KR20230094870A - Non-oriented electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

In the non-oriented electrical steel sheet according to an embodiment of the present invention, by weight, Si: 1.5 to 4%, Al: 0.1 to 2%, Mn: 0.05 to 2%, P: 0.1% or less, C: 0.005% or less, S: 0.005% or less, N: 0.005% or less, the balance including Fe and other unavoidably added impurities, and the average value of the magnetic flux density in the circumferential direction satisfies the following [Equation 1].
[Equation 1]
B50, ring ≥ 1.88+0.1*t-0.067*(Si%)-0.0458*(Al%)-0.022*(Mn%)
(Where t is the thickness of the steel sheet, (Si%), (Al%), and (Mn%) mean the weight% of Si, Al, and Mn, respectively)

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 manufacturing method thereof. Specifically, one embodiment of the present invention relates to a non-oriented electrical steel sheet having low high-frequency core loss, high magnetic flux density, and excellent thickness variation by optimizing process conditions for manufacturing an electrical steel sheet in consideration of constituent elements, and a manufacturing method thereof.

A motor or generator is one of the energy conversion devices that convert electrical energy into mechanical energy or mechanical energy into electrical energy. These motors and generators are being demanded to further improve the efficiency of their magnetic characteristics as regulations on environmental preservation and energy saving have recently been strengthened.

These motors, generators, and small transformers use materials for iron cores, and non-oriented electrical steel sheets are mainly used as materials for iron cores, so the magnetic properties of electrical steel sheets are closely related to the efficiency of motors or generators. And the magnetic properties of non-oriented electrical steel sheet mainly mean high-frequency iron loss and magnetic flux density.

Here, iron loss is the energy that is changed to heat and disappears during the energy conversion process, so the lower it is, the more efficient it is. In addition to this, since the motor rotates at thousands to tens of thousands of revolutions, it is necessary to suppress vibration and improve durability in addition to improving electrical characteristics. In this way, it is advantageous to reduce the thickness variation of the non-oriented electrical steel sheet in order to improve the vibration characteristics and durability and also to manufacture a symmetrical core.

Recently, countries around the world are competitively adopting policies to reduce greenhouse gas and alternatives to fossil fuel shortages. and the technology is advancing rapidly. Such an HEV or EV is a vehicle that converts part or all of a driving method into an electric motor to achieve better fuel efficiency while reducing the amount of gasoline or diesel, which is a conventional internal combustion engine fuel.

Motors used in such automobiles must implement large torque at low speed or acceleration, and rotate at high speed during constant speed and high speed driving. Therefore, it is preferable that the non-oriented electrical steel sheet, which is the iron core material of the motor used here, has high magnetic flux density characteristics during low-speed rotation and low high-frequency iron loss during high-speed rotation.

In general, high-frequency iron loss means iron loss at a frequency of 200Hz or higher, but in non-oriented electrical steel sheets for electric vehicles, the value of W10/400 is mainly used, and in particular, iron loss and magnetic flux density in the circumferential direction are important due to the characteristics of rotating machines. do.

In order to improve the high-frequency iron loss, the content of alloy elements such as Si, Al, and Mn, which are non-resistive elements of the electrical steel sheet, should be increased, and impurities should be reduced to facilitate magnetic domain movement. However, when a high content of non-magnetic alloy elements such as Si, Al, and Mn occurs, the magnetic flux density becomes low. In particular, it is essential to use a material having a high magnetic flux density for a material that continuously requires weight reduction, such as a driving motor of an eco-friendly electric vehicle.

One embodiment of the present invention is to provide a non-oriented electrical steel sheet and a manufacturing method thereof. Specifically, one embodiment of the present invention is to optimize the manufacturing process conditions of the electrical steel sheet, to provide a non-oriented electrical steel sheet and a method for manufacturing the same, which are excellent in magnetic properties in the circumferential direction and thickness variation characteristics of the steel sheet at the same time.

In the non-oriented electrical steel sheet according to an embodiment of the present invention, by weight, Si: 1.5 to 4%, Al: 0.1 to 2%, Mn: 0.05 to 2%, P: 0.1% or less, C: 0.005% or less, S: 0.005% or less, N: 0.005% or less, including Fe and other unavoidably added impurities, and the average value of the magnetic flux density in the circumferential direction may satisfy the following [Equation 1].

[Equation 1]

B50, ring ≥ 1.88+0.1*t-0.067*(Si%)-0.0458*(Al%)-0.022*(Mn%)

(Where t is the thickness of the steel sheet, (Si%), (Al%), and (Mn%) mean the weight% of Si, Al, and Mn, respectively)

In the non-oriented electrical steel sheet according to another embodiment of the present invention, the average iron loss value in the circumferential direction may satisfy the following [Equation 2].

[Formula 2]

W10/400, ring ≤ 7.2+4000*t ² /(13+11*((Si%)+(Al%)+0.5*(Mn%)))

(Where t is the thickness of the steel sheet, (Si%), (Al%), and (Mn%) mean the weight% of Si, Al, and Mn, respectively)

In the non-oriented electrical steel sheet according to another embodiment of the present invention, thickness deviation in the width direction may satisfy the following [Equation 3].

