KR102276234B1 - Electrical steel sheet and manufacturing method of the same - Google Patents

Abstract

An electrical steel sheet manufacturing method according to an embodiment of the present invention comprises the steps of: manufacturing a hot-rolled sheet by hot-rolling a slab; removing some of the scale formed on the hot-rolled sheet and leaving a scale layer having a thickness of 10 nm or more to prepare a hot-rolled sheet in which the scale layer remains; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet on which the scale layer remains; applying an insulation coating composition to the cold-rolled sheet; and final annealing of the cold-rolled sheet coated with the insulating coating composition, wherein the insulating coating composition includes SiO ₂ , P ₂ O ₅ , CaCO ₃ , Na ₂ CO ₃ and CaF ₂ .

Description

Electrical steel sheet and its manufacturing method

It relates to an electrical steel sheet and a method for manufacturing the same. More specifically, it relates to an electrical steel sheet in which a portion of scale existing on the surface of the hot-rolled sheet is left behind and an insulating film is formed thereon, and a method for manufacturing the same.

In high Si hot-rolled sheet, a phenomenon occurs in which Si component is concentrated on the surface of the substrate during the annealing process. The cause of the phenomenon is that the _{affinity with O 2} is higher than that of the main component Fe of the substrate. Components used as additives, such as Cr and Mn, are also mixed in the formed Si-enriched layer. There is an external scale on the upper part of the base metal and an internal scale exists between the external scale and the base metal. In the conventional NO process, after removing this scale through the pickling process, the substrate is optimized through the final annealing process, and the insulation coating process is performed after cooling. After that, the product is completed by finishing the surface with a drying process.

Since the existing NO insulation coating has to be coated directly on the Fe substrate, an organic-inorganic hybrid insulation coating solution containing elements such as P and Cr with high affinity to Fe was used. However, the use of Cr is decreasing due to environmental issues. In the case of an insulating coating with P element added, it is a cause of lowering the efficiency of weldability when manufacturing the core by punching the substrate. In particular, in the case of a humid area, the P element is extremely close to moisture, so whitening phenomenon that the coating on the surface deteriorates may occur.

Accordingly, in the existing technology, an insulating coating is performed on the surface of the substrate using a solution to which Cr and P are not added. Since the existing solution is an organic-inorganic hybrid, the component system is complicated, and in particular, when drying, each component acts differently, causing yellowing in the case of overdrying components, and uncuring in the case of undried components, resulting in imbalance in surface properties.

In order to solve this problem, SiO ₂ particles were previously applied. However, the SiO ₂ particles on the Fe surface did not bind, and remained on the surface in the form of particles, making it difficult to be coated. In addition, even if SiO ₂ is coated on the Fe surface in the form of particles and passed through the annealing furnace, there is a problem that it is not formed as much as it is coated at a low temperature and a short annealing time of the annealing furnace.

An electrical steel sheet and a manufacturing method thereof are provided. More specifically, the present invention provides an electrical steel sheet in which a portion of scale existing on the surface of a hot-rolled sheet is left behind and an insulating coating is formed after manufacturing the hot-rolled sheet, and a method for manufacturing the same.

The electrical steel sheet of an embodiment of the present disclosure includes an electrical steel sheet substrate; a scale layer positioned on the electrical steel sheet substrate; and an insulating coating layer positioned on the scale layer, wherein the scale layer has a thickness of 5 to 100 nm, and the insulating coating layer contains calcium silicate fluoride in an amount of 25% by weight or more based on the total weight of the insulating coating layer. .

The insulating coating layer may have a calcium silicate network connection degree (NC) of 2 or less, which is indicated by Si-F bonding strength using NMR.

The insulating coating layer may have an F content of 8 to 18% by weight based on the total weight of the insulating coating layer.

The insulating coating layer may have a Ca content of 13 to 30% by weight based on the total weight of the insulating coating layer.

A method of manufacturing an electrical steel sheet according to an embodiment of the present disclosure includes the steps of: preparing a hot-rolled sheet by hot-rolling a slab; removing some of the scale formed on the hot-rolled sheet and leaving a scale layer having a thickness of 10 nm or more to prepare a hot-rolled sheet in which the scale layer remains; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet on which the scale layer remains; applying an insulation coating composition to the cold-rolled sheet; and final annealing of the cold-rolled sheet to which the insulation coating composition is applied, wherein the insulation coating composition may include SiO ₂ , P ₂ O ₅ , CaCO ₃ , Na ₂ CO ₃ and CaF ₂ .

