Grain-oriented electrical steel sheet and method of manufacturing the same

Abstract

A method for manufacturing an oriented electrical steel sheet according to an embodiment of the present invention includes: a step of manufacturing a slab, wherein the slab comprises, by weight %, 0.01% to 0.1% C, 1.5% to 4.5% Si, 0.1% to 1.5% Mn, with the balance being Fe and other unavoidable impurities; a step of hot rolling the slab to manufacture a hot-rolled sheet; a step of cold rolling the hot-rolled sheet to manufacture a cold-rolled sheet; a step of nitriding annealing the cold-rolled sheet; and a step of secondary recrystallization annealing the nitrided sheet, wherein after the nitriding annealing step, the ratio (P2 / P1) of precipitates and inclusions (P2) present in the center portion of the sheet extending from one end to more than 30% to 70% of the total width of the sheet to precipitates and inclusions (P1) present at one end of the sheet or at the upper edge portion extending from one end to 30% of the total width of the sheet is 0.6 to 1.0.

Description

TECHNICAL FIELD

[0001] One embodiment of the present application relates to an oriented electrical steel sheet and a method of manufacturing the same. In particular, one embodiment of the present application relates to an oriented electrical steel sheet and a method of manufacturing the same, in which precipitates or inclusions are appropriately formed in a width direction of the steel sheet during nitriding annealing, thereby reducing magnetic deviation in the width direction of the steel sheet. BACKGROUND

[0002] An oriented electrical steel sheet is a soft magnetic material that forms a so-called Goss texture in which all grains on the surface of the steel sheet are oriented to a {110} plane, and the grain orientation in the rolling direction is parallel to a <001> axis, thereby having excellent magnetic properties in the rolling direction of the steel sheet. In general, the magnetic properties of an electrical steel sheet can be represented by magnetic flux density and iron loss, and a high magnetic flux density can be obtained by precisely arranging the grain orientation to a {110} <001> orientation. An electrical steel sheet having a high magnetic flux density not only enables a reduction in the size of the core material of an electrical device, but also enables miniaturization and high efficiency of the electrical device due to a reduction in hysteresis loss. Iron loss refers to electrical power loss consumed in the form of heat energy when an arbitrary alternating magnetic field is applied to the steel sheet, and significantly varies depending on factors such as the magnetic flux density of the steel sheet, the sheet thickness, the amount of impurities in the steel sheet, the electrical resistivity, and the secondary recrystallized grain size, and the higher the magnetic flux density and the electrical resistivity and the lower the sheet thickness and the amount of impurities in the steel sheet, the smaller the iron loss, thereby improving the efficiency of the electrical device.

[0003] Currently, the world is reducing carbon dioxide emissions to cope with global warming, and energy saving and product efficiency have become a trend, and as the demand for popularization and spread of high-efficiency electrical devices having low power consumption increases, there is an increasing demand in society for the development of an oriented electrical steel sheet having more excellent magnetic flux density and low iron loss characteristics.

[0004] The initially developed oriented electrical steel sheet uses MnS as a grain growth inhibitor and is manufactured by two cold rolling and high-temperature annealing. Through such a manufacturing method, secondary recrystallization is relatively stably formed, but the magnetic flux density (B8, magnetic flux density at 800 A / m) is about 1.80 Tesla, and the iron loss is also higher than the current level. Thereafter, a method of using AlN and MnS precipitates or inclusions in combination as a grain growth inhibitor and manufacturing an oriented electrical steel having excellent magnetic flux density (magnetic flux density (B8) of 1.87 Tesla or more) by one strong cold rolling has been proposed, and this method has been used as a commercialized technology to date.

[0005] In addition, a method for manufacturing electrical steel sheets containing MnS (or MnSe) and Sb through a secondary cold rolling process was proposed, which can yield products with high magnetic flux density. The common feature of the above three technologies is the need for fine and uniform control of precipitates or inclusions, thus requiring high slab heating temperatures. This leads to problems such as excessive energy consumption, increased equipment failure rates, and decreased yield of the final product.

[0006] To replace this high-temperature slab heating method, a method has been proposed that involves infiltrating nitrogen into the slab after decarburization annealing and before the start of the final secondary recrystallization annealing to form inhibitors such as (Al,Si)N required for secondary recrystallization (the so-called low-temperature slab heating method). To form inhibitors such as AlN and (Al,Si)N using nitriding gases after decarburization annealing, nitriding gases need to be blown into the steel plate through gas distribution pipes or nozzles. At this time, the concentration of nitriding gases changes in the width direction, leading to unexpected fluctuations in the nitriding concentration. Even if nitriding is performed at the same concentration, during the subsequent secondary recrystallization annealing process, the slab is rolled into a coil for annealing to achieve a longer annealing time, and it is difficult to uniformly adjust the temperature at the top, middle, and bottom of the coil, resulting in magnetic deviations in the width direction of the steel plate.

[0007] Furthermore, in recent years, in order to improve the production efficiency of grain-oriented electrical steel sheets, not only has the weight of a single coil been increased, but the width of the coil has also been increased. As a result, with the increase in coil width, the magnetic deviation in the width direction of the steel sheet further increases, leading to the deterioration of the magnetic properties of the entire coil. Summary of the Invention

[0008] (a) Technical problems to be solved One embodiment of the present invention provides an oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention provides an oriented electrical steel sheet and a method for manufacturing the same, wherein precipitates or inclusions are appropriately formed in the width direction of the steel sheet during nitriding annealing, thereby reducing the magnetic deviation in the width direction of the steel sheet.

[0009] (II) Technical Solution A method for manufacturing an oriented electrical steel sheet according to an embodiment of the present invention comprises: a step of manufacturing a slab, wherein the slab comprises, by weight %, 0.01% to 0.1% C, 1.5% to 4.5% Si, 0.1% to 1.5% Mn, with the balance being Fe and other unavoidable impurities; a step of hot rolling the slab to manufacture a hot-rolled sheet; a step of cold rolling the hot-rolled sheet to manufacture a cold-rolled sheet; a step of nitriding annealing the cold-rolled sheet; and a step of secondary recrystallization annealing the nitrided sheet.

[0010] After the nitriding annealing step, the ratio (P2 / P1) of the amount of precipitates and inclusions (P2) present in the center portion of the steel plate extending from one end to more than 30% to 70% of the total width of the steel plate to the amount of precipitates and inclusions (P1) present at one end of the steel plate or at the upper edge portion extending from one end of the steel plate extending to 30% of the total width of the steel plate is 0.6 to 1.0.

[0011] The slab may also contain Al: 0.020% to 0.040%, N: 0.0030% to 0.0060% and S: 0.0030% to 0.0065% by weight.

[0012] The slab may also contain Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07% and P: 0.01% to 0.04% by weight.

[0013] The slab can satisfy the following formula 1.

[0014] [Formula 1] 0.0330≤[P]+0.5×[Sb]≤0.062 In Equation 1, [P] and [Sb] represent the contents (by weight%) of P and Sb in the slab, respectively.

[0015] The slab may also contain one or more of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15% by weight.

