KR102175064B1 - Non-orientied electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

(단, 식 1에서 [Si], [Al] 및 [Mn]은 각각 Si, Al 및 Mn의 함량(중량%)을 나타낸다.)Non-oriented electrical steel sheet according to an embodiment of the present invention is a weight percent, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 to 1.0% , P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance contain Fe and other inevitable impurities, satisfy the following Equation 1, and the average size of oxides in the precipitate is larger than the average size of non-oxides.
[Equation 1]

(However, [Si], [Al] and [Mn] in Equation 1 represent the contents (% by weight) of Si, Al and Mn, respectively.)

Description

Non-oriented electrical steel sheet and its manufacturing method {NON-ORIENTIED ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME}

It relates to a non-oriented electrical steel sheet and a manufacturing method thereof.

Non-oriented electrical steel is used as a material for iron cores in rotating equipment such as motors and generators and stationary equipment such as small transformers, and plays an important role in determining the energy efficiency of electric equipment. Accordingly, recent demands for energy savings and miniaturization of electric devices are demanding to improve the efficiency of electric devices, which leads to a demand for improvement of characteristics of non-oriented electrical steel sheets. The characteristics of the electrical steel sheet are typically iron loss and magnetic flux density. The smaller the iron loss and the higher the magnetic flux density, the better. This is when the magnetic field is induced by adding electricity to the core, the lower the iron loss, the less energy lost as heat. This is because the higher the magnetic flux density, the greater the magnetic field can be induced with the same energy. Therefore, in order to save energy and respond to the increasing demand for eco-friendly products, it is necessary to develop a non-oriented electrical steel sheet manufacturing technology with low iron loss and high magnetic flux density.

Among the magnetic properties of non-oriented electrical steel sheets, representative methods for improving iron loss include a method of greatly thinning the thickness and a method of adding an element having a high specific resistance such as Si and Al. However, the thickness is determined by the characteristics of the product used, and the thinner the thickness, the lower the productivity and the higher the cost. In the method of adding Si, Al, Mn, etc., which are alloy elements with high specific resistance, which is a method of reducing iron loss by increasing the electrical resistivity of general materials, adding an alloying element reduces iron loss, but decreases the magnetic flux density due to the decrease in saturation magnetic flux density. It has a contradiction that it cannot be avoided. In addition, when the amount of Si added is 4% or more, workability decreases and cold rolling becomes difficult, resulting in a decrease in productivity. As more Al and Mn are added, the rollability decreases, the hardness increases, and the workability decreases. Therefore, there is a need for a technique to improve magnetism while lowering cost by most appropriately adding these additive elements.

On the other hand, in the steel, Fe, SI, Al, Mn, etc., which are additive elements, and C, S, N, O, Ti, etc., which are inevitable added impurity elements, are combined to form fine precipitates to suppress the growth of crystal grains and to prevent magnetic domain movement. It interferes and degrades magnetic properties. Precipitates in these steels include carbides, nitrides, sulfides and oxides. These are shown alone or in combination. These fine compounds are classified into inclusions or precipitates depending on their size or formation cause.Since the inclusions have a size of 100 nm or more, they do not have a significant effect on grain growth, and precipitates found to be less than 100 nm are known to inhibit grain growth.

If these precipitates are fine, the quantity of these precipitates increases accordingly to suppress the movement of magnetic domains or grain growth, so it is important to increase the size of the precipitates or to make two or more complex precipitates.

An embodiment of the present invention is to provide a non-oriented electrical steel sheet with improved magnetism and a method of manufacturing the same by limiting the amount of alloying elements added and allowing the precipitate to grow large, thereby facilitating the movement of magnetic domains during grain growth and magnetization.

Non-oriented electrical steel sheet according to an embodiment of the present invention is a weight percent, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 to 1.0% , P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance contain Fe and other inevitable impurities, satisfy the following Equation 1, and the average size of oxides in the precipitate is larger than the average size of non-oxides.

[Equation 1]

(However, [Si], [Al] and [Mn] in Equation 1 represent the contents (% by weight) of Si, Al and Mn, respectively.)

Among the precipitates, the number of oxides may be greater than that of non-oxides.

It may further contain 0.01 to 0.2% by weight of Sn and Sb alone or in combination, respectively.

