KR101977510B1 - Non-oriented electrical steel sheet having exelleant magnetic properties low deviation of thickness and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a non-oriented electrical steel sheet having excellent magnetic properties and a low thickness deviation and a manufacturing method thereof. According to an embodiment of the present invention, the non-oriented electrical steel sheet having excellent magnetic properties and a low thickness deviation comprises 2.8- 4.0 wt% of Si, 0.1-1.5 wt% of Al, 0.05-1.5 wt% of Mn, 0.005-0.2 wt% of Sn, 0.002-0.15 wt% of P, 0.0005-0.0035 wt% of Ca, and the remainder consisting of Fe and inevitable impurities. The Si, Al, Mn, Sn, and P satisfy the following relation 1. The average size of ferrite crystal grains is 70-110 μm. The deviation between the thickness at 10 mm from the edge in the width direction of a strip and the thickness at the center is lower than or equal to 4.5 μm. The iron loss (W10/400) is lower than or equal to 13.6 W/kg. The relation 1 is as follows: 13+10Si+9.5Al+4.5Mn+7.5Sn+50P >= 50, wherein Si, Al, Mn, Sn, and P represent the respective content (wt%).

Description

Non-oriented electrical steel sheet having excellent magnetic properties and small thickness variation and a method for manufacturing the same

The present invention relates to a non-oriented electrical steel sheet having excellent magnetic properties and small thickness variation and a method of manufacturing the same.

Unlike general motors, drive motors should have excellent magnetic characteristics in all areas from low speed to high speed. Particularly, high strength is required because it must have a large magnetic flux density characteristic at low speed rotation, high frequency iron loss at high speed rotation region, and withstand the centrifugal force generated at high speed rotation. In particular, in the manufacture of the drive motor, the widthwise thickness deviation, that is, the appearance shape quality is very important, because the raw material is manufactured by slitting, laminating after lamination and manufacturing the final part. Therefore, the thickness must be uniform with respect to the width or length direction of the strip.

On the other hand, there exists patent document 1 as a technique regarding the non-oriented electrical steel sheet which improves a magnetic characteristic. Patent Document 1 discloses a non-oriented electrical steel sheet in which 0.1 to 5% of Co is added to steel having Si of 4% or less. In addition, Patent Literature 2 sets the content of P to 0.07 to 0.20% and the content of Si to 0.17 to 3.0%, and conducts hot-rolled sheet annealing by box annealing with a slow cooling rate. By controlling, a technique for achieving high magnetic flux density has been proposed. In addition, Patent Literature 3 proposes a method for achieving high magnetic flux density by making the Al content 0.017% or less. Patent Literature 4 proposes a technique for adding high magnetic flux density by adding Sb and Sn as elements other than those described above. In addition, Patent Literature 5 proposes a technique for improving magnetic characteristics by controlling Ti, Nb, V, and B. As described above, in the case of non-oriented electrical steel sheet, there are many techniques for improving the magnetic properties by controlling alloy components, and the research on shape quality is very small.

In the conventional hot rolling process, slabs having a thickness of 200 mm or more are produced through low-speed casting, and the slabs are reheated in a heating furnace and hot rolled in batches to reduce the thickness of the slabs. In the case of batch rolling of this type, since the top part is introduced into the rolling mill and the tail part must exit the rolling mill for each slab, operation accidents frequently occur, and thus in manufacturing hot rolled steel sheet and excellent electrical steel sheet. There are many limits.

Japanese Unexamined Patent Publication No. 2000-129410 Japanese Patent Publication No. 3870893 Japanese Patent Publication No. 4126479 Japanese Patent Publication No. 2500033 Korean Unexamined Patent Publication No. 10-2016-0078183

One aspect of the present invention is to provide a non-oriented electrical steel sheet excellent in magnetic properties, small thickness variation and a method of manufacturing the same.

The problem of the present invention is not limited to the above description. Anyone of ordinary skill in the art will have no difficulty understanding the additional subject matter of the present invention from the general contents of the present specification.

One embodiment of the present invention is by weight, Si: 2.8-4.0%, Al: 0.1-1.5%, Mn: 0.05-1.5%, Sn: 0.005-0.20%, P: 0.002-0.15%, Ca: 0.0005- 0.0035%, balance Fe and other unavoidable impurities, wherein Si, Al, Mn, Sn, and P satisfy the following Equation 1, and the average size of the ferrite grains is 70 to 110 µm, and 10 mm from the edge in the width direction of the strip. The thickness of the center and the thickness of the central deviation is 4.5㎛ or less, the iron loss (W10 / 400) is excellent in magnetic properties, and provides a non-oriented electrical steel sheet with a small thickness variation.

13 + 10Si + 9.5Al + 4.5Mn + 7.5Sn + 50P ≧ 50

(Si, Al, Mn, Sn, and P in the relation 1 indicate the respective contents (% by weight).)

One embodiment of the present invention is by weight, Si: 2.8-4.0%, Al: 0.1-1.5%, Mn: 0.05-1.5%, Sn: 0.005-0.20%, P: 0.002-0.15%, Ca: 0.0005- 0.0035%, balance Fe and other unavoidable impurities, wherein Si, Al, Mn, Sn, and P are obtained by continuously casting molten steel that satisfies Equation 1 below to obtain a thin slab; Rough rolling the thin slab to obtain a bar; Heating the bar; Rolling the heated bar to finish rolling, at the first rolling mill, rolling at 950-1180 ° C., and rolling at the last rolling mill at 680-850 ° C. to obtain a hot rolled steel sheet; And winding the hot rolled steel sheet, wherein each step is performed continuously, and cold rolling the wound hot rolled steel sheet to obtain a cold rolled steel sheet; And recrystallizing annealing the cold rolled steel sheet, wherein the molten steel in the tundish during the continuous casting satisfies the following Equation 2, and the temperature variation in the first rolling mill during the finish rolling is excellent in magnetic properties of 60 ° C. or less, Provided is a method for manufacturing a non-oriented electrical steel sheet having a small thickness variation.

13 + 10Si + 9.5Al + 4.5Mn + 7.5Sn + 50P ≧ 50

(Relationship 2) (1538-13.2Si-0.7Al-5.1Mn) +5 ≤ tundish molten steel temperature (° C) ≤ (1538-13.2Si-0.7Al-5.1Mn) +25

(Si, Al, Mn, Sn and P in the above relations 1 and 2 represent the respective contents (% by weight).)

