KR20220089075A - Double oriented electrical steel sheet method for manufacturing the same - Google Patents

Abstract

Bi-oriented electrical steel sheet according to an embodiment of the present invention by weight, Si: 2.0 to 5.0%, Al: 1.5% or less (excluding 0%), S: 0.0004 to 0.02%, Ti: 0.001 to 0.008% , Mn: 0.05 to 0.3%, N: 0.01% or less (excluding 0%), and the balance contains Fe and other unavoidable impurities.

Description

Bidirectional electrical steel sheet and its manufacturing method

An embodiment of the present invention relates to a bidirectional electrical steel sheet and a method for manufacturing the same. Specifically, in one embodiment of the present invention, by appropriately controlling the component and density of the Ti precipitate and appropriately adjusting the temperature increase rate during the hot-rolled sheet annealing process, the fraction of crystal grains having an orientation favorable to magnetism is greatly increased, so that the rolling direction and rolling It relates to a bidirectional electrical steel sheet having excellent magnetism in the temperature range of low and high temperatures in the vertical direction and a method for manufacturing the same.

In order to improve the magnetic flux density of the electrical steel sheet, the most effective method is to improve the texture of the steel to align the <100> axes in parallel in the magnetization direction. By bringing the magnetic flux closer to that of pure iron, a method of improving the magnetic flux density is used. Of these, in the case of grain-oriented electrical steel sheet, {110}<001> orientation, called Goss orientation, is used, which can be obtained through the decarburization-nitriding-secondary high-temperature annealing process during slab-hot rolling-hot-rolled sheet annealing-cold rolling-primary recrystallization. have. In this case, an electrical steel sheet having excellent magnetism in the rolling direction can be manufactured by arranging the <100> axis, which is the axis of easy magnetization, in a rolling direction. However, in the electrical steel sheet manufactured in this way, the easy axis of magnetization is arranged only in the rolling direction (Rd direction), and the <110> axis, which is not favorable for magnetization, is arranged in the rolling direction (TD direction), so that the rolling vertical In the direction (TD direction), magnetism is inferior.

On the other hand, since a wind power generator has a circular core among electric and electronic devices manufactured by utilizing the high magnetic flux density characteristics of an electrical steel sheet, it is necessary to have excellent magnetism in both the rolling direction and the rolling direction. Therefore, unlike grain-oriented electrical steel sheet, it is required to manufacture an electrical steel sheet having excellent magnetism in both the rolling direction and the rolling direction. In addition, wind power generators tend to be installed in high-rise, high-latitude regions with high wind speed in order to improve power generation efficiency. This is a condition of low operating temperature because the core's operating temperature is not on the ground, but at 150 m above sea level in the case of the sea or at 1000 m or higher in the case of a high mountain area. In addition, since it is being installed in extreme environments where the difference between the highest and lowest temperatures of the year exceeds 70℃ according to the Earth's revolution, electrical steel sheets with excellent magnetic properties in both rolling and vertical directions in a very wide temperature range is required

Since the direction of magnetization in a rotating machine normally rotates within the plate surface, the <100> axis, which is the easy axis of magnetization, should be arranged parallel to the magnetic line. 001> is defense. Since it has <100> easy magnetization axes in both the rolling direction and the rolling direction (TD direction), it has excellent magnetism in both the rolling direction and the rolling direction. However, this orientation is a stable orientation for cold rolling, and most of the recrystallization nuclei disappear during recrystallization annealing, making it very difficult to manufacture from electrical steel sheet materials. As a representative manufacturing technology, there is a method of manufacturing through a tool that is impossible for actual large-scale industrial production, such as cross rolling or vacuum annealing.

In particular, the cross rolling method cannot be utilized due to the impossibility of continuous production of materials. In the case of a large generator, a cylindrical core with a diameter of several meters must be manufactured. It cannot be applied to the process to be made in the form of

Therefore, it can be said that a new method is needed in order to manufacture in a process with high productivity and high applicability.

On the other hand, in the case of generators, magnetic properties at 50 Hz and 60 Hz are important because general turbine generators produce electricity according to each station's commercial electric frequency of 50 Hz or 60 Hz, but the rotational speed of wind turbines, etc. In slow generators, these DC and magnetic properties below 30 Hz are important.

Therefore, in the above device, the magnetic flux density characteristic indicating the degree of magnetization is more important than the iron loss caused by the alternating current magnetism, and it is generally evaluated with the B50 magnetic flux density. B50 magnetic flux density refers to the magnetic flux density value of the steel sheet when the magnetic field strength is 5000 A/m, which is mainly measured in 50 Hz AC magnetic field, but the difference in B50 magnetic flux density value according to the frequency range within 0.001 Hz to 100 Hz Because it is not large, it is usually measured at a frequency of 50 Hz.

An embodiment of the present invention is to provide a bidirectional electrical steel sheet and a method for manufacturing the same. Specifically, in one embodiment of the present invention, by appropriately controlling the component and density of the Ti precipitate and appropriately adjusting the temperature increase rate during the hot-rolled sheet annealing process, the fraction of crystal grains having an orientation favorable to magnetism is greatly increased, so that the rolling direction and rolling An object of the present invention is to provide a bidirectional electrical steel sheet having very excellent magnetism in the temperature range of low and high temperatures in the vertical direction and a method for manufacturing the same.

Bi-oriented electrical steel sheet according to an embodiment of the present invention by weight, Si: 2.0 to 5.0%, Al: 1.5% or less (excluding 0%), S: 0.0004 to 0.02%, Ti: 0.001 to 0.008% , Mn: 0.05 to 0.3%, N: 0.01% or less (excluding 0%), the balance contains Fe and other unavoidable impurities.

The area fraction of the crystal grains having an orientation of an angle within 20° from the orientation ｛100｝<001> may be 25 to 99%.

The area fraction of the crystal grains having an orientation of an angle within 20° from the orientation b110b<116> may be 40% or less (0 is not included).