Among the precipitates, the number of precipitates containing FeO or FeO may be 40% or more.

The average grain size may be 50 to 180㎛.

The method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention is in weight %, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 To 1.0%, P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (excluding 0%) , O: 0.005% or less (excluding 0%) and the balance contains Fe and other inevitable impurities, heating a slab that satisfies Equation 1 below, and then hot rolling to prepare a hot-rolled sheet; winding a hot-rolled sheet After cooling; Annealing and cooling the hot-rolled sheet; Cold rolling a hot-rolled annealed sheet to manufacture a cold-rolled sheet; And final annealing and cooling the cold-rolled sheet, and in the step of cooling the hot-rolled sheet after winding it, maintaining it at 600°C or higher for 30 minutes or more, and cooling the hot-rolled sheet by annealing and cooling the hot-rolled sheet for 5 seconds or more at 600°C or higher. After cooling, the cold-rolled sheet is cooled at 600°C or higher for 5 seconds or longer in the final annealing and cooling step.

[Equation 1]

(However, [Si], [Al] and [Mn] in Equation 1 represent the contents (% by weight) of Si, Al and Mn, respectively.)

The slab may further contain 0.01 to 0.2% by weight of Sn and Sb individually or in combination, respectively.

In the step of manufacturing the hot-rolled sheet, the slab may be heated to 1200°C or less.

In the step of cooling the hot-rolled sheet after winding, the winding temperature may be 600 to 800°C.

In the step of annealing and cooling the hot-rolled sheet, the annealing temperature of the hot-rolled sheet may be 850 to 1,150°C.

In the step of cold rolling the hot-rolled annealed sheet to produce a cold-rolled sheet, it may be cold-rolled to a thickness of 0.1 to 0.7 mm.

In the step of cold rolling a hot-rolled annealed sheet to produce a cold-rolled sheet, the cold rolling may include primary cold rolling, intermediate annealing, and secondary cold rolling.

During annealing in the final annealing and cooling step of the cold rolled sheet, the cracking temperature of the annealing may be 850 to 1,100°C.

The average size of oxides among the precipitates of the manufactured electrical steel sheet may be larger than that of non-oxides.

Among the precipitates, the number of oxides may be greater than that of non-oxides.

Among the precipitates, the number of precipitates containing FeO or FeO may be 40% or more.

The average grain size may be 50 to 180㎛.

The non-oriented electrical steel sheet according to an exemplary embodiment of the present invention can improve magnetism by facilitating movement of magnetic domains during crystal grain growth and magnetization by allowing the precipitate to grow large.

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 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 referring only to specific embodiments and is not intended to limit the present invention. Singular forms as used herein also include plural forms unless the phrases clearly indicate the opposite. As used in the specification, the meaning of “comprising” specifies a specific characteristic, region, integer, step, action, element and/or component, and the presence of another characteristic, region, integer, step, action, 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 another part, or other parts may be involved in between. In contrast, when a part is referred to as being “directly above” another part, no other part is intervened.

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

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

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

Non-oriented electrical steel sheet according to an embodiment of the present invention is a weight percent, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 to 1.0% , P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance contain Fe and other inevitable impurities, satisfy the following Equation 1, and the average size of oxides in the precipitate is larger than the average size of non-oxides.

[Equation 1]

(However, [Si], [Al] and [Mn] in Equation 1 represent the contents (% by weight) of Si, Al and Mn, respectively.)

In one embodiment of the present invention, among the components of the non-oriented electrical steel sheet, in particular, components such as Si, Al, and Mn are precisely controlled to produce the precipitates as large as possible, and the precipitates do not exist alone and are precipitated in a complex manner. This largely attempted to precipitate. In addition, the average size of oxides in the precipitate is formed larger than that of non-oxides, thereby improving magnetism.

Elements added in an embodiment of the present invention are Si, Mn, Al, P, or Sn, Sb as needed, and Fe of the parent material. Other elements to be added include O, C, N, and S, and they need to be kept low. There are nitrides and carbides made by these elements N and C with other elements, oxides made by O, such as Al, Mn, Si, and Fe, and sulfides made by Mn and Cu, and S, and these occur alone or in combination. .

In an embodiment of the present invention, the precipitate was to be coarsened, and in particular, it was intended to be grown more easily by allowing the precipitate to precipitate in a complex rather than singly. Among them, oxides were more easily coarsened because they were possible without adding additional elements. Through this, it was confirmed that the magnetic properties of the electrical steel sheet were improved.

