JP7255761B1 - Manufacturing method of grain-oriented electrical steel sheet - Google Patents

Abstract

Provided is a production method for obtaining a grain-oriented electrical steel sheet having a defect-free, uniform coating with excellent adhesion over the entire width and length of a coil and having excellent magnetic properties. 1300 steel slabs containing C, Si, Mn, Ti, Al, N, and further containing one or two of S and Se, the balance being Fe and unavoidable impurities The slab is heated to ℃ or higher, hot-rolled to form a hot-rolled sheet, the hot-rolled sheet is subjected to hot-rolled sheet annealing or not, and optionally cold-rolled one or more times with intermediate annealing, and then cooled. A cold-rolled sheet is subjected to decarburization annealing to obtain a decarburized annealed sheet, an annealing separator is applied to the surface of the decarburized annealed sheet, and then finish annealing is performed to obtain a grain-oriented electrical steel sheet. In the method for manufacturing an electrical steel sheet, the total rolling reduction of finish rolling in hot rolling is 83% or more, the total rolling reduction of the first cold rolling is 50% or more, and the surface of the cold-rolled sheet before decarburization annealing A method for producing a grain-oriented electrical steel sheet, wherein a compound containing Si is attached to the surface of the grain-oriented electrical steel sheet in an amount of 0.1 mg/m2 or more and 7.0 mg/m2 or less in terms of Si weight per side.

Description

The present disclosure relates to a method for manufacturing a grain-oriented electrical steel sheet.

Electrical steel sheets are widely used as cores for transformers, motors, and the like. Electrical steel sheets are broadly classified into grain-oriented electrical steel sheets and non-oriented electrical steel sheets. For grain-oriented electrical steel sheets, the <001> orientation, which is the axis of easy magnetization of iron, has a texture that is highly aligned in the rolling direction of the steel sheet. It is characteristic that Such a texture is formed by causing secondary recrystallization in the final annealing. Here, the secondary recrystallization refers to a phenomenon in which crystal grains of {110}<001> orientation, so-called Goss orientation, preferentially grow into large grains by utilizing grain boundary energy. As a representative technique for causing the above secondary recrystallization, there is a technique that utilizes precipitates called inhibitors. For example, a method using AlN and MnS described in Patent Document 1, a method using MnS and MnSe described in Patent Document 2, and the like are known and have been industrially put into practical use. Methods using these inhibitors are useful for stably developing secondary recrystallized grains. In these methods, in order to finely disperse the inhibitor in the steel, it is necessary to heat the slab at a high temperature of 1300° C. or higher to dissolve the inhibitor component once.

On the other hand, Patent Document 3 and the like disclose a technique for developing Goss-oriented crystal grains by secondary recrystallization in a material that does not contain an inhibitor component. By eliminating impurities such as inhibitor components as much as possible, the dependence of the grain boundary energy on the grain boundary during the primary recrystallization on the grain boundary misorientation angle is revealed, and the Goss orientation can be obtained without using an inhibitor. It is a technique for secondary recrystallization of grains with grains, and its effect is called texture inhibition effect. Since this method does not require fine dispersion of the inhibitor in the steel, it does not require high-temperature slab heating, which was essential, and thus has advantages over the method using the inhibitor in terms of production.

Japanese Patent Publication No. 40-15644 Japanese Patent Publication No. 51-13469 JP-A-2000-129356

The inventors of the present invention have found that when producing a grain-oriented electrical steel sheet using a composition system that utilizes an inhibitor, a striped pattern with a pitch of several millimeters may occur in the film appearance of the product sheet, and the location where the striped pattern occurs We found that the coating adhesion deteriorated in

The present invention has been made in view of the above problems, and provides a grain-oriented electrical steel sheet that has a defect-free uniform coating with excellent adhesion over the entire width and length of the coil and also has excellent magnetic properties. This paper proposes a manufacturing method.

Through intensive studies, the present inventors have found that the total reduction ratio of finish rolling of hot rolling and the total reduction ratio of the first cold rolling are increased, and Si compounds are added to the surface of the cold rolled sheet before decarburization annealing. The inventors have found that the adhesion of the film improves by adhering it.

The present invention has been made based on the above findings. That is, the gist and configuration of the present invention are as follows.

[1] in % by mass,
C: 0.01% or more and 0.10% or less,
Si: 2.0% or more and 4.0% or less,
Mn: 0.01% or more and 0.30% or less,
Ti: 0.010% or less,
Contains Al: 0.010% or less and N: 0.0050% or less, further contains one or two of S and Se in a total of 0.005% or more and 0.10% or less, and the balance is A steel slab having a chemical composition consisting of Fe and unavoidable impurities is slab-heated to 1300 ° C. or higher and hot-rolled to form a hot-rolled sheet,
Then, the hot-rolled sheet is cold-rolled one or more times with or without hot-rolled sheet annealing, optionally with intermediate annealing, to obtain a cold-rolled sheet;
Then, the cold-rolled sheet is subjected to decarburization annealing to obtain a decarburization-annealed sheet,
Next, in the method for producing a grain-oriented electrical steel sheet, an annealing separator is applied to the surface of the decarburized annealed sheet, and then finish annealing is performed to obtain a grain-oriented electrical steel sheet,
The total rolling reduction of the finish rolling in the hot rolling is 83% or more, and the total rolling reduction of the first cold rolling is 50% or more,
A method for producing a grain-oriented electrical steel sheet, wherein a compound containing Si is attached to the surface of the cold-rolled steel sheet before the decarburization annealing in an amount of 0.1 mg/m ² or more and 7.0 mg/m ^{2 or} less per side in terms of Si weight.

[2] dividing the decarburization annealing into a pre-stage annealing and a post-stage annealing;
In the pre-annealing, the atmosphere oxidation P(H ₂ O)/P(H ₂ ) is 0.3 or more and 0.7 or less,
The method for producing a grain-oriented electrical steel sheet according to the above [1], wherein the post-annealing is performed in an annealing atmosphere in which the atmosphere oxidizing P(H ₂ O)/P(H ₂ ) is 0.005 or more and 0.2 or less.

