KR20050066235A - Non-oriented electrical steel sheets with improved magnetic property and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a non-oriented electrical steel sheet having a low iron loss and high magnetic flux density, which are used as iron cores of electric devices such as motors, transformers, and magnetic shields, and a method of manufacturing the same. 4.5% or less, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 to 1.5%, N: 0.003% or less, O: 0.003% or less, and C / P ratio is 0.2 to Slab composed of 6.0, remainder Fe and other inevitably added impurities, and the slab is reheated to a temperature of 1050 ° C. or higher and 1200 ° C. or lower, and then hot rolled, wound up to a temperature of 680 ° C. or lower, hot rolled sheet annealing and Pickling, cold rolling by 1 cold rolling method or 1st cold rolling, then intermediate annealing and 2nd cold rolling, cold rolling by 2 times cold rolling method, and annealing the cold rolled plate within 10 seconds to 300 seconds at the temperature of 800 ~ 1070 ℃ The non-oriented electrical steel sheet having excellent magnetic properties is produced.

According to the present invention, it is possible to improve the magnetic properties of the non-oriented electrical steel sheet to produce a certain amount of impurity, which can significantly reduce the cost of removing these impurities, and to improve the productivity by reducing the labor Can be.

Description

Non-oriented electrical steel sheets with improved magnetic property and Method for manufacturing the same

The present invention relates to a method for manufacturing a non-oriented electrical steel sheet used as an iron core of an electric device such as a motor, a transformer and a magnetic shield, and more particularly, to a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density. It is about.

Non-oriented electrical steel sheet is an important component necessary for converting electrical energy into mechanical energy in electrical equipment. In order to reduce energy, it is necessary to lower magnetic properties, ie, iron loss and increase magnetic flux density.

Iron loss turns into heat and disappears during the energy conversion process, and magnetic flux density appears as a power generating force. Therefore, when the magnetic flux density is high, the copper loss of an electric apparatus can be reduced and miniaturization is possible.

In order to manufacture materials with low iron loss and high magnetic flux density, they may be made of clean steel with less impurities of steel or special elements may be added. Impurity elements include elements that generate C, S, P, N and other carbides and nitrides.

Japanese Patent Laid-Open No. Hei 10-212555 adds P, but it explains because it improves punching workability. In addition, Japanese Patent Laid-Open No. Hei 10-18005 adds P to improve mechanical properties. As such, previous patents add or contain P to improve mechanical properties.

On the other hand, Korean Patent Application 2000-45785 claims that the range of P is 0.001 ~ 0.005%, but does not mention the relationship with other elements such as C in this low P category.

In the non-oriented electrical steel sheet containing Si, Mn and Al, elements such as C, P, S and N, which are known as impurity elements, are preferably contained as little as possible in order to improve magnetic properties. In order to remove these elements, however, a large manufacturing cost is required.

The present invention was created in order to further improve the development in view of the disadvantages of the prior art as described above, and to some extent left as little as possible to contain C, P, S, N, etc., known as impurity elements in non-oriented electrical steel sheet. It is an object of the present invention to provide such a non-oriented electrical steel sheet and a method of manufacturing the same having excellent magnetic properties even in a laid state.

The present invention, in order to achieve the above technical problem, by weight% C: 0.0010 ~ 0.0030%, Si: 4.5% or less, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 ~ It provides 1.5%, N: 0.003% or less, O: 0.003% or less, C / P ratio of 0.2-6.0, and provides excellent magnetic non-oriented electrical steel sheet composed of residual Fe and other unavoidable impurities. There is a characteristic.

In the present invention, C: 0.0010% to 0.0030%, Si: 4.5% or less, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 to 1.5%, N: 0.003% O: 0.003% or less, C / P ratio is 0.2-6.0, the sum of C and P is formed at least 0.002% or more, excellent magnetic non-aromatic electricity consisting of the remaining Fe and other unavoidable impurities It is also characterized by providing a steel sheet.

Furthermore, in the present invention, C: 0.0010 to 0.0030%, Si: 4.5% or less, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 to 1.5%, N: 0.003% O: 0.003% or less, C / P ratio of 0.2 ~ 6.0, and the remainder Fe and other unavoidable addition of the slab composed of impurities are re-heated to a temperature of 1050 ℃ to 1200 ℃ hot rolled Cold rolled by cold rolling method, wound or annealed and pickled at a temperature of 680 ° C or lower, and cold rolled by 800 ° C to 1070 ° C. It is characterized by providing a method for producing an excellent non-oriented electrical steel sheet, characterized in that the cold-rolled annealing within 10 seconds to 300 seconds at a temperature.

In particular, as a result of various investigations and studies to constitute the invention, it has been found that grain boundaries exist within the metal material, and that there are many impurity elements, particularly P and C, in the grain boundaries. These elements have many segregation characteristics, and it was judged that these elements exist to some extent inside the grain boundary.

