Manufacturing method of grain-oriented electrical steel sheet

Abstract

To provide a grain-oriented electromagnetic steel sheet that has a good appearance and magnetic property.SOLUTION: One aspect of the present invention provides a method for manufacturing grain-oriented electromagnetic steel sheet that comprises a hot rolling step, a shot blasting and pickling step, a cold rolling step, a primary recrystallization annealing step, a finish annealing step and a flattening annealing step. In the shot blasting treatment, the relationship of the product of a projection velocity VC and a projection amount MC of the projection material in the width direction center part and the product of a projection velocity VE and a projection amount ME of the projection material in the width direction edge part satisfies the formula (1): VE×ME / 3≤VC×MC≤VE×ME×2 / 3 ...formula (1), and the pickling solution contains one or two or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in a predetermined amount, the pH is -1.5 or more and less than 7, the liquid temperature is 15°C or more and 100°C or less, and the time for the steel sheet to be immersed in pickling solution is 5 seconds or more and 200 seconds or less.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Grain-oriented electrical steel sheets contain about 2% to 5% by mass of Si, and the grain orientation of the steel sheet is called the Goss orientation, {110} <001> Grain-oriented electrical steel has excellent magnetic properties and is used, for example, as the core material for static inductors in transformers and other equipment.

[0003] In order to improve the magnetic properties of such grain-oriented electrical steel sheets, various developments have been made. In particular, with the recent demand for energy saving, grain-oriented electrical steel sheets are required to have even lower iron loss. In order to reduce the iron loss of grain-oriented electrical steel sheets, it is effective to increase the concentration of the crystal grains in the Goss orientation of the steel sheet to improve the magnetic flux density and reduce the hysteresis loss.

[0004] In the manufacture of grain-oriented electrical steel sheets, the crystal orientation is controlled by utilizing a catastrophic grain growth phenomenon called secondary recrystallization. However, in order to appropriately control the crystal orientation in secondary recrystallization, it is important to improve the heat resistance of fine precipitates in the steel, called inhibitors.

[0005] For example, the inhibitor is completely dissolved when the slab is heated before hot rolling, and then finely precipitated during hot rolling and the subsequent annealing process. Specifically, the inhibitor is used as an inhibitor in a method in which MnS and AlN are used as inhibitors and rolling is performed at a reduction rate of more than 80% in the final cold rolling process, as exemplified in Patent Document 1 below, or the inhibitor is used as an inhibitor in a method in which MnS and MnSe are used as inhibitors and two cold rolling processes are performed, as exemplified in Patent Document 2 below.

[0006] Patent Document 3 discloses a technique for manufacturing grain-oriented electrical steel sheet with excellent coating properties by controlling the conditions for hot-rolled sheet annealing and the conditions for pickling treatment. Patent Document 4 discloses a method for manufacturing grain-oriented electrical steel sheet with less variation in magnetic properties at the edge by controlling the cooling rate of hot-rolled sheet annealing in the coil width direction. Furthermore, Patent Document 5 discloses a technique for manufacturing grain-oriented electrical steel sheet with excellent magnetic properties by controlling the temperature rise process of primary recrystallization annealing and introducing microstrain during the temperature rise process.

[0007] Also, the following Patent Document 6 discloses a technique for manufacturing grain-oriented electrical steel sheet with low iron loss over the entire coil length by controlling the heat pattern during the temperature increase process of primary recrystallization annealing.Furthermore, the following Patent Document 7 discloses a technique for reducing the iron loss value of grain-oriented electrical steel sheet by strictly controlling the average grain size of crystal grains after secondary recrystallization and the deviation angle from the ideal orientation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 40-15644 [Patent Document 2] Special Publication No. 51-13469 [Patent Document 3] JP 2019-99827 A [Patent Document 4] Japanese Patent Application Publication No. 9-137225 [Patent Document 5] Japanese Patent Application Publication No. 6-212274 [Patent Document 6] International Publication No. 2014 / 049770 [Patent Document 7] Japanese Patent Application Publication No. 7-268567 Summary of the Invention [Problem to be solved by the invention]

[0009] In recent years, the demand for reducing iron loss in grain-oriented electrical steel sheets has been growing due to the progress of global transformer efficiency regulations. On the other hand, since transformers are important equipment that supports social infrastructure over the long term, it is important that they continue to operate stably. For this reason, grain-oriented electrical steel sheets, which are a major component of transformers, are also required to be reliable enough to contribute to the stable operation of transformers. In particular, from the perspective of suppressing quality variation in transformer manufacturing, it is important for grain-oriented electrical steel sheets to have no significant difference in iron loss between the edge and center in the sheet width direction in order to gain the trust of customers.

[0010] The above-mentioned Patent Document 3 discloses a technique for improving coating adhesion by creating a difference in the concentration of Mn or Cu between the surface of a steel sheet and the center of the sheet thickness. However, the technique for concentrating a specific component on the steel sheet surface is aimed only at improving the coating properties, and no technique for obtaining stable and good magnetic properties in the coil width direction of the steel sheet has been considered.

[0011] Patent Document 4 discloses a technique for reducing the variation in magnetic properties of the edge parts of a steel sheet by slowing the cooling rate of the edge parts of the steel sheet compared to the center part of the steel sheet in the cooling process of hot-rolled sheet annealing. However, this technique focuses on the fact that the temperature fluctuations are larger in the edge parts than in the center part, and the precipitation behavior (size, distribution density) of precipitates such as MnS is unstable, and does not consider strengthening the precipitates themselves.

[0012] Furthermore, in Patent Document 5, control of the temperature rise process in the primary recrystallization annealing is considered, but strengthening of the inhibitor in the coil width direction is not considered.

[0013] In addition, as disclosed in the above Patent Document 6, it has been confirmed that the magnetic properties of grain-oriented electrical steel sheets can be significantly affected by rapidly increasing the temperature between 500°C and 600°C at 100°C / s or more during the temperature increase process of primary recrystallization annealing. The above Patent Document 7 discloses that the temperature increase rate up to 850°C is set to 300°C / s or 450°C / s during the temperature increase process of primary recrystallization annealing.

[0014] However, the above Patent Documents 6 and 7 did not examine in detail what effect would be caused on the magnetic properties of the grain-oriented electrical steel sheet when the inhibitor is changed in the coil width direction of the steel sheet.