According to an aspect of the present invention, it is possible to provide an electrical steel sheet having excellent magnetic properties and shape quality and a method of manufacturing the same by using the high speed casting and the continuous rolling mode in the performance-rolling direct connection process.

In addition, the hot rolled electrical steel sheet manufactured through the continuous rolling process is excellent in the width / length direction thickness crown deviation compared to the electrical steel sheet of the conventional hot rolling produced through the batch process. Therefore, it is excellent in dimension / shape at the time of manufacturing the final part, and the material can be laminated uniformly, making the part easy to manufacture.

 In addition, the thin slab playing method can be used to melt the scrap steel, such as scrap iron in the electric furnace can increase the recycling of resources.

Figure 1 shows a state diagram of the general steel (0.04% C) calculated using Thermo-Calc (TCFE6).
Figure 2 shows the change in high temperature yield strength of ordinary steel (0.04% C) calculated using JmaPro v-9.
3 is a state diagram of a non-oriented electrical steel sheet containing 3.0% Si calculated using Thermo-Calc (TCFE6).
Figure 4 shows the high temperature yield strength change of the non-oriented electrical steel sheet containing 3.0% Si calculated using JmaPro v-9.
5 is a schematic diagram of equipment for a performance-rolling direct connection process applicable to the present invention.
Figure 6 is another schematic diagram of the installation for the performance-rolling direct connection process applicable to the present invention.
Figure 7 shows a TEM inclusion tissue picture of Inventive Example 1 according to an embodiment of the present invention.
Figure 8 shows a TEM inclusion tissue picture of Comparative Example 1 according to an embodiment of the present invention.
9 is an enlarged view of a TEM inclusion picture of Comparative Example 1 according to an embodiment of the present invention.
Figure 10 shows the inclusion size distribution of Inventive Example 1 according to an embodiment of the present invention.
Figure 11 shows the inclusion size distribution of Comparative Example 1 according to an embodiment of the present invention.
12 shows the change in high temperature strength according to the temperature change of Inventive Example 1 according to an embodiment of the present invention.

Hereinafter, the present invention will be described.

The new steel manufacturing process that has recently attracted attention, the so-called thin mill slab manufacturing process (mini-mill process), especially the direct rolling-rolling process, has a small temperature deviation in the width and length direction of the strip due to the process characteristics of isothermal isothermal. It is attracting attention as a process having excellent material deviation and the potential to manufacture thin-film hot rolled electrical steel sheets. This is because, unlike the existing process of rolling every slab or bar in batch form, this operation accident occurs because the top part is inserted only in the first thin slab and the tail part occurs only in the final coil in the play-rolling direct connection process. It can significantly reduce and produce products through isothermal isothermal rolling, so it has better thickness and width dimensions than existing batch materials and has a small plate crown variation. However, in order to secure excellent magnetic properties and strength, the non-oriented electrical steel sheet for a driving motor has a low carbon content (<50ppm), and Si content is more than 2.5%, so it is difficult to cast at high speed.

1 and 2 are the state and high temperature yield strength change of ordinary steel (0.04% C), respectively. As can be seen in Figure 1 solidification of the molten steel of the general steel is transformed sequentially from liquid (L) → L + δ-Fe (ferrite) → δ-ferrite + γ-Fe (austenite) → γ-Fe (austenite) As shown in FIG. 2, the high temperature strength is very small in the δ-Fe (ferrite) region, and the high temperature strength increases as the transformation to γ-Fe (austenite) occurs. 3 and 4, however, as can be seen from the state diagram and the high temperature strength change of the non-oriented electrical steel sheet containing 3.0% of Si, the non-oriented electrical steel sheet has a single phase δ-Fe without γ-Fe (austenite) transformation. The strength is very low at high temperatures because only (ferrite) transformation occurs. Therefore, when manufacturing non-oriented electrical steel sheet thin slab through high-speed casting, the strength of the solidified shell (Shell) is very low, mold level hunting (Mold Level Hunting, MLH) is severe, so that the separation of the inclusions does not occur well, Inclusions can be incorporated into the slab and the magnetism deteriorates.

On the other hand, as a method of improving the strength of the solidified shell (Shell), by adding a large amount of Ti crystallization and precipitation of TiN in the liquid phase can be used to refine the solidification shell and precipitation strengthening, Ti is TiN, Ti (C, N) Alone or carbonitrides can be produced, adversely affecting iron loss. Therefore, it is most effective to increase the thickness of the solidification shell by optimizing the playing process conditions when manufacturing thin slabs.

Accordingly, in order to manufacture non-oriented electrical steel sheet having excellent magnetic properties and small thickness variation, it is necessary to optimize the performance of the rolling and rolling process in the performance-rolling direct connection process by using the high speed casting and the continuous rolling rolling process.

Hereinafter, the electrical steel sheet of the present invention and a manufacturing method thereof will be described in detail.

First, the alloy composition of the electrical steel sheet of the present invention will be described. The alloy compositions described below are based on weight percent, unless otherwise specified.

Si: 2.8 to 4.0%

Silicon (Si) is generally added as a steel deoxidizer, but is an important element in electrical steel sheets because it has an effect of reducing electrical loss at high frequencies by increasing electrical resistance, and 2.8% or more is required to obtain such effects. However, if it exceeds 4.0%, the rolling load may increase during cold rolling, resulting in shape defects. Therefore, it is preferable that the said Si content is 2.8 to 4.0%, It is more preferable that it is 3.0 to 3.8%, It is still more preferable that it is 3.1 to 3.7%.

Al: 0.1 ~ 1.5%

Aluminum (Al), like Si, is generally used as a steel deoxidizer and is an element having a great effect of increasing electrical resistance and reducing iron loss, and therefore, addition of 0.1% or more is preferable. However, if the content exceeds 1.5%, the mold flux may be picked up during continuous casting, and the properties of the mold flux may be changed, thereby lubricating and casting interruption may occur. May occur. Accordingly, the Al content is preferably 0.1 to 1.5%, more preferably 0.2 to 1.3%, and even more preferably 0.3 to 1.0%.

Mn: 0.05-1.5%

Since manganese (Mn) is an element that can lower the iron loss by increasing the specific resistance in steel, the addition of 0.05% or more is preferable. However, if the content exceeds 1.5%, it combines with S in steel to form coarse MnS precipitates, not only to form an austenite phase in the annealing temperature range of the present invention, but also to make grain coarsening for iron loss reduction difficult. . Therefore, it is preferable that the said Mn has a range of 0.05-1.5 %%, It is more preferable that it is 0.1-1.3%, It is still more preferable that it is 0.2-1.0%.

