JP5958501B2 - Method for evaluating grain-oriented electrical steel sheet and method for producing grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to an evaluation method for a grain-oriented electrical steel sheet, and particularly relates to an evaluation method capable of determining a grain-oriented electrical steel sheet having excellent iron loss characteristics. The present invention also relates to a method for producing a grain-oriented electrical steel sheet.

  A grain-oriented electrical steel sheet is a soft magnetic material that is widely used as a core material for transformers, and is required to have excellent magnetic properties, particularly iron loss properties (low iron loss). A grain-oriented electrical steel sheet with a high level of integration of the {110} <001> orientation called the Goth orientation in the rolling direction of the steel sheet was developed and put into practical use to satisfy good iron loss. As is well known.

  As a method of highly accumulating the {110} <001> orientation in the rolling direction on a steel plate, a method of controlling secondary recrystallization using precipitates called inhibitors is common. However, when precipitates (inhibitors) remain in the product steel plate, the magnetic properties are deteriorated. For this reason, for example, as disclosed in Patent Documents 1 and 2, after the secondary recrystallization by finish annealing, so-called purification annealing is performed to remove impurities by subsequent high-temperature annealing. . In this purification annealing, it is necessary that the inhibitor dissolves and diffuses in the steel and escapes from the surface layer. Therefore, in the manufacturing process of the grain-oriented electrical steel sheet, annealing at a temperature of 1100 to 1250 ° C. for 3 hours or more is performed at a high temperature for a long time. Perform under conditions.

Japanese Patent Laid-Open No. 11-158557 JP 05-009666 A

  By the way, in recent years, further reduction of iron loss has been demanded for the purpose of energy saving. For this purpose, it is required to improve the technology for removing the inhibitor component and the inhibitor-less technology to reliably remove impurities (inhibitor component) in the final product.

  However, defects due to remaining impurities become apparent after the end of the purification annealing process. The manufacturing process of grain-oriented electrical steel sheets takes a long time, such as steelmaking, hot rolling, cold rolling, primary recrystallization annealing, secondary recrystallization annealing (finish annealing), and purification annealing. Therefore, the magnetic properties of the obtained grain-oriented electrical steel sheet cannot be measured unless the manufacturing process for the grain-oriented electrical steel sheet is completed. For this reason, the yield of the final product sheet of grain-oriented electrical steel sheet is greatly reduced.

  The present invention has been made in view of the above-mentioned problems of the prior art, and predicts iron loss failure in a product plate with high accuracy in the initial stage of the production process of grain-oriented electrical steel sheet, and is excellent in iron loss characteristics. An object of the present invention is to provide a method for evaluating a grain-oriented electrical steel sheet and a method for producing the grain-oriented electrical steel sheet, which can provide the grain-oriented electrical steel sheet inexpensively and stably.

  In order to solve the above-mentioned problems, the inventors focused on the steel sheet in each manufacturing process from hot rolling to purification annealing, and made extensive studies. After performing a simple heat treatment simulating the temperature raising process of the purification annealing, it was found that the iron loss property good / bad can be predicted with high accuracy by the number of inhibitors remaining on the surface layer of the steel sheet. Was completed.