[0015] Therefore, the present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a new and improved method for producing grain-oriented electrical steel sheet which is capable of producing grain-oriented electrical steel sheet with excellent magnetic properties by controlling the shot blasting and pickling treatment conditions to enhance the inhibitor heat resistance of the coil width edge portion to achieve high magnetic flux density. [Means for solving the problem]

[0016] In order to solve the above problems, according to one aspect of the present invention, a step of heating a slab containing, by mass%, C: 0.02% or more and 0.10% or less, Si: 2.5% or more and 4.5% or less, Mn: 0.01% or more and 0.50% or less, the total of one or more of S, Se and Te: 0.001% or more and 0.050% or less, acid-soluble Al: more than 0.05% or less, N: more than 0% and 0.015% or less, with the balance being Fe and impurities, and hot rolling the slab to obtain a hot-rolled steel sheet; A step of obtaining a pickled sheet by subjecting the hot-rolled steel sheet to shot blasting and pickling, or obtaining a hot-rolled annealed sheet by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing, and then obtaining a pickled sheet by subjecting the hot-rolled annealed sheet to shot blasting and pickling; A step of obtaining a cold-rolled steel sheet by cold rolling the pickled sheet; A step of subjecting the cold-rolled steel sheet to primary recrystallization annealing; A step of applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after the primary recrystallization annealing, and then performing finish annealing; A step of applying an insulating coating to the steel sheet after the finish annealing and then performing planarization annealing, In the shot blasting process, the relationship between the product of the projection velocity VC and projection amount MC of the projection material at the width direction center portion and the product of the projection velocity VE and projection amount ME of the projection material at the width direction edge portion satisfies formula (1), VE×ME / 3 ≦ VC×MC ≦ VE×ME×2 / 3 ··· Formula (1) In the pickling, the pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, the total concentration of each element is 0.0001% or more and 1.0000% or less, the pH is -1.5 or more and less than 7, the liquid temperature is 15°C or more and 100°C or less, and the steel sheet is immersed in the pickling solution for 5 seconds or more and 200 seconds or less. The present invention provides a method for producing a grain-oriented electrical steel sheet.

[0017] In addition, in the heating for the primary recrystallization, the average heating rate in the temperature range of 550° C. to 700° C. may be 100° C. / s or more and 3000° C. / s or less. Effect of the Invention

[0018] According to the present invention, by combining a technique for enhancing the inhibitor heat resistance of the coil width edge portions by controlling the conditions for shot blasting and pickling treatment, and a technique for increasing the Goss orientation grains in the coil width edge portions by performing a rapid heating treatment in the temperature rise process of primary recrystallization annealing, it is possible to provide a new and improved method for producing grain-oriented electrical steel sheet which realizes high magnetic flux density and enables the production of grain-oriented electrical steel sheet with excellent magnetic properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Preferred embodiments of the present invention will be described in detail below. Unless otherwise specified, the expression "A to B" for numerical values ​​A and B means "A or more and B or less." In such an expression, when a unit is added only to numerical value B, the unit is also applied to numerical value A.

[0020] [Method of manufacturing grain-oriented electrical steel sheets] Means for Solving the Problems The present inventors have conducted extensive research into methods for producing grain-oriented electrical steel sheets in order to improve the magnetic properties of the grain-oriented electrical steel sheets, and as a result have discovered the following.

[0021] Specifically, the present inventors discovered that by optimizing the conditions of shot blasting and pickling, it is possible to control inhibitors at the coil width edge portions of the steel sheet and improve the magnetic properties.

[0022] The present inventors have taken the above findings into consideration and arrived at the present invention. One embodiment of the present invention is a method for producing a grain-oriented electrical steel sheet having the following configuration.

[0023] a step of heating a slab containing, by mass%, C: 0.02% or more and 0.10% or less, Si: 2.5% or more and 4.5% or less, Mn: 0.01% or more and 0.50% or less, the total of one or more of S, Se and Te: 0.001% or more and 0.050% or less, acid-soluble Al: more than 0% and 0.05% or less, N: more than 0% and 0.015% or less, with the balance being Fe and impurities, and hot rolling the slab to obtain a hot-rolled steel sheet; A step of obtaining a pickled sheet by subjecting the hot-rolled steel sheet to shot blasting and pickling, or obtaining a hot-rolled annealed sheet by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing, and then obtaining a pickled sheet by subjecting the hot-rolled annealed sheet to shot blasting and pickling; A step of obtaining a cold-rolled steel sheet by cold rolling the pickled sheet; A step of subjecting the cold-rolled steel sheet to primary recrystallization annealing; A step of applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after the primary recrystallization annealing, and then performing finish annealing; A step of applying an insulating coating to the steel sheet after the finish annealing and then performing planarization annealing, In the shot blasting process, the relationship between the product of the projection velocity VC and projection amount MC of the projection material at the width direction center portion and the product of the projection velocity VE and projection amount ME of the projection material at the width direction edge portion satisfies formula (1), VE×ME / 3 ≦ VC×MC ≦ VE×ME×2 / 3 ··· Formula (1) In the pickling, the pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, the total concentration of each element is 0.0001% or more and 1.0000% or less, the pH is -1.5 or more and less than 7, the liquid temperature is 15°C or more and 100°C or less, and the time for which the steel sheet is immersed in the pickling solution is 5 seconds or more and 200 seconds or less. In the heating for the primary recrystallization, the average heating rate in the temperature range of 550° C. to 700° C. may be 100° C. / s or more and 3000° C. / s or less.

[0024] The method for manufacturing the grain-oriented electrical steel sheet according to this embodiment will be specifically described below.

[0025] [Slab composition] First, the composition of the slab used in the grain-oriented electrical steel sheet according to this embodiment will be described. In the following, unless otherwise specified, the notation "%" will represent "mass %". The remainder of the slab other than the elements described below is Fe and impurities. Here, impurities refer to components contained in raw materials or components mixed in during the manufacturing process, and components that are not intentionally contained in the steel sheet. The chemical composition of the slab, which is the material for the grain-oriented electrical steel sheet, is basically similar to the composition of the grain-oriented electrical steel sheet. However, in the manufacture of general grain-oriented electrical steel sheets, some of the contained elements are discharged outside the system by decarburization annealing and purification annealing during the manufacturing process, so that the chemical composition of the slab, which is the material, and the grain-oriented electrical steel sheet, which is the final product, are different. The slab composition can be appropriately adjusted in consideration of the effects of decarburization annealing and purification annealing during the manufacturing process so that the grain-oriented electrical steel sheet has the desired characteristics.

