Title of Invention: Non-oriented electrical steel sheet and its manufacturing method
technical field
[One]
It relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, it relates to a non-oriented electrical steel sheet in which annealing of the hot-rolled sheet is omitted and magnetism is improved at the same time, and a method for manufacturing the same.
background
[2]
Motors or generators are energy conversion devices that convert electrical energy into mechanical energy or mechanical energy into electrical energy. Accordingly, there is an increasing demand for the development of materials having superior properties even in non-oriented electrical steel sheets used as materials for iron cores such as motors, generators and small transformers.
[3]
In a motor or generator, energy efficiency is the ratio of input energy to output energy. In order to improve efficiency, it is important how much energy loss such as iron loss, copper loss, and mechanical loss that is eventually lost in the energy conversion process can be reduced. This is because the medium, iron loss and copper loss are greatly affected by the characteristics of the non-oriented electrical steel sheet. The typical magnetic properties of non-oriented electrical steel sheet are iron loss and magnetic flux density. The lower the iron loss of non-oriented electrical steel sheet, the lower the iron loss lost in the process of iron core magnetization, and the higher the magnetic flux density, the more the same energy. Since a larger magnetic field can be induced and a small current can be applied to obtain the same magnetic flux density, copper loss can be reduced and energy efficiency can be improved. Therefore, it can be said that it is essential to develop a non-oriented electrical steel sheet with low iron loss and excellent magnetism with high magnetic flux density in order to improve energy efficiency.
[4]
As an effective method for lowering the iron loss of non-oriented electrical steel sheet, there is a method of increasing the addition amount of Si, Al, and Mn, which are elements with high specific resistance. However, increasing the amount of Si, Al, and Mn added increases the specific resistance of the steel and reduces the eddy current loss among the iron loss of the non-oriented electrical steel sheet, thereby reducing iron loss. Conversely, since an increase in the amount of alloying element added lowers the magnetic flux density, it is not easy to secure excellent magnetic flux density while lowering iron loss even by optimizing the component system and manufacturing process. However, improving the texture is a method that can improve both iron loss and magnetic flux density at the same time without sacrificing either one. For this purpose, in non-oriented electrical steel sheets with excellent magnetic properties, a technique for improving the texture by performing an annealing process for a hot-rolled sheet after hot-rolling a slab for the purpose of improving the texture is widely used. However, this method also causes an increase in manufacturing cost due to the addition of a process called a hot-rolled sheet annealing process, and contains problems such as inferior cold rolling properties when grains are coarsened by hot-rolled sheet annealing. Therefore, if the non-oriented electrical steel sheet having excellent magnetism can be manufactured without performing the hot-rolled sheet annealing process, the manufacturing cost can be reduced and the problem of productivity caused by the hot-rolled sheet annealing process can be solved.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[5]
Provided are a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, to provide a non-oriented electrical steel sheet in which annealing of the hot-rolled sheet is omitted and magnetic properties are improved at the same time, and a method for manufacturing the same.
means of solving the problem
[6]
Non-oriented electrical steel sheet according to an embodiment of the present invention by weight%, C: 0.005% or less (excluding 0%), Si: 0.5 to 2.4%, Mn: 0.4 to 1.0%, S: 0.005% or less ( excluding 0%), Al: 0.01% or less (excluding 0%), N: 0.005% or less (excluding %), Ti: 0.005% or less (excluding 0%), Cu: 0.001 to 0.02 %, and the balance contains Fe and unavoidable impurities, satisfies the following formula 1, and the volume fraction of crystal grains in which the {111} plane of the steel sheet has an angle of 15° or less with the rolling plane is 27% or more.
[7]
[Equation 1]
[8]

[9]
(In Equation 1, [Mn], [Si] and [Al] represent the contents (wt%) of Mn, Si and Al, respectively.)
[10]
The volume fraction of the grains having an angle between the {111} plane and the rolling plane of the steel sheet of 15° or less may be 27% to 35%.
[11]
The thickened layer including Si oxide may exist in a depth range of 0.15 μm or less from the surface.
[12]
The thickening layer may include Si: 3 wt % or more, O: 5 wt % or more, and Al: 0.5 wt % or less.
[13]
The product (F count × F ) of the yield ratio (F count ) of sulfides with a diameter of 0.05 μm or more among sulfides with a diameter of 0.5 μm or less, including sulfides, and the area ratio of sulfides with a diameter of 0.05 μm or more among sulfides with a diameter of 0.5 μm or less (F area ) area ) may be greater than or equal to 0.15.
[14]
The number ratio (F count ) of sulfides having a diameter of 0.05 μm or more among sulfides including sulfides and having a diameter of 0.5 μm or less may be 0.2 or more.
[15]
Among sulfides having a diameter of 0.5 μm or less, an area ratio (F area ) of a sulfide having a diameter of 0.05 μm or more may be 0.5 or more.
[16]
0.9 ≤ (V cube +V goss +V r-cube )/Intensity max ≤ 2.5 may be satisfied.
[17]
(However, V cube , V goss , V r-cube are volume % of cube, goss, rotated cube texture, respectively, and Intensity max represents the maximum intensity value that appears on the ODF image (Φ2=45 degree section).)
[18]
YP/TS≥0.7 can be satisfied.
[19]
(However, YP indicates yield strength and TS indicates tensile strength.)
[20]
The area ratio of the fine grains that is 0.3 times or less of the average grain size may be 0.4% or less, and the area ratio of the coarse grains that is more than twice the average grain size may be 40% or less.
[21]
The average grain size may be 50 to 100 μm.
[22]
The method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention is, by weight, C: 0.005% or less (excluding 0%), Si: 0.5 to 2.4%, Mn: 0.4 to 1.0%, S: 0.005 % or less (excluding 0%), Al: 0.01% or less (excluding 0%), N: 0.005% or less (excluding %), Ti: 0.005% or less (excluding 0%), Cu: Heating a slab that contains 0.001 to 0.02%, and satisfies the following Equation 1; preparing a hot-rolled sheet by hot-rolling the slab; It includes the steps of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet without annealing the hot-rolled sheet and final annealing of the cold-rolled sheet.
[23]
[Equation 1]
[24]

[25]
(In Equation 1, [Mn], [Si] and [Al] represent the contents (wt%) of Mn, Si and Al, respectively.)
[26]
During final annealing, the Si and Al components and the hydrogen atmosphere (H 2 ) in the annealing furnace may satisfy 10×([Si]+1000×[Al])-[H 2 ]≤90.
[27]
(However, [Si] and [Al] represent the content (weight %) of Si and Al, respectively, and [H 2 ] represents the volume fraction (volume %) of hydrogen in the annealing furnace.)
[28]
In the step of heating the slab, the equilibrium precipitation amount of MnS (MnS SRT ) and the maximum precipitation amount of MnS (MnS Max ) may satisfy the following formula.
[29]
MnS SRT /MnS Max ≥ 0.6
[30]
In the step of heating the slab, when the equilibrium temperature at which austenite is 100% transformed into ferrite is A1 (℃), the slab heating temperature SRT (℃) and the A1 temperature (℃) may satisfy the following relationship.
