Production method of oriented electrical steel sheet and rolling facility therefor

Abstract

To provide a production method of an oriented electrical steel sheet with extremely low iron loss by further enhancing the effect of strain aging during rolling.SOLUTION: Disclosed is a production method of an oriented electrical steel sheet comprising: a hot rolling step in which a steel slab is hot-rolled to form a hot-rolled steel sheet; a hot-rolled sheet annealing step in which the hot-rolled steel sheet is optionally annealed to form a hot-rolled annealed sheet; a cold rolling step in which the hot-rolled steel sheet or the hot-rolled annealed sheet is cold-rolled once or twice or more including intermediate annealing to form a cold-rolled steel sheet having a final sheet thickness; a decarburizing annealing step in which the cold-rolled steel sheet is decarburized and annealed to form a decarburizing annealed sheet; and a finishing annealing step in which the decarburizing annealed sheet is subjected to secondary recrystallization annealing. In the cold rolling to make the final thickness of the cold rolling step, a steel sheet surface vibration step for imposing vibration to the steel sheet surface is performed between at least one passes. In the steel sheet surface vibration step, it is preferable that the surface of the steel sheet is irradiated with acoustic waves, the sound pressure on the surface of the steel sheet is 30 dB or more, and the temperature of the steel sheet is 50°C or more and 400°C or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the manufacture of grain-oriented electrical steel sheets having excellent magnetic properties. [Background technology]

[0002] Grain-oriented electrical steel is a soft magnetic material used as the core material for transformers and generators. It has an easy magnetization axis of iron, {110} <001> This steel sheet has excellent magnetic properties and a crystal structure in which the orientation, or Goss orientation, is highly aligned in the rolling direction of the steel sheet.

[0003] As a method for increasing the concentration in the Goss orientation, for example, Patent Document 1 discloses a method in which a cold-rolled steel sheet is heat-treated at a low temperature during cold rolling and then aged. Patent Document 2 discloses a technique in which the cooling rate during hot-rolled sheet annealing or intermediate annealing before final cold rolling is set to 30°C / sec or more, and interpass aging for 2 minutes or more is performed at a sheet temperature of 150 to 300°C at least twice during final cold rolling. Patent Documents 3 to 5 disclose a technique that utilizes dynamic strain aging in which dislocations introduced during rolling are immediately fixed with C or N by warm rolling at an elevated steel sheet temperature during rolling.

[0004] In the techniques of Patent Documents 1 to 3, the steel sheet temperature is maintained at an appropriate temperature before cold rolling, during rolling, or between rolling passes. This allows solute elements carbon (C) and nitrogen (N) to diffuse at low temperatures, pinning dislocations introduced during cold rolling, preventing dislocation movement during subsequent rolling, and increasing shear deformation, thereby improving the rolling texture. By applying these techniques, many Goss orientation seed crystals are formed at the time of the primary recrystallized sheet. The grain growth of these Goss orientation seed crystals during secondary recrystallization can increase the concentration of Goss orientation after secondary recrystallization.

[0005] In addition, as a technique for further enhancing the effect of the above-mentioned strain aging, Patent Document 4 discloses that fine carbides are precipitated in steel in an annealing process immediately prior to the final cold rolling in the cold rolling process, and that the final rolling is divided into a first half and a second half. In the first half of the final rolling, rolling is performed at a low temperature of 140°C or less with a reduction ratio of 30-75%, and in the second half, at least two reduction passes are performed at a high temperature of 150-300°C, and the total reduction ratio of the first and second half is 80-95%. In this way, a technique is disclosed for obtaining a material that is highly concentrated in the Goss orientation in a stable manner. Patent Document 5 also discloses that before cold rolling performed in tandem, a 0.5 kg / mm 2 A technique is disclosed in which fine carbides are precipitated in steel by carrying out a heat treatment at 50 to 150° C. for 30 seconds to 30 minutes while applying the above tension. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 50-016610 [Patent Document 2] Japanese Patent Application Publication No. 08-253816 [Patent Document 3] Japanese Patent Application Publication No. 01-215925 [Patent Document 4] Japanese Patent Application Publication No. 09-157745 [Patent Document 5] Japanese Patent Application Publication No. 04-120216 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, the demand for low-loss grain-oriented electrical steel sheets has been increasing due to the need for energy conservation in society, and there is a need to develop technology to manufacture low-loss grain-oriented electrical steel sheets. To achieve this, it is necessary to improve the effect of strain aging during rolling. However, the conventional techniques disclosed in the above-mentioned patent documents have the following problems.

[0008] In the technology of heating the steel sheet during rolling as in Patent Documents 1 to 3, the rise in the steel sheet temperature causes insufficient rolling lubrication, which leads to a decrease in yield due to deterioration of the steel sheet shape, so there is an upper limit to the steel sheet temperature during aging. Therefore, there is also an upper limit to the magnetic improvement effect. In addition, although the technology of performing carbide precipitation treatment in the annealing process before final cold rolling as in Patent Documents 4 and 5 enhances the effect of strain aging, a technology to further enhance the effect of strain aging is required.