[0026] The C (carbon) content is 0.02% or more and 0.10% or less. C has various roles, but if the C content is less than 0.02%, the grain size becomes excessively large when the slab is heated, which increases the iron loss value of the final grain-oriented electrical steel sheet, which is not preferable. If the C content exceeds 0.10%, the decarburization time becomes long during decarburization after cold rolling, which is not preferable, and the manufacturing cost increases. In addition, if the C content exceeds 0.10%, decarburization is likely to be incomplete, which is not preferable, as there is a possibility that magnetic aging will occur in the final grain-oriented electrical steel sheet. Therefore, the C content is 0.02% or more and 0.10% or less, and preferably 0.05% or more and 0.09% or less.

[0027] The content of Si (silicon) is 2.5% or more and 4.5% or less. Si increases the electrical resistance of the steel sheet, thereby reducing eddy current loss, which is one of the causes of iron loss. If the content of Si is less than 2.5%, it is not preferable because it becomes difficult to sufficiently suppress the eddy current loss of the final grain-oriented electrical steel sheet. If the content of Si is more than 4.5%, it is not preferable because the workability of the grain-oriented electrical steel sheet decreases. Therefore, the content of Si is 2.5% or more and 4.5% or less, and preferably 2.7% or more and 4.0% or less.

[0028] The content of Mn (manganese) is 0.01% or more and 0.50% or less. Mn forms MnS, MnSe, MnTe, etc., which are inhibitors that affect secondary recrystallization. If the content of Mn is less than 0.01%, the absolute amount of MnS, MnSe, and MnTe that cause secondary recrystallization is insufficient, which is not preferable. If the content of Mn is more than 0.50%, it is not preferable because it becomes difficult to dissolve Mn during slab heating. In addition, if the content of Mn is more than 0.50%, it is not preferable because the precipitate size of MnS, MnSe, and MnTe, which are inhibitors, tends to become coarse, and the optimal size distribution as an inhibitor is impaired. Therefore, the content of Mn is 0.01% or more and 0.50% or less, preferably 0.01% or more and 0.30% or less. More preferably, it is 0.03% or more and 0.15% or less.

[0029] The total content of S (sulfur), Se (selenium) and Te (tellurium) is 0.001% or more and 0.050% or less. S, Se and Te form an inhibitor together with the above-mentioned Mn. All three of S, Se and Te may be contained in the slab, but at least one of them should be contained in the slab. If the total content of S, Se and Te is outside the above range, it is not preferable because a sufficient inhibitor effect cannot be obtained. Therefore, the total content of S, Se and Te is 0.001% or more and 0.050% or less, preferably 0.001% or more and 0.040% or less.

[0030] The content of acid-soluble Al (acid-soluble aluminum) is more than 0% and not more than 0.05%. Acid-soluble Al constitutes an inhibitor necessary for producing a grain-oriented electrical steel sheet with high magnetic flux density. When the content of acid-soluble Al is 0, AlN does not exist, and the inhibitor strength is insufficient, so that good magnetic properties may not be obtained, which is not preferable. When the content of acid-soluble Al is more than 0.05%, AlN precipitated as an inhibitor becomes coarse, which reduces the inhibitor strength, which is not preferable. Therefore, the content of acid-soluble Al is more than 0% and not more than 0.05%, and preferably more than 0% and not more than 0.04%.

[0031] The N (nitrogen) content is more than 0% and not more than 0.015%. N forms AlN, which is an inhibitor, together with the above-mentioned acid-soluble Al. If the N content is outside the above range, it is not preferable because a sufficient inhibitor effect cannot be obtained. Therefore, the N content is more than 0% and not more than 0.015%, preferably more than 0% and not more than 0.012%.

[0032] P (phosphorus) may be contained in an amount of more than 0% and not more than 1.0%. P has the effect of increasing strength without decreasing magnetic flux density. However, excessive P content impairs the toughness of the steel, making the steel sheet more susceptible to fracture. Therefore, the upper limit of the P content is set to 1.0%, preferably 0.150% or less, and more preferably 0.120% or less. There is no particular lower limit for the P content, but taking into consideration the manufacturing cost, it is set to 0.001% or more.

[0033] Furthermore, the slab used in the manufacture of the grain-oriented electrical steel sheet according to this embodiment may contain, in addition to the above-mentioned elements, one or more of Cu, Sn, Ni, Cr, Sb, and Bi as elements that stabilize secondary recrystallization. When the slab contains the above-mentioned elements, the magnetic flux density of the grain-oriented electrical steel sheet to be manufactured can be further improved. In one embodiment, the slab may contain, in place of a portion of the Fe, one or more selected from the group consisting of Cu: 1.0% or less, Sn: 1.0% or less, Ni: 1.0% or less, Cr: 1.0% or less, Sb: 1.0% or less, and Bi: 1.0% or less.

[0034] A slab is formed by casting molten steel adjusted to the above-described composition. The method for casting the slab is not particularly limited. In research and development, even if a steel ingot is formed in a vacuum melting furnace or the like, the same effects as when a slab is formed can be confirmed for the above-described components.

[0035] [Process to make hot-rolled steel sheet] The slab is then heated and hot-rolled to be processed into a hot-rolled steel sheet. The slab heating temperature is not particularly limited. When the inhibitor components in the slab are completely dissolved, the slab may be heated to, for example, 1280°C or higher. The upper limit of the slab heating temperature is not particularly specified, but is preferably 1450°C from the viewpoint of equipment protection. For example, the slab heating temperature may be 1280°C or higher and 1450°C or lower. On the other hand, when the inhibitor components in the slab are not completely dissolved, the slab heating temperature may be less than 1280°C, for example. In this case, the steel sheet may be subjected to a nitriding treatment in any of the steps from the hot-rolled sheet annealing step to the finish annealing step.

