KR101263845B1 - Method for manufacturing non-oriented electrical steel sheets with excellent magnetic properties and low hardness - Google Patents

Abstract

The present invention relates to the production of non-oriented electrical steel sheet, in weight%, Al: 0.7-2.7%, Si: 0.2-1.0%, Mn: 0.2-1.7%, N: 0.001-0.004%, S: 0.0005-0.004 %, The balance Fe and other inevitable impurities, Al, Mn, N, S is {[Al] + [Mn]} ≤2.0, 0.002≤ {[N] + [S]} ≤0.006, Slave contained to satisfy the composition formula 230≤ {([Al] + [Mn]) / ([N] + [S])} ≤1,000 is heated and then hot rolled and cold rolling is started in performing cold rolling. Provided is a method of producing a non-oriented electrical steel sheet having an excellent magnetic property of having a temperature of 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or more and final annealing of the cold rolled cold rolled sheet. Accordingly, by optimizing the additive ingredients of Al, Si, Mn, N, and S to increase the distribution density of coarse inclusions, it improves grain growth and mobility of magnetic walls, and has excellent magnetic properties and low hardness. The non-oriented electrical steel sheet can be manufactured stably.

Description

Method for manufacturing non-oriented electrical steel sheets with excellent magnetic properties and low hardness}

The present invention relates to the manufacture of non-oriented electrical steel sheet, by setting the additive component of the steel to the optimum to increase the distribution density of coarse inclusions in the steel to improve the growth of the grain and the mobility of the magnetic wall to secure excellent magnetic properties, low hardness It relates to a manufacturing method of the highest quality non-oriented electrical steel sheet to improve the product productivity and punchability.

The present invention relates to the production of non-oriented electrical steel sheet used as the iron core material of the rotating machine, the non-oriented electrical steel sheet is an important component for converting electrical energy into mechanical energy, the magnetic properties are very important. Mainly mentioned as magnetic properties are iron loss and magnetic flux density. Iron loss is energy that disappears as heat during the energy conversion process, the lower the better, the higher the magnetic flux density is the power source of the rotor, the higher the better the energy efficiency.

In general, non-oriented electrical steel sheet adds Si as a main element to reduce iron loss. When the content of Si increases, the magnetic flux density decreases, and when the content of Si exceeds 3%, workability is lowered, which makes it difficult to cold roll. In addition, the die life is reduced when the customer punches. Therefore, attempts have been made to improve the magnetic and mechanical properties by reducing the content of Si and increasing the content of Al, but are not yet commercialized due to the difficulty of the high-quality non-oriented electrical steel sheet and the difficulty in mass production process. .

On the other hand, in order to obtain good magnetism in the non-oriented electrical steel sheet, it is necessary to control the impurities such as C, S, N, Ti, such as fine inclusions present in the steel to extremely low, thereby improving the growth of crystal grains. However, it is not easy to manage impurities very low in the manufacturing process of ordinary electrical steel sheet, and there is a disadvantage in that an increase in cost occurs in the steelmaking stage.

Impurities not removed in the steelmaking stage exist in the form of nitrides or sulfides in the slab during continuous casting, and inclusions such as nitrides or sulfides are redissolved as the slab is reheated to a temperature above 1,100 ° C for hot rolling. At the end of rolling, fine precipitates again.

The inclusions MnS and AlN, which are precipitated in general non-oriented electrical steel sheets, are observed to have a fine average size of about 50 nm, and the fine inclusions thus produced not only increase the hysteresis loss by inhibiting the growth of grains during annealing, but also magnetization. This reduces the permeability by preventing the city wall from moving.

Therefore, in the manufacturing process of the non-oriented electrical steel sheet, it is important to properly control the impurities from the steelmaking stage so that such fine inclusions do not exist, and to suppress the remaining inclusions to be re-used during hot rolling and to be deposited more finely.

The present invention has been made to solve the problems of the prior art as described above, coarse inclusions in steel by managing the ratio of the components of the alloying elements Al, Si, Mn and impurity elements N and S of the steel under optimum conditions Its purpose is to provide the highest quality non-oriented electrical steel sheet with high productivity and releasability due to its low hardness, which improves the grain growth and the mobility of magnetic walls by increasing the distribution density and reducing the frequency of occurrence of fine inclusions. will be.

Method for producing a non-oriented electrical steel sheet of the present invention for solving the above problems by weight, Al: 0.7 ~ 2.7%, Si: 0.2 ~ 1.0%, Mn: 0.2 ~ 1.7%, N: 0.001 ~ 0.004%, S : 0.0005% to 0.004%, remainder Fe and other unavoidable impurities, and Al, Mn, N, and S are {[Al] + [Mn]} ≤2.0, 0.002≤ {[N] + [S] } ≤ 0.006, 230 ≤ {([Al] + [Mn]) / ([N] + [S])} ≤ 1,000 to heat the slab contained to satisfy the composition formula and then hot-rolled, cold rolling In this case, the cold rolling start temperature is 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or more, and the cold rolled cold rolled sheet is finally annealed. [Al], [Mn], [N], [S], and [Si] are the contents (wt%) of Al, Mn, N, S, and Si, respectively.

