JP2016156068A - Method for producing grain-oriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grain-oriented silicon steel sheet in which variation of the magnetic properties in the longitudinal direction of a product is suppressed, and stably having satisfactory magnetic flux density in a method for producing a silicon steel sheet where, in a componential system in accordance with an inhibitorless component in which Al is suppressed to 0.010 mass% or lower, while high temperature slab heating is evaded, carbide control is positively performed, and cold rolling is performed for one or more times.SOLUTION: Provided is a method for producing a grain-oriented silicon steel sheet characterized in that, regarding a steel having a prescribed componential composition, precipitates satisfying the relation of XFeKα/XCKα≤12 in an SEM-EDX analysis spectrum intensity ratio are precipitated in the steel structure before any cold rolling till the time of the final cold rolling from hot rolling; where the XCKα and XFeKα respectively denote the maximum value of the SEM-EDX analysis spectrum intensity to the Kα rays of C and Fe.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties.

  Oriented electrical steel sheet is a soft magnetic material used as a core material for transformers and generators, and has a crystal structure in which the <001> orientation, which is the easy axis of iron, is highly aligned in the rolling direction of the steel sheet. . Such a texture preferentially grows grains of (110) [001] orientation, which is called the Goss orientation, during secondary recrystallization annealing during the manufacturing process of grain-oriented electrical steel sheets. Formed through secondary recrystallization.

  Conventionally, such grain-oriented electrical steel sheets were heated to 1300 ° C or higher by heating a slab containing an inhibitor component such as MnS, MnSe, and AlN to a mass of about 4.5 mass% or less to temporarily dissolve the inhibitor component. After that, it is hot-rolled and subjected to hot-rolled sheet annealing as necessary, to obtain a final sheet thickness by one or more cold rollings sandwiching intermediate annealing, followed by primary recrystallization annealing in a wet hydrogen atmosphere After performing primary recrystallization and decarburization, an annealing separator mainly composed of magnesia (MgO) is applied, and then the final recrystallization and inhibitor components are purified at 1200 ° C for about 5 hours. It has been manufactured by performing finish annealing (for example, Patent Document 1 and Patent Document 2).

  As described above, in manufacturing conventional grain-oriented electrical steel sheets, precipitates (inhibitor components) such as MnS, MnSe, and AlN are included in the slab stage, and these inhibitor components are heated by slab heating at a high temperature of 1300 ° C or higher. Has been adopted in which secondary recrystallization is manifested by solid-dissolving the solution once and finely precipitating it in a subsequent step.

  In other words, the conventional manufacturing process for grain-oriented electrical steel sheets required slab heating at a high temperature exceeding 1300 ° C, so the manufacturing cost has to be extremely high, and in recent years, there has been a demand for a reduction in manufacturing cost. I left a problem where I couldn't respond.

  Therefore, studies have been made on a technique for developing secondary recrystallization without containing an inhibitor component in the slab in the first place, and Patent Document 3 discloses a technique (inhibitorless method) capable of performing secondary recrystallization without containing an inhibitor component. It is disclosed.

  This inhibitorless method is a technology that uses secondary steel with higher purity and develops secondary recrystallization by texture (control of texture). The inhibitor-less method does not require high-temperature slab heating and enables production of grain-oriented electrical steel sheets at a low cost. However, because it does not have an inhibitor, it is affected by temperature variations during production and during intermediate processes. As a result, the magnetic characteristics of the product are likely to vary.

  In addition, texture control is an important factor in this technology. If this texture control is not sufficient, Goss orientation after secondary recrystallization ((110) [001] ) Is low and the magnetic flux density is often low.

U.S. Pat. No. 1,965,559 Japanese Patent Publication No. 56-21050 Japanese Patent No. 3707268 Japanese Patent No. 3551849 Japanese Patent No. 4123653

  On the other hand, Patent Document 4 discloses a primary recrystallization texture that is advantageous for the secondary recrystallization of the Goss orientation. Further, Patent Document 5 discloses a technique for combining the crystal grain size before the final cold rolling and the range of the rolling reduction as one of the methods for controlling the texture. As described above, many techniques have been proposed for controlling the texture, but the value of the magnetic flux density obtained and the degree of variation thereof have not been sufficient.

