KR101707452B1 - Non-oriented electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

According to an embodiment of the present invention, a non-oriented electrical steel sheet comprises: 0.005 wt% or less of C (excluding 0 wt%); 0.5-4 wt% of Si; 0.4-2.0 wt% of Mn; 0.01-0.2 wt% of P; 0.001-0.005 wt% of S; 0.09 wt% or less of Al (excluding 0 wt%); 0.005 wt% or less of N (excluding 0 wt%); 0.005 wt% or less of Ti (excluding 0 wt%); 0.002-0.2 wt% of Sn; and the remainder consisting of Fe and inevitable impurities. The non-oriented electrical steel sheet satisfies the formula 1 below. An average size of crystal grains is 30-100 m. [Formula 1] 0.1 <= [Mn] / ([Si] + 10 [Al]) <= 0.6. (In formula 1, [Mn], [Si], and [Al] mean contents of Mn, Si, and Al respectively). The purpose of the present invention is to provide the non-oriented electrical steel sheet having excellent magnetic properties and obtaining high productivity without annealing.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a non-oriented electrical steel sheet,

A non-oriented electrical steel sheet and a manufacturing method thereof.

The nonoriented electrical steel sheet is used as an iron core material in rotating equipment such as motors, generators, and stationary equipment such as small transformers, and it transforms electrical energy into mechanical energy. Since energy saving is emerging as a social issue, it is necessary to improve the characteristics of non-oriented electric steel sheet, which is a very important material for determining the energy efficiency of electric devices.

The iron loss and magnetic flux density are the typical magnetic properties of the non-oriented electrical steel sheet, and the iron loss is the energy lost. Therefore, the lower the magnetic loss and the higher the magnetic flux density, the more magnetic field can be induced with the same energy. In order to obtain the same magnetic flux density, The higher the better, because it can reduce the hands.

The essential alloying elements which are importantly added to the non-oriented electrical steel sheet include Si, Al and Mn. Si, Al, and Mn are alloying elements with high resistivity and are added to improve iron loss, which is an important magnetic property of nonoriented electrical steel sheet. However, the addition of Si, Al, Mn, and other alloying elements with high resistivity reduces the iron loss, but it can not avoid reduction of the magnetic flux density due to the decrease of the saturation magnetic flux density. Therefore, the magnetic flux density is also low in the case of the non- . As described above, the problem of improving the magnetic flux density while lowering the iron loss is a difficult part.

Therefore, in order to improve the magnetic flux density while lowering the iron loss, a technique of introducing additional manufacturing processes such as improving the magnetic properties by improving the texture by using special additional elements such as REM or annealing twice twice of rolling is used. However, all of these technologies cause a rise in manufacturing costs and difficulties in mass production, so it is necessary to develop a technology that can improve productivity while exhibiting excellent magnetic characteristics.

There have been continuous efforts to solve these problems and many technologies have been developed. As a method for developing a non-oriented electrical steel sheet having a high magnetic flux density, hot rolling is carried out at a temperature of A3 or higher. When cooling after hot rolling, the cooling rate from A3 temperature to 200 ° C is 50 ° C / s for better magnetic properties, s, annealing the hot-rolled sheet, cold rolling and annealing the cold-rolled sheet. However, there is a disadvantage in that the additional cost is required to control the cooling rate.

In order to manufacture a non-oriented electrical steel sheet having excellent magnetic properties in the rolling direction, a skin pass rolling is performed at a rolling reduction of 3 to 10% in addition to the processes of hot rolling, hot rolling annealing, cold rolling and cold rolling annealing, Respectively. This also has the problem of cost increase due to the additional process.

In order to improve the magnetic properties by improving the texture, the composition weight ratio (MnO / SiO ₂ ) of MnO and SiO ₂ in the oxide inclusions in the steel is set to 0.43 or less. In the hot rolling, the finishing rolling is performed under a condition that the friction coefficient between steel and roll is 0.2 A method of annealing a hot-rolled sheet, annealing a cold-rolled sheet, and annealing a cold-rolled sheet after a finishing rolling temperature of 700 ° C or more is proposed. In this case, since the hot-rolled sheet must be controlled to a thickness of 1.0 mm or less, .