[0009] An object of the present invention is to provide a method for producing grain-oriented electrical steel sheet with extremely low core loss by further enhancing the effect of strain aging during rolling, and rolling equipment for rolling grain-oriented electrical steel sheet to be used in said method. [Means for solving the problem]

[0010] In order to solve the above problems, the inventors have conducted extensive research into a method for improving the effect of strain aging during rolling. Hereinafter, the experiments that led to the invention will be described.

[0011] A steel slab was prepared having a composition, by mass, of C: 0.037%, Si: 3.4%, Mn: 0.05%, S: 31 ppm, Se: 31 ppm, N: 50 ppm, and sol.Al: 85 ppm, with the balance being Fe and unavoidable impurities. The steel slab was then heated to 1210°C and hot-rolled to form a hot-rolled steel sheet having a thickness of 2.0 mm.

[0012] The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 1000°C for 60 seconds to obtain a hot-rolled annealed sheet, which was then wound into a coil. The obtained hot-rolled annealed sheet was rolled five times using a Sendzimir rolling mill to obtain a cold-rolled steel sheet having a thickness of 0.20 mm. At that time, between the first and second passes, a sound wave of 8000 Hz was irradiated by a sound wave generator for 10 minutes at the sound pressure shown in Figure 1. The sound pressure was measured by installing a sound pressure meter near the surface of the steel sheet coil. During the sound wave irradiation, the steel sheet was held at 80°C. In addition, a steel sheet was prepared by only holding the temperature and not irradiating the sound wave for comparison.

[0013] The cold-rolled steel sheet was then subjected to primary recrystallization annealing, which also served as decarburization annealing, with a soaking temperature of 840°C and a soaking time of 100 seconds, after which an annealing separator mainly composed of MgO was applied to the steel sheet surface, and then finish annealing was performed to cause secondary recrystallization. A coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2 was applied to the steel sheet surface after the secondary recrystallization annealing, and flattening annealing was performed at 800°C for 30 seconds to produce a product coil.

[0014] A sample with a total weight of 500g or more was cut from the product coil, and an Epstein test was performed to measure the iron loss. The results are shown in Figure 1. Figure 1 shows that the material irradiated with sound waves that generated a sound pressure of 30dB or more near the steel sheet surface during cold rolling had a low iron loss of 0.82W / kg or less.

[0015] The inventors believe that the mechanism by which iron loss was reduced in the above experiment is as follows. By irradiating the steel plate with sound waves and forcibly vibrating it, repeated bending deformation is applied to the steel plate. As a result, the lattice spacing near the material surface is expanded, and the mobility of carbon atoms, which are interstitial solid solution elements, increases. It is believed that the diffusion of carbon in the steel to dislocations is promoted, and the effect of strain aging is enhanced, resulting in the secondary recrystallized plate structure being more concentrated in the Goss orientation. Based on these findings, further investigations were carried out and the present invention was completed.

[0016] The method for producing a grain-oriented electrical steel sheet according to the present invention, which was developed based on the above findings, is configured as follows. [1] A method for producing a grain-oriented electrical steel sheet, comprising: a hot rolling step of hot rolling a steel slab to obtain a hot rolled steel sheet; a hot rolled sheet annealing step of optionally annealing the hot rolled steel sheet to obtain a hot rolled annealed sheet; a cold rolling step of cold rolling the hot rolled steel sheet or the hot rolled annealed sheet once or at least twice with intermediate annealing in between to obtain a cold rolled steel sheet having a final sheet thickness; a decarburization annealing step of decarburization annealing the cold rolled steel sheet to obtain a decarburization annealed sheet; and a finish annealing step of secondary recrystallization annealing the decarburization annealed sheet, wherein a steel sheet surface vibration step of imparting vibration to the steel sheet surface is carried out between at least one pass in the cold rolling step to obtain the final sheet thickness. [2] In the above [1], the method for producing a grain-oriented electrical steel sheet comprises irradiating the steel sheet with sound waves in the steel sheet surface vibration step so that the sound pressure on the steel sheet surface is 30 dB or more. [3] The method for producing a grain-oriented electrical steel sheet according to the above [1] or [2], wherein the steel sheet surface vibration step sets the steel sheet temperature at 50°C or higher and 400°C or lower. [4] In any one of the above [1] to [3], the steel slab contains, by mass%, C: 0.01 to 0.10%, Si: 2.0 to 4.5%, and Mn: 0.01 to 0.5%, and the following components are added to the steel slab: Group A; Al: 0.0100 to 0.0400%, N: 0.0050 to 0.0120%, and at least one of S and Se is 0.01 to 0.05% in total; Group B; Al: less than 0.0100%, S: 0.0100% or less, Se: 0.0100% or less, N: 0.0050% or less, and the balance being Fe and unavoidable impurities. [5] The method for producing a grain-oriented electrical steel sheet according to the above item [4], wherein the steel slab further contains, by mass %, at least one component selected from the following groups C to E: Group C: at least one selected from Sb: 0.005-0.50%, Cu: 0.01-1.50%, P: 0.005-0.500%, Cr: 0.01-1.50%, Ni: 0.005-1.500%, Sn: 0.01-0.50%, Nb: 0.0005-0.0100%, Mo: 0.01-0.50%, B: 0.0010-0.007%, and Bi: 0.0005-0.0500%, D group: Ti: 0.0005-0.0400%, V: 0.001-0.020% and W: at least one selected from 0.001 to 0.020%, Group E: At least one selected from Zn: 0.0005 to 0.020%, Zr: 0.001 to 0.020%, Pb: 0.0001 to 0.0100%, As: 0.001 to 0.020%, Ag: 0.001 to 0.050%, Au: 0.001 to 0.050%, Ga: 0.0001 to 0.0050%, Ge: 0.0001 to 0.0050%, Ca: 0.0005 to 0.020%, Mg: 0.0005 to 0.020%, REM: 0.0005 to 0.0200%, and Hf: 0.001 to 0.020%.

