JP2021025128A - Grain oriented electrical steel sheet - Google Patents

Abstract

To provide a grain oriented electrical steel sheet having a linear groove formed on the surface of the steel sheet and excellent in threading performance.SOLUTION: The grain oriented electrical steel sheet is provided in which a groove is formed in the surface thereof, the groove extending in a direction intersecting a rolling direction and having a depth in a direction being a sheet thickness direction, the grain oriented electrical steel sheet has fine structures in the ranges of at least 10 mm from both ends in the width direction to the width center direction of the steel sheet. The fine structure in the range of at least 10 mm to the width center direction from both ends has an average grain size of 5 mm or less, and the existence frequency of a crystal grain having 10° or less of a deviation angle from a Goss orientation is 50% or less.SELECTED DRAWING: Figure 3

Description

The present invention relates to a grain-oriented electrical steel sheet, and more particularly to a grain-oriented electrical steel sheet having linear grooves formed on the surface of the steel sheet and having excellent sheet-passability.

Grain-oriented electrical steel sheets with excellent magnetic characteristics are mainly used as materials for iron cores of transformers, and in order to improve the energy use efficiency of transformers, it is required to reduce the iron loss. As a method for reducing the iron loss of the grain-oriented electrical steel sheet, a method of highly aligning the secondary recrystallized grains in the steel sheet in the Goss direction (sharpening) and an increase in the coating tension of the tension coating formed on the surface of the steel sheet. In addition to the method and thinning of the steel sheet, a method of surface processing of the steel sheet is known.

The iron loss reduction technology by surface processing of a steel sheet is to introduce non-uniform strain to the surface of the steel sheet by a physical method and subdivide the width of the magnetic domain to reduce the iron loss. , There is a method (projection roll method) of forming a groove on the surface of a steel sheet that has been finish-annealed by using a tooth mold roll. According to this method, the magnetic domain on the surface of the steel sheet can be subdivided by forming the groove, and the iron loss of the steel sheet can be reduced. Further, it is known that even when heat treatment such as strain removal annealing is performed after groove formation, the introduced groove does not disappear, so that the iron loss reduction effect is maintained. However, this method is manufactured by heating the roll or applying a lubricant to suppress the wear of the tooth mold roll, in addition to the fact that the groove shape tends to be uneven due to the heavy wear of the tooth mold roll. There was a problem that the cost increased.

Therefore, a method of forming a linear groove on the surface of a steel sheet by etching has been developed without using a mechanical means such as a tooth mold roll. Specifically, after applying a resist ink in a pattern on the surface of the steel sheet before the forsterite film is formed, the portion to which the resist ink is not applied is selectively etched by a method such as electrolytic etching. By doing so, grooves are formed on the surface of the steel sheet. In this method, since there is almost no mechanical wear of the device, maintenance is easier than in the method using a tooth mold roll.

By the way, it is known that a grain-oriented electrical steel sheet in which such a linear groove is formed is inferior in sheet-passability to a grain-oriented electrical steel sheet in which the linear groove is not formed. This is due to the difference in plate thickness between the groove-formed portion and the groove-unformed portion. When the steel sheet is discharged from the coil and passed through, tension is applied to the steel sheet, but if the tension is set according to the thickness of the non-grooved portion, excessive stress is applied to the thin portion of the groove-formed portion and the steel plate breaks. Risk increases. On the other hand, if the tension is set according to the groove-formed portion, the tension becomes insufficient in the groove-formed portion, which causes meandering and poor shape and deteriorates the plate-passability.

As a means for improving the plate-passability, it is effective to prevent deterioration of the coil shape and reduce the tension required for shape correction and the like. As a technique for preventing deterioration of the coil shape, a technique for suppressing lateral strain deformation (buckling deformation due to its own weight) at the lower end of the coil in contact with the coil cradle during finish annealing is disclosed.

For example, in Patent Document 1 and Patent Document 2, in order to suppress lateral strain deformation, a processing deformation strain is applied by applying a fine granulating agent to the lower end of the coil or by using a roll with protrusions or the like. A technique is disclosed in which the crystal at the lower end of the coil is intentionally made into fine particles to change the mechanical strength of the lower end of the coil. When this technique is applied, the mechanical strength of the lower end of the coil changes, that portion becomes less likely to be deformed, and lateral distortion is suppressed by a certain amount.

Further, in Patent Documents 3 to 6, in order to suppress lateral strain deformation, secondary recrystallization of a strip-shaped portion having a constant width from the lower end of the coil is promoted, the crystal grain size is increased at an early stage of finish annealing, and the temperature is high. Methods for improving strength are disclosed. Further, Patent Document 7 discloses a technique for introducing a melt resolidification portion that is easily deformed at the lower end portion of the coil by laser irradiation. When these techniques are applied, lateral distortion is suppressed to some extent, and the tension required for feeding out the steel sheet from the coil and passing the sheet is reduced, but in particular, the sheet-passability of the grooved grain-oriented electrical steel sheet is improved. Was not enough.

Japanese Unexamined Patent Publication No. 63-100131 JP-A-64-42530 Japanese Unexamined Patent Publication No. 2-97622 Japanese Unexamined Patent Publication No. 3-177518 Japanese Unexamined Patent Publication No. 2000-38616 Japanese Unexamined Patent Publication No. 2001-323322 International Publication No. 2014-080763

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a grain-oriented electrical steel sheet having linear grooves formed on the surface of the steel sheet and having excellent sheet-passability. To do.