[0036] Next, the heated slab is hot-rolled to be processed into a hot-rolled steel sheet. The thickness of the hot-rolled steel sheet after processing may be, for example, 1.8 mm or more and 3.5 mm or less. If the thickness of the hot-rolled steel sheet is less than 1.8 mm, the shape of the steel sheet after hot rolling may be inferior, which is not preferable. If the thickness of the hot-rolled steel sheet is more than 3.5 mm, the rolling load in the cold rolling process becomes large, which is not preferable. The hot-rolled steel sheet may be annealed to obtain a hot-rolled annealed sheet. When hot-rolled steel sheet annealing is performed, the shape of the steel sheet becomes better, so that the possibility of the steel sheet breaking during the subsequent cold rolling process can be reduced.

[0037] [Shot blasting process] Next, the hot-rolled steel sheet or the hot-rolled annealed sheet is subjected to a shot blasting treatment. The shot blasting treatment introduces defects such as cracks and voids into the surface of the hot-rolled steel sheet, and in the subsequent pickling treatment, the pickling solution penetrates into the steel sheet through these spaces, so that the pickling solution reaches not only the outermost surface of the steel sheet but also a certain depth range. The pickling, which will be described in detail later, replaces Mn on the surface of MnS, MnSe, and MnTe (which may be referred to as "MnS, etc." in this specification), which are precipitates and act as inhibitors, with Cu, thereby improving the heat resistance of the inhibitor. Therefore, the shot blasting allows the pickling solution to penetrate not only the outermost surface of the steel sheet but also to a certain depth of the steel sheet, thereby strengthening the strength of the inhibitors such as MnS present therein.

[0038] In shot blasting, the relationship between the product of the projection velocity VC and projection amount MC of the projection material at the width direction center of the steel plate (or coil) and the product of the projection velocity VE and projection amount ME of the projection material at the width direction edge satisfies the following formula (1). VE×ME / 3 ≦ VC×MC ≦ VE×ME×2 / 3 ··· Formula (1) As a result, the strength of the shot blasting is stronger at the edge portions than at the center portion in the width direction of the steel plate. In other words, the introduction of defects such as cracks and voids is promoted more at the edge portions of the steel plate relative to the center portion of the steel plate, and the heat resistance of the inhibitor MnS, etc. is improved in the subsequent pickling treatment. On the other hand, if the shot blasting at the edge portions is too strong, defects such as cracks and voids are introduced further to the inner layer side, and secondary recrystallization (abnormal grain growth) of Goss-oriented grains from the surface layer side to the inner layer side, which will be described later, cannot be appropriately controlled, which is undesirable. The edge portion refers to the area within 200 mm from both edges in the coil width direction, and the center portion refers to the central area in the width direction that is 200 mm from both edges in the coil width direction. VE and ME are the projection speed and projection amount of the shot blasting treatment aimed at an area within 200 mm from the edge of the coil in the width direction, and when the treatment is performed using two or more devices, they may be the average values ​​of those treatments. VC and MC are the projection speed and projection amount of the shot blasting treatment aimed at the range from 200 mm away from the edge of the coil in the width direction to the center of the width direction, and when the treatment is performed using two or more devices, they may be the average values ​​of those treatments. The short blasting treatment of the present invention may be applied to both edges, or, if there is a problem with the magnetic properties of only one edge, it may be applied to only one edge.

[0039] The strength of shot blasting is determined by the relative magnitude of the product of the blasting velocity and the blasting amount, and the blasting velocities VC and VE and the blasting amounts MC and ME are not particularly limited and can be appropriately selected and adjusted according to the practical means for shot blasting. As an example, the blasting velocities VC and VE may be 10 to 150 m / s, and the blasting amounts MC and ME may be 200 to 2000 kg / min.

[0040] The shot blasting conditions may be such that the average particle size of the shot material is 0.1 mm or more and 5.0 mm or less. This introduces fine cracks into the steel plate surface through which the pickling solution penetrates. As the blast material (shot material), a general one may be used, and iron balls with a hardness of about Hv500 may be used. The shape of the blast material may be either angular or round.

[0041] [Process for obtaining pickled board] In this process, a hot-rolled steel sheet or a hot-rolled annealed sheet that has been shot blasted is immersed in a pickling solution to obtain a pickled sheet. Pickling is performed at least once after hot rolling and before primary recrystallization annealing in order to control inhibitors at the coil width edge portion, which will be described later. In one embodiment, pickling is performed before the cold rolling process in order to reduce roll wear in cold rolling.

[0042] The pickling treatment conditions are as follows: the pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn, and Ni, the total concentration of each element is 0.0001% or more and 1.0000% or less, the pH is -1.5 or more and less than 7, the liquid temperature is 15°C or more and 100°C or less, and the time for which the steel sheet is immersed in the pickling solution is 5 seconds or more and 200 seconds or less. If the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is less than 0.0001%, the inhibitor control effect at the coil width edge portion becomes insufficient, which is not preferable. If the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution exceeds 1.0000%, the effect of improving the magnetic property becomes saturated and the cost of the pickling solution increases, which is not preferable. Therefore, the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is 0.0001% or more and 1.0000% or less. In addition, if the pH of the pickling solution is less than -1.5, the acidity becomes too strong and the handling of the pickling solution becomes difficult, which is not preferable. If the pH of the pickling solution is 7 or more, the inhibitor control effect in the thickness direction by the pickling process becomes insufficient, which is not preferable. Therefore, the pH of the pickling solution is -1.5 or more and less than 7. In addition, if the temperature of the pickling solution is less than 15°C, the inhibitor control effect in the thickness direction by the pickling treatment becomes insufficient, which is not preferable. If the temperature of the pickling solution is more than 100°C, the handling of the pickling solution becomes difficult, which is not preferable. Therefore, the temperature of the pickling solution is 15°C or more and 100°C or less. In addition, when the time for which the steel sheet is immersed in the pickling solution in the pickling treatment is less than 5 seconds, the effect of the pickling treatment in controlling inhibitors in the sheet thickness direction becomes insufficient, which is not preferable. When the time for which the steel sheet is immersed in the pickling solution in the pickling treatment exceeds 200 seconds, the equipment becomes long and large, which is not preferable. Therefore, the time for which the steel sheet is immersed in the pickling solution in the pickling treatment is 5 seconds or more and 200 seconds or less.

