KR100538595B1 - A grain-oriented electrical steel sheet with excellent magnetic properties and its manufacturing method - Google Patents

Abstract

The present invention is a grain-oriented electrical steel sheet having an average value of a shearing angle of 4 ° or less from the rolling direction of the crystal orientation [001] of secondary recrystallized grains, the secondary recrystallization having a length of 60 mm or more in the rolling perpendicular direction. The area ratio of the crystal grains is 85% or more, and the area ratio of the crystal grains having a particle diameter of 2 to 20 mm with respect to the fine recrystallization is 0.2% to 10%, and the average value of the angles of the crystal orientation [001] with the steel sheet surface is 1.5 ° to 5.0. It relates to a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that it is °. In a grain-oriented electrical steel sheet having a high magnetic flux density (B ₈ ≥ 1.96T), which has conventionally been difficult to stably obtain low iron loss without a magnetic zone refinement, a stable low iron loss can be obtained without performing magnetic zone refinement. . In addition, by forming grooves on the surface of the steel sheet, it is possible to obtain an electronic steel sheet having a very low iron loss value by magnetic zone segmentation, smoothing of the steel sheet surface, or a combination thereof.

Description

A grain-oriented electrical steel sheet with excellent magnetic properties and a manufacturing method

The present invention relates to a low iron loss grain-oriented electrical steel sheet suitable for use in iron cores of transformers and other electrical equipment.

A grain-oriented electrical steel sheet is used as the iron core of transformers and other electrical equipment, and has to have good magnetic properties, in particular low iron loss. Iron loss can usually be expressed as the sum of hysteresis loss and eddy current loss. In order to lower the iron loss of the grain-oriented electrical steel sheet, it is necessary to reduce one or both of the hysteresis loss and the eddy current loss.

Until now, the hysteresis loss has been greatly improved by using an inhibitor having a function of suppressing the growth of crystal grains, thereby increasing the magnetic transmittance by highly integrating the crystal grains of the steel sheet in the Goss orientation, that is, the {110} <001> orientation. Could be reduced. On the other hand, for the eddy current loss, the eddy current loss can be reduced by increasing the Si content in the steel sheet, making the plate thickness thin, making the grain size of the secondary recrystallized particles fine, and forming a tension coating on the metal surface.

Recently, a method of artificially narrowing the magnetic zone width to reduce the eddy current loss has been developed, and laser light (Japanese Patent Laid-Open No. 82-2252), plasma flame (Japanese Patent Laid-Open No. 87-96617), and the like have been developed. A method of investigation has been disclosed. In addition, as a heat-resistant magnetic zone subdividing method, a method of forming a groove by mechanically processing a steel plate after secondary recrystallization (Japanese Patent Laid-Open No. 87-53579) and a linear notch perpendicular to the rolling direction before finish annealing Japanese Patent Laid-Open No. 91-39968 and the like have been disclosed. Also, Japanese Patent Application Laid-open No. 84-177349 discloses a method of reducing eddy current loss by appropriately controlling the inclination angle from the rolling surface of the <001> orientation of the crystal to reduce the magnetic region width.

As described above, in the prior art, the aggregation of the crystal grains in the goth orientation is aimed at reducing the hysteresis loss, and also the reduction of the magnetic domain width is mainly aimed at reducing the eddy current loss.

However, the above-described conventional iron loss reduction techniques have the problems listed in (1) to (3) below and cannot sufficiently reduce iron loss:

(1) Iron loss increases due to uneven distribution of magnetic flux densities caused by differences in crystal orientation of secondary recrystallized particles adjacent to each other in a direction orthogonal to the rolling direction (rolling perpendicular direction). do.

(2) In the case where the secondary recrystallized grain size is fine, a magnetic pole resulting from the difference in crystal orientation of each crystal grain is generated, thereby decreasing the magnetic transmittance and increasing the hysteresis loss.

(3) As the crystal orientation approaches the goth orientation, the amount of magnetic poles appearing on the surface of the steel sheet decreases, and the width of the magnetic zone increases, thereby increasing the eddy current loss.

The present inventors have disclosed a method of preventing deterioration of iron loss with respect to the above problem (1) in Japanese Patent Laid-Open No. 96-49045. This method is a technique of uniformizing the local magnetic flux density change throughout the steel sheet. Regarding a specific method of carrying out this technique, the present inventors have disclosed a method of controlling the aspect ratio of components and secondary recrystallized particles in a coating in Japanese Patent Laid-Open No. 96-288115. These methods provide a non-uniform distribution of magnetic flux densities resulting from the difference in the α angle (inclined angle from the rolling direction of the [001] orientation in the rolling plane) of the secondary recrystallized particles adjacent to the rolling perpendicular direction of the secondary recrystallized particles in the rolling direction. The growth can be prevented by inhibiting growth to promote growth of secondary recrystallized particles in the rolling perpendicular direction. However, when the particle size of the secondary recrystallized particles in the rolling perpendicular direction is large, the growth rate of the secondary recrystallized particles in the rolling direction also tends to increase. As a result, appropriate aspect ratios are not obtained depending on the material, and iron loss may not be sufficiently reduced.

Although the above-described artificial magnetic zone subdivision method is effective for the problem of (2), this magnetic zone subdivision process causes deterioration of magnetic permeability at the same time. Therefore, relying only on conventional magnetic zone segmentation techniques, it is difficult to sufficiently subdivide the magnetic zone width without deterioration of magnetic transmission.

In addition, with respect to the problem of (3), Japanese Patent Laid-Open Publication No. 94-89805 discloses that in addition to the reconstituted secondary recrystallized particles, only a predetermined number of fine particles having a diameter of 5 mm or less exist within a range of a predetermined orientation. A method of reducing iron loss has been disclosed. However, in this method, since the problem of (1) is not solved, if the magnetic flux density in the steel sheet is unevenly distributed due to the orientation difference of the secondary recrystallized particles adjacent to the rolling perpendicular direction, the desired iron loss reduction effect is obtained. There was a problem that it could not be obtained.

It is an object of the present invention to propose a grain-oriented electrical steel sheet having a high magnetic transmittance and excellent magnetic properties with low iron loss without a decrease in magnetic flux density, and a method of manufacturing the same. The present invention advantageously solves the above problems by specifying specifically the distribution and crystal orientation of the recrystallized particles.

