JP3482833B2 - Grain-oriented electrical steel sheets with excellent iron loss, distortion resistance and magnetic properties in actual machines - Google Patents

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 the core of a transformer or a generator, and in particular, iron loss characteristics ,
The present invention relates to a grain-oriented electrical steel sheet having excellent strain resistance and magnetic properties in an actual machine.

[0002]

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

As a method of reducing iron loss, a method of increasing electric resistance by containing Si which is effective for reducing eddy current loss, a method of reducing a steel plate thickness, a method of reducing a crystal grain size, and a hysteresis loss. There is a method of aligning the orientation of crystal grains that is effective in reducing Of these, the method of increasing the electrical resistance by containing Si causes a decrease in the saturation magnetic flux density when Si is excessively contained, and also causes an increase in the size of the iron core.Therefore, there is a limit, and the steel plate thickness is made thin. 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 (which is generally represented by the magnetic flux density B ₈ (T) at a magnetizing force of 800 A / m) and the crystal grain size. However, there is a trade-off that increasing the degree of integration of crystal orientations inevitably increases the crystal grain size and deteriorates iron loss, so in order to obtain the minimum iron loss value, It was necessary to adjust to the optimum crystal orientation integration degree, 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 laser light has been developed, and it is no longer necessary to reduce the crystal grain size to reduce iron loss. Therefore, the method of increasing the degree of integration of crystal orientation to reduce iron loss becomes the mainstream, and the magnetic flux density (B ₈ ) is
Materials from 1.93 to 2.00T have been developed.

As the magnetic domain refining treatment, the roughness of the interface between the metal surface of the steel sheet and the non-metal coating is reduced, and the crystal orientation is emphasized on the metal surface, including the formation of linear grooves and the introduction of linear strain. The method of applying the treatment was developed, and the iron loss characteristics of the material were greatly improved by these domain refinement treatments.

By the way, in order to increase the degree of integration of crystal orientation, it is necessary to completely control the secondary recrystallization. Secondary recrystallization is performed by using AlN and Mn called inhibitors.
Precipitates such as Se and MnS are finely dispersed and precipitated in the 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 In addition to this, grain boundary segregation-type elements such as Sb, Sn, and Bi are used as sub-inhibitors. By combining these techniques with the technique of controlling the texture of crystal grains, the production technique of the electromagnetic steel sheet having the above-mentioned excellent magnetic flux density has been completed.

[0008]

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

Conventionally, when a product transformer is manufactured using a grain-oriented electrical steel sheet having a high magnetic flux density, a problem that desired actual machine characteristics cannot be obtained occurs, and various investigations have been conducted. , This is a peculiar phenomenon when a material with a high magnetic flux density is used, because undesired wraparound of magnetic flux occurs in the T coupling part of the transformer in a direction deviating from the magnetic flux flow direction, and unnecessary loss occurs. It was explained that the prescribed iron loss reduction effect could not be obtained, and there was no room for improvement. However, when using recent materials with even higher magnetic flux density, when actually incorporated in a transformer
The amount of deterioration of the magnetic properties, that is, the properties of the actual machine is so great that even the benefits of material development cannot be enjoyed.

Further, it has been recognized that as the magnetic flux density is improved, the iron loss characteristics are greatly deteriorated due to the strain applied during shearing and stacking. This is still under study, and at present, the only practical countermeasure is to pay attention to the handling of the material and suppress the addition of strain as much as possible.

Furthermore, although the iron loss characteristics of the material are certainly improved by the various magnetic domain subdivision 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.

In the present invention, in the material in which the crystal orientation of the secondary recrystallized grains is highly integrated, the cause of the deterioration of the actual machine characteristics relative to the level estimated from the iron loss of the material and the strain added in the working process It is an object of the present invention to elucidate the cause of its high sensitivity to, and to propose a grain-oriented electrical steel sheet that does not cause such characteristic deterioration and further improves the characteristics.

[0013]

Means for Solving the Problems The clarification process of the present invention will be described below. A method for increasing the magnetic flux density of grain-oriented electrical steel sheets has been well known in the past, and it is known that the addition of Al, Sb, Sn, Bi, etc. 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 A value of 1.95T is reported as B ₈ by the grain-oriented electrical steel sheet containing Bi and 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 in many cases a desired value cannot be obtained as the iron loss of an actual machine. This is due to the high degree of integration of the crystal of the material, which has been unavoidable in the past as described above.

Therefore, the present inventors have investigated various factors affecting the wraparound of the magnetic flux in the T coupling portion of the stacking transformer using the high magnetic flux density material. As a result, it was newly found that the cause of the characteristic deterioration is not only due to the high degree of integration of crystal orientation, which has been conventionally said, but also due to the influence of the crystal grain size. Moreover, regarding the effect of the strain introduced in the processing step on the characteristic deterioration, the following new findings were made.

That is, when the degree of integration of crystal orientation is high,
Regarding the magnetic poles appearing on the surface of the steel sheet, the magnetic poles appearing at the crystal grain boundaries are overwhelmingly larger than the crystal grain surfaces. Reduction of iron loss due to subdivision of magnetic domains is achieved by a mechanism that reduces the magnetostatic energy increased by the generation of magnetic poles due to subdivision of magnetic domains. In the case of high magnetic flux density grain-oriented electrical steel sheet, it appears at grain boundaries. The effect of the magnetic poles is therefore predominant.
However, in the case of this material, the crystal grain size is inevitably large, so the distance between the crystal grain boundaries is large, and even if the same amount of magnetic pole appears in the crystal grain boundaries, the increase in magnetostatic energy is Smaller than small diameter material. In addition, in a material that has undergone magnetic domain refinement processing to minimize iron loss of the material, once strain is added to this, the energy balance is easily disrupted and the magnetic domain refinement effect is lost, increasing the magnetic domain width. To do. This is the reason why the high magnetic flux density magnetic steel sheet has high strain sensitivity.

The experiments that lead 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.
A hot rolled sheet for grain-oriented electrical steel containing 008 wt% and the balance of inevitable impurities and Fe was annealed at 1000 ° C for 30 seconds, pickled, and then cold rolled at a reduction rate of 30%. After intermediate rolling, heat treatment at 1050 ° C for 1 minute as intermediate annealing, then pickling again, rolling at 150-200 ° C with rolling reduction of 85% and final thickness: 0.22mm Steel plate. Then, after degreasing treatment, on the surface of the steel sheet as magnetic domain refinement treatment,
A linear groove was formed with a depth of 25 μm and a width of 50 μm in a direction tilted by 10 ° from the plate width direction and with a repeating pitch in the longitudinal direction of 3 mm. Then, after decarburization and primary recrystallization annealing at 850 ° C for 2 minutes, the steel sheet was divided into two parts, one was used as it was as a conventional material, and the other was 1.5
Dotted with a size of mm diameter, 20 mm in the width direction and 30 in the longitudinal direction
Energy dose of 40-45 Ws (1000-1200
Instantaneous heat treatment was performed by discharge treatment under the condition of (estimated temperature of ° C). After that, TiO ₂ : 10 wt% and
After MgO added with 2 wt% of Sr (OH) ₂ was applied as an annealing separator, it was wound on a coil and subjected to final finish annealing.
Final finish annealing is performed 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 purification by holding at 1150 ° C. for 5 hours in H ₂ were simultaneously performed. After the final finish annealing,
After removing the unreacted annealing separator, a tension coat consisting 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 to measure the characteristics of the transformer, and then the steel sheet was macro-etched to measure the crystal grain size. . In addition, although the above-mentioned slit processing, shearing processing, and stacking processing were performed with the utmost care, the addition of strain was suppressed as much as possible, but in order to experimentally evaluate the effect of strain imparting, a sphere with a diameter of 50 mm was used during these processing. An experiment was also conducted in which casters were pressed with a load of 5 kg to add strain when intended. The results obtained are summarized in Table 1.

[0019]

[Table 1]

As is clear from Table 1, after decarburization / primary recrystallization annealing, a product having a size of 1.5 mm and subjected to a momentary high temperature treatment and then secondary recrystallization (symbol (a ), (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, whereas In products without such treatment (symbols (c) and (d)), the iron loss of the model transformer is greatly deteriorated, and especially when strain is added by using casters in the machining process, the factor of realization is large. , It was found that the degree of deterioration of the iron loss of the transformer is extremely large, that is, the strain sensitivity is large.

In order to elucidate the reason why the above results were obtained, the state of crystal grains of the steel plate by macro etching and the state of the magnetic flux distribution of the model transformer were investigated in detail. In the products (a) and (b) that were subjected to secondary high-temperature heat treatment after being subjected to a point-like instantaneous high-temperature heat treatment, fine crystal grains with a diameter of 0.5 to 2.5 mm were formed on the steel plate at the location where such treatment was applied. Although the product was formed from the front surface to the back surface, that is , through the sheet thickness direction, most of the products (c) and (d) that were not subjected to such treatment had a thickness of 20 to 70 mm within the plane of the steel sheet. It was composed of coarse particles.

