Method and facility for producing magnetic domain refined grain-oriented electrical steel sheet

Abstract

To provide a method and a facility for producing a magnetic domain refined grain-oriented electrical steel sheet, which can suppress a decrease in the degree of vacuum in a vacuum tank and can suppress a variation in iron loss of the magnetic domain refined grain-oriented electrical steel sheet subjected to a magnetic domain refining treatment in the vacuum tank, regardless of the environment in which the steel sheet is produced and the residence time until the magnetic domain refining treatment is performed in the vacuum tank.SOLUTION: A method for producing a magnetic domain refined grain-oriented electrical steel sheet includes a step of removing H2O adhering to a final finish-annealed grain-oriented electrical steel sheet by an H2O removing apparatus, and a step of performing a magnetic domain refining treatment by irradiating the final finish-annealed grain-oriented electrical steel sheet from which the H2O has been removed in the previous step with an electron beam in a vacuum tank. The output of the H2O removing apparatus is changed according to the vacuum degree of the vacuum tank.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and equipment for producing a domain-refined grain-oriented electrical steel sheet. [Background technology]

[0002] Grain-oriented electrical steel sheets are primarily used as transformer cores. They are required to have excellent magnetic properties, particularly low iron loss. To achieve this, it is important to highly align the secondary recrystallized grains in the steel sheet with the (110)

[0001] orientation (Goss orientation) and to reduce impurities in the product. Furthermore, because there are limits to controlling crystal orientation and reducing impurities, technologies have been developed to reduce iron loss by forming grooves or introducing local strain into the steel sheet surface, thereby introducing magnetic flux nonuniformity and refining the magnetic domain width (hereinafter referred to as magnetic domain refinement processing). Hereinafter, grain-oriented electrical steel sheets that have undergone magnetic domain refinement processing will also be referred to as magnetic domain refined grain-oriented electrical steel sheets.

[0003] As a method for forming grooves in a steel sheet, for example, an electrolytic etching method (Patent Document 1) has been proposed, in which grooves are formed on the surface of the steel sheet by electrolytic etching. Other proposed methods include a laser method (Patent Document 2) in which a high-power laser is used to locally melt and vaporize the steel sheet, and a gear press method (Patent Document 3) in which a gear-shaped roll is pressed against the steel sheet to create an indentation. Furthermore, as a method for introducing local strain into a steel sheet, for example, a method for introducing local thermal strain by irradiating the steel sheet with an electron beam (Patent Document 4) and a method for introducing local thermal strain by irradiating the steel sheet with a plasma flame (Patent Document 5) have been proposed.

[0004] As described above, magnetic domain refinement processes can be broadly divided into two types: a method of directly forming grooves in steel sheet, and a method of introducing thermal strain into steel sheet. The former is called heat-resistant magnetic domain refinement process because the magnetic domain refinement effect is not lost even when stress relief annealing is performed after core forming. On the other hand, the latter is called non-heat-resistant magnetic domain refinement process because the effect of introducing thermal strain is lost due to stress relief annealing.

[0005] In the heat-resistant magnetic domain refinement process, linear grooves are directly introduced into the steel sheet, but this process is known to degrade the magnetic permeability of the steel sheet. In contrast, in the non-heat-resistant magnetic domain refinement process, localized strain is introduced, so no degradation of magnetic permeability occurs. Therefore, in transformers using stacked cores that do not require annealing in the manufacturing process, steel sheets that have undergone the non-heat-resistant magnetic domain refinement process are generally used as the core material. Here, stress relief annealing is a heat treatment to relieve strain that is inevitably introduced by bending processes, etc., to turn grain-oriented electrical steel sheets into wound cores. This strain differs from the strain introduced by the magnetic domain refinement process and has a negative effect on iron loss.

[0006] Here, non-heat-resistant magnetic domain refinement treatment using an electron beam is generally performed in a vacuum space (hereinafter also referred to as a vacuum chamber), and from the viewpoint of productivity, it is performed by irradiating the electron beam onto the steel sheet while it is being threaded at a certain speed. However, when non-heat-resistant magnetic domain refinement treatment is performed using an electron beam, there is a correlation between the sheet threading speed, the pressure in the vacuum chamber (hereinafter also referred to as the degree of vacuum), and the iron loss of the grain-oriented electrical steel sheet that has been subjected to this treatment (domain refined grain-oriented electrical steel sheet). As the sheet threading speed increases, the pressure in the vacuum chamber increases (the degree of vacuum decreases), and the iron loss of the domain refined grain-oriented electrical steel sheet tends to deteriorate.

[0007] If the iron loss of domain-refined grain-oriented electrical steel sheet deteriorates, it will no longer be able to meet the required properties for use as an iron core material, resulting in a decrease in yield, so it is important to maintain a low pressure (high degree of vacuum) inside the vacuum chamber.In addition, if the sheet threading speed is slow, productivity will decrease, so it is important to make the sheet threading speed as fast as possible.

