KR101677447B1 - Non-orientied electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

A method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes: preparing a hot rolled steel sheet by heating a slab and hot rolling; Cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; And finally annealing the cold-rolled sheet at an annealing temperature of 650 ° C to 850 ° C, wherein the cold-rolled sheet is manufactured by cold rolling once at a reduction ratio of 55% to 80% A cold rolled sheet may be produced or subjected to cold rolling at least twice, and intermediate annealing may be performed at least twice between cold rolling at least two times, and the reduction ratio of the last cold rolling may be 55% to 80%.

Description

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

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

The non-oriented electrical steel sheet is mainly used in equipment that converts electrical energy into mechanical energy, and it requires excellent magnetic properties in order to achieve high efficiency in the process. The iron loss and the magnetic flux density are the magnetic properties. The lower the iron loss, the lower the energy loss in the energy conversion process. If the magnetic flux density is high, the larger electric power can be produced by the same electric energy. Is low and the magnetic flux density is high, the energy efficiency of the motor can be increased. In particular, the driving motor of an environmentally-friendly automobile, which has recently been attracting attention, needs to continuously develop a non-directional electric steel sheet having high magnetic flux density and low iron loss at high frequency while minimizing energy loss during high- .

An embodiment of the present invention is to provide a non-oriented electrical steel sheet.

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

The non-oriented electrical steel sheet according to one embodiment of the present invention includes crystal grains having an L / T value of 4 or more, where L is the length of the grain in the rolling direction of the steel sheet and T is the length in the thickness direction of the grain .

Also, the electrical steel sheet may contain 0.02% to 0.25% of Sn, Sb, P, or a combination thereof with respect to 100% by weight of the entire steel sheet, and the balance may include Fe and other unavoidable impurities.

The electrical steel sheet may further include 2.5% to 4.0% of Si, 0.3% to 1.5% of Al, and 1.0% or less of Mn (not including 0%).

The thickness of the electrical steel sheet may be 0.30 mm or less.

A method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes: preparing a hot rolled steel sheet by heating a slab and hot rolling; Cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; And finally annealing the cold-rolled sheet at an annealing temperature of 650 ° C to 850 ° C, wherein the cold-rolled sheet is manufactured by cold rolling once at a reduction ratio of 55% to 80% A cold rolled steel sheet is produced or subjected to two or more cold rolling steps, wherein at least one intermediate annealing is carried out between two or more cold rolling steps, and the rolling reduction ratio of the last cold rolling is 55% to 80% Manufacturing method: Here, the reduction rate is (thickness of steel sheet before cold rolling - thickness of steel sheet after cold rolling) / (thickness of steel sheet before cold rolling).

The slab may comprise 0.02% to 0.25% Sn, Sb, P, or a combination thereof, based on 100% by weight of the total slab composition, and the remainder may include Fe and other unavoidable impurities.

The slab may further comprise 2.5% to 4.0% of Si, 0.3% to 1.5% of Al, and 1.0% or less of Mn (not including 0%).

The method may further include a step of annealing the hot-rolled steel sheet after the step of hot-rolling the slab to produce a hot-rolled steel sheet.

In the intermediate annealing step, the annealing temperature may be 850 ° C to 1100 ° C.

The size of the grain of the steel sheet after completion of the annealing of the cold rolled sheet may be 50 탆 to 150 탆.

According to an embodiment of the present invention, a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss can be provided.

1 is a cross-sectional view of a non-oriented electrical steel sheet produced 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 be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with 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. Like reference numerals refer to like elements throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

Unless otherwise stated,% means weight%.

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

First, slabs are provided. The slab may comprise 0.02% to 0.25% of Sn, Sb, P, or a combination thereof, based on 100% by weight of the total slab composition, and the remainder may include Fe and other unavoidable impurities. The slab may further comprise 2.5% to 4.0% of Si, 0.3% to 1.5% of Al, and 1.0% or less of Mn (not including 0%).

The reason for limiting the components of the slab will be described.

When Si is added in an amount of less than 2.5%, the effect of improving iron loss is insufficient, and when added in an amount exceeding 4%, the brittleness of the material may be increased.

