Grain-oriented electrical steel sheet and method for manufacturing same

Abstract

A grain-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight %, 1.0% to 5.0% of Si, more than 0% and 0.005% or less of C, 0.03% to 0.3% of Mn, 0.030% to 0.3% of Cu, 0.0005% to 0.01% of As, and 0.0002% to 0.01% of Bi, with the balance being Fe and unavoidable impurities.

Description

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

[0001] The present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same. Specifically, the invention relates to a grain-oriented electrical steel sheet capable of improving magnetism by appropriately controlling the content of Cu, As, and Bi, and a method for manufacturing the same.

[0002] Grain-oriented electrical steel sheets have a texture of the steel sheet with respect to the rolling direction {110} <001> It is a soft magnetic material that exhibits a Goss texture and has excellent magnetic properties in one direction or the rolling direction. In order to improve the magnetic properties of oriented electrical steel sheets by expressing this texture, complex processes such as composition control during steelmaking, slab reheating and hot rolling process parameter control during hot rolling, hot-rolled sheet annealing heat treatment, cold rolling, primary recrystallization annealing, and secondary recrystallization annealing are required and must be managed very precisely and strictly.

[0003] In addition, as one of the factors influencing the expression of Goss texture, it is becoming important to control the inhibitor, which is a grain growth inhibitor that suppresses the indiscriminate growth of primary recrystallized grains and ensures that only the Goss texture grows when secondary recrystallization occurs. In order for Goss texture to be obtained during secondary recrystallization annealing, the growth of all primary recrystallized grains must be suppressed until just before secondary recrystallization occurs. To achieve this, the amount of inhibitor must be sufficiently large and the distribution of the inhibitor must be uniform.

[0004] In order to induce secondary recrystallization during the high-temperature secondary recrystallization annealing process, the inhibitor must have excellent thermal stability and not decompose easily. Secondary recrystallization is a phenomenon that can occur when the inhibitor that inhibits the growth of primary recrystallized grains decomposes or loses its inhibitory power within the appropriate temperature range during secondary recrystallization annealing. In this case, specific grains, such as Goss grains, may grow rapidly within a relatively short period of time.

[0005] The quality of grain-oriented electrical steel sheets can be evaluated based on their representative magnetic properties, such as magnetic flux density and iron loss. The higher the precision of the Goss texture, the superior the magnetic properties. The aforementioned high-quality grain-oriented electrical steel sheets enable the manufacture of high-efficiency power equipment due to their properties, allowing for both miniaturization and increased efficiency of the equipment.

[0006] As a technology to improve the magnetic properties of oriented electrical steel sheets, a technology is proposed that increases the fraction of the Goss texture after secondary recrystallization annealing by adding an alloying element capable of obtaining a level of inhibition effect similar to that of precipitates, unlike a technology that uses the inhibition of grain growth by precipitates; a technology that increases the fraction of the Goss texture among the primary recrystallization textures during the primary recrystallization annealing process and increases the fraction of the secondary recrystallization microstructure of the Goss texture after secondary recrystallization high-temperature annealing; and a technology that uniformly distributes the size of the primary recrystallized grains so that textures that cannot improve magnetic properties due to the non-uniformity of the primary recrystallization microstructure do not grow.

[0007] A technology involving the addition of copper (Cu) is proposed to improve the magnetism of grain-oriented electrical steel sheets. Conventional technology provides molybdenum (Mo) to control the size of precipitates using copper, but there is a problem in that precipitates become coarse and non-uniform depending on the content of tin (Sn) or manganese (Mn).

[0008] The present invention provides a grain-oriented electrical steel sheet and a method for manufacturing the same. Specifically, the invention provides a grain-oriented electrical steel sheet with improved magnetism by appropriately controlling the content of Cu, As, and Bi, and a method for manufacturing the same.

[0009] A oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 1.0 to 5.0%, C: 0.005% or less (excluding 0%), Mn: 0.03 to 0.3%, Cu: 0.030 to 0.3%, As: 0.0005 to 0.01% and Bi 0.0002 to 0.01%, and the remainder being Fe and unavoidable impurities.

[0010] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of S: 0.020 wt% or less, Al: 0.050 wt% or less, N: 0.020 wt% or less, and Se: 0.050 wt% or less.

[0011] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Sn: 0.1 wt% or less and Sb: 0.1 wt% or less.

[0012] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

[0013] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.1 wt% or less, Cr: 0.5 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

[0014] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Pb: 0.200 wt% or less and Ge: 0.200 wt% or less.

[0015] A grain-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Zr: 0.005 wt% or less, and Mg: 0.0050 wt% or less.