The insulating coating composition is based on 100 parts by weight of the total weight of the composition P ₂ O ₅ 0.1 to 2 parts by weight, CaCO ₃ 10 to 45 parts by weight, Na ₂ CO ₃ 15 to 25 parts by weight, CaF ₂ 3 to 35 parts by weight and the remainder SiO ₂ may be included.

The application amount of the insulating coating composition may be ^{1 to 100 g/m 2 based} on the surface area of the electrical steel sheet.

The final annealing step may be performed at 100 to 1200° C. for 1 to 10 minutes.

The slab is in wt%, C: 0.1% or less, Si: 6.0% or less, P: 0.5% or less, S: 0.005% or less, Mn: 1.0% or less, Al: 2.0% or less, N: 0.005% or less, Ti : 0.005% or less, Cr: 0.5% or less, and may contain Fe and unavoidable impurities as the balance.

In the step of manufacturing the hot-rolled sheet on which the scale layer remains, the step of leaving the scale layer includes a rotation speed of 300 to 2500 rpm, an amount of included particles of 300 to 1200 kg/min, and a particle size of 0.10 to 0.8 cm, the moving speed of the substrate may be a step of blasting the hot-rolled sheet by 20 to 60 mpm.

In the step of manufacturing the hot-rolled sheet in which the scale layer remains, the remaining scale may include Si: 1 to 80% by weight, O: 1 to 50% by weight, and the remainder Fe and unavoidable impurities by weight.

In the step of manufacturing the hot-rolled sheet on which the scale layer remains, the step of leaving the scale layer may further include controlling a surface roughness of the hot-rolled sheet on which the scale layer remains.

In the step of controlling the surface roughness of the hot-rolled sheet, the roughness may be controlled to 1 to 3㎛.

The controlling of the surface roughness may include passing the hot-rolled sheet on which the scale layer remains between the rubber-coated blades.

The elasticity of the rubber may be 5 to 75 MPa.

In the step of manufacturing the hot-rolled sheet on which the scale layer remains, the method may further include a step of pickling after the step of leaving the scale layer.

The pickling may include immersing in an acid solution having a concentration of 8 to 16% by weight for 20 to 70 seconds.

After the cold rolling step, the thickness of the scale layer may be 5 to 100 nm.

According to one embodiment of the present invention, it is possible to provide an electrical steel sheet comprising an internal scale layer and an insulating coating layer.

In addition, according to one embodiment of the present invention, it is possible to provide an electrical steel sheet having an insulating coating layer having excellent punchability.

In addition, according to one embodiment of the present invention, it is possible to provide an electrical steel sheet having an insulating coating layer having an excellent insulating effect.

In addition, according to one embodiment of the present invention, it is possible to provide an electrical steel sheet formed with an insulating coating layer that does not easily deteriorate such as the surface is peeled off by external moisture.

1 shows an electrical steel sheet including an insulating coating in an embodiment of the present invention.
2 is a scanning electron microscope (SEM) photograph of a cross-section of a steel sheet after pickling in an embodiment of the present invention.
3 is a scanning electron microscope (SEM) photograph of a cross-section of a steel sheet after pickling in a comparative example of the present invention.
4 is a result of measuring the surface of the hot-rolled sheet after pickling of the present invention by EPMA. The left side is a comparative example of the present invention, and the right side is an exemplary embodiment of the present invention.
5 is a scanning electron microscope (SEM) photograph of the surface of the steel sheet after annealing the cold-rolled sheet in an embodiment of the present invention.
6 is a schematic diagram of a process in which calcium fluorosilicate is formed in the insulating coating layer according to an embodiment of the present invention.
7 is an XRD graph of the insulating coating layer of the electrical steel sheet manufactured in an embodiment of the present invention.
8 is a scanning electron microscope (SEM) photograph of the surface of the insulating coating layer formed in an embodiment of the present invention.

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. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and includes 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.

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.

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.

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 addition, the scale layer 20 of the present disclosure means a scale layer generated in the manufacturing process of the electrical steel sheet. For example, the scale layer 20 of the present disclosure may refer to a scale layer generated in the hot rolling step of the electrical steel sheet manufacturing process.

1 schematically shows a cross section of an electrical steel sheet 100 according to an embodiment of the present invention. Referring to Figure 1, the structure of the electrical steel sheet according to an embodiment of the present invention will be described. The electrical steel sheet of FIG. 1 is only for illustrating the present invention, and the present invention is not limited thereto. Therefore, the structure of the electrical steel sheet can be variously modified.