In one embodiment of the present invention, oxides of the precipitates accounted for 50% or more of the total number of precipitates, and especially FeO accounted for 40% or more among oxides. In particular, the effect of oxides had a great effect on the complex precipitation of precipitates. These oxides lowered O during steelmaking, but it is believed that they remain as oxides in the steel or precipitate after annealing. Sulfides precipitated in a considerable amount when the slab was reheated and cooled after hot rolling, and these were precipitated as CuS, MnS, or complex precipitates thereof. However, oxides have more complex precipitates of oxides such as FeO, Al ₂ O ₃ , and SiO ₂ than sulfides, and oxides have relatively little bonds with nitrides and carbides.

Among the precipitates generated in an embodiment of the present invention, oxides exist alone or in combination and have an average size of 15 nm to 70 nm, and the average amount was found to be from 10,000 to 400,000 per 1 mm ² . In addition, non-oxides among the precipitates were found to have an average size of 10 nm to 50 nm, alone or in combination, and an average amount of 5,000 to 200,000 per 1 mm ² .

As described above, the average size of the oxide in the precipitate is formed larger than the average size of the non-oxide, thereby facilitating grain growth, and specifically, the average grain size may be 50 to 180 μm. At this time, the grain size means the grain size measured by the intercept method generally used in the field of electrical steel.

The reasons for limiting the components of the non-oriented electrical steel sheet will be described below.

Si: 1.0 to 4.0% by weight

Silicon (Si) is a major element added because it is a component that lowers eddy current loss during iron loss by increasing the specific resistance of steel and is an element that easily forms oxides. If too little Si is contained, it is difficult to obtain low iron loss characteristics, and if too much Si is added, cold rolling may be difficult. Therefore, it can be limited to 1.0 to 4.0% by weight.

Mn: 0.1 to 1.0% by weight

Manganese (Mn) is added for the purpose of improving iron loss by adding at least 0.1% by weight of Mn since it has an effect of lowering iron loss by increasing specific resistance along with Si and Al. However, since the saturation magnetic flux density decreases as the amount of Mn added increases, the magnetic flux density decreases, and it combines with S to form fine MnS precipitates to inhibit crystal grain growth and hinder magnetic wall movement, thereby increasing hysteresis loss, especially among iron losses. It is added at 1.0% by weight or less.

Al: 0.15 to 1.5% by weight

Aluminum (Al) is an element that is inevitably added for deoxidation of steel in the steel making process, and is a major element that increases the specific resistance, so it is often added to lower iron loss, but it also plays a role in reducing the saturation magnetic flux density by adding it. In addition, when the amount of Al added is excessively small, fine AlN is formed to suppress crystal grain growth, thereby reducing magnetism. In addition, if too much Al is added, it causes the magnetic flux density to decrease, so the amount of Al may be limited to 0.15 to 1.5% by weight.

P: 0.2% by weight or less

Phosphorus (P) increases the specific resistance, lowers iron loss, and segregates at grain boundaries to suppress the formation of a grainy structure that is harmful to magnetism, and forms an advantageous texture, {100}. However, if too much is added, it is limited to 0.2% by weight or less because it lowers the rollability. can do.

C: 0.005% by weight or less

When a large amount of carbon (C) is added, it expands the austenite region, increases the phase transformation section, and suppresses the grain growth of ferrite when annealing, thereby increasing the iron loss. Also, it combines with Ti to form carbides, resulting in poor magnetism. When used after processing from the final product to an electrical product, it can be limited to 0.005% by weight or less because the iron loss is increased by magnetic aging.

N: 0.005% by weight or less

Nitrogen (N) is an element that is harmful to magnetism, such as forming nitride by strongly bonding with Al, Ti, etc. to suppress crystal grain growth, so it is preferable to contain less nitrogen (N), and may be limited to 0.005% by weight or less.

S: 0.001 to 0.006% by weight

Sulfur (S) is an element that forms sulfides such as MnS, CuS, and (Cu,Mn)S, which are harmful to magnetic properties, so it is preferable to add it as low as possible. However, if too little is added, the magnetism may be deteriorated because it is disadvantageous to the formation of the texture. In addition, if too much is added, magnetism may be deteriorated due to the increase of fine sulfides. Therefore, it can be limited to 0.001 to 0.006% by weight.

