KR20220089080A - Grain oriented electrical steel sheet and method for menufacturing the same - Google Patents

Abstract

Grain-oriented electrical steel sheet according to an embodiment of the present invention is Si: 2.5 to 4.0%, acid soluble Al: 0.020 to 0.040%, Mn: 0.20% or less (excluding 0%), N: 0.0055 in weight% on the steel sheet substrate % or less (excluding 0%), C: 0.005% or less (excluding 0%), S: 0.0055% or less (excluding 0%), Sb: 0.005 to 0.02%, and acid solubility Mg: 0.002 to 0.005%, and the balance includes Fe and other unavoidable impurities.

Description

Grain-oriented electrical steel sheet and its manufacturing method

One embodiment of the present invention relates to a grain-oriented electrical steel sheet and a manufacturing method thereof. Specifically, one embodiment of the present invention relates to a grain-oriented electrical steel sheet having excellent surface adhesion and excellent magnetic properties by supplementing the grain growth inhibition with Mg-Sb precipitates, and a method for manufacturing the same.

The grain-oriented electrical steel sheet exhibits a Goss texture in which the texture of the steel piece is {110}<001> with respect to the rolling direction, so it is a soft magnetic material having excellent magnetic properties in one direction or in the rolling direction. In order to express this texture, complex processes such as component control in steelmaking, slab reheating and hot rolling process factor control in hot rolling, hot-rolled sheet annealing heat treatment, primary recrystallization annealing, secondary recrystallization annealing are required, and these processes They must also be managed very precisely and strictly. On the other hand, it is also very important to control the inhibitor, which is one of the factors that express the Gossian aggregate, that is, the grain growth inhibitor, which suppresses the reckless growth of primary recrystallization and allows only the Goth aggregate to grow when the secondary recrystallization occurs. In order to obtain a Goss texture in the final annealing, growth of all primary recrystallization grains should be suppressed until just before secondary recrystallization occurs. . On the other hand, in order for secondary recrystallization to occur simultaneously during the high-temperature final annealing process, the inhibitor should not be easily decomposed due to excellent thermal stability. Secondary recrystallization is a phenomenon that occurs when the inhibitor that suppresses the growth of primary recrystallization grains during final annealing is decomposed or loses its inhibitory power in an appropriate temperature range. do.

In general, the quality of grain-oriented electrical steel sheet can be evaluated by magnetic flux density and iron loss, which are representative magnetic properties, and the higher the precision of the goth texture, the better the magnetic properties. In addition, high-quality grain-oriented electrical steel sheet can manufacture high-efficiency power devices due to its re-characteristics, thereby achieving high efficiency as well as miniaturization of power devices.

R&D to lower the iron loss of grain-oriented electrical steel sheet was first carried out from R&D to increase the magnetic flux density. The initial grain-oriented electrical steel sheet was manufactured by a two-fold cold rolling method using MnS as a grain growth inhibitor. The secondary recrystallization was stably formed, but the magnetic flux density was not very high and the iron loss was high. Afterwards, it was possible to manufacture grain-oriented electrical steel sheets with high magnetic flux density and low iron loss by using AlN and MnS precipitates in combination and performing cold rolling. By greatly improving the {110}<001> orientation in the rolling direction by strong grain growth inhibitor and cold rolling, high magnetic flux density could be obtained, and the resulting hysteresis loss was greatly improved to obtain the characteristic of low iron loss. became

On the other hand, as a part of further improving the magnetic properties of the electrical steel sheet, unlike the technology through the crystal grain growth suppression power by the precipitate, an alloy element that can obtain the inhibitory effect at a level similar to that of the precipitate is added after secondary recrystallization high temperature annealing. A technology to further increase the fraction of the goth texture, a technology to increase the fraction of the goth texture among the primary recrystallization textures during the primary recrystallization annealing process to increase the fraction of the secondary recrystallization microstructure of the goth texture after secondary recrystallization high-temperature annealing , a technique for uniformly distributing the size of the primary recrystallized grains to prevent the growth of the texture, which is not at all conducive to improving magnetic properties due to the non-uniformity of the primary recrystallized microstructure.

As a method conventionally proposed to implement various means for improving the magnetic properties of the grain-oriented electrical steel sheet as described above, there is a method using a precipitate having a relatively low alloy component and a solid solution temperature in the steel sheet.

For this purpose, by utilizing Sn and Sb in the decarburization process, the magnetism was improved by allowing the primary recrystallized grains to be stably maintained until the secondary recrystallization annealing. However, when Sb is introduced in excess, the surface oxide layer cannot be stably formed, so there is a problem in that adhesion is poor.

