KR20210079859A - Method of grain oriented electrical steel sheet - Google Patents

Abstract

The present invention provides a method for manufacturing a grain-oriented electrical steel sheet having excellent magnetic flux density and excellent adhesion to a glass film. A method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises: a step of heating a slab comprising 0.01 to 0.08 wt% of C, 2.5 to 3.5 wt% of Si, 0.02 to 0.1 wt% of Mn, 0.020 to 0.040 wt% of acid-soluble Al, 0.0030 to 0.0060 wt% of N, 0.0030 to 0.0065 wt% of S, and the remnant of Fe and other unavoidable impurities to 1150℃ or less; a step of preparing a hot-rolled sheet by hot-rolling the slab; a step of preparing a cold-rolled sheet by cold-rolling the hot-rolled sheet; a step of performing primary recrystallization annealing on the cold-rolled sheet; and a step of performing secondary recrystallization annealing on the cold-rolled sheet on which the primary recrystallization annealing has been performed.

Description

Manufacturing method of grain-oriented electrical steel sheet {METHOD OF GRAIN ORIENTED ELECTRICAL STEEL SHEET}

One embodiment of the present invention relates to a method of manufacturing a grain-oriented electrical steel sheet. Specifically, an embodiment of the present invention induces the formation of secondary recrystallization consisting of exact Goss grains of {110} <001> orientation, so that the magnetic flux density is very excellent and the glass film adhesion is excellent in the method of manufacturing a grain-oriented electrical steel sheet. it's about

The grain-oriented electrical steel sheet has a so-called Goss texture in which the orientation of all grains on the surface of the steel sheet is the {110} plane and the crystal orientation in the rolling direction is parallel to the <001> axis, so that magnetic properties in the rolling direction of the steel sheet are formed. This is a very good soft magnetic material. In general, the magnetic properties of an electrical steel sheet can be expressed in terms of magnetic flux density and iron loss, and high magnetic flux density can be obtained by accurately arranging grain orientations in {110}<001> orientations. Electrical steel sheet with a high magnetic flux density can reduce the size of the iron core material of electrical equipment, as well as lower hysteresis loss, enabling miniaturization and high efficiency of electrical equipment at the same time. Iron loss is the power loss consumed as thermal energy when an arbitrary AC magnetic field is applied to the steel sheet. It varies greatly depending on the magnetic flux density and thickness of the steel sheet, the amount of impurities in the steel sheet, specific resistance, and secondary recrystallization grain size. The higher the resistivity and the lower the plate thickness and the amount of impurities in the steel plate, the lower the iron loss and the efficiency of the electrical equipment increases.

Currently, there is a trend toward energy saving and high-efficiency commercialization in order to cope with global warming by reducing _{CO 2 emission worldwide.} The social demand for the development of grain-oriented electrical steel sheet having high magnetic flux density and low iron loss characteristics is increasing.

The grain-oriented electrical steel sheet developed in the early stage was manufactured through two cold rolling and high temperature annealing using MnS as a grain growth inhibitor. The secondary recrystallization was relatively stable by this manufacturing method, but the magnetic flux density (magnetic flux density at B8, 800A/m) was 1.80 Tesla, and the iron loss was higher than the current level. Afterwards, a method of manufacturing a grain-oriented electrical steel sheet having an excellent magnetic flux density of 1.87 Tesla or more with a magnetic flux density (B8) of 1.87 Tesla by using AlN and MnS precipitates in combination as a grain growth inhibitor and cold rolling once was proposed. is being used

However, this magnetic flux density level still needs improvement compared to the theoretical saturation magnetic flux density of grain-oriented electrical steel sheet, and it is necessary to improve the magnetic flux density in order to respond to the recent demand for high efficiency and miniaturization of transformers.

Conventionally, a method for manufacturing a grain-oriented electrical steel sheet through temperature gradient annealing during secondary recrystallization annealing has been proposed. However, in view of the mass production process in which the secondary recrystallization annealing is performed in a coil state, this method has high energy loss and cannot be implemented as an inefficient manufacturing method because it has to be heated from one side of the coil.

As another method of improving magnetic flux density, a manufacturing method of adding a Bi-containing material to molten steel of a grain-oriented electrical steel sheet using AlN and MnS precipitates was proposed. In addition, a method for manufacturing a grain-oriented electrical steel sheet having a high magnetic flux density was proposed through a method of containing Bi in the composition and rapidly heating in an oxidizing atmosphere after decarburization annealing.

All of the methods for manufacturing high magnetic flux density grain-oriented electrical steel sheets proposed so far are component systems that use AlN and MnS precipitates in combination, and in order to efficiently use these precipitates, a slab containing AlN and MnS precipitate forming elements is heated to a high temperature to form precipitates. Heat treatment to completely dissolve the solution was required. This heat treatment can be seen as a high-cost, low-efficiency manufacturing method in which the energy cost increases due to high-temperature heating of the slab, and the error rate decreases due to edge cracks during slab washing and hot rolling in which the slab melts at high temperatures. In addition, although it is possible to secure high magnetic flux density characteristics through the addition of Bi, most of the previously proposed patents focus on the problem of surface and secondary recrystallization instability formation due to the main addition of Bi. Various ideas have been proposed for this purpose, and it is difficult to produce stably in the actual manufacturing process and requires a lot of trial and error.

An embodiment of the present invention provides a method of manufacturing a grain-oriented electrical steel sheet. Specifically, in an embodiment of the present invention, a method of manufacturing a grain-oriented electrical steel sheet having excellent magnetic flux density and excellent glass film adhesion by inducing secondary recrystallization consisting of exact Goss crystal grains of {110} <001> orientation. to provide.

The method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention is, by weight, C: 0.01% to 0.08%, Si: 2.5% to 3.5%, Mn: 0.02% to 0.1%, acid soluble Al: 0.020% to 0.040%, N: 0.0030% to 0.0060%, and S: 0.0030% to 0.0065% containing, the balance heating the slab containing Fe and other unavoidable impurities to 1150 ℃ or less; preparing a hot-rolled sheet by hot-rolling the 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.

The slab may satisfy Equation 1 below.