[Formula 3]

ΔT (width direction thickness deviation) = (Tavg, center - Tavg,15)/Tavg,center

(Here, Tavg,center is the average thickness in the longitudinal direction of the center of the mocoil, and Tavg,15 is the average thickness in the longitudinal direction at 15mm from both sides of the mocoil.)

In the method for manufacturing a non-oriented electrical steel sheet according to another embodiment of the present invention, in weight%, Si: 1.5 to 4%, Al: 0.1 to 2%, Mn: 0.05 to 2%, P: 0.1% or less, C : 0.005% or less, S: 0.005% or less, N: 0.005% or less, preparing a slab containing the balance of Fe and other unavoidably added impurities; heating the slab; Preparing a hot-rolled sheet by hot-rolling the slab; And a step of cold-rolling the hot-rolled sheet to produce a cold-rolled sheet, and performing intermediate rolling by reheating the hot-rolled sheet in the range of 700 to 1,000 ° C. during or before the hot-rolled sheet annealing process after the hot rolling can include

In this intermediate rolling step, the rolling reduction may be intermediate rolling at 20 to 50%. And at this time, the reheating method of the hot-rolled sheet for intermediate rolling may be any one of a direct fire method, an energization method, and an induction heating method.

And the step of heating the slab is preferably heated at 1,100 to 1,150 ℃.

In addition, cold rolling can be performed with a reduction ratio of 70 to 85%.

The method for manufacturing a non-oriented electrical steel sheet according to another embodiment of the present invention may further include annealing the intermediately rolled hot-rolled sheet at a temperature of 850 to 1,150°C.

And the manufactured cold-rolled steel sheet may further include the step of final annealing at 900 to 1,070 ℃.

The non-oriented electrical steel sheet according to an embodiment of the present invention improves the texture of the manufactured steel sheet by considering the composition of the steel sheet in performing intermediate rolling between hot rolling and cold rolling processes, and also has excellent magnetic properties. A grain-oriented electrical steel sheet may be provided.

The non-oriented electrical steel sheet manufactured according to an embodiment of the present invention has a thickness deviation of less than 2% in the width direction and is excellent in both magnetic flux density in the circumferential direction and high-frequency iron loss in the circumferential direction, so that the eco-friendly vehicle driving motor rotates at high speed. It can be used as a suitable material, etc.

The non-oriented electrical steel sheet according to an embodiment of the present invention is reheated at a temperature in the range of 700 to 1,000 ° C after hot rolling, and intermediate rolling is performed at a reduction rate of 20 to 50%, so that the thickness in the width direction is corrected. It has the effect of reducing the deviation, reducing the cold rolling reduction in the subsequent cold rolling process, and further suppressing the generation of the GOSS texture to improve the magnetic properties in the circumferential direction. Due to these technical effects, the non-oriented electrical steel sheet manufactured according to an embodiment of the present invention can greatly improve the efficiency of a device rotating at high speed, such as a drive motor of an electric vehicle.

1 is a graph showing changes in magnetic properties according to intermediate rolling conditions of a hot rolled sheet of non-oriented electrical steel sheet according to an embodiment of the present invention.

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 only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is only for referring to specific embodiments 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. The meaning of "comprising" as used herein specifies particular characteristics, regions, integers, steps, operations, elements and/or components, and the presence or absence of other characteristics, regions, integers, steps, operations, elements and/or components. Additions are not excluded.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part or may be followed by another part therebetween. In contrast, when a part is said to be “directly on” another part, there is no intervening part between them.

Although not defined differently, all terms including technical terms 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. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with related technical literature and currently disclosed content, and are not interpreted in ideal or very formal meanings unless defined.

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

In one embodiment of the present invention, the meaning of further including an additional element means replacing and including iron (Fe) as much as the additional amount of the additional element.

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

Hereinafter, an embodiment of the present invention will be described in order of composition and manufacturing process of a steel sheet.

In the non-oriented electrical steel sheet according to an embodiment of the present invention, by weight, Si: 1.5 to 4%, Al: 0.1 to 2%, Mn: 0.05 to 2%, P: 0.1% or less (excluding 0%) , C: 0.005% or less (excluding 0%), S: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), the balance including Fe and unavoidable impurities.

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

[Si: 1.5 to 4.0% by weight]

Silicon (Si) is a major element added to lower iron loss by increasing the resistivity of steel. If too little Si is added, the effect of improving high-frequency iron loss is insufficient, so increasing the Si content is advantageous in terms of iron loss. can do. Therefore, Si is preferably 1.5 to 4.0% by weight.

[Al: 0.1 to 2% by weight]

Aluminum (Al), along with Si, plays an important role in reducing iron loss by increasing the specific resistance of steel, and also improves rollability or improves workability during cold rolling. If too little Al is added, there is no effect on reducing high-frequency iron loss, and the precipitation temperature of AlN is lowered, so that fine nitride is formed and magnetism may be deteriorated. Conversely, if too much Al is added, nitride is excessively formed, deteriorating magnetism, and causing problems in all processes such as steelmaking and continuous casting, which can greatly reduce productivity. Therefore, Al is preferably 0.1 to 2% by weight.

