KR100721818B1 - Non-oriented electrical steel sheets with excellent magnetic properties and method for manufacturing the same - Google Patents

Abstract

The present invention, in the production of non-oriented electrical steel sheet, a technique for manufacturing an electrical steel sheet having excellent magnetic properties by controlling the hot rolled structure using the phase transformation of the steel, by controlling the alloying elements and optimizing the hot rolling conditions The present invention relates to a non-oriented electrical steel sheet having low iron loss and improved magnetic flux density even without performing the same, and a method of manufacturing the same.

The present invention is made up by weight, C: 0.005% or less, Si: 1.0-3.0%, Mn: 0.1-2.0%, P: 0.1% or less, Al: 0.1-1.5%, remaining Fe and other unavoidable impurities, but Mn The relationship between and Al satisfies the formula of -0.2 <m (= Mn-Al) <1.0, and the hot-rolled sheet annealing omission is characterized by having an austenite + ferrite abnormal region at a temperature of Ar1 to 1250 ° C when the slab is reheated. It is possible to provide a non-oriented electrical steel sheet capable of excellent magnetic properties.

In addition, the present invention is to reheat the slab composed of the alloying components as described above, and then start hot finishing (de-phase) rolling is carried out in the austenite + ferrite two-phase region of Ar1 + 50 ℃ or more, the hot finish rolling temperature is Ar1- It is made at 80 ℃ or higher, and at the time of hot finishing rolling, 70% or more of the total hot rolling reduction rate is performed in the austenite + ferrite two-phase zone, and the reduction in the ferrite single phase zone is less than 30% of the total hot rolling reduction rate. The final pass reduction rate is less than {20- (960-finishing rolling finish temperature) / 20}%, finishing the hot finishing rolling, winding in the range of 650 ~ 800 ° C, and omitting or performing hot rolling annealing, and then pickling The present invention provides a method for producing a non-oriented electrical steel sheet having excellent magnetic properties, characterized in that cold rolling and final annealing.

Description

Non-oriented electrical steel sheets with excellent magnetic properties and method for manufacturing the same

1 and 2 are the phase transformation diagrams of the inventive steel and the comparative steel calculated using the FactSage program,

(1a) is a phase transformation diagram shown by fixing Mn content to 0.3%, Al content to 0.6%, and changing Si content,

(1b) is the phase transformation degree shown by fixing the content of Mn and Al at 0.4% and changing the content of Si.

(1c) is the phase transformation degree shown by fixing the content of Mn to 1.6%, the content of Al to 0.8% and changing the content of Si,

(1d) is the phase transformation degree shown by fixing the content of Mn to 1.6%, the content of Al to 0.4% and changing the content of Si,

(1e) is a phase transformation diagram shown by changing the content of Si to 1.6% of Mn and 0.2% of Al,

(2a) is the phase transformation degree shown by fixing the content of Mn to 0.6%, the content of Al to 0.4% and changing the content of Si,

(2b) is a phase transformation diagram in which Mn content is 0.8%, Al content is 0.4%, and Si content is changed.

The present invention relates to 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, iron loss without performing hot-rolled sheet annealing by controlling the component elements and optimizing the hot rolling conditions The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same, which lowers the flux density and improves the magnetic flux density.

Non-oriented electrical steel sheet is an important component necessary for converting electrical energy into mechanical energy in electrical equipment. In order to save energy, it is necessary to lower magnetic properties, ie, iron loss and increase magnetic flux density. Iron loss refers to energy that turns into heat and disappears in the process of energy conversion, and magnetic flux density is shown as a power generating force. If the iron loss is low, the energy loss can be reduced, and if the magnetic flux density is high, the copper loss of the electric device can be reduced, thereby miniaturizing.

In order to manufacture materials with low iron loss and high magnetic flux density, it is necessary to improve the texture of the final annealing plate and the improvement of texture is very affected by the component design and hot rolling. Therefore, it is necessary to develop the proper component system and optimize the hot rolling conditions. .

For this purpose, in the conventional manufacturing process, the hot rolled sheet is homogenized, and the hot rolled sheet is annealed to coarsen the grain size. However, the hot-rolled sheet annealing process is a major driver of the cost increase. Recently, as the demand for electric steel sheet continues to expand, the necessity of productivity improvement and cost reduction is increasing, and researches on techniques for omitting the hot rolled sheet annealing process, which are the main factors of the cost increase, are being actively conducted.

