KR20120072926A - Grain-oriented electrical steel sheets with extremely low core-loss and high flux-density and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A method for manufacturing grain-oriented electrical steel sheets with low core-loss and high flux-density is provided to stabilize second recrystallized gains by maintaining proper balance between forces for activating and suppressing the growth of grains, thereby obtaining high integrity and fine grains after final recrystallization. CONSTITUTION: A method for manufacturing grain-oriented electrical steel sheets with low core-loss and high flux-density comprises the steps of: heating slab, which comprises Si of 2.0-4.5wt%, Al of 0.005-0.040wt%, Mn of 0.20wt% or less, N of 0.010wt% or less, S of 0.010wt% or less, P of 0.005-0.05wt%, C of 0.04-0.10wt%, Sn of 0.08-0.10wt%, and Fe and inevitable impurities of the remaining amount, hot-rolling the heated slab, annealing the hot-rolled slab, cooling the slab at a speed of 15°C/s, cold-rolling the slab, carbonizing and nitriding the slab, and second recrystallization-annealing the slab using Sn as grain growth inhibitor.

Description

Grain-oriented electrical steel sheets with extremely low core-loss and high flux-density and Method for manufacturing the same

The present invention relates to the manufacture of oriented electrical steel sheet used as a core material of electronic devices such as generators and transformers, by using Sn as the main grain growth inhibitors to increase the fraction of goth aggregates in the primary recrystallized texture, the final high temperature A method for producing a low iron loss high magnetic flux density oriented electrical steel sheet having improved magnetic properties by optimizing the secondary recrystallized grain size after annealing.

A grain-oriented electrical steel sheet exhibits a Goss texture having a texture of {110} <001> with respect to the rolling direction, and is a soft magnetic material having excellent magnetic properties in one direction or in the rolling direction. To express this goth aggregate structure, various process conditions such as component control in steelmaking stage, slab reheating and hot rolling process factor control in hot rolling, hot plate annealing, primary recrystallization annealing, and secondary recrystallization annealing are very precise and It must be strictly controlled.

Inhibitor, one of the factors expressing goth aggregates, has a very important function as a grain growth inhibitor that suppresses indiscriminate growth of primary recrystallized grains and allows only goth aggregates to grow when secondary recrystallization occurs. To do. After the second recrystallization annealing, in order to obtain a final steel sheet having a good goth aggregate structure, the growth of all primary recrystallization grains must be suppressed until the second recrystallization occurs, and the amount of inhibitor must be large enough to obtain sufficient restraining force. The distribution should also be uniform. In addition, in order for secondary recrystallization to occur simultaneously during high temperature secondary recrystallization annealing (final high temperature annealing), the thermal stability of the inhibitor should be excellent and not easily decomposed. Secondary recrystallization occurs when the inhibitor decomposes or loses restraining force at the appropriate temperature range during the final high temperature annealing. In this case, specific grains such as goth grains grow rapidly in a relatively short time.

In general, the quality of oriented electrical steel sheet can be evaluated by the magnetic flux density and iron loss, which are typical magnetic properties. The higher the precision of the goth assembly, the better the magnetic properties. In addition, high-quality directional electrical steel sheet is capable of manufacturing high-efficiency power equipment due to its characteristics, and thus, miniaturization of power equipment and high efficiency can be obtained.

R & D for reducing iron loss of oriented electrical steel sheet was first made for R & D to increase magnetic flux density. The initial grain-oriented electrical steel sheet was MnS proposed by M. F. Littman as a grain growth inhibitor, and was produced by two cold rolling methods. According to this, secondary recrystallization was relatively stable, but the magnetic flux density was not so high and iron loss was high.

Since, Taguchi (田 口), Al by using a combination of AlN, MnS precipitates as grain growth inhibitor, a technique for producing a grain-oriented electrical steel sheet by cold-rolling once at a cold rolling rate of more than 80%. It is a technique of obtaining a high magnetic flux density by improving the orientation of {110} <001> azimuth in the rolling direction by a strong grain growth inhibitor and cold rolling, and it is possible to obtain low iron loss characteristics by greatly improving hysteresis loss. .

In general, reducing the thickness of the steel sheet is effective to reduce the iron loss by reducing the eddy current loss. This method can be obtained by adding deformation during cold rolling. In this case, since the driving force of grain growth is increased, there is a problem that secondary recrystallization is unstable because the original grain growth inhibitor is not sufficiently suppressed.

In order to reduce the thickness while balancing the grain growth driving force and the inhibitory force, rolling must be performed at an appropriate cold rolling rate during final cold rolling, and the appropriate cold rolling rate depends on the inhibitory power of the grain growth inhibitor.

When using the AlN and MnS composite precipitates proposed by Taguchi as grain growth inhibitors, a cold rolling rate of about 87% is appropriate, and when using MnS precipitates proposed by Littman as grain growth inhibitors, about 50 to 70% of cold The rolling rate is appropriate. However, these strict cold rolling conditions place a burden on the production process.

In addition to the above-described techniques, techniques for adding alloying elements capable of obtaining a level of suppression similar to the precipitates have been proposed, as opposed to techniques through grain growth suppression by precipitates, as part of improving magnetic properties of oriented electrical steel sheets.

In this regard, a technique of adding B and Ti has been proposed to reinforce the weakening of grain growth inhibition by one cold rolling. However, the technique of adding B is difficult to control in the steelmaking step by adding a small amount, and the added B is likely to form coarse BN in steel. In addition, the technique of adding Ti also acts as a factor to increase the iron loss as the TiN or TiC having a solid solution temperature of 1300 ° C or higher is present after the secondary recrystallization.

Another method for improving grain growth inhibition is a technique for producing a grain-oriented electrical steel sheet using MnSe and Sb as a grain growth inhibitor. However, this method has the advantage of obtaining high magnetic flux density due to high grain growth suppression ability, but the material itself is considerably hardened, so it cannot be manufactured by one cold rolling, and thus two colds which are essentially passed through intermediate annealing. Since rolling must be performed and toxic and expensive Sb or Se are used, a separate facility for handling toxic substances is essential, which increases manufacturing costs.

In another proposal, a grain-oriented electrical steel sheet was added by adding Sn and Cr in combination and heating the slab at a temperature of 1200 ° C. or below, followed by hot rolling, intermediate annealing, one or two cold rolling, and denitrification followed by nitriding using ammonia gas. A manufacturing method has been proposed. However, this has a very strict manufacturing standard for manufacturing low directional high magnetic flux density thin grain oriented electrical steel sheets, that is, the temperature of the hot-rolled sheet annealing process must be strictly controlled according to the acid-soluble Al and the content of the nitrogen-heated steel. In addition, since the toxic Cr must be added in combination with Sn, not only the manufacturing cost is high but also the oxide layer formed in the decarburization and nitriding annealing process due to the strong oxygen affinity is formed very densely, so that decarburization is not easy and nitriding is easy. There is a disadvantage that is not.

