JP7052391B2 - Manufacturing method of grain-oriented electrical steel sheet and grain-oriented electrical steel sheet - Google Patents

Description

The present invention relates to a grain-oriented electrical steel sheet having good magnetic characteristics and a method for manufacturing a grain-oriented electrical steel sheet.

The grain-oriented electrical steel sheet is a steel sheet containing Si in an amount of about 2% by mass to 5% by mass, and the orientation of the crystal grains of the steel sheet is highly integrated in the {110} <001> orientation called the Goss orientation. The grain-oriented electrical steel sheet has excellent magnetic characteristics and is used, for example, as an iron core material for a static induction device such as a transformer.

Various developments have been made for such grain-oriented electrical steel sheets in order to improve their magnetic properties. In particular, with the recent demand for energy saving, grain-oriented electrical steel sheets are required to have further low iron loss. In order to reduce the iron loss of the grain-oriented electrical steel sheet, it is effective to increase the degree of integration in the Goss direction with respect to the orientation of the crystal grains of the steel sheet to improve the magnetic flux density and reduce the hysteresis loss.

Further, in order to reduce the iron loss of the grain-oriented electrical steel sheet, it is also effective to reduce the abnormal eddy current loss by the magnetic domain subdivision treatment. The magnetic domain subdivision process includes a method of irradiating the surface of the steel sheet with a laser, plasma, electron beam, etc. to apply thermal strain to the steel sheet to subdivide the magnetic domain, and a method of forming grooves in the steel sheet to subdivide the magnetic domain. There is a method. The method of applying thermal strain to the steel sheet is extremely effective in reducing the abnormal eddy current loss, but there is a problem that the magnetic domain subdivision effect disappears when the steel sheet is strain-removed and annealed.

On the other hand, in the method of forming grooves in a steel sheet, the magnetic domain subdivision effect remains even after strain relief annealing (heat-resistant magnetic domain control). When a grain-oriented electrical steel sheet such as a wound steel sheet is formed to form an iron core, strain is introduced into the steel sheet, so that strain-removal annealing is required after molding. In such a case, the method of forming a groove in the steel sheet and subdividing the magnetic domain is very effective.

As a method of forming a groove in a steel sheet and subdividing the magnetic domain, for example, in Patent Documents 1 to 4, a groove is formed on the surface of the steel sheet, and the scattered alloy layer and the solidified portion of the groove are controlled in a controlled direction. A grain-oriented electrical steel sheet and a grain-oriented electrical steel sheet having a controlled groove shape are disclosed. Patent Document 5 discloses a grain-oriented electrical steel sheet having grooves on one side or both sides of the steel sheet while controlling the crystal orientation and grain shape of the secondary recrystallized grains of the steel sheet. Patent Document 6 discloses a method of forming a groove in an exposed portion of a base metal on at least one side of a steel sheet by electrolytic etching using a neutral salt solution. Patent Document 7 discloses an electromagnetic steel sheet in which linear or dotted grooves and / or heat-affected layers are formed on both the front and back surfaces of the steel sheet. In Patent Document 8, a resist film containing a photosensitive resin is applied to one or both sides of a cold-rolled steel sheet, and the applied surface is locally exposed for patterning, and is continuously or unsuccessfully developed in the plate width direction. A technique for forming a continuous linear groove is disclosed.

Special Table 2015-510543 JP-A-2015-117435 JP-A-2015-92028 Special Table 2016-523776 Gazette Japanese Unexamined Patent Publication No. 2001-26847 Japanese Unexamined Patent Publication No. 2001-316896 Japanese Unexamined Patent Publication No. 2000-109961 Japanese Patent No. 6146535

In recent years, with the progress of global transformer efficiency regulations, the demand for reducing iron loss of grain-oriented electrical steel sheets has become even greater. The magnetic domain subdivision method for forming grooves on the surface of a steel sheet is an excellent method for reducing iron loss in which the magnetic domain subdivision effect remains even after strain relief annealing, but there are two main problems. The first is that the cross-sectional area of the steel plate at the bottom of the groove is reduced by forming the groove, so that the magnetic flux is locally concentrated, so that the magnetic flux density B8 value decreases and the hysteresis loss increases. Is. The second is that the effect of reducing the abnormal eddy current loss due to groove formation is small. The deeper the groove, the greater the effect of reducing the abnormal eddy current loss, but since the magnetic flux density B8 value decreases and the hysteresis loss increases, it is necessary to solve the two problems at the same time.

With the techniques disclosed in Patent Documents 1 to 4 above, it is not possible to suppress the decrease in the magnetic flux density B8 value and reduce the abnormal eddy current loss at the same time, or even if it is possible to achieve both, the groove shape must be strictly controlled. Because it does not become, the production cost becomes large.

In the technique disclosed in Patent Document 5 above, it is necessary not only to control the crystal orientation and grain shape of the secondary recrystallized grains of the steel sheet, but also to suppress the decrease in the magnetic flux density B8 value due to the groove formation in detail. It was not considered.

In the technique disclosed in Patent Document 6 above, it is necessary to form a groove by electrolytic etching after removing the film of the directional electromagnetic steel plate having an insulating film after finish annealing, so that the production cost is not only high. No, the decrease in the magnetic flux density B8 value due to groove formation has not been investigated in detail.

In the technique disclosed in Patent Document 7, it is necessary to control the deviation of the groove on both the front and back surfaces and / or the formation position of the heat-affected layer to be equal to or less than the rolling direction width of the groove or the heat-affected layer, and the production cost is high. ..

In the technique disclosed in Patent Document 8 above, since groove formation requires resist film coating, patterning by local exposure, and electrolytic etching, not only the equipment cost is high, but also the magnetic flux density B8 due to groove formation is high. Suppression of price decline has not been investigated in detail.

Therefore, the present invention has been made in view of the above problems and the like, and an object of the present invention is to reduce the magnetic flux density B8 value when a groove is provided on a steel sheet to control a heat-resistant magnetic domain. A new and improved method for manufacturing grain-oriented electrical steel sheets, which can inexpensively produce grain-oriented electrical steel sheets with low iron loss by reducing abnormal eddy current loss due to the effect of subdividing magnetic domains, and the method thereof. It is an object of the present invention to provide a grain-oriented electrical steel sheet manufactured by a manufacturing method.

In order to solve the above problems, according to a certain viewpoint of the present invention, in terms of mass%, C: 0.02% or more and 0.10% or less, Si: 2.5% or more and 4.5% or less, Mn: 0. 0.01% or more and 0.15% or less, total of 1 or 2 of S and Se: 0.001% or more and 0.050% or less, acid-soluble Al: 0.010% or more and 0.050% or less , N: 0.002% or more and 0.015% or less, Cu: 0% or more and 0.30% or less, Sn: 0% or more and 0.30% or less, Ni: 0% or more and 0.30% or less, Cr: 0 % Or more and 0.30% or less, Sb: 0% or more and 0.30% or less, and Bi: 0% or more and 0.0500% or less, and the balance is Fe and impurities. In the process of making a hot-rolled steel plate by hot-rolling, and after hot-rolling the hot-rolled steel plate, one cold rolling or two or more cold rolling sandwiching an intermediate annealing. A step of making a cold-rolled steel sheet, a step of decarburizing and annealing the cold-rolled steel sheet, and applying a shrinking separator to the surface of the cold-rolled steel sheet after decarburization and annealing, and then performing finish annealing. It includes a step of applying an insulating film to a steel plate after finish annealing and then applying a flattening annealing step, and includes the cold rolling step, after decarburization annealing, after finish annealing, after applying an insulating film, or flattening. After annealing, the groove depth is 10 μm or more and 25 μm or less, the groove spacing is 2 mm or more and 10 mm or less, the angle of at least one side of the groove from the rolling direction is 65 ° or more and 85 ° or less, and the grooves on both sides of the steel plate are formed on the surface of the steel plate. When projected onto a plane parallel to, linear or dotted grooves are formed on both sides of the steel plate so that the grooves on one surface intersect with the grooves on the other surface, and the magnetic flux density B8 value is 1. Provided is a method for manufacturing a directional electromagnetic steel sheet having a low iron loss, which comprises obtaining a directional electromagnetic steel sheet having an iron loss of 82 T or more and an iron loss W17 / 50 of 0.78 W / kg or less .