As a result of investigating measures for improving the passability of grain-oriented electrical steel sheets having grooves formed on the surface, the present inventors have obtained the following findings. In the present specification, unless otherwise specified, the "end" of the steel plate or coil shall mean the end portion of the steel plate or coil in the width direction.

(1) Fracture troubles frequently occur after finish annealing (after the secondary recrystallization structure is formed) in the manufacturing process of grain-oriented electrical steel sheets, so that the sheet passability of the steel sheets after finish annealing is improved. This is very important.

(2) Since fractures often start from the ends of the steel sheet, increasing the mechanical strength of both ends of the steel sheet is particularly effective in improving the passability of the steel sheet, from both ends of the steel sheet toward the center of the width. It is important to refine the structure in the range of at least 10 mm to an average crystal grain size of 5 mm or less. However, even if the crystal grains are made finer, if the orientations of the crystal grains are almost the same, the slip system is the same, and only the yield strength in a certain direction is increased. Therefore, it is preferable that the crystal orientations are as random as possible. Therefore, it is necessary to set the abundance frequency of crystal grains having a deviation (deviation angle) of at least 10 ° or less from the Goss orientation to 50% or less.

(3) As a means for increasing the mechanical strength of both ends of the steel sheet, which is effective for improving the passability of the steel sheet, it is effective to have non-grooved portions having no grooves formed at both ends of the steel sheet. In order to improve the plate-passability more effectively, it is preferable that no groove is formed at least in the range from both ends of the steel sheet to 1 mm in the width center direction.

(4) Since the starting point of fracture can be other than both ends of the steel sheet, it occurs when the grooves formed on the surface are continuously extended in the direction intersecting the rolling direction and the grooves are formed discontinuously. It is also effective to improve the plate-passability by preventing the area where the plate thickness is thin due to the wrapped portion of the groove, which is easy to increase.

The present invention has been made based on the above findings and has the following configurations.
[1] A grain-oriented electrical steel sheet in which a groove extending in a direction intersecting the rolling direction and having a groove depth direction in the plate thickness direction is formed on the surface.
The structure in the range from both ends in the width direction to at least 10 mm in the width center direction of the steel sheet is miniaturized.
In the finely divided structure from both ends to 10 mm in the center width direction, the abundance frequency of crystal grains having an average crystal grain size of 5 mm or less and a deviation angle from the Goss direction of 10 ° or less is 50% or less. A directional electromagnetic steel plate.
[2] The grain-oriented electrical steel sheet according to [1], wherein no groove is formed in the range from both ends of the steel sheet surface in the width direction to at least 1 mm in the width center direction.
[3] The grain-oriented electrical steel sheet according to [1] or [2], wherein the grooves formed on the surface of the steel sheet extend continuously in a direction intersecting the rolling direction.

According to the present invention, it is possible to provide a grain-oriented electrical steel sheet having linear grooves formed on the surface of the steel sheet and having excellent sheet-passability.
According to the present invention, the mechanical strength of the directional electromagnetic steel plate coil in which the groove is formed on the surface of the steel plate is significantly improved. Therefore, when the steel plate is discharged from the coil and passed through the coil, the plate passing property is improved. Productivity reduction due to breakage is prevented.

FIG. 1 is a graph showing the relationship between the steel plate (structure) and the fracture-generated tension ratio after each process. FIG. 2 is a graph showing the relationship between the grinding width from the end of the steel sheet and the fracture-generated tension ratio for the steel sheet after finish annealing (secondary recrystallization structure) and after tension coating formation (secondary recrystallization structure). .. FIG. 3 is a graph showing the relationship between the average crystal grain size of the structure of the end region of the steel sheet and the fracture-occurring tension ratio. FIG. 4 is a graph showing the relationship between the abundance frequency of secondary recrystallized grains and the fracture occurrence tension ratio in the steel sheet structure in the range of 10 mm from the end of the steel sheet to the center of the width. FIG. 5 is a graph showing the relationship between the width of the non-grooved portion from both ends of the steel plate in the width center direction and the fracture-occurring tension ratio. FIG. 6 is a diagram for explaining the formation pattern of the linear groove when the linear groove is formed by using a plurality of laser irradiation devices. FIG. 7 is an enlarged view of the lap portion in the lower part of FIG. 6 (c). FIG. 8 is a graph showing the relationship between the lap allowance and the fracture occurrence tension ratio. FIG. 9 is an explanatory diagram illustrating a tissue observation area. FIG. 10 is an explanatory diagram illustrating a method of setting a secondary recrystallized structure as a reference when determining a region of a fine crystal structure. FIG. 11 is an explanatory diagram illustrating a method of measuring the number of intersections of grain boundaries per unit distance in the rolling direction at each pitch. FIG. 12 is an explanatory diagram illustrating a method for determining a region of a fine crystal structure.

<Experiment 1>
First, the experimental results that clarified the relationship between the structure of the end of the steel sheet and the mechanical strength will be described. A cold rolled plate with a plate thickness of 0.23 mm and a plate width of 800 mm coated with resist ink on the surface is scanned with a laser in a direction orthogonal to the rolling direction, and the laser is irradiated at intervals of 5 mm in the rolling direction to resist. The ink was peeled off. In this method, the resist ink in the portion irradiated with the laser is peeled off (removed). Laser irradiation is performed by installing two single-mode fiber lasers in the width direction of the steel sheet, using a galvano scanner method with a laser irradiation energy of 25 J / m and a laser scanning width of 400 mm, from one end to the other end in the width direction of the steel sheet. The resist ink was continuously completely peeled off.

