JP6579078B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet, and more particularly to a method for producing a grain-oriented electrical steel sheet having high film tension and low iron loss and transformer noise at a high yield.

  The grain-oriented electrical steel sheet is mainly used as an iron core material of a transformer, and therefore is strongly required to have excellent magnetic properties, particularly low iron loss. Therefore, the grain-oriented electrical steel sheet is subjected to decarburization annealing that also serves as primary recrystallization annealing to the cold-rolled Si-containing steel sheet, and after applying an annealing separator mainly composed of MgO, secondary recrystallization is performed in finish annealing. In this way, the crystal grains are manufactured in a highly aligned manner in the {110} <001> orientation (so-called Goth orientation). The above-mentioned finish annealing requires about 10 days in total including annealing for secondary recrystallization and purification treatment for raising the temperature to a maximum of about 1200 ° C. Therefore, it is usually performed by batch annealing performed in a state of being wound around a coil. Yes.

During the above-mentioned finish annealing, the subscale mainly composed of SiO ₂ formed on the steel sheet surface during decarburization annealing and the annealing separator mainly composed of MgO applied to the steel sheet surface after decarburization annealing are MgO + SiO ₂ → A reaction of Mg ₂ SiO ₄ occurs, and a glassy forsterite film is formed on the surface of the steel sheet. The forsterite film has an effect of improving the magnetic properties by imparting tensile stress to the steel sheet surface in addition to imparting insulating properties and corrosion resistance, and is therefore required to be uniform and excellent in adhesion.

  However, this forsterite film is damaged by the flattening annealing performed after the finish annealing, and a desired tension cannot be obtained. Usually, after finishing annealing is completed, unreacted annealing separation agent is removed by washing or the like, a coating solution is applied, and planarization annealing is also performed for this baking. The flattening annealing is performed by applying tension in the rolling direction in order to correct the part of the coil that has been wound and deformed due to its own weight during the final annealing. By annealing under this tension, forsterite will crack in the direction perpendicular to the rolling. As a result, the tension in the rolling direction decreases while the tension in the direction perpendicular to the rolling remains. As a result, a compressive force is generated in the L direction according to the Young's modulus and Poisson's ratio of the steel sheet, and the magnetic properties deteriorate.

In order to solve such problems, in Patent Document 1, the amount of Al of the steel material to be used is set to 100 ppm or less, SnO ₂ or SnO is added to the annealing separator, and the tension during planarization annealing is 11.8 MPa. The following methods are proposed.

On the other hand, Patent Document 2 discloses a method of adjusting the addition amount of SnO ₂ in the annealing separator according to the concentration ratio of Al and N of the raw material. This technology increases SnO ₂ when the Al / N concentration ratio of the material is low, and conversely decreases SnO ₂ when the concentration ratio is high.

JP-A-2015-86414 Japanese Patent No.3734191

  By the method described in Patent Document 1, it has become possible to effectively suppress deterioration of the film tension due to planarization annealing. However, if the in-furnace tension of flattening annealing is lowered, correction of deformation due to coil winding and edge buckling becomes insufficient, so the coil ends must be cut off in large quantities when shipped as products. In other words, there arises a problem that the yield decreases. In addition, this technology can only be used for low-concentration materials with an Al concentration of 100 ppm or less, but in order to produce grain-oriented electrical steel sheets with higher characteristics, it is required to produce Al in a higher region. However, the method of Patent Document 1 could not be used with such a high Al material.

The technique described in Patent Document 2 is a technique for stabilizing secondary recrystallization, not considering the deterioration of the tension of the film due to the flattening annealing as described above. Therefore, SnO ₂ is reduced when the Al / N concentration ratio of the raw material is high, so that a sufficient tension improving effect cannot be obtained. In addition, SnO ₂ content can be increased when the Al / N concentration ratio of the material is low, but when the Al / N ratio is decreased with a high Al material, the N content must be increased. During steelmaking to hot rolling, gas is generated in the steel and surface defects such as blisters and holes are likely to occur.