[Equation 1]

4.0 ≤ [Al]/[N] ≤ 9.0

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

The primary recrystallization annealing step includes a heating step, a first cracking step, and a second cracking step, wherein the degree of oxidation (P1) in the heating step is 0.01 to 0.50, and the degree of oxidation (P2) in the first cracking step is 0.20 to 0.65, and the oxidation degree (P3) in the second cracking stage may be 0.01 to 0.30.

The slab may further include one or more of Sn: 0.005% to 0.10%, Sb: 0.0005% to 0.10%, P: 0.005% to 0.05%, Cu: 0.001% to 0.1%, and Cr: 0.01 to 0.1% .

A difference (P2-P1) between the degree of oxidation (P2) in the first cracking step and the degree of oxidation (P1) in the heating step may be 0.10 to 0.55.

A difference (P2-P3) of the degree of oxidation (P3) in the second cracking step with respect to the degree of oxidation (P2) in the first cracking step may be 0.10 to 0.45.

Ratio (Af/As) of absorbance (Af) of _{fayalite (Fayalite, Fe 2} SiO ₄ ) to absorbance (As) of _{silica (Silica, SiO 2} ) by reflection infrared spectrum on the surface of cold-rolled sheet subjected to primary recrystallization annealing (Af/As) This may be 0.30 to 0.60.

The amount of oxygen in the cold-rolled sheet subjected to the primary recrystallization annealing may be 500 to 1000 ppm.

The heating step may be a step of heating the cold-rolled sheet to a cracking temperature of the first cracking step, and the first cracking step and the second cracking step may be steps of cracking at a cracking temperature of 800 to 900°C.

The heating step may be performed for 1 to 60 seconds, the first cracking step may be performed for 1 to 5 minutes, and the second cracking step may be performed for 1 to 30 seconds.

At least one of the heating step, the first cracking step, and the second cracking step may be performed in an atmosphere comprising ammonia.

The nitrogen content of the cold-rolled sheet subjected to the primary recrystallization annealing may be 0.010 wt% to 0.030 wt%.

The method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention forms fine MnS precipitates capable of securing crystal growth inhibitory power, and then together with (Al, Si, Mn) N precipitates precipitated through decarburization and immersion annealing after cold rolling 1 It is possible to suppress the growth of tea recrystallized grains.

The method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention can improve magnetic flux density by appropriately suppressing the growth of primary recrystallized grains, thereby forming secondary recrystallization of exact Goss orientation in the secondary recrystallization annealing process.

The method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention is a grain-oriented electrical steel sheet having a good glass film (primary film, metal oxide film) properties advantageous for magnetization properties by precisely controlling the degree of oxidation in the primary recrystallization annealing process. can be manufactured.

Terms such as first, second and third 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 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 refers to 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, they 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 to which the present invention pertains can easily implement them. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In the meantime, various studies have been attempted to manufacture grain-oriented electrical steel sheets with excellent magnetic flux density.

In order to have excellent magnetic flux density, it is sufficient that there are many exact Goss-oriented grains, which are the nucleus of secondary recrystallization. As a method to form many exact Goss-oriented grains in the primary recrystallization microstructure, addition of segregation elements such as Bi, hot rolling asymmetric rolling, and cold rolling at a certain temperature or higher Various methods such as rolling have been studied.

Another method is to secure strong crystal growth inhibition so that only exact Goss-oriented grains already present in the primary recrystallization microstructure can be secondary recrystallized. For this purpose, a method of using AlN precipitates and MnS precipitates together has been developed, but in order to secure a strong inhibitory power, the formation of fine precipitates is important and the slab had to be heated to 1400°C.

As in the above method, grain-oriented electrical steel sheet manufacturing technology has been developed in a direction in which the manufacturing cost is high, the manufacturing process is complicated, and it is difficult to control, such as the addition of alloying elements and high temperature heating of the slab. The present inventors reviewed the development process of the high magnetic flux density grain-oriented electrical steel sheet manufacturing technology so far, and studied ways to fundamentally improve the magnetic flux density. As a result, the following conclusions were reached.

First, it is important to minimize the decrease in the saturation magnetic flux density and to secure the grain suppression force through fine precipitation. For this, it is necessary to properly control the alloy composition in the slab.

In addition, it is necessary to control the heating temperature of the slab in order to finely precipitate MnS.

In addition, it is necessary to control the _{degree of oxidation (PH 2} O/PH ₂ ) in the primary recrystallization annealing process to form a glass film advantageous for the movement of magnetic domains.

In summary, by optimizing the Mn content to secure excellent magnetic flux density characteristics, fine MnS precipitates are formed even when the slab is heated at 1150°C, and (Al,Si,Mn)N precipitates secured by decarburization and nitriding annealing after cold rolling and Together, it strongly inhibits the crystal growth of primary recrystallized grains to promote secondary recrystallization of exact Goss orientation grains, and at the same time forms high-quality fayalite and silica on the surface of steel sheet through precise control of atmospheric oxidation in the primary recrystallization annealing process. As a result, it is possible to manufacture a grain-oriented electrical steel sheet having a glass film with excellent adhesion to the steel sheet after final annealing.

The method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention is, by weight, C: 0.01% to 0.08%, Si: 2.5% to 3.5%, Mn: 0.02% to 0.1%, acid soluble Al: 0.020% to 0.040%, N: 0.0030% to 0.0060% and S: 0.0030% to 0.0065% containing, the balance is heated to 1150 ℃ or less of the slab containing Fe and other unavoidable impurities; preparing a hot-rolled sheet by hot-rolling the 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 in wt%, C: 0.01% to 0.08%, Si: 2.5% to 3.5%, Mn: 0.02% to 0.1%, acid soluble Al: 0.020% to 0.040%, N: 0.0030% to 0.0060%, and S : 0.0030% to 0.0065%, and the balance includes Fe and other unavoidable impurities.

Hereinafter, the reason for limiting the addition amount for each element will be described.