Next, the resist-peeled sample is subjected to electrolytic etching treatment to form a groove having a depth (plate thickness direction) of 20 μm and a width of 100 μm on the surface of the steel sheet, 820 ° C. × 120 sec, N ₂ : H ₂ = 40: 60. Decarburization annealing was carried out at a dew point of 50 ° C. (volume ratio). Then, both ends of the steel sheet were ground to change the subscale properties formed on the surface of the steel sheet. At this time, the grinding width from both ends in the width direction of the steel sheet to the center of the width was changed from 0 to 100 mm. Here, the grinding widths at both ends of the steel sheet (grinding width at one end and grinding width at the other end) are the same. Then, an annealing separator was applied, finish annealing, tension coating was formed, and the like by a known method to produce grain-oriented electrical steel sheets. For comparison, grain-oriented electrical steel sheets that do not form grooves were also manufactured under the same manufacturing conditions other than the formation of grooves.

Steel sheets during the above manufacturing process and after the completion of the final process, specifically, after etching (cold rolling structure), after decarburization annealing (primary recrystallization structure), after finish annealing (secondary recrystallization structure), tension coating After formation (secondary recrystallization structure), tension is applied to the grooved steel sheet and the non-grooved steel sheet until a test break occurs (hereinafter referred to as the break occurrence tension). And the relationship between the breakage of the steel sheet (structure) after each process was investigated.

The result was expressed by the ratio of the fracture-generated tension of the grooved steel sheet (with grooves) to the fracture-generated tension of the steel sheet without grooves (hereinafter referred to as the fracture-generated tension ratio). The test was conducted at room temperature of 25 ° C. The grinding of both ends of the steel sheet was carried out with the aim of changing the secondary recrystallization behavior by changing the properties of the subscale and changing the mechanical strength of the steel sheet due to the change in the structure of both ends of the steel sheet.

FIG. 1 shows the relationship between the steel sheet (structure) after each process and the fracture-generated tension ratio investigated for the steel sheet without grinding (grinding width 0 mm). From FIG. 1, when grooves are formed on the surface of the steel sheet, the tension generated at breakage is significantly reduced when the secondary recrystallization structure (after finish annealing) is obtained. As a measure for improving the passability, the steel sheet has a secondary recrystallization structure. It turns out that it is important to consider when.

FIG. 2 shows the relationship between the grinding width from the end of the steel sheet and the fracture-generated tension ratio for the steel sheet after finish annealing (secondary recrystallization structure) and after tension coating formation (secondary recrystallization structure). The horizontal axis represents the width (mm) ground from the ends (both ends) of the steel sheet toward the center of the width. It can be seen that by grinding both ends of the steel sheet in the direction of the center of the width of at least 10 mm or more, the decrease in the tension generated at breakage is significantly suppressed and the plate-passability is improved. In order to investigate the cause of the improvement in the plate-passability by grinding, each of the ground steel sheets was pickled and etched, and the structure was observed. As a result of observation, the structure of the ground portion (the region where the subscale properties changed due to grinding) was a fine crystal structure, and the average crystal grain size was 0.8 mm.

In the present invention, the region of the refined structure (fine crystal structure) is determined by the following method. The method for determining the region of the fine crystal structure in the present invention will be described with reference to FIGS. 9 to 12.
(I) A region of the total width of the steel plate x 100 mm in the rolling direction of the steel plate is defined as a structure observation region (FIG. 9). Structure observation and crystal orientation measurement are performed on a region of [width direction 100 mm] × [rolling direction 100 mm] at the center of the plate width direction (FIG. 10).
(Ii) From the crystal orientation measurement result, if the abundance frequency of crystal grains having a deviation angle from the Goss orientation of 10 ° or less is 90% or more in the above-mentioned region of [width direction 100 mm] × [rolling direction 100 mm], The region is set to the "reference secondary recrystallization structure" (FIG. 10).
(Iii) From the structure observation results, the grain boundaries intersecting the rolling direction are measured at a pitch of 5 mm over the entire width of the steel sheet (FIG. 11).
(Iv) The number of crossings per unit distance in the rolling direction at each pitch is calculated (FIG. 11).
(V) When points that have more than twice the average number of intersections in the reference secondary recrystallization structure (region) appear continuously, the range (between pitches) is defined as the fine crystal structure. (Fig. 12).

Further, when the crystal orientation analysis was performed on the fine crystal structure, the frequency of existence of crystal grains having a deviation angle from the Goss orientation of 10 ° or less was 5% or less, and most of them were not secondary recrystallized structures but primary. It was found that the recrystallized grains were grown normally by finish annealing after being ground. From the above results, in the steel sheet whose main structure is the secondary recrystallization structure, the decrease in the fracture-generated tension of the grooved steel sheet was significantly suppressed by the increased mechanical strength due to the fine-grained structure at both ends of the steel strip. Is thought to be the cause.