Japanese Patent Application Laid-Open No. 6-220537 is a conventional technique for improving the magnetic characteristics by omitting hot rolled sheet annealing in non-oriented electrical steel sheet. In the prior art, Si + Al is thermally rolled to a steel containing 1.8% by weight or less, and the reduction ratio is 40% in the range of austenite to ferrite transformation temperature at -20 ° C at austenitic ferrite transformation start temperature at + 20 ° C. Hereinafter, a non-oriented electrical steel sheet manufacturing technology characterized in that the finishing rolling strain is limited to 50s-1 or more. If the above conditions are met, the deformation resistance due to the transformation of austenite to ferrite is reduced, and thus the rolling is stabilized and the magnetism is also improved.However, due to the low Si content, the transformation temperature is lowered and the grains are expected to be fine. (W _15/50) is a technique used in the production of 7.00 degree in electrical steel, it is determined in an advantageous technique to improve the shape of the rolled plate, rather than magnetic properties improved.

Japanese Patent Application Laid-Open No. 2000-297326. In the above prior art, the magnetic properties were improved by limiting the condition of the parameter Z of the rolling pass. However, the rolling pass parameter should be less than 16 and the variation range should be less than 2.0. To do this, the deformation rate of hot rolling must be small and the rolling temperature must be high. However, it is not easy to apply to various conditions because the limit of rolling temperature or strain rate is determined by the ability of hot steam. And, in order to satisfy the above conditions, there is a problem in that winding is performed twice at a high temperature and rewinding.

Another conventional technique is Japanese Patent Application Laid-Open No. 2002-356752, which limits the technology for improving magnetism by optimizing basic ingredients and improving the manufacturing process without adding special elements. Particularly, the size and number of emulsions and nitrides are limited. It is limited. However, measuring the size and number of emulsions and nitrides produced during the manufacturing process is a very narrow field of observation, which includes a lot of errors.

The present invention is to solve the problems of the prior art, the non-directional electrical to reduce the iron loss and improve the magnetic flux density by appropriately controlling the alloying elements and hot rolling process of the non-oriented electrical steel sheet to omit or perform hot rolled sheet annealing The present invention provides a steel sheet and a method of manufacturing the same.

In order to solve the above technical problem, the present inventors have investigated the effects of alloying elements on the magnetic properties, the phase transformation and the hot rolling conditions on the magnets, respectively. Among the alloying elements, C, Si, Mn, Al The magnetic properties and phase transformation are greatly influenced. Also, the hot rolling phase (austenite, ferrite or aberrant region of austenite and ferrite), hot finishing rolling temperature, finish temperature and final pass reduction rate It was found to have a big impact.

In addition, the present inventors, when omitting the hot rolled sheet annealing, the deformation due to the hot rolling is present in the hot rolled plate, the strain energy by the hot rolling promotes the formation of {111} texture at the time of final annealing and recrystallization nucleation The fact that it provides a site to make grains finer, worsens the magnetism, and that the deformation caused by hot rolling accumulates more when rolling in the ferrite region than in the austenitic region due to the influence of temperature. I could confirm it.

Therefore, in order to achieve the above object, the present inventors need to reduce the strain energy through the alloy element design in which the austenitic + ferrite two-phase region exists and the austenitic region rolling, and the hot rolling schedule also minimizes the strain energy and hot-rolled sheet grains. The present invention has been completed by paying attention to the fact that it should be set to be large.

The present invention is composed of C: 0.005% or less by weight, Si: 1.0-3.0%, Mn: 0.1-2.0%, P: 0.1% or less, Al: 0.1-1.5%, remaining Fe and other unavoidable impurities, but the Mn Magnetic properties characterized by having a relationship of -0.2 <m (= Mn-Al) <1.0 and having an abnormal region of austenite + ferrite at a temperature of Ar1-1250 ° C. when the slab is reheated. This excellent non-oriented electrical steel sheet is provided.