C: 0.01 to 0.08 wt%

Carbon (C) is an element that promotes austenite phase transformation and is an important element in making the hot-rolled structure of the grain-oriented electrical steel sheet uniform and promoting the formation of grains in the Goss orientation during cold rolling to manufacture a grain-oriented electrical steel sheet with excellent magnetism. If too little C is added, the above-described effect cannot be sufficiently obtained. In addition, secondary recrystallization may be unstable due to the non-uniform hot-rolled structure. If C is added too much, the primary recrystallized grains become fine due to the formation of a fine hot-rolled structure due to austenite phase transformation during hot rolling, and coarse carbide can be formed in the winding process after hot rolling or in the cooling process after hot-rolled sheet annealing. It is easy to cause non-uniformity in the tissue by forming Fe3C (Cementite) at room temperature. In addition, the time required for decarburization to 30 ppm or less in the decarburization process after cold rolling increases, resulting in excessive formation of Fayalite and Silica on the surface of the steel sheet. Accordingly, the content of C may be 0.01 to 0.08% by weight. More specifically, it may include 0.03 to 0.07 wt%.

C is removed by decarburization in the primary recrystallization annealing process, and may be included in an amount of 0.005 wt% or less in the grain-oriented electrical steel sheet to be finally manufactured.

Si: 2.5 to 3.5 wt%

Silicon (Si, silicon) is a basic composition of the electrical steel sheet, and serves to increase the resistivity of the material, that is, to lower the core loss (core loss), that is, the iron loss. When Si is added too little, the resistivity decreases, the effect of reducing eddy current loss is weak, and the amount of fayalite formed in the decarburization process becomes absolutely insufficient, and the glass film formation may become unstable. Conversely, when Si is added too much, the brittleness of the steel increases, making cold rolling difficult, and as a large amount of fayalite is formed in the decarburization process, the surface quality may deteriorate. Accordingly, it may contain 2.5 to 3.5 wt% of Si. More specifically, it may include 2.8 to 3.4% by weight.

Mn: 0.02 to 0.1 wt%

Manganese (Mn) has the same effect as Si to increase specific resistance and reduce iron loss. However, when a large amount of Mn is added, the suppression of grain growth is weakened by a decrease in saturation magnetic flux density and formation of coarse MnS precipitates rather than an effect of reducing iron loss due to an increase in specific resistance, thereby lowering the magnetic flux density after secondary recrystallization annealing and forming in the decarburization process. It also affects the Fayalite and Silica components, which prevents the formation of a good glass film.

Therefore, it is necessary to optimize the Mn content in order to form a glass film having excellent adhesion with excellent magnetic flux density characteristics. If Mn is added too little, the burden of refining in steelmaking may increase, and the amount of fine MnS precipitation that can be utilized to suppress crystal growth may decrease. If Mn is added too much, coarse MnS precipitation is promoted, and there is a problem in that the slab must be heated to 1150° C. or more in order to solutionize the MnS precipitate. In addition, it may interfere with the formation of high quality Fayalite and Silica during the decarburization process.

Acid soluble Al: 0.020 to 0.040 wt%

Acid-soluble aluminum (Al) combines with N to form AlN precipitates, and is a representative component of grain growth inhibitors for secondary recrystallization of grain-oriented electrical steel sheets. In one embodiment of the present invention, by forming (Al, Si, Mn) N precipitates through decarburization and nitridation annealing after cold rolling, the effect of inhibiting grain growth is secured. In the steelmaking step, it is preferable to add 0.020 to 0.040 wt% of acid-soluble Al. However, if too little Al is added, the total amount of (Al,Si,Mn)N precipitates formed in the primary recrystallization and nitriding processes is insignificant. The ability to inhibit recrystallization growth may be insufficient. Conversely, if too much Al is added, coarse microstructures are formed during decarburization and quenching annealing as the precipitates grow coarsely in the slab manufacturing and hot rolling process, resulting in unstable secondary recrystallization during the high temperature annealing process. have. Therefore, the content of acid-soluble Al may be 0.020 to 0.040 wt%. More specifically, it may be 0.020 to 0.035 wt%. Acid-soluble Al refers to Al that is soluble in acid, and refers to an Al content excluding Al such as Al ₂ O _{3 that is not soluble in acid among the total Al.}

N: 0.0030 to 0.0060 wt%

Nitrogen (N) is an important element that reacts with acid-soluble Al to form AlN precipitates that inhibit grain growth. In the manufacturing method for securing (Al, Si, Mn)N precipitates through nitriding after cold rolling, it is not necessary to contain a lot of N in the steelmaking step. However, if too little N is added, fine AlN precipitates are formed in the slab manufacturing step to make the primary recrystallization grain size fine, so that the exact Goss orientation makes secondary recrystallization of the grains easily occur. Conversely, if N is added too much, coarse AlN precipitates are formed in the slab manufacturing step, which creates a coarse primary recrystallization microstructure and makes secondary recrystallization unstable. Therefore, the range of N may be limited to 0.0030 to 0.0060 wt%. More specifically, it may include 0.0035 to 0.0055 wt%.

Acid-soluble Al and N may satisfy Equation 1 below.

4.0 ≤ [Al]/[N] ≤ 9.0

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

The formation of precipitates to suppress strong crystal growth is basically made in the primary recrystallization annealing (decarburization nitridation) process after cold rolling. Therefore, in order to secure a strong suppression power of (Al, Si, Mn) N precipitates by nitriding annealing, it is preferable that the amount of AlN precipitated in the steelmaking and slab manufacturing steps be as small as possible. For this, the ratio of the acid-soluble Al content and N added in the steelmaking step is very important. When the Al/N ratio is small, it means that the content of acid-soluble Al that is precipitated as AlN in the steelmaking and slab manufacturing steps is large, and it is impossible to secure a large amount of (Al,Si,Mn)N precipitates through decarburization and quenching annealing. Conversely, if the Al/N ratio is too large, the AlN precipitation amount is small in the steelmaking and slab manufacturing steps, and coarse grains are present in the slab. Accordingly, the primary recrystallization grains are also coarsened, making the secondary recrystallization unstable. Therefore, the Al/N ratio may be limited to 4.0 to 9.0. More specifically, it may be limited to a range of 4.0 to 8.0.