Ti: 0.005% by weight or less

Titanium (Ti) suppresses grain growth by forming fine carbides and nitrides, and as more carbides and nitrides are added, the texture becomes inferior due to the increased carbides and nitrides, resulting in poor magnetic properties. Therefore, it can be limited to 0.005% by weight or less.

O: 0.005% by weight or less

Oxygen (O) can be contained as low as possible because it suppresses grain growth by making various oxides. Therefore, it can be limited to 0.005% by weight or less.

Sn, Sb: 0.01 to 0.2% by weight

Tin (Sn) and antimony (Sb) are segregation elements in the grain boundaries, suppressing the diffusion of nitrogen through the grain boundaries, suppressing the {111} texture harmful to magnetism, and increasing the advantageous {100} aggregate structure to improve magnetic properties. If the Sn and Sb are added alone or too much, the grain growth may be suppressed to lower the magnetism and the rolling properties may deteriorate. Therefore, when it contains Sn or Sb, it may be limited to 0.01 to 0.2% by weight of each of Sn and Sb alone or as a sum.

In particular, in an embodiment of the present invention, Si, Mn, and Al among the added elements are adjusted to satisfy Equation 1 below, so that the Mn content is not high and the Si content is high, and Al is also contained in a significant amount to suppress AlN, etc. .

[Equation 1]

(However, [Si], [Al] and [Mn] in Equation 1 represent the contents (% by weight) of Si, Al and Mn, respectively.)

The method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention is in weight %, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 To 1.0%, P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (excluding 0%) , O: 0.005% or less (excluding 0%) and the balance comprises Fe and other unavoidable impurities, heating the slab satisfying the following formula 1 and then hot rolling to prepare a hot-rolled sheet; Cooling the hot-rolled sheet after winding; Annealing and cooling the hot-rolled sheet; Cold rolling a hot-rolled annealed sheet to manufacture a cold-rolled sheet; And final annealing and cooling the cold-rolled sheet, and in the step of cooling the hot-rolled sheet after winding it, maintaining it at 600°C or higher for 30 minutes or more, and cooling the hot-rolled sheet by annealing and cooling the hot-rolled sheet for 5 seconds or more at 600°C or higher. After cooling, the cold-rolled sheet is cooled at 600°C or higher for 5 seconds or longer in the final annealing and cooling step.

In one embodiment of the present invention, after the hot-rolled sheet is manufactured, the hot-rolled sheet is annealed, and then the cold-rolled sheet is annealed and then cooled, slowly cooling to have a time for the precipitate to grow, thereby improving magnetic properties.

Hereinafter, the process will be described for each step.

First, the slab is heated and then hot-rolled to produce a hot-rolled sheet. The reason for limiting the addition ratio of each composition is the same as the reason for limiting the non-oriented electrical steel sheet described above. Since the composition of the slab does not change substantially during the process of hot rolling, hot-rolled sheet annealing, cold rolling, and final annealing to be described later, the composition of the slab and the composition of the non-oriented electrical steel sheet are substantially the same.

It can be heated to 1,200℃ or less by charging the slab to the heating furnace. If the heating temperature is too high, precipitates such as AlN and MnS present in the slab are re-dissolved and then finely precipitated during hot rolling, thereby inhibiting grain growth and lowering magnetism. More specifically, it can be heated at 1,050°C to 1,200°C.

The heated slab is made into a hot-rolled sheet by hot rolling to 1.4mm to 3mm. When hot rolling, finish rolling in finish rolling is finished in ferrite, and the final rolling reduction ratio is less than 20% for plate shape correction.

Next, the hot-rolled sheet is wound and cooled. The hot-rolled sheet is wound at a temperature of 600°C to 800°C, and cooled by putting it in air or in a separate furnace. When cooling, the temperature should be kept above 600℃ for at least 30 minutes. If the temperature is too low or the time is kept short, the growth of the precipitate is difficult and may be finely precipitated. More specifically, it may be maintained for 30 minutes to 3 hours at a temperature of 600 to 800 ℃.