[Mn: 0.05 to 2% by weight]

Manganese (Mn) is an element that reduces iron loss by increasing resistivity along with Si, Al, etc., forms sulfide, and improves texture. If too little Mn is added, sulfides may be finely precipitated to deteriorate magnetism. Conversely, if too much Mn is added, the formation of {111} texture, which is unfavorable to magnetism, may be promoted and the magnetic flux density may decrease. Therefore, considering this point, Mn is preferably 0.05 to 2% by weight.

[P: 0.1% by weight or less (excluding 0%)]

Phosphorus (P) not only serves to increase the specific resistance of the material, but also serves to increase the specific resistance and lower the iron loss by improving the texture by segregating at grain boundaries. However, if the added amount of P is too large, it may cause problems in production because it is segregated at the grain boundaries and the toughness of the steel may be deteriorated, thereby deteriorating productivity and punchability. Therefore, P is preferably 0.1% by weight or less.

[S: 0.005% by weight or less (excluding 0%)]

Sulfur (S) forms fine sulfides such as MnS or CuS inside the base material to suppress crystal grain growth and weaken iron loss, so it is preferable to add sulfur (S) as low as possible. In addition, S is an indispensable element in steel, and it is desirable to remove it if possible during refining in steelmaking. desirable.

[N: 0.005% by weight or less (excluding 0%)]

Nitrogen (N) combines with Al, Ti, etc. to form fine and long precipitates such as AlN, TiN, etc. inside the base material, and also combines with other impurities to form fine nitrides, suppressing crystal grain growth, and worsening iron loss. It is preferable to contain. Therefore, N is preferably limited to 0.005% by weight or less.

In addition to the above component elements, impurities that are unavoidably incorporated, such as carbon (C) or titanium (Ti), may be included. Since C causes self-aging, it is preferable to limit it to 0.005% or less, preferably 0.003% or less. In addition, since Ti and Nb promote the growth of the [111] texture, which is an undesirable crystal orientation in non-oriented electrical steel sheets, it is preferable to limit them to 0.004% or less, more preferably 0.002% or less.

The non-oriented electrical steel sheet according to an embodiment of the present invention may further include other unavoidably included elements in addition to the above components.

The unavoidable impurities refer to impurities that are intentionally introduced or unavoidably mixed during the manufacturing process of steelmaking and non-oriented electrical steel sheet. Since unavoidable impurities are widely known, detailed descriptions are omitted. In addition, in one embodiment of the present invention, the addition of elements other than the above-described alloy components is not excluded, and may be variously included within a range that does not impair the technical spirit of the present invention. When additional elements are included, they are included in place of Fe, which is the remainder.

Among the magnetic properties of the non-oriented electrical steel sheet according to an embodiment of the present invention, the average value of the magnetic flux density in the circumferential direction is as shown in [Equation 1] below.

[Formula 1]

B50, ring ≥ 1.88+0.1*t-0.067*(Si%)-0.0458*(Al%)-0.022*(Mn%)

(Where t is the thickness of the steel sheet, (Si%), (Al%), and (Mn%) mean the weight% of Si, Al, and Mn, respectively)

Among the magnetic properties of the non-oriented electrical steel sheet according to an embodiment of the present invention, the average value of iron loss in the circumferential direction is as shown in [Equation 2] below.

[Equation 2]

W10/400, ring ≤ 7.2+4000*t ² /(13+11*((Si%)+(Al%)+0.5*(Mn%)))

(Where t is the thickness of the steel sheet, (Si%), (Al%), and (Mn%) mean the weight% of Si, Al, and Mn, respectively)

In the non-oriented electrical steel sheet according to an embodiment of the present invention, thickness deviation in the width direction is as shown in [Equation 3] below.

[Formula 3]

ΔT (width direction thickness deviation) = (Tavg, center - Tavg,15)/Tavg,center

(Here, Tavg,center is the average thickness in the longitudinal direction of the center of the mocoil, and Tavg,15 is the average thickness in the longitudinal direction at 15mm from both sides of the mocoil.)

Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention will be described.

In the manufacturing method of a non-oriented electrical steel sheet according to an embodiment of the present invention, Si: 1.5 ~ 4%, Al: 0.1 ~ 2%, Mn: 0.05 ~ 2%, P: 0.1% or less (0% is excluding), C: 0.005% or less (excluding 0%), S: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), the balance being Fe and unavoidable impurities Preparing a slab comprising; heating the slab; Preparing a hot-rolled sheet by hot-rolling the slab; Cold-rolling the hot-rolled sheet to produce a cold-rolled sheet and final annealing the cold-rolled sheet.

Hereinafter, each step is described in detail.

In the method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention, it is preferable to use high-purity alloy elements in the steelmaking step in order to minimize pick-up of impurities. In the slab manufacturing step, a slab is manufactured by solidifying molten steel whose components are controlled in a continuous casting process.

In the next slab heating step, the prepared slab is charged into a heating furnace and heated at 1,100 ° C to 1,150 ° C. When heating the slab, it is necessary to heat at 1,150 ° C. or less because it is preferable to heat at a temperature as low as possible in order to prevent re-dissolution of precipitates. However, since the deformation resistance during hot rolling is excessively large at less than 1,100 ° C., it is difficult to roll to 2.0 mmt or less, so it is preferable to heat at 1,100 ° C. or more.