  The present invention advantageously solves the above-described problems, and is a component system according to an inhibitorless component in which Al is suppressed to 0.010 mass% or less, and actively performs carbide control while avoiding high-temperature slab heating, To provide a method for producing a grain-oriented electrical steel sheet having a stable and good magnetic flux density while suppressing variations in magnetic properties in the longitudinal direction of the product in a method for producing a grain-oriented electrical steel sheet that is cold-rolled one or more times. With the goal.

The inventors have intensively studied to solve the above problems. As a result, by performing heat treatment for a certain time or more in a certain temperature range during or after cooling of any pre-cold rolling annealing including hot-rolled sheet annealing, an excellent magnetic flux density with small longitudinal variation is obtained. It came to develop the manufacturing method of a series of grain-oriented electrical steel sheets which perform one or more cold rolling.
In the following, experiments that triggered the development of the present invention will be described.

<Experiment>
C: 0.04 mass%, Si: 3.0 mass%, acid-soluble Al: 0.006 mass%, N: 0.004 mass%, Mn: 0.03 mass%, S: 0.002 mass%, Cu: 0.02 mass%, Cr: 0.02 mass%, The steel consisting of the remaining Fe and unavoidable impurities is melted, heated to 1250 ° C, hot rolled to a hot rolled sheet with a thickness of 2.4mm, and annealed at 1030 ° C for 40 seconds, 700 ° C * Cold rolling was performed with or without heat treatment for 1 minute to 480 hours to obtain a cold-rolled sheet having a final sheet thickness of 0.27 mm. Next, primary recrystallization annealing was performed in a humid atmosphere of 55 vol% H ₂ -45 vol% N ₂ , which also served as decarburization annealing at 860 ° C. for 100 seconds. Thereafter, an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, dried, and then subjected to finish annealing including purification treatment and secondary recrystallization at 1200 ° C. for 5 hours in a hydrogen atmosphere. Further, the coil is divided into four, and 10 test pieces each having a width of 100 mm are sampled from a total of five locations including two end portions and three division points of the original coil, and magnetic flux is obtained by the method described in JIS C 2556. density _{B 8} were measured. The average value of the magnetic flux density B ₈ were measured is shown in FIG.

From the figure, it was found that the heat treatment after the hot-rolled sheet annealing gave an excellent magnetic flux density with little variation in the longitudinal direction, and the heat treatment time has an optimum range. Further, the carbide precipitated by heat treatment at 700 ° C. in the optimum time range satisfied the relationship of XFeKα / XCKα ≦ 12 in the SEM-EDX analysis spectral intensity ratio. However, XCKα and XFeKα are the maximum values of the SEM-EDX analysis spectrum intensities for the Cα and Kα rays, respectively. In addition, JEOL's JSM-7001F was used as the device, and a 30-point integration point analysis was performed at an acceleration voltage of 15 kV.
The present invention has been completed through further studies based on the above findings.

The gist of the present invention is as follows.
1. C: 0.02 to 0.08 mass%, Si: 2.0 to 5.0 mass%, acid-soluble Al: 0.001 to 0.010 mass% and Mn: 0.005 to 0.50 mass%, N is less than 0.005 mass%, and Se and / or S is contained. Suppressed to less than 0.005 mass% in total, the remainder is a slab for grain-oriented electrical steel sheets composed of Fe and inevitable impurities, heated at a temperature of 1300 ° C or lower, hot-rolled, hot-rolled sheet annealed, In a series of manufacturing methods for grain-oriented electrical steel sheets that are subjected to primary recrystallization annealing that also serves as decarburization annealing, and then performs final annealing, by performing cold rolling twice or more times with intermediate cold rolling or intermediate annealing. Precipitates satisfying the relationship XFeKα / XCKα ≦ 12 in the SEM-EDX analysis spectral intensity ratio in any steel structure before cold rolling until after the final cold rolling. A method for producing a grain-oriented electrical steel sheet, comprising:
XCKα and XFeKα are the maximum values of the SEM-EDX analysis spectrum intensity with respect to the Kα rays of C and Fe, respectively.