One embodiment of the present invention provides a grain-oriented electrical steel sheet and a method for manufacturing the same. Specifically, an embodiment of the present invention provides a grain-oriented electrical steel sheet having excellent surface adhesion and excellent magnetic properties and a method for manufacturing the same by supplementing grain growth inhibition with Mg-Sb precipitates.

Grain-oriented electrical steel sheet according to an embodiment of the present invention is Si: 2.5 to 4.0%, acid soluble Al: 0.020 to 0.040%, Mn: 0.20% or less (excluding 0%), N: 0.0055 in weight% on the steel sheet substrate % or less (excluding 0%), C: 0.005% or less (excluding 0%), S: 0.0055% or less (excluding 0%), Sb: 0.005 to 0.02%, and acid solubility Mg: 0.002 to 0.005%, and the balance includes Fe and other unavoidable impurities.

The steel plate substrate may satisfy Equation 1 below.

[Equation 1]

[Sb] ≥ 2.5×[acid soluble Mg]

(In Equation 1, [Sb] and [acid-soluble Mg] represent the contents (weight %) of Sb and acid-soluble Mg in the steel sheet substrate, respectively.)

The steel plate substrate may further include at least one of Sn: 0.005% to 0.10%, P: 0.02% to 0.075%, Cu: 0.001% to 0.1%, and Cr: 0.05 to 0.35%.

The steel plate substrate may include 20/μm ² to 100/μm ² Mg-Sb precipitates having a diameter of 10 nm or less.

The grain-oriented electrical steel sheet according to an embodiment of the present invention may have an iron loss of 0.89W/kg or less at 1.7T and 50Hz, and a magnetic flux density of 1.91T or more at 800A/m.

The metal oxide layer is positioned on the surface of the steel sheet substrate, and the adhesion test value performed by the bending test method may be 5 mm or less.

The method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention is Si: 2.5 to 4.0% by weight, acid soluble Al: 0.020 to 0.040%, Mn: 0.20% or less (excluding 0%), N: 0.0055 % or less (excluding 0%), C: 0.04 to 0.07%, S: 0.0055% or less (excluding 0%), Sb: 0.005 to 0.02%, and acid soluble Mg: 0.002 to 0.005% The step of producing a hot-rolled sheet by hot-rolling a slab that contains Fe and other unavoidable impurities, and satisfies the following Equation 1; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; primary recrystallization annealing of the cold-rolled sheet; and performing secondary recrystallization annealing of the cold-rolled sheet subjected to the primary recrystallization annealing.

[Equation 1]

[Sb] ≥ 2.5×[acid soluble Mg]

(In Formula 1, [Sb] and [acid-soluble Mg] represent the content (weight %) of Sb and acid-soluble Mg in the slab, respectively.)

After the step of manufacturing the hot-rolled sheet, the method further includes annealing the hot-rolled sheet, and after annealing the hot-rolled sheet, the average particle diameter of the precipitates in the hot-rolled sheet may be 200 to 3000 Å.

After the primary recrystallization annealing, the Mg-Sb precipitates having a diameter of 10 nm or less may include 20/㎛ ² to 100/㎛ ² .

In the method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, it is possible to manufacture a grain-oriented electrical steel sheet having excellent surface adhesion and excellent magnetic properties by forming Mg-Sb precipitates capable of securing crystal growth inhibitory power.

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.

In the grain-oriented electrical steel sheet according to an embodiment of the present invention, by adding appropriate amounts of Sb and Mg, the grain growth inhibitory power is supplemented with Mg-Sb precipitates to form a Goss texture with a very high degree of integration in the {110}<001> direction. can In addition, by adding Mg, which is a main component of the metal oxide layer, to the steel plate substrate, the adhesion between the steel plate substrate and the metal oxide layer can be improved.

Grain-oriented electrical steel sheet according to an embodiment of the present invention is Si: 2.5 to 4.0%, acid soluble Al: 0.020 to 0.040%, Mn: 0.20% or less (excluding 0%), N: 0.0055 in weight% on the steel sheet substrate % or less (excluding 0%), C: 0.005% or less (excluding 0%), S: 0.0055% or less (excluding 0%), Sb: 0.005 to 0.02%, and acid solubility Mg: 0.002 to 0.005%, and the balance includes Fe and other unavoidable impurities.

Hereinafter, the steel plate base component will be described in detail.

The steel sheet substrate means the inner portion of the electrical steel sheet excluding the metal oxide layer (base coating layer, glass layer, forsterite layer) formed near the surface of the grain-oriented electrical steel sheet.