The slab is heated and then hot-rolled to produce a hot-rolled sheet. At this time, it is preferable to manufacture a hot plate as thin as possible in hot rolling. This is necessary to minimize the disadvantageous (111) recrystallized texture when the cold rolling reduction is high during subsequent cold rolling.

In order to make the thickness thinner in the hot rolling process, the hot rolling reduction ratio must be increased. As the thickness decreases, the temperature drop range also increases, so the deformation resistance also increases. Therefore, the required hot-rolling rolling reduction force may rapidly increase. Therefore, in the actual operation process, it is not easy to lower the thickness below 1.8 mmt, and even if the thickness is lowered, the thickness deviation in the width direction may increase due to the bending of the rolling roll.

Such manufacturing conditions in the hot-rolled sheet manufacturing process affect the thickness deviation of the steel sheet, so that when an end user manufactures a core for an iron core, a problem in that the shape is defective may occur.

In order to solve this problem, in one embodiment of the present invention, intermediate rolling is performed by reheating the hot-rolled sheet after hot rolling. In one embodiment of the present invention, intermediate rolling means performing additional rolling between processes after hot rolling and before cold rolling.

As such, by additionally performing intermediate rolling between the hot rolling and cold rolling processes, the rolling reduction in the subsequent cold rolling process is reduced and, as a result, the magnetism of the steel sheet is improved.

The reduction ratio of the intermediate rolling is preferably 20 to 50%. If the reduction ratio of the intermediate rolling is less than 20%, the effect of performing the intermediate rolling is not large, and on the contrary, if the reduction ratio is 50% or more, it is not easy to control the shape of the steel sheet, and as a result, the thickness deviation may rather increase.

In this way, as the rolling reduction ratio progresses in the range of 20 to 50% in the intermediate rolling process, there is an effect of correcting the shape of the hot-rolled sheet, thereby reducing the thickness deviation of the final steel sheet in the width direction.

The reheating temperature of the hot-rolled sheet during intermediate rolling is preferably 700 ° C to 1,000 ° C. If the intermediate rolling is carried out at less than 700 ° C., it is not easy to correct the thickness deviation in the width direction because a high rolling force is required. In addition, when the intermediate rolling is performed at less than 700 ° C., GOSS texture of the steel sheet is generated, so that the magnetic properties around 45 degrees from the rolling direction of the final product sheet are rapidly deteriorated, resulting in deterioration of magnetic properties in the circumferential direction.

On the contrary, when the intermediate rolling is performed at 1,000 ° C. or higher, the rigidity of the roll itself is weakened, and the bending of the rolling roll becomes severe, and furthermore, the ductility of the hot-rolled sheet itself is weakened, so it is not easy to control. Therefore, in this case, the thickness deviation in the width direction may rather increase. Therefore, it is preferable to perform intermediate rolling by heating the hot-rolled sheet at 700 ° C to 1,000 ° C during intermediate rolling.

When the hot-rolled sheet is reheated for such intermediate rolling, various heating methods such as a direct fire method, an energization method, and an induction heating method can be used to heat the hot-rolled sheet. In addition to the direct heating method for reheating the hot-rolled sheet for intermediate rolling, latent heat remaining during winding may be used by immediately heating the hot-rolled sheet immediately after performing hot rolling. Another hot-rolled sheet reheating method may be expected to save energy by performing intermediate rolling together with the hot-rolled sheet annealing by selectively arranging rolling rolls directly on the heating zone of the annealing furnace during subsequent hot-rolled sheet annealing after the hot-rolling process.

The next intermediately rolled hot-rolled sheet may optionally be annealed hot-rolled sheet. When performing the hot-rolled sheet annealing, the heating temperature is preferably 850 ~ 1,150 ℃. In this way, when the hot-rolled sheet is annealed, it is possible to suppress the generation of the (111) crystal orientation, which is disadvantageous to magnetism, in the recrystallization process after subsequent cold rolling. However, such hot-rolled sheet annealing may be omitted if the manufacturing cost needs to be considered first.

In one embodiment of the present invention, a preferred example of performing intermediate rolling together with annealing of the hot-rolled sheet by using latent heat of the coil immediately after winding the hot-rolled sheet after the hot-rolling will be described.

In this way, when intermediate rolling is performed together with hot rolled sheet annealing, the reduction ratio is reduced in the subsequent cold rolling process, and crystal grain growth is induced before cold rolling to secure better magnetism compared to steel sheets that do not perform this method. there is.

On the other hand, in the case of hot-rolled sheet annealing, if the hot-rolled sheet annealing temperature is less than 850 ℃, the structure does not grow or grows finely, and the effect of increasing the magnetic flux density is small. If the annealing temperature exceeds 1,150 ℃, the magnetic properties are rather deteriorated, Deformation may deteriorate rolling workability. Therefore, it is preferable to limit the hot-rolled sheet annealing to 850 ~ 1,150 ℃. A more preferable annealing temperature of the hot-rolled sheet is 950 to 1,150 ° C.

