JP5600991B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

The present invention is a square oriented electrical steel sheet, to a method for producing stably at an industrial scale.

  The grain-oriented electrical steel sheet is a steel sheet containing about 2 to 5% Si and highly accumulating the crystal grain orientation of the product in the {110} <001> orientation, and is mainly used for stationary inductors such as transformers. Used as iron core material. Control of crystal orientation in the production of such grain-oriented electrical steel sheets is achieved by utilizing a catastrophic grain growth phenomenon called secondary recrystallization.

  As a method for controlling this secondary recrystallization, a fine precipitate called an inhibitor is completely dissolved at the time of heating the steel slab before hot rolling, and then finely precipitated in hot rolling and subsequent annealing steps. There is. In this method, MnS and AlN as exemplified in Patent Document 1 are used as inhibitors, rolling at a rolling reduction exceeding 80% in the final cold rolling step, and MnS and MnSe as exemplified in Patent Document 2 are performed. A method of carrying out the cold rolling step twice using the above as an inhibitor has been practiced industrially. In this method, the steel slab before hot rolling is heated at a high temperature of 1280 ° C. or higher in order to completely dissolve the precipitate.

  Further, as another method for controlling secondary recrystallization, as exemplified in Patent Documents 3 and 4, heating of the steel slab before hot rolling is performed at a temperature lower than 1280 ° C., and nitriding after cold rolling is performed. A method of using AlN formed by treatment as an inhibitor has been industrially implemented.

In the production of the grain-oriented electrical steel sheet as described above, many developments have been made to obtain a steel sheet having superior magnetic properties. However, as the demand for energy saving increases in recent years, the iron loss has been further reduced. Is required.
There are various methods for reducing the iron loss of the grain-oriented electrical steel sheet, but it is effective to increase the magnetic flux density and reduce the hysteresis loss as shown in Patent Document 1 described above.

In order to improve the magnetic flux density of the grain-oriented electrical steel sheet, it is necessary to highly accumulate the crystal grain orientation of the product plate in the {110} <001> orientation. There is a method using an auxiliary additive element that is considered to be strengthened.
Patent Documents 5 to 7 disclose methods using Te as such an additive element.

  In order to reduce the iron loss of the grain-oriented electrical steel sheet, it is effective to subdivide the magnetic domain by grooving the product plate or irradiate with a laser, or subdivide the macro structure. As a method of reducing the iron loss by subdividing the macro structure, after recrystallizing the cold-rolled sheet, a linear groove is formed by machining within 30 ° from the direction perpendicular to the rolling direction, and then decarburized in wet hydrogen. Patent Document 8 discloses a method of performing secondary recrystallization annealing after annealing.

  According to the study by the present inventor, it has been found that even if Te is added to improve the magnetic flux density, a grain-oriented electrical steel sheet with extremely low iron loss may not be obtained. When Te is added, the steel plate macro grain structure after secondary recrystallization becomes a unique shape extending in the rolling direction. Under industrial production conditions, finish annealing in which secondary recrystallization occurs is performed in a coil shape, so if the macro grains become too large in the rolling direction, the deviation angle of the crystal orientation becomes large based on the coil set, resulting in iron loss. Was found to be due to deterioration.

  Moreover, simply subdividing the macro structure is not sufficient to achieve the low iron loss required in the market, and the orientation of crystal grains of the product plate is highly accumulated in the {110} <001> orientation. It turned out that it is necessary to make it compatible with the technology which raises magnetic flux density.

Japanese Patent Publication No. 40-15644 Japanese Patent Publication No. 51-13469 Japanese Examined Patent Publication No. 62-45285 Japanese Patent Laid-Open No. 2-77525 Japanese Patent Laid-Open No. 06-184640 Japanese Patent Laid-Open No. 06-207220 Japanese Patent Laid-Open No. 10-273727 JP 2002-294416 A

Accordingly, the present invention is a square oriented electrical steel sheet, at industrial scale, and to provide a method for stably manufacturing.

  The gist of the present invention for solving the above problems is as follows.

(1) By mass%, C: 0.02 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.01 to 0.15%, S: 0.001 to 0.050% Slab containing acid-soluble Al: 0.01 to 0.05%, N: 0.002 to 0.015%, Te: 0.0005 to 0.10%, the balance Fe and inevitable impurities, After heating to 1280 ° C. or higher and performing hot rolling, it is subjected to hot rolled sheet annealing, and after performing cold rolling of two times or more sandwiching one cold rolling or intermediate annealing to make a cold rolled steel sheet, In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of performing decarburization annealing and applying a finish annealing after applying an annealing separator mainly composed of MgO to the steel sheet surface,
By groove granted during decarburization annealing, or by recrystallization annealing after the grooves applied after decarburization annealing method for producing a grain-oriented electrical steel sheet characterized by dividing the secondary recrystallized grains in the groove position .

