Grain-oriented electrical steel sheet and manufacturing method therefor

Abstract

A method for manufacturing a grain-oriented electrical steel sheet, according to one embodiment of the present invention, comprises the steps of: preparing a slab comprising, by wt%, 0.01-0.1% of C, 1.5-4.5% of Si and 0.1-1.5% of Mn and comprising the balance of Fe and other inevitable impurities; hot rolling the slab, thereby manufacturing a hot rolled sheet; cold rolling the hot rolled sheet, thereby manufacturing a cold rolled sheet; nitriding annealing the cold rolled sheet; and secondarily recrystallization annealing the nitriding-annealed steel sheet, wherein after the nitriding annealing step, the ratio (P2 / P1) of the number (P2) of precipitates and inclusions present in from one end of the steel sheet to the center part of more than 30% to 70% of the total width of the steel sheet to the number (P1) of precipitates and inclusions present in one end of the steel sheet or the edge part on the upper surface of the steel sheet from one end thereof to up to 30% of the total width of the steel sheet is 0.6 to 1.0.

Description

Grain-oriented electrical steel sheet and its manufacturing method

[0001] One embodiment of the present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same, wherein the grain-oriented electrical steel sheet reduces magnetic deviation in the width direction of the steel sheet by appropriately forming precipitates or inclusions in the width direction of the steel sheet during a nitriding annealing process.

[0002] Grain-oriented electrical steel sheets have the orientation of all crystal grains on the steel sheet surface as {110} planes and the crystal orientation in the rolling direction is <001> It is a soft magnetic material with excellent magnetic properties in the rolling direction of the steel sheet by forming a so-called Goss texture parallel to the axis. In general, the magnetic properties of electrical steel sheets can be expressed in terms of magnetic flux density and iron loss, and high magnetic flux density means that the grain orientation is {110}. <001> It can be obtained by arranging it precisely in the direction. Electrical steel sheets with high magnetic flux density can not only reduce the size of the core material of electrical devices, but also reduce the hysteresis loss, so it is possible to make the electrical devices smaller and more efficient at the same time. Iron loss is the power loss consumed as heat energy when an arbitrary alternating magnetic field is applied to the steel sheet, and it varies greatly depending on the magnetic flux density and thickness of the steel sheet, the amount of impurities in the steel sheet, resistivity, and the size of secondary recrystallized grains, and the higher the magnetic flux density and resistivity, and the lower the plate thickness and the amount of impurities in the steel sheet, the lower the iron loss, which increases the efficiency of the electrical device.

[0003] Currently, the global trend is to reduce CO2 emissions and address global warming by pursuing energy conservation and high-efficiency products. As demand for the expansion of high-efficiency electrical devices that use less electrical energy increases, the social demand for the development of grain-oriented electrical steel sheets with superior high-magnetic flux density and low core loss characteristics is increasing.

[0004] Initially developed grain-oriented electrical steel sheets were manufactured using MnS as a grain-growth inhibitor and through two rounds of cold rolling and high-temperature annealing. This manufacturing method formed secondary recrystallization relatively stably, but the magnetic flux density (B8, flux density at 800 A / m) was around 1.80 Tesla, and the iron loss was also higher than the current level. Later, a method was proposed to manufacture grain-oriented electrical steel sheets with excellent magnetic flux density (B8) of 1.87 Tesla or higher by using a combination of AlN and MnS precipitates or inclusions as grain-growth inhibitors and a single round of cold rolling. This method is still used as a commercial technology today.

[0005] In addition, a method for manufacturing electrical steel sheets containing MnS (or MnSe) and Sb using a double cold rolling process was proposed, and a product with a relatively high magnetic flux density could be obtained. The three technologies mentioned above have in common that they require high slab heating temperatures as a technique for finely and uniformly controlling precipitates or inclusions, which causes problems such as excessive energy consumption, increased equipment damage rate, and decreased yield in the final product.

[0006] Instead of this high-temperature slab heating method, the inhibitor required for secondary recrystallization was proposed to form (Al, Si)N by infiltrating N into the steel after the completion of decarburization annealing and before the start of secondary recrystallization in the final secondary recrystallization annealing (aka low-temperature slab heating method). In order to form inhibitors such as AlN and (Al, Si)N using nitriding gas after the completion of decarburization annealing, the nitriding gas must be blown into the steel sheet using a gas header or nozzle. At this time, the concentration of the nitriding gas in the width direction changes, which may unintentionally change the nitriding concentration in the width direction, or even if nitriding is performed at the same concentration, it is difficult to uniformly control the temperatures at the top, middle, and bottom of the coil during the subsequent secondary recrystallization annealing process, which causes a deviation in the magnetism in the width direction of the steel sheet.

[0007] In addition, in order to increase the production efficiency of oriented electrical steel sheets, not only is the coil weight increased but also the coil width is increased. As such, as the coil width increases, the magnetic deviation in the direction of the steel sheet width becomes larger, and this has caused a problem of deterioration of the magnetic properties of the entire coil.

[0008] One embodiment of the present invention provides a grain-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention provides a grain-oriented electrical steel sheet and a method for manufacturing the same, wherein the grain-oriented electrical steel sheet reduces magnetic deviation in the width direction of the steel sheet by appropriately forming precipitates or inclusions in the width direction of the steel sheet during a nitriding annealing process.

[0009] A method for manufacturing a oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: manufacturing a slab containing, in wt%, C: 0.01% to 0.1%, Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, and the remainder including Fe and other unavoidable impurities; hot-rolling the slab to manufacture a hot-rolled sheet; cold-rolling the hot-rolled sheet to manufacture a cold-rolled sheet; nitriding annealing the cold-rolled sheet; and secondary recrystallization annealing the nitriding annealed steel sheet.

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

[0011] The slab may further contain, in wt%, Al: 0.020% to 0.040%, N: 0.0030% to 0.0060%, and S: 0.0030% to 0.0065%.

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

[0013] Slavs can satisfy the following equation 1.

[0014] [Formula 1]

[0015] 0.0330 ≤ [P] + 0.5×[Sb] ≤ 0.062

[0016] (In Equation 1, [P] and [Sb] represent the contents (weight%) of P and Sb in the slab, respectively.)

[0017] The slab may further contain, in wt%, one or more of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15%.

[0018] After the nitriding annealing step, the ratio of the number of precipitates and inclusions (P3) present on the upper edge from more than 70% of the total width of the steel sheet at one end of the steel sheet to the number of precipitates and inclusions (P1) present on the lower edge to the other end of the steel sheet (P3 / P1) may be 0.7 to 1.0.

[0019] In the nitriding annealing step, the ratio (AF1 / AF2) of the flow rate of ammonia (AF1) injected into the upper edge portion to the flow rate of ammonia (AF2) injected into the center portion may be 1.03 to 1.40.

[0020] Additionally, in the nitriding annealing step, the ratio (AF3 / AF2) of the flow rate of ammonia (AF3) injected into the lower edge portion to the flow rate of ammonia (AF2) injected into the center portion may be 1.03 to 1.40. In the nitriding annealing step, the soaking temperature may be 820 to 900°C.

[0021] In the nitriding annealing step, decarburization occurs simultaneously with nitriding, and the oxidation level of the atmosphere during decarburization (P) H2O / P H2 ) can be 0.45 to 0.75.