The gist of the present invention is as follows.
[1] An annealing separator is applied to a steel sheet in an arbitrary manufacturing process after the hot rolling process, and then secondary recrystallization annealing at a maximum attained temperature of 1100 ° C or higher and purification annealing at 980 ° C or higher and 1025 ° C or lower. The material that has been subjected to
Starting from an arbitrary position in the region of 30 to 60 μm from the surface of the specimen, electrolytic extraction is performed after dissolving a predetermined amount of the specimen, and a predetermined number of inhibitors are contained in the obtained melt. An evaluation method for a grain-oriented electrical steel sheet, wherein the following are accepted.
[2] An annealing separator was applied to a steel sheet in an arbitrary manufacturing process after the hot rolling process, followed by secondary recrystallization annealing at a maximum attained temperature of 1100 ° C. or higher and purification annealing at 1000 ° C. As a test material,
Starting from an arbitrary position in the region of 30 to 60 μm from the surface of the specimen, electrolytic extraction is performed after dissolving a predetermined amount of the specimen, and a predetermined number of inhibitors are contained in the obtained melt. An evaluation method for a grain-oriented electrical steel sheet, wherein the following are accepted.
[3] The test material contains C: 0.01 to 0.08 mass%, Si: 2.00 to 8.00 mass%, Mn: 0.005 to 1.00 mass% as a component composition, The method for evaluating a grain-oriented electrical steel sheet according to [1] or [2], comprising at least one of the following (1) to (3), the balance being Fe and inevitable impurities: .
(1) Al: 0.010-0.065 mass% and N: 0.005-0.012 mass%
(2) S: 0.005-0.030 mass%
(3) Se: 0.005 to 0.030 mass%
[4] The size of the surface to be electrolytically extracted of the test material is 1000 mm ² , the predetermined amount is 0.1 g, and the number of the inhibitors is 2500 or less [1] to [3 ] The evaluation method of the grain-oriented electrical steel sheet according to any one of the above.
However, the inhibitor is an inhibitor observed in a range of 0.01 mm ² on the filter after filtering the lysate using a filter having a filtration area of 1020 mm ² .
[5] The test material further includes Cu: 0.03 to 3.00 mass%, Sb: 0.005 to 0.50 mass%, Ni: 0.01 to 1.50 mass%, and P: 0 as component compositions. 0.03 to 0.50 mass%, Sn: 0.005 to 0.50 mass%, Mo: 0.005 to 0.10 mass%, or one or more selected from [3] ] Or the evaluation method of the grain-oriented electrical steel sheet according to [4].
[6] For a steel sheet that is determined to be acceptable by the evaluation method for the grain-oriented electrical steel sheet according to any one of [1] to [5], the manufacturing process after the arbitrary manufacturing process is performed, thereby performing the direction. A method for producing a grain-oriented electrical steel sheet, comprising producing a directional electrical steel sheet.

  According to the present invention, the steel sheet in an arbitrary manufacturing process after the hot rolling process is subjected to a simple heat treatment simulating the temperature rising process of the purification annealing, and then the number of inhibitors remaining on the surface layer of the steel sheet It is possible to accurately predict whether the loss characteristic is good or bad. For this reason, at the initial stage of the production process of grain-oriented electrical steel sheets, it is possible to determine a steel sheet that has a poor iron loss characteristic, that is, a rejected steel sheet. Can not. Therefore, it becomes possible to provide a grain-oriented electrical steel sheet having excellent iron loss characteristics at low cost and stably.

Inhibitors at various positions on the surface of the steel sheet for samples subjected to purification annealing from 850 ° C. to 1050 ° C. after applying an annealing separator after the primary recrystallization annealing and performing secondary recrystallization annealing at a maximum temperature of 1100 ° C. or higher. It is a graph which shows the relationship between the number of particles and the purification annealing temperature. The steel sheet in any manufacturing process stage was subjected to secondary recrystallization annealing at a maximum temperature of 1100 ° C. or higher with an annealing separator applied, and then subjected to purification annealing at 980 ° C. or higher and 1025 ° C. or lower. It is the graph which showed the relationship between the number and the iron loss of a product board.

<Evaluation method of the present invention>
The background of finding the evaluation method of the present invention will be described below, but before that, the grain-oriented electrical steel sheet according to the present invention will be briefly described.

  First, the component composition of the grain-oriented electrical steel sheet according to the present invention is not particularly limited as long as it is basic, but C: 0.01-0.08 mass%, Si: 2.00-8. It is common to contain 00mass% and Mn: 0.005-1.00mass%.

  Further, the grain-oriented electrical steel sheet of the present invention has a Cu: 0.03 to 3.00 mass%, Ni: 0.01 to 1.50 mass%, Sn: One or two selected from 0.005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, P: 0.03 to 0.50 mass%, Mo: 0.005 to 0.10 mass% You may further contain a seed | species or more.