2. In the series of manufacturing methods of the grain-oriented electrical steel sheet, the heat treatment at 600 to 800 ° C. for 15 minutes or more is performed after the cooling process or annealing of any pre-cold rolling annealing including hot-rolled sheet annealing. The manufacturing method of the grain-oriented electrical steel sheet according to 1 above.

3. The slab is further Cu: 0.01 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, P: 0.005 to 0.50 mass%, Sn: 0.01 to 0.50 mass%, Mo: 0.01 to 0.50 mass%, Ni: 0.005 to 1.50 mass%, Cr: 0.01 to 1.50 mass%, Bi: 0.005 to 0.50 mass%, B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.010 mass%, Nb: 0.001 to 0.010 mass%, V: 0.001 to 0.010 mass % And Ta: One or more selected from 0.001 to 0.010 mass% are contained, The method for producing a grain-oriented electrical steel sheet according to 1 or 2 above.

4). 4. The method for producing a grain-oriented electrical steel sheet according to 2 or 3 above, wherein, in the primary recrystallization annealing, a temperature range of 200 to 700 ° C. is rapidly heated at 50 ° C./s or more.

5). In any stage after the cold rolling, grooves are formed in the direction crossing the rolling direction on the surface of the steel sheet, or magnetic domain subdivision treatment is performed to irradiate an electron beam or a laser continuously or intermittently. The method for producing a grain-oriented electrical steel sheet according to any one of 1 to 4 above.

  According to the present invention, the texture after cold rolling and further after primary recrystallization annealing can be improved by carbide control before cold rolling, so that excellent magnetic flux density can be obtained without high-temperature slab heating. A grain-oriented electrical steel sheet is obtained.

It is the figure which showed the relationship between heat processing time and magnetic flux density. It is a figure which shows the SEM-EDX analysis spectrum of the graphite which precipitated by heat processing.

Hereinafter, the present invention will be specifically described.
First, the necessary component composition of the steel material (slab) of the method electrical steel sheet to which the present invention is applied will be described.
C: 0.02-0.08 mass%
If C is less than 0.02 mass%, the carbide itself decreases, and the effect of carbide control becomes difficult to appear. On the other hand, if it exceeds 0.08 mass%, it will be difficult to reduce to 0.005 mass% or less at which no magnetic aging occurs due to decarburization annealing. Therefore, C is in the range of 0.02 to 0.08 mass%. Preferably it is the range of 0.025-0.05 mass%.

Si: 2.0-5.0mass%
Si is an element necessary for increasing the specific resistance of steel and reducing iron loss. For the above effect, addition of less than 2.0 mass% is not sufficient. On the other hand, if it exceeds 5.0 mass%, the workability is lowered and it is difficult to roll and manufacture. Therefore, Si is set to a range of 2.0 to 5.0 mass%. Preferably it is the range of 2.5-4.0 mass%.

Acid-soluble Al: 0.001 to 0.010 mass%
Since Al forms a dense oxide film on the surface and may inhibit decarburization, the amount of acid-soluble Al is set to 0.010 mass% or less, preferably 0.007 mass% or less. However, Al with high oxygen affinity should be 0.001 mass% or more, because it can reduce the amount of dissolved oxygen in the steel by adding a small amount in the steelmaking stage and reduce oxide inclusions that lead to property deterioration. Is in the range of 0.003 mass% or more.

Mn: 0.005-0.50mass%
Mn is an element necessary for improving the hot workability of steel. The addition of less than 0.005 mass% is not sufficient for the above effect. On the other hand, if it exceeds 0.5 mass%, the magnetic flux density of the product plate will decrease. Therefore, Mn is set to a range of 0.005 to 0.50 mass%. Preferably it is the range of 0.02-0.20 mass%.

N: Less than 0.005 mass% Since N may cause defects such as blisters during slab heating, it is necessary to suppress it to less than 0.005 mass%.