As shown in FIG. 1 , the electrical steel sheet 100 according to an embodiment of the present invention includes a scale layer 20 present in an inward direction from the surface of the electrical steel sheet substrate 10 . By including the scale layer 20 as described above, a firm bond between the insulating coating layer 30 and the scale layer 20 may be formed, and adhesion with the insulating coating layer 30 may be improved. In addition, since the scale layer 20 itself has an insulating property, it is possible to improve the insulating property of the electrical steel sheet.

Hereinafter, each configuration will be described in detail.

First, the electrical steel sheet substrate 10 may use all of the alloy components used in the electrical steel sheet. For example, the electrical steel sheet substrate 10 is C: 0.1% or less, Si: 6.0% or less, P: 0.5% or less, S: 0.005% or less, Mn: 1.0% or less, Al: 2.0% or less, N: 0.005% or less, Ti: 0.005% or less, Cr: 0.5% or less, and may include Fe and unavoidable impurities as the balance.

The scale layer 20 is present in an inward direction from the surface of the electrical steel sheet substrate 10 . The thickness of the scale layer 20 may be 5 to 100 nm. More specifically, it may be 5 to 20 nm. If the scale layer 20 is too thin, it is difficult to obtain the effect of improving adhesion and insulating properties with the metal oxide layer 30 caused by the presence of the scale layer 20 described above. In addition, if the scale layer 20 is too thick, it may rather give a bad shape to the magnetism.

The scale layer 20 may include Si: 1 to 80% by weight, and O: 1 to 50% by weight, and the balance Fe and unavoidable impurities by weight%. More specifically, the scale layer 20 may include Si: 5 to 40% by weight, O: 5 to 40% by weight, and the remainder Fe and unavoidable impurities.

The scale layer 20 has a smaller Fe content than the electrical steel sheet base 10, but has a relatively high Si content, so that the OH and O components and bonding force act greatly. Therefore, when the insulating coating layer 30 is formed, the insulating coating layer 30 is uniformly formed, and adhesion is improved. In addition, the scale layer 20 has an oxygen (O) content higher than that of the electrical steel sheet substrate 10 , and thus provides insulating properties by itself.

In FIG. 1 , the surface of the scale layer 20 (ie, the interface between the scale layer 20 and the insulating coating layer 30 ) is expressed as flat, but it is substantially rough as shown in FIG. 6 . The scale layer 20 may have a roughness of 1 to 3 μm. If the illuminance is too high, it may adversely affect the magnetism. Conversely, when trying to control the illuminance too low, a problem in which the scale layer 20 is all removed may occur. Therefore, it is possible to control the illuminance of the scale layer 20 within the above-described range.

_{Since the SiO 2} component remains in the scale layer 20 _{, CaCO 3} , CaF ₂ After applying an insulating coating containing the CaCO 3 and CaF 2 component on the electrical steel sheet substrate including the scale layer, when the substrate is final annealed, the SiO already formed on the surface _{2 Since} CaO/CaF ₂ /Na ₂ O is applied to the thick film, an insulating coating layer containing a strong glass polymer coating called calcium fluorosilicate is formed on the surface even at an annealing temperature of 100 ° C (Fig. 6). That is, the glass coating film has a melting temperature of 100° C. or less, so the weldability is improved, and the film is formed as a part of the base material in close contact and solidity to prevent the cracking phenomenon in which the surface coating film is peeled off during punching. Also, when P ₂ O ₅ is punched, it improves the elasticity of the surface film and prevents cracking.

In addition, the insulating coating layer may include calcium silicate fluoride in an amount of 25% by weight or more based on the total weight of the insulating coating layer. Specifically, the calcium silicate fluoride may be included in an amount of 27 to 56 wt%, more specifically 30 to 50 wt%, and more specifically 37 to 50 wt%, based on the total weight of the insulating coating layer. When the content of calcium silicate fluoride is too low, the adhesion is poor, or the iron loss repair effect is inferior.

In addition, the insulating coating layer may have a calcium silicate network connection degree (NC) of 2 or less, which is indicated by Si-F bonding strength using NMR. Specifically, the network connection degree may be -1 to 2, more specifically -1 to 1.5, and more specifically -1 to 1. The smaller the network connection value, the more linear the calcium silicate network, and the more linear the network, the greater the effect of lowering iron loss.