[0008] Generally, surface-adsorbed gases such as HO and O2 are present on the surface of steel sheets at invisible levels, and these surface-adsorbed gases (especially HO) are desorbed within the vacuum chamber. In other words, surface-adsorbed gases such as HO are brought into the vacuum chamber as the steel sheet passes through. When this happens, as the sheet passing speed increases, the amount of surface-adsorbed gases brought into the vacuum chamber increases, and it is thought that the evacuation capacity of the vacuum pump will gradually be unable to keep up, causing a decrease in the degree of vacuum.

[0009] Furthermore, if impurities such as H2O increase in the vacuum chamber and the degree of vacuum decreases, the irradiated electron beam has more opportunities to interfere with the impurities, making the amount of electron beam reaching the steel sheet unstable, which is thought to result in a decrease in the iron loss of magnetic domain refined grain-oriented electrical steel sheet.

[0010] To address this issue, Patent Document 6 states that by heating the steel sheet to 50°C or higher before it reaches the vacuum chamber where the magnetic domain refinement treatment is performed, it is possible to remove HO adsorbed to the steel sheet surface, and the degree of vacuum can be maintained even when the sheet passing speed increases, preventing a decrease in iron loss. Furthermore, if the magnetic domain refinement treatment is performed in the vacuum chamber while the steel sheet is still heated to 50°C or higher, the thermal strain introduced by the electron beam decreases and iron loss deteriorates, so it is possible to prevent a deterioration in iron loss by cooling the steel sheet to below 50°C before it enters the vacuum chamber. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-77380 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-129135 [Patent Document 3] Japanese Patent Application Publication No. 62-86121 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-172191 [Patent Document 5] Japanese Patent Application Publication No. 7-192891 [Patent Document 6] Japanese Patent Application Publication No. 2017-166016 Summary of the Invention [Problem to be solved by the invention]

[0012] To maintain a high degree of vacuum in the vacuum chamber regardless of the strip threading speed, it is necessary to quickly exhaust gases such as H2O that are absorbed by the steel strip and adsorbed to the surface. In other words, increasing the pumping capacity of the vacuum pump is effective. However, increasing the pumping capacity of the vacuum pump requires a significant increase in cost.

[0013] Furthermore, the amount of HO molecules adsorbed to the surface is generally considered to depend on humidity, exposure time at that humidity, the state of surface contamination, and other factors. Therefore, the amount of HO adhering to a steel sheet varies depending on the environment in which the steel sheet is manufactured (e.g., whether it is a high-humidity environment or a low-humidity environment). For example, the amount of HO adhering to a steel sheet varies depending on the time of manufacturing the steel sheet (e.g., whether it is a high-humidity season or a low-humidity season). Furthermore, the amount of HO adhering to a steel sheet varies depending on the residence time after final annealing and before irradiation with an electron beam. Therefore, even if a method of heating a steel sheet to 50°C or higher is adopted as described in Patent Document 6, the degree of vacuum in the vacuum chamber varies depending on the heating temperature, the environment in which the steel sheet is manufactured, and the residence time in that environment. As a result, the iron loss of a magnetic domain refined grain-oriented electrical steel sheet manufactured by magnetic domain refinement treatment in such a vacuum chamber varies, and the steel sheet may not satisfy the required properties as an iron core material.

[0014] The present invention has been made in view of the above circumstances, and aims to provide a manufacturing method and manufacturing equipment for a domain refinement grain-oriented electrical steel sheet that can suppress fluctuations in the degree of vacuum within a vacuum tank, regardless of the environment in which the steel sheet is manufactured or the residence time in the vacuum tank until magnetic domain refinement treatment is performed, and that can suppress fluctuations in iron loss of a domain refinement grain-oriented electrical steel sheet that has been subjected to magnetic domain refinement treatment in the vacuum tank. [Means for solving the problem]

[0015] The present invention provides the following. [1] A step of removing HO adhering to the grain-oriented electrical steel sheet that has been final-annealed using an HO removal device; a step of irradiating the grain-oriented electrical steel sheet, from which HO has been removed in the step above, with an electron beam in a vacuum chamber to perform a magnetic domain refinement treatment, The method for producing a magnetic domain refined grain-oriented electrical steel sheet includes changing the output of the H2O removal device depending on the degree of vacuum in the vacuum chamber. [2] The method for producing a magnetic domain refined grain-oriented electrical steel sheet according to [1], wherein the H2O removal device is one or more of an induction heating device, a current heating device, a resistance heating device, an infrared heating device, and a far-ultraviolet irradiation device. [3] The method for producing a magnetic domain refined grain-oriented electrical steel sheet according to [1] or [2], wherein the grain-oriented electrical steel sheet that has been subjected to final annealing has a surface that has been subjected to tension coating. [4] A vacuum chamber through which grain-oriented electrical steel sheets that have undergone final annealing pass; an electron gun that irradiates the grain-oriented electrical steel sheet that has been subjected to final annealing and that passes through the vacuum chamber with an electron beam; a vacuum gauge for measuring the degree of vacuum in the vacuum chamber; an HO removal device that is installed upstream of the vacuum chamber and removes HO adhering to the grain-oriented electrical steel sheet that has been final-annealed, The H2O removal device changes its output depending on the degree of vacuum measured by the vacuum gauge. [5] The manufacturing equipment for magnetic domain refined grain-oriented electrical steel sheet according to [4], which has differential pressure chambers on both the inlet and outlet sides of the vacuum chamber. [Effects of the Invention]

