JPH10140243A - Production of high magnetic flux density grain oriented electrical steel sheet having extremely low iron loss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate coarsening of crystal grain and deterioration of iron loss characteristic by particularly regulating hot-rolling condition. SOLUTION: The precipitation of B and N in the components of an inhibitor in the hot-rolling is restrained as much as possible, and the restraining action of the inhibitor is displayed by precipitating extremely fine B, N in the temp. raising process of a hot-rolled sheet in the following cold-rolled process. There are three points important for preventing the precipitation of B, N in the hot- rolling process are: First, the finish temp. of the hot-rolling is held as high as 950-1150 deg.C so that B, N may exist in the steel in supersaturated solid condition. Second, the steel sheet finished of the hot-rolling is rapidly cooled at >=20 deg.C/s cooling speed. In this way, B is kept remaining in the steel in supersaturated condition. Third, the coiling temp. after finishing the hot-rolling is kept to <=670 deg.C. By this method, the coil is held at near the coiling temp. for long time to prevent the precipitation of B, N.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention proposes a method of manufacturing a grain-oriented electrical steel sheet having a particularly high magnetic flux density and extremely low iron loss, among grain-oriented electrical steel sheets used for an iron core of a transformer or a generator. Things.

[0002] It contains Si and has a crystal orientation of (110)
[001] orientation or (100) [001] orientation
Grain-oriented electrical steel sheets have excellent soft magnetic properties and
Widely used as various iron core materials in the
You. At that time, the characteristics required for electrical steel sheets are generally
Loss when magnetized to 1.7 T at a frequency of 50 Hz
 W _17/50It is important that the iron loss is low. Power generation
The iron loss of the iron core as a machine or transformer_17/50Is the value of
What can be greatly reduced by using lower materials?
W as iron loss_17/50Demand for low-cost materials is increasing year by year
It is being used.

[0003]

2. Description of the Related Art In general, in order to reduce iron loss of a material, a method of increasing an effective Si content to reduce an eddy current loss to increase electric resistance, a method of reducing a thickness of a steel sheet, a method of reducing a crystal grain, There are known a method of reducing the diameter and a method of increasing the degree of integration of the crystal orientation to improve the magnetic flux density. Among them, we studied methods to increase the Si content, to reduce the thickness of the steel sheet, and to reduce the crystal grain size. And the workability is deteriorated, which is unfavorably limited, and the method of reducing the thickness of the steel sheet has an inherent limit because it extremely increases the manufacturing cost.

[0004] Among the above-mentioned techniques for improving the magnetic flux density, many studies have been made so far. For example, Japanese Patent Publication No. 46-23820 (heat treatment method for high magnetic flux density electromagnetic steel sheet) discloses a method for improving the magnetic flux density in steel. Al added and 10 after hot rolling
A proposal is made of a technique in which fine AlN is precipitated by hot-rolled sheet annealing at a temperature range of 00 to 1200 ° C and high temperature, followed by quenching, and a high-pressure reduction of 80 to 95% in the final cold rolling is performed. It is disclosed, and thereby obtain a very high magnetic flux density and 1.95T in B _10. This is because finely dispersed AlN
Has a strong effect as an inhibitor that suppresses the growth of primary recrystallized grains, and secondary recrystallizes only nuclei with excellent crystal orientation to obtain a product having a crystal structure with excellent orientation. It is assumed that.

However, in this technique, it is generally difficult to obtain a small iron loss by coarsening the crystal grains.
Further, since it is difficult to completely dissolve AlN into solid solution in hot-rolled sheet annealing, it has been difficult to stably obtain a product having a high magnetic flux density.

[0006] Separately, Japanese Patent Publication No. 58-43445 (a method for producing a cubic edge oriented silicon steel) has a value of 0.0006 to 0.0006.
With 0.0080% B and 0.0100% or less of the steel containing the N, techniques flux density of 1.89T in B ₈ by congeal devised to decarburization annealing can be obtained is disclosed. This method was not industrialized because the magnetic flux density was low and the iron loss was not so good.However, the product obtained by this method exhibited relatively stable magnetic properties, so it was an industrially preferable technique. is there.

[0007]

SUMMARY OF THE INVENTION According to the present invention, B and N are used as inhibitor components to increase the degree of integration of crystal orientations to obtain a high magnetic flux density, to reduce crystal grain coarsening and deterioration of iron loss characteristics. An object of the present invention is to propose a method for manufacturing a grain-oriented electrical steel sheet that can be eliminated.

That is, when the degree of integration of the crystal orientation is increased, the crystal grains are inevitably coarsened, leading to deterioration and instability of the iron loss. And the magnetic flux density is reduced. Due to such a trade-off state, conventionally, it has not been possible to stably produce a low iron loss material with an extremely high magnetic flux density. Therefore, in the present invention is a method for producing a grain-oriented electrical steel sheet and inhibitors of BN, the magnetic flux density B ₈ is extremely high, and seeks to eliminate the instability of the crystal grain coarsening of the product essentially internalized is there.