The area fraction of the crystal grains having an orientation of an angle within 20° from the orientation b110b<001> may be 30% or less (0 is not included).

A fraction of grains having an angular orientation within 20° from {110｝<116> may be smaller than the fraction of grains having an angular orientation within 20° from {100｝<001>, in which case {110}<001 The fraction of grains having an angular orientation within 20° from > may be smaller than the fraction of grains having an angular orientation within 20° from {110}<116>.

The bi-directional electrical steel sheet according to an embodiment of the present invention may further include Sn: 0.1 wt% or less.

The bidirectional electrical steel sheet according to an embodiment of the present invention may further include Sb: 0.1 wt% or less.

The bi-directional electrical steel sheet according to an embodiment of the present invention may further include Ca: 0.0007 to 0.005 wt% or less.

The bi-directional electrical steel sheet according to an embodiment of the present invention may further include Mg: 0.0007 to 0.005 wt% or less.

Bi-oriented electrical steel sheet according to an embodiment of the present invention Bi: 0.1% by weight or less, Pb: 0.1% by weight or less, As: 0.1% by weight or less, Be: 0.1% by weight or less, and Sr: one of 0.1% by weight or less More may be included.

In the bidirectional electrical steel sheet according to an embodiment of the present invention, the density of inclusions having a diameter of greater than 0.2 μm among inclusions including Ti may be 20 or more per 1 mm ² .

The bi-directional electrical steel sheet according to an embodiment of the present invention may contain more than twice the density of inclusions containing Ti and not containing oxygen than the density of inclusions containing both oxygen and Ti.

In the bidirectional electrical steel sheet according to an embodiment of the present invention, the density of inclusions having a diameter of more than 1 μm among inclusions containing Ti and not containing oxygen may be 1/3 or less of the density of inclusions having a diameter of 1 μm or less.

When the B50 magnetic flux density in the rolling direction is measured at temperatures of -30°C, 20°C and 70°C, the values may be 1.79T or more, respectively.

When the B50 magnetic flux density is measured in the vertical direction of rolling at temperatures of -30°C, 20°C and 70°C, the values may be 1.79T or more, respectively.

When the B50 magnetic flux density in the circumferential direction is measured at temperatures of -30°C, 20°C, and 70°C, the values may be 1.74T or more, respectively.

The method of manufacturing a bi-directional electrical steel sheet according to an embodiment of the present invention, by weight%, Si: 2.0 to 5.0%, Al: 1.5% or less (excluding 0%), S: 0.0004 to 0.02%, Ti: 0.001 to 0.008%, Mn: 0.05 to 0.3%, N: 0.01% or less (excluding 0%), the remainder comprising the steps of preparing a slab containing Fe and other unavoidable impurities; preparing a hot-rolled sheet by hot-rolling the slab; annealing the hot-rolled sheet; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; The cold-rolled sheet is subjected to primary recrystallization annealing and the cold-rolled sheet subjected to the primary recrystallization annealing is subjected to secondary recrystallization annealing.

In the step of annealing the hot-rolled sheet, it includes the step of raising the temperature at a rate of 10°C/sec or more in a temperature range of 700°C to 900°C.

In the step of manufacturing the hot-rolled sheet, the hot-rolled sheet may be manufactured to a thickness of 3.0 mm or less.

After the primary recrystallization annealing step, the average grain size may be 30 to 70 μm.

The bidirectional electrical steel sheet according to an embodiment of the present invention controls the component and density of Ti precipitates and adjusts the hot-rolled sheet annealing conditions, so that the rolling direction and the rolling vertical direction are excellent in magnetism under various temperature conditions.

In particular, it can be usefully used in a generator with a slow rotation speed, such as a wind power generator.

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

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” specifies a particular characteristic, region, integer, step, operation, element and/or component, and the presence or absence of another characteristic, region, integer, step, operation, element and/or component It does not exclude additions.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part, or the other part may be involved in between. In contrast, when a part is referred to as being "directly above" another part, the other part is not interposed therebetween.

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, are not interpreted in an ideal or very formal meaning.

In addition, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

In an embodiment of the present invention, the meaning of further including the additional element means that the remaining iron (Fe) is included by replacing the additional amount of the additional element.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement them. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

Bi-oriented electrical steel sheet according to an embodiment of the present invention by weight, Si: 2.0 to 5.0%, Al: 1.5% or less (excluding 0%), S: 0.0004 to 0.02%, Ti: 0.001 to 0.008% , Mn: 0.05 to 0.3%, N: 0.01% or less (excluding 0%), the balance contains Fe and other unavoidable impurities.

First, the reason for the limitation of the components of the bidirectional electrical steel sheet will be described.

Si: 2.00 to 5.00 wt%

Silicon (Si) is an element that forms austenite in hot rolling, and it is necessary to limit the addition amount in order to have an austenite fraction of about 10% in the vicinity of the slab heating temperature and the hot-rolled sheet annealing temperature. In addition, in the secondary recrystallization annealing, it is necessary to limit the ferrite single phase to components that are single phase ferrite because formation of the secondary recrystallization microstructure can occur smoothly during annealing. In pure iron, when 2.0 wt% or more is added, a ferrite single phase is formed, and the austenite fraction can be adjusted by adding C thereto, so the lower limit of the Si content can be limited to 2.0 wt%. In addition, when it exceeds 5% by weight, a secondary phase is formed, making cold rolling difficult, and the saturation magnetic flux is lowered, so this is limited. More specifically, Si may be included in an amount of 2.2 to 3.6 wt%. More specifically, in order to obtain a steel sheet having a high magnetic flux density, Si may be included in an amount of 2.4 to 3.0 wt%.