On the other hand, Japanese Laid-Open Patent Publication No. 2006-241503 proposes a technique of improving the magnetic properties of an electrical steel sheet by adding elements such as Sb, P, Sn to the steel sheet. This technology specifically includes P: 0.015 ~ 0.07wt%, and if necessary, adds one or two selected from Sb: 0.005 ~ 0.2wt% and Sn: 0.01 ~ 0.5wt% to have stable magnetic properties. Suggesting.

In addition, Japanese Patent Laid-Open No. 2007-254829 proposes a technique of adding Sb, P, and Sn alone or in combination. This suggests to improve the magnetic properties by containing 0.02 ~ 0.30wt% of Sn, Sb, P or more, if necessary.

In addition, Japanese Patent Application Laid-Open No. 2007-051338 adds P to 0.2 wt% or less in steel and further includes at least one element selected from Sb: 0.001 to 0.02 wt% and Sn: 0.002 to 0.1 wt%. A method of manufacturing an electrical steel sheet is disclosed, and the magnetic property is characterized by excellent appearance in the 45 ° direction in the rolling direction.

In addition, Japanese Laid-Open Patent Publication No. 11-335794 discloses the production of electrical steel sheet in which 0.0005 to 2.0% of one or more elements selected from elements such as Sb, P, Sn, B, Bi, Mo, Te, and Ge are added to the component system of the electrical steel sheet. A method is disclosed.

As described above, although a schematic configuration for manufacturing a grain-oriented electrical steel sheet by adding alloying elements such as Sb, P, Sn, and B has been described, the range of alloying elements is generally described too broadly, respectively. The effect of the addition of the alloying elements alone is not the main, but most of the two or more of the alloying elements are described only to the extent that it contains at least one. In addition, a specific method for utilizing the above alloying elements as a major grain growth inhibitor is not proposed. That is, according to the current techniques, only the degree to which magnetism can be improved by adding at least one of alloy elements such as Sb, P, Sn, and B is known, and each element is used as a major grain growth inhibitor. There was no detailed identification of the titration content and process conditions or the causal relationship to them. In addition, the techniques in which the alloying elements are added as described above, despite the differences in the behavior of the primary recrystallization and the secondary recrystallization of the grain-oriented electrical steel sheet, do not provide a solution for this.

JP2006-241503 A JP2007-254829 A JP2007-051338 A JP1999-335794 A

The present invention has been made to solve all the problems of the prior art as described above, the purpose is to add Sn in the step of steel, but control in an appropriate range that can be utilized as a major grain growth inhibitor goth in the primary recrystallized structure The purpose of the present invention is to provide a method for manufacturing a low iron loss high magnetic flux density oriented electrical steel sheet having improved magnetic properties by increasing the aggregate fraction and optimizing the size of secondary recrystallized grains.

In addition, the present invention is to control the slab heating temperature to control the high capacity of the steel N, and after cooling the hot rolled sheet annealing to control the cooling rate of 15 ℃ or more to form a hard martensite or bainite structure in the hot rolled sheet To increase the secondary recrystallization nucleation site with high orientation in the {110} <001> direction in the cold rolled steel sheet, and to control the temperature raising conditions during decarburization and annealing in order to maximize the effect of Sn as a major grain growth inhibitor. In order to maintain the balance between the growth driving force and the restraining force, by appropriately controlling the decarbonized annealing temperature conditions to form a primary recrystallized grain of an appropriate size to produce a grain-oriented electrical steel sheet having extremely excellent magnetic properties without causing a decrease in productivity It aims to provide.

Low iron loss high magnetic flux density oriented electrical steel sheet manufacturing method of the present invention for solving the above problems by weight, Si: 2.0 ~ 4.5%, Al: 0.005 ~ 0.040%, Mn: 0.20% or less, N: 0.010% or less, S: 0.010% or less, P: 0.005 to 0.05%, C: 0.04 to 0.10%, Sn: 0.08 to 0.10%, and after heating the slab made of the remaining Fe and other unavoidably mixed impurities, hot rolling, After performing hot-rolled sheet annealing but controlling the cooling rate to 15 ℃ / s or more after the hot-rolled sheet annealing, followed by cold rolling, decarburization and nitride annealing, and then performing a second recrystallization annealing Sn is used as a major grain growth inhibitor.

The decarburization and nitride annealing is carried out at a temperature range of 800 to 950 ° C. to control the size of the primary recrystallized grain to 18 to 25 μm, and is maintained at a temperature of 600 ° C. or more and 700 ° C. or less during the temperature increase of the decarburization and nitride annealing. It is preferable to carry out the process, and the temperature increase rate in the temperature range of 600 to 700 ° C. at the temperature of decarburization and annealing is 1 ° C./s×[Sn(% by weight)] or higher 12 ° C./s×[Sn(% by weight) It is particularly preferable to control the following.

In addition, in the method for producing a grain-oriented electrical steel sheet of the present invention, it is preferable to heat the slab before hot rolling to a temperature of 1050 to 1250 ° C., and to control the heating of the slab so that the solid solution amount of N is in the range of 20 to 50 ppm in the steel.

In addition, the method for manufacturing a grain-oriented electrical steel sheet of the present invention is controlled so that the β angle is less than 3 ° as the area weighted average of the absolute value of the crystal orientation in the secondary recrystallized steel sheet, the average grain size of the secondary recrystallized steel sheet 1 ~ 2cm It characterized in that the control to be.

In addition, the method for producing a grain-oriented electrical steel sheet of the present invention is characterized by controlling the bainite or martensite fraction by 9% or more by cooling after hot-rolled sheet annealing.

According to the present invention, the Sn added in an appropriate amount acts as a major grain growth inhibitor, thereby increasing the fraction of Goth-bearing grains in the primary recrystallized texture, thereby increasing the degree of integration in the {110} <001> orientation after the final secondary recrystallization. It is possible to manufacture ultra-low iron loss high magnetic flux density oriented electrical steel sheet composed of goth aggregate structure having high grain size and fine grain size.

