KR20160078175A - Non-orientied electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

According to an embodiment of the present invention, a method to manufacture a non-oriented electrical steel sheet comprises: a step of manufacturing a hot-rolled plate by hot-rolling a slab after heating the slab, wherein the slab includes 0.05 wt% or less (excluding 0 wt%) of Cu; 0.003-0.1 wt% of Mo; 0.001-0.01 wt% of S; 0.005 wt% or less (excluding 0 wt%) of N; and the remaining consisting of Fe and inevitable impurities; a step of manufacturing a cold-rolled plate by annealing the hot-rolled plate or cold-rolling the hot-rolled plate after omitting annealing of the hot-rolled plate; and a step of annealing the cold-rolled plate. The step of annealing the cold-rolled plate comprises a temperature increasing step and a crack step. In the temperature increasing step, a temperature is increased up to 700ºC at a temperature increasing speed of 10 ºC/second or more; and after reaching the temperature of 700ºC, the temperature is increased up to a crack temperature at a temperature increasing speed of 5 ºC/second or more. The non-oriented electrical steel sheet has a low iron loss and high magnetic flux density.

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 nonoriented electrical steel sheets used as iron core materials for various motors and small transformers are the most important part of the electrical product design because they occupy the largest part of the energy loss. In order to reduce the energy loss of such electric products, electric steel sheets are required to have low iron loss and high magnetic flux density. If the iron loss of the nonoriented electric steel sheet is low, energy loss as heat can be reduced when magnetic field is applied. Also, when magnetic flux density is high among magnetic properties, energy can be reduced through reduction of copper wire at the iron core, Lt; / RTI >

The material of the motor can vary depending on the frequency used. Particularly, electric steel sheets used in the general commercial frequency range of 100 Hz or less have a method of improving the characteristics by improving the texture of the steel by producing pure steel with a low impurity content or by adding additional elements in order to lower the iron loss and increase the magnetic flux density. It can also be used in combination. However, in the case of the former, the cost of additional processing increases in the manufacturing process, and in the latter case, the cost of additional elements increases. Among the methods for lowering the iron loss, there is a problem that the magnetic flux density is reduced although the elements that increase the resistivity such as Si or Al are increased. Thus, there is a need for research to produce a non-oriented electrical steel sheet containing as few alloying elements as possible and having excellent magnetic properties.

One 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 producing a non-oriented electrical steel sheet.

The non-oriented electrical steel sheet according to one embodiment of the present invention comprises 0.05% or less of Cu (not including 0%), 0.003% to 0.1% of Mo, 0.001% to 0.01% of S, 0.005% or less (excluding 0%), and the remainder may contain Fe and impurities.

The electric steel sheet according to any one of the above items (1) to (3), wherein the electric steel sheet comprises 0.01 to 0.1% of Al, 0.005% or less of C (does not include 0%), 0.1 to 4.5% of Si, ), P: not more than 0.2% (not including 0%), and Ti: not more than 0.005% (not including 0%), and Sn, Sb, % ≪ / RTI >

The grain size of the grain of the electrical steel sheet may be 40 탆 to 200 탆.

A method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention comprises: 0.05% or less of Cu (not including 0%), 0.003% to 0.1% of Mo, 0.001% to 0.01% of S, And N: not more than 0.005% (not including 0%), the balance being Fe and impurities; and hot rolling the slab to produce a hot rolled steel sheet; Performing a hot-rolled sheet annealing on the hot-rolled sheet or omitting the annealing of the hot-rolled sheet, followed by cold rolling to produce a cold-rolled sheet; And annealing the cold rolled sheet, wherein the step of annealing the cold rolled sheet includes a temperature elevating step and a cracking step, wherein the temperature elevating step raises the temperature to 700 캜 at a heating rate of 10 캜 / The temperature may be raised to the cracking temperature at a temperature raising rate of 5 deg. C / sec or more.

The cracking temperature in the cracking step may be 850 ° C to 1100 ° C.

Wherein the slab comprises, by weight%, Al: 0.01 to 0.1%, C: 0.005% or less (not including 0%), Si: 0.1 to 4.5% , P: not more than 0.2% (not including 0%), and Ti: not more than 0.005% (not including 0%), and Sn, Sb, May include.

The grain size of the grain of the steel sheet after completion of annealing of the cold rolled sheet may be 40 탆 to 200 탆.

According to one embodiment of the present invention, it is possible to provide a non-oriented electrical steel sheet having a low content of alloying elements, a low iron loss, a high magnetic flux density, and a small magnetic flux density variation.

Brief Description of the Drawings The advantages and features of the present invention, and how to accomplish them, will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the embodiments disclosed herein 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 implementations, 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%.