In addition, the present invention by weight% C: 0.005% or less, Si: 1.0 ~ 3.0%, Mn: 0.1 ~ 2.0%, Al: 0.1 ~ 1.5%,

P: 0.1% or less of the remaining Fe and other unavoidably mixed impurities, the Mn and Al relationship between -0.2 <m (= Mn-Al) <1.0 to satisfy the formula of Ar-1250 ℃ Reheating until

The reheated slab is rolled to at least 70% of the total thermal rolling reduction rate in the abnormal region of austenite and ferrite, and then rolled to less than 30% of the total thermal rolling reduction rate in the ferrite single phase region, but the final pass reduction. A hot rolling step in which the rate is less than {20- (960-finishing finish temperature) / 20}%,

Winding the hot rolled steel sheet at a temperature of 650-800 ° C.,

Cold rolling the wound plate to a predetermined thickness;

It provides a method for producing a hot rolled sheet annealing-omitted non-oriented electrical steel sheet excellent in magnetic properties, characterized in that consisting of the final annealing the cold rolled steel sheet.

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated in detail.

Si and Al are ferrite forming elements, and C and Mn are austenite forming elements. Therefore, in order to make the austenite + ferrite two-phase region, the Si and Al contents should be reduced and the C and Mn contents should be increased. However, since Si and Al are elements with a large resistivity, too much reduction in iron loss deteriorates, so an appropriate component system setting is necessary. In addition, if the C content is increased, the austenite fraction increases, but C causes magnetic aging on the final annealing plate, which deteriorates the magnetism, and thus an additional process of decarburizing the final annealing is required.

In addition, N and S in the impurity elements combine with Al and Mn to form fine nitrides and emulsions of AlN and MnS, respectively, thereby suppressing grain growth and encouraging the aggregate structure of {111} planes which are harmful to magnetism. Therefore, in order to reduce the influence of N, it is desirable to reduce N through impurity control or to add Al as much as possible. Such Al helps the grain growth by suppressing the formation of fine AlN of N and increases the specific resistance to reduce iron loss. In order to reduce the influence of S, it is preferable to add Mn as much as possible. Such Mn suppresses formation of fine MnS of S and helps grain growth.

The austenite fraction is determined according to the C, Si, Al and Mn content, and the austenite fraction can be controlled by adjusting the Si content when the C, Al and Mn contents are fixed. Therefore, it is necessary to set an appropriate Si content to make a two-phase region. If the Si content is too small, iron loss deteriorates due to a decrease in resistivity, and austenite single phase is formed during reheating, which facilitates the employment of AlN and MnS precipitates. In hot rolling and winding, the number of precipitates re-precipitated increases and the magnetism deteriorates. In addition, if the Si content is too high, it becomes a ferrite single phase during reheating, which increases the accumulation of strain energy due to hot rolling, and the final grain annealing promotes the formation of fine grains and the formation of {111} texture structure, which is detrimental to magnetism. Therefore, the ratio of Mn / Al is sufficiently secured to maintain the austenite region, and then the Si content is controlled to have an austenitic + ferrite two phase during reheating, so that the Ar1 temperature is 960 to 1060 ° C. Based on this fact, the composition of the alloy of the present invention was limited.

First, look at the reasons for limiting the components of the present invention.

C: 0.005 wt% or less

Since the C causes the magnetic aging in the final product to lower the magnetic properties during use, the lower the content of C is generally known to be preferable for the magnetic properties. Therefore, the amount is reduced in the steel refining step, and the slag is contained at 0.005% by weight or less, thereby improving the magnetism. If the slab is contained in an amount of 0.005% by weight or more, decarbon annealing should be performed before cold rolling or final annealing. In this case, a wet atmosphere is used. Therefore, the magnetic content of the slab is reduced to 0.005% in the slab. In the final product, containing less than 0.003% by weight, if possible, can suppress self-aging.

Si: 1.0-3.0 wt%

The Si is a component that decreases the eddy current loss during iron loss by increasing the specific resistance, but when added to more than 3.0% by weight, it is difficult to cold rolling and is limited to 3.0% by weight because it becomes a steel having a ferrite single-phase region does not occur phase transformation. .