[0009]

The present invention focuses on the precipitation and dispersion state of BN, which is an inhibitor, in order to eliminate such a trade-off state, and adopts a completely different deposition method from the conventional method to achieve a very fine structure. It has been found that it is possible to obtain a strong inhibitory effect on the growth of primary recrystallized grains by precipitating BN into the steel and to make effective use of this. That is, the gist of the present invention is as follows.

C: 0.025 to 0.095 wt%, Si: 1.5 to
A steel slab containing 7.0 wt%, Mn: 0.03 to 2.5 wt%, and one or two of S or Se: 0.003 to 0.040 wt% is used as a raw material, and the slab is heated to a temperature of 1350 ° C. or more. After hot rolling, hot-rolled sheet annealing and then cold rolling once, or hot rolling and hot-rolled sheet annealing followed by double cold rolling with intermediate annealing, or after hot rolling The final cold-rolled sheet thickness is obtained by any one of the two cold rolling methods including the intermediate annealing, followed by primary recrystallization annealing, and then applying an annealing separator, and then final finishing annealing In producing a grain-oriented electrical steel sheet by a series of steps of applying B, B:
0.0008-0.0085wt% and N: 0.0030-0.0100wt%, hot rolling finish rolling reduction 85-99%
In the range of 950 to 1150 ° C and the relationship between the Si content and the B content of the material,
After performing hot rolling within the range that satisfies (1), 20 ° C /
Rapid cooling at a cooling rate of at least s and winding at a temperature of 670 ° C or less, and both hot-rolled sheet annealing and intermediate annealing
The temperature is raised to a temperature of 0 ° C. at a rate of 5 to 25 ° C./s and the holding time is 150 seconds or less in a temperature range of 900 to 1150 ° C., and cold rolling is performed once. Cold rolling is performed in the range of reduction ratio: 80 to 95% to obtain the final cold-rolled sheet thickness, or the first rolling is performed by double cold rolling in the range of reduction ratio: 15 to 60%. After the second annealing after intermediate annealing
The second rolling is performed in a rolling reduction range of 80 to 95% to obtain a final cold-rolled sheet thickness, and at least during the final heating of the final annealing.
A method of manufacturing a high magnetic flux density grain-oriented electrical steel sheet having extremely low iron loss, which is sequentially combined with increasing the temperature in an atmosphere containing H ₂ from a temperature of 900 ° C. or more (first invention) ). [Note] 745 + 35 × + 3Y ≦ T ≦ 900 + 35 × + 3Y ---- (1) where T: finish rolling end temperature (° C) X: Si (wt%) Y: B (wtppm)

[0011] The high magnetic flux density direction with extremely low iron loss according to the first invention, wherein the cooling in the hot rolled sheet annealing or intermediate annealing immediately before the final cold rolling is a quenching treatment for increasing the amount of solid solution C in the steel sheet. A method for producing a conductive electrical steel sheet (second invention).

[0012] The high magnetic flux with extremely low iron loss according to the first or second invention, wherein decarburization of 0.005 to 0.025 wt% is performed by hot-rolled sheet annealing or intermediate annealing immediately before final cold rolling. Method for producing density-oriented electrical steel sheet (third invention).

[0013] The final cold rolling is performed by warm rolling in a temperature range of 90 to 350 ° C or by aging treatment between passes in a temperature range of 100 to 300 ° C for a time range of 10 to 60 minutes. The method for producing a high magnetic flux density grain-oriented electrical steel sheet having extremely low iron loss according to claim 1, 2, or 3.

Here, the quenching treatment in the third invention is
A process performed in a cooling process to make the state of the amount of C solid-dissolved by high-temperature annealing into a supersaturated state, in which a gas and / or a liquid is sprayed as a cooling medium onto the steel sheet so as to have a cooling rate faster than natural cooling. Processing. By this treatment, in addition to the effect of increasing the solid solution C, a fine carbide precipitation effect by combination with the low-temperature holding treatment during cooling can be obtained, and the magnetic properties can be further improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the process of achieving the present invention will be described below based on experimental examples. Experiment 1 C: 0.08 wt% (hereinafter simply expressed as%), Si: 3.36%,
Mn: 0.07%, Al: 0.009%, Se: 0.018%, Sb: 0.025
%, B: 0.0020% and N: 0.008%, and two slabs for grain-oriented electrical steel sheets each consisting essentially of Fe and having a thickness of 250 mm and having a thickness of 1390 ° C. were heated to 1390 ° C. After finishing the rough rolling at a temperature of 1020 ° C and finishing the finish rolling at a temperature of 1020 ° C and a sheet thickness of 45 mm, a large amount of cooling water is injected to cool at a cooling rate of 50 ° C / s. The coil was wound at a temperature of 550 ° C. (coil A), and the other was finished with rough rolling at a temperature of 1200 ° C. and a thickness of 45 mm, and then finished with a roll of 2.2 mm at a temperature of 935 ° C. After that, a normal amount of cooling water is injected to cool at a cooling rate of 25 ° C./s,
It was wound on a coil at a temperature of ° C. (coil B).

