KR102271303B1 - Non-oriented electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

According to one embodiment of the present invention, a non-oriented electrical steel sheet comprises: 1.5 to 4.0 wt% of Si; 0.0005 to 0.02 wt% of Al; 0.02 to 3.0 wt% of Mn; 0.005 to 0.15 wt% of Sn; 0.001 to 0.15 wt% of P; and the remainder Fe and unavoidable impurities. An area fraction of texture within 15˚ from (45, 10, and 45) expressed in an Euler's azimuth angle is more than twice as high as the area fraction of the texture within that of the texture within 15˚ from (0, 20, and 45).

Description

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

An embodiment of the present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention controls the cooling rate condition during annealing of hot-rolled sheet and the relationship between temperature increase time and cracking time during annealing of cold-rolled sheet, thereby forming a number of specific textures, thereby improving magnetic flux density and iron loss characteristics. It relates to a steel plate and a method for manufacturing the same.

Non-oriented electrical steel sheet is used as a material for iron cores in rotating equipment such as motors and generators and stationary equipment such as small transformers, and plays an important role in determining the energy efficiency of electric equipment. In particular, when used in a rotating machine, the average value of the rolling direction and the vertical direction of the steel sheet represents the characteristic of the steel sheet. The reason is to consider the in-plane anisotropy of the steel sheet.

Typical characteristics of such an electrical steel sheet include iron loss and magnetic flux density. The lower the iron loss and the higher the magnetic flux density, the better. Core loss refers to the energy that is lost due to heat generated from a material during magnetization, and it is very important because the lower the iron loss, the less energy lost as heat. In addition, the magnetic flux density is a value indicating the degree of magnetization under the strength of a magnetic field of a unit size. Since a larger magnetization can be induced with the same energy as it is higher, the larger this value, the greater energy can be delivered than in an electrical steel sheet of the same volume. can

In general, among the magnetic properties of non-oriented electrical steel sheets used in motors, iron loss is evaluated as the energy loss when magnetized up to 1.5T at a frequency of 50Hz using W15/50 as an index, and the magnetic flux density is at 5000A/m using B50 as an index. is evaluated by the magnetic flux density of the electrical steel sheet. In order to reduce electricity consumption, the magnetic properties in the low magnetic field are becoming more important because the electrical steel sheet is magnetized to have a magnetic flux density of 1.0 T or less after 2000, when the utilization increased due to the high efficiency of power equipment. The values representing the magnetic properties of electrical steel sheets are mainly used for the existing W15/50, B50, and W10/400.

Among them, since the magnetic flux density is evaluated by the magnetization force in the unit volume, the ratio of the element in which magnetization easily occurs in the steel sheet in the unit volume, that is, the ratio of iron atoms is very important. In general, since Si, Al, and Mn, which are elements mainly used in non-oriented electrical steel sheets, are nonmagnetic atoms, the saturation magnetic flux density value that the steel sheet can have is maximally magnetized under a large magnetic field as the amount of these alloys increases. and B50, the magnetic flux density value, is also lowered under the unit magnetic field strength. However, since the specific resistance of the steel sheet must be increased in order to reduce the eddy current loss induced in the steel sheet, the amount of alloy such as Si, Al, Mn, which is a non-magnetic alloying element, must be added inevitably to overcome the decrease in magnetic flux density. For this purpose, the technology to control the collective organization has been developed.

In the unit lattice structure, iron has a characteristic that it is easily saturated even in a magnetic field with very small magnetization along the <100> axis, but it is very difficult to magnetize along the <111> axis, so it is not saturated even under a large magnetic field of hundreds of thousands of A/m. has a Therefore, even in a non-oriented electrical steel sheet having the same alloy amount, the magnetization value B50 under a unit magnetic field strength depends on the direction of magnetization and how much the <100> axis is distributed.

When integrating into the {100} plane as a double crystal orientation, since there are two <100> axes perpendicular to the plate plane, it is very advantageous to improve the magnetic flux density. In particular, technologies for increasing the degree of integration of {100} orientations such as lowering the hot rolling temperature or performing hot rolling in an abnormal zone are being developed. Specifically, a method for developing {100} orientation by increasing hot-rolling deformation in a narrow temperature section after phase transformation is proposed, but it is difficult to operate during hot-rolling work and has limitations in that it cannot be used in steel that does not undergo phase transformation.

In addition, as a method for developing a non-oriented electrical steel sheet with high magnetic flux density, an attempt was made to improve the texture by performing hot rolling in the austenite section and cooling faster than normal rolling. It has limitations that make it impossible to use in rivers that do not.

An embodiment of the present invention is to provide a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, in one embodiment of the present invention, by controlling the relationship between the cooling rate condition during annealing of the hot-rolled sheet and the temperature increase time and cracking time during annealing of the cold-rolled sheet, a number of specific textures are formed, thereby improving magnetic flux density and iron loss characteristics. An object of the present invention is to provide a steel sheet and a manufacturing method thereof.

