Non-oriented electrical steel sheet and its manufacturing method

Abstract

Provided are non-oriented electrical steel sheets that are excellent in unidirectional core loss and magnetic flux density, and methods for manufacturing the same. [Solution] The non-oriented electrical steel sheet of the present invention is characterized by the following: by weight % Si: 2.2-4.5%, Mn: 1.0% or less (excluding 0%), Al: 0.020-0.100%, Sn: 0.10-0.30%, As: 0.0005-0.0100%, Bi: 0.0005-0.0150%, C: 0.0050% or less (excluding 0%), S: 0.0030% or less, N: 0.0050% or less, with the balance being Fe and other unavoidable impurities; F{110} is 30% or more, F[Goss] is 20% or more, F{100} is 10% or more, and F[Goss] > F{100} is satisfied; and the crystal grain size in the microstructure is 30-250 μm.

Description

[Technical Field]

[0001] The present invention relates to a non-oriented electrical steel sheet and a manufacturing method thereof, and more particularly to a non-oriented electrical steel sheet having excellent unidirectional core loss and magnetic flux density, and a manufacturing method thereof. [Background technology]

[0002] Non-oriented electrical steel sheets are used as iron core materials in rotating equipment such as motors and generators, and stationary equipment such as small transformers, and play an important role in determining the energy efficiency of electrical equipment. Most motors are typically radial motors, in which magnetic flux flows in the surface direction. For these motors, the magnetic flux changes as the motor rotates, requiring steel sheets with excellent average magnetic properties in all directions parallel to the surface. In contrast, for axial motors, magnetic flux flows in the axial direction, making unidirectional magnetism important. Axial motors have high power density and can be used in motors requiring a high power ratio, such as urban air mobility and in-wheel motors for electric vehicles, which are currently being developed. For these axial motors, excellent unidirectional magnetism is essential.

[0003] Grain-oriented electrical steel sheets, which have excellent unidirectional properties, require a long process and batch-type high-temperature annealing, which increases processing costs, and have large grain sizes of several centimeters. Non-oriented electrical steel sheets are typically manufactured using punching to create complex shapes such as motor cores, and excessively large grain sizes can significantly hinder processability. Grain-oriented electrical steel sheets also have excellent unidirectional magnetic properties, but they have a ceramic coating called forsterite (Mg2SiO4) on their surface. Therefore, die wear is significant during motor punching, making motor processing difficult. Burrs are also common during punching, resulting in significant degradation of motor performance after motor processing, even if the steel sheet has excellent properties.

[0004] Furthermore, only the Goss orientation is properly aligned, and even a slight deviation from the rolling direction on the surface will approach the

[0110] orientation, causing rapid deterioration in magnetic properties. Therefore, there is a need for an electrical steel sheet that has excellent unidirectional magnetic properties, a grain size smaller than the thickness of the steel sheet, can be produced by continuous annealing, and does not have a ceramic coating layer on the surface. In addition, there is a need for an electrical steel sheet that has excellent unidirectional magnetic properties and also has excellent magnetic properties in the circumferential direction of the surface, so there is a need for an electrical steel sheet that contains a lot of Goss orientation and has a grain size smaller than the thickness of the steel sheet, can be produced by continuous annealing, and does not have a ceramic coating layer on the surface. <100> Steel sheets with appropriate orientation are required. In other words, unidirectional properties are important, and when considering the magnetic flux rotation at the corners, the ratio of Goss orientation is high and the steel sheets with appropriate orientation in the surface direction are required. <100> It is necessary to form a texture that contains some degree of orientation.

[0005] Furthermore, because grain-oriented electrical steel sheets require a long high-temperature annealing process, batch annealing is the only option. Typically, after final cold rolling, decarburization annealing, batch high-temperature annealing, and then flattening annealing are required. In other words, because the steel undergoes a lengthy process even after cold rolling, a ceramic coating is formed using an annealing separator, which is necessary during high-temperature annealing. While there are technologies that can remove this ceramic coating, they also have the disadvantage of requiring a long processing line after cold rolling. Therefore, a technology is needed that can complete the process in one step after final cold rolling by applying an insulating coating immediately after annealing via a continuous line.

[0006] The magnetic properties of electrical steel sheets are typically iron loss and magnetic flux density. The lower the iron loss, the higher the magnetic flux density. This is because, when electricity is applied to the iron core to induce a magnetic field, the lower the iron loss, the less energy is lost as heat, and the higher the magnetic flux density, the stronger the magnetic field that can be induced with the same amount of energy.

[0007] To reduce iron loss, alloy elements with high resistivity such as Si, Al, and Mn are added, but although this method reduces iron loss, it also has the problem of reducing saturation magnetic flux density. Furthermore, when the amount of Si added exceeds 4%, workability decreases, making cold rolling difficult and reducing productivity. However, the more Al and Mn are added, the worse the rollability becomes, the higher the hardness becomes, and the worse the workability becomes. To improve the magnetic flux density and core loss, the texture must be improved.

[0008] Patent Document 1 proposes a method of annealing a cold-rolled steel sheet so that selective crystal growth of (100) crystal grains occurs on the surface, and the surface of the annealed sheet has a (100)[0vw] crystal orientation. Hereinafter, crystal orientations are expressed in Miller index. The crystal orientations are expressed as {hkl} <uvw>Or, when expressed as (hkl)[uvw], {hkl} is the plane index of the crystal plane parallel to the surface orientation, <uvw>indicates a crystal direction parallel to the rolling direction. h, k, l, u, v, and w are integers. In the above Patent Document 1, the average crystal grain size y and thickness x of the annealed sheet after final annealing are characterized in that when S is less than 0.007 wt%, the relationship is y≧2.2x+0.1 (unit: mm), and when S is 0.007 wt% or more, the relationship is y≧1.48x+0.04 (unit: mm). In other words, all the crystal grain sizes are larger than the thickness, and the crystal grains are very large, resulting in a structure that penetrates the thickness.