(2) By mass%, C: 0.02 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.01 to 0.15%, S and Se in total: 0.001 -0.050%, acid-soluble Al: 0.010-0.050%, N: 0.002-0.015%, Te: 0.0005-0.10%, the balance Fe and inevitable impurities The slab made of is heated to 1280 ° C. or higher, hot-rolled, then subjected to hot-rolled sheet annealing, and cold-rolled by performing two or more cold rollings with one cold rolling or intermediate annealing. In the method for producing a grain-oriented electrical steel sheet comprising a series of steps in which a steel sheet is subjected to decarburization annealing, and a finish annealing is performed after applying an annealing separator mainly composed of MgO to the steel sheet surface.
By groove granted during decarburization annealing, or by recrystallization annealing after the grooves applied after decarburization annealing method for producing a grain-oriented electrical steel sheet characterized by dividing the secondary recrystallized grains in the groove position .

(3) By mass%, C: 0.02 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.05 to 0.50%, S alone or S and Se in total In: 0.02% or less, acid-soluble Al: 0.010 to 0.050%, N: 0.001 to 0.015%, Te: 0.0005 to 0.10%, balance Fe and inevitable A slab made of a general impurity is heated below 1280 ° C., hot-rolled, then subjected to hot-rolled sheet annealing, and subjected to one or more cold rolling or two or more cold rolling sandwiching intermediate annealing. In the manufacturing method of grain-oriented electrical steel sheet, which consists of a series of steps in which after cold-rolled steel sheet, decarburization annealing and nitridation annealing are performed, and an annealing separator containing MgO as a main component is applied to the steel sheet surface and then finish annealing is performed. ,
By groove granted during decarburization annealing, or by recrystallization annealing after the grooves applied after decarburization annealing method for producing a grain-oriented electrical steel sheet characterized by dividing the secondary recrystallized grains in the groove position .
(4) In the manufacturing method of the grain-oriented electrical steel sheet according to any one of (1) to (3),
It is possible to divide the secondary recrystallized grains at the groove position by applying grooves by a mechanical method during decarburization annealing or by recrystallization annealing after applying grooves by a mechanical method after decarburization annealing. A method for producing a grain-oriented electrical steel sheet.
(5) In the manufacturing method of the grain-oriented electrical steel sheet according to (4),
It is possible to divide the secondary recrystallized grains at the groove position by applying grooves with a gear-type roll during decarburization annealing or by applying recrystallization annealing after applying grooves with a gear-type roll after decarburization annealing. A method for producing a grain-oriented electrical steel sheet.

(6) the slab, further Bi: wherein characterized in that it contains from 0.0005 to 0.10% (1) to the production method of the oriented electrical steel sheet towards according to any one of (5).

( 7 ) In the method for producing a grain-oriented electrical steel sheet according to any one of (1) to ( 6 ), a heating rate of 50 ° C./sec or more immediately before decarburization annealing or in a temperature rising process of decarburization annealing is 800. The manufacturing method of the grain-oriented electrical steel sheet characterized by performing the process heated to the temperature more than degreeC.

  According to the present invention, a grain-oriented electrical steel sheet with extremely low iron loss can be stably produced on an industrial scale. Therefore, the present invention can satisfy the increasing demand for high-quality grain-oriented electrical steel sheets accompanying an increase in the amount of power generation around the world while meeting the recent demand for energy saving, and the effect is enormous.

  Hereinafter, embodiments of the present invention will be described in detail.

The steel sheet to which Te is added has a unique shape in which the steel sheet macrostructure after secondary recrystallization is stretched in the rolling direction. Under industrial production conditions, finish annealing in which secondary recrystallization occurs is performed in a coil shape, so if the macro grains become too large in the rolling direction, the deviation angle of the crystal orientation becomes large based on the coil set, resulting in iron loss. Deteriorates. Therefore, the present inventors conducted the following experiment in order to suppress the stretching of the macrostructure after secondary recrystallization in the rolling direction and to establish a stable production technique for a grain-oriented electrical steel sheet with extremely low iron loss.
In a vacuum melting furnace, in mass%, C: 0.08%, Si: 3.26%, Mn: 0.08%, S: 0.024%, acid-soluble Al: 0.03%, N: 0.00. A slab having a composition containing 008% and Te: 0.011% was produced, and after annealing at 1300 ° C. for 1 hour, hot rolling was performed.

The obtained hot-rolled sheet was annealed at 1100 ° C. for 120 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.23 mm. This cold-rolled sheet was decarburized and annealed at 850 ° C. for 150 seconds in wet hydrogen, and then a straight groove was formed on a surface of a part of the steel sheet with a gear-type roll at an angle of 10 ° from a right angle in the rolling direction. Then, recrystallization annealing was performed at 850 ° C. for 20 seconds. The groove depth was 10 μm and the groove pitch was 5 mm. The heating rate of decarburization annealing was 25 ° C./s.
An annealing separator containing MgO as a main component is applied to the steel sheet after decarburization annealing with water slurry, and after giving a curvature with a radius of curvature of 500 mm for the purpose of providing a coil set, an average heating rate of 750 ° C or higher is 20 ° C. Heat annealing was performed at a maximum temperature of 1150 ° C. for 20 hours.