In terms of mass%, the slab has Cu: 0.01% or more and 0.30% or less, Sn: 0.01% or more and 0.30% or less, Ni: 0.01% or more and 0.30% or less, Cr: 0. It may contain any one or more of 0.01% or more and 0.30% or less, or Sb: 0.01% or more and 0.30% or less.

The slab may contain Bi: 0.0005% or more and 0.0500% or less.

When the groove formation is carried out after the insulating film is applied and / or after the flattening annealing, the magnetic flux density B8 value before the groove formation may be 1.92 T or more.

When the groove formation is performed after the insulating film is applied and / or after the flattening annealing, the difference between the magnetic flux density B8 values before and after the groove formation is 0.1 T or less, and the reduction rate of the iron loss W17 / 50 is 7. It may be% or more.

In the groove formation described above, the groove formation on one side or both sides of the steel sheet may be due to laser irradiation.

Further, in order to solve the above-mentioned problems, according to another viewpoint of the present invention, in terms of mass%, Si: 2.5% or more and 4.5% or less, Mn: 0.01% or more and 0.15% or less, Cu: 0% or more and 0.30% or less, Sn: 0% or more and 0.30% or less, Ni: 0% or more and 0.30% or less, Cr: 0% or more and 0.30% or less, and Sb: 0% or more. It has a base steel sheet containing 0.30% or less and the balance is Fe and impurities, and has an insulating film on the surface of the steel sheet. Below, when it has linear or dotted grooves, the angle of the groove on at least one side from the rolling direction is 65 ° or more and 85 ° or less, and the grooves on both sides of the steel sheet are projected onto a surface parallel to the surface of the steel sheet. In addition, the groove on one surface is arranged so as to intersect the groove on the other surface, and the magnetic flux density B8 value is 1.82T or more and the iron loss W17 / 50 is 0.78W / kg or less. A featured grain-oriented electrical steel sheet is provided.

In terms of mass%, the base steel sheet has Cu: 0.01% or more and 0.30% or less, Sn: 0.01% or more and 0.30% or less, Ni: 0.01% or more and 0.30% or less, Cr. : 0.01% or more and 0.30% or less, or Sb: 0.01% or more and 0.30% or less, whichever one or more may be contained.

With the above configuration, when heat-resistant magnetic domain control is applied to a grain-oriented electrical steel sheet, when the grooves on both sides of the steel sheet are projected onto a surface parallel to the surface of the steel sheet, the grooves on one surface intersect with the grooves on the other surface. By forming the grooves in this way, it is possible to inexpensively manufacture grain-oriented electrical steel sheets having low iron loss while suppressing a decrease in the magnetic flux density B8 value.

As described above, according to the present invention, when the heat-resistant magnetic domain control is applied to the grain-oriented electrical steel sheet, the grain-oriented electrical steel sheet having low iron loss can be manufactured at low cost while suppressing the decrease in the magnetic flux density B8 value. Is possible.

It is a figure which projected the arrangement of the steel plate, the groove formed on the upper surface of a steel plate, and the groove formed on the lower surface of a steel plate onto a plane parallel to the surface of the steel plate, schematically shown.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The "groove angle" defined in the present invention is "the angle between the stretching direction of the groove and the rolling direction of the steel sheet when the groove on the surface of the steel sheet is projected onto a surface parallel to the surface of the steel sheet". Strictly speaking, the groove may not be a perfect straight line, but in this case, the overall stretched shape of one groove is defined as the “groove stretching direction”. In the present specification, this may be simply referred to as "groove angle", "angle from the rolling direction of the groove" and the like.

Further, the spatial arrangement of the grooves in the present invention is "when the grooves on both sides of the steel plate are projected onto a surface parallel to the surface of the steel plate, the grooves on one surface intersect with the grooves on the other surface". .. Hereinafter, this may be simply described as "grooves intersect", "grooves overlap", "grooves are formed so as to intersect", etc., but in the present invention, the groove on one surface and the groove on the other surface are described. It does not intersect spatially, but merely means "intersection on the projection surface" when the grooves on both sides of the steel sheet are projected onto a surface parallel to the surface of the steel sheet.

The angle from the rolling direction of the groove is "the angle formed by the stretching direction of the groove and the rolling direction of the steel plate when the upper surface and the lower surface of the steel plate are viewed from the surface side of each steel plate". The angle formed by the two straight lines (directions) can be determined between an acute angle and an obtuse angle, but in the present invention, the angle of the groove is defined by the angle of the acute angle, that is, the angle of 0 to 90 °.

Furthermore, the surface of a steel sheet may be described as "upper and lower (face)", but it does not represent a specific relationship with respect to the spatial position of the steel sheet, and "any one surface" and "the other surface". It is intended to distinguish between.

In order to inexpensively manufacture grain-oriented electrical steel sheets with low iron loss while suppressing a decrease in the magnetic flux density B8 value when grooves are formed in the grain-oriented electrical steel sheets and heat-resistant magnetic domain control is performed. As a result of diligent studies on the manufacturing method of grain-oriented electrical steel sheets, the following findings were found.

Specifically, the present inventors suppress a decrease in the magnetic flux density B8 value and reduce anomalous eddy current loss due to subdivision of the magnetic domain when a groove is formed on the surface of the grain-oriented electrical steel sheet to control the heat-resistant magnetic domain. To solve the problem of achieving both reduction, by forming grooves so as to intersect both the upper and lower surfaces of the steel sheet, it is possible to inexpensively manufacture a grain-oriented electrical steel sheet with low iron loss while suppressing a decrease in the magnetic flux density B8 value. Found that is possible.

The present inventors have come up with the present invention by considering the above findings. One embodiment of the present invention is a method for manufacturing a grain-oriented electrical steel sheet having the following configuration.

By mass%, C: 0.02% or more and 0.10% or less, Si: 2.5% or more and 4.5% or less, Mn: 0.01% or more and 0.15% or less, one of S and Se Or the total of the two types: 0.001% or more and 0.050% or less, acid-soluble Al: 0.01% or more and 0.05% or less, N: 0.002% or more and 0.015% or less, Cu: 0% or more 0.30% or less, Sn: 0% or more and 0.30% or less, Ni: 0% or more and 0.30% or less, Cr: 0% or more and 0.30% or less, Sb: 0% or more and 0.30% or less, And Bi: A step of heating a slab containing 0% or more and 0.05% or less and having a balance of Fe and impurities to 1280 ° C. or higher and hot rolling to obtain a hot-rolled steel sheet, and the above-mentioned step. After hot-rolling the hot-rolled steel sheet, it is cold-rolled once or cold-rolled two or more times with intermediate baking in between to make a cold-rolled steel sheet, and the cold-rolled steel sheet is removed. A step of applying charcoal annealing, a step of applying a shrinking separator to the surface of the cold-rolled steel sheet after decarburization, a step of applying a finish annealing, and a step of applying an insulating film to the steel sheet after finish annealing, and then flattening and annealing. The groove depth is 10 μm or more and 25 μm or less, and the groove spacing is 1, Linear or dotted grooves are formed on both sides of the steel plate so that the angle from the rolling direction of the groove on at least one side is 65 ° or more and 85 ° or less, and the grooves intersect, 2 mm or more and 10 mm or less.

Hereinafter, the method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment will be specifically described.