Non-oriented electrical steel sheet according to an embodiment of the present invention in weight %, Si: 1.5 to 4.0%, Al: 0.0005 to 0.02%, Mn: 0.02 to 3.0%, Sn: 0.005 to 0.15% and P: 0.001 to 0.15% %, the remainder contains Fe and unavoidable impurities, and the area fraction of the texture within 15˚ from (45,10,45) expressed in Euler's azimuth angle is within 15˚ from (0,20,45) of the texture It is more than twice as high as the area fraction.

In the non-oriented electrical steel sheet according to an embodiment of the present invention, the area fraction of <100>//ND may be 15% or more.

(Here, <100>//ND means a texture in which the <001> axis forms an angle within 15˚ with the normal direction of the rolling surface.)

The fraction of texture within 15˚ from (45, 10, 45) may be 8.0% or more.

The area fraction of the texture within 15˚ from (0,20,45) may be 4.0% or less.

The non-oriented electrical steel sheet according to an embodiment of the present invention may have an average grain size of 60 to 500 μm.

The non-oriented electrical steel sheet according to an embodiment of the present invention may further include Sb: 0.001 to 0.15% by weight.

The non-oriented electrical steel sheet according to an embodiment of the present invention may further include one or more of C: 0.005 wt% or less, N: 0.005 wt% or less, S: 0.015 wt% or less, and Ti: 0.003 wt% or less .

The non-oriented electrical steel sheet according to an embodiment of the present invention may further include at least one of Cu, Ni, and Cr in an amount of 0.05% by weight or less, respectively.

The non-oriented electrical steel sheet according to an embodiment of the present invention may further include at least one of Zr, Mo, and V in an amount of 0.01 wt% or less, respectively.

The non-oriented electrical steel sheet according to an embodiment of the present invention may have a Br value of 1.75 or more expressed by Equation 1 below, and a W value of 110 or less expressed by Equation 2 below.

[Equation 1]

[Br] = 7.87/(7.87-0.065×[Si]-0.1105×[Al])×[B50]

(In Equation 1, [Si] and [Al] are the Si and Al contents (wt%), respectively, and [B50] is the magnetization at 5000 A/m measured in the rolling direction (L) and the rolling direction (C). It is the average value (Tesla) of the value B50.)

[Equation 2]

[W] = [W15/50] × [W10/400] / [T]

(In Equation 2, [W15/50] is the energy loss (W/kg) when magnetized to 1.5T at 50Hz frequency, and [W10/400] is the energy loss (W) when magnetized to 1.0T at 400Hz frequency. /kg), and [T] is the thickness (mm) of the electrical steel sheet.)

Si: 1.5 to 4.0%, Al: 0.0005 to 0.02%, Mn: 0.02 to 3.0%, Sn: 0.005 to 0.15% and P: 0.001 to 0.15% according to an embodiment of the present invention, the balance being Fe and inevitable manufacturing a hot-rolled sheet by hot-rolling a slab containing impurities; annealing the hot-rolled sheet; It includes the steps of manufacturing a cold-rolled sheet by cold-rolling the annealed hot-rolled sheet, and final annealing of the cold-rolled sheet.

After the step of annealing the hot-rolled sheet, the hot-rolled sheet is cooled at a rate of 3°C/s or less from the annealing cracking temperature of the hot-rolled sheet, and in the final annealing step, compared to the temperature increase time of increasing the temperature from 700°C to 950°C, 1000°C or more Long holding time at the temperature.

Before the step of manufacturing the cold-rolled sheet, the average grain size of the surface of the hot-rolled sheet may be 120 μm or more.

The cracking temperature of the annealing step of the hot-rolled sheet may be 1000 to 1150° C., and the holding time at the cracking temperature may be 30 to 60 seconds.

The cracking temperature of the final annealing step may be 1000 to 1150 °C.

In the final annealing step, the temperature increase time from 700 ℃ to 950 ℃ may be 10 seconds or more and less than 40 seconds.

In the final annealing step, the holding time maintained at a temperature of 1000° C. or higher may be 40 to 120 seconds.

The non-oriented electrical steel sheet according to an embodiment of the present invention controls the hot rolling process of the non-oriented electrical steel sheet without phase transformation, the hot-rolled sheet annealing process, and the cold-rolled sheet annealing process after the cold rolling process, thereby clarifying the texture of the steel sheet during final annealing. The magnetic flux density is excellent by concentrating it in a texture that is favorable to magnetism

In addition, the non-oriented electrical steel sheet according to an embodiment of the present invention can be used in various ways, such as a high-efficiency motor, a high-output, high-torque motor, and a core material of a generator.

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and includes the presence or absence of another characteristic, region, integer, step, operation, element and/or component. It does not exclude additions.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part, or the other part may be involved in between. In contrast, when a part refers to being "directly above" another part, the other part is not interposed therebetween.

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.

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

In an embodiment of the present invention, the meaning of further including the additional element in the steel component means that the iron (Fe) is included as the remainder by the additional amount of the additional element.

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

Non-oriented electrical steel sheet according to an embodiment of the present invention in weight %, Si: 1.5 to 4.0%, Al: 0.0005 to 0.02%, Mn: 0.02 to 3.0%, Sn: 0.005 to 0.15% and P: 0.001 to 0.15% %, and the balance includes Fe and unavoidable impurities.