[0016] According to the present invention, fluctuations in the degree of vacuum within a vacuum tank can be suppressed regardless of the environment in which the steel sheet is manufactured or the residence time in the vacuum tank until magnetic domain refinement treatment is performed, and fluctuations in iron loss of a magnetic domain refinement-oriented electrical steel sheet that has been subjected to magnetic domain refinement treatment in the vacuum tank can be suppressed. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of manufacturing equipment for a domain-refined grain-oriented electrical steel sheet. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will be described below with reference to the drawings. Note that the embodiment shown below exemplifies an apparatus and a method for embodying the technical concept of the present invention, and the present invention is not limited to the following embodiment.

[0019] (Grain-oriented electrical steel sheet) In this embodiment, the chemical composition of the slab for grain-oriented electrical steel sheet is not particularly limited as long as it is a chemical composition that allows secondary recrystallization. Furthermore, when an inhibitor is used, for example, when an AlN-based inhibitor is used, it is sufficient to add appropriate amounts of Al and N, and when an MnS·MnSe-based inhibitor is used, it is sufficient to add appropriate amounts of Mn and Se and / or S. Of course, both inhibitors may be used in combination. In this case, the preferred contents of Al, N, S, and Se are, respectively, 0.01 to 0.065 mass% Al, 0.005 to 0.012 mass% N, 0.005 to 0.03 mass% S, and 0.005 to 0.03 mass% Se.

[0020] Furthermore, grain-oriented electrical steel sheets may be those in which the contents of Al, N, S, and Se are limited and no inhibitor is used. In this case, the amounts of Al, N, S, and Se are preferably controlled to less than 100 ppm by mass of Al, less than 50 ppm by mass of N, less than 50 ppm by mass of S, and less than 50 ppm by mass of Se, respectively.

[0021] Next, the basic components and optional additional components of the slab for the grain-oriented electrical steel sheet will be specifically described.

[0022] C: 0.08% by mass or less C is added to improve the hot-rolled sheet structure. However, if the C content exceeds 0.08 mass%, it becomes difficult to reduce the C content to 50 mass ppm or less, at which point magnetic aging does not occur during the manufacturing process, so the C content is preferably 0.08 mass% or less. Note that there is no need to set a lower limit for the C content, as secondary recrystallization is possible even in materials that do not contain C. In other words, the C content may be 0 mass%. When C is added to improve the hot-rolled sheet structure, the C content is preferably 0.01 mass% or more.

[0023] Si:2.0~8.0% by mass Silicon is an element effective in increasing the electrical resistance of steel and improving iron loss, and for this reason, the Si content is preferably 2.0% by mass or more. On the other hand, if the Si content is 8.0% by mass or less, it becomes easier to prevent a decrease in workability and a decrease in magnetic flux density. Therefore, the Si content is preferably in the range of 2.0 to 8.0% by mass.

[0024] Mn:0.005~1.0% by mass Mn is an element necessary for improving hot workability, and therefore its content is preferably 0.005% by mass or more. On the other hand, if the Mn content is 1.0% by mass or less, it is easy to suppress a decrease in the magnetic flux density of the product sheet. Therefore, the Mn content is preferably in the range of 0.005 to 1.0% by mass.

[0025] The slab for grain-oriented electrical steel sheet preferably has the above-mentioned components as its basic components. In addition to the above-mentioned basic components, the slab may optionally contain the following elements. The following elements are effective in improving magnetic properties. One or more selected from Ni: 0.03 to 1.50 mass%, Sn: 0.01 to 1.50 mass%, Sb: 0.005 to 1.50 mass%, Cu: 0.03 to 3.0 mass%, P: 0.03 to 0.50 mass%, Mo: 0.005 to 0.10 mass%, and Cr: 0.03 to 1.50 mass%

[0026] Ni is an element useful for improving the hot-rolled sheet structure and enhancing magnetic properties, and it is preferable to contain 0.03% by mass or more of Ni. On the other hand, if the Ni content is 1.50% by mass or less, it is possible to prevent secondary recrystallization from becoming unstable, and it is easy to reduce the risk of deterioration of the magnetic properties of the product sheet. Therefore, if Ni is contained, the Ni content is preferably in the range of 0.03 to 1.50% by mass.