Se and / or S total less than 0.005 mass%
Since Se and S are inhibitor-forming components, in the present invention, a steel material in which the total of both is reduced to less than 0.005 mass% is used.

  As mentioned above, although the required component of the steel plate of this invention was described, in addition to the said component, in order to improve a magnetic characteristic, Cu: 0.01-0.50mass%, Sb: 0.005-0.50mass%, P: 0.005-0.50mass %, Sn: 0.01 to 0.50 mass%, Mo: 0.01 to 0.50 mass%, Ni: 0.005 to 1.50 mass%, Cr: 0.01 to 1.50 mass%, Bi: 0.005 to 0.50 mass%, B: 0.0002 to 0.0025 mass%, One or more selected from Te: 0.0005 to 0.010 mass%, Nb: 0.001 to 0.010 mass%, V: 0.001 to 0.010 mass%, and Ta: 0.001 to 0.010 mass% may be added as appropriate.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
In the present invention, a steel material (slab) may be produced by a conventionally known ingot-bundling rolling method or continuous casting method after melting the steel having the above-described component composition by a conventional refining process. Alternatively, a thin cast piece having a thickness of 100 mm or less may be manufactured by a direct casting method. The slab is heated to a temperature of 1300 ° C. or lower according to a conventional method and then subjected to hot rolling. In addition, you may hot-roll immediately after casting, without heating. In the case of a thin cast slab, hot rolling may be performed, or the hot rolling may be omitted and the subsequent process may proceed.

  Subsequently, the hot-rolled sheet obtained by hot rolling is subjected to hot-rolled sheet annealing as necessary. However, hot-rolled sheet annealing is always performed when cold rolling is performed only once. The annealing temperature of this hot-rolled sheet annealing is preferably in the range of 800 to 1150 ° C. in order to obtain good magnetic properties. If it is less than 800 degreeC, the band structure formed by hot rolling will remain, it will become difficult to obtain the primary recrystallized structure of grain size, and the development of secondary recrystallization will be inhibited. On the other hand, when the temperature exceeds 1150 ° C., the grain size after the hot-rolled sheet annealing is excessively coarsened, so that it becomes difficult to obtain a primary recrystallized structure of sized particles.

The hot-rolled sheet after hot-rolling or after hot-rolled sheet annealing is subjected to one or more cold rollings or two or more cold-rolling sandwiching the intermediate annealing to form a cold-rolled sheet having a final thickness. The annealing temperature of the intermediate annealing is preferably in the range of 900 to 1200 ° C. When the temperature is lower than 900 ° C., the recrystallized grains after intermediate annealing become finer, and the Goss nuclei in the primary recrystallized structure tend to decrease and the magnetic properties of the product plate tend to deteriorate. On the other hand, when the temperature exceeds 1200 ° C., the crystal grains become too coarse as in the case of hot-rolled sheet annealing, and it becomes difficult to obtain a primary recrystallized structure of the sized grains.
In the cold rolling (final cold rolling) with the final sheet thickness, the rolling reduction is preferably 80 to 95% in order to sufficiently develop the <111> // ND orientation.

  Here, in this invention, the heat processing which anneal for 15 minutes or more at 600-800 degreeC after the cooling process of any annealing before cold rolling including a hot-rolled sheet annealing or annealing is performed. At that time, the carbides finely precipitated in the pearlite structure after annealing in the hot-rolled sheet or in the crystal grains change from the metastable phase cementite to the stable phase graphite and condense, and the number of precipitates decreases. That is, it is possible to effectively reduce the number of carbides that cause non-uniform strain in the steel sheet by cold rolling.

  Furthermore, because graphite is softer than cementite, even if present, non-uniform strain caused by rolling is reduced. As a result, in the texture after the primary recrystallization annealing, crystal grains with {111} <112> orientation and {12 4 1} <014> orientation which are optimal for increasing the degree of Goss orientation accumulation increase.

  When the above heat treatment is performed at a temperature exceeding 800 ° C., α-γ transformation occurs and graphite is not precipitated. Therefore, it is important to perform the treatment at a temperature lower than that. Desirably, it is performed at 760 ° C or lower. On the other hand, when the above heat treatment is performed at a temperature lower than 600 ° C., the diffusion rate of C is slow, and enormous time is required until the precipitation of graphite. Therefore, the above heat treatment is performed at 600 ° C. or higher, desirably 650 ° C. or higher.