[0016] A method for manufacturing a oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: hot rolling a slab containing, in weight percent, Si: 1.0 to 5.0%, C: 0.001 to 0.100%, Mn: 0.03 to 0.3%, Cu: 0.001 to 0.3%, As: 0.0005 to 0.01% and Bi 0.0002 to 0.01%, and the remainder being Fe and unavoidable impurities to produce a hot-rolled sheet; cold rolling the hot-rolled sheet to produce a cold-rolled sheet; a step of primary recrystallizing annealing of the cold-rolled sheet and a step of secondary recrystallizing annealing of the primary recrystallized annealed sheet.

[0017] The slab may further include one or more of S: 0.001 to 0.020 wt%, Al: 0.001 to 0.050 wt%, N: 0.001 to 0.020 wt%, and Se: 0.001 to 0.050 wt%.

[0018] The slab may further include one or more of Sn: 0.1 wt% or less and Sb: 0.1 wt% or less.

[0019] The slab may further include one or more of Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

[0020] The slab may further include one or more of P: 0.1 wt% or less, Cr: 0.5 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

[0021] The slab may further include one or more of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

[0022] The slab may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Zr: 0.005 wt% or less, and Mg: 0.0050 wt% or less.

[0023] Before the step of manufacturing the hot-rolled plate, the step of heating the slab to 1000 to 1250°C may be further included.

[0024] After the step of manufacturing a hot-rolled plate, the method may further include a hot-rolled plate annealing step of annealing the hot-rolled plate at 600 to 1100°C.

[0025] The average grain size of the primary recrystallized annealed steel sheet may be 10 to 30 μm.

[0026] A directional electrical steel sheet according to one embodiment of the present invention can eliminate magnetic variation within the entire steel sheet by uniformly distributing the primary recrystallization grain size in a steel composition containing a large amount of Cu.

[0027] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0028] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of “comprising” specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0029] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0030] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0031] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0032] In one embodiment of the present invention, the meaning of including additional elements is that the remainder of iron (Fe) is replaced by an amount of the additional element.

[0033] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0034] A oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 1.0 to 5.0%, C: 0.005% or less (excluding 0%), Mn: 0.03 to 0.3%, Cu: 0.030 to 0.3%, As: 0.0005 to 0.01% and Bi 0.0002 to 0.01%, and the remainder being Fe and unavoidable impurities.

[0035] The reason for limiting the alloy composition is explained below.

[0036]

[0037] Si: 1.00 to 5.00 wt%

[0038] Silicon (Si) is a basic component of electrical steel sheets and plays a role in lowering core loss by increasing the resistivity of the material. If the Si content is too low, the resistivity decreases, leading to increased eddy current loss and deterioration of core loss characteristics. Furthermore, during the first recrystallization annealing, the phase transformation between ferrite and austenite becomes active, severely damaging the first recrystallization texture. Additionally, during the second recrystallization annealing, the phase transformation between ferrite and austenite occurs, which not only makes the second recrystallization unstable but also severely damages the {110} Goss texture. On the other hand, if the Si content is excessive, the SiO2 and Fe2SiO4 oxide layers are formed excessively and densely during the first recrystallization annealing, delaying decarburization behavior. Consequently, the phase transformation between ferrite and austenite continues throughout the first recrystallization annealing process, which can lead to severe damage to the first recrystallization texture. In addition, due to the decarburization behavior delay effect resulting from the formation of the dense oxide layer described above, the nitriding behavior is also delayed, so nitrides such as (Al,Si,Mn)N and AlN are not sufficiently formed, and thus it may not be possible to secure sufficient grain suppression power required for secondary recrystallization during high-temperature annealing.

[0039] In addition, if Si is included in excess, the mechanical properties of brittleness increase and toughness decrease, which exacerbates the rate of plate breakage during the rolling process and impairs weldability between plates, making it impossible to secure easy workability. Consequently, if the Si content is not controlled within the aforementioned predetermined range, the formation of secondary recrystallization becomes unstable, severely damaging magnetic properties and worsening workability. More specifically, Si may be included in an amount of 2.00 to 4.00 weight%. Even more specifically, it may be included in an amount of 2.50 to 3.50 weight%.