[0009] Patent Document 2 also discloses a (100)[0vw] non-oriented electrical steel sheet with excellent magnetic properties, which contains, by weight, C: more than 0 and 0.005%, Si: 2-4%, Mn: 0.05% or more but less than 1.0%, S: 0.0001-0.035%, Al: more than 0 and 0.20%, P: more than 0 and 0.2%, N: more than 0 and 0.003%, with the remainder being Fe and other unavoidable impurities, and which is characterized in that the average crystal grain size on the sheet surface is equal to or larger than the sheet thickness. That is, Patent Document 2 also suggests that the average crystal grain size is equal to or larger than the sheet thickness.

[0010] Typically, non-oriented electrical steel sheets are manufactured into complex shapes, such as motor cores, by punching, so excessively large grain size significantly impairs workability. The method proposed in Patent Document 2 uses a steel sheet with a chemical composition that adds S as the most important element and exhibits a ferrite structure at all temperatures during the manufacturing process. Furthermore, the segregation of S causes selective crystal growth of (100)[0vw] grains on the surface, eroding other grains and forming a (100)[0vw] texture. To achieve this texture, the grain size must be larger than the thickness. However, there is a limit to how well a steel sheet can achieve excellent unidirectional magnetic properties.

[0011] Meanwhile, Patent Document 3 proposes a method for forming a {100} plane parallel to the surface of a metal sheet. The method includes a heat-treating step of heat-treating the metal sheet at a temperature at which the austenite phase is stabilized while reducing oxygen in at least one of the internal and surface regions of the metal sheet or isolating the metal sheet from external oxygen, and a phase transformation step of transforming the heat-treated metal sheet into a ferrite phase. This method requires vacuum heat treatment, which is difficult to implement industrially because it requires isolation from external oxygen, and requires a long heat treatment time, making it very difficult to achieve industrial success. Furthermore, it is difficult to achieve excellent unidirectional magnetism with this method. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Korean Patent Registration No. 10-1203791 [Patent Document 2] Korean Patent No. 10-1227767 [Patent Document 3] Korean Patent Registration No. 10-0797895 Summary of the Invention [Problem to be solved by the invention]

[0013] The purpose of this invention is to control the alloying elements and process conditions of the steel so that the grain size is smaller than the plate thickness, and to control the texture so that the grains are oriented in the Goss direction and in the direction parallel to the surface without forming a ceramic coating on the surface. <100> The present invention provides a non-oriented electrical steel sheet that can be oriented and produced through a continuous annealing line, and that has excellent iron loss and magnetic flux density in one direction, and a method for manufacturing the same. [Means for solving the problem]

[0014] The non-oriented electrical steel sheet of the present invention is The alloy is characterized by the following composition by weight: Si: 2.2 to 4.5%, Mn: 1.0% or less (excluding 0%), Al: 0.020 to 0.100%, Sn: 0.10 to 0.30%, As: 0.0005 to 0.0100%, Bi: 0.0005 to 0.0150%, C: 0.0050% or less (excluding 0%), S: 0.0030% or less, N: 0.0050% or less, with the remainder being Fe and other unavoidable impurities; F{110}: 30% or more, F[Goss]: 20% or more, F{100}: 10% or more, and satisfying F[Goss]>F{100}; and the crystal grain size within the microstructure is 30 to 250 μm. Here, F{110} means the volume fraction of crystal grains whose {110} plane forms an angle of 15° or less with the steel sheet surface, F[Goss] means the volume fraction of crystal grains whose angle with the Goss orientation is 15° or less, and F{100} means the volume fraction of crystal grains whose {100} plane forms an angle of 15° or less with the steel sheet surface.

[0015] The non-oriented electrical steel sheet has a {001} <001> The volume fraction of crystal grains having an orientation deviated by 15° or less from the orientation can be 8% or more. The above non-oriented electrical steel sheet has a B 50 / B s It is desirable to satisfy ≧0.870. 50 means the magnitude (Tesla) of the magnetic flux density induced when a magnetic field of 5000 A / m is applied, and B S is the saturation magnetic flux density value. The above non-oriented electrical steel sheets have a B average value in the rolling direction and the direction perpendicular to the rolling direction. 50 / B s It is preferable that ≧0.855 is satisfied. The non-oriented electrical steel sheet can satisfy the iron loss requirement of 1.76 W / kg or less in the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz. The non-oriented electrical steel sheet may further contain Cu: 0.015% or less.

[0016] Further, the method for producing a non-oriented electrical steel sheet of the present invention comprises the steps of: The method includes the steps of providing a slab containing the above-mentioned compositional components, reheating the slab to 1050 to 1180 ° C. and then rolling it to produce a hot-rolled steel sheet, cold-rolling the hot-rolled steel sheet and then hot-rolling it, or annealing the hot-rolled steel sheet without cold rolling, cold-rolling the hot-rolled annealed steel sheet to produce a cold-rolled steel sheet, and final-annealing the cold-rolled steel sheet, During cold rolling of the annealed steel sheet, the reduction is controlled to a range of 50 to 85%, The method is characterized in that the rate of temperature rise in the region of 300 to 850°C during the final annealing is controlled to 30°C / s or more, and the coil state is annealed not in a batchwise manner but in a continuous manner.

[0017] The temperature during the final annealing is preferably 900 to 1150°C. The final annealing time can be 30 to 600 seconds. The hot-rolled sheet annealing can be carried out at 900 to 1150°C. In addition, the atmosphere during the final annealing contains hydrogen, and the oxidation degree is P H2 / P H2O It is preferable that the value satisfies ≦0.015.

