JPH10183313A - Oriented silicon steel sheet having low core loss and having excellent strain resistance and machine mounting property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silicon steel sheet having a low core loss and having an excellent strain resistance and a machine mounting property by specifying the number ratio of a prescribed grain size of crystal grain in the surface of a steel sheet among crystal grains piercing in the direction of the plate thickness and moreover applying a magnetic domain subdividing treatment. SOLUTION: The important crystal grain in the steel sheet is pierced in the direction of the plate thickness. Many magnetic poles are formed in crystal boundaries with pierced grains like these and a large magnetostatic energy is increased. It is essential that the number ratio of the crystal grain of <=3mm in grain size is specified to be >=65% but <=98% with respect to the distribution of the pierced grain. Further, it is profitable to apply the magnetic domain subdividing treatment in order to more reduce the core loss. As the concrete method, any of such methods is executed that grooves having a prescribed depth and width are repeatedly provided in the rolling direction on the surface of the steel sheet, that linear local strain including zones are repeatedly provided in the surface layer part, that the boundary between the metallic surface and non-metallic coating of the steel sheet is smoothed and that the crystal orientation emphasizing treatment is applied on the metallic surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet used for an iron core of a transformer or a generator, and more particularly to a grain-oriented electrical steel sheet having low iron loss and excellent in distortion resistance and actual machine characteristics. .

[0002]

2. Description of the Related Art Si is contained and the crystal orientation is (110).
Oriented electrical steel sheets oriented in the [001] or (100) [001] orientation are widely used as various core materials in the commercial frequency range because of their excellent soft magnetic properties. The characteristics required for this type of electrical steel sheet are particularly low iron loss (generally expressed as W _17/50 (W / kg), which is the loss when magnetized to 1.7 T at a frequency of 50 Hz). is important.

[0003] As a method of reducing iron loss, a method of increasing electric resistance by containing Si effective for reducing eddy current loss, a method of reducing the thickness of a steel sheet, a method of reducing a crystal grain size, and a method of reducing hysteresis loss There is a method of aligning the orientation of crystal grains which is effective for reducing the crystallinity. Among them, the method of increasing the electric resistance by containing Si causes a decrease in the saturation magnetic flux density when excessively containing Si, which causes an increase in the size of the iron core, so there is a limit, and the thickness of the steel sheet is reduced. The method is also limited because it causes an extreme increase in manufacturing cost.

Therefore, the technical development for reducing iron loss is to improve the degree of integration of crystal orientation (this is generally represented by the magnetic flux density B ₈ (T) at a magnetization force of 800 A / m) and the crystal grain size. Although there was a trade-off that increasing the degree of integration of the crystal orientation inevitably increases the crystal grain size and deteriorates iron loss, in order to obtain the minimum iron loss value, It was necessary to adjust the degree of integration of the crystal orientation, that is, the optimum B ₈ value.

However, in recent years, a technique for artificially subdividing the magnetic domain width by irradiating a plasma jet or a laser beam has been developed, and the necessity of reducing the crystal grain size to reduce iron loss has been eliminated. Therefore, the mainstream method is to reduce the core loss by increasing the degree of integration of the crystal orientation, and the magnetic flux density (B ₈ )
Materials up to 1.93-2.00T have been developed.

In addition, as a magnetic domain refining treatment, the roughness of the interface between the metal surface of the steel sheet and the non-metallic film is reduced, including the formation of linear grooves and the introduction of linear strain, and the crystal orientation is enhanced on the metal surface. A method for performing the treatment has been developed, and the iron loss characteristics of the material have been greatly improved by the magnetic domain refining treatment.

Incidentally, in order to increase the degree of integration of the crystal orientation, it is necessary to completely control the secondary recrystallization. Secondary recrystallization is performed by using an inhibitor called AlN or Mn.
Precipitates such as Se and MnS are finely dispersed and precipitated in steel to suppress normal growth of crystal grains, and only grains having a specific preferred orientation ((110) [001] orientation and its neighboring orientation) called Goss orientation It is a technique for growing GaN greatly, and other inhibitors such as grain boundary segregation elements such as Sb, Sn, and Bi are used as sub-inhibitors. These techniques and the technique of controlling the texture of crystal grains are combined to complete the technique of manufacturing an electromagnetic steel sheet having the above-described excellent magnetic flux density.

[0008]

However, when a transformer is manufactured by using a grain-oriented electrical steel sheet having such excellent soft magnetic properties, there are many cases where desired properties cannot be obtained as an actual machine. It became so. In particular, in the case of a product transformer used without performing strain relief annealing after shearing, the gap between the material characteristics and the transformer characteristics was particularly large.

Conventionally, when a product transformer was manufactured using a grain-oriented electrical steel sheet having a high magnetic flux density, there was a problem that desired characteristics of an actual machine could not be obtained, and various investigations have been made. This is a unique phenomenon when a material having a high magnetic flux density is used. Unwanted magnetic flux wraps around the T-junction of the transformer in a direction deviating from the flow direction of the magnetic flux, causing unnecessary loss. It has been described that a predetermined iron loss reduction effect cannot be obtained, and it has been said that there is no room for improvement. However, when a modern material having a further improved magnetic flux density is used, the amount of deterioration of the characteristics of the actual machine is so great that even the benefits of material development cannot be enjoyed.

[0010] In addition, it has been observed that with the improvement of the magnetic flux density, the iron loss characteristic is greatly degraded by the strain applied during the shearing or laminating. This is still in the midst of research, and at present, there is no realistic countermeasure that can be applied to the handling of materials and the addition of distortion is suppressed as much as possible.

[0011] Furthermore, although the iron loss characteristics of the material are certainly improved by the various magnetic domain refining techniques described above, when the actual machine is manufactured using the actually developed material, particularly when the actual machine is used in a high magnetic field. In addition, there is a problem that desired characteristics cannot be obtained.

According to the present invention, in a material in which the crystal orientation of secondary recrystallized grains is highly integrated, the characteristics of the actual machine are greatly degraded with respect to the level estimated from the iron loss of the material, and the strain added in the processing step. It is an object of the present invention to elucidate the cause of high susceptibility to heat and to propose a grain-oriented electrical steel sheet which does not cause such deterioration of characteristics and further improves characteristics.

[0013]

The details of the invention will be described below. A method for increasing the magnetic flux density of a grain-oriented electrical steel sheet is well known in the art, and it is known that the addition of Al, Sb, Sn, Bi, or the like as an inhibitor element is effective. For example, in JP-B-46-23820, the value of 1.981T as B ₁₀ by a directional electromagnetic steel sheet containing Al and S, but also in JP-B-62-56923, Al as an inhibitor, Se, Sb value of 1.95T is reported as B ₈ and the grain-oriented electrical steel sheet containing Bi.

The magnetic properties of these grain-oriented electrical steel sheets are excellent. However, when a transformer is manufactured using these high magnetic flux density electromagnetic steel sheets, the characteristics are significantly deteriorated, and a desired value of iron loss of an actual machine is often not obtained. The cause of this is the high degree of integration of the crystal of the material, and as described above, it has been regarded as inevitable in the past.

[0015] The present inventors have investigated various factors affecting the wraparound of the magnetic flux at the T junction of the stacked transformer using the high magnetic flux density material. As a result, the inventors have newly found that the cause of the characteristic deterioration is not only the high degree of integration of the crystal orientation, which has been conventionally known, but also the influence of the crystal grain size. In addition, regarding the effect of the strain introduced in the processing step on the characteristic deterioration, the following was newly found.

That is, when the degree of integration of the crystal orientation is high,
The magnetic poles appearing on the surface of the steel sheet are much larger at the magnetic poles appearing at the crystal grain boundaries than at the crystal grain surfaces. Reduction of iron loss due to magnetic domain subdivision is achieved by a mechanism that reduces the magnetostatic energy increased by the generation of magnetic poles by magnetic domain subdivision, but appears in grain boundaries in the case of high magnetic flux density oriented magnetic steel sheets The effect of the magnetic pole is therefore predominant.
However, in the case of this material, since the crystal grain size is inevitably large, the distance between the crystal grain boundaries is large, and even if the same amount of magnetic poles appear at the crystal grain boundaries, the amount of increase in the magnetostatic energy is small. Smaller than small diameter materials. Also, in a material that has been subjected to magnetic domain refining to minimize iron loss in the material, once strain is applied to the material, the energy balance easily collapses, the magnetic domain refining effect is lost, and the magnetic domain width increases. I do. This is the reason why the high magnetic flux density magnetic steel sheet has high strain sensitivity.

An experiment which has led to the above findings will be described below. C: 0.08 wt%, Si: 3.35 wt%, Mn: 0.07 wt%, Al: 0.02
5 wt%, Se: 0.020 wt%, Sb: 0.040 wt% and N: 0.
008 wt%, with the balance being unavoidable impurities and Fe, the hot-rolled steel sheet for directional magnetic steel was annealed at 1000 ° C for 30 seconds, pickled, and then cooled with a rolling reduction of 30%. After rolling, heat treatment is performed at 1050 ° C. for 1 minute as intermediate annealing, pickling is again performed, and rolling is performed at a rolling reduction of 85% at a temperature of 150 to 200 ° C. to obtain a final thickness of 0.22 mm. Steel plate. Then, after degreasing, the surface of the steel sheet as a magnetic domain refining process,
A linear groove having a depth of 25 μm and a width of 50 μm was provided in a direction inclined at 10 ° from the width direction of the plate under a condition of a repetition pitch in the longitudinal direction: 3 mm. Then, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes, the steel sheet is divided into two parts, one of which is used as it is as a conventional material, and the other is
20 mm in the width direction and 30 in the longitudinal direction
40-45 Ws energy delivery at 1000 mm pitch (1000-1200
An instantaneous heat treatment was performed by a discharge treatment under the condition of (estimated temperature of ° C.). After that, TiO ₂ : 10wt% and
After applying MgO to which Sr (OH) ₂ : 2 wt% was added as an annealing separator, it was wound around a coil and subjected to final finish annealing.
Final finish annealing in N ₂ up to 850 ° C, H ₂ up to 1150 ° C
A treatment for the purpose of secondary recrystallization in a mixed atmosphere of N ₂ and N ₂ and a treatment for the purpose of purifying the mixture by holding it at 1150 ° C. in H ₂ for 5 hours were simultaneously performed. After final finishing annealing,
After removing the unreacted annealing separating agent, a tension coat composed of 50% colloidal silica and magnesium phosphate was applied to obtain a product.