[0016] After the nitriding annealing step, the ratio (P3 / P1) of the amount of precipitates and inclusions (P3) at the lower edge of the steel plate from one end to the other end of the steel plate, which is more than 70% of the total width of the steel plate, to the amount of precipitates and inclusions (P1) present at the upper edge can be 0.7 to 1.0.

[0017] In the nitriding annealing step, the ratio (AF1 / AF2) of the flow rate of ammonia gas fed into the upper edge (AF1) to the flow rate of ammonia gas fed into the center (AF2) can be 1.03 to 1.40.

[0018] Furthermore, in the nitriding annealing step, the ratio (AF3 / AF2) of the flow rate of ammonia gas fed into the lower edge (AF3) to the flow rate of ammonia gas fed into the center can be 1.03 to 1.40. In the nitriding annealing step, the soaking temperature can be 820 to 900°C.

[0019] In the nitriding annealing step, nitriding and decarburization occur simultaneously. The oxidation degree (P) of the atmosphere during decarburization is... H2O / P H2 The value can be between 0.45 and 0.75.

[0020] According to an embodiment of the present invention, the oriented electrical steel sheet, by weight percent, comprises C: less than 0.005% and excluding 0%, Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, with the balance including Fe and other unavoidable impurities. The ratio (P2 / P1) of precipitates and inclusions (P2) present in the central portion of the steel sheet extending from one end to more than 30% to 70% of the total width of the steel sheet to precipitates and inclusions (P1) present at one end of the steel sheet or at the upper edge portion extending from one end of the steel sheet to 30% of the total width of the steel sheet is 0.6 to 1.0.

[0021] According to one embodiment of the present invention, the oriented electrical steel sheet may further contain less than 0.040% Al, less than 0.0050% N and less than 0.005% S by weight.

[0022] According to an embodiment of the present invention, the oriented electrical steel sheet may further contain, by weight %, Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07% and P: 0.01% to 0.04%.

[0023] According to an embodiment of the present invention, the oriented electrical steel sheet can satisfy the following formula 1.

[0024] [Formula 1] 0.0330≤[P]+0.5×[Sb]≤0.062 In Equation 1, [P] and [Sb] represent the contents (by weight%) of P and Sb in the steel plate, respectively.

[0025] According to one embodiment of the present invention, the oriented electrical steel sheet may contain one or more of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15% by weight.

[0026] According to an embodiment of the present invention, in an oriented electrical steel sheet, the ratio (P3 / P1) of the amount of precipitates and inclusions (P3) at the lower edge portion from one end of the steel sheet to the other end of the steel sheet at more than 70% of the total width of the steel sheet to the amount of precipitates and inclusions (P1) present at the upper edge portion can be 0.7 to 1.0.

[0027] (III) Beneficial Effects According to an embodiment of the present invention, the oriented electrical steel sheet can reduce the magnetic deviation in the width direction of the steel sheet and uniformly improve the magnetism in the width direction of the steel sheet. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating an oriented electrical steel sheet according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram illustrating the coil-shaped steel sheet in the secondary recrystallization annealing step of one embodiment of the present invention. Detailed Implementation

[0030] The terms "first," "second," "third," etc., are used to describe parts, components, regions, layers, and / or segments, but these parts, components, regions, layers, and / or segments should not be limited by these terms. These terms are only used to distinguish one part, component, region, layer, or segment from another. Therefore, without departing from the scope of the invention, the first part, component, region, layer, or segment described below can also be described as a second part, component, region, layer, or segment.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. Unless the context clearly indicates otherwise, the singular forms used herein are intended to include the plural forms as well. The word "comprising" as used in the specification can specifically refer to a particular feature, domain, integer, step, action, element, and / or component, but does not exclude the presence or addition of other features, domains, integers, steps, actions, elements, components, and / or groups.

[0032] When one part is described as being on top of another part, there can be other parts directly on top of the other part or in between. When one part is described as being directly on top of another part, there are no other parts in between.

[0033] Although not otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in dictionaries should be interpreted as having the same meaning as disclosed in relevant technical literature and herein, and should not be interpreted in an idealized or overly formal sense.

[0034] Furthermore, unless otherwise specified, % means by weight, and 1 ppm is 0.0001 by weight.

[0035] In one embodiment of the present invention, the inclusion of additional elements refers to the replacement of a portion of the remaining iron (Fe) by additional elements, the replacement amount being equivalent to the amount of additional elements added.

[0036] Embodiments of the present invention will be described in detail below to enable those skilled in the art to implement the invention. However, the invention can be implemented in various different ways and is not limited to the embodiments described herein.

[0037] A method for manufacturing an oriented electrical steel sheet according to an embodiment of the present invention comprises: a step of manufacturing a slab, wherein the slab comprises, by weight %, 0.01% to 0.1% C, 1.5% to 4.5% Si, 0.1% to 1.5% Mn, with the balance being Fe and other unavoidable impurities; a step of hot rolling the slab to manufacture a hot-rolled sheet; a step of cold rolling the hot-rolled sheet to manufacture a cold-rolled sheet; a step of nitriding annealing the cold-rolled sheet; and a step of secondary recrystallization annealing the nitrided sheet.

[0038] The following sections will describe each step in detail.

[0039] First, the slab is manufactured.

[0040] The slab contains, by weight percent, 0.01% to 0.1% C, 1.5% to 4.5% Si, 0.1% to 1.5% Mn, with the balance being Fe and other unavoidable impurities.

[0041] The reasons for limiting the amount added are described below for each element.

[0042] C: 0.01 to 0.10% by weight Carbon (C) is an element that promotes the austenite phase transformation, resulting in a uniform microstructure during hot rolling of grain-oriented electrical steel sheets. During cold rolling, it promotes the formation of Gaussian-oriented grains, making it a crucial element for manufacturing magnetically superior grain-oriented electrical steel sheets. If too much C is added, the austenite phase transformation during hot rolling leads to a finer hot-rolled microstructure. This results in finer primary recrystallized grains, which may form carbides during the coiling process after hot rolling or during cooling after annealing, and may also form Fe3C (cementite) at room temperature, easily causing microstructure inhomogeneity. Simultaneously, the time required for decarburization to below 30 ppm during the post-cold rolling decarburization process increases, leading to excessive formation of fayalite and silica on the steel sheet surface. Therefore, the C content can be from 0.01 to 0.10% by weight. More specifically, it can be from 0.03 to 0.08% by weight.

[0043] C is removed through decarburization during nitriding annealing, and the final oriented electrical steel sheet may contain less than 0.005% by weight. More specifically, it may contain less than 0.003% by weight. More specifically, it may contain 0.0001 to 0.0030% by weight.

[0044] Si: 1.5% to 4.5% by weight Silicon (Si) is a fundamental component of electrical steel sheets, its role being to increase the material's resistivity to reduce core loss, i.e., iron loss. If too little Si is added, the resistivity decreases, the reduction in eddy current loss is weak, and the amount of fir olivine formed during decarburization will be insufficient, potentially leading to unstable magnesium olivine coating formation. On the other hand, if too much Si is added, the steel becomes more brittle, making cold rolling difficult, and the surface quality may deteriorate due to the large amount of fir olivine formed during decarburization. Therefore, Si can be contained from 1.5 wt% to 4.5 wt%. More specifically, it can be contained from 2.5 wt% to 3.8 wt%.