[0040]

[0041] C: 0.005 wt% or less

[0042] Carbon (C) is an element that contributes to grain refinement and improved elongation by inducing phase transformations between ferrite and austenite; it is an essential element for improving the rollability of electrical steel sheets, which have poor rollability due to their high brittleness. Since C, if remaining in the final product, precipitates carbides formed by magnetic aging effects within the product sheet, thereby deteriorating magnetic properties, it is desirable to control its content to an appropriate level. If the slab contains too little C, the phase transformation between ferrite and austenite does not occur sufficiently, which can lead to microstructure non-uniformity in the slab and hot-rolled material. Consequently, precipitates form coarsely and non-uniformly, which not only makes secondary recrystallization unstable but can also impair cold rolling performance following hot rolling. Furthermore, microstructure non-uniformity and precipitates may occur due to thermal variations in the skid within the furnace during slab heating. If the slab contains too much C, the carbides become too coarse and the amount of precipitation increases excessively, so decarburization does not occur sufficiently. Consequently, the accumulation density of the Goss texture is reduced, the secondary recrystallization texture is severely damaged, and furthermore, this can lead to the deterioration of magnetic properties due to self-aging in the final product. Therefore, the C content of the slab is 0.001 to 0.100 weight%. More specifically, the C content in the slab can be 0.001 to 0.050 weight%. Meanwhile, to minimize the occurrence of self-aging during the use of the final product, i.e., the oriented electrical steel sheet, the C content of the final oriented electrical steel sheet product after secondary recrystallization annealing is 0.005 weight% or less. More specifically, it can be 0.003 weight% or less.

[0043]

[0044] Mn: 0.030 to 0.300 wt%

[0045] Manganese (Mn), similar to Si, has the effect of reducing overall iron loss by increasing resistivity and thereby reducing eddy current losses. Furthermore, it is an important element that affects the surface quality of the final product, as it not only forms Mn-based sulfides by reacting with S in the quenching state but also inhibits the growth of primary recrystallized grains and causes secondary recrystallization by reacting with nitrogen introduced through nitriding treatment along with Si to form (Al,Si,Mn)N precipitates. If too little Mn is included, the surface quality of the final product may deteriorate. If too much Mn is included, the austenite phase fraction increases significantly, damaging the Goss texture and reducing magnetic flux density, and the oxide layer may form excessively during decarburization annealing, which can hinder decarburization. More specifically, Mn may be included in an amount of 0.040 to 0.200 weight%. More specifically, Mn may be included in an amount of 0.050 to 0.130 weight%.

[0046]

[0047] Cu: 0.030 to 0.300 wt%

[0048] When the copper (Cu) content increases, fine Cu2S precipitates are formed, which increases the grain growth inhibition during secondary recrystallization annealing, allowing grains with a high degree of orientation toward the Goss orientation to grow and improve magnetism. If too little Cu is included, coarse MnS precipitates are formed instead of Cu2S precipitates, and the effect of improving grain growth inhibition may not be sufficient. If too much Cu is included, Cu2S precipitates remain after secondary recrystallization annealing, resulting in inferior magnetism and an increase in coarse precipitates. More specifically, Cu may be included in an amount of 0.035 to 0.150 weight%.

[0049] As 0.0005 to 0.0100 weight%

[0050] In thin products, if the oxide layer thickness is excessive, there is a problem in that the packing factor increases, leading to an increase in transformer no-load losses. When arsenic (As) is added, it helps to form a dense oxide layer during decarburization nitriding without forming an excessively deep layer, thereby ensuring that the primary film is also formed well. If the amount of As is too small, it cannot affect the formation of the oxide layer, and if too much As is added, excessive surface segregation occurs, hindering the formation of the oxide layer and preventing the primary film from forming well, which may lead to deterioration of magnetism. More specifically, it may contain 0.0006 to 0.0095 weight% of As.

[0051] Bi 0.0002 to 0.0100 wt%

[0052] Adding bismuth (Bi) promotes the formation of fine precipitates, which increases the inhibition of grain growth during high-temperature annealing and improves magnetism. If too little Bi is included, it cannot affect precipitate formation, and if too much Bi is added, the adhesion of the primary film decreases, causing various surface defects. More specifically, Bi may be included in an amount of 0.0010 to 0.0098 weight%.

[0053] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of S: 0.020 wt% or less, Al: 0.050 wt% or less, N: 0.020 wt% or less, and Se: 0.050 wt% or less.

[0054] S: 0.020 wt% or less

[0055] Sulfur (S) is an element with a high solid solution temperature and severe segregation during hot rolling, so it is desirable to avoid including it as much as possible, and it is a type of unavoidable impurity included during steelmaking. In addition, since S forms MnS and affects the primary recrystallization grain size, the S content can be limited to 0.02 weight% or less. More specifically, S may be included in an amount of 0.0001 to 0.0100 weight%. More specifically, S may be included in an amount of 0.0010 to 0.0050 weight%.