In addition, since the scale layer 20 is properly formed in one embodiment of the present invention, the adhesion of the insulating coating layer 30 can be improved, and sufficient insulation can be secured even when the thickness of the insulating coating layer 30 is formed thin. there will be Specifically, the thickness of the insulating coating layer 30 may be 0.7 to 1.0 ㎛.

In addition, in an embodiment of the present invention, the insulating coating layer 30 may have an F content of 8 to 18 wt% based on the total weight of the insulating coating layer. Specifically, it may be 11 to 17% by weight. More specifically, it may be 12 to 16% by weight.

In addition, in one embodiment of the present invention, the insulating coating layer 30 may have a Ca content of 13 to 30 wt% based on the total weight of the insulating coating layer. More specifically, it may be 17 to 29% by weight, more specifically 19 to 26% by weight.

An electrical steel sheet manufacturing method according to an embodiment of the present invention comprises the steps of: manufacturing a hot-rolled sheet by hot-rolling a slab; removing some of the scale formed on the hot-rolled sheet and leaving a scale layer having a thickness of 10 nm or more to prepare a hot-rolled sheet in which the scale layer remains; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet on which the scale layer remains; applying an insulation coating composition to the cold-rolled sheet; and final annealing of the cold-rolled sheet coated with the insulating coating composition.

Hereinafter, each step will be described in detail.

First, the alloy component of the slab is not particularly limited, and any alloy component used in the electrical steel sheet may be used. In one example, the slab is in wt%, C: 0.1% or less, Si: 6.0% or less, P: 0.5% or less, S: 0.005% or less, Mn: 1.0% or less, Al: 2.0% or less, N: 0.005% or less , Ti: 0.005% or less, Cr: 0.5% or less, and may include Fe and unavoidable impurities as the balance.

First, the slab is heated. The heating temperature of the slab is not limited, but when the slab is heated to a temperature of 1300° C. or less, coarse growth of the columnar structure of the slab is prevented, thereby preventing the occurrence of cracks in the plate in the hot rolling process. Therefore, the heating temperature of the slab may be 1050 to 1300 ℃.

Next, the slab is hot-rolled to manufacture a hot-rolled sheet. The hot rolling temperature is not limited, and in one embodiment, the hot rolling may be terminated at 950° C. or less.

Next, some of the scales formed on the hot-rolled sheet are removed to leave scales having a thickness of 10 nm or more. Specifically, it may be 10 nm to 300 nm, more specifically 30 nm to 150 nm.

Since hot rolling is performed at a high temperature, scale is inevitably formed on the surface of the hot-rolled sheet. Since this scale adversely affects magnetism and may break during rolling, it was common to remove all of it.

In an embodiment of the present invention, by intentionally remaining the scale layer to a thickness of 10 nm or more, adhesion with the insulating coating layer was improved, and additional insulating properties were obtained. It can be seen that the scale has less Fe content compared to the steel plate base material, and is composed of complex components such as Si and Cr. In addition, the Si content is relatively high, and the bonding force with the OH and O components is large. Therefore, when all the scale is removed as in a general method, only Fe is present on the surface, _{and the intimacy with CaCO 3} or CaF ₂ which is an insulating coating solution to be used in the present disclosure is low, so that it is not effectively applied. However, Si present in a large amount in the scale layer has a large bonding force with O, remains as _{SiO 2 , and CaCO 3} or CaF ₂ can be effectively applied, so that the insulating coating layer is uniformly formed and adhesion is improved.

Specifically, the scale may include Si: 1 to 80% by weight, O: 1 to 50% by weight, and the remainder Fe and unavoidable impurities. More specifically, the scale may include Si: 1 to 40% by weight, O: 1 to 40% by weight, and the balance Fe and unavoidable impurities. More specifically, the scale may include Si: 5 to 40% by weight, O: 5 to 40% by weight, and the balance Fe and unavoidable impurities.

The method of leaving scale is not specifically limited. For example, the rotation speed is 300 to 2500 rpm, the amount of particles included is 300 to 1200 kg/min, the size of the particle ball is 0.1 to 0.8 cm, and the moving speed of the substrate is 20 to 60 mpm. can The blast method is a method of removing scale by colliding fine particles with a steel plate at a high speed. In this case, the speed of the fine particles may be 0.5 to 200 km/s.

This is a condition in which the input amount and speed of fine particles are small compared to the existing blasting method that removes all scale. As such, the scale may be left to an appropriate thickness by the blasting method described above. If it is larger or smaller than the above range, it is impossible to leave scale with an appropriate thickness, such as not removing all of the scale or not too much.