[31]
SRT ≥ A1+150℃
[32]
In the step of heating the slab, it can be maintained for 1 hour or more in the austenite single phase region.
[33]
The step of hot rolling includes rough rolling and finishing rolling, and the finishing rolling start temperature (FET) may satisfy the following relationship.
[34]
Ae1 ≤ FET ≤ (2×Ae3+Ae1)/3
[35]
(However, Ae1 is the temperature at which austenite is completely transformed into ferrite (°C), Ae3 is the temperature at which austenite is transformed into ferrite (°C), and FET is the finishing rolling start temperature (°C).)
[36]
The step of hot rolling includes rough rolling and finishing rolling, and the rolling reduction of the finishing rolling may be 85% or more.
[37]
The step of hot rolling includes rough rolling and finishing rolling, and the reduction ratio at the front end of finishing rolling may be 70% or more.
[38]
The step of hot rolling includes rough rolling and finishing rolling, and the deviation of the finishing rolling termination temperature (FDT) in the entire length of the hot-rolled sheet may be 30° C. or less.
[39]
The step of hot rolling includes rough rolling, finishing rolling and winding step, and the temperature (CT) in the winding step may satisfy the following relationship.
[40]
0.55≤CT×[Si]/1000≤1.75
[41]
(However, CT represents the temperature (°C) in the winding step, and [Si] represents the content (weight%) of Si.)
[42]
The microstructure of the hot-rolled sheet may satisfy the following relationship.
[43]
GS center /GS surface ≥1.15
[44]
(However, in GS center , GScenter indicates the average grain size of 1/4 to 3/4t portion in the thickness direction, and GS surface indicates the average grain size of the surface to 1/4t portion in the thickness direction .)
[45]
The microstructure of the hot-rolled sheet may satisfy the following relationship.
[46]
GS center × recrystallization rate/10≥2
[47]
(GS center indicates the average grain size of the 1/4 to 3/4t portion in the thickness direction, and the recrystallization rate indicates the area fraction of the crystal grains recrystallized after hot rolling.)
Effects of the Invention
[48]
According to an embodiment of the present invention, even when the non-oriented electrical steel sheet is processed, the magnetism is not deteriorated, and the magnetism is excellent before and after processing.
[49]
Therefore, after machining, stress relief annealing (SRA) for magnetic improvement is not required.
Modes for carrying out the invention
[50]
Terms such as first, second and third are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.
[51]
The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” specifies a particular characteristic, region, integer, step, operation, element and/or component, and the presence or absence of another characteristic, region, integer, step, operation, element and/or component; It does not exclude additions.
[52]
When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part, or the other part may be involved in between. In contrast, when a part refers to being “directly above” another part, the other part is not interposed therebetween.
[53]
In addition, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.
[54]
In an embodiment of the present invention, the meaning of further including the additional element means that the remaining iron (Fe) is included by replacing the additional amount of the additional element.
[55]
Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, they are not interpreted in an ideal or very formal meaning.
[56]
Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.
[57]
Non-oriented electrical steel sheet according to an embodiment of the present invention by weight%, C: 0.005% or less (excluding 0%), Si: 0.5 to 2.4%, Mn: 0.4 to 1.0%, S: 0.005% or less ( excluding 0%), Al: 0.01% or less (excluding 0%), N: 0.005% or less (excluding %), Ti: 0.005% or less (excluding 0%), Cu: 0.001 to 0.02 %, and the balance includes Fe and unavoidable impurities.
[58]
Hereinafter, the reason for the limitation of the components of the non-oriented electrical steel sheet will be described.
[59]
C: 0.005% by weight or less
[60]
Carbon (C) combines with Ti, Nb, etc. to form carbide, thereby inferior to magnetism. When used after processing into electrical products in the final product, iron loss increases due to magnetic aging, thereby reducing the efficiency of electrical equipment. . More specifically, C may be included in an amount of 0.0001 to 0.0045 wt %.
[61]
Si: 0.5 to 2.4 wt%
[62]
Silicon (Si) is a major element added to increase the resistivity of steel to lower the eddy current loss during iron loss. When too little Si is added, a problem of deterioration of iron loss arises. Conversely, if Si is added too much, the austenite region is reduced, and thus the upper limit may be limited to 2.4 wt% in order to utilize the phase transformation phenomenon when the hot-rolled sheet annealing process is omitted. More specifically, Si may include 0.6 to 2.37 wt%.
[63]
Mn: 0.4 to 1.0 wt%
[64]
Manganese (Mn), along with Si and Al, is an element that increases specific resistance to lower iron loss and also improves texture. When the amount added is small, not only the effect of increasing the specific resistance is small, but, unlike Si and Al, an appropriate amount of the austenite stabilizing element is required to be added according to the amount of Si and Al added. If excessive, magnetic flux density may be greatly reduced. More specifically, Mn may include 0.4 to 0.95 wt%.
[65]
S: 0.005% by weight or less
[66]
Sulfur (S) is an element that forms sulfides such as MnS, CuS, and (Cu,Mn)S which are harmful to magnetic properties, so it can be added as low as possible. If too much sulfur is added, the magnetism may be inferior due to the increase of fine sulfides. More specifically, S may include 0.0001 to 0.0045 wt%.
[67]
Al: 0.01 wt% or less
[68]
Aluminum (Al) plays an important role in reducing iron loss by increasing specific resistance together with Si, but it is an element that stabilizes ferrite more than Si, and the magnetic flux density is greatly reduced as the amount added increases. In an embodiment of the present invention, since the annealing of the hot-rolled sheet is omitted by utilizing the phase transformation phenomenon, the content of Al is limited. More specifically, Al may be included in an amount of 0.0001 to 0.0095 wt %.
[69]
N: 0.005% by weight or less
[70]
Nitrogen (N) is an element harmful to magnetism, such as forming a nitride by strongly bonding with Al, Ti, Nb, etc. to suppress grain growth, so it may be included in a small amount. More specifically, N may be included in an amount of 0.0001 to 0.0045% by weight.
[71]
Ti: 0.005 wt% or less
[72]
Titanium (Ti) forms fine carbides and nitrides by combining with C and N to suppress grain growth, and the more titanium (Ti) is added, the poorer the texture due to the increased carbides and nitrides, and the magnetism deteriorates, so it can contain less. More specifically, it may include 0.0001 to 0.0045 wt% of Ti.
[73]
Cu: 0.001 to 0.02 wt%
[74]
Copper (Cu) is an element that forms (Mn,Cu)S sulfide together with Mn. When the amount added is large, copper (Cu) forms a fine sulfide to lower magnetism, so the amount of copper (Cu) may be limited to 0.001 to 0.02 wt%. More specifically, Cu may include 0.0015 to 0.019 wt%.
[75]
In addition to the above elements, P, Sn, and Sb, which are known as elements for improving texture, may be added to further improve magnetism. However, when the amount of addition is too large, there is a problem of suppressing grain growth and lowering productivity, so that the amount can be controlled to be added to 0.1 wt% or less, respectively.