  Among the above component compositions, the grain-oriented electrical steel sheet according to the evaluation method of the present invention uses an inhibitor for causing secondary recrystallization. For example, when using an AlN-based inhibitor, Al and N, It contains in the range of Al: 0.010-0.065 mass% and N: 0.005-0.012 mass%. Or when using a MnS * MnSe type | system | group inhibitor, it contains in the range of S: 0.005-0.030 mass% and / or Se: 0.005-0.030 mass%. Further, an AlN-based inhibitor and a MnS / MnSe-based inhibitor may be used in combination, and in that case, Al, N, S, and Se are contained in the above range.

  Further, the balance other than the above components here is Fe and inevitable impurities.

  Below, an example is demonstrated about the other manufacturing conditions of the grain-oriented electrical steel sheet which concerns on the evaluation method of this invention.

  For example, a steel slab having the above component composition is reheated according to a conventional method, hot-rolled, hot-rolled as necessary, and then cold-rolled twice or more with intermediate or intermediate annealing. The final thickness of the cold-rolled sheet is obtained. Thereafter, the cold-rolled sheet is subjected to primary recrystallization annealing also serving as decarburization, and an annealing separator is applied to perform secondary recrystallization annealing and purification annealing for secondary recrystallization and purification. In addition, although decarburization can be performed by making the said primary recrystallization annealing into a humid atmosphere, you may perform separately.

  As described above, among such grain-oriented electrical steel sheets, the present inventors have conducted a hot rolling process on the precipitation state (for example, the form, number, and size) of the inhibitor that greatly affects the iron loss. Steel sheets of each of the subsequent arbitrary manufacturing steps were collected and examined.

Specifically, a steel sheet collected from any manufacturing process from hot-rolled sheet to finish-annealed sheet is used as a sheet thickness of a certain thickness (for example, 0.2 to 3.0 mm) (for example, rolled). The plate thickness is reduced or the plate thickness is kept as it is.) After removing the scale by pickling, etc., after applying an annealing separator mainly composed of MgO to the steel plate surface, the maximum temperature reached 1100 ° C. or higher A test material was prepared which was subjected to secondary recrystallization annealing at 1 ° C. and purification annealing at 1000 ° C. A test piece (sample) having a size of 20 mm × 50 mm was prepared from the test material, polished by 30 μm from the surface of 20 mm × 50 mm, and then subjected to electrolytic extraction from the newly formed surface to obtain a 0.1 g sample. Was dissolved. In this case, the size (area) of the surface to be electrolytically extracted is 1000 mm ² . Subsequently, the entire amount of the lysate obtained by electrolytic extraction was filtered through a filter having a filtration area of 1020 mm ² and dried. Thereafter, the inhibitor remaining on the filter was observed using a scanning electron microscope (SEM). At this time, among the inhibitors that were uniformly dispersed on the filter, an area of 100 μm in length × 100 μm in width (0.01 mm ² ) was observed, and those having an equivalent circle diameter in the region of 5 μm or less were observed.

  As a result, the inhibitor that precipitates (hereinafter sometimes referred to simply as “inhibitor or precipitate”) is present in the steel sheet in a size of about 30 to 150 nm (equivalent circle diameter), and after the hot rolling step. Thus, it was found that the precipitation form of the inhibitor was as described below in the steel sheets in any manufacturing stage up to the stage where the finish annealing was finished, and it existed with almost no change.

That is, it was found that AlN or MnS as an Al-based inhibitor is precipitated as the precipitated inhibitor. Moreover, when MnSe or Cu was included in the component composition, it was found that Cu ₂ S or Cu ₂ Se was precipitated as an inhibitor. Some of these inhibitors precipitate alone, while other inhibitors cause AlN to precipitate together using MnSe, Cu ₂ S, Cu ₂ Se, and MnS as nuclei. As described above, these inhibitors are present in the steel sheet with an equivalent circle diameter of about 30 to 150 nm.