[0043] The mechanism by which pickling treatment enables inhibitor control at the coil width edge is presumed to be as follows: When the pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn, and Ni (these elements are sometimes referred to as "Cu, etc." in this specification), these elements have a very high affinity with S, Se, and Te in the solution, and therefore substitute for Mn in MnS, MnSe, and MnTe (these elements are sometimes referred to as "MnS, etc." in this specification) precipitates exposed on the steel sheet surface to form compounds. This reaction is likely to occur in the MnS, etc. precipitates, particularly on the surface side that comes into contact with the pickling solution. When Mn is replaced by other metal elements (Cu, etc.) on the surface side of MnS precipitates, the compounds on the surface side act as a barrier to suppress the dissolution of Mn, S, Se, and Te in the center of MnS precipitates into the steel, which suppresses the Ostwald ripening of MnS during the final annealing process, and is thought to increase the heat resistance of MnS precipitates, i.e., the inhibitor strength. This reaction occurs when a pickling solution containing one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn, and Ni comes into contact with MnS, MnSe, or MnTe. Therefore, defects such as cracks and voids are generated in the surface layer of the steel sheet by shot blasting, and the pickling solution penetrates into the steel sheet through the spaces such as cracks and voids, and reacts not only with MnS exposed on the outermost surface of the steel sheet, but also with MnS within a certain depth range of the steel sheet surface layer, thereby increasing the inhibitor strength. In particular, defects such as cracks and voids increase in the coil width edge parts that are heavily subjected to shot blasting, facilitating the penetration of the subsequent pickling solution, and further increasing the inhibitor strength. Since the inhibitor strength of the coil width edge parts may become lower than that of the coil width center part during hot rolling and finish annealing, selectively strengthening the inhibitor strength of the coil width edge parts is effective in uniforming the magnetic properties in the coil width direction.

[0044] [Process to make cold-rolled steel sheet] The obtained pickled sheet is then processed into a cold-rolled steel sheet by rolling it through one cold rolling or multiple cold rolling with intermediate annealing. When rolling it through multiple cold rolling with intermediate annealing and / or pickling, it is possible to omit the hot-rolled sheet annealing in the previous stage. In addition, both hot-rolled sheet annealing and intermediate annealing may be performed. In order to control the inhibitors at the coil width edge portion described above, pickling may be performed at least once after hot rolling and before primary recrystallization annealing. From the viewpoint of reducing roll wear in cold rolling, it is preferable to perform pickling before each cold rolling process.

[0045] In addition, the steel sheet may be heat-treated at about 300°C or less between passes of cold rolling, between rolling roll stands, or during rolling. In such a case, the magnetic properties of the final grain-oriented electrical steel sheet can be improved. The hot-rolled steel sheet may be rolled by three or more cold rolling passes, but since multiple cold rolling passes increase the manufacturing cost, it is preferable that the hot-rolled steel sheet is rolled by one or two cold rolling passes. When cold rolling is performed by reverse rolling such as a Sendzimir mill, the number of passes in each cold rolling pass is not particularly limited, but is preferably 9 passes or less from the viewpoint of manufacturing cost.

[0046] [Primary recrystallization annealing process] Next, the cold-rolled steel sheet is heated and then decarburized. These processes are also called primary recrystallization annealing, and are preferably performed continuously. By rapidly heating the temperature in the primary recrystallization annealing, it is possible to increase the number of Goss-oriented grains before secondary recrystallization in the cold-rolled steel sheet, and it is expected that grains with an orientation closer to the ideal Goss orientation will be secondary recrystallized in the secondary recrystallization process.

[0047] (Temperature rise process) In the present invention, the average heating rate between 550°C and 700°C during the heating process in the primary recrystallization annealing may be 100°C / s or more and 3000°C / s or less. This can increase the number of Goss-oriented grains before secondary recrystallization in the cold-rolled steel sheet, and improve the magnetic flux density of the final grain-oriented electrical steel sheet. The temperature range for rapid heating is 550°C to 700°C. If the start temperature of rapid heating is more than 550°C, dislocation recovery progresses significantly in the steel sheet, and primary recrystallization of grains other than the Goss-oriented grains begins, which is undesirable as it reduces the effect of increasing the Goss-oriented grains. If the end temperature of rapid heating is less than 700°C, the primary recrystallization of other grains is completed before the primary recrystallization of the Goss-oriented grains is completed, which is undesirable as it reduces the effect of increasing the Goss-oriented grains.

[0048] In addition, when the average heating rate between 550°C and 700°C is 400°C / s or more, the number of Goss-oriented grains before the secondary recrystallization can be further increased, and the magnetic flux density of the final grain-oriented electrical steel sheet can be further improved, which is more preferable, and when the average heating rate between 550°C and 700°C is 700°C / s or more, the magnetic flux density of the grain-oriented electrical steel sheet can be further improved, which is extremely preferable. When the average heating rate between 550°C and 700°C is less than 100°C / s, it is not preferable because sufficient Goss-oriented grains cannot be obtained to improve the magnetic properties by the secondary recrystallization. On the other hand, the upper limit of the average heating rate between 550°C and 700°C is not particularly limited, but may be, for example, 3000°C / s from the viewpoint of equipment and manufacturing costs. The heating start temperature of the primary recrystallization annealing, the heat pattern other than the rapid heating from 550°C to 700°C, and the final temperature are not particularly limited.

[0049] The increase in inhibitor strength on the surface layer side of the steel sheet, particularly at the coil width edge portion, due to the pickling treatment, and the increase in Goss oriented grains due to the rapid temperature rise in the primary recrystallization annealing bring about a synergistic effect on the improvement of magnetic properties. Although not necessarily bound by a specific theory, the following is considered as the mechanism of the synergistic effect. In the surface layer of the coil width edge portion, the inhibitor constituent components are reduced due to reactions with the atmosphere during high-temperature slab heating, and it is possible that the inhibitor strength of the coil width direction edge portion is reduced. According to an embodiment of the present invention, the coil width direction edge portion is strongly shot blasted, and the inhibitor strength is increased by the subsequent pickling treatment. Therefore, it is considered that, during the final annealing temperature rise process, abnormal grain growth other than that of Goss oriented grains is suppressed at the coil width direction edge portion, and as a result, abnormal grain growth of a large number of Goss oriented grains is promoted.

[0050] Such a rapid temperature rise can be achieved, for example, by using a current heating method or an induction heating method.