[3] In the hot rolling, after the slab is heated, the steel slab is subjected to one pass or more of rough rolling at 1100°C or higher and 1300°C or lower, followed by two or more passes of finish rolling at 800°C or higher and 1100°C or lower. and the winding temperature is 400° C. or higher and 750° C. or lower,
In the hot-rolled sheet annealing, the hot-rolled sheet is held at 800° C. or higher and 1250° C. or lower for 5 seconds or longer, and then cooled from 800° C. to 350° C. at an average cooling rate of 5° C./s or higher and 100° C./s or lower. ,
The total rolling reduction of the cold rolling is 50% or more and 92% or less, and the total rolling reduction of the cold rolling each time is 50% or more and 92% or less,
In the intermediate annealing, after holding in a temperature range of 800° C. or higher and 1250° C. or lower for 5 seconds or longer, cooling is performed at an average cooling rate of 5° C./s or higher and 100° C./s or lower from 800° C. to 350° C.,
In the decarburization annealing, the cold-rolled sheet is held at 750° C. or more and 950° C. or less for 10 seconds or more in an atmosphere containing H ₂ and N ₂ ,
Before the finish annealing, the annealing separator containing MgO is applied to the surface of the decarburized annealed sheet in an amount of 2.5 g/m ² or more per side,
In the final annealing, the decarburization-annealed sheet is held at 1050° C. or higher and 1300° C. or lower for 3 hours or more under conditions in which the atmosphere in at least a part of the temperature range of 800° C. or higher contains H ₂ . Or the method for producing a grain-oriented electrical steel sheet according to [2].

[4] The component composition is further mass % or mass ppm,
Ni: 0% or more and 1.50% or less,
Cr: 0% or more and 0.50% or less,
Cu: 0% or more and 0.50% or less,
P: 0% or more and 0.50% or less,
Sb: 0% or more and 0.50% or less,
Sn: 0% or more and 0.50% or less,
Bi: 0% or more and 0.50% or less,
Mo: 0% or more and 0.50% or less,
B: 0 ppm or more and 25 ppm or less,
Nb: 0% or more and 0.020% or less,
V: 0% or more and 0.010% or less and Zr: 0% or more and 0.10% or less, containing one or more selected from the group consisting of 0% or more and 0.10% or less, according to any one of the above [1] to [3] A method for producing a grain-oriented electrical steel sheet.

[5] The component composition further includes, in mass %,
Co: 0% or more and 0.050% or less and Pb: 0% or more and 0.0100% or less, containing one or two selected from the group consisting of 0% or more and 0.0100% or less, according to any one of [1] to [4] A method for producing a grain-oriented electrical steel sheet.

[6] The component composition further includes, in mass %,
As: 0% or more and 0.0200% or less,
Zn: 0% or more and 0.020% or less,
W: 0% or more and 0.0100% or less Ge: 0% or more and 0.0050% or less Ga: 0% or more and 0.0050% or less ] to [5], the method for producing a grain-oriented electrical steel sheet.

According to the present invention, it is possible to obtain a grain-oriented electrical steel sheet which has a defect-free, uniform coating with excellent adhesion over the entire width and length of the coil, and which also has excellent magnetic properties.

It is a figure which shows the relationship between the total rolling reduction of hot-rolling finish rolling, the total rolling reduction of the 1st cold-rolling, and film adhesion. FIG. 4 is a diagram showing the relationship between the adhesion amount of Si compound before decarburization annealing and film adhesion. It is the figure which expanded and showed the part enclosed with the dotted line of FIG.

In order to solve the above-mentioned problems, the present invention specifies the total rolling reduction of hot rolling and cold rolling, and adheres a compound containing Si to the surface of the steel sheet before decarburization annealing. We succeeded in improving peeling characteristics.
The experiments that have led to the success of the present invention are described below.

<Experiment 1>
% by mass, C: 0.051%, Si: 3.08%, Mn: 0.09%, Se: 0.020%, Ti: 0.002%, Al: 0.002%, N: 0.02% A steel slab having a chemical composition containing 0007% and the balance being Fe and unavoidable impurities was slab-heated to a temperature of 1400 ° C. and subjected to hot rolling consisting of rough rolling and finish rolling to obtain a hot-rolled sheet. . The sheet thickness after rough rolling was varied between 15 and 40 mm, and was finished to 2.0 to 3.3 mm by finish rolling. The total reduction in finish rolling ranged from 78.0% to 95.0%. Next, after removing the scale on the surface of the hot-rolled sheet by pickling, various sheet thicknesses of 0.60 to 1.8 mm were produced by the first cold rolling. The total rolling reduction of the first cold rolling was from 10.0% to 81.8%. Next, intermediate annealing was performed at 1020° C. for 100 seconds, followed by second cold rolling to finish a cold-rolled sheet with a thickness of 0.23 mm. Subsequently, the cold-rolled steel sheet was subjected to electrolytic treatment in a 5% sodium orthosilicate aqueous solution, also serving as electrolytic degreasing, so that 2.0 mg/m ² of Si compound was deposited on the surface of the steel sheet. Then, decarburization annealing was performed at 850° C.×120 seconds, 50% H ₂ +50% N ₂ , dew point 60° C. to obtain a decarburization-annealed sheet. Next, after coating the surface of the decarburized annealed sheet with an annealing separator containing 85% by mass or more of MgO in terms of solid content, finish annealing was performed at 1200 ° C. for 5 hours in an H ₂ atmosphere to obtain a directional property. An electromagnetic steel sheet was obtained. A sample was cut out from the obtained grain-oriented electrical steel sheet, and the film adhesion was evaluated. Coating adhesion was evaluated by winding samples around cylinders having various diameters and determining the minimum diameter at which the coating did not peel off. The smaller the minimum diameter, the better the film adhesion. The winding direction was the rolling direction of the sample. That is, the sample was wound so that the rolling direction drew an arc. FIG. 1 shows the relationship between the total rolling reduction of the hot finish rolling, the total rolling reduction of the first cold rolling, and the film adhesion. As is clear from FIG. 1, when the total rolling reduction in the finish rolling of the hot rolling is 83% or more and the total rolling reduction in the first cold rolling is 50% or more, excellent film adhesion is obtained. I found that it can be done.