Al: 1.50 wt% or less

Aluminum (Al) may be used as an inhibitor of secondary recrystallization by forming AlN. In one embodiment of the present invention, since a cube texture can be obtained even when an inhibitor is used other than the nitriding process of a general grain-oriented electrical steel sheet, the amount of Al added can be controlled in a wider range than that of a general grain-oriented electrical steel sheet. More specifically, it is preferable to add 0.007 to 0.050 wt%. When less than 0.007% by weight is added, it cannot maintain the crystal growth inhibitory power of the steel and cannot induce secondary recrystallization during high-temperature annealing, making it impossible to obtain the desired orientation. By raising the temperature at which vehicle re-crystallization occurs too much, the production cost is greatly increased.

S: 0.0004 to 0.0200 wt%

Sulfur (S) is combined with Cu or Mn in steel to form MnS finely, and since the finely formed precipitates help secondary recrystallization, the amount of sulfur (S) may be 0.0004 to 0.02 wt%. When S is added in excess, the fraction of Goss in steel may increase during secondary recrystallization due to segregation of S, and the desired texture cannot be obtained during secondary recrystallization because the precipitates in the hot-rolled sheet are not controlled. can More specifically, S may be included in an amount of 0.001 to 0.006% by weight.

Ti: 0.0010 to 0.0080 wt%

Titanium (Ti) is an alloy element with very high reactivity in steel, and reacts with C, N, O, etc. in steel to form inclusions and precipitates rapidly from playing. In the case of inclusions containing TI rather than nitrides containing Al that are usually used in secondary recrystallization, it is understood that they play an important role in the secondary recrystallization growth of Cube orientation. It is important to allow the Ti inclusion to act as an inhibitor. Therefore, an addition of 0.001 wt % or more is desirable to create a size and distribution to function properly as an auxiliary inhibitor working with AlN. When added in excess of 0.0080 wt %, the secondary recrystallization temperature is greatly increased when operating as an inhibitor, making it difficult to produce industrially, so it is limited. More specifically, it may include 0.0020 to 0.0080 wt% of Ti.

Mn: 0.050 to 0.300 wt%

Manganese (Mn) is inevitably present in the molten steel, but can be used as a precipitate if it is added in a small amount, and can be added to the steel as an element that changes to MnS after the formation of FeS. However, when too much is added, the bond between Mn and S is maintained strongly even during high-temperature annealing, preventing the bonding of Mg and Ca with S, which forms fine precipitates. Conversely, if too little is included, it may become difficult to control the texture during secondary recrystallization. Accordingly, Mn may be included in an amount of 0.05 to 0.30 wt%. More specifically, Mn may be included in an amount of 0.05 to 0.20 wt%.

N: 0.0100 wt% or less

Nitrogen (N) is an element forming AlN, and since AlN is used as an inhibitor, it is necessary to secure an appropriate content. When N is included too little, the degree of tissue non-uniform deformation during cold rolling is sufficiently increased to promote the growth of Cube during primary recrystallization and it is impossible to suppress the growth of Goss. When N is included in excess, it not only causes surface defects such as blisters due to nitrogen diffusion in the process after hot rolling, but also makes it difficult to roll because excess nitride is formed in the state of hot-rolled steel sheet. It causes the unit price to rise.

In the slab, N may be included in 0.0100 wt% or less. In an embodiment of the present invention, the nitriding process is included during the primary recrystallization annealing, but when 0.01 wt% to 0.02 wt% is added in the hot-rolled steel sheet, sufficient inhibitor can be made even if this nitriding process is omitted, 2 Since some N is removed during the secondary recrystallization annealing, the N content in the slab and the final manufactured electrical steel sheet may be different.

C: 0.005 wt% or less

When carbon (C) is contained in a large amount even after secondary recrystallization annealing, it causes self-aging and iron loss greatly increases. Therefore, the upper limit is set to 0.005% by weight. More specifically, it may contain 0.0001 to 0.0050 wt% of C.

In the slab, C may be included in an amount of 0.04% by weight or less. Through this, stress concentration and goss formation in the hot-rolled sheet can be suppressed, and precipitates can be miniaturized. In addition, C increases the degree of tissue non-uniform deformation during cold rolling, thereby promoting the growth of Cube during primary recrystallization and suppressing the growth of Goss. However, if it is added in excess, stress concentration in the hot-rolled sheet can be resolved, but the formation of Goss cannot be suppressed and it is difficult to refine the precipitate. Even during cold rolling, since cold rolling is greatly inferior, the amount of addition is limited. In an embodiment of the present invention, since the process of decarburization is included during the primary recrystallization annealing, the C content of the slab and the finally manufactured electrical steel sheet may be different.

Sn: 0.10 wt% or less

Tin (Sn) plays a role in that the Goss orientation stability during rolling is lowered, so that the Goss fraction after rolling decreases and the Cube orientation fraction increases. In addition, during recrystallization, Sn serves to assist the suppression force. Therefore, in order to remove the Goss orientation at an appropriate reduction ratio and suppress growth outside the direction conducive to magnetism during high-temperature annealing, the amount of Sn added may be 0.1 wt% or less. However, when added in excess of 0.1% by weight, corner cracks occur during reheating of the slab before hot rolling, and there is a risk of slipping between the roll and the surface during rolling during cold rolling, so this is limited. More specifically, it may further include 0.001 to 0.01 wt% of Sn.

Sb: 0.10 wt% or less

Antimony (Sb) is an element that operates similarly to Sn, and the stability of the Goss orientation during rolling is lowered, so that the Goss fraction after rolling decreases and the Cube orientation fraction increases. In addition, during recrystallization, Sn serves to assist the suppression force. Therefore, in order to remove the Goss orientation at an appropriate reduction ratio and suppress growth outside the direction conducive to magnetism during high-temperature annealing, the amount of Sn added may be 0.1 wt% or less. However, when added in excess of 0.1% by weight, corner cracks occur during reheating of the slab before hot rolling, and there is a risk of slipping between the roll and the surface during rolling during cold rolling, so this is limited. More specifically, it may further include 0.001 to 0.01% by weight of Sb.

