KR101308725B1 - Non-oriented electrical steel sheet with low core-loss and high strength and method for manufacturing the same - Google Patents

Abstract

The present invention relates to the production of non-oriented electrical steel sheet, by weight C: 0.005% or less, Si: 4.0% or less (excluding 0), P: 0.1% or less (excluding 0), S: 0.03% or less, Mn: Hot slab consisting of 0.1 to 2.0%, Al: 0.3 to 2.0%, N: 0.003% or less, Ti: 0.005% or less, Nb: 0.003% or less, V: 0.003% or less, balance Fe and other unavoidable impurities After rolling and cold rolling, there is provided a method for producing a low iron loss high strength non-oriented electrical steel sheet which is subjected to final annealing so that the area fraction of the unrecrystallized structure in the cross section of the steel sheet is in the range of 1 to 50%.
Therefore, by controlling the area fraction of the unrecrystallized structure in the cross section of the steel sheet to an appropriate level and controlling the average grain size of the recrystallized grains, non-oriented electrical steel sheet having high strength and low iron loss can be produced. By performing final annealing in a temperature range where the rate of change of yield strength is low due to temperature change, it is possible to prevent the lowering of elongation and to reduce the variation in magnetic properties and strength, thereby stably securing low iron loss and high strength properties. In addition, by restricting the Nb, V content to suppress the production of carbonitrides, the magnetic properties are greatly improved when partially heat treated according to the needs of customers.

Description

Non-oriented electrical steel sheet with low core-loss and high strength and method for manufacturing the same

The present invention relates to the manufacture of non-oriented electrical steel sheet used in parts such as electric devices such as generators and automobile motors, and more particularly, for high strength characteristics and energy efficiency that can withstand high-speed rotating devices with high stress. The present invention relates to a non-oriented electrical steel sheet and a non-oriented electrical steel sheet produced thereby to achieve the magnetic properties of low iron loss.

As interest in the efficient use of energy has recently increased, the efficiency of motors used in electric devices such as large-scale generators, environmentally friendly vehicles such as hybrid electric vehicles (HEV), or electric vehicles (EV) can be improved. Efforts are being made to increase. As part of such efforts, efforts have been made to obtain a faster rotational speed than general motors by modulating the frequency like a BLDC motor.

In particular, in the case of a motor used in a driving unit of a hybrid vehicle or an electric vehicle, it is necessary to obtain a large output with a limited size, and a rotation speed of 10000 rpm or more is required. In this case, since the centrifugal force received by the rotor of the motor is proportional to the square of the rotation speed, it exceeds the yield strength that general electrical steel can withstand at high speed of rotation, which threatens the stability and durability of the motor. Therefore, the rotor of the high speed rotating apparatus requires a high strength material.

In addition, in the case of the material used as the rotor of the motor, it is necessary to reduce the eddy current loss caused by the high frequency in addition to the strength. The losses are greater, which reduces the overall efficiency of the motor.

Therefore, it is necessary to study the manufacturing technology of electrical steel sheet that can satisfy both high strength and low iron loss characteristics. As a part of this, the technology to improve the strength by forming a structure other than ferrite in the steel, the technology to improve the strength by the addition of alloying elements such as Nb, V, Cu, grain size before cold rolling or further processing It has been proposed a technique to control the iron loss characteristics and strength characteristics by controlling to 20㎛ or more.

However, in the technique of forming a structure other than ferrite, iron loss and magnetic flux density deteriorate rapidly due to the presence of non-magnetic abnormalities such as pearlite, martensite, and austenite inside the steel, and when used in a rotor, the efficiency of the motor rapidly increases. There is a drawback to being reduced. The technology of adding alloying elements such as Nb, V, and Cu also causes a problem of rapid deterioration of magnetism, and a limitation occurs depending on the intended use. In addition, the effect of the technique of controlling the size of the cold-rolled structure to 20㎛ or more is a characteristic that appears in the process and intermediate products that are performed in a conventional electrical steel sheet, the experiment results by the present inventors in high-strength electrical steel sheet with a lot of uncrystallized structure It has been found that the effect is insignificant, and there is a problem that it is difficult to bring about an effective improvement of magnetic properties as compared with the case of using a material having a grain size of less than 20㎛.