[0022] According to one embodiment of the present invention, a grain-oriented electrical steel sheet comprises, in wt%, C: 0.005% or less (excluding 0%), Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, and the remainder Fe and other unavoidable impurities, and a number ratio (P2 / P1) of precipitates and inclusions (P1) present in an upper surface edge portion from one end of the steel sheet to 30% of the total width of the steel sheet at one end of the steel sheet to a center portion from more than 30% to 70% of the total width of the steel sheet at one end of the steel sheet is 0.6 to 1.0.

[0023] A directional electrical steel sheet according to one embodiment of the present invention may further include, in wt%, Al: 0.040% or less, N: 0.0050% or less, and S: 0.005% or less.

[0024] The directional electrical steel sheet according to one embodiment of the present invention may further include, in wt%, Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07%, and P: 0.01% to 0.04%.

[0025] A directional electrical steel sheet according to one embodiment of the present invention can satisfy the following equation 1.

[0026] [Formula 1]

[0027] 0.0330 ≤ [P] + 0.5×[Sb] ≤ 0.062

[0028] (In Equation 1, [P] and [Sb] represent the contents (weight%) of P and Sb in the steel plate, respectively.)

[0029] The directional electrical steel sheet according to one embodiment of the present invention may further include, in wt%, at least one of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15%.

[0030] In one embodiment of the present invention, a directional electrical steel sheet may have a ratio (P3 / P1) of the number of precipitates and inclusions (P3) present in the upper edge portion from more than 70% of the total width of the steel sheet at one end of the steel sheet to the number of precipitates and inclusions (P1) present in the lower edge portion of the steel sheet to the other end of the steel sheet, which may be 0.7 to 1.0.

[0031] A directional electrical steel sheet according to one embodiment of the present invention can reduce magnetic deviation in the width direction of the steel sheet and uniformly improve magnetism in the width direction of the steel sheet.

[0032] Figure 1 is a schematic diagram schematically illustrating a directional electrical steel sheet according to one embodiment of the present invention.

[0033] FIG. 2 is a schematic diagram schematically illustrating a coil-shaped steel sheet during a second recrystallization annealing step in one embodiment of the present invention.

[0034] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising," as used herein, specifies particular features, regions, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0036] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0037] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0038] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0039] In one embodiment of the present invention, the inclusion of additional elements means including the remaining iron (Fe) in an amount equivalent to the additional amount of the additional elements.

[0040] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0041]

[0042] A method for manufacturing a oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: manufacturing a slab containing, in wt%, C: 0.01% to 0.1%, Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, and the remainder including Fe and other unavoidable impurities; hot-rolling the slab to manufacture a hot-rolled sheet; cold-rolling the hot-rolled sheet to manufacture a cold-rolled sheet; nitriding annealing the cold-rolled sheet; and secondary recrystallization annealing the nitriding annealed steel sheet.

[0043] Below, each step is explained in detail.

[0044] First, manufacture the slab.

[0045] The slab contains, by weight %, C: 0.01% to 0.1%, Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, and the remainder includes Fe and other inevitable impurities.

[0046] Below, we explain the reasons for limiting the amount added for each element.

[0047]

[0048] C: 0.01 to 0.10 wt%

[0049] Carbon (C) is an element that promotes austenite phase transformation. It is an important element for producing grain-oriented electrical steel with excellent magnetism by making the hot-rolled structure of grain-oriented electrical steel uniform and promoting the formation of Goss-oriented grains during cold rolling. If too little C is added, the aforementioned effects cannot be fully achieved. In addition, the non-uniform hot-rolled structure may cause secondary recrystallization to form unstably. If too much C is added, the primary recrystallized grains become fine due to the formation of a fine hot-rolled structure due to the austenite phase transformation during hot rolling. This can lead to the formation of coarse carbides during the coiling process after hot rolling or the cooling process after hot-rolled sheet annealing, and it is easy for Fe3C (Cementite) to form at room temperature, causing non-uniformity in the structure. In addition, the time required for decarburization to less than 30 ppm during the decarburization process after cold rolling increases, which causes the excessive formation of fayalite and silica on the surface of the steel sheet. Therefore, the content of C may be comprised in an amount of 0.01 to 0.10 wt%. More specifically, it may be comprised in an amount of 0.03 to 0.08 wt%.

[0050] C is removed by decarburization during the nitriding annealing process, and may be included in the final manufactured grain-oriented electrical steel sheet at 0.005 wt% or less. More specifically, it may be included at 0.003 wt% or less. More specifically, it may be included at 0.0001 to 0.0030 wt%.

[0051]

[0052] Si: 1.5 wt% to 4.5 wt%

[0053] Silicon (Si) is a basic component of electrical steel and increases the resistivity of the material, thereby reducing core loss, or iron loss. If too little Si is added, the resistivity decreases, resulting in a weak eddy current loss reduction effect. In addition, the amount of fayalite formed during the decarburization process will be absolutely insufficient, which may result in unstable forsterite film formation. Conversely, if too much Si is added, the steel becomes brittle, making cold rolling difficult. In addition, the surface quality may deteriorate as a large amount of fayalite is formed during the decarburization process. Therefore, Si may be included in an amount of 1.5 wt% to 4.5 wt%. More specifically, it may be included in an amount of 2.5 wt% to 3.8 wt%.

[0054]

[0055] Mn: 0.1 wt% to 1.5 wt%

[0056] Manganese (Mn), like Si, increases resistivity and reduces iron loss. However, adding large amounts of Mn weakens grain growth inhibition by reducing saturation magnetic flux density and forming coarse MnS precipitates or inclusions, rather than reducing iron loss through increased resistivity. This reduces the magnetic flux density after secondary recrystallization annealing and also affects the fayalite and silica components formed during the decarburization process, hindering the formation of a good forsterite film.

[0057] Therefore, it is necessary to optimize the Mn content to form a forsterite film with excellent adhesion along with excellent flux density characteristics. If Mn is added too little, the burden of refining in steelmaking increases and the amount of fine MnS precipitates that can be utilized to suppress crystal growth may decrease. If Mn is added too much, it promotes coarse MnS precipitation, which causes the problem of having to heat the slab above 1150℃ to dissolve the MnS precipitates or inclusions. In addition, it can interfere with the formation of good-quality fayalite and silica during the decarburization process.

[0058] The slab may further contain, in wt%, Al: 0.020% to 0.040%, N: 0.0030% to 0.0060%, and S: 0.0030% to 0.0065%.

[0059]

[0060] Al: 0.020 wt% to 0.040 wt%

[0061] Aluminum (Al) combines with N to form AlN precipitates or inclusions, and is a representative component of grain growth inhibitors for forming secondary recrystallization of grain-oriented electrical steel sheets. In one embodiment of the present invention, by forming (Al, Si, Mn)N precipitates or inclusions through nitriding annealing after cold rolling, the grain growth inhibition effect is secured, and in particular, by controlling the precipitation of precipitates or inclusions in the width direction of the steel, the magnetic deviation in the width direction is reduced. It is preferable to add 0.020 to 0.040 wt% of Al in the steelmaking step, but if too little Al is added, the total amount of (Al, Si, Mn)N precipitates or inclusions formed during the first recrystallization and nitriding annealing processes may be small, so that the first recrystallization grain growth inhibition effect may be insufficient. Conversely, if too much Al is added, coarse precipitates or inclusions may grow during the slab manufacturing and hot rolling processes, thereby forming a coarse microstructure during nitriding annealing, which may make secondary recrystallization unstable during the subsequent secondary recrystallization annealing process. Therefore, the Al content in the slab may be 0.020 wt% to 0.040 wt%. More specifically, it may be 0.020 wt% to 0.035 wt%.