In order to improve the magnetic properties, the method of annealing twice twice including intermediate annealing as the hot-rolled steel sheet has been proposed, but the productivity is decreased and the manufacturing cost is increased.
BACKGROUND ART 1: Published patent publication No. 10-2009-0014383
BACKGROUND ART 2: Japanese Patent Application Laid-Open No. 10-2015-0062245

An embodiment of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties and high productivity without precisely controlling the content of Si, Al, and Mn in the steel additive components and without annealing the hot-rolled steel sheet.

Another embodiment of the present invention is to provide a method for manufacturing a non-oriented electrical steel sheet.

The non-oriented electrical steel sheet according to an embodiment of the present invention may contain, by weight%, 0.005% or less of C (excluding 0%), 0.5-4% of Si, 0.4-2.0% of Mn, S: 0.001 to 0.005%, Al: 0.09% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% 0.2%, the balance including Fe and unavoidable impurities, satisfying the following formula 1, and having an average grain size of 30 to 100 탆.

[Formula 1]

0.1? [Mn] / ([Si] + 10 x [Al])? 0.6

([Mn], [Si] and [Al] in the formula 1 represent contents of Mn, Si and Al, respectively.

Cu, Ni and Cr in an amount of 0.05 wt% or less (excluding 0 wt%), respectively.

Zr, Mo, and V in an amount of 0.01 wt% or less (excluding 0 wt%), respectively.

An iron loss (W _15/50 ) of 3.5 W / kg or less, and a magnetic flux density (B ₅₀ ) of 1.70 T or more.

A method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes: 0.005% or less (excluding 0%) of C; 0.5 to 4% of Si; 0.4 to 2.0% of Mn; (Excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), and Sn : 0.002 to 0.2%, the balance comprising Fe and unavoidable impurities, and heating the slab satisfying the following formula (1) and then hot rolling to produce a hot rolled steel sheet; Winding the hot rolled sheet; Cold rolling the rolled hot rolled sheet directly to produce a cold rolled sheet; Wherein the slab heating temperature (SRT), the hot rolling finishing temperature (FDT), and the hot rolled sheet coiling temperature (CT) satisfy the following formulas 2 and 3, and the recrystallization annealing temperature T _ann ) satisfies the following expression (4).

[Formula 1]

0.1? [Mn] / ([Si] + 10 x [Al])? 0.6

 [Formula 2]

([SRT] - [FDT]) ≤300

[Formula 3]

([FDT] - [CT])? 200

[Formula 4]

900 + 500 * ([P] + [Sn]) ≤ [T _ann ]

Si, Al, P and Sn represent contents of Mn, Si, Al, P and Sn, respectively, and [SRT] (CT) represents the coiling temperature (占 폚), and [T _ann ] represents the recrystallization annealing temperature (占 폚).

In the step of winding the hot rolled sheet, the volume fraction of the crystal grains recrystallized in the hot rolled sheet may be 50% or more.

The slab heating temperature (SRT) may be between 1100 and 1300 ° C.

In the step of recrystallization annealing, the recrystallization annealing temperature (T _ann ) is 920 to 1060 ° C and can be annealed for 1 minute to 5 minutes.

The slab may further contain 0.05 wt% or less (excluding 0 wt%) of Cu, Ni and Cr, respectively.

The slab may further contain Zr, Mo and V in an amount of 0.01 wt% or less (excluding 0 wt%), respectively.

The produced electric steel sheet may have an iron loss (W15 / 50) of 3.5 W / kg or less and a magnetic flux density (B50) of 1.70 T or more.

The non-oriented electrical steel sheet according to an embodiment of the present invention has excellent magnetic characteristics and excellent productivity.

The terms first, second and third, etc. are used to describe various portions, components, regions, layers and / or sections, but are not limited thereto. These terms are only used to distinguish any moiety, element, region, layer or section from another moiety, moiety, region, layer or section. Thus, 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 for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified and that the presence or absence of other features, regions, integers, steps, operations, elements, and / It does not exclude addition.

When referring to a portion as being "on" or "on" another portion, it may be directly on or over another portion, or may involve another portion therebetween. In contrast, when referring to a part being "directly above" another part, no other part is interposed therebetween.

Unless otherwise defined, 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 this invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Unless otherwise stated,% 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 skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

An embodiment of the present invention is to provide a non-oriented electrical steel sheet having excellent productivity and magnetic properties by controlling the components of Si, Mn, and Al among the alloying elements of the steel and controlling the grain size of the crystal grains at the same time.