Next, the hot-rolled sheet is annealed and cooled. The hot-rolled sheet is annealed for magnetic improvement, and the hot-rolled sheet annealing temperature is set at 850 to 1,150°C. If the hot-rolled sheet annealing temperature is too low, grain growth may be insufficient. If the hot-rolled sheet annealing temperature is too high, grains may grow excessively and surface defects of the sheet may become excessive.

When cooling the hot-rolled sheet after annealing, the cooling is not rapidly cooled and maintained at 600℃ or higher for 5 seconds or longer. If the temperature is too low during cooling or the holding time is short, the precipitate may be difficult to coarsen and the plate may be bent. More specifically, the temperature during cooling may be 600 to 800°C, and may be maintained for 5 to 30 seconds.

It can also be pickled after annealing the hot-rolled sheet.

Next, the hot-rolled annealed sheet is cold-rolled to produce a cold-rolled sheet. Cold rolling is finally rolled to a thickness of 0.1mm to 0.7mm, and if necessary, primary cold rolling, intermediate annealing, and secondary cold rolling can be performed, and the final rolling reduction can be in the range of 50 to 95%.

Next, the cold-rolled sheet is finally annealed and cooled. When annealing in the process of annealing the cold-rolled sheet, the cracking temperature of the annealing of the cold-rolled sheet is 850 to 1,100°C. Cold-rolled sheet When the annealing temperature is 850℃ or less, grain growth is insufficient, resulting in an increase in the texture of {111}, which is harmful to magnetism, and above 1100℃, the grains grow excessively and adversely affect magnetism. The cracking temperature of is set to 850 to 1100°C.

When cooling after annealing the cold rolled sheet, the cooling is not rapidly cooled and maintained at 600℃ or higher for 5 seconds or longer. If the temperature is too low or the holding time is short during cooling, fine precipitates may be precipitated alone. More specifically, the temperature during cooling may be 600 to 800°C, and may be maintained for 5 to 30 seconds.

The annealed plate is shipped to the customer after insulating film treatment. The insulating film may be treated as an organic, inorganic, and organic-inorganic composite film, or may be treated with other insulating film. Customers can use the steel plate as it is after processing.

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 One

Inventive steels A1 to A7 satisfying Equation 1 and A8 not satisfying Equation 1 by producing a steel ingot composed as shown in Table 1 and Table 2 below. Comparative steel was dissolved up to A12.

Vacuum melted steels A1 to A7 are manufactured with Si, Al, Mn content within the scope of the invention, and each steel ingot is heated at 1120℃, hot-rolled to a thickness of 2.2mm, wound, and slowly cooled in the atmosphere as shown in Table 2. The taken and cooled hot-rolled steel sheet was annealed in a nitrogen atmosphere for 5 minutes, slowly cooled at a temperature of 600° C. or higher in an atmosphere in which nitrogen and oxygen are mixed, and then quenched by sprinkling final water. The annealed hot-rolled sheet was pickled and then cold-rolled to a thickness of 0.35 mm, and the final annealing of the cold-rolled sheet was annealed for 2 minutes in a mixed atmosphere of 30% hydrogen and 70% nitrogen. The cooling zone was cooled in an atmosphere of 40% hydrogen and nitrogen. In the final annealed plate, the sizes and quantities of oxides, sulfides, carbides, nitrides, and complex precipitates thereof were investigated for each specimen, and crystal grains and magnetic properties were measured and summarized in Table 3 below.

As a method for analyzing the size, type and distribution of precipitates, a carbon replica extracted from the specimen was observed with TEM and analyzed with EDS. TEM observation was a randomly selected area without bias, and the type of precipitate was analyzed through EDS spectrum.

The iron loss (W _15/50 ) was measured as the average loss (W/kg) in the rolling direction and the vertical direction in the rolling direction when the magnetic flux density of 1.5 Tesla was induced at 50 Hz frequency.