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

Si: 1.5 to 4.0 wt%

Silicon (Si) is a major element added because it is a component that increases the resistivity of steel and lowers eddy current loss during iron loss. When Si is included too little, it is difficult to obtain a desired low iron loss characteristic, it is difficult to make a steel without phase transformation in the hot rolling process, which is a prerequisite of the present invention, and also problems occur in that it can undergo phase transformation during final annealing. Conversely, when too much Si is included, the rollability may be deteriorated. Therefore, the content of Si is limited to 1.5 to 4.0% by weight. More specifically, it may contain 2.0 to 3.5 wt%. More specifically, it may contain 2.5 to 3.3 wt%.

Al: 0.0005 to 0.0200 wt%

Aluminum (Al) is a component added for the purpose of reducing iron loss by increasing the specific resistance of the steel sheet, similar to Si. Al is an element that is unavoidably added for deoxidation of steel in the steelmaking process, and it is difficult to contain less than 0.0005 wt% of Al. When Al is included too much, the magnetic flux density may be reduced. In addition, by forming a fine nitride such as AlN, it is possible to suppress the growth of crystal grains, thereby reducing the magnetism. Therefore, the content of Al is limited to 0.0005 to 0.02% by weight. More specifically, it may include 0.0010 to 0.015 wt%. More specifically, it may include 0.0015 to 0.01 wt%.

Mn: 0.02 to 3.00 wt%

Manganese (Mn) has the effect of lowering iron loss by increasing the resistivity together with Si and Al. If too little Mn is added, the above-described effect cannot be sufficiently obtained. Conversely, it is necessary to limit the amount added because the saturation magnetic flux density decreases as Mn is added. In addition, if a large amount of Mn is added, it may be difficult to produce steel without phase transformation during the hot rolling process, which is a prerequisite of the present invention. According to the spirit of the invention, in the present invention, the Mn addition amount is limited to 0.02 to 3.0% by weight in order to improve the magnetic flux density and prevent an increase in iron loss due to inclusions. More specifically, it may contain 0.05 to 2.0% by weight. More specifically, it may contain 0.1 to 1.0 wt%.

Sn: 0.005 to 0.150 wt%

Tin (Sn, tin) is an element that segregates at grain boundaries during annealing and inhibits the formation of a {111} texture harmful to magnetism. When Sn is contained too little, the above-mentioned effect cannot be obtained properly. Containing too much Sn may cause a decrease in rollability including surface defects in hot and cold rolling processes. Therefore, the content of Sn is limited to 0.005 to 0.15 wt%. More specifically, it may include 0.010 to 0.10 wt%. More specifically, it may contain 0.05 to 0.10 wt%.

P: 0.001 to 0.150 wt%

Phosphorus (P) is an element that increases specific resistance, lowers iron loss, and inhibits the formation of {111} texture harmful to magnetism by segregation at grain boundaries, and forms {100}, which is an advantageous texture. If too little P is contained, the above-described effect cannot be properly obtained. When too much P is contained, cold rolling property may be reduced. Therefore, the content of P is limited to 0.001 to 0.15% by weight. More specifically, it may include 0.005 to 0.100 wt%. More specifically, it may contain 0.01 to 0.05 wt%.

The non-oriented electrical steel sheet according to an embodiment of the present invention may further include 0.005 to 0.15 wt% of Sb.

Sb: 0.005 to 0.150 wt%

Antimony (Sb) is an element that segregates at grain boundaries during annealing, similar to Sn, and has the effect of suppressing the formation of a {111} texture harmful to magnetism and strengthening the <411>||ND texture. If too little Sb is contained, the effect cannot be obtained properly. When Sb is included too much, it may cause deterioration of the surface quality of the steel sheet in the pickling process before cold rolling, and also may cause deterioration of the rollability. Therefore, the content of Sb is limited to 0.005 to 0.15 wt%. More specifically, it may include 0.010 to 0.10 wt%. More specifically, it may contain 0.05 to 0.10 wt%.

The non-oriented electrical steel sheet according to an embodiment of the present invention may further include one or more of C: 0.005 wt% or less, N: 0.005 wt% or less, S: 0.015 wt% or less, and Ti: 0.003 wt% or less .

C: 0.005 wt% or less

When a lot of carbon (C) is added, it expands the austenite region and increases the temperature range where phase transformation occurs, and has the effect of suppressing the grain growth of ferrite during final annealing, thereby increasing iron loss. In addition, it is combined with Ti, etc. to form carbide, which is inferior to magnetism, and when used after processing from a final product to an electrical product, iron loss can be increased by magnetic aging. Therefore, when C is further included, the amount added is limited to 0.005 wt% or less. More specifically, it may be included in an amount of 0.003% by weight or less. More specifically, it may include 0.0001 to 0.003 wt%.

N: 0.005 wt% or less

Nitrogen (N) is an element harmful to magnetism, such as inhibiting grain growth by forming a nitride by strongly bonding with Al, Ti, etc., so when it is further included, it can be contained in a small amount. In particular, when combined with Al, Ti, Nb, etc. to delay recrystallization of steel, which is disadvantageous to crystal growth, when it is further included, its upper limit can be limited. Therefore, when N is further included, the amount added is limited to 0.005% by weight or less. More specifically, it may be included in an amount of 0.003% by weight or less. More specifically, it may include 0.0001 to 0.003 wt%.