[0018] In the manufacturing method, the steel sheet after final annealing preferably has an F{110} of 30% or more, an F[Goss] of 20% or more, an F{100} of 10% or more, and F[Goss] > F{100}, while the grain size in the microstructure is 30 to 250 μm. Here, F{110} means the volume fraction of grains whose {110} plane forms an angle of 15° or less with the steel sheet surface, F[Goss] means the volume fraction of grains whose angle with the Goss orientation is 15° or less, and F{100} means the volume fraction of grains whose {100} plane forms an angle of 15° or less with the steel sheet surface. [Effects of the Invention]

[0019] The non-oriented electrical steel sheet according to the present invention can improve the texture and grow the {001} orientation along with the Goss orientation by appropriately controlling the contents of Si, Mn, Al, Sn, and As among the alloying elements added to the steel and by optimally managing the cold rolling reduction and final annealing conditions. Furthermore, by preventing nitriding due to segregation of Sn and As, it is possible to solve the problem of deterioration of magnetic properties due to the Al content or nitrogen atmosphere in the atmosphere, even though the alloy contains a portion of Al. Furthermore, since this technology is not related to grain-oriented electrical steel sheets, there is no need to use an annealing separator to form an Mg2SiO4 film on the steel sheet surface. Therefore, the non-oriented electrical steel sheet according to the present invention has low iron loss in the rolling direction (W 15 / 50 ) is 1.76 W / Kg or less, making it possible to provide a non-oriented electrical steel sheet with excellent core loss and dramatically improved magnetic properties. DETAILED DESCRIPTION OF THE INVENTION

[0020] The advantages and features of the present invention, as well as the manner in which they are achieved, will become apparent from the following detailed description of the embodiments. Iron loss in electrical steel sheets is generally divided into hysteresis loss, eddy current loss, and anomalous eddy current loss. Iron loss measured at 1.5T and 50Hz varies depending on the grade, but in the case of the highest quality materials, the proportion of hysteresis loss is very high. In the case of a 0.35 mm thick magnetic steel sheet with an iron loss of approximately 2.1 W / kg, when the iron loss is separated, the hysteresis loss accounts for approximately 70-75% of the iron loss. The crystal orientation, precipitates, and impurities have a significant impact on the hysteresis loss. From this perspective, texture control and precipitate control are extremely important in order to improve this hysteresis loss.

[0021] In the case of axial motors, the iron loss and magnetic flux density in one direction are important. Therefore, if the proportion of Goss orientation, which has superior iron loss in one direction compared to existing non-oriented electrical steel sheets, is increased, iron loss and magnetic flux density in the rolling direction can be improved. <001> ) is formed most frequently, and the direction perpendicular to the surface is <100> The Cube orientation ({100}) has excellent magnetic properties in the RD direction. <001> When a large amount of ) is formed, the magnetic properties in the rolling direction are excellent and significant deterioration of the magnetic properties in the direction perpendicular to the rolling direction can be prevented.

[0022] Therefore, in order to simultaneously form the Goss and Cube orientations, the present invention appropriately controls the crystal orientation by appropriately utilizing the segregation elements Sn and As, and appropriately controls the final cold rolling reduction. Furthermore, while the segregation element Sn has been known as an element for controlling texture, the present invention also adds As to maximize its effect, and through various experiments, a method for forming both the Goss and Cube orientations has been derived. In other words, in the present invention, in order to achieve excellent properties in one direction, the Goss and {100} <001> The formation of the {100}<0uv> orientation other than the {100} orientation is reduced. <001> Forming a direction RD / / <001> Improved orientation.

[0023] The non-oriented electrical steel sheet of the present invention contains, by weight, 2.2 to 4.5% Si, 1.0% or less (excluding 0%) Mn, 0.020 to 0.100% Al, 0.10 to 0.30% Sn, 0.0005 to 0.0100% As, 0.0005 to 0.0150% Bi, 0.0050% or less C (excluding 0%), 0.0030% or less S, 0.0050% or less N, and the remainder being Fe and other unavoidable impurities, and has an F{110} of 30% or more, an F[Goss] of 20% or more, an F{100} of 10% or more, and F[Goss] > F{100}, while the crystal grain size in the microstructure is 30 to 250 μm. Here, F{110} means the volume fraction of crystal grains whose {110} plane forms an angle of 15° or less with the steel sheet surface, F[Goss] means the volume fraction of crystal grains whose angle with the Goss orientation is 15° or less, and F{100} means the volume fraction of crystal grains whose {100} plane forms an angle of 15° or less with the steel sheet surface. The chemical composition of the steel of the non-oriented electrical steel sheet of the present invention and the reasons for limiting its content will be explained below, where "%" means % by weight unless otherwise specified.

[0024] Sn: 0.10 to 0.30% The Sn element acts as a grain boundary segregating element, suppressing the diffusion of nitrogen through the grain boundaries, suppressing the formation of {111} and {112} textures that are harmful to magnetic properties, and increasing {100} and {110} textures that are advantageous to magnetic properties, thereby improving magnetic properties. Addition of 0.10% or more is required. However, if the addition amount exceeds 0.30%, it may suppress grain growth, reducing magnetic properties, deteriorating rollability, and even deteriorating adhesion. Therefore, in the present invention, it is preferable to control the addition amount of Sn to a range of 0.10 to 0.30%.

[0025] As: 0.0005 to 0.0100% The above-mentioned As plays a role as an auxiliary element that enhances the effect of Sn. As a segregation element, it has the effect of controlling the {111} texture, and when added simultaneously with Sn, it is an element that can maximize the effect of the Sn addition, and an addition of 0.0005% or more is required. However, if added in excess, coating adhesion deteriorates, so in the present invention, it is preferable to control the addition amount of the above-mentioned As to 0.0005 to 0.0100%.

[0026] Bi: 0.0005 to 0.0150% Bi also has the effect of increasing the Goss orientation by segregating at grain boundaries, but if the content is too low, this effect is reduced, while if the content is too high, there is a risk of deterioration in rollability and coating adhesion. Therefore, in the present invention, it is preferable to control the Bi content to 0.0005 to 0.0150%.

[0027] On the other hand, in the present invention, when the above Sn, As, and Bi are added simultaneously, the rolling direction <001> This is advantageous for simultaneously forming the Goss orientation and the Cube orientation parallel to the orientation, and the simultaneous formation of the Goss and Cube orientations prevents the crystal grain size from growing excessively, which is advantageous for motor processability.

[0028] Si: 2.2 to 4.5% Si is an element that increases resistivity and reduces eddy current loss in iron loss. However, if there is an excess amount, there is a risk of plate breakage. Therefore, in the present invention, it is preferable to add Si in an amount of 4.5% or less. In the present invention, the composition in which no solid-state phase transformation occurs over the entire temperature range is used as the standard, so it is preferable to add 2.2% or more of Si.