Sn: 0.005-0.20%

Tin (Sn) is a grain boundary segregation element that suppresses the diffusion of nitrogen through grain boundaries, inhibits the formation of {111} and {112} textures that are harmful to magnetism, and increases {100} and {110} textures that are beneficial to magnetism. In order to improve a magnetic characteristic, it is preferable to add 0.005% or more in order to enlarge an addition effect. However, when added in excess of 0.20%, grain growth is suppressed to decrease magnetism and inferior rollability. Accordingly, the Sn content is preferably 0.005 to 0.20%, more preferably 0.01 to 0.15%, and even more preferably 0.02 to 0.10%.

P: 0.002 ~ 0.15%

Phosphorus (P) is an element that can lower the iron loss by increasing the specific resistance in steel, and is an element that can improve the magnetic flux density when added to a magnetic material, and it is preferable to add 0.002% or more for the above effect. However, if the content exceeds 0.15%, it exists as a segregation element that attracts the rolled plate fracture to the ferrite grain boundary during the rolling at room temperature, which greatly weakens the bonding force between the grain boundaries. Therefore, the content of P is preferably in the range of 0.002 to 0.15%, more preferably 0.004 to 0.10%, even more preferably 0.006 to 0.05%.

Ca: 0.0005-0.0035%,

Calcium (Ca) is precipitated as CaS, an element effective for improving the iron loss while suppressing the precipitation of fine sulfides, yet a low melting point in response to Al, O and the molten steel inclusions in spherical (12CaO · 17Al ₂ O ₃₎ formed To prevent nozzle clogging. If the Ca content is less than 0.0005% it is difficult to secure the effect. However, if the content exceeds 0.0035%, oxides in the steel may be formed to adversely affect the iron loss. Therefore, the Ca content is preferably in the range of 0.0005 to 0.0035%, more preferably 0.0006 to 0.0030%, even more preferably 0.0007 to 0.0025%.

On the other hand, in the electrical steel sheet of the present invention, the Si, Al, Mn, Sn and P preferably satisfy the following relational formula (1). The following Equation 1 may be represented by a specific resistance (μΩ · cm), and when the value of the Equation 1 is less than 50, the specific resistance may not be low to obtain a target high frequency iron loss.

13 + 10Si + 9.5Al + 4.5Mn + 7.5Sn + 50P ≧ 50

(Si, Al, Mn, Sn, and P in the relation 1 indicate the respective contents (% by weight).)

The remaining component of the present invention is iron (Fe). However, in the conventional manufacturing process, impurities which are not intended from the raw material or the surrounding environment may be inevitably mixed, and thus cannot be excluded. Since these impurities are known to those skilled in the art, all of them are not specifically mentioned in the present specification.

On the other hand, the electrical steel sheet of the present invention, in addition to the alloy composition described above, contains at least one of C, S, and N as an impurity in the range of 0.05% by weight or less as an impurity. The total of one or more selected from the group consisting of Cr, Ni, Zn, Se, Sb, Zr, W, Ga, Ge, and Mg may be 0.2% or less. When the sum of at least one of C, S, and N is less than 0.05% by weight, carbonitrides, sulfides, etc. may be formed to increase iron loss. The tramp element is an impurity element derived from scrap used as a raw material in the steelmaking process, ladle and tundish refractory, etc., and when the sum exceeds 0.2%, it is liquefied at high temperature to deteriorate playability or , Precipitates, sulfides and inclusions can form to worsen iron loss.

In the electrical steel sheet of the present invention, the average size of the ferrite grains is preferably 70 to 110 µm in circular equivalent diameter. If it is less than 70㎛ deteriorates the magnetism due to insufficient growth of the grain, if it is more than 110㎛ magnetic flux density may be lowered, rather iron loss may increase. Therefore, the average size of the ferrite grains is preferably 70 to 110 µm or less, more preferably 70 to 100 µm or less, and even more preferably 70 to 90 µm, in a circular equivalent diameter.

In addition, it is preferable that the electrical steel sheet of this invention contains the inclusion whose average size is 10 nm or more. If the average size of the inclusion is less than 10nm, the pinning effect is increased, which hinders grain growth, and the high frequency iron loss may be increased. Therefore, the average size of the inclusions is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more.

On the other hand, the inclusions may be one or more single or complex inclusions whose components are selected from the group consisting of Si, Al, Ca, Mn, Cu, Zr, W, Se, Mg, W, Sn, Ti, O. In addition, impurity elements which are not intended from the raw materials or the surrounding environment may be inevitably incorporated, and not all of them are specifically mentioned herein.

Moreover, it is preferable that the electrical steel sheet of this invention contains the inclusion of 2.5 pieces / micrometer <^2> or less. If the number of inclusions exceeds 2.5 / μm ² , high frequency iron loss may increase due to interference with grain growth and movement of magnetic domains. If the occupancy rate of each inclusion size exceeds the above value, it may interfere with grain growth and movement of magnetic domains, thereby increasing the high frequency iron loss.

In addition, the electrical steel sheet of the present invention includes less than 15% of inclusions having an average size of 10 nm or less, less than 30% of inclusions of 15 nm or less, less than 50% of inclusions of 20 nm or less, and less than 30 nm of the total inclusions. It is preferable to include 80% or less of inclusions.

In the electrical steel sheet of the present invention, a deviation of the thickness of the center and the thickness of the 10 mm point from the width direction edge of the strip may be 4.5 μm or less. It is more preferable that it is 4.0 micrometers, and, as for the said thickness deviation, it is still more preferable that it is 3.5 micrometers. In addition, the electrical steel sheet of the present invention may be less than 13.6W / kg iron loss (W10 / 400). The iron loss (W10 / 400) is the average loss (W / kg) in the rolling direction and the perpendicular direction in the rolling direction when the magnetic flux density of 1.0 Tesla is induced at the 400 Hz frequency.

In addition, the electrical steel sheet of the present invention may have a thickness of 0.15 ~ 0.35mm. When the thickness is less than 0.15 mm, productivity is reduced, and when the thickness exceeds 0.35 mm, the effect of reducing iron loss may be small.

Hereinafter, the non-oriented electrical steel sheet manufacturing method of the present invention will be described.

