KR20140060726A - Non-oriented electrical steel steet and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a non-oriented electrical steel sheet and a manufacturing method for the same, including: 2.5-3.5 wt% of Si, 0.5-1.5 wt% of Al, 0.05-0.8 wt% of Mn, 0.07 wt% or less (except 0 wt%) of P, 0.08 wt% or less (except 0 wt%) of Sn, 0.05 wt% or less (except 0 wt%) of Sb, 0.025 wt% or less (except 0 wt%) of Cu; and remaining amount of Fe and other unavoidable impurities. The non-oriented electrical steel sheet and a manufacturing method for the same also satisfy a composition formula, Cu < 0.03-0.35 * P.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet and a method of manufacturing the same, and more particularly, to a non-oriented electrical steel sheet having improved magnetic properties by a compositional relationship formula of copper and phosphorus and a method of manufacturing the same.

In recent years, technologies for converting existing internal combustion engine vehicles into hybrid vehicles (HEV) or electric vehicles (EVs) have been studied as measures for the shortage of fossil fuels and greenhouse gas reduction. Hybrid vehicles or electric vehicles, To an electric motor to reduce the consumption of gasoline or diesel fuel, which is a fuel for existing internal combustion engines, and to achieve better fuel economy.

The motors used in such automobiles require a large torque at low speeds or accelerations, and a high speed rotation at constant speeds and high speeds. Therefore, the nonoriented electric steel sheet, which is a motor iron core material, should have a large magnetic flux density characteristic at low speed rotation and a low iron loss at high speed. In general, high-frequency iron loss means iron loss at a frequency of 200 Hz or more, _but the value of W _10/400 is usually used for non-oriented electrical steel sheets for automobiles.

In order to improve the high-frequency iron loss, the alloy elements such as Si, Al, and Mn, which are the resistivity elements of the electric steel sheet, should be raised, impurities should be reduced, and grain growth should be improved.

However, in order to do so, it is necessary that the inclusions and precipitates should not be present in every manufacturing process of the electric steel sheet. Particularly, in the steelmaking step, the impurities must be controlled so as not to generate fine impurities at extremely low levels. It is necessary to positively prevent dissolution and fine precipitation.

It is observed that MnS, CuS, and AlN, which are well-known inclusions in a general nonoriented electric steel sheet, have a fine average size of about 50 nm, and the minute inclusions thus generated hinder the growth of crystal grains during annealing to increase hysteresis loss However, it impedes the movement of the magnetic domain wall during magnetization and reduces the permeability.

In recent years, in non-oriented electrical steel sheets, P is segregated at grain boundaries to increase the fraction of cube-fibers favorable to magnetism and to improve magnetic properties. However, when the amount of P added increases, the material is not only hardened but also exists in the form of Cu ₃ P in combination with Cu.

It is generally understood that Cu exists alone to form a fine dispersed phase or to form CuS inclusions by binding with S, and they are understood to cause magnetic dislocation. Thus, There was little. Japanese Unexamined Patent Application, First Publication No. 2002-297862 is a technique for improving the magnetism by controlling the size and distribution density of CuS, and Japanese Unexamined Patent Publication (Kokai) No. 2004-135675 attempts to improve the magnetic property by controlling the number and distribution density of inclusions present in the steel sheet.

That is, since the prior arts have only a simple inclusion or control technique for CuS, the relationship between Cu and Cu, which are closely related to P, has not been clarified.

In order to solve the above problems, the present invention provides a non-oriented electrical steel sheet having excellent magnetic properties by controlling the relationship between P and Cu in an electrical steel sheet containing P and segregated segregated elements to improve grain growth and a manufacturing method thereof.

In one or more embodiments of the present invention, it is preferable that the steel sheet contains 2.5 to 3.5% of Si, 0.5 to 1.5% of Al, 0.05 to 0.8% of Mn, 0.07% or less of P (exclusive of 0% (Excluding 0%), Sb: not more than 0.05% (excluding 0%), Cu: not more than 0.025% (excluding 0%) and the balance Fe and other inevitably added impurities, A non-oriented electrical steel sheet satisfying -0.35 * P can be provided.