Si: 2.5 to 4.0 wt%

Silicon (Si, silicon) is a basic composition of an electrical steel sheet, and serves to increase the specific resistance of the material to lower the core loss. When the Si content is too small, the specific resistance decreases, eddy current loss increases, and the iron loss characteristic deteriorates. During the secondary recrystallization annealing, a phase transformation between ferrite and austenat occurs, which not only makes the secondary recrystallization unstable but also severely damages the texture. do. On the other hand, if the Si content is too large, cold rolling may become difficult. Accordingly, Si may be included in the above-described range in the steel sheet substrate. More specifically, Si may include 2.8 to 3.6 wt%.

Acid soluble Al: 0.02 to 0.04 wt%

Aluminum (Al), in addition to AlN that is finely precipitated during hot rolling and annealing of hot-rolled sheets, combines with Al, Si, and Mn present in a solid solution state in the steel with nitrogen ions introduced by ammonia gas in the annealing process after cold rolling. It acts as a strong grain growth inhibitor by forming (Al,Si,Mn)N and AlN type nitrides. If the acid-soluble Al content is too small, the inhibitory power may not be sufficient. If the Al content is too high, the ability to inhibit grain growth may decrease by forming coarse nitrides. Therefore, Al may be included in the above-mentioned range in the steel plate substrate. More specifically, it may contain 0.025 to 0.035 wt%. Here, the acid-soluble Al refers to Al that is soluble in acids except for Al ₂ O ₃ , which is insoluble in acids, among Al. Compared to the amount of Al, Al ₂ O ₃ and the like are very small, and the total Al may include 0.02 to 0.04 wt%.

Mn: 0.20 wt% or less

Manganese (Mn) has an effect of reducing total iron loss by reducing eddy current loss by increasing specific resistance in the same way as Si. By forming Mn, Cu)S precipitates, it is an important element to inhibit the growth of primary recrystallized grains to cause secondary recrystallization. However, when Mn is added too much, a large amount of (Fe, Mn) and Mn oxides are formed on the surface of the steel sheet in addition to Fe ₂ SiO ₄ , which interferes with the formation of the metal oxide layer formed during the secondary recrystallization annealing, thereby reducing the surface quality. , because it induces a phase transformation between ferrite and austenite in the secondary recrystallization annealing process, the texture is severely damaged and the magnetic properties are greatly deteriorated. Therefore, Mn is included in an amount of 0.20% by weight or less. More specifically, it may contain 0.01 to 0.15 wt% of Mn.

N: 0.0055 wt% or less

Nitrogen (N) is an important element that reacts with Al and Si to form (Al,Si,Mn)N. If nitrogen is added too much, it causes a surface defect called blister due to nitrogen diffusion in the process after hot rolling, and because too much nitride is formed in the slab state, rolling becomes difficult, making subsequent processes complicated and manufacturing cost rises. do. On the other hand, N, which is additionally required to form (Al, Si, Mn)N nitride, is reinforced by nitriding in steel using ammonia gas in the primary recrystallization annealing process after cold rolling. At this time, it can be reinforced in 0.01 to 0.05 wt%. Thereafter, nitrogen is removed in the secondary recrystallization annealing process, and N may be included in an amount of 0.0055 wt% or less in the grain-oriented electrical steel sheet to be finally manufactured.

C: 0.005 wt% or less

Carbon (C) is an element that causes a phase transformation between ferrite and austenite to refine crystal grains and improve elongation. It is an essential element for improving the rollability of electrical steel sheets with poor rollability due to strong brittleness, but remains in the final product. Since it is an element that deteriorates magnetic properties by precipitating carbides formed due to the magnetic aging effect in the product plate, it needs to be controlled to an appropriate content. Specifically, C may be included in an amount of 0.005 wt % or less in the base material of the final prepared grain-oriented electrical steel sheet. More specifically, it may be included in an amount of 0.003 wt% or less.

On the other hand, in the slab, C is included in an amount of 0.04 to 0.07% by weight. If too little C is included in the above-mentioned range of Si content, it may cause non-uniformity of the microstructure of the slab and hot rolling because the phase transformation between ferrite and austenite does not work properly. On the other hand, after the annealing heat treatment of the hot-rolled sheet, the residual carbon in the steel sheet activates the fixation of dislocations during cold rolling to increase the shear strain zone and increase the place of Goss nuclei generation, thereby increasing the Goss crystal grain fraction of the primary recrystallization microstructure. It seems that more C is more beneficial, but if too much C is contained in the above-mentioned Si content range, it is not possible to obtain sufficient decarburization in the decarburization annealing process unless a separate process or equipment is added, as well as the phase transformation phenomenon caused by this As a result, the secondary recrystallization structure is severely damaged, and furthermore, when the final product is applied to an electric power device, magnetic properties deteriorate due to self-aging. Therefore, C in the slab may include 0.04 to 0.07% by weight. In the primary recrystallization annealing process to be described later, C is removed through decarburization, and C is included in an amount of 0.005 wt % or less in the grain-oriented electrical steel sheet substrate to be finally manufactured.