5 is a schematic diagram of equipment for a performance-rolling direct connection process applicable to the present invention, and is a schematic view of a performance-rolling direct connection process equipment applicable to the production of hot rolled steel sheet of a thin film to obtain a final electrical steel sheet. The thin electrical steel sheet excellent in shape quality according to one embodiment of the present invention may be manufactured from a hot rolled steel sheet produced by applying a performance-rolling direct connection facility as shown in FIG. 5. Performance-rolling direct connection equipment is largely composed of a continuous casting machine 100, rough rolling mill 400, the finishing rolling mill 600. The performance-rolling direct connection facility includes a high speed continuous casting machine 100 producing a thin slab (a) of a first thickness, and rolling the slab into a bar (b) of a second thickness thinner than the first thickness. The rough rolling mill 400, the finishing mill 600 for rolling the bar of the second thickness into a strip (c) of the third thickness, and a winding machine 900 for winding the strip may be included. In addition, rough mill scale breaker 300 (Rough Mill Scale Breaker, hereinafter 'RSB') in front of the roughing mill 400 and finishing mill scale breaker (500) (Fishing Mill Scale Breaker, hereinafter 'in front of the finishing mill 600) FSB ') may be further included, and the surface scale may be easily removed to produce electrical steel sheets having excellent surface quality in a later process. In addition, isothermal isothermal rolling is possible through the direct process of rolling to rolling, so that the steel plate width and longitudinal temperature deviation are very low, and precise cooling control is possible in ROT [Run Out Table (700)] (hereinafter referred to as "runout table"). It is possible to produce thin hot rolled electrical steel sheets with excellent isotropy. The strips thus rolled and cooled are cut by the high speed shears 800 and wound by the winding machine 900 to be produced as products. On the other hand, in front of the finish rolling scale breaker 500 may be provided with a heater 200 for further heating the bar.

Figure 6 is another schematic diagram of the installation for the performance-rolling direct connection process applicable to the present invention. The play-rolling direct connection facility disclosed in FIG. 6 has the same configuration as the facility disclosed in FIG. 5, but is provided with a heater 200 ′ that additionally heats the slab in front of the rough rolling mill 400, thereby easily securing the slab edge temperature. It is possible to reduce the occurrence of edge defects, which is advantageous for securing the surface quality. In addition, a space equal to the length of one or more slabs is secured before rough rolling, and batch rolling is also possible.

The hot rolled electrical steel sheet excellent in magnetic properties and shape of the present invention can be produced in both the performance-rolling direct connection facilities disclosed in FIGS. 5 and 6.

First, molten steel having the alloy composition described above is continuously cast to obtain a thin slab. At this time, it is important to control the temperature of the molten steel in the tundish. The tundish molten steel temperature may be defined as a value obtained by adding theoretical solidification temperature and superheat.

When manufacturing thin slab, molten steel with high superheat develops columnar tablets that deteriorate slab internal quality and adversely affects the growth of solidification shell, so that solid solidification thickness is not secured at the mold exit side. Breakout can be interrupted, and mold level hunting (MLH) is so severe that inclusions are not separated from each other, and a large amount of inclusions can be mixed into the slab and adversely affect magnetism. If the degree of superheat is too low, the molten steel may freeze and casting stoppage may occur. Therefore, it is preferable that superheat degree of the said tundish is 5-25 degreeC, It is advantageous to control to 10-20 degreeC more preferably.

In addition, it is preferable that the molten steel temperature in the tundish satisfies the following relational expression 2. If the molten steel temperature in the tundish is less than (1538-13.2Si-0.7Al-5.1Mn) +5, the molten steel may freeze during casting, causing casting breakage, and (1538-13.2Si-0.7Al- In the case of exceeding 5.1Mn) +25, the columnar tablet deteriorates the slab internal quality and adversely affects the growth of the solidification shell, so that the solidification shell thickness cannot be secured at the exit of the mold. It can lead to blackout, which can lead to casting interruption, and mold level hunting (MLH) is so severe that inclusions are not separated from each other, and large amounts of inclusions can be mixed into slabs, which can adversely affect magnetism. have.

(Relationship 2) (1538-13.2Si-0.7Al-5.1Mn) +5 ≤ tundish molten steel temperature (° C) ≤ (1538-13.2Si-0.7Al-5.1Mn) +25

(Si, Al and Mn in the relation 2 indicate the respective contents (% by weight).)

On the other hand, the continuous casting is preferably performed at a casting speed of 3.5 ~ 8.0mpm (m / min). The reason why the casting speed is more than 3.5mpm is because the high-speed casting and the rolling process are connected, and a certain casting speed is required to secure the target rolling temperature. If the casting speed is less than 3.5mpm, Al increases the pick-up amount in the mold flux, thereby changing the physical properties of the mold flux, thereby reducing the lubrication action, thereby causing the casting stoppage. If it exceeds 8.0mpm, the operation success rate may be reduced due to instability of the molten steel. Therefore, the casting speed is preferably in the range of 3.5 to 8.0mpm, more preferably in the range of 4.0 to 7.5mpm. More preferably, it is in the range of 4.5 to 6.5 mpm.

The thin slab is preferably 80 ~ 120mm in thickness. When the thickness of the thin slab exceeds 120mm, not only the high speed casting is difficult, but also the rolling load increases during rough rolling, and when the thickness of the slab is less than 80mm, the temperature of the cast slab rapidly occurs, making it difficult to form a uniform structure. In order to solve this problem, it is possible to additionally install a heating device, but this is a factor to improve the production cost, it is desirable to exclude as possible. Therefore, the thickness of the thin slab is preferably controlled to 80 to 120 mm, more preferably 85 to 115 mm, even more preferably 90 to 110 mm or less.

When manufacturing the thin slab by the above method, the cooling specific water amount is preferably 2.0 to 3.5 L / kg. If the specific quantity exceeds 3.5ℓ / kg, the edge of the slab / bar is severely dropped in the temperature drop, and if it is less than 2.0ℓ / kg, it is difficult to secure a healthy solidification cell. As mold level hunting (MLH) occurs severely, the inclusions are not separated from each other, and a large amount of inclusions may be mixed into the slab, which may adversely affect magnetism. On the other hand, it is preferable that the said cooling specific quantity is a secondary cooling specific quantity.

In the continuous casting, the mold level hunting is preferably an average hit ratio of 90% or more that satisfies ± 3mm or less. If the mold level hunting is less than 90% of the hit ratio satisfies less than ± 3mm, the inclusions are not separated by separation, large amounts of inclusions into the slab may adversely affect the magnetism. The mold level hunting is more preferably an average of 94% or more, more preferably an average of 96% or more.

Thereafter, the thin slab is roughly rolled to obtain a bar. At this time, the roughly rolled bar is preferably 10 ~ 30mm in thickness. When the thickness of the bar exceeds 30mm, the rolling load may increase during finishing rolling, and when the thickness of the bar is less than 10 mm, the rolling deformation resistance may increase, causing difficulty in operation, and it is difficult to secure the temperature during finishing rolling.