Further, when the crystal orientation of the fine crystal grains artificially generated in this way was measured, it was found to be a random orientation, which was 15 ° or more from the Goss orientation which is the usual orientation of secondary recrystallized grains. It was off. By the way, for decarburized annealing plate
In the same manner as in the case of secondary recrystallization after subjecting to a point-shaped instantaneous high-temperature heat treatment with a diameter of 1.5 mm, the interval in the strip width direction: 10 mm pitch, in the rolling direction Interval: An example of artificially generating fine particles on a steel plate at a pitch of 15 mm is shown in FIG. 1, and the (100) pole figure of FIG. 2 shows its orientation in comparison with that of naturally occurring fine particles. . In FIG. 1, naturally occurring fine particles are also scattered, but fine particles are surely generated at positions where instantaneous high temperature heat treatment is performed. Further, as shown in FIG. 2, the orientation of the fine particles artificially generated is randomly distributed, whereas that of the naturally occurring fine particles is extremely close to the Goth orientation.

Next, Table 2 shows the results of measuring the grain size distribution of the crystal grains penetrating in the plate thickness direction of the above two types of products. 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. Was calculated and expressed by the diameter of the circle corresponding to the area.

[0024]

[Table 2]

From Table 2, the products (c) and (d), which have a large factor of realization and inferior 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 occupy about 60%. On the other hand, products with excellent iron loss characteristics of transformers with low actualization factor (a) and (b) are 2.5 mm.
It can be seen that the number ratio of the following fine particles is about 90%, and the number ratio of the crystal grains having a size of 15 to 70 mm is 8%, which is extremely low.

As described above, it was found that there is a large difference in the number ratio of the fine crystal grains between the two types of materials having different values of the realization factor. However, due to the existence of such fine grains, any mechanism may be used. Next, it was investigated whether or not the chemical conversion factor and the reduction in strain sensitivity, that is, the effect of improving the strain resistance characteristic was obtained. First, when the flow of the magnetic flux at the T-junction in the model transformer was investigated, it was found that the presence of fine particles suppressed the wraparound 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 in the degree of integration of the orientation of the coarse crystal grains. Therefore, the materialization factor was suppressed to a low level even though the material had a high magnetic flux density.

Next, due to the strain added in the processing step
A study was made on the resistance to deterioration of magnetic properties, that is , the effect on strain resistance . When strain is applied to the steel sheet, the magnetic energy of the steel sheet due to the strain is increased and the ratio of magnetostatic energy is relatively reduced, so that the subdivision effect of the magnetic domains is diminished. In order to counter this, it is effective to preliminarily give the type of energy, such as elastic energy or magnetostatic energy, that contributes to the subdivision of the magnetic domain to the steel sheet in advance in an amount at least superior to the amount of energy increase due to the added strain. Is. As such an energy applying method, there is a tension applying method, and other methods include a magnetostatic energy increasing method. Among these, regarding tension application, no coating that can apply tension higher than the current situation is found, and means for increasing the coating thickness causes a decrease in space factor,
Transformer characteristics deteriorate.

Therefore, considering the magnetostatic energy, when the magnetic flux density is improved and the degree of integration of the orientation of the crystal grains of the steel sheet is improved, magnetic poles are accumulated at the crystal grain boundaries and the crystal grain size is The magnitude of the magnetostatic energy is drastically reduced due to the increase in the spacing of the grain boundaries due to the coarsening. However, the orientation of artificially generated fine grains is largely deviated from the Goss orientation (usually 15 ° or more), so that the presence of such fine grains in the coarse crystal grains causes magnetostatic energy to be increased. It is possible to increase the strain resistance, and the strain resistance of the product is improved accordingly.

In order to maximize this effect,
It is important that the particle size of the fine particles penetrates the plate thickness.
This is because if 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 magnetostatic energy is increased. Is also weak, and the effect of suppressing the wraparound of the magnetic flux is also inferior, so that the factor for realization is also increased.

Next, the result of investigation on the relationship between the ratio of the number of fine crystal grains of 3 mm or less to the total number of crystal grains penetrating the plate thickness of the steel sheet and the factor of practical use including strain resistance was shown in FIG. Shown in. As shown in the figure, when the number ratio of fine grains is between 65% and 98%, especially between 75% and 98%, the materialization factor is low and the strain resistance characteristics (evaluated by the materialization factor at the time of strain imparting processing) Has improved.

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

The mechanism for suppressing the increase of the factor for practical use and the mechanism for improving the strain resistance by the generation of the fine grains penetrating the plate thickness have been described above. Next, the results of an examination of the manufacturing conditions necessary to generate the fine particles necessary to obtain such effects will be described.

As a result of various experiments, in order to generate fine grains having the above effect, it is necessary to locally increase the driving force for promoting abnormal grain growth before secondary recrystallization. It has been found that it is particularly effective to allow a certain amount of strain to exist inside the steel sheet. Secondary recrystallization is a phenomenon in which crystal grains in a specific orientation grow by rapidly eroding other primary recrystallized grains. In recent years, 1 has been required for the nucleation and growth of these secondary recrystallized grains.
It is becoming clear that the selectivity of the secondary recrystallized grains has a strong effect, and it is said that it is not easy to generate and grow nuclei of grains having an orientation other than the Goss orientation and the vicinity thereof.

However, according to the research by 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. It becomes possible to grow the crystal grains in the direction greatly deviated from the direction at an early stage. Abnormal grain growth here is a general term for a phenomenon in which a very small number of crystal grains grows rapidly by eroding an overwhelmingly large number of other crystal grains, and secondary recrystallization is a primary recrystallization aggregation. The two are distinctly different in that only a small number of crystal grains having a specific orientation depending on the structure grow rapidly.

Further, according to the research conducted by the inventors, abnormal grain growth due to the treatment for increasing the driving force is only in the region, and the selectivity due to the texture of the primary recrystallized grains is present outside this region. It was also determined that it worked so strongly that the grains could no longer grow any further. Such a phenomenon is a very convenient property for the purpose of the present invention. This point will be described below.

First, when introducing strain into the steel sheet, it is possible to control the size of fine grains by controlling only the magnitude of strain and the size of the strain introduction region. For example, as shown in the above-mentioned experiment, the proper size of the fine grains penetrating the steel plate is 3 mm or less when evaluated by the equivalent circle diameter, so that the strain introduction region to be present inside the steel plate before the secondary recrystallization is also If it is controlled to 3 mm or less, the size of fine particles can be controlled appropriately.

Secondly, since the fine particles artificially generated in this way are largely deviated from the Goss orientation ((110) [001] orientation) which is the orientation of the usual coarse secondary recrystallized grains. Thus, the magnetic poles are generated at a high density at the crystal grain boundaries between the coarse secondary recrystallized grains and the fine grains, and the above-described good strain resistance characteristics and the strong effect of suppressing the realization factor can be obtained. Incidentally, such fine particles may be spontaneously generated also in the manufacturing process of the grain-oriented electrical steel sheet, but it can be said that the naturally occurring fine particles have the same action as described above. the development process is a grain that has lost the growth competition with other grain that was naturally occurring, essentially no change in Toko is a secondary recrystallized grains is in, so very close to the Goss orientation, the crystal grain boundaries Magnetic poles with a very high density are not generated, and therefore, the strain resistance improving effect and the realization factor suppressing effect are weak.

Thirdly, since it is artificially generated, it becomes possible to generate fine particles at the most preferable position in the product. Since the fine particles artificially generated are largely deviated from the Goss orientation as described above and the crystal orientation is inferior, they should not be present in the product at a high density. That is, it is preferable that they exist as discretely as possible, and ideally they exist in an isolated state inside the coarse crystal grains. Such a state can be easily realized by forming the strain introduction regions locally and discretely in advance. Also, if inside the coarse crystal grains,
A state in which several fine particles are aggregated is suitable.

Next, the results of studying the mechanism by which such fine grains are artificially obtained by subjecting the steel sheet after decarburization and primary recrystallization annealing to instantaneous high temperature heat treatment will be described. Now, the change in the crystal structure at the position where the steel sheet was instantaneously subjected to the high temperature heat treatment was investigated in detail during the course of the secondary recrystallization annealing. 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 1.5 to 3.0 times as large as the surrounding primary recrystallized grain. The temperature at which such coarsening of crystal grains occurs is much lower than the normal temperature at which secondary recrystallization occurs, and the time for subsequent growth until penetrating in the plate thickness direction is also extremely short. After penetrating in the plate thickness direction, it rapidly grows up to the inside of the high temperature heat treated region, but thereafter the growth is slow even if the temperature of the steel plate is further continued, and the growth of these crystal grains is almost the same. It will be stopped.