  In this way, a technology that has a high magnetic flux density with a high Al material, no shape defects after flattening annealing, no surface defects such as blisters and holes, and a high iron loss improvement due to the tension effect of the coating has been developed so far It was not proposed.

  The present invention has been made in view of the above circumstances, and it is possible to improve the film tension and reduce the iron loss by using a high Al material capable of obtaining a high magnetic flux density without reducing the yield. It aims at providing the manufacturing method of a grain-oriented electrical steel sheet.

Hereinafter, experiments that led to the present invention will be described.
<Experiment 1>
Smelting steel containing C: 0.060 mass%, Si: 3.40 mass%, Mn: 0.07 mass%, Al: 0.030 mass%, N: 0.007 mass% (Al / N: 4.3), S: 0.015 mass% After steel slab by continuous casting method, heated to 1400 ° C, hot rolled to a hot rolled sheet with a thickness of 2.2mm, subjected to hot rolled sheet annealing of 1050 ° C x 60 seconds, then cold rolled The intermediate thickness was set to 1.7 mm, and after intermediate annealing at 1100 ° C. × 80 seconds, a cold rolled sheet having a final thickness of 0.23 mm was obtained by warm rolling at 200 ° C.

Subsequently, decarburization annealing was performed in a wet atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 57 ° C. and held at 830 ° C. for 100 seconds. After that, magnesium oxide is used as the main ingredient, titanium oxide as additive is 5% by mass in terms of Ti, tin monoxide is 1 to 15% by mass in terms of Sn, and SiO ₂ is variously in the range of 0.05 to 0.5% by mass in terms of Si. The annealing separator changed to was applied to the steel sheet surface and dried. In addition, Si and Sn were hardly contained in the impurity of MgO at this time. Further, when the particle size distribution of tin monoxide was measured, the content rate of particles having a particle diameter of 1.5 μm or more was 42%.

  This steel sheet is subjected to secondary recrystallization annealing and finish annealing including purification treatment at 1200 ° C for 7 hours in a hydrogen atmosphere, then the unreacted annealing separator is removed, and then a coating solution is applied to form a coating film. The flattening annealing was performed at 800 ° C. for 30 seconds for the same baking. At this time, the in-furnace tension of the flattening annealing was 12.8 MPa. About the steel plate after the flattening annealing, the magnetic properties and the tension of the undercoat after removing the coating film were measured. The tension of the base coating was calculated from the amount of warpage of the steel plate after removing the coating on one side by pickling. The results are shown in FIG. 1 and FIG.

  As shown in Fig. 1, the undercoat film tension is improved when the Sn content in the annealing separator is in the range of 2 to 10% by mass, but this tension value changes greatly due to slight differences in the Si concentration. You can see that That is, the effect of improving the tension is large when the Si content is in the range of 0.1 to 0.3% by mass, whereas the effect of improving by Sn is small when the Si content is 0.05% by mass or less or 0.4% by mass or more. Further, as shown in FIG. 2, the iron loss was greatly improved when the Si content was 0.1 to 0.3 mass% and the Sn content was 2 to 10 mass%, similar to the result of the base film tension.

  As described in Patent Document 1, it is conventionally known that the film tension changes depending on the amount of Sn, but in the high Al material, the present inventors contain a small amount of Si in the annealing separator. As a result, it was newly found that the effect of improving the tension of Sn is further enhanced. In such a high Al material, the present inventors consider the reason why the film tension and magnetic properties are improved by the coexistence of Sn + Si as follows.

  Patent Document 1 also describes that when Sn is added, cracks are less likely to occur in the coating. This is because the presence of Sn in the steel suppresses the elongation of the steel sheet during the flattening annealing and makes the coating less susceptible to damage. However, if the tension during flattening annealing is increased too much, this effect alone is insufficient, and the film tension is not necessarily increased. This is considered to be because when the tension during the flattening annealing is increased, the elongation of the steel sheet becomes too large and cracks occur in the coating.