After measuring the magnetic characteristics of each product, a model transformer was prepared by slitting, shearing, and stacking, and the characteristics of the transformer were measured. Thereafter, the steel plate was macro-etched to measure the crystal grain size. . In addition, during the above-mentioned slitting, shearing, and laminating, the addition of distortion was suppressed as much as possible with the utmost care, but in order to experimentally evaluate the effect of imparting distortion, a sphere having a diameter of 50 mm was used during these processing. An experiment was also performed in which a caster was pressed with a load of 5 kg to add distortion when intended. Table 1 summarizes the obtained results.

[0019]

[Table 1]

As is clear from Table 1, after decarburization and primary recrystallization annealing, a point-shaped instantaneous high-temperature treatment with a diameter of 1.5 mm was performed, followed by secondary recrystallization of the product (symbol (a ) and (b)), the iron loss of the model transformer was extremely good, and the ratio of the iron loss of the transformer to the iron loss of the product (hereinafter referred to as the realization factor) was low. For products that do not perform such treatments (symbols (c) and (d)), the core loss of the model transformer is greatly deteriorated. It was found that the degree of deterioration of the core loss of the transformer was extremely large, that is, the strain sensitivity was large.

In order to clarify the reason why the above results were obtained, the state of the crystal grains by the macro-etching of the steel sheet and the state of the magnetic flux distribution of the model transformer were examined in detail. In the products (a) and (b), which were subjected to instantaneous high-temperature heat treatment in the form of spots having a diameter and then subjected to secondary recrystallization, fine crystal grains with a diameter of 0.5 to 2.5 mm (C), (d)
Most of the samples consisted of coarse grains having a grain size of 20 to 70 mm in the plane of the steel sheet.

Further, when the crystal orientation of the fine crystal grains artificially generated in this way was measured, the crystal orientation was found to be random, which was 15 ° or more from the Goss orientation, which is the orientation of the normal secondary recrystallized grains. Was also off. By the way, for decarburized annealing plate
In the same manner as in the case where a point-shaped instantaneous high-temperature heat treatment of 1.5 mm diameter is performed and then secondary recrystallization (products (a), (b)), the interval in the sheet width direction: 10 mm pitch, in the rolling direction FIG. 1 shows an example in which fine grains are artificially formed on a steel plate at a pitch of 15 mm, and the orientation is shown in the (100) pole figure of FIG. 2 in comparison with that of naturally occurring fine grains. . In FIG. 1, spontaneously generated fine particles are scattered, but fine particles are surely generated at the position where the instantaneous high-temperature heat treatment is performed. Also, as shown in FIG. 2, it can be seen that the orientation of the artificially generated fine grains is randomly distributed, whereas that of the naturally occurring fine grains is very close to the Goss orientation.

Next, the results of measuring the particle size distribution of the crystal grains penetrating in the thickness direction of the above two types of products are shown in Table 2. Here, the grain size of each crystal grain is calculated by the diameter of a circle corresponding to the area, and the average crystal grain size is calculated by counting the number of crystal grains existing in a certain area, and calculating the average area per one grain. Was calculated and expressed by the diameter of a circle corresponding to the area.

[0024]

[Table 2]

From Table 2, it can be seen that the products (c) and (d), which have a large realization factor and poor transformer characteristics, have about 30% of fine particles of 2.5 mm or less, and have a size of 15 to 70 mm. It can be seen that the crystal grains account for about 60%. In contrast, (a) and (b), which have low transformer factor and excellent iron loss characteristics of transformers, are 2.5mm
It can be seen that the number ratio of the following fine grains is about 90%, and the number ratio of crystal grains having a size of 15 to 70 mm is as extremely low as 8%.

As described above, it was found that there was a large difference in the number ratio of fine crystal grains between the two types of materials having different values of the realization factor. Next, it was investigated whether the effect of reducing the strain factor and the strain sensitivity, that is, the effect of improving the strain resistance characteristics, was obtained. First, when the flow of the magnetic flux at the junction of the T section in the model transformer was investigated, it was found that the presence of the fine particles suppressed the flow of the magnetic flux. That is, it has been newly found that the fine crystal grains existing in the coarse crystal grains suppress the wraparound of the magnetic flux, despite the improvement of the degree of integration of the orientation of the coarse crystal grains. Therefore, despite the fact that it is a material having a high magnetic flux density, the factor of realization was suppressed low.

Next, the effect on the distortion resistance was examined. When strain is applied to the steel sheet, the magnetic energy of the steel sheet caused by the strain increases, and the ratio of the magnetostatic energy relatively decreases, so that the effect of subdividing the magnetic domains is reduced. To counter this, the types of energy that contribute to magnetic domain refinement, such as elastic energy and magnetostatic energy,
It is effective to provide the steel sheet with an amount at least superior to the increase in energy due to the applied strain in advance. As such an energy applying method, there is a method of applying tension, and there is also a method of increasing magnetostatic energy. Among them, regarding the application of tension, there is no coating that can apply a higher tension than the current state, and the means for increasing the coating thickness causes a decrease in the space factor and deteriorates the transformer characteristics.

Considering the magnetostatic energy, when the magnetic flux density is improved and the degree of integration of the crystal grain orientation of the steel sheet is improved, the magnetic poles are accumulated at the crystal grain boundaries for the above-described reason, and the crystal grain size is reduced. The magnitude of the magnetostatic energy is drastically reduced due to an increase in the interval between crystal grain boundaries accompanying the coarsening. However, since the orientation of the artificially generated fine grains is largely deviated from the Goss orientation (usually 15 ° or more), the presence of such fine grains in the coarse crystal grains reduces the magnetostatic energy. It is possible to increase the resistance, and the strain resistance of the product is improved accordingly.

In order to maximize this effect,
It is important that the grain size of the fine grains penetrate the plate thickness.
This is because if the fine grains do not penetrate the plate thickness, the grain boundary area projected in the direction perpendicular to the plate thickness is small, and the amount of magnetic poles generated on the crystal grain boundaries is small, so the effect of increasing the magnetostatic energy Is also weak, and the effect of suppressing the wraparound of the magnetic flux is similarly inferior, so that the factor of realization increases.

Next, FIG. 3 shows the results of an investigation on the relationship between the ratio of the number ratio of fine crystal grains of 3 mm or less to the entire crystal grains penetrating the steel sheet thickness and the factor of realization including distortion resistance. Shown in As shown in the figure, when the number ratio of fine grains is between 65 and 98%, particularly between 75 and 98%, the realization factor is low and the strain resistance characteristics (evaluated by the realization factor at the time of strain imparting processing) are also high. Has improved.

Next, an appropriate value as an average particle size of all the crystal grains penetrating the plate thickness was obtained by an experiment. That is, as the magnetic flux density increases, the coarse crystal grains become more and more coarse, and the number ratio of the fine crystal grains numerically increases accordingly. However, since the distance between fine crystal grains substantially increases with the increase in coarse crystal grains at the same fine particle number ratio, the effect of increasing the magnetostatic energy due to the presence of fine grains is not so large. You can't expect it. Therefore, a preferable upper limit exists as the average crystal grain size. FIG. 4 shows the results of an experiment conducted on this point. As is apparent from the figure, when the average crystal grain diameter of all the crystal grains penetrating the plate thickness is in the range of 8 to 50 mm, particularly excellent realization factor and the effect of improving the strain resistance are obtained.

As described above, the mechanism for suppressing the increase in the factor of realization and the mechanism for improving the strain resistance characteristics by the generation of fine grains penetrating the plate thickness have been described. Next, the results of examining the manufacturing conditions necessary for producing the fine particles required for obtaining such effects will be described.

As a result of various experiments, it is necessary to locally increase the driving force for promoting abnormal grain growth before secondary recrystallization in order to produce fine grains having the above-mentioned effects. In particular, it has been found that it is effective to cause a certain amount of strain to exist inside the steel sheet. Secondary recrystallization is a phenomenon in which a crystal grain of a specific orientation grows rapidly by eating other primary recrystallized grains. In recent years, nucleation and growth of secondary recrystallized grains have
It is becoming clear that the selectivity due to the texture of the secondary recrystallized grains is acting strongly, and it is said that nucleation and growth of crystal grains having a Goss orientation and an orientation other than the vicinity thereof are not easy.

However, according to the study of the inventors,
By performing a process for increasing the driving force for abnormal grain growth in a certain region inside the steel sheet, for example, a process for introducing a certain amount of strain, it becomes possible to increase the driving force for nucleation and growth of general crystal grains. Crystal grains having an orientation greatly deviated from the orientation can be grown at an early stage. The abnormal grain growth referred to here is a general term for a phenomenon in which a very small number of crystal grains overwhelm a large number of other crystal grains and grow rapidly, and secondary recrystallization is a primary recrystallization aggregate. They are distinctly different in that only a small number of crystal grains having a specific orientation depending on the structure grow rapidly.

According to the study of the inventors, the abnormal grain growth caused by the treatment for increasing the driving force is only in that region, and the selectivity due to the texture of the primary recrystallized grains is outside this region. It was also determined that the crystal worked hard and could no longer grow anymore. Such a phenomenon is a very advantageous property for the purposes of the present invention. Hereinafter, this point will be described.

First, when strain is introduced into a steel sheet, the size of the fine grains can be controlled by controlling only the magnitude of the strain and the size of the strain-introduced region. For example, as shown in the above-mentioned experiment, the appropriate size of the fine grains penetrating the steel sheet is 3 mm or less as evaluated by the equivalent circle diameter. If the size is controlled to 3 mm or less, the size of the fine particles can be appropriately controlled.