In the method for producing a non-oriented electrical steel sheet of the present invention, Al, Si, Mn in the slab composition formula 1.0≤ {[Al] + [Si] + [Mn] / 2} ≤2.0, 1≤ [Al] / [Mn] It is characterized by containing so as to satisfy the composition formula of ≤8.

In the method for producing a non-oriented electrical steel sheet of the present invention, the inclusion of a nitride or a sulfide alone or a combination thereof is formed in the final annealed steel sheet, and to control the distribution density of inclusions having an average size of 300nm or more to 0.02 pieces / mm ² or more There is a characteristic.

Method for producing a non-oriented electrical steel sheet of the present invention is characterized in that the cross-sectional Vickers hardness (Hv1) of the final annealed steel sheet to 140 or less.

According to the method of manufacturing the non-oriented electrical steel sheet of the present invention, it is possible to control the fraction of the aggregated structure (<111> // ND) in which the <111> plane is arranged in a direction perpendicular to the surface of the steel sheet in the final annealed steel sheet. It features.

In the manufacturing method of the non-oriented electrical steel sheet of the present invention is added to 0.3 ~ 0.5% Al to be deoxidized, and then the remaining alloy element is added, after the addition of the remaining alloy element to maintain the temperature of the molten steel to 1,500 ~ 1,600 ℃ Manufacturing the slab is another feature.

According to the present invention, by appropriately managing the component ratios of the alloying elements of Al, Si, and Mn and the impurity elements of N and S to increase the distribution density of coarse inclusions, the growth of crystal grains and the mobility of the magnetic walls are improved, thereby providing excellent magnetic properties. High quality non-oriented electrical steel sheet having low hardness can be stably manufactured. In addition, the customer's processability and productivity is excellent, and the cost is reduced by lowering the production cost of the product.

1 is a view showing a composite inclusion in the non-oriented electrical steel sheet of the present invention.
FIG. 2 is divided based on whether [N] + [S] is the horizontal axis and [Al] + [Mn] is the vertical axis, and the distribution density of a large composite inclusion having an average size of 300 nm or more is 0.02 / mm ² or more. Graph shown by.

The present inventors have investigated the effects of alloying elements, impurity elements, and relationships between elements on the formation of inclusions, and on the effects of magnetic properties and workability, respectively. As a result, Al, Si, Mn and , The content of N and S as impurity elements is properly adjusted and the ratio of Al / Si and Al / Mn, Al + Si + Mn / 2, Al + Mn, N + S, (Al + Mn) / (N + S) By optimally managing the steel sheet, it is possible to reduce the hardness of the steel sheet and increase the distribution density of the large composite inclusions having an average size of 300 nm or more in the steel sheet, thereby greatly improving the magnetic properties of the non-oriented electrical steel sheet, as well as the productivity and the punchability of the product. The present invention has been completed by paying attention to the fact that it is improved.

In the present invention, by weight, Al: 0.7-2.7%, Si: 0.2-1.0%, Mn: 0.2-1.7%, N: 0.001-0.004%, S: 0.0005-0.004%, balance Fe and other unavoidably incorporated. It is composed of impurities, and Al, Mn, N, and S are {[Al] + [Mn]} ≤2.0, 0.002≤ {[N] + [S]} ≤0.006, 230≤ {([Al] + [Mn ]) / ([N] + [S])} ≤1,000, 1.0≤ {[Al] + [Si] + [Mn] / 2} ≤2.0, 1≤ [Al] / [Mn] ≤8 It is characterized by increasing the distribution density of nitrides and sulfides having an average size of 300 nm or more, or inclusions including them, to 0.02 pieces / mm ² or more, so that the magnetic content is excellent and the cross section Vickers hardness (Hv1) Due to the low hardness of 140 or less, it is possible to produce the highest quality non-oriented electrical steel sheet having excellent workability.

In the present invention, 0.3 to 0.5% of Al is first added in the steelmaking step to perform deoxidation, and then the remaining alloying elements are added, and after the addition of the remaining alloying elements, the temperature of the molten steel is maintained at 1,500 to 1,600 ° C. A slab having a composition is prepared, and the slab is heated to a temperature of 1,100 to 1,250 ° C. and then hot rolled, but hot finishing rolling is performed at 800 ° C. or higher, and the hot rolled hot rolled sheet is annealed at a temperature range of 850 ° C. or higher. Omitted and pickled, cold rolling was carried out at a reduction ratio of 70 to 95%, but the cold rolling start temperature was 100 × (0.7 × [Si] +0.6 so that the <111> // ND fraction was controlled to 30% or less. × [Al]) / 3.3 or more, characterized in that the non-oriented electrical steel sheet excellent in magnetic properties and workability by the final annealing of the cold-rolled cold rolled sheet in the temperature range of 750 ~ 1,100 ℃.

In the case of Al, Si, and Mn, which are alloying elements of steel, the alloying elements are elements added to lower iron loss of electrical steel sheet, but as the added content thereof increases, the magnetic flux density decreases and the workability of the material is deteriorated. These alloying components should be properly set to improve magnetic flux density as well as iron loss, and maintain hardness at an appropriate level.

In addition, Al and Mn combine with N and S, which are impurity elements, to form inclusions such as nitride and sulfide. Since such inclusions have a great influence on the magnetism, it is necessary to increase the frequency of formation of the inclusions so as to minimize deterioration of the magnetic properties.