Mn: 0.1-2.0 wt%

The Mn is an austenite forming element that not only increases the resistivity but also improves the texture, and when added in excess of 2.0% by weight, the magnetic enhancement effect is saturated, so that the content is limited to 0.1 to 2.0% by weight. desirable.

P: 0.1 wt% or less,

The P increases the resistivity, segregates at the grain boundaries, and when hot-rolled sheet annealing is used as an element that develops the texture, it must be added at least 0.01 wt% or more, and if a large amount is added, cold rolling becomes difficult. Since segregation increases and the magnetism decreases, it is preferable to limit the content to 0.1% by weight or less. If the hot-rolled sheet annealing is not performed, P is not uniformly distributed in the grain boundary, so the above effect cannot be obtained and it is preferable to minimize the grain growth.

Al: 0.1-1.5 wt%

Al is a ferrite-forming element, which is effective in lowering the eddy current loss by increasing the specific resistance, and when it is added less than 0.1 wt%, its addition effect is not, and when it is added more than 1.5 wt%, the degree of magnetic improvement decreases compared to the addition amount, and is cold. Since rollability is also inferior, it is preferable to limit the content to 0.1-1.5 weight%. Al is a ferrite-forming element and is added in consideration of Mn content in order to design a steel in which an appropriate phase transformation occurs. In addition, when Al is added in an amount of 0.2% or more and 1.0% or less, the effect is further increased. This is because the effect of oxygen is greatly reduced through the addition of Al, and finely precipitated AlN is formed into coarse AlN precipitate.

-0.2 <m (= Mn-Al) <1.0,

If m is less than -0.2, the austenite region is too small to make an ideal abnormal region. If m is 1.0 or more, the austenite region is too large, so that the Si content having an appropriate Ar1 temperature is too high. Therefore, m is limited to -0.2-1,0.

In addition to the above compositions, the remainder is composed of Fe and other unavoidable impurities.

In the present invention, the Si content is controlled to have an austenitic + ferrite two phase during reheating, and the Ar1 temperature is designed to be 960 to 1060 ° C. It does not end at the temperature, so the amount of reduction in the ferrite region increases, so that the deformation energy due to hot rolling increases, which promotes the formation of {111} aggregate structure. If the Ar1 temperature is too low, austenite phase transforms into ferrite and small grains are formed. Formed, worsening magnetism. When hot flake rolling is carried out in the two-phase zone, crystal grains are coarsened due to exothermic reaction due to ferrite phase transformation of austenite, and uniform grains are obtained throughout the hot-rolled sheet due to phase transformation. When the reduction ratio is low, a more coarse and uniform structure in the plate thickness direction can be obtained.

The manufacturing method of this invention is demonstrated below.

The present invention is made up by weight, C: 0.005% or less, Si: 1.0-3.0%, Mn: 0.1-2.0%, P: 0.1% or less, Al: 0.1-1.5%, the remaining Fe and other unavoidable impurities, The slab whose relationship between Mn and Al satisfy -0.2 <m (= Mn-Al) <1.0 is reheated to a temperature of Ar1-1250 ° C., and then hot rolling is carried out in the two-phase region of haute-tenite + ferrite. In the beginning, the hot rolling is finished on a ferrite, wound up in the range of 650 to 800 ° C., followed by omission or performing hot roll annealing, followed by pickling, cold rolling and final annealing.

In the present invention, in order to minimize the strain energy due to hot rolling and grow grains, hot rolling is started in an austenite + ferrite two phase region of Ar1 + 50 ° C. or higher, and hot finish rolling is performed in a ferrite region of Ar1−80 ° C. or higher. Conduct,

In addition, 70% or more of the total reduction rate is performed in the abnormal region, and the reduction in the ferrite single phase region is performed at less than 30% of the total reduction ratio, and the final pass reduction rate is {20- (960-finishing rolling finish temperature) / 20. It is possible to achieve the object of the present invention by adopting a hot rolling schedule to be carried out at a temperature of Ar1-80 ℃ or more with less than}%.

In the case of hot rolling according to the rolling schedule, the grains of the hot rolled sheet were coarsened to improve the magnetic properties.