[0045] Mn: 0.1 wt% to 1.5 wt% Like Si, manganese (Mn) increases resistivity and reduces iron loss. However, when a large amount of Mn is added, compared with the reduction in iron loss caused by the increase in resistivity, the decrease in saturation magnetic flux density and the formation of coarse MnS precipitates or inclusions weaken the grain growth inhibition force, resulting in a decrease in magnetic flux density after secondary recrystallization annealing. It also affects the composition of fir olivine and silica formed during decarburization, thus hindering the formation of a good magnesium olivine coating.

[0046] Therefore, to form a forsterite coating with excellent magnetic flux density and adhesion, the Mn content needs to be optimized. If too little Mn is added, the refining burden during steelmaking increases, reducing the amount of fine MnS precipitates that can suppress grain growth. If too much Mn is added, it promotes the precipitation of coarse MnS, requiring the slab to be heated to above 1150°C to dissolve the MnS precipitates or inclusions, which can cause problems. Furthermore, it may hinder the formation of high-quality fir olivine and silica during decarburization.

[0047] The slab may also contain Al: 0.020% to 0.040%, N: 0.0030% to 0.0060% and S: 0.0030% to 0.0065% by weight.

[0048] Al: 0.020% to 0.040% by weight Aluminum (Al) combines with nitrogen to form AlN precipitates, which are typical grain growth inhibitors used in the secondary recrystallization of grain-oriented electrical steel sheets. In one embodiment of the invention, (Al,Si,Mn)N precipitates or inclusions are formed by nitriding annealing after cold rolling, thereby ensuring the grain growth inhibition effect, particularly by controlling the precipitation of precipitates or inclusions in the width direction of the steel sheet to reduce magnetic deviation in the width direction. In the steelmaking process, the amount of Al added is preferably 0.020% to 0.040% by weight. If too little Al is added, the total amount of (Al,Si,Mn)N precipitates or inclusions formed during the primary recrystallization and nitriding annealing processes will be very limited, which may result in insufficient inhibition of grain growth during primary recrystallization. On the other hand, if too much Al is added, the precipitates or inclusions will grow coarsely during slab manufacturing and hot rolling processes, thus forming coarse microstructures during nitriding annealing, which may lead to instability in the formation of secondary recrystallization during the subsequent secondary recrystallization annealing process. Therefore, the Al content in the slab can be from 0.020 wt% to 0.040 wt%. More specifically, it can be from 0.020 wt% to 0.035 wt%.

[0049] During the secondary recrystallization annealing process, some Al can be removed by purification annealing, and the final oriented electrical steel sheet can contain less than 0.040% by weight of Al. More specifically, it can contain 0.010% to 0.040% by weight.

[0050] N: 0.0030 wt% to 0.0060 wt% Nitrogen (N) is a crucial element that reacts with Al to form AlN precipitates or inclusions that inhibit grain growth. In manufacturing methods that ensure (Al,Si,Mn)N precipitates or inclusions through nitriding after cold rolling, the steelmaking process does not require a large amount of N. However, if too little N is added, fine AlN precipitates or inclusions form during slab manufacturing, resulting in smaller primary recrystallized grains and making precisely Gaussian oriented grains more susceptible to secondary recrystallization. Conversely, if too much N is added, coarse AlN precipitates or inclusions form during slab manufacturing, resulting in coarse primary recrystallized microstructures and consequently, instability in secondary recrystallization. Therefore, the range of N can be limited to 0.0030 wt% to 0.0060 wt%. More specifically, it can contain 0.0035 wt% to 0.0055 wt%.

[0051] On the other hand, in one embodiment of the present invention, by controlling the ammonia flow rate in the width direction of the steel plate during the nitriding annealing process, (Al,Si,Mn)N precipitates or inclusions can be precipitated in different ways in the width direction of the steel plate. This reduces the magnetic deviation in the width direction of the steel plate.

[0052] Specifically, in the nitriding annealing step, the ratio (AF1 / AF2) of the flow rate of ammonia gas fed into the upper edge (AF1) to the flow rate of ammonia gas fed into the center can be 1.03 to 1.40.

[0053] Furthermore, in the nitriding annealing step, the ratio (AF3 / AF2) of the flow rate of ammonia gas fed into the lower edge (AF3) to the flow rate of ammonia gas fed into the center can be 1.03 to 1.40.

[0054] Furthermore, in the nitriding annealing step, the ratio (AF3 / AF1) of the flow rate of ammonia gas fed into the lower edge (AF3) to the flow rate of ammonia gas fed into the upper edge (AF1) can be 0.85 to 1.15.

[0055] The inventors have discovered that, during the nitriding annealing step, the flow rate of ammonia gas supplied along its width can be adjusted by changing the position of the ammonia gas inlet pipe. In one embodiment of the invention, the ammonia flow rate refers to the mass of ammonia gas supplied per unit area and per unit time.

[0056] By adjusting the amount of ammonia gas supplied to different parts of the steel plate within the aforementioned range, the precipitates or inclusions generated in each part can be appropriately adjusted. In other words, by independently maintaining pipelines supplying ammonia to the upper edge, lower edge, and center, the flow rate of the supplied ammonia gas can be adjusted, thereby achieving the adjustment of the nitriding amount and the precipitates or inclusions at the upper edge, center, and lower edge, as described above. The aforementioned adjustment of the ammonia gas supply amount is just one example; in addition, the degree of oxidation in the width direction, the annealing time, and the annealing temperature can also be used to adjust the precipitates or inclusions at different locations.

[0057] After the nitriding annealing step, the nitrogen content in the steel sheet can be from 0.0135% by weight to 0.028% by weight.

[0058] During the secondary recrystallization annealing process, some nitrogen can be removed through purification annealing, and the final oriented electrical steel sheet can contain less than 0.005% by weight of nitrogen. More specifically, it can contain 0.001 to 0.005% by weight.

[0059] S: 0.0030% by weight to 0.0065% by weight Sulfur (S) typically reacts with Mn and Cu to form MnS or Cu₂S precipitates, thus acting as an inhibitor of primary recrystallization grain growth. To ensure fine MnS precipitates, the added Mn and S need to be completely dissolved under slab heating conditions below 1150°C to achieve an effective inhibitory effect. Therefore, it is preferable to add S within the range of Mn addition amount and reactive S content. If too little S is added, the amount of MnS precipitation will be insufficient, potentially making it difficult to ensure inhibitory effect. If too much S is added, complete dissolution is difficult, potentially forming coarse MnS precipitates. Simultaneously, S is an element prone to grain boundary or surface segregation, especially during high-temperature annealing when S diffuses to the surface of the steel plate, causing surface segregation. This hinders the formation of the forsterite coating through the reaction of fir olivine and silica with MgO, resulting in poor adhesion of the forsterite coating. Therefore, S can be contained in amounts from 0.0030% to 0.0065% by weight. More specifically, it may contain 0.0040 wt% to 0.0065 wt%. During the secondary recrystallization annealing process, some N can be removed by purification annealing, and the final oriented electrical steel sheet may contain less than 0.005 wt% S. More specifically, it may contain 0.001 wt% to 0.005 wt%.