Therefore, under the assumption that the appropriate amount of C and P should be present, the results of experiments varying the amount of P and C were found to be less than 0.005% and control the amount of C in the range of 0.0010 to 0.0030%, and the ratio of C / P Maintaining the proper amount of C and P to maintain the proper amount of iron loss was low, the magnetic flux density was investigated.

And the sum of C and P was required at least 0.002% or more. At this time, since the amount of O decreases, the effect of P reduction decreases.

As a result, when the non-oriented electrical steel sheet is manufactured under the conditions of the present invention, the grain size lowering the iron loss is greatly increased, and the texture of the (200) plane containing a lot of <100> directions, which is easy for magnetization, is well developed and the magnetic flux. It can be seen that the density is also increased.

In the present invention, C: 0.001% to 0.003%, Si: 4.5% or less, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 to 1.5%, N: 0.003% Less than or equal to O: 0.0030% or less, hot-rolled steel slab composed of remaining Fe and other unavoidable impurities, followed by annealing the hot-rolled sheet after winding and cold-rolling or two cold-rolling including intermediate annealing if necessary. Provided is a method for producing a non-oriented electrical steel sheet having excellent magnetic properties for final annealing of a cold rolled sheet.

Hereinafter, numerical limitation of the component system according to the present invention will be described. In addition, it is assumed that all the indications which are not described and described only as a% are by weight.

[C: 0.0010-0.0030%]

C is known to be preferable for the magnetic properties, because the lower the magnetic properties during use to lower the magnetic properties during use in the final product.

However, the present invention confirmed that the magnetism is lowered even if C is excessively low at less than 0.0010%, in particular, when P is lowered at less than 0.005%, the magnetism is significantly reduced.

Moreover, even if C was too high, it confirmed that a magnetic property fell.

Therefore, C is in the range of 0.0010% to 0.0030% in the steelmaking component manufacturing step.

[Si: 4.5% or less]

Si is an element that decreases the eddy current loss during iron loss by increasing the specific resistance, but in the steel of the present invention, it is added below 4.5% in consideration of cold rolling property.

[Mn: 0.5% or less]

Mn is added to increase the resistivity and improves the texture, and is added less than 0.5% because the improvement of the texture is too small.

[P: 0.005% or less]

P is a segregation element, the impurity element C is contained in 0.0010 ~ 0.0030%, P is less than 0.005%, and the C / P ratio is contained so that 0.2 to 6.0, the magnetic properties are improved. When P is added in an amount of 0.005% or more, grain growth is suppressed and the magnetism is reduced. The sum of C and P should be maintained at least 0.002%.

That is, if the content is less than 0.002%, elements such as O and N easily move to the grain boundary and penetrate into the steel, causing excessive internal oxides or nitrides. These nitrides and oxides inhibit grain growth and inhibit magnetism. do.

In addition, the C / P ratio is at least 0.2 or higher to increase the magnetism, which is the minimum content ratio of C to the maximum P content, and maintains the invasive element C at an appropriate level to prevent intrusion of O or N into the grain boundary. There is an inhibitory effect, and the magnetism is improved when C / P is 6 or less, which means the maximum content of C to the minimum P, where P is required to be 0.0010% or more.

[S: 0.005% or less]

S is advantageously contained as low as possible to form a fine precipitate MnS adversely affects the magnetic properties, in the present invention is to be contained less than 0.005%.

[Al: 0.2-1.5%]

Al is added because it decreases the eddy current loss by increasing the specific resistance, and when it is added below 0.2%, fine precipitates of AlN are formed in the steel. In addition, when the addition of more than 1.5%, the degree of magnetic improvement is lower than the added amount. Therefore, Al is added in 0.2 ~ 1.5%.

[N: 0.003% or less]

N is made to contain as little as possible by forming a fine and long AlN precipitate, in the present invention is less than 0.003%.

[O: 0.003% or less]

O produces fine oxides and ductile oxides, and if they contain low grain boundary segregation elements, they should be kept low because they easily penetrate into the interior of the material to make oxides. In the present invention, it was investigated that the effect of the addition of low P steel can be seen by less than 0.003%.

Hereinafter, the manufacturing method of this invention is demonstrated.

The slab of the steel composition as described above is made of molten steel in the steelmaking and then solidified into the slab in the continuous casting process, charged into the heating furnace for hot rolling, the temperature of the slab during heating is in the range of 1100 ~ 1200 ℃.

If it is lower than 1100 ° C., the rolling load during rolling is too large, and if it is heated higher than 1200 ° C., impurity elements are precipitated as fine precipitates to suppress grain growth of the final product.

Therefore, reheating temperature shall be in the range of 1050-1200 degreeC.

