KR20120074011A - Method for manufacturing non-oriented electrical steel sheets with excellent magnetic properties - Google Patents

Abstract

PURPOSE: A non-oriented electrical steel sheet with excellent magnetic property and a manufacturing method thereof are provided to reduce manufacturing costs with improving magnetic properties using elements having the affinity with S(Sulfur). CONSTITUTION: A method for manufacturing a non-oriented electrical steel sheet with excellent magnetic property is as follows. A slab is made of Al(Aluminum) 1.0~3.0wt.%, Si(Silicon) 0.5~2.5wt.%, Mn(Manganese) 0.5~2.0wt.%, N(Nitrogen) 0.001~0.004wt.%, S 0.0005~0.004wt.%, residual Fe(Iron), and inevitable impurities. The Al, Mn, N, and S satisfy the empirical formula; {[Al]+[Mn]}Δ3.5, 0.002Δ{[N]+[S]}Δ0.006, 300Δ{([Al]+[Mn])/([N]+[S])}Δ1,400. The slab is heated, hot-rolled, and cold-rolled at initial temperature; more than 30°C. A cold-rolled plate is finally annealed.

Description

Method for manufacturing non-oriented electrical steel sheets with excellent magnetic properties

The present invention relates to the production of non-oriented electrical steel sheet, such as iron core material of the rotating machine, by optimally setting the additive composition of the steel to increase the distribution density of coarse inclusions in the steel, improve the grain growth and the mobility of the magnetic wall to improve the magnetism The present invention relates to a method for manufacturing a high quality non-oriented electrical steel sheet which has improved product productivity and punchability by securing low hardness.

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.

In terms of the aggregate structure, the non-oriented electrical steel sheet has excellent magnetic properties as the degree of integration and fraction of <100> // ND where <100>, which is easy to magnetize in the direction ND perpendicular to the steel plate surface, is located. Do. On the contrary, since the <111> orientation includes a difficult magnetization axis that is difficult to magnetize, the lower the fraction, the better the magnetic properties. Therefore, the <111> // ND density that is not easily magnetized is preferably low.

The formation of this texture is closely related to alloying system, recrystallization temperature condition, grain size and growth. Therefore, it is important to increase the strength of the {001} <100> texture, which is called a cube, which is advantageous for magnetism, in order to manufacture non-oriented electrical steel sheets having excellent magnetic properties, but it is also very important to lower the density and fraction of <111> // ND. It is a task.

The present invention was created to solve all the problems of the prior art as described above, by managing the component ratios of Al, Si, Mn, which are alloy elements of steel, and N and S, which are impurity elements, under optimum conditions. The purpose is to provide the highest quality non-oriented electrical steel sheet with high productivity and releasability due to its low hardness, which improves grain growth and mobility of magnetic walls by increasing the distribution density of the inclusions and reducing the incidence of fine inclusions. It is to be done.

Method for producing a non-oriented electrical steel sheet of the present invention for solving the above problems by weight, Al: 1.0 ~ 3.0%, Si: 0.5 ~ 2.5%, Mn: 0.5 ~ 2.0%, N: 0.001 ~ 0.004%, S : 0.0005 to 0.004%, remainder Fe and other unavoidably mixed impurities, Al, Mn, N, S is {[Al] + [Mn]} ≤3.5, 0.002≤ {[N] + [S] } ≤0.006, 300≤ {([Al] + [Mn]) / ([N] + [S])} ≤1,400 The slab is heated to satisfy the compositional formula and then hot rolled and cold rolled. The cold rolling start temperature is 30 ° C. or higher, and the cold rolled cold rolled sheet is finally annealed.

In the method for producing a non-oriented electrical steel sheet of the present invention, Al, Si, Mn is 1.7≤ {[Al] + [Si] + [Mn] / 2} ≤5.5, 0.6≤ [Al] / [Si] ≤ 4.0, 1≤ [Al] / [Mn] ≤8, so as to satisfy the composition formula.

In the manufacturing method of the 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 the distribution density of inclusions having an average size of 300 nm or more is controlled to 0.02 pieces / mm ² or more. It features.