[0027] Furthermore, Sn, Sb, Cu, P, Mo, and Cr are also elements useful for improving magnetic properties, and when the content of each element is equal to or greater than the lower limit of the above-mentioned element, the effect of improving magnetic properties is more likely to be achieved. On the other hand, when the content of each element is equal to or less than the upper limit of the above-mentioned element, the risk of inhibiting the development of secondary recrystallized grains is more likely to be reduced. Therefore, when Sn, Sb, Cu, P, Mo, and Cr are contained, the content of each of the above elements is preferably set within the above-mentioned range.

[0028] The balance other than the above components is Fe and unavoidable impurities.

[0029] Next, a method for manufacturing grain-oriented electrical steel sheet will be described. A slab having the above-mentioned composition is heated in a conventional manner and subjected to hot rolling. In this case, the slab may be hot rolled 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 slab may proceed directly to the subsequent steps.

[0030] Furthermore, if necessary, hot-rolled sheet annealing is performed. At this time, in order to highly develop the Goss structure in the product sheet, the hot-rolled sheet annealing temperature is preferably in the range of 800 to 1100°C. That is, if the hot-rolled sheet annealing temperature is less than 800°C, the band structure from hot rolling remains, making it difficult to realize a grain-regulated primary recrystallization structure, and the development of secondary recrystallization may be inhibited. On the other hand, if the hot-rolled sheet annealing temperature exceeds 1100°C, the grain size after hot-rolled sheet annealing becomes too coarse, making it extremely difficult to realize a grain-regulated primary recrystallization structure.

[0031] After annealing the hot-rolled sheet, it is cold-rolled once or twice or more times with intermediate annealing in between, then recrystallization annealing is performed and an annealing separator is applied. After the annealing separator is applied, final annealing is performed for the purpose of secondary recrystallization and the formation of a forsterite film.

[0032] After the final annealing, it is preferable to perform flattening annealing to correct the shape. Furthermore, it is preferable to apply an insulating coating to the surface of the steel sheet before or after the flattening annealing. This insulating coating refers to a coating that can impart tension to the steel sheet in order to reduce iron loss (hereinafter also referred to as tension coating). Examples of this tension coating include inorganic coatings containing silica and ceramic coatings formed by physical vapor deposition, chemical vapor deposition, etc.

[0033] The above steps provide a grain-oriented electrical steel sheet that has been subjected to final annealing. Note that the steel sheet of the present invention also includes a steel strip.

[0034] (Magnetic domain refinement grain-oriented electrical steel sheet manufacturing equipment) Next, a manufacturing facility for a magnetic domain refined grain-oriented electrical steel sheet of the present invention will be described. Fig. 1 is a schematic diagram showing an example of a manufacturing facility for a magnetic domain refined grain-oriented electrical steel sheet. The manufacturing facility shown in Fig. 1 has, in this order, an HO remover 6 and a vacuum chamber 1 along a threading line for grain-oriented electrical steel sheet (steel sheet S) that has undergone final annealing. That is, the manufacturing facility of the present invention has a vacuum chamber through which the steel sheet passes, and an HO remover installed upstream of the vacuum chamber.

[0035] An electron gun 3 is installed in the vacuum chamber 1 to irradiate an electron beam onto the steel sheet S passing through the vacuum chamber 1. A vacuum gauge 7 is also installed in the vacuum chamber 1 to measure the degree of vacuum within the vacuum chamber 1. Note that a vacuum is a space with a pressure lower than atmospheric pressure. The pressure (degree of vacuum) within the vacuum chamber 1 is adjusted as appropriate, but can be set to 0.5 Pa or less, for example.

[0036] As shown in FIG. 1, it is preferable to provide differential pressure chambers (inlet-side differential pressure chamber 2a and outlet-side differential pressure chamber 2b) on the inlet and outlet sides of vacuum chamber 1, respectively. When providing differential pressure chambers on the inlet and outlet sides of vacuum chamber 1, the number of chambers is not limited, and one differential pressure chamber may be provided on each side of vacuum chamber 1, or multiple differential pressure chambers may be provided on each side. The number of inlet-side differential pressure chambers and outlet-side differential pressure chambers may be the same or different. The internal pressure of inlet-side differential pressure chamber 2a and outlet-side differential pressure chamber 2b is adjusted to be lower than atmospheric pressure and higher than vacuum chamber 1. This allows the pressure of the environment through which steel sheet S passes to be adjusted in stages.

[0037] The manufacturing equipment shown in FIG. 1 includes a payoff reel 4 that dispenses the steel sheet S and a tension reel 5 that winds up the magnetic domain refined grain-oriented electrical steel sheet that has been subjected to magnetic domain refinement treatment in the vacuum chamber 1. A vacuum gauge 7 and an H2O removal device 6 are connected by wire or wirelessly, and the output of the H2O removal device 6 can be changed depending on the degree of vacuum measured by the vacuum gauge 7. In the manufacturing equipment shown in FIG. 1, the vacuum gauge 7 and the H2O removal device 6 are directly connected, but this is not a limitation. For example, the vacuum gauge 7 and the H2O removal device 6 may be connected via a control device (not shown). The control device is not particularly limited, but an electronic computer such as a personal computer can be used.

