KR20200066510A - Electrical steel sheet and manufacturing method of the same - Google Patents

Abstract

Provided are an electric steel sheet in which a Si reinforcement layer is formed and a manufacturing method thereof. The manufacturing method of the electric steel sheet according to one embodiment of the present invention includes the following steps of: hot-rolling a slab to manufacture a hot-rolled sheet; removing some of scales formed on the hot-rolled sheet, and leaving a scale layer having a thickness of equal to or more than 10 nm; cold-rolling the hot-rolled sheet in which the scale layer remains to manufacture a cold-rolled sheet; forming the Si reinforcement layer on the surface of the cold-rolled sheet; and annealing the cold-rolled sheet.

Description

Electrical steel sheet and its manufacturing method{ELECTRICAL STEEL SHEET AND MANUFACTURING METHOD OF THE SAME}

It relates to an electric steel sheet and a method of manufacturing the same. More specifically, it relates to an electric steel sheet having a Si reinforcing layer formed thereon, and partially forming a scale existing on the surface of the hot rolled sheet after manufacturing the hot rolled sheet.

Electric steel sheet is a product used for transformers, motors, and electrical equipment. Unlike ordinary carbon steel, which emphasizes processability such as mechanical properties, it is a functional product that emphasizes electrical properties. The electrical characteristics required include low iron loss, high magnetic flux density, high magnetic permeability, and a large drop.

The electrical steel sheet is further divided into a grain-oriented electrical steel sheet and a non-oriented electrical steel sheet. The grain-oriented electrical steel sheet is an electrical steel sheet with excellent magnetic properties in the rolling direction by forming Goss aggregate ({110}<001> aggregate) on the entire steel sheet using an abnormal grain growth phenomenon called secondary recrystallization. The non-oriented electrical steel sheet is an electrical steel sheet having uniform magnetic properties in all directions on a rolled sheet.

As a production process of non-oriented electrical steel sheet, after the slab is manufactured, an insulating coating layer is formed through hot rolling, cold rolling and final annealing.

As a production process of grain-oriented electrical steel, after the slab is manufactured, an insulating coating layer is formed through hot rolling, cold rolling, primary recrystallization annealing, and secondary recrystallization annealing.

In the production process of the electric steel sheet, after hot rolling, it was common to remove the scale generated on the surface to improve the efficiency of the process developed later.

However, a large amount of Fe is present on the surface of the steel sheet after pickling, and the surface of the steel sheet does not significantly affect the OH and O functional groups and the bonding force. When forming an insulating coating layer containing an oxide composed of O and OH components on such a surface, there was a problem that the insulating coating layer was not uniformly formed and the adhesion between the steel sheet and the insulating coating layer deteriorated.

Provided is an electrical steel sheet and a method of manufacturing the same. More specifically, after manufacturing the hot-rolled sheet, a portion of the scale remaining on the surface of the hot-rolled sheet is partially provided, and an electric steel sheet having a Si reinforcement layer and a method of manufacturing the same are provided.

A method of manufacturing an electric steel sheet according to an embodiment of the present invention comprises: hot rolling a slab to produce a hot rolled sheet; Removing some of the scale formed on the hot-rolled sheet, and remaining a scale layer having a thickness of 10 nm or more; Cold rolling the hot rolled sheet in which the scale layer remains to produce a cold rolled sheet; Forming a Si reinforcement layer on the surface of the cold rolled sheet; And annealing the cold rolled sheet.

Slabs in weight percent, 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 may include Fe and unavoidable impurities.

The scale may include Si: 5 to 80% by weight, O: 5 to 80% by weight, and the balance Fe and unavoidable impurities.

Velocity of a particle in the step of the remaining scale, the amount of particles by using a blasting method, the steel sheet per unit area 20g / m ³ to 1000g / m ³ may be treated with 0.1 km / s to 200km / s. After the step of remaining the scale layer, the step of controlling the roughness of the hot-rolled sheet in which the scale layer remains may be further included.