In contrast, in this experiment, first, a steel ingot with a high Al concentration is used as the material. Thus, MgAl ₂ O ₄ is easily formed on the steel sheet surface during finish annealing. Here, the Si compound to be contained in trace amounts in the annealing separating agent react with MgO in the annealing earlier this Si compound finish annealing, Mg ₂ SiO ₄ is formed in the annealing separator. Therefore, Mg and O ions entering the surface of the steel sheet are trapped by the Si compound when the steel sheet in the initial stage of annealing is at a low temperature, and at the stage where Mg and O ions enter the steel sheet surface, the temperature of the steel sheet becomes high. It is thought that there is.

If a high Al material is simply used without adding a Si compound, the MgAl is formed because the Mg ions enter the steel sheet surface layer from the low temperature stage before the Al surface layer is concentrated. ₂ O ₄ is formed in the steel plate in a form separated from the upper part of the film, and cannot contribute to tension generation or film damage in the upper part of the film. On the other hand, Mg ion intrusion can be shifted to a high temperature side by adding a Si compound. For this reason, after the Al is sufficiently concentrated on the surface layer, Mg ions enter and MgAl ₂ O ₄ is formed on the upper part of the coating. It is considered that the MgAl ₂ O ₄ formed on the upper part of the film strengthens the film and suppresses film damage during flattening annealing.

  It is important that the Si compound is contained in a very small amount. When the content is large, Mg ions consumed in the annealing separator increase, so that the film formation performed on the surface layer of the steel sheet becomes poor and the film tension decreases.

Furthermore, it has been said that magnetic properties are deteriorated when a large amount of SnO ₂ is added with high Al / N, but the iron loss is suppressed by Si in the annealing separator. Conventionally, as disclosed in Patent Document 2, at high Al / N, Sn improves the wettability of MgO, thereby promoting film formation and increasing the atmospheric pressure between the coil layers by releasing released oxygen. It was said that the steel sheet was inhibited from absorbing nitrogen and the magnetic properties deteriorated. However, the inclusion of Si compound, the coil layer is opened by the reaction of MgO and SiO _2, by preventing the increase interlayer ambient pressure, would be able to suppress the deterioration of magnetic properties and easy to absorb nitrogen It is done.

  Such an effect becomes more effective by increasing the particle size of the Sn compound. This is because the reaction temperature range is shifted to a higher level by suppressing the solid-phase reactivity of the Sn compound, and the Sn compound decomposes to secure the coil layer and suppress the increase of the interlayer atmosphere pressure. .

The present invention is based on the above-described novel findings, and the gist of the present invention is as follows.
1. % By mass
C: 0.020% to 0.080%,
Si: 2.50% to 4.50%,
Mn: 0.03% to 0.30%,
Al: more than 0.010% and less than 0.030% and
N: 0.003% or more and 0.012% or less, with the balance being Fe and an inevitable impurity component composition subjected to one cold rolling or two or more cold rolling sandwiching intermediate annealing Cold-rolled steel sheet with the final thickness,
Subjecting the cold-rolled steel sheet to primary recrystallization annealing,
Applying an annealing separator to the cold-rolled steel sheet after the primary recrystallization annealing, and performing a finish annealing,
A method for producing a grain-oriented electrical steel sheet that is applied with a coating liquid and baked on the cold-rolled steel sheet after the finish annealing, and is subjected to flattening annealing at 800 ° C. or more and 900 ° C. or less,
The annealing separator contains 50% by mass or more of MgO, 2% by mass to 10% by mass of Sn compound in terms of Sn, and 0.10% by mass to 0.30% by mass of Si compound in terms of Si,
A method for producing a grain-oriented electrical steel sheet, wherein the furnace tension during flattening annealing is 6.9 MPa or more.

2. 2. The method for producing a grain-oriented electrical steel sheet according to 1 above, wherein a proportion of the Sn compound having a particle size of 1.5 μm or more is 30% or more.