First, the component composition of the slab used for the grain-oriented electrical steel sheet according to the present embodiment will be described. In the following, unless otherwise specified, the notation "%" means "mass%". The rest of the slabs other than the elements described below are Fe and impurities.

The content of C (carbon) is 0.02% or more and 0.10% or less. C has various roles, but when the C content is less than 0.02%, the crystal grain size becomes excessively large when the slab is heated, resulting in iron loss of the final grain-oriented electrical steel sheet. It is not preferable because it increases the value. When the C content is more than 0.10%, the decarburization time becomes long and the manufacturing cost increases during decarburization after cold rolling, which is not preferable. Further, when the C content is more than 0.10%, decarburization tends to be incomplete, which may cause magnetic aging in the final grain-oriented electrical steel sheet, which is not preferable. Therefore, the content of C is 0.02% or more and 0.10% or less, preferably 0.05% or more and 0.09% or less.

The content of Si (silicon) is 2.5% or more and 4.5% or less. Si reduces the eddy current loss, which is one of the causes of iron loss, by increasing the electric resistance of the steel sheet. When the Si content is less than 2.5%, it becomes difficult to sufficiently suppress the eddy current loss of the final grain-oriented electrical steel sheet, which is not preferable. When the Si content is more than 4.5%, the workability of the grain-oriented electrical steel sheet is deteriorated, which is not preferable. Therefore, the Si content is 2.5% or more and 4.5% or less, preferably 2.7% or more and 4.0% or less.

The content of Mn (manganese) is 0.01% or more and 0.15% or less. Mn forms MnS, MnSe and the like, which are inhibitors that influence secondary recrystallization. When the Mn content is less than 0.01%, the absolute amounts of MnS and MnSe that cause secondary recrystallization are insufficient, which is not preferable. When the Mn content is more than 0.15%, it is not preferable because it becomes difficult to dissolve Mn during slab heating. Further, when the Mn content is more than 0.15%, the precipitation sizes of the inhibitors MnS and MnSe tend to be coarse, and the optimum size distribution as an inhibitor is impaired, which is not preferable. Therefore, the Mn content is 0.01% or more and 0.15% or less, preferably 0.03% or more and 0.13% or less.

The total content of S (sulfur) and Se (selenium) is 0.001% or more and 0.050% or less. S and Se form an inhibitor together with Mn described above. Both S and Se may be contained in the slab, but at least one of them may be contained in the slab. If the total content of S and Se is out of the above range, a sufficient inhibitory effect cannot be obtained, which is not preferable. Therefore, the total content of S and Se is 0.001% or more and 0.050% or less, preferably 0.001% or more and 0.040% or less.

The content of acid-soluble Al (acid-soluble aluminum) is 0.01% or more and 0.05% or less. The acid-soluble Al constitutes an inhibitor necessary for producing a grain-oriented electrical steel sheet having a high magnetic flux density. When the content of the acid-soluble Al is less than 0.01%, the acid-soluble Al is insufficient in quantity and the inhibitor strength is insufficient, which is not preferable. When the content of the acid-soluble Al is more than 0.05%, AlN precipitated as an inhibitor is coarsened and the inhibitor strength is lowered, which is not preferable. Therefore, the content of acid-soluble Al is 0.01% or more and 0.05% or less, preferably 0.01% or more and 0.04% or less.

The content of N (nitrogen) is 0.002% or more and 0.015% or less. N forms the inhibitor AlN together with the acid-soluble Al described above. If the content of N is out of the above range, a sufficient inhibitory effect cannot be obtained, which is not preferable. Therefore, the content of N is 0.002% or more and 0.015% or less, preferably 0.002% or more and 0.012% or less.

Further, in the slab used for manufacturing the grain-oriented electrical steel sheet according to the present embodiment, in addition to the above-mentioned elements, any of Cu, Sn, Ni, Cr, or Sb is used as an element for stabilizing secondary recrystallization. It may contain one kind or two or more kinds. When the slab contains the above elements, the magnetic flux density of the manufactured grain-oriented electrical steel sheet can be further improved.

The content of each of these elements may be 0.01% or more and 0.30% or less. When the content of each of these elements is less than 0.01%, the effect of stabilizing secondary recrystallization is not sufficiently obtained, which is not preferable. When the content of each of these elements is more than 0.30%, the effect of stabilizing secondary recrystallization is saturated, which is not preferable from the viewpoint of suppressing an increase in production cost.

Further, the slab used for manufacturing the grain-oriented electrical steel sheet according to the present embodiment may contain Bi (bismuth) as an element for sharpening secondary recrystallization in addition to the above-mentioned elements.

The Bi content may be 0.0005% or more and 0.0500% or less. Bi is presumed to have the effect of enhancing the heat resistance of the inhibitors MnS and AlN, raising the secondary recrystallization temperature, and improving the magnetic flux density. When the Bi content is less than 0.0005%, it is not preferable because a sufficient inhibitor heat resistance enhancing effect cannot be obtained. When the Bi content is more than 0.0500%, the brittleness of the steel sheet in hot rolling deteriorates, making it difficult to pass the sheet, and the productivity is lowered, which is not preferable. Therefore, the Bi content may be 0.0005% or more and 0.0500% or less, and more preferably 0.0010% or more and 0.0200% or less.

A slab is formed by casting molten steel adjusted to the composition of the composition described above. The method of casting the slab is not particularly limited. Further, in research and development, even if a steel ingot is formed in a vacuum melting furnace or the like, the same effect as when a slab is formed can be confirmed for the above components.

Subsequently, the slab is heated to 1280 ° C. or higher to completely dissolve the inhibitor component in the slab. When the heating temperature of the slab is less than 1280 ° C., it becomes difficult to sufficiently dissolve the inhibitor components such as MnS, MnSe, and AlN, which is not preferable. The upper limit of the heating temperature of the slab at this time is not particularly determined, but is preferably 1450 ° C. from the viewpoint of equipment protection. For example, the heating temperature of the slab may be 1300 ° C. or higher and 1450 ° C. or lower.

Next, the heated slab is hot-rolled and processed into a hot-rolled steel sheet. The thickness of the hot-rolled steel sheet after processing may be, for example, 1.8 mm or more and 3.5 mm or less. When the thickness of the hot-rolled steel sheet is less than 1.8 mm, the temperature of the steel sheet after hot rolling becomes low and the amount of AlN deposited in the steel sheet increases, resulting in unstable secondary recrystallization, for example. It is not preferable for a grain-oriented electrical steel sheet having a final thickness of 0.23 mm or less because the magnetic properties are deteriorated. When the thickness of the hot-rolled steel sheet exceeds 3.5 mm, the rolling load in the cold rolling process becomes large, which is not preferable.

Subsequently, the processed hot-rolled steel sheet is cold-rolled by being subjected to hot-rolled sheet annealing and then rolled by one cold rolling or a plurality of cold rollings sandwiching intermediate annealing. It is processed into a steel plate. When rolling by cold rolling a plurality of times with intermediate annealing sandwiched between them, it is possible to omit the hot-rolled sheet annealing in the previous stage. However, when hot-rolled sheet is annealed, the shape of the steel sheet becomes better, so that the possibility of the steel sheet breaking during cold rolling can be reduced.

Further, the steel sheet may be heat-treated at about 300 ° C. or lower between the cold rolling passes, between the rolling roll stands, or during rolling. In such a case, the magnetic properties of the final grain-oriented electrical steel sheet can be improved. The hot-rolled steel sheet may be rolled by cold rolling three or more times, but since the cold rolling a large number of times increases the manufacturing cost, the hot-rolled steel sheet is cold-rolled once or twice. It is preferably rolled by rolling. When the cold rolling is performed by reverse rolling such as Zendimia mill, the number of passes in each cold rolling is not particularly limited, but from the viewpoint of manufacturing cost, 9 times or less is preferable.