In addition, according to the present invention, the secondary recrystallization nucleation with high degree of orientation in the {110} <001> direction in the cold rolled steel sheet by controlling the content of N employed in reheating the slab and controlling the cooling rate after the annealing of the hot rolled sheet at a cooling rate of 15 ° C. or more. By increasing the location, hard martensite or bainite structure is formed in the hot rolled plate, and the temperature raising conditions during decarburization and annealing are controlled to maximize the effect of Sn as a major grain growth inhibitor, and decarburization and nitride annealing are conventional. The primary recrystallized grains are formed at a temperature slightly higher than the conditions so that the primary recrystallized grains are formed to an appropriate size. Thus, a grain-oriented electrical steel sheet having excellent magnetic properties can be manufactured by stabilizing the secondary recrystallization by properly maintaining the balance between the grain growth driving force and the suppressing force. Can be.

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

The present inventors have studied and studied the effects of various alloying elements on the magnetism in the production of grain-oriented electrical steel sheet, and the effects of the processing conditions such as slab heating and decarburization annealing on the component system containing each alloying element. As a result, when Sn was added as 0.08 ~ 0.10% by weight and used as the main grain growth inhibitor, the fraction of Goth-bearing grains in the primary recrystallized texture increased and the {110} <001> orientation after the final secondary recrystallization. It was found that secondary recrystallized structure composed of goth aggregated structure with very high integration density and fine grain size can be manufactured to produce oriented electrical steel sheet with extremely low iron loss and high magnetic flux density.

Furthermore, the present inventors control the content of N employed in the reheating of the slab to 20 to 50 ppm in order to stably regenerate the secondary recrystallization using the slab of the component system in which Sn is added in the above composition range, and the Sn is a goth assembly structure. A process of maintaining at a temperature of 600 to 700 ° C. during decarburization and nitride annealing so as to segregate at the grain boundaries of other grains except for the first one is carried out, and decarburization and nitride annealing are carried out under normal conditions so as to maintain a balance between the grain growth driving force and the inhibitory force. The present invention could be completed by paying attention to the fact that the size of the primary recrystallized grains should be formed to a size of 18 to 25 μm by performing at a slightly higher temperature range (800 to 950 ° C.).

In the present invention, by weight%, Si: 2.0 to 4.5%, Al: 0.005 to 0.040%, Mn: 0.20% or less, N: 0.010% or less, S: 0.010% or less, P: 0.005 to 0.05%, C: 0.04 to The slab containing 0.10%, Sn: 0.08 ~ 0.10% and consisting of remainder Fe and other unavoidable impurities are heated to 1050 ~ 1250 ℃ to control the high capacity of N in the small steel in the range of 20 ~ 50ppm, and hot rolling After performing the hot rolled sheet annealing at a temperature of 900 ~ 1200 ℃, and then cold rolling, and then maintained at a temperature of 600 ℃ or more than 700 ℃ and then heated up and subjected to decarburization and nitride annealing at a temperature of 800 ~ 950 ℃ 1 By controlling the size of the vehicle recrystallized grain to 18 ~ 25㎛, and then performing a second recrystallization annealing to control the average grain size of the secondary recrystallized steel sheet to 1 ~ 2cm to produce a grain-oriented electrical steel sheet having excellent magnetic properties, Sn is characterized by being utilized as a major grain growth inhibitor.

In the present invention, Sn acts as a major grain growth inhibitor, which segregates at grain boundaries other than Goth grains and hinders the movement of grain boundaries. In order to generate stable secondary recrystallization, Sn should be added in an appropriate amount of 0.08 to 0.10%. When the appropriate amount of Sn is added, the {110} <001> azimuth goose grain fraction of the primary recrystallized texture is increased to increase the degree of integration, and the nucleus of the goth defense grown to the secondary recrystallized texture is increased.

The present invention uses a component-based slab to which the appropriate amount of Sn is added as described above, and when the slab is reheated, the slab heating temperature is controlled so that the solid solution of N is in the range of 20 to 50 ppm, and Sn is other grains except for Goth grains. In order to ensure segregation at the grain boundary, the first recrystallization grain is controlled by maintaining the temperature at 600 ~ 700 ℃ during the temperature raising process during decarburization and nitriding annealing, and controlling the decarbonization annealing temperature to maintain the balance between crystal growth driving force and suppression force. Is formed into an appropriate size of 18 ~ 25㎛, the size of the secondary recrystallized grains in the final product to 1 ~ 2cm, as a result of which the nucleation site of the goth aggregate tissue is increased and the β angle of the final steel sheet less than 3 ° It becomes possible to manufacture a grain-oriented electrical steel sheet having extremely excellent magnetic properties. Here, β angle is the deviation angle between the [100] direction and the rolling direction with respect to the rolling right angle direction of the secondary recrystallized texture.

First, the reason for component limitation of this invention is demonstrated.

[Si: 2.0 ~ 4.5 wt%]

Si is a basic composition of electrical steel sheet to increase the specific resistance of the material serves to lower the core loss (core loss). If the Si content is less than 2.0%, the resistivity decreases, which leads to deterioration of iron loss characteristics and phase transformation between ferrite and austenite at high temperature annealing, resulting in not only unstable secondary recrystallization but also severely damaged texture. When the Si content exceeds 4.5%, the brittleness, which is the mechanical property of the electrical steel sheet, increases, and the toughness decreases, causing the occurrence of plate breakage during the rolling process, and unstable secondary recrystallization. Therefore, Si is preferably limited to 2.0 to 4.5% by weight.

[Al: 0.005-0.04 weight%]

Al combines with Al, Si, and Mn in solid solution in the steel in which nitrogen ions introduced by ammonia gas in the annealing process after cold rolling, in addition to AlN precipitated finely during hot rolling and hot-rolled sheet annealing (Al, The formation of nitrides in the Si, Mn) N form serves as a powerful grain growth inhibitor. When Al is less than 0.005%, since the number and volume of formation are considerably low, sufficient effect as an inhibitor cannot be expected. When the content is more than 0.040%, Al forms coarse nitrides, thereby suppressing grain growth. Will fall. Therefore, the content of Al is limited to 0.005 ~ 0.040% by weight.

[Mn: 0.02% by weight or less]

Mn also has the effect of reducing the iron loss by increasing the specific resistance and reducing the eddy current loss, like Si, by reacting with the nitrogen introduced by the nitriding treatment with Si to form a precipitate of (Al, Si, Mn) N 1 It is an important element for causing secondary recrystallization by suppressing growth of secondary recrystallized grains. However, when added in excess of 0.20%, a large amount of (Fe, Mn) and Mn oxides are formed on the surface of the steel sheet in addition to Fe ₂ SiO ₄ , which hinders the formation of the base coating formed during high temperature annealing, thereby deteriorating the surface quality. Due to the phase transformation between ferrite and austenite in the process, the texture is severely damaged and the magnetic properties are greatly deteriorated. Therefore, Mn is made into 0.20 weight% or less.