  On the other hand, the inhibitor dissolves and disappears in the purification annealing after the finish annealing. In order to investigate this behavior, an inhibitor on the surface layer of the steel sheet was observed using a SEM for a sample subjected to a simple heat treatment simulating the temperature raising process of purification annealing.

FIG. 1 shows a simple heat treatment that simulates the temperature raising process of purification annealing, after applying an annealing separator after primary recrystallization annealing and performing secondary recrystallization annealing at a maximum temperature of 1100 ° C. or higher, Regarding the sample annealed at 1050 ° C., the relationship between the number of inhibitors and the purification annealing temperature when electrolytic extraction was started from the steel sheet surface position (outermost layer), the position 10 μm from the steel sheet surface, and the position 30 μm from the steel sheet surface It is a graph which shows. As shown in FIG. 1, in the case of a steel plate with good iron loss characteristics (iron loss W _17/50 is 0.90 or less, OK material in Table 1), the electrolytic extraction start position is 30 μm in depth from the steel plate surface. In the position where it does not reach, that is, the position of the outermost layer or 10 μm from the steel sheet surface, the number of inhibitors is drastically decreased at 975 ° C. or more. About this correlation, the same correlation was acquired also in the steel plate of any manufacturing stage until the stage where finish annealing is complete | finished after a hot rolling process. Therefore, it is considered that dissolution of the inhibitor occurs at a high temperature of 975 ° C. or higher in the temperature raising process of the purification annealing.

  Furthermore, it was found that in the region from the surface of the steel sheet to the vicinity of a depth of 60 μm, the dissolution of the inhibitor by heating is significant, and there is a difference in dissolution behavior between the steel sheet with good iron loss characteristics and the bad steel sheet. Specifically, in the case of a steel sheet with poor iron loss characteristics, it was found that the inhibitor is difficult to dissolve in a region where the depth from the steel sheet surface is in the vicinity of 30 to 60 μm. For example, as shown in FIG. 1, in the case of electrolytic extraction from a position having a depth of 30 μm starting from the surface of the steel sheet, the number of inhibitors with a melting temperature of 975 ° C. or more is higher in the NG material than in the OK material. It can be seen that the amount of decrease is small. About this correlation, the same correlation was acquired also in the steel plate of any manufacturing stage until the stage where finish annealing is complete | finished after a hot rolling process. Therefore, in the case of a steel sheet with poor iron loss characteristics, it can be said that the inhibitor is difficult to dissolve at a melting temperature of 975 ° C. or higher.

  Further, from FIG. 1, when the temperature exceeds 1025 ° C., the dissolution of the inhibitor proceeds too much, so that there is no clear difference in the number of inhibitors between a steel plate with good iron loss characteristics and a steel plate with poor iron loss characteristics.

  In addition, the correlation between the grain-oriented electrical steel sheet, which is an actual product plate, and the test material obtained by the simple manufacturing process of the present invention was examined. Specifically, the number of inhibitors when the position where the electrolytic extraction was started on the actual product plate was 30 μm deep (surface standard), and the position where the electrolytic extraction was started with the test material of the present invention was 30 μm deep ( The number of inhibitors at the time of (surface standard) was compared. As a result, it was found that the actual product plate and the test material of the present invention had almost the same number of inhibitors, that is, a high degree of correlation and no difference in iron loss characteristics.

Furthermore, the correlation between the number of inhibitors and the iron loss characteristics of the product plate was investigated. FIG. 2 shows a case where an annealing separator (MgO) is applied using a steel sheet obtained by collecting hot-rolled sheets and cold-rolled in a laboratory, or a steel sheet having a thickness as it is. For samples subjected to crystal annealing and purification annealing at 980 ° C. or more and 1025 ° C. or less, the number of inhibitors when the position where electrolytic extraction was started was 30 μm deep (surface standard) and the iron loss characteristics of the product plate It is a graph which shows a relationship. As shown in FIG. 2, when the number of inhibitors is less than 2500, the iron loss characteristics are good (◯ in FIG. 2). On the other hand, when the number of inhibitors exceeds 2500, the iron loss is 0.90 or more, indicating that the iron loss characteristics are poor (× in FIG. 2). Therefore, when the number of inhibitors per predetermined area (0.01 mm ² ) is 2500 or less by SEM observation, it can be said that the iron loss characteristic of the product plate is good.