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 190 or less.

The method for producing a non-oriented electrical steel sheet according to the present invention is characterized in that the cold rolling start temperature is set to 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or more.

In the method of manufacturing the non-oriented electrical steel sheet of the present invention, to control the fraction of the texture (<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 to 25% or less 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 magnetic walls are improved, and the magnetic properties are excellent. High quality non-oriented electrical steel sheets having very 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.

In order to solve the above technical problems, the present inventors have investigated the effects of alloying elements, impurity elements, and the relationship between the elements on the formation of inclusions, and the effects on magnetic properties and workability, respectively. In the alloying elements, Al, Si, Mn and the impurity elements N and S content are appropriately controlled, and Al / Si and Al / Mn, Al + Si + Mn / 2, Al + Mn, N + S, (Al + Mn By optimally managing the ratio of) / (N + S), it is possible to reduce the hardness of the steel sheet and to 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 magnetic properties, The present invention has been completed by paying attention to the fact that punchability is improved.

The present invention is by weight, Al: 1.0 ~ 3.0%, Si: 0.5 ~ 2.5%, Mn: 0.5 ~ 2.0%, 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]} ≤3.5, 0.002≤ {[N] + [S]} ≤0.006, 300≤ {([Al] + [Mn ]) / ([N] + [S])} ≤1,400, 1.7≤ {[Al] + [Si] + [Mn] / 2} ≤5.5, 0.6≤ [Al] / [Si] ≤4.0, 1≤ By containing so as to satisfy the composition formula of [Al] / [Mn] ≤8, the distribution density of nitrides and sulfides having an average size of 300 nm or more or inclusions thereof is increased to 0.02 pieces / mm ² or more. Accordingly, it is possible to manufacture the highest quality non-oriented electrical steel sheet having excellent machinability due to its excellent magnetic properties and low hardness of 190 Vickers hardness (Hv1) or less.

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 was prepared, and the slab was heated to a temperature of 1,100 to 1,250 ° C. and then hot rolled, but hot finishing rolling was performed at 800 ° C. or higher, and the hot rolled hot rolled sheet was annealed at a temperature range of 850 to 1,100 ° C. After pickling or omitting, pickling, cold rolling is carried out at a reduction ratio of 70 to 95%, and the cold rolling start temperature is set to 30 ° C. or higher so that the <111> // ND fraction is controlled to 25% or less, and cold rolling. The final cold-annealed cold rolled sheet at a temperature range of 750 ~ 1,100 ℃ characterized in that the non-oriented electrical steel sheet having excellent magnetic properties and workability.

In the case of Al, Si, and Mn, which are alloying elements of steel, the alloying elements are added to lower iron loss of the steel sheet, but as the added content thereof increases, the magnetic flux density decreases and the workability of the material is deteriorated. In addition, these alloying components should be set properly 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, there is a need 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: 1.0-3.0 wt%]

Al is added because it increases the specific resistance of the material, lowers iron loss and forms nitride, and is added in 1.0 to 3.0% to form coarse nitride. If the Al content is less than 1.0%, the inclusions cannot be sufficiently grown. If the Al content is more than 3.0%, the workability is degraded and problems occur in all processes such as steelmaking and continuous casting.

[Si: 0.5-2.5 wt%]

Si serves to lower the iron loss by increasing the specific resistance of the material, it is difficult to expect the iron loss reduction effect when contained less than 0.5%, productivity and punchability is inferior due to the increase in the hardness of the material when contained above 2.5%.

[Mn: 0.5-2.0 wt%]

Mn contains more than 0.5% because it increases the specific resistance of the material to improve iron loss and form sulfides, and when it contains more than 2%, it promotes the formation of [111] aggregates, which is disadvantageous to magnetism. Preferably limited to ˜2.0%.

[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.