The non-oriented electrical steel sheet according to an embodiment of the present invention may contain, by weight%, 0.005% or less of C (excluding 0%), 0.5-4% of Si, 0.4-2.0% of Mn, S: 0.001 to 0.005%, Al: 0.09% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% 0.2%, the remainder comprising Fe and unavoidable impurities.

First, the reason for limiting the components of the non-oriented electrical steel sheet will be described.

C: 0.005 wt% or less

Carbon (C) is combined with Ti to form carbide to dislocate magnetism. Since it increases iron loss by magnetic aging when it is used as an electrical product in the final product, it is made to be 0.005 wt% or less.

Si: 0.5 to 4.0 wt%

Silicon (Si) is a major element added to increase the resistivity of the steel and to reduce vortex loss during iron loss. In order to obtain low core loss properties, it should be added in an amount of 0.5 wt% or more. On the other hand, as the addition amount is increased, the magnetic flux density is decreased. Therefore, it is difficult to obtain the characteristics of the high magnetic flux density as the addition amount is increased. When the Si is added in an amount exceeding 4% by weight, the magnetic flux density becomes low and commercial production is difficult. By weight to 4% by weight or less.

Mn: 0.4 to 2.0 wt%

Manganese (Mn) is an element that lowers iron loss by increasing resistivity along with Si and Al, and is an austenite stabilizing element unlike Si and Al, which influences the phase transformation behavior. When it is added too much, the magnetic flux density is greatly reduced, so that the addition amount is limited to 0.4 to 2.0 wt%.

P: 0.01 to 0.2 wt%

Phosphorus (P) plays a role of lowering the iron loss by increasing the resistivity and segregating at grain boundaries and improving the texture. It is required to be added in an amount of 0.01 wt% or more in order to increase the effect of the addition, and it is added in an amount in the range of 0.01 to 0.2 wt.

S: 0.001 to 0.005 wt%

Sulfur (S) is an element which forms sulfides such as MnS, CuS and (Cu, Mn) S harmful to the magnetic properties, and therefore it is preferable to add as low as possible. However, when it is added in an amount of less than 0.001% by weight, it is rather disadvantageous to the formation of aggregate structure and the magnetic property is deteriorated. If it is added in an amount of more than 0.005% by weight, the magnetism tends to be heated due to the increase of fine sulfides, so that it is contained in an amount of 0.001 to 0.005% by weight.

Al: 0.09 wt% or less

Aluminum (Al) is added because it increases the resistivity and reduces the iron loss, and also reduces the magnetic anisotropy and reduces the magnetization deviation in the rolling direction and in the direction perpendicular to the rolling direction. However, as the addition amount is increased, the magnetic flux density is greatly reduced, so that the addition amount is limited to 0.09 wt% or less.

N: 0.005 wt% or less

Nitrogen (N) is an element harmful to magnetism such as nitrides formed by binding strongly with Al and Ti to inhibit crystal growth, and therefore it is preferable to contain N in an amount as small as 0.005 wt% or less.

Ti: 0.005 wt% or less

Titanium (Ti) forms fine carbides and nitrides to inhibit crystal growth. As the amount of titanium (Ti) increases, the magnetization deteriorates due to increased carbides and nitrides.

Sn: 0.002 to 0.2 wt%

Tin (Sn) is a grain boundary element that suppresses the diffusion of nitrogen through grain boundaries and inhibits the formation of {111}, {112} texture that is harmful to magnetism and increases {100} and {110} In order to improve the magnetic properties, the amount of Sn added is preferably 0.002 to 0.2% by weight, more preferably 0.002 to 0.2% by weight to increase the effect of addition, By weight.

Sb which is a grain boundary segregation element may be further added and may be added so that the sum of the amounts of Sn and Sb added is 0.002 to 0.2% by weight.

Other impurities

In addition to the above-mentioned elements, Cu, Ni, and Cr, which are inevitably added in steelmaking processes, react with impurity elements to form fine sulfides, carbides, and nitrides, thereby detrimentally affecting the magnetic properties. . Further, since Zr, Mo and V are strong carbonitride-forming elements, they are preferably not added as much as possible, and each is contained in an amount of 0.01% by weight or less.