[76]
Ni and Cr, which are elements that are inevitably added in the steelmaking process, react with impurity elements to form fine sulfides, carbides, and nitrides, which have a detrimental effect on magnetism.
[77]
In addition, since Zr, Mo, and V are strong carbonitride forming elements, it is preferable not to be added as much as possible, and each may be contained in an amount of 0.01 wt% or less.
[78]
The balance contains Fe and unavoidable impurities. The unavoidable impurities are impurities that are mixed in the steelmaking step and the manufacturing process of the grain-oriented electrical steel sheet, which are widely known in the art, and thus a detailed description thereof will be omitted. In one embodiment of the present invention, addition of elements other than the above-described alloy components is not excluded, and may be included in various ways within a range that does not impair the technical spirit of the present invention. When additional elements are included, they are included by replacing the remainder of Fe.
[79]
In an embodiment of the present invention, the non-oriented electrical steel sheet may satisfy Equation 1.
[80]
[Equation 1]
[81]

[82]
(In Equation 1, [Mn], [Si] and [Al] represent the contents (wt%) of Mn, Si and Al, respectively.)
[83]
In the case of Al, the effect of stabilizing ferrite is very large, so it should be added in a small amount, and Mn needs to be added at an appropriate level to coarsen the sulfide. When Equation 1 is satisfied, it has a sufficient austenite single-phase region at high temperature, and during hot rolling, it is possible to secure a recrystallized structure after hot rolling through phase transformation, and it is possible to form coarse sulfides through hot rolling recrystallization temperature control. In addition, when Equation 1 is satisfied, it is possible to suppress the oxide layer formation through the atmosphere control in the annealing furnace during the final annealing.
[84]
In an embodiment of the present invention, the volume fraction of grains having an angle between the {111} plane and the rolling plane of the steel sheet of 15° or less may be 27% or more. In one embodiment of the present invention, by omitting the annealing of the hot-rolled sheet, the volume fraction of the crystal grains having an angle between the {111} side of the steel sheet and the rolling side of 15° or less is increased. However, by controlling the alloy composition and process conditions to be described later, the magnetism can be improved. More specifically, the volume fraction of the crystal grains having an angle between the {111} surface and the rolling surface of the steel sheet of 15° or less may be 27 to 35%.
[85]
In an embodiment of the present invention, the concentrated layer including Si oxide may exist in a depth range of 0.15 μm or less from the surface. Since the concentrating layer including Si oxide is inferior to magnetism, it is necessary to control the formation thickness to be as thin as possible. In an embodiment of the present invention, the thickness of the thickening layer may be 0.15 μm or less. More specifically, the thickness of the thickening layer may be 0.01 to 0.13 μm.
[86]
The thickening layer may include Si: 3 wt % or more, O: 5 wt % or more, and Al: 0.5 wt % or less. The thickening layer is distinguished from the steel sheet substrate in that it contains 3 wt% or more of Si and 5 wt% or more of O. When Al is concentrated on the surface, it may cause the magnetism to be inferior, but as described above, since the content of Al is limited in one embodiment of the present invention, the magnetic is It can prevent being inferior. The control method of the thickening layer will be described in detail in the method for manufacturing a non-oriented electrical steel sheet to be described later.
[87]
In addition, in one embodiment of the present invention, by controlling the yield and area ratio of the sulfide having a specific diameter, it is possible to improve the magnetism. Specifically, the finer the sulfide, the lower the magnetism by inhibiting grain growth and interfering with the movement of the magnetic domain wall. Therefore, in one embodiment of the present invention, by coarsening a sulfide of a specific size to increase the number of 0.05 μm or more in diameter and increase the area ratio, the magnetism can be improved.
[88]
Specifically, the product (F count ) of the yield ratio (F count ) of sulfides with a diameter of 0.05 μm or more among sulfides with a diameter of 0.5 μm or less, including sulfides, and the area ratio (F area ) of sulfides with a diameter of 0.05 μm or more among sulfides with a diameter of 0.5 μm or less (F count) × F area ) may be 0.15 or more. More specifically, it may be 0.15 to 0.3.
[89]
The number ratio (F count ) of sulfides having a diameter of 0.05 μm or more among sulfides including sulfides and having a diameter of 0.5 μm or less may be 0.2 or more. More specifically, it may be 0.2 to 0.5.
[90]
Among sulfides having a diameter of 0.5 μm or less, an area ratio (F area ) of a sulfide having a diameter of 0.05 μm or more may be 0.5 or more. More specifically, it may be 0.5 to 0.8. The sulfide may comprise MnS, CuS or a complex of MnS and CuS.
[91]
A method of controlling the yield and area ratio of sulfide will be described in detail in the method of manufacturing a non-oriented electrical steel sheet to be described later.
[92]
In addition, in an embodiment of the present invention, by controlling the texture, it is possible to improve the magnetism.
[93]
0.9 ≤ (V cube +V goss +V r-cube )/Intensity max ≤ 2.5 may be satisfied.
[94]
(However, V cube , V goss , V r-cube are volume % of cube, goss, rotated cube texture, respectively, and Intensity max represents the maximum intensity value that appears on the ODF image (Φ2=45 degree section).)
[95]
V cube , V goss , and V r-cube are volume % of the texture within 15° from (100)[001], (110)[001], and (100)[011], respectively.
[96]
In an embodiment of the present invention, the cube, goss and rotated cube, which are advantageous in magnetic among the aggregates, are more developed to satisfy the above-described relational expression, and as a result, the magnetic is improved.
[97]
The method of controlling the texture will be described in detail in the manufacturing method of the non-oriented electrical steel sheet to be described later.
[98]
In addition, in general, when the hot-rolled sheet annealing process is omitted, the maximum intensity is greatly increased by strengthening the texture unfavorable to magnetism compared to when the hot-rolled sheet annealing process is performed.
[99]
On the other hand, in an embodiment of the present invention, the increase in intensity is not large, and the relational expression of Intensity(max, HB)/Intensity(max, HBA) ≤ 1.5 is satisfied.
[100]
(However, Intensity(max, HB) and Intensity(max, HBA) represent the maximum strength of texture when hot-rolled sheet annealing is not performed and when hot-rolled sheet annealing is performed, respectively.)
[101]
That is, even when hot-rolled sheet annealing is omitted, the magnetism is excellent.
[102]
In one embodiment of the present invention, since the hot-rolled sheet annealing is omitted, the YP/TS ratio is high. Specifically, YP/TS≥0.7 may be satisfied. However, YP stands for yield strength and TS stands for tensile strength. Machinability is improved due to high YP/TS, and magnetic inferiority caused by deformation during operation can be suppressed by manufacturing products using non-oriented electrical steel sheets such as motors.
[103]
In addition, in one embodiment of the present invention, by controlling the distribution of grain size, it is possible to improve the magnetism. The iron loss responds sensitively to the grain size, and when the grain size is too large or too small, the iron loss increases. Specifically, the area ratio of the fine grains that are 0.3 times or less of the average grain size may be 0.4% or less, and the area ratio of the coarse grains that is twice the average grain size or more may be 40% or less.