[0056] Al: 0.050 wt% or less

[0057] Aluminum (Al) acts as a powerful grain growth inhibitor by forming nitrides in the form of (Al,Si,Mn)N, (Al,Si)N, and AlN, in addition to the finely precipitated AlN during hot rolling and annealing of hot-rolled sheets, through the combination of nitrogen ions introduced by ammonia gas during the annealing process after cold rolling with Al, Si, and Mn existing in a solid solution state in the steel. If there is too much Al, the grain growth inhibitory power may decrease due to the formation of coarse nitrides. More specifically, it may contain 0.005 to 0.040 weight% of Al. More specifically, it may contain 0.010 to 0.030 weight% of Al.

[0058] N: 0.020 weight % or less

[0059] Nitrogen (N) is an important element that reacts with Al to form Al-based nitrides, and it can be added to the slab in an amount of 0.020 wt% or less. If there is too much N in the slab, it causes surface defects called blistering due to nitrogen diffusion during processes after hot rolling. Furthermore, because too much nitride is formed in the slab state, rolling becomes difficult, which complicates subsequent processes and causes manufacturing costs to rise. More specifically, N can be included in an amount of 0.010 wt% or less. Meanwhile, additional N required to form nitrides such as (Al,Si,Mn)N, AlN, and (Si,Mn)N can be reinforced by performing nitriding treatment in the steel using ammonia gas during the annealing process after cold rolling. However, since N is removed again during the secondary recrystallization annealing process, the N remaining in the final electrical steel sheet can be 0.020 wt% or less.

[0060] Se: 0.050 wt% or less

[0061] Selenium (Se) is an important element that reacts with Mn to form MnSe, similar to S. In one embodiment of the present invention, additional auxiliary inhibitory power can be added by precipitates such as MnSe along with MnS. In one embodiment of the present invention, it is necessary to limit the S content to 0.050 wt% or less to achieve complete solid solution of the MnSe precipitates. More specifically, Se may be further included in an amount of 0.0001 to 0.0200 wt%.

[0062]

[0063] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Sn: 0.1 wt% or less and Sb: 0.1 wt% or less.

[0064] Sn: 0.1 wt% or less

[0065] Tin (Sn) is known as a grain growth inhibitor because it is a grain boundary segregation element that hinders the movement of grain boundaries, and in one embodiment of the present invention, magnetism can be further improved by additionally including Sn. If Sn is added in excess, the grain growth inhibitory power is too strong, so stable secondary recrystallization cannot be obtained. More specifically, Sn may be included in an amount of 0.01 to 0.08 weight%. More specifically, Sn may be included in an amount of 0.03 to 0.07 weight%.

[0066] Sb: 0.1 wt% or less

[0067] Antimony (Sb) can be added as it has the effect of inhibiting grain growth by segregating at grain boundaries and stabilizing secondary recrystallization. However, due to its low melting point, it easily diffuses to the surface during decarburization annealing, i.e., primary recrystallization annealing, thereby hindering decarburization, oxide layer formation, and nitriding. Therefore, since adding Sb above a certain level hinders decarburization and suppresses the formation of the oxide layer that forms the basis of the base coating, there is an upper limit to the content. More specifically, it may contain 0.01 to 0.05 weight% of Sb. More specifically, it may contain 0.02 to 0.05 weight%.

[0068] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.1 wt% or less, Cr: 0.5 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

[0069] P: 0.1000 wt% or less

[0070] Phosphorus (P) can play an auxiliary role by segregating at grain boundaries to hinder grain boundary movement and simultaneously inhibit grain growth, and in terms of microstructure, {110} <001> It has the effect of improving the texture. If the amount of P added is too high, brittleness increases and rolling performance deteriorates significantly. More specifically, it may further contain 0.005 to 0.050 weight% of P. More specifically, it may contain 0.01 to 0.035 weight%.

[0071] Cr: 0.5000 wt% or less

[0072] Chromium (Cr) promotes the formation of hard phases within hot-rolled sheets, resulting in the {110} of the Goss texture during cold rolling. <001> It promotes the formation of and promotes decarburization during the primary recrystallization annealing process, thereby exhibiting the effect of reducing the austenite phase transformation holding time to prevent damage to the texture caused by the prolonged holding time of the austenite phase transformation. Additionally, by promoting the formation of a surface oxide layer during the primary recrystallization annealing process, it can be added to resolve the disadvantage of oxide layer formation being inhibited by Sn and Sb, which are alloying elements used as grain growth aids and inhibitors. If an excessive amount of Cr is added, it promotes the formation of a denser oxide layer during the primary recrystallization annealing process, which can actually lead to inferior oxide layer formation and hinder decarburization and nitriding. More specifically, Cr may be included in an amount of 0.01 to 0.20 weight%. More specifically, it may be included in an amount of 0.03 to 0.10 weight%.