[0051] Here, the heating process may be performed by a plurality of devices. For example, holding or slow cooling at a temperature lower than 550°C at which recovery of the steel sheet occurs, i.e., a decrease in dislocation density in the steel sheet, may be performed because this can improve the temperature uniformity of the steel sheet before heating. Furthermore, the heating process including heating from 550°C to 700°C may also be performed by one or more devices.

[0052] The point at which heating starts is the point at which the temperature of the steel plate transitions from a decreasing state to an increasing state on the low-temperature side of 550°C or less (i.e., the point at which the temperature change is at a minimum value), while the point at which heating ends is the point at which the temperature of the steel plate transitions from an increasing state to a decreasing state on the high-temperature side of 700°C or more (i.e., the point at which the temperature change is at a maximum value).

[0053] However, depending on the arrangement of the multiple heating devices, there is a possibility that the temperature of the steel sheet may continue to rise at a temperature higher than the temperature of the heating process including 700° C. In such a case, for example, the end point of the rapid heating may be a point at or above 700° C. where the rate of change of the heating rate is a negative value and is minimal.

[0054] Here, the method of determining the temperature rise start point and the rapid temperature rise end point is not particularly limited, but for example, it is possible to determine by measuring the steel sheet temperature using a radiation thermometer or the like. The method of measuring the steel sheet temperature is not particularly limited. Furthermore, even if the temperature rise end temperature of the primary recrystallization is lower or higher than the subsequent decarburization annealing temperature, the effect of the present invention is not impaired. When the temperature rise end temperature of the primary recrystallization is lower than the decarburization annealing temperature, the steel sheet may be heated in the decarburization annealing process. When the temperature rise end temperature of the primary recrystallization is higher than the decarburization annealing temperature, the steel sheet may be cooled by performing a heat radiation treatment or a gas cooling treatment. Furthermore, after cooling to a temperature lower than the decarburization annealing temperature, the steel sheet may be reheated in the decarburization annealing process.

[0055] However, when it is difficult to measure the steel sheet temperature and difficult to estimate the exact positions of the temperature rise start point and the rapid temperature rise end point, these positions may be estimated by analogy with the heat patterns of the temperature rise process and the cooling process. Furthermore, the entry and exit temperatures of the steel sheet into the temperature rise device during the temperature rise process may be set as the temperature rise start point and the rapid temperature rise end point.

[0056] (Decarburization annealing) Next, the cold-rolled steel sheet is decarburized and annealed. From the viewpoint of decarburization, the decarburization may be performed at a temperature of 900° C. or less in a moist atmosphere containing hydrogen and nitrogen. In order not to inhibit the decarburization, the oxygen partial pressure ratio of the decarburization annealing atmosphere, i.e., the water vapor partial pressure P H2O and hydrogen partial pressure P H2 Compared to P H2O / P H2 may be set to 0.35 or more and 0.60 or less.

[0057] In the step of primary recrystallization annealing, the cold-rolled steel sheet may be subjected to reduction annealing following decarburization annealing in order to improve magnetic properties and coating properties.

[0058] [Finish annealing process] Thereafter, the cold-rolled steel sheet after the primary recrystallization annealing is subjected to a finish annealing. In this case, an annealing separator mainly composed of MgO may be applied before the finish annealing for the purpose of preventing seizure between steel sheets, forming a primary coating, controlling secondary recrystallization behavior, etc. The annealing separator is generally applied to the steel sheet surface in the form of a water slurry and dried, but an electrostatic application method or the like may also be used.

[0059] Then, the coiled steel sheet is subjected to a finish annealing for the purpose of forming a primary coating and secondary recrystallization. The finish annealing may be performed by heat treating the coiled steel sheet using, for example, a batch-type heating furnace. Furthermore, in order to further reduce the iron loss value of the final grain-oriented electrical steel sheet, the coiled steel sheet may be subjected to a purification treatment in which the temperature is raised to about 1200°C and then held at that temperature.

[0060] Finish annealing is generally performed by raising the temperature from about room temperature, and the temperature raising rate of finish annealing is various, but is not particularly limited in the present invention, and general finish annealing conditions can be used. For example, the rate may be 5°C / h to 100°C / h from the viewpoint of productivity and general equipment constraints. In addition, other known heat patterns may be used. The heat pattern in the cooling process is also not particularly limited.

[0061] The atmosphere gas composition in the final annealing is not particularly limited. In the secondary recrystallization process, a mixed gas of nitrogen and hydrogen may be used. A dry atmosphere or a wet atmosphere may be used. In the purification annealing, dry hydrogen gas may be used.

[0062] [Planarization annealing process] Next, after the finish annealing, an insulating coating mainly composed of, for example, aluminum phosphate or colloidal silica is applied to the surface of the steel sheet in order to provide the steel sheet with insulation and tension. Then, flattening annealing is performed in order to bake the insulating coating and flatten the shape of the steel sheet by the finish annealing. Note that the components of the insulating coating are not particularly limited as long as the steel sheet is provided with insulation and tension. Note that in this embodiment, it goes without saying that the grain-oriented electrical steel sheet may be subjected to a magnetic domain control treatment depending on the purpose of the customer.

[0063] The above steps allow the final grain-oriented electrical steel sheet to be manufactured. According to the manufacturing method according to the present embodiment, it is possible to manufacture a grain-oriented electrical steel sheet that is excellent in magnetic properties, particularly in the magnetic properties not only in the center portion of the coil width but also at the edges of the coil width.