<Experiment 2>
% by mass, C: 0.070%, Si: 3.41%, Mn: 0.15%, Se: 0.015%, Ti: 0.001%, Al: 0.001%, N: 0.01%. 0008%, Sb: 0.042%, and the balance being Fe and unavoidable impurities. to obtain a hot-rolled sheet. The sheet thickness after rough rolling was set to 35 mm, and was further finished to 2.5 mm by finish rolling. The total reduction in finish rolling was 92.9%. Next, after removing the scale on the surface of the hot-rolled sheet by pickling, the sheet was made to have a sheet thickness of 0.72 mm by the first cold rolling. The total rolling reduction of the first cold rolling was 71.2%. Next, intermediate annealing was performed at 925° C. for 100 seconds, followed by second cold rolling to finish a cold-rolled sheet with a thickness of 0.23 mm. Subsequently, an electrolytic treatment was performed in a 3% sodium orthosilicate aqueous solution, also serving as electrolytic degreasing, to attach a Si compound to the surface of the cold-rolled sheet. At this time, the adhesion amount of the Si compound was set under various conditions including no adhesion of 0 mg/m ² . After that, the cold-rolled sheet to which the Si compound was attached was subjected to decarburization annealing at 850° C.×120 seconds, 50% H ₂ +50% N ₂ , dew point 64° C. to obtain a decarburization-annealed sheet. Next, after applying an annealing separator containing 85% by mass or more of MgO in terms of solid content to the surface of the decarburized annealed sheet, it was subjected to finish annealing at 1200 ° C. for 10 hours in an H ₂ atmosphere, and the directionality An electromagnetic steel sheet was obtained. A sample was cut out from the obtained grain-oriented electrical steel sheet, and the film adhesion was evaluated. Coating adhesion was evaluated by winding samples around cylinders having various diameters and determining the minimum diameter at which the coating did not peel off. In addition, the amount of Si deposited on the cold-rolled sheet before decarburization annealing was measured using a fluorescent X-ray spectrometer. A calibration curve was prepared in advance using a fluorescent X-ray analyzer, and the Si deposition amount was calculated based on the calibration curve. In preparing the calibration curve, the result of the fluorescent X-ray analysis of the grain-oriented electrical steel sheet that was not subjected to the Si deposition treatment was taken as zero Si deposition. FIG. 2 shows the relationship between the adhesion amount of the Si compound before decarburization annealing and the film adhesion. Also, FIG. 3 shows an enlarged portion surrounded by a dotted line in FIG. As is clear from FIGS. 2 and 3, a compound containing Si is attached to the surface of the cold-rolled sheet before decarburization annealing in an amount of 0.1 mg/m ² or more and 7.0 mg/m ² or less per side in terms of Si weight. , it was found that excellent film adhesion can be obtained.

To summarize the results of Experiments 1 and 2, the total rolling reduction in the finish rolling of hot rolling and the total rolling reduction in the first cold rolling are increased, and Si compounds are added to the surface of the cold-rolled sheet before decarburization annealing. It was found that the adhesion of the film is improved by adhering the The reasons for these are not clear, but the inventors believe as follows.

A clear difference was observed in the appearance of the product sheet between a sample with good coating adhesion (good sample) and a sample with poor coating adhesion (bad sample) in this experiment. That is, the good samples had a uniform appearance and almost no color unevenness, whereas the bad samples had striped patterns extending in the rolling direction at a pitch of several millimeters in the sheet width direction. In order to investigate the cause of the striped pattern, the cold-rolled sheet after intermediate annealing was observed. As a result, it was found that, in the cold-rolled sheets of the defective samples after the intermediate annealing, ridging occurred at substantially the same pitch. Ridging is unevenness on the steel sheet surface, and is known to be highly related to the crystal orientation of the steel sheet. The occurrence of this ridging was observed even under the conditions of the good samples, but the unevenness was clearly smaller in the steel sheets under the conditions of the good samples than under the conditions of the bad samples. Assuming the effect of unevenness on coating adhesion, since the step subsequent to intermediate annealing is the second cold rolling, it is conceivable that this unevenness affects the roughness of the surface after cold rolling. That is, in the second cold rolling, since the convex portions selectively contact the rolling rolls, it is thought that the surface is flat and the roughness is relatively small, while the concave portions cause the material to fall from the convex portions. It is conceivable that there is a possibility that the roughness will be relatively high at In other words, even if unevenness such as ridging is eliminated by the second cold rolling and a flat shape is secured, areas with low roughness and areas with high roughness are arranged alternately to form a striped pattern. there is a possibility. It is presumed that this difference in roughness affects the formation of subscales on the steel sheet surface during decarburization annealing. That is, the structure of the subscale changed into a striped pattern, and it is thought that this affected the film formation during the final annealing, resulting in the striped pattern in the product sheet. The subscale structure affects not only the appearance of the coating, but also the formation of a shape called an anchor, in which the coating bites into the base iron. It is known that if this anchor shape is developed, the film adhesion is good, but if the anchor formation is poor, the film adhesion is deteriorated. In this experiment, it is thought that the subscale structure differs in a striped pattern after decarburization annealing. It is presumed that the film adhesion deteriorated at

As described above, it is clear from the present inventors' own studies that deterioration of film adhesion can be prevented by increasing the total rolling reduction in the finish rolling of hot rolling and the total rolling reduction in the first cold rolling. became. This is because by increasing the reduction rate and increasing the amount of strain introduced into the steel sheet, dynamic and static recrystallization is promoted, grains with various crystal orientations are generated, and the unevenness of the steel sheet, the so-called This is probably because the occurrence of ridging could be greatly suppressed.

However, some unevenness was observed after the intermediate annealing even in the sample with good film adhesion. Therefore, it is not enough just to define the rolling reduction, and it is also necessary to deposit a Si compound before the decarburization annealing. Adhering the Si compound before the decarburization annealing made it possible to alleviate the influence of the difference in subscale structure on the film formation, and effectively prevented the deterioration of the film adhesion. In other words, the total rolling reduction in the finish rolling of hot rolling and the total rolling reduction in the first cold rolling are increased to suppress unevenness on the surface of the steel sheet after intermediate annealing to some extent. By adding the Si compound, it is considered that the subscale structure change caused by the roughness change due to the unevenness was effectively suppressed, and the deterioration of the coating adhesion was prevented. The Si compound used in the present invention is substantially composed of Si, O, H or Si, O, that is, silica represented by SiO ₂ or a compound in which H ₂ O is bonded thereto. .