S: 0.0055 wt% or less

When sulfur (S) is contained too much, MnS precipitates are formed in the slab to suppress grain growth, and it is difficult to control the microstructure in the subsequent process because it segregates in the center of the slab during casting. In addition, since MnS is not used as a grain growth inhibitor in the present invention, it is not preferable to add more than the amount of S inevitably to cause precipitation. Therefore, the content of S may be 0.0055 wt% or less. More specifically, S may be included in an amount of 0.0010 to 0.0050 wt%.

Sb: 0.005 to 0.02 wt%

Antimony (Sb) basically segregates at grain boundaries to inhibit excessive growth of primary recrystallized grains, and in particular, in one embodiment of the present invention, it combines with Mg to form Mg-Sb precipitates to form primary recrystallized grain size and It plays a role of supplementing the grain suppression power by controlling the distribution.

When Sb is included in too little amount, it is difficult to exert its action properly. On the other hand, if too much Sb is added, the production of anchors that determine adhesion with the base iron produced by the oxide layer after the primary recrystallization annealing may be limited. Accordingly, it may contain 0.0050 to 0.0200 wt% of Sb. More specifically, it may include 0.0070 to 0.0180 wt% of Sb.

Acid soluble Mg: 0.0020 to 0.0050 wt%

Magnesium (Mg) is maintained in a solid solution in steel and then combined with Sb to supplement the inhibitor, and serves to improve adhesion between the steel plate substrate and the metal oxide layer. If the content of Mg is too small, the amount of inhibitor is insufficient to effectively control the primary recrystallization grain size. When the content of Mg is too large, the amount of the inhibitor is increased, excessively inhibiting the growth of primary recrystallization, and thus a secondary recrystallized structure with poor orientation may be obtained. Accordingly, it may contain 0.0020 to 0.0050 wt% of acid-soluble Mg. Here, the acid-soluble Mg means Mg soluble in an acid except for MgO, which is insoluble in an acid, among Mg. Compared to the total amount of Mg, MgO and the like are very small, and the total Mg may be included in an amount of 0.0020 to 0.0050 wt%.

The steel plate substrate may satisfy Equation 1 below.

[Equation 1]

[Sb] ≥ 2.5×[acid soluble Mg]

(In Equation 1, [Sb] and [acid-soluble Mg] represent the contents (weight %) of Sb and acid-soluble Mg in the steel sheet substrate, respectively.)

As described in Equation 1, when the correlation between Sb and acid-soluble Mg is properly satisfied, Mg-Sb precipitates are properly formed, and secondary recrystallization with a very high degree of integration in the {110}<001> orientation can be formed. That is, when Sb is too little or contains too much acid-soluble Mg, and thus Equation 1 is not satisfied, a secondary recrystallized structure having poor orientation may be obtained.

The balance contains iron (Fe). In addition, it may contain unavoidable impurities. Inevitable impurities mean impurities that are unavoidably mixed in the manufacturing process of steelmaking and grain-oriented electrical steel sheets. Since the unavoidable impurities are widely known, a detailed description is omitted. In one embodiment of the present invention, the addition of elements other than the above-described alloy components is not excluded, and may be included in various ways within the scope of not impairing the technical spirit of the present invention. When additional elements are included, they are included by replacing the remainder of Fe. For example, it is also possible within the scope of the present invention to contain at least one of Ni, Mo, Zr, Bi, Pb, As, Ge and Ga components in the steel.

The steel plate substrate may further include at least one of Sn: 0.005% to 0.10%, P: 0.02% to 0.75%, Cu: 0.001% to 0.1%, and Cr: 0.05 to 0.35%.

Sn: 0.005 to 0.100 wt%

Tin (Sn) is an auxiliary grain growth inhibitor with an excellent effect of segregating at grain boundaries and preventing the movement of grain boundaries. In addition, it is stably present at the grain boundary even at high temperatures and does not significantly affect decarburization and surface oxide layer formation. In addition, it promotes the generation of grains in the Goss orientation during hot rolling, helping to develop excellent magnetic secondary recrystallization. When too little Sn is added, the above-described effect cannot be sufficiently obtained. Conversely, when Sn is added too much, grain boundaries and surface segregation occur severely, and the load of the decarburization process gradually increases, and the possibility of plate breakage during cold rolling increases. Accordingly, the Sn content may be further included in an amount of 0.005 to 0.100 wt%. More specifically, it may further include 0.010 to 0.080 wt%.