[0038] (Method of manufacturing magnetic domain refined grain-oriented electrical steel sheet) A method for manufacturing a domain refined grain-oriented electrical steel sheet will now be described. In this embodiment, a case where a domain refined grain-oriented electrical steel sheet is manufactured using the manufacturing equipment shown in FIG.

[0039] In this embodiment, the grain-oriented electrical steel sheet (steel sheet S) that has been subjected to final annealing and manufactured as described above is paid off from the payoff reel 4 and wound up on a tension reel 5, and the steel sheet S is passed through the vacuum chamber 1. In this embodiment, an HO remover 6 installed upstream of the vacuum chamber 1 and between the payoff reel 4 removes adsorbed gas (HO) adhering to the surface of the steel sheet S before it reaches the inlet differential pressure chamber 2a provided on the inlet side of the vacuum chamber 1. This removes moisture that is brought into the vacuum chamber 1 by the steel sheet S and that causes fluctuations in the degree of vacuum. This improves the accuracy of processing within the vacuum chamber 1.

[0040] The HO removal device 6 may be, for example, a heating device that heats the steel sheet to remove HO from it. The heating device is not particularly limited, and one or more of conventionally known heating devices such as an induction heating device, a current heating device, a resistance heating device, or an infrared heating device may be used. The atmosphere in which heating is performed is also not particularly limited, and heating can be performed in the air without any problems.

[0041] Furthermore, when a heating device is used as the HO removal device, it is desirable to control the heating temperature of the steel sheet S from the viewpoint of efficiently removing HO adhering to the steel sheet S, and the heating temperature is preferably at least 50°C or higher. This is because if the heating temperature is lower than 50°C, it becomes difficult to efficiently remove HO adhering to the steel sheet S. Furthermore, from the viewpoint of efficiently removing HO, it is preferable that the time for which the steel sheet S is held at 50°C or higher be 1.0 second or longer.

[0042] When a heating device is used as an HO remover to heat the steel sheet, the temperature of the entire steel sheet is high, which reduces the local thermal strain induced by electron beam irradiation in the vacuum chamber 1 and deteriorates the absolute value of the iron loss of the magnetic domain refined grain-oriented electrical steel sheet. Therefore, a refrigerant may be sprayed onto the steel sheet S between the HO remover 6 and the inlet differential pressure chamber 2a to lower the temperature of the steel sheet S. In this case, a gas such as air may be sprayed onto the steel sheet S, but if the temperature of the steel sheet S is high, there is a concern that surface oxidation may occur, so it is preferable to use an inert gas such as Ar or N as the refrigerant.

[0043] When a heating device is used as the HO removal device, the temperature of the steel sheet S is not particularly limited and can be measured using, for example, a commercially available thermometer. The temperature of the steel sheet S can be measured using, for example, a spot radiation thermometer that can measure the temperature at one point. In this case, it is sufficient to measure a representative point, such as the center in the width direction of the steel sheet S. Alternatively, instead of the spot thermometer, a two-dimensional radiation thermometer can be used to measure the temperature of the entire surface of the steel sheet S.

[0044] Furthermore, the HO removal device 6 can be, for example, a far-ultraviolet irradiator that irradiates far-ultraviolet rays. HO has a strong absorption strength for light in the wavelength range of 200 nm or less, known as far-ultraviolet rays. Furthermore, the energy of light generally depends on wavelength, with the shorter the wavelength, the greater the energy. When far-ultraviolet rays of this wavelength are irradiated, HO adsorbed on the steel sheet surface absorbs the far-ultraviolet rays and becomes excited, which may promote desorption from the steel sheet surface.

[0045] Since far-ultraviolet rays are absorbed and attenuated in the atmosphere, they are preferably irradiated in a vacuum. For this reason, it is preferable that the far-ultraviolet irradiating device is equipped with a vacuum chamber, and that a light source for irradiating the far-ultraviolet rays is located within the vacuum chamber. Furthermore, the distance between the light source of the far-ultraviolet irradiating device and the steel sheet (steel sheet surface) is preferably 1 mm or more and 10 mm or less. By setting the distance to 1 mm or more, the risk of the light source coming into contact with the steel sheet and being damaged when the steel sheet vibrates during passing can be reduced. Furthermore, if the distance is 10 mm or less, attenuation of the far-ultraviolet rays before they reach the steel sheet surface can be suppressed, and the effect of removing HO can be further enhanced. Note that when far-ultraviolet rays are irradiated in the atmosphere, the distance between the light source and the steel sheet is preferably 1 mm or more and 3 mm or less. The reasons for this are the same as those described above.

[0046] Light sources capable of irradiating such far ultraviolet rays include, but are not limited to, low-pressure mercury lamps, excimer lamps, etc. Low-pressure mercury lamps have main emission peaks at 185 nm and 254 nm. On the other hand, excimer lamps have peaks at essentially only specific wavelengths, depending on the type of rare gas enclosed in the lamp. For example, Xe gas has an emission peak at 172 nm, and Ar gas has an emission peak at 126 nm.