The present inventors first discovered that when Al, Mn, Si, N, and S were contained so as to satisfy specific conditions, a huge complex inclusion composed of nitrides or sulfides was formed, and the workability was adjusted by adjusting the distribution density of such composite inclusions. The present invention has been proposed in view of the fact that the magnetism is greatly improved despite having a minimum amount of deteriorating alloying elements.

First, the reason for limiting the content ratio between the range and the component elements constituting the present invention will be described.

[Al: 0.7-2.7 wt%]

Al is added because it increases the specific resistance of the material, lowers iron loss and forms nitride, and is added at 0.7-2.7% to form coarse nitride. If the Al content is less than 0.7%, the inclusions cannot be sufficiently grown. If the Al content is more than 2.7%, the workability is deteriorated and problems occur in all processes such as steelmaking and continuous casting, so that it cannot be produced by the normal process.

[Si: 0.2-1.0 wt%]

Si serves to lower the iron loss by increasing the specific resistance of the material, it is difficult to expect the effect of reducing iron loss when contained less than 0.2%, productivity and punchability is inferior due to the increase in hardness of the material when contained above 1.0%.

[Mn: 0.2-1.7 wt%]

Mn improves iron resistivity and forms sulfides by increasing the specific resistance of the material, and the inclusion coarsening effect is exerted when the content is 0.2% or more. When Mn is contained in excess of 1.7%, the content of Mn is preferably limited to 0.2 to 1.7% because it promotes the formation of [111] aggregates, which is disadvantageous to magnetism.

[N: 0.001-0.004 wt%]

N is an impurity element, in which fine nitride is formed during the manufacturing process to suppress grain growth and inferior iron loss. Therefore, it is necessary to suppress the formation of nitride, but this requires additional cost and processing time, so it is not economical. It is more desirable to reduce the impact. In order to grow the inclusions in this manner, it is essential to control the N to 0.001% to 0.004%. When N exceeds 0.004%, coarsening of inclusions is not achieved and iron loss is increased, and more preferably, N is contained in 0.003% or less.

[S: 0.0005-0.004 wt%]

S is an impurity element, which forms fine sulfides during the manufacturing process, inhibits grain growth, and infers iron loss. Therefore, the formation of sulfides should be suppressed, but this requires additional cost and processing time, and thus it is not economical. Therefore, as described below, the inclusions are coarsely grown by using an element having a high affinity for S as an impurity element to crystal grain growth. It is more desirable to reduce the impact. In order to grow the inclusions in this way, it is essential to control the S in the range 0.0005 to 0.004%. If S exceeds 0.004%, coarsening of inclusions is not achieved, and iron loss is increased. More preferably, S is contained at 0.003% or less.

In addition to the impurity elements described above, impurities that are inevitably mixed such as C and Ti may be included. Since C causes self aging, the C content should be limited to 0.004% or less, preferably 0.003% or less. Ti promotes the growth of the [111] aggregate structure, which is an undesirable crystal orientation in the non-oriented electrical steel sheet, so it is preferable to limit it to 0.004% or less, more preferably 0.002% or less.

[Al] + [Mn], which is the total amount (wt%) of Al and Mn in the present invention, is limited to 2.0% or less, which is the fraction of the [111] aggregate tissue that is disadvantageous to magnetism when the total amount of Al and Mn exceeds 2.0%. This is because the magnetism heats up. When the total amount of Al and Mn is less than 0.9%, nitrides, sulfides, or two complex inclusions are not coarse to form magnetic heat. However, in the present invention, Al is contained in an amount of 0.7% or more and Mn is 0.2% or more. Since the total amount of Al and Mn is 0.9% or more, magnetic deterioration is prevented.

In the present invention, the total amount of N and S [N] + [S] is limited to 0.002% to 0.006%, because inclusions grow coarsely in this range. When the total amount of N and S exceeds 0.006%, the fraction of fine inclusions increases and the magnetism deteriorates.

In the present invention, Al, Mn, N, and S are contained so as to satisfy the composition formula of 230≤ ([Al] + [Mn]) / ([N] + [S]) ≤1,000. [Al], [Mn], [N], and [S] are the contents (wt%) of Al, Mn, N, and S, respectively. Within this range, magnetism is improved by coarse inclusions, which increases the density of distribution of large composite inclusions. Outside this range, coagulation of inclusions does not become coarse, and the formation frequency of huge composite inclusions is low. Is formed.

1 is a view showing a composite inclusion in the non-oriented electrical steel sheet of the present invention.

Within the range in which the addition amount of Al, Mn, N, and S is optimally managed, the inclusions grow more than several times as compared to the conventional materials, resulting in a high frequency of formation of coarse composite inclusions having an average size of 300 nm or more. The fine inclusions having an average size is reduced to improve the magnetism, and when the distribution density of the giant composite inclusion is 0.02 pieces / mm ² or more, the magnetism is greatly improved.

The formation of such coarse composite inclusions is assumed to occur in the steelmaking stage, and the exact mechanism of formation thereof is not clear yet, but Al-based oxides and nitrides are formed by deoxidation during initial Al injection in the steelmaking stage. When adding alloying elements such as Al and Mn and bubbling, the Al-based oxide / nitride is grown in the component system satisfying the component ratios of Al, Mn, Si, N, and S as defined in the present invention, and at the same time, the Mn-based sulfide Presumably due to precipitation in the stomach.