The steel plate after the finish annealing was washed with water, then sheared to a single plate magnetic measurement size, and an insulating coating mainly composed of aluminum phosphate and colloidal silica was applied and baked to prepare a sample.
The steel sheet was excited to a magnetic flux density B8 value (magnetic flux density value when a magnetic field of 800 A / m was applied at 50 Hz) and iron loss W17 / 50 value (1.7 T magnetic flux density at 50 Hz) of the obtained sample. After measuring the iron loss value), the coating film of the sample was removed, and the average value of the maximum length in the rolling direction of the steel plate macro grain was measured. Evaluation was performed on 10 samples.

  Table 1 shows the average value of magnetic flux density with and without groove: B8 value, iron loss: W17 / 50 value, and maximum length in the rolling direction of the steel plate macro grain: D value. Here, B8 is a magnetic flux density value when a magnetic field of 800 A / m is applied at 50 Hz. W17 / 50 is a value of iron loss when the steel plate is excited to 1.7 T at 50 Hz. The length in the rolling direction of the secondary recrystallization macro grain structure was defined as the maximum length in the rolling direction of each macro grain. As shown in the table, the iron loss is reduced by providing the grooves. The magnetic flux density is decreased because the magnetic flux is hindered in the groove, and it was confirmed by X-ray diffraction that the degree of orientation integration was improved. Since the steel plate macro grains were divided at the groove position, the average value of the maximum length in the rolling direction: Dave was significantly reduced to 4.2 mm.

From these, Te is added and a groove is imparted during decarburization annealing, or a groove is imparted after decarburization annealing, and then recrystallization annealing is performed, and then the length in the rolling direction of the steel plate macro grain structure after secondary recrystallization. By subdividing the thickness, it was newly found out that a remarkably low iron loss can be industrially realized, and the present invention was completed based on this finding.

Hereinafter, embodiments of the present invention will be described in detail.
As described above, the manufacturing method of industrially oriented grain-oriented electrical steel sheets is as follows. (1) The slab before hot rolling is heated at 1280 ° C. or higher depending on whether the inhibitor is formed before cold rolling. In some cases, (2) heating may be performed at less than 1280 ° C.
In the present invention, the effect of adding Te and the effect of subdividing the length of the steel plate macro grain structure in the rolling direction are mainly expressed in the secondary recrystallization, so the difference in the manufacturing method until finish annealing. However, any manufacturing method may be adopted.
Therefore, first, each manufacturing method will be described, and then the heat treatment immediately before the decarburization annealing or in the temperature raising process of the decarburization annealing will be described.

The production method (1) will be described.
In this production method, by mass%, C: 0.02 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.01 to 0.15%, S alone, or S and Se In total: 0.001 to 0.050%, acid-soluble Al: 0.01 to 0.05%, N: 0.002 to 0.015%, the balance Fe and steel consisting of inevitable impurities are used as a basis . In the present invention, the steel further contains Te: 0.0005 to 0.10% alone, or Te: 0.0005 to 0.10% and Bi: 0.0005 to 0.10% simultaneously.

  The reason why the steel composition is selected as described above is as follows. Hereinafter, the content of the element may be simply expressed as%, but% means mass%.

C has various roles, but if it is less than 0.02% by mass, the crystal grain size at the time of slab heating becomes too large and the iron loss of the product deteriorates. On the other hand, if it exceeds 0.10% by mass, decarburization annealing after cold rolling requires not only a long time, but is not economical, and decarburization tends to be incomplete. This is not preferable because it causes a magnetic defect called magnetic aging.
For this reason, the lower limit of the C content is 0.02%, and the upper limit is 0.10%. A more appropriate range within this range is 0.05 to 0.09%.

  Si is an extremely effective element for increasing the electrical resistance of steel and reducing the eddy current loss that constitutes a part of the iron loss. The mass% ranges from 2.5% to 4.5%. Must be controlled. If it is less than 2.5%, eddy current loss of the product cannot be suppressed, and if it exceeds 4.5%, workability deteriorates, which is not preferable.

  Mn is an important element for forming MnS and / or MnSe, which is an inhibitor that influences secondary recrystallization, and it is necessary to control Mn in a range of 0.01% to 0.15%. If it is less than 0.01%, the absolute amount of MnS and MnSe necessary for causing secondary recrystallization is insufficient, which is not preferable. On the other hand, if it exceeds 0.15%, not only the solid solution during slab heating becomes difficult, but also the precipitation size tends to become coarse, and the optimum size distribution as an inhibitor is impaired.

  S is an important element that forms an inhibitor with Mn as described above, and its content needs to be controlled in the range of 0.001% to 0.050%. If it deviates from the above range, a sufficient inhibitor effect cannot be obtained.

  Se is an important element that forms an inhibitor with Mn as described above, and may be contained together with S. When it contains, it is necessary to control to 0.001% or more and 0.05% or less of the total amount with S. If it deviates from the above range, a sufficient inhibitor effect cannot be obtained.