3. The component composition further includes:
% By mass
Se: 0.003% to 0.030%,
S: 0.002% to 0.030%,
Ni: 0.010% or more and 1.500% or less,
Cr: 0.01% to 0.50%,
Cu: 0.01% or more and 0.50% or less,
P: 0.005% or more and 0.200% or less,
Sb: 0.005% or more and 0.200% or less,
Sn: 0.005% or more and 0.500% or less,
Bi: 0.005% or more and 0.100% or less,
Mo: 0.005% or more and 0.100% or less,
B: 0.0002% or more and 0.0025% or less,
Te: 0.0005% or more and 0.010% or less,
Nb: 0.001% to 0.010%,
V: 0.001% to 0.010%,
Ti: 0.001% to 0.010% and
Ta: The method for producing a grain-oriented electrical steel sheet according to 1 or 2 above, containing one or more selected from 0.001% to 0.010%.

  According to the present invention, using a high Al material capable of obtaining a high magnetic flux density, the film tension can be improved and the iron loss can be reduced without reducing the yield.

It is a graph which shows the relationship between Si and Sn addition amount in an annealing separation agent, and base film tension. It is a graph which shows the relationship between Si and Sn addition amount in an annealing separation agent, and an iron loss.

[Ingredient composition]
Hereinafter, the manufacturing method of the grain-oriented electrical steel sheet by one Embodiment of this invention is demonstrated. First, the reasons for limiting the component composition of the steel material (slab) will be described. In the present specification, “%” representing the content of each component element means “% by mass” unless otherwise specified.

C: 0.020% to 0.080%
When C is less than 0.020%, the grain boundary strengthening effect due to C is lost, and defects such as cracks in the slab are produced. On the other hand, if it exceeds 0.080%, it becomes difficult to reduce to 0.005% or less, which does not cause magnetic aging, by decarburization annealing. Therefore, C is in the range of 0.020% to 0.080%. Preferably it is 0.025% or more and 0.075% or less of range.

Si: 2.50% to 4.50%
Si is an element necessary for increasing the specific resistance of steel and reducing iron loss. If this effect is less than 2.50%, it is not sufficient. On the other hand, if it exceeds 4.50%, the workability deteriorates, and it becomes difficult to produce by rolling. Therefore, Si is set in the range of 2.50% to 4.50%. Preferably it is 2.80% or more and 4.00% or less of range.

Mn: 0.03% to 0.30%
Mn is an element necessary for improving the hot workability of steel. If this effect is less than 0.03%, it is not sufficient. On the other hand, if it exceeds 0.30%, the magnetic flux density of the product plate decreases. Therefore, Mn is set in the range of 0.03% to 0.30%. Preferably it is 0.04% or more and 0.20% or less of range.

Al: more than 0.010% and less than 0.030%
Al is an essential element in the present invention as an inhibitor constituent element. If it is 0.010% or less, the inhibitor effect is not sufficiently obtained. On the other hand, if it exceeds 0.030%, the secondary recrystallization becomes unstable and the magnetic characteristics greatly vary. Therefore, Al is more than 0.010% and 0.030% or less. Preferably, it is 0.015% or more and 0.030% or less. More preferably, it is 0.015% or more and less than 0.027%.

N: 0.003% to 0.012%
N is an element that constitutes AlN as an inhibitor together with Al. If it exceeds 0.012%, surface defects such as blisters and holes will occur. The lower limit may or may not be increased during the production process, but in either case it should be 0.003% or more. Below this value, even if a nitrogen increase treatment is performed, the inhibitor repressive power is insufficient, and secondary recrystallization is not sufficiently performed. Other than this, it is also possible to use S or Se.

  The basic components in the present invention are as described above, and the balance is Fe and inevitable impurities. Examples of such unavoidable impurities include impurities inevitably mixed from raw materials, production facilities, and the like. Further, in the present invention, other elements described below can be appropriately contained.

  In addition to the above components in the grain-oriented electrical steel sheet of the present invention, Se: 0.003% to 0.030%, S: 0.002% to 0.030%, Ni: 0.010% to 1.500%, Cr for the purpose of further improving the magnetic properties : 0.01% to 0.50%, Cu: 0.01% to 0.50%, P: 0.005% to 0.200%, Sb: 0.005% to 0.200%, Sn: 0.005% to 0.500%, Bi: 0.005% to 0.100 %, Mo: 0.005% to 0.100%, B: 0.0002% to 0.0025%, Te: 0.0005% to 0.010%, Nb: 0.001% to 0.010%, V: 0.001% to 0.010%, Ti: One or more selected from 0.001% to 0.010% and Ta: 0.001% to 0.010% may be added as appropriate.