FIG. 2 is divided based on whether [N] + [S] is the horizontal axis and [Al] + [Mn] is the vertical axis, and the distribution density of a large composite inclusion having an average size of 300 nm or more is 0.02 / mm ² or more. It is a graph shown.

Referring to the illustration of Fig. 2, the total amount of Al and Mn [Al] + [Mn] is 2.0% or less, and the total amount of N and S [N] + [S] is 0.002 to 0.006 and Al and In the scope of the present invention (inside the thick line) where ([Al] + [Mn]) / ([N] + [S]), which is the ratio of the total amount of Mn to the total amount of N and S, is 230 to 1,000, the inclusions While the distribution density of the large composite inclusions having an average size of 300 nm or more is greater than 0.02 / mm ² , the magnetic properties are excellent, while the coarse inclusions do not form within the range outside the present invention, and the distribution density of large composite inclusions having an average size of 300 nm or more is exceeded. Is lower than 0.02 pieces / mm ² and the magnetism is degraded due to inferior texture.

Coarse inclusions have been observed to have an average size of 300 nm or more mainly due to the compounding of nitrides and sulfides, but also includes several nitrides or several sulfides having an average size of 300 nm or more, and nitrides or sulfides alone It can be included also grown to 300nm or more. Here, the average size of the inclusions was determined by measuring the longest length and the shortest length of the inclusions observed in the cross section of the steel sheet and averaging them.

[Al] / [Si] which is a ratio of Al to Si in the present invention is preferably limited to 0.7 to 14.0. This is because when the ratio of Al to Si is 0.7 to 14.0, the grain growth is excellent and the hardness of the material is lowered, thereby improving productivity and punchability. If [Al] / [Si] is less than 0.7, the inclusions do not grow significantly, and the grain growth is deteriorated and the magnetism is deteriorated. If [Al] / [Si] exceeds 14.0, the texture of the material deteriorates and the magnetic flux density becomes heat. To be harmed.

[Al] / [Mn], which is a ratio of Al to Mn in the present invention, is preferably limited to 1-8. This is because when the ratio of Al to Mn is 1 to 8, the inclusion loss is excellent and the iron loss characteristics are excellent. On the contrary, when the Al ratio is out of this range, the growth rate of the inclusion is lowered and the fraction of the texture that is favorable for magnetism is reduced.

Next, the ratio limitation of the alloy component related to a specific resistance is demonstrated. Recently, the demand for high magnetic flux density products to achieve high efficiency in the motor is rapidly increasing, and accordingly, the demand for non-oriented electrical steel sheet to improve the magnetic flux density by lowering the specific resistance is increasing. Therefore, the specific resistance (intrinsic resistance) is lowered to 36 or less to raise the magnetic flux density, and it is appropriate to manage the specific resistance to 25 or more to cope with high-speed rotation.

The relationship between the component system and the resistivity was calculated using the following empirical formula.

ρ = 13.25 + 11.3 × ([Al] + [Si] + [Mn] / 2) (ρ: resistivity)

According to this empirical formula, [Al] + [Si] + [Mn] / 2 should be managed at 1.0 ~ 2.0% to satisfy specific resistivity 25 ~ 36.

Hereinafter, a method of manufacturing a non-oriented electrical steel sheet according to the present invention. In the method for producing a non-oriented electrical steel sheet according to the present invention, it is preferable to first add 0.3 to 0.5% of the total Al content in the steelmaking step, and then add residual alloy elements to sufficiently deoxidize the steel. After the alloying element is added, the molten steel is maintained at a temperature of 1,500 to 1,600 ° C. so that the inclusions in the steel are sufficiently grown, and then solidified in a continuous casting process to manufacture the slab. Subsequently, the slab is charged to a heating furnace and reheated to a temperature of 1,100 ° C or more and 1,250 ° C or less. When the slab is heated to a temperature exceeding 1,250 ℃, the precipitate that harms the magnetic can be re-dissolved and finely precipitated after hot rolling, so the slab is heated at a temperature below 1,250 ℃.

Once the slab is reheated, it is then hot rolled. It is preferable to perform hot finishing rolling at the time of hot rolling at the temperature of 800 degreeC or more.

The hot rolled hot rolled sheet is annealed at a temperature of 850 ° C. or higher. If the hot-rolled sheet annealing temperature is less than 850 ° C., the tissue does not grow or grows finely, so that the synergy effect of the magnetic flux density decreases. If the hot rolled sheet annealing temperature is too high, the magnetic properties are rather deteriorated, and the rolling workability may deteriorate due to the deformation of the plate shape. Therefore, the hot rolled sheet annealing temperature is preferably performed at a temperature of 1,100 ° C. or lower. The more preferable annealing temperature of a hot rolled sheet is 950-1,100 degreeC. Hot-rolled sheet annealing is performed in order to increase the crystal orientation favorable to magnetic as needed, but it is also possible to omit hot-rolled sheet annealing.

As described above, the hot rolled sheet is annealed or omitted, and then the hot rolled sheet is pickled and then cold rolled to a predetermined sheet thickness. Cold rolling may be applied differently depending on the plate thickness, but by applying a reduction ratio of about 70 ~ 95% can be produced cold rolled plate.