[N: 0.010 wt% or less]

N is an important element that reacts with Al to form AlN and is preferably added at 0.010% by weight or less in the steelmaking step. If it is added in excess of 0.01% by weight, it causes surface defect called blister due to nitrogen diffusion in the process after hot rolling, and nitride is excessively formed in the slab state, making rolling difficult, complicated secondary process, and manufacturing cost. Because it raises, it suppresses below 0.01%. On the other hand, N needed to form nitrides such as (Al, Si, Mn) N and AlN is strengthened by nitriding in steel using ammonia gas in the annealing process after cold rolling.

[C: 0.04-0.10 wt%]

C is an element that causes phase transformation between ferrite and austenite. It is brittle and is an essential element for improving the rollability of electrical steel sheets with poor rolling properties, but when it remains in the final product, carbides formed due to magnetic aging effects Since it is an element which worsens magnetic properties, it is preferable to be controlled to an appropriate content. When the C content is less than 0.04% in the above-described Si content, the phase transformation between ferrite and austenite does not work properly, causing unevenness of the slab and the hot rolled microstructure. Therefore, the minimum content of C is preferably made 0.04% or more. On the other hand, after the hot-rolled annealing heat treatment, residual carbon in the steel sheet activates dislocation fixation during cold rolling to increase shear deformation zone, thereby increasing the generation site of goose nucleus, thereby increasing the goth grain fraction of the primary recrystallized microstructure. It may be considered to increase the C content, but if C contains more than 0.10% in the above Si content range, sufficient decarburization cannot be obtained in the decarburization and nitriding annealing process unless additional process or equipment is added. In addition, the secondary transformation crystal structure is severely damaged by the phase transformation phenomenon caused by this, and furthermore, when the final product is applied to the power equipment, the deterioration of the magnetic properties by the magnetic aging. Therefore, it is preferable to contain C at 0.10% at maximum. When the C content is more than 0.07%, decarburization is not easy, so it is more preferable that C is contained at 0.07% or less.

[S: 0.010 wt% or less]

When S is contained in excess of 0.01%, precipitates of MnS are formed in the slab to suppress grain growth, and segregation at the center of the slab during casting makes it difficult to control the microstructure in subsequent processes. In addition, in this invention, since MnS is not used as a main grain growth inhibitor, it is unpreferable to precipitate more than content which S inevitably mixes. Therefore, the content of S is preferably made 0.010% by weight or less.

[Sn: 0.08-0.10 wt%]

Sn is an alloy element, which is the core of the present invention, and acts as an inhibitor that segregates in the grain boundary and inhibits grain growth by preventing movement of the grain boundary. In addition, by increasing the fraction of Goth grains in the {110} <001> azimuth in the primary recrystallization aggregates and monitoring the aggregates that facilitate the growth of goth aggregates such as {111} and {411}, secondary recrystallization aggregates The nucleus of the Goth defense which grows to a lot increases. Therefore, when an appropriate amount of Sn is added, the size of the secondary recrystallized microstructure is reduced, and thus the grain size is reduced in the final product, so that the eddy current loss is reduced, thereby making it possible to manufacture a directional electrical steel sheet having excellent magnetic properties.

As such, Sn plays an important role in suppressing grain growth through segregation at the grain boundary, which not only enhances the effect of suppressing the grain growth driving force of the refined primary recrystallized microstructure, but also for forming secondary recrystallized texture. Coarse particles causing grain growth inhibition (Al, Si, Mn) N and AlN during the high temperature annealing process to reduce grain growth inhibition, and the number of particles with grain growth inhibitory effect decreases numerically by increasing Si content This prevents the grain growth inhibition from weakening. This in turn guarantees successful expression of secondary recrystallized texture at high Si content as well as low Si content.

Sn also compensates for the thermal instability of particles, which is pointed out as a problem of thin grain oriented electrical steel sheets having grain growth inhibition by grains in order to increase the rolling rate in order to reduce the thickness of the final product for thinning. Compensate for successful growth of the vehicular decision-making organization. Therefore, the addition of an appropriate amount of Sn increases the fraction of goth aggregates in the primary recrystallized texture, and increases the grain growth inhibitory ability, so that better texture, stable grain growth inhibition, and iron loss reduction due to thinning can be simultaneously obtained. As a result, it is possible to secure a secondary recrystallization aggregate structure composed of goth grains having a very high density.

When the Sn content is less than 0.08% by weight, the results of the present inventors confirmed that the magnetic properties are improved, but the effect of improving the density of the Goth aggregate tissue is small, but rather to the particles present in the matrix. Due to the small effect of compensating for grain growth inhibition, the effect of improving magnetism was only minimal.

Conversely, if Sn is contained in excess of 0.10% by weight, the grain growth inhibitory force is excessively increased, and the grain size of the primary recrystallized microstructure must be reduced in order to increase the grain growth driving force. As a result, it is difficult to control the proper oxide layer and a good surface cannot be secured. In addition, since the brittleness is increased due to excessive segregation of the grain boundary segregation element in terms of mechanical properties, it may cause plate breakage during the manufacturing process, and therefore, Sn is preferably contained in an amount of 0.08 to 0.10% by weight.

[P: 0.005-0.05 wt%]

P is an element exhibiting a similar effect to Sn, and may have a secondary role of segregating in the grain boundary to hinder the movement of the grain boundary and at the same time inhibiting grain growth, and improving the {110} <001> aggregate structure in terms of microstructure. There is. If the content of P is less than 0.005% by weight, there is no effect of addition, and if it is added in excess of 0.05% by weight, brittleness is increased and rollability is greatly deteriorated, so it is preferable to limit it to 0.005 to 0.05% by weight.

The grain-oriented electrical steel sheet manufactured by using the slab having the composition has a beta orientation (β angle; TD orientation based on the TD orientation as one of azimuth relationship between the goth assembly structure and the rolling direction by increasing the nucleation site of the goth assembly structure). Azimuth between the azimuth and the RD azimuth) is secured to within 3 ° and has extremely good magnetic properties.

Hereinafter will be described a low iron loss high magnetic flux density oriented electrical steel sheet manufacturing method of the present invention.

First, the slab is reheated prior to hot rolling, and the slab reheating is preferably carried out in a temperature range in which N and S to be in solution solidified. When the slab is heated to a temperature at which N and S are completely dissolved, fine amounts of nitrides or sulfides are formed after the annealing of the hot rolled sheet. Therefore, cold rolling, which is a subsequent process, cannot be performed by one cold rolling. The production process is increased due to the additional process, and the size of the primary recrystallized grains becomes considerably fine, so that proper secondary recrystallization may not be expressed.