Ca: 0.0007 to 0.0050 wt%

Calcium (Ca) is a highly reactive alloying element in steel, and not only reacts with S and O in steel, but also reacts with Si, Al, etc. to form inclusions and precipitates quickly from playing. Accordingly, since it is an element that is stabilized even at a high temperature where secondary recrystallization of the Cube orientation occurs, it is understood that inclusions containing Ca rather than nitrides containing Al usually play an important role in the secondary recrystallization growth of the Cube orientation. For the growth of cube-oriented crystal grains, it is important to leave an appropriate amount of Ca in the steel so that the inclusions containing Ca operate as an inhibitor until secondary recrystallization. Therefore, an addition of 0.0007% by weight or more is desirable to create a size and distribution to function properly as an auxiliary inhibitor working with AlN. When added in excess of 0.005% by weight, the secondary recrystallization temperature is greatly increased when operating as an inhibitor, making it difficult to produce industrially, so it is limited.

Mg: 0.0007 to 0.0050 wt%

Magnesium (Mg) is generally regarded as an impurity generated during the steelmaking process, but plays an important role in one embodiment of the present invention. Mg is a highly reactive alloying element in steel, and not only reacts with S, O, etc. in steel, but also reacts with Si, Al, N, etc. to form inclusions and precipitates rapidly from playing. Accordingly, since it is an element that is stabilized even at a high temperature where secondary recrystallization of the Cube orientation occurs, it is understood that the inclusions containing Mg rather than the commonly used nitrides containing Al play an important role in the secondary recrystallization growth of the Cube orientation. For the growth of cube-oriented crystal grains, it is important to leave an appropriate amount of Mg in the steel so that the inclusions containing Mg act as an inhibitor until secondary recrystallization. Therefore, an addition of 0.0007% by weight or more is desirable to create a size and distribution to function properly as an auxiliary inhibitor working with AlN. When added in excess of 0.005% by weight, the secondary recrystallization temperature is greatly increased when operating as an inhibitor, making it difficult to produce industrially, so it is limited.

As described above, when an additional element is included, it is included by replacing the remainder Fe. For example, the composition of the bi-directional electrical steel sheet further comprising 0.1% by weight or less of Sb is, by weight, Si: 2.0 to 5.0%, Al: 1.5% or less (excluding 0%), S: 0.0004 to 0.002%, Ti : 0.001 to 0.005%, Mn: 0.05 to 0.3%, N: 0.01% or less (excluding 0%), and Sb: 0.1% or less, and the balance contains Fe and other unavoidable impurities.

Bi-oriented electrical steel sheet according to an embodiment of the present invention Bi: 0.0100 wt% or less, Pb: 0.100 wt% or less, As: 0.100 wt% or less, Be: 0.100 wt% or less and Sr: 0.100 wt% or less More may be included.

Bismuth (Bi), lead (Pb), arsenic (As), beryllium (Be) and strontium (Sr) are elements in which oxides, nitrides, and carbides are formed finely in steel and are elements that help secondary recrystallization. can be added. However, when it is added in excess of 0.1% by weight, it is necessary to limit the amount added because it causes a problem in that secondary recrystallization is unstable.

In addition, in the bidirectional electrical steel sheet of the present invention, the balance other than the above-mentioned components is Fe and unavoidable impurities. However, as long as it exists in the range which does not impair the effect of this invention, containing of another element is not excluded.

As such, in the bidirectional electrical steel sheet according to an embodiment of the present invention, it is possible to precisely control the alloy composition to obtain a magnetically advantageous texture through secondary recrystallization.

The bidirectional electrical steel sheet according to an embodiment of the present invention may have an area fraction of 25 to 99% of crystal grains having an orientation of an angle within 20° from the {100} <001> orientation. In obtaining an orientation within 20° from the {100}<001> orientation during secondary recrystallization, exceeding 99% suppresses the formation of island grains that are unavoidably formed during secondary recrystallization, and also completely removes precipitates. This means that the annealing time at high temperature is greatly increased, and for this purpose, it is limited to 25 to 99% because it means excluding the inhibitor that is stable at high temperature. More specifically, it may be 50 to 90%. In this case, the reference area is the area with respect to one end surface of the steel sheet. More specifically, it means a surface parallel to the rolling surface (ND surface).

In addition, in an embodiment of the present invention, the area fraction of the crystal grains having an orientation of an angle within 20° from the orientation b110b<116> may be 40% or less (0 is not included). In the case of obtaining an orientation within 20° from the {110}<116> orientation, 40% or less means that the {110}<116> orientation has a <100> magnetic easy axis deviated by 13° from the rolling direction, so In all of them, the magnetism in the rolling direction is excellent, and since the magnetism is not inferior even in the vertical direction of rolling, this can be tolerated within 40%. In particular, as the fraction of grains having the {110}<116> orientation becomes more than a certain level, it is possible to effectively reduce the fraction of {110}<001>, which greatly deteriorates the magnetism at low and high temperatures in the vertical direction of rolling. More specifically, the area fraction of the crystal grains having an orientation of an angle within 20° from the {110｝<116> orientation may be 1 to 30%.

Also, in an embodiment of the present invention, the area fraction of the crystal grains having an orientation of an angle within 20° from the {110｝<001> orientation may be 30% (0 is not included). To obtain an orientation within 20° from the {110}<001> orientation, within 30% means that the {110}<001> orientation exactly coincides with the <100> magnetic easy axis from the rolling direction, so the low and high temperature in the rolling direction In all of them, the magnetism can be very good, but the magnetism is inferior in the vertical direction of rolling. In addition, as the {110}<001> fraction increases during secondary recrystallization, the {100}<001> fraction tends to decrease. In order to obtain excellent magnetism in both the rolling direction and the vertical rolling direction at low and high temperatures, it is necessary to use 30 It is allowed only within %. More specifically, it may be 1 to 20%.

A fraction of grains having an angular orientation within 20° from {110｝<116> may be smaller than the fraction of grains having an angular orientation within 20° from {100｝<001>, in which case {110}<001 The fraction of grains having an angular orientation within 20° from > may be smaller than the fraction of grains having an angular orientation within 20° from {110}<116>. That is, the fraction of crystal grains may be formed in the order of {100｝<001> > {110｝<116> > {110}<001>.