In one embodiment of the present invention, the thickness of the scale remaining on the hot-rolled sheet is 10 nm or more. The thickness of the scale may be non-uniform over the entire steel sheet, and unless otherwise specified, the thickness of the scale means the average thickness over the entire surface of the steel sheet. If the scale thickness remains too thick, it may adversely affect magnetism. Accordingly, the thickness of the remaining scale may be 10 to 300 nm. More specifically, the thickness of the remaining scale may be 30 to 150 nm.

Next, the roughness of the hot-rolled sheet in which the scale remains is controlled. In this case, it means the roughness of the roughened outermost surface of the hot-rolled sheet, that is, the roughness of the scale. When the scale remains, the illuminance becomes very large. This adversely affects the magnetism. Therefore, it is necessary to control only the illuminance without removing the scale.

In an embodiment of the present invention, the roughness of the hot-rolled sheet may be controlled to 1 to 3 μm through the step of controlling the roughness. Specifically, it may be 1.5 to 3 μm, more specifically 2.0 to 2.5 μm. If the illuminance is too high, it may adversely affect the magnetism. Conversely, if the illuminance is controlled to be too low, a problem in which all scale is removed may occur. Accordingly, it is possible to control the illuminance within the above-described range.

As a method of controlling the roughness, it may include passing the hot-rolled sheet between blades coated with rubber.

At this time, the elasticity of the rubber may be 5 to 75 MPa. Specifically, the elasticity may be 7 to 45 MPa, more specifically, 7 to 35 MPa, or 15 to 25 MPa, or 20 to 23 MPa. When the elasticity is out of the range, it may be difficult to control the illuminance to a desired range.

After the step of controlling the roughness of the hot-rolled sheet, the step of pickling may be further included. The roughness of the hot-rolled sheet can be further controlled through pickling. During pickling, if the concentration of the acid solution is high or the immersion time is long, a problem in which all scale is removed may occur. Therefore, it can be immersed for 20 to 70 seconds in an acid solution of 8 to 16% by weight or less having a temperature of 65 to 76°C.

Next, the hot-rolled sheet is cold-rolled to manufacture a cold-rolled sheet. It can be applied differently depending on the thickness of the hot-rolled sheet, but it can be cold-rolled to a final thickness of 0.2 to 0.65 mm by applying a reduction ratio of 70 to 95%. Cold rolling may be performed by one cold rolling, or it is also possible to perform cold rolling two or more times with intermediate annealing in between as needed.

In the cold rolling process, the scale layer is also rolled to decrease the thickness. After cold rolling, the thickness of the scale layer may be 5 to 100 nm. More specifically, it may be 5 to 20 nm.

Next, it may include the step of applying an insulation coating to the cold-rolled cold-rolled sheet. The insulating coating composition may include SiO ₂ , P ₂ O ₅ , CaCO ₃ , Na ₂ CO ₃ and CaF ₂ . The insulating coating composition is based on 100 parts by weight of the total weight of the composition P ₂ O ₅ 0.1 to 2 parts by weight, CaCO ₃ 10 to 45 parts by weight, Na ₂ CO ₃ 15 to 25 parts by weight, CaF ₂ 3 to 35 parts by weight and the remainder SiO ₂ may be included. _{Specifically, the insulation coating composition is P 2} O ₅ 0.5 to 1 parts by weight, CaCO ₃ 15 to 20 parts by weight, Na ₂ CO ₃ 17 to 22 parts by weight, CaF ₂ 17 to 33 parts by weight based on 100 parts by weight of the total weight of the composition and the remainder SiO ₂ . When the insulating coating composition was used in the above composition range, an insulating film containing calcium silicate fluoride having an excellent network connection degree could be formed, and thus, excellent adhesion and iron loss improvement effect could be obtained.

The insulating coating composition may use water as a solvent, and the concentration of the composition may be 10 to 60% by weight based on the total weight.

It may include applying the insulating coating composition to the surface of the cold-rolled steel sheet. At this time, the application amount of the insulating coating composition may be ^{1 to 100 g/m 2 with respect to the surface area of the electrical steel sheet.} Specifically, it may be 20 to 30 g/m ^{2 .}

Thereafter, the step of final annealing the cold-rolled steel sheet to which the insulation coating solution is applied may be further included. In the final annealing step, CaCO ₃ contained in the insulation coating solution may be decomposed into CO ₂ and CaO, and Na ₂ CO ₃ may be reacted with CO ₂ and Na _{2 O.}

In the final annealing of the cold-rolled steel sheet coated with the insulating coating solution, the annealing temperature may be 100 to 1200° C., and the annealing time may be 1 to 10 minutes.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are for illustrative purposes only, and the present invention is not limited thereto.