Al increases the resistivity of the material to lower the iron loss, but forms an in-situ nitride. When Al is added in an amount of less than 0.3%, the effect of reducing iron loss is insufficient and nitride is formed finely to deteriorate the magnetic property. When Al is added in an amount exceeding 1.5%, saturation magnetic flux density can be decreased.

Mn improves the specific resistance of the material to improve the iron loss, but if it is added in excess of 1.0%, the saturation magnetic flux density decreases and MnS and the like precipitate and the iron loss can be deteriorated.

Sn, Sb, and P are segregated on the surface and grain boundaries to inhibit surface oxidation during annealing and prevent the diffusion of elements through the grain boundaries, thereby preventing the growth of texture unfavorable to magnetism. Sn, Sb and P may be added singly or two or more of them may be added in combination. If it is less than 0.02%, the aggregate structure unfavorable to magnetism can be grown, and if it exceeds 0.25%, the iron loss can be deteriorated due to an increase in segregation amount.

In addition to the above elements, elements such as C, S, N, Ti, and Nb may be included.

C may be 0.004% or less, more specifically 0.003% or less, because it causes self-aging when carbides are formed to deteriorate magnetic properties and used as a final product.

S is an element that forms sulfides such as MnS and CuS to worsen iron loss, so it may be 0.004% or less, more specifically 0.002% or less.

N is an element which forms a nitride which bonds with Al, Ti or the like to deteriorate iron loss, so it may be 0.004% or less, more specifically 0.002% or less.

Ti and Nb form carbides or nitrides and develop an aggregate structure unfavorable to magnetism, so that each content can be 0.004% or less, more specifically 0.002% or less.

The slab of the substrate is heated. The heating temperature of the slab may be between 1100 ° C and 1200 ° C. When the temperature exceeds 1200 ° C, the precipitate is re-dissolved and can be finely precipitated after hot rolling. If it is less than 1100 ° C, hot rolling may become impossible.

When the slab heating is completed, hot rolling is performed to produce a hot rolled sheet.

The hot-rolled sheet can be subjected to hot-rolled sheet annealing if necessary. When the hot-rolled sheet annealing is carried out, the annealing temperature may be 850 to 1150 ° C. If the temperature is less than 850 DEG C, the structure does not grow or grows finely and the synergistic effect of the magnetic flux density is small. If the annealing temperature exceeds 1150 DEG C, the magnetic properties are rather deteriorated and deformation of the plate shape may occur. More specifically, 950 캜 to 1150 캜.

Thereafter, cold rolling is performed to produce a cold rolled steel sheet.

The cold rolled sheet is manufactured by cold rolling one time at a reduction ratio of 55% to 80% to produce a cold rolled sheet having a final thickness or performing cold rolling twice or more, And the rolling reduction of the last cold rolling may be 55% to 80%.

Here, the reduction rate is (thickness of steel sheet before cold rolling-thickness of steel sheet after cold rolling) / (thickness of steel sheet before cold rolling). As a result of experiments conducted by the present inventors, crystal grains having an L / T value of 4 or more were produced when the reduction ratio of the last cold rolling satisfies the above range. Here, the length in the rolling direction of the crystal grains in the electrical steel sheet is denoted by L, and the length in the thickness direction is denoted by T.

The annealing temperature during the intermediate annealing may be 850 ° C to 1100 ° C. If the temperature is less than 850 DEG C, recrystallization is not sufficiently generated. If the annealing temperature of the recrystallization exceeds 1100 DEG C, the crystal grain diameter becomes too large, which may cause plate breakage and plate breakage during subsequent cold rolling.

In addition, the annealing temperature and the annealing time can be adjusted in the intermediate annealing so that the size of the crystal grains is adjusted to be 50 to 150 mu m. When the thickness is less than 50 탆, the crystal grains do not grow sufficiently and the magnetic properties deteriorate. When the thickness exceeds 150 탆, the plate defects and the subsequent cold rolling may cause sheet breakage.

The steel sheet is rolled to a thickness of 0.30 mm or less by cold rolling. If the thickness exceeds 0.30 mm, the iron loss in the high frequency region may increase. The thickness may be greater than 0 and less than or equal to 0.30 mm.