S: 0.015 wt% or less

Since sulfur (S) is an element that forms sulfides such as MnS, CuS and (Cu,Mn)S that are harmful to magnetic properties, it is known that it is desirable to add it low in order to suppress an increase in iron loss. However, when S is segregated on the surface of the steel, it has an effect of lowering the surface energy of the {100} plane, so by adding S, a strong texture of the {100} plane favorable for magnetism can be obtained. However, if too much is added, workability is greatly reduced due to segregation of grain boundaries, and problems due to surface segregation may occur. Therefore, when S is further included, the amount added is limited to 0.015% by weight or less. More specifically, it may include 0.0008 to 0.015% by weight. More specifically, it may include 0.0010 to 0.0100 wt%.

Ti: 0.003 wt% or less

Titanium (Ti) forms fine carbides and nitrides to suppress grain growth, and the more it is added, the poorer the texture due to the increased carbides and nitrides, and the magnetism deteriorates. Therefore, when Ti is further included, it is limited to 0.003 wt% or less. More specifically, it may include 0.0001 to 0.003 wt%.

other impurities

In addition to the elements described above, impurities that are unavoidably incorporated may be included. The remainder is iron (Fe), and when an additional element other than the above-described elements is added, the remainder is included in place of iron (Fe).

Inevitably added impurities may be Cu, Ni, Cr, Zr, Mo, V, or the like.

Copper (Cu), nickel (Ni), and chromium (Cr) can be inevitably added in the steel manufacturing process, and Cu, Ni, and Cr react with impurity elements to form fine sulfides, carbides and nitrides, which are harmful to magnetism. Therefore, these contents are limited to 0.05% by weight or less, respectively.

In addition, since zirconium (Zr), molybdenum (Mo), vanadium (V), etc. are strong carbonitride forming elements, it is preferable not to be added as much as possible, and each contains 0.01 wt% or less.

In an embodiment of the present invention, the magnetism is improved through the concentration of a specific texture. Therefore, it is very important to quantitatively express the degree of concentration of the collective organization. The texture of the crystalline material is displayed as the fraction of the texture on the ODF calculated from the pole figure using X-ray, a method usually used to indicate the texture of the crystalline material, or as the fraction of the texture calculated using the EBSD method. to display In the case of X-ray, since it is more advantageous to measure a large area than EBSD, the texture characteristics of the steel sheet can be more appropriately expressed statistically, but the precision of measurement is worse than that of EBSD. Therefore, in the present invention, the expression of the texture was calculated using the EBSD method, and the numerical value of the texture was calculated by examining 5000 or more crystal grain sizes recrystallized from the final annealed plate and calculating the fraction. However, this does not actually limit the measurement method, but a measurement method is proposed for convenience for accuracy of measurement, and a method using X-ray and neutron diffraction may be used in calculating the fraction.

Since Fe atoms have crystal magnetic anisotropy, a magnetic field that is several thousand times larger than that of the <100> crystal axis is required for saturation magnetization of the <111> crystal axis, so a texture in which the <100> crystal axis is parallel to the magnetization direction is selected. In the case of a non-oriented electrical steel sheet having a lot of it, the magnetic flux density characteristic is excellent. In particular, the texture (usually expressed as Cube orientation) expressed as (45,0,45) in Euler azimuth angles is very excellent in magnetism in non-oriented electrical steel sheets. However, it is difficult to produce a non-oriented electrical steel sheet with a high degree of integration of such a cube orientation through a conventional process.

Therefore, in the present invention, through the control of the hot rolling process and the annealing process, the integration of (45,10,45) is improved in the Euler azimuth angle, while the integration of (0,20,45) is lowered (45,10,45)/ A technique for making a non-oriented electrical steel sheet having excellent magnetic flux density characteristics with a ratio of (0, 20, 45) of 2 or more was proposed. At this time, the (45,10,45) orientation expressed in Euler orientation represents all the same orientations according to the symmetry of the crystal structure, such as (225,10,45), and the (0,20,45) orientation also exhibits symmetry in the same way. It is a representative orientation that is taken into account. In addition, the degree of integration of the texture represented by each direction shall be the addition of the fraction within 15 ˚ in each direction in the same way as in the usual method. At this time, (45,10,45) and (0,20,45) overlapped with the calculated orientation is calculated to be overlapped with each orientation. The fraction specifically refers to an area fraction, and in this case, a plane parallel to the rolling plane (ND plane) may be used as the reference. More specifically, a ratio of (45,10,45)/(0,20,45) may be 2.0 to 3.0.

The fraction of texture within 15˚ from (45, 10, 45) may be 8.0% or more. More specifically, it may be 8.5% to 10.0%.

The area fraction of the texture within 15˚ from (0,20,45) may be 4.0% or less. More specifically, it may be 2.0 to 3.8%.