  In addition, the heat treatment is not sufficient if the heat treatment time is less than 15 minutes in order to sufficiently precipitate the graphite uniformly in the longitudinal direction, and is performed for 15 minutes or longer, preferably 30 minutes or longer. Furthermore, this heat treatment may be performed in the cooling process of hot-rolled sheet annealing or intermediate annealing after cold rolling, but from the standpoint of operation, after cooling once, in a batch-type annealing furnace in a time of 10 hours or less. It is good also as annealing.

At that time, as the degree of graphitization from cementite, point analysis by SEM-EDX is performed with an acceleration voltage of 15 kV and integration for 30 seconds, and the SEM-EDX analysis spectral intensity ratio satisfies the relationship of XFeKα / XCKα ≦ 12. This is particularly important in the present invention (FIG. 2). However, XCKα and XFeKα are the maximum values of the SEM-EDX analysis spectrum intensity for the Cα and Fe Kα rays, respectively. The lower limit of XFeKα / XCKα is not particularly limited, and may be zero.

Furthermore, the cold-rolled sheet having the final thickness is then subjected to primary recrystallization annealing that also serves as decarburization annealing. In this primary recrystallization, from the viewpoint of decarburization, the annealing temperature is preferably in the range of 800 to 900 ° C., and the atmosphere is preferably a wet atmosphere.
In addition, by rapidly heating the temperature range of 200-700 ° C in the temperature increase process of primary recrystallization annealing at 50 ° C / s or more, the recrystallization nuclei of Goss orientation grains increased, and the iron loss of the steel sheet was reduced. Therefore, according to the present invention, it is possible to produce a grain-oriented electrical steel sheet having both high magnetic flux density and low iron loss.

  The steel sheet that has undergone primary recrystallization annealing is coated with an annealing separator mainly composed of MgO on the steel sheet surface, dried, and then subjected to finish annealing to develop a secondary recrystallized structure highly accumulated in the Goss orientation. And forming a forsterite film. The annealing temperature for this final annealing should be 800 ° C or higher for secondary recrystallization to be manifested, and it must be kept at a temperature of 800 ° C or higher for 20 hours or longer to complete the secondary recrystallization. Each is advantageous. Furthermore, in order to form a good forsterite film, it is preferable to raise the temperature of the steel sheet to about 1200 ° C. and hold it for 1 hour or longer.

  Furthermore, the steel sheet after the finish annealing can be subjected to flattening annealing and then straightened after performing washing, brushing, pickling, etc. to remove the unreacted annealing separator adhering to the steel sheet surface. It is effective in reducing iron loss. This is because finish annealing is generally performed in a coil state, so that the coil has wrinkles, which may cause deterioration in characteristics when measuring iron loss.

  In addition, when using laminated steel sheets, it is effective to form an insulating film on the steel sheet surface before or after the above-mentioned flattening annealing, in particular, in order to reduce iron loss, As the insulating coating, it is preferable to apply a tension applying coating capable of applying tension to the steel sheet. In addition, when forming a tension-imparting film, a method of applying a tension film through a binder or a method of depositing an inorganic substance on the surface of a steel sheet by a physical vapor deposition method or a chemical vapor deposition method has excellent film adhesion and iron loss. It is possible to form an insulating film having an extremely large reduction effect.

  Furthermore, in order to further reduce the iron loss, the present invention can perform a magnetic domain subdivision process. In addition, as the treatment method, as in general practice, a groove is formed in the final product plate, or heat distortion or linear distortion is formed by electron beam irradiation, laser irradiation, plasma irradiation, or the like. A method of introducing impact strain, a method of forming a groove by etching the steel plate surface in an intermediate process, such as a steel plate cold-rolled to the final plate thickness, or the like can be used.