  Acid-soluble Al is a main inhibitor constituting element for producing a high magnetic flux density grain-oriented electrical steel sheet and needs to be controlled in a range of 0.01% to 0.05% by mass. If it is less than 0.01%, the quantity is insufficient, and the inhibitor strength is insufficient. On the other hand, if it exceeds 0.05%, AlN precipitated as an inhibitor becomes coarse, and as a result, the inhibitor strength is lowered, which is not preferable.

  N is an important element that forms the above-described acid-soluble Al and AlN, and is required to be controlled in a range of 0.002% to 0.015% by mass. If it deviates from the above range, a sufficient inhibitor effect cannot be obtained.

  Te is an element effective for strengthening the inhibitor and improving the magnetic flux density of the steel sheet. In order to obtain the effect, it is necessary to control the addition amount in the range of 0.0005 to 0.10%. If it is less than 0.0005%, a sufficient effect cannot be obtained, and if it exceeds 0.10%, the rollability deteriorates, which is not preferable.

  Bi is further added to Te to further improve the magnetic flux density. In order to obtain the effect, it is necessary to control the addition amount in the range of 0.0005 to 0.10%. If it is less than 0.0005%, a sufficient effect cannot be obtained, and if it exceeds 0.10%, the rollability is deteriorated.

  In addition, as an element for stabilizing secondary recrystallization, Sn, Sb, Cu, Ag, As, Mo, Cr, P, Ni, B, Pb, V, Ge, Ti, or one or more of It is also useful to contain 0.0005 to 1.0% by mass in total. If the amount of these elements is less than 0.0005%, the effect of stabilizing the secondary recrystallization is not sufficient, and if it exceeds 1.0%, the effect is saturated. Is limited to 1.0%.

  The molten steel for producing grain-oriented electrical steel sheets with the components adjusted as described above is cast by a normal method. There is no particular limitation on the casting method. Next, slab heat treatment is performed, and the lower limit of the heating temperature is set to 1280 ° C. in order to completely dissolve the inhibitor. If it is less than 1280 degreeC, inhibitor components, such as MnS, MnSe, and AlN, cannot fully be made into solution. The upper limit is not particularly defined, but is preferably 1450 ° C. or less from the viewpoint of equipment protection.

  The slab heated as described above becomes a hot-rolled sheet by subsequent hot rolling. The thickness of the hot-rolled sheet is not particularly specified, but is usually 1.8 to 3.5 mm because it is related to the cold rolling rate described later. This hot-rolled sheet is cold-rolled after being annealed for a short time. The annealing is performed in a temperature range of 750 to 1200 ° C. for 30 seconds to 10 minutes, and is effective for enhancing the magnetic properties of the product.

Cold rolling is performed once or divided into two or more times with intermediate annealing in between. One cold rolling means that one or a plurality of rollings are performed without including an annealing process in which the plate temperature exceeds 600 ° C. At that time, it is preferable for the magnetic properties to perform annealing at about 300 ° C. or less during rolling.
When cold rolling is divided into two or more times, intermediate annealing is performed during cold rolling. The intermediate annealing is preferably performed in a temperature range of 750 to 1200 ° C. for 30 seconds to 10 minutes.

When the cold rolling is performed once, the full width characteristics of the product are likely to be unstable, and when the cold rolling is performed twice or more, the product characteristics are stabilized but the ultimate magnetic flux density tends to be low. For this reason, the number of cold rolling is appropriately selected in consideration of the desired characteristic level and cost of the product.
In any case, the final cold rolling reduction is preferably in the range of 80 to 95%.

Subsequently, the cold-rolled steel sheet is decarburized and annealed at a temperature of 900 ° C. or lower in a wet atmosphere containing hydrogen nitrogen, and C is reduced to 20 ppm or lower, which is essential for product characteristics. In the present invention, as will be described later, the length in the rolling direction of the steel plate macro grain structure after the secondary recrystallization is controlled by applying a groove during decarburization annealing or by applying recrystallization annealing after applying the groove after decarburization annealing. To do.
Thereafter, a powder mainly composed of MgO is applied and coiled. Then, batch-type finish annealing is performed on the wound coil, and then unwinding, removing powder, applying a slurry liquid mainly composed of aluminum phosphate and colloidal silica, baking, and directional electrical steel sheet Complete the product.

  The finish annealing is a step of secondary recrystallization of {110} <001> oriented grains, and is extremely important for improving the magnetic flux density of the steel sheet. Usually, after secondary recrystallization is developed in the process of raising the temperature to 900 to 1200 ° C. in a nitrogen-hydrogen mixed atmosphere, it is switched to a hydrogen atmosphere and annealed at an annealing temperature of 1100 to 1200 ° C. for about 20 hours. By carrying out the process, N, S, Se, etc. are diffused and removed out of the steel sheet to improve the magnetic properties of the product plate.

  The annealing atmosphere in the finish annealing is preferably a mixed atmosphere of nitrogen and hydrogen as described above from the viewpoint of product characteristics and productivity. Increasing the nitrogen partial pressure tends to stabilize secondary recrystallization, and decreasing the nitrogen partial pressure provides high magnetic flux density characteristics but tends to destabilize secondary recrystallization.