Second, since the fine grains artificially generated in this manner are largely displaced from the Goss orientation ((110) [001] orientation) which is the orientation of ordinary coarse secondary recrystallized grains. In addition, magnetic poles are generated at a high density at the crystal grain boundary between the coarse secondary recrystallized grains and the fine grains, so that the above-mentioned good strain resistance and strong effect of suppressing the factor of realization can be obtained. In addition, such fine particles may be spontaneously generated in the manufacturing process of the grain-oriented electrical steel sheet, but the naturally generated fine particles have the same action as above, The generation process is a grain that lost the growth competition with other spontaneously generated Sato Yuki. It is essentially a secondary recrystallized grain, and is very close to the Goss orientation. In this case, a magnetic pole having a very high density is not generated, and therefore, the effect of improving the strain resistance and the effect of suppressing the factor for realization are weak.

Third, since the particles are artificially generated, it is possible to generate fine particles at the most preferable positions in the product. Note that the artificially generated fine grains are greatly deviated from the Goss orientation as described above, and have poor crystal orientations, and therefore must not be present at high density in the product. In other words, it is preferable that they exist as discretely as possible, and ideally they exist in an isolated state inside coarse crystal grains. Such a state can be easily realized by previously forming the strain introduction region locally and discretely. Also, if it is inside a coarse crystal grain,
A state in which several fine grains are assembled is advantageously adapted.

Next, a description will be given of the results of a study on the mechanism by which such fine grains were artificially obtained by subjecting a steel sheet after decarburization and primary recrystallization annealing to instantaneous high-temperature heat treatment. The change in the crystal structure at the position where the steel sheet was instantaneously subjected to the high-temperature heat treatment during the secondary recrystallization annealing was examined in detail. As a result, immediately after the high-temperature heat treatment, the crystallographic changes such as the crystal grain size and the precipitation inhibitor were not so large and were negligible. However, at the very early stage of the secondary recrystallization annealing, it was observed that one primary recrystallized grain was coarsened to 1.5 to 3.0 times the surrounding primary recrystallized grains. The temperature at which such coarsening of the crystal grains occurs is much lower than the normal temperature at which secondary recrystallization occurs, and the growth time until the crystal grains penetrate in the thickness direction is very short. After penetrating in the sheet thickness direction, it grows up to the high-temperature heat-treated region in the same manner, but thereafter, even if the temperature of the steel sheet is further increased, the growth is slow, and the growth of the crystal grains is almost complete. It will be stopped.

Further, as the temperature is increased, normal secondary recrystallization nuclei are generated in the non-processed area not subjected to the high-temperature heat treatment, and the growth proceeds. However, the crystal grains grown from the early stage in the region subjected to the high-temperature heat treatment are not eaten by the subsequent secondary recrystallization, and eventually remain as fine crystal grains in the product.

The inventors have found that such a phenomenon occurs by the following mechanism. That is, in the region subjected to the high-temperature heat treatment, a certain amount or more of strain is introduced into each primary recrystallized grain, and a part of the strain is lost in the temperature rise process of the final finish annealing. In addition, high-density dislocations remain in each crystal grain. The remaining dislocations have the effect of increasing the driving force for crystal growth in abnormal grain growth. When the driving force of abnormal grain growth becomes sufficiently high, it overcomes the selectivity of the crystal orientation by the primary recrystallization texture,
The crystal grains of the general orientation start nucleation and grain growth. Since this phenomenon occurs because of a large driving force for abnormal grain growth, it occurs at a temperature much lower than the normal secondary recrystallization nucleation and grain growth occurring in the non-processed region. However, the crystal cannot be grown outside the region where the driving force for abnormal grain growth is increased, because the orientation selectivity of crystal growth is very strong.

As described above, the crystal grain orientation in which abnormal grain growth occurs in the high-temperature heat treatment region is characterized by a random orientation because the crystal orientation selectivity is relatively weak, but it is a type of abnormal grain growth. Therefore, the existence of the growth suppressing power for the normal grain growth of the primary recrystallized grains is indispensable,
Requires strong inhibitor action. That is, the conventional method of applying a chemical or performing a heat treatment at a high temperature for a long time causes the precipitation inhibitor to be coarsened and the suppressing power is reduced, so that abnormal grain growth is unlikely to occur, and a large number of fine grains due to normal grain growth are hardly generated. It is unsuitable because it results in an outbreak and is inherently different from the method of the present invention and should be avoided.

As described above, in order to artificially generate fine grains, in a region where growth of the fine grains is intended,
It has already been mentioned that it is an essential condition to increase the driving force for abnormal grain growth to a level exceeding the crystal orientation selectivity. Here, the driving forces for abnormal grain growth include (1) the presence of strain, and (2) 1
Increasing the superheat to the crystal grain size by refinement of the secondary recrystallized grains and (3) strengthening the inhibitory force of the inhibitor, etc. can be mentioned, but the method (3) makes it difficult to control the generation of grains with random orientation. In some cases, grains having a crystal orientation close to the Goss orientation often grow and grow coarsely beyond a region where fine grains are intended to be formed, so that it is extremely difficult to control the size of the fine grains. Therefore, as a method of increasing the driving force for the crystal growth, it is advantageous to (1) make the strain exist or (2) reduce the size of the primary recrystallized grains. Various experiments have shown that the method of presence is the most advantageous technique.

For example, in the above-mentioned instantaneous high-temperature heat treatment, as a result of investigation, since the heat treatment is instantaneous, even at a high temperature, crystallographic phenomena such as an increase in the crystal grain size and a coarsening of the precipitation inhibitor occur. It has been found that the small change and the presence of a large amount of thermal strain advantageously act to increase the driving force for crystal growth. In other words, the rapid increase and decrease in temperature advantageously suppresses the crystallographic change in structure and introduces only physical strain into the steel sheet. However, a slight increase in the crystal grain size and coarsening of the precipitation inhibitor have the property of suppressing the increase in the number of nuclei generated during abnormal grain growth, thereby reducing the number of fine grains generated in a single region. Since it has a restricting action, it is considered preferable unless the driving force for crystal growth is reduced.

In addition to the above-described heat treatment, various methods for introducing a physical strain into a steel sheet while suppressing crystallographic structure change can be considered, but the present inventors have developed from many experiments as the most advantageous method. The method of pressing an object harder than the steel sheet having small projections on the surface of the steel sheet, the method of applying a high voltage to locally energize or discharge the steel sheet surface, and the method of locally applying a pulsed laser And so on.

As another method for increasing the driving force for crystal growth, a method for atomizing primary recrystallized grains is as follows. The method of locally atomizing using transformation was particularly effective. Furthermore, as a method of strengthening the inhibitory force of the inhibitor, a method of locally increasing the inhibitory force by locally nitriding the steel sheet surface to generate silicon nitride or aluminum nitride, although the effect stability is low, Was effective.

As described above, in recent years, as a technique for reducing iron loss of a grain-oriented electrical steel sheet, a linear strain is locally introduced by irradiating a plasma jet or a laser beam, or a linear A technique for artificially subdividing the magnetic domain width by providing grooves has been developed. Also in the present invention, further improvement in characteristics can be expected if such a magnetic domain segmentation technique is also utilized. Therefore, the inventors conducted intensive research to further improve the characteristics of the actual device, including the magnetic domain segmentation technology, and found that these magnetic domains could be effectively reflected in the characteristics of the actual device. It has been found that it is important to control the control factors for the subdivision and the fine grains within a predetermined range according to the crystal grain size. Hereinafter, this will be described.

The grain-oriented electrical steel sheet is mainly used as an iron core material of a transformer, and the range of the magnetic flux density used at this time varies depending on the design of equipment. In general, the higher the magnetic flux density of a material, the more advantageous it is in use at a high magnetic flux density. As described above, it is well known that the characteristics of a grain-oriented electrical steel sheet having a high magnetic flux density are deteriorated in actual machine characteristics as compared with the magnetic properties of the material. Here, the crystal grain size of the magnetic steel sheet is inevitably coarsened when the material properties are increased in magnetic flux density, but the depth of the groove or the region of local strain is changed according to the crystal grain size. As a result, it has been found that the factor for realization can be advantageously reduced, that is, the material characteristics can be reflected on the characteristics of the real device. This experiment is described below.

C: 0.08 wt%, Si: 3.40 wt%, Mn: 0.07 wt
%, Al: 0.025 wt%, Se: 0.018 wt%, Sb: 0.040 wt%
%, Ni: 0.12 wt%, Bi: 0.004 wt% and N: 0.008 wt%
% (Bi-containing steel), the remainder being the composition of Fe and unavoidable impurities, hot-rolled sheet for directional electromagnetic steel, hot-rolled at 750 ° C for 3 seconds to adjust carbides, and then pickled. Then, after cold rolling at a rolling reduction of 30%, an intermediate annealing of 10% was performed.
After heat treatment at 50 ° C for 45 seconds and rapid cooling at 40 ° C / s, pickling is performed again, then rolling is performed at a rolling rate of 87% at a warming temperature of 150 to 200 ° C to obtain a final thickness. : A steel sheet of 0.22 mm was used. Also, C: 0.05wt%, Si: 3.20wt%, Mn: 0.15wt
%, Al: 0.014 wt%, S: 0.008 wt%, Sb: 0.005 wt%
%, B: 0.0005 wt% and N: 0.007 wt% (B
Steel), the remainder is a hot-rolled steel sheet for directional magnetic steel that has a composition of Fe and unavoidable impurities, after hot-rolled sheet annealing at 800 ° C for 30 seconds, pickling, and then rolling reduction at a warm temperature of 170 ° C. : 87% rolling to obtain a steel sheet having a final thickness of 0.34 mm.