First, 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 one embodiment of the present invention comprises 0.05% or less of Cu (not including 0%), 0.003% to 0.1% of Mo, 0.001% to 0.01% of S, 0.005% or less (excluding 0%), and the remainder may contain Fe and impurities.

The electrical steel sheet may further contain 0.01% to 0.1% of Al, 0.005% or less of C (not including 0%), 0.1% to 4.5% of Si, and 1.0% or less of Mn (Not including 0%), P: not more than 0.2% (not including 0%), and Ti: not more than 0.005% (not including 0%) and Sn, Sb, To 0.2%. ≪ / RTI >

First, the reason for limiting the components will be described.

When Al is added, the resistivity is increased but the magnetic flux density is lowered. When Al is added by 0.01% or more, Al ₂ O ₃ precipitates are formed, and AlN is precipitated by co-precipitation, thereby precipitating coarse precipitates. When the Al content is less than 0.01%, a large amount of fine AlN is generated and the magnetic property is lowered. When the Al content is more than 0.1%, the magnetic flux density may be decreased.

When Cu is more than 0.05%, it can bond with S to form fine precipitates to suppress grain growth and deteriorate magnetism.

Mo reduces the variation of permeability in the Al content added in one embodiment of the present invention. If the content is less than 0.003%, there is no effect of decreasing the permeability variation. If the content is more than 0.1%, the effect of decreasing the permeability variation relative to the addition amount may be deteriorated.

When N is more than 0.005%, AlN precipitates are formed to suppress grain growth and deteriorate magnetic properties. And more specifically 0.003% or less.

S is segregated at grain boundaries and prevents N from entering during annealing. If the content of S is less than 0.001%, the penetration of N increases to deteriorate the magnetic properties, and if it exceeds 0.01%, the iron loss may be increased.

When C is more than 0.005%, it can cause magnetic aging in the final product, and it can form carbide and increase iron loss.

When Si content is less than 0.1%, vortex loss increases and iron loss can be increased. When 4.5% is exceeded, brittleness increases and plate breakage may occur.

Mn can be added by 0.2% or more to grow crystal grains and develop aggregate structure. If it exceeds 1.0%, the cold rolling property may be lowered.

P increases the resistivity to lower the iron loss and forms a texture favorable to magnetism, but if it exceeds 0.2%, the cold rolling property may be deteriorated.

When Ti is more than 0.005%, fine carbides or nitrides may be formed and adversely affect the magnetic properties.

Sn and Sb segregate in the grain boundaries to suppress the diffusion of nitrogen through the grain boundaries and improve the texture in the steel. Sn and Sb may be added singly or in combination. If Sn, Sb, or a combination thereof is less than 0.01%, the magnetism is adversely affected to open the aggregate structure, and when 0.2% is exceeded, the rolling property may be deteriorated.

The grain size of the grain of the electrical steel sheet may be 40 탆 to 200 탆. If the thickness is less than 40 탆, the growth of aggregate structure is insignificant, thereby increasing the iron loss, and when the thickness exceeds 200 탆, the magnetic flux density may be lowered and the magnetic permeability variation may increase.

The variation of the permeability of the electrical steel sheet may be 30% or less. The permeability variation is {(rolling direction permeability - permeability in the direction perpendicular to the rolling direction) x100 / (permeability in the rolling direction + permeability in the direction perpendicular to the rolling direction)}. Here, the direction perpendicular to the rolling direction means the width direction of the steel sheet.

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

First, we provide slabs. Wherein the slab contains, by weight%, at most 0.05% Cu, at least 0.003% Mo, at least 0.001% S, at least 0.001% S, and at most 0.005% And the remainder may contain Fe and impurities. The slabs may contain, by weight%, Al: 0.01 to 0.1%, C: 0.005% or less (not including 0%), Si: 0.1 to 4.5%, Mn: 1.0% ), P: not more than 0.2% (not including 0%), and Ti: not more than 0.005% (not including 0%), and Sn, Sb, % ≪ / RTI > The reason for limiting the constituents of the slab is the same as the reason for limiting the constituents in the non-oriented electrical steel sheet.

Thereafter, the slab is heated. When heating the slab, the heating temperature may be 1250 ° C or less. When the temperature exceeds 1250 DEG C, precipitates such as AlN and MnS are excessively reused and can be precipitated as fine precipitates upon hot rolling.

Thereafter, the slab is hot-rolled to produce a hot-rolled sheet. In the production of hot rolled sheets, the finish rolling can be finished in the ferrite phase, and the final rolling reduction can be performed at 20% or less for plate shape calibration.

Thereafter, the hot-rolled sheet can be subjected to hot-rolled sheet annealing if necessary. When the hot-rolled sheet annealing is performed, the annealing temperature may be 10 minutes or less at 850 to 1150 ° C.

Thereafter, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet having a thickness of 0.1 mm to 0.7 mm.