After hot rolling, the coiling temperature of the hot rolled sheet is conducted at 680 ℃ or lower, and can be cooled in air in a coiled state or in a non-oxidizing atmosphere. If it exceeds 680 ℃, the magnetic properties are deteriorated due to the difficulty of magnetization due to internal oxidation of the material during cooling Can be.

The cold-rolled hot rolled sheet may be omitted or annealed and cold rolled after hot rolled sheet annealing.

Cold rolling can be rolled by a single cold rolling method to be the final product, or it can be used as a two cold rolling method which is subjected to intermediate cold annealing after primary cold rolling and then subjected to secondary cold rolling.

The intermediate annealing temperature is in the range of 830 ~ 1000 ℃. If the temperature is lower than 830 ° C., sufficient recrystallization is not performed. If the temperature is higher than 1000 ° C., excessive grain growth may result in insufficient grain growth during recrystallization annealing after secondary cold rolling.

The final cold rolled steel sheet is annealed, and the annealing temperature is 800 ° C or more and 1070 ° C or less.

If the annealing temperature is lower than 800 ℃ grain growth is insufficient, if higher than 1070 ℃ the surface temperature is excessively high may cause surface defects on the surface of the plate and the magnetic properties may be worsened.

Annealing time is 10 seconds or more and 300 seconds or less. The annealing time must be at least 10 seconds to sufficiently recrystallize, and if it is 300 seconds or more, internal oxidation can occur, so it is within 10 seconds to 300 seconds.

At this time, the annealing atmosphere may be a dry non-oxidizing mixed atmosphere with nitrogen of 10% or more of hydrogen.

When the hydrogen is less than 10%, fine non-metallic inclusions Al ₂ O ₃ , MnO and FeO are generated directly under the surface of the steel sheet, resulting in deterioration of the texture and deterioration of magnetic properties.

Annealed plates are shipped at demand after insulation coating. Insulation coatings can be treated with organic, inorganic and organic-inorganic composite coatings, and can be coated with other insulating coatings.

Hereinafter, the embodiment will be described in more detail.

Example 1

Inventive steel slabs having the components shown in Table 1 were prepared, and comparative steel slabs similar in composition to the inventive steel were prepared.

Subsequently, these slabs were reheated as shown in Table 2, and hot-rolled to 1.8 mm, then wound up and cooled at a temperature of 650 ° C.

The cooled hot rolled sheet was annealed for 3 minutes at annealing temperature of 1050 ° C, pickled, and then cold rolled once to 0.35mm thickness or intermediately annealed and cold rolled secondly after primary cold rolling.

Cold-rolled annealing was carried out by varying the annealing time at 1070 ℃, the annealing plate was investigated the magnetic properties and grain size after cutting. The annealing atmosphere was operated with a mixed atmosphere of hydrogen and nitrogen.

As a result, it was found that the magnetic properties were excellent in the component range and manufacturing conditions of the present invention.

River bell C Si Mn P S Al N O C / P Inventive Steel a 0.0010 2.15 0.25 0.0012 0.001 0.38 0.0018 0.0015 0.8 Inventive Steel b 0.0015 2.94 0.26 0.0020 0.001 1.40 0.0017 0.0012 0.7 Invention steel c 0.0020 2.92 0.27 0.0040 0.001 1.42 0.0016 0.0010 0.5 Invention 0.0012 2.90 0.25 0.0050 0.002 1.43 0.0018 0.0012 0.2 Invention Steele 0.0026 2.92 0.25 0.0006 0.002 1.10 0.0017 0.0018 4.3 Comparative Steel a 0.0005 2.93 0.26 0.0105 0.001 1.40 0.0017 0.0016 0.04 Comparative Steel b 0.0035 2.91 0.25 0.0080 0.001 1.42 0.0017 0.0018 0.4 Comparative Steel c 0.0025 2.92 0.25 0.0003 0.001 1.39 0.0018 0.0017 8.3 Comparative strength d 0.0009 2.92 0.25 0.0003 0.001 1.39 0.0018 0.0040 8.3

Comparative steel a has excessively low C and low C / P.

Comparative steel b has high C and P, comparative steel c has C and P satisfying the management range, but the ratio of C / P is too high, comparative steel d has high O and low sum of C and P.

In addition, as shown in Table 2 below, Comparative Material 1 had a high reheating temperature and a cold rolled sheet annealing time. Comparative material 2 was not homogenized due to excessively low reheating temperature, and the intermediate annealing temperature was also low. Comparative materials 3 and 4 were not suitable in component ratio.