Further, as the temperature rise is continued, normal secondary recrystallization nuclei are generated and the growth proceeds in the region of the non-treated part which is not subjected to the high temperature heat treatment. However, the crystal grains grown from the early stage in the region subjected to the high temperature heat treatment are not silkworm eroded by the normal secondary recrystallization generated later, and eventually remain as fine crystal grains in the product.

The inventors have clarified 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 inside each primary recrystallized grain, and part of the strain is lost in the temperature rising process of final finish annealing. , High-density dislocations remain in each crystal grain. The remaining dislocations act to increase the driving force for crystal growth in abnormal grain growth. When the driving force for abnormal grain growth becomes sufficiently high, the selectivity of the crystal orientation due to the primary recrystallization texture is overcome,
Crystal grains in a general orientation start nucleation and grain growth. Since this phenomenon occurs because the driving force for abnormal grain growth is large, it occurs at a temperature much lower than the usual nucleation of secondary recrystallization and grain growth that occur in the non-treated region. However, outside the region where the driving force for abnormal grain growth is increased, the orientational selectivity of crystal growth is so strong that it cannot grow.

As described above, the crystal grain orientation for abnormal grain growth 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 kind of abnormal grain growth. Therefore, it is indispensable that the growth suppressing effect on the normal grain growth of the primary recrystallized grains is
Requires a strong inhibitory action. That is, the conventional method of applying a chemical or heat treatment at a high temperature for a long time coarsens the precipitation inhibitor and reduces the suppression power, so that abnormal grain growth is unlikely to occur and a large number of fine grains due to normal grain growth are formed. It is unsuitable because it results in development, and is essentially different from the method of the present invention and is a method to be repelled.

In order to artificially generate fine particles as described above, in the region where the growth of fine particles is intended,
It has already been stated that it is essential to increase the driving force for abnormal grain growth to a level exceeding the crystal orientation selectivity. The driving force for abnormal grain growth is (1) existence of strain, (2) 1
It can be said that the secondary recrystallized grains become finer and (3) the superheat is increased with respect to the grain size by strengthening the inhibitory force of the inhibitor. Often, grains having a crystal orientation close to the Goss orientation grow and grow coarsely beyond a region intended to generate fine grains, which makes it extremely difficult to control the size of fine grains. Therefore, as a method of increasing the driving force for crystal growth, (1) existence of strain or (2) reduction of the size of primary recrystallized grains is an advantageous method. Various experiments have shown that the method present is the most advantageous technique.

For example, in the above-mentioned instantaneous high-temperature heat treatment, as a result of investigation, the heat treatment is instantaneous, so that even at a high temperature, the crystal grain size is increased and the precipitation inhibitor is coarsened. It was found that the small change and the presence of a large amount of thermal strain had an advantageous effect on increasing the driving force for crystal growth. In other words, it is advantageous that the crystallographic structure change can be suppressed and only the physical strain can be introduced into the steel sheet by the rapid temperature rise and temperature drop. 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 nucleation of abnormal grain growth, and the number of fine grains generated in the region is made uniform. Since it has a limiting effect, it is considered preferable unless the driving force for crystal growth is reduced.

Besides the heat treatment described above, various methods of suppressing the crystallographic structure change and introducing physical strain into the steel sheet are conceivable, but the inventors have developed as the most advantageous method from many experiments. What was done is a method of pressing an object harder than a steel plate having small projections on the surface of the steel plate, a method of applying a high voltage to locally energize or discharge the steel plate surface, and a method of locally applying a pulse laser. Etc.

As another method for increasing the driving force for crystal growth, as a method for atomizing primary recrystallized grains, as a result of experiments, as a result of local carburization from the steel sheet surface, α-γ in heat treatment was used. The method of locally atomizing by utilizing the transformation was particularly effective. Further, as a method of strengthening the inhibitory power of the inhibitor, a method of locally nitrifying the steel sheet surface to generate silicon nitride or aluminum nitride to locally increase the inhibitory power is not as stable as the effect. It was effective.

By the way, as described above, in recent years, as a technique for reducing the iron loss of grain-oriented electrical steel sheets, a linear jet is locally introduced by irradiating a plasma jet or laser light, or a linear steel sheet surface is introduced. A technique for artificially subdividing the magnetic domain width by providing a groove has been developed. In the present invention as well, if such a magnetic domain subdivision technique is also utilized, further improvement in characteristics can be expected. Therefore, the inventors of the present invention have conducted earnest research to further improve the characteristics of the actual machine, including the magnetic domain subdivision technology. In order to effectively reflect the material characteristics in the characteristics of the actual machine, the magnetic domain It has been found that it is important to control the control factors for subdivision and fine grains within a predetermined range according to the crystal grain size. This will be described below.

The grain-oriented electrical steel sheet is mainly used as a core material of a transformer, and the magnetic flux density range used at this time varies depending on the design of the equipment. Generally, the higher the magnetic flux density of a material, the more advantageous it is to use at a high magnetic flux density, so that it is required that the characteristics of the actual machine in the high magnetic flux density region are excellent. As described above, it is well known that the grain-oriented electrical steel sheet having a high magnetic flux density deteriorates the actual machine characteristics as compared with the magnetic characteristics of the material. Here, the crystal grain size that constitutes the electromagnetic steel sheet inevitably becomes coarser as the material characteristics increase in magnetic flux density, but the depth of the groove or the region of local strain is changed according to the crystal grain size. Therefore, it has been found that the actual machine factor can be advantageously reduced, that is, the material characteristics can be reflected in the actual machine characteristics. 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) with the balance being Fe and unavoidable impurities in the composition Hot-rolled sheet for grain-oriented electrical steel, hot-annealed at 750 ° C for 3 seconds to adjust carbides, then pickled Then, after cold rolling at a reduction rate of 30%, an intermediate annealing of 10 was performed.
After soaking at 50 ° C for 45 seconds and quenching at 40 ° C / s, it is pickled again, and then rolled at a rolling reduction of 87% at a temperature of 150 to 200 ° C to give the final sheet thickness. : A 0.22 mm steel plate was used. In addition, C: 0.05 wt%, Si: 3.20 wt%, Mn: 0.15 wt
%, Al: 0.014 wt%, S: 0.008 wt%, Sb: 0.005 wt
%, B: 0.0005 wt% and N: 0.007 wt% (B
Steel, the balance of which is Fe and inevitable impurities in the composition. Hot-rolled steel sheet for grain-oriented electrical steel is annealed at 800 ℃ for 30 seconds, pickled, and then rolled at 170 ℃. : 87% rolled to obtain a steel plate with a final thickness of 0.34 mm.

Next, after degreasing these steel sheets, Bi
Both the contained steel and the B-containing steel were divided into seven small coils with symbols a) to g), and the following treatments were applied to the small coils. The coil in a) was subjected to a magnetic domain refinement treatment by forming linear grooves with a depth of 25 μm and a width of 250 μm on the surface of the steel plate in the width direction of 10 μm.
It was installed in a tilted direction at a repeating pitch of 3 mm in the longitudinal direction: 3 mm, 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 in the shape of dots with a size of mm diameter
With a sparse distribution such as a pitch of 65 Ws, an instantaneous heat treatment for several milliseconds was performed by an electric discharge treatment under an energy application condition of 65 Ws. With a dense distribution of 15 mm in the longitudinal direction and 30 mm in the longitudinal direction, an instantaneous heat treatment for several milliseconds was performed by an electric discharge treatment under an energy application condition of 65 Ws.

The coil of b) is subjected to magnetic domain subdivision processing,
A linear groove with a depth of 10 μm and a width of 50 μm was provided on the surface of the steel sheet in a direction inclined by 10 ° from the width direction of the steel sheet, with a repeating pitch in the longitudinal direction of 3 mm, and then decarburized at 850 ° C. for 2 minutes.・
After the primary recrystallization annealing, on the surface of the steel sheet, in the case of Bi-containing steel, with a size of 1.5 mm diameter, a sparse distribution of 30 mm in the width direction and 60 mm in the longitudinal direction with a sparse distribution of 65 Ws By electric discharge treatment under energy application condition, instantaneous heat treatment for a few milliseconds is performed, while in the case of B-containing steel, the size is 1.5 mm in diameter, and the dots are 15 mm in the width direction and 30 mm in the longitudinal direction. In a dense distribution, an instantaneous heat treatment for several milliseconds was performed by an electric discharge treatment under an energy application condition of 65 Ws.

The coils of c) to e) were 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 sheet with a size of 1.5 mm was formed into dots. 30 mm in the width direction,
With a sparse distribution such as a pitch of 60 mm in the longitudinal direction, a momentary heat treatment for several milliseconds was performed by an electric discharge treatment under the energy application condition of 65 Ws, while 1.5 mm in the case of B-containing steel.
With a dense distribution of 15 mm in the width direction and a pitch of 30 mm in the longitudinal direction in the size of diameter, an instantaneous heat treatment for several milliseconds was performed by an electric discharge treatment under an energy application condition of 65 Ws.