  S and Se can be used as elements constituting inhibitors such as MnSe and MnS together with Mn. The composite precipitation of these precipitates and AlN makes it possible to stably exert a suppressive force even at a high temperature of secondary recrystallization annealing. If S: 0.002% or more or Se: 0.003% or more, a good secondary recrystallized structure can be obtained. Further, by making S: 0.030% or less and Se: 0.030% or less, better surface properties can be obtained. Therefore, it is preferable to set it within the range of Se: 0.003% to 0.030% and S: 0.002% to 0.030%.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
After melting the steel having the above-described component composition by a conventional refining process, a slab (steel material) may be produced by a conventionally known ingot-bundling rolling method or continuous casting method, or directly. A thin cast piece (steel material) having a thickness of 100 mm or less may be manufactured by a casting method.

[Heating and hot rolling]
The steel material is heated to about 1350 ° C. and subjected to hot rolling according to a conventional method. The conditions for hot rolling may be the same as before. For example, the rolling reduction is about 70% to 90%, and the thickness after hot rolling is 1.5 mm to 3.5 mm. The rolling end temperature is desirably 800 ° C. or higher. The coiling temperature after hot rolling is preferably about 300 ° C to 800 ° C.
Moreover, in the case of a thin slab, it may be hot-rolled, or the hot-rolling may be omitted and the process may proceed as it is.

[Hot rolled sheet annealing]
The hot-rolled sheet obtained by hot rolling is subjected to hot-rolled sheet annealing as necessary. In order to obtain good magnetic properties, the annealing temperature of this hot-rolled sheet annealing is preferably in the range of 800 to 1150 ° C. If it is less than 800 degreeC, the band structure formed by hot rolling will remain, it will become difficult to obtain the primary recrystallized structure of grain size, and the development of secondary recrystallization will be inhibited. On the other hand, when the temperature exceeds 1150 ° C., the grain size after hot-rolled sheet annealing becomes too coarse, and it becomes difficult to obtain a primary recrystallized structure of sized particles.

[Cold rolling]
The hot-rolled sheet or thin cast slab after heating, hot-rolling or after hot-rolled sheet annealing is cold-rolled to the final sheet thickness by cold-rolling at least twice with one cold-rolling or intermediate annealing. A board. The annealing temperature of the intermediate annealing is preferably in the range of 900 to 1200 ° C. Below 900 ° C, the recrystallized grains after the intermediate annealing tend to be finer, and the Goss nuclei in the primary recrystallized structure tend to decrease, leading to a decrease in the magnetic identification of the product plate. On the other hand, when the temperature exceeds 1200 ° C., the crystal grains become too coarse as in the case of hot-rolled sheet annealing, and it becomes difficult to obtain a primary recrystallized structure of grain size. The intermediate annealing time is preferably about 5 to 180 seconds. In addition, the process of the said cold rolling shall include warm rolling.
Moreover, the hot-rolled sheet described in the following steps includes thin cast pieces.

  Cold rolling with the final thickness (final cold rolling) is performed by raising the steel plate temperature during cold rolling to 100 to 300 ° C, or aging at a temperature of 100 to 300 ° C during the cold rolling. Applying the treatment once or a plurality of times is effective in improving the primary recrystallization texture and improving the magnetic properties.

[Primary recrystallization annealing]
The cold-rolled sheet having the final thickness is subjected to decarburization annealing that also serves as primary recrystallization annealing. The annealing temperature is 700 to 900 ° C., and the annealing time is 30 to 300 seconds. If it is less than 700 ° C. or less than 30 seconds, decarburization becomes insufficient or the primary recrystallized grain size becomes too small, resulting in deterioration of magnetic properties. On the other hand, when the temperature exceeds 900 ° C. or exceeds 300 seconds, the primary recrystallized grain size becomes too large and the magnetic properties are deteriorated.