[0062] During the secondary recrystallization annealing process, some of the aluminum may be removed through purification annealing, and the final grain-oriented electrical steel sheet may contain 0.040 wt% or less of aluminum. More specifically, it may contain 0.010 wt% to 0.040 wt%.

[0063] N: 0.0030 wt% to 0.0060 wt%

[0064] Nitrogen (N) is an important element that reacts with Al to form AlN precipitates or inclusions that inhibit grain growth. In a manufacturing method that secures (Al, Si, Mn)N precipitates or inclusions through nitriding after cold rolling, there is no need to include a lot of N in the steelmaking step. However, if too little N is added, fine AlN precipitates or inclusions will be formed in the slab manufacturing step, making the primary recrystallized grain size fine and facilitating secondary recrystallization of grains with exact Goss orientations. Conversely, if too much N is added, coarse AlN precipitates or inclusions will be formed in the slab manufacturing step, creating a coarse primary recrystallized microstructure and making secondary recrystallization unstable. Therefore, the range of N can be limited to 0.0030 wt% to 0.0060 wt%. More specifically, it can include 0.0035 wt% to 0.0055 wt%.

[0065] Meanwhile, in one embodiment of the present invention, by controlling the ammonia input flow rate in the width direction of the steel sheet during the nitriding annealing process, (Al, Si, Mn)N precipitates or inclusions can be precipitated differently in the width direction of the steel sheet, thereby reducing the magnetic deviation in the width direction of the steel sheet.

[0066] Specifically, in the nitriding annealing step, the ratio (AF1 / AF2) of the flow rate of ammonia (AF1) injected into the upper edge portion to the flow rate of ammonia (AF2) injected into the center portion may be 1.03 to 1.40.

[0067] Additionally, in the nitriding annealing step, the ratio (AF3 / AF2) of the flow rate of ammonia (AF3) injected into the lower edge portion to the flow rate of ammonia (AF2) injected into the center portion may be 1.03 to 1.40.

[0068] Additionally, in the nitriding annealing step, the ratio (AF3 / AF1) of the flow rate of ammonia (AF3) injected into the lower edge portion to the flow rate of ammonia (AF1) injected into the upper edge portion may be 0.85 to 1.15.

[0069] The inventors of the present invention have found that, in the nitriding annealing step, the flow rate of ammonia injected in the width direction can be controlled by adjusting the position of the ammonia injection pipe. In one embodiment of the present invention, the flow rate of ammonia refers to the mass of ammonia injected per unit area and per unit time.

[0070] By controlling the amount of ammonia injected into each part of the steel plate within the aforementioned range, the precipitates or inclusions generated in each part can be appropriately controlled. That is, by separately maintaining the ammonia pipes injected into the upper edge, lower edge, and center parts and controlling the ammonia injection flow rate, it becomes possible to control the nitriding amount and the precipitates or inclusions in the upper edge, center, and lower edge parts as described above. The aforementioned control of the ammonia injection amount is merely an example, and in addition, it is also possible to control the precipitates or inclusions by location by controlling the oxidation degree in the width direction, the annealing time, the annealing temperature, etc.

[0071]

[0072] After the nitriding annealing step, the nitrogen content in the steel sheet can be 0.0135 wt% to 0.028 wt%.

[0073] During the secondary recrystallization annealing process, some of the N may be removed through purification annealing, and the final grain-oriented electrical steel sheet may contain N in an amount of 0.005 wt% or less. More specifically, it may contain 0.001 to 0.005 wt%.

[0074] S: 0.0030 wt% to 0.0065 wt%

[0075] Sulfur (S) generally reacts with manganese (Mn) and copper (Cu) to form MnS or Cu2S precipitates, acting as an inhibitor that suppresses the growth of primary recrystallized grains. In order to secure fine MnS precipitates, the added Mn and S must be completely dissolved under slab heating conditions of 1150℃ or lower to function as an effective inhibitor. Therefore, it is desirable to add S within the range of the amount of Mn added and the amount that can react. If too little S is added, the amount of MnS precipitate may be too small to secure the inhibitory effect. If too much S is added, complete solid solution may become difficult, which may lead to the formation of coarse MnS precipitates. In addition, S is an element that is prone to grain boundary or surface segregation. In particular, during the high-temperature annealing process, S diffuses to the surface of the steel sheet, causing surface segregation, which interferes with the forsterite film reaction formed by the reaction of fayalite, silica, and MgO, resulting in poor adhesion of the forsterite film. Therefore, it may contain 0.0030 wt% to 0.0065 wt% of S. More specifically, it may contain 0.0040 wt% to 0.0065 wt%. Some of the N may be removed through purification annealing in the secondary recrystallization annealing process, and the final grain-oriented electrical steel sheet may contain 0.005 wt% or less of S. More specifically, it may contain 0.001 wt% to 0.005 wt%.

[0076] The slab may further contain, by weight %, Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07%, and P: 0.01% to 0.04%.

[0077]

[0078] Sb: 0.01 wt% to 0.04 wt%

[0079] Antimony (Sb) segregates at grain boundaries and acts to suppress excessive growth of primary recrystallized grains. Therefore, if more Sb is added, it can have a beneficial effect on magnetism. If too little Sb is added, the aforementioned effect cannot be sufficiently obtained. On the other hand, if too much Sb is added, the size of the primary recrystallized grains becomes excessively small, which lowers the initiation temperature of secondary recrystallization, thereby deteriorating magnetic properties, or the suppression of grain growth becomes excessively large, which may cause a problem in which secondary recrystallization is not formed. Therefore, when more Sb is added, it may be added in an amount of 0.01 wt% to 0.04 wt%. More specifically, it may be added in an amount of 0.015 wt% to 0.035 wt%.

[0080] Sn: 0.03 wt% to 0.07 wt%

[0081] Tin (Sn) is an excellent auxiliary grain growth inhibitor that segregates at grain boundaries and inhibits grain boundary movement. This compensates for the weakening of the grain growth inhibitory effect as AlN particles become coarser and the Si content increases. Consequently, even with a relatively high Si content, {110} <001> Successful formation of a secondary recrystallized aggregate structure can be guaranteed, i.e. {110} <001> The Si content can be increased and the final thickness can be reduced without any degradation of the completeness of the secondary recrystallization structure. Therefore, when Sn is added further, it can have a beneficial effect on magnetism. If Sn is added too little, the aforementioned effect cannot be sufficiently obtained. Conversely, if Sn is added too much, brittleness can increase. Therefore, when Sn is added further, it can be added 0.03 wt% to 0.07 wt% more. More specifically, it can be added 0.04 wt% to 0.06 wt% more.