P: 0.020 to 0.075 wt%

Phosphorus (P) segregates at grain boundaries and can play an auxiliary role in preventing grain boundaries and inhibiting grain growth at the same time, and has the effect of improving the {110}<001> aggregate structure in terms of microstructure. If the content of P is too small, it may be difficult to properly obtain the effect of addition. If the content of P is too large, the brittleness may increase and the rollability may be greatly deteriorated. Accordingly, it may further include 0.020 to 0.075 wt% of P. More specifically, it may further include 0.025 to 0.050 wt% of P.

Cu: 0.001 to 0.100 wt%

Copper (Cu) reacts with S to form Cu ₂ S precipitates and acts as an inhibitor to suppress the growth of primary recrystallized grains. When added together with Mn, it affects the size of MnS precipitates by forming [MnCu]S composite precipitates. If too little Cu is added, Cu ₂ S precipitate formation may be small, and thus the effect as an inhibitor may be small. Conversely, if too much Cu is added, S and precipitation may occur in the steel before Mn. Therefore, Cu may be further included in the range of 0.001 to 0.100 wt %. More specifically, it may further include 0.010 to 0.070 wt%.

Cr: 0.05 to 0.35 wt%

Chromium (Cr) is an element that reacts the fastest with oxygen to form Cr ₂ O ₃ on the surface of the steel sheet. Through this, the carbon component in the steel rapidly diffuses to the surface of the steel sheet and reacts with oxygen in the atmosphere gas to form CO gas, thereby accelerating decarburization. If too little Cr is added, the above-described effect cannot be sufficiently obtained. If too much Cr is added, it may not have a significant effect on the formation of the surface oxide layer. Therefore, it may further include 0.05 to 0.35 wt% of Cr. More specifically, it may further include 0.10 to 0.20 wt%.

As described above in an embodiment of the present invention, Mg-Sb precipitates are formed due to the addition of Mg and Sb, and they act as inhibitors to improve the {110}<001> aggregate structure. Mg-Sb precipitate means that Mg and Sb are aggregated and precipitated in the form of granules, and Mg and Sb in the precipitate are aggregated exceeding the upper limit of Mg and Sb of the steel sheet substrate. The Mg-Sb precipitate may be expressed in the form of a chemical formula of Mg _x Sb _y , and more specifically, may be expressed as Mg ₂ Sb ₃ . A precipitate in which Mg or Sb is deposited alone is not recognized as an Mg-Sb precipitate in an embodiment of the present invention.

In an embodiment of the present invention, the steel sheet substrate may include 20/μm ² to 100/μm ² Mg-Sb precipitates having a diameter of 10 nm or less. In this case, the diameter refers to the diameter of an imaginary circle having the same area as that of the Mg-Sb precipitate. Since Mg and Sb are added in relatively small amounts, Mg-Sb precipitates with a diameter of more than 10 nm are not substantially formed, and Mg-Sb precipitates that affect secondary recrystallization have a diameter of 10 nm or less. Calculate.

If the Mg-Sb precipitate is included too little, it is difficult to sufficiently exhibit the effect of improving the {110}<001> texture described above. In addition, when too much Mg-Sb precipitate is included, a secondary recrystallization structure with poor orientation may be obtained. More specifically, Mg-Sb precipitates having a diameter of 10 nm or less may include 20/㎛ ² to 50/㎛ ² .

As described above, due to the addition of Sb and Mg, the magnetism and adhesion can be improved at the same time. Specifically, the grain-oriented electrical steel sheet according to an embodiment of the present invention may have an iron loss of 0.890 W/kg or less at 1.7T and 50Hz, and a magnetic flux density of 1.910T or more at 800A/m. More specifically, the iron loss at 1.7T and 50Hz may be 0.850 to 0.885W/kg, and the magnetic flux density at 800A/m may be 1.910 to 1.930T.

In addition, the adhesion test value performed by the bending test method may be 5 mm or less. The bending test method is a method of measuring the minimum arc diameter without film peeling when the specimen is bent 180° in contact with the arc.

A method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises the steps of: manufacturing a hot-rolled sheet by hot-rolling a slab; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; primary recrystallization annealing of the cold-rolled sheet; and performing secondary recrystallization annealing of the cold-rolled sheet subjected to the primary recrystallization annealing.

Hereinafter, each step will be described in detail.

First, the slab is heated.

Slab is Si: 2.5 to 4.0% by weight, acid soluble Al: 0.020 to 0.040%, Mn: 0.20% or less (excluding 0%), N: 0.0055% or less (excluding 0%), C: 0.005 % or less (excluding 0%), S: 0.0055% or less (excluding 0%), Sb: 0.005 to 0.02%, and acid soluble Mg: 0.002 to 0.005%, and the balance contains Fe and other unavoidable impurities include

The alloy composition of the slab is substantially the same except for the alloy composition and C content of the base material of the grain-oriented electrical steel sheet, so the overlapping description will be omitted. Except for C, there is no substantial change in the alloy composition during the manufacturing process of the grain-oriented electrical steel sheet.