[Application of annealing separator]
An annealing separator is applied to the steel sheet after the primary recrystallization annealing. As the main component of annealing separator, it contains 50% or more of MgO, Sn compound is 2% or more and 10% or less with respect to the whole separating agent in terms of Sn, and Si compound is 0.10% or more and 0.30 or more with respect to the whole separating agent in terms of Si. % Or less.

The Sn compound is used for allowing Sn to penetrate into the steel during the finish annealing and suppressing the elongation of the steel sheet during the flattening annealing. For this purpose, if the Sn conversion is less than 2%, the effect is small, while if it exceeds 10%, the secondary recrystallization structure changes and the magnetic properties deteriorate. Therefore, the range is 2% or more and 10% or less. Moreover, Si compound brings about the effect of the further improvement of tension | tensile_strength and prevention of deterioration of a magnetic characteristic by using it in combination with Sn compound. If it is less than 0.10% in terms of Si, the desired effect cannot be obtained. On the other hand, if it exceeds 0.30%, the coating becomes too thin and the adhesion deteriorates. Therefore, the range is from 0.10% to 0.30%. Both Sn and Si may be added as separating agent additives, or may be contained as MgO impurities.
Examples of the Sn compound include oxides, sulfates, borates, hydroxides, and oxalates, and any of them can be applied. Examples of the Si compound include oxides and various silicates such as Mg, Ca, Sr, and Al, and any of them can be applied.

  Further, the Sn compound contains 30% or more of particles having a particle diameter of 1.5 μm or more, thereby enhancing the effect of improving the film tension. This is because, by coarsening, the decomposition rate of Sn during the finish annealing is shifted to a higher temperature side, thereby raising the interlayer atmosphere pressure between the steel plates to the higher temperature side to suppress the influence on nitriding.

  In addition to the above, various conventionally known additives can be used for the annealing separator. For example, Mn, Mo, Fe, Cu, Ca, Sr, Ba, Zn, Ni, Al, K, Li, Ti, Na, Sb oxide, hydroxide, sulfate, carbonate, nitrate, borate, Chloride, sulfide and the like. These may be one kind or a mixture of two or more.

[Finish annealing]
After the annealing separator is applied, finish annealing is performed in a state where the steel sheet is wound in a coil shape, and a secondary recrystallized structure highly accumulated in the Goss orientation is developed and a forsterite film is formed.
The finish annealing temperature is preferably 800 ° C. or higher for the purpose of secondary recrystallization, and preferably 1100 ° C. or lower for the completion of the secondary recrystallization. Thereafter, in order to form a forsterite film, it is preferable that the temperature is subsequently increased to about 1200 ° C.

[Application of coating solution]
After the finish annealing, the steel plate coil is then subjected to water washing, brushing, pickling, etc. to remove the unreacted annealing separator adhering to the steel plate surface. Then, a coating solution is applied.
As the coating liquid, those conventionally used can be applied. For example, magnesium phosphate-silica coating, aluminum phosphate-silica coating, calcium phosphate-silica coating, etc. are often used. Further, chromate, titanate, and other additives can be added to these for improving hygroscopicity and heat resistance.

[Flatening annealing]
Thereafter, planarization annealing is performed. The annealing temperature at this time is in the range of 800 ° C. or higher and 900 ° C. or lower, and the furnace tension at that time is 6.9 MPa or higher. If the temperature is too low (less than 800 ° C.) or if the furnace tension is less than 6.9 MPa, the shape correction ability is insufficient and the yield decreases. On the other hand, if flattening annealing is performed at a temperature exceeding 900 ° C., the steel sheet creeps and iron loss is deteriorated. Therefore, the annealing temperature is set within the range of 800 ° C or higher and 900 ° C or lower. In order to further improve the shape, the furnace tension is preferably 12.0 MPa or more.