[0060] The slab may also contain Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07% and P: 0.01% to 0.04% by weight.

[0061] Sb: 0.01% to 0.04% by weight Antimony (Sb) segregates at grain boundaries, thus inhibiting excessive growth of primary recrystallized grains. Therefore, further addition of Sb may improve magnetism. If too little Sb is added, the aforementioned effect cannot be achieved. On the other hand, if too much Sb is added, the size of the primary recrystallized grains becomes excessively small, the initiation temperature of secondary recrystallization decreases, leading to deterioration of magnetic properties or excessive inhibition of grain growth, potentially resulting in the failure of secondary recrystallization. Therefore, when further adding Sb, 0.01 wt% to 0.04 wt% can be added. More specifically, 0.015 wt% to 0.035 wt% can be added.

[0062] Sn: 0.03% to 0.07% by weight Tin (Sn) is an auxiliary grain growth inhibitor; it segregates at grain boundaries, thus hindering grain boundary movement, with a significant effect. This compensates for the weakening effect of inhibiting grain growth as AlN particles coarsen and Si content increases. Therefore, even with a relatively high Si content, successful {110} formation can be guaranteed. <001> Secondary recrystallization texture. That is, without weakening {110} at all. <001> While maintaining the integrity of the secondary recrystallization structure, not only can the Si content be increased, but the final thickness can also be reduced. Therefore, further addition of Sn may improve magnetism. If too little Sn is added, the aforementioned effects cannot be fully obtained. On the other hand, if too much Sn is added, brittleness may increase. Therefore, when further adding Sn, it is possible to add 0.03 wt% to 0.07 wt%. More specifically, it is possible to add 0.04 wt% to 0.06 wt%.

[0063] P: 0.01 wt% to 0.04 wt% Phosphorus (P) promotes the growth of primary recrystallized grains, thus increasing the secondary recrystallization temperature and consequently improving the final product's {110} content. <001> The role of orientation concentration. When the primary recrystallized grains are too large, secondary recrystallization becomes unstable. However, as long as secondary recrystallization occurs, larger primary recrystallized grains are beneficial for magnetism in order to increase the secondary recrystallization temperature. On the other hand, P not only increases the {110} ion concentration in the steel sheet after primary recrystallization. <001> The number of oriented grains reduces the iron loss in the final product, and also reduces the iron loss in the primary recrystallized plate {111} <112> The highly developed texture enhances the final product's {110}. <001> The concentration of phosphorus (P) increases the magnetic flux density. Furthermore, during secondary recrystallization annealing, P segregates to the grain boundaries at temperatures up to approximately 1000°C, delaying the decomposition of precipitates or inclusions and thus enhancing the suppressive force. Therefore, further addition of P may be beneficial to magnetism. If too little P is added, the aforementioned effects cannot be fully achieved. On the other hand, if too much P is added, the size of the primary recrystallized grains decreases, making secondary recrystallization unstable and potentially increasing brittleness and impairing cold-rollability. Therefore, when further adding P, it is advisable to add 0.01% to 0.04% by weight. More specifically, it is advisable to add 0.015% to 0.035% by weight.

[0064] The slab can satisfy the following formula 1.

[0065] [Formula 1] 0.0330≤[P]+0.5×[Sb]≤0.062 In Equation 1, [P] and [Sb] represent the contents (by weight%) of P and Sb in the slab, respectively.

[0066] When Equation 1 is satisfied, the improvement in iron loss is more significant due to the synergistic effect of simultaneously adding P and Sb. If the value of Equation 1 is too small, it is not possible to fully obtain the effect that promotes the formation of primary or secondary recrystallized grains. If the value of Equation 1 is too large, it is not only difficult to control the size of primary recrystallized grains, but it may also have an adverse effect on cold rollability. More specifically, the value of Equation 1 can be between 0.035 and 0.060.

[0067] The slab may also contain one or more of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15% by weight. More specifically, the slab may also contain Cu: 0.001% to 0.1% and Cr: 0.01% to 0.1% by weight.

[0068] Cu: 0.001 wt% to 0.1 wt% Copper (Cu) reacts with sulfur (S) to form Cu₂S precipitates, thereby acting as an inhibitor of primary recrystallization grain growth. When added together with Mn, the formation of [MnCu]S composite precipitates also affects the size of MnS precipitates or inclusions. If too little Cu is added, only a small amount of Cu₂S precipitates will form, potentially reducing its inhibitory effect. On the other hand, if too much Cu is added, it will precipitate in the steel before Mn reacts with S, making it impossible to obtain the fine MnS precipitates desired in this invention. Therefore, the Cu content is preferably limited to 0.001% to 0.100% by weight. More specifically, it can contain 0.010% to 0.070% by weight.

[0069] Cr: 0.01 wt% to 0.15 wt% Chromium (Cr) is the first element to react with oxygen to form Cr₂O₃ on the steel plate surface. This allows carbon components in the steel to rapidly diffuse to the surface and react with oxygen in the atmosphere to form CO gas, thus promoting decarburization. If too little Cr is added, the aforementioned effect cannot be fully achieved. If too much Cr is added, it will not significantly affect the formation of the surface oxide layer. Therefore, the amount of Cr added is limited to 0.01% to 0.15% by weight. More specifically, it can contain 0.03% to 0.12% by weight.

[0070] Iron (Fe) is included as a balance. In addition, unavoidable impurities may be included. Unavoidable impurities are those that are unavoidably introduced during the steelmaking and manufacturing processes of grain-oriented electrical steel sheets. Since unavoidable impurities are well-known, specific descriptions are omitted. In one embodiment of the invention, the addition of other elements besides the aforementioned alloy composition is not excluded, and various elements may be included without affecting the technical concept of the invention. When additional elements are further included, they replace a portion of the balance Fe. For example, within the composition range of the invention, the steel may also contain at least one of Ni, Mo, Zr, Bi, Pb, As, Ge, and Ga.

[0071] Returning to the description of the manufacturing process, the slab is heated to below 1150°C. The slab can be manufactured using segmented casting, continuous casting, thin slab casting, or casting methods. When segmented casting, continuous casting, or thin slab casting are used, the slab is manufactured first, and then heated and hot rolled in subsequent processes.

[0072] Slab heating is essentially based on the manufacturing method of grain-oriented electrical steel sheets. This method ensures the formation of AlN-based precipitates, i.e., (Al,Si,Mn)N precipitates, the main crystal growth inhibitor required for secondary recrystallization of Gaussian orientation, through decarburization and nitriding annealing after cold rolling. Therefore, hot rolling can be performed after heating the slab to below 1150°C. In this slab heating and hot rolling process, in order to successfully form fine MnS as an auxiliary crystal growth inhibitor, the amount of Mn and S added is limited in the steelmaking steps so that the solution temperature of the MnS precipitates formed by the reaction of added Mn and S is below 1150°C.

[0073] If the slab is heated to excessively high temperatures, the AlN precipitates formed during the solidification process of slab manufacturing will undergo excessive dissolution during the slab heating step. These precipitates will then precipitate finely during subsequent hot rolling, leading to finer grain sizes during hot rolling and decarburization, thus hindering the secondary recrystallization of precisely Gaussian oriented grains. Within the range where the precipitated MnS can be completely dissolved, depending on the added Mn and S content, a lower slab heating temperature is better. However, considering the specific hot rolling load, heating can be performed between 1000°C and 1150°C.