Next, examples of the present invention will be described.
<Example 1>
C: 0.050 mass%, Si: 2.8 mass%, acid-soluble Al: 0.007 mass%, N: 0.003 mass%, Mn: 0.006 mass%, Se: 0.001 mass%, S: 0.002 mass%, the balance being Fe Steel slabs made of unavoidable impurities are manufactured by a continuous casting method, heated to 1250 ° C, hot rolled to a hot rolled sheet with a thickness of 2.4mm, then hot rolled at 1000 ° C for 30 seconds After annealing, the heat treatment described in Table 1 was performed, and cold rolling was performed to obtain a cold-rolled sheet having a final thickness of 0.27 mm.
Next, primary recrystallization annealing was performed in a humid atmosphere of 55 vol% H ₂ -45 vol% N ₂ that also served as decarburization annealing at 840 ° C. for 100 seconds. Thereafter, an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, dried, and then subjected to finish annealing including purification treatment and secondary recrystallization at 1200 ° C. for 5 hours in a hydrogen atmosphere. Divide the coil into four parts, and collect 10 test pieces each having a width of 100 mm from a total of 5 locations, 2 ends of the original coil and 3 split points, and magnetic flux density B according to the method described in JIS C 2556. ₈ (T) was measured, and the average value of the whole (50 sheets) and the average value of each part (10 sheets) were obtained. The difference between the maximum value and the minimum value of the measurement values at each measurement point was ΔB (T), which was used as an index of magnetic variation in the coil longitudinal direction. The results are also shown in Table 1.
At the same time, SEM-EDX analysis spectral intensity ratio XFeKα / XCKα at an acceleration voltage of 15 kV of carbide in the steel plate after heat treatment is also shown in Table 1. However, XCKα and XFeKα are the maximum values of the SEM-EDX analysis spectrum intensities for the Cα and Kα rays, respectively.

  From the table, it can be seen that by applying the present invention, there is little variation in magnetism in the coil longitudinal direction, and a directional electrical steel sheet with excellent magnetic flux density can be obtained.

<Example 2>
A steel composed of the components listed in Table 2, the balance Fe and inevitable impurities is melted, heated to 1280 ° C, hot-rolled to form a hot-rolled sheet having a thickness of 2.0 mm, and heated at 1030 ° C for 30 seconds. The sheet was annealed, heat-treated at 700 ° C. for 1 hour in a batch furnace, and cold-rolled to obtain a cold-rolled sheet having a final sheet thickness of 0.27 mm. Next, primary recrystallization annealing was performed in a humid atmosphere of 55 vol% H ₂ -45 vol% N ₂ , which also served as decarburization annealing at 840 ° C. for 100 seconds. Thereafter, an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, dried, and then subjected to finish annealing including purification treatment and secondary recrystallization at 1200 ° C. for 5 hours in a hydrogen atmosphere. Ten test pieces having a width of 100 mm were sampled from the steel sheet obtained as described above under each condition, and the magnetic flux density B ₈ (T) was measured by the method described in JIS C 2556 to obtain an average value. The results are also shown in Table 2.
At the same time, SEM-EDX analysis spectrum intensity ratio XFeKα / XCKα at an acceleration voltage of 15 kV of carbide in the steel plate after heat treatment is also shown in Table 2. However, XCKα and XFeKα are the maximum values of the SEM-EDX analysis spectrum intensities for the Cα and Kα rays, respectively.

  It can be seen from the table that a directional electrical steel sheet having excellent magnetic flux density can be obtained by applying the present invention.