[0017] The rolling equipment for grain-oriented electrical steel sheets according to the present invention, which was developed based on the above findings, is configured as follows: [6] A rolling facility for rolling grain-oriented electrical steel sheets, equipped with a device for irradiating sound waves with a sound pressure level of 30 dB or more on the steel sheet surface. Effect of the Invention

[0018] According to the present invention, the effect of strain aging during rolling can be further enhanced, and a grain-oriented electrical steel sheet with extremely low core loss can be produced. [Brief description of the drawings]

[0019] [Figure 1] 1 is a graph showing the effect of the sound pressure of a sound wave irradiated onto a steel sheet surface on iron loss of the steel sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] First, a rolling facility for manufacturing grain-oriented electrical steel sheets according to this embodiment will be described. <Rolling equipment> The manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment includes a hot rolling process, an optional hot-rolled sheet annealing process, a cold rolling process, a decarburization annealing process, and a finish annealing process, and a steel sheet surface vibration process is carried out in the cold rolling process. Known devices and equipment can be used for carrying out the hot rolling process, the hot-rolled sheet annealing process, the decarburization annealing process, and the finish annealing process. The type of rolling mill for carrying out the cold rolling is not particularly limited. For example, a tandem rolling mill, a reverse rolling mill, or the like is suitable.

[0021] The sonication device used in the steel plate surface vibration process is preferably a device that irradiates sonic waves with a sound pressure level of 30 dB or more. The sonic wave frequency is preferably 10 Hz or more. More preferably, it is 100 Hz or more. It is also preferably 500 Hz or more, 1000 Hz or more, and further preferably 3000 Hz or more. The upper limit is preferably 100 kHz. The sonication device is preferably installed between the stands in a tandem rolling mill, and is preferably installed on one or both winders of the rolling mill in a reverse rolling mill.

[0022] Next, a method for producing the grain-oriented electrical steel sheet according to this embodiment will be described. The manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment includes a hot rolling step, an optional hot-rolled sheet annealing step, a cold rolling step, and a finish annealing step. In the hot rolling step, the steel slab is hot rolled to obtain a hot-rolled steel sheet. In the hot-rolled sheet annealing step, the hot-rolled steel sheet is annealed to obtain a hot-rolled annealed sheet. In the cold rolling step, the hot-rolled steel sheet or the hot-rolled annealed sheet is cold rolled once or two or more times with intermediate annealing in between to obtain a cold-rolled steel sheet having a final sheet thickness. In the decarburization annealing step, the cold-rolled steel sheet is decarburized annealed to obtain a decarburized annealed sheet. In the finish annealing step, the decarburized annealed sheet is subjected to secondary recrystallization annealing.

[0023] In this embodiment, a steel sheet surface vibration process is performed to apply vibration to the steel sheet surface between at least one pass in cold rolling to obtain a final sheet thickness in the cold rolling process. Here, the cold rolling to obtain a final sheet thickness refers to the cold rolling when no intermediate annealing is performed in the cold rolling, and refers to the cold rolling after the final intermediate annealing in the cold rolling when intermediate annealing is performed in the cold rolling, in which the thickness of the steel sheet after the cold rolling becomes the final sheet thickness.

[0024] <Steel slab> The steel slab (steel material) of this embodiment can be produced by, for example, steelmaking-continuous casting, ingot making-bloom rolling, etc. In steelmaking, molten steel obtained in a converter, electric furnace, etc. can be refined to a desired composition through secondary refining such as vacuum degassing.

[0025] The composition of the steel slab may be the composition for manufacturing grain-oriented electrical steel sheets. It is preferable that the steel slab contains C, Si, and Mn, since grain-oriented electrical steel sheets having excellent magnetic properties can be obtained. The contents of C, Si, and Mn are as follows. In the following explanation, the "%" indication regarding the composition means "mass %" unless otherwise specified.