The present inventors concentrated on the shape of the secondary recrystallized particles having both the uniformity effect of the magnetic flux and the magnetic zone refinement effect even when the secondary recrystallized particles grow to some extent in the rolling direction. As a result, in a grain-oriented electrical steel sheet having high magnetic permeability, the magnetic flux density does not deteriorate, and there are specific recrystallized particle distributions and crystal orientations capable of exhibiting the maximum iron loss reduction effect regardless of the presence or absence of magnetic zone refinement treatment. The present invention was completed.

That is, the present invention contains 2.0 to 5.0% by mass of Si, contains one or two or more of As, Sb and Bi in a total of 0.0003 to 0.1% by mass, rolling the crystal orientation of the secondary recrystallized particles [001] In a grain-oriented electrical steel sheet having an average inclination angle of 4 ° or less from the direction, secondary recrystallized grains having a maximum length of 60 mm or more in the perpendicular direction of rolling in relation to the distribution of secondary grains of large grain diameter occupy 85% or more as an area ratio with respect to the steel sheet area Regarding the recrystallized grain size of the small grain size, the crystal grain having a particle diameter in the range of 2 mm to 20 mm occupies the range of 0.2% to 10% by area ratio with respect to the steel sheet area, and the grain diameter is in the range of 2 mm to 20 mm. It is a grain-oriented electrical steel sheet excellent in magnetic properties, in which the average value (area average value) of the angle at which the crystal orientation [001] forms with the steel plate surface is in the range of 1.5 ° to 5.0 °, and a manufacturing method thereof.

In the present invention, in the case of having a group of linear grooves having an angle of 30 ° or less with a rolling perpendicular direction, having a depth of 10 μm or more, a width of 20 μm to 300 μm, and an interval of 1 mm or more, By reducing iron loss.

Further, in the present invention, the absence of a forsterite coating on the surface of the steel sheet is preferable to reduce the iron loss by reducing the hysteresis loss.

First, the experiment on which the present invention is based will be described.

As a component composition, it contains C 0.063 mass% (it shows simply in% below), Si 3.20%, Mn 0.065%, Se 0.020%, Al 0.022%, N 0.0090%, Mo 0.020%, Sb 0.050%, and Bi 0.02%, Silicon steel (silicon containing steel) small steel ingot (100 kg) consisting mainly of Fe was heated induction at a temperature of 1450 ° C., followed by hot rolling to hot rolled sheets having a thickness of 2.4 mm. rolled sheet). The hot rolled sheet was annealed (1050 ° C. for 40 seconds in nitrogen) and then cold rolled into a cold rolled sheet having a thickness of 1.7 mm. Thereafter, after performing intermediate annealing (1000 DEG C. for 2 minutes in wet hydrogen), secondary cold rolling was carried out to a final cold rolled sheet thickness of 0.23 mm. The steel sheet temperature was 250 degreeC in the final 4 passes in this secondary cold rolling.

Subsequently, after decarburization annealing was performed at 850 ° C. for 2 minutes, the decarburization annealing plate was subjected to a stress introduction treatment at a rolling reduction of 0.1%. Then, after apply | coating the annealing separator which has MgO as a main component, final finishing annealing was performed at 1200 degreeC. In this final finishing annealing, secondary recrystallization nucleation treatment was performed at a temperature of 850 ° C. for 20 hours by correction. After the final finishing annealing, the steel sheet was subjected to an insulating coating composed mainly of colloidal silica and magnesium phosphate.

From the steel sheet thus obtained, a test piece of a single sheet test (SST) having a width of 100 mm and a length of 280 mm was taken, and the iron loss (W _17/50 ) and the magnetic flux density (B ₈ ) were measured. After magnetic measurement, each test piece was subjected to macro-notching to emerge secondary recrystallized particles. The size of the secondary recrystallized particles was measured by image analysis, and the crystal orientations of the respective secondary recrystallized particles were measured by the Laue method.

In the present invention, the mean value (area average value) of the crystal orientation [001] of the crystal grains in the range of 2 mm to 20 mm in particle size and the steel sheet surface means that the individual crystal grain orientation [001] forms the steel sheet surface. The mean value of each value is multiplied by the area ratio of the said crystal grain with respect to the whole area of the crystal grain whose particle diameter of a crystal grain is 2 mm-20 mm.

In addition, the crystal grain size (R) refers to the diameter corresponding to the circle, represented by the following equation (1):

[Equation 1]

Where

S is the area of crystal grains.

These measurement results are described below.

1 is a graph showing the relationship between the magnetic flux density (B ₈ ) and the iron loss (W _17/50 ) of each test piece.

As can be seen from Figure 1, the higher the magnetic flux density (B ₈₎ decreases optimum value of the iron loss (W _17/50), and when B is ₈ or more when 1.96T W _17/50 is less than 0.80W / ㎏ Is present. On the other hand, there are many cases that B ₈ in spite of the high 1.96T or more and the deterioration of iron loss W _17/50 as a exceeds 0.95W / ㎏. The deterioration of the iron loss in the high magnetic flux density range is such that the magnetic pole amount on the surface of the steel sheet decreases due to the decrease of the inclination angle (hereinafter referred to as β angle) from the rolling surface of the crystal orientation [001], thereby increasing the magnetic zone width. It is the cause.

Therefore, for samples having B ₈ of 1.96T or more, the product of the area ratio of each secondary recrystallized particle measured by the Lauer method multiplied by the respective area ratio is added to an average β angle, and this and the iron loss (W _17/50). ) Relationship was investigated. The result is shown by the graph of the relationship of an average (beta) angle and iron loss ( _{W17 / 50} ) in FIG. In FIG. 2, the tendency of iron loss to decrease with the increase of average (beta) angle is observed. However, the relationship between them is dissipated and is not necessarily clear. Therefore, it is judged that it is impossible to reduce iron loss to 0.80 W / kg or less by controlling only the average β angle in a material having a high magnetic flux density such as a material having B ₈ of 1.96T or more. In addition, in the sample B not less than ₈ is 1.96T but examine the average particle diameter of the secondary recrystallization relationship as iron loss, a clear relationship between the two was not observed.