  As described above, in the present invention, as a simple heat treatment simulating the temperature raising process of the purification annealing, the secondary recrystallization annealing at the maximum attained temperature of 1100 ° C. or higher, and the subsequent purification annealing at 980 ° C. or higher and 1025 ° C. or lower. After applying, the iron loss characteristics can be determined by the number of inhibitors remaining in the region of about 30 to 60 μm of the steel sheet.

  If the secondary recrystallization annealing temperature is less than 1100 ° C., the desired inhibitor effect cannot be obtained. Further, when the purification annealing temperature is lower than 980 ° C., as shown in FIG. 1, the inhibitor dissolution behavior does not proceed so much in both the steel sheet having good iron loss characteristics and the bad steel sheet. On the other hand, when the purification annealing temperature exceeds 1025 ° C., the dissolution of the inhibitor proceeds excessively, so that there is no clear difference in the number of inhibitors between a steel plate with good iron loss characteristics and a steel plate with poor iron loss characteristics. For this reason, in this invention, it is set as 980 degreeC or more and 1025 degrees C or less whose dissolution behavior is clear. More preferably, it is 1000 ° C. from the viewpoint that the above difference is most clearly seen. Moreover, as shown in FIG. 2, if the number of inhibitors is 2500 or less, the iron loss characteristics are good.

  Therefore, the evaluation method of the grain-oriented electrical steel sheet according to the present invention is a secondary recrystallization annealing at a maximum ultimate temperature of 1100 ° C. or higher after applying the annealing separator to the steel sheet in any manufacturing process after the hot rolling process. Then, the material obtained by subjecting the material to purification annealing at 980 ° C. or more and 1025 ° C. or less following the test sample was obtained by SEM observation of the melt obtained by electrolytic extraction of a predetermined amount of steel sheet after removing the surface scale. If the number of inhibitors to be obtained is less than or equal to a predetermined number, it is judged as good and passed.

Here, the predetermined amount is about 20 mm × 50 mm test piece (the area of the surface to be electrolytically extracted is 1000 mm ² ) in consideration of the operability of analysis, that is, the area of the surface to be electrolytically extracted is 800 to 8000 mm. ² , 0.005-0.1 g. When the predetermined amount is less than 0.005 g, the analysis accuracy is lowered, and when it exceeds 0.1 g, electrolytic extraction is performed from the steel sheet surface to a deep place, so that a high degree of correlation is lost. Further, the predetermined number means, for example, that 0.1 g is electrolytically extracted in a test piece of 20 mm × 50 mm prepared from the grain-oriented electrical steel sheet having the above-described component composition, and the dissolved product is filtered through a filter having a filtration area of 1020 mm ² . Later, when an area of 100 μm in length and 100 μm in width (0.01 mm ² ) was observed using SEM for the inhibitors present on the filter, there were 2500 circle equivalent diameters of 5 μm or less. In a grain-oriented electrical steel sheet whose component composition deviates somewhat from the above-described component composition, various iron loss characteristics are generated at the beginning of production, that is, when starting to supply product sheets to the market. A predetermined number of inhibitors can be determined using good / bad product plates.

Further, according to the present invention, it is not necessary to measure the iron loss characteristic after manufacturing the product plate, and the iron loss characteristic of the product plate can be determined using the steel plate in the middle stage.
<Production method of the present invention>
Below, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.