On the other hand, the entrance temperature during the rough rolling may be 1000 ~ 1200 ℃. When the rough rolling entrance temperature is less than 1000 ° C., the rough rolling load may increase and cracks may occur at the edge portion of the bar. On the other hand, if the temperature exceeds 1200 ° C., the hot rolled scale may remain to degrade the hot rolled surface quality.

The bar is then heated. At this time, the heating temperature of the bar is preferably 1000 ~ 1200 ℃. The reason for controlling the heating temperature of the bar is to stably produce the hot rolled electrical steel sheet and to secure the surface quality. If the temperature is less than 1000 ° C, the exit temperature of the finish rolling is lowered and the rolling load increases rapidly, resulting in poor sheet flow. As a result, plate breaking may occur. If the temperature exceeds 1200 ° C., excessive scale may be generated and surface quality may be degraded.

Thereafter, the heated bar is finish rolled to obtain a hot rolled steel sheet. The finish rolling can be performed in a finish rolling mill consisting of 3 to 6 stands of the bar plate.

At this time, it is preferable to roll at 950-1180 degreeC in the 1st rolling mill at the time of finishing rolling at the said finish rolling, and to roll it at 680-850 degreeC in the last rolling mill. When the finish rolling temperature in the first rolling mill exceeds 1180 ℃ high temperature ductility is too high, it is difficult to control the tension may cause breakage, and the scale is generated a large amount may reduce the surface quality. On the other hand, when the temperature in the first rolling mill is less than 950 ° C, the high temperature strength is high, so that the thickness variation in the width direction may increase due to the increase in the rolling load, and the entrance temperature in the last rolling mill cannot be secured.

In addition, the temperature deviation in the first rolling mill during the finish rolling is preferably less than 60 ℃. When the temperature deviation in the first rolling mill exceeds 60 ° C a rolling load deviation occurs in one strip may be a wide variation in width and longitudinal thickness.

On the other hand, the rolling reduction in the first rolling mill during the finish rolling is preferably 40 to 75%. If it exceeds 75%, the rolling load may increase rapidly and plate breakage may occur due to poor plateability, and if it is less than 40%, the rolling reduction increases in the last rolling mill. This can be.

It is preferable that the temperature in the last rolling mill at the time of finishing rolling is 680-850 degreeC. If the temperature exceeds 850 ° C., excessive scale may be generated, resulting in poor surface quality, and high temperature ductility may be so high that a wave plate may be generated beyond the tension control. If the temperature is less than 650 ° C., the strength may increase rapidly during rolling, and plate breakage may occur due to poor plateability due to an increase in rolling load.

Thereafter, the hot rolled steel sheet is wound up. It is preferable that the said winding temperature is 490-700 degreeC. If the wound winding temperature is less than 490 ℃, the yield strength is too high, and the rolling load increases during cold rolling, so that the thickness variation in the width direction may be severe due to poor sheet flow. If the temperature is over 700 ℃, the yield strength is low. While advantageous for control, secondary scales may occur that degrade the quality, such as roughness and surface whiteness.

It is preferable that the hot rolled steel sheet obtained as mentioned above is 1.6 mm or less in thickness. As the thickness of the hot rolled steel sheet decreases, the recrystallized texture increases, thereby securing a uniform structure after annealing, and decreasing the cold rolling rate to decrease the crystal orientation of γ-fiber, thereby improving magnetic properties. Deviation can also be reduced. However, if it exceeds 1.6mm the effect may not be sufficient. Therefore, the thickness of the hot rolled electrical steel sheet is preferably 1.6 mm or less, and more preferably 1.4 mm or less.

In addition, the hot-rolled steel sheet may have a thickness of 30 mm from the width direction edge of the strip and a deviation of the thickness of the central portion from 40 μm or less.

On the other hand, the method for producing a hot rolled steel sheet described above is a continuous rolling mode used in the play-rolling direct connection process, characterized in that each of the above-described process is carried out continuously.

Thereafter, the wound hot rolled steel sheet is cold rolled to obtain a cold rolled steel sheet. On the other hand, before the cold rolling may further include a step of removing the oxide layer by pickling the hot rolled steel sheet. At this time, pickling can be carried out under ordinary conditions, and the pickling treatment which can be used in the present invention is not particularly limited, as long as all of the treatment methods used in the electrical steel sheet pickling process are applicable.

Thereafter, the cold rolled steel sheet is recrystallized annealed. The recrystallization annealing may also use conditions conventionally performed in the art.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, it is necessary to note that the following examples are only for illustrating the present invention in more detail, and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the claims and the matters reasonably inferred therefrom.

(Example 1)

After the molten steel having the alloy composition of Table 1 was prepared, a 90 mm thick thin slab and a 1.4 mm thick hot rolled steel sheet (Hot Rolled, HR) were manufactured using the manufacturing conditions shown in Table 2 through a performance-rolling direct connection process. The resultant was cold rolled at a cold reduction rate of 81% to produce a cold rolled steel sheet having a thickness of 0.27 mm, and then subjected to annealing to produce a final product. The annealing conditions at the time of annealing were applied to conventional manufacturing conditions (Line Speed: 120mpm, heating zone temperature: 780 ℃, crack zone temperature: 980 ℃).

For the invention examples and comparative examples prepared as described above, tundish molten steel temperature, mold level hunting (MLH) ± 3 mm or less hit ratio, ferrite grain size, average size of inclusions, number of inclusions, After measuring the occupancy and high frequency iron loss (W10 / 400, W / kg) by size of the inclusions, the results are shown in Table 3 below.

The mold level was obtained by measuring the change in radiation transmittance on the hot water surface by the X-ray detection method (Co-60). In Table 2, the theoretical solidification temperature was calculated using Thermo-Calc-3.0.1 Console Mode (Database: TCFE6).

Ferrite Grain Size (FGS) is the average value measured by the original equivalent diameter using the Image-Plus Pro software after 10 random images were taken at 500 times magnification using an optical microscope. Calculated as

Inclusion size is sampled by Carbon Replica method, photographed continuously at 40,000x magnification by TEM (Transmission Electron Microscope), and each inclusion size is measured by Image-Plus Pro software. And averaged. The number of inclusions was measured the number of inclusions in the area (31.5㎛ ² ) of the TEM tissue photograph taken 40,000 times. The occupancy of each inclusion size is TEM (Transmission Electron Microscope), and the photographs are taken continuously (10 images) at a magnification of 40,000 times, the number of inclusions present in the photographed image is measured, and the number of each inclusion size is measured. The total number of inclusions is divided and multiplied by 100.