The non-oriented electrical steel sheet according to one embodiment of the present invention satisfies the following formula (1).

[Formula 1]

0.1? [Mn] / ([Si] + 10 x [Al])? 0.6

([Mn], [Si] and [Al] in the formula 1 represent contents of Mn, Si and Al, respectively.

Si, Mn and Al both have an effect of reducing iron loss and reducing magnetic flux density. However, the effects of Si and Al are larger than those of Si and Al because the effect is larger than that of Si and Al. In the case of Mn, it is necessary to control the proper amount of addition because the effect is smaller than that of Si and Al. Therefore, it is necessary to limit the above.

In one embodiment of the present invention, slab heating must occur in austenite single phase or austenite / ferrite ideal region in order to exhibit excellent magnetic properties without undergoing a hot-rolled sheet annealing process. For this purpose, Si and Al are ferrite stabilizing elements and Mn is an austenite stabilizing element, so that it is necessary to control the added amount properly. When the above-mentioned formula 1 is satisfied, excellent magnetism can be exhibited even without annealing the hot-rolled sheet.

The non-oriented electrical steel sheet according to an embodiment of the present invention has an average grain size of 30 to 100 탆. In the above-mentioned range, the fine line and magnetic flux density are very excellent. Specifically, the core loss (W15 / 50) may be 3.5 W / kg or less and the magnetic flux density (B50) may be 1.70 T or more.

A method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes: 0.005% or less (excluding 0%) of C; 0.5 to 4% of Si; 0.4 to 2.0% of Mn; (Excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), and Sn : 0.002 to 0.2%, the balance comprising Fe and unavoidable impurities, and heating the slab satisfying the following formula (1) and then hot rolling to produce a hot rolled steel sheet; Winding the hot rolled sheet; Cold rolling the rolled hot rolled sheet directly to produce a cold rolled sheet; And recrystallization annealing the cold-rolled sheet.

The slab heating temperature SRT, the hot rolling finishing temperature FDT and the coiling temperature CT satisfy the following formulas 2 and 3, and the recrystallization annealing temperature T _ann satisfies the following formula 4:

[Formula 1]

0.1? [Mn] / ([Si] + 10 x [Al])? 0.6

 [Formula 2]

([SRT] - [FDT]) ≤300

[Formula 3]

([FDT] - [CT])? 200

[Formula 4]

900 + 500 * ([P] + [Sn]) ≤ [T _ann ]

Si, Al, P and Sn represent contents of Mn, Si, Al, P and Sn, respectively, and [SRT] (CT) represents the coiling temperature (占 폚), and [T _ann ] represents the recrystallization annealing temperature (占 폚).

Generally, in order to improve the magnetic properties, the hot-rolled sheet is annealed after the hot-rolling. The annealing process of the hot-rolled sheet involves a great deal of cost. Therefore, if the annealed sheet is not used, the manufacturing cost can be greatly reduced. . As in the embodiment of the present invention, when the steel sheet is directly subjected to cold rolling without passing through the hot-rolled sheet annealing step, the hot-rolled sheet is directly cold-rolled and annealed, so that the material properties of the hot- In addition, since it is impossible to obtain crystal grains for cold rolling that can be ensured through hot-rolled sheet annealing, it is difficult to obtain the optimum crystal grain diameter in order to open the growth performance of the crystal grains during the final annealing of the cold-rolled sheet after cold rolling. Therefore, when the slabs in which the addition amounts of Si, Mn, Al, P and Sn are optimally controlled among the alloying elements added to steel are subjected to the hot rolling of the slab heating temperature (SRT), the hot rolling finishing temperature (FDT) ) Is appropriately controlled and the annealing temperature of the cold-rolled sheet after cold-rolling is optimized, whereby excellent magnetism can be obtained without annealing the hot-rolled sheet.

By controlling the slab heating temperature (SRT), the hot rolling finishing temperature (FDT), the coiling temperature (CT) and the annealing temperature (T _ann ) of the recrystallization to satisfy the formulas 2 to 4, the grain growth is excellent even without annealing the average grain diameter of 30 to 100㎛, yet it is possible to obtain the iron loss (W _15/50) is 3.5W / Kg or less, the magnetic flux density (B ₅₀₎ is an excellent non-oriented electrical steel with magnetic least 1.70T.