[0073] Ni: 0.05 wt% or less

[0074] Nickel (Ni) is an effective alloying element for increasing the magnetization of iron to improve magnetic flux density, and at the same time, it is an alloying element that reduces iron loss by increasing resistivity. If too much Ni is added, the amount of austenite phase transformation increases, which may have a negative effect on the microstructure, precipitates, and texture. Therefore, when adding Ni, it may be further included in an amount of 0.05 weight% or less. More specifically, it may be further included in an amount of 0.005 to 0.03 weight%.

[0075] Zn: 0.01 wt% or less

[0076] If the content of zinc (Zn) is excessive, it can act as an impurity and impair magnetism. Therefore, Zn may be added within the aforementioned range. More specifically, Zn may be included in an amount of 0.001 to 0.005 weight%.

[0077]

[0078] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

[0079] Titanium (Ti), niobium (Nb), and vanadium (V) have a very strong tendency to form precipitates in steel and can degrade iron loss by forming fine carbides, nitrides, or sulfides inside the base material, thereby suppressing grain growth and domain wall movement. More specifically, it may further include one or more of Ti: 0.0005 to 0.0035 wt%, Nb: 0.0005 to 0.0035 wt%, and V: 0.0005 to 0.0035 wt%.

[0080] A oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Pb: 0.200 wt% or less and Ge: 0.200 wt% or less.

[0081] Pb and Ge

[0082] Lead (Pb) and germanium (Ge) improve magnetic flux density when added. When added appropriately, the aforementioned effects can be obtained, but if included in too much, a large amount of segregation occurs, which may result in inferior magnetic flux density and iron loss. More specifically, the lower limit of each element may be 0.0001 weight%.

[0083] A grain-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Zr: 0.005 wt% or less, and Mg: 0.0050 wt% or less.

[0084] When Mo, B, Ca, Zr, Mg, etc. are added appropriately, the effect of enhancing magnetism can be achieved, but if they are included in large amounts, the magnetism may actually decrease due to suppression of segregation of segregated elements, or the formation of inclusions and sulfides. More specifically, the lower limit of each element may be 0.0001 weight%.

[0085] The remainder contains iron (Fe). Additionally, it may contain unavoidable impurities. Unavoidable impurities refer to impurities that are inevitably incorporated during the steelmaking and manufacturing processes of grain-oriented electrical steel sheets. Since unavoidable impurities are widely known, a detailed description is omitted. In one embodiment of the present invention, the addition of elements other than the aforementioned alloy components is not excluded, and various elements may be included within a scope that does not impair the technical spirit of the present invention. If additional elements are included, they replace the remainder, Fe.

[0086]

[0087] A method for manufacturing a oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: hot rolling a slab to produce a hot-rolled sheet; cold rolling the hot-rolled sheet to produce a cold-rolled sheet; first recrystallization annealing of the cold-rolled sheet; and second recrystallization annealing of the first recrystallized annealed sheet.

[0088] Below, each step is explained in detail.

[0089] First, a hot-rolled steel sheet is manufactured by hot-rolling a slab. Since the alloy composition of the slab has been explained in relation to the alloy composition of oriented electrical steel sheets, a redundant explanation is omitted. Specifically, the slab contains, in weight percent, Si: 1.0 to 5.0%, C: 0.001 to 0.100%, Mn: 0.03 to 0.3%, Cu: 0.001 to 0.3%, As: 0.0005 to 0.01%, and Bi 0.0002 to 0.01%, and the remainder is Fe and unavoidable impurities.

[0090] Returning to the description of the manufacturing method, the step of heating the slab to 1300°C or lower may be further included prior to the step of manufacturing the hot-rolled steel sheet. The slab heating may be performed at a temperature range of 1000 to 1250°C, which is the temperature range where N and S are incompletely dissolved. If N and S are completely dissolved, a large amount of fine nitrides or sulfides precipitate after the annealing of the hot-rolled sheet, making it impossible to perform the subsequent process of one-turn cold rolling, and the primary recrystallization grain size is formed to be considerably fine, making it impossible to form appropriate secondary recrystallization. More specifically, the slab may be heated to 1000 to 1250°C.

[0091] Next, a hot-rolled steel sheet is manufactured by hot-rolling a slab. The step of manufacturing a hot-rolled steel sheet by hot-rolling a slab may include a rough rolling step, a finish rolling step, and a coiling step.

