JPH10183312A - Grain oriented silicon steel sheet low in core loss and excellent in strain resisting characteristic and execution characteristic, and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grain oriented silicon steel sheet low in core loss and excellent in strain resisting characteristic and execution characteristic by specifying the ratio of the number of crystal grains with a prescribed grain size on the sheet surface among the crystal grains penetrating in the direction of thickness of the sheet. SOLUTION: The component composition of the objective steel sheet is, by weight, 1.5-7.0 % Si and 0.03-2.5% Mn, and the impurities <=0.003% C and <=0.002% each of S and N. The important crystal grains of such a sheet penetrate in the direction of thickness of the sheet. Such penetrating grains form many magnetic poles on the grain boundaries and increase big stationary magnetic energy. Regarding the distribution of such penetrating grains, it is an indispensable condition that the ratio of the number of crystal grains with grain size <=3mm is >=65% to <=98%. Such fine grains of <=3mm, in addition to those of natural generation are preferably arranged artificially and regularly so that the magnetic poles staying on the grain boundaries may be distributed evenly in the sheet and the static magnetic energy distribution may be uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

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

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

However, in recent years, a technique has been developed for irradiating a plasma jet or a laser beam to artificially narrow the magnetic domain width to reduce iron loss, and it is necessary to reduce the crystal grain size to reduce iron loss. Due to the elimination of the properties, the method of reducing the core loss by increasing the degree of integration of the crystal orientation has become the mainstream, and materials having a magnetic flux density (B ₈ ) of 1.93 to 2.00 T have been developed.

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

[0007]

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

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

[0009] Further, with the improvement of the magnetic flux density, a phenomenon was observed in which iron loss characteristics were greatly deteriorated by strain applied during shearing and laminating. This is still in the midst of research, and at present there is no realistic countermeasure that can be applied to the handling of materials while suppressing distortion as much as possible.

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

[0011]

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

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

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

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

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

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

[0017]

[Table 1]

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

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

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

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

[0022]

[Table 2]

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

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

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

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

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

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

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

The mechanism for suppressing the increase in the factor of realization and the mechanism for improving the strain resistance by the generation of fine grains penetrating the plate thickness have been described above. The result of examining the manufacturing conditions necessary for producing the necessary fine particles will be described below.

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

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

According to the study by the inventors, the abnormal grain growth caused by 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 outside the region. It was also determined that the crystal worked hard and could no longer grow anymore. Such a phenomenon is a very advantageous property for the purposes of the present invention. Hereinafter, this point will be described.

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

Second, since the fine grains artificially generated in this way are largely deviated from the Goss orientation ((110) [001] orientation) which is the orientation of ordinary coarse secondary recrystallized grains. In addition, magnetic poles are generated at a high density at the crystal grain boundary between the coarse secondary recrystallized grains and the fine grains, so that the above-mentioned good strain resistance and strong effect of suppressing the factor of realization can be obtained. In the manufacturing process of the grain-oriented electrical steel sheet, such fine particles may be generated spontaneously, and the naturally generated fine particles have the same action as described above. However, the generation process is a grain that has lost the growth competition with other spontaneously generated grains, and is essentially a secondary recrystallized grain, and its orientation is very close to the Goss orientation. On the other hand, no magnetic poles having a high density are formed at the crystal grain boundaries, so that the effect of improving the strain resistance and the effect of suppressing the factor for realization are weak.

Third, since the fine particles are artificially generated, it is possible to generate fine particles at the most preferable positions in the product. In addition, since the artificially generated fine grains are greatly deviated from the Goss orientation and are inferior in crystal orientation,
It must not be present at high density in the product. In other words, it is preferable that they exist as discretely as possible, and ideally they exist in a state of being isolated inside coarse crystal grains. Here, the discrete interval is 5 mm
It is preferable to make the above. Such a state can be easily realized by previously forming the strain introduction region locally and discretely. In addition, within a coarse crystal grain, a state in which several fine grains are aggregated is advantageously adapted.