[0026] C: 0.01 to 0.10% C is an element necessary for improving the primary recrystallization texture by fixing dislocations introduced during final cold rolling. Since this technology is a technology for promoting carbon diffusion by ultrasonic irradiation, the inclusion of C is the most preferable. If the C content exceeds 0.10%, it may be difficult to reduce the C content to 0.0050% or less at which magnetic aging does not occur by decarburization annealing. On the other hand, if the C content is less than 0.01%, the texture improvement effect may be insufficient. Therefore, the C content is preferably 0.01 to 0.10%, and more preferably 0.01 to 0.08%.

[0027] Silicon: 2.0 to 4.5% Silicon is an element effective in increasing the electrical resistance of steel and improving iron loss. If the silicon content exceeds 4.5%, the workability is significantly reduced, and it may be difficult to manufacture the steel by rolling. On the other hand, if the silicon content is less than 2.0%, it may be difficult to obtain a sufficient effect of reducing iron loss. Therefore, the silicon content is preferably 2.0 to 4.5%, and more preferably 2.5 to 4.5%.

[0028] Mn: 0.01 to 0.5% Mn is an element necessary for improving hot workability. If the Mn content exceeds 0.5%, the primary recrystallized texture may deteriorate, and it may be difficult to obtain secondary recrystallized grains in which the Goss orientation is highly accumulated. On the other hand, if the Mn content is less than 0.01%, it may be difficult to obtain sufficient hot rolling workability. Therefore, the Mn content is preferably 0.01 to 0.5%, and more preferably 0.03 to 0.5%.

[0029] <Utilization of inhibitors> Group A: Al: 0.0100-0.0400%, N: 0.0050-0.0120%, and at least one of S and Se, 0.01-0.05% in total The composition preferably contains, in addition to C, Si, and Mn, Al: 0.0100-0.0400% and N: 0.0050-0.0120% as inhibitor components in secondary recrystallization. If the Al content and N content are less than the above lower limits, it may be difficult to obtain a desired inhibitor effect. On the other hand, if they exceed the above upper limits, the dispersion state of the precipitates may become non-uniform, making it difficult to obtain a desired inhibitor effect. Furthermore, in addition to Al and N, at least one of S and Se may be contained as an inhibitor component in a total amount of 0.01-0.05%. By containing these, sulfides such as MnS and Cu2S and selenides such as MnSe and Cu2Se can be formed. The sulfides and selenides may be precipitated in combination. When the S content, Se content, or the total of them is equal to or greater than the above lower limit, the inhibitor effect can be sufficiently obtained, and when it is equal to or less than the above upper limit, the precipitates are uniformly dispersed and the inhibitor effect can be sufficiently obtained.

[0030] <Inhibitor-less> Group B: Al: less than 0.0100%, S: 0.0100% or less, Se: 0.0100% or less, and N: 0.0050% or less; The composition can be adapted to an inhibitor-less system by suppressing the Al content to less than 0.0100%. In this case, the N content is set to N: 0.0050% or less, S: 0.0100% or less, and Se: 0.0100% or less.

[0031] In order to improve the magnetic properties, in addition to the elements of the basic composition above, at least one component from the following groups C to E may be contained as an optional additive element.

[0032] Group C: at least one selected from Sb: 0.005-0.50%, Cu: 0.01-1.50%, P: 0.005-0.500%, Cr: 0.01-1.50%, Ni: 0.005-1.500%, Sn: 0.01-0.50%, Nb: 0.0005-0.0100%, Mo: 0.01-0.50%, B: 0.0010-0.007%, and Bi: 0.0005-0.0500%. Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B and Bi are elements useful for improving magnetic properties. In order to obtain a sufficient effect of improving magnetic properties without inhibiting the development of secondary recrystallized grains, it is preferable that the contents of these elements be within the above-mentioned ranges when they are contained.

[0033] Group D: at least one selected from Ti: 0.0005 to 0.0400%, V: 0.001 to 0.020%, and W: 0.001 to 0.020% Ti, V and W all form fine carbides and nitrides, which refine the crystal grains after intermediate annealing, thereby improving bending properties and improving sheet passing properties. However, if the content is less than the lower limit, the above effects are not sufficiently obtained, while if the content exceeds the upper limit, the above effects are saturated, which may lead to an increase in raw material costs.