The coil of f) was decarburized at 850 ° C for 2 minutes.
After performing the primary recrystallization annealing, in the case of Bi-containing steel, the surface of the steel sheet was densely distributed with a 1.5 mm diameter die in a dotted pattern of 15 mm in the width direction and 30 mm in the longitudinal direction at 65 Ws. An instantaneous heat treatment for a few milliseconds is performed by an electric discharge treatment under the condition of energy application, while in the case of B-containing steel, the size is 1.5 mm and the dots are 30 mm in the width direction and 60 mm in the longitudinal direction. In a sparse distribution, an instantaneous heat treatment for several milliseconds was performed by an electric discharge treatment under an energy application condition of 65 Ws.

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

Then, all of the coils a) to g) are
M with TiO ₂ : 10% and Sr (OH) ₂ 2% by weight added to the surface
After applying gO as an annealing separator, it was wound into a coil and subjected to final finishing annealing. The 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 treatment for the purpose of purification for time holding was performed at the same time. After final finishing annealing, after removing unreacted annealing separator, 50wt%
% Of colloidal silica and magnesium phosphate was applied to obtain a product.

However, with respect to the coil of c), a plasma jet (PJ) with a width of 0.5 mm was used as a magnetic domain refining process.
In the width direction of the steel sheet, and the repeating interval in the rolling direction: 10
After irradiating with mm, a local linear strain area was provided, and the product was obtained. As for the coil of d), as a domain refinement treatment, a plasma jet (PJ) with a width of 1.5 mm was irradiated linearly in the width direction of the steel sheet at a repeating interval of 3 mm in the rolling direction to form a local linear shape. The product was made after the strained area was provided.

Samples were cut from each of the product plates thus obtained, and had an iron loss value of W _18/50 for Bi-containing steel often used in high magnetic fields, and B-containing steel often used in low magnetic fields. For that purpose, the iron loss value of W _15/50 was measured respectively. In addition, using each product, a model transformer is created by slit processing, shearing processing, and stacking processing, and W _15/50
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 slit processing, shearing processing, and stacking processing, the addition of strain was suppressed as carefully as possible. The obtained results are summarized and shown in Table 3.

[0058]

[Table 3]

As is clear from Table 3, iron loss at high magnetic field
W_18/50B is required to be low ₈With high Bi content
In steel, the higher the percentage of fine particles (f), the core loss
It is also excellent in realization factor, and the number ratio of fine particles is
Even if it is low, make the groove shallow (b), and illuminate the PJ.
High magnetism due to the combined effect of increasing the distance between the irradiation areas (c)
It is possible to reduce iron loss in the field and factor of realization.
Conversely, iron loss W in a low magnetic field_15/50Requested to be low
B₈For B-containing steels with a low
The lower the value (f) is, the more excellent the iron loss is.
Even if the number ratio is high, deep grooves (a),
Low due to the combined effect of shortening the PJ irradiation interval (d)
It was found that it is possible to reduce iron loss in the magnetic field and the factor of actualization.
It

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

Based on the above, in order to obtain a favorable realization factor, 1) the range of the proper volume density of the grooves in the unit area of the steel plate, 2) the proper density of the region to which the local strain is applied in the unit area of the steel sheet. Range, 3) a range of appropriate roughness of the steel plate metal surface, and 4) suppressing formation of forsterite coating, or
After removing the stellite film, water-soluble halogen compounds
Electrolyte the surface of the steel sheet in the liquid to adjust the grain boundary step.
Grain boundary step in the crystal orientation emphasizing treatment that (BS; Bo
It was experimentally determined how the appropriate region of the "UndaryStep" changes depending on the value of D. The obtained results are shown in FIG. 5, FIG. 6, FIG. 7 and FIG.
Shown in.

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 constant area by the area (mm ² ) of the steel plate, that is, the volume ratio (mm) of the groove per unit steel plate area. And S
Is a value obtained by dividing a region (mm ² ) to which a local strain is present on the surface of a steel sheet having a constant area by the surface of the steel sheet, that is, a total area ratio S (dimensional number) of local strains per unit steel sheet area,
Ra is the average roughness (μm) of the metal surface after removing the non-metal coating of the steel sheet, and BS is the step difference (μm) of the steel sheet surface that occurs at the location of the crystal grain boundaries when crystal orientation enhancement processing is performed. ) Is the average value. Further, using the above-mentioned value of D which is an average value excluding grains of 3 mm or less among the crystal grains constituting the steel plate, Bm =
Bm was calculated from the formula of 0.2 × logD + 1.4 and calculated B
The iron loss of the transformer with respect to m was measured and the factor of actualization was calculated.

As is clear from FIG. 5, FIG. 6, FIG. 7 and FIG. 8, according to the average grain size D of the crystal grains exceeding 3 mm, (1) the volume ratio V of the groove to the surface area of the steel plate (unit: mm)
Is a range satisfying the relationship of the following expression (1), or log ₁₀ V ≦ −2.3-0.01 × D-(1) (2) Local strain imparting area ratio S to the steel plate surface area Is a range satisfying the relation of the following expression (2), or log ₁₀ S ≦ −0.7 + 0.005 × D (2) (3) Average of interface between steel plate metal surface and non-metal coating Roughness R
a is set in a range satisfying the following expression (3), or Ra ≦ 0.3-0.1 × log ₁₀ D --- (3) (4) Forsterite film formation is suppressed, or
After removing the rusterite film, water containing a halogen compound is used.
Electrolyte the steel plate surface in the solution to adjust the grain boundary step
The crystal orientation emphasizing treatment of, its grain boundary average step BS
By setting BS ≦ 3.0−log ₁₀ D-(4) so that the value satisfies the relationship of the following expression (4), the factor for realizing the grain-oriented electrical steel sheet could be further improved.

As described above, the combination of the technique for forming fine grains and the technique for subdividing magnetic domains can not only lower the iron loss value of the product, but also increase the size of secondary recrystallized grains due to the increase in magnetic flux density. It is possible to effectively suppress the increase in the factor of realization due to the improvement, and to improve the characteristics of the transformer to the performance corresponding to the improvement of the product characteristics. The present invention was completed after earnest research based on the numerous experiments and investigations described above.

That is, the gist 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 is C: 0.003 wt% or less, S: 0.002 wt% or less, N: 0.002 wt% % Or less, with the balance being Fe and inevitable impurities in the composition, which is a magnetic steel sheet, and among the crystal grains constituting the steel sheet , the steel sheet
Of penetrating from the surface to the back surface, and the crystal grain number ratio crystal <br/> grain size in the steel sheet surface is less than 3mm is at least 65%, 98
% Or less, and the surface of the steel sheet is subjected to magnetic domain refinement treatment, which is a grain-oriented electrical steel sheet excellent in iron loss characteristics , strain resistance characteristics and magnetic characteristics in an actual machine.

2. In the above 1, from the front surface of the steel plate to the back surface
The average value of the crystal grain size in the crystal grains of the steel sheet surface which penetrates to at least 8 mm, and wherein the at 50mm or less,
A grain-oriented electrical steel sheet with excellent iron loss characteristics , strain resistance characteristics, and magnetic characteristics in actual machines.

3. In 1 or 2 above, the surface of the steel plate
Passing from to the back, and the crystal grains the crystal grain size in the steel sheet surface is less than 3mm, characterized in that it consists of naturally occurring crystal grains and artificially produced were regularly arranged crystal grains, core loss A grain-oriented electrical steel sheet with excellent characteristics , strain resistance, and magnetic characteristics in an actual machine.

4. In the above 1, 2 or 3, the magnetic domain refining treatment is (1) Depth: 50 μm or less and width: 350 μm on the steel plate surface
The following grooves are repeatedly provided in the rolling direction, (2) the region where a linear local strain is introduced in the steel sheet surface layer portion is repeatedly provided in the rolling direction, (3) the interface between the steel sheet metal surface and the non-metal coating is averaged. Roughness R
smoothing to 0.3 μm or less with a, (4) suppressing formation of forsterite coating, or
After removing the rusterite film, water containing a halogen compound is used.
Electrolyte the steel plate surface in the solution to adjust the grain boundary step
A grain-oriented electrical steel sheet excellent in iron loss characteristics, strain resistance characteristics, and magnetic characteristics in an actual machine, which is obtained by performing a crystal orientation enhancement treatment.