Experimental Example 1- Comparison according to the remaining scale layer

Example 1 - When the scale layer remained

A slab was prepared that contains silicon (Si) in an amount of 3.4% by weight, and the balance is made of Fe and other unavoidable impurities. The slab was heated at 1130° C. and then hot-rolled to a thickness of 2.3 mm to prepare a hot-rolled sheet.

The hot-rolled sheet was treated with a shot blaster at a moving speed of 40 mpm, a particle usage of 700 kg/min, a particle size of 0.6 cm, and a rotation speed of 2300 rpm to leave a scale layer with a thickness of about 200 nm. Thereafter, the surface roughness was controlled to about 1.5 to 1.9 nm by passing between the blades coated with rubber having an elasticity of 20 to 23 MPa. Then, it was pickled by immersion for about 70 seconds in a hydrochloric acid solution (concentration of about 15% by weight) at a temperature of about 78°C. Thereafter, washing was performed.

2 shows a scanning electron microscope (SEM) photograph of a cross section of a steel sheet after pickling. As shown in FIG. 2 , the scale layer is displayed as a white part, and it can be confirmed that the scale layer remains. As a result of measuring the surface of the pickled hot-rolled sheet by EPMA, it can be confirmed that Si is present in a large amount (thin film pretreatment in Fig. 4).

Then, it cold-rolled and set the plate|board thickness to 0.23 mm. A cross section of the cold rolled sheet after cold rolling is shown in FIG. 5 .

As shown in FIG. 5 , as a result of TEM-FIB cross-sectional analysis, the scale layer remains at 15 to 20 nm even after cold rolling, Si: 35.25 wt%, O: 34.02 wt%, and the remainder Fe and impurities, Si and O are abundant. could confirm that

Comparative Example 1 Completely Remove Scale

A slab was prepared that contains silicon (Si) in an amount of 3.4% by weight, and the balance is made of Fe and other unavoidable impurities. The slab was heated at 1130° C. and then hot-rolled to a thickness of 2.3 mm to prepare a hot-rolled sheet.

The hot-rolled sheet was treated with a shot blaster at a moving speed of 20 to 50 mpm, a rotation speed of 1000 rpm, an amount of used particles 2300 kg/min, and a particle size of 0.6 cm to remove all scale layers. Then, it was pickled by immersion for about 78 seconds in a hydrochloric acid solution (concentration of about 15% by weight) at a temperature of about 82°C. Thereafter, washing was performed.

3 shows a scanning electron microscope (SEM) photograph of a cross section of a steel sheet after pickling. As shown in FIG. 3 , it was confirmed that all of the scale layer was removed. As a result of measuring the surface of the pickled hot-rolled sheet with EPMA, it can be confirmed that the Si content is present in a trace amount (general in FIG. 4 ).

Then, it cold-rolled and set the plate|board thickness to 0.23 mm.

Comparative Example 2 Existence of large amounts of scale

A slab was prepared that contains silicon (Si) in an amount of 3.4% by weight, and the balance is made of Fe and other unavoidable impurities.

A hot-rolled sheet was prepared by hot-rolling the slab to a thickness of 2.3 mm.

The hot-rolled sheet was processed at a speed of 20 to 50 mpm using a shot blaster to leave a scale layer having a thickness of about 500 nm. Then, it was immersed in a hydrochloric acid solution (about 9wt%) at a temperature of about 72°C for about 30 seconds to carry out pickling treatment. Thereafter, washing was performed.

Then, it cold-rolled and set the plate|board thickness to 0.23 mm.

Experimental Example 2 - Comparison of Adhesion and Insulation according to Insulation Coating Composition

An insulating coating layer was formed on the cold-rolled sheets of Example 1 and Comparative Example 1 by the following process.

The insulating coating composition having the composition of Table 1 below and having a concentration of 30 wt% was applied to ^{the cold-rolled sheet of Example 1 and Comparative Example 1 in an amount of 20 g/m 2 .} Thereafter, final annealing was performed at a temperature of 150° C. for 1 minute to form an insulating coating layer having a thickness of 20 μm.