The reason why the steel slab formed as described above is reheated in an abnormal region of Ar1-1250 ° C. and then hot rolled is that if the reheating temperature is too high, the reusable amount of AlN or MnS increases, and the solubility of AlN and MnS in austenite is increased. Is higher than the solubility in ferrite, which hinders grain growth due to fine re-precipitation of AlN and MnS re-used during hot rolling and winding.The reason why the Ar1 temperature is designed to be 960-1060 ℃ is too high for the ferrite. As the area is enlarged, the effect of abnormal reverse rolling cannot be seen, and due to the equipment problem, hot finishing rolling does not end at the temperature of Ar1-80 ℃ or more, so that the amount of reduction in the ferrite area increases, so that the deformation energy due to hot rolling increases {111 } Encouraging the formation of aggregated tissues. If the Ar1 temperature is too low, austenite phase-transforms into ferrite and small grains form. It is due to a worsening of the magnetic,

The reason why hot roll rolling starts in the austenitic + ferrite two-phase region of Ar1 + 50 ℃ or higher is that if the hot roll rolling temperature is low, the temperature of the last pass will be too low to hinder grain growth. If the temperature is set to Ar1 + 50 ℃ or higher, and the thermal dosing rolling is performed in the two-phase region, grains are coarsened due to the exothermic reaction due to the ferrite phase transformation of austenite, and uniform grains can be obtained throughout the hot-rolled sheet due to the phase transformation. to be.

In addition, the reduction in the ferrite single-phase region is performed at a temperature of Ar1-80 ° C or more with the reduction of 30% of the total reduction rate and the final pass reduction ratio of less than {20- (960-finishing rolling finish temperature) / 20}%. This is because if the last pass is reduced in the ferrite region, micro residual stress exists, and grain growth is promoted when winding over 650 ° C.

The hot rolled sheet prepared as described above is wound at a temperature of 650 ~ 800 ℃, and then cooled in air in a coiled state or in a non-oxidizing atmosphere. When the coiling temperature exceeds 800 ° C, oxidation may increase during cooling, resulting in poor pickling. Therefore, the coiling temperature is preferably limited to 800 ° C or lower. In addition, when the coiling temperature is less than 650 ° C, grain growth is insufficient, so it is wound in the range of 650 ~ 800 ° C.

The wound hot rolled sheet is cold rolled immediately without annealing the hot rolled sheet. However, if necessary, the wound hot rolled sheet may be subjected to annealing, followed by pickling and cold rolling.

The cold rolling may be cold rolled by one cold rolling method, or may be used by cold rolling two times after the first cold rolling and annealing after the second cold rolling.

The cold rolled steel sheet to the target thickness is finally annealed at 800 ~ Ar1 + 50 ° C. If the annealing temperature is less than 800 ℃ crystal grain growth is insufficient, if the Ar1 + 50 ℃ ℃ surface temperature is excessively high plate shape is bad, surface defects may occur and due to excessive phase transformation from ferrite to austenite This can be fined.

In addition, the annealing atmosphere during annealing is performed in a dry atmosphere without humidity in a non-oxidizing atmosphere. If there is moisture, oxygen in the water may be decarburized by bonding with C of the steel, but by combining with Si and Al of the steel sheet, an oxide layer is formed in the steel sheet to lower the magnetic properties, thereby annealing in a dry reducing atmosphere. The annealing plate is shipped at the demand price after the insulation coating. The insulating coating may be treated with an organic, inorganic and organic-inorganic composite coating, and may be treated with other insulating coating.

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

Example 1

The steel slab formed as shown in Table 1 was reheated at a temperature of 1180 ° C., hot rolled to 2.5 mm, and then wound and cooled in air at 720 ° C. The wound cooled hot rolled plate was pickled and then cold rolled to a thickness of 0.5 mm. The cold rolled steel sheet was finally annealed at a temperature of 1000 ° C. (steel grades 1 and 2) and 900 ° C. (steel grades 3 and 4 and 5) for 90 seconds in a 30% hydrogen and 70% nitrogen mixed gas atmosphere. The annealing plate was investigated after the magnetic properties, the results are shown in Table 2 below.

Figure 1 shows the phase transformation of each steel grade according to the change of the composition of Si, Al, Mn. Figure 1 shows the phase change according to the temperature (y-axis) and Si content (x-axis) changes as calculated using the FactSage program. The value of m (= Mn-Al) is 1a for -0.3, 1b for 0, 1c for 0.8, 1d for 1.2 and 1e for 1.4.