Hereinafter, each process will be described in detail.

First, the slab is heated and hot-rolled to produce a hot-rolled sheet. The reason why the addition ratio of each composition is limited is the same as the reason for limiting the composition of the non-oriented electrical steel sheet described above. The composition of the slab is substantially the same as that of the non-oriented electrical steel sheet because the composition of the slab is substantially unchanged in the processes of hot-rolled sheet winding, cold rolling and recrystallization annealing described below.

The slab is charged into a furnace and heated in austenite single phase or austenite / ferrite fault region. Specifically, the slab heating temperature (SRT) may be 1100 to 1300 ° C.

The heated slab is hot-rolled to 2 to 2.3 mm to produce a hot-rolled sheet. In this case, the hot rolling finishing temperature (FDT) in particular can be adjusted to satisfy the above-described equations (2) and (3).

Next, the hot rolled sheet is wound. The coiling temperature (CT) can be adjusted to satisfy the above-mentioned formula (3). In the step of winding the hot-rolled sheet, the volume fraction of the recrystallized grains in the hot-rolled sheet is 50% or more, so that excellent magnetism can be obtained without annealing the hot-rolled sheet.

Next, the wound hot-rolled sheet is immediately cold-rolled to produce a cold-rolled sheet. In this case, the meaning immediately means cold rolling without any intermediate process such as annealing of the rolled hot rolled sheet. As described above, by optimally controlling the alloying elements of the steel and optimally controlling the slab heating temperature (SRT), the hot rolling finishing temperature (FDT), the coiling temperature (CT) and the recrystallization annealing temperature ( _Tann ) It is possible to obtain a non-oriented electrical steel sheet excellent in magnetic properties.

The cold rolling can be finally rolled to a thickness of 0.10 mm to 0.70 mm.

The final cold-rolled cold-rolled sheet is subjected to final recrystallization annealing. The recrystallization annealing temperature (T _ann ) is adjusted so as to satisfy the above-mentioned formula (4).

The recrystallized annealed sheet is treated with insulation coating and shipped to the customer. The insulating coating can be treated with an organic, inorganic or organic composite coating, and other insulating coatings can be used. The customer can use this steel sheet as it is and can use it after stress relieving annealing if necessary.

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

Example  One

The slabs formed as shown in Table 1 were heated and hot-rolled to produce hot-rolled sheets having a thickness of 2.4 mm. The hot-rolled steel sheet taken up in the air and cooled was cold-rolled into a thickness of 0.50 mm without annealing the hot-rolled sheet, and recrystallization annealing was performed at the temperature listed in Table 2 for 80 seconds. For each specimen, by using an optical microscope, such as EBSD measuring recrystallized fraction and the iron loss (W _15/50), the magnetic flux density (B ₅₀₎ of the hot-rolled steel sheet are shown in Table 2. The results are.

_Iron loss (W _15/50 ) is the average loss (W / kg) in the rolling direction and in the rolling direction perpendicular to the magnetic flux density of 1.5 Tesla at 50 Hz frequency. The magnetic flux density (B ₅₀ ) is the magnitude of the magnetic flux density (Tesla) induced when a magnetic field of 5000 A / m is added.

Steel grade C Si Mn P S Al N Ti Sn A1 0.0008 0.7 0.4 0.02 0.004 0.05 0.0017 0.0019 0.07 A2 0.0018 1.9 0.6 0.07 0.002 0.04 0.0025 0.0039 0.05 A3 0.0036 2.4 0.8 0.11 0.002 0.02 0.0014 0.0038 0.08 A4 0.0014 0.6 0.8 0.02 0.002 0.06 0.0023 0.0023 0.11 A5 0.0032 1.3 0.3 0.03 0.004 0.04 0.004 0.0043 0.09 A6 0.0032 2.2 0.2 0.07 0.002 0.20 0.0025 0.0028 0.02 A7 0.0039 1.5 0.7 0.02 0.003 0.05 0.0011 0.0021 0.03 A8 0.0008 1.2 0.8 0.03 0.003 0.04 0.0037 0.0008 0.07 A9 0.0035 2.4 0.6 0.05 0.004 0.08 0.0026 0.003 0.04 A10 0.0044 2.5 0.9 0.12 0.002 0.01 0.0034 0.0018 0.09 A11 0.0035 1.8 0.6 0.06 0.001 0.07 0.0032 0.0038 0.03 A12 0.0024 2.1 0.4 0.09 0.001 0.07 0.0021 0.0015 0.03