Glass SiO ₂ P ₂ O ₅ CaCO ₃ Na ₂ CO ₃ CaF ₂ NC ^* A 49.47 1.07 23.08 26.38 - 2.13 B 47.12 1.02 21.98 25.13 4.75 1.82 C 44.88 0.97 20.94 23.93 9.28 1.49 D 42.73 0.92 19.94 22.79 13.62 1.15 E 40.68 0.88 18.98 21.69 17.76 0.78 F 36.83 0.8 17.18 19.64 25.54 -0.01 G 33.29 0.72 15.53 17.75 32.71 -0.9 H 44.88 0.97 44.87 - 9.28 1.49

In Table 1, the composition ratio was prepared based on 100 parts by weight of the total insulating coating layer formed. NC ^* means network connectivity and represents the Si-F bond strength of NMR. The lower the number, the more linear the calcium silicate network. The more linear the network, the greater the effect of lowering iron loss. Therefore, it can be seen that in the case of compositions E, F, and G, the effect of lowering the iron loss is large.

As a result of annealing, in the case of the example in which the composition G was applied, it was found that a large amount of calcium fluoride network was formed as a result of XRD measurement (see FIG. 7), and the surface was photographed using a scanning electron microscope (SEM) (see FIG. 8). ). In the case of the insulating coating layer formed on the electrical steel sheet, it was confirmed with the naked eye that it had a light blue color due to the _{CaF 2 residue.}

The insulating coating compositions of each composition from A to H were applied to Example 1 and Comparative Example 1, respectively, and the properties of the insulating coating layer formed by final annealing were compared and disclosed in Table 2 below.

Insulation properties were measured using a Franklin measuring instrument according to ASTM A717 international standard. In addition, adhesion was judged by the presence or absence of film peeling when the specimen was bent by 180 degrees. When observed under a microscope x100, if there is none at all, it is indicated as very good, and less than 3 defects per 5cm*5cm area on x100 are indicated as good. The iron loss (W15/50) means the power loss that occurs when a magnetic field with a frequency of 50 Hz is magnetized to 1.5 Tesla in alternating current.

division fluorination
Calcium silicate content (wt%) F
(weight%) Ca
(weight%) Insulation characteristics
(mA) adhesion iron loss
(W _15/50 ,
W/kg) scale thickness
(nm) Example 1 A 23.7 7.55 12.17 990 Good 2.307 54 B 27.4 8.75 14.09 990 Good 1.249 55 C 31.0 9.89 15.93 990 Good 1.226 53 D 34.4 10.98 17.70 990 very good 1.225 52 E 37.7 12.02 19.37 880 very good 1.165 50 F 43.8 13.98 22.53 850 very good 1.156 51 G 49.5 15.79 25.44 910 Good 1.141 52 H 55.5 17.72 28.55 990 Good 1.22 51 Comparative Example 1
(scale completely removed) A 23.7 7.55 12.17 1030 bad 2.7684 0 B 27.4 8.75 14.09 1030 bad 1.4988 0 C 31.0 9.89 15.93 1030 bad 1.4712 0 D 34.4 10.98 17.70 1030 Good 1.47 0 E 37.7 12.02 19.37 920 Good 1.398 0 F 43.8 13.98 22.53 890 Good 1.3872 0 G 49.5 15.79 25.44 950 bad 1.3692 0 H 55.5 17.72 28.55 1030 bad 1.464 0 Comparative Example 2
(A large amount of scale exists) A 23.7 7.55 12.17 1010 bad 2.5377 200 B 27.4 8.75 14.09 1010 bulryang 1.3739 210 C 31.0 9.89 15.93 1010 bad 1.3486 300 D 34.4 10.98 17.70 1010 bad 1.3475 320 E 37.7 12.02 19.37 900 bad 1.2815 300 F 43.8 13.98 22.53 870 bad 1.2716 310 G 49.5 15.79 25.44 930 bad 1.2551 210 H 55.5 17.72 28.55 1010 bad 1.342 300

As shown in Table 2, it can be seen that the examples in which the scale layer is present have superior insulating properties and improved adhesion compared to Comparative Examples 1 and 2. Furthermore, it can be confirmed that the iron loss is also improved.