[104]
In addition, the average grain size may be 50 to 100㎛. In an embodiment of the present invention, the measurement standard of the grain size may be a plane parallel to the rolling plane (ND plane). The grain size means a diameter of a sphere assuming an imaginary sphere having the same area.
[105]
A method of controlling the distribution of grain size will be described in detail in a method for manufacturing a non-oriented electrical steel sheet to be described later.
[106]
The non-oriented electrical steel sheet according to an embodiment of the present invention has excellent iron loss and magnetic flux density due to the above-described alloy components and properties.
[107]
Specifically, the iron loss (W15/50) when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz may be 3.5 W/Kg or less. More specifically, it may be 2.5 to 3.5 W/Kg.
[108]
When a magnetic field of 5000 A/m is added, the induced magnetic flux density (B50) may be 1.7 Tesla or more. More specifically, it may be 1.7 to 1.8 Tesla. The thickness of the magnetic measurement reference may be 0.50 mm.
[109]
The non-oriented electrical steel sheet according to an embodiment of the present invention may satisfy the following relationship.
[110]
(W15/50 C -W15/50 L )/(W15/50 C +W15/50 L )×100 ≥ 7
[111]
W15/50 L and W15/50 C mean iron loss (W15/50) in the rolling direction and the rolling vertical direction, respectively.
[112]
B50 L -B50 C ≥ 0.006
[113]
B50 L , B50 C mean the magnetic flux density (B50) in the rolling direction and the rolling perpendicular direction.
[114]
By satisfying the above-described relationship, the magnetic flux density in the rolling direction may be further improved and the average magnetic flux density may be improved.
[115]
A method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention comprises the steps of heating a slab; preparing a hot-rolled sheet by hot-rolling the slab; It includes the steps of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet without annealing the hot-rolled sheet and final annealing of the cold-rolled sheet.
[116]
First, the slab is heated.
[117]
Since the alloy composition of the slab has been described in the alloy composition of the non-oriented electrical steel sheet, the overlapping description will be omitted. Since the alloy composition is not substantially changed in the manufacturing process of the non-oriented electrical steel sheet, the alloy composition of the non-oriented electrical steel sheet and the slab is substantially the same.
[118]
Specifically, the slab is in weight%, C: 0.005% or less (excluding 0%), Si: 0.5 to 2.4%, Mn: 0.4 to 1.0%, S: 0.005% or less (excluding 0%), Al: 0.01% or less (excluding 0%), N: 0.005% or less (excluding %), Ti: 0.005% or less (excluding 0%), Cu: 0.001 to 0.02%, and satisfy the following formula 1 can
[119]
[Equation 1]
[120]

[121]
(In Equation 1, [Mn], [Si] and [Al] represent the contents (wt%) of Mn, Si and Al, respectively.)
[122]
Since the other additional elements have been described in the alloy composition of the non-oriented electrical steel sheet, the overlapping description will be omitted.
[123]
In the step of heating the slab, when the equilibrium temperature at which austenite is 100% transformed into ferrite is A1 (℃), the slab heating temperature SRT (℃) and the A1 temperature (℃) may satisfy the following relationship.
[124]
SRT ≥ A1+150℃
[125]
When the slab heating temperature is high enough to satisfy the above-mentioned range, it is possible to sufficiently secure a recrystallized structure after hot rolling, and even if the hot-rolled sheet annealing is not performed, the magnetism can be improved.
[126]
A1 temperature (℃) is determined by the alloy composition of the slab. Since this is widely known in the technical field, a detailed description thereof will be omitted. For example, it can be calculated with commercial thermodynamic programs such as Thermo-Calc. and Factsage.
[127]
In the step of heating the slab, the equilibrium precipitation amount of MnS (MnS SRT ) and the maximum precipitation amount of MnS (MnS Max ) may satisfy the following formula.
[128]
MnS SRT /MnS Max ≥ 0.6
[129]
If the slab reheating temperature is too high, MnS is re-dissolved and finely precipitated in the hot rolling and annealing process. It is difficult to secure a recrystallization organization.
[130]
At this time, the equilibrium precipitation amount of MnS (MnS SRT ) is the amount of thermodynamic equilibrium precipitation of MnS at the slab heating temperature (SRT), and the maximum precipitation amount of MnS (MnS Max ) is the Mn, S alloy present in the silver slab. It means the theoretical maximum amount that can be thermodynamically precipitated from an element.
[131]
In the step of heating the slab, it can be maintained for 1 hour or more in the austenite single phase region. This is the time required for coarsening of the sulfide, and it is also necessary for coarsening the recrystallization structure after hot rolling by coarsening the grain size of austenite before hot rolling.
[132]
Next, a hot-rolled sheet is manufactured by hot-rolling the slab. The step of manufacturing a hot-rolled sheet by hot rolling may specifically include a rough rolling step, a finishing rolling step, and a winding step.
[133]
In an embodiment of the present invention, by appropriately controlling the reduction ratio and temperature of the rough rolling step, the finishing rolling step, and the winding step, the magnetism can be improved even if the hot-rolled sheet annealing is not performed.
[134]
First, the rough rolling step is a step of rough rolling the slab to manufacture a bar (Bar).
[135]
The finishing rolling step is a step of manufacturing a hot-rolled sheet by rolling a bar.
[136]
The winding step is a step of winding the hot-rolled sheet.
[137]
When the phase transformation is finished, the rolling in the finishing rolling remains as a deformed structure, thereby refining the microstructure of the non-oriented electrical steel sheet, and also making the texture inferior, thereby greatly reducing the magnetism. Conversely, when too much phase transformation occurs in finishing rolling, if the crystal grains of the hot-rolled recrystallization structure are refined, the improvement effect of the texture by the strain energy is reduced, and finally the magnetism is greatly inferior.
[138]
When the finishing rolling start temperature (FET) satisfies the following relationship, the cube, goss and rotated cube, which are advantageous textures for magnetism among the textures after the final annealing, are better developed, so that the magnetism can be improved.
[139]
Ae1 ≤ FET ≤ (2×Ae3+Ae1)/3
[140]
However, Ae1 is the temperature at which austenite is completely transformed into ferrite (°C), Ae3 is the temperature at which austenite is transformed into ferrite (°C), and FET is the finishing rolling start temperature (°C).
[141]
Specifically, by controlling the finishing rolling start temperature (FET), 0.9 ≤ (V cube +V goss +V r-cube )/Intensity max ≤ 2.5 may be satisfied.
[142]
Ae1 temperature (℃) and Ae3 temperature (℃) are determined by the alloy composition of the slab. Since this is widely known in the technical field, a detailed description thereof will be omitted.
[143]
In addition, the reduction ratio in the finishing rolling can also contribute to the development of the texture described above. Specifically, the rolling reduction of the finishing rolling may be 85% or more. When the finishing rolling consists of a plurality of passes, the rolling reduction of the finishing rolling may be the cumulative reduction ratio of the plurality of passes. More specifically, the rolling reduction of the finishing rolling may be 85 to 90%.