In the present invention, the total amount of Al and Mn [Al] + [Mn] is limited to 3.5% or less, which means that if the total amount of Al and Mn exceeds 3.5%, the fraction of the [111] aggregate tissue, which is disadvantageous to magnetism, increases and the magnetic Because it gets feverish. When the total amount of Al and Mn is less than 1.5%, nitrides, sulfides, or both complex inclusions are not coarse to form magnetic heat. However, in the present invention, Al is contained in an amount of 1.0% or more, and Mn is 0.5% or more. Since the total amount of Al and Mn is 1.5% 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 300≤ ([Al] + [Mn]) / ([N] + [S]) ≤1,400. Here, [Al], [Mn], [N], and [S] mean content (wt%) of Al, Mn, N, and S, respectively. Within this range, iron loss is improved by increasing coarse inclusions and increasing the density of distribution of large composite inclusions. Outside this range, coarsening of inclusions is not coarse, formation frequency of huge composite inclusions is low, and it is disadvantageous to magnetism. 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 3.5% 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]) is 300 to 1,400, the ratio of the total amount of Mn to the total amount of N and S, 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 taken as the value obtained by measuring the longest length and the shortest length of the inclusions 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 0.6 ~ 4.0. This is because when the ratio of Al to Si is 0.6 to 4.0, the grain growth is excellent and the hardness of the material is lowered, thereby improving productivity and punchability. If [Al] / [Si] is less than 0.6, the inclusions do not grow significantly, resulting in poor growth of the crystal grains and thermal deterioration of magnetic properties. If [Al] / [Si] exceeds 4.0, the texture of the material will deteriorate, causing the magnetic flux density to heat up.

[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 alloying component related to a specific resistance (intrinsic resistance) is demonstrated. Recently, as the demand for eco-friendly cars is rapidly increasing, the demand for non-oriented electrical steel sheets that can be used for motors of eco-friendly cars is also increasing. The motor used in such an eco-friendly vehicle should increase the number of revolutions significantly. As the number of revolutions increases, the ratio of the eddy current loss among the iron core losses of the motor increases. To reduce this eddy current loss, the resistivity must be increased to 32 or more. However, if the resistivity exceeds 75, the addition amount of the alloying element should be increased, so that the workability is poor and the production cannot be performed by the conventional method. Therefore, it is appropriate to manage the resistivity between 32 and 75.

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 1.7 ~ 5.5% to satisfy specific resistance 32 ~ 75.

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.

Hot rolled hot rolled sheet is annealed at a temperature of 850 ~ 1,100 ℃. If the hot-rolled sheet annealing temperature is less than 850 ℃, the structure does not grow or grow fine, the magnetic flux density is less synergistic effect, if the annealing temperature exceeds 1,100 ℃ magnetic properties are rather deteriorated, rolling workability due to the deformation of the plate shape This can be worse, the temperature range is limited to 850 ~ 1,100 ℃. 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.

After annealing or omitting the hot rolled sheet as described above, the hot rolled sheet is pickled and 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. Cold rolling reduction may be applied differently depending on the plate thickness, it can be produced by applying a rolling reduction of about 70 ~ 95%.

In the present invention, it is important to control the start temperature of cold rolling. It is desirable to increase the cold rolling initiation temperature to 30 ° C or higher, because increasing the cold rolling initiation temperature may cause dynamic recovery during cold rolling and reduce the density of aggregates that are unfavorable to magnetism during recrystallization annealing. . According to the experiments of the present inventors, when cold rolling is performed under the condition that the cold rolling start temperature is less than 30 ° C., the fraction of <111> // ND in the final annealed steel sheet exceeds 25%.

In addition, it is more preferable to set the cold rolling start temperature differently according to the alloy component during cold rolling. That is, it is preferable to set the cold rolling start temperature to 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or higher. The reason is that, firstly, when the cold rolling start temperature is increased, it causes dynamic recovery during cold rolling. This is because when the recrystallization annealing can reduce the density of aggregates that are unfavorable to magnetism, 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 many experiments of the present inventors, it was found that the amount of increase in cold rolling initiation temperature required to cause dynamic recovery with increase in Si content is about 1.17 times the increase in amount of cold rolling initiation with increase in 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.

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.