[0034] Group E: at least one selected from Zn: 0.005-0.020%, Zr: 0.001-0.020%, Pb: 0.0001-0.0100%, As: 0.001-0.020%, Ag: 0.001-0.050%, Au: 0.001-0.050%, Ga: 0.0001-0.0050%, Ge: 0.0001-0.0050%, Ca: 0.0005-0.020%, Mg: 0.0005-0.020%, REM: 0.0005-0.0200%, and Hf: 0.001-0.020%. Zn, Zr, Pb, As, Ag, Au, Ga, Ge, Ca, Mg, REM and Hf all have the effect of strengthening grain boundaries by concentrating at the grain boundaries or forming compounds at the grain boundaries and being present there, thereby suppressing the occurrence of defects due to grain boundary fracture. However, if the content is less than the lower limit, the above effect cannot be sufficiently obtained, while if the content exceeds the upper limit, the above effect may saturate, leading to an increase in raw material costs.

[0035] The steel slab used in this embodiment basically contains Fe and inevitable impurities as the remainder, other than the basic composition elements and the optional added elements. However, for the purpose of further improving magnetic properties, improving properties such as corrosion resistance, tensile strength, and fatigue properties, improving castability and threading properties, and improving productivity by using scrap, a trace element such as In, Te, Ce, Os, Re, Ta, Y, La, and Yb may be contained in a total amount of 5.0% or less, preferably 2.0% or less, and more preferably 1.0% or less, in place of a part of the remaining Fe. In addition, elements other than those listed above may be contained in the steel as inevitable impurities, as long as they do not impair the effects of this embodiment.

[0036] The balance of the composition of the steel slab is Fe and unavoidable impurities. For example, O (oxygen) may be contained in an amount of 0.0060% or less. Note that the content of the optional added elements below the lower limit does not affect the properties of the grain-oriented electrical steel sheet of this embodiment, and is therefore permitted as an unavoidable impurity.

[0037] <Hot rolling process> In the manufacturing method of this embodiment, a steel slab is hot-rolled to obtain a hot-rolled steel sheet. The steel slab can be heated before being subjected to hot rolling. The heating temperature is preferably about 1050°C or higher from the viewpoint of ensuring hot rolling properties. There is no particular upper limit to the heating temperature, but a temperature above 1450°C is close to the melting point of steel and it is difficult to maintain the shape of the slab, so the heating temperature is preferably 1450°C or lower. Other hot rolling conditions are not particularly limited, and known conditions can be applied.

[0038] <Hot-rolled sheet annealing process> The hot-rolled steel sheet may be optionally subjected to hot-rolled sheet annealing. At that time, the annealing conditions are not particularly limited, and known conditions can be applied.

[0039] <Cold rolling process> The hot-rolled steel sheet is annealed as necessary and then cold-rolled to obtain a cold-rolled steel sheet. Before the cold rolling, the steel sheet may be descaled by pickling or the like.

[0040] A cold-rolled steel sheet of the final thickness may be obtained by one cold rolling, or may be obtained by two or more cold rollings with intermediate annealing in between. The total reduction in cold rolling is preferably 70% or more and 95% or less. The reduction in the final cold rolling is preferably 60% or more and 95% or less. The final thickness is preferably 0.1 mm or more and 1.0 mm or less.

[0041] <Steel plate surface vibration process> The surface of the steel sheet is irradiated with sound waves during at least one pass of cold rolling to obtain the final sheet thickness. This irradiation partially expands the crystal lattice spacing of the steel sheet, making it easier for solute carbon to move between the crystal lattices, which is thought to promote the diffusion of solute carbon into dislocations.

[0042] Here, a pass refers to a steel sheet being rolled once by one rolling mill. Rolling at each stand of a tandem rolling mill is also called a pass, and one rolling by a reversing rolling mill is also called a pass. Interpass refers to the timing between passes.

[0043] The sound pressure of the sound waves irradiated to the steel sheet is preferably 30 dB or more. If the sound pressure is less than 30 dB, the vibration to be imparted to the steel sheet by the irradiated sound waves may be hindered by the rigidity of the steel sheet itself, and the effect of promoting the diffusion of solute carbon may not be sufficiently obtained. The sound pressure is more preferably 60 dB or more, and even more preferably 80 dB or more. The sound pressure can be measured by installing a sound pressure meter near the surface of the steel sheet. There is no upper limit for the sound pressure. From the viewpoint of preventing noise disturbance, the sound pressure is preferably 150 dB or less, and even more preferably 130 dB or less.

[0044] The frequency of the irradiated sound waves is not particularly limited, and can be set according to the thickness and rigidity of the steel sheet coil. From the viewpoint of ensuring the number of vibrations per unit time, the frequency is preferably 10 Hz or more. The higher the frequency, the higher the directivity of the sound waves, making it easier to control the sound wave irradiation position. Therefore, the frequency of the sound waves is more preferably 100 Hz or more, more preferably 500 Hz or more, 1000 Hz or more, and even more preferably 3000 Hz or more. The upper limit of the frequency of the sound waves is not particularly limited, but is preferably 100 kHz or less, and more preferably 80 kHz or less.