[144]
The reduction ratio at the final rolling shear may be 70% or more. The front end of finishing rolling means up to (the total number of passes)/2 when finishing rolling is performed with two or more even passes. When finishing rolling is performed with two or more odd passes, it means up to (total number of passes+1)/2. More specifically, the reduction ratio at the front end of the finishing rolling may be 70 to 87%.
[145]
The deviation of the finishing rolling termination temperature (FDT) in the entire length of the hot-rolled sheet may be 30° C. or less. That is, the difference between the maximum temperature of the finishing rolling end temperature and the finishing rolling end temperature minimum temperature may be 30° C. or less. As such, by controlling the deviation of the finishing rolling end temperature (FDT) to be small, it is possible to control the area fractions of the fine grains and the coarse grains after the final annealing. Ultimately, it has excellent magnetic properties even without hot-rolled sheet annealing. More specifically, the deviation of the finishing rolling termination temperature (FDT) in the entire length of the hot-rolled sheet may be 15 to 30 ℃.
[146]
In addition, by appropriately controlling the temperature of the winding step, it is possible to contribute to the control of the area fraction of the fine grains and the coarse grains after the final annealing. Specifically, the temperature (CT) in the winding step may satisfy the following relationship.
[147]
0.55≤CT×[Si]/1000≤1.75
[148]
However, CT indicates the temperature (°C) in the winding step, and [Si] indicates the content (weight %) of Si.
[149]
The microstructure of the hot-rolled sheet is improved by the above-described finishing rolling end temperature and winding temperature control. In one embodiment of the present invention, since the hot-rolled sheet annealing process is not performed, the microstructure of the hot-rolled sheet greatly affects the microstructure of the non-oriented electrical steel sheet to be finally manufactured.
[150]
Specifically, the microstructure of the hot-rolled sheet may satisfy the following relationship.
[151]
GS center /GS surface ≥1.15
[152]
However, in GS center , GScenter indicates the average grain size of 1/4 to 3/4t portion in the thickness direction, and GS surface indicates the average grain size of the surface to 1/4t portion in the thickness direction .
[153]
As described above, by increasing the grain size at the center of the hot-rolled sheet, it is possible to contribute to the control of the area fractions of fine grains and coarse grains after final annealing.
[154]
The 1/4 to 3/4t portion means a thickness portion that is 1/4 to 3/4t with respect to the total thickness (t) of the hot-rolled sheet.
[155]
In addition, the microstructure of the hot-rolled sheet may satisfy the following relationship.
[156]
(GS center × recrystallization rate)/10≥2
[157]
However, GS center indicates the average grain size of the 1/4 to 3/4t portion in the thickness direction, and the recrystallization rate indicates the area fraction of the crystal grains recrystallized after hot rolling.
[158]
In an embodiment of the present invention, the component system is designed so that phase transformation occurs, and recrystallization occurs through phase transformation by controlling the hot rolling temperature condition, so that the recrystallization structure can be secured after hot rolling. At this time, the higher the recrystallization rate, the better the magnetic properties of the non-oriented electrical steel sheet finally manufactured. In one embodiment of the present invention, since the hot-rolled sheet annealing process is not performed, the recrystallization rate in hot rolling is important.
[159]
Recrystallized grains and non-recrystallized grains can be distinguished by the presence/absence of a deformed tissue, and by observing the microstructure through an optical microscope, the presence/absence of a deformed tissue can be distinguished.
[160]
Next, a cold-rolled sheet is manufactured by cold-rolling the hot-rolled sheet without annealing the hot-rolled sheet. As described above, in an embodiment of the present invention, a non-oriented electrical steel sheet having excellent magnetic properties can be manufactured even without hot-rolled sheet annealing through alloy composition and various process control.
[161]
Cold rolling is final rolling to a thickness of 0.10mm to 0.70mm. If necessary, secondary cold rolling may be performed after primary cold rolling and intermediate annealing, and the final rolling reduction may be in the range of 50 to 95%.
[162]
Next, the cold-rolled sheet is final annealed. In the process of annealing the cold-rolled sheet, the annealing temperature is not particularly limited as long as it is a temperature that is usually applied to the non-oriented electrical steel sheet. Since the iron loss of the non-oriented electrical steel sheet is closely related to the grain size, it is suitable if it is 900 to 1100°C. If the temperature is too low, the crystal grains are too fine and the hysteresis loss increases.
[163]
In an embodiment of the present invention, during final annealing, Si and Al components and the hydrogen atmosphere (H 2 ) in the annealing furnace may satisfy 10×([Si]+1000×[Al])-[H 2 ]≤90. . By annealing in the hydrogen atmosphere described above, the concentrated layer containing Si oxide is generated to an appropriate depth, and it is possible to prevent Al from being contained in the concentrated layer. Such a thickening layer may contribute to magnetic enhancement.
[164]
After final annealing, an insulating film may be formed. The insulating film may be treated with an organic, inorganic, and organic/inorganic composite film, and may be treated with other insulating film materials.
[165]
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.
[166]
Example 1
[167]
A slab containing the alloy components and the remainder Fe and unavoidable impurities summarized in Table 1 was prepared. The slab was heated at 1150° C., hot rolled to a thickness of 2.5 mm, and then wound up. The wound hot-rolled steel sheet was pickled without hot-rolled sheet annealing, and then cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealing was performed. At this time, the atmosphere during annealing of the cold-rolled sheet was controlled to satisfy the relational expression of 10×([Si]+1000×[Al])-[H 2 ]≤90, and the annealing temperature was carried out between 900 and 950° C.
[168]
After final annealing, the distribution of inclusions was measured for each specimen, and the iron loss (W 15/50 ) and magnetic flux density (B 50 ) were also measured, and the results are shown in Table 2 below.
[169]
The iron loss (W 15/50 ) is the average loss (W/kg) in the rolling direction and perpendicular to the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz.
[170]
The magnetic flux density (B 50 ) is the magnitude (Tesla) of the magnetic flux density induced when a magnetic field of 5000 A/m is added.
[171]
As a measurement method of MnS SRT / MnS Max, the fraction that can be reached under the condition of maintaining the MnS SRT for 1 hour or more at the reheating temperature (SRT) was calculated using a commercial thermodynamic program.
[172]
[Table 1]
[173]
[Table 2]
[174]
As shown in Tables 1 and 2, A1, A2, A3, A6, A7, A10, A12 satisfying all alloy components and manufacturing processes proposed in an embodiment of the present invention are (Mn, Cu)S sulfide It can be confirmed that it precipitates appropriately and is excellent in magnetism.
[175]
On the other hand, A4 does not satisfy the value of Equation 1, so it can be confirmed that the magnetism is inferior.
[176]
A5 did not satisfy the Mn content and the value of Equation 1, and did not satisfy MnS SRT /MnS Max ≥ 0.6 or more when heating the slab . As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[177]
A8 did not satisfy the amount of Al added, and as a result, it can be confirmed that the magnetism is inferior.
[178]
A9 did not satisfy the value of Equation 1, and did not satisfy MnS SRT /MnS Max ≥ 0.6 or more when heating the slab . As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[179]
A11 did not satisfy Mn content and Equation 1. As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[180]
A13 did not satisfy Al content and Equation 1. As a result, it can be confirmed that the magnetism is inferior.