(Excluding 0%), Pb: 0.07% or less (excluding 0%), Sn: 0.08% or less (excluding 0%), Sb : 0.05% or less (excluding 0%), Cu: 0.025% or less (excluding 0%), and the balance Fe and other inevitably added impurities, and satisfies the compositional relation Cu <0.03-0.35 * ; Heating the slab at a temperature ranging from 1,100 to 1,250 ° C; Hot rolling the slab to produce a hot rolled sheet; Annealing the hot-rolled sheet in the temperature range of 850 to 1,150 캜, omitting the hot-rolled sheet, and pickling the hot-rolled sheet; Cold rolling the hot rolled sheet twice or twice including intermediate annealing to produce a cold rolled sheet; And finally annealing the cold-rolled steel sheet.

And the final annealing is performed in a temperature range of 750 to 1,100 ° C.

The inevitably added impurities may include C, S, N, and Ti, and the content thereof is 0.004 wt% or less.

And the fine Cu dispersed phase or Cu ₃ P inclusion in the electric steel sheet has a diameter of less than 5 nm.

(W _10/400 ) of 14.5 W / kg or less and a magnetic flux density (B ₅₀ ) of _1.67 T or more based on a steel sheet thickness of 0.30 mm.

According to the embodiment of the present invention, the magnetic properties can be improved by effectively controlling the Cu inclusions and precipitates which adversely affect the magnetism in the P-added steel to facilitate the crystal grain growth and the magnetic domain movement in the electric steel sheet.

1 is a graph showing the compositional relationship between Cu and P in an electrical steel sheet according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims.

In the steel according to the embodiment of the present invention, not only Si, Al, and Mn, but also the amount of P, which is the calcite source, and Cu, which is an impurity, were added. That is, the electrical steel sheet according to the present invention comprises 2.5 to 3.5% of Si, 0.5 to 1.5% of Al, 0.05 to 0.8% of Mn, 0.07% or less of P (excluding 0%), , Cu: not more than 0.08% (excluding 0%), Sb: not more than 0.05% (excluding 0%), Cu: not more than 0.025% (excluding 0%) and the balance Fe and other inevitably added impurities, <0.03-0.35 * P The composition formula is satisfied.

In addition to the above impurity elements, inevitably incorporated impurities such as C, S, N and Ti may be included.

First, the reason why the range of the constituent elements constituting the electrical steel sheet according to the embodiment of the present invention and the addition ratio between the constituent elements are limited will be described. Unless otherwise stated, the unit of component content is weight percent.

Si: 2.5 to 3.5 wt%

When Si is added in an amount of less than 2.5%, the effect of improving the high-frequency iron loss is insufficient. When the Si content exceeds 3.5%, the hardness of the material increases, The content of Si in the embodiment according to the present invention is limited to the above range.

Al: 0.5 to 1.5 wt%

Al increases the resistivity of the material and lowers the iron loss and forms nitride. When Al is added in an amount less than 0.5%, there is no effect on reduction of high-frequency iron loss, and nitride is formed finely to deteriorate magnetism. When Al is added in excess of 1.5%, problems occur in all processes such as steelmaking and continuous casting, The content of Al in the examples according to the present invention is limited to the above range.

Mn: 0.05 to 0.8 wt%

Mn enhances the resistivity of the material to improve the iron loss and form sulphide. When the Mn content is less than 0.05%, MnS is precipitated finely and deteriorates the magnetism. If Mn is added in excess of 0.8%, the formation of [111] texture unfavorable to magnetism is promoted and the magnetic flux density is reduced, so that the content of Mn in the examples according to the present invention is limited to the above range.

Sn: 0.08 wt% or less (excluding 0%)

Sn is a special element that is added to the surface of the steel sheet and segregates on the surface of the steel sheet and suppresses surface oxidation during annealing and improves the texture of the steel sheet. However, if added in excess of 0.08%, the grain is segregated to deteriorate toughness, The productivity is deteriorated, so the content of Sn in the examples according to the present invention is limited to the above range.