An object of the present invention is to manage the area fraction of the unrecrystallized structure in the cold-rolled steel sheet to an appropriate level, to control the average grain size of the recrystallized grains, and to limit the impurity elements forming the fine carbonitride precipitates to increase the crystal growth By improving the strength of the partially heat treatment according to the customer's needs to produce a low iron loss high strength non-oriented electrical steel sheet significantly improved.

In addition, the present invention is carried out in the temperature range where the rate of change in yield strength according to the temperature change of the final annealing is low to maintain the elongation of the steel sheet above a certain level, and the low iron loss high strength characteristics by reducing the variation of the magnetic and strength stable Another object of the present invention is to provide a method of manufacturing a non-oriented electrical steel sheet to ensure.

Method for producing a low iron loss high strength non-oriented electrical steel sheet of the present invention for solving the above problems, by weight, C: 0.005% or less, Si: 4.0% or less (excluding 0), P: 0.1% or less (excluding 0) ), S: 0.03% or less, Mn: 0.1-2.0%, Al: 0.3-2.0%, N: 0.003% or less, Ti: 0.005% or less, Nb: 0.003% or less, V: 0.003% or less, balance Fe and others The slab made of inevitably mixed impurities is hot rolled and cold rolled, and then subjected to final annealing so that the area fraction of the unrecrystallized structure in the cross section of the steel sheet is in the range of 1 to 50%.

In the method of manufacturing a low iron loss high strength non-oriented electrical steel sheet according to the present invention, the final annealing is performed in a temperature range where the yield strength change rate is 3.0 MPa or less according to the final annealing temperature, and the average grain size of the crystal grains recrystallized after the final annealing is 10. It is also characterized by controlling the thickness of the final annealed steel sheet to 20% or more, controlling the yield strength of the final annealed steel sheet to 500 MPa or more, and the temperature of the final annealing to 720 to 760 ° C. have.

Low iron loss high strength non-oriented electrical steel sheet of the present invention for solving the above problems, by weight, C: 0.005% or less, Si: 4.0% or less (excluding 0), P: 0.1% or less (excluding 0), S : 0.03% or less, Mn: 0.1-2.0%, Al: 0.3-2.0%, N: 0.003% or less, Ti: 0.005% or less, Nb: 0.003% or less, V: 0.003% or less, balance Fe and other unavoidably incorporation It is made of impurities, characterized in that the area fraction of the non-recrystallized structure in the cross section of the steel sheet is 1 to 50%.

The low iron loss high strength non-oriented electrical steel sheet of the present invention is characterized in that the average grain size of the recrystallized crystal grains in the steel sheet cross section is 10 µm or less, the elongation is 20% or more, and the yield strength is 500 MPa or more.

According to the present invention, the non-oriented electrical steel sheet having high strength and low iron loss can be manufactured by managing the area fraction of the unrecrystallized structure in the cold rolled steel sheet at an appropriate level and controlling the average grain size of the recrystallized grains. In addition, by limiting impurities such as Nb and V to reduce fine carbonitride precipitates and improve crystal growth, it is possible to manufacture low iron loss high strength non-oriented electrical steel sheet significantly improved magnetic during heat treatment of the customer. In addition, by performing the final annealing in a temperature range where the rate of change in yield strength according to the temperature change of the final annealing is prevented, the lowering of the elongation can be prevented, and the variation of magnetic and strength can be reduced to ensure low iron loss and high strength characteristics.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated more concretely.

The inventors have investigated the effect of various alloying elements on the production of non-oriented electrical steel sheet having both low iron loss characteristics and high strength characteristics, and recrystallization behavior or structure change by adjusting various process factors such as hot rolling, cold rolling and final annealing. As a result of investigating the characteristics, it was found that in the component system having the composition of a specific alloying component, the area fraction of the unrecrystallized structure in the cross section of the steel sheet and the recrystallized grain size of the final annealed steel sheet were controlled to an appropriate level so as to provide excellent strength characteristics and low iron loss characteristics. It was found that non-oriented electrical steel sheet having at the same time can be produced.