Next, after degreasing these steel sheets, Bi
Both the steel containing steel and the steel containing B were divided into 7 small coils each having the symbols a) to g), and were subjected to the following treatments. In the coil of a), a linear groove having a depth of 25 μm and a width of 250 μm is formed on the surface of the steel sheet as a magnetic domain refining process by 10 mm from the plate width direction.
設 け Provided in the inclined direction under the condition of a repetition pitch of 3 mm in the longitudinal direction, followed by decarburization and primary recrystallization annealing at 850 ° C for 2 minutes.
30 mm in the width direction and 60 mm in the longitudinal direction
With a sparse distribution, such as a pitch, an instantaneous heat treatment is applied for several milliseconds by a discharge treatment under the conditions of 65 Ws energy application, while the B-containing steel has a dot width of 1.5 mm in diameter. An instantaneous heat treatment for several milliseconds was performed by a discharge treatment under a 65 Ws energy administration condition with a dense distribution of 15 mm in the direction and 30 mm in the longitudinal direction.

The coil of b) is subjected to magnetic domain refining processing.
A linear groove with a depth of 10μm and a width of 50μm is provided on the surface of the steel plate at a pitch of 3mm in the longitudinal direction in a direction inclined 10 ° from the width direction of the plate, and then decarburized at 850 ° C for 2 minutes.・
After the primary recrystallization annealing, the surface of the steel sheet has a sparse distribution such as a 1.5 mm diameter in the case of Bi-containing steel and a pitch of 30 mm in the width direction of the sheet and 60 mm in the longitudinal direction. By the electric discharge treatment under the energy administration condition, an instantaneous heat treatment is applied for several milliseconds, while in the case of B-containing steel, the diameter is 1.5 mm, the dot width is 15 mm in the plate width direction, and the pitch is 30 mm in the longitudinal direction. An instantaneous heat treatment was applied for several milliseconds by a discharge treatment under a tightly distributed energy supply condition of 65 Ws.

The coils (c) to (e) are subjected to decarburization and subsequent recrystallization annealing at 850 ° C. for 2 minutes, and then, on the steel sheet surface, in the case of Bi-containing steel, a 1.5 mm diameter spot-like sheet is formed. 30mm in width direction,
With a sparse distribution such as a pitch of 60 mm in the longitudinal direction, an instantaneous heat treatment is applied for several milliseconds by a discharge treatment under the energy administration condition of 65 Ws, while 1.5 mm for B-containing steel.
An instantaneous heat treatment was applied for several milliseconds by a discharge treatment under the condition of 65 Ws energy administration, with a dense distribution of 15 mm in the width direction of the plate and a pitch of 30 mm in the longitudinal direction.

The coil of f) is decarburized at 850 ° C. for 2 minutes.
After the primary recrystallization annealing, the surface of the steel sheet has a dense distribution of 15 mm in the width direction and 15 mm in the longitudinal direction with a 1.5 mm diameter die in the case of Bi-containing steel. By electric discharge treatment under energy administration condition, instantaneous heat treatment is applied for several milliseconds, while in the case of B-containing steel, the diameter of 1.5 mm is 30 mm in the dot width direction and 30 mm in the longitudinal direction with a pitch of 60 mm in the longitudinal direction. With a sparse distribution, an instantaneous heat treatment for several milliseconds was performed by a discharge treatment under 65 Ws energy dosing conditions.

The coil of g) was used as a comparative material only for 850
Decarburization and primary recrystallization annealing were performed at 2 ° C. for 2 minutes.

Next, all of the coils a) to g)
M with TiO ₂ : 10 wt% and Sr (OH) ₂ : 2 wt% added to the surface
After applying gO as an annealing separator, it was wound into a coil and subjected to final finishing annealing. Final finish annealing is 850
Among ° C. until N _2, and treatment for secondary recrystallization in a mixed atmosphere of H ₂ and N ₂ up to 1150 ° C., from subsequently 1150 ° C. in H ₂ 5
The processing for the purpose of purifying for keeping the time was simultaneously performed. After the final finish annealing, after removing the unreacted annealing separator, 50wt
% Of colloidal silica and magnesium phosphate was applied to obtain a product.

However, for the coil of c), a 0.5 mm width plasma jet (PJ)
In the width direction of the steel sheet, repeated in the rolling direction: 10
Irradiated in mm and provided a local linear strain region, and then a product was obtained. As for the coil d), a 1.5 mm-wide plasma jet (PJ) is irradiated linearly in the width direction of the steel sheet at a repetition interval of 3 mm in the rolling direction as a magnetic domain refining treatment, and a local linear shape is formed. After providing the strain region, the product was obtained.

Samples were cut from each of the product sheets obtained in this _manner , and the iron loss values of W _18/50 for Bi-containing steels often used in high magnetic fields and the B-containing steels often used in low magnetic fields were used. For each test, the iron loss value of W _15/50 was measured. In addition, using each product, a model transformer was created by slitting, shearing, and stacking, and the _{W15 / 50}
And W _18/50 were measured, and then the steel sheet was macro-etched to measure the crystal grain size. In addition, in the above-mentioned slitting, shearing and laminating, great care was taken to minimize the addition of distortion. Table 3 summarizes the obtained results.

[0058]

[Table 3]

As is clear from Table 3, iron loss at high magnetic field
W_18/50B that is required to be low ₈High Bi content
In steel, the higher the number ratio of fine grains (f), the lower the iron loss
And the factor of realization is excellent.
Even if it is low, the groove may be made shallower (b),
High magnetic properties due to the combined effect of extending the interval between the irradiation regions (c)
Iron loss and factor of realization in the field can be reduced.
Conversely, iron loss W in a low magnetic field_15/50Requested to be low
B₈In B-containing steels with low
(F) is excellent in iron loss, and
Even when the number ratio is high, the groove may be deepened (a),
Reduced due to the combined effect of shortening the PJ irradiation interval (d)
It is found that iron loss and the factor of realization in the magnetic field can be reduced.
You.

By the way, the magnetic field characteristics of a material depend substantially on the crystal grain size, and the higher the magnetic flux density of the material, the better the characteristics in a high magnetic field, the larger the crystal grain size. However, fine grains of 3 mm or less, which characterize the present invention, present in coarse crystal grains do not greatly affect the magnetic flux density of the material, and thus need to be excluded. Therefore, among the crystal grains constituting the steel sheet, 3
The remainder excluding crystal grains of mm or less, that is, the average grain diameter of crystal grains having a grain size of more than 3 mm: D (mm) was used as an index of high magnetic field characteristics.

Based on the above, 1) the range of the appropriate volume density of the groove in the unit area of the steel sheet, and 2) the appropriate density of the area of the local strain application in the unit area of the steel sheet to obtain a good factor of realization. Range, 3) range of appropriate roughness of steel sheet metal surface, and 4) how appropriate region of grain boundary step (BS: Boundary Step) in crystal orientation enhancement process changes according to the value of D Was determined by experiment. The obtained results are shown in FIG. 5, FIG. 6, FIG. 7, and FIG.

Here, V is a value obtained by dividing the volume (mm ³ ) of the groove existing on the surface of the steel plate having a certain area by the area (mm ² ) of the steel plate, that is, the volume ratio of the groove per unit steel plate area (mm). And S
Is the value obtained by dividing the area (mm ² ) with local strain present on the surface of the steel sheet of a certain area by the surface of the steel sheet, that is, the total area ratio S (dimensionless number) of local strain per unit steel sheet area. Yes, Ra is the average roughness (μm) of the metal surface after removing the non-metallic coating on the steel sheet, and BS is the step of the steel sheet surface generated at the location of the crystal grain boundary when the crystal orientation enhancement process is performed. (μm). Also, 3mm of the crystal grains constituting the steel sheet
Using the above value of D, which is the average value excluding the following grains,
Bm was calculated from the equation: m = 0.2 × logD + 1.4, and the iron loss of the transformer with respect to the calculated Bm was measured to determine the factor for realization.

As is clear from FIGS. 5, 6, 7 and 8, according to the average grain size D of the crystal grains exceeding 3 mm,
(1) The volume ratio V (unit: mm) of the groove to the steel sheet surface area is
The range of satisfying the relationship of the following formula (1) or log ₁₀ V ≦ −2.3 −0.01 × D --- (1) (2)
Make sure that the range of (2) is satisfied, or log ₁₀ S ≦ −0.7 + 0.005 × D --- (2) (3) Average roughness Ra of the interface between the metal surface of the steel sheet and the non-metallic coating
Is within the range satisfying the relationship of the following formula (3), or Ra ≦ 0.3− 0.1 × log ₁₀ D --- (3) (4) By setting BS ≦ 3.0−log ₁₀ D −− (4) so that the field average step BS satisfies the relationship of the following formula (4), the factor for realizing grain-oriented electrical steel sheets could be further improved. .

As described above, the combination of the fine grain formation technique and the magnetic domain refining technique not only can reduce the iron loss value of the product, but also can reduce the secondary recrystallized grains due to the high magnetic flux density. It is possible to effectively suppress the increase in the factor of actualization due to the factor, and to improve the characteristics of the transformer to the performance corresponding to the improvement of the product characteristics. The present invention has been completed after intensive studies based on the numerous experiments and investigations described above.

That is, the gist configuration of the present invention is as follows. 1. Si: 1.5 to 7.0 wt%, Mn: 0.03 to 2.5 wt%, and contamination of C, S and N as impurities, C: 0.003 wt% or less, S: 0.002 wt% or less, N: 0.00
The electromagnetic steel sheet is controlled to 2 wt% or less, and among the crystal grains constituting the steel sheet, the number ratio of the crystal grains having a grain diameter of 3 mm or less on the steel sheet surface of the crystal grains penetrating in the thickness direction is reduced.
It is 65% or more and 98% or less, and has a low iron loss characterized by magnetic domain refinement treatment on the surface of the steel sheet.
Grain-oriented electrical steel sheet with excellent strain resistance and actual machine characteristics.