Grade 1 and grade 2 have similar levels of resistivity, but due to differences in composition ratios, grade 2 has a high austenite fraction. As a result, the steel sheet 1 had a large amount of reduction in the ferrite region, and the optical structure of the hot-rolled sheet was fine and the magnetism deteriorated due to the stretched tissues. Grades 3, 4, and 5 have similar levels of resistivity, but when reheated by Si, Al, and Mn, grades 3 have an abnormal range, and grades 4 and 5 have austenite single-phase ranges. Is the highest. In case of steel grades 4 and 5, not only the austenite phase is reheated but also the transformation temperature is so low that the crystal grains of the hot rolled sheet are fine and the magnetism is bad. Therefore, in order to have the proper structure for the purpose of the present patent, -0.2 <m <1.0, Ar1 temperature is 960 ~ 1060 ℃, and must be set up the component system having an ideal range when reheating. If m is less than -0.2, the austenite region is too small to make an ideal abnormal region. If m is 1.0 or more, the austenite region is too large, and the content of Si having an appropriate Ar1 temperature becomes too high.

Table 1

Steel grade C Si Mn Al P Fe One 0.0025 1.0 0.30 0.60 0.010 Bal 2 0.0026 1.30 0.40 0.40 0.010 Bal 3 0.0025 1.60 1.60 0.80 0.011 Bal 4 0.0026 2.0 1.60 0.40 0.010 Bal 5 0.0023 2.4 1.60 0.20 0.009 Bal

[Table 2]

Steel grade On reheating m Ar1 W15 / 50 (W / kg) B50 (T) Remarks One Gamma + Alpha -0.3 1055 3.98 1.733 compare 2 Gamma + Alpha 0 1017 3.65 1.755 invent 3 Gamma + Alpha 0.8 990 2.72 1.693 invent 4 gamma 1.2 918 2.91 1.671 compare 5 gamma 1.4 916 2.80 1.668 compare

W _15/50: loss that occurs when the magnetization from 50Hz to 1.5Tesla

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

 Example 2

The steel slab formed as shown in Table 3 was reheated at a temperature of 1180 ° C., hot rolled to 2.5 mm, and then wound and cooled in air at 720 ° C. The wound cooled hot rolled plate was pickled and then cold rolled to a thickness of 0.5 mm. The cold rolled steel sheet was finally annealed at a temperature of 1000 ° C. for 90 seconds in a 30% hydrogen and 70% nitrogen mixed gas atmosphere. The annealing plate was investigated after the magnetic properties, the results are shown in Table 4 below.

Table 3

Steel grade C Si Mn Al P Fe 6 0.0025 1.2 0.6 0.4 0.010 Bal. 7 0.0026 1.6 0.6 0.4 0.010 Bal. 8 0.0025 1.9 0.6 0.4 0.011 Bal. 9 0.0026 1.4 0.8 0.4 0.010 Bal. 10 0.0024 1.7 0.8 0.4 0.010 Bal. 11 0.0025 2.2 0.8 0.4 0.010 Bal. 12 0.0017 2.02 0.12 0.21 0.01 Bal.

Table 4

Steel grade On reheating m Ar1 W15 / 50 (W / kg) B50 (T) Remarks 6 gamma 0.2 973 3.65 1.734 compare 7 Gamma + Alpha 0.2 1030 3.04 1.743 invent 8 Gamma + Alpha 0.2 1100 3.20 1.711 compare 9 gamma 0.4 970 3.55 1.726 compare 10 Gamma + Alpha 0.4 1005 2.87 1.735 invent 11 Alpha 0.4 - 3.05 1.674 compare 12 Alpha -0.09 - 3.5 1.725 compare

- W _15/50: loss that occurs when the magnetization from 50Hz to 1.5Tesla

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

Figure showing the phase transformation of each steel grade is shown in FIG. 2 shows a phase change according to temperature (y-axis) and Si content (x-axis) changes calculated using the FactSage program.