Method for producing a non-oriented electrical steel sheet according to the present invention, in weight%, C: 0.005% or less, Si: 4.0% or less (excluding 0), P: 0.1% or less (excluding 0), S: 0.03% or less, Mn : 0.1 to 2.0%, Al: 0.3 to 2.0%, N: 0.003% or less, Ti: 0.005% or less, Nb: 0.003% or less, V: 0.003% or less, remainder Fe and other unavoidable impurities After hot rolling and cold rolling, the final annealing is performed so that the area fraction of the unrecrystallized structure in the cross section of the steel sheet is in the range of 1 to 50%.

In addition, the present inventors have carefully studied the effect of the area fraction of the non-recrystallized structure on the variation of the magnetic properties and strength of the non-oriented electrical steel sheet, the higher the area fraction of the non-recrystallized structure, the higher the yield strength and accordingly the high strength characteristics Along with the fact that the area of unrecrystallized tissue exceeds 50%, the elongation decreases to less than 20%, and finally the fatigue strength decreases even though the yield strength increases. It became.

In addition, the inventors have found that the grain size together with the area fraction of the unrecrystallized structure is an important factor in determining the characteristics of the electrical steel sheet. The grain size and strength tend to be inversely proportional, and it is preferable to keep the grain size small in order to increase the strength. As a result of the experiment, the strength of the non-oriented electrical steel sheet is usually controlled by controlling the average size of the recrystallized grain to 10 μm or less. It can be seen that it can be improved by more than 30%.

In addition to this fact, the present inventors have investigated and studied various factors to reduce the variation in magnetic properties and strength of non-oriented electrical steel sheet, and as a result, there exists a temperature range where the rate of change of yield strength with the change of the final annealing temperature is low. It was found that the final annealing, in particular, is characterized by the final annealing in the temperature range where the yield strength change rate is lower than 3MPa / ° C, preferably 720 ~ 760 ° C. It was also found that it could be stabilized.

First, the reason for component limitation of the non-oriented electrical steel sheet of this invention is demonstrated. Unless otherwise noted, the content below means weight percent.

[C: 0.005% or less]

C should be contained in 0.005% by weight or less because it causes magnetic aging in the final product, degrading magnetic properties during use. The lower the content of C is preferable for the magnetic properties, it is more preferable to limit to 0.003% by weight or less in the final product.

[Si: 4.0% or less (excluding 0)]

Si is added as a component that increases the specific resistance and lowers the eddy current loss during iron loss. However, if Si is contained in excess of 4.0%, cold rolling is poor and plate breakage occurs. Therefore, the Si content is preferably limited to 4.0% or less (excluding 0).

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

P is added to increase the resistivity, improve the texture, and improve the magnetism. However, when excessively added, the cold rolling property deteriorates, so the content of P is preferably limited to 0.1% or less (excluding 0).

[S: 0.03% or less]

S is preferably managed low because MnS and CuS, which are fine precipitates, deteriorate the magnetic properties. In the present invention, the S content is limited to 0.03% or less.

[Mn: 0.1 to 2.0%]

When Mn is added below 0.1%, fine MnS precipitates are formed to inhibit crystal growth, thereby degrading magnetism. Therefore, it is preferable to add at 0.1% or more so that MnS precipitates are formed coarsely. In addition, when Mn is added in an amount of 0.1% or more, the S component can be prevented from being precipitated by CuS, which is a finer precipitate, thereby preventing magnetic deterioration. However, when Mn is excessively added, the magnetic properties are rather deteriorated, so the Mn content is preferably 0.1 to 2.0%.

[Al: 0.3 to 2.0%]

Al is an effective component to lower the eddy current loss by increasing the specific resistance. If Al is added in less than 0.3%, AlN is finely precipitated to deteriorate the magnetism. On the contrary, if Al is added in excess of 2.0%, the workability is deteriorated. Therefore, the Al content is preferably limited to 0.3 to 2.0%.

[N: 0.003% or less]

N is preferable to contain as little as possible because it forms a fine and long AlN precipitate inside the base material to inhibit grain growth and inferior iron loss, the present invention limits the N content to 0.003% or less.

[Ti: 0.005% or less]

Ti forms fine TiN and TiC precipitates to suppress grain growth. When Ti is contained in an amount exceeding 0.005%, many fine precipitates occur and worsen the magnetic structure by worsening the texture, so the Ti content is limited to 0.005% or less.