S: 0.0030 to 0.0065 wt%

Sulfur (S) generally reacts with Mn and Cu _{to form MnS or Cu 2} S precipitates and acts as an inhibitor to inhibit the growth of primary recrystallized grains. In order to secure fine MnS precipitates, the added Mn and S must be completely dissolved under the heating conditions of the slab at 1150° C. or less to act as an effective inhibitor. Therefore, it is preferable to be added within the range of the content of S capable of reacting with the addition amount of Mn. When too little S is added, the MnS precipitation amount is too small, so it may be difficult to secure the suppression power. If too much S is added, complete solid solution becomes difficult, and coarse MnS precipitates can be formed. In addition, S is an element with good grain boundary or surface segregation. In particular, during the high-temperature annealing process, S diffuses to the surface of the steel sheet and causes surface segregation, which interferes with the reaction of the glass film formed by the reaction of fayalite, silica, and MgO. Adhesion becomes inferior. Accordingly, S may be included in an amount of 0.0030 to 0.0065% by weight. More specifically, it may include 0.0040 to 0.0065 wt%.

The slab may further include one or more of Sn: 0.005% to 0.10%, Sb: 0.0005% to 0.10%, P: 0.005% to 0.05%, Cu: 0.001% to 0.1%, and Cr: 0.01 to 0.1% . More specifically, the slab may further include Sn: 0.005% to 0.10%, Sb: 0.0005% to 0.10%, P: 0.005% to 0.05%, Cu: 0.001% to 0.1%, and Cr: 0.01 to 0.1%.

Sn: 0.005 to 0.100 wt%

Tin (Sn) is an auxiliary grain growth inhibitor with an excellent effect of interfering with the movement of grain boundaries by segregation at grain boundaries. In addition, it is stably present at grain boundaries even at high temperatures and does not have a significant effect on 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. If 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 fracture during cold rolling increases. Accordingly, the Sn content is limited to 0.005 to 0.100 wt%. More specifically, it may contain 0.010 to 0.080 wt%.

Sb: 0.0005 to 0.10 wt%

Antimony (Sb) is an element having an excellent effect of interfering with the movement of grain boundaries by segregation at grain boundaries, like Sn. In addition, by controlling the depth of the inner oxide layer (Silica) formed in the decarburization process, magnetic domain movement is suppressed due to the inner oxide layer, thereby reducing the magnetic flux density and minimizing the increase in iron loss. When the effect of Sb is added alone, the grain boundary and surface segregation effects are strong, resulting in the possibility of plate breakage during cold rolling and delay of decarburization in the decarburization process. Therefore, it is preferable to compound it with Sn. When too little Sb is added, the above-described effect cannot be sufficiently obtained. Conversely, if too much Sb is added, cold rolling plate fracture and decarburization delay may occur. Therefore, the Sb content is limited to 0.0005 to 0.1000 wt%. More specifically, it may contain 0.010 to 0.080 wt%.

P: 0.005% to 0.05% by weight

Phosphorus (P), as a grain boundary segregation element, has the effect of inhibiting the growth of grains by interfering with the movement of grain boundaries, and has the effect of improving the {110}<001> Goss texture in terms of texture. When too little P is added, the above-described effect cannot be sufficiently obtained. If too much P is added, the brittleness may increase and the rollability may deteriorate significantly. Accordingly, it may contain 0.005% to 0.05% by weight of P. More specifically, it may contain 0.02 to 0.05 wt%.

Cu: 0.001 to 0.1 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, the fine MnS precipitates to be obtained in the present invention cannot be obtained by precipitating with S in the steel before Mn. Therefore, the Cu content is preferably limited to 0.001 to 0.100 wt%. More specifically, it may contain 0.010 to 0.070 wt%.

Cr: 0.01 to 0.10 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, the amount of Cr added is limited to 0.01 to 0.10 wt%. More specifically, it may include 0.03 to 0.08 wt%.

The balance contains iron (Fe). It may also 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 alloy components described above 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 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.

Returning to the description of the manufacturing process, the slab is heated to 1150 °C or less. Slabs can be cast by ingot method, continuous casting method, thin slab casting, or strip casting. In the case of ingot method, continuous casting and thin slab casting, slabs are manufactured and then slab heating and hot rolling are performed in the subsequent process.

Slab heating is basically a grain-oriented electrical steel sheet manufacturing method that secures (Al,Si,Mn)N precipitates through decarburization and quenching annealing after cold rolling of AlN-based precipitates, which are the main crystal growth inhibitors required for secondary recrystallization of Goss orientation. Therefore, after heating the slab to 1150° C. or less, hot rolling may be performed. The amount of Mn and S added in the steelmaking step so that the solid solution temperature of the MnS precipitate formed by the reaction of Mn and S added to form fine MnS as an auxiliary crystal growth inhibitor in the slab heating and hot rolling process is 1150° C. or less was limited.

If the slab is heated at too high a temperature, the AlN precipitates formed during the solidification process of the slab manufacturing step are excessively dissolved in the slab heating step, and then finely precipitated in the hot rolling process to make the crystal grain size fine in the hot rolling and decarburization process to make exact Goss It prevents the formation of secondary recrystallization of the orientation grains. The lower the slab heating temperature is within the range in which MnS precipitated according to the added Mn and S content can be completely dissolved, but specifically, considering the hot rolling load, it can be heated at 1000°C to 1150°C.

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

Hot rolling is performed to a thickness of 1.0 to 3.5 mm, and in consideration of the rolling load, rolling may be finished at a temperature of 850° C. or higher, and then cooled to a temperature of 600° C. or less and wound up.

The hot-rolled steel sheet can be made to smoothly roll up to the thickness of the final product in the cold-rolling process, which is a post-process, by recrystallizing the deformed structure hot-rolled in the subsequent hot-rolled sheet annealing process. In general, the annealing temperature of the hot-rolled sheet is preferably heated to a temperature of 800° C. or higher for recrystallization and maintained for a certain period of time, and annealing at a plurality of temperatures is also possible to control the distribution and size of the precipitate. The hot-rolled sheet annealing may be omitted if necessary.