Based on these findings, it was conceived as an iron loss determinant other than the average β angle and the average particle diameter, noting that the improvement of the uniformity of the magnetic flux density distribution of the steel plate surface was not effective for reducing the iron loss. More detailed studies were done.

3 shows a graph of the relationship between the average value of the maximum lengths in the perpendicular direction of rolling of secondary recrystallized particles (particle diameter: 20 mm or more) and the nonuniformity of the local magnetic flux density of the steel sheet.

Here, the nonuniformity r of the local magnetic flux density is defined by Equation 2 below. The local magnetic flux density (B _i ^local ) is a measurement method called a probe method, and the width of the local magnetic flux density measurement portion is set to 10 mm, and the rolling direction and the rolling perpendicular direction are set to a pitch of 10 mm. And 200 points of probe numbers N were measured in the area | region of 200 mm of rolling directions. The excitation magnetic flux density (B _m ) of the whole steel sheet at the time of measuring the magnetic flux density of this local region was 1.0T.

[Equation 2]

It can be seen from FIG. 3 that the nonuniformity r of the local magnetic flux tends to decrease when the average value of the maximum length in the rolling perpendicular direction of the secondary recrystallized particles is 60 mm or more.

Therefore, the relationship between the ratio which the secondary recrystallized particle whose maximum length of a perpendicular | vertical rolling direction is 60 mm or more occupies in the whole steel plate and the magnetic flux density of the steel plate surface (r) was investigated. At the same time, relatively small crystal grains having a crystal grain size of 2 to 20 mm were also distinguished at the level according to the average β angle. The particle diameter was made into the diameter corresponded to the circle | round | yen determined by Formula (1).

This finding is shown in FIG. 4 is a graph showing the relationship between the ratio of secondary recrystallized grains having a maximum length of 60 mm or more in the rolling perpendicular direction in the whole steel sheet and the nonuniformity of the local magnetic flux density of the steel sheet. Here, crystal grains having a crystal grain size of 2 to 20 mm were leveled according to the average β angle.

As can be seen from FIG. 4, the average β angle of the crystal grains having a ratio of 85% or more and a particle size of 2 to 20 mm in the overall steel sheet is occupied by the secondary recrystallized particles having a maximum length of 60 mm or more in the right-angle direction in the rolling direction. In the case of, the nonuniformity r of the magnetic flux density of the steel sheet surface determined by the formula (2) is 0.15 or less. Therefore, the iron loss reduction effect can be expected in such a condition that r is small.

Therefore, the inventors of the present invention conceived at the ratio of the secondary recrystallized particles having a maximum length of 60 mm or more in the rolling right direction in the whole steel sheet and the average β angle of 2 to 20 mm in particle size, so that the magnetic flux density (B ₈ ) was 1.96T or more. Iron loss was investigated.

5, the ratio of secondary recrystallized grains having a maximum length of 60 mm or more in the rolling right direction occupies the whole steel sheet, the average β angle of crystal grains having a particle diameter of 2 to 20 mm, and the proportion of crystal grains having a particle diameter of 2 to 20 mm in the whole steel sheet. And iron loss (W _17/50 ) is shown.

As can be seen from FIG. 5, the area ratio of the secondary recrystallized particles having a maximum length of 60 mm or more in the right-angle rolling direction is 85% or more, and the average β angle of the crystal particles having a particle diameter of 2 to 20 mm is 1.5 ° to 5 °, and the particle size 2 20㎜ to area ratio of crystal grains it may be seen that in the condition of 0.2 to 10%, a low iron loss of W _17/50 ≤ 0.80W / ㎏ obtained.

Next, the present invention will be described in more detail.

Si as a metal component of a grain-oriented electrical steel sheet is important as a component which raises specific resistance and reduces eddy current loss. When the Si content is too small, the above effect cannot be sufficiently exhibited, so the Si content is made 2.0% or more. In addition, when there is too much Si content, since rolling becomes difficult, the upper limit is made into 5.0%.

It is effective to obtain one or two or more of the Group 5B elements As, Sb, and Bi as the inhibitory strengthening component in the grain-oriented electrical steel sheet material to obtain a high magnetic flux density. Further, by adding As, Sb, and Bi, the coarsening of the secondary recrystallized particles is promoted, and secondary recrystallized particles long in the rolling right direction are easily obtained. In the necessity of the lower limit of the content of these components, in order to continuously retain the normal grain growth suppression force up to the high temperature region by secondary recrystallization annealing to generate high density secondary recrystallized grains throughout the steel sheet, these components can be contained in the metal in the high temperature region as much as possible. I think it should remain. Therefore, it is considered that good magnetic properties are obtained when these components remain in a small amount in the product plate. However, if these components are excessively present in the product plate, the increase in the precipitate causes the hysteresis loss to increase. As mentioned above, the content of As, Sb and Bi in the product plate is a condition for obtaining high magnetic flux density without increasing hysteresis loss, and the lower limit of one or two or more of these is 0.0003%, and the upper limit is 0.1%. Shall be.

An object of the present invention is to stably obtain low iron loss in a grain-oriented electrical steel sheet having a large secondary recrystallized grain size and having a high degree of orientation integration. In the case of a grain-oriented electrical steel sheet having a low degree of orientation integration, iron loss can be reduced by simply miniaturizing the secondary recrystallized grain size. Therefore, in the present invention, as a prerequisite for reducing the iron loss by the uniformity of the magnetic flux density, the inclination angle θ (angle formed between the rolling direction and the [001] direction of the crystal grains) of the average crystal orientation of the steel sheet to 4 ° or less Set it. As a method for obtaining the average crystallographic orientation θ, there is a method using a measurement value of magnetic flux density B ₈ as a simple method, but is not limited thereto. When B ₈ without magnetic zone refinement is 1.94T or more, the inclination angle of the crystal orientation is 4 ° or less. The crystallographic orientation can also be measured directly by the X-ray Lauer method or the like. As a method for obtaining θ in this case, there are a method of measuring the azimuth of each secondary recrystallization, multiplying the area ratios, averaging them, and performing azimuth measurement at a grid point of about 5 to 20 mm pitch to obtain a simple average.