  The method for producing a grain-oriented electrical steel sheet according to the present invention uses the above-described evaluation method to produce iron loss by producing up to the final production stage using a steel sheet whose iron loss characteristics are determined to be good and passed. A grain-oriented electrical steel sheet having excellent characteristics is obtained.

  The component composition of the grain-oriented electrical steel sheet in the production method of the present invention is C: 0.01 to 0.08 mass%, Si: 2.00 to 8.00 mass%, Mn: 0.005 to 1.00 mass%, Further, depending on the type of inhibitor used, (1) Al: 0.010 to 0.065 mass% and N: 0.005 to 0.012 mass%, (2) S: 0.005 to 0.030 mass% (3) Se: It contains at least one of 0.005 to 0.030 mass%, and the balance is Fe and inevitable impurities. The reason for limitation will be shown below.

C: 0.01-0.08 mass%
C is an element necessary for improving the texture at the time of primary recrystallization, and is contained in an amount of 0.01 mass% or more in order to obtain the effect. On the other hand, when the amount of C exceeds 0.08 mass%, it becomes difficult to reduce to 0.0050 mass% or less at which no magnetic aging occurs due to decarburization annealing. Therefore, C is in the range of 0.01 to 0.08 mass%.

Si: 2.00 to 8.00 mass%
Si is an element effective for increasing the electrical resistance of steel and improving iron loss. However, if the content is less than 2.00 mass%, a sufficient iron loss reduction effect cannot be obtained. On the other hand, if it exceeds 8.00 mass%, the workability is remarkably lowered, it becomes difficult to roll and manufacture, and the magnetic flux density is also lowered. Therefore, Si is set to a range of 2.00 to 8.00 mass%.

Mn: 0.005 to 1.00 mass%
Mn is an element necessary for improving hot workability. However, if the content is less than 0.005 mass%, the above effect cannot be obtained. On the other hand, if it exceeds 1.00 mass%, the magnetic flux density decreases. Therefore, Mn is set to a range of 0.005 to 1.00 mass%.

  Moreover, the grain-oriented electrical steel sheet of the manufacturing method of this invention may further contain the following elements in addition to the said component composition for the purpose of the improvement of a magnetic characteristic.

Cu: 0.03-3.00 mass%, Ni: 0.01-1.50 mass%, Sn: 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, P: 0.03- One or more selected from 0.50 mass%, Mo: 0.005 to 0.10 mass% Cu is an element useful for improving magnetic properties. However, if it is less than 0.03 mass%, the effect of improving the magnetic properties is small. On the other hand, if it exceeds 3.00 mass%, the development of secondary recrystallized grains is inhibited, so 0.03 to 3.00 mass%. Range.

  Ni is an element useful for improving the magnetic properties by improving the hot-rolled sheet structure. However, if the amount is less than 0.01 mass%, the above effect is small. On the other hand, if it exceeds 1.50 mass%, the secondary recrystallization becomes unstable and the magnetic characteristics deteriorate.

  Sn, Sb, P and Mo are elements useful for improving the magnetic properties, but any of them is less effective in improving the magnetic properties if it is less than each lower limit value. On the other hand, if it exceeds each upper limit value, Since the development is inhibited, each is contained in the above range.

Among the component compositions described above, in the method for producing a grain-oriented electrical steel sheet according to the present invention, at least one or more of the following (1) to (3) are used in order to cause secondary recrystallization.
(1) Al: 0.010-0.065 mass% and N: 0.005-0.012 mass%
(2) S: 0.005-0.030 mass%
(3) Se: 0.005 to 0.030 mass%
For example, when using an AlN-based inhibitor, it is preferable to contain Al and N in the range of Al: 0.010 to 0.065 mass% and N: 0.005 to 0.012 mass%. Or when using a MnS * MnSe type | system | group inhibitor, it is preferable to make it contain in the range of S: 0.005-0.030 mass% and / or Se: 0.005-0.030 mass%. Moreover, you may use both together. Outside this range, the inhibitor required to cause secondary recrystallization cannot be obtained.

  Further, the balance other than the above components is Fe and unavoidable impurities.