<Example 3>
C: 0.028 mass%, Si: 3.5 mass%, acid-soluble Al: 0.008 mass%, N: 0.003 mass%, Mn: 0.01 mass%, S: 0.003 mass%, Ni: 0.01 mass%, Sb: 0.02 mass%, P: A steel slab containing 0.01% by mass and the balance being Fe and inevitable impurities is manufactured by a continuous casting method, heated to 1250 ° C., hot-rolled into a hot rolled sheet having a thickness of 2.2 mm, 1040 Hot-rolled sheet annealed at ℃ x 40 seconds, cold rolled to an intermediate sheet thickness of 1.3 mm, intermediate annealed at 1100 ° C x 30 seconds, cold-rolled, and final sheet thickness: 0.23 mm It was. However, heat treatment was performed at 700 ° C. for 10 hours using a batch furnace at the timing shown in Table 3. Next, primary recrystallization annealing was performed in a humid atmosphere of 55 vol% H ₂ -45 vol% N ₂ , which also served as decarburization annealing at 840 ° C. for 100 seconds. Here, the temperature increase rate of the primary recrystallization annealing was as shown in Table 3. Thereafter, an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, dried, and then subjected to finish annealing including purification treatment and secondary recrystallization at 1200 ° C. for 5 hours in a hydrogen atmosphere. Furthermore, some of the steel sheets listed in Table 3 were subjected to magnetic domain refinement using a laser or electron beam. The magnetic domain refinement process was performed in a row form with a laser or in a point form with an electron beam at intervals of 5 mm in a direction perpendicular to the rolling direction of the steel sheet. From the steel plate obtained as described above, 10 test pieces each having a width of 100 mm in the width direction of the steel plate were sampled under each condition, the magnetic flux density B ₈ (T) was measured by the method described in JIS C 2556, and the average value was obtained. Asked. The results are also shown in Table 3.
At the same time, SEM-EDX analysis spectral intensity ratio XFeKα / XCKα at an acceleration voltage of 15 kV of carbide in the steel plate after heat treatment is also shown in Table 3. However, XCKα and XFeKα are the maximum values of the SEM-EDX analysis spectrum intensities for the Cα and Kα rays, respectively.

It can be seen from the table that a grain-oriented electrical steel sheet having excellent magnetism can be obtained by applying the present invention.

Claims (5)

C: 0.02 to 0.08 mass%, Si: 2.0 to 5.0 mass%, acid-soluble Al: 0.001 to 0.010 mass% and Mn: 0.005 to 0.50 mass%, N is less than 0.005 mass%, and Se and / or S is contained. Suppressed to less than 0.005 mass% in total, the remainder is a slab for grain-oriented electrical steel sheets composed of Fe and inevitable impurities, heated at a temperature of 1300 ° C or lower, hot-rolled, hot-rolled sheet annealed, In a series of manufacturing methods for grain-oriented electrical steel sheets that are subjected to primary recrystallization annealing that also serves as decarburization annealing, and then performs final annealing, by performing cold rolling twice or more times with intermediate cold rolling or intermediate annealing. Precipitates satisfying the relationship XFeKα / XCKα ≦ 12 in the SEM-EDX analysis spectral intensity ratio in any steel structure before cold rolling until after the final cold rolling. A method for producing a grain-oriented electrical steel sheet, comprising:
XCKα and XFeKα are the maximum values of the SEM-EDX analysis spectrum intensity with respect to the Kα rays of C and Fe, respectively.   In the series of manufacturing methods of the grain-oriented electrical steel sheet, the heat treatment at 600 to 800 ° C. for 15 minutes or more is performed after the cooling process or annealing of any pre-cold rolling annealing including hot-rolled sheet annealing. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1.   The slab is further Cu: 0.01 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, P: 0.005 to 0.50 mass%, Sn: 0.01 to 0.50 mass%, Mo: 0.01 to 0.50 mass%, Ni: 0.005 to 1.50 mass%, Cr: 0.01 to 1.50 mass%, Bi: 0.005 to 0.50 mass%, B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.010 mass%, Nb: 0.001 to 0.010 mass%, V: 0.001 to 0.010 mass % And Ta: One or more selected from 0.001 to 0.010 mass% is contained, The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2.   4. The method for producing a grain-oriented electrical steel sheet according to claim 2, wherein, in the primary recrystallization annealing, a temperature range of 200 to 700 ° C. is rapidly heated at 50 ° C./s or more. 5.   In any stage after the cold rolling, grooves are formed in the direction crossing the rolling direction on the surface of the steel sheet, or magnetic domain subdivision treatment is performed to irradiate an electron beam or a laser continuously or intermittently. The manufacturing method of the grain-oriented electrical steel sheet according to any one of claims 1 to 4.