[0029] Mn: 1.0% or less (excluding 0%) As the amount of Mn added increases, the saturation magnetic flux density decreases. Since Mn is an austenite-forming element, it is preferable not to add it in order to satisfy the range in which solid-state phase transformation does not occur. However, if the Si content is high, even if the manganese content is high, austenite will not be formed and the Mn content may increase. Furthermore, adding excessive Mn can partially deteriorate the texture, so it is best not to add too much. Mn has the effect of increasing resistivity and can improve iron loss, so it is preferable to add some Mn. However, it is preferable to control the amount of Mn added to 1.0% or less within the range in which austenite is not formed, excluding 0%.

[0030] Al: 0.020 to 0.100% Al is an element that increases resistivity and reduces eddy current loss, but increasing the Al content changes the texture. Furthermore, Al oxides are distributed on the surface, and Al nitrides have a negative effect on magnetic properties and subsequently reduce coating adhesion. Therefore, to maximize the texture-improving effects of Sn and Sb, the Al content should be 0.100% or less. If Al is added too little, it reacts with the trace amounts of N contained in the steel to form very fine AlN, which reduces magnetic properties. Therefore, it is recommended to add 0.020% or more of Al.

[0031] C: 0.0050% or less C combines with Ti, Nb, V, etc. to form carbides, which degrades magnetism. If this is used in the final product after processing into electrical appliances, it increases iron loss due to magnetic aging, reducing the efficiency of electrical equipment, so it is controlled to 0.0050% or less. The non-oriented electrical steel sheet of the present invention may also contain Cu, S, and N, which may be added in amounts of Cu: 0.015% or less, S: 0.0030% or less, and N: 0.0050% or less.

[0032] It is preferable not to add N because it forms fine and long AlN precipitates and inhibits the growth of crystal grains. However, taking into consideration the amount that is inevitably added in the steelmaking process, it is preferable to add 0.0050% or less, more preferably 0.0020% or less.

[0033] S forms fine precipitates, MnS and CuS, which inhibit the growth of crystal grains and deteriorate the magnetic properties, so it is preferable that it is not added. However, taking into consideration the amount that is inevitably added in the steelmaking process, it is preferable that S be added in an amount of 0.0030% or less, and more preferably 0.0010% or less.

[0034] Cu reacts with impurity elements added during the steelmaking process to form fine sulfides, carbides and nitrides, which have a detrimental effect on magnetic properties, so it is preferable to control the content to 0.015% or less.

[0035] The remaining components are Fe and inevitable impurities. The electrical steel sheet of the present invention does not exclude the addition of other component elements. The inevitable impurities mentioned above cannot be excluded because they may be unintentionally mixed in from raw materials or the surrounding environment during the normal steel manufacturing process. The meaning of the inevitable impurities mentioned above would be understood by a person skilled in the field of normal steel manufacturing.

[0036] The non-oriented electrical steel sheet of the present invention preferably has an F{110} of 30% or more, an F[Goss] of 20% or more, an F{100} of 10% or more, and satisfies F[Goss]>F{100}, while the grain size in the microstructure is 30 to 250 μm, where F{110} is the volume fraction of grains whose {110} plane forms an angle of 15° or less with the steel sheet surface, F[Goss] is the volume fraction of grains whose angle with the Goss orientation is 15° or less, and F{100} is the volume fraction of grains whose {100} plane forms an angle of 15° or less with the steel sheet surface.

[0037] Generally, when the RD direction is used as the reference, the best direction for magnetism is <100> direction, then <110> , and finally <111> is the worst for magnetism. Generally, when the Si content is increased, the decrease in the saturation magnetic flux value due to Si can be expressed by the following relational expression 1. [Equation 1] B s [T]=2.1561-0.0413×[Si%]-0.0198×[Mn%]-0.0604×[Al%] Here, the content of each element is in weight percent. In addition, <112> The orientation develops so strongly that the magnetic flux density becomes much worse than the value to which the saturation magnetic flux density has fallen.

[0038] Non-oriented electrical steel sheets have a surface orientation <100> When the magnetic fields are uniformly arranged, they have ideal magnetic properties. <112> When the orientation is too strong, the magnetic properties become very poor. In addition, in non-oriented electrical steel sheets with a high Si content that do not undergo phase transformation, the volume fraction of crystal grains with an angle of 15° or less between the {112} plane and the rolling surface is considered to be even more abundant than those with the {111} orientation.

[0039] As mentioned above, the present invention seeks to achieve superior unidirectional magnetism to be more advantageous for use in axial motors than steel sheets that have uniformly excellent magnetism in the surface direction, which is required for general non-oriented electrical steel sheets.To achieve this, it is necessary to simultaneously form the Goss orientation and the Cube orientation. Therefore, in the present invention, Sn, As, and Bi are added to the chemical composition, and the cold rolling reduction and final annealing conditions are optimally controlled to improve the texture, so that F{110} is 30% or more, F[Goss] is 20% or more, and F{100} is 10% or more.

[0040] In the present invention, the non-oriented electrical steel sheet has a {001} <001> It is preferable that the volume fraction of crystal grains having an orientation deviated by 15° or less from the orientation satisfies 8% or more. Furthermore, the non-oriented electrical steel sheet can satisfy the iron loss requirement of 1.76 W / kg or less in the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz. The non-oriented electrical steel sheet can have an average crystal grain size in the microstructure of 30 to 150 μm.

[0041] Conventional non-oriented electrical steel sheets containing approximately 3.2% Si and 30 ppm or less of C and S each have an F{110} of approximately 7%, an F[Goss] of approximately 1.5%, and an F{100} of approximately 16%, of which the F[Cube] is only approximately 2.7%. In contrast, the non-oriented electrical steel sheets of the present invention, which contain 0.1% or more Sn, As, and Bi, have an F{110} of 41%, an F[Goss] of 23%, and even up to 37%, and can achieve an F[Cube] of approximately 8% or more. This significantly improves the rolling direction magnetic flux density, and under certain conditions, even steel sheets containing 3% or more Si can often achieve a value of 1.80 W / kg or more.