Returning to the description of the manufacturing process, the slab can be manufactured by the fragmentation method, the continuous casting method, and the thin slab casting or strip casting.

Before the slab is hot-rolled to produce a hot-rolled sheet, the slab may be heated. When heating the slab, it is preferable to do it in a temperature range in which N and S are dissolved in incomplete solution. If N and S are completely solutionized, a large amount of nitride or sulfide is formed after the annealing heat treatment of the hot-rolled sheet, so that one-time cold rolling, which is a subsequent process, becomes impossible, and an additional process is required. In addition, since the primary recrystallization grain size becomes quite fine, it may not be possible to express appropriate secondary recrystallization. Specifically, it is possible to heat the slab to a temperature of 1250 ℃ or less.

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

Hot rolling is performed to a thickness of 1.0 to 3.5 mm, and in consideration of the rolling load, rolling is terminated at a temperature of 850° C. or higher, and the rolling can be performed by cooling to a temperature of 600° C. or less.

In a hot-rolled hot-rolled sheet, a strained structure elongated in the rolling direction exists due to stress, and AlN, (Mn. Cu)S, and Mg-Sb precipitates are precipitated during hot rolling. Therefore, in order to have a uniform recrystallization microstructure and fine precipitate distribution before cold rolling, the hot-rolled sheet is heated to below the slab heating temperature once again to recrystallize the deformed structure, and to secure a sufficient austenite phase to inhibit the grain growth of the precipitates. can promote employment. That is, after the step of manufacturing the hot-rolled sheet, the step of annealing the hot-rolled sheet may be further included. At this time, the hot-rolled sheet annealing temperature may be subjected to a crack heat treatment at 900 to 1200 ℃ in order to take the austenite fraction to the maximum. After the annealing of the hot-rolled sheet, the average particle diameter of the precipitates in the hot-rolled sheet may be in the range of 200 to 3000 Å.

Next, the hot-rolled sheet is cold-rolled to manufacture a cold-rolled sheet.

Cold rolling can be carried out with a thickness of 0.10mm or more and 0.50mm or less by using a reverse rolling mill or a tandem rolling mill. Cold rolling can be performed once or twice or more with intermediate annealing in between. During one-time cold rolling, the orientations with low integration in the {110}<001> orientation rotate in the deformed orientation, and only Goss grains with the best alignment in the {110}<001> orientation exist in the cold-rolled sheet. On the other hand, in the two or more rolling methods, orientations with a low degree of integration also exist in the cold-rolled sheet, so that the secondary recrystallization occurs during the secondary recrystallization annealing, resulting in low magnetic flux density and iron loss. Therefore, cold rolling can be made into one cold rolling. The rolling ratio can be rolled to 87% or more.

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

During the primary recrystallization, the cold-rolled sheet undergoes decarburization and nitridation as well as recrystallization of the deformed structure. Primary recrystallization, decarburization and nitridation may be performed after decarburization and recrystallization, or nitridation may be performed simultaneously with primary recrystallization and decarburization. Primary recrystallization annealing may be heat-treated in the range of 800 to 950 ℃. If the temperature is too low, it takes a lot of time to decarburize, and the SiO ₂ oxide layer is densely formed on the surface of the steel sheet, and defects in the metal oxide layer may occur. If the temperature is too high, the primary recrystallization grains grow coarsely, and the crystal growth driving force is lowered, so that a stable secondary recrystallization is not formed. And although the annealing time is not a big problem to exhibit the effect of the present invention, it can be processed within 5 minutes in consideration of productivity.

After the primary recrystallization annealing, Mg-Sb precipitates having a diameter of 10 nm or less may include 20/㎛ ² to 100/㎛ ² . In this case, the diameter refers to the diameter of an imaginary circle having the same area as that of the Mg-Sb precipitate. Since Mg and Sb are added in relatively small amounts, Mg-Sb precipitates with a diameter of more than 10 nm are not substantially formed, and Mg-Sb precipitates that affect secondary recrystallization have a diameter of 10 nm or less. Calculate.

If the Mg-Sb precipitate is included too little, it is difficult to sufficiently exhibit the effect of improving the {110}<001> texture described above. In addition, when too much Mg-Sb precipitate is included, a secondary recrystallization structure with poor orientation may be obtained. More specifically, Mg-Sb precipitates having a diameter of 10 nm or less may include 20/㎛ ² to 50/㎛ ² . This Mg-Sb precipitate may remain in the above-mentioned range even after secondary recrystallization.

After the primary recrystallization annealing, an annealing separator may be applied.