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

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

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

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

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

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

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

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

By the way, there have been examples of studies on fine grains in the crystal structure of a product. For example, in Japanese Patent Publication No. Hei 6-80172, fine grains of 1.0 mm or more and 2.5 mm or less have a particle size of 5.0 mm or more. The technology to find the effect of reducing iron loss by allowing it to exist in the form of mixed grains in crystal grains of 10.0 mm or less and to optimize the ratio of fine grains and the proportion of coarse grains to obtain the minimum iron loss value has been developed. It has been disclosed. Japanese Patent Publication No. 62-56923 also discloses that the number ratio of fine particles of 2 mm or less is 15
There is disclosed a technique for controlling the iron loss value to about 70% to reduce the iron loss value. However, none of these techniques was a technique at the time when the technique of magnetic domain refining was common, and was not intended to positively increase the value of magnetic flux density. The value is also smaller than the proper range in the present invention. In addition, these fine grains promote the generation of naturally occurring secondary recrystallized grains,
Since it is not an artificially generated fine grain, its orientation is close to the Goss orientation, and the function of improving the strain resistance characteristics and the characteristics of the actual device, which are recognized in the material of the present invention, is extremely weak.

Japanese Patent Application Laid-Open No. 56-130454 discloses that a steel sheet after secondary recrystallization is strained and annealed to produce a large number of recrystallized grains. Although a technique for reducing the loss is disclosed, in this technique, the steel sheet to be strained is a steel sheet after secondary recrystallization, so that the crystal orientation is close to the Goss orientation, and furthermore, because no inhibitor exists in the steel sheet. Since normal grain growth does not occur without abnormal grain growth, the grains to be recrystallized at this time consist of a large number of recrystallized grains, and the size of each recrystallized grain is small and not more than 1/2 of the steel sheet thickness. Therefore, the effect of the present invention is not obtained. Furthermore, in this technique, it is indispensable to distribute fine particles linearly in the width direction of the steel sheet for magnetic domain refining, so that the magnetic flux density is reduced, and unlike the fine particles in the present invention. Therefore, the effect of improving the actualization factor and the effect of improving the distortion resistance characteristics cannot be obtained.

On the other hand, the effect of the presence of the fine grains in the technique of the present invention not only reduces the iron loss value of the product, but also reduces the iron loss of the product. This is a technique for suppressing the increase in factors and making the characteristics of the transformer a performance commensurate with the improvement of the product characteristics.

The present invention has been completed after intensive studies based on the numerous experiments and investigations described above. That is, the gist configuration of the present invention is as follows. 1. Si: 1.5 to 7.0 wt%, Mn: 0.03 to 2.5 wt%, and contamination of C, S and N as impurities, C: 0.003 wt% or less, S: 0.002 wt% or less, N: 0.00
In the electromagnetic steel sheet suppressed to 2 wt% or less, among the crystal grains penetrating in the thickness direction of the steel sheet, the number ratio of crystal grains having a grain size of 3 mm or less on the steel sheet surface is 65% or more and 98%. A grain-oriented electrical steel sheet having low iron loss, excellent in strain resistance and actual machine characteristics, characterized in that:

2. In the above item 1, the average value of the grain size on the steel sheet surface of the entire crystal grain penetrating in the thickness direction is 8 mm.
Above, 50mm or less, characterized by low iron loss,
Grain-oriented electrical steel sheet with excellent strain resistance and actual machine characteristics.

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

4. C: 0.010 to 0.120 wt%, Si: 1.5 to
A silicon steel slab containing 7.0 wt% and Mn: 0.03 to 2.5 wt% and having a composition containing a predetermined amount of an inhibitor component is hot-rolled and, if necessary, subjected to hot-rolled sheet annealing. In producing a grain-oriented electrical steel sheet by a series of steps of performing cold rolling one or more times including intermediate annealing to obtain a final thickness, and then performing primary recrystallization annealing and then secondary recrystallization annealing. During the period from the recrystallization annealing to the start of the secondary recrystallization, a region in which the driving force for crystal growth is increased inside the steel plate, and a region projected onto the steel plate surface is a circle equivalent diameter.
A method for producing a grain-oriented electrical steel sheet having low iron loss, excellent in strain resistance and excellent in actual machine characteristics, characterized by being artificially and discretely provided in a size of 0.05 to 3.0 mm.