Finally, the steel sheet is finally annealed. The annealing temperature at the final annealing may be 650 ° C to 850 ° C. When the annealing temperature exceeds 850 ° C, recrystallization and crystal grain growth occur in the whole deformed structure, so that the high frequency iron loss is damped. At a temperature of 650 ° C or lower, the strain stress is not sufficiently relaxed and the iron loss can be dulled.

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

The non-oriented electrical steel sheet according to an embodiment of the present invention may include crystal grains having an L / T value of 4 or more, where L denotes the length of the grain in the rolling direction of the steel sheet, and T denotes the length in the thickness direction of the grain.

1 is a cross-sectional view of a non-oriented electrical steel sheet produced according to an embodiment of the present invention.

As a result of the inventors' experiments, the non-oriented electrical steel sheet produced according to one embodiment of the present invention has a value of L / T when the length of the grain in the rolling direction is L and the length of the grain in the thickness direction is T, 4 or more. When such elongation grains were included, the fraction of crystal grains in {111} orientation unfavorable to magnetism was lowered and the magnetic flux density and iron loss were improved.

In addition, the electrical steel sheet preferably contains 2.5 to 4.0% of Si, 0.3 to 1.5% of Al, and 1.0% or less of Mn (not including 0%) and Sn, Sb, P, Or a combination thereof in an amount of 0.02% to 0.25%, and the remainder may contain Fe and other unavoidable impurities. The reason for limiting the components in the electric steel sheet is the same as the reason for limiting the components in the slab.

The thickness of the electrical steel sheet may be 0.30 mm or less. The thickness is described above.

Further, the volume fraction of the {111} orientation parallel to the plate surface of the steel sheet within 15 DEG of the above-described steel sheet was 20% or less. This is because the fraction of the {111} orientation decreases because the elongation grains containing L / T value of 4 or more are included.

Here, the plate surface of the steel plate means the xy plane when the rolling direction of the steel plate is the x axis, the width direction is the y axis, and the thickness direction is the z axis.

Hereinafter, the embodiment will be described in detail. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

[Example 1]

≪ Production of hot rolled sheet &

Slabs of the same composition as in Table 1 were prepared. The slab at room temperature was heated to 1150 占 폚 and hot rolled at 870 占 폚 to produce a hot rolled steel sheet having a thickness of 2.0 mm.

≪ Hot-rolled sheet annealing &

The hot-rolled sheet was heated to 1100 占 폚, annealed for 110 seconds, and cooled to room temperature.

<Production of cold rolled sheet>

Thereafter, the steel sheet was subjected to primary cold rolling to a thickness of 0.5 mm, followed by heating from room temperature to 1050 ° C and then intermediate annealing for 45 seconds. Thereafter, the cold rolled steel sheet was subjected to secondary cold rolling to produce a cold rolled steel sheet having a thickness of 0.15 mm.

&Lt; Final annealing &

The cold-rolled sheet was heated from room temperature to 800 占 폚, and final annealing was performed for 35 seconds.

Steel grade Si
(%) Al
(%) Mn
(%) Sn
(%) Sb
(%) P
(%) S
(ppm) C
(ppm) N
(ppm) Ti
(ppm) Nb
(ppm) A1 3.40 0.85 0.4 0.035 0.035 0.002 12 17 17 17 14 A2 3.40 0.85 0.4 0.015 0.000 0.001 17 21 12 14 13 A3 3.40 0.85 0.4 0.000 0.010 0.001 20 11 18 19 12 A4 3.40 0.85 0.4 0.080 0.050 0.152 19 17 14 15 22 A5 3.40 0.85 0.4 0.085 0.040 0.034 12 12 21 20 17 B1 3.30 0.90 0.3 0.005 0.005 0.002 11 12 19 22 19 B2 3.30 0.90 0.3 0.030 0.050 0.031 20 22 21 14 22 B3 3.30 0.90 0.3 0.050 0.050 0.057 12 11 11 13 12 B4 3.30 0.90 0.3 0.150 0.080 0.082 18 21 21 15 14 B5 3.30 0.90 0.3 0.080 0.065 0.057 14 14 17 17 19