2. In the above item 1, the average value of the grain size of the crystal grains penetrating in the sheet thickness direction on the surface of the steel sheet is not less than 8 mm and not more than 50 mm. The iron loss is low, and the strain resistance and the actual machine characteristics are excellent. Oriented magnetic steel sheet.

3. In the above item 1 or 2, a crystal grain penetrating in the sheet thickness direction and having a grain size of 3 mm or less on the surface of the steel sheet includes a crystal grain which is artificially regularly arranged, and has a low iron loss and a low iron loss. Grain-oriented electrical steel sheet with excellent distortion characteristics and actual machine characteristics.

4. In the above 1, 2 or 3, the magnetic domain refining treatment is performed by: (1) Depth: 50 μm or less and width: 35
Repeatedly providing grooves of 0 μm or less in the rolling direction, (2)
(3) smoothing the interface between the metal surface of the steel sheet and the non-metallic coating to an average roughness Ra of 0.3 μm or less in the surface direction of the steel sheet in the rolling direction; )
A grain-oriented electrical steel sheet with low iron loss, which is one of applying a crystal orientation enhancement treatment to the metal surface of the steel sheet, and having excellent distortion resistance characteristics and actual machine characteristics.

5. In the above item 4, among the crystal grains constituting the steel sheet, the crystal grains penetrate in the thickness direction and have a grain size of 3 mm.
When the average grain size of the crystal grains having a size exceeding D is defined as D (mm), (1) The total volume ratio V (unit: mm) of the grooves per unit area of the steel sheet is as follows for the grooves repeatedly provided in the rolling direction. formula
To make the range satisfying the relationship of (1), or log ₁₀ V ≦ −2.3 −0.01 × D --- (1) (2)
Total area ratio S of local strain per unit area of steel sheet (unit:
(Dimensionless) is within the range satisfying the relationship of the following formula (2), or log ₁₀ S ≦ −0.7 + 0.005 × D --- (2) (3) Average of the interface between the metal surface of the steel sheet and the nonmetal coating Regarding the roughness Ra, make sure this Ra satisfies the relationship of the following formula (3), or Ra ≦ 0.3− 0.1 × log ₁₀ D --- (3) (4) The crystal orientation given to the steel sheet metal surface In the emphasis processing, the grain boundary average step BS is set to a range that satisfies the relationship of the following equation (4): BS ≦ 3.0−log ₁₀ D (4) Grain-oriented electrical steel sheet with excellent characteristics and actual machine characteristics.

[0070]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. First, the reason why the component composition of the magnetic steel sheet of the present invention is limited to the above range will be described. Si: 1.5 to 7.0 wt% Si is an effective component to increase the electrical resistance of the product and reduce iron loss. For this reason, 1.5 wt% or more is contained.
If the content exceeds 7.0 wt%, the hardness becomes high and the production and processing become difficult. Therefore, the content is limited to the range of 1.5 to 7.0 wt%.

Mn: 0.03 to 2.5 wt% Mn, like Si, has a function of increasing electric resistance and a function of facilitating hot working during production.
Although it is necessary to contain 0.03 wt%, if it exceeds 2.5 wt%, γ transformation is induced at the time of heat treatment to deteriorate magnetic properties. Therefore, the content is set in the range of 0.03 to 2.5 wt%.

C: 0.003 wt% or less, S: 0.002 wt% or less, N: 0.002 wt% or less Each of C, S and N has a harmful effect on magnetic properties, and particularly degrades iron loss. C: 0.003 wt
%, S: 0.002 wt% or less, N: 0.002 wt% or less.

In the production of an electrical steel sheet, it is essential that the steel contains an inhibitor component for inducing secondary recrystallization, in addition to the above-mentioned elements, and these inhibitor components include Al, B, Bi, Sb, Mo, Te,
Se, S, Sn, P, Ge, As, Nb, Cr, Ti, Cu, Pb, Zn, In and the like are advantageously suitable, and these elements can be contained alone or in combination.

Next, the reasons for limiting the crystal grains constituting the steel sheet will be described. The important crystal grains in the present invention penetrate in the thickness direction. This is because such penetrating grains generate many magnetic poles at the grain boundaries, and a large increase in magnetostatic energy can be expected. Here, the particle size of each crystal grain is represented by the diameter of a circle having the same area as the area of the crystal grain on the steel sheet surface (equivalent circle diameter). The average crystal grain size is represented by the circle equivalent diameter of the value obtained by dividing the area by the number of such crystal grains contained in a certain area.

Now, in order to obtain a grain-oriented electrical steel sheet having excellent anti-strain properties expected in the present invention and excellent actual machine properties, it is necessary to consider the distribution of the penetrating grains and the number of crystal grains having a grain size of 3 mm or less. It is an essential requirement that the ratio be 65% or more and 98% or less. If the number ratio of the fine crystal grains of 3 mm or less is less than 65%, the effect of increasing the magnetostatic energy due to the presence of the fine grains cannot be obtained, resulting in deterioration of the strain resistance characteristics and increase of the factor for realization, and This is because the iron loss of
If the number ratio of the fine particles having a size of 3 mm or less exceeds 98%, the magnetic flux density of the product decreases, and iron loss deteriorates. In addition,
With respect to the number ratio of the fine grains, when it is 75% or more, a particularly remarkable effect of reducing the factor of realization and improving the strain resistance is recognized.

The fine crystal grains having a size of 3 mm or less may be fine crystals that are naturally generated. In addition, the magnetic poles existing at the grain boundaries are uniformly distributed in the steel sheet, and the static To make the distribution of magnetic energy uniform,
It is more preferable to arrange them artificially and regularly. Thereby, the flow of the magnetic flux becomes uniform, and an increase phenomenon of iron loss such as an abnormal increase of eddy current loss locally is suppressed.

Therefore, the area where various processes for generating fine grains as described above are performed is within the plane of the steel sheet as shown in FIG.
It is effective to distribute discretely as shown in
In particular, the more uniformly dispersed, the less the harm such as lowering the magnetic flux density, and the more the effect of lowering the strain sensitivity is also increased. Instead, as shown in FIG. 10 and FIG. 11, it is natural to obtain the most excellent effect by artificially arranging them regularly. In this regard, for example, when artificial crystal grains elongated linearly as shown in FIG. 12 are generated, the magnetic flux density of the product is significantly deteriorated, and the iron loss increases. Here, it is preferable that the interval at which fine particles are discretely present is 5 mm or more.

Further, regarding the average grain size of the steel sheet,
It is preferable that the thickness be 8 mm or more and 50 mm or less. If the average grain size is less than 8 mm, the degree of integration of the crystal orientation and the magnetic flux density may decrease, so it is difficult to obtain a stable and excellent iron loss value. If the diameter is more than 50 mm, the factor for realization of the device or the distortion resistance is likely to deteriorate.

As described above, by mixing fine grains of 3 mm or less with coarse grains of 15 mm or more in steel, the magnetic flux density is high, the iron loss is low, and the distortion resistance and the actual machine characteristics are also improved. Although an excellent grain-oriented electrical steel sheet can be obtained, it is advantageous to further perform a magnetic domain refining treatment in order to further reduce iron loss characteristics. Therefore, in the present invention, the application of linear strain, the formation of linear grooves, the surface smoothing process, the crystal orientation enhancement process, and the like are used in combination as the magnetic domain refinement technology.

According to the research conducted by the inventors, any of the above-described magnetic domain refining techniques can reduce the average grain size of the crystal grains of the steel sheet, particularly the crystal grains having a grain size exceeding 3 mm. There was a strong correlation, and it was determined that there was a suitable range according to the average particle size of the crystal grains. That is, among the crystal grains constituting the steel sheet, the average grain size of the crystal grains penetrating in the thickness direction and having a grain size exceeding 3 mm is represented by D (mm).
(1) With respect to the grooves repeatedly provided in the rolling direction, the total volume ratio V of the grooves per unit area of the steel sheet (unit:
mm) is within the range satisfying the relationship of the following equation (1), or log ₁₀ V ≦ −2.3 −0.01 × D --- (1) (2) Regarding linear local strain repeatedly provided in the rolling direction,
Total area ratio S of local strain per unit area of steel sheet (unit:
(Dimensionless) is within the range satisfying the relationship of the following formula (2), or log ₁₀ S ≦ −0.7 + 0.005 × D --- (2) (3) Average of the interface between the metal surface of the steel sheet and the nonmetal coating Regarding the roughness Ra, make sure this Ra satisfies the relationship of the following formula (3), or Ra ≦ 0.3− 0.1 × log ₁₀ D --- (3) (4) The crystal orientation given to the steel sheet metal surface For the emphasis processing, it is preferable that the grain boundary average step BS be in a range satisfying the relationship of the following equation (4): BS ≦ 3.0−log ₁₀ D --- (4) More advantageous improvements in the distortion characteristics and the actual device characteristics are realized.

Here, V (unit: mm) is obtained by dividing the total volume (mm ³ ) corresponding to the groove cross-sectional area × the groove length × the number of grooves by the surface area (mm ² ) of the target steel sheet. And S (unit:
Dimensionless) is the total area of the local strain areas corresponding to the width × length × number of linear local distortion (mm ^2), a value obtained by dividing by the surface area of the steel sheet of interest (mm ^2), Ra Is the value (μm) obtained by measuring the center line average roughness of the metal surface of the steel sheet. is there.

The grooves may be formed by etching the surface of the steel sheet or by pressing a gear roll to form the grooves. The local strain may be introduced by pressing with a rotating body, laser irradiation, or plasma. Any conventionally known method such as jet irradiation is suitable. In addition, as a method of smoothing the interface between the metal surface of the steel sheet and the non-metallic film, the formation of the forsterite film is suppressed, or the forsterite film is removed, and then pickling, polishing, chemical polishing or grinding is performed. Any method for reducing the roughness of the steel sheet surface is suitable. Furthermore, the crystal orientation enhancement process
This method is to suppress the formation of a forsterite film or remove the forsterite film, and then electrolytically treat the steel sheet surface in an aqueous solution of a halogen compound to preferentially leave only the crystal orientation plane of the characteristic. This method is also advantageously adapted.