[0047] In addition, due to the recent tightening of regulations on mercury, it is currently preferable to use an excimer lamp as the light source. Furthermore, from the viewpoint of efficiently removing H2O adsorbed on the steel sheet, it is preferable to control the integrated illuminance of far ultraviolet light. Here, the integrated illuminance is the illuminance (unit: mW / cm2) which is the light intensity per unit area. 2 ) multiplied by the irradiation time (unit: seconds). However, since the strip threading speed and the equipment length of the far-ultraviolet irradiation equipment are basically constant, it is the irradiance that should actually be controlled.

[0048] The illuminance can be measured using a commercially available irradiance meter, but is not particularly limited thereto, and the measurement probe of the irradiance meter may be a product having spectral sensitivity in the required wavelength range. In this embodiment, the distance between the position on the line along which the steel sheet passes and the light source is measured, and the value measured by separately arranging the light source and the measurement probe at the same distance is taken as the illuminance.

[0049] However, as mentioned above, the amount of HO that adheres to the steel sheet varies depending on the environment in which the steel sheet is manufactured (whether it is a humid or low humidity environment, or whether it is a humid or low humidity season, etc.) and the residence time after final annealing before being irradiated with the electron beam. Therefore, it is not always possible to sufficiently remove HO using a constant heating temperature or irradiance.

[0050] Therefore, in the present invention, a vacuum gauge 7 installed in the vacuum chamber 1 is utilized. If the amount of H2O adhering to the steel sheet is large, the preset output (heating temperature or irradiance) of the H2O removal device cannot completely remove the H2O, and the amount of H2O in the vacuum chamber 1 increases, i.e., the pressure in the vacuum chamber 1 increases (the degree of vacuum decreases). Conversely, if the amount of H2O adhering to the steel sheet is small, the preset output (heating temperature or irradiance) of the H2O removal device can remove the H2O, and the amount of H2O in the vacuum chamber 1 decreases, i.e., the pressure in the vacuum chamber 1 decreases (the degree of vacuum increases). The output of the H2O removal device 6 is changed according to the degree of vacuum in the vacuum chamber 1; in other words, the heating temperature or irradiance of the H2O removal device is changed, thereby performing so-called feedback control. This makes it possible to prevent fluctuations in the degree of vacuum in the vacuum chamber and fluctuations in the iron loss of the manufactured magnetic domain refined grain-oriented electrical steel sheet, regardless of the steel sheet manufacturing environment or the residence time after final annealing before electron beam irradiation. For example, when the pressure inside the vacuum chamber 1 is higher than the target value (the degree of vacuum is lower than the target value), the H2O removal device installed upstream of the vacuum chamber 1 can increase its output to promote the removal of H2O adhering to the steel sheet. Also, when the pressure inside the vacuum chamber 1 is at or lower than the target value (the degree of vacuum is higher than the target value), the H2O removal device can maintain or reduce its output.

[0051] A commercially available vacuum gauge (vacuum gauge) can be used to measure the degree of vacuum, but there are no particular limitations and it may be selected depending on the range of the degree of vacuum to be measured.

[0052] As the above-mentioned feedback control, for example, the simplest proportional control shown in the following equation (1) can be used. x n =(p t -p m )×K+x s ···(1) Here, x is a control parameter of the H2O removal device 6. If the H2O removal device 6 is a steel plate heating device, it is the heating temperature of the steel plate heating device. If the H2O removal device 6 is a far-ultraviolet irradiation device, it is the irradiance of the far-ultraviolet rays. The subscript n is the new target value of the control parameter, and s is the currently measured value. Also, p t is the target vacuum level (Pa), p m is the vacuum level (Pa) of the vacuum chamber 1 measured by the vacuum gauge 7, and K is the proportional gain. The target control parameter value x n The output of the H2O removal device 6 can be changed in response to the above. Naturally, more advanced, general proportional-integral control or proportional-integral-derivative control may also be used as feedback control. Such control can be performed by a calculation device attached to the vacuum gauge or the H2O removal device. As described above, the vacuum gauge and the H2O removal device may be connected via a control device, and the control may be performed by the control device. The H2O removal device can then change its output in response to the control.

[0053] Furthermore, from the viewpoint of changing the output of the H2O removal device 6 as quickly as possible, the vacuum gauge 7 may be attached to the differential pressure chamber 2a on the more upstream side, and the degree of vacuum measured in the differential pressure chamber 2a may be used.

[0054] Additionally, an HO measuring device capable of directly measuring HO may be provided in the vacuum chamber 1 or the differential pressure chamber 2a together with or instead of the vacuum gauge. The HO measuring device is not limited as long as it is capable of measuring HO, and a quadrupole mass spectrometer (QMS) or the like may be used, for example. The atoms and molecules to be measured are not limited to HO but may also include Ar, CO, CO, O, N, and the like, which are generally present in the atmosphere and can become adsorbed molecules.