  The method for producing a grain-oriented electrical steel sheet according to the present invention comprises a steel slab having the above-described composition composition, slab reheating according to a conventional method, hot rolling, and hot-rolled sheet annealing as necessary, once or intermediate annealing. Cold rolling is performed twice or more with a final thickness of the cold rolled sheet. Thereafter, the cold-rolled sheet is subjected to primary recrystallization annealing also serving as decarburization, and after applying an annealing separator, secondary recrystallization and finish annealing for purification are performed. Here, the above-described evaluation is performed on the steel sheet collected in an arbitrary manufacturing process after the hot rolling process, and those determined to be passed are advanced to the subsequent process and the final process. That is, the rejected product is removed in the manufacturing process. In addition, although decarburization can be performed by making the said primary recrystallization annealing into a humid atmosphere, you may perform separately.

  Therefore, according to the method of manufacturing a grain-oriented electrical steel sheet of the present invention, it is possible to remove in advance the material that is determined to be defective at the stage of the product plate without requiring several months of time required for the final manufacture of the product plate. Can do. That is, what is determined to be unacceptable in the present invention cannot be advanced to the subsequent process (post process), and the load of the post process is reduced. For this reason, a yield improves and it becomes possible to manufacture the grain-oriented electrical steel sheet excellent in the iron loss characteristic stably and cheaply.

  About the grain-oriented electrical steel sheets having the composition shown in Table 1, a part of each of the production stages after the hot rolling step (hot rolled sheet), after normal annealing (normal plate), or after primary recrystallization annealing (1H sheet) ( (Size of 20 mm × 50 mm). The hot-rolled sheet and the normal sheet were cold-rolled in a laboratory to obtain a cold-rolled sheet having a final sheet thickness of 0.27 mm. Thereafter, primary recrystallization annealing that also served as decarburization was performed according to a conventional method, the scale was removed by pickling, and an annealing separator mainly composed of MgO was applied. Subsequently, after performing secondary recrystallization annealing at a maximum ultimate temperature of 1100 ° C. or higher as a heat treatment that simulates secondary recrystallization annealing with a maximum ultimate temperature of 1100 ° C. and purification annealing at 850 ° C. to 1050 ° C., 850 ° C. to Purification annealing at 1050 ° C. was performed. In addition, for the 1H plate, after the primary recrystallization annealing, an annealing separator mainly composed of MgO is applied, and after the secondary recrystallization annealing is performed at a maximum attained temperature of 1100 ° C. or higher, purification annealing at 850 ° C. to 1000 ° C. is performed. Went.

A test piece (sample) having a size of 20 mm × 50 mm is cut out from the above test material, polished by 30 μm from the surface, and then subjected to electrolytic extraction from the newly formed surface to dissolve a 0.1 g sample. did. The basic conditions for electrolytic extraction were constant current electrolysis of 500 mA in 250 ml of MA electrolyte (10% by mass maleic anhydride-2% by mass tetramethylammonium chloride-2% by mass acetylacetone-methanol). Thereafter, the total amount of the extract obtained by electrolytic extraction was filtered through a filter having a filtration area of 1020 mm ² and dried, and the inhibitor remaining on the filter was observed using a scanning electron microscope (SEM). At this time, among the inhibitors uniformly dispersed on the filter, an area (region) of 100 μm × 100 μm □ was observed, and an equivalent circle diameter in the region was 5 μm or less. Moreover, the Epstein test piece was cut out and the iron loss W _17/50 was measured.

Further, a steel slab having the composition shown in Table 1 is hot-rolled according to a conventional method, cold-rolled into a cold-rolled sheet having a final thickness of 0.27 mm, and then decarburized according to a conventional method. Directional electromagnetic that is recrystallized annealed, coated with an annealing separator based on MgO, and then subjected to secondary recrystallization annealing and finish annealing including soaking at a soaking temperature of 1200 ° C. for 10 hr. Seven coils of a steel plate (product plate) were prepared. The Epstein test piece was cut out from the longitudinal center and the width center of each product coil thus obtained, and the iron loss W _17/50 was measured. The iron loss is 0.90 or less.