Steel grade [Sn] + [Sb] + [P]
(%) B50
(T) W10 / 800
(W / kg) {111} // ND
Bearing fraction
(%) Cold rolling
Plate break Stretching
Crystal grain Remarks A1 0.072 1.66 21.3 13 Not occurring include Honor A2 0.016 1.63 24.9 21 Not occurring Without Comparative Example A3 0.011 1.64 25.1 23 Not occurring Without Comparative Example A4 0.282 - - - Occur . Comparative Example A5 0.159 1.67 22.7 11 Not occurring include Honor B1 0.012 1.64 25.9 24 Not occurring Without Comparative Example B2 0.111 1.66 22.9 12 Not occurring include Honor B3 0.157 1.67 22.8 9 Not occurring include Honor B4 0.312 - - - Occur . Comparative Example B5 0.202 1.67 22.1 11 Not occurring include Honor

In Table 1 and Table 2, 1 ppm is 0.0001% by weight.

In Table 1 and Table 2,% is wt%. Also, the {111} // ND bearing fraction means the volume fraction of the {111} orientation parallel to the plate surface of the steel sheet within 15 ° of the steel sheet. The term &quot; stretched crystal grains &quot; means a grain having a value of L / T of not less than 4, where L is the length of the grain in the rolling direction and T is the length in the thickness direction of the grain.

Referring to Table 2, when the total content of Sn, Sb, and P is less than the range of the present invention, no crystal grain is formed and all the tissues are recrystallized and the {111} orientation fraction is high.

[Example 2]

&Lt; Production of hot rolled sheet &

Slabs having the same composition as in Table 3 were prepared. The slab at room temperature was heated to 1150 占 폚 and hot rolled at 870 占 폚 to produce a hot rolled steel sheet having a thickness of 2.0 mm.

&Lt; Hot-rolled sheet annealing &

The hot-rolled sheet was heated to 1100 占 폚, annealed for 110 seconds, and cooled to room temperature.

<Production of cold rolled sheet>

After the first cold rolling, the thicknesses were made different from each other, and then the mixture was heated from room temperature to 1050 ° C and then subjected to intermediate annealing for 45 seconds. The cold-rolled steel sheet was subjected to secondary cold rolling at a reduction ratio as shown in Table 4 to produce a cold-rolled steel sheet having a thickness of 0.15 mm.

&Lt; Final annealing &

The cold-rolled sheet was heated from room temperature to 800 占 폚, and final annealing was performed for 35 seconds.

Steel grade Si
(%) Al
(%) Mn
(%) Sn
(%) Sb
(%) P
(%) S
(ppm) C
(ppm) N
(ppm) Ti
(ppm) Nb
(ppm) C1 3.40 1.0 0.3 0.050 0.035 0.013 19 19 13 24 24 C2 3.40 1.0 0.3 0.045 0.035 0.002 14 13 22 14 17 C3 3.40 1.0 0.3 0.060 0.030 0.002 24 18 14 23 12 C4 3.40 1.0 0.3 0.075 0.045 0.003 12 17 13 20 12 C5 3.40 1.0 0.3 0.055 0.035 0.028 15 19 12 11 24 C6 3.40 1.0 0.3 0.055 0.035 0.032 17 22 22 21 14 C7 3.40 1.0 0.3 0.060 0.045 0.003 14 12 12 20 19 C8 3.40 1.0 0.3 0.080 0.015 0.026 17 14 24 17 13 C9 3.40 1.0 0.3 0.075 0.025 0.004 12 13 14 20 22 C10 3.40 1.0 0.3 0.070 0.020 0.003 13 23 19 14 14 D1 3.15 1.2 0.2 0.055 0.075 0.002 23 20 14 13 13 D2 3.15 1.2 0.2 0.080 0.060 0.026 20 11 11 12 21 D3 3.15 1.2 0.2 0.075 0.045 0.028 21 21 21 22 20 D4 3.15 1.2 0.2 0.070 0.020 0.003 17 12 24 19 17 D5 3.15 1.2 0.2 0.050 0.075 0.002 13 14 14 21 20 D6 3.15 1.2 0.2 0.055 0.035 0.032 22 13 23 11 14