It is more important for the inventors to control the high dose of N employed by slab reheating than to control the total amount of N contained in the steel cavity through various experiments and studies. It has been found that controlling the slab heating conditions to be from 20 to 50 ppm is extremely effective for improving the magnetism.

The N employed by slab reheating influences the size and amount of additional AlN formed in the decarburization and nitriding annealing process. If the amount of AlN is the same, the amount of N formed increases and the grain growth inhibition is increased so that the goth aggregate structure is increased. It becomes impossible to obtain a suitable secondary recrystallized microstructure. On the contrary, if the amount of AlN is too small, the grain growth driving force of the primary recrystallized microstructure increases, so that it is impossible to obtain an appropriate secondary recrystallized microstructure similar to the above phenomenon. Therefore, it is preferable to control the slab heating conditions so that the content of N dissolved in the steel by the slab reheating is 20 ~ 50ppm.

The content of N employed by slab reheating should take into account the content of Al in the steel cavity, since the nitrides used as grain growth inhibitors are (Al, Si, Mn) N and AlN. The correlation between the employment temperature and the solubility of Al and N in pure 3% silicon-containing steel sheet was proposed by Iwayama.

According to the solubility formula by Iwayama, the theoretical solid solution temperature T (K) is 1258 ° C, assuming that acid-soluble Al is 0.028% by weight and N is 0.0050% by weight. For this purpose, the slab of the steel sheet is heated to about 1300 ° C. Should be.

However, when the slab is heated to a temperature above 1280 ℃, iron olivine (Fe ₂ SiO ₄ ; fayalite), which is a compound of low melting point silicon and iron, is dissolved in the steel sheet, and the surface of the steel sheet melts, resulting in poor hot rolling workability. The molten water causes the problem of repairing the furnace. Therefore, it is desirable to incomplete solution by reheating the slab to a temperature of 1050 ~ 1250 ℃ to reduce the downtime due to the repair of the furnace, and to enable the appropriate control of cold rolling and primary recrystallized texture.

The slab is heated to a temperature in the above range, followed by hot rolling. In the hot rolled hot rolled sheet, there is a strain structure drawn in the rolling direction due to stress, and AlN or MnS is precipitated during hot rolling.

In order to have a uniform recrystallized microstructure and fine AlN precipitate distribution before cold rolling, the hot rolled sheet is heated to below slab heating temperature once again to recrystallize the deformed structure and to secure sufficient austenite phase to grow grains such as AlN and MnS. It is desirable to promote the employment of inhibitors. It is preferable to take such a method that the hot-rolled sheet annealing is heated to a temperature of 900 to 1200 ° C, subjected to a crack heat treatment, and then cooled in order to maximize the austenite fraction. The average size of precipitates in the steel sheet annealed hot-rolled is formed to have a range of 200 ~ 3000Å. Cooling after the hot-rolled sheet annealing may be performed by a method such as air cooling, water cooling, or oil cooling, or by a cooling method of mixing two or more types.

On the other hand, during annealing, the austenite phase undergoes phase transformation recrystallization and fine grains. Subsequently, when the quenching is performed after annealing the hot rolled sheet, the austenite phase is transformed into a hard bainite or martensite phase having high strength, and also cold rolled. During the process, recrystallization is promoted to form a uniform microstructure.

Particularly, AlN is more uniformly dissolved due to the fine and uniform matrix structure before cold rolling, and the deformation stress is large around the bainite or martensite phase with high strength transformed during the quenching process after annealing. The shear strain band is formed inside the steel sheet, and the grains in the {110} <001> direction, which are the nuclei of the secondary recrystallization, are easily recrystallized in the shear strain band, and thus, {110} <001> in the primary recrystallization texture. The aggregate of defenses will increase. This increases the degree of integration of the second recrystallized {110} <001> goth aggregate structure to improve the magnetic properties of the grain-oriented electrical steel sheet.

According to the researches and experiments of the present inventors, it was found that bainite or martensite can be formed in the steel sheet at a fraction of 9% or more by controlling the cooling rate to 15 ° C. or more when performing cooling after annealing.

After annealing the hot rolled sheet, cold rolling is performed using a reverse rolling mill or a tandem rolling mill to produce a cold rolled sheet of 0.10 mm to 0.50 mm. In cold rolling, it is most preferable to use one-time cold rolling which rolls from the initial hot rolling thickness to the thickness of the final product without performing annealing heat treatment (intermediate annealing) of the deformed structure in the middle. With one cold rolling, the low-density orientations of the {110} <001> orientation are rotated in the deflection direction, and only the best aligned goth grains in the {110} <001> orientation exist on the cold rolled plate. Therefore, in two or more rolling methods, orientations with low integration are also present in the cold rolled plate, and thus the magnetic flux density and iron loss deteriorate since the secondary recrystallization is performed at the time of the final high temperature annealing. Therefore, cold rolling is most preferably rolled so that the cold rolling rate is 87% or more by one cold rolling.

This cold rolled plate is subjected to decarburization and annealing. This removes carbon below a certain level to prevent self aging, allows the deformed tissue to recrystallize, and nitriding with ammonia gas. In the nitriding treatment, nitrides such as (Al, Si, Mn) N and AlN, which are tin extracts, can be formed by introducing nitrogen ions into the steel sheet using ammonia gas. This nitriding treatment may be carried out after the decarburization and recrystallization, or may be carried out using ammonia gas simultaneously so as to carry out the nitriding treatment simultaneously with decarburization, either of which has no problem in achieving the effect of the present invention.

In the present invention, the use of Sn as a major grain growth inhibitor is a technical idea, and for this purpose, it is necessary to allow Sn to segregate at the grain boundaries of other grains except for grains having a goth aggregate structure.

The present inventors have conducted research and experiments on the process conditions that Sn can be effectively segregated at the grain boundaries of other grains except for the Goth-assembly grains, and Sn effectively grain boundaries at temperatures of 600 ° C to 700 ° C. In particular, it was confirmed that the function as a major grain growth inhibitor can be maximized by carrying out the process of maintaining at a temperature of 600 ° C. or more and 700 ° C. or less especially during the decarburization and annealing.

In the temperature increase process of decarburization and annealing, the grain boundary segregation of Sn does not occur even if it is maintained at a temperature of less than 600 ° C., and the selective grain boundary segregation does not occur at temperatures exceeding 700 ° C. regardless of the texture of grains. For the above reason, the heat treatment for decarburization and nitride annealing for grain boundary segregation of Sn is preferably carried out at a temperature in the range of 600 ° C to 700 ° C.

In addition, the present inventors investigated the effect of the temperature increase rate of decarburization and nitride annealing on the magnetism, the temperature increase rate in the 600 ~ 700 ℃ temperature range according to the content of Sn 1 ℃ / s × [Sn (wt%)] or more 12 It has been found that it is preferable to control the temperature at or below C / s × [Sn (wt%)].