[0064] In the grain-oriented electrical steel sheet according to the present embodiment, the magnetic flux density B8 value may be further controlled. Specifically, in the grain-oriented electrical steel sheet according to the present embodiment, the magnetic flux density B8 value may be 1.90 T or more, preferably 1.91 T or more, and more preferably 1.92 T or more. Here, the magnetic flux density B8 value is the magnetic flux density when a magnetic field of 800 A / m at 50 Hz is applied to the grain-oriented electrical steel sheet. If the magnetic flux density B8 value is less than 1.90 T, the iron loss value (particularly, hysteresis loss) of the grain-oriented electrical steel sheet becomes large, which is not preferable. The upper limit of the magnetic flux density B8 value is not particularly limited, but may be, for example, 2.0 T in reality. In addition, the difference in the B8 value between the coil width edge portion and the center portion is 0.03 T or less. If the difference in the B8 value between the coil width edge portion and the center portion exceeds 0.03 T, the magnetic properties in the coil width direction become non-uniform, which is not preferable. The magnetic properties of the grain-oriented electrical steel sheet, such as the magnetic flux density, can be measured by a known method. For example, the magnetic properties of grain-oriented electrical steel sheets can be measured by using a method based on the Epstein test specified in JIS C2550, or the Single Sheet Tester (SST) method specified in JIS C2556. In research and development, when steel ingots are formed in a vacuum melting furnace or the like, it is difficult to obtain test pieces of the same size as those produced by actual equipment. In this case, for example, a test piece with a width of 60 mm and a length of 300 mm may be obtained, and measurements may be performed in accordance with the Single Sheet Magnetic Property Test Method. Furthermore, the obtained results may be multiplied by a correction factor so that the same measured values ​​as those obtained by the method based on the Epstein test are obtained. In this embodiment, measurements are performed using a measurement method in accordance with the Single Sheet Magnetic Property Test Method.

[0065] The grain-oriented electrical steel sheet according to the present embodiment has been described above. The grain-oriented electrical steel sheet according to the present embodiment can be manufactured by the above-mentioned method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment. However, the method is not limited to this method. EXAMPLES

[0066] The method for producing a grain-oriented electrical steel sheet according to an embodiment of the present invention and the grain-oriented electrical steel sheet will be described in more detail below with reference to examples. Note that the examples shown below are merely examples of the grain-oriented electrical steel sheet according to this embodiment, and the grain-oriented electrical steel sheet according to this embodiment is not limited to the examples shown below.

[0067] Example 1 <Manufacturing of grain-oriented electrical steel sheets> First, a slab containing 0.08% C, 3.2% Si, 0.08% Mn, 0.024% S, 0.03% acid-soluble Al, 0.008% N, and the balance being Fe and impurities was prepared. The slab was annealed at 1350°C for 1 hour, and then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2.3 mm. Samples were taken from the edge and center of the coil width direction from the obtained hot-rolled steel sheet. Here, the edge samples were taken within a range of 200 mm from the coil edge, and the center samples were taken from the center of the coil width direction 300 mm from the edge in the coil width direction. These hot-rolled sheets were annealed at a maximum temperature of 1100°C for 140 seconds, shot-blasted and pickled, and then cold-rolled to obtain a cold-rolled steel sheet having a thickness of 0.23 mm. The shot blasting treatment and the pickling treatment after the hot-rolled sheet annealing were carried out under the conditions shown in Table 1.

[0068] The cold-rolled steel sheet thus obtained was then subjected to primary recrystallization annealing in a wet hydrogen atmosphere at 850°C for 180 seconds. Here, the heating rate was 20°C / s. Next, an annealing separator containing MgO was applied in the form of a water slurry to the surface of the steel sheet after the primary recrystallization annealing, and dried. Thereafter, a finish annealing was performed, and the steel sheet after the finish annealing was washed with water. Thereafter, an insulating coating mainly composed of aluminum phosphate and colloidal silica was applied to the surface of the steel sheet, and then flattening annealing was performed for the purpose of baking the insulating coating and flattening the steel sheet.

[0069] The grain-oriented electrical steel sheet samples obtained above after the flattening annealing were sheared and stress relief annealed, and then the magnetic flux density B8 value of the grain-oriented electrical steel sheets according to each of the present invention examples and comparative examples was measured using a single sheet magnetic property measurement method (based on the method described in JIS C2556) with a sample size of 60 mm x 300 mm. Here, the B8 value is the magnetic flux density of the steel sheet when the grain-oriented electrical steel sheet is excited at 50 Hz and 800 A / m. In the present invention, the average value of five samples was used.

[0070] Here, the condition where the difference in B8 value between the edge part and the center part in the coil width direction is 0.03 T or less and the magnetic flux density B8 value of the grain-oriented electrical steel sheet in the center part in the coil width direction is 1.92 T or more was judged to be good (B). Anything other than the above was judged to be unacceptable (C).

[0071] Table 1 shows the manufacturing conditions, measurement results, and evaluations of the above examples of the present invention and comparative examples.

[0072] [Table 1]

[0073] Referring to the results in Table 1, it was found that the grain-oriented electrical steel sheet satisfying the conditions of this embodiment was judged to be good.

[0074] Example 2 First, a slab containing 0.08% C, 3.2% Si, 0.08% Mn, 0.024% S, 0.03% acid-soluble Al, 0.008% N, and the balance being Fe and impurities was prepared. The slab was annealed at 1350°C for 1 hour, and then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2.3 mm. Samples were taken from the edge and center of the coil width direction of the obtained hot-rolled steel sheet. Here, the edge samples were taken within a range of 200 mm from the coil edge, and the center samples were taken from the center of the coil width direction 300 mm from the edge in the coil width direction. These hot-rolled sheets were annealed at a maximum temperature of 1100°C for 140 seconds, shot-blasted and pickled, and then cold-rolled to obtain a cold-rolled steel sheet having a thickness of 0.23 mm. The shot blasting conditions were as shown in Table 2. The pickling conditions after annealing of the hot-rolled sheet were as follows: Cu concentration in the pickling solution: 0.001%, pickling solution: hydrochloric acid, pickling solution pH: 3, pickling solution temperature: 70°C, contact time between the pickling solution and the steel sheet: 30 seconds.

[0075] The cold-rolled steel sheet thus obtained was then subjected to primary recrystallization annealing in a wet hydrogen atmosphere at 850°C for 180 seconds. The heating rate was set to the conditions shown in Table 2. Next, an annealing separator containing MgO was applied in the form of a water slurry to the surface of the steel sheet after the primary recrystallization annealing, and the steel sheet was dried. Then, a finish annealing was performed, and the steel sheet after the finish annealing was washed with water. Then, an insulating coating mainly composed of aluminum phosphate and colloidal silica was applied to the surface of the steel sheet, and the steel sheet was subjected to flattening annealing for the purpose of baking the insulating coating and flattening the steel sheet.

[0076] The grain-oriented electrical steel sheet samples obtained above after the flattening annealing were sheared and stress relief annealed, and then the magnetic flux density B8 value of the grain-oriented electrical steel sheets according to each of the present invention examples and comparative examples was measured using a single sheet magnetic property measurement method (based on the method described in JIS C2556) with a sample size of 60 mm x 300 mm. Here, the B8 value is the magnetic flux density of the steel sheet when the grain-oriented electrical steel sheet is excited at 50 Hz and 800 A / m. In the present invention, the average value of five samples was used.