The limit relating to the area ratio of the secondary recrystallized particles having a maximum length of 60 mm or more in the direction perpendicular to the rolling and the limit related to the β angle of the crystal grains having a particle diameter of 2 to 20 mm are local magnetic flux densities inside the steel sheet as shown in FIG. 4. It is a condition for reducing the iron loss by making the distribution uniform. By increasing the length of the secondary recrystallized grain in the rolling perpendicular direction, the same as in the above-described Japanese Patent Laid-Open Publication No. 96-288115, the α angle (the [001] direction and the rolling direction in the rolling plane of the secondary recrystallized grain adjacent to the rolling rectangular direction) It is possible to suppress the occurrence of nonuniformity in the magnetic flux density due to the difference of the angle), and to reduce the iron loss.

The reason for the effect due to the beta angle of the crystal grains having a particle diameter of 2 to 20 mm in the range of 1.5 ° to 5.0 ° is not necessarily clear, even when the secondary recrystallized particles which occupy most of the steel sheet are elongated in the rolling direction. , it is considered that the nonuniformity of the magnetic flux density distribution is alleviated by the presence of the microparticles in which the β angle slightly deviates from surrounding crystal grains. In addition, the magnetic poles generated at the grain boundaries of the fine particles having β angles of 1.5 ° to 5.0 ° and the coarse particles having β angles close to 0 ° do not cause a decrease in magnetic flux density, and the magnetic zone can be further segmented. It is thought to be. The particle size can achieve the uniformity effect of the magnetic flux distribution and the subdividing effect of the magnetic zone at 2 mm or more, but the particle size of the fine particles is limited to the range of 2 to 20 mm, since the particle diameter is lowered when the particle size is larger than 20 mm. do. In addition, with respect to the area ratio occupied by the microparticles, the uniformity of the magnetic flux is obtained at 0.2% or more, but if it exceeds 10%, there is a possibility of causing nonuniformity of the magnetic flux distribution, so it is limited to the range of 0.2% to 10%.

When the average value of the β angle is smaller than 1.5 ° or exceeds 5.0 °, the uniformity effect of the magnetic flux distribution is not obtained, as shown in FIG. 4, so that the angle is limited to 1.5 ° to 5.0 °.

The above-mentioned microparticles having a particle diameter of 2 to 20 mm may be any of secondary recrystallized particles and refined primary recrystallized particles. In addition, artificially forming fine particles having a smaller particle diameter and irregular crystal orientation than the fine recrystallized particles having a particle diameter of 2 to 20 mm as defined above in the present invention further reduces iron loss. Combination of such techniques is advantageous.

The iron loss reduction due to the uniformity of the magnetic flux density distribution can be achieved by satisfying the above-mentioned conditions, but this effect is due to a mechanism different from the iron loss reduction due to the refinement of the conventional magnetic zone. The losses are synergistically reduced and can exhibit low iron losses that are not conventional. Therefore, in the present invention, in order to reduce the iron loss by magnetic zone subdivision, an angle of 30 ° or less with the rolling right direction of the steel sheet is formed, and the linear groove is 10 μm or more in depth, 20 μm to 300 μm in width, and 1 mm or more in interval. A group of linear grooves made is provided on the steel plate surface.

Regarding the depth and width of the linear grooves, when the depth is less than 10 μm and the width is less than 20 μm, since sufficient magnetic pole generation amount is not obtained and the magnetic zone is not sufficiently subdivided, the depth is 10 μm or more and the width is 20 μm or less. Shall be. Regarding the upper limit of the width of the groove, when the width of the groove exceeds 300 µm, the magnetic permeability is deteriorated, so the width is limited to 300 µm or less. The groove spacing is set at an interval of 1 mm or more because the magnetic permeability is deteriorated when the spacing is less than 1 mm. The upper limit is preferably 30 mm from the viewpoint of the effect of magnetic zone subdivision. Regarding the angle of the linear groove, when the angle formed with the direction orthogonal to the rolling direction exceeds 30 °, the magnetic zone subdividing effect is reduced, so it is limited to 30 ° or less.

The method disclosed in Japanese Patent Laid-Open No. 84-197520 was used to form a groove in the steel sheet before the finish annealing. In the case where the grooves are formed in the steel sheet after finish annealing, a stress relief annealing was performed after applying a load to the steel sheet to form the grooves. This method is disclosed in Japanese Patent Laid-Open No. 86-117218.

In the present invention, the absence of forsterite coating on the surface of the steel sheet is preferable to reduce the iron loss by reducing the hysteresis loss.

If forsterite is present on the surface of the steel sheet, the hysteresis loss increases due to forsterite sticking to the metal interface. Therefore, hysteresis loss is reduced by not forming a forsterite film on the metal surface or by removing the formed forsterite film. Iron loss can be further reduced by firing the tension-imparting coating. Iron loss reduction by the uniformity of the magnetic flux density of the present invention is a method of reducing iron loss by a mechanism different from that of iron loss due to the reduction of hysteresis loss. Therefore, in the grain-oriented electrical steel sheet of the present invention, when there is no forsterite coating on the surface of the steel sheet, it is possible to obtain lower iron loss than the iron loss material by the manufacturing method which does not have a conventional forsterite coating. A better low iron loss product can be obtained by performing a polishing treatment or a grain direction-intensifying treatment as disclosed in Japanese Patent Laid-Open No. 94-37694 on a material having no forsterite coating on the steel sheet surface. Since it can obtain, combined use of such a technique is also preferable.

The material component for producing the grain-oriented electrical steel sheet product of the present invention is not particularly limited to those other than Si, As, Sb, and Bi, but C, Mn, S, Se, Al, N, Mo, Cu, P, Sn, etc. can be added.

C is a component that is useful for improving hot rolled tissue using transformation, and it requires 0.005% or more, but it is not preferable because C causes decarburization failure during decarburization annealing.

Mn not only contributes effectively to the improvement of hot workability of steel, but when S or Se is mixed, it forms a precipitate, such as MnS and MnSe, and serves as an inhibitor, so it is preferably in the range of 0.03 to 0.20%. Do.

Moreover, addition of Al, N, S, and Se to the steel of the said composition as an inhibitory reinforcement component (component which functions as an inhibitor) is effective in obtaining a favorable magnetic characteristic. By containing Al and N in steel, it precipitates as AlN, which acts as an inhibitor and has an effect of suppressing normal grain growth. At this time, Al is preferably contained in the range of 0.010 to 0.050% as soluble Al, and N is preferably about 0.005 to 0.015%.