In addition, in an embodiment of the present invention, the <100>//ND fiber orientation (<100> direction including the (45,10,45) and (0,20,45) orientations (the <100> direction is the normal direction of the rolling surface (ND direction) ) and the minimum area fraction of grains having a degree of parallelism) to 15% or more is also restricted. At this time, the fraction is calculated as the sum of the orientations within 15° from the ND||<100> orientation, as in a normal degree. The reason for limiting to 15% or more in the present invention is that even if the difference between the ratios of (45,10,45) and (0,20,45) is large, the fraction of each orientation in the actual steel sheet affects the magnetic flux density. This is because each direction does not exist meaningfully. More specifically, the area fraction of <100>//ND may be 15 to 25%.

The average grain size in the microstructure of the electrical steel sheet may be 60 to 500㎛. If the grain size is too small, the hysteresis loss greatly increases and the iron loss deteriorates. In addition, in order to improve the magnetic flux density due to the effect of fine precipitates and segregation, it is preferable to have an appropriate grain size. However, if the grain size is too large, there may be a problem in processing when punching the coated product after annealing. More specifically, the average grain size may be 120 to 200㎛.

The grains constituting the non-oriented electrical steel sheet consist of a non-recrystallized structure processed in the cold rolling process and a recrystallized structure recrystallized in the final annealing process, and the recrystallized structure is 99% by volume or more.

As described above, the non-oriented electrical steel sheet according to an embodiment of the present invention has excellent magnetic properties.

Specifically, the non-oriented electrical steel sheet according to an embodiment of the present invention uses a magnetic flux density (Br) value in consideration of the density of the steel sheet in order to evaluate the magnetic flux density of the steel sheet. To obtain this, the magnetic flux density value at 5000A/m of the steel sheet was measured in the rolling direction and the rolling direction and the averaged value was taken as [B50], derived from the formula of 7.87-0.065×[Si]-0.1105×[Al]. The value is calculated as the density of the steel sheet, and Br is derived using the following formula.

[Equation 1]

[Br] = 7.87/(7.87-0.065×[Si]-0.1105×[Al])×[B50]

(In Equation 1, [Si] and [Al] are the Si and Al contents (wt%), respectively, and [B50] is the magnetization at 5000 A/m measured in the rolling direction (L) and the rolling direction (C). It is the average value (Tesla) of the value B50.)

In one embodiment of the present invention, Br may have a very high magnetic flux density value of 1.75 or more. The reason for considering the density rather than the normal magnetic flux density value is that as the addition amount of Si and Al in the steel increases, the iron atom fraction in the steel decreases and the saturation magnetic flux decreases accordingly to improve the magnetic flux density due to the texture. because it can be considered.

When the amount of Al in the steel satisfies the range of the present invention, Al combines with N to form fine precipitates. When these fine precipitates are distributed at grain boundaries, they have the effect of making crystal growth difficult and strengthening the texture with a strong <111>//ND orientation, which is a texture unfavorable to magnetism. Conversely, Sn and P, which are elements segregated at grain boundaries during annealing, have the effect of strengthening a texture having a strong <100>//ND orientation favorable to magnetism and a texture having a strong <110>//ND orientation. S has an effect of precipitating MnS and the like by combining with Mn, but has a smaller effect on recrystallization because the size of the precipitate is larger than that of AlN. In addition, S, which is not combined with Mn and the like and is not precipitated as a sulfide, segregates at grain boundaries, helping to form a <100>//ND orientation favorable to magnetism.

More specifically, the Br value is 1.750 to 1.775. More specifically, the Br value is 1.750 to 1.765.

The non-oriented electrical steel sheet according to an embodiment of the present invention uses the iron loss (W) value in consideration of the thickness of the steel sheet in order to evaluate the iron loss of the steel sheet.

[Equation 2]

[W] = [W15/50] × [W10/400] / [T]

(In Equation 2, [W15/50] is the energy loss (W/kg) when magnetized to 1.5T at 50Hz frequency, and [W10/400] is the energy loss (W) when magnetized to 1.0T at 400Hz frequency. /kg), and [T] is the thickness (mm) of the electrical steel sheet.)

The W value may be 110 or less. More specifically, the W value may be 90 to 110. More specifically, it may be 93 to 108.0.

Si: 1.5 to 4.0%, Al: 0.0005 to 0.02%, Mn: 0.02 to 3.0%, Sn: 0.005 to 0.15% and P: 0.001 to 0.15% according to an embodiment of the present invention, the balance being Fe and inevitable manufacturing a hot-rolled sheet by hot-rolling a slab containing impurities; annealing the hot-rolled sheet; A step of cold-rolling the annealed hot-rolled sheet and the final annealing of the cold-rolled sheet.

Hereinafter, each step will be described in detail.

First, the slab is hot rolled. The reason for limiting the addition ratio of each composition in the slab is the same as the reason for limiting the composition of the non-oriented electrical steel sheet described above, and thus repeated description is omitted. Since the composition of the slab does not substantially change in the manufacturing process of hot rolling, hot rolled sheet annealing, cold rolling, final annealing, etc. to be described later, the composition of the slab and the composition of the non-oriented electrical steel sheet are substantially the same.

The slab can be manufactured by melting steel of a suitable component composition with a converter or a degassing device, and the like, by continuous casting or ingot-ingot rolling.