In the step of controlling the roughness of the hot rolled sheet, the roughness may be controlled to 0.1 to 2.0 nm.

Controlling the roughness of the hot rolled sheet may include passing the hot rolled sheet between rubber coated blades.

The elasticity of the rubber may be 7 to 45 MPa.

After the step of controlling the roughness of the hot rolled sheet, the step of pickling may be further included.

The step of pickling may be immersed in an acid solution of 15% by weight or less for 20 to 70 seconds.

After the step of manufacturing the cold rolled sheet, the thickness of the scale layer may be 1 to 100 nm.

Forming the Si reinforcement layer on the surface of the cold rolled sheet may include applying a Si reinforcement layer forming composition containing a silicon compound.

The composition for forming the Si reinforcing layer may include 80 to 99% by weight of the silicone compound and the balance aluminum compound as a solid content.

The average particle diameter of the silicone compound may be 5 to 50 nm.

In the step of forming the Si reinforcement layer, the Si reinforcement layer may be formed to a thickness of 10 to 1000 nm.

The electrical steel sheet according to an embodiment of the present invention includes an electrical steel sheet substrate, a scale layer existing in an inner direction from the surface of the electrical steel sheet substrate, and a Si reinforcement layer positioned on the scale layer.

The thickness of the scale layer may be 1 to 100 nm.

The scale layer may include Si: 5 to 80% by weight, O: 5 to 80% by weight, and the balance Fe and unavoidable impurities.

The Si reinforcement layer may include Si: 80 to 99% by weight and Al: 1 to 20% by weight.

An insulating coating layer positioned on the Si reinforcement layer may be further included.

According to one embodiment of the present invention, by forming a solid bond between the insulating coating layer and the scale layer, it is possible to improve the adhesion with the insulating coating layer.

In addition, according to one embodiment of the present invention, since the insulating properties exist in the scale layer itself, it is possible to improve the insulating properties.

In addition, according to an embodiment of the present invention, when the hot-rolled coil is in the standby state, oxidation of the hot-rolled sheet from oxygen in air can be prevented.

In addition, according to an embodiment of the present invention, by forming a Si reinforcement layer, it is possible to reinforce the defects formed in the scale layer, thereby improving the magnetism.

1 is a schematic view of a section of an electric steel sheet according to 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.
3 is a scanning electron microscope (SEM) photograph of the surface of a steel sheet after pickling in an example.
4 is a scanning electron microscope (SEM) photograph of a cross section of a steel sheet after hot rolling in a comparative example.
5 is a scanning electron microscope (SEM) photograph of the surface of a steel sheet after hot rolling in a comparative example.
6 is a scanning electron microscope (SEM) photograph of the surface of the steel sheet after annealing the cold rolled sheet in the embodiment.
7 is a scanning electron microscope (SEM) photograph of a section of a steel sheet after annealing a cold rolled sheet in an embodiment.
8 is a scanning electron microscope (SEM) photograph of a section of a steel sheet after annealing a cold rolled sheet in an embodiment.

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

The terminology used herein is only to refer to a specific embodiment and is not intended to limit the invention. The singular forms used herein also include plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” embodies a particular property, region, integer, step, action, element, and/or component, and the presence or presence of other properties, regions, integers, steps, action, element, and/or component. It does not exclude addition.

When referring to a part being "on" or "on" another part, it may be directly on or on the other part, or another part may be involved therebetween. In contrast, if one part is referred to as being “just above” another part, no other part is interposed therebetween.

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

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

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. Commonly used dictionary-defined terms are further interpreted as having meanings consistent with related technical documents and currently disclosed contents, and are not interpreted as ideal or very formal meanings unless defined.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

A method of manufacturing an electric steel sheet according to an embodiment of the present invention comprises: hot rolling a slab to produce a hot rolled sheet; Removing some of the scale formed on the hot-rolled sheet, and remaining a scale layer having a thickness of 10 nm or more; Forming a Si reinforcement layer on the surface of the hot rolled sheet where the scale layer remains; Cold rolling to produce a cold rolled plate; And annealing the cold rolled sheet.