High-frequency iron loss was averaged after cutting three specimens in a rolling direction and three sheets in a rolling vertical direction with a size of 305 mm × 30 mm and measuring them with an Epstein tester. The high frequency iron loss (W10 / 400) represents the average loss (W / kg) in the rolling direction and the perpendicular direction in the rolling direction when the magnetic flux density of 1.0 Tesla is induced at the 400 Hz frequency.

division Steel grade Alloy composition (% by weight) Relationship 1 Si Al Mn Sn P Ca Inventive Steel 1 A 3.39 0.78 0.31 0.051 0.008 0.0012 56.5 Inventive Steel 2 B 3.41 0.65 0.36 0.059 0.010 0.0009 55.8 Invention Steel 3 C 3.52 0.85 0.36 0.058 0.012 0.0011 58.9 Inventive Steel 4 D 3.15 0.95 0.31 0.049 0.009 0.0014 55.7 Inventive Steel 5 E 3.73 0.75 0.42 0.052 0.010 0.0012 60.2 Inventive Steel 6 F 2.95 0.81 0.38 0.051 0.011 0.0013 52.8 Inventive Steel 7 G 3.45 0.78 0.51 0.049 0.015 0.0008 58.3 Inventive Steel 8 H 3.05 0.89 0.42 0.053 0.012 0.0010 54.8 Inventive Steel 9 I 3.41 0.55 0.30 0.058 0.009 0.0011 54.6 Inventive Steel 10 J 3.09 0.58 0.41 0.057 0.012 0.0012 52.3 Inventive Steel 11 K 3.42 0.71 0.36 0.052 0.009 0.0013 56.4 Inventive Steel 12 L 3.46 0.75 0.41 0.049 0.011 0.0014 57.5 Inventive Steel 13 M 3.39 0.71 0.36 0.052 0.012 0.0012 56.3 Inventive Steel 14 N 3.41 0.71 0.42 0.047 0.008 0.0014 56.5 Comparative Steel 1 O 2.56 0.71 0.30 0.058 0.012 0.0013 47.7 Comparative Steel 2 P 3.01 0.16 0.41 0.045 0.011 0.0015 47.4 Comparative Steel 3 Q 2.71 0.64 0.31 0.049 0.009 0.0014 48.4 Comparative Steel 4 R 3.41 0.69 0.35 0.042 0.011 0.0039 56.1 Comparative Steel 5 S 3.39 0.75 0.32 0.051 0.010 0.0051 56.3 Comparative Steel 6 T 3.38 0.58 0.35 0.048 0.013 0.0045 54.9 13 + 10Si + 9.5Al + 4.5Mn + 7.5Sn + 50P ≧ 50

division Steel grade Week
(mpm) Theoretical solidification temperature
(℃) Tundish Molten Steel Temperature
(℃) Tundish Superheat
(℃) Cooling water quantity
(ℓ / kg) Inventive Example 1 A 6.0 1491 1503 12 2.80 Inventive Example 2 B 6.2 1490 1505 15 2.82 Inventive Example 3 C 6.0 1488 1501 13 2.81 Inventive Example 4 D 6.2 1495 1510 15 2.86 Inventive Example 5 E 6.4 1484 1495 11 2.80 Inventive Example 6 F 6.5 1497 1510 13 2.81 Inventive Example 7 G 6.2 1488 1501 13 2.80 Inventive Example 8 H 6.6 1495 1510 15 2.82 Inventive Example 9 I 6.8 1490 1507 17 2.84 Inventive Example 10 J 6.4 1495 1503 8 2.79 Comparative Example 1 K 6.0 1490 1522 32 2.82 Comparative Example 2 L 6.0 1489 1492 3 2.81 Comparative Example 3 M 6.0 1490 1502 12 1.85 Comparative Example 4 N 6.0 1490 1503 13 3.62 Comparative Example 5 O 6.2 1504 1519 15 2.81 Comparative Example 6 P 6.4 1496 1509 13 2.85 Comparative Example 7 Q 6.0 1502 1516 One 2.82 Comparative Example 8 R 6.2 1490 1506 16 2.87 Comparative Example 9 S 6.4 1491 1506 15 2.83 Comparative Example 10 T 6.2 1491 1501 10 2.85

division MLH
Hit rate
(%) Final product (cold rolled material) ferrite
Grain
size
(Μm) Inclusions
Average
size
(nm) Inclusions
Count
(Piece / μm ² ) Share of Inclusion Size (%) High frequency iron loss
(W10 / 400
, W / kg) 10 nm
Below 15 nm
Below 20 nm
Below 30 nm
Below Inventive Example 1 98 78 35 1.7 7 12 42 64 12.72 Inventive Example 2 98 82 32 1.5 8 11 39 59 12.84 Inventive Example 3 98 80 38 1.3 5 15 41 61 12.53 Inventive Example 4 97 83 34 1.8 6 17 35 60 12.63 Inventive Example 5 98 85 35 1.6 8 14 38 63 12.52 Inventive Example 6 96 78 37 1.5 9 11 31 58 12.94 Inventive Example 7 98 80 36 1.7 9 12 34 61 12.63 Inventive Example 8 97 77 39 1.5 8 14 36 59 12.84 Inventive Example 9 96 78 36 2.0 8 13 45 67 12.75 Inventive Example 10 98 79 33 1.6 7 17 38 61 13.21 Comparative Example 1 75 62 39 3.5 19 33 66 88 15.93 Comparative Example 2 Casting stop Comparative Example 3 68 64 36 3.3 17 31 61 82 15.37 Comparative Example 4 Edge cracking Comparative Example 5 98 72 36 1.6 9 15 39 70 13.81 Comparative Example 6 98 71 39 1.6 11 15 41 69 13.92 Comparative Example 7 98 72 37 1.8 8 14 40 67 13.88 Comparative Example 8 98 67 39 2.8 9 26 54 82 14.12 Comparative Example 9 97 65 43 3.1 10 28 59 83 14.56 Comparative Example 10 98 68 40 2.9 8 27 56 83 14.21

As can be seen from Tables 1 to 3, Inventive Examples 1 to 10 satisfying all of the alloy composition, tundish molten steel temperature, tundish superheat degree, and cooling specific water amount proposed in the present invention target MLH hit ratio, specific resistance, and crystal grain. It can be seen that the high frequency iron loss is excellent with both size / number / occupation rate.