[0082] P: 0.01 wt% to 0.04 wt%

[0083] Phosphorus (P) promotes the growth of primary recrystallized grains, thereby increasing the secondary recrystallization temperature and forming {110} in the final product. <001> It plays a role in increasing the degree of integration of the orientation. If the primary recrystallized grains are too large, the secondary recrystallization becomes unstable, but as long as the secondary recrystallization occurs, it is advantageous for magnetism to have large primary recrystallized grains to increase the secondary recrystallization temperature. Meanwhile, P is {110} in the primary recrystallized steel sheet. <001> Not only does it reduce the iron loss of the final product by increasing the number of grains with {111} orientation, but it also reduces the iron loss of the final product by increasing the number of grains with {111} orientation in the first recrystallization plate. <112> By developing a strong collective organization, the final product {110} <001> Since the degree of integration is improved, the magnetic flux density also increases. In addition, P has the function of reinforcing the suppression force by segregating at grain boundaries up to a high temperature of about 1000℃ during secondary recrystallization annealing and delaying the decomposition of precipitates or inclusions. Therefore, if more P is added, it can have a beneficial effect on magnetism. If too little P is added, the aforementioned effect cannot be sufficiently obtained. On the other hand, if too much P is added, the size of the primary recrystallized grains is reduced, which not only makes the secondary recrystallization unstable but also increases brittleness, which can hinder the cold rolling property. Therefore, when more P is added, it can be added by 0.01 wt% to 0.04 wt%. More specifically, it can be added by 0.015 wt% to 0.035 wt%.

[0084] Slavs can satisfy the following equation 1.

[0085] [Formula 1]

[0086] 0.0330 ≤ [P] + 0.5×[Sb] ≤ 0.062

[0087] (In Equation 1, [P] and [Sb] represent the contents (weight%) of P and Sb in the slab, respectively.)

[0088] When Equation 1 is satisfied, the iron loss is further improved due to the synergistic effect of the simultaneous addition of P and Sb. If the value of Equation 1 is too small, the beneficial effect in forming primary or secondary recrystallized grains cannot be sufficiently obtained. If the value of Equation 1 is too large, not only will it be difficult to control the size of primary recrystallized grains, but it may also impair cold rolling properties. More specifically, the value of Equation 1 may be 0.035 to 0.060.

[0089]

[0090] The slab may further comprise, by weight %, one or more of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15%. More specifically, the slab may further comprise, by weight %, Cu: 0.001% to 0.1% and Cr: 0.01% to 0.1%.

[0091] Cu: 0.001 wt% to 0.1 wt%

[0092] Copper (Cu) reacts with S to form Cu2S precipitates, which act as an inhibitor to suppress the growth of primary recrystallized grains. When added together with Mn, it forms [MnCu]S composite precipitates, thereby affecting the size of MnS precipitates or inclusions. If too little Cu is added, the formation of Cu2S precipitates is small, which may reduce the effect as an inhibitor. Conversely, if too much Cu is added, S precipitates in the steel before Mn, making it impossible to obtain the fine MnS precipitates desired in the present invention. Therefore, the Cu content is preferably limited to the range of 0.001 wt% to 0.100 wt%. More specifically, it may include 0.010 wt% to 0.070 wt%.

[0093]

[0094] Cr: 0.01 wt% to 0.15 wt%

[0095] Chromium (Cr) is the element that reacts most quickly with oxygen to form Cr2O3 on the surface of the steel sheet. This allows the carbon component in the steel to rapidly diffuse to the surface of the steel sheet and react with oxygen in the ambient gas to form CO gas, thereby promoting decarburization. If too little Cr is added, the aforementioned effect cannot be sufficiently obtained. If too much Cr is added, it may not have a significant effect on the formation of a surface oxide layer. Therefore, the amount of Cr added is limited to 0.01 wt% to 0.15 wt%. More specifically, it may include 0.03 wt% to 0.12 wt%.

[0096]

[0097] The remainder includes iron (Fe). In addition, inevitable impurities may be included. Unavoidable impurities refer to impurities that are inevitably mixed in during the manufacturing process of steelmaking and grain-oriented electrical steel sheets. Since inevitable impurities are widely known, a detailed description thereof is omitted. In one embodiment of the present invention, the addition of elements other than the alloy components described above is not excluded, and various elements may be included within a range that does not impair the technical spirit of the present invention. When additional elements are further included, they are included in place of the remainder Fe. For example, it is also possible to include at least one element among Ni, Mo, Zr, Bi, Pb, As, Ge, and Ga in the steel within the component range of the present invention.

[0098]

[0099] Returning to the manufacturing process, the slab is heated to 1150℃ or lower. Slabs can be produced using the ingot method, continuous casting, thin slab casting, or strip casting. In the case of the ingot method, continuous casting, and thin slab casting, the slab is manufactured, and subsequent processes include heating and hot rolling.

[0100] Slab heating is basically a grain-oriented electrical steel manufacturing method that secures (Al, Si, Mn) N precipitates through decarburization and nitriding annealing after cold rolling to obtain AlN precipitates, which are the main crystal growth inhibitors required for Goss orientation secondary recrystallization. Therefore, the slab can be heated to 1150℃ or lower and then hot rolled. In this slab heating and hot rolling process, in order to form fine MnS as an auxiliary crystal growth inhibitor, the amount of Mn and S added was limited in the steelmaking stage so that the solid solution temperature of the MnS precipitates formed by the reaction of the added Mn and S would be lower than 1150℃.

[0101] If the slab is heated at too high a temperature, the AlN precipitates formed during the solidification process in the slab manufacturing step will be excessively dissolved in the slab heating step and will be finely precipitated during the subsequent hot rolling process, which will make the grain size fine during the hot rolling and decarburization processes and hinder the formation of secondary recrystallization of exact Goss orientation grains. Depending on the added Mn and S contents, the lower the slab heating temperature, the better, as long as the precipitated MnS can be completely dissolved. However, specifically, considering the hot rolling load, it can be heated at 1000℃ to 1150℃.

[0102] Next, the slab is hot rolled to produce a hot-rolled plate.

[0103] Hot rolling is performed to a thickness of 1.0 to 3.5 mm, and considering the rolling load, rolling can be completed at a temperature of 850°C or higher, cooled to a temperature of 600°C or lower, and then coiled.

[0104] Hot-rolled steel sheets can be subjected to a hot-rolled sheet annealing process to recrystallize the hot-rolled deformation structure, facilitating smooth rolling to the final product thickness in the subsequent cold rolling process. Generally, it is desirable to heat the hot-rolled sheet to a temperature above 800°C for recrystallization and maintain it for a certain period of time. Annealing at multiple temperatures is also possible to control the distribution and size of precipitates or inclusions. Hot-rolled sheet annealing can also be omitted if necessary.

[0105] Next, the hot-rolled sheet is cold rolled to produce a cold-rolled sheet.

[0106] Hot-rolled steel sheets are pickled to remove the oxide layer on the steel sheet surface, and then cold-rolled. Cold rolling is a process to reduce the thickness of the steel sheet to the final product thickness. Cold rolling is performed once or more times including intermediate annealing to roll to the final product thickness. At this time, the cold rolling ratio affects the increase in the Goss orientation density and thus the magnetic flux density after the final secondary recrystallization annealing, so cold rolling can be performed at a rolling ratio of at least 80%. If the cold rolling ratio is too low, the Goss orientation density is low, which reduces the magnetic flux density of the final product. Therefore, the cold rolling ratio should be at least 80%, and the maximum rolling ratio can be rolled to the maximum rolling range depending on the rolling capacity of the rolling equipment. In addition, if the temperature of the cold-rolled steel sheet is raised to 50℃ or higher during the cold rolling process, many secondary recrystallization nuclei in the Goss orientation are generated due to work hardening by the dissolved carbon, which can improve the magnetic flux density of the final product. If the temperature of the cold-rolled steel sheet is too low, the generation of secondary recrystallization nuclei in the Goss orientation is minimal, and conversely, if it exceeds 300℃, the work hardening effect by the dissolved carbon is weakened, and the generation of secondary recrystallization nuclei in the Goss orientation is weakened. Therefore, in the cold rolling process, the steel sheet can be maintained in the temperature range of 50 to 300℃ at least once in the intermediate rolling stage. The thickness of the cold-rolled sheet after cold rolling can be 0.10 to 0.35 mm.