Embodiments of the present invention will be described below. In addition, this invention is not limited to the following embodiment. First, the appropriate range of the chemical composition of the steel sheet and the reasons for its limitation will be described. In the following description, "%" representing the content of the constituent elements of the steel sheet means "% by mass" unless otherwise specified. "ppm" means "ppm by mass" unless otherwise specified. In the present specification, a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.

C: 0.01% or more and 0.10% or less If the amount of C exceeds 0.10%, magnetic aging may occur after decarburization annealing. On the other hand, if the amount of C is less than 0.01%, secondary recrystallized grains become coarse, causing an increase in core loss and deterioration in bending workability. Therefore, C is limited to 0.01% or more and 0.10% or less. The amount of C is preferably 0.03% or more. Moreover, the amount of C is preferably 0.06% or less.

Si: 2.0% or more and 4.0% or less Si is an element necessary for increasing the resistivity of steel and improving iron loss. %, the secondary recrystallization becomes unstable and the magnetic properties deteriorate, so the Si content is limited to 2.0% or more and 4.0% or less. The amount of Si is preferably 3.0% or more. The amount of Si is preferably 3.6% or less.

Mn: 0.01% or more and 0.30% or less Mn is an element necessary for using MnS or MnSe as an inhibitor. If it exceeds 0.30%, the secondary recrystallization becomes unstable and the magnetic properties deteriorate. Therefore, the Mn content is set to 0.01% or more and 0.30% or less. The amount of Mn is preferably 0.03% or more. The Mn content is preferably 0.20% or less, more preferably 0.15% or less.

Ti: 0.010% or less Al: 0.010% or less N: 0.0050% or less In addition, Ti and Al form nitrides, impairing the inhibitory effects of MnS and MnSe and degrading the magnetic properties. Therefore, Ti: 0.010% or less, Al: 0.010% or less, and N: 0.0050% or less. Preferably, Ti, Al and N are each 0.0020% or less. However, since reducing these elements may increase the cost, there is no problem even if they remain within the above ranges. These elements are preferably as small as possible, and may be 0%, but from the viewpoint of cost reduction, Ti and Al are each preferably 0.001% or more, and N is 0.0005% or more.

0.005% or more and 0.10% or less in total of any one or two of S and Se S and Se combine with Mn to form MnS and MnSe, which act as inhibitors. However, if it is less than 0.005% alone or in total, the effect cannot be sufficiently obtained. On the other hand, if it exceeds 0.10%, it cannot be dissolved sufficiently by heating the slab, and fine dispersion in the steel cannot be achieved, which greatly deteriorates the magnetic properties. Therefore, the total content of S and Se should be in the range of 0.005% or more and 0.10% or less. It is preferably 0.010% or more and 0.040% or less.

The basic components of the present invention have been described above, but in the present invention, the following elements can be included as appropriate.

For the purpose of improving magnetic properties, Ni: 0% to 1.50%, Cr: 0% to 0.50%, Cu: 0% to 0.50%, P: 0% to 0.50% Below, Sb: 0% to 0.50%, Sn: 0% to 0.50%, Bi: 0% to 0.50%, Mo: 0% to 0.50%, B: 0 ppm 25 ppm or less, Nb: 0% or more and 0.020% or less, V: 0% or more and 0.010% or less, and Zr: 0% or more and 0.10% or less. can be added as By setting the amount of these elements added to the above upper limit or less, it is possible to prevent the growth of secondary recrystallized grains from being suppressed and to obtain particularly good magnetic properties. From the viewpoint of further improving the magnetic properties, Ni: 0.01% or more, Sb: 0.005% or more, Sn: 0.005% or more, Cu: 0.01% or more, Cr: 0.01% Above, P: 0.005% or more, Mo: 0.005% or more, Nb: 0.001% or more, V: 0.001% or more, B: 0.0002% or more, Bi: 0.005% or more and Zr: It is preferable to add 0.001% or more.

For the purpose of improving film adhesion, one or two selected from the group consisting of Co: 0% or more and 0.050% or less and Pb: 0% or more and 0.0100% or less can be added. If the amounts of Co and Pb added are not more than the above upper limits, the magnetic properties are more favorable. From the viewpoint of further improving film adhesion, it is preferable to add Co: 0.002% or more and Pb: 0.0001% or more.

For the purpose of improving magnetic properties and further improving film adhesion, As: 0% to 0.0200%, Zn: 0% to 0.020%, W: 0% to 0.0100% , Ge: 0% or more and 0.0050% or less, and Ga: 0% or more and 0.0050% or less. Magnetic properties are more favorable if each is equal to or less than the above upper limit. From the viewpoint of further improving film adhesion, As: 0.0010% or more, Zn: 0.001% or more, W: 0.0010% or more, Ge: 0.0001% or more, and Ga: 0.0001% or more It is preferable to add at

Next, manufacturing conditions for the grain-oriented electrical steel sheet of the present disclosure will be described.

First, a steel slab is manufactured using molten steel having the chemical composition described above. The method of manufacturing the steel slab is not particularly limited, and the steel slab may be manufactured by a normal ingot casting method and continuous casting method, or a steel slab with a thickness of 100 mm or less may be manufactured by a direct casting method. These steel slabs are subjected to hot rolling after slab heating in the usual manner. Hot rolling may be performed immediately after casting without heating.

Prior to hot rolling, the steel slab is slab heated to 1300°C or higher. By slab-heating the steel slab to 1300° C. or higher, the inhibitor component can be sufficiently solid-dissolved. The slab heating temperature is based on the slab surface temperature.

Then, the steel slab after heating is hot-rolled to obtain a hot-rolled sheet. For the reason described above, the total rolling reduction in finish rolling of hot rolling must be 83% or more. A grain-oriented electrical steel sheet having a defect-free uniform coating with excellent adhesion and excellent magnetic properties by increasing the coating adhesion by setting the total rolling reduction of the finish rolling of hot rolling to 83% or more. can be obtained. The total reduction in finish rolling of hot rolling is preferably 87% or more, more preferably 90% or more. Although the upper limit of the total rolling reduction in finish rolling of hot rolling is not particularly limited, it is preferably 96% or less from the viewpoint of cost. The number of hot rolling passes and the rolling reduction in each pass are not particularly limited.