Before hot rolling the slab, the slab is charged into a heating furnace and heated to 1,100 to 1,250°C. When heated at a temperature exceeding 1,250° C., precipitates such as AlN and MnS present in the slab are re-dissolved and then finely precipitated during hot rolling to suppress grain growth and reduce magnetism.

When the slab is heated, hot-rolling is performed to 2.0 to 3.5 mm, and the hot-rolled hot-rolled sheet is wound. Finish rolling in finishing rolling at the time of hot rolling is terminated in the ferrite phase region. In addition, it is possible to add a large amount of ferrite phase expanding elements such as Si, Al, and P during hot rolling, or to contain a small amount of elements such as Mn and C for suppressing the ferrite phase. In this way, when rolling on ferrite, a large number of {100} planes are formed in the texture, and thus the magnetism can be improved.

After the step of manufacturing the hot-rolled sheet, the hot-rolled sheet is annealed. In this case, the cracking temperature of the hot-rolled sheet annealing step may be 1,000 to 1,150° C., and the holding time at the cracking temperature may be 30 to 60 seconds.

If the hot-rolled sheet annealing temperature is too small, the structure does not grow or grows fine, so the synergistic effect of magnetic flux density is small. If the annealing temperature is too high, the magnetic properties are rather deteriorated, and the rolling workability may deteriorate due to the deformation of the sheet shape. .

After the step of annealing the hot-rolled sheet, the hot-rolled sheet is cooled from the annealing cracking temperature to 890°C at a rate of 3°C/s or less. By cooling at the above-mentioned rate, the texture of the plate center and the plate surface of the hot-rolled sheet is advantageously formed in the magnetic properties of the electrical steel sheet. In particular, by controlling the cooling rate, the coarse crystal grains located on the surface are deformed through the process of surface processing to remove the oxide layer on the surface, which is inevitably passed during annealing of the hot-rolled sheet, and the passage of the curved part of the continuous annealing furnace. The desired texture can be obtained after the cold rolling is completed by cold rolling the work-hardened surface to such deformation. Specifically, it can be cooled at a rate of 1.0 to 3.0 °C / s from the hot-rolled sheet annealing cracking temperature to 890 °C. More specifically, it may be cooled at a rate of 2.0 to 3.0 °C/s.

The average grain size of the surface portion of the hot-rolled sheet before the cold rolling step may be 120㎛ or more. As such, by cold rolling after forming the average grain size of the hot-rolled sheet large, deformation is imparted to the coarse grains located on the surface portion, and the desired texture after cold rolling is completed by cold rolling the work-hardened surface to such deformation. can get In this case, the surface means a depth from the outermost surface of the hot-rolled sheet to 100 μm in the thickness direction. More specifically, the average grain size of the surface portion of the hot-rolled sheet may be 120㎛ to 200㎛.

Next, the hot-rolled sheet is cold-rolled to a predetermined thickness. It may be applied differently depending on the thickness of the hot-rolled sheet, but cold rolling may be performed to a final thickness of 0.2 to 0.5 mm by applying a reduction ratio of 50 to 95%. Cold rolling may be carried out by one cold rolling or by performing cold rolling two or more times with intermediate annealing therebetween as needed.

The cold-rolled cold-rolled sheet is subjected to final annealing (cold-rolled sheet annealing). In the final annealing process of the cold-rolled sheet, the cracking temperature during annealing is 1,000 to 1,150°C.

When the cold-rolled sheet annealing temperature is too low, it may be difficult to obtain crystal grains of sufficient size to obtain low iron loss. If the annealing temperature is too high, the plate shape during annealing is uneven and the precipitates are re-dissolved at a high temperature and then finely precipitated during cooling, which may adversely affect magnetism.

In one embodiment of the present invention, in the final annealing step, compared to the temperature increase time of raising the temperature from 700 ℃ to 950 ℃, the holding time of maintaining at a temperature of 1000 ℃ or more is long. As such, by adjusting the temperature increase time and the holding time of the final annealing step, it is possible to obtain a texture in which the fraction of (45,10,45) orientation is twice as high as that of (0,20,45) orientation. At this time, the (45,10,45) fraction favorable to magnetism at the time of temperature increase tends to decrease, while at a temperature above 1000°C, the (45,10,45) fraction increases, whereas the (0,20,45) fraction is Since it tends to decrease, it is necessary to make the holding time longer than the temperature increase time.

Specifically, in the final annealing step, the temperature increase time from 700 ℃ to 950 ℃ may be 10 seconds or more and less than 40 seconds.

In the final annealing step, the holding time maintained at a temperature of 1000° C. or higher may be 40 to 120 seconds.

The final annealed steel sheet may be treated with an insulating coating. Since the method for forming the insulating layer is widely known in the field of non-oriented electrical steel sheet technology, a detailed description thereof will be omitted. Specifically, as the composition for forming the insulating layer, any one of a chromium-based (Cr-type) or a chromium-free (Cr-free type) can be used without limitation.

Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited thereto.