[0055] In the present invention, after the above-mentioned HO removal, magnetic domain refinement treatment is performed using an electron beam in a vacuum chamber 1. The electron beam irradiation conditions at this time may be conventionally known irradiation conditions, such as an acceleration voltage of 10 to 200 kV, a beam current of 0.1 to 100 mA, a beam scanning speed of 1 to 200 m / s, an irradiation point interval in the direction perpendicular to the rolling direction of 0.01 to 1.0 mm, and an irradiation line interval in the rolling direction of 1 to 20 mm. [Example]

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0057] A steel slab containing 0.07% by mass of C, 3.45% by mass of Si, 0.05% by mass of Mn, 0.10% by mass of Ni, 240 ppm by mass of Al, 110 ppm by mass of N, 150 ppm by mass of Se, 12 ppm by mass of S, and 23 ppm by mass of O, with the remainder being Fe and unavoidable impurities, was produced by continuous casting, heated to 1410°C, and hot-rolled to a thickness of 2.5 mm, followed by hot-rolled sheet annealing at 1000°C for 30 seconds. Subsequently, the intermediate sheet was cold-rolled to a thickness of 2.0 mm, and intermediate annealing was performed under the conditions of an oxidation degree PHO / PHO = 0.39, a temperature of 1060°C, and a time of 100 seconds. The steel sheet was then pickled with hydrochloric acid to remove subscale from the surface, and cold-rolled again to produce a cold-rolled sheet with a thickness of 0.215 mm. The sheet was then subjected to decarburization annealing, with an oxidation degree of PH2O / PH2 = 0.47 and a soaking temperature of 840°C for 200 seconds. An annealing separator primarily composed of MgO was then applied, and final annealing was performed at 1220°C for 100 hours for the purposes of secondary recrystallization, forsterite film formation, and purification. An insulating coating solution containing colloidal silica and aluminum phosphate with a concentration of 60% by mass was then applied, followed by baking at 850°C for tension coating. This baking treatment also served as planarization annealing. In this manner, a grain-oriented electrical steel sheet with a tension coating and final annealing was produced.

[0058] The grain-oriented electrical steel sheet that had undergone final finish annealing was then threaded and irradiated with an electron beam under two irradiation conditions in a vacuum chamber to produce a magnetic domain refined grain-oriented electrical steel sheet. In this example, an infrared heating device and a far-ultraviolet irradiation device were used as the HO removal device. The electron beam irradiation conditions, threading conditions, and N number (the number of coils of grain-oriented electrical steel sheet that had undergone final finish annealing and were subjected to the test) are as shown in Table 1. Infrared heating and far-ultraviolet irradiation were performed under various conditions upstream of the vacuum chamber (before reaching the inlet differential pressure chamber of the vacuum chamber). Among these multiple coils, some had different environments for producing the steel sheet (dates and times with different humidity) and some had different residence times before the grain-oriented electrical steel sheet that had undergone final finish annealing was irradiated with the electron beam.

[0059] The far-ultraviolet irradiation equipment used was a 4m long far-ultraviolet irradiation equipment using Xe gas as a light source, and the irradiance of the far-ultraviolet rays was determined sequentially according to the above-mentioned formula (1), and the output was changed (varied). At this time, the target vacuum degree p t The pressure was 0.1 Pa, and the proportional gain K was changed according to the strip running speed. For comparison, magnetic domain refined grain-oriented electrical steel sheets were also manufactured in the same way without irradiation with far-UV rays and with a constant irradiance of far-UV rays.

[0060] Similarly, for the infrared heating device, the equipment length was set to 4 m, and the heating temperature was determined sequentially according to the above formula (1), and the output was changed (varied). At this time, the target vacuum degree p t The pressure was 0.1 Pa, and the proportional gain K was changed according to the sheet passing speed. For comparison, a magnetic domain refined grain-oriented electrical steel sheet was similarly produced under the condition that the heating temperature was constant.

[0061] An ionization vacuum gauge was used as the vacuum gauge, and the evaluation results of the variation (standard deviation) in the degree of vacuum and the variation (standard deviation) in the iron loss of the manufactured magnetic domain refined grain-oriented electrical steel sheets are also shown in Table 1.

[0062] [Table 1]

[0063] Among Nos. 1 to 3, which had the same electron beam irradiation conditions in the vacuum chamber, Comparative Example No. 2 and Inventive Example No. 3, which were irradiated with far-ultraviolet rays upstream of the vacuum chamber, had smaller variations in the degree of vacuum than Comparative Example No. 1, which was not irradiated with far-ultraviolet rays upstream of the vacuum chamber. Therefore, compared to Comparative Example No. 1, Nos. 2 and 3 achieved better results by reducing the variations in the iron loss of the magnetic domain refined grain-oriented electrical steel sheets. Furthermore, Inventive Example No. 3 further reduced the variations in the degree of vacuum and iron loss compared to Comparative Example No. 2 because the output (illuminance) of the far-ultraviolet irradiation device was feedback-controlled according to the vacuum level of the vacuum chamber in accordance with the above-mentioned formula (1).