[0042] In addition, the electrical steel sheet of the present invention has a B content in the rolling direction by adjusting the steel composition and controlling the atmosphere during final annealing. 50 / B S ≧0.870. 50 means the magnitude (Tesla) of the magnetic flux density induced when a magnetic field of 5000 A / m is applied, and B S is the saturation magnetic flux density value. In addition, the non-oriented electrical steel sheet of the present invention has a B average value in the rolling direction and the direction perpendicular to the rolling direction. 50 / B S ≧0.855 can be satisfied.

[0043] Only by dividing the magnetic flux density by the saturation magnetic flux density according to the Si content can the degree of texture formation advantageous for magnetic properties be evaluated through process improvement. In other words, even if a high magnetic flux density is obtained with a low silicon content, the iron loss characteristics are significantly deteriorated, and therefore the degree of texture formation with excellent magnetic properties, low iron loss and high magnetic flux density, is limited by B. 50 / B S It must be evaluated by value.

[0044] In addition, the electrical steel sheet of the present invention, together with Goss, has a {100} orientation, particularly {100} <001> The orientation is strongly developed, and in this case, the characteristics in the R direction are very good. Next, a method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention will be described in detail.

[0045] The method for producing a non-oriented electrical steel sheet of the present invention includes the steps of providing a slab containing the above-described compositional components, reheating the slab to 1050 to 1180°C and rolling it to produce a hot-rolled steel sheet, cold-rolling the hot-rolled steel sheet and then hot-rolling it, or annealing it without cold rolling, cold-rolling the annealed steel sheet to produce a cold-rolled steel sheet, and final-annealing the cold-rolled steel sheet, wherein the reduction during cold-rolling of the hot-rolled-annealed steel sheet is controlled to a range of 50 to 85%, and the heating rate during final annealing is controlled to 30°C / s or more in a range including 300 to 850°C, and the annealing is performed continuously rather than batchwise in a coil state.

[0046] First, the present invention provides a slab having the above-mentioned compositional components. A slab having such a compositional component range may not form an austenite phase in the solid-state temperature range. The slab is then reheated to 1050 to 1180°C and rolled to produce a hot-rolled steel sheet. 15 / 50 The iron loss (measured at 1.5 T, 50 Hz) is a large hysteresis loss, which is largely influenced by the texture and fine precipitates. Therefore, in the present invention, it is necessary to control the slab reheating temperature, which will be described later, along with a composition that can reduce the formation of fine precipitates in the composition. If the reheating temperature exceeds 1180°C, there is a problem that precipitates redissolve in the slab and then precipitate finely. If the reheating temperature is less than 1050°C, hot rolling may become difficult.

[0047] The reheated slab is hot rolled to produce a hot rolled steel sheet. Next, in the present invention, the hot-rolled steel sheet is cold-rolled and then annealed, or the hot-rolled steel sheet is annealed without cold rolling. That is, the hot-rolled steel sheet is annealed, but in the present invention, since the final cold reduction is important, partial cold rolling can be performed before the hot-rolled steel sheet annealing to match the final cold reduction after annealing. Depending on the hot-rolled thickness, the hot-rolled steel sheet is cold-rolled, or if the hot-rolled thickness satisfies the final cold reduction, the hot-rolled steel sheet can be annealed immediately without cold rolling.

[0048] The hot-rolled sheet annealing conditions are preferably 900 to 1150° C. In the present invention, the Sn content is high and grain growth is suppressed, so if the temperature during hot-rolled sheet annealing is less than 900° C., the raw steel will contain excessive Sn, resulting in reduced grain growth, and if the temperature exceeds 1150° C., surface defects may occur, so it is preferable to control the hot-rolled sheet annealing temperature in this manner. Then, the hot-rolled steel sheet that has been subjected to the above-mentioned hot-rolled sheet annealing can be subjected to pickling. In the present invention, the annealed hot-rolled sheet is cold-rolled, preferably with a cold reduction of 50 to 85%. If the cold reduction is too low, productivity during intermediate annealing becomes very poor and Goss orientation does not develop. If the cold reduction is too high, the {111} <112> 50-85% is preferable as this will strengthen the development of orientation. More preferably, it is 55 to 83%, which is advantageous for simultaneously forming the Goss orientation and the Cube orientation.

[0049] Next, in the present invention, the cold-rolled steel sheet produced by the above-mentioned cold rolling is subjected to final annealing, and the temperature rise rate in the temperature range of 300 to 850°C during the final annealing is controlled to be 30°C / s or more, and the steel sheet is annealed in a continuous manner instead of batchwise in a coil state. The temperature rise rate in the temperature range of 300 to 850°C during the final annealing is 30°C / s or more, and the annealing soaking temperature is preferably 950 to 1150°C, more preferably 970 to 1050°C.

[0050] In the present invention, in order to suppress the formation of the {111} and {112} orientations and to grow the Goss and Cube orientations in the composition system, the appropriate contents of Sn, Bi, and As, the appropriate cold rolling reduction, and the heating rate are very important. This is because increasing the heating rate suppresses the growth of the {111} and {112} orientations and favors the growth of the {100} orientation. Furthermore, the heating rate in the range of 300 to 850°C, where recovery and recrystallization occur, is particularly important. However, when the heating rate is 30°C / s or higher, the growth of the {100} orientation was observed.

[0051] In one embodiment of the present invention, since the Sn content is high and grain growth is suppressed, the final annealing is preferably performed at a temperature of 900° C. or higher, more preferably 950° C. or higher. In the present invention, the coiled steel is annealed not in a batchwise manner but in a continuous manner. In order to prevent abnormal grain growth, final annealing is preferably carried out at 1150°C or less, more preferably at 1050°C or less. The final annealing time is preferably 30 to 600 seconds, but if it is less than 30 seconds, the high S content in the present invention will cause segregation at the grain boundaries, hindering grain growth and reducing the grain size, while if it exceeds 600 seconds, continuous annealing may become difficult. Furthermore, a shorter annealing time is more economical, so from the viewpoint of improving economic efficiency, the annealing time is preferably 30 to 600 seconds.