When the temperature increase rate of decarburization and nitride annealing is lower than 1 ° C / s × [Sn (wt%)] in the temperature range of 600 to 700 ° C., the annealing time and equipment become long enough to be unsuitable for commercial production. On the contrary, if the temperature increase rate exceeds 12 ° C / s × [Sn (wt%)] in the temperature range of 600 to 700 ° C. during decarburization and nitride annealing, Sn is segregated to grain boundaries having a goth aggregate structure and There arises a problem that the selective grain growth inhibitory power of the grains having the aggregate structure is lost.

In addition, the present inventors pay attention to the fact that the balance between the grain growth inhibiting force and the grain growth driving force acts differently when the grain-oriented electrical steel sheet is to be manufactured using the slab containing Sn, and needs to be strictly considered. As a result of this study, in order to secure extremely excellent magnetism in the component system proposed in the present invention, the balance of the grain growth driving force and the grain growth inhibiting force must be properly adjusted. We found that we should control the range from 18um to 25um.

In order to control the primary recrystallized grain size from 18 μm to 25 μm as described above, decarburization and annealing are at least 10 ° C. and at most 30 ° C., compared to the case of using a slab composed of a conventional component system containing a lower Sn content than the present invention. This should be done in the high temperature range.

Hereinafter, the above knowledge will be described in more detail. In order to manufacture a grain-oriented electrical steel sheet using a slab having a composition range of the present invention, the effect of making the fine grains of the primary recrystallized grains and the segregation of the grains at the grain boundaries are enhanced at the same time. do. In other words, when manufacturing a grain-oriented electrical steel sheet using a slab having a composition range of the present invention, the size of the recrystallized grains is miniaturized, so that secondary recrystallization occurs well. Since the secondary recrystallization is less likely to occur, it is necessary to examine the decarbonized annealing temperature condition by closely examining which factor is more predominant among the grain growth driving force and the grain growth suppression force. The present inventors have found that the increase factor of the grain growth driving force acts more strongly than the increase factor of grain growth inhibition in the component composition range of the present invention, so that secondary recrystallization tends to occur quickly. .

That is, in the case where the grain boundary segregation element Sn is added in the same content as in the present invention, when the decarbonization annealing is carried out in the normal temperature range, the primary recrystallized structure becomes finer, and the grain growth driving force becomes stronger than when using the general component system. Therefore, decarbonization annealing needs to be performed at a temperature range higher than a normal temperature range to stabilize the primary recrystallized microstructure.

Therefore, in the present invention, it is necessary to set the decarbonized annealing temperature range to 800 to 950 ° C., more preferably 850 to 950 ° C., at least 10 ° C. or more and 30 ° C. or more as compared with the conventional case. If the decarbonization annealing temperature is lower than 800 ° C, the size of the primary recrystallized grain becomes too small to increase the driving force for grain growth, and decarburization takes a long time due to annealing heat treatment at a low temperature, thereby lowering production. In addition, Fe ₂ SiO ₄ is formed on the surface of the steel sheet is very dense, the decarburization and internal oxide layer formation is delayed, the SiO ₂ oxide layer is formed densely in a narrow area, the base coating defects occur. On the contrary, when the decarbonization temperature exceeds 950 ° C, recrystallized grains and nitrides grow coarsely, so that the crystal growth driving force is excessively lowered so that a stable secondary recrystallization is not formed.

Therefore, in the present invention, by adjusting the balance of the grain growth driving force and the grain growth inhibiting force as described above, the primary recrystallized grains are formed to have an appropriate size of 18 to 25㎛ to obtain a suitable secondary recrystallization made of goth aggregate structure. .

Finally, in the manufacture of a grain-oriented electrical steel sheet, the {110} plane of the steel sheet is parallel to the rolled surface by applying an annealing separator based on MgO to the steel sheet, followed by final high temperature annealing, to cause secondary recrystallization. To form a grain-oriented electrical steel sheet having excellent magnetic properties by forming a {110} <001> texture in the direction parallel to the rolling direction. The purpose of the final high temperature annealing is to form the {110} <001> texture by secondary recrystallization, and to remove the impurities imparting insulation and damaging magnetic properties by forming a glassy film formed by the reaction of the oxide layer formed by decarburization with MgO. In the method of final high temperature annealing, in the temperature rising section before the secondary recrystallization occurs, the secondary recrystallization is well developed by maintaining the mixed gas of nitrogen and hydrogen to protect the nitride which is a particle growth inhibitor, and after the secondary recrystallization is completed. Is kept in 100% hydrogen atmosphere for a long time to remove impurities.

The grain-oriented electrical steel sheet manufactured by the above-described method using the slab having the composition range of the present invention is a beta orientation (β angle), which is one of the orientation relations of the goth-assembly structure and the rolling direction by increasing the nucleation site of the goth-assembly structure. The angle between the [001] direction and the RD direction) is secured within 3 °, and the average grain size of the secondary recrystallized steel sheet is formed in a range of 1 to 2 cm, with extremely excellent magnetic properties.

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

By weight%, Si: 3.2%, C: 0.055%, Mn: 0.099%, S: 0.0045%, N: 0.0043%, Sol. An ingot was prepared after vacuum melting of a slab containing Al: 0.028%, P: 0.028%, Sn, balance Fe, and other inevitable impurities. The content of Sn was changed as shown in Table 1 below. Then it was heated to a temperature of 1200 ℃ and hot rolled to a thickness of 2.3mm. The hot rolled hot rolled plate was heated to a temperature of 1050 ℃ and then maintained at 950 ℃ for 180 seconds annealing and then water-cooled at a cooling rate of 15 ℃ / s. The hot-rolled annealing plate was cold rolled once to be 0.23mm thick after pickling, and the cold-rolled plate was maintained at a temperature of 870 ° C. for 180 seconds in a humid hydrogen, nitrogen, and ammonia mixed gas atmosphere so that the nitrogen content was 200 ppm. Simultaneous decarburization and nitriding annealing. MgO, an annealing separator, was applied to the steel sheet, followed by final annealing onto a coil. The final annealing was performed at a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1200 ° C. After reaching 1200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for 10 hours or more and then cooled. Magnetic properties were measured for each condition and are shown in Table 1 below.