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

100: electrical steel sheet
10: electrical steel plate substrate
20: scale layer
30: insulating coating layer

Claims (18)

electrical steel plate substrate;
a scale layer positioned on the electrical steel sheet substrate; and
Including an insulating coating layer located on the scale layer,
The scale layer has a thickness of 5 to 100 nm,
The insulating coating layer contains calcium silicate fluoride in an amount of 25 wt% or more based on the total weight of the insulating coating layer, electrical steel sheet. According to claim 1,
The insulating coating layer has a calcium silicate network connection degree (NC) of 2 or less, which is indicated by Si-F bonding strength using NMR, an electrical steel sheet. According to claim 1,
The insulating coating layer has an F content of 8 to 18% by weight based on the total weight of the insulating coating layer, an electrical steel sheet. According to claim 1,
The insulating coating layer has a Ca content of 13 to 30% by weight based on the total weight of the insulating coating layer, electrical steel sheet. manufacturing a hot-rolled sheet by hot-rolling the slab;
removing some of the scale formed on the hot-rolled sheet and leaving a scale layer having a thickness of 10 nm or more to prepare a hot-rolled sheet in which the scale layer remains;
manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet on which the scale layer remains;
applying an insulation coating composition to the cold-rolled sheet; and
Comprising the step of final annealing of the cold-rolled sheet coated with the insulation coating composition,
The insulating coating composition is SiO ₂ , P ₂ O ₅ , CaCO ₃ , Na ₂ CO ₃ And CaF _{2 A} method of manufacturing an electrical steel sheet comprising a. 6. The method of claim 5,
The insulating coating composition is based on 100 parts by weight of the total weight of the composition P ₂ O ₅ 0.1 to 2 parts by weight, CaCO ₃ 10 to 45 parts by weight, Na ₂ CO ₃ 15 to 25 parts by weight, CaF ₂ 3 to 35 parts by weight and the remainder SiO _{2 A} method of manufacturing an electrical steel sheet, including. 6. The method of claim 5,
The insulating coating composition is applied in an amount of 1 to 100 g/m ² based on the surface area of the electrical steel sheet, the method of manufacturing an electrical steel sheet. 6. The method of claim 5,
The final annealing step is performed at 100 to 1200 ℃ for 1 to 10 minutes, the method of manufacturing an electrical steel sheet. 6. The method of claim 5,
The slab is in wt%, C: 0.1% or less, Si: 6.0% or less, P: 0.5% or less, S: 0.005% or less, Mn: 1.0% or less, Al: 2.0% or less, N: 0.005% or less, Ti : 0.005% or less, Cr: 0.5% or less, and the balance containing Fe and unavoidable impurities, a method of manufacturing an electrical steel sheet. 6. The method of claim 5,
In the step of manufacturing the hot-rolled sheet on which the scale layer remains,
In the step of remaining the scale layer, the rotation speed is 300 to 2500 rpm, the amount of particles included is 300 to 1200 kg/min, the size of the particles is 0.10 to 0.8 cm, and the moving speed of the substrate is 20 to 60 mpm. A method of manufacturing an electrical steel sheet, which is a step of blasting the sheet. 6. The method of claim 5,
In the step of manufacturing the hot-rolled sheet on which the scale layer remains,
The remaining scale is Si: 1 to 80% by weight, O: 1 to 50% by weight, and the remainder Fe and unavoidable impurities in weight %, the method of manufacturing an electrical steel sheet. 6. The method of claim 5,
In the step of manufacturing the hot-rolled sheet on which the scale layer remains,
The step of leaving the scale layer, further comprising the step of controlling the surface roughness of the hot-rolled sheet on which the scale layer remains, the method of manufacturing an electrical steel sheet. 13. The method of claim 12,
In the step of controlling the surface roughness of the hot-rolled sheet, the roughness is controlled to 1 to 3㎛, a method of manufacturing an electrical steel sheet. 13. The method of claim 12,
The controlling of the surface roughness comprises passing the hot-rolled sheet on which the scale layer remains between the rubber-coated blades. 15. The method of claim 14,
The elasticity of the rubber is 5 to 75 MPa, the method of manufacturing an electrical steel sheet. 6. The method of claim 5,
In the step of manufacturing the hot-rolled sheet on which the scale layer remains,
After the step of leaving the scale layer, the method of manufacturing an electrical steel sheet further comprising the step of pickling. 17. The method of claim 16,
The pickling step comprises immersing in an acid solution having a concentration of 8 to 16% by weight for 20 to 70 seconds, the method of manufacturing an electrical steel sheet. 6. The method of claim 5,
After the cold rolling step, the thickness of the scale layer is 5 to 100 nm, the method of manufacturing an electrical steel sheet.

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