From the viewpoint of controlling the structure of the hot-rolled sheet, the rough rolling is preferably performed at 1100° C. or higher, more preferably at 1300° C. or lower for one or more passes. Subsequently, from the viewpoint of controlling the structure of the hot-rolled sheet, it is preferable to carry out two or more passes of finish rolling at a temperature of 800° C. or higher and 1100° C. or lower. Further, it is preferable to set the winding temperature to 400° C. or higher and 750° C. or lower from the viewpoint of both control of carbide structure and prevention of defects such as cracks. The winding temperature is more preferably 500°C or higher and 700°C or lower. The temperature in hot rolling and the coiling temperature are based on the surface of the steel sheet immediately before coiling.

The hot-rolled sheet can then optionally be subjected to hot-rolled sheet annealing. By performing hot-rolled sheet annealing, it is possible to homogenize the structure and reduce variations in magnetic properties. From the viewpoint of homogenizing the structure, the annealing conditions for hot-rolled sheet annealing are preferably 800° C. or higher and 1250° C. or lower and held for 5 seconds or longer. Annealing conditions for hot-rolled sheet annealing are more preferably 900° C. or higher and 1150° C. or lower and held for 10 seconds or longer and 180 seconds or shorter. In the cooling after holding in the above temperature range, the average cooling rate is 5 ° C./s or more and 100 ° C./s or less in the temperature range from 800 ° C. to 350 ° C. The second phase and the form of precipitates It is preferable from the viewpoint of control. In the cooling after holding in the above temperature range, the average cooling rate in the temperature range from 800°C to 350°C is more preferably 15°C/s or more and 45°C/s or less.

Optionally, surface scale formed during hot rolling is then removed prior to cold rolling. A method for removing scale is not particularly limited, and known methods such as a method using heated acid (pickling) and a method for mechanically removing scale may be used.

After optionally descaling, the sheet is subjected to one or more cold rolling steps, optionally with intermediate anneals, to produce a cold rolled sheet having a final thickness. In the first cold rolling, it is essential to set the total rolling reduction to 50% or more for the reasons described above. A grain-oriented electrical steel sheet having a defect-free uniform coating with excellent adhesion and excellent magnetic properties by increasing the coating adhesion by setting the total rolling reduction of the first cold rolling to 50% or more. can be obtained. The total rolling reduction of the first cold rolling is preferably 53% or more, more preferably 55% or more, still more preferably 60% or more. Although the upper limit of the total rolling reduction in the first cold rolling is not particularly limited, it is preferably 92% or less from the viewpoint of reducing the rolling load. In cold rolling, it is preferable to use a lubricant such as rolling oil in order to reduce the rolling load and improve the rolling shape.

After the first cold rolling, an optional intermediate anneal is performed. In the intermediate annealing, it is preferable to hold the temperature in the temperature range of 800° C. or higher and 1250° C. or lower for 5 seconds or longer. By setting the annealing temperature of the intermediate annealing to 800° C. or higher, it is possible to prevent the recrystallized grains from becoming excessively fine, to allow the nuclei of the Goss orientation crystal grains to grow well in the primary recrystallized structure, and to further improve the magnetic properties. can. By setting the temperature of the intermediate annealing to 1250° C. or lower, the rapid growth and decomposition of the inhibitor can be prevented, and the magnetic properties can be further improved.

In the cooling after holding in the above temperature range, the average cooling rate from 800 ° C. to 350 ° C. is 5 ° C./s or more and 100 ° C./s or less, from the viewpoint of controlling the morphology of the second phase and precipitates. is preferred. More preferably, the average cooling rate from 800°C to 350°C is 15°C/s or more and 45°C/s or less. In addition, the temperature in the intermediate annealing is based on the surface of the steel sheet.

After the first cold rolling and before intermediate annealing, the surface of the cold-rolled sheet after the first cold rolling is preferably degreased in order to remove the lubricant used during the first cold rolling. Moreover, after the intermediate annealing, it is preferable to remove the scale on the surface of the cold-rolled sheet. A method for removing scale is not particularly limited, and known methods such as a method using heated acid (pickling) and mechanical scale removal may be used.

The optionally intermediate annealed cold rolled sheet may then be further cold rolled one or more times. When cold rolling is performed multiple times, it is preferable from the viewpoint of structure control that the total rolling reduction of the multiple cold rollings is 50% or more and 92% or less. When cold rolling is performed a plurality of times, the total rolling reduction is preferably 50% or more and preferably 92% or less in each cold rolling.

Next, it is preferable to clean the surface of the cold-rolled steel sheet by degreasing or pickling it prior to attaching the compound containing Si to the surface. Conditions for degreasing and pickling can be according to conventional methods.

In the present invention, it is essential for the above reason that a compound containing Si is attached to the surface of the cold-rolled sheet before decarburization annealing in the range of 0.1 to 7.0 mg/m ² per side in terms of Si weight. is. A compound containing Si (hereinafter also referred to as a Si compound) consists essentially of Si, O, H or Si, O. That is, silica represented by SiO ₂ or a compound in which H ₂ O is bonded thereto corresponds to the Si compound. Preferably, a compound containing Si is attached to the surface of the cold-rolled steel sheet before decarburization annealing in an amount of 0.2 to 6.1 mg/m ² , more preferably 1 to 5 mg/m ² per side in terms of Si weight. Let Techniques for attaching this Si compound to the surface of the cold-rolled sheet include, for example, orthosilicic acid (H ₄ SiO ₄ ), metasilicic acid (H ₂ SiO ₃ ), water-soluble ultrafine SiO ₂ such as colloidal silica, and alkali silicate. Examples include electrolytic treatment of the steel sheet in an aqueous solution.

Then, the cold-rolled sheet is subjected to decarburization annealing to obtain a decarburization-annealed sheet. Conditions for decarburization annealing are not particularly limited, and conventional methods can be used. The decarburization annealing is preferably carried out in a temperature range of 750° C. or higher and 950° C. or lower because the temperature range promotes decarburization. Moreover, the holding time in the above temperature range is preferably 10 seconds or more in order to sufficiently decarburize the C in the steel. The atmosphere in the above temperature range for decarburization annealing preferably contains _H2 , which affects oxidizability, and _N2 , which is an inert gas, to facilitate control of oxidizability. Furthermore, at least part of the decarburization annealing is preferably performed in a moist atmosphere with a dew point of 20° C. or higher and 80° C. or lower. More preferably, in the decarburization annealing, the temperature range is 800°C or higher and 900°C or lower, and the dew point is set to 40°C or higher and 70°C or lower. In addition, the temperature in decarburization annealing is based on the steel plate surface.