Steel grade Mn / (Si + 10 * Al) SRT-FDT (占 폚) FDT-CT (占 폚) Hot-rolled plate
Recrystallization volume fraction (%) Cold rolled plate
Annealing temperature (캜) Iron loss W15 / 50 Magnetic flux density B50 Remarks A1 0.33 286 184 95 970 3.40 1.76 Honor A2 0.26 294 190 67 990 2.87 1.74 Honor A3 0.31 270 189 74 1010 2.59 1.73 Honor A4 0.67 284 196 77 980 6.95 1.71 Comparative Example A5 0.18 305 191 31 970 5.84 1.71 Comparative Example A6 0.05 346 224 14 950 4.79 1.69 Comparative Example A7 0.35 255 185 68 960 3.15 1.75 Honor A8 0.50 226 194 76 1020 3.24 1.75 Honor A9 0.19 234 176 65 950 2.64 1.73 Honor A10 0.35 265 177 72 1040 2.75 1.73 Honor A11 0.24 319 210 46 960 5.24 1.7 Comparative Example A12 0.14 292 245 22 990 4.67 1.69 Comparative Example

As shown in Table 2, the slab heating was controlled so as to be performed in the austenite single phase or the austenite / ferrite abnormal region in the hot rolling while satisfying [Si], [Mn], [Al] A2, A3, A7, and A6 having a volume fraction of the crystal grains recrystallized in the hot-rolled sheet of 50% or more by controlling the hot rolling finish temperature (FDT) and the coiling temperature (CT) A8, A9, A10 are the iron loss W _15/50 and magnetic flux density B ₅₀ is shown as excellent.

 On the other hand, A4 satisfies the control range of Si, Mn, and Al respectively, but the iron loss and magnetic flux density are inferior even though the hot rolling condition is properly controlled because the formula 1 is not satisfied.

A5 did not satisfy the control range of Mn, and slab heating temperature and hot rolling finishing rolling temperature did not satisfy Equation 2, and the volume fraction of hot rolled sheet recrystallization was less than 50%, and iron loss and magnetic flux density were inferior.

A6 did not satisfy the control range of Mn and Al and did not satisfy the formula 1. The slab heating temperature (SRT), the hot rolling finishing temperature (FDT), and the coiling temperature (CT) And the recrystallization fraction of the hot - rolled sheet was less than 50%. As a result, iron loss and magnetic flux density were inferior.

A11 indicates that the Si, Mn and Al satisfy the control range and the formula 1, respectively. However, when the slab heating temperature SRT, the hot rolling finishing temperature FDT and the coiling temperature CT satisfy the relations of Equation 2 and Equation 3 And the recrystallization fraction of hot - rolled sheet was less than 50%. As a result, iron loss and magnetic flux density were inferior.

In the case of A12, Si, Mn and Al satisfy the control range and the formula 1, respectively, and the slab heating temperature (SRT) and the hot rolling finishing temperature (FDT) The temperature (CT) did not satisfy the equation (3), and the fraction of recrystallized hot - rolled sheet was less than 50%. As a result, core loss and magnetic flux density were inferior.

Example  2

The slabs prepared as shown in Table 3 below were heated and hot-rolled to produce a hot-rolled sheet having a thickness of 2.3 mm. The hot-rolled steel sheet taken up in the air and cooled was cold-rolled to a thickness of 0.50 mm without annealing the hot-rolled sheet, and recrystallization annealing was performed at the temperature listed in Table 4 for 90 seconds. For each specimen, by using an optical microscope, such as EBSD measuring recrystallized fraction and the iron loss (W _15/50), the magnetic flux density (B ₅₀₎ of the hot-rolled steel sheet. The results are shown in Table 4 below.