Steel grade Elongation grain B50
(T) W10 / 800
(W / kg) Secondary cold rolling reduction ratio
(%) Final annealing temperature
(° C) Remarks C1 Without 1.63 24.9 52 820 Comparative Example C2 include 1.66 21.2 67 790 Honor C3 include 1.66 21.6 78 750 Honor C4 Without 1.64 25.4 89 750 Comparative Example C5 Without 1.63 25.8 67 620 Comparative Example C6 include 1.67 22.0 72 820 Honor C7 include 1.66 21.8 78 790 Honor C8 Without 1.63 24.8 72 890 Comparative Example C9 include 1.66 21.8 67 750 Honor C10 Without 1.64 25.3 52 890 Comparative Example D1 Without 1.64 25.5 89 620 Comparative Example D2 include 1.67 22.0 72 790 Honor D3 include 1.67 22.7 67 820 Honor D4 Without 1.63 25.5 78 620 Comparative Example D5 Without 1.64 25.6 89 880 Comparative Example D6 include 1.66 22.3 78 750 Honor

In Table 3 and Table 4, 1 ppm is 0.0001% by weight. The term &quot; stretched crystal grains &quot; means a grain having a value of L / T of not less than 4, where L denotes the length of the grain in the rolling direction and T denotes the length in the thickness direction of the grain. In Table 3,% is wt%.

As can be seen from Table 4, when the reduction rate and the final annealing temperature falling within the range of one embodiment of the present invention were satisfied, an electrical steel sheet excellent in magnetic properties including stretched crystal grains was produced.

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 (13)

A non-oriented electrical steel sheet comprising crystal grains having a value of L / T of not less than 4, wherein the length in the rolling direction of the crystal grains in the electrical steel sheet is L and the length in the thickness direction of the grains is T,
Wherein said electric steel sheet comprises 2.5 to 4.0% of Si, 0.3 to 1.5% of Al, 1.0% or less of Mn (not including 0%), Sn, Sb and P of 100% 0.02% to 0.25% by weight, the balance being Fe and other unavoidable impurities.
delete delete The method according to claim 1,
Wherein the volume fraction of the {111} orientation parallel to the plate surface of the steel sheet within 15 DEG of the electrical steel sheet is 20% or less.
The method according to claim 1 or 4,
Wherein the thickness of the electrical steel sheet is 0.30 mm or less.
Heating the slab and then hot rolling to produce a hot rolled steel sheet;
Cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; And
And finally annealing the cold-rolled sheet at an annealing temperature of 650 ° C to 850 ° C,
The step of producing the cold-
Cold rolling is performed at a reduction ratio of 55% to 80% for one time to produce a cold rolled sheet having a final thickness,
The method of manufacturing a non-oriented electrical steel sheet according to any one of the preceding claims, wherein cold rolling is performed twice or more, and intermediate annealing is performed at least once between cold rolling two times or more and the reduction ratio of cold rolling at the last time is 55%
Wherein the slab is composed of 2.5 to 4.0% of Si, 0.3 to 1.5% of Al, 1.0% or less of Mn (not including 0%), Sn, Sb and P in a total amount of 100% 0.02% to 0.25% by weight, the balance comprising Fe and other unavoidable impurities,
Wherein the length of the grain in the rolling direction of the electric steel sheet is L and the length of the grain in the thickness direction is T, the value of L / T is 4 or more.
Here, the reduction rate is (thickness of steel sheet before cold rolling-thickness of steel sheet after cold rolling) / (thickness of steel sheet before cold rolling).
delete delete The method according to claim 6,
Wherein the volume fraction of the {111} orientation parallel to the plate surface of the steel sheet is less than or equal to 20% within 15 ° of the electrical steel sheet.
delete The method according to claim 6,
After the slab is heated and hot rolled to produce a hot rolled steel sheet,
Further comprising the step of annealing the hot-rolled sheet by hot-rolled sheet annealing.
12. The method of claim 11,
Wherein the annealing temperature in the intermediate annealing step is 850 to 1100 占 폚.
13. The method of claim 12,
Wherein the grain size of the steel sheet after annealing of the cold-rolled sheet is in the range of 50 탆 to 150 탆.

Images