In the present invention, the addition amount of Si, Mn, Al alloy elements affecting the cold rolling is appropriately adjusted, and thus the cold rolling is excellent. Therefore, high rolling reduction can be applied. Thus, only one cold rolling can be used as a thin plate having a thickness of about 0.15 mm. Manufacturing is possible. When cold rolling is required, two cold rolling including intermediate annealing may be performed, or two annealing may be applied.

In the present invention, it is important to control the start temperature of cold rolling. The cold rolling start temperature is preferably set to 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or higher in consideration of the addition amount of the alloy component. It is possible to reduce the density of aggregates that are unfavorable to magnetism during recrystallization annealing by causing dynamic recovery at second, and secondly, the cold rolling initiation temperature required to cause dynamic recovery in proportion to the increase of Si and Al content must be increased.

According to the research of the present inventors, the increase in cold rolling initiation temperature required to cause dynamic recovery with increasing Si content was found to be about 1.17 times the increase in cold rolling initiation temperature with increasing Al content. Therefore, it was concluded that the cold rolling start temperature should be set to 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or more.

As described above, the cold rolling is performed at a cold rolling start temperature of 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or more, so that the fraction of <111> // ND in the final annealed steel sheet is 30% or less. Can be controlled.

The cold rolled sheet cold rolled under the above conditions is subjected to final annealing. If the final annealing temperature is less than 750 ℃ recrystallization does not occur sufficiently, if the final annealing temperature exceeds 1,100 ℃ because the surface layer of the oxide layer is deeply formed and the magnetic is lowered, the final annealing is preferably carried out at 750 ~ 1,100 ℃ temperature.

The final annealed steel sheet is shipped to the customer after insulation coating treatment in the usual way. 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.

Hereinafter, the present invention will be described in detail with reference to Examples. Unless stated otherwise in the examples below, the ingredient content is expressed in weight percent.

Were vacuum-melted in a laboratory to produce ingots having the compositions shown in Table 1 below. Impurities C, S, N, and Ti of the material were all controlled to 0.002%, 0.3 to 0.5% of Al was added to the molten steel to promote the formation of inclusions, and the remaining Al, Si, and Mn were added to prepare a steel ingot. Each material was heated to 1,150 ° C. and hot-rolled at 850 ° C. to produce a hot rolled sheet having a plate thickness of 2.3 mm. The hot rolled hot rolled sheet was annealed at 1,050 ° C. for 4 minutes and then pickled. After cold rolling, the sheet thickness was 0.50 mm and final annealing was performed at 900 ° C. for 30 seconds.

Inclusion size and inclusion distribution density, iron loss, magnetic flux density and hardness for each are shown in Table 2 below. Sample preparation for observation of inclusions was performed using a replica method, which is a common method for steel materials, and a transmission electron microscope was used as a device. At this time, the acceleration voltage was applied to 200kV.

Steel grade Al Si Mn C S N Ti A1 1.5 0.2 0.2 0.002 0.002 0.002 0.002 A2 1.5 0.2 0.5 0.002 0.002 0.002 0.002 A3 0.7 0.2 0.5 0.002 0.002 0.002 0.002 A4 2.7 0.5 0.3 0.002 0.002 0.002 0.002 A5 1.7 0.5 0.3 0.002 0.002 0.002 0.002 A6 0.7 0.5 0.3 0.002 0.002 0.002 0.002 A7 0.5 0.5 0.5 0.002 0.002 0.002 0.002 A8 0.5 0.5 0.5 0.002 0.002 0.002 0.002 A9 2.2 0.5 0.2 0.002 0.002 0.002 0.002 A10 1.2 0.5 0.2 0.002 0.002 0.002 0.002 A11 1.0 0.1 0.2 0.002 0.002 0.002 0.002 A12 1.2 0.2 0.2 0.002 0.002 0.002 0.002 A13 1.0 0.2 0.2 0.002 0.002 0.002 0.002 A14 2.2 0.7 0.2 0.002 0.002 0.002 0.002 A15 0.7 0.7 0.2 0.002 0.002 0.002 0.002 A16 1.3 0.2 0.7 0.002 0.002 0.002 0.002 A17 1.5 0.2 1.0 0.002 0.002 0.002 0.002 A18 1.2 0.2 1.0 0.002 0.002 0.002 0.002 A19 0.9 0.5 1.0 0.002 0.002 0.002 0.002 A20 0.9 0.7 0.8 0.002 0.002 0.002 0.002 A21 1.0 0.5 0.8 0.002 0.002 0.002 0.002