[0045] The irradiation of the sound waves may be performed while the steel sheet is heated. Since the diffusion of carbon in steel is a thermally activated physical phenomenon, it is possible to further promote the diffusion of carbon to dislocations by heating. Therefore, the steel sheet temperature when irradiating the sound waves is preferably 50°C or higher, more preferably 80°C or higher. If the steel sheet temperature is too high, the shape of the steel sheet may be poor due to insufficient lubrication during rolling, and the yield may decrease. Therefore, the upper limit of the steel sheet temperature is preferably 400°C or lower, more preferably 350°C or lower. The method of heating the steel sheet between passes is not particularly limited. For example, a method of using heat generated during rolling or a method of blowing hot air generated outside into the steel sheet coil can be applied.

[0046] The type of rolling mill used for cold rolling to the final thickness is not particularly limited. For example, a tandem rolling mill, a reverse rolling mill, etc. are suitable. In the case of a tandem rolling mill, the ultrasonic irradiation device may be installed between the stands, and in the case of a reverse rolling mill, the ultrasonic irradiation device may be installed on one or both winders.

[0047] The means for vibrating the steel plate surface is not limited to the use of sound waves. For example, there is a method of contacting the steel plate with a vibrator that applies mechanical vibrations, or a method of applying an alternating magnetic field to the steel plate to vibrate it by magnetostriction.

[0048] <Decarburization annealing process> In this embodiment, a grain-oriented electrical steel sheet can be obtained by subjecting a cold-rolled steel sheet having a final sheet thickness to decarburization annealing and then secondary recrystallization annealing. After secondary recrystallization annealing, an insulating coating may be formed.

[0049] The conditions of the decarburization annealing are not particularly limited. In general, the decarburization annealing often doubles as the primary recrystallization annealing, and can also double as the primary recrystallization annealing in this embodiment. In that case, for example, the annealing conditions include annealing at 800° C. for 2 minutes in a warm hydrogen atmosphere.

[0050] <Finish annealing process> After the cold-rolled steel sheet is subjected to decarburization annealing, it is subjected to finish annealing for secondary recrystallization. Before the finish annealing, an annealing separator can be applied to the surface of the steel sheet. The annealing separator is not particularly limited, and examples thereof include one containing MgO as the main component and, as necessary, adding TiO2 or the like, and one containing SiO2 or Al2O3 as the main component.

[0051] After the finish annealing, it is preferable to apply an insulating coating to the surface of the steel sheet, bake it, and, if necessary, perform planarization annealing to adjust the shape of the steel sheet. The type of insulating coating is not particularly limited, and when forming an insulating coating that imparts tensile tension to the steel sheet surface, it is preferable to use a coating liquid containing phosphate-colloidal silica and bake it at about 800°C. EXAMPLES

[0052] Example 1 A steel slab was prepared having a composition, by mass, of C: 0.037%, Si: 3.4%, Mn: 0.05%, S: 31 ppm, Se: 31 ppm, N: 50 ppm, and sol.Al: 85 ppm, with the balance being Fe and unavoidable impurities. The steel slab was then heated to 1210°C and hot-rolled to form a hot-rolled steel sheet having a thickness of 2.0 mm.

[0053] The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 1000 ° C for 60 seconds and wound into a coil. The obtained hot-rolled annealed sheet was rolled five times using a Sendzimir rolling mill to produce a cold-rolled steel sheet with a sheet thickness of 0.20 mm. At that time, 300 Hz sound waves were irradiated for 5 minutes using a sound wave generator so that the sound pressure on the steel sheet surface was 50 dB between the passes shown in Table 1. The steel sheet was held at the temperature shown in Table 1 during the sound wave irradiation. Thereafter, the cold-rolled steel sheet was subjected to primary recrystallization annealing, which also served as decarburization annealing, with a soaking temperature of 840 ° C and a soaking time of 100 seconds, and then an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and then finish annealing was performed to cause secondary recrystallization. A coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2 was applied to the steel sheet surface after the secondary recrystallization annealing, and the steel sheet was subjected to flattening annealing at 800°C for 30 seconds to obtain a product coil.

[0054] A sample with a total weight of 500g or more was cut from the product coil, and an Epstein test was performed to measure the iron loss. The results are shown in Table 1. Iron loss W17 / 50 indicates the iron loss at a frequency of 50Hz and a maximum magnetic flux density of 1.7T. The same applies below.

[0055] The materials that were irradiated with sound waves a total of one or more times between each pass (conditions No. 1 to 15, 17 to 28) had low iron loss of 0.84 W / kg or less, and when the steel plate temperature during sound wave irradiation was kept above 50°C (conditions No. 7 to 15, 17 to 25), the iron loss was 0.82 W / kg or less, indicating that the magnetic properties had improved.

[0056] [Table 1]

[0057] Example 2 A steel slab was used that contained, by mass, 0.06% C, 3.4% Si, 0.06% Mn, 90 ppm N, 250 ppm sol.Al, 0.02% S, and 0.02% Se, with the remainder being Fe and unavoidable impurities. The steel slab was heated to 1400°C and then hot-rolled to produce a hot-rolled steel sheet with a thickness of 2.0 mm.