[0064] Among Nos. 1, 4, and 5, which had the same electron beam irradiation conditions in the vacuum chamber, Comparative Example No. 4 and Inventive Example No. 5, which performed infrared heating upstream of the vacuum chamber, had smaller variations in the degree of vacuum than Comparative Example No. 1, which did not perform infrared heating upstream of the vacuum chamber. Therefore, compared to Comparative Example No. 1, Inventive Example Nos. 4 and 5 achieved better results by reducing the variations in the iron loss of the magnetic domain refined grain-oriented electrical steel sheets. Furthermore, Inventive Example No. 5 further reduced the variations in the degree of vacuum and iron loss compared to Comparative Example No. 4 because the output (heating temperature) of the infrared heating device was feedback-controlled according to the degree of vacuum in the vacuum chamber in accordance with the above-mentioned formula (1).

[0065] Among Nos. 6 to 8, which had the same electron beam irradiation conditions in the vacuum chamber, Comparative Example No. 7 and Inventive Example No. 8, which were irradiated with far-ultraviolet rays upstream of the vacuum chamber, had smaller variations in the degree of vacuum than Comparative Example No. 6, which was not irradiated with far-ultraviolet rays upstream of the vacuum chamber. Therefore, compared to Comparative Example No. 6, Nos. 7 and 8 achieved better results by reducing the variations in the iron loss of the magnetic domain refined grain-oriented electrical steel sheets. Furthermore, Inventive Example No. 8 further reduced the variations in the degree of vacuum and iron loss than Comparative Example No. 7 because the output (illuminance) of the far-ultraviolet irradiation device was feedback-controlled according to the vacuum level of the vacuum chamber in accordance with the above-mentioned formula (1).

[0066] Among Nos. 6, 9, and 10, which had the same electron beam irradiation conditions in the vacuum chamber, Comparative Example No. 9 and Inventive Example No. 10, which were subjected to infrared heating upstream of the vacuum chamber, had smaller variations in the degree of vacuum than Comparative Example No. 6, which was not subjected to infrared heating upstream of the vacuum chamber. Therefore, compared to Comparative Example No. 6, Nos. 9 and 10 achieved better results by reducing the variations in the iron loss of the magnetic domain refined grain-oriented electrical steel sheets. Furthermore, Inventive Example No. 10 further reduced the variations in the degree of vacuum and iron loss compared to Comparative Example No. 9 because the output (heating temperature) of the infrared heating device was feedback-controlled according to the degree of vacuum in the vacuum chamber in accordance with the above-mentioned formula (1). [Explanation of symbols]

[0067] 1 Vacuum chamber 2a Differential pressure chamber (inlet differential pressure chamber) 2b Differential pressure chamber (outlet differential pressure chamber) 3 Electron gun 4 Payoff Reel 5 Tension Reel 6 H2O removal device 7 Vacuum gauge

Claims

1. H adhered to the grain-oriented electrical steel sheet after final annealing ２ O to H ２ removing the O using an O removal device; In the above process, H ２ a step of irradiating the grain-oriented electrical steel sheet, from which O has been removed and which has been subjected to final annealing, with an electron beam in a vacuum chamber to perform a magnetic domain refinement treatment; Depending on the degree of vacuum in the vacuum chamber, ２ A method for manufacturing a magnetic domain refined grain-oriented electrical steel sheet by changing the output of an O removal device.

2. The H ２ The method for producing a domain-refined grain-oriented electrical steel sheet according to claim 1, wherein the O removal device is one or more of an induction heating device, a current heating device, a resistance heating device, an infrared heating device, and a far-ultraviolet irradiation device.

3. The method for producing a magnetic domain refined grain-oriented electrical steel sheet according to claim 1 or 2, wherein the grain-oriented electrical steel sheet that has been subjected to final annealing has a surface that is subjected to tension coating.

4. a vacuum chamber through which grain-oriented electrical steel sheets that have undergone final annealing pass; an electron gun that irradiates the grain-oriented electrical steel sheet that has been subjected to final annealing and that passes through the vacuum chamber with an electron beam; a vacuum gauge for measuring the degree of vacuum in the vacuum chamber; The H attached to the grain-oriented electrical steel sheet that has been subjected to the final annealing is removed by a vacuum chamber. ２ H to remove O ２ an O removal device; The H ２ The O removal device changes its output depending on the degree of vacuum measured by the vacuum gauge. This is equipment for manufacturing magnetic domain refined grain-oriented electrical steel sheets.

5. 5. The manufacturing facility for magnetic domain refined grain-oriented electrical steel sheet according to claim 4, further comprising differential pressure chambers on both the inlet and outlet sides of the vacuum chamber.

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