[0052] The atmosphere during the final annealing contains hydrogen, and the oxidation degree is P H2 / P H2O Preferably, P is ≦0.015. H2 is the partial pressure of hydrogen, and P H2O means the partial pressure of water vapor. Furthermore, the hydrogen partial pressure in the mixed gas during the final annealing is not limited, but is more preferably 51 vol % or more.

[0053] On the other hand, because hydrogen is present during the final annealing, most of the Fe-based oxides on the surface are reduced, and some of the Al is oxidized or nitrided. Depending on the degree of oxidation, either an internal oxide layer is formed or Al-based oxides are formed on the surface. Furthermore, the presence of Al nitrides on the surface deteriorates core loss and adhesion. To prevent this, in the present invention, the Al content is reduced, and the oxidation degree of the atmosphere in the final annealing is reduced to P. H2 / P H2O It is preferable to control the oxidation degree P to ≦0.015. H2 / P H2O If the value exceeds 0.015, excessive Sn will segregate below the surface oxide layer, resulting in poor adhesion. In addition, to improve adhesion and surface, the degree of oxidation is H2 / P H2O It is more preferable to control it to ≦0.008. [Example]

[0054] Hereinafter, the method for manufacturing a non-oriented electrical steel sheet according to the present invention will be described in detail with reference to examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited to the following examples.

[0055] Example 1 A slab containing, by weight, 0.0025% C, 0.1% Mn, 0.035% Al, Si, Sn, As, and Bi as shown in Table 1 below, with the remainder being Fe and other unavoidable impurities, was prepared. This slab was reheated to 1150°C and hot-rolled to a thickness of 1.8 mm to produce a hot-rolled steel sheet. Thereafter, after finish-rolling to a thickness of 0.8 mm, the finish-hot-rolled steel sheet was hot-rolled at 1050°C for 50 seconds, then slowly cooled to 750°C and air-cooled. The air-cooled steel sheet was then pickled and cold-rolled to a thickness of 0.27 mm. Subsequently, the cold-rolled steel sheet was oxidized in an atmosphere of 95% hydrogen, 5% nitrogen, and a dew point of -25°C (at which time, the oxidation degree P H2 / P H20 The value was 0.00076) and final annealing was carried out at 1020°C for 300 seconds to produce electrical steel sheets. At this time, the heating rate up to 850°C was as shown in Table 1 below.

[0056] The magnetic properties of the electrical steel sheets manufactured in this manner were measured, and measurements were taken in the rolling direction and in the direction perpendicular to the rolling direction. These were expressed as the measured value in the rolling direction and the average of the two values, and the results are shown in Table 2 below. The texture was then measured by EBSD to calculate the orientation fraction, and the results are also shown in Table 2 below. Meanwhile, in Table 2 below, the iron loss W 15 / 50 is the average iron loss in the direction perpendicular to the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz, and its unit is W / kg.

[0057] [Table 1]

[0058] [Table 2] *In Table 2, A* is the magnetic flux density in the rolling direction B 50 , B* is the iron loss in the rolling direction W 15 / 50 , C* is the average magnetic flux density B in the rolling direction and perpendicular to the rolling direction 50 , D* is the rolling direction B 50 / B S , E* is the rolling direction and the direction perpendicular to the rolling direction B 50 / B S , F* is F{110}, G* is F[Goss](%), H* is F{100}(%), I* is F{111}(%), and J* is {100} <001> Show the fraction.

[0059] As shown in Tables 1 and 2, when the Si content is 2.2% or more and the Sn content is controlled appropriately without solid-state phase transformation, the {111} orientation decreases and the Goss orientation increases significantly. In addition, the {100} orientation increases, and in particular, the {100} orientation increases. <001> It can be seen that the values ​​are high, and it can be confirmed that the magnetic flux density and iron loss in the rolling direction are improved.

[0060] Example 2 A slab containing, by weight, 0.0021% C, 0.12% Mn, 0.032% Al, Si, Sn, As, and Bi as shown in Table 3 below, with the remainder being Fe and other unavoidable impurities, was prepared. This slab was reheated to 1150°C and hot-rolled to a thickness of 1.8 mm to produce a hot-rolled steel sheet. After finish-rolling to a thickness of 1.0 mm, the finish-hot-rolled steel sheet was hot-rolled at 1050°C for 50 seconds, then slowly cooled to 750°C, and air-cooled. The air-cooled steel sheet was pickled and then cold-rolled to a thickness of 0.30 mm. The cold-rolled steel sheet was then oxidized in an atmosphere of 95% hydrogen, 5% nitrogen, and a dew point of -25°C (at which point the oxidation degree P H2 / P H20 The value was 0.00076) and final annealing was performed at 980°C for 300 seconds to produce electrical steel sheets. The heating rate up to 850°C was as shown in Table 3 below.

[0061] The magnetic properties of the electrical steel sheets manufactured in this manner were measured, and measurements were taken in the rolling direction and in the direction perpendicular to the rolling direction. These were expressed as the average of the two values ​​and the measured value in the rolling direction, and the results are shown in Table 4 below. The texture was then measured by EBSD to calculate the orientation fraction, and the results are also shown in Table 4 below. Meanwhile, in Table 4 below, the iron loss W 15 / 50 is the average iron loss in the direction perpendicular to the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz, and its unit is W / kg.

[0062] [Table 3]

[0063] [Table 4] *In Table 4, A* is the magnetic flux density in the rolling direction B 50 , B* is the iron loss in the rolling direction W 15 / 50 , C* is the average magnetic flux density B in the rolling direction and perpendicular to the rolling direction 50 , D* is the rolling direction B 50 / B S , E* is the rolling direction and the direction perpendicular to the rolling direction B 50 / B S , F* is F{110}, G* is F[Goss](%), H* is F{100}(%), I* is F{111}(%), and J* is {100} <001> Show the fraction.

[0064] As shown in Tables 3 and 4, the addition of As and Bi increases the Goss orientation and improves the magnetic flux density and iron loss in the rolling direction. However, it can be seen that adding these elements in excess is undesirable as it results in poor adhesion.