[0092] The rough rolling step may roll the heated slab to a thickness of 50 to 70 mm. In one embodiment, the rough rolling step may be performed in a temperature range of 950 to 1,100 ℃.

[0093] The finishing rolling step may roll the rough-rolled bar to a thickness of 2.0 to 4.0 mm. In one embodiment, the finishing rolling step may be performed in a temperature range of 800 to 1,000 ℃.

[0094] In one embodiment, a hot-rolled steel sheet that has undergone a finishing rolling step can be coiled. In one embodiment, the coiling step can be performed in a temperature range of 600 to 800 ℃. Specifically, the temperature range can be performed in a temperature range of 650 to 750 ℃. If the temperature exceeds the upper limit of the temperature range, the fraction of Goss grains after annealing increases, but cracks on the side edges of the steel sheet increase, which may impair productivity, and there is a problem in that good and stable magnetism cannot be obtained because precipitates and microstructures become coarse. If the temperature exceeds the lower limit of the temperature range, the precipitates and surface grain size are fine, so the fraction of Goss texture may not be obtained appropriately.

[0095] The thickness of the hot-rolled steel sheet may be 1.0 to 4.0 mm. Specifically, the thickness of the hot-rolled steel sheet may be 1.5 to 3.0 mm.

[0096] The hot-rolled sheet may be subjected to hot-rolled annealing as needed, or cold-rolled without hot-rolled annealing. When hot-rolled sheet annealing is performed, in order to make the hot-rolled structure uniform, it may be heated to a temperature of 600 to 1100°C, cracked for an appropriate period of time, and then cooled. More specifically, the hot-rolled sheet may be annealed at 800 to 900°C.

[0097] Next, the hot-rolled plate is cold-rolled to manufacture a cold-rolled plate.

[0098] The step of manufacturing a cold-rolled sheet may involve one cold rolling or two or more cold rollings including intermediate annealing. Specifically, it may consist of a step of cold-rolling a hot-rolled steel sheet once.

[0099] The thickness of the cold-rolled steel sheet should be 0.65 mm or less. Meanwhile, when performing cold rolling, the cold reduction ratio can be 87% or more. This is because the density of the Goss texture increases as the cold reduction ratio increases. However, it is also possible to apply a cold reduction ratio lower than this.

[0100] Next, the cold-rolled sheet is subjected to primary recrystallization annealing. At this time, the primary recrystallization annealing step may include a decarburization step and a nitriding step. The decarburization step and the nitriding step may be performed regardless of the order. That is, the nitriding step may be performed after the decarburization step, the decarburization step may be performed after the nitriding step, or the decarburization step and the nitriding step may be performed simultaneously. In the decarburization step, C may be decarburized to 0.005 wt% or less. More specifically, C may be decarburized to 0.003 wt% or less. During the nitriding process, N may be nitrided to 0.015 wt% or more.

[0101] The cracking temperature of the first recrystallization annealing step may be 840°C to 900°C. Even if the first recrystallization annealing is performed at a temperature lower than 840°C or higher than 900°C, there is no problem in performing the function presented in the present invention.

[0102] The average grain size of the steel sheet subjected to primary recrystallization annealing may be 10 to 30 μm. When a grain size of the primary recrystallization annealing is formed within an appropriate range, uniform secondary recrystallization grains are formed during the secondary recrystallization annealing process, thereby improving magnetism. More specifically, it may be 15 to 25 μm.

[0103] After the first recrystallization annealing step, an annealing separating agent can be applied to the steel plate. Since annealing separating agents are widely known, a detailed explanation is omitted. As an example, an annealing separating agent with MgO as the main component can be used.

[0104]

[0105] Next, the cold-rolled sheet that has undergone primary recrystallization annealing is subjected to secondary recrystallization annealing.

[0106] Broadly speaking, the purpose of secondary recrystallization annealing is {110} due to secondary recrystallization <001> The process involves forming a texture, imparting insulation through the formation of a glassy film by the reaction of the oxide layer formed during the first recrystallization annealing with MgO, and removing impurities that impair magnetic properties. For the second recrystallization annealing method, during the heating phase before the second recrystallization occurs, the material is maintained with a mixed gas of nitrogen and hydrogen to protect the nitride, which acts as a grain growth inhibitor, thereby allowing the second recrystallization to develop well. After the second recrystallization is completed, during the cracking phase, the material is maintained in a 100% hydrogen atmosphere for a long time to remove impurities.