[0107] Next, the cold rolled sheet is nitrided and annealed.

[0108] In one embodiment of the present invention, by applying different process conditions in the width direction of the steel sheet in the nitriding annealing step, the arrangement characteristics of precipitates or inclusions in the width direction of the steel sheet appear differently, thereby reducing the magnetic deviation in the width direction of the steel sheet.

[0109] FIG. 1 is a schematic diagram schematically illustrating a oriented electrical steel sheet according to one embodiment of the present invention. As shown in FIG. 1, the oriented electrical steel sheet according to one embodiment of the present invention can be divided into an upper edge portion (110), a center portion (120), and a lower edge portion (130) along the width direction (or rolling vertical direction, TD direction) of the steel sheet.

[0110] The upper edge portion (110) refers to a portion from one end (101) of the steel plate to 30% of the total width of the steel plate in the width direction of the steel plate. The center portion (120) refers to a portion from more than 30% to 70% of the total width of the steel plate from one end (101) of the steel plate. The lower edge portion (130) refers to a portion from more than 70% of the total width of the steel plate from one end (101) of the steel plate to the other end (102) of the steel plate.

[0111] Figure 2 schematically illustrates a coil-shaped steel sheet when coiling the steel sheet for long-term annealing in the secondary recrystallization annealing step described later.

[0112] In Fig. 1, one end (101) corresponds to the upper end (101) of the coil, and in Fig. 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 secondary recrystallization annealing, and thus has a relatively low temperature, whereas the upper end (101) of the coil has a relatively high temperature without such heat loss. In this way, since the steel sheet is wound into a coil shape and annealed for a long time during secondary recrystallization annealing, a temperature gradient inevitably occurs in the width direction of the steel sheet, and this temperature gradient leads to a magnetic deviation in the width direction of the steel sheet.

[0113] In one embodiment of the present invention, in response to such a temperature gradient, a relatively large amount of precipitates or inclusions are formed at the upper surface edge portion (110), thereby reducing the magnetic deviation in the width direction of the steel sheet, thereby ultimately securing constant magnetic properties in the width direction.

[0114] Specifically, after the nitriding annealing step, the number ratio (P2 / P1) of precipitates and inclusions (P1) present in the upper edge portion (110) to the number of precipitates and inclusions (P2) present in the center portion (120) is 0.6 to 1.0. At this time, precipitates and inclusions mean that one or more elements among C, Si, Mn, Al, Cu, N, O, and S in the steel plate coagulate with each other and appear in the form of particles. When analyzing the cross-section of the steel plate using elemental analysis, when a part having a higher concentration than the steel component of the steel plate substrate appears in the form of particles, this is regarded as a precipitate or inclusion. Precipitates or inclusions are recognized as precipitates or inclusions if their particle size is at least 1 nm and not more than 10 μm. If the particle size is smaller than that, they do not function significantly as precipitates or inclusions. Therefore, in one embodiment of the present invention, only precipitates or inclusions with a particle size of at least 1 nm are included in the counting. In this case, the particle size means the diameter of a circle having the same area as the area occupied by the precipitate or inclusion based on the measured cross-section of the steel plate.

[0115] In one embodiment of the present invention, precipitates refer to nitrides, carbides or sulfides newly formed as stable phases during melting or during the manufacture of electrical steel sheets, and inclusions refer to spinel oxides such as Al2O3 or MgAl2O4 formed when nitrides such as AlN formed during the nitriding annealing process react with oxygen in the annealing furnace during secondary recrystallization annealing.

[0116] There are various analysis methods for precipitates or inclusions, but in one embodiment of the present invention, a conventional replica method is used to obtain photographs of at least 10 sheets at a point 1 / 4t of the steel sheet thickness, and then the area is analyzed using an image analyzer. The formation point of precipitates or inclusions formed within the grain boundaries directly under the oxide layer can be analyzed by obtaining photographs of at least 10 sheets using a scanning electron microscope or transmission electron microscope of the same scale, and then analyzing the area using an image analyzer.

[0117] When precipitates or inclusions exist across the edge portion (110) and the center portion (120), the portion with a large occupied area is included. Typical examples of precipitates or inclusions include (Al, Si, Mn)N, (Mn, Cu)(S, Se). In one embodiment of the present invention, by appropriately controlling the number ratio (P2 / P1) of precipitates or inclusions, secondary recrystallization in the upper edge portion (110), where the temperature is relatively high during secondary recrystallization annealing and where the soaking temperature is reached quickly, can be relatively delayed, and conversely, secondary recrystallization in the center portion (120), where the temperature is relatively low and where the soaking temperature is reached slowly, can be advanced, and secondary recrystallization can be controlled to occur uniformly in the width direction. If the number ratio (P2 / P1) of precipitates and inclusions is too high, it is difficult to sufficiently obtain the aforementioned secondary recrystallization control effect. If the number ratio of precipitates and inclusions (P2 / P1) is too small, the secondary recrystallization of the upper surface edge portion (110) may be excessively delayed, which may result in a magnetic deviation in the width direction. More specifically, the number ratio of precipitates and inclusions (P2 / P1) may be 0.6 to 1.0.

[0118] The edge portion (130) also comes into contact with the bottom surface during the secondary recrystallization annealing process, just like the center portion (120), so the temperature is relatively low, and secondary recrystallization occurs later than the upper edge portion (110).

[0119] In one embodiment of the present invention, in response to such a temperature gradient, a relatively large amount of precipitates or inclusions are formed at the upper surface edge portion (110), thereby reducing the magnetic deviation in the width direction of the steel plate.

[0120] Specifically, after the nitriding annealing step, the ratio of the number of precipitates and inclusions (P3) of the lower edge portion (130) to the number of precipitates and inclusions (P1) present in the upper edge portion (110) (P3 / P1) may be 0.7 to 1.0. In one embodiment of the present invention, by appropriately controlling the number ratio of precipitates and inclusions (P3 / P1), secondary recrystallization in the upper edge portion (110), which has a relatively high temperature during secondary recrystallization annealing and quickly reaches the soaking temperature, can be relatively delayed, and conversely, secondary recrystallization in the lower edge portion (130), which has a relatively low temperature and slowly reaches the soaking temperature, can be advanced, so that secondary recrystallization can be uniformly performed in the width direction. If the number ratio of precipitates and inclusions (P3 / P1) is too high, it is difficult to sufficiently obtain the aforementioned secondary recrystallization control effect. If the number ratio of precipitates and inclusions (P3 / P1) is too small, the secondary recrystallization of the upper surface edge portion (110) may be excessively delayed, which may result in a magnetic deviation in the width direction. More specifically, the number ratio of precipitates and inclusions (P3 / P1) may be 0.75 to 0.99.

[0121] There may be a temperature difference between the edge portion (130) and the center portion (120) during the secondary recrystallization annealing process, and the secondary recrystallization may occur later in the center portion (120) than in the edge portion (130).

[0122] In one embodiment of the present invention, in response to such a temperature gradient, a relatively large amount of precipitates or inclusions are formed in the center portion (120), thereby reducing the magnetic deviation in the width direction of the steel sheet.