  In addition, the steel sheet added with Te tends to have a high secondary recrystallization temperature, and the temperature increase rate on the high temperature side in the temperature increasing process may be a slow rate of 20 ° C./h or less. It is effective for stabilization. In addition, it is also effective to perform retention annealing in the middle of the temperature rise for the purpose of reducing the moisture contained in the MgO powder and improving the adhesion of the glass coating in the product to the steel plate.

Next, the production method (2) will be described.
In this production method, by mass%, C: 0.02 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.05 to 0.50%, S alone, or S and Se. Total: 0.02% or less, acid-soluble Al: 0.010 to 0.050%, N: 0.001 to 0.015%, based on steel consisting of the balance Fe and unavoidable impurities, Similarly, steel further containing Te: 0.0005 to 0.10% is used.

  In this manufacturing method, since (Al, Si) N is used as an inhibitor, MnS is not particularly required as an inhibitor. Therefore, the contents of Mn, S and Se are selected for the following reasons. About other components, it is the same as that of the case of the manufacturing method of (1).

Mn is contained in the range of 0.05% or more and 0.50% or less for the purpose of increasing specific resistance and reducing iron loss, and for the purpose of preventing the occurrence of cracks in hot rolling. . If the addition amount is less than 0.05%, these objects cannot be achieved. On the other hand, if it exceeds 0.5%, the magnetic flux density of the product is lowered, which is not preferable.
Since S and Se adversely affect the magnetic properties, the total amount is 0.02% or less.

From the molten steel for producing grain-oriented electrical steel sheets, the components of which are adjusted as described above, the slab is cast by a normal method and heat-treated before hot rolling. The heating temperature at that time is sufficient to be less than 1280 ° C.
Thereafter, in the same manner as the production method (1), hot rolling and cold rolling are performed. The steel sheet after cold rolling is subjected to decarburization annealing in a humid atmosphere in order to remove C contained in the steel, and then finish annealing.

In this manufacturing method, in order to form (Al, Si) N as an inhibitor, a process of increasing nitrogen in the steel sheet between cold rolling and finish annealing is performed. The treatment for increasing nitrogen is performed by nitridation annealing in an atmosphere containing a gas having nitriding ability such as ammonia.
The time of this nitridation annealing may be between cold rolling and finish annealing, and may be performed either before or after decarburization annealing. Moreover, the same effect is acquired even if it performs decarburization annealing and nitridation annealing simultaneously.

As described above, the steel sheets cold-rolled in accordance with the respective production methods are subsequently decarburized and finish-annealed as described above. Effect of reducing iron loss by shortening the rolling direction length of the steel grain macro grain structure after finish annealing by applying grooves during carbon annealing or by recrystallization annealing after applying grooves after decarburization annealing. Get.

You may implement the process which provides this groove | channel during either decarburization annealing or between decarburization annealing and recrystallization annealing. By coarsening the grain structure at the bottom of the groove, in the subsequent finish annealing, the progress of secondary recrystallization is suppressed at the bottom of the groove, and the length in the rolling direction of the steel plate macro grain structure after the finish annealing is shortened. However, if finish annealing is performed immediately after the groove is applied, the grain structure at the bottom of the groove is not sufficiently coarsened during the secondary recrystallization process during finish annealing, and the length in the rolling direction of the macro grain structure of the steel sheet after finish annealing is shortened. The effect to do is not fully obtained. The atmosphere and annealing time for recrystallization annealing are not particularly limited, and if the grain structure at the bottom of the groove becomes coarse due to annealing, the length in the rolling direction of the macro grain structure of the steel sheet after finish annealing is shortened to reduce iron loss. An effect sufficient for reduction can be obtained.

  The method for providing the groove is not particularly limited. For example, there is a method for mechanically providing the groove by pressing a gear-type roll or a linear blade. The angle at which the grooves are provided is not particularly limited, but from the viewpoint of shortening the length in the rolling direction of the steel grain macro grain structure after finish annealing, it is preferably within 45 ° from the right angle to the rolling direction, and 30 from the right angle to the rolling direction. More preferably, it is within ±.

  The groove may be linear or curved, and the length in the rolling direction of the steel grain macro grain structure after finish annealing may be shortened, but it is more efficient to provide the linear groove. Moreover, although a continuous shape is preferable, even if it is discontinuous, what is necessary is just to affect the steel plate macro grain structure after finishing annealing. The shape, width, and depth of the groove are not particularly limited, but the width is preferably 10 to 300 μm, the depth is 5 to 50 μm, and the groove interval is preferably 1 to 20 mm in the rolling direction. Moreover, a groove | channel may be provided to a steel plate single side | surface, and may be provided to both surfaces.

  The steel sheet macrostructure after the finish annealing of the Te additive has a unique shape extending in the rolling direction. The reason for such a stretched macrostructure is not clear, but the steel sheet orientation integration degree is remarkably high and the magnetic properties are good. However, in industrial production conditions, the finish annealing that causes secondary recrystallization is performed in a coil shape, so if the grain size becomes too large in the rolling direction, the deviation angle of the crystal orientation becomes large based on the coil set, The degree of azimuth accumulation decreases and iron loss deteriorates. In this invention, the above groove | channel grant processing is performed and the rolling direction length of the steel plate macro grain structure | tissue after finish annealing is shortened.