Next, the cold-rolled steel sheet is decarburized and annealed. Rapid heating in the process of raising the temperature is also effective in improving the magnetic characteristics. These processes are also referred to as primary recrystallization annealing, and in the case of rapid heating, they are preferably performed continuously with decarburization annealing. Decarburization annealing is carried out in a moist atmosphere containing hydrogen and nitrogen, for example, at a temperature of 900 ° C. or lower. The cold-rolled steel sheet may be subjected to reduction annealing following decarburization annealing for the purpose of improving magnetic properties and coating properties.

After that, an annealing separator is applied to the cold-rolled steel sheet after decarburization annealing for the purpose of preventing seizure between the steel sheets in the subsequent finish annealing, forming a primary film, and controlling the secondary recrystallization behavior. At this time, an annealing separator containing MgO as a main component may be applied. The annealing separator is generally applied and dried on the surface of a steel sheet in the state of a water slurry, but an electrostatic coating method or the like may be used. Here, when Bi is added to the slab, the adhesion between the primary coating and the steel sheet after _finish annealing may deteriorate. Alkaline earth metal compounds and the like may be added in combination. When the primary film is not formed on the surface of the steel sheet in the finish annealing, an annealing separator containing Al ₂ O ₃ may be applied as the annealing separator.

Subsequently, finish annealing is performed for the purpose of secondary recrystallization. Finish annealing may be performed by holding the coiled steel sheet for 20 hours or more at a temperature of 800 ° C. to 1000 ° C. using, for example, a batch type heating furnace or the like. Further, in order to further reduce the iron loss value of the final grain-oriented electrical steel sheet, a purification treatment for raising the temperature of the coiled steel sheet to a temperature of about 1200 ° C. may be performed.

The average heating rate in the process of raising the temperature of the finish annealing is not particularly limited, and general finish annealing conditions can be used. For example, the average heating rate in the heating process of the finish annealing including the secondary recrystallization annealing may be 5 ° C./h to 100 ° C./h from the viewpoint of productivity and general equipment constraints. Further, the temperature raising process of finish annealing may be performed by another known heat pattern.

The atmospheric gas composition in the finish annealing is not particularly limited. In the process of secondary recrystallization, a mixed gas of nitrogen and hydrogen may be used. It may be a dry atmosphere or a moist atmosphere. The purified annealing may be dry hydrogen gas.

Subsequently, after finish annealing, an insulating film containing, for example, aluminum phosphate or colloidal silica as a main component is applied to the surface of the steel sheet for the purpose of imparting insulating properties to the steel sheet. After that, flattening annealing is performed for the purpose of baking the insulating film and flattening the steel sheet shape by finish annealing. As long as the steel sheet is provided with insulating properties, the components of the insulating film are not particularly limited. Here, applying tension to the steel sheet by the insulating film also has a magnetic domain subdivision effect, and is effective in reducing iron loss. The tension is preferably strong as long as the insulating film does not peel off. Further, since the insulating film may be peeled off due to the formation of the groove, it is preferable to provide the step of applying the insulating film even after the formation of the groove.

The heat-resistant magnetic domain control for forming grooves on the surface of the steel sheet may be performed after the cold rolling step, after decarburization annealing, after finish annealing, after applying an insulating film, or after flattening annealing. However, in consideration of production risks such as coil breakage and secondary recrystallization failure in the manufacturing process of grain-oriented electrical steel sheet, the step of forming a groove on the surface of the steel sheet is preferable as it approaches the final step. Grooves are formed on each of the upper surface and the lower surface of the steel sheet surface, but either surface may be the first, the grooves may be formed at the same time, or the grooves may be formed in another step.

As shown in FIG. 1A, the groove is formed so that the grooves intersect the upper surface and the lower surface of the steel sheet surface. By intersecting the grooves, it is possible to suppress a decrease in the magnetic flux density B8 value while maintaining the iron loss reduction effect due to the subdivision of the magnetic domain. The details of this mechanism are not clear, but it is presumed as follows. That is, the heat-resistant magnetic domain control in which the groove is formed on the surface of the steel sheet has a smaller magnetic domain subdivision effect and a smaller effect of reducing the abnormal eddy current loss than the magnetic domain control in which thermal strain is applied by laser irradiation or the like. The deeper the groove, the more the magnetic domain subdivision effect increases and the abnormal eddy current loss also decreases, but the cross-sectional area of the base steel sheet decreases, so the magnetic flux density B8 value decreases, and the hysteresis loss increases. At the same time, it leads to an increase in the size of the iron core of the transformer, which is not preferable.

When grooves are formed on both the upper surface and the lower surface of the steel sheet, the effect of superimposing the magnetic domain subdivision effect of the groove on the upper surface and the magnetic domain subdivision effect of the groove on the lower surface can be expected, but the magnetic flux density B8 value is not necessarily the same. It was not possible to suppress the decrease in magnetic flux. As a result of diligently working on the problem, the present inventors have found that the decrease in the magnetic flux density B8 value can be suppressed by crossing the groove on the upper surface and the groove on the lower surface.

If the groove on the upper surface and the groove on the lower surface are arranged without deviation, the cross-sectional area of the base steel plate is locally reduced, and the magnetic flux density B8 value is the same as in the case where the deep groove is arranged on one side. The decrease is large. As shown in FIG. 1 (b), when the groove on the upper surface and the groove on the lower surface are displaced and arranged in parallel, the decrease in the magnetic flux density B8 value is smaller than that in the case where there is no displacement, but the iron loss. The decrease in the magnetic flux density B8 value is large compared to the reduction effect. It is presumed that the cause is that the magnetic flux flows inside the base metal plate meandering in the plate thickness direction in a short cycle of the groove spacing while avoiding the grooves. On the other hand, when the groove on the upper surface and the groove on the lower surface are arranged so as to intersect each other, the magnetic flux inside the base steel plate meanders in the in-plane direction of the base steel plate while avoiding the place where the grooves on the upper and lower surfaces overlap. It becomes possible to flow. It is presumed that such an effect cannot be obtained when the grooves on the upper and lower surfaces are arranged in parallel, because there is no energy gain even if the magnetic flux meanders in the in-plane direction of the base steel plate. To.

Further, according to the manufacturing method in which the grooves are formed so as to intersect the upper and lower surfaces, it is possible to inexpensively manufacture the grain-oriented electrical steel sheet in which the heat-resistant magnetic domain control treatment is uniformly applied to the entire steel sheet. For example, when the grooves on the upper and lower surfaces are arranged in parallel, the state of the decrease in the magnetic flux density B8 value changes greatly depending on the position of the grooves, so it is necessary to strictly control the position where the grooves are formed. In this case, since it is necessary to introduce special equipment or slow down the groove formation speed, the production cost becomes high, which is not preferable. On the other hand, when the grooves are formed so as to intersect the upper and lower surfaces of the steel sheet, it is not necessary to consider the groove forming position, so that the magnetic domain control process can be uniformly applied to the entire plate surface at low cost.

The groove direction is such that the angle from the rolling direction of the groove on at least one side is 65 ° or more and 85 ° or less. When the angle from the rolling direction is less than 65 °, the effect of magnetic domain subdivision is reduced and a sufficient iron loss reduction effect cannot be obtained, which is not preferable. When the angle from the rolling direction is more than 85 °, the grooves on the upper surface and the lower surface approach parallel to each other, and the effect of suppressing the decrease in the magnetic flux density B8 value is reduced, which is not preferable. Therefore, the groove direction is such that the angle from the rolling direction of the groove on at least one side is 65 ° or more and 85 ° or less. Whether the angle of the groove from the rolling direction is tilted counterclockwise or clockwise, the same effect can be obtained by arranging the grooves so that the grooves intersect on the upper surface and the lower surface of the steel sheet. Here, the angle of the groove on the other surface from the rolling direction is preferably 65 ° or more and 90 ° or less. Further, when the grooves on both sides of the steel sheet are projected onto a surface parallel to the surface of the steel sheet, the angle at which the grooves on both sides intersect is preferably 5 ° or more, and the angle between the grooves on one surface and the groove on the other side is inclined. It is more preferable that the angle of the groove on the surface is tilted in the opposite direction when the angle of the groove on the other surface from the rolling direction is not 90 °.