[181]
Example 2
[182]
A slab containing the alloy components and the remainder Fe and unavoidable impurities summarized in Table 3 was prepared. The slab was heated at 1100 to 1250° C., hot rolled to a thickness of 2.7 mm, and then wound up. When heating the slab, the holding time of the austenite single phase was changed as shown in Table 4 below, and the effect of the holding time was also reported. The wound hot-rolled steel sheet was pickled without hot-rolled sheet annealing, then cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealing was performed. At this time, 10×([Si]+1000×[Al])-[H 2 ] ? 90 was annealed in an atmosphere that satisfies the relation, and the temperature was carried out between 900 and 950°C.
[183]
After final annealing, the number and distribution of inclusions were measured for each specimen, and the iron loss (W15/50) and magnetic flux density (B50) were also measured, and the results are shown in Table 5 below.
[184]
[Table 3]
[185]
[Table 4]
[186]
[Table 5]
[187]
As shown in Tables 3 to 5, B1, B3, B4, B7, B8, B12, B13 satisfying all of the alloy components and manufacturing processes proposed in an embodiment of the present invention are (Mn, Cu)S sulfide It can be confirmed that it precipitates appropriately and is excellent in magnetism.
[188]
On the other hand, B2 did not satisfy MnS SRT /MnS Max ≥ 0.6 during slab heating . As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[189]
B5 did not satisfy Equation 1 and MnS SRT /MnS Max ≥ 0.6. As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[190]
B6 did not satisfy MnS SRT /MnS Max ≥ 0.6 and austenite single phase retention time during slab heating . As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[191]
B9 did not satisfy the austenite single phase retention time during slab heating. As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[192]
B10 had a low slab heating temperature. As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[193]
B11 had a low slab heating temperature and did not satisfy the austenite single phase retention time. As a result, it can be confirmed that the sulfide is not properly precipitated and the magnetism is poor.
[194]
B14 showed inferior magnetism as it was heat-treated in austenite (γ)/ferrite (α) abnormal region, not in austenite single phase (γ) region when heating the slab.
[195]
Example 3
[196]
In weight %, C: 0.0023%, Si: 2%, Mn: 0.7%, P: 0.02%, S: 0.0017%, Al: 0.009%, N: 0.002%, Ti: 0.001%, Sn: 0.01%, Cu : A slab containing 0.01% and the remainder Fe and other impurities was prepared. The slab was heated at 1180° C., hot rolled to a thickness of 2.6 mm, and then wound up. After pickling and cold rolling, the wound hot-rolled steel sheet was pickled without hot-rolled sheet annealing, then cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealing was performed. The cold-rolled sheet annealing temperature was carried out between 900 and 950 ° C. At this time, by changing the hydrogen atmosphere in the annealing furnace, the relational expression of 10×([Si]+1000×[Al])-[H 2 ]≤90 formed the surface oxide layer and The purpose of this study was to report the effect on magnetism.
[197]
The thickness of the Al oxide layer indicates the thickness of a region containing Al and O as main components from the surface, and the thickness of the Si enriched layer indicates the thickness of a region containing 3 wt% or more of Si from the surface.
[198]
[Table 6]
[199]
As shown in Table 6, it can be confirmed that, in the invention example in which the hydrogen atmosphere of the final annealing was appropriately controlled, Al was not concentrated on the surface, and the Si enriched layer was formed to an appropriate thickness and had excellent magnetism. On the other hand, in the comparative example in which the hydrogen atmosphere of the final annealing was not properly controlled, Al rather than Si was concentrated on the surface, and it could be confirmed that the magnetism was deteriorated.
[200]
Example 4
[201]
In weight %, C: 0.0023%, Si: 2%, Mn: 0.7%, P: 0.02%, S: 0.0017%, N: 0.002%, Ti: 0.001%, Sn: 0.01%, Cu: 0.01% and the following A slab containing the Al content of Table 5 and the remainder Fe and other impurities was prepared. The slab was reheated at 1180° C. and then hot-rolled to a thickness of 2.6 mm and then wound up. After pickling and cold rolling, the wound hot-rolled steel sheet was pickled without hot-rolled sheet annealing, then cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealing was performed. The cold-rolled sheet annealing temperature was carried out between 900 and 950 ° C. At this time, by changing the hydrogen atmosphere in the annealing furnace, 10×([Si]+1000×[Al])-[H 2 ]≤90 according to the change in the amount of Al added . The purpose of this study was to investigate the effect of the relational expression on surface oxide layer formation and magnetism.
[202]
For each specimen, the oxide layer and its thickness were measured using SEM and TEM, and the iron loss (W15/50) and magnetic flux density (B50) were also measured, and the results are shown in Table 7 below.
[203]
[Table 7]
[204]
As shown in Table 7, in the invention example that satisfies both the alloy component and the final annealing atmosphere proposed in one embodiment of the present invention, Al is not concentrated on the surface, and the Si concentration layer is formed to an appropriate thickness and has excellent magnetic properties. that can be checked
[205]
On the other hand, in the comparative example in which the alloy composition is not satisfied or the final annealing atmosphere is not controlled, it can be confirmed that Al rather than Si is concentrated on the surface or the thickness of the Si enriched layer is thickened, thereby deteriorating the magnetism.
[206]
Example 5
[207]
A slab containing the alloy components and the remainder Fe and unavoidable impurities summarized in Table 8 was prepared. The slab was heated at 1150° C. and wound up after hot rolling to a thickness of 2.6 mm. The effect of the FET was changed by changing the FET at the input side of the finishing rolling as shown in Table 9, and hot rolling was performed with a rolling reduction of 87% and a shear reduction during finishing rolling of 73%. After hot rolling, the wound hot-rolled steel sheet was pickled without hot-rolled sheet annealing, then cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealing was performed. At this time, the cold-rolled sheet annealing temperature was carried out between 900 to 950 ℃.
[208]
In order to obtain Intensity(max, HBA), Intensity(max, HBA) was measured by adding a hot-rolled sheet annealing process during the same alloy composition and process.
[209]
After final annealing, the texture was measured using EBSD, and the iron loss (W15/50) and magnetic flux density (B50) were also measured, and the results are shown in Table 10 below.
[210]
[Table 8]
[211]
[Table 9]
[212]
[Table 10]
[213]
As shown in Tables 8 to 10, C2, C4, C5, C8, C9, C11, C13 that satisfies all of the alloy components and finish rolling start temperature proposed in an embodiment of the present invention have a texture after final annealing. It can be seen that properly formed, Intensity (max, HB) / Intensity (max, HBA) is also formed small.
[214]
On the other hand, C1 did not satisfy Equation 1 and did not properly control the finishing rolling start temperature. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[215]
C3 did not satisfy Mn content and Equation 1. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[216]
C6 did not properly control the S content and the finishing rolling start temperature. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[217]
C7 did not satisfy the Al content. Therefore, Intensity(max, HB)/Intensity(max, HBA) showed a large value. As a result, the magnetism deteriorated.