Similarly, S and Se also precipitate as MnS, MnSe and the like to function as inhibitors. Suitable contents are S and Se of 0.005 to 0.020% and 0.01 to 0.04%, respectively.

In addition to these, the following components may be added to reinforce the inhibitory power. That is, it is effective to add Mo, Cu, P, Sn and the like.

Cu, like Mn, is a component that combines with Se and S to form a precipitate and enhances the inhibitory force, and its effect is remarkable in the range of 0.01 to 0.30%.

P, like Sb, is a component that segregates at grain boundaries to increase the inhibitory force. If P is less than 0.010%, P is insufficient. On the other hand, P is 0.010 to 0.030% because it destabilizes magnetic properties and surface properties. It is preferable.

Mo has an effect which directs the nucleus of a secondary recrystallized particle to a goth orientation, and it is preferable to add in 0.005 to 0.20% of range.

Sn, like Sb, segregates at grain boundaries and has an effect of strengthening the inhibitory force, and the effect is remarkable in the range of 0.010 to 0.10%.

In each of the above components, C, S, Se, N, Al, etc. are removed after completing their respective functions, C is mainly removed in the decarburization annealing and S, Se, N, Al, P, etc. in the late finishing annealing As it is removed from the purified annealing, only a small amount of residue remains as impurities in the metal of the product.

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

Slab heating temperature over 1250 ℃

In the manufacturing process of the grain-oriented electrical steel sheet of the present invention, the inhibitor component of the precipitation dispersion type in the steel is completely solidified at the time of slab heating, and in the subsequent hot rolling process, MnSe, MnS, Cu _2-x Se, Cu _2-x S, AlN It is important to obtain fine dispersions of inhibitors and the like. If this condition is not satisfied, during the final finish annealing, before the normal grain growth inhibitory force such as As, Sb, Bi, or the like is expressed, coarsening of primary particles occurs and the magnetic properties deteriorate. Therefore, a slab heating temperature of 1250 ° C. or higher is required.

Hot rolling temperature above 900 ℃

When the temperature of the slab or hot rolled sheet decreases excessively from the end of slab heating to the end of finish hot rolling, the inhibitor in steel precipitates in a crude state, and normal grain growth inhibitory ability such as As, Sb, Bi is expressed during the final finish annealing. Prior to this, coarsening of the primary particles takes place and the magnetic properties deteriorate. Therefore, 900 degreeC or more is required as hot rolling temperature.

Hot rolled sheet annealing temperature 800 to 1100 ℃ and annealing time 20 to 300 seconds

Hot-rolled sheet annealing is an important process because it promotes homogenization of hot-rolled sheet structure and suppresses precipitation of inhibitors such as AlN. If the hot rolled sheet annealing temperature of 800 ° C. and time 20 seconds is not satisfied, the adjustment effect of such a tissue and inhibitor is insufficient. If the temperature exceeds 1100 ° C. and time of 200 seconds, the inhibitor becomes coarse and the magnetic properties become unstable. Shall be in the range of.

Intermediate annealing temperature 800 to 1150 ° C. and annealing time 20 to 300 seconds

The intermediate annealing is mainly aimed at adjusting the structure by recrystallization after pre-cold rolling, controlling the precipitation of carbide in steel, adjusting the dispersion state of the precipitation inhibitor, and the like. In the present invention, as described above, it is necessary to harmonize the strength of the precipitation inhibitor with the inhibitory action strengthening action by As, Sb, Bi or the like, and therefore, it is necessary to appropriately control the intermediate annealing temperature and the annealing time. When the intermediate annealing temperature is 800 ° C. or less and the time is 20 seconds or less, the strength of the precipitation inhibitor is so strong that a large amount of secondary particles are deviated from the crystal orientation. On the other hand, when it exceeds 1150 degreeC and when it exceeds 300 second, a precipitation inhibitor deteriorates and secondary recrystallization is bad. Therefore, in the present invention, the intermediate annealing temperature was limited to the range of 800 to 1150 ° C and the time was limited to the range of 20 to 30 seconds.

Cold rolling temperature above 150 ℃ and roll exit tension 25 to 45kg / mm ² (At least 1 pass or more)

The gist of the present invention is to suppress the nonuniformity of magnetic flux density inside the steel sheet caused by the refining of the secondary particles to achieve low iron loss. For this purpose, the width of the secondary particles in the rolling perpendicular direction is 60 mm or more. It is necessary to make predetermined fine particles exist in a steel plate in a predetermined area ratio.

The cold rolling temperature and the suppression of the roll exit tension during rolling are necessary conditions for the production of fine particles. When the roll exit tension does not satisfy 25 kg / mm ² , the area ratio of particles having a particle diameter of 2 to 20 mm is increased. Less than 0.2% or the average β angle of the microparticles does not satisfy 1.5 ° occurs. In addition, when the roll exit tension exceeds 45 kg / mm ² , the area ratio of such fine particles exceeds 10%, and the average β angle of the microparticles exceeds 5.0 °. Further, even when the rolling tension is in the range of 25 to 45 kg / mm ^{2, when} the rolling temperature does not satisfy 150 ° C., fine particles are hardly produced due to the change of the texture. Therefore, in order to satisfy the conditions relating to the fine particles of the present invention, the cold rolling must have a maximum temperature of 150 ° C. or more and a roll exit tension of 25 to 45 kg / mm ² (at least one pass or more).

Shot blast treatment to decarburizing annealing plate

In order to produce the said fine particle, in addition to controlling rolling tension suitably, the method of applying a short stress to a decarburizing annealing board and applying a micro stress is effective. By colliding the micro-rigid bodies with the decarburized annealing plate, the steel sheet is locally stressed to generate microparticles at the beginning of the finish annealing to produce microparticles having a particle diameter of 2 to 20 mm as defined in claim 1. You can.

Finish annealing 1130 ℃ and 5 hours or more

As a condition for achieving low iron loss by removing impurities such as Al, N, S, Se, etc. contained in the steel sheet and improving hysteresis loss, in finish annealing, the temperature of 1130 ° C. and a time of 5 hours or more after the completion of secondary recrystallization need.