Steel grade Al /
Si Al /
Mn Al +
Mn N + S (Al + Mn)
/ (N + S) Al + Si
+ Mn / 2 Inclusion
size
(Nm) Inclusion
Distribution density
(1 / mm ² ) Iron loss
(W15 / 50;
W / Kg) Magnetic flux density
(B50;
Tesla) Hardness
(Hv1) Remarks A1 7.5 7.5 1.7 0.0040 425 1.8 450 0.40 3.2 1.73 140 Inventive Example A2 7.5 3.0 2.0 0.0040 500 2.0 500 0.35 3.0 1.73 140 Inventive Example A3 3.5 1.4 1.2 0.0040 300 1.2 300 0.30 4.0 1.74 110 Inventive Example A4 5.4 9.0 3.0 0.0040 750 3.4 250 0.01 3.0 1.68 157 Comparative example A5 3.4 5.7 2.0 0.0040 500 2.4 250 0.01 2.9 1.69 145 Comparative example A6 1.4 2.3 1.0 0.0040 250 1.4 450 0.05 3.5 1.74 115 Inventive Example A7 1.0 1.0 1.0 0.0040 250 1.3 50 0.01 4.5 1.74 110 Comparative example A8 1.0 1.0 1.0 0.0040 250 1.3 75 0.01 4.5 1.74 110 Comparative example A9 4.4 11.0 2.4 0.0040 600 2.8 400 0.01 2.8 1.68 150 Comparative example A10 2.4 6.0 1.4 0.0040 350 1.8 600 0.15 3.2 1.73 130 Inventive Example A11 10 5.0 1.2 0.0040 300 1.2 250 0.01 4.5 1.74 105 Comparative example A12 6.0 6.0 1.4 0.0040 350 1.5 400 0.20 3.5 1.74 105 Inventive Example A13 5.0 5.0 1.2 0.0040 300 1.3 300 0.18 3.6 1.74 110 Inventive Example A14 3.1 11.0 2.4 0.0040 600 3.0 400 0.01 2.8 1.69 160 Comparative example A15 1.0 3.5 0.9 0.0040 225 1.5 150 0.01 3.9 1.74 130 Comparative example A16 6.5 1.9 2.0 0.0040 500 1.9 350 0.25 2.9 1.72 130 Inventive Example A17 7.5 1.5 2.5 0.0040 625 2.2 250 0.01 2.8 1.69 140 Comparative example A18 6.0 1.2 2.2 0.0040 550 1.9 250 0.01 2.9 1.70 130 Comparative example A19 1.8 0.9 1.9 0.0040 475 1.9 200 0.01 3.2 1.70 135 Comparative example A20 1.3 1.1 1.7 0.0040 425 2.0 350 0.05 3.5 1.73 140 Inventive Example A21 2.0 1.3 1.8 0.0040 450 1.9 400 0.05 3.3 1.73 140 Inventive Example

In the case of steel grades A1 to A3, A6, A10, A12, A13, A16, A20, and A21 belonging to the scope of the present invention, the hardness is low, so that the productivity and customer punchability are excellent, and coarse inclusions of 300 nm or more in size are observed and the distribution thereof. Its density is higher than 0.02 (1 / mm ² ) and it is excellent in magnetism.

On the other hand, steel grades A4, A9, and A14 contained Al / Mn ratios and Al + Mn contents outside the scope of the present invention, and no inclusions having a size of more than 300 nm were observed, and iron loss and magnetic flux density were inferior. In steel grades A17 and A18, inclusions having Al + Mn outside the scope of the present invention having a size of 300 nm or more were not observed, and iron loss and magnetic flux density were inferior. In steel A19, inclusions having a size of 300 nm or more out of the range of Al / Mn were not observed, and iron loss and magnetic flux density were inferior. Steel grades A4, A5, A9 and A14 were inferior in productivity and punchability because Al + Si + Mn / 2 had high hardness outside the scope of the present invention.

Vacuum dissolution in the lab produced a steel ingot as shown in Table 3 below. At this time, the content was controlled by varying the content of impurities N and S of the material, and added 0.3-0.5% of Al to the molten steel to promote the formation of inclusions. It was. Each material was heated to 1,150 ° C. and hot-rolled at 850 ° C. to produce a hot rolled sheet having a plate thickness of 2.3 mm. The hot rolled hot rolled sheet was annealed at 1,050 ° C. for 4 minutes and then pickled. After cold rolling, the sheet thickness was 0.50 mm and final annealing was performed at 900 ° C. for 30 seconds.

Inclusion size and inclusion distribution density, iron loss, magnetic flux density, and hardness for each are shown in Table 4 below. Sample preparation for observation of inclusions was performed using a replica method, which is a common method for steel materials, and a transmission electron microscope was used as a device. At this time, the acceleration voltage was applied to 200kV.

Steel grade Al Si Mn C S N Ti B1 1.0 0.5 0.3 0.0030 0.0010 0.0010 0.0020 B2 0.7 0.3 0.2 0.0030 0.0030 0.0030 0.0020 B3 0.7 0.3 0.5 0.0030 0.0020 0.0030 0.0020 B4 0.7 0.5 0.3 0.0030 0.0010 0.0025 0.0020 B5 1.0 0.3 0.7 0.0030 0.0005 0.0005 0.0020 B6 1.0 0.3 0.7 0.0030 0.0040 0.0020 0.0020 B7 1.2 0.5 1.0 0.0030 0.0020 0.0020 0.0020 B8 1.2 0.2 0.3 0.0030 0.0015 0.0010 0.0020 B9 0.9 0.5 0.8 0.0030 0.0020 0.0020 0.0020 B10 0.9 0.5 0.8 0.0030 0.0040 0.0030 0.0020 B11 0.9 0.5 0.5 0.0030 0.0030 0.0030 0.0020 B12 0.9 0.5 0.5 0.0030 0.0020 0.0025 0.0020 B13 0.9 0.5 0.5 0.0030 0.0005 0.0005 0.0020