[Magnetic domain subdivision processing]
In order to further reduce the iron loss, it is possible to perform a magnetic domain fragmentation treatment after the flattening annealing. As a processing method, a method in which grooves are formed in a final product plate as in general, or a thermal strain or impact strain is introduced linearly or in a dot shape by laser irradiation or electron beam irradiation, and finally. For example, a method of forming a groove by etching the steel plate surface in an intermediate process, such as a steel plate cold-rolled to a plate thickness, can be used.
Other manufacturing conditions may follow the general manufacturing method of a grain-oriented electrical steel sheet.

Example 1
A steel slab consisting of C: 0.070%, Si: 3.43%, Mn: 0.08%, Se: 0.020%, Al: 0.020%, N: 0.007%, the balance Fe and unavoidable impurities is manufactured by a continuous casting method at 1350 ° C. After hot-rolling to a hot rolled sheet with a thickness of 2.4 mm, hot-rolled sheet annealed at 1000 ° C. for 50 seconds, and then with an intermediate thickness of 1.8 mm by primary cold rolling After intermediate annealing at 1100 ° C. for 20 seconds, secondary cold rolling was performed to finish a cold-rolled sheet having a final thickness of 0.23 mm, followed by decarburization annealing. Decarburization annealing was performed by holding at 840 ° C. for 100 seconds in a humid atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 55 ° C.

Then, as the annealing separator, the main ingredient MgO, and 0.10% of Si, and 2% of TiO ₂ in terms of Ti, of the different particle sizes various Sn compound was contained 3% of Sn terms powder The slurry was applied to the surface of the steel sheet and dried. Further, finish annealing accompanied by a purification treatment at 1200 ° C. for 10 hours was performed. The atmosphere of the finish annealing was H _{2 at} the time of maintaining at 1200 ° C. for purification treatment, and N ₂ at the time of temperature increase and decrease.

  Thereafter, the unreacted separating agent was removed, the coating liquid was applied, and flattening annealing was performed at 850 ° C. × 20 s at a furnace tension of 13.7 MPa to obtain a final product. Table 1 shows the film tension and iron loss at this time. From Table 1, good iron loss and tension were obtained when the annealing separator contained predetermined amounts of Si and Sn. Furthermore, it can be seen that the effect of improving the tension is further enhanced when an Sn compound containing 30% or more of particles having a particle size of 1.5 μm or more is used.

(Example 2)
A steel slab consisting of C: 0.065%, Si: 3.40%, Mn: 0.07%, Se: 0.020%, Al: 0.020%, N: 0.008%, balance Fe and unavoidable impurities is manufactured by continuous casting, 1400 ° C After hot-rolling to a hot-rolled sheet with a thickness of 2.4 mm, hot-rolled sheet annealed at 1000 ° C for 50 seconds, and then with an intermediate thickness of 1.5 mm by primary cold rolling After intermediate annealing at 1100 ° C. for 20 seconds, secondary cold rolling was performed to finish a cold rolled sheet having a final thickness of 0.20 mm and decarburized annealing. Decarburization annealing was performed by holding at 840 ° C. for 100 seconds in a humid atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 55 ° C.

Next, MgO is the main ingredient as an annealing separator, TiO ₂ is 2% in terms of Ti and 0.10% Si ₃ N ₄ in terms of Si, and tin monoxide with a particle size of 1.5 μm or more is 50% in terms of Sn. Powders containing 3% and 0% were applied in the form of a slurry to the steel sheet surface and dried. Further, finish annealing accompanied by a purification treatment at 1200 ° C. for 10 hours was performed. The atmosphere of the finish annealing was H ₂ when maintaining at 1200 ° C. for purification, and N ₂ when raising and lowering the temperature. Thereafter, the unreacted separating agent was removed, the coating liquid was applied, and planarization annealing was performed at 850 ° C. × 20 s and in-furnace tension: 5.9 MPa and 12.7 MPa to obtain a final product.

  Table 2 shows the film tension, iron loss, and coil shape defect occurrence rate at this time. From Table 2, it can be seen that when the annealing separator contains predetermined amounts of Si and Sn, good iron loss and tension can be obtained. These are not deteriorated even when the furnace tension is increased. On the other hand, under the condition where Sn is not added, when the in-furnace tension is increased, the film tension is remarkably deteriorated and the iron loss is reduced. Further, when the furnace tension was low, the shape defect occurrence rate was remarkably increased. From this, it can be seen that shape defects such as ear elongation and ear distortion are not corrected by flattening annealing. Under the conditions in which the Sn compound is added and the in-furnace tension is increased, the film tension, the iron loss, and the shape defect rate are compatible and good results are obtained.