The magnetic flux density (B ₅₀ ) was measured as the magnitude of the magnetic flux density (Tesla) induced when a magnetic field of 5000A/m was added.

division C Si Al Mn P S N Ti Sn Sb A1 0.0025 1.56 0.25 0.42 0.031 0.0024 0.0014 0.0002 0.026 0.012 A2 0.0028 2.64 0.22 0.4 0.036 0.0021 0.0021 0.0015 0.019 0 A3 0.0025 2.82 0.82 0.8 0.045 0.0028 0.0014 0.0017 0 0 A4 0.0022 2.95 0.78 0.62 0.055 0.0021 0.0012 0.0016 0 0 A5 0.0025 2.82 1.3 0.45 0.032 0.0015 0.0025 0.0011 0 0.031 A6 0.0028 2.91 0.32 0.52 0.031 0.0018 0.0021 0.0011 0.024 0.021 A7 0.0022 3.3 0.25 0.4 0.035 0.0032 0.0026 0.0015 0.036 0.015 A8 0.0021 0.52 0.002 0.45 0.031 0.0024 0.0014 0.0002 0.026 0.012 A9 0.0026 1.43 0.25 0.62 0.045 0.0001 0.0015 0.0019 0.025 0.031 A10 0.0023 2.24 0.12 0.72 0.055 0.0032 0.0018 0.0021 0 0.019 A11 0.0027 2.51 0.45 0.9 0.023 0.0035 0.0021 0.0021 0.035 0 A12 0.0029 2.96 0.74 1.3 0.019 0.0019 0.0019 0.0025 0.043 0

Steel grade Whether Equation 1 is satisfied Cooling after winding Hot rolled sheet annealing Cold rolled sheet annealing Remark Temperature(℃) Time (minutes) Annealing temperature (℃) Holding time over 600℃ (sec) Annealing temperature (℃) Holding time over 600℃ (sec) A1 O 700 60 900 10 900 8 Invention Lesson 1 A2 O 650 60 1000 12 1030 15 Invention Lesson 2 A3 O 650 60 1000 10 1030 15 Invention Lesson 3 A4 O 650 60 1000 7 1030 15 Invention Lesson 4 A5 O 650 60 1000 7 1050 15 Invention Lesson 5 A6 O 650 60 1000 10 1050 15 Invention Lesson 6 A7 O 650 60 1000 10 1050 15 Invention Lesson 7 A8 X 700 60 900 10 900 8 Comparative Steel 1 A9 X 700 60 900 12 900 8 Comparative lecture 2 A10 X 650 60 1000 12 1050 15 Comparative lecture 3 A11 X 650 60 1000 12 1050 15 Comparative lecture 4 A12 X 650 60 1000 12 1050 15 Comparative lecture 5

Steel grade Grain size
(㎛) Oxides in the precipitate Among the precipitates
FeO ratio (%) Non-oxides in the precipitate _Iron loss (W _15/50 ) W/kg Magnetic flux density (B ₅₀ ) Tesla Remark Size (nm) ratio(%) Size (nm) ratio(%) A1 60 45 55 45 40 45 3.72 1.78 Invention Lesson 1 A2 80 48 60 50 43 40 2.21 1.73 Invention Lesson 2 A3 87 60 62 54 45 38 2.12 1.71 Invention Lesson 3 A4 120 65 65 48 46 35 1.85 1.69 Invention Lesson 4 A5 120 58 70 55 45 30 1.92 1.68 Invention Lesson 5 A6 110 45 72 62 40 28 1.95 169 Invention Lesson 6 A7 160 48 70 55 35 30 1.93 1.68 Invention Lesson 7 A8 40 32 35 28 38 65 6.43 1.71 Comparative Steel 1 A9 45 33 40 35 38 60 4.52 1.69 Comparative lecture 2 A10 60 31 35 32 37 65 2.52 1.66 Comparative lecture 3 A11 65 22 40 36 39 60 2.54 1.65 Comparative lecture 4 A12 70 28 45 30 35 55 2.32 1.62 Comparative lecture 5

As shown in Tables 1 to 3, A1 to A7 satisfy the composition range and Equation 1 of the electrical steel sheet, and it can be seen that the size of the oxide in the precipitate is larger than the size of the non-oxide. And it can be confirmed that the magnetic flux density is excellent. On the other hand, A8 to A12 do not satisfy the composition range and Equation 1 of the electrical steel sheet, and in some cases, it can be seen that the size of the oxide in the precipitate is smaller than the size of the non-oxide. Therefore, it can be confirmed that the iron loss and magnetic flux density are poor.

Example 2

Inventive steels A13 to A15 were dissolved in the amount of Si, Al, and Mn by weight% satisfying Equation 1 through vacuum melting to prepare steel ingots as shown in Tables 4 and 5 below.