The depth of the groove is 10 μm or more and 25 μm or less. If the groove depth is less than 10 μm, a sufficient iron loss reduction effect cannot be obtained, which is not preferable. When the depth of the groove is more than 25 μm, the decrease in the magnetic flux density B8 value becomes too large, which is not preferable. Therefore, the groove depth is 10 μm or more and 25 μm or less. The groove depth may be the same or different on the upper surface and the lower surface of the steel sheet.

The groove spacing is 2 mm or more and 10 mm or less. If the groove spacing is less than 2 mm, the decrease in the magnetic flux density B8 value becomes too large, which is not preferable. When the groove spacing is more than 10 mm, a sufficient iron loss reduction effect cannot be obtained, which is not preferable. Therefore, the groove spacing is 2 mm or more and 10 mm or less. The spacing between the grooves may be the same or different on the upper surface and the lower surface of the steel sheet.

The shape of the groove may be linear or dotted, but in either case, it is preferable that the groove is arranged along a straight line without being curved. The upper surface and the lower surface of the steel sheet may be the same or different. However, in order to uniformly exert the magnetic domain subdivision effect on the entire steel sheet, the linear shape is preferable. The width of the groove, the bottom, and the shape of the side surface are not particularly limited.

As for the method of forming a groove on the surface of the steel sheet, a tooth mold or a gear may be mechanically pressed, chemical etching may be used, or the steel sheet base material may be locally melted and evaporated by laser irradiation. .. However, if tooth molds or gears are mechanically pressed against both the upper and lower surfaces of the steel sheet, the possibility of creases and wrinkles in the steel sheet increases. It is preferable to form grooves by irradiation, not only because it is easy to change the angle, spacing, and depth of the grooves, but also from the viewpoints of productivity, equipment maintainability, and cost.

Since the magnetic flux density B8 value of the base steel sheet forming the groove is lowered due to the formation of the groove, it is preferable that the magnetic flux density B8 value is high before the groove is formed. For example, when the groove is formed after the insulating film is applied and / or after the flattening annealing, the magnetic flux density B8 value is preferably 1.92 T or more in the state before the groove is formed. Here, the magnetic flux density B8 value is the magnetic flux density when a magnetic field of 800 A / m is applied to the grain-oriented electrical steel sheet at 50 Hz.

The decrease in the magnetic flux density B8 value when the grooves are formed on the upper surface and the lower surface of the steel sheet is preferably small in order to suppress an increase in hysteresis loss and an increase in the size of the core of the transformer. For example, when the formation of the groove is carried out after the insulating film is applied and / or after the flattening annealing, the decrease in the magnetic flux density B8 value due to the formation of the groove is preferably 0.1 T or less.

The reduction rate of the iron loss W17 / 50 when the grooves are formed on the upper surface and the lower surface of the steel sheet is preferably large because it leads to the reduction of the energy loss when the transformer is used. For example, when the groove is formed after the insulating film is applied and after flattening and annealing, the reduction rate of the iron loss W17 / 50 is 7% or more based on the iron loss W17 / 50 before the groove formation. Is preferable. Here, W _17/50 is the iron loss when the grain-oriented electrical steel sheet is excited to 1.7 T at 50 Hz.

The magnetic properties of grain-oriented electrical steel sheets such as magnetic flux density and iron loss can be measured by known methods. For example, the magnetic properties of grain-oriented electrical steel sheets are measured by using a method based on the Epstein test specified in JIS C2550, or a single plate magnetic property test method (Single Sheet Tester: SST) specified in JIS C2556. be able to.

The thickness of the base steel plate forming the groove is not particularly limited. However, the thinner the plate thickness, the greater the decrease in the magnetic flux density B8 value when the groove is formed. Therefore, the present invention is preferably applied to, for example, a grain-oriented electrical steel sheet having a plate thickness of 0.30 mm or less. It is more preferable to apply it to grain-oriented electrical steel sheets having a plate thickness of 0.23 mm or less.

By the above steps, the final grain-oriented electrical steel sheet can be manufactured. When the grain-oriented electrical steel sheet thus obtained is processed into a transformer, for example, in a wound iron core transformer, it is wound into a predetermined size and then shape-corrected by a mold or the like. Here, since the strain introduced at the time of shape straightening increases the iron loss among the magnetic properties, the iron core after the shape straightening is subjected to strain removal annealing. In order to maintain excellent magnetic properties even after such strain removal annealing, it is effective to apply heat-resistant magnetic domain control. According to the manufacturing method according to the present embodiment, when the heat-resistant magnetic domain control is applied to the grain-oriented electrical steel sheet, the grain-oriented electrical steel sheet having low iron loss is manufactured at low cost while suppressing the decrease in the magnetic flux density B8 value. Can be done.

Even if a grain-oriented electrical steel sheet having a magnetic flux density B8 value of 1.92T or more when no grooves are formed is manufactured by a manufacturing method different from the above, the above-mentioned heat-resistant magnetic domain control is performed. If this is the case, the effect of inexpensively manufacturing grain-oriented electrical steel sheets with low iron loss is expected while suppressing a decrease in the magnetic flux density B8 value in the same manner as described above.

In the grain-oriented electrical steel sheet according to the present embodiment, it is important to control the content of the following elements in the component composition contained in the grain-oriented electrical steel sheet in order to increase the magnetic flux density and reduce the iron loss. be.

Si reduces the eddy current loss that forms part of the iron loss by increasing the electrical resistance of the steel sheet. Si is contained in the grain-oriented electrical steel sheet in the range of 2.5% or more and 4.5% or less in mass%, and is contained in the grain-oriented electrical steel sheet in the range of 2.7% or more and 4.0% or less. Is preferable. When the Si content is less than 2.5%, it becomes difficult to suppress the eddy current loss of the grain-oriented electrical steel sheet, which is not preferable. When the Si content is more than 4.5%, the workability of the grain-oriented electrical steel sheet is deteriorated, which is not preferable.

Mn forms MnS and MnSe, which are inhibitors that influence secondary recrystallization. Mn is contained in the grain-oriented electrical steel sheet in the range of 0.01% or more and 0.15% or less in mass%, and is contained in the grain-oriented electrical steel sheet in the range of 0.03% or more and 0.13% or less. Is preferable. When the Mn content is less than 0.01%, the absolute amounts of MnS and MnSe that cause secondary recrystallization are insufficient, which is not preferable. When the Mn content is more than 0.15%, it becomes difficult to dissolve Mn during slab heating, and the precipitation size of the inhibitor becomes coarse, which impairs the optimum size distribution of the inhibitor, which is not preferable.

The balance of the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present invention consists of Fe and impurities. Here, the impurities are those mixed from the ore as a raw material, scrap, or the manufacturing environment when the base steel sheet is industrially manufactured, or are not completely purified by purification annealing and are contained in the steel. It means the following remaining elements and the like that are permissible as long as they do not adversely affect the grain-oriented electrical steel sheet of the present invention.

Further, according to the heat-resistant magnetic domain control method found by the present inventors, which has excellent magnetic properties, the surface of the steel sheet has an insulating coating, the groove depth is 10 μm or more and 25 μm or less on both sides of the steel sheet, and the groove spacing is large. It is 2 mm or more and 10 mm or less, has linear or dotted grooves, has an angle of at least one side of the groove from the rolling direction of 65 ° or more and 85 ° or less, and is arranged so that the grooves on both sides intersect.