(Example 3)
A steel slab having the composition shown in Table 3 and the balance consisting of Fe and inevitable impurities is manufactured by a continuous casting method, heated to a temperature of 1350 ° C., and then hot-rolled to a thickness of 2.4 mm. After hot-rolled sheet annealed at 1000 ° C for 50 seconds, intermediate sheet thickness of 1.8mm by primary cold rolling, after intermediate annealing at 1100 ° C for 20 seconds, secondary cold It was rolled and finished into a cold-rolled sheet with a final sheet thickness of 0.27 mm and decarburized and annealed. Decarburization annealing was performed by holding at 840 ° C. for 100 seconds in a humid atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 55 ° C.

Next, MgO with an impurity Si concentration of 0.05% as the main agent as an annealing separator, TiO ₂ with 2% in terms of Ti, and SnO ₂ with a particle size of 1.5 μm or more containing 30% is 6% in terms of Sn with ₂ %. Was applied to the surface of the steel sheet in the form of a slurry and dried, with various changes made so that the total amount of Si in the annealing separator was 0.05 to 0.20%. Further, finish annealing accompanied by a purification treatment at 1200 ° C. for 10 hours was performed. The atmosphere of the finish annealing was H _{2 at} the time of maintaining at 1200 ° C. for purification treatment, and N ₂ at the time of temperature increase and decrease. Thereafter, the unreacted separating agent was removed, the coating liquid was applied, and planarization annealing was performed at 820 ° C. for 15 seconds at an in-furnace tension of 10 MPa to obtain a final product. Table 3 shows the film tension and iron loss at this time. From Table 3, it can be seen that good iron loss and film tension are obtained by applying the present invention.

Claims (3)

% By mass
C: 0.020% to 0.080%,
Si: 2.50% to 4.50%,
Mn: 0.03% to 0.30%,
Al: more than 0.010% and less than 0.030% and
N: 0.003% or more and 0.012% or less, with the balance being Fe and an inevitable impurity component composition subjected to one cold rolling or two or more cold rolling sandwiching intermediate annealing Cold-rolled steel sheet with the final thickness,
Subjecting the cold-rolled steel sheet to primary recrystallization annealing,
Applying an annealing separator to the cold-rolled steel sheet after the primary recrystallization annealing, and performing a finish annealing,
A method for producing a grain-oriented electrical steel sheet that is applied with a coating liquid and baked on the cold-rolled steel sheet after the finish annealing, and is subjected to flattening annealing at 800 ° C. or more and 900 ° C. or less,
The annealing separator contains 50% by mass or more of MgO, 2% by mass to 10% by mass of Sn compound in terms of Sn, and 0.10% by mass to 0.30% by mass of Si compound in terms of Si,
A method for producing a grain-oriented electrical steel sheet, wherein the furnace tension during flattening annealing is 6.9 MPa or more.   The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein a proportion of the Sn compound having a particle size of 1.5 µm or more is 30% or more. The component composition further includes:
% By mass
Se: 0.003% to 0.030%,
S: 0.002% to 0.030%,
Ni: 0.010% or more and 1.500% or less,
Cr: 0.01% to 0.50%,
Cu: 0.01% or more and 0.50% or less,
P: 0.005% or more and 0.200% or less,
Sb: 0.005% or more and 0.200% or less,
Sn: 0.005% or more and 0.500% or less,
Bi: 0.005% or more and 0.100% or less,
Mo: 0.005% or more and 0.100% or less,
B: 0.0002% or more and 0.0025% or less,
Te: 0.0005% or more and 0.010% or less,
Nb: 0.001% to 0.010%,
V: 0.001% to 0.010%,
Ti: 0.001% to 0.010% and
Ta: The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 or 2, comprising one or more selected from 0.001% to 0.010%.

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