[0077] Here, the condition where the difference in B8 value between the edge part and the center part in the coil width direction is 0.03 T or less and the magnetic flux density B8 value of the grain-oriented electrical steel sheet in the center part in the coil width direction is 1.92 T or more was judged as good (B), the condition where it is 1.93 T or more was judged as even better (A), and the condition where it is 1.94 T or more was judged as extremely good (S). Anything other than the above was judged as unacceptable (C).

[0078] Table 2 shows the manufacturing conditions, measurement results, and evaluations of the above-mentioned examples of the present invention and comparative examples.

[0079] [Table 2]

[0080] Referring to the results in Table 2, it was found that the grain-oriented electrical steel sheet satisfying the conditions of this embodiment was judged to be good.

[0081] Example 3 First, a steel ingot was prepared containing, by mass%, C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.025%, acid-soluble Al: 0.03%, N: 0.008%, and the balance being the components shown in Table 3, Fe, and impurities. The steel ingot was annealed at 1350°C for 1 hour, and then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2.3 mm. Here, under conditions simulating the coil width direction center portion, the final pass temperature of hot rolling was 1050°C, and under conditions simulating the coil width direction edge portion, the final pass temperature of hot rolling was 1000°C. The obtained hot-rolled steel sheet was annealed at a maximum temperature of 1100°C for 140 seconds, shot-blasted and pickled, and then cold-rolled to obtain a cold-rolled steel sheet having a thickness of 0.23 mm. Here, the shot blasting treatment after the annealing of the hot-rolled sheet was performed with a projection speed VC of 50 m / s and a projection amount MC of 500 kg / min for the center sample and a projection speed VE of 50 m / s and a projection amount ME of 800 kg / min for the edge sample. The pickling conditions were as follows: Cu concentration in the pickling solution: 0.001%, pickling solution: hydrochloric acid, pickling solution pH: 3, pickling solution temperature: 70°C, and contact time between the pickling solution and the steel sheet: 30 seconds.

[0082] The cold-rolled steel sheet thus obtained was then subjected to primary recrystallization annealing in a wet hydrogen atmosphere at 850°C for 180 seconds. The heating rate was as shown in Table 3. Next, an annealing separator containing MgO was applied in the form of a water slurry to the surface of the steel sheet after the primary recrystallization annealing, and the steel sheet was dried. Then, the steel sheet was subjected to finish annealing, and the steel sheet after the finish annealing was washed with water. Then, an insulating coating mainly composed of aluminum phosphate and colloidal silica was applied to the surface of the steel sheet, and the steel sheet was subjected to flattening annealing for the purpose of baking the insulating coating and flattening the steel sheet.

[0083] The grain-oriented electrical steel sheet samples obtained above after the flattening annealing were sheared and stress relief annealed, and then the magnetic flux density B8 value of the grain-oriented electrical steel sheets according to each of the present invention examples and comparative examples was measured using a single sheet magnetic property measurement method (based on the method described in JIS C2556) with a sample size of 60 mm x 300 mm. Here, the B8 value is the magnetic flux density of the steel sheet when the grain-oriented electrical steel sheet is excited at 50 Hz and 800 A / m. In the present invention, the average value of five samples was used.

[0084] Here, the condition where the difference in the B8 value between the edge part and the center part in the coil width direction is 0.03 T or less and the magnetic flux density B8 value of the directional electrical steel sheet in the center part in the coil width direction is 1.92 T or more was judged to be good (B), the condition where it is 1.93 T or more was judged to be even better (A), the condition where it is 1.94 T or more was judged to be extremely good (S), and the condition where it is 1.95 T or more was judged to be best (SS).

[0085] Table 3 shows the manufacturing conditions, measurement results, and evaluations of the above examples of the present invention and comparative examples.

[0086] [Table 3]

[0087] Referring to the results in Table 3, it was found that the grain-oriented electrical steel sheet satisfying the conditions of this embodiment was judged to be good.

Claims

1. a step of heating a slab containing, by mass%, C: 0.02% or more and 0.10% or less, Si: 2.5% or more and 4.5% or less, Mn: 0.01% or more and 0.50% or less, one or more of S, Se and Te in total: 0.001% or more and 0.050% or less, acid-soluble Al: more than 0% and 0.05% or less, N: more than 0% and 0.015% or less, with the balance being Fe and impurities, and hot rolling the slab to obtain a hot-rolled steel sheet; A step of obtaining a pickled sheet by subjecting the hot-rolled steel sheet to shot blasting and pickling, or obtaining a hot-rolled annealed sheet by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing, and then obtaining a pickled sheet by subjecting the hot-rolled annealed sheet to shot blasting and pickling; A step of obtaining a cold-rolled steel sheet by cold rolling the pickled sheet; A step of subjecting the cold-rolled steel sheet to primary recrystallization annealing; A step of applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after the primary recrystallization annealing, and then performing finish annealing; A step of applying an insulating coating to the steel sheet after the final annealing and then performing planarization annealing, In the shot blasting process, the relationship between the product of the projection velocity VC and the projection amount MC of the projection material at the width direction center portion and the product of the projection velocity VE and the projection amount ME of the projection material at the width direction edge portion satisfies formula (1), VE×ME / 3 ≦ VC×MC ≦ VE×ME×2 / 3 ... Formula (1) the pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, the total concentration of each element is 0.0001% or more and 1.0000% or less, the pH is -1.5 or more and 6 or less, the solution temperature is 15°C or more and 100°C or less, and the steel sheet is immersed in the pickling solution for 5 seconds or more and 200 seconds or less.

2. 2. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein in the rapid heating in the primary recrystallization annealing, an average heating rate in a temperature range of 550° C. to 700° C. is 100° C. / s or more and 3000° C. / s or less.

3. 3. The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, characterized in that the slab contains, in place of a portion of the Fe, one or more elements selected from the group consisting of Cu: 1.0% or less, Sn: 1.0% or less, Ni: 1.0% or less, Cr: 1.0% or less, Sb: 1.0% or less, and Bi: 1.0% or less.

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