Thereafter, the cold rolled sheet cooled to room temperature is annealed by cold rolling. The step of annealing the cold rolled sheet includes a heating step and a cracking step.

The temperature raising step may be a temperature raising to 700 deg. C at a temperature raising rate of 10 deg. C / sec or more. More specifically, the temperature may be raised to 700 ° C at a temperature raising rate of 10 ° C / sec to 30 ° C / sec. When the heating rate of 10 ° C / second to 30 ° C / second is maintained, the crystal grains are uniformly distributed, and an electric steel sheet excellent in magnetic properties can be produced. If the annealing temperature is less than 10 ° C / sec, the grain growth may be insignificant when the cold rolled sheet is annealed, and the iron loss may be reduced.

After reaching 700 캜 in the temperature raising step, the temperature may be raised to the cracking temperature at a temperature raising rate of 5 캜 / second or more. More specifically, after reaching 700 캜, the temperature can be raised at a rate of 10 캜 / sec to 25 캜 / sec. When the heating rate is 10 deg. C / sec to 25 deg. C / sec, the crystal grains are uniform and the magnetism can be excellent. If the heating temperature is less than 5 ° C / second, the grain growth may be insufficient and the iron loss may be deviated.

The difference between the heating rate before 700 ° C and the heating rate after 700 ° C may be 3 ° C to 10 ° C. If the above range is maintained, the crystal grains can be uniform and the magnetic property can be excellent.

Also, the cracking temperature in the cracking step may be 850 ° C to 1100 ° C. If the temperature is lower than 850 DEG C, the crystal growth may be insufficient and the iron loss may be lowered. When the temperature exceeds 1100 DEG C, the crystal grains may excessively grow and the magnetism may be lowered.

The grain growth occurs at the annealing of the cold rolled sheet. At this time, the annealing temperature and the annealing time may be adjusted so that the grain size of the steel sheet becomes 40 탆 to 200 탆. If the thickness is less than 40 탆, the growth of the aggregate structure is insignificant and the iron loss is increased. When the thickness exceeds 160 탆, the magnetic flux density is lowered and the magnetic permeability variation may increase.

Thereafter, the electric steel sheet after annealing of the cold rolled sheet can be rolled at a reduction ratio of 1% to 5%, if necessary. Here, the reduction rate means the thickness of the steel sheet before rolling (the thickness of the steel sheet after rolling) / (the thickness of the steel sheet before rolling).

When the rolling of the electric steel sheet after annealing of the cold rolled sheet is performed at a reduction ratio of 1% to 5%, the grain growth may occur in the stress relief annealing process. If the rolling reduction is less than 1%, the rolling effect is small, and when the rolling reduction exceeds 5%, the crystal grains may grow excessively.

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.

Steel slabs prepared as shown in Table 1 were heated at 1140 占 폚, hot-rolled to a thickness of 2.4 mm, and then rolled at 650 占 폚. The hot-rolled steel sheet cooled in air was annealed at 1070 ° C for 5 minutes, pickled, cold-rolled to a thickness of 0.35 mm, and annealed at a cold rolled sheet as shown in Table 2 to examine its magnetic properties.

River name C Si Mn P S Al Cu Mo N Ti Sn Sb Inventive Steel 1 0.0035 2.45 0.15 0.03 0.0023 0.022 0.01 0.035 0.0018 0.001 0.03 0.01 Invention river 2 0.0032 2.42 0.42 0.05 0.0027 0.02 0.03 0.026 0.0014 0.002 - - Invention steel 3 0.0034 2.42 0.54 0.06 0.0041 0.019 0.02 0.019 0.0013 0.002 0.04 0.01 Inventive Steel 4 0.0029 2.41 0.23 0.01 0.0031 0.035 0.007 0.059 0.0013 0.001 0.08 - Invention steel 5 0.0025 2.43 0.23 0.05 0.0018 0.024 0.01 0.041 0.0013 0.002 - 0.02 Comparative River 1 0.0025 2.45 0.24 0.02 0.0006 0.017 0.01 0.041 0.0012 0.002 0.05 - Comparative River 2 0.0026 2.44 0.45 0.03 0.0024 0.008 0.02 0.024 0.0015 0.002 0.04 0.01 Comparative Steel 3 0.0023 2.42 0.4 0.03 0.003 0.024 0.08 0.021 0.0014 0.001 - - Comparative Steel 4 0.0025 2.49 0.32 0.02 0.0025 0.029 0.02 0.124 0.0012 0.001 - - Comparative Steel 5 0.0021 2.48 0.42 0.03 0.0029 0.021 0.02 - 0.0013 0.002 0.03 -

In Table 1, the content of each element is% by weight.