  Table 1 shows the component composition, and Table 2 shows the measurement results.

As is apparent from Table 2, it can be seen that all the inventive examples can obtain grain-oriented electrical steel sheets excellent in product stability with no variation in magnetic properties. On the other hand, in Comparative Example 8 in which the number of inhibitors is out of the scope of the present invention, the iron loss characteristics of the test material and the product plate are poor. In Comparative Examples 9 to 11 and 17, the number of inhibitors is out of the scope of the present invention, and the correlation between the iron loss characteristics of the test material and the product plate (the iron loss W of the test material and the product plate). the difference of _17/50 is, in absolute value is less than 0.04W / kg.) is not taken. This can be said to be because the purification annealing temperature does not satisfy 980 ° C. or more and 1025 ° C. or less, so that there is no correlation with the iron loss characteristic of the product plate. As described above, by using the evaluation method of the present invention, it is not necessary to measure the iron loss characteristic after manufacturing the product plate, and the iron loss characteristic of the product plate can be determined.

Claims (6)

An annealing separator was applied to the steel sheet in any manufacturing process after the hot rolling process, followed by secondary recrystallization annealing at a maximum attained temperature of 1100 ° C or higher and purification annealing at 980 ° C or higher and 1025 ° C or lower. Using a sample as a test material,
Starting from an arbitrary position in the region of 30 to 60 μm from the surface of the specimen, electrolytic extraction is performed after dissolving a predetermined amount of the specimen, and a predetermined number of inhibitors are contained in the obtained melt. An evaluation method for a grain-oriented electrical steel sheet, wherein the following are accepted. Tested by applying an annealing separator to the steel sheet in any manufacturing process after the hot rolling process, followed by secondary recrystallization annealing at a maximum temperature of 1100 ° C or higher and purification annealing at 1000 ° C. Material,
Starting from an arbitrary position in the region of 30 to 60 μm from the surface of the specimen, electrolytic extraction is performed after dissolving a predetermined amount of the specimen, and a predetermined number of inhibitors are contained in the obtained melt. An evaluation method for a grain-oriented electrical steel sheet, wherein the following are accepted. The sample material contains C: 0.01 to 0.08 mass%, Si: 2.00 to 8.00 mass%, Mn: 0.005 to 1.00 mass%, and the following ( The method for evaluating a grain-oriented electrical steel sheet according to claim 1 or 2, wherein any one or more of 1) to (3) are contained, and the balance is Fe and inevitable impurities.
(1) Al: 0.010-0.065 mass% and N: 0.005-0.012 mass%
(2) S: 0.005-0.030 mass%
(3) Se: 0.005 to 0.030 mass% The sample material further includes Cu: 0.03-3.00 mass%, Sb: 0.005-0.50 mass%, Ni: 0.01-1.50 mass%, P: 0.03- It contains 1 type (s) or 2 or more types chosen from 0.50mass%, Sn: 0.005-0.50mass%, Mo: 0.005-0.10mass%, It is characterized by the above-mentioned. Evaluation method for grain-oriented electrical steel sheets. In magnitude 1000 mm ² of the surface of electrowinning of the test material, the predetermined amount is 0.1 g, claim 1-4, wherein the number of said inhibitor is 2500 or less 1 Evaluation method of grain-oriented electrical steel sheet according to item.
However, the inhibitor is an inhibitor observed in a range of 0.01 mm ² on the filter after filtering the lysate using a filter having a filtration area of 1020 mm ² . By performing the evaluation method of the grain-oriented electrical steel sheet according to any one of claims 1 to 5, and performing the manufacturing process after the arbitrary manufacturing process for the steel sheet determined to be acceptable by the evaluation method , A method for producing a grain-oriented electrical steel sheet, comprising producing a grain-oriented electrical steel sheet.

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