In Tables 1 and 2, the derived equation 1 can be obtained from the correlation between the alloy composition and the theoretical solidification temperature. In derivation (1), 1538 means the solidification temperature (melting point) of pure iron.

Theoretical solidification temperature (° C) = 1538-13.2Si-0.7Al-5.1Mn

(In Derivation 1, Si, Al, and Mn represent respective contents (% by weight).)

Comparative Example 1 satisfies the alloy composition of the present invention, but does not satisfy the tundish superheat degree proposed in the present invention, the mold level hunting (MLH) is severe and does not meet the target grain size, the number of inclusions and the occupancy rate of high frequency iron loss It can be seen that this increased.

Comparative Example 2 satisfies the alloy composition of the present invention, but lower than the tundish superheat proposed by the present invention, the molten steel is freezing during the casting process, so that the casting stop occurs.

Comparative Example 3 satisfies the alloy composition of the present invention, but because the target mold level hunting (MLH) is lower than the specific amount proposed in the present invention, the target grain size, the number of inclusions and the occupancy rate are not satisfied. It can be seen.

Comparative Example 4 satisfies the alloy composition of the present invention, but because the slab and bar edge temperature is too low than the specific amount proposed in the present invention, the edge crack is generated, the surface quality is inferior.

On the other hand, the derived equation 2 can be obtained from the correlation between the components of Table 1 and the specific resistance. Derivatives 2 to 13 represent the specific resistance of pure iron.

Derivation Expression 2 Specific Resistance (μ (· cm) = 13 + 10Si + 9.5Al + 4.5Mn + 7.5Sn + 50P

(In Derivative 2, Si, Al, Mn, Sn, and P represent the respective contents (% by weight).)

In the case of Comparative Examples 5 to 7 does not satisfy the relation 1 proposed by the present invention, that is, the specific resistance is low, it can be seen that the iron loss is increased.

Comparative Examples 8 to 10 do not satisfy the Ca content proposed in the present invention and the relational formula 1, it can be seen that the high frequency iron loss is increased by not satisfying the grain size, the number and occupancy of the inclusions.

7 is a TEM tissue photograph of Inventive Example 1, Figures 8 and 9 show the TEM tissue photograph and Comparative Example 1, respectively. 10 and 11 show the inclusion size distributions of Inventive Example 1 and Comparative Example 1, respectively. As shown in FIGS. 7 to 11, Comparative Example 1, in which mold level hunting (MLH) was severe, had many fine inclusions compared to Inventive Example 1, and as shown in FIG. It is believed that the grain growth is disturbed and adversely affects high frequency iron loss.

(Example 2)

Inventive Steel 1 (Steel Class A) of Example 1 was studied on the relationship between temperature, temperature deviation, rolling reduction, temperature at the last rolling mill, and thickness variation in the width direction of the hot rolled material and the final product strip during finish rolling. After that, the results are shown in Tables 4 and 5 below. The width thickness deviation of the hot rolled strip is the difference between the thickness of the strip center and the thickness 30 mm away from the width edge, and the width difference of the finished product is the thickness of the end strip after 30 mm side trimming of the hot rolled material. The difference between the thickness and the thickness at a point 10 mm away from the widthwise edge was measured. In the meantime, the thickness variation of the hot rolled material and the final product refers to an average value of the top part, the middle part, and the tail part.

division Steel grade bar
thickness
(mm) Finish rolling First Rolling Mill
Rolling temperature (℃) First Rolling Mill
Temperature range (℃) First Rolling Mill
Rolling reduction (%) Last rolling mill
Rolling temperature (℃) Inventive Example 11 A 16 1080 25 58 806 Inventive Example 12 17 1100 26 56 822 Inventive Example 13 16 980 27 60 716 Inventive Example 14 16 1120 32 58 834 Comparative Example 13 17 910 25 58 661 Comparative Example 14 15 1200 36 58 869 Comparative Example 15 16 1070 69 58 807 Comparative Example 16 16 1105 95 58 811 Comparative Example 17 16 1060 25 78 810 Inventive Example 16 16 1030 31 60 752 Inventive Example 17 16 995 40 65 726 Inventive Example 18 16 1030 46 58 750

division Finish rolling Hot rolled material
Thickness deviation
(Edge ~ 30mm
Point) (μm) Hot rolled material
side
Trim width (mm) Final product
Thickness deviation
(Edge ~ 10mm
Point) (μm) High temperature strength of first rolling mill bar
(MPa) First Rolling Mill
Rolling load
Deviation (ton) Last rolling mill
Bar high temperature strength
(MPa) Inventive Example 11 8 45 58 35 30 2.8 Inventive Example 12 7 43 50 34 30 3.0 Inventive Example 13 17 48 116 38 30 3.5 Inventive Example 14 6 46 43 35 30 2.9 Comparative Example 13 28 46 164 58 30 4.9 Comparative Example 14 4 46 Breaking Comparative Example 15 9 85 59 60 30 5.2 Comparative Example 16 8 110 49 69 30 5.7 Comparative Example 17 10 45 Breaking Inventive Example 16 12 46 82 18 30 2.6 Inventive Example 17 15 48 104 20 30 3.1 Inventive Example 18 12 43 85 17 30 2.8

As can be seen from Tables 4 and 5, Examples 11 to 18 of the present invention satisfying the first rolling mill rolling temperature, rolling temperature deviation, rolling reduction and the last rolling mill rolling temperature proposed by the present invention is the hot rolled material and the final product strip It can be seen that the thickness variation in the width direction is good.

On the other hand, high temperature strength during finish rolling requires analysis because it affects the rolling load and tension control of bars and strips. Therefore, the high temperature strength of the strip according to the temperature change of Example 11 was measured, and the results are shown in FIG. 12. From this result, the derived equation 3 can be obtained from the correlation between the rolling temperature and the high temperature yield strength, and it can be seen that the high temperature strength decreases with power as the temperature increases. Therefore, it is possible to predict the high temperature strength at the first rolling mill temperature and the last rolling mill temperature from Derivation Equation 3, and the results are shown in Table 5 above.

[Derivation expression 3] High temperature strength (MPa) = 16116e ^{-0.007 * temperature}

(The temperature (° C.) in the derivation formula 3 represents the rolling temperature of the first mill and the last mill.)

Comparative Example 13 was lower than the rolling temperature of the first rolling mill proposed in the present invention, and the thickness variation in the width direction was inferior as the rolling load increased because the high temperature strength in the first and last rolling mills was high.