[0074] Next, the slab is hot-rolled to produce hot-rolled plates.

[0075] For hot rolling, the thickness is 1.0 to 3.5 mm. Considering the rolling load, rolling can be completed at a temperature above 850°C and then cooled to a temperature below 600°C for coiling.

[0076] For hot-rolled steel sheets, the subsequent hot-rolled sheet annealing process recrystallizes the deformed structure formed during hot rolling, ensuring smooth rolling to the final product thickness in the subsequent cold rolling process. Typically, for hot-rolled sheet annealing, to facilitate recrystallization, it is preferable to heat to a temperature above 800°C and hold for a certain time. To control the distribution and size of precipitates or inclusions, annealing at multiple temperatures can also be used. Hot-rolled sheet annealing can also be omitted if necessary.

[0077] Next, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet.

[0078] For hot-rolled sheets, the oxide layer on the steel surface is removed by pickling before cold rolling. Cold rolling is a process that reduces the thickness of the steel sheet to the final product thickness, achieved through a single cold rolling operation or multiple cold rolling operations with intermediate annealing. At this stage, the cold rolling rate increases the concentration of Gaussian orientation, thus affecting the increase in magnetic flux density after the final secondary recrystallization annealing. Therefore, cold rolling can be performed at a minimum rolling rate of 80% or higher. If the cold rolling rate is too low, the concentration of Gaussian orientation will be low, and the magnetic flux density of the final product will decrease. Therefore, the minimum cold rolling rate is 80% or higher, and for the maximum rolling rate, rolling is performed to the maximum rollable range based on the rolling capacity of the rolling equipment. Furthermore, when the plate temperature of the cold-rolled steel sheet increases by more than 50°C during cold rolling, work hardening caused by dissolved carbon will generate many secondary recrystallization nuclei with Gaussian orientation, thereby increasing the magnetic flux density of the final product. If the temperature of the cold-rolled steel sheet is too low, the formation of secondary recrystallization nuclei in the Gaussian orientation is very limited. If the temperature exceeds 300°C, the work hardening effect caused by solid solution carbon is weakened, and the formation of secondary recrystallization nuclei in the Gaussian orientation becomes less pronounced. Therefore, in the cold rolling process, the steel sheet undergoes at least one temperature range of 50 to 300°C during intermediate rolling steps. The thickness of the cold-rolled sheet can be 0.10 to 0.35 mm.

[0079] Next, the cold-rolled sheet is subjected to nitriding annealing.

[0080] In one embodiment of the present invention, by applying different process conditions along the width direction of the steel plate during the nitriding annealing step, the precipitates or inclusions exhibit different distribution characteristics in the width direction of the steel plate. This reduces the magnetic deviation in the width direction of the steel plate.

[0081] Figure 1 This is a schematic diagram illustrating an oriented electrical steel sheet according to an embodiment of the present invention. Figure 1 As shown, according to an embodiment of the present invention, the oriented electrical steel sheet can be divided into an upper edge portion 110, a center portion 120 and a lower edge portion 130 along the width direction of the steel sheet (or the rolling vertical direction, TD direction).

[0082] The upper edge 110 refers to the portion of the steel plate extending from one end 101 to 30% of the total width of the steel plate in the width direction. The center 120 refers to the portion extending from one end 101 to more than 30% to 70% of the total width of the steel plate. The lower edge 130 refers to the portion extending from one end 101 to more than 70% of the total width of the steel plate to the other end 102 of the steel plate.

[0083] Figure 2 The diagram schematically illustrates a steel sheet in coil shape for long-term annealing in the secondary recrystallization annealing step described below.

[0084] Figure 1 One end 101 corresponds to the upper end 101 of the roll plate. Figure 2 The other end 102 corresponds to the lower end 102 of the coil. The lower end 102 of the coil is in contact with the bottom surface during the secondary recrystallization annealing, and therefore has a relatively low temperature, while the upper end 101 of the coil does not have such heat loss and has a relatively high temperature. Thus, since the steel sheet is rolled into a coil shape and annealed for a long time during the secondary recrystallization annealing, a temperature gradient is inevitably generated in the width direction of the steel sheet, and this temperature gradient will cause magnetic deviation in the width direction of the steel sheet.

[0085] In one embodiment of the present invention, corresponding to such a temperature gradient, a large number of precipitates or inclusions are formed on the upper edge portion 110, thereby reducing the magnetic deviation in the width direction of the steel plate and ultimately ensuring certain magnetic properties in the width direction.

[0086] Specifically, after the nitriding annealing step, the ratio (P2 / P1) of the number of precipitates and inclusions (P2) present in the central portion 120 to the number of precipitates and inclusions (P1) present in the upper edge portion 110 is 0.6 to 1.0. At this time, precipitates and inclusions refer to substances in the steel plate where one or more elements from C, Si, Mn, Al, Cu, N, O, and S aggregate and appear in particulate form. When the cross-section of the steel plate is analyzed using elemental analysis, if the portion with a concentration higher than that of the steel component in the steel plate matrix appears in particulate form, it is considered a precipitate or inclusion. For precipitates or inclusions, those with a minimum particle size of 1 nm or more and less than 10 μm are considered precipitates or inclusions; when the particle size is smaller than this, it cannot play a meaningful role as a precipitate or inclusion. Therefore, in one embodiment of the present invention, only precipitates or inclusions with a minimum particle size of 1 nm or more are included in the quantity calculation. At this point, the particle size is determined by the cross-section of the steel plate. If there is a circle whose area is the same as the area occupied by the precipitates or inclusions, then the diameter of the circle is the particle size.

[0087] In one embodiment of the present invention, precipitates refer to nitrides, carbides or sulfides generated as new stable phases during the smelting or manufacturing of electrical steel sheets, and inclusions refer to spinel oxides such as Al2O3 or MgAl2O4 formed by the reaction of AlN and other nitrides formed in the nitriding annealing process with oxygen in the annealing furnace during the secondary recrystallization annealing process.

[0088] Although there are various methods for analyzing precipitates or inclusions, in one embodiment of the present invention, the replica method is used to obtain at least 10 images at 1 / 4t of the steel plate thickness, and the area is analyzed using an image analyzer. For the location of precipitates or inclusions formed in the grain boundaries directly below the oxide layer, at least 10 images are obtained using a scanning electron microscope or a transmission electron microscope of the same magnification, and the area can be analyzed using an image analyzer.