FIG. 2A shows the results for steel grades 6, 7, and 8 containing 0.6 wt% Mn and 0.4 wt% Al, and Si contents 1.2, 1.6, and 1.9 wt%, respectively. When reheated to ℃, it has an austenite (gamma) single phase region, steels 7, 8 have an austenite + ferrite abnormal region, and the Ar1 temperature is shown in Table 4.

FIG. 2B shows the results for steel grades 9, 10 and 11 containing 0.8 wt% Mn and 0.4 wt% Al and Si contents 1.4, 1.7 and 2.2 wt%, respectively. When reheated to &lt; RTI ID = 0.0 &gt; C, &lt; / RTI &gt; it has an austenite (gamma) single phase region, steel 10 has an austenite + ferrite abnormal region, and steel 11 has a ferrite single phase. The Ar1 temperatures are shown in Table 4.

As shown in Table 4, the invention material manufactured under the manufacturing conditions of the present invention using the invention steel (7,10) that satisfies the components of the present invention and the hot rolling conditions are comparative steel (6, 8, 9, 11) It can be seen that the iron loss is low and the magnetic flux density is high as compared with the above. Steel 6 had a low Si content compared with steels 7 and 8, and hot rolling was performed on the austenitic single phase. As a result, magnetic flux density remained similar, but iron loss was much higher. In the case of steel 8, there was an abnormal area when reheating, but because of the high Ar1, thermal doping was performed in the ferrite region, and the magnetic flux density was lowered. Steel 9 had an austenite single-phase region when reheated, and hot rolling was performed in an abnormal region.

Steel 12 is a conventional example disclosed in Japanese Patent Application Laid-Open No. 2000-297326, which has a ferrite single phase upon reheating. When rolling conditions similar to those of steels 1 to 9 are performed, the Z parameter is about 15.5, and the iron loss is 3.5 W / kg and magnetic flux density is 1.725T, which is inferior to the present invention.

The 7, 10, and 12 steel slabs of Table 3 were reheated at a temperature of 1180 ° C., hot rolled to 2.5 mm, and then wound and cooled in air at 720 ° C. The wound cooled hot rolled sheet was annealed at 1000 ° C. for 5 minutes, pickled, and cold rolled to a thickness of 0.5 mm. The cold rolled steel sheet was finally annealed at a temperature of 1000 ° C. for 90 seconds in a 30% hydrogen and 70% nitrogen mixed gas atmosphere. The annealed plate was cut to 20 magnetic properties after cutting, the results are shown in Table 5. According to Table 5 it was confirmed that even better magnetic properties can be obtained when the AP.

Table 5

Steel grade On reheating m Ar1 W15 / 50 (W / kg) B50 (T) Remarks 7 Gamma + Alpha 0.2 1030 2.82 1.757 invent 10 Gamma + Alpha 0.4 1005 2.67 1.745 invent 12 Alpha -0.09 - 3.23 1.736 compare

- W _15/50: loss that occurs when the magnetization from 50Hz to 1.5Tesla

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

Example 3

The steel slabs No. 7, 10 in Table 3 were reheated at 1180 ° C., hot rolled to a final thickness of 2.5 mm as shown in Table 6, and then wound as shown in Table 6 below. The wound hot rolled sheet was pickled, not annealed, and then cold rolled to a thickness of 0.5 mm. The cold rolled steel sheet was cold-annealed at 1000 ° C. for 90 seconds in a mixed gas atmosphere of 30% hydrogen and 70% nitrogen. The annealing plate was investigated after the magnetic properties, the results are shown in Table 6.