Vacuum dissolution in a laboratory produced a steel ingot of the same component as shown in Table 1 below. The contents of impurities C, S, N, and Ti of the material were controlled to 0.002%, respectively, and 0.3 to 0.5% of Al was added to the molten steel to promote the formation of inclusions, and then the remaining Al, Si, and Mn were added to the steel ingot. Prepared. Each material was heated to 1,150 ° C. and hot-rolled at 850 ° C. to produce a hot rolled sheet having a thickness of 2.0 mm. The hot rolled hot rolled sheet was annealed at 1,050 ° C. for 4 minutes and then pickled. Thereafter, cold rolling was performed to make the plate thickness 0.35 mm, followed by final annealing for 38 seconds at 1,050 ° C.

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 3 0.5 1.0 0.002 0.002 0.002 0.002 A2 2.5 0.5 1.0 0.002 0.002 0.002 0.002 A3 1.0 0.5 1.0 0.002 0.002 0.002 0.002 A4 3.0 1.0 1.0 0.002 0.002 0.002 0.002 A5 2.0 1.0 1.0 0.002 0.002 0.002 0.002 A6 1.0 1.0 1.0 0.002 0.002 0.002 0.002 A7 0.5 1.0 1.0 0.002 0.002 0.002 0.002 A8 3.5 1.5 1.0 0.002 0.002 0.002 0.002 A9 2.5 1.5 1.0 0.002 0.002 0.002 0.002 A10 1.5 1.5 1.0 0.002 0.002 0.002 0.002 A11 3.0 2.0 1.0 0.002 0.002 0.002 0.002 A12 1.5 2.0 1.0 0.002 0.002 0.002 0.002 A13 3.0 2.5 1.0 0.002 0.002 0.002 0.002 A14 2.5 2.5 1.0 0.002 0.002 0.002 0.002 A15 1.0 2.5 1.0 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 Inclusions
size
(Nm) Inclusions
Distribution density
(1 / mm ² ) Iron loss
(W15 / 50;
W / Kg) Magnetic flux density
(B50;
Tesla) Hardness
(Hv1) Remarks A1 6.0 3.0 4.0 0.0040 1000 4.0 250 0 2.2 1.62 165 Comparative example A2 5.0 2.5 3.5 0.0040 875 3.5 200 0 2.3 1.62 160 Comparative example A3 2.0 1.0 2.0 0.0040 500 2.0 300 0.02 2.5 1.72 140 Inventive Example A4 3.0 3.0 4.0 0.0040 1000 4.5 250 0 2.4 1.62 157 Comparative example A5 2.0 2.0 3.0 0.0040 750 3.5 500 0.07 2.0 1.67 155 Inventive Example A6 1.0 1.0 2.0 0.0040 500 2.5 450 0.05 2.1 1.68 150 Inventive Example A7 0.5 0.5 1.5 0.0040 375 2.0 50 0 2.5 1.66 145 Comparative example A8 2.3 3.5 4.5 0.0040 1125 5.5 75 0 2.5 1.64 190 Comparative example A9 1.7 2.5 3.5 0.0040 875 4.5 400 0.05 2.0 1.67 185 Inventive Example A10 1.0 1.5 2.5 0.0040 625 3.5 600 0.08 2.0 1.68 170 Inventive Example A11 1.5 3.0 4.0 0.0040 1000 5.5 250 0 2.3 1.62 195 Comparative example A12 0.8 1.5 2.5 0.0040 625 4.0 400 0.04 2.0 1.68 183 Inventive Example A13 1.2 3.0 4.0 0.0040 1000 6.0 75 0 2.0 1.61 210 Comparative example A14 1.0 2.5 3.5 0.0040 875 5.5 400 0.03 1.9 1.65 190 Inventive Example A15 0.4 1.0 2.0 0.0040 500 4.0 60 0 2.4 1.67 195 Comparative example

In the case of steel grades A3, A5, A6, A9, A10, A12, and A14 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 density is 0.02 It is higher than 1 / mm ² ) and its magnetic property is excellent.