Next, secondary recrystallization annealing is performed. By causing secondary recrystallization, a grain-oriented electrical steel sheet with excellent magnetic properties is manufactured by forming a {110}<001> texture in which the {110} surface of the steel sheet is parallel to the rolling surface and the <001> direction is parallel to the rolling direction . The purpose of secondary recrystallization annealing is broadly to form a {110}<001> texture by secondary recrystallization, to provide insulation by forming a glassy film by the reaction between the oxide layer formed during decarburization and MgO, and to remove impurities that impair magnetic properties. As the method of secondary recrystallization annealing, in the temperature increase section before secondary recrystallization occurs, the nitrogen and hydrogen mixed gas atmosphere is maintained to protect nitride, which is a grain growth inhibitor, so that secondary recrystallization can develop well, and secondary recrystallization is After completion, it is maintained in a hydrogen atmosphere for a long time to remove impurities.

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

The alloy components of Tables 1 and 2 and the remaining components are vacuum-melted by vacuum melting the component system containing the remainder Fe and other unavoidably contained impurities, and the ingot is heated to a temperature of 1200° C., and then hot rolled to a thickness of 2.6 mm. did The hot-rolled sheet was heated to a temperature of 1050° C., maintained at 950° C. for 180 seconds, and then rapidly cooled in water. After pickling, the hot-rolled annealed plate is cold-rolled once to a thickness of 0.27mm, and the cold-rolled plate is maintained at a temperature of 870°C for 180 seconds in a humid hydrogen, nitrogen and ammonia mixed gas atmosphere so that the carbon content is 30ppm or less, nitrogen Simultaneous decarburization annealing was performed so that the content was 200ppm.

MgO, an annealing separator, was applied to this steel sheet, and final annealing was performed in a coil shape. The final annealing was performed in a mixed atmosphere of 25 v% nitrogen and 75 v% hydrogen until 1200°C, and after reaching 1200°C, it was maintained in a 100 v% hydrogen atmosphere for more than 10 hours and then furnace cooled. Table 1 shows the precipitate density measured by the TEM replication method for the primary recrystallization annealed plate for each condition, the magnetic properties of the final plate, and the values measured for surface adhesion through a bending test.

Steel type (wt%) Si C Mn S N Sol. Al Etc A 3.3 0.06 0.12 0.0045 0.004 0.028 P:0.03 B 3.1 0.05 0.11 0.0050 0.005 0.030 Sn:0.05 C 3.4 0.06 0.12 0.0047 0.005 0.029 Cr:0.05 D 3.5 0.06 0.09 0.0055 0.005 0.032 Cu:0.02

steel grade Sb
(ppm) Sol.Mg
(ppm) Whether Equation 1 is satisfied P17/50
(W/kg) B8
(T) 10nm or less Mg-Sb precipitate density
(pcs/㎛ ² ) 5mm adhesion note A 15 10 X 0.988 1.874 6 O Comparative Goods 1 A 80 11 O 0.94 1.884 10 O Comparative Goods 2 A 120 12 O 0.933 1.886 12 O Comparative Goods 3 A 180 9 O 0.946 1.876 12 O Comparative Goods 4 A 230 12 O 0.943 1.877 13 X Comparative Goods 5 A 45 22 X 0.934 1.872 15 O Comparative Goods 6 A 70 21 O 0.882 1.917 24 O invention material 1 B 120 22 O 0.862 1.914 25 O invention material 2 B 180 21 O 0.871 1.912 26 O Invention 3 B 220 22 O 0.865 1.922 28 X Comparative Goods 7 B 250 23 O 0.855 1.928 30 X Comparative Goods 8 B 30 31 X 0.94 1.884 10 O Comparative Goods 9 B 60 30 X 0.939 1.88 12 O Comparative Goods 10 B 100 31 O 0.871 1.921 24 O Invention 4 B 150 30 O 0.871 1.913 28 O invention 5 C 160 32 O 0.874 1.928 30 O invention 6 C 130 34 O 0.872 1.917 31 O invention 7 C 120 35 O 0.87 1.914 29 O invention 8 C 190 31 O 0.855 1.919 34 O invention 9 C 250 32 O 0.843 1.914 36 X Comparative Goods 11 C 90 45 X 0.941 1.888 15 O Comparative Goods 12 C 120 42 O 0.872 1.911 23 O invention 10 C 150 48 O 0.873 1.921 35 O Invention 11 D 180 46 O 0.871 1.922 43 O Invention 12 D 230 42 O 0.861 1.92 53 X Comparative Goods 13 D 105 55 X 0.932 1.884 105 O Comparative Goods 14 D 160 56 O 0.944 1.879 124 O Comparative Goods 15 D 185 58 O 0.941 1.871 150 O Comparative Goods 16 D 230 57 O 0.936 1.882 140 X Comparative Goods 17 D 210 72 O 0.941 1.871 146 X Comparative Goods 18 D 240 78 O 0.932 1.873 180 X Comparative Goods 19 D 230 82 O 0.938 1.887 175 X Comparative Goods 20

As shown in Table 1, when Mg and Sb are included in appropriate amounts at the same time, Mg-Sb precipitates are properly formed, and it can be confirmed that the magnetic flux density, iron loss and adhesion are excellent.