The magnetic anisotropy of Fe is greatly affected by temperature. In particular, magnetization occurs easily along the <100> axis, which is the easy axis, as the temperature decreases, whereas when the temperature increases, the magnetic anisotropy itself decreases, which tends to weaken the relationship between magnetism and texture. Therefore, in order to maintain high magnetic flux at both low and high temperatures, the <100> axis, which is easy to magnetize in both the rolling direction and the rolling direction, is arranged in an appropriate amount in the rolling direction and the rolling direction, while orientations having other axes are also used. By distributing an appropriate amount, it is possible to reduce the magnetic deviation according to the temperature. Through this, the B50 magnetic flux density at -30°C to 70°C, which can be considered as the operating temperature condition of the generator, can exhibit excellent characteristics in the rolling direction, the rolling vertical direction, and the circumferential direction.

In the bidirectional electrical steel sheet according to an embodiment of the present invention, the density of inclusions having a diameter of more than 0.2 μm among inclusions including Ti may be 20 or more per 1 mm ² . More specifically, it may be 50 to 300 pieces.

The bi-directional electrical steel sheet according to an embodiment of the present invention may contain more than twice the density of inclusions containing Ti and not containing oxygen than the density of inclusions containing both oxygen and Ti.

In the bidirectional electrical steel sheet according to an embodiment of the present invention, the density of inclusions having a diameter of greater than 1 μm among inclusions containing Ti and not containing oxygen may be less than 1/3 of the density of inclusions having a diameter of 1 μm or less.

As such, by controlling the properties of the Ti inclusions, it may be helpful to form grains having an appropriate orientation.

In an embodiment of the present invention, a forsterite layer interposed between the substrate surface and the insulating layer may be further included. For grain-oriented electrical steel sheet, an oxide layer containing forsterite (Mg ₂ SiO ₄ ) is formed from the surface to a thickness of 2 to 3 μm in order to apply tension in the rolling direction, and tension is applied using the difference between this and the coefficient of thermal expansion of the base material. . However, in the case of an embodiment of the present invention, since the tension in the rolling direction means compression in the vertical direction of rolling, it is preferable to extremely reduce it. Since a thin forsterite layer with a thickness of 2.0 μm or less has a very low tension-imparting effect, the tension applied to the entire plate can be removed by forming such a thin forsterite layer. The forsterite layer is formed from the annealing separator applied before the secondary recrystallization annealing. The annealing separator includes MgO as a main component, and since it is the same as widely known, a detailed description thereof will be omitted. After the secondary recrystallization annealing, the forsterite layer may be removed.

As described above, the bidirectional electrical steel sheet composed of a texture advantageous for magnetism at low and high temperatures has excellent magnetism at low temperature (-30°C) and room temperature (20°C) or high temperature (70°C). An electrical steel sheet without such a texture has a problem in that the magnetism is excellent at a low temperature, but the magnetism is inferior at a high temperature.

When the B50 magnetic flux density in the rolling direction is measured at temperatures of -30°C, 20°C and 70°C, the values may be 1.79T or more, respectively. More specifically, when the B50 magnetic flux density in the rolling direction is measured at temperatures of -30°C, 20°C and 70°C, the values may be 1.83 to 2.1 T, respectively.

When the B50 magnetic flux density is measured in the vertical direction of rolling at temperatures of -30°C, 20°C and 70°C, the values may be 1.79T or more, respectively. More specifically, when the B50 magnetic flux density in the rolling direction is measured at temperatures of -30°C, 20°C and 70°C, the values may be 1.80 to 2.1 T, respectively.

When the B50 magnetic flux density in the circumferential direction is measured at temperatures of -30°C, 20°C, and 70°C, the values may be 1.74T or more, respectively. More specifically, when the B50 magnetic flux density in the circumferential direction is measured at temperatures of -30°C, 20°C and 70°C, the values may be 1.77 to 2.0T, respectively.

The difference between the maximum value and the minimum value of the B50 magnetic flux density in the rolling direction, the rolling vertical direction, and the circumferential direction measured at -30°C to 70°C may be 0.05T or less.

On the other hand, the bi-directional electrical steel sheet according to an embodiment of the present invention can be used in a wind power generator. Wind power generators tend to be installed in high-rise, high-latitude regions with high wind speed in order to improve power generation efficiency. Excellent power generation efficiency can be obtained regardless of the annual temperature difference.

The method of manufacturing a bidirectional electrical steel sheet according to an embodiment of the present invention, by weight%, Si: 2.0 to 4.0%, Al: within 1.5%, S: 0.0004 to 0.02%, Ti: 0.001 to 0.005%, Mn: 0.05 to 0.3%, N: including 0.01% or less (excluding 0%), and the remainder is Fe and other unavoidable impurities to prepare a slab; preparing a hot-rolled sheet by hot-rolling the slab; annealing the hot-rolled sheet; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; The cold-rolled sheet is subjected to primary recrystallization annealing and the cold-rolled sheet subjected to the primary recrystallization annealing is subjected to secondary recrystallization annealing.

Hereinafter, each step will be described in detail.

First, a slab is manufactured. The reason for limiting the addition ratio of each composition in the slab is the same as the reason for limiting the composition of the bi-directional electrical steel sheet described above, and thus repeated description is omitted. In the manufacturing process of hot rolling, hot-rolled sheet annealing, cold rolling, primary recrystallization annealing, secondary recrystallization annealing, etc. to be described later, the composition of slabs other than C and N does not substantially change, so the composition and bidirectionality of slabs other than C and N The composition of the electrical steel sheet is substantially the same.

The slab can be manufactured using a thin slab method or a strip casting method. The thickness of the slab can be 50 to 300 mm. The slab can be heated as needed.

Next, a hot-rolled sheet is manufactured by hot-rolling the slab.