5. In the above 4, among the crystal grains constituting the steel sheet, the average grain diameter of the crystal grains that penetrates from the front surface to the back surface of the steel sheet and has a crystal grain size of more than 3 mm on the steel sheet surface is D (mm (1) For a groove that is repeatedly provided in the rolling direction, the total volume ratio V (unit: mm) of the groove per unit area of the steel plate is in a range that satisfies the relationship of the following expression (1), or log ₁₀ V ≦ −2.3−0.01 × D (1) (2) Regarding linear local strain repeatedly provided in the rolling direction, the total area ratio S of local strain per unit area of the steel sheet (unit: (Dimensionless) is in a range satisfying the relation of the following expression (2), or log ₁₀ S ≦ −0.7 + 0.005 × D (2) (3) Interface between steel plate metal surface and non-metal coating Average roughness R
Regarding a, the Ra is set to a range that satisfies the relation of the following expression (3), or Ra ≦ 0.3-0.1 × log ₁₀ D --- (3) (4) Suppression of formation of forsterite film , Or
After removing the rusterite film, water containing a halogen compound is used.
Electrolyte the steel plate surface in the solution to adjust the grain boundary step
The crystal orientation emphasizing treatment of, its grain boundary average step BS
Is excellent in iron loss characteristics, strain resistance characteristics, and magnetic characteristics in an actual machine, which is BS ≦ 3.0-log ₁₀ D-(4) within a range satisfying the following expression (4). Grain oriented electrical steel sheet.

[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 electromagnetic steel sheet of the present invention is limited to the above range will be described. Si: 1.5-7.0 wt% Si is an effective component for increasing the electrical resistance of the product and reducing iron loss. For this reason, 1.5 wt% or more is contained, but
If it exceeds 7.0 wt%, the hardness becomes high and it becomes difficult to manufacture and process, so the range was limited to 1.5 to 7.0 wt%.

Mn: 0.03 to 2.5 wt% Like Mn, Mn also has a function of increasing electric resistance and a function of facilitating hot working at the time of manufacturing.
It is necessary to contain 0.03 wt%, but if it exceeds 2.5 wt%, γ-transformation will be induced during heat treatment and magnetic properties will be deteriorated, so the content was made 0.03 to 2.5 wt%.

C: 0.003 wt% or less, S: 0.002 wt% or less, N: 0.002 wt% or less C, S and N all have a detrimental effect on the magnetic properties and particularly deteriorate iron loss. C: 0.003 wt
%, S: 0.002 wt% or less, N: 0.002 wt% or less.

In the production of magnetic steel sheets, it is essential to contain an inhibitor component for inducing secondary recrystallization in the steel in addition to the above-mentioned elements. B, Bi, Sb, Mo, Te,
Se, S, Sn, P, Ge, As, Nb, Cr, Ti, Cu, Pb, Zn and In are suitable, and these elements can be contained alone or in combination. These inhibitor components
Acts as an inhibitor during secondary recrystallization annealing.
After that, it was removed from the steel sheet by the subsequent purification annealing.
It is left behind or remains in the steel sheet as an impurity.

Next, the reasons for limiting the crystal grains constituting the steel sheet will be described. The crystal grains important in the present invention are those that penetrate in the plate thickness direction. This is because such penetrating grains cause many magnetic poles to be generated at the grain boundaries, and a large increase in magnetostatic energy can be expected. Here, the grain 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 surface of the steel sheet (circle equivalent diameter). Further, the average crystal grain size is expressed by the circle equivalent diameter of this value by dividing the area by the number of such crystal grains contained in a certain area.

Now, in order to obtain the grain-oriented electrical steel sheet excellent in the strain resistance characteristic and the actual machine characteristic expected in the present invention, regarding the distribution of such penetrating grains, the number of crystal grains having a grain size of 3 mm or less is used. It is essential that the ratio be 65% or more and 98% or less. The reason is that if the number ratio of fine crystal grains of 3 mm or less is less than 65%, the magnetostatic energy increase action due to the presence of fine grains cannot be obtained, which leads to deterioration of strain resistance characteristics and increase of factors for realization of equipment. This is because the iron loss of
This is because if the number ratio of fine particles of 3 mm or less exceeds 98%, the magnetic flux density of the product is reduced and the iron loss is deteriorated. In addition,
With regard to the number ratio of fine grains, when it is 75% or more, a particularly remarkable reduction factor of the practical machine factor and an improvement effect of the strain resistance characteristic are recognized.

Further, such fine crystal grains of 3 mm or less can be used as naturally occurring fine crystals, but in addition to that, the magnetic poles existing at grain boundaries are evenly distributed in the steel sheet, and To make the distribution of magnetic energy uniform,
It is more preferable to arrange them artificially and regularly. As a result, the flow of the magnetic flux becomes uniform, and an increase phenomenon of iron loss such that the eddy current loss locally abnormally increases is suppressed.

Therefore, the region where various kinds of processing for producing the fine particles as described above is performed in the plane of the steel sheet as shown in FIG.
It is effective to distribute it discretely as shown in
Especially, if the particles are uniformly dispersed, there is less harm such as lowering the magnetic flux density, and the effect of lowering strain sensitivity is also increased. Instead, as shown in FIG. 10 and FIG. 11, artificially arranging regularly will naturally obtain the best effect. In this respect, for example, when artificial linearly elongated artificial crystal grains are generated as shown in FIG. 12, the magnetic flux density of the product is significantly deteriorated, and iron loss is increased. Here, it is preferable that the interval in which the fine particles are discretely present is 5 mm or more.

Further, regarding the average crystal grain size of the steel sheet,
It is preferably 8 mm or more and 50 mm or less. If the average grain size is less than 8 mm, it may be difficult to obtain a stable and excellent iron loss value because the degree of integration of crystal orientation may be reduced and the magnetic flux density may be reduced. This is because if the diameter exceeds 50 mm, the factor for realization of the machine may deteriorate and the strain resistance may deteriorate.

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

By the way, according to the research conducted by the inventors, in each of the above-described magnetic domain refinement techniques, the average grain size of the crystal grains of the steel sheet, particularly the crystal grain size of the grain size exceeding 3 mm It was found that there is a strong correlation and there is a suitable range depending on the average grain size of the crystal grains. That is, among the crystal grains forming the steel plate, the average grain size of the crystal grains penetrating in the plate thickness direction and having a grain size exceeding 3 mm is D
(1) Regarding the groove to be repeatedly provided in the rolling direction, whether the total volume ratio V (unit: mm) of the groove per unit area of the steel plate satisfies the relationship of the following expression (1). , Log ₁₀ V ≦ −2.3-0.01 × D (1) (2) Regarding linear local strain repeatedly provided in the rolling direction, the total area ratio S (of local strain per unit area of the steel sheet) Unit: dimensionless) is in a range satisfying the relation of the following expression (2), or log ₁₀ S ≦ −0.7 + 0.005 × D (2) (3) Steel plate metal surface and non-metal coating Roughness of the interface of
Regarding a, the Ra is set to a range that satisfies the relation of the following expression (3), or Ra ≦ 0.3-0.1 × log ₁₀ D --- (3) (4) Suppression of formation of forsterite film , Or
After removing the rusterite film, water containing a halogen compound is used.
Electrolyte the steel plate surface in the solution to adjust the grain boundary step
The crystal orientation emphasizing treatment of, its grain boundary average step BS
Is preferably in the range of satisfying the following equation (4): BS ≦ 3.0-log ₁₀ D --- (4), and thus, not only the iron loss characteristics but also the strain resistance characteristics and the actual machine characteristics are more advantageous. That's a big improvement.

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. It is a value, 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, and BS is the average value (μm) of the steps generated at the crystal grain boundaries when the crystal orientation enhancement treatment is applied to the steel sheet surface. is there.

The method of forming the groove may be a method of etching the steel plate surface or a method of pressing the gear roll to form the groove, and the method of introducing the local strain may be pressing by a rotating body, laser irradiation and plasma. Any conventionally known method such as jet irradiation is suitable. Further, as a method for smoothing the interface between the steel plate metal surface and the non-metal coating, by suppressing the formation of the forsterite coating or removing the forsterite coating, a method such as pickling, polishing, chemical polishing or grinding is used. Any method of reducing the roughness of the steel plate surface is suitable. Furthermore, the crystal orientation enhancement processing is
After suppressing the formation of the forsterite film or removing the forsterite film, the surface of the steel sheet is electrolytically treated in an aqueous solution of a halogen compound to eliminate the grain boundary step between adjacent crystal grains.
Adjusting only the surface of the crystal orientation of a specific a method for remaining preferentially, this method is also advantageously compatible with this invention.

Next, the manufacturing method of the present invention will be described. By the way, a steel piece adjusted to a desired suitable component composition is formed into a hot-rolled steel sheet by a known hot-rolling method, and then subjected to hot-rolled sheet annealing as needed, and is performed once or twice or more with intermediate annealing interposed. The final plate thickness is obtained by cold rolling. In this final cold rolling, the orientation of the crystal that grows during secondary recrystallization is controlled by adjusting the reduction ratio, but if the reduction ratio is less than 80%, many crystal grains with poor orientation tend to recrystallize. In some cases, 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 become unstable. The rolling reduction is 80 ~
It is preferably 95%.