5. 4. The method for producing a grain-oriented electrical steel sheet according to 4 above, wherein the regions in which the driving force for crystal growth is increased are regularly arranged, the iron loss being low, the strain resistance characteristics and the characteristics of the actual machine being excellent.

6. In the above item 4 or 5, the region in which the driving force for crystal growth is increased is a region in which primary recrystallized grains are atomized or a region into which strain is introduced. A method for producing grain-oriented electrical steel sheets with excellent properties.

7. In the above item 6, in the case where the region where the driving force for crystal growth is increased is a strain-introduced region, the region is characterized by introducing a strain of 0.005 to 0.70 as a maximum strain amount into the region. A method for producing grain-oriented electrical steel sheets having excellent strain resistance and actual machine characteristics.

8. In the above 4, 5, 6, or 7, the method of introducing a strain for increasing the driving force for crystal growth is a method of pressing an object harder than a steel sheet having small projections on the surface thereof, the method comprising: Low iron loss and strain resistance, which is a method of applying a high voltage during the period to locally conduct or discharge, a method of irradiating a high-temperature spot laser instantaneously, or a method of locally irradiating a pulse laser. A method for producing grain-oriented electrical steel sheets with excellent characteristics and actual machine characteristics.

[0056]

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

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

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

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

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

The fine grains having a size of 3 mm or less can be fine grains generated naturally, but in addition, the magnetic poles existing at the grain boundaries are uniformly distributed in the steel sheet, and static To make the distribution of magnetic energy uniform,
It is more preferable to arrange them artificially and regularly. The interval is preferably 5 mm or more. Thereby, the flow of the magnetic flux becomes uniform, and an increase phenomenon of iron loss such as an abnormal increase of eddy current loss locally is suppressed.

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

The surface of the grain-oriented electrical steel sheet is used in a state where an insulator is present as necessary. At this time,
Forsterite (Mg ₂ S) formed during final finish annealing
An insulating coating mainly composed of iO ₄ ) may be present, or a tensile coating may be further formed thereon.

Next, a method of manufacturing a grain-oriented electrical steel sheet according to the present invention will be described. First, the reasons for limiting the component composition of the material will be described. C: 0.010 to 0.120 wt% If the C content is less than 0.010 wt%, the effect of improving the structure cannot be obtained, the secondary recrystallization is incomplete, and the magnetic properties deteriorate, whereas if the C content exceeds 0.120 wt%. Since the decarburization annealing does not allow sufficient removal, and also causes deterioration of magnetic properties, the C content is 0.010%.
Limited to the range of ~ 0.120 wt%.

Si: 1.5-7.0 wt% Si effectively contributes to increase the electric resistance and reduce iron loss, but if it is less than 1.5 wt%, the effect of its addition is poor. If it exceeds, processability deteriorates, and it becomes extremely difficult to manufacture and process the product itself.
The range was limited to 0 wt%.

Mn: 0.03 to 2.5 wt% Mn, like Si, is not only useful for improving electric resistance,
Although it effectively contributes to the improvement of hot workability, if it is less than 0.03% by weight, the effect of its addition is poor. On the other hand, if it exceeds 2.5% by weight, γ transformation is induced during heat treatment, leading to deterioration of magnetic properties. It was limited to the range of 0.03 to 2.5 wt%.