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

The hot-rolled sheet is subjected to pickling to remove the oxide layer on the surface of the steel sheet, and then cold-rolled. Cold rolling is a process of lowering the thickness of a steel sheet to the thickness of the final product, and it is rolled to the thickness of the final product by performing one or more cold rolling including intermediate annealing. At this time, cold rolling can be performed at a rolling rate of at least 80% or more because the cold rolling rate affects the improvement of magnetic flux density after the final secondary recrystallization annealing by strengthening the degree of integration in the Goss direction. If the cold rolling rate is too low, the degree of integration in the Goss direction is low and the magnetic flux density of the final product is lowered. Therefore, the cold rolling rate should be at least 80% or more, and the maximum rolling rate may be rolled up to the maximum rolling possible range according to the rolling capacity of the rolling equipment. In addition, when the plate temperature of the cold-rolled steel sheet is raised to 50° C. or higher during the cold rolling process, a large number of secondary recrystallization nuclei in the Goss orientation are generated due to work hardening by solid solution carbon, thereby improving the magnetic flux density of the final product. If the temperature of the cold-rolled steel sheet is too low, the secondary recrystallization nuclei in the Goss orientation are insignificant. Conversely, if it exceeds 300°C, the work hardening effect by solid solution carbon is weakened and the secondary recrystallization nuclei in the Goss orientation are weakened. Accordingly, in the cold rolling process, the steel sheet may be maintained in the region of 50 to 300° C. at least once in the intermediate rolling step.

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

In the primary recrystallization annealing step, the carbon component present in the steel sheet diffuses the surface of the steel sheet and reacts with oxygen present in the atmospheric gas to form CO gas, thereby causing decarburization reaction. If the temperature is too low, since the decarburization reaction is slowed, the steel sheet can be heated to 800° C. or higher in order to cause a smooth decarburization reaction. Along with this decarburization reaction, a new structure without deformation is formed in the microstructure deformed by cold rolling, which is called primary recrystallization. The primary recrystallization structure is greatly affected by the content of the steelmaking components, especially the precipitate forming elements, the amount of deformation received during cold rolling, and the temperature at which the steel sheet is heated. When the temperature at which the steel sheet is decarburized is 800° C. or less, a lot of recrystallization occurs from the deformed structure, and the primary recrystallization microstructure becomes very fine. In this case, secondary recrystallization of the Goss-oriented grains easily occurs, resulting in inferior magnetic flux density. Conversely, when the decarburization temperature of the steel sheet is 900°C or higher, the Si present in the steel also reacts with oxygen to actively form silica, thereby inhibiting the decarburization reaction, and the size of the crystal grains recrystallized from the deformed structure becomes very coarse, so that in high-temperature annealing It makes the secondary recrystallization of Goss-oriented grains unstable. Accordingly, the cracking temperature of the first cracking stage of the primary recrystallization and the cracking temperature of the second cracking stage of the primary recrystallization may be 800 to 900°C.

In order to secure a glass film with excellent adhesion to the final product, it is very important to control the _{degree of oxidation (PH 2} O /PH _{2 ) during the primary recrystallization annealing process.} When the steel sheet is annealed in the temperature range of 800 to 900°C, the rate of decarburization reaction is changed by the degree of oxidation of the gas atmosphere, and the type of oxide layer formed on the surface layer of the steel sheet is also changed. In general, the oxide layer formed on the surface layer of the steel sheet in the decarburization process includes fayalite (Fayalite, Fe2SiO4), silica (Silica, SiO ₂ ), and iron oxides such as _{FeO, Fe 2} O ₃ , and Fe ₃ O _{4 .} Among them, the oxide layer of fayalite and silica plays a very important role in forming the glass film of the final product, and it is very important to control the formation amount of fayalite and silica well in the decarburization and quenching process.

Specifically, the step of primary recrystallization annealing includes a heating step, a first cracking step, and a second cracking step, and the degree of oxidation (P1) in the heating step is 0.01 to 0.50, and the degree of oxidation (P2) in the first cracking step ) may be 0.20 to 0.65, and the oxidation degree (P3) in the second cracking stage may be 0.01 to 0.30.

The heating step is a step of heating the cold-rolled sheet to the cracking temperature of the first cracking step. That is, it is a step of heating the cold-rolled sheet to a temperature of 800 to 900°C.

The degree of oxidation (P1) in the heating step is 0.01 to 0.50. If the degree of oxidation (P1) in the heating step is too small, a large amount of Fayalite oxide layer is formed at the primary cracking temperature of 800 to 900° C. without the formation of the silica oxide layer at the initial 800° C. or lower, and the surface called Fe mound in the final product Adhesion may be deteriorated along with defects. Even if the degree of oxidation (P1) in the heating step is too large, the formation of Fayalite is promoted in the same way, and adhesion may be deteriorated along with surface defects. More specifically, the degree of oxidation (P1) in the heating step may be 0.03 to 0.45.

The heating step may be performed for 1 second to 60 seconds.

The first cracking step is a step of cracking the steel sheet that has undergone the heating step at a cracking temperature of 800 to 900°C.

The degree of oxidation (P2) in the first cracking stage is 0.20 to 0.65. In the first cracking stage, the decarburization reaction takes place in earnest, and silica and fayalite oxides are actively formed along with the decarburization reaction on the surface of the steel sheet. In particular, Fayalite is formed in the outermost layer of the steel sheet, and the degree of oxidation of the atmosphere at this time is very important. If the oxidation degree (P2) in the first cracking stage is too small, the formation of fayalite is small and silica is deeply formed as an internal oxide layer in the steel sheet. In this case, the forsterite layer formed by reacting with MgO, an annealing separator, penetrates deeply into the steel sheet during the high-temperature annealing process to lower the magnetic flux density of the steel sheet. If the oxidation degree P2 in the first cracking stage is large, a large amount of Fayalite is formed and the density of the oxide layer formed on the surface of the steel sheet is decreased. In this case, the decomposition of (Al, Si, Mn) N precipitates formed by immersion annealing in the high temperature annealing process occurs easily, and secondary recrystallization of exact Goss orientation does not occur stably, resulting in inferior magnetic flux density. More specifically, the oxidation degree (P2) in the first cracking stage may be 0.25 to 0.65.

The first cracking step may be performed for 1 to 5 minutes.

A difference (P2-P1) between the degree of oxidation (P2) in the first cracking step and the degree of oxidation (P1) in the heating step may be 0.10 to 0.55. Silica and Fayalite oxides can be properly formed only when the above-described difference in oxidation degree exists appropriately.

The second cracking step is a step of cracking the steel sheet that has undergone the first cracking step at a cracking temperature of 800 to 900°C. The first cracking stage and the second cracking stage can be distinguished through the degree of oxidation of the atmosphere.