Sn (% by weight) _Iron loss (W _17/50 , W / kg) Magnetic flux density (B ₁₀ , Tesla) division 0.000 0.948 1.882 Comparative Material 1 0.012 0.942 1.881 Comparative Material 2 0.025 0.913 1.885 Comparative Material 3 0.033 0.919 1.884 Comparative Material 4 0.041 0.884 1.902 Comparative Material 5 0.052 0.882 1.903 Comparative Material 6 0.060 0.864 1.906 Comparative Material7 0.071 0.860 1.905 Comparative Material 8 0.080 0.783 1.942 Invention 1 0.083 0.791 1.941 Invention 2 0.085 0.784 1.947 Invention 3 0.089 0.783 1.946 Invention 4 0.092 0.790 1.945 Invention 5 0.095 0.787 1.948 Invention 6 0.097 0.792 1.942 Invention Material7 0.105 0.953 1.872 Comparative Material 9 0.113 0.961 1.870 Comparative Material 10 0.122 1.010 1.851 Comparative Material 11

As can be seen from Table 1, Inventive Materials 1 to 7 containing Sn in the range of 0.08 to 0.10% by weight are lower in iron loss and higher magnetic flux density than Comparative Materials 1 to 11.

In Comparative Materials 1 to 11, the tendency of lowering iron loss and increasing magnetic flux density in proportion to the amount of Sn added is recognized to some extent. have. This is because Sn must be added at 0.08% or more and 0.10% or less to act as a major grain growth inhibitor.

By weight%, Si: 3.2%, C: 0.055%, Mn: 0.099%, S: 0.0045%, N: 0.0043%, Sol. Al: 0.028%, P: 0.028%, Sn, the balance Fe and other inevitable slabs containing impurities are vacuum dissolved after the ingot was made, the Sn content was changed as shown in Table 2 below. Then it was heated to a temperature of 1200 ℃ and hot rolled to a thickness of 2.3mm. The hot rolled hot rolled plate was heated to a temperature of 1050 ℃ and then maintained at 950 ℃ for 180 seconds annealing and then water-cooled at a cooling rate of 15 ℃ / s. The water-cooled hot-rolled annealing plate was pickled and then cold-rolled once to be 0.23 mm thick. The cold rolled plate was maintained at a temperature of 870 ° C. for 180 seconds in a humid atmosphere of mixed hydrogen, nitrogen, and ammonia, and simultaneously decarburized and nitrified to a nitrogen content of 200 ppm. MgO, an annealing separator, was applied to the steel sheet, followed by final annealing onto a coil. The final annealing was performed at a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1200 ° C. After reaching 1200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for 10 hours or more and then cooled. Magnetic properties (W _{17 / 5O} , B ₈ ) were measured for each condition and are shown in Table 3 below. Also, after calculating the absolute value of the angle deviating from the {110} <001> ideal orientation of the secondary recrystallized grains, the weight-averaged area was measured at all positions, and the β angle was measured. Together. The secondary recrystallized grain size is calculated by dividing the maximum length and the shortest length of the secondary recrystallized microstructures observed on the surface of the secondary recrystallized steel plate in half and calculating the size of each secondary recrystallized grain, The size of the vehicle recrystallized grains was calculated as an average value.

Sn (% by weight) Iron loss (W / kg) Magnetic flux density (Tesla) β angle (°) Secondary recrystallized grain size (cm) division 0.012 0.942 1.881 4.8 6.2 Comparative Material 2 0.025 0.913 1.885 4.5 5.9 Comparative Material 3 0.033 0.919 1.884 4.1 5.9 Comparative Material 4 0.041 0.884 1.902 3.4 5.2 Comparative Material 5 0.052 0.882 1.903 3.6 5.0 Comparative Material 6 0.060 0.864 1.906 3.5 4.8 Comparative Material7 0.071 0.860 1.905 3.4 4.8 Comparative Material 8 0.083 0.791 1.941 2.1 1.8 Invention 2 0.089 0.783 1.946 2.3 1.9 Invention 4 0.095 0.787 1.948 2.3 1.4 Invention 6 0.097 0.792 1.942 2.2 1.3 Invention Material7 0.122 1.010 1.851 3.4 0.7 Comparative Material 11

As can be seen in Table 2, Inventive Materials 2, 4, 6, and 7 containing Sn in the range of 0.08 to 0.10% by weight are the final steel sheets showing the degree of deviation from the goth orientation due to the effect of increasing the nucleation site of the goth assembly tissue. Although the beta angle of is less than 3 °, the orientation is greatly improved, and the secondary recrystallized grains are formed to an appropriate size of 1 to 2 cm, which is excellent in magnetism, but Comparative materials 2 to 8 and 11, in which Sn is out of the scope of the present invention, The beta angle of the steel sheet exceeded 3 ° and the magnetic inferiority.

By weight%: Si: 3.2%, C: 0.054%, Mn: 0.093%, S: 0.0046%, N: 0.0042%, Sol. Al: 0.029%, P: 0.025%, Sn, the balance Fe and other inevitable slabs containing impurities are vacuum dissolved after the ingot was made, the content of Sn was changed as shown in Table 3 below. Then it was heated to a temperature of 1200 ℃ and hot rolled to a thickness of 2.3mm. The hot rolled hot rolled plate was heated to a temperature of 1050 ° C and then maintained at 950 ° C for 180 seconds to anneal and then water cooled. The water-cooled hot-rolled annealing plate was pickled and then cold-rolled once to be 0.23 mm thick. The cold rolled plate is heated up at 600 ℃ to 700 ℃ while raising the temperature to 865 ℃, and maintained at 865 ℃ for 180 seconds in humid hydrogen, nitrogen and ammonia mixed gas atmosphere. Simultaneous decarburization and nitriding annealing were carried out to 200 ppm. MgO, an annealing separator, was applied to the steel sheet, followed by final annealing onto a coil. The final annealing was performed at a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1200 ° C. After reaching 1200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for 10 hours or more and then cooled. For each condition, the heating rate and the magnetic properties (W _{17 / 5O} , B ₈ ) measured in the temperature range of 600 ℃ to 700 ℃ during decarburization and nitride annealing are shown in Table 3.