The crystal orientation measurement in the present invention is measured at a pitch of 1 mm by using the X-ray Rawe method, and the fluctuation width in the crystal grains from all the measurement points in one crystal grain and the average crystal orientation (α angle, β) of the crystal grains. I asked for a corner). In the present invention, measurements were made in a region of the total width of the steel sheet × 100 mm in the rolling direction of the steel sheet (see FIG. 9). The frequency of existence of crystal grains having a deviation angle of 10 ° or less from the Goss orientation is such that the deviation angle (deviation amount) from the Goss orientation is 10 ° or less in the region from the plate edge to 10 mm in the direction of the center of the plate width. Find the area of the grain and its ratio to the area of the area up to 10 mm [(Area of crystal grains with a deviation angle from the Goss direction of 10 ° or less / Area of the area from the plate edge to the center of the width) x 100] Was defined as the frequency of existence, and the deviation angle was ^{defined as √ (α 2} + β ^2). The α angle is the deviation angle from the (110) <001> ideal orientation in the rolling surface normal direction (ND) axis of the secondary recrystallized grain orientation, and the β angle is the rolling perpendicular direction (TD) axis of the secondary recrystallized grain orientation. (110) <001> is the deviation angle from the ideal direction. The average crystal grain size in the region from the plate edge to the center width of 10 mm is a circle based on the number of crystal grains measured by observing the crystal grains existing in the region with an optical microscope or a microscope and the area of the region. Obtained from the equivalent diameter.

<Experiment 2>
Next, the relationship between the average crystal grain size and the breaking tension was investigated. The differences from Experiment 1 are as follows. In this experiment, grinding was not performed. Instead, after applying an annealing separator, an aqueous boric acid solution was additionally sprayed with a nozzle within a range of 10 mm from the end of each steel sheet toward the center of the width, and then the baking process was performed. went. At that time, the concentration of the boric acid aqueous solution was changed to 0% by mass to 10% by mass. Other than that, the experiment was carried out in the same manner as in Experiment 1. The boric acid aqueous solution was applied because it was intended that boron would infiltrate the steel sheet during finish annealing and affect the secondary recrystallization behavior.

FIG. 3 shows the relationship between the average crystal grain size and the fracture-generated tension ratio in the range in which the boric acid aqueous solution is sprayed (the range of 10 mm from the end of the steel sheet to the center of the width) of the steel sheet after the tension coating is formed. When the average crystal grain size in the above range was 5 mm or less, the rupture generation tension ratio varied greatly. However, it was found that the decrease in the breaking tension cannot be suppressed when the average crystal grain size exceeds at least 5 mm. In addition, when the average crystal grain size was in the range of 2 to 5 mm, the rupture occurrence tension ratio varied widely, suggesting that factors other than the average crystal grain size had an effect.

When observing a structure having an average crystal grain size of 2 to 5 mm in the above range, it was found that secondary recrystallized grains and primary recrystallized grains were often mixed. On the other hand, when the average crystal grain size was 1 mm or less, the primary recrystallized structure was dominant, and when the average crystal grain size was more than 5 mm, the secondary recrystallized structure was dominant. This change in the tissue is considered to be due to the addition of boric acid. Therefore, for samples with average crystal grain sizes of 5 mm and 3 mm in the above range, the relationship between the abundance frequency of secondary recrystallized grains (here, crystal grains with a deviation angle of 10 ° or less from the Goss orientation) and the fracture occurrence tension ratio is examined. investigated. The results are shown in FIG. 4. When the abundance frequency of the secondary recrystallized grains is 50% or less, the decrease in the fracture-generated tension of the grooved steel sheet can be suppressed, and the improvement of the plate-passability can be remarkable. found.

<Experiment 3>
As a further measure to improve the passability, it was examined not to intentionally form grooves in the regions at both ends of the steel sheet. If the groove is not formed, the effect of subdividing the magnetic zone cannot be obtained, which causes a problem that the magnetic characteristics deteriorate. However, at both ends of the steel sheet, the coil weight at the lower end of the coil when the steel sheet is originally wound and placed as a coil. Due to buckling deformation due to the above, deformation due to stress caused by the temperature distribution difference due to overheating during coil annealing occurs at the upper end of the coil, and a certain range from both ends of the steel sheet is inevitably a part where the product cannot be collected. Therefore, if the unformed portion of the groove required for improving the plate-passability is not large, the unformed portion of the groove will fit in the portion where such a product cannot be collected, and the feasibility is considered to be high.

A resist ink was applied to a cold-rolled plate having a plate thickness of 0.18 mm and a plate width of 800 mm obtained by a known method by a known gravure offset printing. At that time, the coating pattern has an uncoated portion extending in a direction intersecting the rolling direction of the steel sheet, and both ends of the steel sheet are intentionally uncoated in a range of 0 to 15 mm from both ends of the steel sheet in the width center direction. A range was provided so as not to form a portion. That is, the coating pattern was adjusted so that the non-grooved portion in which the groove was not formed was formed in the range of 0 to 15 mm in the width center direction from both ends of the steel sheet by the subsequent electrolytic etching. After that, by electrolytic etching and resist peeling in an alkaline solution, linear grooves having a width of 200 μm and a depth of 25 μm are formed at intervals of 4.5 mm at an inclination angle of 7.5 ° with respect to the direction orthogonal to the rolling direction. Formed. Then, an edge heater was used to perform additional heat treatment on a range of 10 mm from both ends of the steel sheet in the width center direction to change the inhibitor state and the primary recrystallization particle size of that portion. Then, after performing decarburization annealing in which the atmospheric oxidation degree P (H ₂ O) / P (H ₂ ) = 0.55 and the soaking temperature: 840 ° C. for 60 seconds, an annealing separator was applied by a known method. Finish annealing, tension coating application, etc. were performed to obtain a product. The evaluation of the breaking tension was carried out by the same method as in Experiments 1 and 2.