Each steel ingot is heated at 1120℃, hot-rolled to a thickness of 2.2mm, wound up, slowly cooled in the atmosphere as shown in Table 5, and wound up, and the cooled hot-rolled steel sheet is annealed in a nitrogen atmosphere for 5 minutes, Slow cooling was performed at a temperature of 600°C or higher in the atmosphere, and the final water was sprinkled for rapid cooling. The annealed hot-rolled sheet was pickled and then cold-rolled to a thickness of 0.35 mm, and the final annealing of the cold-rolled sheet was annealed for 2 minutes in a mixed atmosphere of 30% hydrogen and 70% nitrogen. The cooling zone was cooled in an atmosphere of 40% hydrogen and nitrogen. In the final annealed plate, the sizes and quantities of oxides, sulfides, carbides, nitrides, and complex precipitates thereof were investigated for each specimen, and crystal grains and magnetic properties were measured and summarized in Table 6 below.

division C Si Al Mn P S N Ti Sn Sb A13 0.0035 2.12 0.31 0.2 0.032 0.0044 0.0025 0.0013 0 0.035 A14 0.0024 2.52 0.26 0.21 0.043 0.0022 0.0029 0.0011 0.041 0 A15 0.0021 3.12 0.51 0.8 0.045 0.0045 0.0022 0.0009 0.031 0

Steel grade Whether Equation 1 is satisfied Cooling after winding Hot rolled sheet annealing and cooling Cold rolled sheet annealing and cooling Remark Temperature(℃) Time (minutes) Annealing temperature (℃) Maintain over 600℃ (sec) Annealing temperature (℃) Holding time over 600℃ A13 O 650 50 950 12 980 10 Invention Lecture 8 A13 O 650 50 800 2 980 2 Comparative lecture 6 A14 O 620 80 1020 10 1020 11 Invention Lecture 9 A14 O 620 80 1020 2 1020 11 Comparative Steel 7 A14 O 620 One 1020 2 900 2 Comparative lecture 8 A14 O 520 80 1020 2 1020 2 Comparative lecture 9 A15 O 650 30 1020 15 1020 12 Invention Lesson 10 A15 O 650 One 1020 2 1020 2 Comparative Steel 10 A15 O 650 30 1020 2 1020 2 Comparative Steel 11

Steel grade Grain size (㎛) Oxides in the precipitate Among the precipitates
FeO ratio (%) Non-oxides in the precipitate _Iron loss (W _15/50 ) W/kg Magnetic flux density (B ₅₀ ) Tesla Remark Size (nm) ratio(%) Size (nm) ratio(%) A13 75 47 68 52 35 32 2.81 1.75 Invention Lecture 8 A13 45 30 41 35 38 59 3.52 1.72 Comparative lecture 6 A14 78 52 65 45 46 35 2.23 1.71 Invention Lecture 9 A14 60 28 38 38 35 62 2.52 1.68 Comparative Steel 7 A14 40 31 35 35 35 65 2.43 1.67 Comparative lecture 8 A14 60 28 36 32 36 64 2.61 1.68 Comparative lecture 9 A15 120 65 80 57 38 20 2.11 1.71 Invention Lesson 10 A15 72 25 45 35 33 55 2.43 1.65 Comparative Steel 10 A15 67 21 42 36 33 58 2.64 1.63 Comparative Steel 11

As shown in Tables 4 to 6, compared to the comparative steel, the invention steel gave sufficient cooling time after winding, and after annealing the hot-rolled and cold-rolled sheets, sufficient time was given at 600°C or higher to form oxides including FeO oxides. It can be seen that the crystal grains grew well and the magnetism was excellent.

On the other hand, Comparative Steel 6 had a low hot-rolled sheet annealing temperature and a short holding time of over 600℃ when cooled, and the size of oxides in the precipitate was small, and the quantity was small. The cooling time after annealing of the comparative steel 7 degree hot-rolled sheet was short, so the size of oxides in the precipitate was relatively small and the yield was smaller than that of non-oxides, and the proportion of FeO oxide was also low, 40% or less. Comparative steel 8 was cooled quickly by water cooling after winding, and the cooling time was short at 600℃ or higher after hot-rolled sheet annealing, and the time after cold-rolled sheet annealing was also short, so iron loss was relatively insufficient due to insufficient formation of oxides including FeO in the precipitate. High and low magnetic flux density. Comparative strength 9 degree component is satisfactory, but the coiling temperature is low, and the annealing time is short when cooling after hot-rolled sheet annealing, so the size of oxides alone or complex precipitates including FeO is small and the number of oxides is small compared to non-oxides, so the size of crystal grains is small It can be confirmed that it is poor. As a result of shortening the cooling time after annealing of the hot-rolled and cold-rolled sheets together with Comparative Steel 11 after winding, the comparative steel 10 has a low FeO ratio in the precipitate and the formation of oxides, so that the crystal grains are small and the magnetism is insufficient. have.