Hereinafter, each step will be described in detail.

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

The alloy component of the slab is not particularly limited, and any alloy component used in the electric steel sheet can be used. As an example, the slab is by weight, 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 may include Fe and unavoidable impurities.

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, it is possible to prevent the columnar crystal structure of the slab from growing coarsely and prevent cracking of the plate in the hot rolling process. Therefore, the heating temperature of the slab may be 1050 ℃ to 1300 ℃.

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

Next, some of the scale formed on the hot-rolled sheet is removed, and a scale of 10 nm or more in thickness remains.

Since hot rolling is performed at a high temperature, scale is inevitably formed on the surface of the hot rolled sheet. It was common for this scale to adversely affect the magnetism and to remove all of it due to breakage during rolling.

In one embodiment of the present invention, by intentionally retaining the scale layer to a thickness of 10 nm or more, adhesion to the insulating coating layer is improved, and additional insulating properties can be obtained. In the scale, Fe content is less than that of the steel sheet substrate, and instead, the Si content is relatively high, so that the OH and O components and the bonding force act largely. Therefore, when forming the insulating coating layer, the insulating coating layer is uniformly formed, and adhesion is improved.

In addition, the scale has a higher O content than the steel plate base material, and thus provides insulating properties by itself.

Specifically, the scale may include Si: 5 to 80% by weight, O: 5 to 80% by weight, and the balance Fe and unavoidable impurities. More specifically, the scale may include Si: 10 to 60% by weight, O: 10 to 60% by weight, and the balance Fe and unavoidable impurities. More specifically, the scale may include Si: 15 to 40% by weight, O: 15 to 40% by weight, and the balance Fe and unavoidable impurities.

It does not specifically limit as a method of leaving a scale. As an example, a blast method may be used. The blasting method is a method of removing scale by colliding fine particles with a steel plate at high speed. At this time, input of the fine particles may be with respect to the steel plate surface area 20g / m ³ to 1000g / m ^3. The speed of the particles may be 0.1 km/s to 200 km/s.

This has a smaller amount and speed of fine particles compared to the blasting method of removing all scales. In this way, the scale can be left at an appropriate thickness by the blast method described above. If it is larger or smaller than the above-mentioned range, a scale of appropriate thickness may not remain.

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

After the step of remaining the scale layer, the method may further include controlling the roughness of the hot-rolled sheet in which the scale remains. At this time, the roughness of the hot rolled sheet means the roughness of the 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 magnetism. Therefore, it is necessary to control only the illuminance without removing the scale.

In one embodiment of the present invention, the illuminance of the hot rolled sheet may be controlled to 0.1 to 2.0 nm through the illuminance control. If the illuminance is too high, it may adversely affect magnetism. Conversely, when trying to control the illuminance too low, a problem may occur that all scales are removed. Therefore, the illuminance can be controlled within the above-described range.

As a method of controlling the roughness, a step of passing a hot-rolled sheet between rubber-coated blades may be included.

At this time, the elasticity of the rubber may be 7 to 45 Mpa. When the elasticity is not appropriate, the roughness control may be difficult.

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. When pickling, if the concentration of the acid solution is high, or if the immersion time is long, a problem may occur in which all the scales are removed. Therefore, it can be immersed in an acid solution of 15% by weight or less for 20 to 70 seconds.

Next, the hot rolled sheet is cold rolled to produce a cold rolled sheet. It may be applied differently depending on the thickness of the hot rolled sheet, but may 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 carried out by one cold rolling or by performing two or more cold rolling between intermediate annealing as necessary.

In the cold rolling process, the scale layer is also rolled, and the thickness is reduced. After cold rolling, the thickness of the scale layer may be 1 to 100 nm. More specifically, it may be 5 to 20 nm.