Sb: 0.05% by weight or less (excluding 0%)

Sb segregates on the surface and grain boundaries of the steel sheet and suppresses surface oxidation during annealing and improves the texture. Therefore, when Sb is added in an amount exceeding 0.05%, Sb tends to deteriorate toughness of the material The productivity is lowered as compared with the magnetic improvement. Therefore, the content of Sb in the examples according to the present invention is limited to the above range.

P: 0.07% by weight or less (excluding 0%)

P is dissolved in the steel or segregated in the grain boundaries to improve the magnetic property. However, when the content of P increases to exceed 0.07%, Cu is combined with Cu to form Cu ₃ P, thereby iron loss is lowered in the embodiment of the present invention Is limited to the above range.

Cu: 0.025 wt% or less (excluding 0%)

Cu is required to be controlled to 0.025% or less since it forms a fine dispersed phase by itself or forms fine inclusions by binding with an additive element in the steel, thereby interfering with grain growth potential and magnetic domain movements. Particularly, it forms Cu ₃ P by bonding with P, which is an additive element in steel, so that the compositional relation of Cu <0.03-0.35 * P must be satisfied. If the content of Cu is larger than that of the compositional formula, a fine dispersed phase or Cu ₃ P is formed to dislocate the magnetism.

In addition to the above impurity elements, the electrical steel sheet according to the embodiment of the present invention may contain inevitably impurities such as C, S, N and Ti, C causes self-aging, and S and N are sulfides and nitrides And promotes the growth of [111] texture, which is an undesirable crystal orientation in the non-oriented electrical steel sheet, and these components are limited to 0.004% or less, respectively. And more preferably 0.003% or less.

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

First, in terms of% by weight, Si: 2.5 to 3.5%, Al: 0.5 to 1.5%, Mn: 0.05 to 0.8%, P: 0.07% or less (excluding 0%), Sn: 0.08% : 0.05% or less (excluding 0%), Cu: 0.025% or less (excluding 0%), and the balance Fe and other inevitably added impurities, and satisfies the compositional relation Cu <0.03-0.35 * And the slab is heated to a temperature of 1,100 to 1,250 DEG C, followed by hot rolling while hot rolling is performed at 800 DEG C or higher.

The hot-rolled hot-rolled steel sheet is annealed at a temperature in the range of 850 to 1,150 占 폚, or omitting the hot-rolled sheet, pickled, cold rolled at a reduction ratio of 70 to 95% The cold-rolled cold-rolled sheet is finally annealed in the temperature range of 750 to 1,100 ° C to produce a non-oriented electrical steel sheet.

In the steelmaking step of the embodiment according to the present invention, it is preferable to use one having a high purity of the alloy element in order to minimize the content of impurities. The molten steel thus controlled is solidified in a continuous casting process to produce a slab.

When the slab is heated to a temperature exceeding 1,250 DEG C, the inclusions which deteriorate the magnetic properties are re-dissolved and the fine slab is precipitated after hot rolling. The slab is heated at a temperature of 1,250 ° C or less.

After the slab is reheated, hot rolling is performed, and hot rolling at the time of hot rolling is performed at a temperature of 800 캜 or higher.

At this time, the hot-rolled hot-rolled sheet can increase the crystal orientation favorable to magnetism by annealing the hot-rolled sheet at a temperature of 850 to 1,150 ° C. If the annealing temperature of the hot-rolled sheet is less than 850 ° C, the structure does not grow or grows finely and the effect of increasing the magnetic flux density is small. If the annealing temperature of the hot-rolled sheet exceeds 1,150 ° C, the magnetic properties deteriorate rather. The rolling workability may be deteriorated. Therefore, the annealing temperature range of the hot-rolled sheet in the embodiment according to the present invention is limited to 850 to 1,150 ° C. More preferably, the annealing temperature of the hot-rolled sheet is 950 to 1,150 ° C.

The hot rolled steel sheet is pickled and then cold rolled twice, including once or intermediate annealing, to form a predetermined thickness. The electric steel sheet used for hybrid automatic teeth or electric automobiles has a thickness of 0.35 mm to 0.2 mm.