[0123] Specifically, after the nitriding annealing step, the ratio (P2 / P3) of the number of precipitates and inclusions (P2) present in the center portion (120) to the number of precipitates or inclusions (P3) of the lower edge portion (130) may be 0.7 to 1.0. In one embodiment of the present invention, by appropriately controlling the number ratio (P2 / P3) of precipitates and inclusions, the secondary recrystallization in the center portion (120) where the temperature is relatively high and the soaking temperature is reached quickly during the secondary recrystallization annealing can be relatively delayed, and conversely, the secondary recrystallization in the lower edge portion (130) where the temperature is relatively low and the soaking temperature is reached slowly can be advanced, thereby controlling the secondary recrystallization to occur uniformly in the width direction. If the number ratio (P2 / P3) of precipitates and inclusions is too high, it is difficult to sufficiently obtain the aforementioned secondary recrystallization control effect. If the number ratio of precipitates or inclusions (P2 / P3) is too small, the secondary recrystallization of the center portion (120) may be excessively delayed, which may result in a magnetic deviation in the width direction. More specifically, the number ratio of precipitates and inclusions (P2 / P3) may be 0.75 to 0.98.

[0124] More specifically, after the nitriding annealing step, the density of precipitates and inclusions (P1) present on the upper surface edge (110) is 0.01 to 0.8 / cm 2 It can be. More specifically, 0.3 to 0.8 pieces / cm 2 It could be.

[0125] The density of precipitates and inclusions (P2) present in the center (120) is 0.01 to 0.50 / cm 2 It can be. More specifically, 0.3 to 0.48 pieces / cm 2 It could be.

[0126] The density of precipitates and inclusions (P3) present in the edge portion (130) is 0.01 to 0.8 / cm 2 It can be. More specifically, 0.3 to 0.8 pieces / cm 2 It could be.

[0127] There are no specific limitations on the method for varying the number of precipitates or inclusions in the width direction. For example, methods such as controlling the ammonia flow rate to promote the formation of precipitates or inclusions in the width direction, changing the annealing time and temperature, and installing a screen to change the flow of atmospheric gas within the annealing furnace may also be possible.

[0128] In the nitriding annealing step, the soaking temperature may be 820 to 900°C. If the temperature is too low, even if the desired amount of oxygen is reached, there may be a lack of Fe-based oxides (Fe2SiO4 or FeSiO3) that are important for stably forming a forsterite film as an oxide quality, or the density of the oxide may be insufficient. If the temperature is too high, the density of the oxide film or the formation of Fe-based oxides is advantageous, but the decarburization may be poor due to the initially formed oxide. The soaking temperature may be configured in two stages, and the first soaking temperature may be configured to be 830 to 860°C, and the second soaking temperature may be configured to be 850 to 890°C. In this case, the quality of the oxide can be further improved.

[0129] In the nitriding annealing step, decarburization occurs simultaneously with nitriding, and the oxidation level (P) of the atmosphere during the decarburization H2O / P H2 ) can be 0.45 to 0.75. If the oxidation degree is low, it is difficult for oxidation or decarburization to occur sufficiently. If the oxidation degree is too high, the outermost layer of the oxide film may become an unstable oxide in which FeO is rapidly generated. More specifically, the oxidation degree can be 0.48 to 0.75.

[0130] After nitriding annealing, the nitrogen content in the steel sheet may be 0.0135 wt% to 0.0280 wt%. If the nitrogen content is too low, it may not be sufficiently effective as an inhibitor before the secondary recrystallization begins. If the nitrogen content is too high, it may not only inhibit the normal formation of secondary recrystallization by excessive formation of nitrides, but also form film defects such as bare spots due to N2 gas decomposed during the purification process after the secondary recrystallization. More specifically, the nitrogen content in the steel sheet may be 0.0150 wt% to 0.0250 wt%.

[0131] In addition, the precipitates or inclusions within the grain boundaries directly beneath the oxide, mainly SiO2, formed by the aforementioned decarburization conditions, must be less than 15% of the total precipitates or inclusions. The precipitates or inclusions precipitated at the grain boundaries and within the grains of the decarburized plate are mostly nitrides, oxides or sulfides combined with Si, Cu, Sb, Mo, B, Mn, etc., including mainly Al-based nitrides. As is well known, these precipitates or inclusions are decomposed through a phenomenon called secondary recrystallization during secondary recrystallization annealing, and must then be removed from the steel through a purification process. If the precipitates or inclusions within the grain boundaries directly beneath the oxide exceed 15% of the total precipitates or inclusions, it means that excessive precipitates or inclusions are formed within the grain boundaries, which affects the initiation temperature of secondary recrystallization in the secondary recrystallization annealing, and thus causes non-uniform magnetic properties, and therefore is restricted. In particular, as the coil width increases, the coil edge may experience more active oxidation and nitriding reactions than the center due to the influence of the annealing temperature and the atmosphere flow in the annealing furnace, so in the case of a final product coil width of 1050 mm or more, it is necessary to maintain the precipitates or inclusions within the grain boundaries directly beneath the oxide at 15% or less of the total precipitates or inclusions after decarburization. In one embodiment of the present invention, directly beneath the oxide means from the surface oxide layer to the 1 / 4t point in the direction of the thickness of the steel sheet.

[0132] Next, the nitriding annealed steel plate undergoes secondary recrystallization annealing.

[0133] The nitriding annealed steel sheet is coated with an annealing agent based on MgO, then heated to 1000℃ or higher and subjected to a long-term crack annealing process to cause secondary recrystallization, so that the {110} plane of the steel sheet is parallel to the rolling surface. <001> The direction forms a Goss orientation aggregate structure parallel to the rolling direction.

[0134] During secondary recrystallization annealing, the steel sheet is wound into a coil shape and annealed for a long period of time. The coil shape is described with reference to Fig. 2. Secondary recrystallization annealing can be heat treated at a temperature of 1170 to 1220°C for 1 to 25 hours.

[0135] After the secondary recrystallization annealing, the annealing separator is washed away, pickled, and an insulating film is applied. Then, heat flattening treatment, which includes annealing treatment of the insulating film, shape correction, and stress relief annealing, can be performed.

[0136] According to one embodiment of the present invention, a grain-oriented electrical steel sheet comprises, in wt%, C: 0.005% or less (excluding 0%), Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, and the remainder Fe and other unavoidable impurities, and a number ratio (P2 / P1) of precipitates and inclusions (P1) present in an upper surface edge portion from one end of the steel sheet to 30% of the total width of the steel sheet at one end of the steel sheet to a center portion from more than 30% to 70% of the total width of the steel sheet at one end of the steel sheet is 0.6 to 1.0.

[0137] Since the steel component of the grain-oriented electrical steel sheet has been described in the steel component of the slab in the manufacturing method of the grain-oriented electrical steel sheet mentioned above, a duplicate description will be omitted.

[0138] As mentioned above, in the manufacturing method of grain-oriented electrical steel sheets, the magnetic deviation in the width direction of the steel sheet is reduced by precipitating precipitates or inclusions differently along the width direction of the steel sheet during the nitriding annealing process. After nitriding annealing, the precipitates or inclusions are decomposed during the secondary recrystallization annealing process, but some precipitates or inclusions remain and are ultimately produced in the grain-oriented electrical steel sheet.