Next, a Si reinforcement layer is formed on the surface of the cold rolled sheet. The scale layer is naturally formed in contact with oxygen in the air during the hot rolling process, and then cold-rolled, and thus has a lower density and a large number of defects than the steel plate substrate. In one embodiment of the present invention, the strength and magnetic properties of the steel sheet are further improved by reinforcing defects present in the scale layer.

Specifically, forming the Si reinforcing layer on the surface of the cold rolled sheet may include applying a Si reinforcing layer forming composition containing a silicon compound. At this time, the silicon compound can be used without limitation as long as it is a compound containing Si. For example, it may include one or more silicone compounds selected from silica, silicate and silane compounds. More specifically, the silicon compound may be silica.

The average particle diameter of the silicone compound may be 5 to 50 nm. When a silicon compound having an appropriate particle size is used, dispersion can be easily performed in the Si reinforcing layer forming composition, and a uniform Si reinforcing layer can be formed. More specifically, the average particle diameter of the silicon compound may be 10 to 30 nm.

The composition for forming the Si reinforcing layer may include 80 to 99% by weight of the silicone compound and the balance aluminum compound as a solid content. When an aluminum compound is added, it is advantageous in strengthening the surface strength. The aluminum compound may include, for example, alumina. More specifically, the composition for forming the Si reinforcing layer may include 85 to 95% by weight of the silicone compound and the balance aluminum compound as a solid content.

The Si reinforcing layer forming composition may further include a solvent. Solvents may include water or organic solvents. The organic solvent may include ethanol, isopropanol, and the like.

After applying the Si reinforcing layer forming composition, the steel sheet may be heated to form a Si reinforcing layer. The Si reinforcement layer may be formed to a thickness of 10 to 1000 nm. If the thickness of the Si reinforcement layer is too thin, it is difficult to sufficiently achieve the effect of forming the Si reinforcement layer. If the thickness of the Si reinforcing layer is too thick, after the electrical steel sheet is manufactured, cracks may occur in the Si reinforcing layer in the punching process during the production process of the product for manufacturing the electrical steel sheet.

As described above, the Si reinforcing layer is formed after the cold rolled sheet is prepared and before annealing, and the Si reinforcing layer forming composition does not contain a resin or the like other than a silicone compound.

Next, the cold-rolled sheet is annealed. At this time, the process of annealing the cold rolled sheet is different depending on the use of the non-oriented electrical steel sheet or the grain-oriented electrical steel sheet.

Specifically, when manufacturing a non-oriented electrical steel sheet, it can be annealed at a temperature of 850 to 1050°C for 30 seconds to 3 minutes. If the crack temperature is too high, rapid growth of crystal grains may occur and magnetic flux density and high-frequency iron loss may deteriorate. More specifically, final annealing may be performed at a crack temperature of 900 to 1000°C. In the final annealing process, all the processed tissues formed in the cold rolling step (ie, 99% or more) may be recrystallized.

In the case of manufacturing grain-oriented electrical steel sheets, cold rolled cold rolled sheets are subjected to primary recrystallization annealing. In the first recrystallization annealing step, primary recrystallization occurs in which nuclei of goth grains are generated. In the first recrystallization annealing process, decarburization and nitriding of the steel sheet may be performed. For decarburization and nitriding, primary recrystallization annealing can be performed under a mixed gas atmosphere of water vapor, hydrogen and ammonia.

To form nitrides such as (Al,Si,Mn)N and AlN, which are tin extracts by introducing nitrogen ions into the steel sheet using ammonia gas for nitriding, nitriding is performed after decarburization or at the same time as decarburization. There is no problem in exerting the effect of the present invention either by performing nitriding treatment at the same time or by first performing nitriding treatment and then decarburization so as to be able to do the same.

The primary recrystallization annealing can be carried out in a temperature range of 800 to 900°C.

Next, the second recrystallization annealing of the cold rolled sheet in which the first recrystallization annealing is completed. At this time, after the first recrystallization annealing is applied to the cold rolled sheet, the second recrystallization annealing can be applied. At this time, the annealing separator is not particularly limited, and an annealing separator containing MgO as a main component may be used.