In the grain-oriented electrical steel sheet according to the present embodiment, the magnetic flux density B8 value is further controlled. Specifically, it is 1.82T or more in the grain-oriented electrical steel sheet according to the present embodiment. If it is less than 1.82T, not only the hysteresis loss increases, but also the size of the core of the transformer becomes large, which is not preferable. The upper limit is not particularly set because the higher the magnetic flux density is, the more preferable it is.

In the grain-oriented electrical steel sheet according to the present embodiment, the iron loss W17 / 50 is further controlled. Specifically, it is 0.78 W / kg or less in the grain-oriented electrical steel sheet according to the present embodiment. If it exceeds 0.78 W / kg, energy loss increases when it is used as an iron core material of a transformer, which is not preferable. The lower limit is not particularly set because the lower the iron loss is, the more preferable it is.

Further, the grain-oriented electrical steel sheet according to the present embodiment may contain any one or more of Cu, Sn, Ni, Cr, or Sb as an element for stabilizing secondary recrystallization. When the grain-oriented electrical steel sheet contains the above elements, the iron loss value can be further reduced, so that better magnetic properties can be obtained.

The content of each of these elements may be 0.01% or more and 0.30% or less. When the content of each of these elements is less than 0.01%, the effect of stabilizing secondary recrystallization is not sufficiently obtained, which is not preferable. When the content of each of these elements is more than 0.30%, the effect of stabilizing secondary recrystallization is saturated, which is not preferable from the viewpoint of suppressing an increase in the manufacturing cost of grain-oriented electrical steel sheets.

Hereinafter, a method for manufacturing a grain-oriented electrical steel sheet and a grain-oriented electrical steel sheet according to an embodiment of the present invention will be described more specifically with reference to examples. It should be noted that the examples shown below are merely examples of the grain-oriented electrical steel sheets according to the present embodiment, and the grain-oriented electrical steel sheets according to the present embodiment are not limited to the examples shown below.

(Example 1)
First, in terms of mass%, C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.024%, acid-soluble Al: 0.03%, N: 0.009%. Steel ingot A containing Fe and impurities as the balance, and by mass%, C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.024%, acid-soluble Al. A steel ingot B containing: 0.008% and N: 0.009% and the balance of which was Fe and impurities was prepared. The ingot was annealed at 1350 ° C. for 1 hour and then hot-rolled to obtain a hot-rolled steel sheet having a plate thickness of 2.3 mm. The obtained hot-rolled steel sheet was annealed at a maximum temperature of 1100 ° C. for 140 seconds, pickled and then cold-rolled to obtain a cold-rolled steel sheet having a plate thickness of 0.23 mm.

Subsequently, the obtained cold-rolled steel sheet was decarburized and annealed in a wet hydrogen atmosphere at 850 ° C. for 180 seconds. Next, an annealing separator containing MgO was applied to the surface of the steel sheet after decarburization and annealing, then finish annealing was performed, and the steel sheet after finish annealing was washed with water. Then, an insulating film containing aluminum phosphate and colloidal silica as main components was applied to the surface of the steel sheet, and then flattening annealing was performed for the purpose of baking the insulating film and flattening the steel sheet.

After shearing and annealing the sample of the grain-oriented electrical steel sheet obtained above, the grain-oriented electrical steel sheet according to each of the examples of the present invention and the comparative example is used by a single plate measuring method having a sample size of 60 mm × 300 mm. The magnetic flux density B8 value and the iron loss W17 / 50 were measured. Here, the B8 value is the magnetic flux density of the grain-oriented steel sheet when the grain-oriented electrical steel sheet is excited at 800 A / m at 50 Hz, and W17 / 50 is the magnetic flux density of the grain-oriented electrical steel sheet excited at 1.7 T at 50 Hz. It is an iron loss when it is done.

Further, for the above sample, grooves were formed on the surface of the steel sheet under the conditions shown in Tables 1 and 2. Here, the angle from the rolling direction of the groove is a positive value when the angle from the rolling direction of the groove is an acute angle from the rolling direction when facing the surface on which the groove is formed. I wrote it down. On the other hand, when the angle of the groove from the rolling direction is an acute angle counterclockwise from the rolling direction, a negative value is described. That is, when the groove on the surface of the steel plate is projected onto a surface parallel to the surface of the steel plate, if the angle from the rolling direction of the groove is rotated in the opposite direction on the upper and lower surfaces, the groove angle shown in Table 1 is , Both the upper surface and the lower surface have positive or negative values. For example, when the grooves are arranged in parallel on the upper and lower surfaces, the groove angles shown in Table 1 have the same absolute value on the upper surface and the lower surface. The positive and negative are reversed. Table 1 also describes whether the grooves are arranged at the same position on the front and back, parallel to each other, or intersect. Further, after applying an insulating film containing aluminum phosphate and colloidal silica as main components to the surface of the steel sheet, the insulating film is baked and annealed by strain removal, and then the final magnetic characteristics are shown in the examples of the present invention and comparative examples. The magnetic flux density B8 value and the iron loss W17 / 50 of the grain-oriented electrical steel sheet were measured.

Here, it was determined that the condition that the magnetic flux density B8 value of the grain-oriented electrical steel sheet was 1.82 T or more and the iron loss W17 / 50 was 0.78 W / kg or less was good.

Tables 1 and 2 show the manufacturing conditions and measurement results of the above-mentioned examples of the present invention and comparative examples.

With reference to the results in Tables 1 and 2, it was found that the grain-oriented electrical steel sheets satisfying the conditions of the present embodiment were judged to be good. Further, under the condition that the judgment is good, the magnetic flux density B8 value before the groove formation is 1.92T or more, the difference between the magnetic flux density B8 values before and after the groove formation is 0.1T or less, and the iron loss before and after the groove formation. The reduction rate of W17 / 50 was 7% or more. The method of groove formation may be one-sided or two-sided laser irradiation.

(Example 2)
First, in terms of mass%, C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.024%, acid-soluble Al: 0.03%, N: 0.009%. A steel ingot containing Fe and impurities in the balance was prepared. The ingot was annealed at 1350 ° C. for 1 hour and then hot-rolled to obtain a hot-rolled steel sheet having a plate thickness of 2.3 mm. The obtained hot-rolled steel sheet was annealed at a maximum temperature of 1100 ° C. for 140 seconds, pickled and then cold-rolled to obtain a cold-rolled steel sheet having a plate thickness of 0.23 mm.

Subsequently, the obtained cold-rolled steel sheet was decarburized and annealed in a wet hydrogen atmosphere at 850 ° C. for 180 seconds. Next, an annealing separator containing MgO was applied to the surface of the steel sheet after decarburization and annealing, then finish annealing was performed, and the steel sheet after finish annealing was washed with water. Then, an insulating film containing aluminum phosphate and colloidal silica as main components was applied to the surface of the steel sheet, and then flattening annealing was performed for the purpose of baking the insulating film and flattening the steel sheet.

Here, in the process shown in Table 3, a linear groove was formed on the surface of the base steel sheet. Groove formation was performed by laser irradiation so as to intersect the upper surface and the lower surface of the steel sheet. Here, the angle from the rolling direction of the groove is set to be an acute angle of 75 ° clockwise from the rolling direction when facing the surface on which the groove is formed. The groove depth was 15 μm, and the groove spacing was 5 mm.

After shearing and annealing the sample of the grain-oriented electrical steel sheet obtained above, the grain-oriented electrical steel sheet according to each of the examples of the present invention and the comparative example is used by a single plate measuring method having a sample size of 60 mm × 300 mm. The magnetic flux density B8 value and the iron loss W17 / 50 were measured. Here, the B8 value is the magnetic flux density of the grain-oriented steel sheet when the grain-oriented electrical steel sheet is excited at 800 A / m at 50 Hz, and W17 / 50 is the magnetic flux density of the grain-oriented electrical steel sheet excited at 1.7 T at 50 Hz. It is an iron loss when it is done.