[Nb: 0.003% or less]

Nb forms fine NbN and NbC precipitates to suppress grain growth. When Nb is contained in excess of 0.003%, a lot of fine precipitates are generated, thereby inhibiting grain growth by inhibiting grain growth during heat treatment of the customer. In particular, when high-strength products need to be used as low-iron loss products through heat treatment of customers, the use of Nb is limited to 0.003% or less.

[V: 0.003% or less]

V forms fine VN and VC precipitates to suppress grain growth. When V is contained in an amount exceeding 0.003%, many fine precipitates are generated, which inhibits grain growth by inhibiting grain growth during heat treatment of the customer. In particular, when high-strength products are to be used as low-iron loss products through heat treatment of customers, the use of the products can be limited, so the V content is limited to 0.003% or less.

Hereinafter, the manufacturing method of the non-oriented electrical steel sheet of this invention is demonstrated.

In the method for producing a non-oriented electrical steel sheet of the present invention, a slab having the composition described above is first charged into a heating furnace and heated. The heating temperature of the slab is preferably 1100 ~ 1250 ℃. When the slab is heated to a temperature exceeding 1250 ° C, precipitates that spoil the magnetic may be re-dissolved and finely precipitated after hot rolling.

When the slab is heated, then hot rolling is performed, and the hot rolled hot rolled sheet is wound up. The wound hot rolled sheet is subjected to hot rolled sheet annealing as necessary. Hot-rolled sheet annealing is preferably carried out in the production of high-grade electrical steel sheet without phase transformation, and is effective for improving the magnetic flux density by improving the texture of the final annealed sheet. When performing hot-rolled sheet annealing, it is good to perform hot-rolled sheet annealing at the temperature of 850-1100 degreeC. If the hot-rolled sheet annealing temperature is less than 850 ℃ it is difficult to expect a synergistic effect of the magnetic flux density because the tissue does not grow or grow fine. If the hot-rolled sheet annealing temperature is higher than 1100 ° C, the magnetic properties deteriorate, and the rolling workability may deteriorate due to the deformation of the plate shape.

When the hot-rolled sheet annealing as described above can improve the magnetic flux density, in order to manufacture a non-oriented electrical steel sheet in which the magnetic flux density characteristics are not considered, there is no need to perform the hot-rolled sheet annealing, especially high Even in the case where final annealing is to be performed at a temperature, it is possible to omit the hot rolled sheet annealing.

The hot rolled sheet is subjected to annealing as described above or omitted, and then the hot rolled sheet is pickled and cold rolled to produce a cold rolled sheet having a desired thickness. Cold rolling may be carried out by one cold rolling or by carrying out two or more cold rolling with intermediate annealing as necessary.

The cold-rolled cold-rolled sheet is subjected to final annealing. Final annealing is carried out under the condition that the area fraction of the unrecrystallized structure in the cross section of the steel sheet is in the range of 1 to 50%. When the final annealing is performed under the condition that the area fraction of the unrecrystallized structure in the cross section of the steel sheet is larger than 50%, the magnetism deteriorates, and even though the yield strength increases, the elongation decreases to less than 20%, and ultimately the fatigue strength is sharply reduced. Will decrease. On the contrary, when the final annealing is performed under the condition that the area fraction of the unrecrystallized structure in the cross section of the steel sheet is less than 1%, the strength becomes too low, making it difficult to achieve high strength. Therefore, final annealing is performed under the condition that the area fraction of the unrecrystallized structure in the cross section of the steel sheet is in the range of 1 to 50%.

In the component system of the present invention, by performing the final annealing at a temperature in the range of 720 ~ 760 ℃, the area fraction of the non-recrystallized structure can be controlled to 1 to 50%. Even if the final annealing time is less than 5 minutes, it is possible to secure the area fraction of the unrecrystallized structure as in the present invention.

In addition to the area fraction of the non-recrystallized structure, the grain size is also an important factor, and the final annealing is preferably carried out under the condition that the average grain size is 10 μm or less. The size of the grains is inversely proportional to the strength. When the grain size is controlled to 10 μm or less, the grain size is improved by 30% or more as compared to the general non-oriented electrical steel sheet product. The grain size defined herein means the average size of the recrystallized grains observed in the steel sheet cross section.