[0058] The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 1000 ° C for 60 seconds and wound into a coil. The obtained hot-rolled sheet annealed sheet was subjected to the first cold rolling with a tandem rolling mill (roll diameter 300 mm, number of stands 5). Next, in an atmosphere of 75 vol% N2, 25 vol% H2, and a dew point of 46 ° C, intermediate annealing was performed at 1100 ° C for 80 seconds, and then final cold rolling was performed with a tandem rolling mill (roll diameter 300 mm, number of stands 5) to obtain a cold-rolled steel sheet with a sheet thickness of 0.20 mm. During the final cold rolling, a sound wave irradiation device was installed between each stand, and sound waves with sound pressure and frequency shown in Table 2 were irradiated between the stands. The sound pressure was measured with a sound pressure meter attached near the surface of the steel sheet. The frequency was adjusted with the sound wave irradiation device. During the final rolling, the steel sheet temperature between the stands where ultrasonic waves were irradiated was adjusted to various temperatures shown in Table 2 by adjusting the amount of strip coolant sprayed. The steel sheet temperature was measured with a radiation thermometer.

[0059] The cold-rolled steel sheet was then subjected to primary recrystallization annealing, which also served as decarburization annealing, with a soaking temperature of 840°C and a soaking time of 100 seconds, after which an annealing separator mainly composed of MgO was applied to the steel sheet surface, and then finish annealing was performed to cause secondary recrystallization. A coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2 was applied to the steel sheet surface after the secondary recrystallization annealing, and flattening annealing was performed at 800°C for 30 seconds to produce a product coil.

[0060] Test pieces with a total weight of 500 g or more were cut out from the product coil, and an Epstein test was performed to measure the iron loss. The results are shown in Table 2.

[0061] It can be seen that even when a steel slab containing a large amount of inhibitor is used and intermediate annealing is inserted in the cold rolling process, the iron loss is good if the final cold rolling is performed under the specified ultrasonic irradiation conditions.

[0062] [Table 2]

[0063] Example 3 A steel having a composition containing, by mass, 0.036% C, 3.4% Si, 0.06% Mn, 50 ppm N, 72 ppm sol.Al, 31 ppm S, and 31 ppm Se, with other components being Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, and Bi, as shown in Table 3, with the balance being Fe and unavoidable impurities, was melted and formed into a steel slab. Next, the steel slab was heated to 1210°C and hot-rolled to form a hot-rolled steel sheet having a thickness of 2.0 mm.

[0064] The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 1000°C for 60 seconds and wound into a coil. The obtained hot-rolled sheet annealed sheet was made into a cold-rolled steel sheet with a sheet thickness of 0.20 mm by one tandem rolling using a tandem rolling mill (roll diameter 300 mm, number of stands 5). During the final cold rolling, a sound wave irradiation device was installed between the first stand and the second stand, and a sound wave of 4000 Hz was irradiated with a sound pressure of 70 dB to the passing steel sheet. The temperature and pressure were measured using a sound pressure meter attached near the steel sheet surface. The steel sheet temperature between the first stand and the second stand was adjusted to 100°C. Thereafter, the cold-rolled steel sheet was subjected to primary recrystallization annealing, which also served as decarburization annealing, with a soaking temperature of 840°C and a soaking time of 100 seconds, and then an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and then the steel sheet was subjected to finish annealing to cause secondary recrystallization. A coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2 was applied to the steel sheet surface after the secondary recrystallization annealing, and the steel sheet was subjected to flattening annealing at 800°C for 30 seconds to obtain a product coil.

[0065] Test pieces with a total weight of 500 g or more were cut out from the product coil, and an Epstein test was performed to measure the iron loss. The results are shown in Table 3.

[0066] It can be seen that steel sheets containing at least one of Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, and Bi have iron loss of less than 0.77 W / kg, further improving the characteristics.

[0067] [Table 3]

[0068] Example 4 A steel having a composition, by mass%, containing C: 0.06%, Si: 3.4%, Mn: 0.06%, N: 90 ppm, sol.Al: 250 ppm, S, Se: 0.02% each, and other components selected from groups C to E as shown in Tables 4-1 and 4-2, with the balance being Fe and unavoidable impurities, was melted and formed into a steel slab. The steel slab was then heated to 1400°C and hot-rolled to form a hot-rolled steel sheet having a thickness of 2.0 mm.