[0139] At this time, since the ratio of precipitates or inclusions removed or remaining from the grain-oriented electrical steel sheet is constant with respect to the steel sheet width, after nitriding annealing, the ratio of precipitates and inclusions between the upper edge portion (110), the center portion (120), and the lower edge portion (130) and the ratio 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 are roughly maintained. Since the ratio of precipitates and inclusions between the upper edge portion (110), the center portion (120), and the lower edge portion (130) has been described in the aforementioned method for manufacturing grain-oriented electrical steel sheets, a redundant description will be omitted.

[0140]

[0141] More specifically, in the final manufactured oriented electrical steel sheet, the density of precipitates and inclusions (P1) present in the upper edge portion (110) is 0.001 to 0.55 / cm 2 It can be. More specifically, 0.30 to 0.55 pieces / cm 2 It could be.

[0142] The density of precipitates or inclusions or inclusions (P2) present in the center portion (120) is 0.001 to 0.40 / cm 2 It can be. More specifically, 0.30 to 0.40 pieces / cm 2 It could be.

[0143] The density of precipitates or inclusions or inclusions (P3) present in the edge portion (130) is 0.001 to 0.55 / cm 2 It can be more specific 0.30 to 0.55 pieces / cm 2 It could be.

[0144]

[0145] A oriented electrical steel sheet according to one embodiment of the present invention has excellent iron loss and magnetic flux density, while at the same time having a very small iron loss and magnetic flux density deviation in the width direction.

[0146] A directional electrical steel sheet according to one embodiment of the present invention has a magnetic flux density (B8) of 1.90 T or more and a core loss (W 17 / 50 ) may be less than 0.90 W / kg. At this time, the magnetic flux density B8 is the size (Tesla) of the magnetic flux density induced under a magnetic field of 800 A / m, and the iron loss W 17 / 50 is the magnitude of the iron loss (W / kg) induced under 1.7 Tesla and 50 Hz conditions. More specifically, when the magnetic flux density (B8) is 1.91 T to 1.95 T and the iron loss (W 17 / 50 ) can be 0.75 to 0.85 W / kg.

[0147] In one embodiment of the present invention, the oriented electrical steel sheet may have a ratio (W2 / W1) of the core loss (W2) of the center portion to the core loss (W1) of the upper edge portion of the upper surface, which may be 0.99 to 1.03. In addition, the ratio (B2 / B1) of the magnetic flux density (B2) of the center portion to the magnetic flux density (B1) of the upper edge portion of the upper surface, which may be 0.99 to 1.01.

[0148]

[0149] Additionally, the forsterite film adhesion is excellent. Adhesion can be measured by the minimum arc diameter that does not cause film peeling when bent 180° in contact with a circular arc of a specific diameter. Specifically, the forsterite film adhesion can be 20 mmΦ or less.

[0150]

[0151] Specific examples of the present invention are described below. However, the following examples are only specific examples of the present invention, and the present invention is not limited to the following examples.

[0152]

[0153] Example 1

[0154] A slab containing C: 0.058%, Si: 3.32%, Mn: 0.105%, N: 0.0056%, Sb: 0.03%, Sn: 0.05%, P: 0.02% in wt% and the remainder Fe and unavoidable impurities was made, and the slab was heated to a temperature of 1150℃, hot-rolled to a thickness of 2.3 mm, and then rapidly cooled to 600℃ and coiled. The hot-rolled sheet was annealed at 1080℃, pickled, and then cold-rolled once to a thickness of 0.20 mm. For the cold-rolled sheet, decarburization annealing was performed under the conditions summarized in Table 1 below, and nitriding conditions were changed to perform decarburization annealing on the upper edge, center, and lower edge. In Table 1, the nitriding gas flow rate means the mass of nitriding gas introduced per unit area and per unit time. At this time, the oxygen content in the steel plate was 900-1100 ppm. After that, the annealing separator MgO was dried and wound into a coil. Then, the heating rate was maintained at 15℃ / hr up to 1200℃, and secondary recrystallization annealing was performed at 1200℃ for 20 hours, and then an insulating coating solution was applied in a continuous line and heat treatment was performed at 850℃. The secondary recrystallization annealing was performed in a mixed gas atmosphere of 25v% N2 and 75v% H2 up to 1200℃, and after reaching 1200℃, it was maintained in a 100v% H2 gas atmosphere and then slowly cooled.

[0155] After nitriding annealing and secondary recrystallization annealing, the density of precipitates or inclusions was analyzed using an image analyzer on 10 photographs obtained using the replica method at 1 / 4t of the steel sheet thickness, and the results are summarized in Table 2 below.

[0156] For the final manufactured oriented electrical steel sheet, the density of precipitates or inclusions was measured, and the results are summarized in Table 3 below. In addition, 10 specimens were collected by shearing them to the Epstein specimen size [60 mm (width) X 300 mm (length)] from the upper edge, center, and lower edge, and the magnetic flux density (B8) and core loss (W 17 / 50) were measured and summarized in Table 4 below. The deviation was calculated as the ratio of the iron loss (W2) of the center to the iron loss (W1) of the upper edge (W2 / W1) and the ratio of the magnetic flux density (B2) of the center to the magnetic flux density (B1) of the upper edge (B2 / B1).

[0157] The results of the adhesion evaluation of the forsterite film are shown in Table 4. The adhesion was measured as the minimum arc diameter without film peeling when the film was bent 180° in contact with arcs of diameters of 10, 15, 20, 25, and 30 mm.

[0158] Decarburization conditions Nitrogen gas flow rate Nitrogen amount (ppm, center) Annealing temperature (℃) Oxidizing capacity (P H2O / P H2 ) Top edge / Center bottom edge / Center bottom edge / Top edge Example 18500.581.351.290.96145 Example 28500.581.331.170.88178 Example 38500.581.201.100.92202 Example 48500.581.051.051.00231 Example 58500.581.041.041.00252 Comparative Example 18500.580.800.801.00208 Comparative Example 28500.581.451.350.93199 Comparative Example 38500.581.702.301.35105 Comparative Example 48500.401.101.050.95288 Comparative Example 58500.850.850.901.06209 Comparative Example 58500.58---62 Example 68500.581.351.351.00204 Example 78500.451.101.050.95225

[0159] Density of precipitates or inclusions or inclusions after nitriding annealing (units / cm) 2)P2 / P1P3 / P1P2 / P3 Top surface edge (P1) Center (P2) Bottom surface edge (P3) Example 10.570.430.510.750.890.84 Example 20.510.440.480.860.940.92 Example 30.430.390.410.910.950.95 Example 40.450.420.430.930.960.98 Example 50.630.480.570.760.900.84 Comparative example 10.780.420.750.540.960.56 Comparative example 20.920.40.680.430.740.59 Comparative example 30.680.440.870.551.280.51Comparative Example 40.990.60.780.510.790.77Comparative Example 50.240.280.271.171.131.04Comparative Example 60.020.0080.010.400.500.80Example 60.670.430.660.640.990.65Example 70.720.480.640.670.890.75

[0160] Density of precipitates or inclusions or inclusions in oriented electrical steel sheets (units / cm) 2 )P2 / P1P3 / P1P2 / P3Upper surface edge (P1)Center (P2)Bottom surface edge (P3)Example 10.4520.3520.3820.780.850.92Example 20.3850.2680.3350.700.870.80Example 30.3730.3270.3680.880.990.89Example 40.3460.2980.3020.860.870.99Example 50.4020.2780.3560.690.890.78Comparative example 10.6540.2910.5750.440.880.51Comparative example 20.6910.2520.5340.360.770.47Comparative Example 30.5240.2980.6370.571.220.47Comparative Example 40.7760.4200.6570.540.850.64Comparative Example 50.2980.2550.3120.561.050.82Comparative Example 60.0800.1020.1291.281.610.79Example 60.5220.3580.5100.690.980.70Example 70.4880.3250.4280.670.880.76