[0065] Example 3 A slab was prepared, containing, by weight, 0.0029% C, 3.3% Si, 0.1% Mn, 0.16% Sn, 0.0043% As, 0.0032% Bi, and the remainder being Fe and other unavoidable impurities, with Al and Cu controlled as shown in Table 5 below. This slab was reheated to 1150°C and hot-rolled to a thickness of 1.8 mm to produce a hot-rolled steel sheet. Thereafter, the slab was finish-rolled to a thickness of 0.8 mm, and the finish-hot-rolled steel sheet was hot-rolled at 1050°C, then slowly cooled to 750°C, and then air-cooled. The air-cooled steel sheet was pickled and then cold-rolled to a thickness of 0.30 mm. Subsequently, the cold-rolled steel sheet was oxidized in an atmosphere of 95% hydrogen, 5% nitrogen, and a dew point of -25°C (at this time, the oxidation degree P H2 / P H20 The value was 0.00076) and final annealing was carried out at 1,040°C for 300 seconds to produce electrical steel sheets. At this time, the heating rate up to 850°C was as shown in Table 5 below.

[0066] The magnetic properties of the electrical steel sheets manufactured in this manner were measured, and measurements were taken in the rolling direction and in the direction perpendicular to the rolling direction. These were then expressed as the average of the two values, and the results are shown in Table 6 below. The texture was then measured by EBSD to calculate the orientation fraction, and the results are also shown in Table 6 below. Meanwhile, in Table 6 below, the iron loss W 15 / 50 is the average iron loss in the direction perpendicular to the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz, and its unit is W / kg.

[0067] [Table 5]

[0068] [Table 6] *In Table 6, A* is the magnetic flux density in the rolling direction B 50 , B* is the iron loss in the rolling direction W 15 / 50 , C* is the average magnetic flux density B in the rolling direction and perpendicular to the rolling direction 50 , D* is the rolling direction B 50 / B S , E* is the difference between the rolling direction and the direction perpendicular to the rolling direction 50 / B S , F* is F{110}, G* is F[Goss](%), H* is F{100}(%), I* is F{111}(%), and J* is {100} <001> Show the fraction.

[0069] As shown in Tables 5 and 6 above, when the Al and Cu contents are changed in a composition system that does not undergo solid-state phase transformation, the magnetic flux density of iron loss changes depending on the Al content. If the Al content is too low, fine AlN precipitates, resulting in poor iron loss, and if the Al content is too high, the rollability becomes poor. Furthermore, if Cu is added in excess, deterioration in iron loss occurs due to the formation of CuS, so it can be confirmed that it is preferable not to add excessive Cu.

[0070] Example 4 Slabs containing, by weight, 0.0029% C, 3.3% Si, 0.1% Mn, 0.03% Al, 0.16% Sn, 0.0043% As, 0.0032% Bi, and 0.01% Cu, with the C, N, and S contents controlled as shown in Table 7 below, were prepared. These slabs were reheated to 1150°C and hot-rolled to a thickness of 1.8 mm to produce hot-rolled steel sheets. After finish-rolling to a thickness of 0.8 mm, the finish-hot-rolled steel sheets were hot-rolled at 1050°C and then slowly cooled to 750°C and air-cooled. The air-cooled steel sheets were pickled and then cold-rolled to a thickness of 0.30 mm. The cold-rolled steel sheets were then oxidized in an atmosphere of 95% hydrogen and 5% nitrogen with a dew point of -25°C (at which point the oxidation degree P H2 / P H20 The value was 0.00076) and final annealing was performed at 980°C for 300 seconds to produce electrical steel sheets. The heating rate up to 850°C was as shown in Table 7 below.

[0071] The magnetic properties of the electrical steel sheets manufactured in this manner were measured, and measurements were taken in the rolling direction and in the direction perpendicular to the rolling direction. These were then expressed as the average of the two values, along with the measurement value in the rolling direction, and the results are further shown in Table 7 below. The average grain size calculated by determining the area of ​​the grains was used as the grain size. Measurements were carried out in the following order: measuring the number of grains (boundary calculated at 0.5) → calculating the average area of ​​the grains → calculating the grain size (d = √(average area of ​​the grains)). Meanwhile, in Table 7 below, iron loss W 15 / 50 is the average iron loss in the direction perpendicular to the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz, and its unit is W / kg.

[0072] [Table 7] *In Table 7, A* is the magnetic flux density in the rolling direction B 50 , B* is the iron loss in the rolling direction W 15 / 50 , C* is the average magnetic flux density B in the rolling direction and perpendicular to the rolling direction 50 , D* is the rolling direction B 50 / B S , and E* is the average magnetic flux density B in the rolling direction and perpendicular to the rolling direction. 50 / B S Shows.

[0073] As shown in Table 7 above, when the contents of C, S, and N increase without solid-state phase transformation, It can be seen that not only the crystal grain size cannot grow, but also the magnetic domain movement is hindered, resulting in poor core loss and magnetic flux density.

[0074] Example 5 Slabs containing, by weight, 0.002% C, 3.25% Si, 0.037% Al, 0.19% Sn, 0.1% Mn, 0.0015% N, 0.0017% S, 0.0034% As, 0.0025% Bi, and 0.007% Cu, with the remainder being Fe and other unavoidable impurities, were prepared. These slabs were reheated to 1150°C and hot-rolled to a thickness of 2.3 mm to produce hot-rolled steel sheets. One of the hot-rolled steel sheets was then hot-rolled at 1050°C without intermediate cold rolling, while the other hot-rolled steel sheet was cold-rolled to a thickness of 0.7 mm, hot-rolled at 1050°C, and subsequently slowly cooled to 750°C and air-cooled. The air-cooled steel sheet was pickled and then final cold-rolled to a thickness of 0.30 mm. The cold-rolled steel sheet was then final-annealed under the conditions shown in Table 8 below to produce an electrical steel sheet.