[0069] The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 1000°C for 60 seconds and wound into a coil. The obtained hot-rolled sheet annealed sheet was made into a cold-rolled steel sheet with a sheet thickness of 0.20 mm by one tandem rolling using a tandem rolling mill (roll diameter 300 mm, number of stands 5). During the final cold rolling, a sound wave irradiation device was installed between the first stand and the second stand, and a sound wave of 4000 Hz was irradiated with a sound pressure of 70 dB to the passing steel sheet. The temperature and pressure were measured using a sound pressure meter attached near the steel sheet surface. The steel sheet temperature between the first stand and the second stand was adjusted to 100°C. Thereafter, the cold-rolled steel sheet was subjected to primary recrystallization annealing, which also served as decarburization annealing, with a soaking temperature of 840°C and a soaking time of 100 seconds, and then an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and then the steel sheet was subjected to finish annealing to cause secondary recrystallization. A coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2 was applied to the steel sheet surface after the secondary recrystallization annealing, and the steel sheet was subjected to flattening annealing at 800°C for 30 seconds to obtain a product coil.

[0070] Test pieces with a total weight of 500g or more were cut out from the product coil, and Epstein tests were performed to measure the iron loss. The results are shown in Tables 4-1 and 4-2.

[0071] From Tables 4-1 and 4-2, even when using a steel slab with a large amount of inhibitor added, it can be seen that the iron loss of the steel sheet to which one or more of Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, and Bi are added is 0.77 W / kg or less, and the characteristics are further improved. In addition, the components of groups A and B. The steel sheets to which at least one component selected from Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, Bi, Ti, V, W, Zn, Zr, Pb, As, Ag, Au, Ga, Ge, Ca, Mg, REM, and Hf is added all have an iron loss W17 / 50 lower than 0.82 W / kg, and it can be seen that the magnetic property improvement effect of the present invention by the sound wave irradiation is obtained without any problems.

[0072] [Table 4-1]

[0073]

Table 4-2

Claims

1. a hot rolling process in which the steel slab is hot rolled to produce a hot rolled steel sheet; Optionally, a hot-rolled sheet annealing step of annealing the hot-rolled steel sheet to obtain a hot-rolled annealed sheet; A cold rolling process in which the hot-rolled steel sheet or the hot-rolled annealed sheet is subjected to cold rolling once or two or more times with intermediate annealing therebetween to obtain a cold-rolled steel sheet having a final sheet thickness; a decarburization annealing step of subjecting the cold-rolled steel sheet to decarburization annealing to obtain a decarburization annealed sheet; A finish annealing process in which the decarburized annealed sheet is subjected to secondary recrystallization annealing; Including, The method for producing a grain-oriented electrical steel sheet further comprises carrying out a steel sheet surface vibration step of applying vibration to a surface of the steel sheet between at least one pass of cold rolling to obtain a final sheet thickness in the cold rolling step.

2. The method for producing a grain-oriented electrical steel sheet according to claim 1 , wherein in the steel sheet surface vibration step, the steel sheet is irradiated with sound waves so that a sound pressure on the steel sheet surface is 30 dB or more.

3. The method for producing a grain-oriented electrical steel sheet according to claim 1 , wherein the steel sheet temperature is set to 50° C. or higher and 400° C. or lower in the steel sheet surface vibration step.

4. The method for producing a grain-oriented electrical steel sheet according to claim 2 , wherein the steel sheet temperature is set to 50° C. or higher and 400° C. or lower in the steel sheet surface vibration step.

5. The steel slab comprises, in mass %, C: 0.01 to 0.10%, Si: 2.0 to 4.5% and Mn: 0.01~0.5% Contains Group A; Al: 0.0100-0.0400%, N: 0.0050 to 0.0120% and At least one of S and Se in total is 0.01 to 0.05%; Group B; Al: less than 0.0100%, S: 0.0100% or less, Se: 0.0100% or less; N: 0.0050% or less, and the balance being Fe and unavoidable impurities. The method for producing the grain-oriented electrical steel sheet according to any one of claims 1 to 4.

6. The method for producing a grain-oriented electrical steel sheet according to claim 5, wherein the steel slab further contains, in mass%, at least one component selected from the following groups C to E: Group C; Sb: 0.005-0.50%, Cu: 0.01 to 1.50%, P: 0.005-0.500%, Cr: 0.01-1.50%, Ni: 0.005-1.500%, Sn: 0.01-0.50%, Nb: 0.0005 to 0.0100%, Mo: 0.01-0.50%, B: 0.0010 to 0.007% and Bi: 0.0005-0.0500% At least one selected from the following: Group D; Ti: 0.0005-0.0400%, V: 0.001 to 0.020% and W: 0.001-0.020% At least one selected from the following: Group E; Zn: 0.0005-0.020%, Zr: 0.001 to 0.020%, Pb: 0.0001 to 0.0100%, As: 0.001 to 0.020%, Ag: 0.001-0.050%, Au: 0.001 to 0.050%, Ga: 0.0001-0.0050%, Ge: 0.0001 to 0.0050%, Ca: 0.0005-0.020%, Mg: 0.0005-0.020%, REM: 0.0005 to 0.0200%; and Hf: 0.001-0.020% At least one selected from the above.

7. A rolling facility for rolling grain-oriented electromagnetic steel sheets, comprising a device for irradiating a steel sheet surface with sound waves having a sound pressure level of 30 dB or more.

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