[218]
C10 did not satisfy Equation 1, and did not properly control the finish rolling start temperature. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[219]
C12 did not satisfy the Mn content and Equation 1, and did not properly control the finishing rolling start temperature. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[220]
C14 did not properly control the finishing rolling start temperature. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[221]
Example 6
[222]
A slab containing the alloy components and the remainder Fe and unavoidable impurities summarized in Table 11 was prepared. The slab was heated at 1100 to 1250° C., hot rolled to a thickness of 2.7 mm, and then wound up. The finishing rolling start temperature FET for each steel type was changed as shown in Table 12 below, and the rolling reduction of finishing rolling and shear rolling reduction during finishing rolling were also changed as shown in Table 12 below, and hot rolling was performed. After hot rolling, the wound hot-rolled steel sheet was pickled without hot-rolled sheet annealing, then cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealing was performed. At this time, the cold-rolled sheet annealing temperature was carried out between 900 to 950 ℃.
[223]
In order to obtain Intensity(max, HBA), Intensity(max, HBA) was measured by adding a hot-rolled sheet annealing process during the same alloy composition and process.
[224]
After final annealing, the texture was measured using EBSD, and the iron loss (W15/50) and magnetic flux density (B50) were also measured, and the results are shown in Table 13 below.
[225]
[Table 11]
[226]
[Table 12]
[227]
[Table 13]
[228]
As shown in Tables 11 to 13, D1, D2, D5, D7, D9, D11, D13 that satisfies all alloy components and finishing rolling reduction, shear reduction, and starting temperature proposed in an embodiment of the present invention. After final annealing, it can be seen that the texture is properly formed, and the Intensity(max, HB)/Intensity(max, HBA) is also small.
[229]
On the other hand, D3 did not satisfy the finishing rolling reduction ratio, the shear reduction ratio and the starting temperature. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[230]
D4 did not satisfy the shear reduction ratio. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[231]
D6 did not satisfy the finishing rolling reduction ratio and the starting temperature. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[232]
D8 did not satisfy Equation 1, finishing rolling reduction ratio and starting temperature. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[233]
D10 did not satisfy the finishing rolling reduction ratio and the shear reduction ratio. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[234]
D12 did not satisfy the finishing rolling start temperature and the finishing rolling shear reduction ratio. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[235]
D14 did not satisfy the finishing rolling start temperature and the finishing rolling reduction ratio. Therefore, the texture was not properly formed, and Intensity(max, HB)/Intensity(max, HBA) also showed a large value. As a result, the magnetism deteriorated.
[236]
Example 7
[237]
A slab containing the alloy components and the remainder Fe and unavoidable impurities summarized in Table 14 was prepared. The slab was heated at 1200° C., hot rolled to a thickness of 2.7 mm, and then wound up. The deviation of the finishing rolling end temperature and the winding temperature were adjusted as shown in Table 15 below. After hot rolling, the wound hot-rolled steel sheet was pickled without hot-rolled sheet annealing, then cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealing was performed. At this time, the cold-rolled sheet annealing temperature was carried out between 900 to 950 ℃.
[238]
After final annealing for each specimen, the microstructure was analyzed to measure the average grain size and area distribution according to grain size. The iron loss (W15/50) and magnetic flux density (B50) were also measured, and the results are shown in Table 16 below. .
[239]
[Table 14]
[240]
[Table 15]
[241]
[Table 16]
[242]
As shown in Tables 14 to 16, E1, E2, E4, E6, E9, E12, E13 that satisfies all alloy components, finish rolling end temperature deviation, and coiling temperature proposed in an embodiment of the present invention are final annealing After that, it can be confirmed that the grain size and distribution are properly formed.
[243]
On the other hand, E3 did not satisfy the Mn content and Equation 1, and did not satisfy the finish rolling termination temperature deviation. Therefore, the grain size and distribution were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[244]
E5 did not satisfy Equation 1 and the coiling temperature. Therefore, the grain size and distribution were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[245]
E7 did not satisfy the Al content. Therefore, the grain size and distribution were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[246]
E8 did not satisfy Equation 1 and the finish rolling end temperature deviation. Therefore, the grain size and distribution were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[247]
E10 did not satisfy Mn content, Equation 1, and did not satisfy the temperature deviation at the end of finishing rolling. Therefore, the grain size and distribution were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[248]
E11 did not satisfy the S content. Therefore, the grain size and distribution were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[249]
E14 did not satisfy the temperature deviation at the end of finishing rolling. Therefore, the grain size and distribution were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[250]
Example 8
[251]
A slab containing the alloy components and the remainder Fe and unavoidable impurities summarized in Table 17 was prepared. The slab was heated at 1100 to 1200° C., hot rolled to a thickness of 2.8 mm, and then wound up. The deviation of the finishing rolling end temperature and the winding temperature were adjusted as shown in Table 18 below. After hot rolling, the wound hot-rolled steel sheet was pickled without hot-rolled sheet annealing, then cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealing was performed. At this time, the cold-rolled sheet annealing temperature was carried out between 900 to 950 ℃.
[252]
For each specimen, after hot rolling, the microstructure was analyzed to measure the grain sizes of the center and surface regions, and the recrystallized fractions were also measured and summarized in Table 18 below. In addition, the microstructure after final annealing was analyzed to measure the average grain size and area distribution according to the grain size, and the iron loss (W15/50) and magnetic flux density (B50) were also measured, and the results are shown in Table 19 below.
[253]
[Table 17]
[254]
[Table 18]
[255]
[Table 19]
[256]
As shown in Tables 17 to 19, F2, F3, F6, F7, F8, F11, F12 that satisfies all alloy components, finishing rolling end temperature deviation, and coiling temperature proposed in an embodiment of the present invention are hot-rolled sheets It can be confirmed that the microstructure is properly formed, and the grain size and distribution are properly formed after final annealing.
[257]
On the other hand, F1 did not satisfy the temperature deviation at the end of finishing rolling. Therefore, the microstructure and grain size and distribution of the hot-rolled sheet were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[258]
F4 did not satisfy the temperature deviation at the end of finishing rolling. Therefore, the microstructure and grain size and distribution of the hot-rolled sheet were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[259]
F5 did not satisfy the coiling temperature. Therefore, the microstructure and grain size and distribution of the hot-rolled sheet were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[260]
F9 did not satisfy Equation 1, finish rolling end temperature deviation and coiling temperature. Therefore, the microstructure and grain size and distribution of the hot-rolled sheet were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[261]
F10 did not satisfy the temperature deviation at the end of finishing rolling. Therefore, the microstructure and grain size and distribution of the hot-rolled sheet were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[262]
F13 did not satisfy the finishing rolling end temperature deviation and coiling temperature. Therefore, the microstructure and grain size and distribution of the hot-rolled sheet were not properly formed. As a result, it can be confirmed that the magnetism is inferior.
[263]
The present invention is not limited to the embodiments, but can be manufactured in various different forms, and those of ordinary skill in the art to which the present invention pertains can use other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that this may be practiced. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.