It is advantageous to combine known warm rolling and interpass aging treatment in the above rolling in order to further improve the magnetic flux density. It is also possible to perform weak decarburization treatment in hot-rolled sheet annealing or intermediate annealing. Furthermore, when a linear groove is used as the magnetic domain refining treatment, it is preferable to provide a linear groove on the surface of the steel sheet after the final cold rolling.

Then, a primary recrystallization annealing is performed, and at this time, if necessary, a decarburizing treatment is simultaneously performed to reduce the C content to a predetermined value or less. From the middle of the primary recrystallization annealing to the start of secondary recrystallization, the most important technique of the present invention is to locally provide a region for increasing the driving force for crystal growth inside the steel sheet. Here, since crystal growth in the plate thickness direction occurs relatively easily, such a region does not necessarily have to be provided over the entire plate thickness in the plate thickness direction, and a part of the region in the plate thickness direction does not have to be provided. Even if provided, the effect is the same. However, as the projection area of this area on the steel plate surface, the equivalent circle diameter is 0.
It is necessary to make it between 05 mm and 3.0 mm. This is because when the thickness is less than 0.05 mm, there are many cases in which the secondary recrystallized grains that often occur afterwards often cause the moss to eventually erode and disappear. On the other hand, when the thickness exceeds 3.0 mm, the size of the fine grains generated is also increased.
This is because the diameter exceeds 3.0 mm, which causes a decrease in magnetic flux density and increases iron loss.

For the areas to be subjected to such processing, refer to 3.
It is necessary to have a narrow region of 0 mm or less.For example, when treating a long stretched region, crystal grains with poor orientation are generated in the treated region, causing a significant deterioration of the magnetic flux density of the material, It causes an increase in loss.

As the timing of the manufacturing process for providing such a region, there is no effect because such a region disappears due to the generation of new primary recrystallized grains before the start of the primary recrystallization, while the secondary region is not effective. After the start of recrystallization, the fine grains are eclipsed by the secondary recrystallized grains immediately before nucleation and grain growth in the region, so that the effect is also lost.

As a method for increasing the driving force for crystal growth, as described above, (1) a method of introducing strain, (2)
There are methods such as refining the primary recrystallized grains and (3) strengthening the inhibitory power of the inhibitor. Among them, the methods of (1) and (2) are superior, and among them, the method of (1) Is particularly excellent in artificially generating and controlling fine particles. If the amount of strain introduced into the steel sheet is less than 0.005, the action becomes unstable because fine particles may not be generated.
On the other hand, if it exceeds 0.70, a large number of fine particles are likely to be formed at the same position, and the effect thereof is weakened in spite of efforts. Therefore, the introduced strain amount is preferably in the range of 0.005 to 0.70.

As a method for industrially providing a region in which the driving force for crystal growth is increased with high efficiency and stability, a particularly excellent method is to form small protrusions on the surface as shown in FIG. With an object having, a method of pressing an object harder than a steel plate against the steel plate surface, as shown in FIG. 13 , a method of locally applying or discharging a high voltage between the steel plate surface and the electrode,
Furthermore, there are a method of irradiating with a high-temperature spot laser instantaneously, a method of locally irradiating with a pulse laser, and the like.
Here, a high-temperature spot laser is a laser that continuously oscillates but has a large capacity, such as a carbon dioxide gas laser, which irradiates and locally heats the surface of the steel sheet for a short time of several hundred milliseconds or less. is there. The pulse laser is a high-density light flux formed in a short time by using a Q switch or the like, and is capable of imparting extremely strong impact force locally to the steel sheet.

As described above, after artificially providing the region where the driving force for crystal growth is increased, an annealing separator is applied if necessary, and then final finishing annealing is performed to carry out secondary recrystallization. Let In the final finish annealing, the temperature may be raised to a high temperature of around 1200 ° C., and the purification annealing and the forsterite undercoating may be formed. After that, an insulating coating is applied to the surface of the steel sheet to obtain a product, but the surface of the steel sheet may be mirror-finished or subjected to crystal orientation enhancement treatment before the coating is applied. In addition, 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 performed on the surface of the steel sheet after the secondary recrystallization. Further, at this stage, it is possible to provide the linear groove region with the projection roll. When the interface smoothing treatment or the crystal orientation enhancement treatment is used, the formation of the forsterite coating may be suppressed, or the forsterite coating may be removed, a predetermined treatment may be performed, and then an insulating coating may be applied.

By the manufacturing method described above, the iron loss is low,
It is possible to obtain grain-oriented electrical steel sheets with high magnetic flux density that are excellent in strain resistance and actual machine characteristics.
By mixing together with the above coarse particles, a product having a high magnetic flux density and a low iron loss, and an excellent transformer with an extremely low iron loss in an actual machine can be assembled.

[0093]

【Example】

Example 1 C: 0.08 wt%, Si: 3.35 wt%, Mn: 0.07 wt%, Al: 0.02
steel slab containing wt%, Sb: 0.05 wt% and N: 0.008 wt% with the balance Fe and unavoidable impurities at 1410 ° C.
After heating, the hot-rolled steel sheet with a thickness of 2.2 mm was prepared by a conventional method.
Then, after annealing the hot-rolled sheet at 1000 ℃ for 30 seconds, pickled it to 1.5mm.
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 plate temperature of 220 ° C to 0.
The final plate thickness was 22 mm. Then, after degreasing, decarburization annealing was performed at 850 ° C. for 2 minutes, the steel sheet was divided into two, and one of them was directly coated with an annealing separating agent containing MgO as a main component (comparative example). On the other hand, using the equipment shown in Fig. 14, the surface of the steel sheet was subjected to an instantaneous discharge treatment at 1 kV at a size of 1.5 mm, and the instantaneous high-temperature heat treatment was used to increase the grain growth driving force. Was applied. Then, such regions were repeatedly provided in the pattern shown in FIG. 11 at a pitch of 10 mm in the longitudinal direction of the coil and a pitch of 15 mm in the width direction, and then an annealing separator containing MgO as a main component was also applied ( Invention example).

Then, the obtained coil was subjected to final finish annealing by raising the temperature to 850 ° C. in N ₂ at a temperature rising rate of 30 ° C./h, holding it at 850 ° C. for 25 hours, and then applying 25% N ₂ The temperature was raised to 1200 ° C. at a heating rate of 15 ° C./h in a mixed atmosphere of H ₂ and 75% H ₂ , further held in H ₂ for 5 hours, and then lowered. Then, after removing the unreacted annealing separator, these coils were coated and baked with a tension coating containing 50% colloidal silica, and subjected to a magnetic domain subdivision treatment with a plasma jet to obtain a product. Irradiation of the plasma jet was performed linearly in the plate width direction under the conditions of irradiation width: 0.05 mm and repeating interval in the rolling direction: 5 mm.

Using these steel plates, slit processing, shearing processing, and laminated fixing processing were carried out to manufacture two 3-phase transformers each having leg width: 250 mm, height: 900 mm, thickness: 300 mm. did. At this time, one is manufactured with as little strain as possible, and the other one is a caster having a sphere with a diameter of 50 mm at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of adding strain. By pushing it and adding distortion intentionally,
Manufactured. Table 4 shows the results of the investigation of the iron loss characteristics of these transformers and the values of the realization factors, together with the results of the investigation of the magnetic characteristics of the materials. Table 4 also shows the results of investigations 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.

[0096]

[Table 4]

As is apparent from the table, the actual machine characteristics of the transformer using the grain-oriented electrical steel sheet of the present invention have a low actualization factor and very good distortion resistance, and are suitable as an iron 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: 0.15 wt%, Ni: 0.10 wt%, Bi: 0.005 wt%,
Sb: 0.04 wt% and N: 0.008 wt%, balance Fe
After heating the steel slab consisting of unavoidable impurities to 1430 ° C, a hot rolled steel sheet with a thickness of 2.6 mm was prepared by a conventional method. Then, a carbide conditioning treatment consisting of soaking for 3 seconds at 750 ° C was performed, and after pickling, cold rolling was applied to obtain an intermediate thickness of 1.8 mm, then soaking at 1125 for 30 seconds and spraying mist water.
Intermediate annealing consisting of quenching at 40 ° C / s was performed.