The thickness of the hot-rolled sheet may be within 3.0 mm. In a thicker hot-rolled sheet, it is very difficult to obtain a magnetically advantageous texture after secondary recrystallization due to the difference in the shape of the deformed structure caused by hot rolling.

After the step of manufacturing the hot-rolled sheet, the step of annealing the hot-rolled sheet may be further included.

The step of annealing the hot-rolled sheet in an embodiment of the present invention may include a temperature raising step of raising the temperature at a rate of 10°C/sec or more in a temperature range of 700°C to 900°C. When the temperature increase rate is less than 10° C./sec, the Ti-containing precipitate may change to a Ti sulfide-based precipitate, and thus the inhibitory power at high temperature may be lost. Specifically, the temperature increase rate of the temperature increase step may be 10 to 30 °C / sec.

The step of annealing the hot-rolled sheet may further include cracking at 900 to 1100° C. after the temperature raising step.

Next, the hot-rolled sheet is cold-rolled to manufacture a cold-rolled sheet. In the step of manufacturing the cold-rolled sheet, cold rolling may be performed one or two or more times. In the case of cold rolling a plurality of times, an intermediate annealing process may be added between cold rolling.

Specifically, the manufacturing of the cold-rolled sheet may include primary cold-rolling, intermediate annealing, and secondary cold-rolling.

The intermediate annealing may include a temperature raising step of raising the temperature at a rate of 10°C/sec or more in a range of 700°C to 900°C. As in the case of a hot-rolled sheet, when the temperature increase rate is less than 10° C./sec, the Ti-containing precipitate may change to a Ti sulfide-based precipitate, and thus the inhibitory power at high temperature may be lost. Specifically, the temperature increase rate of the temperature increase step may be 10 to 30 °C / sec.

Next, the cold-rolled sheet is subjected to primary recrystallization annealing.

After the primary recrystallization annealing step, the step of applying an annealing separator containing MgO may be further included.

Since the forsterite layer formed by application of the annealing separator is the same as described above, the overlapping description will be omitted.

After the primary recrystallization annealing step, the average grain size may be 30 to 70 μm.

Next, the primary recrystallization annealed cold-rolled sheet is subjected to secondary recrystallization annealing.

In the secondary recrystallization annealing, the temperature is raised at an appropriate temperature increase rate to cause secondary recrystallization so that the magnetically advantageous texture at high and low temperatures can be strengthened, followed by purification annealing, which is an impurity removal process, and then cooled. In the process, the annealing atmosphere gas is heat-treated using a mixed gas of hydrogen and nitrogen in the temperature increase process as in the usual case, and in the purification annealing, 100% hydrogen gas is used for a long time to remove impurities.

In one embodiment of the present invention, the forsterite layer may be thin or advantageously removed, as described above. Accordingly, the method may further include removing the forsterite layer formed on the surface of the steel sheet either before or after secondary recrystallization occurs. The removal method may use a physical or chemical method.

Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited thereto.

Hereinafter, specific examples of the present invention will be described. However, the following examples are only specific examples of the present invention, and the present invention is not limited thereto.

Example 1

A slab composed of the components shown in Tables 1 and 2 and the remainder Fe and unavoidable impurities was prepared, heated at 1200° C., and then hot rolled in 8 passes to prepare a hot-rolled coil having the thickness shown in the table. The hot-rolled sheet was heated at a temperature increase rate of 12° C./s in the temperature range of 700 to 900° C., and then cooled after annealing at the indicated cracking temperature for 40 seconds.

This was again cold-rolled at 200° C. to a thickness of 0.65 mm.

The cold-rolled sheet was decarburized at 850° C. under an atmosphere of 60° C. and 75 vol. The average grain size at this time is shown in Table 3 below. Thereafter, an annealing separator containing MgO component was applied, and the temperature was raised to 1200°C at a rate of 15°C per hour, followed by secondary recrystallization annealing for 5 hours. After removing the MgO annealing separator, the cooled plate was measured for magnetism without removing the forsterite layer, and is shown in Table 5.

As for the orientation fraction, depending on the grain size, when the average grain size is less than 1 mm, the surface fraction at the surface was measured with an area of 10 mm x 10 mm wide enough to measure 500 or more grains using the EBSD method, and the average grain size was In the case of 1 mm or more, the surface fraction in an area of 300 mm x 60 mm was measured using the X-ray Laue method.

Ti inclusion density was measured using EDS using a high-performance scanning electron microscope to automatically detect and measure inclusions on the steel sheet surface, and measure the size and components of inclusions.

Psalm name Si Al S Ti Mn N Sn Sb A1 3.18 0.22 0.006 0.0066 0.092 0.0103 0.0270 0.0260 A2 3.74 0.24 0.003 0.0054 0.117 0.0072 0.0030 0.0070 A3 3.38 0.29 0.007 0.0050 0.124 0.0087 0.0400 0.0190 A4 3.01 - 0.007 0.0085 0.075 0.0026 0.0220 0.0002 A5 2.48 - 0.005 0.0042 0.104 0.0011 0.0030 0.0002 A6 3.54 - 0.007 0.0024 0.129 0.0057 0.0010 0.0002 A7 3.79 0.14 0.004 0.0093 0.062 - 0.0540 0.0002 A8 2.55 0.19 0.004 0.0116 0.144 0.0057 0.0450 0.0002 A9 3.47 - 0.003 0.0007 0.104 0.0097 0.0002 0.0260 A10 3.83 - 0.005 0.0034 0.075 0.0017 0.0002 0.0220 A11 2.01 0.08 0.005 0.0087 0.073 0.0103 0.0002 0.0330 A12 3.25 0.01 0.010 0.0113 0.080 0.0078 0.0250 0.0200 A13 2.56 0.19 0.009 0.0082 0.080 0.0024 0.0020 0.0040 D1 2.50 0.03 0.001 0.0028 0.051 0.0068 0.0030 0.0260 D2 2.24 0.02 0.010 0.0052 0.099 0.0006 0.0340 0.0390 D3 2.30 0.01 0.005 0.0009 0.054 0.0071 0.0002 0.0340 D4 3.96 0.03 0.007 0.0025 0.113 0.0019 0.0410 0.0002 D5 2.95 0.24 0.009 0.0011 0.099 0.0030 0.0110 0.0002 D6 2.00 0.03 0.007 0.0077 0.081 0.0067 0.0630 0.0002 D7 2.22 0.01 0.008 0.0011 0.129 0.0079 0.0002 0.0420