On the other hand, it can be seen that Comparative Materials 1 to 5 contain too little Mg, so that Mg-Sb precipitates are not properly formed, and magnetic flux density and iron loss are inferior.

It can be seen that Comparative Materials 15 to 20 contain too much Mg, a large amount of Mg-Sb precipitates are formed, and poor magnetic flux density and iron loss.

It can be seen that Comparative Materials 6 and 9 contain too little Sb, so Mg-Sb precipitates are not properly formed, and magnetic flux density and iron loss are inferior.

It can be seen that Comparative Material 5, Comparative Material 7, Comparative Material 8, Comparative Material 11, and Comparative Material 13 contained too much Sb, resulting in poor adhesion.

Comparative material 10 and Comparative material 12 contained appropriate amounts of Mg and Sb, but contained less Sb than Mg, so that Equation 1 was not satisfied, Mg-Sb precipitates were not properly formed, and magnetic flux density and iron loss were poor. can be checked

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 (8)

To the steel sheet substrate, Si: 2.5 to 4.0% by weight, acid soluble Al: 0.020 to 0.040%, Mn: 0.20% or less (excluding 0%), N: 0.0055% or less (excluding 0%), C : 0.005% or less (excluding 0%), S: 0.0055% or less (excluding 0%), Sb: 0.005 to 0.02%, and acid soluble Mg: 0.002 to 0.005%, the balance being Fe and other unavoidable A grain-oriented electrical steel sheet containing impurities, wherein the steel sheet substrate satisfies Equation 1 below.
[Equation 1]
[Sb] ≥ 2.5×[acid soluble Mg]
(In Equation 1, [Sb] and [acid-soluble Mg] represent the contents (weight %) of Sb and acid-soluble Mg in the steel sheet substrate, respectively.) The method of claim 1,
The steel sheet substrate is Sn: 0.005% to 0.10%, P: 0.02% to 0.075%, Cu: 0.001% to 0.1%, and Cr: grain-oriented electrical steel sheet further comprising at least one of 0.05 to 0.35%. According to claim 1,
The steel sheet substrate is a grain-oriented electrical steel sheet comprising Mg-Sb precipitates having a diameter of 10 nm or less and 20 / μm ² to 100 / μm ² . The method of claim 1,
A grain-oriented electrical steel sheet with an iron loss of 0.89W/kg or less at 1.7T and 50Hz and a magnetic flux density of 1.91T or more at 800A/m. According to claim 1,
A grain-oriented electrical steel sheet having a metal oxide layer positioned on the surface of the steel sheet substrate and having an adhesion test value of 5 mm or less conducted by the bending test method. Si: 2.5 to 4.0% by weight, acid soluble Al: 0.020 to 0.040%, Mn: 0.20% or less (excluding 0%), N: 0.0055% or less (excluding 0%), C: 0.04 to 0.07 %, S: 0.0055% or less (excluding 0%), Sb: 0.005 to 0.02%, and acid soluble Mg: 0.002 to 0.005%, the balance contains Fe and other unavoidable impurities, and the following formula 1 is satisfied manufacturing a hot-rolled sheet by hot-rolling the slab;
manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet;
primary recrystallization annealing the cold-rolled sheet; and
A method of manufacturing a grain-oriented electrical steel sheet comprising the step of secondary recrystallization annealing of the cold-rolled sheet subjected to the primary recrystallization annealing.
[Equation 1]
[Sb] ≥ 2.5×[acid soluble Mg]
(In Formula 1, [Sb] and [acid-soluble Mg] represent the content (weight %) of Sb and acid-soluble Mg in the slab, respectively.) 7. The method of claim 6,
After the step of manufacturing the hot-rolled sheet, further comprising the step of annealing the hot-rolled sheet, after the annealing of the hot-rolled sheet, the average particle diameter of the precipitates in the hot-rolled sheet is 200 to 3000 Å method of manufacturing a grain-oriented electrical steel sheet. 7. The method of claim 6,
After the primary recrystallization annealing, Mg-Sb precipitates having a diameter of 10 nm or less are 20 / μm ² to 100 / μm ² A method of manufacturing a grain-oriented electrical steel sheet comprising.