[0075] The magnetic properties of the electrical steel sheets manufactured in this manner were measured, and measurements were taken in the rolling direction and in the direction perpendicular to the rolling direction. These were then expressed as the average of the two values, and the results are shown in Table 9 below. The texture was then measured by EBSD to calculate the orientation fraction, and the results are also shown in Table 9 below. Meanwhile, in Table 9 below, the iron loss W 15 / 50 is the average iron loss in the direction perpendicular to the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz, and its unit is W / kg.

[0076] [Table 8]

[0077] [Table 9] *In Table 9, A* is the magnetic flux density in the rolling direction B 50 , B* is the iron loss in the rolling direction W 15 / 50 , C* is the average magnetic flux density B in the rolling direction and perpendicular to the rolling direction 50 , D* is the rolling direction B 50 / B S , F* is F{110}, G* is F[Goss](%), H* is F{100}(%), I* is F{111}(%), and J* is {100} <001> Show the fraction.

[0078] As shown in Tables 8 and 9, when the final annealing conditions are within the ranges of the present invention, the iron loss and magnetic flux density are excellent. That is, when the annealing temperature, heating rate, and annealing time are within the ranges of the present invention, the iron loss and magnetic flux density in one direction are good, and the overall magnetic properties are also excellent. A low final cold rolling reduction is advantageous for the growth of Goss orientation, but if it is too low, the productivity during annealing will be excessively low and it may be disadvantageous for the formation of texture.

[0079] As described above, the detailed description of the present invention has been given with reference to the preferred embodiment of the present invention, but it goes without saying that a person skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiment, but should be determined by the following claims and their equivalents.< / uvw> < / uvw>

Claims

1. A non-oriented electrical steel sheet comprising, by weight, 2.2 to 4.5% Si, 1.0% or less (not including 0%) Mn, 0.020 to 0.100% Al, 0.10 to 0.30% Sn, 0.0005 to 0.0100% As, 0.0005 to 0.0150% Bi, 0.0050% or less C (not including 0%), 0.0030% or less S, 0.0050% or less N, with the balance being Fe and other inevitable impurities, and having F{110} of 30% or more, F[Goss] of 20% or more, F{100} of 10% or more, and satisfying the relationship F[Goss] > F{100}, and having a crystal grain size of 30 to 250 μm in the microstructure. Here, F{110} means the volume fraction of crystal grains whose {110} plane forms an angle of 15° or less with the steel sheet surface, F[Goss] means the volume fraction of crystal grains whose angle with the Goss orientation is 15° or less, and F{100} means the volume fraction of crystal grains whose {100} plane forms an angle of 15° or less with the steel sheet surface.

2. 2. The non-oriented electrical steel sheet according to claim 1, wherein the volume fraction of crystal grains having an orientation deviated by 15° or less from the {001}<001> orientation is 8% or more.

3. The non-oriented electrical steel sheet has a B ５０ / B ｓ 2. The non-oriented electrical steel sheet according to claim 1, wherein a σ-axis value satisfies a σ-axis value of 0.870 or more. Here, B ５０ means the magnitude (Tesla) of the magnetic flux density induced when a magnetic field of 5000 A / m is applied, and B Ｓ is the saturation magnetic flux density value.

4. The non-oriented electrical steel sheet has an average value of B ５０ / B Ｓ 2. The non-oriented electrical steel sheet according to claim 1, wherein a σ is greater than or equal to 0.

855. Here, B ５０ means the magnitude (Tesla) of the magnetic flux density induced when a magnetic field of 5000 A / m is applied, and B Ｓ is the saturation magnetic flux density value.

5. 2. The non-oriented electrical steel sheet according to claim 1, wherein the non-oriented electrical steel sheet has an iron loss of 1.76 W / kg or less in the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz.

6. The non-oriented electrical steel sheet according to claim 1, further comprising Cu: 0.015% or less.

7. providing a slab containing, by weight percent, Si: 2.2 to 4.5%, Mn: 1.0% or less (not including 0%), Al: 0.020 to 0.100%, Sn: 0.10 to 0.30%, As: 0.0005 to 0.0100%, Bi: 0.0005 to 0.0150%, C: 0.0050% or less (not including 0%), S: 0.0030% or less, N: 0.0050% or less, with the balance being Fe and other inevitable impurities; reheating the slab to 1050 to 1180°C and rolling it to produce a hot-rolled steel sheet; cold-rolling the hot-rolled steel sheet and then hot-rolling it, or hot-rolling it without cold rolling; cold-rolling the hot-rolled annealed steel sheet to produce a cold-rolled steel sheet; and final annealing the cold-rolled steel sheet. During cold rolling of the annealed steel sheet, the reduction is controlled to a range of 50 to 85%; A method for producing a non-oriented electrical steel sheet, characterized in that during the temperature rise in the final annealing, the temperature rise rate in the range of 300 to 850°C is controlled to 30°C / s or more, and the coil state is annealed not in a batchwise manner but in a continuous manner.

8. The method for producing a non-oriented electrical steel sheet according to claim 7, wherein the hot-rolled sheet is annealed in a range of 900 to 1150°C.

9. The method for producing a non-oriented electrical steel sheet according to claim 7, wherein the final annealing is performed at an annealing temperature of 900 to 1150°C for an annealing time of 30 to 600 seconds.

10. The atmosphere during the final annealing contains hydrogen, and the oxidation degree is P Ｈ２ / P Ｈ２Ｏ 8. The method for producing a non-oriented electrical steel sheet according to claim 7, wherein a σ of 0.015 or less is satisfied.

11. 8. The method for producing a non-oriented electrical steel sheet according to claim 7, wherein the steel sheet after the final annealing has F{110} of 30% or more, F[Goss] of 20% or more, F{100} of 10% or more, and satisfies F[Goss]>F{100}, and the crystal grain size in the microstructure is 30 to 250 μm. Here, F{110} means the volume fraction of crystal grains whose {110} plane forms an angle of 15° or less with the steel sheet surface, F[Goss] means the volume fraction of crystal grains whose angle with the Goss orientation is 15° or less, and F{100} means the volume fraction of crystal grains whose {100} plane forms an angle of 15° or less with the steel sheet surface.

12. The method for manufacturing a non-oriented electrical steel sheet according to claim 7, wherein the slab further contains Cu: 0.015% or less.

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