It is essential that the steel contain an inhibitor component for inducing secondary recrystallization in addition to the above-mentioned elements, which is particularly important for producing a grain-oriented electrical steel sheet having an excellent high magnetic flux density. Suitable inhibitor components include Al,
One or more elements selected from B, Bi, Sb and Te are preferred. Here, 0.005 to 0.060 wt% for Al, Sb and Te, and 0.0003 to 0.0025 wt% for B.
wt% and Bi must be contained in the range of 0.0003 to 0.0090 wt%. The reason is that if any of the elements is less than the lower limit, the intended inhibitor 1
This is because the effect of suppressing the growth of the next recrystallized grain cannot be obtained, and if the upper limit is exceeded, adverse effects such as grain boundary cracking occur, and the surface properties of the product deteriorate. In addition, other inhibitors include Se, S, Sn, P, Ge, As, Nb, Cr, Ti,
Cu, Pb, Zn and In etc. are known, 0.005 ~ 0.3 w
It can be appropriately added in the range of t%. In addition, as the inhibitor element, the action is exerted even when only one kind is added alone, but more preferably, two or more kinds are added in combination.

The other additional elements are not necessarily required to obtain a high magnetic flux density.
For example, Mo and the like are effective in improving the surface properties of the steel sheet, so that it is advantageous to appropriately include them.

The steel slab adjusted to the above-mentioned preferable component composition is as follows:
After forming a hot-rolled steel sheet by a known hot-rolling method, hot-rolled sheet annealing is performed as necessary, and the final sheet thickness is obtained by cold rolling once or twice or more with intermediate annealing. In this final cold rolling, the orientation of the crystal grown during the secondary recrystallization is controlled by adjusting the rolling reduction. If the rolling reduction is less than 80%, a large number of crystal grains with poor orientation tend to recrystallize. The magnetic flux density may not be obtained. On the other hand, if it exceeds 95%, the probability of nucleation of secondary recrystallized grains is extremely reduced, and secondary recrystallization tends to be unstable. Of 80
It is preferable to set it to 95%.

In the above-mentioned rolling, it is advantageous to combine the known warm rolling and the inter-pass aging treatment in order to further improve the magnetic flux density. After the final rolling, a linear groove can be provided on the surface of the steel sheet for magnetic domain refining. Further, it is also possible to perform a weak decarburization treatment in hot-rolled sheet annealing or intermediate annealing.

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

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

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

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

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

After the region where the driving force for crystal growth is increased is artificially provided as described above, an annealing separator is applied as necessary, and then a final finish annealing is performed to perform secondary recrystallization. Let it. In the final finish annealing, the temperature may be raised to a high temperature of about 1200 ° C. to form a purification annealing and a forsterite-based undercoating. Thereafter, an insulating coating is applied to the surface of the steel sheet to obtain a product. Before coating, the surface of the steel sheet may be mirror-finished or a crystal orientation enhancement process may be performed. Further, a tension coating may be used as the insulating coating. Further, in order to obtain a further iron loss reduction effect, the steel sheet after the secondary recrystallization has a well-known domain refining treatment,
That is, a process of applying a plasma jet or a laser to a linear region or providing a linear concave region by a projection roll can be performed.

As described above, a grain-oriented electrical steel sheet having a low iron loss, a high magnetic flux density, and excellent strain resistance and actual machine characteristics can be obtained.
By mixing with coarse grains of 15 mm or more, it is possible to assemble an excellent transformer with high magnetic flux density and low iron loss and extremely low iron loss of the actual machine.

It is effective that the regions where various processes for generating the fine particles as described above are performed are distributed discretely in the plane of the steel sheet as shown in FIG. Since the effect of lowering the magnetic flux density and other effects, such as lowering the magnetic flux density, and increasing the effect of lowering the strain sensitivity increase, the various processing regions are not stochastically dispersed in the surface of the steel sheet. As shown in FIG. 8 and FIG.
Naturally, it is natural to obtain the most excellent effect. In this regard, for example, when artificial crystal grains elongated linearly as shown in FIG. 10 are generated, the magnetic flux density of a product is significantly deteriorated, and the iron loss increases.