The purpose of secondary recrystallization annealing is largely to form the {110}<001> aggregate by secondary recrystallization, to form a glassy film by the reaction of the oxide layer and MgO formed upon decarburization, to provide insulation and to remove impurities that impair magnetic properties. . In the method of annealing the secondary recrystallization, the secondary recrystallization is well developed by protecting the nitride, which is a particle growth inhibitor, by maintaining it as a mixed gas of nitrogen and hydrogen in the temperature rising section before the secondary recrystallization occurs, and after completion of the secondary recrystallization 100 % Keep it in a hydrogen atmosphere for a long time to remove impurities.

Thereafter, the step of forming an insulating coating layer may be further included. The insulating layer may be formed using a general method, except that the thickness is thin. Specifically, it can be dried after coating with an organic coating solution such as polyepoxy, polyurethane, polyethylene, polypropylene, starch-based bioplastic, or lignin-based bioplastic. Since the method of forming the insulating coating layer is widely known in the field of electric steel sheet technology, a detailed description is omitted.

1 schematically shows a cross-section of an electric 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 in FIG. 1 is only for illustrating the present invention, and the present invention is not limited thereto. Therefore, the structure of the electric steel sheet can be variously modified.

As shown in Figure 1, the electrical steel sheet 100 according to an embodiment of the present invention is located on the scale layer 20 and the scale layer 20 present in the inner direction from the surface of the electrical steel substrate 10 Reinforcing layer 30 is included. By including the scale layer 20 as described above, a solid bond between the insulating coating layer 40 and the scale layer 20 may be formed, thereby improving adhesion to the insulating coating layer 40. In addition, since the insulating properties exist in the scale layer 20 itself, it is possible to improve the insulating properties. In addition, due to the Si reinforcing layer 30, defects existing in the scale layer 20 can be reinforced, thereby improving magnetic properties.

Hereinafter, each configuration will be described in detail.

First, the electrical steel substrate 10 can use all of the alloy components used in the electrical steel sheet. For example, the electrical steel substrate 10 is weight%, 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 may include Fe and unavoidable impurities.

The scale layer 20 is present in the inner direction from the surface of the electrical steel substrate 10. The thickness of the scale layer 20 may be 1 to 100 nm. More specifically, it may be 5 to 20 nm. If the scale layer 20 is too thin, it is difficult to properly obtain the effect of improving the adhesion with the insulating coating layer 40 and the insulating properties, which are caused by the presence of the scale layer 20 described above. In addition, if the scale layer 20 is too thick, it may rather adversely affect magnetism. Therefore, the thickness of the scale layer 20 may be 1 to 100 nm. More specifically, it may be 5 to 20 nm.

The scale layer 20 may include Si: 5 to 80% by weight, O: 5 to 80% by weight, and the balance Fe and unavoidable impurities. More specifically, the scale may include Si: 10 to 60% by weight, O: 10 to 60% by weight, and the balance Fe and unavoidable impurities. More specifically, the scale may include Si: 15 to 40% by weight, O: 15 to 40% by weight, and the balance Fe and unavoidable impurities.

The scale layer 20 has a Fe content less than that of the electric steel sheet substrate 10, and instead, the Si content is relatively high, so that the OH and O components and the bonding force act largely. Therefore, when forming the insulating coating layer 40, the insulating coating layer 40 is uniformly formed, and adhesion is improved. In addition, the O content of the scale layer 20 is higher than that of the electric steel sheet substrate 10, so that insulating properties are imparted by itself.

In FIG. 1, the surface of the scale layer 20 (that is, the interface between the scale layer 20 and the Si reinforcing layer 30) is represented flat, but is substantially formed very roughly as shown in FIG. 7. The scale layer 20 may have an illuminance of 0.01 to 0.5 nm. If the illuminance is too high, it may adversely affect magnetism. Conversely, when trying to control the illuminance too low, a problem that the scale layer 20 is all removed may occur. Therefore, it is possible to control the roughness of the scale layer 20 in the above-described range.