Example 1

After degassing the molten steel blown in a converter to melt the steel containing the molten steel blown in the table 1 and the remainder Fe and unavoidable impurities in wt%, continuous casting was performed to prepare a 200mm thick slab. After heating the slab at 1150° C., hot rolling was performed to a thickness of 2.5 mm. After hot rolling, hot-rolled sheet annealing was performed. The hot-rolled sheet annealing was maintained at 1100° C. for 40 seconds, and then the average cooling rate in cooling to 890° C. was adjusted as shown in Table 2 below. After cooling and removing the oxide layer on the surface, cold rolling was performed. The thickness of the steel plate at the time of cold rolling was made into 0.2 mm, 0.25 mm, 0.3 mm, and 0.35 mm. This was subjected to final annealing at 1050 ℃ for the time shown in Table 2, at this time, the temperature increase time from 700 ℃ to 950 ℃ is shown in Table 2.

From this, an SST test piece having a width of 60 mm x a length of 60 mm was cut out in the rolling direction (L direction) and the rolling vertical direction (C direction), and in accordance with IEC 60404-3, iron loss W15/50, W10/400 and magnetic flux density B50 were measured, and the results are shown in Table 3.

steel grade
(weight%) Si Al Mn P Sn Sb S C N Ni Cr One 3.0 0.003 0.2 0.04 0.07 0.0006 0.0033 0.002 0.002 0.01 0.01 2 2.7 0.002 0.15 0.03 0.04 0.02 0.0056 0.001 0.001 0.02 0.02 3 3.35 0.005 0.06 0.013 0.06 0.0007 0.0038 0.004 0.0029 0.004 0.04 4 2.1 0.003 0.32 0.063 0.09 0.0005 0.0046 0.002 0.0035 0.02 0.03 5 2.8 0.03 0.21 0.026 0.035 0.0006 0.0033 0.003 0.0035 0.015 0.01 6 3.1 0.003 0.21 0.023 0.001 0.026 0.0041 0.002 0.0012 0.006 0.02

steel grade Cooling rate after hot-rolled sheet annealing
(℃/s) Hot-rolled sheet surface grain size
(μm) cold rolled sheet thickness
(mm) Heating time from 700℃ to 950℃
(second) Holding time over 1000℃
(second) Crystal grain size after final annealing
(μm) Example 1 One 2.5 148 0.2 15 40 123 Example 2 2 2.5 145 0.25 15 40 127 Example 3 3 2.5 133 0.3 15 40 135 Example 4 4 2.5 125 0.35 15 40 161 Comparative Example 1 5 2.5 61 0.25 15 40 96 Comparative Example 2 6 2.5 109 0.25 15 40 101 Comparative Example 3 One 3.5 95 0.2 40 40 85 Comparative Example 4 2 3.5 95 0.25 40 40 96 Comparative Example 5 3 3.5 96 0.3 40 40 93 Comparative Example 6 4 3.5 95 0.35 40 40 102 Comparative Example 7 One 3.5 135 0.2 25 20 53 Comparative Example 8 2 3.5 133 0.25 25 20 59 Comparative Example 9 3 3.5 135 0.3 25 20 51 Comparative Example 10 4 3.5 136 0.35 25 20 58 Comparative Example 11 One 2.5 143 0.2 50 30 84 Comparative Example 12 2 2.5 145 0.25 50 30 73 Comparative Example 13 3 3.5 101 0.3 35 40 96 Comparative Example 14 4 3.5 112 0.35 35 40 109

(45,10,45) fraction
(area%) (0,20,45) fraction
(area%) <100>//ND fraction
(area%) Br W W15/50
(W/kg) W10/400
(W/kg) Example 1 9.1 3.5 20 1.751 94.4 1.7 11.1 Example 2 9.5 3.4 21 1.756 97.9 1.84 13.3 Example 3 9.4 3.6 21 1.754 101.5 1.88 16.2 Example 4 9.3 3.5 20 1.765 107.6 2.08 18.1 Comparative Example 1 5.1 3.2 12 1.713 119 2.14 13.9 Comparative Example 2 4.1 2.9 11 1.729 118.2 2.11 14.0 Comparative Example 3 4.5 3.5 13 1.712 130.1 2.15 12.1 Comparative Example 4 4.7 3.4 12 1.72 113.4 2.1 13.5 Comparative Example 5 5.1 3.6 12 1.725 123.2 2.1 17.6 Comparative Example 6 5.5 3.5 13 1.729 122.6 2.2 19.5 Comparative Example 7 4.3 4.1 11 1.705 124.2 2.16 11.5 Comparative Example 8 4.2 3.9 12 1.715 113.0 2.19 12.9 Comparative Example 9 4.7 3.8 12 1.718 125.6 2.23 16.9 Comparative Example 10 5.1 3.4 11 1.722 117.9 2.28 18.1 Comparative Example 11 4.8 3.6 13 1.712 153.6 2.31 13.3 Comparative Example 12 5.3 4.1 12 1.723 127.5 2.26 14.1 Comparative Example 13 4.2 3.5 10 1.719 112.9 2.13 15.9 Comparative Example 14 5.6 3.6 8 1.728 111.7 2.26 17.3

As shown in Tables 1 to 3, it can be seen that the embodiment satisfying all of the alloy components and the manufacturing process according to an embodiment of the present invention satisfies the characteristic texture characteristics, and both magnetic flux density and iron loss are excellent.