The final annealing temperature also affects the variation in magnetic properties and strength of non-oriented electrical steel sheets. The rate of change of yield strength depends on the temperature of the final annealing, and the rate of change of yield strength according to the change of final temperature should be taken into account when producing high strength electrical steel sheets.

In general, it is difficult to maintain the final annealing temperature within the target temperature ± 5 ℃ due to equipment constraints. In the case of high-strength electrical steel sheet, the final annealing is performed near the recrystallization temperature, so that the change in strength is made very rapidly. In particular, when the area of unrecrystallized structure is large, the yield strength change rate with the temperature change is more rapid, and when the actual product is produced, the characteristic deviation may exceed the management level.

Therefore, in order to stably produce products with the desired characteristics, it is advantageous to perform final annealing in a temperature range where the rate of change in yield strength is 3 MPa / ℃ or less, considering the guaranteed yield strength of electrical steel sheet. Do.

The final annealed steel sheet may be shipped to a customer by insulation coating in a conventional manner. When the insulation coating is applied, it is possible to apply a conventional coating material, and any of chromium-based (Cr-type) or chromium-free (Cr-free type) can be used without limitation.

In addition, when the customer heat treatment as necessary, by limiting the Nb, V content to reduce the fine carbonitride precipitate to prevent the growth of the crystal growth is significantly improved magnetic properties after the heat treatment.

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

By weight, the slab composed of alloy components and impurities of the composition as shown in Table 1 was reheated to 1180 ℃, and then hot rolled to 2.3mm to prepare a hot rolled plate. At this time, Al + Si value was kept constant at 4.2% or 2.2% in order to minimize the effect caused by the difference in resistivity. Each prepared hot rolled sheet was wound at 650 ° C., cooled in air, and subjected to hot rolled sheet annealing at 1040 ° C. for 2 minutes. Subsequently, after pickling a hot rolled sheet, it cold-rolled so that it might become 0.35 mm thick. Subsequently, the cold rolled plate was subjected to final annealing for 1 minute at the temperature given in Table 2 under an atmosphere of 20% hydrogen and 80% nitrogen, and then analyzed magnetic and mechanical properties. The magnetic properties were measured in the rolling direction and the right angle direction using a single plate measuring device of 60X60mm ² size and averaged. Determined by value. The area fraction of the non-recrystallized structure was calculated by taking a cross section of the final annealed steel sheet under an optical microscope, and then analyzing the area of the recrystallized part by image analysis. The rate of change in yield strength according to the final annealing temperature was calculated by the following Equation 1.

Equation 1) Rate of change in yield strength at temperature T = (YP _T -YP _{T + 10} ) / 10

YP _T is the yield strength of the specimen when annealed at T ℃ temperature, YP _{T + 10} is the yield strength of the specimen when annealed at T + 10 ℃ temperature.

Steel grade Si (% by weight) Al (% by weight) Mn (% by weight) C (% by weight) N (% by weight) S (% by weight) Ti (% by weight) P (% by weight) A 3.1 1.1 0.2 0.003 0.002 0.0015 0.002 0.01 B 1.9 0.3 0.2 0.004 0.002 0.0015 0.003 0.02

Psalter
number Steel grade Final annealing
Temperature (℃) Iron loss
(W10 / 400;
W / Kg) Yield strength
(Mpa) Unresolved
Organization area
Fraction (%) Crystal grain
size
(μm) Elongation
(%) Yield strength
Rate of change
(MPa / ℃)
Remarks One A 680 45.1 898 100 - 8 5.2 Comparison 1 2 A 690 42.5 847 85 4 9 6.4 Comparative material 2 3 A 700 41.0 783 70 4 12 5.8 Comparative material 3 4 A 710 37.9 725 62 4 15 7.1 Comparison 4 5 A 720 34.3 654 50 4 20 1.4 Inventory 1 6 A 730 33.3 640 45 4 22 2.9 Inventory 2 7 A 740 32.7 611 34 4 23 1.3 Inventory 3 8 A 750 30.9 597 23 5 23 2.5 Invention 4 9 A 760 29.7 573 15 5 24 3.0 Invention Article 5 10 A 770 28.4 543 5 6 25 2.8 Inventions 6 11 A 780 27.2 515 One 9 25 2.5 Invention 7 12 A 790 25.1 490 0 20 26 2.5 Comparative material 5 13 B 660 59.5 674 100 - 8 3.9 Comparative material 6 14 B 670 56.1 635 86 4 9 4.8 Comparison 7 15 B 680 54.1 587 71 4 12 4.3 COMPARISON 8 16 B 690 50.0 544 62 4 13 5.3 Comparative material 9 17 B 700 45.3 491 48 4 22 1.1 Invention 8 18 B 710 44.0 480 45 5 21 2.2 Invention 9 19 B 720 43.2 458 33 5 25 1.0 Inventions 10 20 B 730 40.8 448 21 5 26 1.8 Invention invention 11 21 B 740 39.2 430 10 5 28 2.2 Invention 12 22 B 750 37.5 407 6 6 30 2.5 Invention invention 13 23 B 760 35.9 383 2 9 32 2.3 Invention Article 14 24 B 770 33.1 360 0 15 31 2.3 Comparative material 10