On the other hand, in steel type A1, an inclusion having an Al / Si ratio and Al + Mn outside the scope of the present invention having a size of 300 nm or more was not observed, and iron loss and magnetic flux density were inferior. In steel grades A2 and A15, inclusions having a size of 300 nm or more out of the Al / Si ratio were not observed, and iron loss and magnetic flux density were inferior. For steel grades A4, A8, A11, and A13, inclusions having a size of 300 nm or more outside Al + Mn were not observed, and iron loss and magnetic flux density were inferior. In the steel grade A7, inclusions having a size of 300 nm or more out of the ratio of Al / Si and Al / Mn 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 3 below. The ingredients were adjusted while varying the content of impurities N and S of the material, and the Al was added to the molten steel by 0.3-0.5% to promote inclusion formation. Then, the remaining Al, Si, and Mn were added to prepare the steel ingot. . Each material was heated to 1,150 ° C. and hot-rolled at 850 ° C. to produce a hot rolled sheet having a thickness of 2.0 mm. The hot rolled hot rolled sheet was annealed at 1,050 ° C. for 4 minutes and then pickled. Thereafter, cold rolling was performed to make the plate thickness 0.35 mm, followed by final annealing for 38 seconds at 1,050 ° C.

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 0.5 0.002 0.001 0.001 0.002 B2 1.0 0.5 0.5 0.002 0.003 0.003 0.002 B3 1.0 0.5 0.5 0.002 0.0005 0.001 0.002 B4 1.0 0.5 1.0 0.002 0.002 0.003 0.002 B5 1.2 0.5 1.2 0.002 0.0015 0.002 0.002 B6 1.2 0.5 1.0 0.002 0.0005 0.0005 0.002 B7 1.2 0.5 1.0 0.002 0.003 0.003 0.002 B8 2.0 0.5 2.0 0.002 0.001 0.003 0.002 B9 2.0 0.5 1.5 0.002 0.001 0.0015 0.002 B10 2.0 0.5 1.5 0.002 0.001 0.003 0.002 B11 2.0 0.5 1.0 0.002 0.003 0.004 0.002 B12 2.0 1.0 1.5 0.002 0.0005 0.0015 0.002 B13 2.0 1.0 1.5 0.002 0.002 0.004 0.002 B14 1.5 1.0 1.5 0.002 0.002 0.0025 0.002 B15 2.5 1.0 1.0 0.002 0.0005 0.0005 0.002

Steel grade Al / Si Al / Mn Al + Mn N + S (Al + Mn) / (N + S) Al + Si
+ Mn / 2 Inclusions
size
(Nm) Inclusions
Distribution density
(1 / mm ² ) Iron loss
(W15 / 50;
W / Kg) Magnetic flux density
(B50;
Tesla) Hardness
(Hv1) Remarks B1 2.0 2.0 1.5 0.0020 750 1.8 350 0.03 2.6 1.74 135 Inventive Example B2 2.0 2.0 1.5 0.0060 250 1.8 75 0 3.2 1.72 135 Comparative example B3 2.0 2.0 1.5 0.0015 1000 1.8 120 0 2.9 1.71 135 Comparative example B4 2.0 1.0 2.0 0.0050 400 2.0 400 0.04 2.6 1.70 140 Inventive Example B5 2.4 1.0 2.4 0.0035 686 2.3 450 0.03 2.2 1.69 150 Inventive Example B6 2.4 1.2 2.2 0.0010 2200 2.2 50 0 2.4 1.67 150 Comparative example B7 2.4 1.2 2.2 0.0060 367 2.2 350 0.02 2.3 1.70 165 Inventive Example B8 4.0 1.0 4.0 0.0040 1000 3.5 250 0 2.3 1.62 185 Comparative example B9 4.0 1.3 3.5 0.0025 1400 3.3 450 0.05 2 1.67 170 Inventive Example B10 4.0 1.3 3.5 0.0040 875 3.3 550 0.08 2 1.68 170 Inventive Example B11 4.0 2.0 3.0 0.0070 429 3.0 250 0 2.2 1.65 170 Comparative example B12 2.0 1.3 3.5 0.0020 1750 3.8 80 0 2.3 1.65 165 Comparative example B13 2.0 1.3 3.5 0.0060 583 3.8 500 0.07 2 1.68 175 Inventive Example B14 1.5 1.0 3.0 0.0045 667 3.3 600 0.07 2 1.68 170 Inventive Example B15 2.5 2.5 3.5 0.0010 3500 4.0 50 0 2.2 1.65 165 Comparative example