On the other hand, it can be seen that Comparative Examples 1 and 2 containing a large amount of Al or a small amount of Sn did not satisfy the texture characteristics, and both magnetic flux density and iron loss were relatively inferior.

In addition, it can be seen that the cooling rate after the annealing of the hot-rolled sheet and the texture characteristics of Comparative Examples 3 to 6 that do not satisfy the temperature increase time and the holding time during final annealing are not satisfied, and both magnetic flux density and iron loss are relatively inferior.

In addition, it can be seen that Comparative Examples 7 to 12, which do not satisfy the temperature increase time and the holding time during the final annealing, do not satisfy the texture characteristics, and both magnetic flux density and iron loss are relatively inferior.

In addition, it can be seen that Comparative Examples 13 and 14, which do not satisfy the cooling rate after the hot-rolled sheet annealing, do not satisfy the texture characteristics, and have relatively poor magnetic flux density and iron loss.

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

Claims (16)

Si: 1.5 to 4.0%, Al: 0.0005 to 0.02%, Mn: 0.02 to 3.0%, Sn: 0.005 to 0.15% and P: 0.001 to 0.15% by weight, the balance comprising Fe and unavoidable impurities, ,
Non-oriented electrical steel sheet in which the area fraction of texture within 15˚ from (45,10,45) expressed in Euler's azimuth angle is more than twice as high as the area fraction of texture within 15˚ from (0,20,45). According to claim 1,
<100>//Non-oriented electrical steel sheet having an area fraction of 15% or more.
(Here, <100>//ND means a texture in which the <001> axis forms an angle within 15˚ with the normal direction of the rolling surface.) According to claim 1,
A non-oriented electrical steel sheet in which the fraction of texture within 15° from (45, 10, 45) is 8.0% or more. According to claim 1,
A non-oriented electrical steel sheet having an area fraction of texture within 15˚ from (0,20,45) of 4.0% or less. According to claim 1,
A non-oriented electrical steel sheet having an average grain size of 60 to 500 μm. According to claim 1,
Sb: Non-oriented electrical steel sheet further comprising 0.001 to 0.15 wt%. According to claim 1,
C: 0.005 wt% or less, N: 0.005 wt% or less, S: 0.015 wt% or less, and Ti: Non-oriented electrical steel sheet further comprising at least one of 0.003 wt% or less. According to claim 1,
A non-oriented electrical steel sheet further comprising 0.05 wt% or less of each of Cu, Ni and Cr at least. According to claim 1,
A non-oriented electrical steel sheet further comprising 0.01 wt% or less of each of Zr, Mo, and at least one of V. According to claim 1,
A non-oriented electrical steel sheet having a Br value of 1.75 or more, expressed by the following formula (1), and a W value of 110 or less, expressed by the following formula (2).
[Equation 1]
[Br] = 7.87/(7.87-0.065×[Si]-0.1105×[Al])×[B50]
(In Equation 1, [Si] and [Al] are the Si and Al contents (wt%), respectively, and [B50] is the magnetization at 5000 A/m measured in the rolling direction (L) and the rolling direction (C). It is the average value (Tesla) of the value B50.)
[Equation 2]
[W] = [W15/50] × [W10/400] / [T]
(In Equation 2, [W15/50] is the energy loss (W/kg) when magnetized to 1.5T at 50Hz frequency, and [W10/400] is the energy loss (W) when magnetized to 1.0T at 400Hz frequency. /kg), and [T] is the thickness (mm) of the electrical steel sheet.) By weight %, Si: 1.5 to 4.0%, Al: 0.0005 to 0.02%, Mn: 0.02 to 3.0%, Sn: 0.005 to 0.15% and P: 0.001 to 0.15%, the balance comprising Fe and unavoidable impurities manufacturing a hot-rolled sheet by hot-rolling the slab;
annealing the hot-rolled sheet;
manufacturing a cold-rolled sheet by cold-rolling the annealed hot-rolled sheet; and
final annealing of the cold-rolled sheet;
After the step of annealing the hot-rolled sheet, the hot-rolled sheet is cooled at a rate of 3°C/s or less from the annealing cracking temperature to 890°C,
In the final annealing step, compared to the temperature increase time of raising the temperature from 700 ℃ to 950 ℃, a method of manufacturing a non-oriented electrical steel sheet having a long holding time maintained at a temperature of 1000 ℃ or more. 12. The method of claim 11,
A method of manufacturing a non-oriented electrical steel sheet having an average grain size of 120 μm or more on the surface of the hot-rolled sheet before the step of manufacturing the cold-rolled sheet. 12. The method of claim 11,
The cracking temperature of the annealing step of the hot-rolled sheet is 1000 to 1150° C., and the holding time at the cracking temperature is 30 to 60 seconds. 12. The method of claim 11,
The cracking temperature of the final annealing step is 1000 to 1150 ℃ method of manufacturing a non-oriented electrical steel sheet. 12. The method of claim 11,
In the final annealing step, the temperature increase time from 700° C. to 950° C. is 10 seconds or more and less than 40 seconds. 12. The method of claim 11,
In the final annealing step, the holding time maintained at a temperature of 1000° C. or higher is 40 to 120 seconds.