TABLE 6

division Steel grade The fraction occupied by the reduction in the ideal area of the total reduction Last pass temperature Last pass rolling rate Winding temperature (℃) Iron loss (W15 / 50) (W / kg) Magnetic flux density (B50) (Tesla) compare One 7 93.5 960 9.7 720 3.04 1.753 invent 2 7 80.6 965 10.0 720 3.08 1.751 invent 3 7 65.9 967 10.4 720 3.47 1.730 compare 4 7 90.2 952 10.1 720 3.10 1.755 invent 5 7 90.5 887 11.3 720 3.25 1.733 compare 6 7 92.0 961 30.0 720 3.21 1.735 compare 7 7 92.7 970 50.3 720 3.46 1.723 compare 8 7 89.7 965 10.8 680 3.15 1.749 invent 9 7 89.7 965 10.8 620 3.34 1.735 compare 10 10 92.7 968 10.7 720 2.87 1.735 invent 11 10 80.8 972 11.2 720 2.86 1.733 invent 12 10 66.1 971 11.5 720 3.02 1.721 compare 13 10 91.1 950 10.6 720 2.84 1.731 invent 14 10 90.3 890 10.2 720 3.09 1.718 compare 15 10 93.5 967 30.6 720 3.17 1.722 compare 16 10 92.2 966 50.0 720 3.25 1.705 compare 17 10 91.0 968 10.7 680 2.92 1.733 invent 18 10 91.0 968 10.7 620 3.17 1.728 compare

- W _15/50: loss that occurs when the magnetization from 50Hz to 1.5Tesla

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

Comparative materials 3 and 12 had a smaller amount of reduction in the abnormal region than the invention materials 1, 2, and 10, 11, and a large amount of reduction in the ferrite region, resulting in high deformation energy due to hot rolling in the hot rolled sheet, and wide uncrystallized regions. During annealing after rolling, {111} aggregates developed and recrystallized, so iron loss increased and magnetic flux density decreased. Comparative materials 5 and 14 had lower last pass temperatures than the invention materials 4 and 13, which suppressed grain growth and deteriorated magnetism. The comparative materials 6, 7, and 15, 16 had a high final pass reduction rate, so that the grains of the surface portion were fine and the deformation energy due to hot rolling was large, which deteriorated the magnetism. In particular, the magnetic flux density decreased. Comparative materials 9 and 18 had a lower coiling temperature than the invention material, so that the hot-rolled sheet grains did not grow sufficiently to deteriorate the magnetism, but the effect was less than that of other conditions.

The present invention can uniformly form the structure of the hot rolled sheet by using the phase transformation at high temperature due to the content of the alloying elements and the hot rolling conditions, in particular, the deformation energy accumulated in the hot rolled plate by controlling the hot rolling rate By reducing the cold rolling, the non-oriented electrical steel sheet having excellent magnetic properties can be produced by suppressing nucleation of the {111} aggregate tissue, which is detrimental to magnetism during final annealing.

Claims (5)

By weight% C: 0.005% or less, Si: 1.0-3.0%, Mn: 0.1-2.0%, P: 0.1% or less, Al: 0.1-1.5%, remaining Fe and other unavoidable impurities The relationship satisfies the expression -0.2 <Mn-Al <1.0, Non-oriented electrical steel sheet having excellent magnetic properties, characterized in that it has a two-phase region of austenite + ferrite at a temperature of Ar1 ~ 1250 ℃ when reheating the slab.  The method of claim 1, Ar1 temperature of the slab is a non-oriented electrical steel sheet excellent magnetic properties, characterized in that 960 ~ 1060 ℃. By weight% C: 0.005% or less, Si: 1.0-3.0%, Mn: 0.1-2.0%, P: 0.1% or less, Al: 0.1-1.5%, the remaining Fe and other unavoidably mixed impurities, but Reheating the slab in which the relationship between the amount of Mn and Al satisfies the formula of -0.2 <Mn-Al <1.0 at a temperature of Ar1 to 1250 ° C, The reheated slab is subjected to 70% or more of the total thermal rolling reduction rate in the two-phase region of austenite and ferrite and the remainder in the ferrite single phase region, with the final pass reduction being [20- (960-finishing rolling temperature) / Hot rolling step to be less than 20]%, Winding the hot rolled steel sheet at a temperature of 650-800 ° C., Cold rolling the wound hot rolled steel sheet; The non-oriented electrical steel sheet manufacturing method having excellent magnetic properties, characterized in that consisting of the final annealing after the cold rolling. The method of claim 3, Ar1 temperature of the slab is 960 ~ 1060 ℃ excellent magnetic properties, characterized in that the non-oriented electrical steel sheet manufacturing method. The method of claim 3, The starting temperature of the hot finish rolling is Ar1 + 50 ℃ or more, finish temperature is Ar1-80 ℃ or more excellent magnetic properties, characterized in that the non-oriented electrical steel sheet manufacturing method.

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