Steel grades B1, B4, B5, B7, B9, B10, B13, and B14, 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 managed 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 B3, B6, B11, and B15, inclusions having a size 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. For steel grade B8, Al + Mn is out of the scope of the present invention and for steel grades B2, B12, (Al + Mn) / (N + S) is out of the scope of the present invention, no coarse inclusions having a size of 300 nm or more were observed. Iron loss and magnetic flux density were inferior.

Vacuum dissolution in the lab produced a steel ingot as shown in Table 5 below. The contents of impurities C, S, N, and Ti of the material were controlled to 0.002%, respectively, and 0.3 to 0.5% of Al was added to the molten steel to promote the formation of inclusions, and then the remaining Al, Si, and Mn were added to the steel ingot. Prepared. Each material was heated to 1,150 ° C. and hot-rolled at 850 ° C. to produce a hot rolled sheet having a thickness of 2.0 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 0.35 mm, and the cold rolled plate was subjected to final annealing at 1,050 ° C. for 38 seconds to have a grain size of 70 to 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 1.5 1.0 0.0020 0.0015 0.0025 0.0025 C2 1.5 1.5 1.0 0.0020 0.0015 0.0025 0.0025 C3 1.5 1.5 1.0 0.0020 0.0015 0.0025 0.0025 C4 1.5 1.5 1.0 0.0020 0.0015 0.0025 0.0025 C5 1.0 1.0 1.0 0.0020 0.0015 0.0025 0.0025 C6 1.0 1.0 1.0 0.0020 0.0015 0.0025 0.0025 C7 1.0 1.0 1.0 0.0020 0.0015 0.0025 0.0025 C8 1.0 1.0 1.0 0.0020 0.0015 0.0025 0.0025 C9 2.0 1.0 1.0 0.0020 0.0015 0.0025 0.0025 C10 2.0 1.0 1.0 0.0020 0.0015 0.0025 0.0025 C11 2.0 1.0 1.0 0.0020 0.0015 0.0025 0.0025 C12 2.0 1.0 1.0 0.0020 0.0015 0.0025 0.0025 C13 3.0 2.0 1.0 0.0020 0.0015 0.0025 0.0025 C14 3.0 2.0 1.0 0.0020 0.0015 0.0025 0.0025 C15 3.0 2.0 1.0 0.0020 0.0015 0.0025 0.0025 C16 3.0 2.0 1.0 0.0020 0.0015 0.0025 0.0025

Steel grade Al / Si Al / Mn Al + Mn N + S (Al + Mn)
/ (N + S) Inclusions
Distribution density
(1 / mm ² ) (0.7 [Si]
+0.6 [Al])
× 100 / 3.3 Cold rolled
Start temperature
(℃) <111>
// ND
Fraction (%) Iron loss
(W15 / 50;
W / Kg) Magnetic flux
density
(B50;
Tesla) Remarks C1 1.0 1.5 2.5 0.0040 625 0.05 59 25 26 2.0 1.68 Comparative example C2 1.0 1.5 2.5 0.0040 625 0.07 59 60 24 1.9 1.68 Inventive Example C3 1.0 1.5 2.5 0.0040 625 0.09 59 80 22 1.9 1.69 Inventive Example C4 1.0 1.5 2.5 0.0040 625 0.12 59 110 21 1.9 1.69 Inventive Example C5 1.0 1.0 2.0 0.0040 500 0.03 39 25 28 2.1 1.68 Comparative example C6 1.0 1.0 2.0 0.0040 500 0.04 39 50 25 2.0 1.69 Inventive Example C7 1.0 1.0 2.0 0.0040 500 0.06 39 80 21 2.0 1.69 Inventive Example C8 1.0 1.0 2.0 0.0040 500 0.09 39 110 19 2.0 1.69 Inventive Example C9 2.0 2.0 3.0 0.0040 750 0.05 58 25 26 2.0 1.67 Comparative example C10 2.0 2.0 3.0 0.0040 750 0.07 58 60 25 1.9 1.67 Inventive Example C11 2.0 2.0 3.0 0.0040 750 0.08 58 80 22 1.9 1.67 Inventive Example C12 2.0 2.0 3.0 0.0040 750 0.11 58 110 20 1.9 1.67 Inventive Example C13 1.5 3.0 4.0 0.0040 1000 0 97 25 32 2.3 1.62 Comparative example C14 1.5 3.0 4.0 0.0040 1000 0 97 50 32 2.2 1.62 Comparative example C15 1.5 3.0 4.0 0.0040 1000 0.01 97 80 30 2.2 1.62 Comparative example C16 1.5 3.0 4.0 0.0040 1000 0.01 97 110 25 2.2 1.62 Comparative example