Psalm name Ca Mg Bi Pb As Be Sr A1 0.0031 0.0069 - 0.0002 0.0238 - - A2 0.0047 0.0038 0.0139 0.0075 - - - A3 0.0031 0.0113 - - 0.0492 - - A4 0.0042 0.0056 0.0311 - - - - A5 0.0001 0.0047 0.0460 - - - - A6 0.0019 0.0051 0.0097 - - - - A7 0.0002 0.0007 0.0185 0.0095 0.0157 - - A8 0.0011 0.0095 0.0410 0.0071 0.0413 - - A9 0.0027 0.0001 0.0447 0.0098 - - - A10 0.0001 0.0014 0.0253 - 0.0613 - - A11 0.0011 0.0074 0.0024 - - - - A12 0.0009 0.0001 0.0555 - - 0.0057 - A13 0.0046 0.0083 0.0332 0.0025 - - - D1 0.0007 0.0046 - 0.0040 0.0071 0.0273 0.0063 D2 0.0037 0.0010 0.0490 - 0.0645 - - D3 0.0003 0.0036 - - - - - D4 0.0020 0.0010 0.0351 - - - - D5 0.0015 0.0031 - - - - - D6 0.0015 0.0002 0.0281 - 0.0080 - - D7 0.0038 0.0021 0.0551 0.0083 - - 0.0036

Psalm name Hot-rolled sheet thickness
(mm) Hot-rolled sheet annealing temperature (℃) Hot-rolled sheet annealing 700-900℃ Temperature increase rate (℃/s) Primary recrystallization grain size
(μm) {100}<001> fraction within 20° (%) {110}<116> Fraction within 20° (%) {110}<001> fraction within 20° (%) A1 2.1 1063 7.6 24.9 19.6 47.8 58.5 A2 2.6 1085 7.4 21.4 21.1 43.7 53.7 A3 2.3 1075 9.2 29.1 24.5 52.6 58.9 A4 2.7 1199 9.5 27.0 14.1 64.9 66.7 A5 2.8 941 8.1 21.8 3.0 64.6 67.9 A6 2.4 1020 7.3 27.3 16.2 60.2 69.1 A7 2.8 950 7.9 23.1 15.9 60.6 62.0 A8 2.6 1119 8.0 28.9 10.4 59.3 63.9 A9 3.0 1101 8.4 25.9 20 52.4 54.1 A10 2.7 997 8.3 29.3 9.9 63.5 65.1 A11 2.8 980 9.6 25.7 15.4 52.8 63.2 A12 2.5 1079 7.3 27.3 0.3 69.8 76.5 A13 2.1 1091 7.0 25.9 20.8 55.4 57.6 D1 2.0 1086 15.8 32.3 71.5 23.7 13.1 D2 2.0 911 13.3 33.3 82.6 10.0 8.4 D3 2.6 1081 18.0 38.3 62.1 23.0 12.0 D4 2.5 952 10.0 34.7 89.5 4.9 5.4 D5 3.0 1014 16.2 35.2 96.2 3.2 3.0 D6 2.0 967 13.4 33.1 83.8 16.8 15.3 D7 2.9 908 11.6 36.3 89.3 13.5 6.5

Psalm name Ti inclusion density
(pcs/mm ² ) Density of O-containing inclusions in Ti inclusions
(pcs/mm ² ) O-free inclusion density among Ti inclusions
(pcs/mm ² ) 1㎛ or less Ti inclusion density
(pcs/mm ² ) Ti inclusion density greater than 1 μm
(pcs/mm ² ) A1 429 328 101 86 343 A2 291 38 253 268 23 A3 395 288 107 92 303 A4 328 258 70 72 256 A5 148 108 40 41 107 A6 227 199 28 46 181 A7 405 362 43 97 308 A8 414 351 63 87 327 A9 12 9 2 2 9 A10 52 40 12 12 40 A11 794 669 125 232 561 A12 1094 801 293 271 823 A13 261 230 31 52 209 D1 123 12 111 120 2 D2 274 12 262 268 6 D3 144 29 115 100 44 D4 181 30 151 175 6 D5 100 11 89 96 3 D6 291 40 251 182 109 D7 195 22 173 190 5

Psalm name -30℃ Rolling direction B50 20℃ rolling direction B50 70℃
Rolling direction B50 -30℃ Rolling vertical direction B50 20℃ Rolling vertical direction B50 70℃ Rolling vertical direction B50 -30℃ circumferential direction B50 20℃ circumferential direction B50 70℃ circumferential direction B50 note A1 1.8 1.79 1.78 1.67 1.67 1.68 1.70 1.69 1.69 comparative example A2 1.71 1.70 1.69 1.59 1.59 1.60 1.60 1.6 1.61 comparative example A3 1.75 1.74 1.72 1.61 1.63 1.65 1.63 1.64 1.63 comparative example A4 1.85 1.83 1.82 1.69 1.70 1.70 1.72 1.72 1.71 comparative example A5 1.71 1.70 1.68 1.56 1.56 1.56 1.60 1.58 1.58 comparative example A6 1.77 1.76 1.75 1.66 1.64 1.65 1.67 1.67 1.65 comparative example A7 1.81 1.80 1.79 1.67 1.68 1.68 1.71 1.69 1.69 comparative example A8 1.75 1.74 1.73 1.60 1.61 1.61 1.64 1.64 1.63 comparative example A9 1.70 1.69 1.68 1.56 1.58 1.56 1.60 1.60 1.58 comparative example A10 1.73 1.72 1.71 1.60 1.60 1.60 1.63 1.61 1.61 comparative example A11 1.83 1.82 1.81 1.69 1.69 1.69 1.71 1.72 1.71 comparative example A12 1.86 1.85 1.84 1.71 1.70 1.71 1.74 1.74 1.72 comparative example A13 1.80 1.79 1.77 1.66 1.67 1.69 1.69 1.69 1.69 comparative example D1 1.95 1.95 1.94 1.91 1.90 1.91 1.88 1.88 1.88 invention example D2 1.83 1.83 1.83 1.82 1.81 1.81 1.78 1.77 1.78 invention example D3 1.96 1.96 1.96 1.89 1.90 1.93 1.88 1.89 1.89 invention example D4 1.85 1.84 1.83 1.84 1.83 1.83 1.80 1.79 1.78 invention example D5 1.93 1.93 1.92 1.92 1.92 1.91 1.88 1.87 1.87 invention example D6 2.02 2.02 2.01 1.99 1.98 1.98 1.90 1.90 1.89 invention example D7 2.03 2.03 2.02 2.00 2.00 1.99 1.90 1.89 1.89 invention example