Preferably, the decarburization annealing is divided into pre-annealing and post-annealing, and the pre-annealing has an atmosphere oxidizing P(H ₂ O)/P(H ₂ ) of 0.3 or more and 0.7 or less, and the post-annealing has an atmosphere oxidizing The annealing is performed in an atmosphere where P(H ₂ O)/P(H ₂ ) is 0.005 or more and 0.2 or less. By performing decarburization annealing under such conditions, part of the highly oxidized fayalite near the surface changes to silica, further improving the coating adhesion.

Next, after applying an annealing separator to both the front and back surfaces of the decarburized annealed sheet, finish annealing is performed to obtain a grain-oriented electrical steel sheet. A known annealing separator can be used as the annealing separator. In particular, it is preferable to apply an annealing separator mainly composed of MgO to the surface of the decarburized annealed steel sheet in an amount of 2.5 g/m ² or more per side, because this can completely prevent fusion between the steel sheets during the final annealing. Here, "mainly composed of MgO" means that the content of MgO in the annealing separator is 60% or more in terms of solid content. The content of MgO in the annealing separator is preferably 80% or more in terms of solid content. The method of applying the annealing separator to the surface of the decarburized annealed sheet is not particularly limited, and any known method may be used. For example, the annealing separator may be applied in the form of a slurry to the surface of the decarburized annealed plate, or dry applied by electrostatic coating. When applying the slurry annealing separator, in order to suppress the viscosity increase, the slurry annealing separator should be kept at a constant temperature of 5 ° C or higher and 30 ° C or lower to prevent fluctuations in liquid properties such as viscosity. It is preferable because it can be applied with a constant weight per unit area. Moreover, in order to equalize the slurry concentration, it is preferable to divide the slurry-like annealing separator into a mixing tank and a coating tank.

After applying the annealing separator, the decarburized annealed sheet is subjected to finish annealing. This makes it possible to develop secondary recrystallized grains and form a forsterite coating, thereby obtaining a grain-oriented electrical steel sheet with excellent magnetic properties. Finish annealing can be carried out by a conventional method. In one example, the decarburization-annealed sheet is coiled into a steel sheet coil, and then subjected to finish annealing. Since finish annealing generally takes a long time, the steel sheet coil is preferably annealed in an up-end state (the central axis of the steel sheet coil is perpendicular to the ground). It is preferable to wind a band or the like around the steel sheet coil before the final annealing. This is because the outer winding of the up-end steel sheet coil can be prevented from unwinding during the finish annealing.

In the final annealing, the temperature is preferably raised to 800° C. or higher in order to complete the secondary recrystallization, and in the case of forming a forsterite film, the temperature is preferably raised to 1050° C. or higher. In addition, in order to obtain good core loss properties by purifying inhibitor components and the like from the steel, it is preferable to hold the steel at 1100° C. or higher and 1300° C. or lower for 3 hours or longer in the final annealing. Moreover, in the final annealing, it is preferable that at least a part of the atmosphere within the temperature range of 800° C. or higher contains H ₂ from the viewpoint of promotion of purification and promotion of film formation.

After finish annealing, washing with water, brushing, or pickling may be performed in order to remove the attached annealing separator. Further flattening annealing the pickled grain-oriented electrical steel sheet to correct the shape is effective for reducing iron loss. Since a grain-oriented electrical steel sheet is often used by laminating steel sheets, an insulating coating may be applied to the surface of the grain-oriented electrical steel sheet in order to ensure insulation. The insulating coating is preferably a coating capable of applying tension to the grain-oriented electrical steel sheet to reduce iron loss. The insulating coating liquid may be applied before flattening annealing, and baking may be performed by flattening annealing. Alternatively, a tension coating application method using a binder, a physical vapor deposition method, or a chemical vapor deposition method may be used to vapor-deposit an inorganic material on the steel sheet surface layer for coating. Coating by these methods is preferable because the coating adhesion is excellent and the effect of significantly reducing iron loss is obtained.

In addition, manufacturing conditions other than the above conditions can be based on a conventional method.

(Example 1)
% by mass, C: 0.051%, Si: 3.08%, Mn: 0.09%, Se: 0.020%, Ti: 0.002%, Al: 0.002%, N: 0.02% A steel slab having a chemical composition containing 0010% and the balance being Fe and unavoidable impurities is heated to a temperature of 1400 ° C. and subjected to 4 passes of rough rolling and 6 passes of finish rolling to form a hot rolled sheet. bottom. At that time, the rolling temperature in the final pass of rough rolling was set to 1200°C, and the rolling temperature in the final pass of finish rolling was set to 950°C. Furthermore, the total reduction in finish rolling was changed as shown in Table 1. Next, after removing the scale on the surface of the hot-rolled sheet by pickling, the total rolling reduction in the first cold rolling was changed as shown in Table 1, and then intermediate annealing was performed at 1000° C. for 200 seconds. The cooling rate from 800°C to 350°C in this intermediate annealing was set to 30°C/s. After that, cold rolling was performed for the second time to finish a cold-rolled sheet with a sheet thickness of 0.23 mm. The total rolling reduction of the second cold rolling was 67.1-87.2%. Subsequently, electrolytic treatment was performed under various conditions in a 5% sodium orthosilicate aqueous solution, also for electrolytic degreasing, to deposit a Si compound on the surface of the cold-rolled sheet before decarburization annealing. The adhesion amount of the Si compound per side was changed as shown in Table 1. Incidentally, the adhesion amount of the Si compound was determined by the method described above. Then, decarburization annealing is performed at 850° C.×120 seconds, 50% H ₂ +50% N ₂ , dew point 60° C. (atmospheric oxidation P(H ₂ O)/P(H ₂ )=0.494), A decarburized annealed sheet was obtained. Next, after applying 10.0 g/m ² of an annealing separating agent containing 85% by mass or more of MgO in terms of solid content to the surface of the decarburized annealed sheet, finish annealing is performed at 1200 ° C. for 5 hours. A flexible electrical steel sheet was obtained. The atmosphere of the final annealing is _N2 atmosphere during temperature rise up to 800°C, 25% _N2 + 75% _H2 atmosphere from 800°C to 1050°C, and H2 atmosphere from 1050°C to the end of holding at 1200°C _. An atmosphere was used, and an Ar atmosphere was used during cooling after holding.