[0089] If precipitates or inclusions are present in the edge portion 110 and the center portion 120, they are counted as the portion occupying the larger area. Typical precipitates or inclusions can be (Al,Si,Mn)N or (Mn,Cu)(S,Se). In one embodiment of the invention, by appropriately adjusting the ratio of precipitates or inclusions (P2 / P1), secondary recrystallization at the upper edge portion 110, where the temperature is relatively higher and reaches the homogenization temperature faster, is achieved during the secondary recrystallization annealing process. Conversely, secondary recrystallization at the center portion 120, where the temperature is relatively lower and reaches the homogenization temperature more slowly, is promoted, thereby allowing secondary recrystallization to occur uniformly in the width direction. If the ratio of precipitates to inclusions (P2 / P1) is too high, it is difficult to fully obtain the aforementioned secondary recrystallization adjustment effect. If the ratio of precipitates to inclusions (P2 / P1) is too small, the secondary recrystallization of the upper edge portion 110 is excessively delayed, and magnetic deviation in the width direction may occur instead. More specifically, the ratio of precipitates to inclusions (P2 / P1) can be from 0.6 to 1.0.

[0090] Like the central part 120, the lower edge 130 is in contact with the bottom surface during the secondary recrystallization annealing process, resulting in a relatively lower temperature. Therefore, the secondary recrystallization occurs later than that of the upper edge 110.

[0091] In one embodiment of the present invention, corresponding to such a temperature gradient, a large number of precipitates or inclusions are formed on the upper edge portion 110, thereby reducing the magnetic deviation in the width direction of the steel plate.

[0092] Specifically, after the nitriding annealing step, the ratio (P3 / P1) of precipitates and inclusions (P3) in the lower edge portion 130 to precipitates and inclusions (P1) in the upper edge portion 110 can be 0.7 to 1.0. In one embodiment of the present invention, by appropriately adjusting the ratio (P3 / P1) of precipitates and inclusions, secondary recrystallization at the upper edge portion 110, where the temperature is relatively higher and reaches the homogenization temperature faster, is promoted during the secondary recrystallization annealing process. Conversely, secondary recrystallization at the lower edge portion 130, where the temperature is relatively lower and reaches the homogenization temperature more slowly, is promoted, thereby allowing secondary recrystallization to occur uniformly in the width direction. If the ratio (P3 / P1) of precipitates and inclusions is too high, it is difficult to fully obtain the aforementioned secondary recrystallization adjustment effect. If the ratio (P3 / P1) of precipitates and inclusions is too small, the secondary recrystallization of the upper edge portion 110 is excessively delayed, and magnetic deviation in the width direction may occur instead. More specifically, the ratio of precipitates to inclusions (P3 / P1) can be 0.75 to 0.99.

[0093] During the secondary recrystallization annealing process, there may be a temperature difference between the lower edge 130 and the central part 120. Compared with the lower edge 130, the central part 120 may undergo secondary recrystallization later.

[0094] In one embodiment of the present invention, corresponding to such a temperature gradient, a large number of precipitates or inclusions are formed in the central portion 120, thereby reducing the magnetic deviation in the width direction of the steel plate.

[0095] Specifically, after the nitriding annealing step, the ratio (P2 / P3) of the amount of precipitates and inclusions (P2) present in the central portion 120 to the amount of precipitates or inclusions (P3) in the lower edge portion 130 can be 0.7 to 1.0. In one embodiment of the present invention, by appropriately adjusting the ratio (P2 / P3) of precipitates and inclusions, secondary recrystallization at the central portion 120, where the temperature is relatively high and reaches the homogenization temperature quickly, is achieved during the secondary recrystallization annealing process. Conversely, secondary recrystallization at the lower edge portion 130, where the temperature is relatively low and reaches the homogenization temperature slowly, is promoted, thereby allowing secondary recrystallization to occur uniformly in the width direction. If the ratio (P2 / P3) of precipitates and inclusions is too high, it is difficult to fully obtain the aforementioned secondary recrystallization adjustment effect. If the ratio (P2 / P3) of precipitates or inclusions is too small, the secondary recrystallization of the central portion 120 is excessively delayed, and magnetic deviation in the width direction may occur instead. More specifically, the ratio of precipitates to inclusions (P2 / P3) can be 0.75 to 0.98.

[0096] More specifically, after the nitriding annealing step, the density of precipitates and inclusions (P1) present in the upper edge 110 can be from 0.01 to 0.8 particles / cm³.2 More specifically, it can be 0.3 to 0.8 per cm. 2 .

[0097] The density of precipitates and inclusions (P2) present in the central portion 120 can be from 0.01 to 0.50 particles / cm³. 2 More specifically, it can be 0.3 to 0.48 per cm. 2 .

[0098] The density of precipitates and inclusions (P3) present in the lower edge portion 130 can be from 0.01 to 0.8 particles / cm³. 2 More specifically, it can be 0.3 to 0.8 per cm. 2 .

[0099] There are no particular limitations on how the amount of precipitates or inclusions in the width direction can be adjusted. For example, methods such as controlling the ammonia flow rate, changing the annealing time and temperature can be used to promote the formation of precipitates or inclusions in the width direction. In addition, methods such as setting baffles to change the flow of gas in the annealing furnace can also be used.

[0100] In the nitriding annealing step, the soaking temperature can be between 820 and 900°C. If the temperature is too low, even if the predetermined oxygen content is achieved, the amount of Fe-based oxides (Fe₂SiO₄ or FeSiO₃), which are crucial for the stable formation of the forsterite coating, will be insufficient, or the oxide density may be insufficient. If the temperature is too high, it will promote the density of the oxide film or the formation of Fe-based oxides, but the initially formed oxides will lead to poor decarburization. The soaking temperature can be divided into two ranges: the first soaking temperature can be between 830 and 860°C, and the second soaking temperature can be between 850 and 890°C. Under these conditions, the quality of the oxide can be further improved.

[0101] In the nitriding annealing step, nitriding and decarburization are carried out simultaneously, wherein the oxidation degree (P) of the atmosphere during decarburization is... H2O / P H2 The oxidation degree can be between 0.45 and 0.75. If the oxidation degree is too low, it is difficult for oxidation or decarburization to occur sufficiently. If the oxidation degree is too high, FeO may rapidly form on the outermost layer of the oxide film, resulting in unstable oxides. More specifically, the oxidation degree can be between 0.48 and 0.75.

[0102] After nitriding annealing, the nitrogen content in the steel sheet can be from 0.0135 wt% to 0.0280 wt%. If the nitrogen content is too low, it will be difficult to act as an inhibitor before secondary recrystallization begins. If the nitrogen content is too high, excessive nitride formation will not only hinder the formation of normal secondary recrystallization, but also, after secondary recrystallization, the N2 gas decomposed during purification may lead to coating defects such as bare spots. More specifically, the nitrogen content in the steel sheet can be from 0.0150 wt% to 0.0250 wt%.

[0103] Furthermore, under the aforementioned decarburization conditions, the precipitates or inclusions formed within the grain boundaries directly below the SiO2-based oxide should account for less than 15% of all precipitates or inclusions. The precipitates or inclusions formed at grain boundaries and within grains of the decarburized plate mainly consist of Al-based nitrides, mostly nitrides, oxides, or sulfides bonded to Si, Cu, Sb, Mo, B, Mn, etc. It is well known that such precipitates or inclusions are decomposed during secondary recrystallization annealing and subsequently removed from the steel through a purification process. If the precipitates or inclusions within the grain boundaries directly below the oxide exceed 15% of all precipitates or inclusions, it indicates excessive formation of precipitates or inclusions within the grain boundaries. This affects the initiation temperature for secondary recrystallization during secondary recrystallization annealing, resulting in the inability to obtain uniform magnetic properties; therefore, this requirement is limited. In particular, as the width of the coil increases, due to the influence of annealing temperature and atmosphere flow within the annealing furnace, the edge portion of the coil may undergo severe oxidation and nitriding reactions relative to the center portion. Therefore, for materials with a final product coil width of 1050 mm or more, the precipitates or inclusions within the grain boundaries directly below the decarburized oxide must be kept below 15% of all precipitates or inclusions. In one embodiment of the present invention, "directly below the oxide" refers to a point from the surface oxide layer along the thickness direction of the steel plate to 1 / 4 t.