[0079]

【Example】

Example 1 C: 0.08 wt%, Si: 3.35 wt%, Mn: 0.07 wt%, Al: 0.02
wt%, Sb: 0.05 wt% and N: 0.008 wt%, the balance being Fe and unavoidable impurities.
Then, a 2.2 mm thick hot-rolled steel sheet was obtained by a conventional method.
Then, after annealing the hot rolled sheet at 1000 ° C for 30 seconds,
It was cold rolled to a thickness. After that, an intermediate treatment was performed at 1080 ° C for 50 seconds, followed by warm rolling at a steel sheet temperature of 220 ° C.
The final thickness was 22 mm. Then, after the degreasing treatment, the steel sheet was subjected to decarburizing annealing at 850 ° C. for 2 minutes, and then the steel sheet was divided into two parts, one of which was directly coated with an annealing separator containing MgO as a main component (comparative example). On the other hand, the apparatus shown in FIG. 6 is used to apply an instantaneous discharge treatment at 1 kV to a 1.5 mm size area on the steel sheet surface, and to increase the driving force for grain growth by such an instantaneous high-temperature heat treatment. Was given. Then, such a region was repeatedly provided in the pattern shown in FIG. 9 at a pitch in the coil longitudinal direction: 10 mm and a pitch in the width direction: 15 mm, and then an annealing separator mainly containing MgO was applied ( Invention example).

[0080] Then, the resulting coil, as a final finish annealing, the temperature was raised at a heating rate of 30 ° C. / h up to 850 ° C. in N _2, was held for 25 hours in 850 ° C., of 25% N ₂ The temperature was raised to 1200 ° C. at a rate of 15 ° C./h in a mixed atmosphere of H ₂ and 75% H ₂ , further kept in H ₂ for 5 hours, and then cooled. Then, after removing the unreacted annealing separator, these coils were coated with a tension coating containing 50% colloidal silica and baked to obtain products.

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

[0082]

[Table 3]

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

Example 2 C: 0.08 wt%, Si: 3.40 wt%, Mn: 0.04 wt%, Al: 0.02
wt%, Cu: 0.15wt%, Mo: 0.010wt%, Bi: 0.005wt%
And N: 0.008 wt%, with the balance being Fe and unavoidable impurities, after heating the steel slab to 1410 ° C,
A 2.6 mm thick hot-rolled steel sheet was obtained by a conventional method. Then in 1125
After applying a hot-rolled sheet annealing consisting of soaking heat treatment of 30 seconds and quenching of 40 ° C / s by spraying mist water, pickling, and hot rolling at a steel sheet temperature of 250 ° C to a final sheet thickness of 0.34 mm did. Next, after the degreasing treatment, the steel sheet was divided into three 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 1). The other is 2 at 850 ° C
Immediately after the decarburizing annealing for 5 minutes, the steel roll was pressed while rotating the ceramic roll having the shape shown in FIG. 11 in synchronization with the running speed of the steel sheet, immediately after the temperature was raised to 850 ° C., and the pattern shown in FIG. 10 was obtained. Then, a driving force increasing treatment of linear grain growth extending in the width direction of the sheet having a width of 2.0 mm was performed at a repetition pitch of 20 mm in the rolling direction. After decarburizing annealing, as in Comparative Example 1, an annealing separator containing MgO as a main component was applied (Comparative Example 2). The other one is 850 ° C when decarburizing annealing at 850 ° C for 2 minutes.
Immediately after the temperature was raised, the steel roll having the shape shown in FIG. 5 was pressed while rotating in synchronization with the traveling speed of the steel sheet, and a local 2.0 mm-sized pattern was formed in the pattern shown in FIG. The steel plate was subjected to a treatment for increasing the driving force for grain growth. Then, such a process is performed at a pitch of 25 m in the coil longitudinal direction.
m, pitch in the width direction: 20 mm.