A sample was cut out from the obtained grain-oriented electrical steel sheet, and the film adhesion and magnetic properties were evaluated. Coating adhesion was evaluated by winding samples around cylinders having various diameters and determining the minimum diameter at which the coating did not peel off. If the minimum diameter at which the coating did not peel off was 25 mm or less, it was judged that the coating adhesion was excellent. For magnetic properties, iron loss W _17/50 (magnetic flux density 1.7 T, iron loss at 50 Hz excitation) was measured by the method described in JIS C2550-1 (2011). If the iron loss W _17/50 was 0.900 W/kg or less, it was determined that the iron loss characteristics were excellent. Table 1 also shows the evaluation results of these film adhesion and magnetic properties.

As is clear from the table, under the conditions within the range of the present invention, the magnetic properties are good and the film adhesion is good.

(Example 2)
A steel slab having the chemical composition shown in Table 2 is heated to a temperature of 1425°C, subjected to four passes of rough rolling from 1270°C, and five passes of finish rolling from 1050°C. A hot-rolled sheet having a thickness of . At this time, the total reduction in finish rolling was 92.5%. Next, after removing scales on the surface of the hot-rolled sheet by pickling, the hot-rolled sheet was annealed at 985° C. for 30 seconds. After holding at 985°C, cooling was performed at an average cooling rate of 70°C/s from 800°C to 350°C. Then, the plate thickness was finished to 0.74 mm by the first cold rolling. The total rolling reduction of the first cold rolling was 75.3%. Then, an intermediate annealing was performed at 1100° C. for 40 seconds. After holding at 1100°C, cooling was performed at an average cooling rate of 20°C/s from 800°C to 350°C. After that, cold rolling was performed for the second time to finish a cold-rolled sheet with a sheet thickness of 0.23 mm. The total rolling reduction of the second cold rolling was 68.9%. Subsequently, an electrolytic treatment in a 2% sodium metasilicate aqueous solution was carried out for electrolytic degreasing, and a Si compound was deposited on the surface of the cold-rolled steel sheet at an amount of 1.2 mg/m ² per side in terms of Si weight. Next, the former stage was set to 840° C.×100 seconds, 54% H ₂ +46% N ₂ , dew point 64° C. (atmospheric oxidation P(H ₂ O)/P(H ₂ )=0.578), and the latter stage was set to 840° C.×100 seconds. Decarburization annealing was performed for 20 seconds in 54% H ₂ +46% N ₂ with a dew point of 30° C. (atmospheric oxidation P(H ₂ O)/P(H ₂ )=0.082) to obtain a decarburization-annealed sheet. rice field. Next, after applying 6.5 g/m ² of an annealing separator mainly composed of MgO to the surface of the decarburized annealed sheet, the sheet was subjected to finish annealing at 1200° C. for 5 hours. The atmosphere of the final annealing is N ₂ atmosphere during temperature rise up to 1000 ° C., H ₂ atmosphere from 1100 ° C. to 1200 ° C. after the end of holding, until the temperature at the time of cooling reaches 1000 ° C., and Ar atmosphere in the subsequent cooling. bottom. The coating adhesion and magnetic properties of the obtained samples were evaluated in the same manner as in Example 1. Table 2 also shows the evaluation results of film adhesion and magnetic properties.

As is clear from the table, under the conditions within the range of the present invention, the magnetic properties are good and the film adhesion is good.

(Example 3)
% by mass, C: 0.040%, Si: 3.00%, Mn: 0.07%, S: 0.007%, Se: 0.020%, Ti: 0.001%, Al: 0.001% 002%, N: 0.0015%, Mo: 0.022%, and Sb: 0.035%, the steel slab is slab-heated to a temperature of 1420 ° C., and rough rolling is performed from 1300 ° C. in four passes, A hot-rolled sheet with a thickness of 2.4 mm was finished by hot-rolling from 1100° C. with 5 passes of finish rolling. At this time, the total reduction in finish rolling was 93.1%. Next, after removing scales on the surface of the hot-rolled sheet by pickling, the sheet was finished to a sheet thickness of 0.65 mm by the first cold rolling. The total rolling reduction of the first cold rolling was 72.9%. Then, an intermediate annealing was performed at 1060° C. for 80 seconds. After holding at 1060°C, cooling was performed at a cooling rate of 40°C/s from 800°C to 350°C. After that, a second cold rolling was performed to finish a cold-rolled sheet having a thickness of 0.27 mm. The total rolling reduction of the second cold rolling was 58.5%. Subsequently, it is degreased by brushing in a 3% sodium orthoate aqueous solution, then pickled in 5% HCl at 60° C. for 3 seconds, and further electrolytically treated in a 3% sodium orthosilicate aqueous solution. , a Si compound was deposited on the surface of the cold-rolled sheet at 3.5 mg/m ² per side in terms of Si weight. Then, various decarburization annealing was performed under the conditions shown in Table 3. Next, an annealing separator containing 85% by mass or more of MgO in terms of solid content was applied to the surface of the decarburized annealed sheet at 4.0 g/m ² per side, and then finish annealing was performed at 1200 ° C. for 5 hours to obtain a directional property. An electromagnetic steel sheet was obtained. The atmosphere of the final annealing is an _N2 atmosphere during the temperature rise up to 900°C, an H2 atmosphere from 900°C or higher to 1200°C, and an _H2 atmosphere until the cooling temperature reaches 1000°C, and an Ar atmosphere in the subsequent cooling. and The coating adhesion and magnetic properties of the obtained samples were evaluated in the same manner as in Example 1. Since the final plate thickness of this example is different from that of Example 1, it was determined that the iron loss characteristic is excellent if the iron loss W _17/50 , which is significantly dependent on the plate thickness, is 1.000 W/kg or less. Table 3 shows the evaluation results of the film adhesion and magnetic properties of the obtained samples.