[0104] Next, the nitrided annealed steel sheet undergoes a second recrystallization annealing.

[0105] For steel plates after nitriding annealing, after coating with an annealing release agent based on MgO, the temperature is raised to above 1000℃ for long-term homogenization annealing to initiate secondary recrystallization, thereby making the {110} plane of the steel plate parallel to the rolling surface and forming... <001> A texture with a Gaussian orientation parallel to the rolling direction.

[0106] During secondary recrystallization annealing, the steel sheet is coiled into a coil shape and annealed for a long time. The coil shape has already been discussed. Figure 2 The instructions state that for secondary recrystallization annealing, heat treatment can be carried out at a temperature of 1170 to 1220°C for 1 to 25 hours.

[0107] After secondary recrystallization annealing, the annealing release agent is removed by water washing, and an insulating coating agent is applied after pickling. Subsequently, heat flattening treatment, which combines insulating coating annealing, shape correction, and stress relief annealing, can be carried out.

[0108] According to an embodiment of the present invention, the oriented electrical steel sheet, by weight percent, comprises C: less than 0.005% and excluding 0%, Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, with the balance including Fe and other unavoidable impurities. The ratio (P2 / P1) of precipitates and inclusions (P2) present in the central portion of the steel sheet extending from one end to more than 30% to 70% of the total width of the steel sheet to precipitates and inclusions (P1) present at one end of the steel sheet or at the upper edge portion extending from one end of the steel sheet to 30% of the total width of the steel sheet is 0.6 to 1.0.

[0109] Regarding the steel composition of grain-oriented electrical steel sheets, the steel composition of the slab has already been described in the aforementioned manufacturing method of grain-oriented electrical steel sheets, so a repeat description is omitted.

[0110] As mentioned earlier, in the manufacturing method of grain-oriented electrical steel sheets, precipitates or inclusions are precipitated to varying degrees along the width direction of the steel sheet during the nitriding annealing process, thereby reducing the magnetic deviation in the width direction of the steel sheet. After nitriding annealing, the precipitates or inclusions are decomposed during the secondary recrystallization annealing process, but some precipitates or inclusions remain, thus remaining in the finally manufactured grain-oriented electrical steel sheet.

[0111] At this point, since the proportion of precipitates or inclusions removed or remaining in the grain-oriented electrical steel sheet remains constant relative to the width of the steel sheet, after nitriding annealing, the proportion of precipitates and inclusions between the upper edge portion 110, the center portion 120, and the lower edge portion 130 is approximately consistent with the proportion of precipitates and inclusions between the upper edge portion 110, the center portion 120, and the lower edge portion 130 in the finally manufactured grain-oriented electrical steel sheet. The proportion of precipitates and inclusions between the upper edge portion 110, the center portion 120, and the lower edge portion 130 has already been described in the aforementioned method for manufacturing grain-oriented electrical steel sheets, therefore, a repetition is omitted.

[0112] More specifically, in the final manufactured grain-oriented electrical steel sheet, the density of precipitates and inclusions (P1) present in the upper edge portion 110 can be from 0.001 to 0.55 per cm³. 2 More specifically, it can be 0.30 to 0.55 per cm. 2 .

[0113] The density of precipitates or inclusions (P2) present in the central portion 120 can be from 0.001 to 0.40 particles / cm³. 2More specifically, it can be 0.30 to 0.40 per cm. 2 .

[0114] The density of precipitates or inclusions (P3) present in the lower edge portion 130 can be from 0.001 to 0.55 particles / cm³. 2 More specifically, it can be 0.30 to 0.55 per cm. 2 .

[0115] According to an embodiment of the present invention, the oriented electrical steel sheet has excellent iron loss and magnetic flux density, while the deviation of iron loss and magnetic flux density in the width direction is very small.

[0116] According to one embodiment of the present invention, the oriented electrical steel sheet has a magnetic flux density (B8) of 1.90T or higher and an iron loss (W). 17 / 50 It can be below 0.90 W / kg. At this point, the magnetic flux density B8 is the magnitude (Tesla) of the magnetic flux density produced under a magnetic field of 800 A / m, and the iron loss W... 17 / 50 This refers to the magnitude of the iron loss (W / kg) generated under conditions of 1.7 Tesla and 50 Hz. More specifically, the magnetic flux density (B8) can be from 1.91 T to 1.95 T, and the iron loss (W / kg) is... 17 / 50 The value can be 0.75 to 0.85 W / kg.

[0117] According to one embodiment of the present invention, the ratio (W2 / W1) of the iron loss (W2) at the center to the iron loss (W1) at the upper edge of the oriented electrical steel sheet can be from 0.99 to 1.03. Furthermore, the ratio (B2 / B1) of the magnetic flux density (B2) at the center to the magnetic flux density (B1) at the upper edge can be from 0.99 to 1.01.

[0118] Furthermore, the forsterite coating exhibits excellent adhesion. Adhesion can be determined by the minimum arc diameter at which the coating does not peel off when bent 180° onto an arc of a specific diameter. Specifically, the forsterite coating adhesion can be below 20 mmΦ.

[0119] Specific embodiments of the present invention will be described below. However, the following embodiments are merely one specific embodiment of the present invention, and the present invention is not limited to the following embodiments.

[0120] Example 1 A slab is manufactured, comprising, by weight percent, 0.058% C, 3.32% Si, 0.105% Mn, 0.0056% N, 0.03% Sb, 0.05% Sn, and 0.02% P, with the balance being Fe and unavoidable impurities. The slab is heated to 1150°C, then hot-rolled to a thickness of 2.3 mm, and then rapidly cooled to 600°C for coiling. The hot-rolled sheet is annealed at 1080°C and pickled, then cold-rolled once to a thickness of 0.20 mm. The cold-rolled sheet is subjected to decarburization annealing heat treatment under the conditions shown in Table 1, while the nitriding conditions are modified for decarburization annealing of the upper edge, center, and lower edge. In Table 1, the nitriding gas flow rate refers to the mass of nitriding gas supplied per unit area and per unit time. At this time, the oxygen content in the steel sheet is 900~1100 ppm. Subsequently, the annealing release agent MgO is dried and wound into coils. Next, a secondary recrystallization annealing is performed at 1200°C for 20 hours, maintaining a heating rate of 15°C / hr until reaching 1200°C. Then, an insulating coating solution is applied on a continuous production line, followed by heat treatment at 850°C. For the secondary recrystallization annealing, the process is carried out up to 1200°C in a mixed gas atmosphere of 25v% N2 and 75v% H2, and after reaching 1200°C, it is held in a 100v% hydrogen atmosphere and then allowed to cool naturally.