FIG. 12 shows an example of the surface shape of the portion pressed by the small projection in three-dimensional roughness display. FIG. 13 shows an example of the strain distribution of the portion pressed by the small projection by EBSD (Electron). B
ackScattering Diffraction).

As a final finish annealing, these coils were heated in N ₂ to 850 ° C. at a rate of 30 ° C./h,
15 ° C. in a mixed atmosphere of 25% N ₂ and 75% H ₂
/ At a Atsushi Nobori rate was raised to 1200 ° C. for h, further in H ₂ 5
After holding for a time, the temperature was lowered. Then, after removing the unreacted annealing separating agent, these coils were coated with a tension coating containing 50% of colloidal silica and baked to obtain products.

Using these steel plates, slitting, shearing, and laminating were performed, and two three-phase transformers each having a leg width of 300 mm, a height of 1100 mm, and a thickness of 250 mm were manufactured. . At this time, one unit was manufactured with as little distortion as possible, and the other unit was cast on a caster with a 50 mm diameter sphere at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of imparting distortion. Press and intentionally add distortion,
Manufactured. Table 4 shows the results of investigating the iron loss characteristics of these transformers and the values of the actualization factors, together with the results of investigating the magnetic characteristics of the materials. Table 4 also shows the results of a survey on the number ratio of crystal grains of 3 mm or less and the average grain size measured by macro-etching the material.

[0088]

[Table 4]

As is clear from the table, in Comparative Example 2 in which the region subjected to the treatment for increasing the driving force for grain growth was linear, the magnetic flux density of the product was significantly reduced, and the factor for realizing the device was also reduced. High and poor transformer characteristics. On the other hand, the transformer using the grain-oriented electrical steel sheet of the present invention had low actual machine characteristics, extremely low distortion resistance, and was extremely excellent as a core material of an actual transformer.

Example 3 A steel slab having the composition shown in Table 5 was heated to 1430 ° C., and then made into a hot-rolled steel sheet having a thickness of 2.66 mm by a conventional method. Then, after annealing the hot-rolled sheet at 1000 ° C for 30 seconds, pickling, cold rolling to a thickness of 1.8 mm, and then performing an intermediate treatment at 1050 ° C for 50 seconds,
The final thickness was 0.26 mm by warm rolling at a steel sheet temperature of 230 ° C. Then, decarburization annealing was performed at 850 ° C. for 2 minutes.
Next, this steel sheet was divided into two parts, and one of them was directly applied with an annealing separator containing MgO as a main component (comparative example). On the other hand, a roll made of high C quenched steel having the shape shown in FIG. 5 is pressed while rotating in synchronization with the running speed of the steel sheet, and a pattern as shown in FIG. 0.
The steel sheet was subjected to a local grain growth driving force increasing treatment for a 1.5 mm size area with 15. Such a region was repeatedly provided with a pitch in the coil longitudinal direction: 25 mm and a pitch in the width direction: 20 mm. Thereafter, an annealing separator containing MgO as a main component was applied (Example of the present invention).

As a final finish annealing, these coils were heated to 850 ° C. in N ₂ at a rate of 30 ° C./h,
After maintaining at 850 ° C. for 25 hours, the temperature was increased to 1200 ° C. at a rate of 15 ° C./h in a mixed atmosphere of 25% N ₂ and 75% H ₂ , and further maintained at H ₂ for 5 hours. Later, the temperature dropped. Then, after removing the unreacted annealing separator, these coils
Tensile coatings containing 50% colloidal silica were applied to baked products.

Using these steel plates, slit processing, shearing processing, and lamination fixing processing were performed to manufacture two three-phase transformers each having a leg width of 200 mm, a height of 800 mm, and a thickness of 350 mm. did. At this time, one unit was manufactured with as little distortion as possible, and the other unit was equipped with a caster having a sphere of 50 mm in diameter at the time of processing for 5 kg in order to experimentally evaluate the effect of applying strain. And intentionally added strain to produce. Table 6 shows the results of the investigation on the iron loss characteristics and the values of the factor of realization of these transformers, together with the results of the investigation on the magnetic characteristics of the materials. Table 6 also shows the results of a survey on the number ratio of crystal grains of 3 mm or less and the average grain size measured by macro-etching the material.