  Immediately before decarburization annealing or in the temperature raising process of decarburization annealing, heating to a temperature of 800 ° C. or higher at a heating rate of 50 ° C./sec or higher is a measure of orientation accumulation of steel plate macro grain structure after finish annealing It is effective to improve and further reduce iron loss. The temperature range that controls the heating rate is at least 800 ° C. If it is less than 800 degreeC, the effect which controls a heating rate is not enough.

  A higher heating rate is preferable because the effect of improving the magnetic flux density and the occurrence of secondary recrystallization failure are suppressed and the production stability is further increased, and a heating rate of 250 ° C./sec or more is particularly preferable. The upper limit of the heating rate is not particularly limited, but a heating rate of about 2000 ° C./sec is sufficient.

  The method for controlling the heating rate is not particularly limited, and an existing heating means is appropriately employed depending on the heating rate. For example, when heat treatment is performed at a rate of 100 ° C / sec or higher in the temperature raising process of decarburization annealing, induction heating, electric heating, etc. are performed before the decarburization annealing equipment using a conventional radiant tube or elema using normal radiant heat. It is also possible to implement by incorporating the electric heating device.

Hereinafter, the feasibility and effects of the present invention will be further described using examples.
The conditions used in the examples are a condition example for the confirmation, and the present invention is not limited to this condition example.

Example 1
A steel slab containing the components shown in Table 2 and the balance consisting of inevitable impurities and Fe was produced in a laboratory vacuum melting furnace. This slab was annealed at 1300 ° C. for 1 hour and then hot-rolled. The obtained hot-rolled sheet was annealed at 1100 ° C. for 120 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.23 mm. Then, after subjecting this cold-rolled sheet to decarburization annealing in wet hydrogen at 850 ° C. for 150 seconds, in some samples, a linear groove is applied with a gear-type roll at an angle of 10 ° from the right angle of the rolling direction, Recrystallization annealing was performed at 850 ° C. for 20 seconds. The groove depth was 10 μm and the groove pitch was 5 mm. The heating rate of decarburization annealing was 25 ° C./s.

  Next, an annealing separator mainly composed of MgO is applied to the steel sheet after decarburization annealing with water slurry, and heated at 750 ° C. or higher at an average temperature increase rate of 20 ° C./h for 20 hours at a maximum reached temperature of 1150 ° C. The finish annealing was performed. After washing the obtained steel sheet with water, it was sheared to a size for single-plate magnetic measurement, and an insulating film mainly composed of aluminum phosphate and colloidal silica was applied and baked to obtain a magnetic flux density B8 value and iron loss W17 / 50 value. It was measured. Thereafter, the coating was removed, and the length D value in the rolling direction of the secondary recrystallized macro grain structure was measured.

  Evaluation is performed on 10 test pieces, and satisfies the condition of satisfying average B8: B8ave ≧ 1.920T and average W17 / 50: W17 / 50ave ≦ 0.750, and further satisfying the average value in the rolling direction length: Dave ≦ 5.0 mm. It was determined to be good.

  The results are shown in Table 3. What satisfy | filled favorable determination was the conditions which provided the groove | channel using the slab B containing Te.

(Example 2)
A steel slab containing the components shown in Table 4 and the balance being inevitable impurities and Fe was produced in a laboratory vacuum melting furnace. The slab was annealed at 1350 ° C. for 1 hour and then hot-rolled. The obtained hot-rolled sheet was annealed at 1000 ° C. for 100 seconds, pickled, and then cold-rolled to obtain a steel sheet having a thickness of 1.7 mm. The steel sheet was subjected to intermediate annealing at 1050 ° C. for 100 seconds and then cold rolled to obtain a cold rolled sheet having a thickness of 0.23 mm. Then, after subjecting this cold-rolled sheet to decarburization annealing in wet hydrogen at 850 ° C. for 150 seconds, in some samples, a linear groove is applied with a gear-type roll at an angle of 10 ° from the right angle of the rolling direction, Recrystallization annealing was performed at 850 ° C. for 20 seconds. The groove depth was 10 μm and the groove pitch was 5 mm. The heating rate of decarburization annealing was 25 ° C./s.

  Next, an annealing separator mainly composed of MgO is applied to the steel sheet after decarburization annealing with water slurry, and heated at 750 ° C. or higher at an average temperature increase rate of 20 ° C./h for 20 hours at a maximum reached temperature of 1150 ° C. The finish annealing was performed. After washing the obtained steel sheet with water, it was sheared to a size for single-plate magnetic measurement, and an insulating film mainly composed of aluminum phosphate and colloidal silica was applied and baked to obtain a magnetic flux density B8 value and iron loss W17 / 50 value. It was measured. Then, the film was removed, and the average value of the length in the rolling direction of the secondary recrystallized macro grain structure was measured. The measurement results of 10 test pieces were evaluated in the same manner as in Example 1.