[0121] After nitriding annealing and secondary recrystallization annealing, 10 photographs were taken at 1 / 4t of the steel plate thickness using a replication method. The density of precipitates or inclusions was analyzed using an image analyzer and is shown in Table 2 below.

[0122] For the final manufactured grain-oriented electrical steel sheet, the density of precipitates or inclusions was measured, and the results are shown in Table 3 below. In addition, Epstein specimens were cut from the upper edge, center, and lower edge, with dimensions of [60 mm (width) × 300 mm (length)], and 10 specimens were taken from each. The magnetic flux density (B8) and iron loss (W) were then measured. 17 / 50 The deviations are shown in Table 4 below. The deviations are calculated by the ratio of the iron loss (W2) in the center to the iron loss (W1) in the upper edge (W2 / W1) and the ratio of the magnetic flux density (B2) in the center to the magnetic flux density (B1) in the upper edge (B2 / B1).

[0123] The adhesion evaluation results of the forsterite coating are shown in Table 4. Adhesion was determined by the smallest arc diameter that did not peel off when the coating was bent 180° on arcs with diameters of 10, 15, 20, 25, and 30 mm.

[0124] Table 1 Table 2 Table 3 Table 4 Tables 1 to 4 confirm that when precipitates or inclusions are appropriately formed at the upper edge 110, center 120, and lower edge 130 during the nitriding annealing process, the iron loss and magnetic deviation in the width direction of the steel plate are relatively small.

[0125] On the other hand, when precipitates or inclusions are not uniformly or appropriately formed on the upper edge 110, the center 120, and the lower edge 130, it can be confirmed that the iron loss and magnetic deviation in the width direction of the steel plate are large.

[0126] This invention is not limited to the above-described embodiments and / or examples, and can be prepared in various different ways. Those skilled in the art will understand that this invention can be implemented in other specific ways without changing the technical concept or essential features of the invention. Therefore, it should be understood that the above-described embodiments and / or examples are exemplary in all respects and are not restrictive.

[0127] [Explanation of reference numerals in the attached figures] 100: Oriented grain electrical steel sheet; 101: One end 102: The other end; 110: The upper edge 120: Center part; 130: Lower edge part

Claims

1. A method for manufacturing an oriented electrical steel sheet, comprising: The step of manufacturing a slab, in weight percent, the slab contains C: 0.01% to 0.1%, Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, with the balance containing Fe and other unavoidable impurities; The step of hot rolling the slab to manufacture a hot-rolled plate; The step of cold rolling the hot-rolled sheet to manufacture a cold-rolled sheet; The steps of nitriding annealing the cold-rolled sheet; and The step of performing secondary recrystallization annealing on the steel sheet after nitriding annealing. After the nitriding annealing step, the ratio (P2 / P1) of the amount of precipitates and inclusions (P2) present in the center portion of the steel plate extending from one end to more than 30% to 70% of the total width of the steel plate to the amount of precipitates and inclusions (P1) present at one end of the steel plate or at the upper edge portion extending from one end of the steel plate extending to 30% of the total width of the steel plate is 0.6 to 1.

0.

2. The method for manufacturing oriented electrical steel sheet according to claim 1, wherein, The slab further comprises, by weight percent, Al: 0.020% to 0.040%, N: 0.0030% to 0.0060% and S: 0.0030% to 0.0065%.

3. The method for manufacturing oriented electrical steel sheet according to claim 1, wherein, The slab also contains, by weight percent, Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07% and P: 0.01% to 0.04%.

4. The method for manufacturing the grain-oriented electrical steel sheet according to claim 3, wherein, The slab satisfies the following formula 1. [Formula 1] 0.0330≤[P]+0.5×[Sb]≤0.062 In Equation 1, [P] and [Sb] represent the contents (by weight%) of P and Sb in the slab, respectively.

5. The method for manufacturing oriented electrical steel sheet according to claim 1, wherein, The slab, by weight percent, further comprises one or more of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15%.

6. The method for manufacturing oriented electrical steel sheet according to claim 1, wherein, After the nitriding annealing step, the ratio (P3 / P1) of the amount of precipitates and inclusions (P3) at the lower edge of the steel plate from one end to the other end of the steel plate, which is more than 70% of the total width of the steel plate, to the amount of precipitates and inclusions (P1) present at the upper edge is 0.7 to 1.

0.

7. The method for manufacturing oriented electrical steel sheet according to claim 1, wherein, In the nitriding annealing step, the ratio (AF1 / AF2) of the flow rate of ammonia gas fed into the upper edge (AF1) to the flow rate of ammonia gas fed into the center is 1.03 to 1.

40.

8. The method for manufacturing oriented electrical steel sheet according to claim 1, wherein, In the nitriding annealing step, the ratio (AF3 / AF2) of the flow rate of ammonia gas fed into the lower edge (AF3) to the flow rate of ammonia gas fed into the center is 1.03 to 1.

40.

9. The method for manufacturing oriented electrical steel sheet according to claim 1, wherein, In the nitriding annealing step, the soaking temperature is 820 to 900°C.

10. The method for manufacturing the grain-oriented electrical steel sheet according to claim 1, wherein, In the nitriding annealing step, nitriding and decarburization are performed simultaneously, and the oxidation degree (P) of the atmosphere during decarburization is... H2O / P H2 The value ranges from 0.45 to 0.

75.

11. A grain-oriented electrical steel sheet, wherein, By weight percent, the oriented electrical steel sheet contains C: less than 0.005% and excluding 0%, Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, with the balance including Fe and other unavoidable impurities. The ratio (P2 / P1) of the amount of precipitates and inclusions (P2) present in the central portion of the steel plate extending from one end to more than 30% to 70% of the total width of the steel plate to the amount of precipitates and inclusions (P1) present at one end of the steel plate or at the upper edge portion extending from one end of the steel plate at 30% of the total width of the steel plate is 0.6 to 1.

0.

12. The grain-oriented electrical steel sheet according to claim 11, wherein, The oriented electrical steel sheet further comprises, by weight percent, less than 0.040% Al, less than 0.0050% N and less than 0.005% S.

13. The grain-oriented electrical steel sheet according to claim 11, wherein, The oriented electrical steel sheet further comprises, by weight percent, Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07% and P: 0.01% to 0.04%.

14. The grain-oriented electrical steel sheet according to claim 13, wherein, The oriented electrical steel sheet satisfies the following formula 1. [Formula 1] 0.0330≤[P]+0.5×[Sb]≤0.062 In Equation 1, [P] and [Sb] represent the contents (by weight%) of P and Sb in the steel plate, respectively.

15. The grain-oriented electrical steel sheet according to claim 11, wherein, The oriented electrical steel sheet comprises, by weight percent, one or more of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15%.

16. The grain-oriented electrical steel sheet according to claim 11, wherein, The ratio (P3 / P1) of the amount of precipitates and inclusions (P3) at the lower edge of the steel plate from one end to the other end of the steel plate, which is more than 70% of the total width of the steel plate, to the amount of precipitates and inclusions (P1) present at the upper edge is 0.7 to 1.0.

Images