As shown in FIG. 1, the Si reinforcement layer 30 is positioned on the scale layer 20. In one embodiment of the present invention, defects existing in the scale layer 20 are removed by the Si reinforcing layer 30, so that the magnetic properties can be further improved.

The thickness of the Si reinforcing layer 30 may be 10 to 1000 nm. If the Si reinforcing layer 30 is too thin, it is difficult to properly obtain the magnetic enhancement effect caused by the presence of the above-described Si reinforcing layer 30. In addition, if the Si reinforcing layer 30 is too thick, cracks may occur in the Si reinforcing layer 30 in a cold rolling process, which may adversely affect magnetism. Therefore, the thickness of the Si reinforcing layer 30 may be 10 to 500 nm. More specifically, it may be 10 to 200 nm.

Si reinforcing layer 30 may include Si: 80 to 99% by weight, Al: 1 to 20% by weight. More specifically, the Si reinforcing layer 30 may include Si: 85 to 95 Al: 5 to 45% by weight. Si and Al can be derived from a Si reinforcing layer forming composition. Other components such as Fe and O may be diffused from the scale layer 20 during annealing or diffused from the air.

As shown in FIG. 1, an insulating coating layer 40 may be further included on the Si reinforcement layer 30. Since the scale layer 20 and the Si reinforcing layer 30 are properly formed, the adhesion of the insulating coating layer 40 can be improved, and sufficient insulating properties can be ensured even if the thickness of the insulating coating layer 40 is thin. Specifically, the thickness of the insulating coating layer 40 may be 0.7 to 1.0㎛. Since the insulating coating layer 40 is widely known in the field of electric steel sheet technology, a detailed description is omitted.

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

Example

A slab consisting of Fe and other unavoidable impurities was prepared by containing silicon (Si) at 3.4% by weight.

The slab was heated at 1130° C. and then hot rolled to a thickness of 2.3 mm, thereby producing a hot rolled sheet.

The hot-rolled sheet was controlled to about 650 g/m ^{3 of} fine particles and an injection speed of about 50 km/s using a Shot Blaster, so that a scale layer of about 100 nm thickness was left. Thereafter, the surface roughness was controlled to about 1.5 nm by passing between blades coated with a rubber having an elasticity of about 30 Mpa. Thereafter, it was immersed in a hydrochloric acid solution (about 15 wt%) at a temperature of about 70° C. for about 50 seconds, followed by pickling. Thereafter, washing was performed.

2 shows a scanning electron microscope (SEM) photograph of a section of a steel sheet after pickling. As shown in FIG. 2, it can be seen that the scale layer is displayed as a white part, and the scale layer remains.

3 shows a scanning electron microscope (SEM) photograph of the surface of the steel sheet after pickling. As shown in FIG. 3, it can be confirmed that the feather-like scale layer covers the surface of the steel sheet.

It was confirmed that the scale layer was about 50 nm thick and the roughness was about 0.1 nm. In addition, the alloy component of the scale layer was analyzed by TEM-FIB. It was confirmed that Si: 35.25 wt%, O: 34.02 wt% and the balance Fe and impurities.

A Si reinforcing layer forming composition was prepared. A sulfuric acid dispersion (product of Levasil Akzonobel) containing 40 wt% of Silica Sol and having a pH of 3.75 was prepared. The average particle diameter of the SiO ₂ particles was about 27.2 nm. In addition, about 0.2 wt% of Al ₂ O ₃ was added to the dispersion. The dispersion (about 210 g) was diluted in a solvent in which ethanol (about 829.5 g) and isopropanol (about 819 g) were mixed. The diluted dispersion was stirred for about 24 hours. Thereafter, the diluted dispersion was filtered with a pressure of 2 atmospheres by three layers of cellulose filter paper (pore size is about 2 μm, 0.8 μm, 0.2 μm). The dispersion was coated on a hot rolled sheet having a scale layer and dried.

After that, it was cold rolled, the plate thickness was 0.25 mm, and final annealing was performed.