Next, the manufacturing method of the present invention will be described. By the way, the steel slab adjusted to the desired suitable component composition is made into a hot-rolled steel sheet by a known hot-rolling method, and then subjected to hot-rolled sheet annealing as necessary, and one or two or more times of intermediate annealing The final thickness is obtained by cold rolling. In this final cold rolling, the orientation of the crystal grown during the secondary recrystallization is controlled by adjusting the rolling reduction. If the rolling reduction is less than 80%, a large number of crystal grains with poor orientation tend to recrystallize. The magnetic flux density may not be obtained. On the other hand, if it exceeds 95%, the probability of nucleation of secondary recrystallized grains is extremely reduced, and secondary recrystallization tends to be unstable. The rolling reduction is 80 ~
Preferably it is 95%.

It is to be noted that, in the above-mentioned rolling, the combination of known warm rolling and inter-pass aging treatment is advantageous in further improving the magnetic flux density. It is also possible to perform a weak decarburization treatment in hot-rolled sheet annealing or intermediate annealing. Further, when a linear groove is used as the magnetic domain refining process, it is preferable to provide a linear groove on the steel sheet surface after the final cold rolling.

Next, primary recrystallization annealing is performed. At this time, if necessary, a decarburizing treatment is simultaneously performed to reduce the C content to a predetermined value or less. Between the middle of the primary recrystallization annealing and the start of the secondary recrystallization, as the most important technique of the present invention, a region for increasing the driving force for crystal growth is locally provided in the steel plate. Here, since crystal growth in the thickness direction occurs relatively easily, such a region does not necessarily need to be provided over the entire thickness in the thickness direction of the steel sheet, and may be provided in a partial region in the thickness direction. Even if provided, the effects are equivalent. However, the projected area of this area on the steel sheet surface is 0.
It is necessary to set it between 05 mm and 3.0 mm. The reason for this is that when the thickness is less than 0.05 mm, the number of cases often eventually disappeared and disappeared by the usual secondary recrystallized grains that frequently occur later, while the size of the fine grains generated when the thickness exceeded 3.0 mm was also reduced.
If it exceeds 3.0 mm, the magnetic flux density will be reduced, and iron loss will increase.

For the area to be subjected to such processing, see 3.
It is necessary to be a narrow area of 0 mm or less.For example, when processing is performed on a long elongated area, crystal grains with inferior orientation are generated in the processed area, causing significant deterioration of the magnetic flux density of the material, It causes an increase in loss.

In the manufacturing process for providing such a region, before the start of the primary recrystallization, the generation of new primary recrystallized grains eliminates such a region, so that there is no effect. After the start of recrystallization, the fine grains are eaten by the secondary recrystallized grains immediately after nucleation and grain growth in the region, so that the effect is also lost.

As described above, the methods for increasing the driving force for crystal growth include (1) a method of introducing strain, and (2)
There are methods to refine primary recrystallized grains and (3) methods to enhance inhibitory power, among which methods (1) and (2) are superior, and among them, method (1) Is particularly excellent in artificially generating and controlling fine grains. When the amount of strain introduced into the steel sheet is less than 0.005, the action becomes unstable because the generation of fine grains may not occur,
On the other hand, if it exceeds 0.70, a large number of fine grains tend to be formed at the same position, and the effect is reduced in spite of the effort. Therefore, the amount of introduced strain is preferably in the range of 0.005 to 0.70.

As a method for industrially providing a region having an increased driving force for crystal growth with high efficiency and stability, a particularly excellent method is to form small projections on the surface as shown in FIG. In the object having, a method of pressing an object harder than the steel sheet against the steel sheet surface, a method of applying a high voltage between the steel sheet surface and the electrode and locally energizing or discharging, as shown in FIG.
Further, there are a method of instantaneously irradiating a high-temperature spot laser and a method of locally irradiating a pulse laser.
Here, a high-temperature spot laser is a laser that continuously oscillates but has a large capacity, such as a carbon dioxide laser, and irradiates a local portion of the steel sheet surface for a short time of several hundred milliseconds or less and heats it. is there. In addition, the pulse laser is a laser beam that is made into a high-density light flux in a short time by using a Q switch or the like, and can apply an extremely strong impact force locally to the steel sheet.

After the region where the driving force for crystal growth is increased is artificially provided as described above, an annealing separator is applied as necessary, and then a final finish annealing is performed to perform secondary recrystallization. Let it. In the final finish annealing, the temperature may be raised to a high temperature of about 1200 ° C. to form a purification annealing and a forsterite-based undercoating. Thereafter, an insulating coating is applied to the surface of the steel sheet to obtain a product. Before coating, the surface of the steel sheet may be mirror-finished or a crystal orientation enhancement process may be performed. Further, a tension coating may be used as the insulating coating.

Here, when plasma jet or laser irradiation is used as the magnetic domain refining treatment, a predetermined treatment may be applied to the steel sheet surface after the secondary recrystallization. Also, at this stage, a linear groove region can be provided by a projection roll. When an interface smoothing process or a crystal orientation enhancement process is used, formation of a forsterite film may be suppressed, or a predetermined process may be performed after removing the forsterite film, and then an insulating coating may be applied.

By the above-described manufacturing method, iron loss is low,
It is possible to obtain grain-oriented electrical steel sheets with high magnetic flux density and excellent strain resistance and actual machine characteristics.
By coexisting with the above coarse particles, it is possible to assemble a transformer having a high magnetic flux density and a low iron loss, and having an extremely low iron loss of an actual machine.

[0093]

【Example】

Example 1 C: 0.08 wt%, Si: 3.35 wt%, Mn: 0.07 wt%, Al: 0.02
wt%, Sb: 0.05 wt% and N: 0.008 wt%, the balance being Fe and unavoidable impurities.
Then, a 2.2 mm thick hot-rolled steel sheet was obtained by a conventional method.
Then, after annealing the hot rolled sheet at 1000 ° C for 30 seconds,
It was cold rolled to a thickness. After that, an intermediate treatment was performed at 1080 ° C for 50 seconds, followed by warm rolling at a steel sheet temperature of 220 ° C.
The final thickness was 22 mm. Then, after the degreasing treatment, the steel sheet was subjected to decarburizing annealing at 850 ° C. for 2 minutes, and then the steel sheet was divided into two parts, one of which was directly coated with an annealing separator containing MgO as a main component (comparative example). On the other hand, using the device shown in Fig. 14, the surface of the steel sheet is subjected to an instantaneous discharge treatment at 1 kV in a 1.5 mm size region, and the instantaneous high-temperature heat treatment is performed to increase the driving force for grain growth. Was given. Then, such a region was repeatedly provided in the pattern shown in FIG. 11 with a pitch in the coil longitudinal direction: 10 mm and a pitch in the width direction: 15 mm, and then an annealing separator mainly containing MgO was applied ( Invention example).

[0094] Then, the resulting coil, as a final finish annealing, the temperature was raised at a heating rate of 30 ° C. / h up to 850 ° C. in N _2, was held for 25 hours in 850 ° C., of 25% N ₂ The temperature was raised to 1200 ° C. at a rate of 15 ° C./h in a mixed atmosphere of H ₂ and 75% H ₂ , and further kept in H ₂ for 5 hours and then lowered. Then, after removing the unreacted annealing separating agent, these coils were coated and baked with a tension coating containing 50% colloidal silica, and subjected to magnetic domain refining treatment with a plasma jet to obtain products. Here, the irradiation with the plasma jet was performed linearly in the plate width direction under the conditions of an irradiation width: 0.05 mm and a repetition interval in the rolling direction: 5 mm.

Using these steel plates, slitting, shearing, and laminating were performed to produce two 3-phase transformers each having a leg width of 250 mm, a height of 900 mm, and a thickness of 300 mm. did. At this time, one unit was manufactured with as little distortion as possible, and the other unit was cast on a caster with a 50 mm diameter sphere at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of imparting distortion. Press and intentionally add distortion,
Manufactured. Table 4 shows the results of the examination of the iron loss characteristics and the values of the factor of realization of these transformers, together with the results of the investigation of the magnetic characteristics of the materials. Table 4 also shows the results of investigation on the number ratio of crystal grains of 3 mm or less measured by macro-etching the material and the average grain size D of crystal grains exceeding 3 mm.

[0096]

[Table 4]

As is clear from the table, the transformer using the grain-oriented electrical steel sheet according to the present invention has low actual machine characteristics and a very low distortion resistance, and is used as a core material of an actual transformer. It was extremely good.

Example 2 C: 0.08 wt%, Si: 3.40 wt%, Mn: 0.04 wt%, Al: 0.02
wt%, Cu: 0.15wt%, Ni: 0.10wt%, Bi: 0.005wt%,
Sb: 0.04 wt% and N: 0.008 wt%, the balance being Fe
After heating the steel slab comprising unavoidable impurities to 1430 ° C., it was made into a hot-rolled steel sheet having a thickness of 2.6 mm by an ordinary method. Next, a carbide adjustment treatment consisting of a soaking treatment at 750 ° C for 3 seconds is performed, and after pickling, cold rolling is performed to make an intermediate thickness of 1.8 mm, followed by a soaking treatment at 1125 for 30 seconds and injection of mist water.
Intermediate annealing consisting of rapid cooling at 40 ° C / s was performed.