As shown in Tables 1 to 5, when Ti is included in an appropriate amount and the temperature increase rate is appropriately adjusted during annealing of the hot-rolled sheet, a large amount of crystal grains within 20° from {100}<001> are formed, and it can be confirmed that the magnetism is excellent. On the other hand, if Ti is not included in an appropriate amount or if the temperature increase rate is not properly adjusted during annealing of the hot-rolled sheet, crystal grains within 20° from {100}<001> cannot be properly formed, and it can be confirmed that the magnetism is inferior. have.

The present invention is not limited to the above embodiments and/or embodiments, but may be manufactured in various different forms, and those skilled in the art to which the present invention pertains may change the technical spirit or essential features of the present invention It will be understood that the present invention may be implemented in other specific forms without not doing so. Therefore, it should be understood that the embodiments and/or embodiments described above are illustrative in all respects and not restrictive.

Claims (15)

By weight%, Si: 2.0 to 5.0%, Al: 1.5% or less (excluding 0%), S: 0.0004 to 0.02%, Ti: 0.001 to 0.008%, Mn: 0.05 to 0.3%, N: 0.01% or less (excluding 0%), the balance contains Fe and other unavoidable impurities,
Bidirectional electrical steel sheet having an area fraction of 25 to 99% of crystal grains having an orientation of an angle within 20° from the orientation of ｛100｝<001>. According to claim 1,
The area fraction of grains having an angular orientation within 20° from the b110｝<116> orientation is 40% or less, and the area fraction of the grains having an angular orientation within 20° from the b110b<001> orientation is 30 % or less bi-directional electrical steel sheet. According to claim 1,
The fraction of angles within 20° from {110｝<116> is smaller than the fraction of angles within 20° from {100｝<001>, and the fraction of angles within 20° from {110}<001> is {110} A bidirectional electrical steel sheet smaller than the fraction of an angle within 20° from <116>. According to claim 1,
Sn: 0.1 wt% or less, and Sb: 0.1 wt%, bidirectional electrical steel sheet further comprising at least one of. According to claim 1,
Ca: 0.0007 to 0.005 wt% or less, Mg: 0.0007 to 0.005 wt% or less bidirectional electrical steel sheet further comprising at least one of. According to claim 1,
Bi: 0.1 wt% or less, Pb: 0.1 wt% or less, As: 0.1 wt% or less, Be: 0.1 wt% or less, and Sr: A bidirectional electrical steel sheet further comprising at least one of 0.1 wt% or less. According to claim 1,
A bi-directional electrical steel sheet having a density of 20 or more per 1 mm ² of inclusions having a diameter of more than 0.2 μm among inclusions containing Ti. 8. The method of claim 7,
A bidirectional electrical steel sheet in which the density of inclusions containing Ti without containing oxygen is more than twice the density of inclusions containing both oxygen and Ti. 8. The method of claim 7,
A bidirectional electrical steel sheet in which the density of inclusions having a diameter of more than 1 μm among inclusions containing Ti and not containing oxygen is 1/3 or less of the density of inclusions having a diameter of 1 μm or less. According to claim 1,
A bidirectional electrical steel sheet having a value of 1.79T or more, respectively, when the B50 magnetic flux density in the rolling direction was measured at temperatures of -30℃, 20℃ and 70℃. According to claim 1,
A bidirectional electrical steel sheet having a value of 1.79T or more when the B50 magnetic flux density is measured in the vertical direction of rolling at temperatures of -30℃, 20℃ and 70℃. According to claim 1,
A bidirectional electrical steel sheet having a value of 1.74T or more when the B50 magnetic flux density in the circumferential direction was measured at temperatures of -30℃, 20℃ and 70℃. By weight%, Si: 2.0 to 5.0%, Al: 1.5% or less (excluding 0%), S: 0.0004 to 0.02%, Ti: 0.001 to 0.008%, Mn: 0.05 to 0.3%, N: 0.01% or less (excluding 0%), and the remainder is Fe and other unavoidable steps to prepare a slab containing impurities;
manufacturing a hot-rolled sheet by hot-rolling the slab;
annealing the hot-rolled sheet;
manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet;
primary recrystallization annealing of the cold-rolled sheet; and
Comprising the step of secondary recrystallization annealing of the cold-rolled sheet subjected to the primary recrystallization annealing,
The step of annealing the hot-rolled sheet is a method of manufacturing a bidirectional electrical steel sheet comprising a temperature raising step of raising the temperature at a rate of 10 °C / sec or more in a temperature range of 700 °C to 1100 °C. 14. The method of claim 13,
To prepare the hot-rolled sheet to a thickness of 3.0 mm or less
A method for manufacturing a bidirectional electrical steel sheet. 14. The method of claim 13,
After the step of primary recrystallization annealing, the method of manufacturing a bidirectional electrical steel sheet having an average grain size of 30 to 70㎛.