[0093]

[Table 5]

[0094]

[Table 6]

As is clear from Table 6, the transformer using the grain-oriented electrical steel sheet according to the present invention has low actual machine characteristics, very low distortion resistance, and is excellent as a core material of an actual transformer. It was extremely good.

Example 4 C: 0.08 wt%, Si: 3.40 wt%, Mn: 0.09 wt%, Al: 0.02
wt%, Cu: 0.05 wt%, Nb: 0.005 wt%, Ni: 0.2 wt%,
Contains Sb: 0.045 wt% and N: 0.008 wt%, with the balance being
A steel slab composed of Fe and unavoidable impurities was heated to 1430 ° C., and then made into a 2.2 mm hot-rolled steel sheet by an ordinary method. Next, after pickling, cold rolling is performed to obtain an intermediate thickness of 1.5 mm, and then heat treatment is performed at 1100 ° C for 30 seconds, and mist water is injected.
Intermediate annealing consisting of quenching at ℃ / s, followed by pickling
The final thickness was 0.22 mm by warm rolling at a steel sheet temperature of 50 ° C. Then, after degreasing, the steel sheet is divided into two parts,
After decarburizing annealing at 50 ° C. for 2 minutes, an annealing separator mainly composed of SiO ₂ was applied (Comparative Example). The other steel sheet was subjected to pulsed laser irradiation after decarburizing annealing at 850 ° C for 2 minutes, and the steel sheet was subjected to a grain growth driving force increasing treatment with a 2.0 mm size and 0.01 to 0.08 strain on the steel sheet. The applied area was discretely provided on the steel plate at an interval of 2 to 30 mm. Then, similarly to the comparative example, an annealing separator mainly composed of SiO ₂ was applied (inventive example).

These coils were heated in N ₂ to 850 ° C. at a rate of 30 ° C./h as final finish annealing.
After maintaining at 850 ° C. for 25 hours, the temperature is raised to 1200 ° C. at a rate of 15 ° C./h in a mixed atmosphere of 25% N ₂ and 75% H ₂ , and further maintained in H ₂ for 5 hours. After that, the temperature was lowered. No formation of a surface oxide film was observed on the thus obtained coil. Then directly applied baking products tension coating containing B ₂ O _3.

Using these steel sheets, slit processing, shearing processing, and lamination fixing processing were performed, and two three-phase transformers each having a leg width of 300 mm, a height of 1100 mm, and a thickness of 250 mm were manufactured. . At this time, one unit was manufactured with as little distortion as possible, and the other unit was cast on a caster with a 50 mm diameter sphere at the time of processing with a load of 5 kg in order to experimentally evaluate the effect of imparting distortion. Press and intentionally add distortion,
Manufactured. Table 7 shows the results of the investigation on the iron loss characteristics and the values of the factor of realization of these transformers, together with the results of the investigation on the magnetic characteristics of the materials. Table 7 also shows the results of investigation on the number ratio of crystal grains of 3 mm or less and the average grain size measured by macro-etching the material.

[0099]

[Table 7]

As shown in Table 7, the actual equipment characteristics of the transformer using the grain-oriented electrical steel sheet of the present invention had a low actualization factor.
The strain resistance was also very good, and it was extremely excellent as an actual transformer core material.

[0101]

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

[Brief description of the drawings]

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

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

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

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

FIG. 5 is an external view of a roll having a large number of small protrusions on its surface.

FIG. 6 is a conceptual diagram of an apparatus for performing a local energization heating process and a local discharge heating process.

FIG. 7 is a diagram showing a state where regions where the driving force for crystal grain growth is increased are discretely provided on the surface of a steel sheet.