Then, after pickling, a final plate thickness of 0.26 mm was obtained by warm rolling at a steel plate temperature of 230 ° C. Then, after degreasing treatment, the steel sheet was divided into 5 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). In addition, the remaining four, when performing decarburization annealing at 850 ° C for 2 minutes, immediately after raising the temperature to 850 ° C, while rotating the ceramic roll of the shape shown in Fig. 13 in synchronization with the running speed of the steel sheet. Press the steel plate and apply the driving force increasing process for the local grain growth of 2.0 mm in the pattern as shown in Fig. 11 to the coil longitudinal pitch: 25 mm, widthwise pitch: 20
It was applied to the steel plate in mm. At this time, for the three coils,
Before decarburization annealing, the ceramic roll with linear protrusions shown in Fig. 15 was rotated in synchronism with the traveling coil on the surface of the steel sheet, and the two were placed in the width direction of depth: 5 μm, width: 100 μm. The pitch was 5 mm in the rolling direction, and the other was a pitch of 2 mm in the rolling direction with a depth of 30 μm and a width of 500 μm. After decarburization annealing, these 4
Similar to the comparative example, the coil was coated with an annealing separator containing MgO as a main component (invention example).

As a final finish annealing, these coils were heated to 850 ° C. in N ₂ at a heating rate of 30 ° C./h,
Then, in a mixed atmosphere of 25% N ₂ and 75% H ₂ at 15 ° C.
/ 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. Thereafter, these coils were manufactured by removing the unreacted annealing separator and then applying a tension coating containing 50% of colloidal silica to bake them. However, one of the two coils with a groove depth of 5 μm was applied with a tension coating and baked, and then a 0.1 mm diameter laser beam was irradiated in the width direction at 0.3 mm intervals (pitch in the rolling direction). : 10 mm), and a linear local strain region was provided.

Using these steel plates, slit processing, shearing processing, and laminated fixing processing were carried out to manufacture two 3-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 is manufactured with as little strain as possible, and the other one is a caster having a sphere with a diameter of 50 mm at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of adding strain. By pushing it and adding distortion intentionally,
Manufactured.

Table 5 shows the results of examining the iron loss characteristics of these transformers and the values of the actualization factors, together with the results of examining the magnetic characteristics of the materials. Table 5 also shows the results of investigations 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. In addition, as Bm for the iron loss measurement of the transformer, from the average D value of these products = 56 mm, Bm =
From 0.2 × log ₁₀ 56 + 1.4 = 1.75, the value was taken as Bm = 1.75T.

[0103]

[Table 5]

As is clear from the table, the iron loss of the product of the invention example subjected to the treatment for increasing the grain growth driving force is significantly lower than that of the comparative example, and the factor of practical use is also 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 strain resistance is extremely good, and it is extremely excellent as the core material of the actual transformer. Was there.

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.
A steel slab containing 008 wt% and the balance Fe and unavoidable impurities was heated to 1180 ° C and
It was a hot rolled steel sheet with a thickness of 2.4 mm. Then, hot-rolled sheet annealing was performed at 800 ° C for 30 seconds, pickling, and warm rolling at a steel sheet temperature of 195 ° C to give a final sheet thickness of 0.34 mm. After degreasing,
Decarburization annealing was performed at 820 ° C for 2 minutes. Next, this steel plate was divided into four, and one was subjected to secondary recrystallization annealing at 1000 ° C for 3 minutes, and then coated with a coating treatment liquid and baked,
Product (comparative example). The remaining 3 coils are 1000
During the secondary recrystallization annealing for 3 minutes at ℃, during the temperature rise process before the start of secondary recrystallization, the spot laser was irradiated in the furnace and the pattern as shown in Fig. 10 was applied to the local area of 2.5 mm size. For the region, the steel sheet was subjected to grain growth driving force increasing treatment. Then, such regions were repeatedly provided at a pitch of 30 mm in the longitudinal direction of the coil and a pitch of 25 mm in the width direction. After that, coating treatment liquid was applied and baked to make a product. Two of the three coils were chemically polished before the coating treatment liquid was applied, and the surface roughness of the steel plate was 0.07.
μm, and the other one was 0.26 μm.

Using these steel plates, slit processing, shearing processing, and laminated fixing processing were carried out 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 is manufactured with as little strain as possible, and the other one is a caster having a sphere with a diameter of 50 mm at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of adding strain. By pushing it and adding distortion intentionally,
Manufactured.

Table 6 shows the results of examining the iron loss characteristics of these transformers and the values of the realization factors, together with the results of examining the magnetic characteristics of the materials. In addition, Table 6 also shows the results of investigations regarding 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. In addition, as Bm for iron loss measurement of the transformer, from the average value of D value of these products = 10 mm, Bm =
From 0.2 × log ₁₀ 10 + 1.4 = 1.60, the value was taken as Bm = 1.60T.

[0108]

[Table 6]

As is clear from the table, the actual machine characteristics of the transformer assembled by using the grain-oriented electrical steel sheet according to the present invention have a low realization factor and a very good distortion resistance characteristic. 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%,
Sb: 0.045 wt% and N: 0.008 wt% are contained, and the balance is
A steel slab consisting of Fe and inevitable impurities was heated to 1440 ° C, and then a hot rolled steel sheet having a thickness of 2.2 mm was prepared by a conventional method.
Then, after pickling, cold rolling to an intermediate thickness of 1.8 mm, and then soaking at 1100 for 30 seconds and spraying mist water
After intermediate annealing consisting of quenching at 40 ° C / s, pickling and further 200
A final plate thickness of 0.22 mm was obtained by warm rolling at a steel plate temperature of ℃. Then, after degreasing, the steel plate is divided into 6 parts, one of which is 850 ℃
After decarburizing and annealing for 2 minutes, an annealing separator containing MgO as a main component was applied (comparative example). The remaining five coils were decarburized and annealed at 850 ° C for 2 minutes, then irradiated with pulsed laser to increase the driving force for grain growth with 2.0 mm size and 0.01-0.08 strain on the steel plate surface. Space, space:
It was provided on the steel plate discretely and locally at 2 to 30 mm. Then,
3 coils of the five coils, as well as the comparative examples, was coated with an annealing separator mainly comprised of MgO, the annealing separator remaining 2 coil composed mainly of SiO ₂ to suppress the formation of the film It was applied (invention example).

These coils were heated in N ₂ to 850 ° C. at a temperature rising rate of 30 ° C./h as final finish annealing,
Then, in a mixed atmosphere of 25% N ₂ and 75% H ₂ at 15 ° C.
/ 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 were applied with a tension coating containing B ₂ O ₃ and baked,
Made as a product. However, among the invention examples, those coated with the annealing separator having SiO ₂ as the main component did not show the formation of the surface oxide film, and therefore, after the crystal orientation enhancement treatment was subsequently performed in the sodium chloride aqueous solution. The above tension coating was applied and baked on. At this time, one of the two coils had an average value of the steps of the aggregate grain boundaries: 2.5 μm, and the other had a value of 0.9 μm. Further, among the invention examples, the one to which the annealing separating agent containing MgO as a main component was applied was applied and baked with the above tension coating on the forsterite film formed on the steel plate surface. Of the coils, two coils were irradiated with the plasma jet linearly in the plate width direction. At this time, one is the width of the local strain area is 0.05mm
Irradiation at a pitch of 15 mm in the steel plate rolling direction (S = 3.3
× 10 ^-3 ), but the other one is the width of the local strain area is 0.8mm.
As the irradiation in the rolling direction of the steel plate at a pitch of 5 mm (S = 1.6
× 10 ^-1 ).

Using these steel plates, slit processing, shearing processing, and laminated fixing processing were performed to manufacture two 3-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 is manufactured with as little strain as possible, and the other one is a caster having a sphere with a diameter of 50 mm at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of adding strain. By pushing it and adding distortion intentionally,
Manufactured.

Table 7 shows the results of examining the iron loss characteristics of these transformers and the values of the realization factors, together with the results of examining the magnetic characteristics of the materials. Table 7 also shows the results of investigations 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. In addition, as Bm for iron loss measurement of the transformer, from the average value of D value of these products = 100.5 mm, Bm
From m = 0.2 x log ₁₀ 100.5 + 1.4 = 1.80, Bm = 1.80T
Value.