From the results in Table 2, it is found that as the final annealing temperature decreases, the area fraction of unrecrystallized tissue and its yield strength increases, but when the area fraction of unrecrystallized tissue exceeds 50%, the elongation decreases to less than 20%. Can be.

In the case of Comparative Materials 1 to 4, the unrecrystallized structure had an area fraction of more than 50% and an elongation of less than 20%, which deteriorated workability and toughness, making it unsuitable for high-strength materials and rapidly deteriorating iron loss above 35 W / Kg. Tend to become. In addition, Comparative Materials 1-4 have a change in mechanical properties with respect to the final annealing temperature higher than 3MPa / ℃, the yield strength deviation of 50 ~ 70Mpa in actual production. In the case of Comparative Material 5, there was no unrecrystallized structure at all, and the elongation was high, so it was excellent in toughness, but the yield strength was lower than 500 MPa, and the strength improvement rate was excessively lower than 30%, considering that the parent material had a yield strength of about 390 Mpa. It is low and it is not useful as a high strength product. In Comparative Materials 6-9, the elongation and iron loss of the non-recrystallized structure was greater than 50%, and the elongation and iron loss dropped sharply, and Comparative Material 10 was not useful as a high strength product.

Inventive materials 1 to 14 have an area fraction of unrecrystallized structure of 1 to 50% and an average grain size of 10 μm or less, which enables stable iron loss and yield strength, and also maintains elongation of 20% or more. It can be seen that it has an advantage as a high-strength product having a high yield strength of 500MPa or more.

By weight, the slab composed of an alloy component and impurities of the composition as shown in Table 3 was reheated to 1130 ℃, and then hot rolled to 2.3mm to prepare a hot rolled plate. Each prepared hot rolled sheet was wound at 650 ° C., cooled in air, and subjected to hot rolled sheet annealing at 1080 ° C. for 2 minutes. Subsequently, after pickling a hot rolled sheet, it cold-rolled so that it might become 0.35 mm thick. Subsequently, the cold rolled sheet was subjected to final annealing at 650 ° C. for 1 minute under an atmosphere of 20% hydrogen and 80% nitrogen, and then measured iron loss and yield strength. In addition, heat treatment was performed at 750 ° C. for 2 hours under nitrogen atmosphere of 100%, which is a general customer heat treatment condition, and iron loss was measured. The magnetic properties were measured in the rolling direction and the right angle direction using a single plate measuring device of 60X60mm ² size and averaged. Determined by value.

Psalter
number Si
(weight%) Al
(weight%) Mn
(weight%) C
(weight%) N
(weight%) S
(weight%) Ti
(weight%) P
(weight%) Nb
(weight%) V
(weight%) 25 3.1 1.1 0.2 0.003 0.002 0.0015 0.002 0.01 0.001 0.001 26 3.1 1.1 0.2 0.003 0.002 0.0015 0.002 0.01 0.002 0.001 27 3.1 1.1 0.2 0.003 0.002 0.0015 0.002 0.01 0.004 0.001 28 3.1 1.1 0.2 0.003 0.002 0.0015 0.002 0.01 0.002 0.004 29 3.1 1.1 0.2 0.003 0.002 0.0015 0.002 0.01 0.005 0.004 30 1.9 0.3 0.2 0.004 0.002 0.0015 0.003 0.02 0.001 0.001 31 1.9 0.3 0.2 0.004 0.002 0.0015 0.003 0.02 0.002 0.001 32 1.9 0.3 0.2 0.004 0.002 0.0015 0.003 0.02 0.004 0.001 33 1.9 0.3 0.2 0.004 0.002 0.0015 0.003 0.02 0.002 0.004 34 1.9 0.3 0.2 0.004 0.002 0.0015 0.003 0.02 0.005 0.004