Sample Number Reheating Temperature (℃) Intermediate Annealing Temperature (℃) Cold Rolled Annealing Time (sec) _Iron loss (W _15/50 ) W / kg Magnetic flux density (B50) Tesla Crystal grain size (㎛) River bell Invention 1 1150 Not carried 50 1.85 1.73 140 Inventive Steel a Invention 2 1150 Not carried 50 1.99 1.66 160 Inventive Steel b Invention 2 1150 930 50 1.90 1.65 170 Inventive Steel b Comparative Material 1 1250 Not carried 5 2.38 1.64 135 Inventive Steel b Invention 3 1120 Not carried 30 1.89 1.69 160 Invention steel c Invention 4 1120 Not carried 60 1.95 1.67 165 Invention Invention 5 1120 Not carried 200 1.89 1.66 170 Invention Steele Comparative Material 2 1000 700 50 2.31 1.64 120 Inventive Steel a Comparative Material 3 1120 900 50 2.12 1.64 145 Comparative Steel b Comparative Material 4 1120 900 50 2.45 1.63 125 Comparative Steel c Comparative Material 5 1120 900 50 2.52 1.64 105 Comparative strength d

W _15/50 : Loss generated when magnetizing to 1.5 Tesla at 50 Hz

B ₅₀ : Induced magnetic flux density when a magnetic field is applied at 50 A at 5000 A / m

Example 2

Weight% C: 0.0023%, Si: 3.2%, Mn: 0.23%, P: 0.002%, S: 0.0005%, Al: 1.24%, N: 0.0017%, O: 0.0017%, C / P = 1.1, The slab composed of the balance Fe and other impurities was heated to 1130 ° C., hot rolled to a thickness of 1.9 mm, and wound-cold to 620 ° C. temperature.

The hot rolled sheet was annealed for 5 minutes at 1020 ℃, 0.5mm after pickling, the first cold rolling, and then intermediately annealed at 930 ℃ for 30 seconds, second cold rolling and cold rolling to a thickness of 0.20mm after pickling.

The cold rolled sheet was annealed at annealing temperature of 1050 ° C. for 1 minute.

After annealing, cutting and magnetic properties were measured. The iron loss (W _10/400 ) was _9.6 W / kg, the magnetic flux density (B ₅₀ ) was 1.66 Tesla, and the grain size was 150 μm.

Example 3

% By weight C: 0.0012%, Si: 0.98%, Mn: 0.25%, P: 0.004%, S: 0.001%, Al: 0.24%, N: 0.0013%, O: 0.0018%, C / P = 0.3 The slab composed of Fe and other impurities was heated to 1150 ° C., hot rolled to a thickness of 2.2 mm, wound up to 680 ° C., and cooled.

The hot rolled sheet was annealed at 950 ° C. for 4 minutes, cold rolled to 0.5 mm after pickling, and then annealed at 950 ° C. for 30 seconds.

After annealing, cutting and magnetic properties were measured. The iron loss (W _15/50 ) was 4.5W / kg, the magnetic flux density (B ₅₀ ) was 1.75 Tesla, and the grain size was 65 μm.

Through these examples, it was confirmed through the composition range and the manufacturing method of the present invention to have excellent magnetic properties while remaining some impurities in the production of non-oriented electrical steel sheet.

As described in detail above, the present invention can improve the magnetic properties of the non-oriented electrical steel sheet production to some extent, leaving a significant reduction in the cost of removing these impurities, reducing the labor Productivity can be improved.

Claims (3)

By weight% C: 0.0010 ~ 0.0030%, Si: 4.5% or less, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 ~ 1.5%, N: 0.003% or less, O: 0.003 A non-oriented electrical steel sheet having a magnetic property of less than or equal to% and having a C / P ratio of 0.2 to 6.0 and consisting of residual Fe and other inevitable impurities. By weight% C: 0.0010 ~ 0.0030%, Si: 4.5% or less, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 ~ 1.5%, N: 0.003% or less, O: 0.003 A non-oriented electrical steel sheet having a magnetic property of less than%, a ratio of C / P of 0.2 to 6.0, a sum of C and P of at least 0.002%, and a balance of Fe and other unavoidable impurities. By weight%, C: 0.0010 ~ 0.0030%, Si: 4.5% or less, Mn: 0.5% or less, P: 0.005% or less, S: 0.005% or less, Al: 0.2 ~ 1.5%, N: 0.003% or less, O: It is 0.003% or less, the ratio of C / P is 0.2 to 6.0, the remainder Fe and other unavoidably added slabs are reheated to a temperature of 1050 ° C or more and 1200 ° C or less and hot rolled. Winding, hot rolled sheet annealing and pickling at a temperature of 680 ℃ or less, Cold rolling by one cold rolling method or two cold rolling methods which are intermediately annealed after the first cold rolling and the second cold rolling, A method of manufacturing an excellent non-oriented electrical steel sheet, characterized in that the cold-rolled sheet annealing within 10 seconds to 300 seconds at a temperature of 800 ~ 1070 ℃.