Steel grade Al /
Si Al /
Mn Al +
Mn N + S (Al + Mn)
/ (N + S) Al + Si
+ Mn / 2 Inclusion
size
(Nm) Inclusion
Distribution density
(1 / mm ² ) Iron loss
(W15 / 50;
W / Kg) Magnetic flux density
(B50;
Tesla) Hardness
(Hv1) Remarks B1 2.0 3.3 1.3 0.0020 650 1.7 350 0.150 3.2 1.73 135 Inventive Example B2 2.3 3.5 0.9 0.0060 150 1.1 200 0.010 4.2 1.71 130 Comparative example B3 2.3 1.4 1.2 0.0050 240 1.3 300 0.200 3.5 1.74 130 Inventive Example B4 1.4 2.3 1.0 0.0035 286 1.4 450 0.050 3.4 1.73 130 Inventive Example B5 3.3 1.4 1.7 0.0010 1700 1.7 50 0.010 3.5 1.69 140 Comparative example B6 3.3 1.4 1.7 0.0060 283 1.7 350 0.200 3.2 1.74 140 Inventive Example B7 2.4 1.2 2.2 0.0040 550 2.2 250 0.010 2.9 1.68 140 Comparative example B8 6.0 4.0 1.5 0.0025 600 1.6 450 0.070 3.3 1.74 140 Inventive Example B9 1.8 1.1 1.7 0.0040 425 1.8 550 0.080 3.1 1.73 135 Inventive Example B10 1.8 1.1 1.7 0.0070 243 1.8 250 0.010 3.5 1.69 135 Comparative example B11 1.8 1.8 1.4 0.0060 233 1.7 500 0.150 3.2 1.73 135 Inventive Example B12 1.8 1.8 1.4 0.0045 311 1.7 600 0.180 3.2 1.74 135 Inventive Example B13 1.8 1.8 1.4 0.0010 1400 1.7 50 0.018 3.7 1.72 135 Comparative example

Steel grades B1, B3, B4, B6, B8, B9, B11, and B12, which satisfy the conditions of Al / Si, Al / Mn, and Al + Mn, which are within the scope of the present invention, and whose total amount of N and S is controlled from 0.0020 to 0.0060. In this case, the hardness is low, the productivity and customer punchability is excellent, coarse inclusions of 300 nm or more in size are observed, and the distribution density is higher than 0.02 (1 / mm ² ), which is excellent in magnetic properties.

On the other hand, in the case of steel grades B5, B10, and B13, inclusions having a size of 300 nm or more beyond the scope of the present invention were not observed, and iron loss and magnetic flux density were inferior. In steel B7, inclusions having Al + Mn in the range of 300 nm or more out of the scope of the present invention were not observed, and iron loss and magnetic flux density were inferior.

Vacuum dissolution in the lab produced a steel ingot as shown in Table 5 below. At this time, 0.3 to 0.5% of Al was added to the molten steel to promote formation of inclusions, and then Al, Si, and Mn were added to prepare a steel ingot. Each material was heated to 1,150 ° C. and hot-rolled at 850 ° C. to produce a hot rolled sheet having a plate thickness of 2.3 mm. The hot rolled hot rolled sheet was annealed at 1,050 ° C. for 4 minutes and then pickled. Thereafter, cold rolling was performed under different cold rolling start temperature conditions to obtain a plate thickness of 0.50 mm, and the cold rolled plate was subjected to final annealing at 900 ° C. for 30 seconds to have a grain size of about 100 μm. Inclusion distribution density, <111> // ND fraction, iron loss, and magnetic flux density for each are shown in Table 6 below. Sample preparation for observation of inclusions was performed using a replica method, which is a common method for steel materials, and a transmission electron microscope was used as a device. At this time, the acceleration voltage was applied to 200kV. The <111> // ND fraction of the final annealing plate was obtained from the Orientation Distribution Function (ODF) obtained by observing the cross section of the steel sheet by EBSD (Electron back scattered diffraction), and the tolerance angle was 15 Set to °.

Steel grade Al Si Mn C S N Ti C1 1.5 0.2 0.5 0.0025 0.0015 0.0015 0.0025 C2 1.5 0.2 0.5 0.0025 0.0015 0.0015 0.0025 C3 1.5 0.2 0.5 0.0025 0.0015 0.0015 0.0025 C4 1.5 0.2 0.5 0.0025 0.0015 0.0015 0.0025 C5 1.2 0.5 0.2 0.0025 0.0015 0.0015 0.0025 C6 1.2 0.5 0.2 0.0025 0.0015 0.0015 0.0025 C7 1.2 0.5 0.2 0.0025 0.0015 0.0015 0.0025 C8 1.2 0.5 0.2 0.0025 0.0015 0.0015 0.0025 C9 0.7 0.7 0.2 0.0025 0.0015 0.0015 0.0025 C10 0.7 0.7 0.2 0.0025 0.0015 0.0015 0.0025 C11 0.7 0.7 0.2 0.0025 0.0015 0.0015 0.0025 C12 0.7 0.7 0.2 0.0025 0.0015 0.0015 0.0025 C13 0.5 0.5 0.5 0.0025 0.0015 0.0015 0.0025 C14 0.5 0.5 0.5 0.0025 0.0015 0.0015 0.0025 C15 0.5 0.5 0.5 0.0025 0.0015 0.0015 0.0025 C16 0.5 0.5 0.5 0.0025 0.0015 0.0015 0.0025