Here, it was determined that the conditions under which the magnetic flux density B8 value of the grain-oriented electrical steel sheet was 1.82 T or more and the iron loss W17 / 50 was 0.78 W / kg or less were good.

Table 3 shows the manufacturing conditions and measurement results of the above examples of the present invention.

With reference to the results in Table 3, it was found that the grain-oriented electrical steel sheets satisfying the conditions of the present embodiment were judged to be good.

(Example 3)
First, in terms of mass%, C: 0.08%, Si: 3.2%, Mn: 0.08%, S: 0.003%, Se: 0.018%, acid-soluble Al: 0.03%, And N: 0.009% and the components shown in Table 4 below were further contained, and a steel ingot was prepared in which the balance was Fe and impurities. The ingot was annealed at 1380 ° C. for 1 hour and then hot-rolled to obtain a hot-rolled steel sheet having a plate thickness of 2.3 mm. The obtained hot-rolled steel sheet was annealed at a maximum temperature of 1100 ° C. for 140 seconds, pickled and then cold-rolled to obtain a cold-rolled steel sheet having a plate thickness of 0.23 mm.

Subsequently, the obtained cold-rolled steel sheet was decarburized and annealed in a wet hydrogen atmosphere at 850 ° C. for 180 seconds. Next, an annealing separator containing MgO was applied to the surface of the steel sheet after decarburization and annealing, then finish annealing was performed, and the steel sheet after finish annealing was washed with water. Then, an insulating film containing aluminum phosphate and colloidal silica as main components was applied to the surface of the steel sheet, and then flattening annealing was performed for the purpose of baking the insulating film and flattening the steel sheet.

After shearing and annealing the sample of the grain-oriented electrical steel sheet obtained above, the grain-oriented electrical steel sheet according to each of the examples of the present invention and the comparative example is used by a single plate measuring method having a sample size of 60 mm × 300 mm. The magnetic flux density B8 value and the iron loss W17 / 50 were measured. Here, the B8 value is the magnetic flux density of the grain-oriented steel sheet when the grain-oriented electrical steel sheet is excited at 800 A / m at 50 Hz, and W17 / 50 is the magnetic flux density of the grain-oriented electrical steel sheet excited at 1.7 T at 50 Hz. It is an iron loss when it is done.

Further, for the above sample, a linear groove was formed on the surface of the base steel sheet. Groove formation was performed by laser irradiation so as to intersect the upper surface and the lower surface of the steel sheet. Here, the angle from the rolling direction of the groove is set to be an acute angle of 75 ° clockwise from the rolling direction when facing the surface on which the groove is formed. The groove depth was 15 μm, and the groove spacing was 5 mm. Further, after applying an insulating film containing aluminum phosphate and colloidal silica as main components to the surface of the steel sheet, the insulating film is baked and annealed by strain removal, and then the final magnetic characteristics are shown in the examples of the present invention and comparative examples. The magnetic flux density B8 value and the iron loss W17 / 50 of the grain-oriented electrical steel sheet were measured.

Further, after removing the insulating film and the primary film of the final product, the steel sheet components were analyzed, and it was confirmed that the contents of Cu, Sn, Ni, Cr and Sb were the same as the values shown in Table 4.

Here, it was determined that the condition that the magnetic flux density B8 value of the grain-oriented electrical steel sheet was 1.82 T or more and the iron loss W17 / 50 was 0.78 W / kg or less was good. The condition that the iron loss W17 / 50 was 0.75 W / kg or less was judged to be better.

Table 4 shows the manufacturing conditions and measurement results of the above examples of the present invention. The evaluation is good in the order of A, B, and C. That is, A is the best, B is good, and C is not.

Referring to the results in Table 4, Cu: 0.01% or more and 0.30% or less, Sn: 0.01% or more and 0.30% or less, Ni: 0.01% or more and 0.30% or less in terms of mass%. , Cr: 0.01% or more and 0.30% or less, or Sb: 0.01% or more and 0.30% or less, any one or more, in the case of further containing one or more, the direction satisfying the condition of this embodiment. It was found that the sex electromagnetic steel plate had a better judgment. Further, under the condition that the judgment is good, the magnetic flux density B8 value before the groove formation is 1.92T or more, the difference between the magnetic flux density B8 values before and after the groove formation is 0.1T or less, and the iron loss before and after the groove formation. The reduction rate of W17 / 50 was 7% or more.

(Example 4)
First, in terms of mass%, C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.024%, acid-soluble Al: 0.03%, and N: 0.009%. And the components shown in Table 5 were further contained, and a steel ingot was prepared in which the balance was Fe and impurities. The ingot was annealed at 1350 ° C. for 1 hour and then hot-rolled to obtain a hot-rolled steel sheet having a plate thickness of 2.3 mm. The obtained hot-rolled steel sheet was annealed at a maximum temperature of 1100 ° C. for 140 seconds, pickled and then cold-rolled to obtain a cold-rolled steel sheet having a plate thickness of 0.23 mm.

Subsequently, the obtained cold-rolled steel sheet was decarburized and annealed in a wet hydrogen atmosphere at 850 ° C. for 180 seconds. Next, an annealing separator containing MgO was applied to the surface of the steel sheet after decarburization and annealing, then finish annealing was performed, and the steel sheet after finish annealing was washed with water. Then, an insulating film containing aluminum phosphate and colloidal silica as main components was applied to the surface of the steel sheet, and then flattening annealing was performed for the purpose of baking the insulating film and flattening the steel sheet.

After shearing and annealing the sample of the grain-oriented electrical steel sheet obtained above, the grain-oriented electrical steel sheet according to each of the examples of the present invention and the comparative example is used by a single plate measuring method having a sample size of 60 mm × 300 mm. The magnetic flux density B8 value and the iron loss W17 / 50 were measured. Here, the B8 value is the magnetic flux density of the grain-oriented steel sheet when the grain-oriented electrical steel sheet is excited at 800 A / m at 50 Hz, and W17 / 50 is the magnetic flux density of the grain-oriented electrical steel sheet excited at 1.7 T at 50 Hz. It is an iron loss when it is done.

Further, for the above sample, a linear groove was formed on the surface of the base steel sheet. Groove formation was performed by laser irradiation so as to intersect the upper surface and the lower surface of the steel sheet. Here, the angle from the rolling direction of the groove is set to be an acute angle of 75 ° clockwise from the rolling direction when facing the surface on which the groove is formed. The groove depth was 15 μm, and the groove spacing was 5 mm. Further, after applying an insulating film containing aluminum phosphate and colloidal silica as main components to the surface of the steel sheet, the insulating film is baked and annealed by strain removal, and then the final magnetic characteristics are shown in the examples of the present invention and comparative examples. The magnetic flux density B8 value and the iron loss W17 / 50 of the grain-oriented electrical steel sheet were measured.

Further, after removing the insulating film and the primary film of the final product, the steel sheet components were analyzed, and it was confirmed that the contents of Cu, Sn, Ni, Cr and Sb were the same as the values shown in Table 5.

Here, it was determined that the condition that the magnetic flux density B8 value of the grain-oriented electrical steel sheet was 1.82 T or more and the iron loss W17 / 50 was 0.78 W / kg or less was good. The condition that the iron loss W17 / 50 was 0.75 W / kg or less was judged to be better.

Table 5 shows the manufacturing conditions and measurement results of the above-mentioned examples of the present invention and comparative examples. The evaluation is good in the order of A, B, and C. That is, A is the best, B is good, and C is not.

Referring to the results in Table 5, when the ingot before hot rolling further contains Bi: 0.0005% or more and 0.0500% or less in mass%, the grain-oriented electrical steel sheet satisfying the conditions of the present embodiment is satisfied. Found that the judgment was better.