The degree of oxidation (P3) in the second cracking stage is 0.01 to 0.30. Although silica and Fayalite of good quality were previously formed in the first cracking stage, Fayalite formed at a high temperature of 800 to 900° C. exists in a non-dense structure. If fayalite that is not dense is present on the surface of the steel sheet, forsterite formed by reacting with MgO in the final high-temperature annealing is also not dense, so the adhesion of the glass film of the final product is deteriorated and the insulation is also poor. In the second cracking step, the degree of oxidation is controlled within the above-mentioned range to make Fayalite dense. If the oxidation degree (P3) in the second cracking stage is too low, Fayalite is excessively reduced to form an oxide such as FeO, which may cause surface defects such as Fe mound. If the oxidation degree (P3) in the second cracking stage is too high, the density of the fayalite is deteriorated as the fayalite is not sufficiently reduced, and the (Al,Si,Mn)N precipitates are easily decomposed during the high-temperature annealing process, resulting in the secondary The recrystallization becomes unstable, the magnetic flux density decreases, and the adhesion of the glass film decreases.

The second cracking step may be performed for 1 to 30 seconds.

A difference (P2-P3) of the degree of oxidation (P3) in the second cracking step with respect to the degree of oxidation (P2) in the first cracking step may be 0.10 to 0.45. Fayalite can be densely formed only when the above-described difference in oxidation degree exists appropriately.

Thus, the steel sheet subjected to the primary recrystallization annealing by controlling the oxidation degree appropriately is the ratio of the absorbance (Af) of _{fayalite (Fayalite, Fe 2} SiO ₄ ) to the absorbance (As) of _{silica (Silica, SiO 2 ) by reflected infrared spectrum (Af)} (Af/As) may be 0.30 to 0.60. If a lot of fayalite is formed on the surface of the steel sheet, it is reduced to FeO through the reduction process during the high-temperature annealing process, or a thin glass film is formed to form a defect called Fe-mound. If there is a lot of silica, black stains during the final high-temperature annealing process It serves as a seed for the formation of _{Fe 3} O _{4 oxide.} These defects eventually act as factors that impede the movement of magnetic domains, making it difficult to secure excellent magnetic flux density. Therefore, it is possible to improve the magnetic flux density by appropriately controlling the formation ratio of Fayalite and Silica. More specifically, Af/As may be 0.31 to 0.60.

In addition, the amount of oxygen of the cold-rolled sheet subjected to the primary recrystallization annealing may be 500 to 1000 ppm. The amount of oxygen may have a concentration gradient depending on the thickness, and the above-described oxygen amount means an average amount of oxygen included in the entire steel sheet based on a steel sheet having a thickness of 0.23 mm.

In the primary recrystallization annealing process, nitridation may proceed simultaneously with decarburization through the above-described degree of oxidation control.

For nitriding, ammonia may be added to a _{wet H 2} and N _{2 atmosphere.}

Nitriding may be performed in one or more of the heating step, the first cracking step, and the second cracking step. That is, at least one of the heating step, the first cracking step, and the second cracking step may be performed in an atmosphere containing ammonia.

Nitriding may be performed so that the nitrogen content of the cold-rolled sheet subjected to the primary recrystallization annealing is 0.010 wt% to 0.030 wt%. As such, it is possible to secure (Al,Si,Mn)N precipitates with strong crystal growth inhibition through nitriding.

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

The cold-rolled sheet subjected to primary recrystallization annealing is subjected to secondary recrystallization by applying an annealing separator based on MgO, then raising the temperature to 1000° C. or higher and performing crack annealing for a long time so that the {110} side of the steel sheet is parallel to the rolling side, The <001> direction forms a texture with a Goss orientation parallel to the rolling direction.

The grain-oriented electrical steel sheet according to an embodiment of the present invention is particularly excellent in iron loss and magnetic flux density characteristics. And the grain-oriented electrical steel sheet according to one embodiment of the invention, the magnetic flux density (B ₈₎ is 1.916T or more, the iron loss (W _17/50) this can be not more than 0.95W / kg. At this time, the magnetic flux density B ₈ is the magnitude of the magnetic flux density (Tesla) induced under a magnetic field of 800 A/m, and the iron loss W 17/50 is the magnitude of the iron loss induced under the conditions of 1.7 _{Tesla and 50 Hz (W/kg).}

Moreover, it is excellent also in glass film adhesiveness. Adhesion can be measured with the minimum arc diameter without film peeling when bending 180° in contact with an arc of a certain diameter. Specifically, the glass film adhesion may be 20mmΦ or less.

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

Example 1

C:0.052%, Si:3.15%, acid soluble Al:0.028%, N:0.0050%, P:0.02%, Sn:0.05%, Sb:0.02%, Cu:0.02, Cr:0.03% based on weight% The composition was made by vacuum melting the component system in which the Mn and S contents were changed as shown in Table 1 below to make a slab, and the slab was heated to a temperature of 1150° C., then hot rolled to a thickness of 2.3 mm, and then rapidly cooled to 600° C. and wound up. .

The hot-rolled sheet was annealed at 1080°C, pickled, and cold-rolled once to a thickness of 0.23 mm. The cold-rolled steel sheet is heated to 850°C and then maintained for 180 seconds in a humid hydrogen, nitrogen, and ammonia mixed gas atmosphere, thereby forming primary recrystallization and nitriding at the same time so that the total nitrogen content of the steel sheet becomes 200 ppm. (Al,Si,Mn)N precipitates were formed. At this time, the degree of oxidation in the heating step was maintained at 0.2, and the degree of oxidation in the first cracking step was maintained at 0.5, and then maintained for 25 seconds at an oxidation degree of 0.15 in the second cracking step before cooling. After the primary recrystallization annealing, the ratio of As/Af measured by the reflected infrared spectrum was 0.5, and the measured oxygen content was 910 ppm and the nitrogen content was 250 ppm. Next, MgO, an annealing separator, was applied to the steel sheet, and secondary material crystal annealing was performed in a coil shape. The secondary recrystallization annealing was _{carried out in a mixed gas atmosphere of 25v% N 2} and 75v% H ₂ up to 1200° C., and after reaching 1200° C., it was _{maintained for 20 hours in a 100v% H 2} gas atmosphere and then slowly cooled.