Sn (% by weight) 12 x [Sn (% by weight)] 600 ℃ or more and 700 ℃ or less Heating rate (℃ / s) Iron loss
(W / kg) Magnetic flux density
(Tesla) division 0.055 0.66 0.03 0.942 1.881 Comparative Material 12 0.055 0.66 0.05 0.933 1.889 Comparative Material 13 0.055 0.66 5.00 0.954 1.880 Comparative Material14 0.064 0.768 0.04 0.921 1.884 Comparative Material 15 0.064 0.768 0.07 0.915 1.885 Comparative Material 16 0.064 0.768 5.00 0.933 1.879 Comparative Material17 0.068 0.816 0.05 0.920 1.893 Comparative Material 18 0.068 0.816 0.08 0.916 1.899 Comparative Material 19 0.068 0.816 5.00 0.931 1.890 Comparative Material 20 0.081 0.972 0.07 0.796 1.940 Comparative Material21 0.081 0.972 0.09 0.790 1.941 Invention Material 8 0.081 0.972 5.00 0.814 1.939 Comparative Material 22 0.090 1.08 0.08 0.791 1.944 Comparative Material 23 0.090 1.08 0.95 0.785 1.946 Invention Material 9 0.090 1.08 5.00 0.804 1.944 Comparative Material 24 0.096 1.152 0.09 0.793 1.944 Comparative Material 25 0.096 1.152 1.10 0.788 1.946 Invention 10 0.096 1.152 5.00 0.811 1.943 Comparative Material 26

As can be seen from Table 3, Sn is contained in the range of 0.08 to 0.10% by weight, and the temperature increase rate in the temperature range of 600 to 700 ° C during decarburization and annealing is 1 ° C / s × [Sn (% by weight)] or more. Inventive materials 12 to 14, which are controlled to 12 ° C / s × [Sn (wt%)] or less and selectively segregate grain boundaries in grain boundaries having a goth aggregate structure, have more magnetic properties than those of comparative materials 29 to 34. Excellent.

By weight%, Si: 3.2%, C: 0.055%, Mn: 0.099%, S: 0.0045%, N: 0.0043%, Sol. An ingot was prepared after vacuum melting of a slab containing Al: 0.028%, P: 0.028%, Sn, balance Fe, and other inevitable impurities. The content of Sn was changed as shown in Table 4 below. Then it was heated to a temperature of 1200 ℃ and hot rolled to a thickness of 2.3mm. The hot rolled hot rolled plate was heated to a temperature of 1050 ℃ and then annealed by holding for 180 seconds at 950 ℃ and then cooled by varying the cooling rate as shown in Table 4. The hot-rolled annealing plate was pickled and cold-rolled once so as to be 0.23mm thick at a predetermined temperature, and the cold-rolled plate was kept at a temperature of 870 ° C for 180 seconds in a humid hydrogen, nitrogen, and ammonia mixed gas atmosphere to provide nitrogen content. Simultaneous decarburization and nitriding annealing were carried out to 200 ppm. MgO, an annealing separator, was applied to the steel sheet, followed by final annealing onto a coil. The final annealing was performed at a mixed atmosphere of 25% nitrogen + 75% hydrogen up to 1200 ° C. After reaching 1200 ° C, the annealing was carried out in a 100% hydrogen atmosphere for 10 hours or more and then cooled. For each condition, the bainite or martensite fraction and magnetic properties (W _17/50 , B ₈ ) were measured and shown in Table 4 below.

Sn
(weight%) After hot rolled annealing
Cooling rate
(℃ / s) Bainite or martensite fraction (%) Iron loss
(W17 / 50) Magnetic flux density
(B8) division 0.033 10 0 0.936 1.879 Comparative material 27 15 10 0.919 1.884 Comparative Material 4 30 13 0.918 1.891 Comparative Material 28 50 24 0.904 1.893 Comparative Material 29 0.085 10 One 0.917 1.881 Comparative Material 30 15 9 0.784 1.947 Invention 3 30 14 0.783 1.942 Invention Material 11 50 21 0.779 1.951 Invention Material12 0.131 10 0 1.149 1.866 Comparative Material 31 15 10 1.010 1.871 Comparative Material32 30 13 1.153 1.867 Comparative Material 33 50 22 1.182 1.866 Comparative Material 34

As can be seen in Table 2, Inventions 3, 11 and 12 containing Sn in the range of 0.08 to 0.10% by weight, and controlling the cooling rate to 15 ° C / s or more after hot-rolled sheet annealing are bainite or martensite The fraction of was more than 9%, and it can be seen that there is a significant improvement in magnetic properties when compared with the comparative material 30.

Claims (10)

By weight%, Si: 2.0-4.5%, Al: 0.005-0.040%, Mn: 0.20% or less, N: 0.010% or less, S: 0.010% or less, P: 0.005-0.05%, C: 0.04-0.10%, Sn: Slab containing 0.08 ~ 0.10%, remainder Fe and other unavoidable impurities, is heated, hot rolled, and then hot-rolled sheet annealing, but controlling the cooling rate to 15 ℃ / s or more after hot-rolled sheet annealing And then cold rolling, followed by decarburization and nitride annealing, followed by secondary recrystallization annealing, and manufacturing low iron loss high magnetic flux density oriented electrical steel sheet in which Sn is used as a major grain growth inhibitor. Way. The method according to claim 1,
The decarburization and nitride annealing method for producing a low iron loss high magnetic flux density oriented electrical steel sheet carried out at a temperature range of 800 ~ 950 ℃. The method according to claim 1,
The decarburization and nitride annealing method of manufacturing a low iron loss high magnetic flux density oriented electrical steel sheet comprising the step of maintaining at a temperature of more than 600 ℃ 700 ℃ during elevated temperature. The method according to claim 3,
The decarburization and nitride annealing has a low iron loss high magnetic flux density controlled at a temperature rising rate of 600 ° C. to 700 ° C. of 1 ° C./s×[Sn(wt%)] or more and 12 ° C./s×[Sn(wt%)] or less. Method for producing oriented electrical steel sheet. The method according to any one of claims 1 to 4,
A method of manufacturing a low iron loss high magnetic flux density oriented electrical steel sheet to control the size of the primary recrystallized grain to 18 ~ 25㎛. The method according to any one of claims 1 to 4,
A method for producing a low iron loss high magnetic flux density oriented electrical steel sheet in which the slab heating temperature before hot rolling is 1050 to 1250 ° C. The method according to any one of claims 1 to 4,
A method for manufacturing a low iron loss high magnetic flux density oriented electrical steel sheet in which the heating of the slab before hot rolling controls the heating temperature so that the solid solution of N in the steel is in the range of 20 to 50 ppm. The method according to any one of claims 1 to 4,
A method for manufacturing a low iron loss high magnetic flux density oriented electrical steel sheet in which secondary angle is recrystallized so that the β angle is less than 3 ° as the area weighted average of the absolute values of the crystal orientations.
However, β angle is the deviation angle between the [100] direction and the rolling direction with respect to the rolling right angle direction of the secondary recrystallized texture. The method according to any one of claims 1 to 4,
A method of manufacturing a low iron loss high magnetic flux density oriented electrical steel sheet to control the average grain size of the secondary recrystallized steel sheet to 1 ~ 2cm. The method according to any one of claims 1 to 4,
A method for producing a low iron loss high magnetic flux density oriented electrical steel sheet in which a bainite or martensite fraction is controlled to 9% or more by cooling after annealing.