If the final annealing temperature is less than 750 캜, recrystallization does not sufficiently occur. If the final annealing temperature exceeds 1,150 캜, the crystal grain diameter becomes too large to cause high-frequency iron loss, The final annealing temperature in the examples according to the present invention is limited to the above range. However, the final annealing is carried out at a temperature of 900 to 1,150 DEG C so that the grain diameter becomes 50 to 150 mu m.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Were vacuum-melted in a laboratory to produce ingots having the compositions shown in Table 1 below. All the impurities C, S, N and Ti of the material were controlled to 0.003% or less. Each material was heated to 1,150 캜 and hot-rolled at 850 캜 to produce a hot-rolled sheet having a thickness of 2.0 mm. The hot-rolled hot-rolled sheet was annealed at 1,100 ° C for 4 minutes and pickled. Thereafter, the sheet was cold-rolled to a thickness of 0.30 mm, and final annealing was performed at the respective temperatures shown in the table for 38 seconds. The cold rolling dullness due to the addition of Sn, Sb and the like is represented by O and X in Table 2, and X represents a steel type in which plate fracture occurred during cold rolling. The magnetic properties were determined by an average value in the rolling direction and the vertical direction using a single sheet tester and are shown in Table 2 below.

Steel grade Si Al Mn Sn Sb C S N Ti A1 2.5 1.5 0.8 0.01 - 0.0023 0.0015 0.0021 0.0015 A2 2.5 1.5 0.8 0.03 0.02 0.0019 0.0012 0.0015 0.0021 A3 2.5 1.5 0.5 0.03 0.04 0.0025 0.0013 0.0019 0.0012 A4 2.5 1.5 0.2 0.07 0.06 0.0022 0.0016 0.0017 0.0015 A5 2.5 1.5 0.05 0.10 0.03 0.0023 0.0019 0.0015 0.0019 B1 3.0 1.0 0.8 - - 0.0015 0.0016 0.0022 0.0017 B2 3.0 1.0 0.8 0.03 0.04 0.0017 0.0012 0.0016 0.0015 B3 3.0 1.0 0.5 0.03 0.05 0.0016 0.0012 0.0015 0.001 B4 3.0 1.0 0.2 0.05 0.07 0.0024 0.0016 0.0021 0.0012 B5 3.0 1.0 0.05 0.05 0.03 0.0025 0.0019 0.0019 0.0019 B6 3.0 1.0 0.2 0.09 - 0.0017 0.0017 0.0015 0.0016 B7 3.0 1.0 0.2 0.05 - 0.0023 0.0012 0.0017 0.0022 B8 3.0 1.0 0.2 0.05 - 0.0016 0.0019 0.001 0.0015 B9 3.0 1.0 0.2 - 0.025 0.0023 0.0016 0.0016 0.0012 C1 3.0 1.0 0.2 - 0.035 0.0017 0.0017 0.0015 0.0019 C2 3.5 0.5 0.8 - 0.02 0.0016 0.0017 0.0022 0.0016 C3 3.5 0.5 0.8 - - 0.0023 0.0019 0.0021 0.0015 C4 3.5 0.5 0.5 0.03 0.02 0.0017 0.001 0.0012 0.0016

Steel grade P Cu Cu < 0.03-0.35P Cold rolling property Final annealing temperature
(° C) Grain size
(mm) Iron loss
(W10 / 400, W / kg) Magnetic flux density
(B50, T) Remarks A1 0.01 0.027 0.027 O 960 32 15.8 1.64 Comparative Example A2 0.015 0.020 0.025 O 960 75 14.0 1.67 Honor A3 0.015 0.010 0.025 O 950 85 13.7 1.67 Honor A4 0.02 0.026 0.023 O 950 45 15.8 1.63 Comparative Example A5 0.01 0.010 0.027 X 950 75 - - Comparative Example B1 0.025 0.022 0.021 O 970 50 15.9 1.63 Comparative Example B2 0.025 0.015 0.021 O 970 80 14.3 1.67 Honor B3 0.03 0.007 0.020 O 970 90 13.5 1.68 Honor B4 0.01 0.010 0.027 X 970 70 - - Comparative Example B5 0.04 0.020 0.016 O 970 55 15.9 1.64 Comparative Example B6 0.01 0.010 0.027 X 970 72 - - Comparative Example B7 0.04 0.010 0.016 O 980 95 13.9 1.67 Honor B8 0.05 0.015 0.013 O 980 60 15.9 1.64 Comparative Example B9 0.05 0.005 0.013 O 980 88 13.4 1.67 Honor C1 0.06 0.020 0.009 O 990 55 15.5 1.63 Comparative Example C2 0.06 0.010 0.009 O 990 58 15.2 1.64 Comparative Example C3 0.06 0.005 0.009 O 990 89 13.2 1.66 Honor C4 0.075 0.005 0.004 X 990 80 - - Comparative Example