The surface of the steel sheet is shown in FIG. 6. As shown in FIG. 6, it can be confirmed that a uniform Si reinforcement layer was formed instead of the feather-like scale layer.

The steel sheet cross sections are shown in FIGS. 7 and 8.

As shown in FIGS. 7 and 8, it can be confirmed that the scale layer remains after the cold rolling and final annealing, and the Si reinforcement layer is present.

The alloy component of the Si reinforcement layer was analyzed by TEM-FIB. It was confirmed that Si: 90% by weight and Al: 10% by weight.

Comparative Example 1

A slab consisting of Fe and other unavoidable impurities was prepared by containing silicon (Si) at 3.4% by weight.

The slab was heated at 1130° C. and then hot rolled to a thickness of 2.3 mm, thereby producing a hot rolled sheet.

The hot-rolled sheet was controlled to 1300 g/m ^{3 of} fine particles by using a shot blaster, and 50 km/s of the injection speed to remove all the scale layers. Thereafter, it was immersed in a hydrochloric acid solution (about 30 wt%) at a temperature of about 80° C. for about 100 seconds, followed by pickling. Thereafter, washing was performed.

4 shows a scanning electron microscope (SEM) photograph of a section of a steel sheet after pickling. As shown in Figure 4, it can be seen that all of the scale layer is removed.

5 shows a scanning electron microscope (SEM) photograph of the surface of the steel sheet after pickling. As shown in Fig. 5, no feather-like scale layer was present, and only scratches were observed on the steel sheet.

After that, it was cold rolled, the plate thickness was 0.25 mm, and final annealing was performed.

Comparative Example 2

A slab consisting of Fe and other unavoidable impurities was prepared by containing silicon (Si) at 3.4% by weight.

The slab was heated at 1130° C. and then hot rolled to a thickness of 2.3 mm, thereby producing a hot rolled sheet.

The hot-rolled sheet was controlled to about 80 g/m ^{3 of} fine particles and a speed of about 50 km/s by using a shot blaster, thereby leaving a scale layer of about 500 nm thick. Thereafter, it was immersed in a hydrochloric acid solution (about 15 wt%) at a temperature of about 70° C. for about 50 seconds, followed by pickling. Thereafter, washing was performed. After that, it was cold rolled, the plate thickness was 0.25 mm, and final annealing was performed. After cold rolling, a scale layer of about 250 nm was confirmed.

Experimental Example 1: Confirmation of rust formation

In the Examples and Comparative Examples, after pickling and washing of the hot rolled sheet, the hot rolled sheet was wound up before cold rolling and left for the time shown in Table 1 below.

The gloss was measured at 2 points and shown in Table 1 below. The gloss was expressed by the ratio of the light intensity when the reflected light was received at the same angle as the incident light using an ASTM D 523 gloss meter and the glass surface gloss of 100 with a refractive index of 1.567. At this time, the angle was set to 60 degrees.

Example Comparative Example 1 Comparative Example 2 Immediately after cleaning 71 72 80 86 89 1 day later 50 46 47 57 61 2 days later 50 49 46 55 65

As shown in Table 1, immediately after washing, the present embodiment of the scale layer was inferior in glossiness compared to the comparative example. However, after 1 day and after 2 days, while the example was prevented from being formed by the scale layer, the comparative example was found to generate rust, and thus it was confirmed that the glossiness was remarkably decreased.

Experimental Example 2: Insulation measurement

After the final annealing in Examples and Comparative Examples, the insulation properties of the steel sheet were measured at 3 points and are shown in Table 2 below. In addition, after forming an insulating coating layer having a thickness of 1 μm, insulation properties were measured and shown in Table 2 below. Insulation properties were measured using a Franklin meter in accordance with ASTM A717 international standards.

In addition, adhesion was judged by the presence or absence of film peeling when the specimen was bent 180°. When observed under a microscope x100, it is very good at all, and less than 3 defects /5cmx5cm were marked as good in x100.