After the hot-rolled sheet is selectively annealed, the hot-rolled sheet is then pickled and cold-rolled to produce a cold-rolled sheet.

Cold rolling is preferably performed at a reduction ratio of 70 to 85%. As such, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet having a thickness of 0.15 mm to 0.30 mm. Since the cold-rolled sheet manufactured to such a thickness has excellent magnetic properties by reducing high-frequency iron loss, it is suitable for use as a non-oriented electrical steel sheet for HEV/EV, in which high-frequency iron loss characteristics are important.

Next, the cold-rolled cold-rolled sheet is subjected to final annealing. Final annealing is preferably in the range of 900 ~ 1,050 ℃. If the temperature of the final annealing is less than 900 ° C, recrystallization does not occur sufficiently, and conversely, if the temperature of the final annealing exceeds 1,050 ° C, the crystal grain size becomes too large and the high frequency iron loss may deteriorate. Therefore, the final annealing is preferably carried out at a temperature of 900 ~ 1,050 ℃, and the grain size of the final annealed steel sheet as described above may be in the range of 50 ~ 150 ㎛.

For the magnetic properties of the final annealed non-oriented electrical steel sheet, the texture of the steel sheet formed by the manufacturing process is important, but the composition of the steel sheet itself and the thickness of the steel sheet also affect the magnetic properties. Needs to be.

In addition, since electric motors used in HEV/EV are generally driven by forming a rotating magnetic field, magnetic properties in the circumferential direction are measured by processing specimens in a ring shape rather than measuring with an Epstein apparatus, which is a conventional magnetic measuring device. Doing so can more accurately predict the efficiency of the motor in the actual use environment.

Therefore, in one embodiment of the present invention, the magnetic properties of the steel sheet are arranged in consideration of the thickness of the steel sheet and the components of the steel sheet based on the magnetic properties in the circumferential direction.

[Equation 1] defining the magnetic flux density (B50, Tesla) in the circumferential direction and the high frequency iron loss (W10/400, W/kg) in the circumferential direction of the non-oriented electrical steel sheet manufactured according to an embodiment of the present invention The criterion of [Equation 2] is satisfied as follows.

[Equation 1]

B50, ring ≥ 1.88+0.1*t-0.067*(Si%)-0.0458*(Al%)-0.022*(Mn%)

[Equation 2]

W10/400, ring ≤ 7.2+4000*t ² /(13+11*((Si%)+(Al%)+0.5*(Mn%)))

(In [Equation 1] and [Equation 2], t is the thickness of the steel sheet, (Si%), (Al%), and (Mn%) mean the weight% of Si, Al, and Mn, respectively)

In addition, a ring-shaped specimen (outer diameter 100mmΦ, inner diameter 90mmΦ) was prepared to evaluate the magnetic flux density (B50, Tesla) in the circumferential direction and the high-frequency iron loss (W10/400, W/kg) in the circumferential direction, respectively, to evaluate the magnetic properties in the circumferential direction. Thus, the magnetic flux density and iron loss values were measured.

As described above, the non-oriented electrical steel sheet manufactured according to an embodiment of the present invention has a magnetic flux density (B50, Tesla) in the circumferential direction that is superior to the calculated value of [Equation 1], so it is manufactured by a process that does not follow an embodiment of the present invention. The magnetic flux density value in the circumferential direction is about 0.03T higher than that of one steel plate.

In addition, the non-oriented electrical steel sheet manufactured according to an embodiment of the present invention has high-frequency iron loss (W10/400, W/kg) characteristics in the circumferential direction superior to the calculated value of [Equation 2], so that one embodiment of the present invention is not followed. It is about 1W/kg lower than that of a steel plate manufactured by an unprocessed process.

In addition, in terms of thickness deviation in the width direction of the steel sheet, considering that a steel sheet manufactured by a process not according to an embodiment of the present invention has a thickness deviation of about 3%, the manufactured according to an embodiment of the present invention It can be seen that the thickness deviation of the cold-rolled steel sheet in the width direction of the non-oriented electrical steel sheet is less than 2%, and shape defects can be greatly improved.

In addition, since the non-oriented electrical steel sheet manufactured according to an embodiment of the present invention has a thickness variation of less than 2% in the width direction of the cold-rolled steel sheet, in the case of a steel sheet having a large deviation, a lot of trimming is required to cut the side surface. Since the steel sheet in the case does not have to consider such side cutting, the error rate is high, so productivity can be increased.

Therefore, the non-oriented electrical steel sheet manufactured according to an embodiment of the present invention has a thickness deviation of less than 2% in the width direction and is excellent in both magnetic flux density in the circumferential direction and high-frequency iron loss in the circumferential direction, driving an eco-friendly car rotating at high speed. It can be used as a material suitable for motors, etc.

Preferred examples and comparative examples of the present invention are described below. However, the following example is only a preferred embodiment of the present invention, but the present invention is not limited to the following example.