In the case of A2, A3, B2, B3, B7, B9 and C3 which belong to the range of the present invention, inclusions observed by a transmission electron microscope show that the diameter is less than 5 nm and the crystal growth hardness is good and the magnetic property of the non- . On the contrary, in the case of the steel which is out of the scope of the present invention, a fine Cu dispersed phase or Cu ₃ P having a size of 5 nm to 15 nm was observed, and these had an adverse effect on the crystal grain growth property and the crystal grain diameter was mostly less than 65 μm at each annealing temperature.

FIG. 1 is a graph showing the relationship between the composition of Cu and P according to the embodiment of the present invention. Referring to FIG. 1, the portion below the bold line is a part belonging to the present invention.

As described above, the non-oriented electrical steel sheet produced according to the present invention has an iron loss (W _10/400 ) of 14.5 W / kg or less and a magnetic flux density (B ₅₀ ) of 1.67 T or more based on a steel sheet thickness of 0.30 mm .

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (9)

(Excluding 0%), Sn: not more than 0.08% (excluding 0%), Sb: 0.05% or less, Si: 2.5 to 3.5%, Al: 0.5 to 1.5% (Excluding 0%), Cu: not more than 0.025% (excluding 0%), the balance Fe and other inevitably added impurities, and satisfying the compositional relation Cu <0.03-0.35 * P Steel plate. The method according to claim 1,
Wherein the inevitably added impurities may include C, S, N, and Ti, and the content thereof is 0.004 wt% or less, respectively. 3. The method according to claim 1 or 2,
Wherein the fine Cu dispersed phase or Cu ₃ P inclusions in the electrical steel sheet have a diameter of less than 5 nm. 3. The method according to claim 1 or 2,
(W _10/400 ) of not more than 14.5 W / kg and a magnetic flux density (B ₅₀ ) of not less than 1.67 _T based on a steel sheet thickness of 0.30 mm. (Excluding 0%), Sn: not more than 0.08% (excluding 0%), Sb: 0.05% or less, Si: 2.5 to 3.5%, Al: 0.5 to 1.5% (Excluding 0%), Cu: not more than 0.025% (excluding 0%), the balance Fe and other inevitably added impurities, and satisfying the compositional relation Cu <0.03-0.35 * P ;
Heating the slab at a temperature ranging from 1,100 to 1,250 ° C;
Hot rolling the slab to produce a hot rolled sheet;
Annealing the hot-rolled sheet in the temperature range of 850 to 1,150 캜, omitting the hot-rolled sheet, and pickling the hot-rolled sheet;
Cold rolling the hot rolled sheet twice or twice including intermediate annealing to produce a cold rolled sheet; And
And finally annealing the cold rolled steel sheet. 6. The method of claim 5,
Wherein the final annealing is performed in a temperature range of 750 to 1,100 ° C. The method according to claim 5 or 6,
Wherein the inevitably added impurities may include C, S, N, and Ti, and the content thereof is 0.004 wt% or less. 8. The method of claim 7,
Wherein the fine Cu dispersed phase or Cu ₃ P inclusions in the electrical steel sheet have a diameter of less than 5 nm. 9. The method of claim 8,
(W _10/400 ) of not more than 14.5 W / kg and a magnetic flux density (B ₅₀ ) of not less than 1.67 _T based on a steel sheet thickness of 0.30 mm.

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