[0107] The secondary recrystallization annealing step can be completed at a temperature of 900 to 1210°C.

[0108] Subsequently, an insulating film can be formed, and flattening annealing can be added.

[0109]

[0110] A grain-oriented electrical steel sheet according to one embodiment of the present invention has particularly excellent iron loss and magnetic flux density characteristics. A grain-oriented electrical steel sheet according to one embodiment of the present invention has a magnetic flux density (B8) of 1.91T or higher and an iron loss (W 17 / 50 ) may be 0.85 W / kg or less. In this case, magnetic flux density B8 is the magnitude of the magnetic flux density induced under a magnetic field of 800 A / m (Tesla), and iron loss W 17 / 50is the magnitude (W / kg) of iron loss induced under conditions of 1.7 Tesla and 50 Hz. More specifically, a oriented electrical steel sheet according to one embodiment of the present invention has a magnetic flux density (B8) of 1.91 to 1.97 T and an iron loss (W 17 / 50 ) can be 0.70 to 0.83 W / kg.

[0111]

[0112] Specific embodiments of the present invention are described below. However, the following embodiments are merely specific examples of the present invention, and the present invention is not limited to the following embodiments.

[0113]

[0114] Examples

[0115] The steel compositions of Tables 1 and 2 below and the remaining components, which contain the remainder Fe and other unavoidably contained impurities, were vacuum-melted to form ingots, then heated to a temperature of 1150°C and hot-rolled to a thickness of 2.3 mm. The hot-rolled sheet was heated to a temperature of 1000°C, held at 1000°C for 120 seconds, and then rapidly cooled in water. Subsequently, the hot-rolled annealed sheet was pickled and cold-rolled to a thickness of 0.23 mm. The cold-rolled steel sheet was then held at a temperature of 850°C for 180 seconds in a mixed gas atmosphere of humid hydrogen and nitrogen to decarburize and perform primary recrystallization annealing to reduce the carbon content to 0.003 wt% or less. After applying MgO, an annealing separator, to this steel sheet, final annealing was performed. Secondary recrystallization annealing was carried out up to 1200°C at a heating rate of 15°C / hour in a mixed gas atmosphere of 25 v% nitrogen and 75 v% hydrogen; upon reaching 1200°C, the temperature was maintained for at least 10 hours in a 100 v% hydrogen gas atmosphere before furnace cooling. Subsequently, after removing unreacted MgO, an insulating coating composition mainly composed of phosphate and silica was applied, followed by heat treatment to form an insulating film, and then planarization annealing was performed. The magnetic properties of the grain-oriented electrical steel sheets according to each component are shown in Table 2. Magnetic flux density was measured using the single sheet measurement method, and magnetic flux density B8 is the magnitude of the magnetic flux density induced under a magnetic field of 800 A / m (Tesla). Iron loss W 17 / 50 is the magnitude of the induced iron loss (W / kg) under conditions of 1.7 Tesla and 50 Hz.

[0116]

[0117] Classification (Weight%) SiCMnCuAsBi13.350.06100.0760.0780.00740.006523.430.05800.1290.1310.00930.002033.410.06300.0720.1100.00110.009843.360.06300.1050. 1040.00250.002453.480.05200.0720.1320.00790.008663.250.05500.0900.0310.00060.004373.360.05900.0870.0800.00680.002283.130.05900.0850.0610 .00120.007793.300.05100.0530.0450.00280.0021103.450.06000.0780.0370.00400.0003113.470.05400.0670.0150.00230.0022123.270.05200.0910.0210. 00100.0022133.350.06200.0600.0590.00030.0019143.320.05700.1020.0700.00040.0015153.470.05300.1240.0810.0018-163.430.06000.1350.0920.0020-

[0118] Classification (Weight%) SAlNSeB8(Tesla)W 17 / 50(W / kg) Remarks 10.009 10.026 0.005 20.009 41.94 0.78 Example 20.008 60.03 0.006 60.006 41.94 0.77 Example 30.008 80.03 10.007 50.009 71.95 0.77 Example 40.006 90.03 10.006 40.006 71.93 0. 80 Example 50.00700.0250.00480.00401.950.76 Example 60.00970.0260.00680.00481.920.83 Example 70.00920.0280.00540.00931.930.79 Example 80.00890.0290.00670.00731.940.80 Example Example 90.004 10.03 00.004 20.0059 1.92 0.81 Example 100.008 20.027 0.006 00.0088 1.91 0.83 Example 110.0068 0.029 0.007 30.0067 1.89 0.88 Comparative Example 120.0096 0.03 00.0055 0.0093 1.89 0.90 Comparative Example 130.008 30.028 0.0049 0.0073 1.900.87 Comparative Example 140.0074 0.026 0.0060 0.00561 900.88 Comparative Example 150.0061 0.027 0.0061 0.0082 1.89 0.89 Comparative Example 160.0072 0.027 0.00560.0052 1.900.87 Comparative Example

[0119] As shown in Tables 1 and 2, it can be confirmed that the examples contain appropriate amounts of Cu, As, and Bi, and thus exhibit excellent magnetic flux density and iron loss. On the other hand, it can be confirmed that the comparative examples, which do not contain appropriate amounts of Cu, As, and Bi, exhibit inferior magnetic flux density and iron loss.