  The results are shown in Table 5. What satisfy | filled favorable determination was the conditions which provided the groove | channel using the slab D containing Te.

(Example 3)
A steel slab containing the components shown in Table 6 and the balance being inevitable impurities and Fe was produced in a laboratory vacuum melting furnace. This slab was annealed at 1150 ° C. for 1 hour and then hot-rolled. The obtained hot-rolled sheet was annealed at 1100 ° C. for 100 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.23 mm. Further, this cold-rolled sheet was subjected to decarburization annealing at 830 ° C. for 150 seconds in wet hydrogen. Nitriding annealing was performed after decarburization annealing or simultaneously with decarburization annealing. Thereafter, in some samples, a linear groove was formed with a gear-type roll at an angle of 10 ° from a right angle in the rolling direction, and recrystallization annealing was performed at 830 ° C. for 20 seconds. The groove depth was 10 μm and the groove pitch was 5 mm. The heating rate of decarburization annealing was 25 ° C./s.

  Next, an annealing separator mainly composed of MgO is applied to the steel sheet after decarburization annealing in a water slurry, and heated at 750 ° C. or higher at an average temperature increase rate of 20 ° C./h for 20 hours at a maximum reached temperature of 1150 ° C. for 20 hours. The finish annealing was performed. After washing the obtained steel sheet with water, it was sheared to a size for single-plate magnetic measurement, and an insulating film mainly composed of aluminum phosphate and colloidal silica was applied and baked to obtain a magnetic flux density B8 value and iron loss W17 / 50 value. It was measured. Then, the film was removed, and the average value of the length in the rolling direction of the secondary recrystallized macro grain structure was measured. The measurement results of 10 test pieces were evaluated in the same manner as in Example 1.

  The results are shown in Table 7. What satisfy | filled favorable determination was the conditions which provided the groove | channel using the slab F containing Te.

Example 4
A steel slab containing the components shown in Table 8 with the balance being inevitable impurities and Fe was prepared in a laboratory vacuum melting furnace. This slab was annealed at 1300 ° C. for 1 hour and then hot-rolled. The obtained hot-rolled sheet was annealed at 1100 ° C. for 120 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.23 mm. Further, this cold-rolled sheet was subjected to decarburization annealing at 850 ° C. in wet hydrogen for 150 seconds. Thereafter, in some samples, a linear groove was applied with a gear-type roll at an angle of 10 ° from a right angle in the rolling direction, and recrystallization annealing was performed at 850 ° C. for 20 seconds. The groove depth was 10 μm and the groove pitch was 5 mm. The heating rate of decarburization annealing was 25 ° C./s.

  Next, an annealing separator mainly composed of MgO is applied to the steel sheet after decarburization annealing in a water slurry, and heated at 750 ° C. or higher at an average temperature increase rate of 20 ° C./h for 20 hours at a maximum reached temperature of 1150 ° C. for 20 hours. The finish annealing was performed. After washing the obtained steel sheet with water, it was sheared to a size for single-plate magnetic measurement, and an insulating film mainly composed of aluminum phosphate and colloidal silica was applied and baked to obtain a magnetic flux density B8 value and iron loss W17 / 50 value. It was measured. Then, the film was removed, and the average value of the length in the rolling direction of the secondary recrystallized macro grain structure was measured. Evaluation is performed on 10 test pieces, and satisfies the condition of satisfying average B8: B8ave ≧ 1.930T and average W17 / 50: W17 / 50ave ≦ 0.720 and further satisfying the average value in the rolling direction length: Dave ≦ 5.0 mm. Furthermore, it judged with it being favorable.

  The results are shown in Table 9. What satisfy | filled the favorable determination was the conditions which provided the groove | channel using the slab H containing Te and Bi.

(Example 5)
A steel slab containing the components shown in Table 10 and the balance being inevitable impurities and Fe was produced in a laboratory vacuum melting furnace. The slab was annealed at 1350 ° C. for 1 hour and then hot-rolled. The obtained hot-rolled sheet was annealed at 1100 ° C. for 120 seconds, pickled, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 0.23 mm. Then, after subjecting this cold-rolled sheet to decarburization annealing in wet hydrogen at 850 ° C. for 150 seconds, in some samples, a linear groove is applied with a gear-type roll at an angle of 10 ° from the right angle of the rolling direction, Recrystallization annealing was performed at 850 ° C. for 20 seconds. The groove depth was 10 μm and the groove pitch was 5 mm. At that time, the heating rate up to 800 ° C. in the temperature raising process of decarburization annealing was changed in the range of 10 to 1000 ° C./sec as shown in Table 11.