Example 1

A slab was cast with the ingredients in Table 1. The cast slab was heated at 1,150 °C and then hot-rolled at 2 to 2.3 mmt. (In Table 1, the calculated values of Equations 1 and 2 are exemplified when the thickness (t) of the steel plate is 0.25 mm.)

ingredient Si
(wt%) Al
(wt%) Mn
(wt%) P
(wt%) C
(wt%) S
(wt%) N
(wt%) [Equation 1]
B50(T) [Equation 2]
W10/400 (W/kg) A 3.2 0.7 0.4 0.05 0.003 0.002 0.0015 1.65 11.5 B 2.5 0.7 0.2 0.05 0.003 0.002 0.0015 1.70 12.3

Then, intermediate rolling was performed under the conditions as shown in Table 2 using the prepared hot-rolled sheet. Then, the hot-rolled sheet produced by performing intermediate rolling was subjected to hot-rolled sheet annealing at 1,100 ° C.

The hot-rolled sheet subjected to hot-rolled sheet annealing was pickled and then cold-rolled to prepare a cold-rolled sheet having a thickness of 0.20 to 0.30 mm. Then, the cold-rolled sheet was charged into a final annealing furnace, and final annealing was performed at 950° C. in an atmosphere of 20% hydrogen and 80% nitrogen for 1 minute.

Magnetism was analyzed for the manufactured steel sheet. The magnetic evaluation of the steel sheet was compared by measuring the RC average value (B50, tesla) and the average magnetic flux density circumferential value (B50, tesla). The average value of magnetic flux density RC was measured after cross-lamination of 32 sheets in the rolling direction and in the direction perpendicular to the rolling direction using an Epstein measuring instrument. After stacking, copper wire was wound around to measure the magnetism.

In addition, thickness deviation was measured for the manufactured steel sheet. Thickness deviation was calculated by measuring the thickness at a point 15 mm from the center of the coil and both sides of the width, and dividing the difference by the thickness of the center.

The above-described manufacturing process conditions, magnetic measurement values, and thickness deviation values are shown in Table 2 below.

ingredient Intermediate rolling conditions steel plate
thickness
(mm) steel plate
thickness deviation
(%) magnetic flux density
RCaverage B50 (T) magnetic flux density
Circumferential average B50 (T) iron loss
circumferential mean
W10/400
(W/kg) note panon
(℃) entrance
thickness
(mm) exit
thickness
(mm) reduction rate
(%) A 300 2.3 1.6 30 0.25 3.0 1.69 1.62 12.2 Comparative material 1 A 500 2.3 1.6 30 0.25 2.6 1.69 1.62 12.1 comparative material 2 A 650 2.3 1.6 30 0.25 2.3 1.69 1.62 12.0 comparative material 3 A 750 2.3 1.6 30 0.25 1.5 1.67 1.66 11.4 Invention 1 A 850 2.3 1.6 30 0.25 1.4 1.67 1.66 11.2 invention 2 A 930 2.3 1.7 26 0.25 1.4 1.67 1.66 11.1 Invention 3 A 950 2.3 1.6 30 0.25 1.6 1.67 1.66 11.0 Invention 4 A 950 2.3 1.3 43 0.25 1.7 1.68 1.67 10.9 invention 5 A 1050 2.3 1.6 30 0.25 2.3 1.67 1.66 10.8 comparative material 4 A 1040 2.3 1.0 57 0.25 3.0 1.68 1.67 10.7 comparative material 5 A 1020 2.3 1.9 17 0.25 2.2 1.66 1.64 11.7 comparative material 6 A 600 2.3 1.9 17 0.25 1.9 1.67 1.63 11.6 comparative material 7 A 600 2.3 1.3 43 0.25 1.8 1.67 1.63 11.6 comparative material 8 A 750 2.3 2.0 13 0.25 1.8 1.67 1.63 11.7 comparative material 9 A 750 2.3 1.7 26 0.25 1.7 1.67 1.66 11.3 invention 6 A 750 2.3 1.6 30 0.25 1.5 1.67 1.66 11.2 invention 7 A 750 2.3 1.4 39 0.25 1.5 1.68 1.66 11.0 invention 8 A 750 2.3 1.2 48 0.25 1.8 1.7 1.67 10.8 invention 9 A 750 2.3 1.0 57 0.25 2.5 1.71 1.68 10.7 comparative material 10 A 800 2 1.8 10 0.20 1.7 1.66 1.63 10.5 comparative material 11 A 800 2 1.3 35 0.20 1.5 1.68 1.65 9.8 Inventive 10 A 800 2 1.2 40 0.20 1.8 1.69 1.66 9.7 Invention 11 A 800 2 0.9 55 0.20 2.5 1.7 1.67 9.5 comparative material 12 B 650 2.3 1.6 30 0.27 2.3 1.74 1.69 13.3 comparative material 13 B 750 2.3 1.6 30 0.27 1.5 1.73 1.71 12.9 Invention 12 B 950 2.3 1.6 30 0.27 1.6 1.74 1.72 12.8 Invention 13 B 1050 2.3 1.6 30 0.27 2.3 1.75 1.73 12.7 comparative material 14 B 750 2.3 2.0 13 0.27 1.8 1.7 1.68 13.3 comparative material 15 B 750 2.3 1.6 30 0.27 1.5 1.73 1.71 12.6 Invention 14 B 750 2.3 1.2 48 0.27 1.8 1.73 1.71 11.4 Invention 15 B 750 2.3 1.0 57 0.27 2.5 1.74 1.72 11.0 comparative material 16 B 800 2.3 1.9 17 0.30 2.1 1.69 1.67 15.3 comparative material 17 B 800 2.3 1.8 22 0.30 1.5 1.73 1.71 14.2 invention 16 B 800 2.3 1.2 48 0.30 1.8 1.74 1.72 14.1 Invention 17 B 800 2.3 1.0 57 0.30 2.5 1.75 1.73 14.0 comparative material 18