FIG. 5 shows the relationship between the width of the non-grooved portion from both ends of the steel plate toward the center of the width and the fracture-occurring tension ratio. In this evaluation sample, in the structure within a range of 10 mm from both ends heated by the edge heater, the abundance frequency of secondary recrystallized grains was 20%, and the average crystal grain size was 4 mm. As shown in FIG. 5, even if there is no groove-unformed portion (the width of the groove-unformed portion is 0 mm), a significant decrease in the fracture-generated tension of the groove-formed steel sheet is suppressed, and the plate-passability is significantly deteriorated. Although it is suppressed, by setting the width of the non-grooved portion from the end of the steel plate to 1 mm or more, the decrease in the fracture-generated tension of the steel plate having the groove is further suppressed, and the deterioration of the plate-passability is suppressed. It became clear. The width of the non-grooved portion from the end of the steel plate is preferably 2 mm or more.

<Experiment 4>
It was clarified that the passability was significantly improved by improving the structure of the edge region of the steel sheet, but it was examined whether further improvement could be achieved by improving the groove formation behavior in the secondary recrystallization structure. As shown in FIG. 6 (c), the groove formation may be formed by one continuous groove (a groove that extends continuously in the direction intersecting the rolling direction), but the resist is formed by laser irradiation or the like. When a groove is formed by etching after peeling, a plurality of laser irradiation devices may be used to join the linear resist peeling. That is, it is not necessary for the laser irradiated from each irradiation device to be scanned over the entire width of the steel sheet, and the sum of the scanning ranges of each irradiation device may be manufactured so as to cover the entire width of the steel sheet. In this case, there is a portion where the groove is discontinuous with respect to the extending direction of the groove. In this case, if the grooves are formed as shown in FIG. 6B, the iron loss deteriorates. Therefore, as shown in FIG. 6A, the adjacent grooves in the plate width direction are on the projection plane orthogonal to the groove width direction. It is common to form grooves so that they overlap with each other. Hereinafter, the region where the grooves overlap when the grooves adjacent to each other in the plate width direction are projected onto the projection plane orthogonal to the groove width direction is referred to as a lap portion (see FIG. 6A). When the groove is formed so as to have the lap portion, the area where the plate thickness is thin becomes large in the lap portion, so that the plate-passability may be deteriorated, and the relationship between the discontinuous groove formation and the plate-passability is considered. I decided to investigate.

A cold rolled plate having a plate thickness of 0.20 mm and a plate width of 1200 mm obtained by a known method in which a resist ink is applied to the surface is used with three laser oscillators by a known laser processing method to provide a wrapping allowance with an adjacent groove. Grooves were formed while changing. Here, the lap allowance (%) is indicated by (wrap width / groove width) × 100, and the lap width is the overlap in the groove width direction when adjacent grooves in the width direction overlap in the groove width direction. The width is shown (see the lower view of FIG. 6 (c) and the enlarged view of the lap portion of FIG. 7). For example, as shown in the upper diagram of FIG. 6 (c), when adjacent grooves completely overlap in the groove width direction, the lap allowance is 100%, and as shown in FIG. 6 (a), they are adjacent in the plate width direction. When the grooves to be formed are separated from each other in the groove width direction, the lap allowance is 0%. The grooves were formed by forming linear grooves having a width of 50 μm and a depth (plate thickness direction) of 15 μm at intervals of 3.0 mm in the rolling direction at an inclination angle of 3.0 ° with respect to the direction orthogonal to the rolling direction. Then, an edge heater was used to perform additional heat treatment on a range of 10 mm from both ends of the steel sheet in the width center direction to change the inhibitor state and the primary recrystallization particle size of that portion. Then, after performing decarburization annealing in which the atmospheric oxidation degree P (H ₂ O) / P (H ₂ ) = 0.55 and the soaking temperature: 840 ° C. for 60 seconds, an annealing separator was applied by a known method. Finish annealing, tension coating application, etc. were performed to obtain a product. The evaluation of the breaking tension was carried out by the same method as in Experiments 1 and 2. In the structure in the range of 10 mm in the width center direction from each end heated by the edge heater, the abundance frequency of secondary recrystallized grains was 5%, and the average crystal grain size was 2 mm.

The evaluation result is shown in FIG. The presence of a lap portion (wrap allowance 0%) in which the ends of adjacent grooves do not overlap each other as shown in FIG. 6A tends to reduce the fracture-generated tension ratio (deteriorate the plate-passability). However, as the lap allowance increased, the decrease in the fracture tension ratio was suppressed. From the above, it was found that the wrap allowance is preferably 5% or more, and more preferably a continuous groove (wrap allowance 100%) is formed.

Based on the above results, the present invention will be specifically described. The following description shows a preferred embodiment of the present invention, and the present invention is not limited to the following description.

[Directional magnetic steel sheet]
The present invention relates to a grain-oriented electrical steel sheet having grooves formed on its surface. Hereinafter, the component composition of the steel material (slab) of the grain-oriented electrical steel sheet of the present invention will be described. As the grain-oriented electrical steel sheet, any one can be used without particular limitation, but from the viewpoint of reducing iron loss, it may have a component composition containing Si in the range of 2.0 to 8.0% by mass. It is preferable, and in addition, it is more preferable to have a component composition containing Si in the range of 2.5 to 4.5% by mass from the viewpoint of plate-passability.

The composition of components other than Si, which is suitable as a steel material (slab) used for producing the grain-oriented electrical steel sheet of the present invention, is as follows. Of course, the composition is not limited to the following, and the applicability of any electromagnetic steel sheet is surely improved as compared with the steel sheet before application by applying the present invention.