[0114]

[Table 7]

As is clear from the table, the actual machine characteristics of the transformer assembled by using the grain-oriented electrical steel sheet according to the present invention have a low actualization factor and very good distortion resistance, and the actual iron 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, the steel slab was heated to 1400 ° C and then made into a 2.4 mm thick hot-rolled steel sheet by the conventional method. Then, after pickling, by cold rolling
After the intermediate thickness of 1.5 mm, after the intermediate annealing consisting of soaking at 1100 for 30 seconds and quenching at 40 ° C / s by spraying mist water,
After pickling and further warm rolling at a steel plate temperature of 200 ° C, 0.
The final plate thickness was 17 mm. Then, after degreasing, the steel plate was divided into four, one was decarburized and annealed at 850 ° C for 2 minutes, and then Mg
An annealing separator containing O as a main component was applied (Comparative Example 1).
The other one is to rotate a roll having linear protrusions as shown in FIG. 15 in synchronization with the traveling coil immediately after the temperature rise in the decarburization annealing, so that the steel plate surface has a depth of 30 μm and a width of 30 μm. : 35μ
Grooves of m 2 were provided with a pitch of 4 mm in the rolling direction (Comparative Example 2). Further, the other one is to rotate the roll having linear protrusions as shown in FIG. 15 in synchronization with the traveling coil immediately after the temperature rise of the decarburization annealing, and the depth of the steel sheet surface: 10 μm, Width: 80 μm, repeating interval in rolling direction: 5
A groove was provided in mm (Comparative Example 3). The other one is to rotate the roll having linear protrusions as shown in FIG. 15 in synchronization with the traveling coil immediately after the temperature rise in the decarburization annealing,
Grooves were formed on the surface of the steel plate with a depth of 10 μm, a width of 80 μm, and a repeating interval in the rolling direction of 5 mm, and then, after decarburization annealing, this time synchronized with the coil running a roll having small protrusions as shown in FIG. Rotate while rotating and size on the steel plate surface:
At 1.5 mm, the pattern as shown in Fig. 9 is used.
0.03-0.15 locally and discretely with a repeat interval of 00 mm
The process for increasing the driving force for grain growth with strain of was applied. Then, an annealing separator containing MgO as a main component was applied to each of these three coils.

These coils were heated in N ₂ to 850 ° C. at a temperature rising rate of 30 ° C./h for final finish annealing,
After keeping at 850 ℃ for 20 hours, 25% N ₂ and 75% H ₂
The temperature was raised to 1200 ° C. at a heating rate of 15 ° C./h in the mixed atmosphere of, and further kept in H ₂ for 5 hours and then lowered. After that, a tension coating containing colloidal silica is applied to these coils, and the coil is also annealed at 800 ° C for flattening annealing.
Burned in.

Using these steel plates, slit processing, shearing processing, and laminated fixing processing were performed to manufacture two 3-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 is manufactured with as little strain as possible, and the other one is a caster having a sphere with a diameter of 50 mm at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of adding strain. By pushing it and adding distortion intentionally,
Manufactured.

Table 8 shows the results of examining the iron loss characteristics of these transformers and the values of the realization factors, together with the results of examining the magnetic characteristics of the materials. Table 8 also shows the results of investigations 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.

[0120]

[Table 8]

The results of the macro etching of the products showed that the comparative examples 1 and 3 had a normal crystal structure, whereas the comparative example 2 showed a
Immediately after the decarburization temperature rise, in a place where a groove with a depth of 25 μm was provided,
Immediately below it, elongated crystal grains were formed along the groove, and the normal secondary recrystallized grains were separated by these grains. On the other hand, in the invention example, fine particles were generated in the region subjected to the grain growth promoting treatment, and it was possible to obtain a material excellent in not only the actual machine characteristics of the transformer but also the strain resistance characteristics.

[0122]

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

[Brief description of drawings]

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

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

FIG. 3 is a graph showing the effect of the number ratio of fine particles of 3 mm or less on the iron loss ratio of the transformer to the iron loss characteristic (actual machine factor) and the strain resistance characteristic (actual machine factor at the time of strain imparting processing). Is.

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

FIG. 5 shows the relationship between the total volume ratio V of the grooves per unit area of the steel plate for obtaining the best factor for practical application of the grooves repeatedly provided in the rolling direction and the average particle diameter D of the crystal grains exceeding 3 mm. It is the graph shown.

FIG. 6 shows the total local strain region S per unit area of the steel plate for obtaining the best actualization factor for the linear local strain repeatedly provided in the rolling direction and the average grain diameter D of the crystal grains exceeding 3 mm. It is the graph shown by the relationship of.

FIG. 7: Regarding the roughness of the interface between the metal surface of the steel sheet and the non-metal coating, the average roughness Ra for obtaining the best actualization factor
Is a graph showing the relationship with the average grain size D of crystal grains exceeding 3 mm.

FIG. 8 shows the grain boundary average step difference BS for obtaining the best actualization factor in the crystal orientation enhancement treatment performed on the steel plate metal surface, 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 where 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 where 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 in which 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 where the driving force for crystal grain growth is increased is linearly provided continuously in the width direction of the steel sheet.

FIG. 13 shows a local electric current heating process and a local electric discharge heating process.
It is a conceptual diagram of the apparatus for performing.

FIG. 14 is an external view of a roll having many small protrusions on the surface.
is there.

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

[Explanation of symbols]

1 Gate pulse that determines processing time 2 High voltage power supply 3 Electrode 4 Area for increasing driving force for grain growth 5 Counter electrode 6 Steel plate 7 Small projection 8 Linear projection 9 Rolling direction 10 Rolling direction for increasing driving force for grain growth Repetitive treatment interval 11 Repeating treatment interval in the direction perpendicular to the rolling of grain growth driving force increasing treatment

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-59045 (JP, A) JP-A-4-202644 (JP, A) JP-A-2-30740 (JP, A) JP-A-8- 73940 (JP, A) JP 60-59044 (JP, A) JP 6-220541 (JP, A) JP 8-269571 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C22C 38/00 303 C21D 8/12 C22C 38/04 H01F 1/147

Claims (5)

(57) [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 is C: 0.003 wt% or less and S: 0.002 wt% or less, respectively. , N: 0.002 wt% or less, with the balance being Fe and unavoidable impurities composition, which is a magnetic steel sheet, of the crystal grains constituting the steel sheet , the steel sheet
Of penetrating from the surface to the back surface, and the crystal grain number ratio crystal <br/> grain size in the steel sheet surface is less than 3mm is at least 65%, 98
% Or less, and the surface of the steel sheet is subjected to magnetic domain refinement treatment, which is a grain-oriented electrical steel sheet excellent in iron loss characteristics , strain resistance characteristics and magnetic characteristics in an actual machine. 2. The steel sheet according to claim 1, wherein the steel sheet has a front surface to a back surface.
The average value of the crystal grain size in the crystal grains of the steel sheet surface which penetrates to at least 8 mm, and wherein the at 50mm or less,
A grain-oriented electrical steel sheet with excellent iron loss characteristics , strain resistance characteristics, and magnetic characteristics in actual machines. 3. The surface of a steel sheet according to claim 1,
Passing from to the back, and the crystal grains the crystal grain size in the steel sheet surface is less than 3mm, characterized in that it consists of naturally occurring crystal grains and artificially produced were regularly arranged crystal grains, core loss A grain-oriented electrical steel sheet with excellent characteristics , strain resistance, and magnetic characteristics in an actual machine. 4. The magnetic domain refining process according to claim 1, 2, or 3, wherein (1) the steel plate surface has a depth of 50 μm or less and a width of 350 μm.
The following grooves are repeatedly provided in the rolling direction, (2) the region where a linear local strain is introduced in the steel sheet surface layer portion is repeatedly provided in the rolling direction, (3) the interface between the steel sheet metal surface and the non-metal coating is averaged. Roughness R
smoothing to 0.3 μm or less with a, (4) suppressing formation of forsterite coating, or
After removing the rusterite film, water containing a halogen compound is used.
Electrolyte the steel plate surface in the solution to adjust the grain boundary step
A grain-oriented electrical steel sheet excellent in iron loss characteristics, strain resistance characteristics, and magnetic characteristics in an actual machine, which is obtained by performing a crystal orientation enhancement treatment. 5. The average grain size of the crystal grains forming the steel sheet according to claim 4, wherein the crystal grain size penetrates from the front surface to the back surface of the steel sheet and the crystal grain size on the steel sheet surface exceeds 3 mm. When the particle size is D (mm), (1) For the groove repeatedly provided in the rolling direction, the total volume ratio V (unit: mm) of the groove per unit area of the steel plate satisfies the relationship of the following expression (1). Range or log ₁₀ V ≦ −2.3-0.01 × D (1) (2) Regarding linear local strain repeatedly provided in the rolling direction, total local strain per unit area of steel sheet The area ratio S (unit: dimensionless) is set to a range that satisfies the relationship of the following expression (2), or log ₁₀ S ≦ −0.7 + 0.005 × D (2) (3) With the steel plate metal surface Average roughness R of the interface with the non-metal coating
Regarding a, the Ra is set to a range that satisfies the relation of the following expression (3), or Ra ≦ 0.3-0.1 × log ₁₀ D --- (3) (4) Suppression of formation of forsterite film , Or
After removing the rusterite film, water containing a halogen compound is used.
Electrolyte the steel plate surface in the solution to adjust the grain boundary step
The crystal orientation emphasizing treatment of, its grain boundary average step BS
Is excellent in iron loss characteristics, strain resistance characteristics, and magnetic characteristics in an actual machine, which is BS ≦ 3.0-log ₁₀ D-(4) within a range satisfying the following expression (4). Grain oriented electrical steel sheet.