Table 1 shows the magnetic properties after high temperature annealing for secondary recrystallization according to the respective Mn and S contents and the evaluation results of the adhesion of the glass film formed on the surface layer of the steel sheet. Adhesion was measured with the minimum arc diameter without film peeling when bending 180° in contact with arcs of 10, 15, 20, 25, and 30 diameters.

Mn
(wt%) S
(wt%) MnS solution temperature
(℃) magnetic flux density
(B8, Tesla) iron loss
(W17/50,
W/kg) Glass film adhesion
(mmΦ) division 0.01 0.0043 820 1.877 0.95 20 Comparative Goods 1 0.02 0.0051 907 1.937 0.81 15 invention material 1 0.03 0.0048 946 1.939 0.81 15 Invention 2 0.05 0.0055 1026 1.945 0.80 20 invention 3 0.05 0.0080 1077 1.918 0.89 25 Comparative Goods 2 0.07 0.0064 1094 1.952 0.78 20 Invention 4 0.07 0.0025 969 1.895 0.89 20 Comparative Good 3 0.09 0.0054 1106 1.935 0.80 20 Invention 5 0.1 0.0045 1094 1.948 0.78 15 invention 6 0.1 0.0076 1175 1.915 0.88 30 Comparative Goods 4 0.12 0.0041 1107 1.891 0.94 35 Comparative Goods 5

As shown in Table 1, when Mn and S are appropriately included, it can be confirmed that the magnetic flux density, iron loss and adhesion are excellent.

On the other hand, Comparative Material 1 contains too little Mn, so it can be seen that the magnetic flux density is inferior.

Comparative material 2 contains too much S, so it can be seen that the adhesiveness is poor.

Comparative material 3 contains too little S, so it can be seen that the magnetic flux density is inferior.

Comparative material 4 contains too much S, so it can be seen that the magnetic flux density and adhesion are inferior.

Comparative material 5 contains too much Mn, and it can be seen that the magnetic flux density and adhesion are inferior.

Example 2

By weight%, C:0.062%, Si:3.4%, Mn:0.05%, S:0.0060%, P:0.05%, Sn:0.07%, Sb:0.02%, Cu:0.05, Cr:0.05% as a basic composition and vacuum dissolution by changing the acid-soluble Al and N contents as shown in Table 2 below, and then heating the slab to 1100°C. Then, hot rolling was performed to prepare a hot-rolled sheet having a thickness of 2.6 mm. The hot-rolled sheet was heated to 1050° C. and maintained for 150 seconds, then cooled, pickled, and cold-rolled. The thickness of cold rolling was 0.30 mm, and cold rolling was performed by maintaining at least 10 minutes at a temperature of 200°C or higher during cold rolling. Thereafter, the primary recrystallization annealing was performed by heating the cold-rolled steel sheet to a temperature of 830° C. and maintaining it for 150 seconds. The oxidation degree in the heating step was maintained at 0.1, the oxidation degree in the first cracking step was maintained at 0.6, and then the oxidation degree in the second cracking step was maintained at 0.10 condition for 5 seconds. The steel sheet subjected to the primary recrystallization annealing had an As/Af ratio of 0.35 as measured by the reflected infrared spectrum, and the amount of oxygen measured in the steel sheet after decarburization and quenching annealing was 650 ppm (848 ppm based on 0.23 mm), and the nitridation amount was 250 ppm. Thereafter, MgO annealing separator coating and secondary recrystallization annealing were performed under the same conditions as in Example 1.

Acid Soluble Al
(wt%) N
(wt%) Al/N ratio magnetic flux density
(B8, Tesla) iron loss
(W17/50,
W/kg) Glass film adhesion
(mmΦ) division 0.018 0.0030 6 1.875 1.15 20 Comparative Goods 1 0.020 0.0025 8 1.903 1.03 20 Comparative Goods 2 0.020 0.0035 5.7 1.936 0.95 20 invention material 1 0.024 0.0025 9.6 1.923 0.99 20 Comparative Good 3 0.024 0.0060 4 1.951 0.92 20 Invention 2 0.026 0.0045 5.8 1.943 0.93 15 invention 3 0.028 0.0040 7 1.935 0.95 15 Invention 4 0.028 0.0025 11.2 1.901 1.03 15 Comparative Goods 4 0.030 0.0050 6 1.948 0.93 15 Invention 5 0.030 0.0025 12 1.882 1.12 20 Comparative Goods 5 0.035 0.0055 6.4 1.953 0.92 20 invention 6 0.040 0.0050 8 1.938 0.95 20 invention 7 0.042 0.0055 7.6 1.894 1.08 20 Comparative Goods 6

As shown in Table 2, when Al and N are appropriately included, it can be confirmed that the magnetic flux density, iron loss and adhesion are excellent.

On the other hand, Comparative Material 1 contains too little Al, so it can be seen that the magnetic flux density and iron loss are inferior.

Comparative material 2 contains too little N, and it can be confirmed that the magnetic flux density and iron loss are inferior.

Comparative material 3 has an Al/N value that is too large, so it can be seen that the iron loss is poor.

It can be seen that Comparative Material 4 has an Al/N value that is too large, and has poor magnetic flux density and iron loss.

It can be seen that Comparative Material 5 has a too large Al/N value, and thus has poor magnetic flux density and iron loss.

Comparative material 6 contains too much Al, and it can be seen that the magnetic flux density and iron loss are inferior.