C: 0.01 to 0.08% by mass
C is an element necessary for improving the texture at the time of primary recrystallization, and is preferably contained in an amount of 0.01% by mass or more in order to obtain the effect. On the other hand, if C exceeds 0.08% by mass, it becomes difficult to reduce it to 0.0050% by mass or less, which does not cause magnetic aging due to decarburization annealing. Therefore, C is preferably in the range of 0.01 to 0.08% by mass. More preferably, it is in the range of 0.03 to 0.07% by mass.

Mn: 0.005 to 1.0% by mass
Mn is an element effective for improving hot workability, but if it is less than 0.005% by mass, the above effect cannot be obtained, while if it exceeds 1.0% by mass, the magnetic flux density decreases. Will be. Therefore, Mn is preferably in the range of 0.005 to 1.0% by mass. More preferably, it is in the range of 0.010 to 0.2% by mass.

Further, the basic components other than the above components of the steel material used for producing the grain-oriented electrical steel sheet of the present invention are divided into a case where an inhibitor is used for causing secondary recrystallization and a case where it is not used.

When an inhibitor is used to cause secondary recrystallization, for example, when an AlN-based inhibitor is used, Al and N are added to Al: 0.01 to 0.065% by mass and N: 0.005 to 0, respectively. It is preferable to contain it in the range of .012% by mass, and when MnS / MnSe-based inhibitors are used, Se and / or S are contained in S: 0.005 to 0.03% by mass and Se: 0.005, respectively. It is preferably contained in the range of ~ 0.03% by mass.

On the other hand, when an inhibitor is not used to cause secondary recrystallization, the inhibitor-forming components Al, N, S and Se are Al: 0.0100% by mass or less and N: 0.0050% by mass, respectively. Hereinafter, it is preferable to reduce S: 0.0050% by mass or less and Se: 0.0050% by mass or less.

Further, the steel material used for producing the grain-oriented electrical steel sheet of the present invention has Ni: 0.03 to 1.50 in addition to the above-mentioned component composition for the purpose of improving the magnetic characteristics in addition to the above-mentioned basic components. Mass%, Sn: 0.01 to 1.50 mass%, Sb: 0.005 to 1.50 mass%, Cu: 0.03 to 3.0 mass%, P: 0.03 to 0.50 mass% , Mo: 0.005 to 0.10% by mass and Cr: 0.03 to 1.50% by mass may be contained in one or more selected from.

Ni is an element useful for improving the hot-rolled plate structure and improving the magnetic properties. However, if it is less than 0.03% by mass, the above effect is small, while if it exceeds 1.50% by mass, the secondary recrystallization becomes unstable and the magnetic characteristics deteriorate. Further, Sn, Sb, Cu, P, Mo and Cr are elements useful for improving the magnetic characteristics, but all of them have a small effect of improving the magnetic characteristics below the above lower limit values, while the above upper limit values are small. If it exceeds, the development of secondary recrystallized grains will be inhibited, so it is preferable to contain each in the above range.

In the steel material used for producing the grain-oriented electrical steel sheet of the present invention, the balance other than the above components is Fe and unavoidable impurities. Since C is decarburized by primary recrystallization annealing and Al, N, S and Se are purified by finish annealing, these components are unavoidable in the steel sheet after finish annealing (directional electromagnetic steel sheet which is a product). The content is reduced to the extent of target impurities.

[heating]
The slab having the above composition is heated according to a conventional method. The heating temperature is preferably 1150 to 1450 ° C.

[Hot rolling]
After the above heating, hot rolling is performed. After casting, hot rolling may be performed immediately without heating. In the case of thin slabs, hot rolling may be performed, or hot rolling may be omitted. When hot rolling is carried out, it is preferable that the rolling temperature of the rough rolling final pass is 900 ° C. or higher and the rolling temperature of the finish rolling final pass is 700 ° C. or higher.

[Annealed hot-rolled plate]
Then, if necessary, hot-rolled sheet is annealed. At this time, in order to highly develop the Goth structure in the product plate, the hot-rolled plate annealing temperature is preferably in the range of 800 to 1100 ° C. If the hot-rolled plate annealing temperature is less than 800 ° C., the band structure in hot rolling remains, it becomes difficult to realize a sized primary recrystallization structure, and the development of secondary recrystallization is hindered. .. On the other hand, when the hot-rolled plate annealing temperature exceeds 1100 ° C., the crystal grain size after hot-rolled plate annealing becomes too coarse, and it becomes extremely difficult to realize a sized primary recrystallized structure.

[Cold rolling]
After that, cold rolling is performed once or twice or more with intermediate annealing in between. The intermediate annealing temperature is preferably 800 ° C. or higher and 1150 ° C. or lower. The intermediate annealing time is preferably about 10 to 100 seconds.

[Decarburization annealing]
After that, decarburization annealing is performed. In decarburization annealing, the annealing temperature should be 750 to 900 ° C., the oxidizing atmosphere P (H ₂ O) / P (H ₂ ) should be 0.25 to 0.60, and the annealing time should be about 50 to 300 seconds. Is preferable.

[Application of annealing separator]
Then, an annealing separator is applied. It is preferable that the main component of the annealing separator is MgO and the coating amount is ^{about 8 to 15 g / m 2.}

[Finish annealing]
Then, finish annealing is performed for the purpose of secondary recrystallization and formation of a forsterite film. The annealing temperature is preferably 1100 ° C. or higher, and the annealing time is preferably 30 minutes or longer.