The iron loss (W _15/50 ) means the power loss that occurs when a magnetic field with a frequency of 50 Hz is magnetized to AC up to 1.5 Tesla.

Example Comparative example Comparative Example 2 Insulation characteristics before forming the insulating coating layer (mA) 910 850 880 990 990 990 990 Insulation characteristics after forming the insulating coating layer (mA) 90 120 100 300 320 310 300 Adhesion (mmφ) Very good Very good Very good Good Good Good Good _Iron loss (W _15/50 , W/kg) 13.5 13.6 13.4 15.2 15.5 15.5 16.5

As shown in Table 2, it can be seen that the examples in which the scale layer and the Si reinforcing layer exist are superior in insulation properties and improved adhesion compared to Comparative Example 1. Furthermore, it can be seen that iron loss is also improved. In Comparative Example 2, in which too many scale layers remained, it was confirmed that iron loss was very inferior.

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

100: electric steel sheet
10: Electrical steel sheet
20: scale layer
30: Si reinforcement layer
40: insulating coating layer

Claims (17)

Electrical steel sheet
A scale layer present in an inner direction from the surface of the electrical steel substrate and
It includes a Si reinforcement layer located on the scale layer,
The electrical steel substrate is weight%, 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, the remainder of the Fe and inevitable impurities. According to claim 1,
The thickness of the scale layer is 1 to 100nm electric steel sheet. According to claim 1,
The scale layer is Si: 5 to 80% by weight, O: 5 to 80% by weight, and the remainder Fe and an electrical steel sheet containing unavoidable impurities. According to claim 1,
The Si reinforcing layer is Si: 80 to 99% by weight, Al: 1 to 20% by weight of the electrical steel sheet. According to claim 1,
An electrical steel sheet further comprising an insulating coating layer positioned on the Si reinforcement layer. Hot rolling the slab to produce a hot rolled plate;
Removing a portion of the scale formed on the hot rolled sheet, and remaining a scale layer having a thickness of 10 nm or more;
Cold rolling the hot rolled sheet in which the scale layer remains to prepare a cold rolled sheet;
Forming a Si reinforcement layer on the surface of the cold rolled sheet; And
Method of manufacturing an electric steel sheet comprising the step of annealing the cold rolled sheet. The method of claim 6,
In the step of residue to the scale layer, the manufacturing method of the electrical steel sheet treated with a rate of particles the amount of particles in the steel sheet per unit area 20g / m ³ to 1000g / m ³ is 0.1 km / s to 200km / s by using a blasting method . The method of claim 6,
After the step of remaining the scale layer, the method of manufacturing an electric steel sheet further comprising the step of controlling the roughness of the hot-rolled sheet in which the scale layer remains. The method of claim 8,
In the step of controlling the roughness of the hot-rolled sheet, a method of manufacturing an electric steel sheet for controlling the roughness to 0.1 to 2.0nm. The method of claim 6,
The step of controlling the roughness of the hot rolled sheet includes a step of passing the hot rolled sheet between rubber coated blades. The method of claim 10,
The elasticity of the rubber is 7 to 45 Mpa method of manufacturing an electric steel sheet. The method of claim 6,
After the step of remaining the scale layer, the method of manufacturing an electric steel sheet further comprising a pickling step. The method of claim 12,
The pickling step comprises a step of immersing in an acid solution of 15% by weight or less for 20 to 70 seconds. The method of claim 6,
The step of forming the Si reinforcing layer comprises a step of applying a Si reinforcing layer forming composition containing a silicon compound. The method of claim 14,
The Si reinforcing layer forming composition is a method of manufacturing an electric steel sheet comprising 80 to 99% by weight of a silicon compound as a solid content and a balance aluminum compound. The method of claim 14,
The method for producing an electric steel sheet having an average particle diameter of the silicon compound is 5 to 50 nm. The method of claim 6,
In the step of forming the Si reinforcing layer, the Si reinforcing layer is a method of manufacturing an electric steel sheet formed to a thickness of 10 to 1000 nm.

Images