Example 1

C 0.065%, Si 3.20%, Mn 0.065%, Se 0.025%, Al 0.025%, N 0.0090%, Mo 0.025%, Sb 0 to 0.05%, Bi 0 to 0.05% and As 0 to 0.05% 20 silicon steel slabs (symbols 1A to 1T) mainly composed of Fe were heated induction at a temperature of 1450 ° C., and then hot rolled to obtain a hot rolled sheet having a thickness of 2.4 mm. The hot rolled sheet was annealed at 1050 ° C. for 40 seconds in nitrogen, followed by primary cold rolling to obtain a cold rolled sheet having a thickness of 1.7 mm. Subsequently, after performing intermediate annealing (1000 DEG C. for 2 minutes in wet hydrogen), secondary cold rolling was carried out to a final cold rolled sheet thickness of 0.23 mm. The rolling tension in the roll exit side of the last 5 passes of secondary cold rolling was 20-50 kg / mm <^2> , and the rolling temperature was 50-250 degreeC in the top part.

Subsequently, after decarburization annealing was performed at 850 ° C for 2 minutes, an annealing separator mainly containing MgO was applied, and then wound in a coil form, and finally finished annealing was performed at a temperature of 1200 ° C. In this final finishing annealing, secondary recrystallization nucleation treatment was performed by temperature correction at 850 ° C for 20 hours. After the final finishing annealing was completed, the steel sheet was subjected to an insulating coating composed mainly of colloidal silica and magnesium phosphate.

An epstein test piece was taken from each steel sheet obtained as described above, and the iron loss (W _17/50 ) and the magnetic flux density (B ₈ ) were measured. In addition, the specimens were taken over the entire width of the steel strip, subjected to large-scale etching (macro-etching) to reveal secondary recrystallized particles, and at the same time measuring the shape of each secondary recrystallized particle by image analysis. The crystal orientation of each secondary recrystallized particle was measured by the Lauer method. In addition, the metal component of the product plate was subjected to wet analysis.

The results of the investigation of the metal components, secondary recrystallized grain morphology, crystal orientation and magnetic properties (magnetic flux density B ₈ and iron loss W _17/50 ) of the _grain- oriented electrical steel sheet product obtained above are summarized in Table 1 below:

TABLE 1

As can be seen from Table 1, it can be seen that the embodiments of the present invention all have very excellent magnetic properties, despite being a grain-oriented electrical steel sheet which has not undergone magnetic zone refinement.

Example 2

15 silicon steel slabs containing C 0.067%, Si 3.30%, Mn 0.068%, Se 0.023%, Al 0.022%, N 0.0085%, Mo 0.020%, Sb 0.05% and Bi 0.04%, the remainder mainly consisting of Fe (Symbols 2A to 2P) were inductively heated to a temperature of 1450 ° C, followed by hot rolling to form a hot rolled plate having a plate thickness of 2.4 mm. The hot rolled sheet was annealed at 1050 ° C. for 40 seconds in nitrogen, followed by primary cold rolling to obtain a cold rolled sheet having a thickness of 1.7 mm. Subsequently, after performing intermediate annealing (1000 DEG C. for 2 minutes in wet hydrogen), secondary cold rolling was carried out to a final cold rolled sheet thickness of 0.23 mm. End 5 of the secondary cold rolling pass and is a steel sheet temperature of 250 ℃, 20㎏ / ㎜ a rolling tension of the final path 5 ² (symbol 2A), 40㎏ / ㎜ ² (sign 2B to 2O), 50㎏ / ㎜ ² ( It was set as three levels of symbol 2P).

Subsequently, a linear groove was formed on the surface of the steel sheet (single side) by resist etching to extend in a direction perpendicular to the rolling perpendicular direction. That is, for cold rolled coils manufactured from symbols 2C, 2D, 2E, and 2F, the groove depth is 5 to 25 µm, the groove width is 50 µm, and the groove spacing is 4 mm, and the groove depth is 12 µm for symbols 2G, 2H, 2I, and 2J. And groove widths of 10 to 400 µm and groove intervals of 5 mm, and for symbols 2K, 2L, 2M, 2N, 2O and 2P, groove depths of 18 µm, groove widths of 100 µm and groove intervals of 0.5 to 5 mm. Incidentally, no groove was formed in the symbols 2A and 2B.

Subsequently, after decarburization annealing was performed at 850 ° C for 2 minutes, an annealing separator mainly containing MgO was applied, and then wound in a coil form, and finally finished annealing was performed at a temperature of 1200 ° C. In this final finishing annealing, secondary recrystallization nucleation treatment was performed by temperature correction at 850 ° C for 20 hours. After the final finishing annealing was completed, the steel sheet was subjected to an insulating coating composed mainly of colloidal silica and magnesium phosphate.

An Epstein test piece was sampled from each steel sheet obtained as described above, and the iron loss (W _17/50 ) and the magnetic flux density (B ₈ ) were measured. Further, the specimens were taken over the entire width of the steel sheet strip, subjected to large-scale etching to reveal secondary recrystallized particles, the shape of each secondary recrystallized particles by image analysis, and the respective secondary by the Lauer method. The crystal orientation of the recrystallized particles was measured.

Moreover, as a result of wet analysis of the metal component of the product plate, 0.04% of Sb and 0.02% of Bi remained in the product plate metal.

The results of the linear groove shape and secondary recrystallized grain morphology, crystal orientation and magnetic properties (magnetic flux density B ₈ , iron loss W _17/50 ) of the _grain- oriented electrical steel sheet product obtained above are summarized in Table 2 below:

TABLE 2

As can be seen from Table 2, the examples of the present invention all have very excellent magnetic properties, and also test specimens having groups of linear grooves having linear grooves spaced at least 1 mm apart from each other (2D, 2E, 2F, 2H, 2L, 2N and 2O) particularly low iron losses were obtained.

Example 3

C 0.065%, Si 3.20%, Mn 0.065%, Se 0.025%, Al 0.025%, N 0.0090%, Mo 0.025%, Sb 0 to 0.05%, Bi 0 to 0.05% and As 0 to 0.05% 15 silicon steel slabs (symbols 3A to 3P) mainly composed of Fe were induction heated to a temperature of 1450 ° C, and then hot-rolled to obtain a hot rolled sheet having a plate thickness of 2.4 mm. The hot rolled sheet was annealed at 1050 ° C. for 40 seconds in nitrogen, followed by primary cold rolling to obtain a cold rolled sheet having a thickness of 1.7 mm. Subsequently, after performing intermediate annealing (1000 DEG C. for 2 minutes in wet hydrogen), secondary cold rolling was carried out to a final cold rolled sheet thickness of 0.23 mm. The final four passes of secondary cold rolling were made into steel plate temperature 200 degreeC, and the rolling tension | pulling was made into 40 kg / mm <^2> . Subsequently, decarburization annealing was performed at 850 ° C for 2 minutes.