Claims
[Claim 1]
By weight%, C: 0.005% or less (excluding 0%), Si: 0.5 to 2.4%, Mn: 0.4 to 1.0%, S: 0.005% or less (excluding 0%), Al: 0.01% or less ( 0%), N: 0.005% or less (excluding %), Ti: 0.005% or less (excluding 0%), Cu: 0.001 to 0.02%, and the balance contains Fe and unavoidable impurities, , A non-oriented electrical steel sheet that satisfies the following Equation 1, and the volume fraction of grains having an angle between the {111} surface and the rolling surface of the steel sheet of 15° or less is 27% or more. [Equation 1] (In Equation 1, [Mn], [Si] and [Al] represent the contents (% by weight) of Mn, Si and Al, respectively.)
[Claim 2]
The non-oriented electrical steel sheet according to claim 1, wherein the volume fraction of grains having an angle between the {111} surface and the rolling surface of the steel sheet of 15° or less is 27% to 35%.
[Claim 3]
The non-oriented electrical steel sheet according to claim 1, wherein the thickened layer containing Si oxide is present in a depth range of 0.15 μm or less from the surface.
[Claim 4]
The non-oriented electrical steel sheet according to claim 3, wherein the thickening layer includes Si: 3% or more, O: 5% or more, and Al: 0.5% or less.
[Claim 5]
According to claim 1, containing sulfides, the number ratio (F count ) of sulfides with a diameter of 0.05 μm or more among sulfides with a diameter of 0.5 μm or less and the area ratio of sulfides with a diameter of 0.05 μm or more among sulfides with a diameter of 0.5 μm or less (F area ) Non-oriented electrical steel sheet whose product (F count × F area ) is 0.15 or more.
[Claim 6]
The non-oriented electrical steel sheet according to claim 1, wherein the non-oriented electrical steel sheet contains sulfides, and the number ratio (F count ) of sulfides having a diameter of 0.05 μm or more among sulfides having a diameter of 0.5 μm or less is 0.2 or more.
[Claim 7]
The non-oriented electrical steel sheet according to claim 1, wherein the area ratio (F area ) of sulfides having a diameter of 0.05 μm or more among sulfides having a diameter of 0.5 μm or less is 0.5 or more.
[Claim 8]
The non-oriented electrical steel sheet according to claim 1, wherein 0.9 ≤ (V cube +V goss +V r-cube )/Intensity max ≤ 2.5. (However, V cube , V goss , V r-cube are volume % of cube, goss, rotated cube texture, respectively, and Intensity max represents the maximum intensity value that appears on the ODF image (Φ2=45 degree section).)
[Claim 9]
The non-oriented electrical steel sheet according to claim 1, wherein YP/TS≥0.7 is satisfied. (However, YP indicates yield strength and TS indicates tensile strength.)
[Claim 10]
The non-oriented electrical steel sheet according to claim 1, wherein the area ratio of fine grains that are 0.3 times or less of the average grain size is 0.4% or less, and the area ratio of coarse grains that is twice or more of the average grain size is 40% or less.
[Claim 11]
The non-oriented electrical steel sheet according to claim 1, wherein the average grain size is 50 to 100 μm.
[Claim 12]
By weight%, C: 0.005% or less (excluding 0%), Si: 0.5 to 2.4%, Mn: 0.4 to 1.0%, S: 0.005% or less (excluding 0%), Al: 0.01% or less ( Excluding 0%), N: 0.005% or less (excluding %), Ti: 0.005% or less (excluding 0%), Cu: 0.001 to 0.02% containing, and heating the slab satisfying the following formula 1 to do; preparing a hot-rolled sheet by hot-rolling the slab; Crystal grains having an angle between the {111} surface of the manufactured steel sheet and the rolling surface of 15° or less, comprising the steps of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet without annealing the hot-rolled sheet and final annealing of the cold-rolled sheet; A method of manufacturing a non-oriented electrical steel sheet having a volume fraction of 27% or more. [Equation 1] (In Equation 1, [Mn], [Si] and [Al] represent the contents (% by weight) of Mn, Si and Al, respectively.)
[Claim 13]
The non-oriented according to claim 12, wherein, during final annealing, Si and Al components and a hydrogen atmosphere (H 2 ) in the annealing furnace satisfy 10×([Si]+1000×[Al])-[H 2 ]≤90. A method for manufacturing an electrical steel sheet. (However, [Si] and [Al] represent the content (weight %) of Si and Al, respectively, and [H 2 ] represents the volume fraction (volume %) of hydrogen in the annealing furnace.)
[Claim 14]
The method of claim 12, wherein the equilibrium precipitation amount of MnS (MnS SRT ) and the maximum precipitation amount of MnS (MnS Max ) in the step of heating the slab satisfy the following formulas. MnS SRT /MnS Max ≥ 0.6
[Claim 15]
13. The method of claim 12, wherein in the step of heating the slab, when the equilibrium temperature at which austenite is 100% transformed into ferrite is A1 (℃), the slab heating temperature SRT (℃) and the A1 temperature (℃) have the following relationship A satisfactory manufacturing method of non-oriented electrical steel sheet. SRT ≥ A1+150℃
[Claim 16]
The method of claim 12, wherein in the step of heating the slab, the non-oriented electrical steel sheet is maintained for 1 hour or more in the austenite single-phase region.
[Claim 17]
The method of claim 12 , wherein the hot rolling includes rough rolling and finishing rolling, and a finishing rolling start temperature (FET) satisfies the following relationship. Ae1 ≤ FET ≤ (2×Ae3+Ae1)/3 (however, Ae1 is the temperature at which austenite is completely transformed into ferrite (°C), Ae3 is the temperature at which austenite begins to transform into ferrite (°C), and FET is The rolling start temperature (°C) is indicated.)
[Claim 18]
The method of claim 12, wherein the hot rolling includes rough rolling and finishing rolling, and the rolling reduction of the finishing rolling is 85% or more.
[Claim 19]
The method of claim 12, wherein the hot rolling includes rough rolling and finishing rolling, and the reduction ratio at the front end of the finishing rolling is 70% or more.
[Claim 20]
The method of claim 12, wherein the hot rolling includes rough rolling and finishing rolling, and the deviation of the finishing rolling termination temperature (FDT) in the entire length of the hot-rolled sheet is 30° C. or less.
[Claim 21]
The method of claim 12 , wherein the hot rolling includes rough rolling, finishing rolling and winding, and the temperature (CT) in the winding step satisfies the following relationship. 0.55≤CT×[Si]/1000≤1.75 (However, CT represents the temperature (°C) in the winding step, and [Si] represents the content of Si (wt%).)
[Claim 22]
The method of claim 12, wherein the microstructure of the hot-rolled sheet satisfies the following relationship. GS center /GS surface ≥1.15 (However, GS center indicates the average grain size of 1/4 to 3/4t in the thickness direction, and GS surface indicates the average grain size of the surface to 1/4t in the thickness direction .)
[Claim 23]
The method of claim 12, wherein the microstructure of the hot-rolled sheet satisfies the following relationship. (GS center × recrystallization rate)/10≥2 (However, GS center represents the average grain size of 1/4 to 3/4t in the thickness direction, and the recrystallization rate represents the area fraction of crystal grains recrystallized after hot rolling. )