As is clear from the table, the magnetic properties are good and the film adhesion is good under the conditions within the range of the present invention. In addition, the pre-annealing of the decarburization annealing has an atmosphere-oxidizing P(H ₂ O)/P(H ₂ ) of 0.3 or more and 0.7 or less, and the post-annealing has an atmosphere-oxidizing P(H ₂ O)/P( H ₂ ) was found to be particularly excellent in coating adhesion when the annealing atmosphere is 0.005 or more and 0.2 or less.

Claims (5)

in % by mass,
C: 0.021 % or more and 0.10% or less,
Si: 2.71 % or more and 4.0% or less,
Mn: 0.03 % or more and 0.30% or less,
Ti: 0.010% or less,
Contains Al: 0.010% or less and N: 0.0037 % or less, further contains one or two of S and Se in a total amount of 0.010 % or more and 0.049 % or less, and the balance is A steel slab having a chemical composition consisting of Fe and unavoidable impurities is slab-heated to 1300 ° C. or higher and hot-rolled to form a hot-rolled sheet,
Then, the hot-rolled sheet is cold-rolled one or more times with or without hot-rolled sheet annealing, optionally with intermediate annealing, to obtain a cold-rolled sheet;
Then, the cold-rolled sheet is subjected to decarburization annealing to obtain a decarburization-annealed sheet,
Next, in the method for producing a grain-oriented electrical steel sheet, an annealing separator is applied to the surface of the decarburized annealed sheet, and then finish annealing is performed to obtain a grain-oriented electrical steel sheet,
The total rolling reduction of the finish rolling in the hot rolling is 83% or more, and the total rolling reduction of the first cold rolling is 50% or more,
A method for producing a grain-oriented electrical steel sheet, wherein a compound containing Si is attached to the surface of the cold-rolled steel sheet before the decarburization annealing in an amount of 0.1 mg/m ² or more and 7.0 mg/m ^{2 or} less per side in terms of Si weight. The decarburization annealing is divided into pre-stage annealing and post-stage annealing,
In the pre-annealing, the atmosphere oxidation P(H ₂ O)/P(H ₂ ) is 0.3 or more and 0.7 or less,
2. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein said post-annealing is performed in an annealing atmosphere in which the ratio of atmospheric oxidation P( _H2O )/P( _H2 ) is 0.005 or more and 0.2 or less. In the hot rolling, after the slab is heated, the steel slab is subjected to one pass or more of rough rolling at 1100° C. or more and 1300° C. or less, followed by two passes or more of finish rolling at 800° C. or more and 1100° C. or less. The taking temperature is 400° C. or higher and 750° C. or lower,
In the hot-rolled sheet annealing, the hot-rolled sheet is held at 800° C. or higher and 1250° C. or lower for 5 seconds or longer, and then cooled from 800° C. to 350° C. at an average cooling rate of 5° C./s or higher and 100° C./s or lower. ,
The total rolling reduction of the cold rolling is 50% or more and 92% or less, and the total rolling reduction of the cold rolling each time is 50% or more and 92% or less,
In the intermediate annealing, after holding in a temperature range of 800° C. or higher and 1250° C. or lower for 5 seconds or longer, cooling is performed at an average cooling rate of 5° C./s or higher and 100° C./s or lower from 800° C. to 350° C.,
In the decarburization annealing, the cold-rolled sheet is held at 750° C. or more and 950° C. or less for 10 seconds or more in an atmosphere containing H ₂ and N ₂ ,
Before the finish annealing, the annealing separator containing MgO is applied to the surface of the decarburized annealed sheet in an amount of 2.5 g/m ² or more per side,
2. The decarburization-annealed sheet is held at 1050° C. or higher and 1300° C. or lower for 3 hours or more under conditions in which the atmosphere in at least part of the temperature range of 800° C. or higher contains _H2 in the final annealing, or 3. The method for producing a grain-oriented electrical steel sheet according to 2. 3. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the component composition further contains at least one component selected from Groups A to C below.
Group A: % by mass or ppm by mass,
Ni: 0% or more and 1.50% or less,
Cr: 0% or more and 0.50% or less,
Cu: 0% or more and 0.50% or less,
P: 0% or more and 0.50% or less,
Sb: 0% or more and 0.50% or less,
Sn: 0% or more and 0.50% or less,
Bi: 0% or more and 0.50% or less,
Mo: 0% or more and 0.50% or less,
B: 0 ppm or more and 25 ppm or less,
Nb: 0% or more and 0.020% or less,
V: 0% or more and 0.010% or less and Zr: 1 or 2 or more selected from the group consisting of 0% or more and 0.10% or less.
Group B: % by mass,
One or two selected from the group consisting of Co: 0% or more and 0.050% or less and Pb: 0% or more and 0.0100% or less.
Group C: % by mass,
As: 0% or more and 0.0200% or less,
Zn: 0% or more and 0.020% or less,
W: 0% or more and 0.0100% or less Ge: 0% or more and 0.0050% or less Ga: 1 or 2 or more selected from the group consisting of 0% or more and 0.0050% or less. 4. The method for producing a grain-oriented electrical steel sheet according to claim 3, wherein the component composition further contains at least one component selected from Groups A to C below.
Group A: % by mass or ppm by mass,
Ni: 0% or more and 1.50% or less,
Cr: 0% or more and 0.50% or less,
Cu: 0% or more and 0.50% or less,
P: 0% or more and 0.50% or less,
Sb: 0% or more and 0.50% or less,
Sn: 0% or more and 0.50% or less,
Bi: 0% or more and 0.50% or less,
Mo: 0% or more and 0.50% or less,
B: 0 ppm or more and 25 ppm or less,
Nb: 0% or more and 0.020% or less,
V: 0% or more and 0.010% or less and Zr: 1 or 2 or more selected from the group consisting of 0% or more and 0.10% or less.
Group B: % by mass,
One or two selected from the group consisting of Co: 0% or more and 0.050% or less and Pb: 0% or more and 0.0100% or less.
Group C: % by mass,
As: 0% or more and 0.0200% or less,
Zn: 0% or more and 0.020% or less,
W: 0% or more and 0.0100% or less Ge: 0% or more and 0.0050% or less Ga: 1 or 2 or more selected from the group consisting of 0% or more and 0.0050% or less.

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