From the results in Table 6, the steel grades C2 to C4, C6 to C8, and C10 to C12 having the cold rolling start temperature controlled at 30 ° C. or higher showed that the fraction of <111> // ND was 25% or less and excellent in magnetic properties. have.

On the other hand, steel grades C1, C5, and C9 whose cold rolling start temperature was controlled to be less than 30 ° C exhibited a magnetic inferiority because the fraction of <111> // ND exceeded 25%. Steel grades C14 to 16 had a cold rolling onset temperature of 30 ° C. or higher, but Al + Mn was inferior to the scope of the present invention and inferior in magnetic properties.

Claims (8)

By weight%, Al: 1.0-3.0%, Si: 0.5-2.5%, Mn: 0.5-2.0%, N: 0.001-0.004%, S: 0.0005-0.004%, balance Fe and other unavoidable impurities Al, Mn, N, and S are {[Al] + [Mn]} ≦ 3.5, 0.002 ≦ {[N] + [S]} ≦ 0.006, 300 ≦ {([Al] + [Mn]) / ([N] + [S])} ≤1,400 The slab contained so as to satisfy the composition formula is heated and then hot rolled, cold rolling start temperature is 30 ℃ or more in performing cold rolling, cold rolled cold rolled sheet Method for producing a non-oriented electrical steel sheet having excellent magnetic annealing.
[Al], [Mn], [N], and [S] mean Al, Mn, N, and S contents (% by weight), respectively. The method according to claim 1,
The slab is a non-oriented electrical steel sheet manufacturing method having excellent magnetic properties containing Al, Si, Mn to satisfy the composition formula of 1.7≤ {[Al] + [Si] + [Mn] / 2} ≤5.5.
[Si] means the content (% by weight) of Si. The method according to claim 1,
The slab is Al, Si, Mn is a method of producing a non-oriented electrical steel sheet having excellent magnetic properties are contained so as to satisfy the composition formula of 0.6≤ [Al] / [Si] ≤4.0, 1≤ [Al] / [Mn] ≤8.
[Si] means the content (% by weight) of Si. 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 190 or less. The method according to any one of claims 1 to 3,
In the final annealed steel sheet, the inclusions of nitrides and sulfides alone or in combination thereof are formed, and the manufacturing method of the non-oriented electrical steel sheet having excellent magnetic properties controlling the distribution density of inclusions having an average size of 300 nm or more to 0.02 pieces / mm ² or more. 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 having a cold rolling start temperature of 100 × (0.7 × [Si] + 0.6 × [Al]) / 3.3 or higher. 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 that controls the <111> // ND fraction of the final annealed steel sheet to 25% 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 the addition of 0.3 ~ 0.5% of Al to deoxidize, the remaining alloying elements are added, and after the addition of the remaining alloying elements, the temperature is maintained at 1,500 ~ 1,600 ℃ to manufacture the excellent magnetic non-oriented electrical steel sheet for producing slabs. Way.

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