Thereafter, decarburization annealing plates of symbols 3B, 3D, 3F, 3H, 3J, 3L, 3O and 3P were subjected to stress introduction treatment by shot blasting. Further, in order to artificially generate fine particles having a particle diameter of less than 2 mm, the coil of symbol 3P was discharged in a lattice form at a pitch of 10 mm in the rolling direction and the rolling perpendicular direction, respectively. The remaining steel sheet strips were not subjected to shot blasting. Subsequently, after applying an annealing separator which contains MgO as a main component, it wound up in coil form and performed the final finishing annealing at the temperature of 1200 degreeC. In the final finishing annealing, secondary recrystallization nucleation treatment was performed by temperature correction at 850 ° C for 20 hours. Subsequently, after removing a forsterite film from the steel plate after finishing annealing by sulfuric acid washing, the surface was polished by electrolysis, and the tensioning insulation coating of phosphoric acid system was then performed.

An Epstein test piece was sampled from each steel sheet obtained as described above, and the iron loss (W _17/50 ) and the magnetic flux density (B ₈ ) were measured. Further, the specimens were taken over the entire width of the steel sheet strip, subjected to large-scale etching to reveal secondary recrystallized particles, the shape of each secondary recrystallized particles by image analysis, and the respective secondary by the Lauer method. The crystal orientation of the recrystallized particles was measured. In addition, the metal component of the product plate was subjected to wet analysis.

The results of the investigation of the metal components, secondary recrystallized grain morphology, crystal orientation and magnetic properties (magnetic flux density B ₈ and iron loss W _17/50 ) of the _grain- oriented electrical steel sheet product obtained above are summarized in Table 3 below:

TABLE 3

As can be seen from Table 3, it can be seen that the embodiments of the present invention all have very excellent magnetic properties.

Example 4

Silicon containing C 0.066%, Si 3.40%, Mn 0.07%, Se 0.025%, Al 0.024%, N 0.0090%, Mo 0.025%, Mo 0.025%, As 0.05% and Bi 0.04%, the remainder mainly consisting of Fe Eight steel slabs (symbols 4A to 4H) were inductively heated to a temperature of 1450 ° C, followed by hot rolling to form a hot rolled plate having a plate thickness of 2.4 mm. The hot rolled sheet was annealed at 1050 ° C. for 40 seconds in nitrogen, followed by primary cold rolling to obtain a cold rolled sheet having a thickness of 1.7 mm. Subsequently, intermediate annealing (1000 DEG C. for 2 minutes and wet hydrogen) was performed, followed by secondary cold rolling to a final cold rolled sheet thickness of 0.23 mm. Aging treatment was performed at 350 ° C for 3 minutes before the final five passes of secondary cold rolling, and the steel sheet temperature of the final four passes of secondary cold rolling was set to 200 ° C. Subsequently, for symbols 4E, 4F, 4G, and 4H, a linear groove having a depth of 25 µm, a width of 100 µm, and a spacing of 1.5 mm, which extends in the direction of 85 ° with the rolling direction on the steel sheet surface (one surface) by resist etching. Formed. No other grooves were formed in the other steel strip.

Subsequently, after decarburization annealing was performed at 850 ° C. for 2 minutes, symbols 4B, 4D, 4F, and 4H were subjected to stress introduction treatment by shot blasting. Thereafter, annealing separators containing Al ₂ O ₃ as a main component were applied to the symbols 4C, 4D, 4G, and 4H. In addition, about symbol 4A, 4B, 4E, and 4F, the annealing separator which has MgO as a main component was apply | coated. The strip of steel sheet after application of the annealing separator was wound in a coil form and subjected to final finish annealing at a temperature of 1200 ° C. In this final finishing annealing, secondary recrystallization nucleation treatment was performed by temperature correction at 850 ° C for 20 hours.

Forsterite was not formed in the symbols 4C, 4D, 4G and 4H coated with an annealing separator mainly composed of Al ₂ O ₃ , and the metal surface was smoother than when forsterite was formed.

The steel plate after the final finishing annealing was given a phosphoric acid-tensioned insulating coating.

An Epstein test piece was sampled from each steel sheet obtained as described above, and the iron loss (W _17/50 ) and the magnetic flux density (B ₈ ) were measured. Further, the specimens were taken over the entire width of the steel sheet strip, subjected to large-scale etching to reveal secondary recrystallized particles, the shape of each secondary recrystallized particles by image analysis, and the respective secondary by the Lauer method. The crystal orientation of the recrystallized particles was measured. Further, as a result of wet analysis of the metal component of the product plate, As 0.04% and Bi 0.01% remained in the product plate metal.

The results of the investigation of the linear groove and secondary recrystallized grain morphology, crystal orientation and magnetic properties (magnetic flux density B ₈ and iron loss W _17/50 ) of the _grain- oriented electrical steel sheet product are summarized in Table 4 below:

TABLE 4

As can be seen from Table 4, the embodiments of the present invention all have very excellent magnetic properties. In particular, among samples 4A to 4D without linear grooves, sample 4D without forsterite coating showed particularly low iron loss. In the case of linear grooves (4E to 4H), Sample 4H without forsterite coating showed particularly low iron loss.

In the present invention, the average orientation of the secondary recrystallized particles is specified, and the area ratio of the secondary recrystallization having a length of 60 mm or more in the rectangular direction of rolling, and the area ratio of crystal grains having a particle diameter of 2 to 20 mm and the orientation in the fine recrystallization are specified. It relates to a grain-oriented electrical steel sheet. In the high magnetic flux density (B ₈ ≥ 1.96T) oriented electrical steel sheet, which has conventionally been difficult to stably obtain low iron loss without magnetic zone refinement, stable low iron loss can be obtained without performing magnetic zone refinement. In addition, an electromagnetic steel sheet having a very low iron loss can be obtained by magnetic zone segmentation, smoothing the surface of the steel sheet, or a combination thereof by a method of forming a groove in the steel sheet surface.