[Flatration annealing and tension coating formation]
It is also possible to correct the shape by performing flattening and annealing at the same time by applying and baking the coating liquid when forming the tension coating. The flattening annealing is preferably carried out at an annealing temperature of 750 to 950 ° C. and an annealing time of about 10 to 200 seconds.

In the present invention, a tension coating is formed on the surface of the steel sheet before or after flattening and annealing. The tension coating here means a coating (tension coating) that applies tension to a steel sheet in order to reduce iron loss. Examples of the tension coating include an insulating tension coating. Further, examples of the tension coating include a phosphate-based coating containing silica, a ceramic coating by a physical vapor deposition method, a chemical vapor deposition method, and the like.

[Groove formation process]
The method for forming a groove on the grain-oriented electrical steel sheet according to the present embodiment is not particularly limited, and the groove can be formed by a known method such as a laser method, a press machine method, or an etching method. The groove formation timing is not particularly limited, and either a cold-rolled plate having a final plate thickness, a primary recrystallization annealed plate after decarburization annealing, or a secondary recrystallization annealed plate after finish annealing is possible. .. The above three methods are preferable from the viewpoint of process reduction because the strain due to grooving can be removed by the final flattening annealing. However, the effect of the present invention is not impaired even if the product plate after forming the tension coating is grooved.

By forming grooves so that ungrooved portions are formed in a range of 1 mm or more in the width center direction from both ends of the steel sheet, that is, grooves are not formed in a range of at least 1 mm in the width center direction from both ends of the steel sheet. By forming a groove in the sheet, the plate-passability is further improved. The non-grooved portion causes deterioration of magnetic characteristics, but even if the coil shape countermeasure as shown in Patent Document 1 is implemented, the shape defect in the range of 15 to 35 mm in the width center direction from the steel plate end portion is defective. Occurrence is inevitable. Therefore, the formation of the non-grooved portion of the present invention does not become a new factor for lowering the yield. Further, it is more preferable to form the grooves without interruption in the width direction of the steel sheet, that is, continuously in the width direction of the steel sheet, because the proportion of the thin region is reduced, and thus the passability is improved.

[Steel plate (coil) end miniaturization process]
The most important points of the present invention are (a) it is effective to increase the mechanical strength at both ends of the steel sheet (coil), and the average crystal grain size of the steel sheet structure is reduced to 5 mm or less in the range from both ends of the steel sheet to at least 10 mm in the center width direction. If the orientation of each crystal grain is almost the same even if it is refined, (b) the slip system will be the same, so only the resistance to a certain direction will increase, so the crystal orientation will be as random as possible. Therefore, the abundance frequency of crystal grains having a deviation angle from at least the Goss direction of 10 ° or less is 50% or less.

The method for reducing the abundance frequency of crystal grains having an average crystal grain size of 5 mm or less and a deviation angle from the Goss direction of 10 ° or less to 50% or less is not particularly limited, but a means that affects the secondary recrystallization behavior is adopted. However, it is more preferable to promote the normal grain growth of the primary recrystallized grains. As a means for affecting the secondary recrystallized grains, (a) the subscale properties are changed by oxidation by grinding or laser irradiation, and the nitriding and inhibitor decomposition behavior during finish annealing are changed only in a specific range at the end of the steel sheet. (B) B, Ti, Sr, Sn, etc., which are known as elements that affect secondary recrystallization, are newly added only to the target range of the end of the steel sheet during the annealing separator coating process. .. Alternatively, if it has already been added, the amount added is changed. The method of changing the addition amount is not particularly limited, but it is preferable to once apply a normal annealing separator to the entire surface, and then additionally supply the above elements to the target range of the steel sheet end portion from a nozzle or the like. (C) It is also effective to coarsen the inhibitor properties and the primary recrystallization particle size. As a method, only the end region of the steel sheet is overheated by using an edge heater or the like, hot-rolled sheet annealing or primary recrystallization annealing. It is also effective to give a temperature gradient in the width direction of the steel sheet by sometimes heating from both ends of the steel sheet (coil) to overheat the end region of the steel sheet. It should be noted that the miniaturization range (region of the fine crystal structure) required for improving the plate-passability is sufficient if the width from the end of the steel sheet is 10 mm, and as mentioned above, due to the finish annealing, both ends of the coil are covered. It is inevitable that a shape defect of 15 to 35 mm will occur. Therefore, even if the groove-unformed portion as described above is formed, it does not become a new factor for lowering the yield. The average crystal grain size is preferably 3 mm or less, more preferably 1 mm or less. The abundance frequency of the crystal grains is preferably 35% or less, more preferably 20% or less. The upper limit of the miniaturization range is not particularly limited, but for example, the structure in the range of 35 mm from both ends of the steel sheet in the width center direction can be miniaturized, and the structure in the range of 25 mm from both ends of the steel sheet in the width center direction can be miniaturized. It can be miniaturized.

Next, the present invention will be specifically described based on Examples. The following examples show a suitable example of the present invention, and the present invention is not limited to the above examples. The embodiments of the present invention can be appropriately modified within a range suitable for the gist of the present invention, and all of them are included in the technical scope of the present invention.