[0120]

[0121] The present invention is not limited to the above embodiments and / or examples but can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments and / or examples described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A grain-oriented electrical steel sheet comprising, in weight%, Si: 1.0 to 5.0%, C: 0.005% or less (excluding 0%), Mn: 0.03 to 0.3%, Cu: 0.030 to 0.3%, As: 0.0005 to 0.01% and Bi 0.0002 to 0.01%, and the remainder being Fe and unavoidable impurities.

2. In Paragraph 1, A grain-oriented electrical steel sheet further comprising one or more of S: 0.020 wt% or less, Al: 0.050 wt% or less, N: 0.020 wt% or less, and Se: 0.050 wt% or less.

3. In Paragraph 1, A grain-oriented electrical steel sheet further comprising one or more of Sn: 0.1 wt% or less and Sb: 0.1 wt% or less.

4. In Paragraph 1, A grain-oriented electrical steel sheet further comprising one or more of Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

5. In Paragraph 1, A grain-oriented electrical steel sheet further comprising one or more of P: 0.1 wt% or less, Cr: 0.5 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

6. In Paragraph 1, A grain-oriented electrical steel sheet further comprising one or more of Pb: 0.200 wt% or less and Ge: 0.200 wt% or less.

7. In Paragraph 1, A grain-oriented electrical steel sheet further comprising one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Zr: 0.005 wt% or less, and Mg: 0.0050 wt% or less.

8. A step of manufacturing a hot-rolled plate by hot-rolling a slab comprising, in weight percent, Si: 1.0 to 5.0%, C: 0.001 to 0.100%, Mn: 0.03 to 0.3%, Cu: 0.001 to 0.3%, As: 0.0005 to 0.01% and Bi 0.0002 to 0.01%, and the remainder being Fe and unavoidable impurities; A step of manufacturing a cold-rolled plate by cold-rolling the above hot-rolled plate; The step of primary recrystallization annealing of the above cold-rolled sheet and A method for manufacturing oriented electrical steel sheets comprising the step of performing a second recrystallization annealing on a steel sheet that has been first recrystallized and annealed.

9. In Paragraph 8, A method for manufacturing a oriented electrical steel sheet, wherein the above slab further comprises one or more of S: 0.001 to 0.020 wt%, Al: 0.001 to 0.050 wt%, N: 0.001 to 0.020 wt%, and Se: 0.001 to 0.050 wt%.

10. In Paragraph 8, A method for manufacturing a oriented electrical steel sheet, wherein the above slab further comprises one or more of Sn: 0.1 wt% or less and Sb: 0.1 wt% or less.

11. In Paragraph 8, A method for manufacturing a oriented electrical steel sheet, wherein the above slab further comprises one or more of Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

12. In Paragraph 8, A method for manufacturing a grain-oriented electrical steel sheet, wherein the above slab further comprises one or more of P: 0.1 wt% or less, Cr: 0.5 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

13. In Paragraph 8, A method for manufacturing a oriented electrical steel sheet, wherein the above slab further comprises one or more of Pb: 0.200 wt% or less and Ge: 0.200 wt% or less.

14. In Paragraph 8, A method for manufacturing a grain-oriented electrical steel sheet, wherein the above slab further comprises one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Zr: 0.005 wt% or less, and Mg: 0.0050 wt% or less.

15. In Paragraph 8, A method for manufacturing a oriented electrical steel sheet, further comprising the step of heating the slab to 1000 to 1250°C prior to the step of manufacturing the hot-rolled sheet.

16. In Paragraph 8, A method for manufacturing a oriented electrical steel sheet, further comprising a hot-rolled sheet annealing step of annealing the hot-rolled sheet at 600 to 1100°C after the step of manufacturing the hot-rolled sheet.

17. In Paragraph 8, A method for manufacturing a oriented electrical steel sheet having an average grain size of 10 to 30 μm of the above primary recrystallized annealed steel sheet.