FIG. 8 is a diagram showing a state in which regions in which the driving force for crystal grain growth is increased are regularly provided on the surface of the steel sheet.

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

FIG. 10 is a diagram showing a state in which a region where the driving force for crystal grain growth is increased is provided linearly continuously in the width direction of the steel sheet.

FIG. 11 is an external view of a roll having linear protrusions on its surface.

FIG. 12 is a diagram showing a surface shape of a portion pressed by a small protrusion.

FIG. 13 is a diagram showing a strain distribution of a portion pressed by small projections (shading indicates the degree of the introduced distortion amount, and the higher the density, the larger the distortion amount).

[Explanation of symbols]

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

Claims (8)

[Claims] (1) Si: 1.5 to 7.0 wt%, Mn: 0.03 to 2.5 wt%, and contamination of C, S and N as impurities respectively: C: 0.003 wt% or less, S: 0.002 wt% or less N: 0.002 wt% or less, wherein the number ratio of crystal grains having a grain size of 3 mm or less on the steel sheet surface among the crystal grains penetrating in the thickness direction of the steel sheet is 65% or more. A grain-oriented electrical steel sheet having a low iron loss, excellent in strain resistance and excellent in actual machine characteristics, characterized by being 98% or less. 2. The method according to claim 1, wherein the average value of the grain size on the steel sheet surface of the entire crystal grain penetrating in the thickness direction is 8 mm.
Above, 50mm or less, characterized by low iron loss,
Grain-oriented electrical steel sheet with excellent strain resistance and actual machine characteristics. 3. The method according to claim 1, wherein the crystal grains penetrating in the thickness direction and having a grain size of 3 mm or less on the surface of the steel sheet include those which are artificially and regularly arranged. Grain-oriented electrical steel sheet with low iron loss and excellent distortion resistance and actual machine characteristics. 4. C: 0.010-0.120 wt%, Si: 1.5-7.
A silicon steel slab containing 0 wt% and Mn: 0.03 to 2.5 wt% and having a composition containing a predetermined amount of an inhibitor component is hot-rolled and, if necessary, subjected to hot-rolled sheet annealing. In producing a grain-oriented electrical steel sheet by a series of steps in which a final thickness is obtained by cold rolling once or twice or more with intermediate annealing, followed by primary recrystallization annealing and then secondary recrystallization annealing, During the period from the recrystallization annealing to the start of the secondary recrystallization, the region where the driving force for crystal growth was increased was placed inside the steel plate, and the projected region on the steel plate surface was 0.05 to 3.0 mm in circle equivalent diameter. Characterized by being artificially and discretely provided by
A method for producing grain-oriented electrical steel sheets with low iron loss and excellent strain resistance and actual machine properties. 5. The directionality according to claim 4, wherein the regions in which the driving force for crystal growth is increased are arranged regularly, characterized by low iron loss, excellent distortion resistance and excellent real machine characteristics. Manufacturing method of electrical steel sheet. 6. A low iron loss according to claim 4, wherein the region in which the driving force for crystal growth is increased is a region in which primary recrystallized grains are atomized or a strain-introduced region. A method for producing grain-oriented electrical steel sheets having excellent strain resistance and actual machine characteristics. 7. The method according to claim 6, wherein when the region where the driving force for crystal growth is increased is a strain-introducing region, a strain of 0.005 to 0.70 is introduced as a maximum strain amount into the region. A method for producing a grain-oriented electrical steel sheet having a low iron loss, and excellent in distortion resistance characteristics and actual machine characteristics. 8. The method according to claim 4, wherein the means for introducing strain for increasing the driving force for crystal growth presses an object harder than a steel sheet having small projections on the surface. A method in which a high voltage is applied between the steel sheet surface and the electrode to locally conduct or discharge, a method in which a high-temperature spot laser is instantaneously irradiated, and a method in which a pulse laser is locally irradiated, iron. A method for producing a grain-oriented electrical steel sheet with low loss and excellent strain resistance and actual machine properties.