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

Claims (17)

In wt%, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 to 1.0%, P: 0.2% or less (excluding 0%) , N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance Contains Fe and other unavoidable impurities,
Satisfies Equation 1 below,
The average size of oxides in the precipitate is larger than the average size of non-oxides,
Non-oriented electrical steel sheet in which the number of oxides among the precipitates is greater than that of non-oxides.
[Equation 1]

(However, [Si], [Al] and [Mn] in Equation 1 represent the contents (% by weight) of Si, Al and Mn, respectively.) delete The method of claim 1,
Non-oriented electrical steel sheet further comprising 0.01 to 0.2% by weight of Sn and Sb, either alone or in combination. The method of claim 1,
Non-oriented electrical steel sheet in which the number of precipitates containing FeO or FeO is 40% or more. The method of claim 1,
Non-oriented electrical steel sheet having an average grain size of 50 to 180㎛. In wt%, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 to 1.0%, P: 0.2% or less (excluding 0%) , N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance Comprising Fe and other unavoidable impurities, heating a slab that satisfies Equation 1 below, and then hot rolling to prepare a hot-rolled sheet;
Cooling the hot-rolled sheet after winding;
Annealing and cooling the hot-rolled sheet;
Cold rolling a hot-rolled annealed sheet to manufacture a cold-rolled sheet; And
Including the step of final annealing and cooling the cold-rolled sheet,
In the step of cooling the hot-rolled sheet after winding, it is cooled by holding it at 600°C or higher for 30 minutes or longer,
In the step of annealing and cooling the hot-rolled sheet, cooling at 600° C. or higher for 5 seconds or more,
In the final annealing and cooling step of the cold-rolled sheet, it is cooled at 600° C. or higher for 5 seconds or more,
The average size of oxides among the precipitates of the prepared non-oriented electrical steel sheet is larger than that of non-oxides,
A method of manufacturing a non-oriented electrical steel sheet in which the number of oxides among the precipitates is greater than that of non-oxides.
[Equation 1]

(However, [Si], [Al] and [Mn] in Equation 1 represent the contents (% by weight) of Si, Al and Mn, respectively.) The method of claim 6,
The slab is a method of manufacturing a non-oriented electrical steel sheet further comprising 0.01 to 0.2% by weight of Sn and Sb individually or in combination, respectively. The method of claim 6,
In the step of manufacturing the hot-rolled sheet, a method of manufacturing a non-oriented electrical steel sheet by heating the slab to 1200°C or less. The method of claim 6,
A method of manufacturing a non-oriented electrical steel sheet having a winding temperature of 600 to 800°C in the step of cooling the hot-rolled sheet after winding. The method of claim 6,
In the step of annealing and cooling the hot-rolled sheet, the annealing temperature of the hot-rolled sheet is 850 to 1,150°C. The method of claim 6,
In the step of cold rolling the hot-rolled annealed sheet to produce a cold-rolled sheet, a method of manufacturing a non-oriented electrical steel sheet by cold rolling to a thickness of 0.1 to 0.7 mm. The method of claim 6,
In the step of producing a cold-rolled sheet by cold rolling the hot-rolled annealed sheet, the cold-rolling is a method of manufacturing a non-oriented electrical steel sheet including primary cold rolling, intermediate annealing, and secondary cold rolling. The method of claim 6,
When annealing in the final annealing and cooling step of the cold-rolled sheet, the cracking temperature of the annealing is 850 to 1,100°C. delete delete The method of claim 6,
A method of manufacturing a non-oriented electrical steel sheet in which the number of precipitates containing FeO or FeO among the precipitates is 40% or more. The method of claim 6,
A method of manufacturing a non-oriented electrical steel sheet having an average grain size of 50 to 180 μm.