Steel grade C Si Mn P S Al N Ti Sn B1 0.0028 0.9 0.7 0.09 0.004 0.04 0.0009 0.0017 0.02 B2 0.0021 1.2 0.5 0.04 0.004 0.01 0.0035 0.0024 0.07 B3 0.0039 1.7 0.8 0.03 0.002 0.09 0.0009 0.0012 0.08 B4 0.0012 1.1 0.5 0.08 0.003 0.04 0.0021 0.0043 0.04 B5 0.0019 1.8 0.7 0.02 0.004 0.02 0.0034 0.0034 0.04 B6 0.0017 1.5 0.5 0.02 0.001 0.04 0.0038 0.0007 0.03 B7 0.0033 2.4 0.9 0.08 0.004 0.04 0.0028 0.003 0.07 B8 0.0037 0.7 0.5 0.06 0.003 0.05 0.0016 0.0027 0.1 B9 0.0035 0.9 0.6 0.05 0.003 0.03 0.0035 0.002 0.06 B10 0.0026 2.1 0.6 0.1 0.003 0.07 0.0012 0.0017 0.09 B11 0.0024 2.3 0.7 0.04 0.002 0.02 0.0011 0.0028 0.05 B12 0.0022 1.9 0.8 0.03 0.001 0.03 0.0041 0.0007 0.07

Steel grade Mn /
(Si + 10 * Al) SRT-FDT (占 폚) FDT-CT (占 폚) Crystalline fraction of hot-rolled plate (%) Cold rolled plate
Annealing temperature
(° C) Grain size (μm) Iron loss W15 / 50 Magnetic flux density B50 Remarks B1 0.54 294 167 62 970 71 3.36 1.76 Honor B2 0.38 264 188 87 980 68 3.21 1.75 Honor B3 0.31 277 182 97 1000 80 2.88 1.74 Honor B4 0.33 282 175 95 950 27 4.76 1.7 Comparative Example B5 0.35 339 205 32 1020 47 4.26 1.69 Comparative Example B6 0.26 285 171 79 950 62 3.15 1.74 Honor B7 0.32 279 194 65 1010 77 2.71 1.73 Honor B8 0.42 278 219 43 920 26 6.24 1.71 Comparative Example B9 0.50 318 188 34 930 29 5.21 1.71 Comparative Example B10 0.21 290 190 73 1020 84 2.75 1.74 Honor B11 0.28 241 194 77 980 74 2.64 1.73 Honor B12 0.36 293 171 53 1060 113 4.35 1.68 Comparative Example

As shown in Table 4, by controlling the slab heating temperature (SRT), the hot rolling finishing temperature (FDT), and the coiling temperature (CT) to satisfy the formula 1 and satisfy the relational expression (2) A volume fraction of the crystal grains recrystallized in the plate is 50% or more, the annealing temperature (T _ann ) of the recrystallization after cold rolling is annealed to satisfy the formula (4), and the steel plates B1, B2 and B3 , B6, B7, B10, B11 is the iron loss W _15/50 and magnetic flux density B ₅₀ is shown as excellent.

B4 indicates that the Si, Mn and Al satisfy the control range and the formula 1 and that the slab heating temperature SRT, the hot rolling finishing temperature FDT and the coiling temperature CT satisfy the relational expressions 2 and 3 , It was satisfied that the fraction of the recrystallized grains in the hot-rolled sheet after hot rolling was 50 vol% or more. However, the annealing temperature T _ann of the recrystallization after cold rolling did not satisfy the formula 4 and the grain size of the grain did not satisfy 30 to 100 탆, As a result, iron loss and magnetic flux density were inferior.

B5 satisfies the following formula (2) and formula (3): Si, Mn and Al satisfy the control range and the formula 1, respectively, but the slab heating temperature (SRT), hot rolling finishing temperature (FDT) And the fraction of grains recrystallized in the hot - rolled sheet after hot rolling and the annealing temperature (T _ann ) after cold rolling did not satisfy Equation (4), so that iron loss and magnetic flux density were inferior.

B8 showed that Si, Mn and Al satisfied the control range and Equation 1, respectively. The slab heating temperature (SRT) and the hot rolling finishing temperature (FDT) satisfied the formula 2, but the hot rolling finishing temperature (FDT) ) Did not satisfy the formula 3, and the fraction of the recrystallized grains in the hot-rolled sheet, the annealing temperature (T _ann ) after the cold rolling did not satisfy the formula 4 and the final grain size of 30 to 100 탆, And magnetic flux densities were low.