[0161] Iron loss (W17 / 50, W / kg) Magnetic flux density (B8, T) Adhesion (mmφ) Top surface Edge Center Bottom surface Edge Deviation Top surface Edge Center Bottom surface Edge Deviation Example 10.67 0.68 0.68 1.01 1.92 1.92 1.92 1.00 15 Example 20.62 0.65 0.64 1.03 1.94 1.93 1.93 0.99 15 Example 30.64 0.66 0.67 1.02 1.94 1.93 1.92 0.99 18 Example 40.63 0.65 0.64 1.02 1.94 1.93 1.94 0.99 15 Example 50.680.700.691.031.921.911.920.9920Comparative Example 10.880.920.891.051.881.871.870.9935Comparative Example 20.950.990.951.041.871.871.871.0035Comparative Example 30.940.890.920.951.871.881.871.0130Comparative Example 40.850.890.871.051.881.871.870.9940Comparative Example 51.351.321.350.981.831.831.831.0028Comparative Example 60.880.910.911.031.881.871.870.9935Example 60.720.750.741.031.901.901.901.0020Example 70.710.730.711.031.921.901.910.9920

[0162] As can be seen in Tables 1 to 4, when precipitates or inclusions were appropriately formed on the upper edge (110), center (120), and lower edge (130) during the nitriding annealing process, it was confirmed that the iron loss and magnetic deviation in the width direction of the steel sheet were small.

[0163] On the other hand, it was confirmed that when precipitates or inclusions were not uniformly formed or properly formed on the upper edge (110), center (120), and lower edge (130), significant iron loss and magnetic deviation occurred in the width direction of the steel plate.

[0164]

[0165] The present invention is not limited to the above-described embodiments and / or examples, but can be manufactured in various different forms. Those skilled in the art will understand that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the above-described embodiments and / or examples should be understood as illustrative in all respects and not restrictive.

[0166]

[0167] [Explanation of symbols]

[0168] 100: Oriented electrical steel sheet, 101: Single end,

[0169] 102: Other end, 110: Top edge,

[0170] 120: Center, 130: Lower edge

Claims

1. A step for manufacturing a slab containing, by weight%, C: 0.01% to 0.1%, Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, and the remainder Fe and other unavoidable impurities; A step of manufacturing a hot-rolled plate by hot-rolling the above slab; A step of manufacturing a cold rolled sheet by cold rolling the hot rolled sheet; A step of nitriding and annealing the cold rolled sheet; and It includes a step of performing secondary recrystallization annealing on a nitriding annealed steel sheet, After the above nitriding annealing step, precipitates and inclusions (P) present at the upper surface edge of one end of the steel plate to 30% of the total width of the steel plate 1 ) Precipitates and inclusions (P) present in the center portion of more than 30% to 70% of the total width of the steel plate at one end of the steel plate 2 ) number ratio (P) 2 / P 1 ) A method for manufacturing a grain-oriented electrical steel sheet having a grain size of 0.6 to 1.

0.

2. In paragraph 1, A method for manufacturing a grain-oriented electrical steel sheet, wherein the above slab further contains, in wt%, Al: 0.020% to 0.040%, N: 0.0030% to 0.0060%, and S: 0.0030% to 0.0065%.

3. In paragraph 1, A method for manufacturing a grain-oriented electrical steel sheet, wherein the above slab further contains, in wt%, Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07%, and P: 0.01% to 0.04%.

4. In paragraph 3, The above slab is a method for manufacturing a oriented electrical steel sheet satisfying the following equation 1. [Formula 1] 0.0330 ≤ [P] + 0.5×[Sb] ≤ 0.062 (In Equation 1, [P] and [Sb] represent the contents (in weight%) of P and Sb in the slab, respectively.) 5. In paragraph 1, A method for manufacturing a grain-oriented electrical steel sheet, wherein the above slab further contains, in wt%, at least one of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15%.

6. In paragraph 1, After the above nitriding annealing step, precipitates and inclusions (P) present at the upper surface edge 1 ) Precipitates and inclusions (P) on the lower edge of the steel plate from more than 70% of the total width of the steel plate to the other end of the steel plate 3 ) ratio of the number of (P) 3 / P 1 ) A method for manufacturing a grain-oriented electrical steel sheet having a grain size of 0.7 to 1.

0.

7. In paragraph 1, In the above nitriding annealing step, the flow rate of ammonia (AF) injected into the center section 2 ) The flow rate of ammonia injected into the upper surface edge portion (AF) 1 ) ratio (AF) 1 / AF 2 ) A method for manufacturing a grain-oriented electrical steel sheet having a grain size of 1.03 to 1.

40.

8. In paragraph 1, In the above nitriding annealing step, the flow rate of ammonia (AF) injected into the center section 2 ) The flow rate of ammonia injected into the edge section (AF) 3 ) ratio (AF) 3 / AF 2 ) A method for manufacturing a grain-oriented electrical steel sheet having a grain size of 1.03 to 1.

40.

9. In paragraph 1, A method for manufacturing grain-oriented electrical steel sheets, wherein the cracking temperature in the above-mentioned nitriding annealing step is 820 to 900°C.

10. In paragraph 1, In the above nitriding annealing step, decarburization occurs simultaneously with nitriding, and the oxidation level (P) of the atmosphere during decarburization H2O / P H2 ) A method for manufacturing a grain-oriented electrical steel sheet having a grain size of 0.45 to 0.

75.

11. Contains C: 0.005% or less (excluding 0%), Si: 1.5% to 4.5%, Mn: 0.1% to 1.5%, and the remainder includes Fe and other unavoidable impurities. Precipitates and inclusions (P) present on the upper surface edge of one end of the steel plate or up to 30% of the total width of the steel plate 1 ) Precipitates and inclusions (P) present in the center portion of more than 30% to 70% of the total width of the steel plate at one end of the steel plate 2 ) number ratio (P) 2 / P 1 ) Grain-oriented electrical steel sheet having a molecular weight of 0.6 to 1.

0.

12. In paragraph 11, Grain-oriented electrical steel sheet further comprising, in weight %, Al: 0.040% or less, N: 0.0050% or less, and S: 0.005% or less.

13. In paragraph 11, Grain-oriented electrical steel sheet further comprising, in weight %, Sb: 0.01% to 0.04%, Sn: 0.03% to 0.07%, and P: 0.01% to 0.04%.

14. In paragraph 13, Grain-oriented electrical steel sheet satisfying the following equation 1. [Formula 1] 0.0330 ≤ [P] + 0.5×[Sb] ≤ 0.062 (In Equation 1, [P] and [Sb] represent the contents (weight%) of P and Sb in the steel plate, respectively.) 15. In paragraph 11, Grain-oriented electrical steel sheet further comprising at least one of Cu: 0.001% to 0.1% and Cr: 0.01% to 0.15% in weight%.

16. In paragraph 11, Precipitates and inclusions (P) present in the upper surface edge portion 1 ) Precipitates and inclusions (P) on the lower edge of the steel plate from more than 70% of the total width of the steel plate to the other end of the steel plate 3 ) ratio of the number of (P) 3 / P 1 ) Grain-oriented electrical steel sheet having a molecular weight of 0.7 to 1.0.

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