division River name Annealing temperature of cold rolled sheet (℃) Heating rate (° C / s) up to 700 ° C during annealing Heating rate over 700 ℃ for annealing
(° C / s) Crystal grain
size
(탆) Iron loss
_{(W 15/50) W /} kg Magnetic flux density
(B ₅₀ )
Tesla Variability of investment ratio
(%) Invented material A Inventive Steel 1 1030 15 12 95 2.06 1.77 26 Invention material B Invention river 2 1000 25 21 130 1.85 1.78 20 Inventive material C Invention steel 3 1030 15 25 102 1.98 1.82 15 Invention D Inventive Steel 4 1040 20 12 98 2.02 1.78 21 Comparative material A Invention steel 5 780 7 4 30 3.21 1.65 36 Invention steel E Invention steel 5 1020 14 15 110 2.15 1.79 23 Comparative material B Comparative River 1 1050 15 10 69 2.85 1.64 42 Comparative material C Comparative River 2 1050 18 10 65 2.72 1.65 41 Comparative material D Comparative Steel 3 1050 15 12 75 2.65 1.68 39 Comparative material E Comparative Steel 4 1050 15 10 70 2.60 1.66 35 Comparative material F Comparative Steel 5 1050 25 10 50 2.68 1.67 37

One) Iron loss (W15 / 50) is the average loss (W / kg) in the rolling direction and in the direction perpendicular to the rolling direction when magnetic flux density of 1.5 Tesla is induced at 50 Hz frequency.

2) The magnetic flux density (B50) is the intensity of the induced magnetic field when excited at 5,000 A / m

3) The permeability is the permeability derived from the magnetic flux density at 1.5 Tesla.

As shown in Table 2, inventive steels (1 to 5) satisfying the composition range according to one embodiment of the present invention were used to produce inventive materials (A to E ) Had low iron loss, high magnetic flux density, and low magnetic permeability. The comparative material A has a low heating rate during annealing even when it is an inventive steel, and therefore the grain growth is insufficient and the permeability variation is high. It can be seen that the comparative materials B, C, D, E and F are comparative steels 1, 2, 3, 4 and 5 in the steel name, and the constituent components do not satisfy the composition range of the present invention, .

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)

Al: 0.01 to 0.1%, Cu: not more than 0.05% (not including 0%), Mo: 0.003 to 0.1%, S: 0.001 to 0.01% And the balance comprising Fe and impurities.
The method according to claim 1,
The steel sheet according to any one of the preceding claims, wherein the electrical steel sheet contains 0.005% or less of C (not including 0%), 0.1% to 4.5% of Si, 1.0% (Not including 0%) and Ti: not more than 0.005% (excluding 0%), and further containing Sn, Sb, or a combination thereof in an amount of from 0.01% to 0.2% .
3. The method according to claim 1 or 2,
Wherein the grain size of the grain of the electrical steel sheet is 40 占 퐉 to 200 占 퐉.
Al: 0.01 to 0.1%, Cu: not more than 0.05% (not including 0%), Mo: 0.003 to 0.1%, S: 0.001 to 0.01% And the remainder comprising a slab containing Fe and impurities, followed by hot rolling to produce a hot rolled steel sheet;
Cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; And
And annealing the cold-rolled sheet for cold-rolled sheet,
The step of annealing the cold-rolled sheet includes a cold-rolled sheet heating step and a cold-rolled sheet cracking step,
The temperature raising step raises the temperature to 700 deg. C at a temperature raising rate of 10 deg. C / sec or more,
After reaching 700 占 폚, the temperature is raised to the cracking temperature at a rate of increase of 5 占 폚 / sec or more,
And the cold-rolled sheet cracking step is performed at the cracking temperature.
5. The method of claim 4,
Wherein the cracking temperature in the cracking step is 850 ° C to 1100 ° C.
The method according to claim 4 or 5,
The cold-rolled steel sheet is heated at about 700 ° C,
And a temperature raising rate of 10 占 폚 / sec to 30 占 sec / sec before 700 占 폚,
And a temperature raising rate of 10 to 25 占 폚 / sec after 700 占 폚.
The method according to claim 6,
The cold-rolled steel sheet is heated at about 700 ° C,
Wherein the difference between a heating rate before 700 ° C and a heating rate after 700 ° C is 3 ° C to 10 ° C.
8. The method of claim 7,
Wherein the slab contains, by weight%, C: not more than 0.005% (not including 0%), Si: 0.1 to 4.5%, Mn: not more than 1.0% (not including 0%), P: not more than 0.2% And no more than 0.01% and not more than 0.2% of Sn, Sb, or a combination thereof, and further comprising 0.005% or less of Ti (not including 0% Way.
9. The method of claim 8,
Wherein the grain size of the grain of the steel sheet after completion of annealing of the cold-rolled sheet is 40 占 퐉 to 200 占 퐉.