Example 3

C:0.045%, Si:2.9%, Mn:0.03%, S:0.0040%, acid soluble Al:0.030%, N:0.0055%, P:0.03%, Sn:0.02%, Sb:0.05%, A grain-oriented electrical steel sheet slab containing Cu: 0.05, Cr: 0.08%, the remainder Fe and other unavoidably added impurities was made, and then heated to a temperature of 1150 ° C., and then hot rolled to a thickness of 2.3 mm. The hot-rolled sheet was heated to 1120° C. and maintained for 100 seconds, then cooled, pickled, and cold-rolled. The thickness of cold rolling was 0.23 mm, and cold rolling was performed by maintaining at least 10 minutes at a temperature of 200°C or higher during cold rolling. The oxidation degree in each heating, first cracking, and second cracking stage of the primary recrystallization annealing was changed as shown in Table 3 below. As a result, the ratio of As/Af was measured using the reflected infrared spectrum and summarized in Table 3, and the amount of oxygen in the steel sheet was measured and summarized in Table 3 below. The nitridation amount was 200 ppm. Thereafter, the MgO annealing separator was applied to the steel sheet, and the secondary recrystallization annealing was performed under the same conditions as in Example 1.

heating stage
degree of oxidation 1st crack stage
degree of oxidation Second crack stage
degree of oxidation As/Af ratio amount of oxygen
(ppm) Glass film adhesion
(mmΦ) magnetic flux density
(B8, Tesla) iron loss
(W17/50,
W/kg) division 0.005 0.500 0.100 0.25 450 25 1.875 0.96 Comparative Goods 1 0.030 0.300 0.100 0.32 620 20 1.938 0.82 invention material 1 0.100 0.500 0.150 0.45 760 20 1.945 0.80 Invention 2 0.100 0.650 0.050 0.53 880 20 1.955 0.78 invention 3 0.100 0.700 0.200 0.73 950 25 1.918 0.87 Comparative Goods 2 0.100 0.600 0.350 0.75 1050 30 1.917 0.88 Comparative Good 3 0.300 0.500 0.100 0.60 930 15 1.957 0.77 Invention 4 0.550 0.550 0.150 0.72 980 25 1.902 0.92 Comparative Goods 4 0.300 0.150 0.100 0.20 620 20 1.891 0.95 Comparative Goods 5 0.200 0.450 0.005 0.28 740 20 1.895 0.93 Comparative Goods 6 0.200 0.450 0.150 0.50 890 15 1.951 0.77 Invention 5 0.400 0.300 0.100 0.50 960 20 1.942 0.80 invention 6 0.450 0.250 0.010 0.41 850 15 1.949 0.78 invention 7 0.100 0.550 0.300 0.60 980 20 1.953 0.77 invention 8

As shown in Table 3, when the degree of oxidation in heating, the first cracking and the second cracking stage is appropriately included, after the primary recrystallization annealing, the As/Af ratio is properly formed, the oxidation amount is appropriate, magnetic flux density, It can be seen that the adhesion is excellent.

On the other hand, Comparative Material 1 has a low oxidation degree in the heating step, a low As/Af ratio, a low oxidation amount, and poor adhesion, magnetic flux density and iron loss.

It can be seen that Comparative Material 2 has a high degree of oxidation in the first cracking stage, a high As/Af ratio, and poor adhesion.

It can be seen that Comparative Material 3 has a high degree of oxidation in the second cracking stage, a high As/Af ratio and oxygen content, and poor adhesion.

It can be seen that Comparative Material 4 has a high degree of oxidation in the heating step, a high As/Af ratio, and poor adhesion and magnetic flux density.

It can be seen that Comparative Material 5 has a low oxidation degree in the first cracking stage, a low As/Af ratio, and a poor magnetic flux density.

It can be seen that Comparative Material 6 has a low oxidation degree in the second cracking stage, a low As/Af ratio, and a poor magnetic flux density.

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 (10)

By weight, C: 0.01% to 0.08%, Si: 2.5% to 3.5%, Mn: 0.02% to 0.1%, acid soluble Al: 0.020% to 0.040%, N: 0.0030% to 0.0060%, and S:0.0030 % to 0.0065%, the remainder including Fe and other unavoidable impurities, heating the slab satisfying Equation 1 to 1150° C. or less;
preparing 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
Comprising the step of secondary recrystallization annealing of the cold-rolled sheet subjected to the primary recrystallization annealing,
The primary recrystallization annealing includes a heating step, a first cracking step and a second cracking step,
The degree of oxidation (P1) in the heating step is 0.01 to 0.50,
The degree of oxidation (P2) in the first cracking stage is 0.20 to 0.65,
A method of manufacturing a grain-oriented electrical steel sheet having an oxidation degree (P3) of 0.01 to 0.30 in the second cracking step.
[Equation 1]
4.0 ≤ [Al]/[N] ≤ 9.0
(In Formula 1, [Al] and [N] represent the content (weight %) of acid-soluble Al and N in the slab.) According to claim 1,
Sn: 0.005% to 0.10%, Sb: 0.0005% to 0.10%, P: 0.005% to 0.05%, Cu: 0.001% to 0.1%, and Cr: grain-oriented electrical steel sheet further comprising at least one of 0.01 to 0.1% manufacturing method. According to claim 1,
The difference (P2-P1) of the degree of oxidation (P1) in the heating step with respect to the degree of oxidation (P2) in the first cracking step is 0.10 to 0.55. According to claim 1,
The difference (P2-P3) of the degree of oxidation (P3) in the second cracking step with respect to the degree of oxidation (P2) in the first cracking step is 0.10 to 0.45. According to claim 1,
A method of manufacturing a grain-oriented electrical steel sheet in which the ratio (Af/As) of the absorbance (Af) of Phayalite to the absorbance (As) of silica by reflection infrared spectrum on the surface of the cold-rolled sheet subjected to the primary recrystallization annealing is 0.30 to 0.60. According to claim 1,
A method of manufacturing a grain-oriented electrical steel sheet having an oxygen content of 500 to 1000 ppm of the cold-rolled sheet subjected to the primary recrystallization annealing. According to claim 1,
The heating step is a step of heating the cold-rolled sheet to the cracking temperature of the first cracking step,
The first cracking step and the second cracking step is a method of manufacturing a grain-oriented electrical steel sheet is a step of cracking at a cracking temperature of 800 to 900 ℃. According to claim 1,
The heating step is performed for 1 second to 60 seconds,
The first cracking step is carried out for 1 to 5 minutes,
The second cracking step is a method of manufacturing a grain-oriented electrical steel sheet is performed for 1 to 30 seconds. According to claim 1,
At least one of the heating step, the first cracking step, and the second cracking step is a method of manufacturing a grain-oriented electrical steel sheet performed in an atmosphere containing ammonia. According to claim 1,
A method of manufacturing a grain-oriented electrical steel sheet having a nitrogen content of 0.010 wt% to 0.030 wt% of the cold-rolled sheet subjected to the primary recrystallization annealing.