Next, after pickling, a final sheet thickness of 0.26 mm was obtained by hot rolling at a steel sheet temperature of 230 ° C. Then, after the degreasing treatment, the steel sheet was divided into five parts, one of which was subjected to decarburization annealing at 850 ° C. for 2 minutes, and then an annealing separator containing MgO as a main component was applied (Comparative Example). The other four are that, when decarburizing annealing is performed at 850 ° C. for 2 minutes, immediately after the temperature is raised to 850 ° C., the ceramic roll having the shape shown in FIG. 13 is rotated in synchronization with the traveling speed of the steel sheet. A steel sheet is pressed and a driving force increasing process for local grain growth of 2.0 mm in a pattern as shown in FIG. 11 is performed. A pitch in the longitudinal direction of the coil: 25 mm, a pitch in the width direction: 20
It was applied to the steel plate in mm. At this time, for the three coils,
Prior to decarburization annealing, a ceramic roll having linear projections as shown in FIG. 15 is rotated on the surface of the steel sheet in synchronization with the running coil, and two of them are in the width direction of 5 μm in depth and 100 μm in width. It was extended in a rolling direction pitch: 5 mm groove, and the other one was formed in a sheet width direction having a depth of 30 μm and a width of 500 μm to form a pitch in the rolling direction: 2 mm. After decarburization annealing, these 4
As in the comparative example, the coil was coated with an annealing separator mainly containing MgO (inventive example).

These coils were heated in N ₂ to 850 ° C. at a rate of 30 ° C./h as final finish annealing.
15 ° C. in a mixed atmosphere of 25% N ₂ and 75% H ₂
/ At a Atsushi Nobori rate was raised to 1200 ° C. for h, further in H ₂ 5
After holding for a time, the temperature was lowered. Then, after removing the unreacted annealing separating agent, these coils were coated with a tension coating containing 50% of colloidal silica and baked to obtain products. However, one of the two coils provided with a groove having a depth of 5 μm is coated with a tension coating and baked, and then irradiated with a 0.1 mm diameter laser beam in the width direction at intervals of 0.3 mm (pitch in the rolling direction). : 10 mm), and a linear local strain region was provided.

Using these steel plates, slitting, shearing, and laminating were performed to produce two three-phase transformers each having a leg width of 300 mm, a height of 1100 mm, and a thickness of 250 mm. . At this time, one unit was manufactured with as little distortion as possible, and the other unit was cast on a caster with a 50 mm diameter sphere at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of imparting distortion. Press and intentionally add distortion,
Manufactured.

Table 5 shows the results of the examination of the iron loss characteristics and the values of the factor of realization of these transformers, together with the results of the investigation of the magnetic characteristics of the materials. Table 5 also shows the results of investigation on the number ratio of crystal grains of 3 mm or less and the average grain size D of crystal grains of more than 3 mm measured by macro-etching the material. In addition, as Bm for iron loss measurement of transformer, Bm =
From 0.2 × log ₁₀ 56 + 1.4 = 1.75, the value was obtained at Bm = 1.75T.

[0103]

[Table 5]

As is evident from the table, in the example of the invention in which the driving force for grain growth was increased, the iron loss of the product was significantly reduced as compared with the comparative example, and the factor of realization was low and the transformer loss was low. It had excellent container characteristics. In particular, when the volume of the groove is set in an appropriate range with respect to the average particle diameter D, the factor for realizing the transformer is the smallest, the distortion resistance is extremely good, and the core material of the actual transformer is extremely excellent. I was

Example 3 C: 0.05 wt%, Si: 3.15 wt%, Mn: 0.35 wt%, Al: 0.01
7 wt%, Sb: 0.005 wt%, B: 0.0005 wt% and N: 0.
After heating a steel slab containing 008 wt%, the balance being Fe and unavoidable impurities, to 1180 ° C,
The hot rolled steel sheet was 2.4 mm thick. Subsequently, hot-rolled sheet annealing was performed at 800 ° C. for 30 seconds, and after pickling, a final sheet thickness of 0.34 mm was obtained by hot rolling at a steel sheet temperature of 195 ° C. Then, after degreasing,
Decarburization annealing was performed at 820 ° C. for 2 minutes. Then, the steel sheet was divided into four parts, one of which was subjected to a secondary recrystallization annealing at 1000 ° C. for 3 minutes, and then a coating solution was applied and baked.
A product (comparative example). The remaining three coils are 1000
During the secondary recrystallization annealing at 3 ° C for 3 minutes, a spot laser was irradiated in the furnace during the heating process before the start of the secondary recrystallization, and a local area of 2.5 mm in size was formed as shown in Fig. 10. In the region, the steel plate was subjected to a treatment for increasing the driving force for grain growth. Such a region was repeatedly provided with a pitch in the coil longitudinal direction: 30 mm and a pitch in the width direction: 25 mm. Thereafter, a coating solution was applied and baked to obtain a product. Two of the three coils were chemically polished before the coating solution was applied, and one of the coils had a surface roughness of 0.07.
μm and the other one was 0.26 μm.

Using these steel plates, slitting, shearing, and laminating were performed to produce two 3-phase transformers each having a leg width of 200 mm, a height of 800 mm, and a thickness of 350 mm. did. At this time, one unit was manufactured with as little distortion as possible, and the other unit was cast on a caster with a 50 mm diameter sphere at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of imparting distortion. Press and intentionally add distortion,
Manufactured.

Table 6 shows the results of the investigation on the iron loss characteristics and the values of the factor of realization of these transformers, together with the results of the investigation on the magnetic characteristics of the materials. Table 6 also shows the results of investigation on the number ratio of crystal grains of 3 mm or less and the average grain size D of crystal grains of more than 3 mm measured by macro-etching the material. In addition, as Bm for iron loss measurement of transformer, Bm =
From 0.2 × log ₁₀ 10 + 1.4 = 1.60, the value was obtained at Bm = 1.60T.

[0108]

[Table 6]

As is clear from the table, the actual characteristics of the transformer assembled by using the grain-oriented electrical steel sheet according to the present invention have a low actualization factor, extremely good distortion resistance, and an actual core of the transformer. It was extremely excellent as a material.

Example 4 C: 0.08 wt%, Si: 3.40 wt%, Mn: 0.09 wt%, Al: 0.02
wt%, Cu: 0.10 wt%, Mo: 0.010 wt%, Ni: 0.2 wt%,
Contains Sb: 0.045 wt% and N: 0.008 wt%, with the balance being
A steel slab composed of Fe and unavoidable impurities was heated to 1440 ° C., and then turned into a 2.2 mm-thick hot-rolled steel sheet by an ordinary method.
Then, after pickling, cold-rolled to an intermediate thickness of 1.8 mm, then heat treated at 1100 for 30 seconds and sprayed with mist water
Intermediate annealing consisting of rapid cooling at 40 ° C / s, pickling,
The final sheet thickness was 0.22 mm by warm rolling at a sheet temperature of ° C. Then, after degreasing, the steel plate is divided into six parts, one of which is 850 ° C.
After decarburizing annealing for 2 minutes, an annealing separator containing MgO as a main component was applied (Comparative Example). The remaining five coils were subjected to pulse laser irradiation after decarburizing annealing at 850 ° C. for 2 minutes, and the steel plate surface was subjected to a driving force increasing treatment for grain growth having a size of 2.0 mm and a strain of 0.01 to 0.08. Area, spacing:
It was provided discretely and locally on a steel plate at 2 to 30 mm. Then
As with the comparative example, three of the five coils were coated with an annealing separator containing MgO as a main component, but the remaining two coils were coated with an annealing separator containing SiO ₂ as a main component to suppress the formation of a film. It was applied (inventive example).

These coils were heated to 850 ° C. in N ₂ at a rate of 30 ° C./h as final finish annealing.
15 ° C. in a mixed atmosphere of 25% N ₂ and 75% H ₂
/ At a Atsushi Nobori rate was raised to 1200 ° C. for h, further in H ₂ 5
After holding for a time, the temperature was lowered. Then, these coils, baking coating tension coating containing B ₂ O _3,
The product. However, among the invention examples, those coated with an annealing separator containing SiO ₂ as a main component did not show the formation of a surface oxide film, and thus were subjected to a crystal orientation enhancement treatment in an aqueous sodium chloride solution. The above tension coating was applied and baked. At this time, one of the two coils had an average value of the step of the aggregated grain boundary: 2.5 μm, and the other had a density of 0.9 μm. Among the invention examples, those coated with an annealing separator containing MgO as a main component applied and baked the above-mentioned tension coating on the forsterite film formed on the steel plate surface. Of the coils, two coils irradiated the plasma jet linearly in the plate width direction. At this time, one is to set the width of the local strain area to 0.05 mm
Irradiation at a pitch of 15 mm in the steel sheet rolling direction (S = 3.3
× 10 ⁻³ ), but the other is to set the width of the local strain region to 0.8 mm.
Irradiation at a pitch of 5 mm in the rolling direction of the steel sheet (S = 1.6
× 10 ^-1 ).

Using these steel plates, slitting, shearing, and laminating were performed, and two three-phase transformers each having a leg width of 300 mm, a height of 1100 mm, and a thickness of 250 mm were manufactured. . At this time, one unit was manufactured with as little distortion as possible, and the other unit was cast on a caster with a 50 mm diameter sphere at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of imparting distortion. Press and intentionally add distortion,
Manufactured.

Table 7 shows the results of the examination of the iron loss characteristics and the values of the factor of realization of these transformers, together with the results of the examination of the magnetic characteristics of the materials. Table 7 also shows the results of investigation on the number ratio of crystal grains of 3 mm or less and the average grain size D of crystal grains of more than 3 mm measured by macro-etching the material. The Bm for the iron loss measurement of the transformer was calculated from the average value of the D value of the product = 100.5 mm.
From m = 0.2 × log ₁₀ 100.5 + 1.4 = 1.80, Bm = 1.80T
The value in.

[0114]

[Table 7]

As is clear from the table, the actual characteristics of the transformer assembled by using the grain-oriented electrical steel sheet according to the present invention have a low actualization factor, extremely good distortion resistance, and an actual core of the transformer. It was extremely excellent as a material.