  Next, an annealing separator containing MgO as a main component is applied to the steel sheet after decarburization annealing with a water slurry, and a curvature with a radius of curvature of 500 mm is imparted for the purpose of providing a coil set, and then an average heating rate of 750 ° C. or higher. Heat annealing was performed at 20 ° C./h, and a final annealing for 20 hours was performed at a maximum temperature of 1150 ° C. After washing the obtained steel sheet with water, it was sheared to a size for single-plate magnetic measurement, and an insulating film mainly composed of aluminum phosphate and colloidal silica was applied and baked to obtain a magnetic flux density B8 value and iron loss W17 / 50 value. It was measured. Then, the film was removed, and the average value of the length in the rolling direction of the secondary recrystallized macro grain structure was measured. Evaluation is performed on 10 test pieces, and satisfies the condition of satisfying average B8: B8ave ≧ 1.930T and average W17 / 50: W17 / 50ave ≦ 0.720 and further satisfying the average value in the rolling direction length: Dave ≦ 5.0 mm. Furthermore, it judged with it being favorable.

  The results are shown in Table 11. What satisfy | filled the favorable determination used the slab J containing Te, and the heating rate to 800 degreeC in the temperature rising process of decarburization annealing was the range of 50 degreeC / sec or more. In particular, when the heating rate was 250 ° C./sec or more, B8> 1.940T, which was very good.

INDUSTRIAL APPLICABILITY Since the grain-oriented electrical steel sheet having extremely low iron loss can be stably produced on an industrial scale, the present invention has great industrial applicability.

Claims (7)

In mass%, C: 0.02 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.01 to 0.15%, S: 0.001 to 0.050%, acid-soluble A slab containing Al: 0.01 to 0.05%, N: 0.002 to 0.015%, Te: 0.0005 to 0.10%, and remaining Fe and unavoidable impurities is 1280 ° C or higher. After performing hot rolling, hot-rolled sheet annealing is performed, and cold rolling steel sheet is subjected to cold rolling of two or more times with one cold rolling or intermediate annealing, followed by decarburization annealing. In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of applying a finish annealing after applying an annealing separator mainly composed of MgO to the steel sheet surface,
By groove granted during decarburization annealing, or by recrystallization annealing after the grooves applied after decarburization annealing method for producing a grain-oriented electrical steel sheet characterized by dividing the secondary recrystallized grains in the groove position . In mass%, C: 0.02-0.10%, Si: 2.5-4.5%, Mn: 0.01-0.15%, S and Se in total: 0.001-0. A slab containing 050%, acid-soluble Al: 0.010 to 0.050%, N: 0.002 to 0.015%, Te: 0.0005 to 0.10%, the balance being Fe and inevitable impurities The steel sheet is heated to 1280 ° C. or higher, hot-rolled, then subjected to hot-rolled sheet annealing, and cold-rolled steel sheet is obtained by performing one or more cold rolling or two or more cold-rolling sandwiches intermediate annealing. Then, in the method for producing a grain-oriented electrical steel sheet comprising a series of steps in which decarburization annealing is performed and finish annealing is performed after applying an annealing separator mainly composed of MgO to the steel sheet surface.
By groove granted during decarburization annealing, or by recrystallization annealing after the grooves applied after decarburization annealing method for producing a grain-oriented electrical steel sheet characterized by dividing the secondary recrystallized grains in the groove position . In mass%, C: 0.02 to 0.10%, Si: 2.5 to 4.5%, Mn: 0.05 to 0.50%, S alone or S and Se in total: 0 0.02% or less, acid-soluble Al: 0.010 to 0.050%, N: 0.001 to 0.015%, Te: 0.0005 to 0.10%, from the remaining Fe and inevitable impurities The resulting slab is heated at less than 1280 ° C., hot-rolled, then subjected to hot-rolled sheet annealing, and subjected to one or more cold rollings or two or more cold rollings sandwiching the intermediate annealing to cold-rolled steel sheet After the decarburization annealing and nitridation annealing, in the manufacturing method of the grain-oriented electrical steel sheet consisting of a series of steps of applying a finishing annealing after applying an annealing separator mainly composed of MgO to the steel sheet surface,
By groove granted during decarburization annealing, or by recrystallization annealing after the grooves applied after decarburization annealing method for producing a grain-oriented electrical steel sheet characterized by dividing the secondary recrystallized grains in the groove position . In the manufacturing method of the grain-oriented electrical steel sheet according to any one of claims 1 to 3,
It is possible to divide the secondary recrystallized grains at the groove position by applying grooves by a mechanical method during decarburization annealing or by recrystallization annealing after applying grooves by a mechanical method after decarburization annealing. A method for producing a grain-oriented electrical steel sheet. In the manufacturing method of the grain-oriented electrical steel sheet according to claim 4,
It is possible to divide the secondary recrystallized grains at the groove position by applying grooves with a gear-type roll during decarburization annealing or by applying recrystallization annealing after applying grooves with a gear-type roll after decarburization annealing. A method for producing a grain-oriented electrical steel sheet. The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 5 , wherein the slab further contains Bi: 0.0005 to 0.10%. The method of manufacturing a grain-oriented electrical steel sheet according to any one of claims 1 to 6
A method for producing a grain-oriented electrical steel sheet, characterized by performing a process of heating to a temperature of 800 ° C. or more at a heating rate of 50 ° C./sec or more immediately before decarburization annealing or in a temperature raising process of decarburization annealing.