As can be seen from Table 2, the inventive materials 1 to 17 had reheating temperatures in the range of 700 to 1,000 ° C during intermediate rolling, and the reduction ratio during intermediate rolling was controlled within the range of 20 to 50%. In the case of Inventive Materials 1 to 17 that were intermediately rolled under these conditions, the thickness deviation of the product plate was less than 2% of the product thickness. Therefore, in the case of the inventive material, since the thickness deviation is small, it is not necessary to consider side cutting when processing the core for an actual iron core, so the real rate is high, and productivity can be increased.

As can be seen from Table 2, in the case of Inventive Materials 1 to 17 intermediately rolled within the scope of the present invention, the circumferential magnetic flux density (B50, Tesla) was 1.65 Tesla or more, based on component A of the steel sheet in Table 1, Table 1 shows that component B of the steel sheet is 1.71 Tesla or more, indicating that the circumferential magnetic flux density value is superior to the calculated value of [Equation 1]. As such, according to Table 2, in the case of the intermediate rolled invention material within the actual range of the present invention, the circumferential magnetic flux density value is higher than the magnetic flux density expected from the components and thickness of the steel sheet by 0.03 Tesla or more, showing excellent effects.

In addition, as can be seen from Table 2, in the case of Inventive Materials 1 to 17 intermediately rolled within the range of the present invention, the circumferential high-frequency iron loss (W10/400, W/kg) was 11, based on the steel sheet component A in Table 1, It was lower than 5 W/kg (0.25 mmt standard), and even when viewed based on steel sheet component B in Table 1, it was lower than 13 W/kg (0.27 mmt standard), which was superior to the calculated value of [Equation 2]. These results showed an improvement of more than 1 W/kg compared to the iron loss expected from the components and thickness of the steel sheet, and thus satisfied the excellent circumferential iron loss value.

In contrast, Comparative Materials 1 to 3, 7, 8, and 13 in Table 2 showed poor circumferential magnetic properties when the intermediate rolling temperature was lower than 700 ° C, and Comparative Materials 4 to 6 and 14 had intermediate rolling temperatures lower than 1,000 ° C. It was high, and the thickness deviation was inferior to 2% or more. In the case of comparative materials 9, 11, 15, and 17, the rolling reduction ratio of intermediate rolling was lower than 20%, resulting in poor magnetism. In the case of comparative materials 10, 12, 16, and 18, the rolling reduction ratio of intermediate rolling was 50% or more It was high, so the magnetism was good, but the thickness deviation was 2% or more, which was bad.

The measured values of the magnetic properties according to the intermediate rolling conditions of the inventive material and the comparative material according to Table 2 above are shown in a graph in FIG. 1.

As can be seen in FIG. 1, according to the range of heating temperature and reduction ratio during intermediate rolling, there was an optimal circumferential magnetic flux density average value and iron loss average value, the intermediate rolling heating temperature was in the range of 700 ~ 1,000 ℃, and the intermediate rolling reduction ratio was When it was in the range of 20 to 50%, it can be seen that the circumferential magnetism and thickness variation exhibit excellent characteristics.

Example 2

In order to examine the effects of magnetism and thickness polarization by intermediate rolling according to the content of alloy elements in non-oriented electrical steel sheets, slabs with the components shown in Table 3 were prepared.

Slabs having different component contents of Si, Al, and Mn were heated at 1,130° C., and hot-rolled at 2.3 mmt to prepare hot-rolled sheets. Then, the coil on which the hot-rolled sheet was wound was reheated to 730 ° C using induction heating, and then intermediate rolling was performed to 1.6 mmt. Then, the intermediate rolled hot-rolled sheet was subjected to hot-rolled sheet annealing at 1,050 ° C.

The hot-rolled annealed hot-rolled sheet was pickled and cold-rolled to a thickness of 0.25 mm to prepare a cold-rolled sheet, and final annealing was performed on the cold-rolled sheet at 950° C. in an atmosphere of 20% hydrogen and 80% nitrogen for 1 minute.

For the non-oriented electrical steel sheet manufactured as described above, the thickness deviation of the steel sheet, the average value of magnetic flux density in the circumferential direction, and the average value of core loss were measured in the same manner as in Example 1, and the results are shown in Table 3.