Psalter
number Before heat treatment After heat treatment Remarks Iron loss
(W10 / 400; W / Kg) Yield strength
(Mpa) Iron loss
(W15 / 50; W / Kg) 25 31.1 586 2.15 Invention material 15 26 30.2 591 2.20 Invention material 16 27 30.6 590 2.45 Comparative material 11 28 31.5 585 2.41 Comparative material 12 29 32.1 591 2.85 Comparative material 13 30 37.2 410 2.91 Invention 17 31 37.6 412 2.93 Invention 18 32 37.4 415 3.64 Comparative material 14 33 37.6 415 3.55 Comparative material 15 34 38.1 413 4.10 Comparative material 16

From the results in Table 4, before the heat treatment of the customer, the iron loss and yield strength did not change significantly as the Nb and V content increased, but Comparative Materials 11 to 16 with Nb and V content exceeding 0.003% showed no iron loss after heat treatment. It can be seen that it is rapidly inferior. The iron loss inferiority is attributed to the occurrence of Nb and V-based carbonitrides that inhibit crystal growth as the Nb and V contents increase. Therefore, if the customer wants to improve the magnetic through the selective heat treatment, it is necessary to control the Nb and V content in the steel to 0.003% or less.

Claims (11)

By weight%, C: 0.005% or less, Si: 4.0% or less (excluding 0), P: 0.1% or less (excluding 0), S: 0.03% or less, Mn: 0.1 to 2.0%, Al: 0.3 to 2.0%, N: 0.003% or less, Ti: 0.005% or less, Nb: 0.003% or less, V: 0.003% or less, a slab made of residual Fe and other unavoidable impurities is hot rolled, cold rolled, and then A method for producing a low iron loss high strength non-oriented electrical steel sheet subjected to final annealing so that the area fraction of unrecrystallized structure is in the range of 1 to 50%. The method according to claim 1,
A low iron loss high strength non-oriented electrical steel sheet for controlling the average grain size of the recrystallized grains after final annealing to 10㎛ or less. The method according to claim 1 or 2,
A method for producing a low iron loss high strength non-oriented electrical steel sheet in which the final annealing is performed in a temperature range where the change rate of yield strength according to the final annealing temperature is 3.0 MPa or less. The method according to claim 1 or 2,
A low iron loss high strength non-oriented electrical steel sheet for controlling the elongation of the final annealed steel sheet 20% or more. The method according to claim 1 or 2,
A method of manufacturing a low iron loss high strength non-oriented electrical steel sheet for controlling the yield strength of the final annealed steel sheet to 500MPa or more. The method according to claim 1 or 2,
The final annealing is carried out at a temperature of 720 ~ 760 ℃ low iron loss high strength non-oriented electrical steel sheet manufacturing method. The method according to claim 1 or 2,
After the hot rolling, the hot rolled sheet annealing before cold rolling, a low iron loss high strength non-oriented electrical steel sheet manufacturing method. By weight%, C: 0.005% or less, Si: 4.0% or less (excluding 0), P: 0.1% or less (excluding 0), S: 0.03% or less, Mn: 0.1 to 2.0%, Al: 0.3 to 2.0%, N: 0.003% or less, Ti: 0.005% or less, Nb: 0.003% or less, V: 0.003% or less, balance Fe and other unavoidable impurities, and the area fraction of the unrecrystallized structure in the cross section of the steel sheet is 1 to Low iron loss high strength non-oriented electrical steel sheet which is 50%. The method according to claim 8,
A low iron loss high strength non-oriented electrical steel sheet having an average grain size of recrystallized grains in a steel sheet cross section of 10 µm or less. The method according to claim 8 or 9,
Low iron loss high strength non-oriented electrical steel sheet with an elongation of 20% or more. The method according to claim 8 or 9,
Low iron loss high strength non-oriented electrical steel sheet with a yield strength of 500 MPa or more.