(Example 5)
First, in terms of mass%, C: 0.08%, S: 0.025%, acid-soluble Al: 0.03%, and N: 0.008%, and the contents of Si and Mn shown in Table 6 were added. A steel ingot containing Fe and impurities in the balance was prepared. The ingot was annealed at 1350 ° C. for 1 hour and then hot-rolled to obtain a hot-rolled steel sheet having a plate thickness of 2.3 mm. The obtained hot-rolled steel sheet was annealed at a maximum temperature of 1100 ° C. for 140 seconds, pickled and then cold-rolled to obtain a cold-rolled steel sheet having a plate thickness of 0.23 mm.

Subsequently, the obtained cold-rolled steel sheet was decarburized and annealed in a wet hydrogen atmosphere at 850 ° C. for 180 seconds. Next, an annealing separator containing MgO was applied to the surface of the steel sheet after decarburization and annealing, then finish annealing was performed, and the steel sheet after finish annealing was washed with water. Then, an insulating film containing aluminum phosphate and colloidal silica as main components was applied to the surface of the steel sheet, and then flattening annealing was performed for the purpose of baking the insulating film and flattening the steel sheet.

After shearing and annealing the sample of the grain-oriented electrical steel sheet obtained above, the grain-oriented electrical steel sheet according to each of the examples of the present invention and the comparative example is used by a single plate measuring method having a sample size of 60 mm × 300 mm. The magnetic flux density B8 value and the iron loss W17 / 50 were measured. Here, the B8 value is the magnetic flux density of the grain-oriented steel sheet when the grain-oriented electrical steel sheet is excited at 800 A / m at 50 Hz, and W17 / 50 is the magnetic flux density of the grain-oriented electrical steel sheet excited at 1.7 T at 50 Hz. It is an iron loss when it is done.

Further, for the above sample, a linear groove was formed on the surface of the base steel sheet. Groove formation was performed by laser irradiation so as to intersect the upper surface and the lower surface of the steel sheet. Here, the angle from the rolling direction of the groove is set to be an acute angle of 75 ° clockwise from the rolling direction when facing the surface on which the groove is formed. The groove depth was 15 μm, and the groove spacing was 5 mm. Further, after applying an insulating film containing aluminum phosphate and colloidal silica as main components to the surface of the steel sheet, the insulating film is baked and annealed by strain removal, and then the final magnetic characteristics are shown in the examples of the present invention and comparative examples. The magnetic flux density B8 value and the iron loss W17 / 50 of the grain-oriented electrical steel sheet were measured.

Further, after removing the insulating film and the primary film of the final product, the steel sheet components were analyzed, and it was confirmed that the contents of Si and Mn were the same as the values shown in Table 6.

Here, it was determined that the condition that the magnetic flux density B8 value of the grain-oriented electrical steel sheet was 1.82 T or more and the iron loss W17 / 50 was 0.78 W / kg or less was good.

Table 6 shows the manufacturing conditions and measurement results of the above-mentioned examples of the present invention and comparative examples.

With reference to the results in Table 6, the grain-oriented electrical steel sheets containing Si: 2.5% or more and 4.5% or less and Mn: 0.01% or more and 0.15% or less in mass% are judged to be good. It turned out to be.

Claims (8)

By mass%,
C: 0.02% or more and 0.10% or less,
Si: 2.5% or more and 4.5% or less,
Mn: 0.01% or more and 0.15% or less,
Total of 1 or 2 of S and Se: 0.001% or more and 0.050% or less,
Acid-soluble Al: 0.010 % or more and 0.050 % or less,
N: 0.002% or more and 0.015% or less,
Cu: 0% or more and 0.30% or less,
Sn: 0% or more and 0.30% or less,
Ni: 0% or more and 0.30% or less,
Cr: 0% or more and 0.30% or less,
Sb: 0% or more and 0.30% or less, and Bi: 0% or more and 0.0500% or less.
A process of heating a slab whose balance is Fe and impurities to 1280 ° C. or higher and hot rolling to obtain a hot-rolled steel sheet.
After hot-rolling the hot-rolled steel sheet, it is cold-rolled once or cold-rolled two or more times with intermediate annealing sandwiched between them to make a cold-rolled steel sheet, and the cold-rolled steel sheet. The process of decarburizing and annealing and
A step of applying an annealing separator to the surface of the cold-rolled steel sheet after decarburization annealing and then performing finish annealing, and
Including the process of applying an insulating film to the steel sheet after finish annealing and then applying flattening annealing.
After the cold rolling step, after decarburization annealing, after finish annealing, after insulating film coating or after flattening annealing, the groove depth is 10 μm or more and 25 μm or less, the groove spacing is 2 mm or more and 10 mm or less, and at least one side. When the angle of the groove from the rolling direction is 65 ° or more and 85 ° or less and the groove on both sides of the steel sheet is projected onto a surface parallel to the surface of the steel sheet, the groove on one side intersects the groove on the other side. It is characterized in that linear or dotted grooves are formed on both surfaces of the steel sheet to obtain a grain-oriented electrical steel sheet having a magnetic flux density B8 value of 1.82 T or more and an iron loss W17 / 50 of 0.78 W / kg or less. Manufacturing method of grain-oriented electrical steel sheet. In terms of mass%, the slab has Cu: 0.01% or more and 0.30% or less, Sn: 0.01% or more and 0.30% or less, Ni: 0.01% or more and 0.30% or less, Cr: 0. The directional electromagnetic steel plate according to claim 1, which contains any one or more of 0.01% or more and 0.30% or less, or Sb: 0.01% or more and 0.30% or less. Manufacturing method. The method for producing grain-oriented electrical steel sheets according to claim 1 or 2, wherein the slab contains Bi: 0.0005% or more and 0.0500% or less in mass%. Claims 1 to 3 are characterized in that the magnetic flux density B8 value before groove formation is 1.92 T or more when the groove formation is carried out after the insulating film is applied and / or after the flattening annealing. The method for manufacturing a grain-oriented electrical steel sheet according to any one of the following items. When the groove formation is performed after the insulating film is applied and / or after the flattening annealing, the difference between the magnetic flux density B8 values before and after the groove formation is 0.1 T or less, and the reduction rate of the iron loss W17 / 50 is 7. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 1 to 4, wherein the content is% or more. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 1 to 5, wherein in the groove formation, the groove formation on one side or both sides of the steel sheet is performed by laser irradiation. By mass%,
Si: 2.5% or more and 4.5% or less,
Mn: 0.01 or more and 0.15% or less,
Cu: 0% or more and 0.30% or less,
Sn: 0% or more and 0.30% or less,
Ni: 0% or more and 0.30% or less,
Cr: 0% or more and 0.30% or less, Sb: 0% or more and 0.30% or less, the balance has a component composition consisting of Fe and impurities, the surface of the steel sheet has an insulating film, and the steel sheet has an insulating film. Both sides have linear or dotted grooves with a groove depth of 10 μm or more and 25 μm or less and a groove spacing of 2 mm or more and 10 mm or less, and the angle of the groove on at least one side from the rolling direction is 65 ° or more and 85 °. Below, when the grooves on both sides of the steel sheet are projected onto a surface parallel to the surface of the steel sheet, the grooves on one surface are arranged so as to intersect the grooves on the other surface, and the magnetic flux density B8 value is 1.82T. A grain-oriented electrical steel sheet characterized in that the iron loss W17 / 50 is 0.78 W / kg or less. The composition of the components is Cu: 0.01% or more and 0.30% or less, Sn: 0.01% or more and 0.30% or less, Ni: 0.01% or more and 0.30% or less, Cr: The directional electromagnetic wave according to claim 7, which contains any one or more of 0.01% or more and 0.30% or less, or Sb: 0.01% or more and 0.30% or less. Steel plate.

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