1 is a graph showing the relationship between magnetic flux density (B ₈ ) and iron loss (W _17/50 ).

2 is a graph showing the relationship between the average β angle and iron loss (W _17/50 ).

3 is a graph showing the relationship between the average value of the maximum lengths in the perpendicular direction of rolling of secondary recrystallized particles (particle diameter: 20 mm or more) and the nonuniformity of the local magnetic flux density of the steel plate surface.

Fig. 4 shows the relation between the ratio of secondary recrystallized particles having a maximum length of 60 mm or more in the right-angled rolling direction with the average β angle of the crystal grains having a particle diameter of 2 to 20 mm in the whole steel sheet and the nonuniformity of the local magnetic flux density on the steel sheet. A graph representing.

Fig. 5 shows the ratio of secondary recrystallized particles having a maximum length of 60 mm or more in the rolling right direction in the whole steel sheet, the average β angle of crystal grains having a particle diameter of 2 to 20 mm, and the proportion of crystal grains having a particle diameter of 2 to 20 mm in the whole steel sheet. And a graph showing the relationship between iron loss (W _17/50 ).

Claims (10)

Inclination angle from the rolling direction of the crystal orientation [001] of the secondary recrystallized particles containing Si at 2.0 to 5.0% by mass, containing at least one of As, Sb and Bi at 0.0003 to 0.1% by mass in total; shearing angle) is 4 ° or less, Secondary recrystallized particles having a maximum length of 60 mm or more in the perpendicular direction of rolling direction occupy 85% or more as an area ratio with respect to the steel sheet area, Crystal grains having a particle diameter in the range of 2 mm to 20 mm occupy a range of 0.2% to 10% by area ratio with respect to the steel plate area, The average value (area average value) of the angle which the crystal orientation [001] of the crystal grain whose particle diameter is in the range of 2 mm-20 mm and a steel plate surface is 1.5 to 5.0 degrees, Grain-oriented electrical steel sheet with excellent magnetic properties. The method of claim 1, The grain-oriented electrical steel sheet which forms an angle of 30 degrees or less with a rolling perpendicular | vertical direction, and has a linear groove which is 10 micrometers or more in depth, and 20 micrometers-300 micrometers in width | variety, and is grouped on the steel plate surface at intervals of 1 mm or more. The method according to claim 1 or 2, A grain-oriented electrical steel sheet in which a finished annealing steel sheet has a smooth metal surface. The method of claim 1, The steel sheet surface has a nonuniformity r of the local magnetic flux, the nonuniformity r of the local magnetic flux measured by the microneedle method is 0.15 or less, and the nonuniformity is a oriented electrical steel sheet defined by the following equation: Equation 2 Where N is the number of probes used to measure non-uniformity, B _i ^local is local magnetic flux density, B _m is the magnetic flux density of the whole steel plate. (a) heating the silicon containing steel slab to 1250 ° C. or higher and then performing hot rolling in a temperature range of 900 ° C. or higher to form a hot rolled sheet; (b) annealing the hot rolled sheet at 800 to 1100 ° C. for 20 to 300 seconds; (c) At least one pass of the two or more passes which constitute cold rolling having an intermediate annealing process at 800 to 1150 ° C. for 20 to 300 seconds at 800 to 1150 ° C. is at least 150 ° C. A process of cold rolling with a steel sheet tension at a roll exit side of 25 to 45 kg / mm ² ; (d) subjecting the cold rolled sheet to decarburization annealing at 800 to 900 ° C. for 30 to 200 seconds; (e) applying an annealing separator to the decarburized annealed steel sheet, and then performing a final finish annealing for at least 5 hours at a maximum temperature of 1130 ° C. or higher; And (f) coating the insulating film on the final annealed steel sheet A method for producing a grain-oriented electrical steel sheet comprising 2.0 to 5.0% by mass of Si, and containing one or two or more of As, Sb and Bi in a total of 0.0003 to 0.1% by mass. (a) heating the silicon steel slab to 1250 ° C. or higher and then performing hot rolling in a temperature range of 900 ° C. or higher to make a hot rolled sheet; (b) annealing the hot rolled sheet at 800 to 1100 ° C. for 20 to 300 seconds; (c) a step of subjecting the hot rolled sheet to cold rolling having a steel sheet temperature of 150 DEG C or more, at least one pass of two or more passes constituting cold rolling having an intermediate annealing process at 800 to 1150 DEG C for 20 to 300 seconds; (d) decarburizing annealing the cold rolled sheet at 800 to 900 ° C. for 30 to 200 seconds; (e) subjecting the surface of the decarburized annealed steel sheet to a shot blast, and then applying an annealing separator; (f) giving a final finish annealing to the steel sheet at a maximum temperature of 1130 ° C. or more for 5 hours or more; And (g) Process of coating insulating film on the final annealed steel sheet A method for producing a grain-oriented electrical steel sheet comprising 2.0 to 5.0% by mass of Si, and containing one or two or more of As, Sb and Bi in a total of 0.0003 to 0.1% by mass. The method of claim 5, After cold rolling, the cold rolled sheet before the primary recrystallization annealing is formed at an angle of 30 ° or less with the perpendicular direction of rolling, and a linear groove having a depth of 10 μm or more and a width of 20 μm to 300 μm spaced apart from each other by 1 mm or more. The manufacturing method of the grain-oriented electrical steel sheet further including the process of providing to a steel plate surface as a group. The method of claim 6, After cold rolling, the cold rolled sheet before the primary recrystallization annealing is formed at an angle of 30 ° or less with the perpendicular direction of rolling, and a linear groove having a depth of 10 μm or more and a width of 20 μm to 300 μm spaced apart from each other by 1 mm or more. The manufacturing method of the grain-oriented electrical steel sheet further including the process of providing to a steel plate surface as a group. The method of claim 5, The manufacturing method of the grain-oriented electrical steel sheet which uses the annealing separator which has alumina as a main component in the application | coating process of an annealing separator. The method of claim 6, The manufacturing method of the grain-oriented electrical steel sheet which uses the annealing separator which has alumina as a main component in the application | coating process of an annealing separator.