B9 was satisfied with the control range and formula 1 for Si, Mn and Al, respectively, and the finishing temperature (FDT) and the coiling temperature (CT) were satisfactory in equation 3 in the hot rolling, but the slab heating temperature (SRT) and the hot rolling finishing temperature FDT) did not satisfy the formula 2, and the fraction of the recrystallized grains in the hot-rolled steel sheet, the annealing temperature T _ann after cold rolling did not satisfy the formula 4 and the final grain size of 30 to 100 탆, As a result, iron loss and magnetic flux density were inferior.

B12 is controlled so that Si, Mn and Al satisfy the control range and the formula 1 and the slab heating temperature (SRT), the hot rolling finishing temperature (FDT) and the coiling temperature (CT) The volume fraction of the recrystallized grains in the hot-rolled sheet after hot rolling was 50% or more. However, the annealing temperature (T _ann ) of the recrystallization after cold rolling did not satisfy the formula 4 and the grain size was 30 to 100 μm As a result, iron loss and magnetic flux density were inferior.

It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. It will be understood that the invention may be practiced. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (11)

0.005% or less (excluding 0%), Si: 0.5 to 4%, Mn: 0.4 to 2.0%, P: 0.01 to 0.2, S: 0.001 to 0.005%, Al: 0.09% or less (Excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%) and Sn: 0.002 to 0.2%, the balance being Fe and unavoidable impurities , And satisfies the following formula (1), and has an average grain size of 30 to 100 占 퐉.
[Formula 1]
0.1? [Mn] / ([Si] + 10 x [Al])? 0.6
(Where, [Mn], [Si] and [Al] in the formula 1 represent the contents of Mn, Si and Al, respectively) The method according to claim 1,
Further comprising 0.05% by weight or less (excluding 0% by weight) of Cu, Ni and Cr, respectively. The method according to claim 1,
Zr, Mo, and V in an amount of 0.01 wt% or less (excluding 0 wt%), respectively. The method according to claim 1,
Wherein the iron loss (W15 / 50) is 3.5 W / kg or less and the magnetic flux density (B50) is 1.70 T or more. 0.005% or less (excluding 0%), Si: 0.5 to 4%, Mn: 0.4 to 2.0%, P: 0.01 to 0.2, S: 0.001 to 0.005%, Al: 0.09% or less (Excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%) and Sn: 0.002 to 0.2%, the balance being Fe and unavoidable impurities Heating the slab satisfying the following formula (1) and hot-rolling the slab to produce a hot-rolled steel sheet;
Winding the hot-rolled sheet;
Cold rolling the rolled hot rolled sheet directly to produce a cold rolled sheet; And
Wherein the slab heating temperature (SRT), the hot rolling finishing temperature (FDT) and the coiling temperature (CT) satisfy the following formulas 2 and 3, and the recrystallization annealing temperature T _ann ) satisfies the following formula (4).
[Formula 1]
0.1? [Mn] / ([Si] + 10 x [Al])? 0.6
[Formula 2]
([SRT] - [FDT]) ≤300
[Formula 3]
([FDT] - [CT])? 200
[Formula 4]
900 + 500 * ([P] + [Sn]) ≤ [T _ann ]
Si, Al, P and Sn represent contents of Mn, Si, Al, P and Sn, respectively, and [SRT] (CT) represents the coiling temperature (占 폚), and [T _ann ] represents the recrystallization annealing temperature (占 폚). 6. The method of claim 5,
Wherein the volume fraction of the crystal grains recrystallized in the hot-rolled sheet is 50% or more in the step of winding the hot-rolled sheet. 6. The method of claim 5,
Wherein the slab heating temperature (SRT) is 1100 to 1300 占 폚. 6. The method of claim 5,
_{Wherein the} recrystallization annealing temperature (T _ann ) in the recrystallization annealing step is 920 to 1060 캜, and the annealing is performed for 1 to 5 minutes. 6. The method of claim 5,
Wherein the slab further comprises 0.05 wt% or less (excluding 0 wt%) of Cu, Ni and Cr, respectively. 6. The method of claim 5,
Wherein the slab further comprises Zr, Mo and V in an amount of 0.01 wt% or less (excluding 0 wt%), respectively. 6. The method of claim 5,
Wherein the produced electric steel sheet has an iron loss (W15 / 50) of 3.5 W / Kg or less and a magnetic flux density (B50) of 1.70 T or more.