Steel grade Al / Si Al / Mn Al + Mn N + S (Al + Mn)
/ (N + S) Inclusion
Distribution density
(1 / mm ² ) (0.7 [Si] +
0.6 [Al])
× 100 / 3.3 Cold rolled
Initiation temperature
(℃) <111>
// ND
Fraction (%) Iron loss
(W15 / 50; W / Kg) Magnetic flux
density
(B50;
Tesla) Remarks C1 7.5 3.0 2.0 0.0030 667 0.05 32 25 32 3.0 1.73 Comparative example C2 7.5 3.0 2.0 0.0030 667 0.07 32 50 30 2.9 1.74 Inventive Example C3 7.5 3.0 2.0 0.0030 667 0.09 32 80 30 2.9 1.74 Inventive Example C4 7.5 3.0 2.0 0.0030 667 0.15 32 110 29 2.8 1.74 Inventive Example C5 2.4 6.0 1.4 0.0030 467 0.03 32 25 34 3.2 1.73 Comparative example C6 2.4 6.0 1.4 0.0030 467 0.05 32 50 30 3.1 1.73 Inventive Example C7 2.4 6.0 1.4 0.0030 467 0.09 32 80 29 3.0 1.74 Inventive Example C8 2.4 6.0 1.4 0.0030 467 0.15 32 110 30 3.0 1.74 Inventive Example C9 1.0 3.5 0.9 0.0030 300 0.01 28 25 32 3.9 1.74 Comparative example C10 1.0 3.5 0.9 0.0030 300 0.03 28 50 30 3.7 1.74 Inventive Example C11 1.0 3.5 0.9 0.0030 300 0.03 28 80 28 3.7 1.74 Inventive Example C12 1.0 3.5 0.9 0.0030 300 0.04 28 110 29 3.8 1.74 Inventive Example C13 1.0 1.0 1.0 0.0030 333 0.01 20 25 35 4.5 1.74 Comparative example C14 1.0 1.0 1.0 0.0030 333 0 20 50 32 4.5 1.74 Comparative example C15 1.0 1.0 1.0 0.0030 333 0 20 80 32 4.2 1.74 Comparative example C16 1.0 1.0 1.0 0.0030 333 0.01 20 110 34 4.3 1.74 Comparative example

From the results in Table 6, the steel grades C2 to C4, C6 to C8, and C10 to C12 which controlled the cold rolling start temperature to 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or more were <111> // The fraction of ND is 30% or less, and it turns out that it is excellent in magnetism.

On the contrary, for steel grades C1, C5, and C9 having a cold rolling start temperature of less than 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3, the fraction of <111> // ND exceeded 30%. Magnetism was inferior. Steel grades C13 to 16 had a cold rolling start temperature of 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or more, but the Al content was inferior to the scope of the present invention and inferior in magnetic properties.

Claims (7)

By weight%, Al: 0.7-2.7%, Si: 0.2-1.0%, Mn: 0.2-1.7%, N: 0.001-0.004%, S: 0.0005-0.004%, balance Fe and other unavoidable impurities Al, Mn, N, and S are {[Al] + [Mn]} ≤2.0, 0.002≤ {[N] + [S]} ≤0.006, 230≤ {([Al] + [Mn]) / ([N] + [S])} The slab contained so as to satisfy the composition formula of 1,000 was heated and then hot rolled, and the cold rolling start temperature was 100 × (0.7 × [Si] + 0.6 ×) in performing cold rolling. A method for producing a non-oriented electrical steel sheet having a magnetic property of [Al]) / 3.3 or more and the final annealing of the cold rolled cold rolled sheet.
[Al], [Mn], [N], [S], and [Si] mean content (wt%) of Al, Mn, N, S, and Si, respectively. The method according to claim 1,
The slab is a method of manufacturing a non-oriented electrical steel sheet having excellent hardness and low hardness containing Al, Si, Mn to satisfy the composition formula of 1.0≤ {[Al] + [Si] + [Mn] / 2} ≤2.0. The method according to claim 1,
The slab is a method for producing a non-oriented electrical steel sheet having excellent hardness and low hardness containing Al, Mn to satisfy the composition formula of 1≤ [Al] / [Mn] ≤8. The method according to any one of claims 1 to 3,
A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, wherein the cross-sectional Vickers hardness (Hv1) of the final annealed steel sheet is 140 or less. The method according to any one of claims 1 to 3,
Inclusions of nitrides and sulfides alone or in combination thereof are formed in the final annealed steel sheet, and have excellent magnetic properties and low hardness non-oriented electrical steel sheet that control the distribution density of inclusions having an average size of 300 nm or more to 0.02 pieces / mm ² or more. Manufacturing method. The method according to any one of claims 1 to 3,
A method for producing a non-oriented electrical steel sheet having excellent magnetic properties to control the <111> / / ND fraction of the final annealed steel sheet to 30% or less.
The <111> // ND means an aggregate structure in which the <111> direction is arranged in a direction perpendicular to the steel plate surface. The method according to any one of claims 1 to 3,
After adding 0.3 ~ 0.5% of Al to make deoxidation, the remaining alloy element is added, and after the addition of the remaining alloy element, the temperature is maintained at 1,500 ~ 1,600 ℃ to produce slabs. Method of manufacturing electrical steel sheet.

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