As the directional electromagnetic steel sheet, C: 0.02% by mass, Si: 3.25% by mass, Mn: 0.09% by mass, Al: 0.012% by mass, N: 0.008% by mass, S: 0 A steel slab having a component composition of .005% by mass and Se: 0.01% by mass and containing an inhibitor-forming component is hot-rolled according to a conventional method and annealed at 900 ° C. for 60 seconds. , Cold rolled to obtain a 0.23 mm cold rolled plate. Then, a groove was formed by (a) gravure offset printing + electrolytic etching method, (b) protrusion roll method, and (c) laser processing method (laser irradiation + electrolytic etching). Information on the groove shape such as the groove width, the groove depth, the presence / absence of the lap portion, and the lap allowance of the formed groove is shown in Tables 1 and 2.

Then, decarburization annealing is performed at a soaking temperature of 830 ° C. for 300 seconds, and then an annealing separator containing MgO as a main component is applied, and finish annealing is performed for the purpose of secondary recrystallization / forsterite film formation and purification. Was carried out at 1200 ° C. for 30 hours. Then, after removing the unreacted separating agent, a coating liquid composed of 60% by mass of colloidal silica and aluminum phosphate was applied and baked at 800 ° C. to form a tension coating. This coating coating process also serves as flattening annealing.

As means for finely granulating the regions at both ends of the steel sheet, (a) additional oxidation treatment by laser irradiation to the target area after decarburization annealing, (b) additional addition _{of TiO 2 to the target area after application of the annealing separator,} (C) This was achieved by performing additional heat treatment on the edges of the steel sheet with an edge heater after annealing the hot-rolled sheet for a soaking time of 20 seconds. The abundance frequency of crystal grains having a deviation of 10 ° or less from the fine graining range and the Goss direction _{changes the laser irradiation range / laser irradiation energy, the coating range / coating amount of the additional nitro 2} , and the additional heating range / heating temperature, respectively. It was realized by that. Samples were taken from the steel sheet after finish annealing, and the grain frequency with a fine grain (fine graining) range (region of fine crystal structure), average crystal grain size, and deviation angle from the Goss orientation of 10 ° or less was measured in Experiment 1. Evaluation was performed in the same manner as described.

The average crystal grain size (mm) and the abundance frequency (%) of crystal grains with a deviation angle of 10 ° or less from the Goss orientation in the structure of the fine grained range shown in Tables 1 and 2 are fine from both ends to 10 mm in the center width direction. The average crystal grain size (mm) and the abundance frequency (%) of crystal grains having a deviation angle of 10 ° or less from the Goss orientation in the transformed structure are shown. The average crystal grain size in the structure from one end (end 1) in the width direction of the steel sheet to 10 mm in the center width direction and the structure from the other end (end 2) in the width direction of the steel sheet to 10 mm in the center width direction. When (mm) and the abundance frequency (%) of crystal grains having a deviation angle of 10 ° or less from the Goss direction are different, the maximum values of each are shown. When the refined structure is less than 10 mm in the width center direction from both ends, the average crystal grain size (mm) and the deviation from the Goss orientation in the refined structure in the region from both ends to the width center direction 10 mm. The abundance frequency (%) of crystal grains having an angle of 10 ° or less is shown. For example, No. 1 in Table 1. The average crystal grain size (mm) in the structure in the fine graining range of 1-7 and the abundance frequency (%) of crystal grains with a deviation angle of 10 ° or less from the Goss orientation are the structure from the edge 1 to the width center direction 5 mm. The maximum values of the average crystal grain size (mm) in the structure from the edge 2 to the width center direction of 5 mm and the abundance frequency (%) of crystal grains having a deviation angle of 10 ° or less from the Goss orientation are shown. The average crystal grain size (mm) in the structure in the fine graining range of 1-9 and the abundance frequency (%) of crystal grains having a deviation angle of 10 ° or less from the Goss orientation are as follows: in the structure from the edge 1 to the center width of 10 mm. The average crystal grain size (mm) and the abundance frequency (%) of crystal grains having a deviation angle of 10 ° or less from the Goss orientation are shown.

Here, the fracture-generated tension (ratio to the fracture-generated tension of the ungrooved steel sheet) after finish annealing (intermediate process material) and after tension coating formation (product plate) was investigated. The evaluation results are shown in Tables 1 and 2. The fracture-generated tension ratios shown in Tables 1 and 2 are obtained by using the larger value of the fracture-generated tension after finish annealing and after forming the tension coating. When the fracture-generated tension ratio is closer to 1, the fracture-generated tension is higher and it can be evaluated that the plate-passability is good.

As can be seen from the results shown in Tables 1 and 2, the grain-oriented electrical steel sheet satisfying the requirements of the present invention is more than the one outside the scope of the present invention regardless of the method of forming the groove or the method of granulating the end region of the steel sheet. It can be seen that the rupture occurrence tension ratio is high and the plate has good passability.

Claims (3)

A grain-oriented electrical steel sheet in which a groove extending in a direction intersecting the rolling direction and having a groove depth direction in the plate thickness direction is formed on the surface.
The structure in the range from both ends in the width direction to at least 10 mm in the width center direction of the steel sheet is miniaturized.
In the finely divided structure from both ends to 10 mm in the center width direction, the presence frequency of crystal grains having an average crystal grain size of 5 mm or less and a deviation angle from the Goss direction of 10 ° or less is 50% or less. There is a directional electromagnetic steel plate. The grain-oriented electrical steel sheet according to claim 1, wherein no groove is formed in a range from both ends in the width direction of the surface of the steel sheet to at least 1 mm in the center direction of the width. The grain-oriented electrical steel sheet according to claim 1 or 2, wherein the grooves formed on the surface of the steel sheet extend continuously in a direction intersecting the rolling direction.

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