Comparative Example 14 is higher than the rolling temperature of the first rolling mill proposed in the present invention, the high temperature ductility is high, causing plate breakage over the tension control.

In Comparative Examples 15 and 16, the first rolling mill temperature variation proposed by the present invention was so severe that the first rolling mill rolling load variation was severely inferior to the target width variation.

In Comparative Example 17, the rolling load increased rapidly because the rolling mill did not satisfy the first rolling reduction ratio proposed in the present invention, and plate breakage occurred due to poor sheet flow.

a: slab b: bar
c: hot rolled steel sheet
100: continuous casting machine 200, 200 ': heater
300: Roughing Mill Scale Breaker (RSB)
400: roughing mill
500: Finishing Mill Scale Breaker (FSB)
502: coolant jet nozzle
504: coolant
600: finish rolling mill 700: runout table
800: high speed shear 900: winder

Claims (19)

By weight%, Si: 2.8-4.0%, Al: 0.1-1.5%, Mn: 0.05-1.5%, Sn: 0.005-0.20%, P: 0.002-0.15%, Ca: 0.0005-0.0035%, balance Fe and others Contains inevitable impurities,
Si, Al, Mn, Sn and P satisfy the following relational formula 1,
Ferrite grain average size is 70 ~ 110㎛,
The deviation of the thickness of the 10 mm point and the thickness of the center part from the width direction edge of the strip is 4.5 µm or less,
Non-oriented electrical steel sheet with excellent magnetic properties and low thickness variation with iron loss (W10 / 400) of 13.6 W / kg or less.
13 + 10Si + 9.5Al + 4.5Mn + 7.5Sn + 50P ≧ 50
(Si, Al, Mn, Sn, and P in the relation 1 indicate the respective contents (% by weight).)
The method according to claim 1,
The electrical steel sheet contains at least one of C, S and N as impurities in a range of 0.05% by weight or less, and includes Nb, V, Ti, Mo, Cu, Cr, Ni, Zn, Se, A non-oriented electrical steel sheet having excellent magnetic properties with a total of at least 0.2% of at least one selected from the group consisting of Sb, Zr, W, Ga, Ge, and Mg, and small thickness variation.
The method according to claim 1,
The electrical steel sheet has excellent magnetic properties including inclusions having an average size of 10 nm or more, and has a small thickness variation.
The method according to claim 1,
The electrical steel sheet is a non-oriented electrical steel sheet having excellent magnetic properties, including less than 2.5 pieces / μm ² inclusions, the thickness variation is small.
The method according to claim 1,
The electrical steel sheet contains less than 15% of inclusions with an average size of less than 10nm, less than 30% of inclusions less than 15nm, less than 50% of inclusions less than 20nm, and less than 30% of inclusions less than 30nm relative to the total inclusions. Non-oriented electrical steel sheet having excellent magnetic properties and less thickness variation included below.
The method according to claim 1,
The electrical steel sheet is excellent in magnetic properties of 0.15 ~ 0.35mm thickness, non-oriented electrical steel sheet having a small thickness variation.
By weight%, Si: 2.8-4.0%, Al: 0.1-1.5%, Mn: 0.05-1.5%, Sn: 0.005-0.20%, P: 0.002-0.15%, Ca: 0.0005-0.0035%, balance Fe and others Containing inevitable impurities, wherein Si, Al, Mn, Sn, and P are obtained by continuously casting molten steel that satisfies Equation 1 below to obtain a thin slab;
Rough rolling the thin slab to obtain a bar;
Heating the bar;
Rolling the heated bar to finish rolling, at the first rolling mill, rolling at 950-1180 ° C., and rolling at the last rolling mill at 680-850 ° C. to obtain a hot rolled steel sheet; And
Winding the hot rolled steel sheet;
Each of the above steps is carried out continuously,
Cold rolling the wound hot rolled steel sheet to obtain a cold rolled steel sheet; And
Recrystallization annealing the cold rolled steel sheet,
The molten steel in the tundish during the continuous casting satisfies the following relation 2,
The temperature deviation in the first rolling mill during the finish rolling is less than 60 ℃,
Cooling specific water during the continuous casting is excellent in magnetic properties of 2.0 ~ 3.5ℓ / kg, a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
13 + 10Si + 9.5Al + 4.5Mn + 7.5Sn + 50P ≧ 50
(Relationship 2) (1538-13.2Si-0.7Al-5.1Mn) +5 ≤ tundish molten steel temperature (° C) ≤ (1538-13.2Si-0.7Al-5.1Mn) +25
(Si, Al, Mn, Sn and P in the above relations 1 and 2 represent the respective contents (% by weight).)
The method according to claim 7,
The molten steel contains at least one of C, S, and N as impurities in a range of 0.05 wt% or less in total, and Nb, V, Ti, Mo, Cu, Cr, Ni, Zn, Se, Sb as tramp elements. A method for producing a non-oriented electrical steel sheet having excellent magnetic properties and having a small thickness variation of one or more selected from the group consisting of Zr, W, Ga, Ge, and Mg with a total of 0.2% or less.
The method according to claim 7,
The superheat degree of the tundish is excellent in magnetic properties of 5 ~ 25 ℃, a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The continuous casting is excellent in the magnetic properties performed at a casting speed of 3.5 ~ 8.0mpm, a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The thin slab is excellent in magnetic properties having a thickness of 80 ~ 120mm, a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The mold level hunting during the continuous casting is excellent in magnetic properties with an average hit ratio of 90% or more, which satisfies ± 3mm or less, and a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The rough rolled bar is excellent in magnetic properties having a thickness of 10 ~ 30mm, a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The temperature during the rough rolling is excellent in the magnetic properties of 1000 ~ 1200 ℃, a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The heating temperature of the bar is excellent in the magnetic properties of 1000 ~ 1200 ℃, a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The rolling reduction in the first rolling mill during the finish rolling is excellent in the magnetic properties of 40 to 75%, the method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The winding is a method of producing a non-oriented electrical steel sheet excellent in magnetic properties performed at 490 ~ 700 ℃, small thickness variation.
The method according to claim 7,
The hot rolled steel sheet is excellent in magnetic properties having a thickness of 1.6 mm or less, a method of manufacturing a non-oriented electrical steel sheet having a small thickness variation.
The method according to claim 7,
The hot-rolled steel sheet is excellent in magnetic properties, the thickness of 30mm from the width direction edge of the strip and the thickness of the central portion is less than 40㎛ excellent manufacturing method of a non-oriented electrical steel sheet having a small thickness variation.

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