Ingredients (wt%) steel plate
thickness deviation
(%) magnetic flux density
RCaverage B50 (T) magnetic flux density
circumferential mean
B50 (T) iron loss
circumferential mean
W10/400
(W/kg) note Si Al Mn 1.5 0.5 0.2 1.8 1.81 1.79 13.8 Invention 1 4.2 0.5 0.2 Panpadan during cold rolling Comparative material 1 3.2 0.05 0.2 1.8 1.71 1.69 15.3 comparative material 2 3.2 1.2 0.2 1.8 1.67 1.65 11 invention 2 3.2 1.8 0.2 1.8 1.65 1.63 10.6 Invention 3 3.2 2.2 0.2 1.7 1.81 1.61 11.5 comparative material 3 3.2 0.7 One 1.6 1.68 1.66 11 Invention 4 3.2 0.7 1.8 1.7 1.67 1.65 10.8 invention 5 3.2 0.7 2.5 1.9 1.66 1.63 11.5 comparative material 4

As can be seen in Table 3, inventive materials 1 to 5 have Si: 1.5 to 4% or less, Al: 0.1 to 2% or less, Mn: 2% or less, and the average value of the magnetic flux density in the circumferential direction is calculated by [Equation 1] It is higher than that of the steel sheet manufactured without following an embodiment of the present invention, and is improved by more than 0.03T, and the circumferential high-frequency iron loss value is lower than the calculated value of [Equation 2], compared to the steel sheet manufactured without following an embodiment of the present invention. It was improved by more than 1W/kg. In addition, inventive materials 1 to 5 have a thickness deviation of less than 2%, so they do not need to consider side cutting when processing them into cores for actual iron cores, so the error rate is high, so productivity can be increased.

On the other hand, in the case of Comparative Material 1, the Si content was 4.2%, so cracks occurred on the side during cold rolling, making it impossible to proceed with cold rolling. .

And in the case of Comparative Material 3, Al was 2.2% high, casting was not smooth during steelmaking, oxides were generated, and excessive magnetostriction occurred, resulting in a poor final high-frequency iron loss value. In addition, in the case of Comparative Material 4, despite the high Mn content, high-frequency iron loss was poor due to excessive magnetostriction.

The present invention is not limited to the above embodiments, but can be manufactured in a variety of different forms, and those skilled in the art to which the present invention pertains may 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, the embodiments described above should be understood as illustrative in all respects and not limiting.

Claims (10)

Si: 1.5 to 4%, Al: 0.1 to 2%, Mn: 0.05 to 2%, P: 0.1% or less, C: 0.005% or less, S: 0.005% or less, N: 0.005% or less, balance Fe and other unavoidably added impurities, and the average value of the magnetic flux density in the circumferential direction satisfies the following [Equation 1].
[Equation 1]
B50, ring ≥ 1.88+0.1*t-0.067*(Si%)-0.0458*(Al%)-0.022*(Mn%)
(Where t is the thickness of the steel sheet, (Si%), (Al%), and (Mn%) mean the weight% of Si, Al, and Mn, respectively) According to claim 1,
The steel sheet is a non-oriented electrical steel sheet in which the average value of iron loss in the circumferential direction satisfies the following [Equation 2].
[Formula 2]
W10/400, ring ≤ 7.2+4000*t ² /(13+11*((Si%)+(Al%)+0.5*(Mn%)))
(Where t is the thickness of the steel sheet, (Si%), (Al%), and (Mn%) mean the weight% of Si, Al, and Mn, respectively) According to claim 1,
The steel sheet is a non-oriented electrical steel sheet having a thickness deviation in the width direction satisfying the following [Equation 3].
[Formula 3]
ΔT (thickness deviation in width direction) = (Tavg, center - Tavg,15)/Tavg,center
(Here, Tavg,center is the average thickness in the longitudinal direction of the center of the mocoil, and Tavg,15 is the average thickness in the longitudinal direction at 15mm from both sides of the mocoil.) Si: 1.5 to 4%, Al: 0.1 to 2%, Mn: 0.05 to 2%, P: 0.1% or less, C: 0.005% or less, S: 0.005% or less, N: 0.005% or less, balance Fe and other unavoidably added impurities to prepare a slab;
heating the slab;
Preparing a hot-rolled sheet by hot-rolling the slab; and
Cold-rolling the hot-rolled sheet to produce a cold-rolled sheet,
Method for producing a non-oriented electrical steel sheet comprising the step of performing intermediate rolling by reheating the hot-rolled sheet in the range of 700 to 1,000 ° C. during or before the hot-rolled sheet annealing process after the hot rolling. According to claim 4,
The intermediate rolling step is a method of manufacturing a non-oriented electrical steel sheet for intermediate rolling with a rolling reduction of 20 to 50%. According to claim 4,
In the intermediate rolling step, the hot-rolled sheet is a method of manufacturing a non-oriented electrical steel sheet by reheating any one of a direct fire method, an energization method, and an induction heating method. In paragraph 4,
Heating the slab is a method of manufacturing a non-oriented electrical steel sheet by heating at 1,100 to 1,150 ° C. According to claim 4,
The cold rolling is a method for producing a non-orientable electrical steel sheet having a rolling reduction of 70 to 85%. According to any one of claims 4 to 8,
The intermediate-rolled hot-rolled sheet is a method of manufacturing a non-oriented electrical steel sheet further comprising the step of annealing the hot-rolled sheet at a temperature of 850 ~ 1,150 ℃. According to claim 9,
The non-directional manufacturing method further comprising the step of final annealing the cold-rolled steel sheet at 900 to 1,070 ° C.

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