After forming an oxide layer containing silica (SiO ₂ ), magnesia: annealing with 100 parts by mass of 2 parts by mass of TiO ₂ , 2 parts by mass of SrSO ₄ and 0.5 parts by mass of MgSO ₄ · 7H ₂ 0 The separating agent was applied in a slurry form with water. Table 5 shows the powder rest characteristics of magnesia used at this time and the amount of hydration after coating and drying controlled by changing the hydration temperature and average hydration time of the slurry.
Then, after holding for 50 hours at 850 ° C in a nitrogen atmosphere and performing secondary recrystallization annealing, the temperature was raised to 1180 ° C at a rate of 25 ° C / h in a hydrogen atmosphere, then 1180 ° C for 5 hours. After the final finish annealing for purification annealing, an insulating coating mainly composed of magnesium phosphate, chromic acid and colloidal silica was applied.

Table 5 shows the results of examining the magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ), coating appearance and coating adhesion of each product plate thus obtained.
The appearance of the coating film was evaluated as the film defect occurrence rate, and the coating film adhesion was evaluated as the bending adhesion of the coating film by wrapping a test piece around a round bar having various diameters at intervals of 5 mm, and the minimum diameter at which the coating film was not peeled off.

  As can be seen from Table 5, all of the inventive examples produced under the conditions according to the present invention exhibit good magnetic properties and coating properties.

Example 3
Contains C: 0.041%, Si: 3.32%, acid solubility: 68ppm, N: 44ppm, Sb: 0.046%, Mn: 0.11%, S + 0.405Se: 18ppm, Cu: 0.12% and Cr: 0.05%, the balance A plurality of slabs for grain-oriented electrical steel sheets having a composition of Fe and inevitable impurities were heated to 1200 ° C. and then hot rolled to form a hot rolled sheet having a thickness of 2.2 mm. Subsequently, after hot-rolled sheet annealing at 1050 ° C. for 1 minute, a cold-rolled sheet having a final sheet thickness of 0.29 mm was formed by cold rolling.

Next, after degreasing the cold-rolled sheet to clean the surface, decarburization and primary recrystallization annealing at 840 ° C for 2 minutes in an H ₂ --H ₂ 0-N ₂ atmosphere was performed on the steel sheet surface layer. After forming an oxidized skin containing silica (SiO ₂ ), an annealing separator containing 3 parts by mass of Ti0 ₂ and ₂ parts by mass of SrSO ₄ was applied to 100 parts by mass of magnesia as a slurry with water. . Table 6 shows the powder characteristics of magnesia used at this time and the amount of hydration after coating and drying controlled by changing the hydration temperature and average hydration time of the slurry.
Then, after holding for 50 h at 850 ° C. in a nitrogen atmosphere and performing secondary recrystallization annealing, the temperature was raised to 1100 ° C. at a rate of 25 ° C./h in a hydrogen atmosphere, then 1200 in an argon atmosphere. After final finishing annealing for 5 hours at 5 ° C., an insulating coating composed mainly of magnesium phosphate, chromic acid and colloidal silica was applied.

Table 6 shows the results of examining the magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ), coating appearance and coating adhesion of each product plate thus obtained.
The appearance of the coating film was evaluated as the film defect occurrence rate, and the coating film adhesion was evaluated as the bending adhesion of the coating film by wrapping a test piece around a round bar having various diameters at intervals of 5 mm, and the minimum diameter at which the coating film was not peeled off.

  As is apparent from Table 6, all of the inventive examples produced under the conditions according to the present invention exhibit good magnetic properties and coating properties.

It is the figure which showed the calculation point of the average hydration time in the case of mix | blending the quantity of 1/3 of the tank capacity | capacitance which stores a slurry at once when preparing a slurry.

Claims (2)

Application method of annealing separator for grain-oriented electrical steel sheet comprising applying and drying annealing separator mainly composed of magnesia to decarburized annealing sheet for grain-oriented electrical steel sheet having oxide film containing SiO ₂ on steel sheet surface layer In
As magnesia in the annealing separator, Cl concentration impurity 0.01~0.04mass%, CaO concentration 0.25~0.70mass%, B concentration 0.05~0.15mass%, SO ₃ concentration 0.05~0.50mass%, CAA40% Satisfying 50 to 90 seconds, hydration amount by hydration test at 20 ° C for 30 minutes is 1.5 to 2.5 mass%, and hydration amount by hydration test at 20 ° C for 180 minutes is 3.0 to 5.0 mass% Using the powder that is
By adjusting the hydration temperature and the average hydration time of the slurry, water was applied so that the amount of hydration of magnesia after the slurry was applied in slurry form with water and dried was 1.0 mass% to 3.5 mass%. A method for applying an annealing separator for grain-oriented electrical steel sheets, wherein the annealed separator is applied to the surface of the steel sheet and dried. A series of steel sheets with the final thickness are decarburized and annealed, an oxide film containing SiO ₂ is formed on the surface of the steel sheet, and then an annealing separator containing magnesia is applied and dried, followed by final finish annealing. In the method for producing a grain-oriented electrical steel sheet comprising the steps of:
As magnesia in the annealing separator, Cl concentration impurity 0.01~0.04mass%, CaO concentration 0.25~0.70mass%, B concentration 0.05~0.15mass%, SO ₃ concentration 0.05~0.50mass%, CAA40% Satisfying 50 to 90 seconds, hydration amount by hydration test at 20 ° C for 30 minutes is 1.5 to 2.5 mass%, and hydration amount by hydration test at 20 ° C for 180 minutes is 3.0 to 5.0 mass% Using the powder that is
By adjusting the hydration temperature and the average hydration time of the slurry, water was applied so that the amount of hydration of magnesia after the slurry was applied in slurry form with water and dried was 1.0 mass% to 3.5 mass%. A method for producing a grain-oriented electrical steel sheet, characterized in that a annealed annealing separator is applied to a steel sheet surface and dried.

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