Example 5 C: 0.08 wt%, Si: 3.45 wt%, Mn: 0.07 wt%, Al: 0.02
wt%, Ge: 0.015 wt%, Mo: 0.010 wt%, Ni: 0.1 wt
%, Sb: 0.050 wt%, Cr: 0.05 wt% and N: 0.008 wt%
%, With the balance being Fe and unavoidable impurities, a steel slab was heated to 1400 ° C., and then made into a 2.4 mm-thick hot-rolled steel sheet by an ordinary method. Then, after pickling, cold rolling
After an intermediate thickness of 1.5 mm, after intermediate annealing consisting of soaking at 1100 for 30 seconds and quenching at 40 ° C / s by spraying mist water,
Pickling followed by warm rolling at a steel sheet temperature of 200 ° C.
The final thickness was 17 mm. Then, after degreasing, the steel sheet was divided into four parts, one of which was subjected to decarburizing annealing at 850 ° C for 2 minutes,
An annealing separator containing O as a main component was applied (Comparative Example 1).
The other one is that immediately after the temperature rise in the decarburizing annealing, the roll having the linear projections as shown in FIG. 15 is rotated in synchronization with the running coil, so that the steel plate surface has a depth of 30 μm and a width of 30 μm. ： 35μ
m grooves were provided at a pitch of 4 mm in the rolling direction (Comparative Example 2). Further, another one is to rotate the roll having linear projections as shown in FIG. 15 in synchronization with the running coil immediately after the temperature rise of the decarburization annealing, and to make the depth of the steel plate surface: 10 μm, Width: 80μm, rolling direction repetition interval: 5
A groove was provided in mm (Comparative Example 3). The other one is that, immediately after the temperature rise of the decarburizing annealing, the roll having linear projections as shown in FIG. 15 is rotated in synchronization with the running coil,
A groove is formed on the surface of the steel sheet at a depth of 10 μm, a width of 80 μm, and a repetition interval of the rolling direction: 5 mm. After the decarburization annealing, this time is synchronized with a coil running on a roll having small projections as shown in FIG. Rotate while rotating, the size on the steel plate surface:
In the pattern shown in Fig. 9 at 1.5 mm,
0.03 to 0.15 locally and discretely with a repetition interval of 00 mm
A driving force increasing treatment for grain growth having a distortion of was performed. Then, an annealing separator containing MgO as a main component was applied to all three coils.

These coils were heated to 850 ° C. at a rate of 30 ° C./h in N ₂ as final finish annealing.
After holding at 850 ° C. for 20 hours, 25% N ₂ and 75% H ₂
The mixture was heated up to 1200 ° C. at a rate of 15 ° C./h in a mixed atmosphere, and further kept in H ₂ for 5 hours and then cooled. After that, a tension coating containing colloidal silica was applied to these coils, and 800 ° C was used for flattening annealing.
Baked in.

Using these steel sheets, slit processing, shearing processing, and lamination fixing processing were performed, and two three-phase transformers each having a leg width of 300 mm, a height of 1100 mm, and a thickness of 250 mm were manufactured. . At this time, one unit was manufactured with as little distortion as possible, and the other unit was cast on a caster with a 50 mm diameter sphere at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of imparting distortion. Press and intentionally add distortion,
Manufactured.

Table 8 shows the results of the investigation on the iron loss characteristics and the values of the factor of realization of these transformers, together with the results of the investigation on the magnetic characteristics of the materials. Table 8 also shows the results of investigation on the number ratio of crystal grains of 3 mm or less measured by macro-etching the material and the average grain size D of crystal grains of more than 3 mm.

[0120]

[Table 8]

The results of macro etching of the products were as follows. Comparative Example 1 and Comparative Example 3 had a normal crystal structure, while Comparative Example 2
Immediately after the decarburization temperature rise, in a place where a groove with a depth of 25 μm
Elongated crystal grains along the groove were formed immediately below the crystal grains, and these grains separated normal secondary recrystallized grains. On the other hand, in the invention example, fine grains were generated in the area subjected to the grain growth promoting treatment, and a material excellent in not only the actual characteristics of the transformer but also the strain resistance was obtained.

[0122]

As described above, according to the present invention, the excellent material characteristics of the product steel plate can be directly reflected in the transformer, and as a result, a transformer having excellent actual machine characteristics even after assembly can be obtained. Can be.

[Brief description of the drawings]

FIG. 1 is a metallographic photograph of a steel sheet in which fine grains are artificially generated according to the present invention.

FIG. 2 is a (100) pole figure showing a comparison between crystal orientations of artificially generated fine grains and naturally generated fine grains.

FIG. 3 is a graph showing the effect of the number ratio of fine grains of 3 mm or less on the iron loss ratio of transformers to iron loss characteristics (actualization factor) and distortion resistance characteristics (actualization factor during strain imparting processing). It is.

FIG. 4 is a graph showing the relationship between the average grain size of penetrating grains and iron loss characteristics of a grain-oriented electrical steel sheet, the factor for realizing a transformer, and the factor for realizing a strain imparting process.

FIG. 5 shows the relationship between the total volume ratio V of the grooves per unit area of the steel sheet to obtain the best factor of realization of the grooves repeatedly provided in the rolling direction and the average particle diameter D of the crystal grains exceeding 3 mm. It is a graph shown.

FIG. 6 shows the total local strain area S per unit area of a steel sheet for obtaining the best realization factor for the linear local strain repeatedly provided in the rolling direction, with the average grain size D of crystal grains exceeding 3 mm. 5 is a graph shown by the relationship.

FIG. 7 shows the average roughness Ra for obtaining the best factor for realizing the roughness of the interface between the metal surface of the steel sheet and the nonmetal coating.
3 is a graph showing the relationship between the average particle diameter D of crystal grains exceeding 3 mm.

FIG. 8 shows the grain boundary average step BS for obtaining the best factor for realizing the crystal orientation enhancement treatment performed on the metal surface of the steel sheet in relation to the average grain size D of crystal grains exceeding 3 mm. It is a graph.

FIG. 9 is a diagram showing a state in which regions in which the driving force for crystal grain growth is increased are discretely provided on the surface of the steel sheet.

FIG. 10 is a diagram showing a state in which regions in which the driving force for crystal grain growth is increased are regularly provided on the surface of the steel sheet.

FIG. 11 is a diagram showing another example of a state where regions where the driving force for crystal grain growth is increased are regularly provided on the surface of the steel sheet.

FIG. 12 is a diagram showing a state in which a region in which the driving force for crystal grain growth is increased is provided linearly continuously in the width direction of the steel sheet.

FIG. 13 is an external view of a roll having a large number of small protrusions on the surface.

FIG. 14 is a conceptual diagram of an apparatus for performing a local energization heating process and a local discharge heating process.

FIG. 15 is an external view of a roll having linear protrusions on its surface.

[Explanation of symbols]

1 Gate pulse to determine processing time 2 High voltage power supply 3 Electrode 4 Driving force increase processing area for grain growth 5 Counter electrode 6 Steel plate 7 Small projection 8 Linear projection 9 Rolling direction 10 To the rolling direction of grain growth driving force increase processing 11 Interval of repetitive processing in the direction perpendicular to the rolling direction of the increase in driving force for grain growth

Claims (5)

[Claims] (1) Si: 1.5 to 7.0 wt%, Mn: 0.03 to 2.5 wt%, and contamination of C, S and N as impurities respectively: C: 0.003 wt% or less, S: 0.002 wt% or less N: 0.002 wt% or less of the electrical steel sheets, and among the crystal grains constituting the steel sheet, the number of crystal grains that penetrate in the thickness direction and have a grain size of 3 mm or less on the steel sheet surface. The ratio is over 65%,
A grain-oriented electrical steel sheet having a core loss of 98% or less and having a magnetic domain refinement treatment applied to the surface of the steel sheet, and having a low core loss and excellent distortion resistance and actual machine characteristics. 2. The steel sheet according to claim 1, wherein the average value of the grain size of the crystal grains penetrating in the sheet thickness direction on the steel sheet surface is not less than 8 mm and not more than 50 mm. Grain-oriented electrical steel sheet with excellent characteristics and actual machine characteristics. 3. The method according to claim 1, wherein the crystal grains penetrating in the thickness direction and having a grain size of 3 mm or less on the surface of the steel sheet include those which are artificially and regularly arranged. Grain-oriented electrical steel sheet with low iron loss and excellent distortion resistance and actual machine characteristics. 4. The magnetic domain refining treatment according to claim 1, 2 or 3, wherein (1) a depth: 50 μm or less and a width: 35
Repeatedly providing grooves of 0 μm or less in the rolling direction, (2)
(3) smoothing the interface between the metal surface of the steel sheet and the non-metallic coating to an average roughness Ra of 0.3 μm or less in the surface direction of the steel sheet in the rolling direction; )
A grain-oriented electrical steel sheet with low iron loss, which is one of applying a crystal orientation enhancement treatment to the metal surface of the steel sheet, and having excellent distortion resistance characteristics and actual machine characteristics. 5. The steel sheet according to claim 4, wherein, among the crystal grains constituting the steel sheet, the crystal grains penetrate in the thickness direction and have a grain size of 3 mm.
When the average grain size of the crystal grains having a size exceeding D is defined as D (mm), (1) The total volume ratio V (unit: mm) of the grooves per unit area of the steel sheet is as follows for the grooves repeatedly provided in the rolling direction. formula
To make the range satisfying the relationship of (1), or log ₁₀ V ≦ −2.3 −0.01 × D --- (1) (2)
Total area ratio S of local strain per unit area of steel sheet (unit:
(Dimensionless) is within the range satisfying the relationship of the following formula (2), or log ₁₀ S ≦ −0.7 + 0.005 × D --- (2) (3) Average of the interface between the metal surface of the steel sheet and the nonmetal coating Regarding the roughness Ra, make sure this Ra satisfies the relationship of the following formula (3), or Ra ≦ 0.3− 0.1 × log ₁₀ D --- (3) (4) The crystal orientation given to the steel sheet metal surface In the emphasis processing, the grain boundary average step BS is set to a range that satisfies the relationship of the following equation (4): BS ≦ 3.0−log ₁₀ D (4) Grain-oriented electrical steel sheet with excellent characteristics and actual machine characteristics.