The two types of hot-rolled sheet coils A and B are divided into two parts (A-1, A-2 and B-1, B-B).
2) The hot-rolled sheet coils of A-1 and B-1 were heated at a heating rate:
After the temperature was raised to a temperature of 1100 ° C. at 12 ° C./s, hot-rolled sheet annealing was performed for 30 seconds and the hot-rolled sheet coils of A-2 and B-2 were heated at a rate of 1170 ° C. After the temperature was raised to the temperature, hot-rolled sheet annealing was performed for 30 seconds.

After the pickling, these annealed sheets are subjected to cold rolling at a temperature of 120 ° C. to a final cold-rolled sheet thickness of 0.27 mm, and after degreasing, decarburized at 850 ° C. for 2 minutes. Next, recrystallization annealing was performed, and an annealing separator containing MgO as a main component was applied to the surface of the steel sheet, and each was wound into a coil.

Then, as final annealing conditions, 800
° C. for up to a temperature of heating at a heating rate of 30 ° C. / h in an N ₂ atmosphere, the Atsushi Nobori of the temperature range of _{800 ~1050 ℃ N 2: 25%} ,
H ₂ : 10% at a rate of 15 ° C./s in a mixed atmosphere of 75%
The temperature in the temperature range of 50 to 1200 ° C. and the soaking in 1200 ° C. for 5 hours are in an H ₂ atmosphere, and the temperature in the temperature range of 1050 to 1200 ° C. is 20 ° C./s. Up to the temperature of H
A thermal cycle and atmosphere were employed in which cooling was performed forcibly in _two atmospheres and cooled to a temperature of 800 ° C. or less in a N ₂ atmosphere.

After the final finish annealing, the unreacted annealing separating agent was removed, and then a tension coat consisting of 50% colloidal silica and magnesium phosphate was applied and baked to obtain products.

From each of the products thus obtained, a test piece of Epstein size having a long side extending in the rolling direction was cut out along the direction perpendicular to the rolling direction, subjected to strain relief annealing at a temperature of 800 ° C. for 3 hours, and then subjected to a magnetic flux of 1.7 T. The iron loss W _17/50 and the magnetic flux density B ₈ in the density were measured, respectively, and these steel sheets were macro-etched to investigate the average crystal grain size.
Table 1 summarizes the results of these investigations.

[0021]

[Table 1]

As is evident from Table 1, the product of coil code A-1 having a high hot rolling end temperature and a low hot rolled sheet annealing temperature is smaller than the product of coil code B-2 which is the conventional condition.
Extremely high magnetic flux density (B ₈ ) and extremely low iron loss (
W _17/50 ). As a result of investigating the reason for obtaining such good results, the following has been found.

That is, in the conventional hot rolling, it is extremely difficult to uniformly and finely precipitate BN as an inhibitor, and it has been impossible to sufficiently exert the inhibitory power of BN as an inhibitor. In the coil symbol A-1, in which good results were obtained in the above experiment, the precipitation of BN in hot rolling was suppressed as much as possible, and extremely fine BN was removed during the temperature rise process of hot-rolled sheet annealing in the subsequent cold rolling process. It has been found that this causes a strong inhibitory action of the inhibitor.

A detailed examination of the process of fine precipitation of BN during the heating process of the hot-rolled sheet revealed that a large number of ultra-fine precipitates already existed in the hot-rolled sheet.
It turned out to be the core of N precipitation. This ultrafine precipitate is composed of sulfides such as MnS and CuS, selenides such as MnSe and CuSe, and composite precipitates thereof, and can be extremely finely precipitated in a range where the hot finish rolling temperature is appropriate. all right. That is, it has been found that it is only necessary to suppress the precipitation of BN in a state where defects due to processing such as dislocation exist in the steel at high density. Here, hot finish rolling
If the temperature is higher than the appropriate temperature, the density of defects existing in the steel decreases, and a sufficiently high precipitation density cannot be obtained. The precipitation density of the part decreases. Since these precipitates are ultrafine, a small amount of 0.003 wt% or more is sufficient, but it is necessary to contain S and / or Se in the steel.

The points to be noted in this technique are as follows.
Is to lower the annealing temperature of the hot-rolled sheet so as not to cause the re-solid solution and ostwald growth of BN deposited on the steel sheet. The lower limit of the proper annealing temperature in the present invention is intended to optimize the size of the crystal structure after annealing, so if the annealing temperature is excessively low, recrystallization after rolling is performed. In the structure, the strength of the (110) grains serving as nuclei for secondary recrystallization is insufficient, and a secondary recrystallized structure having a good orientation cannot be obtained. Therefore, in order to obtain sufficient strength of the (110) grains, it is necessary to coarsen the crystal structure after annealing to a certain size or more. For this purpose, it is essential to raise the temperature to 900 ° C. or more. . On the other hand, the most important point of the upper limit of the annealing temperature of the hot-rolled sheet is to prevent the BN finely precipitated during the heating process from re-dissolving and Ostwald growing. For this, 1150 ° C
It is necessary to perform annealing at the following temperature and for a soaking time of 150 seconds or less.

The precipitation phenomenon of BN at the time of raising the temperature of the hot-rolled sheet annealing ends at a temperature of about 800 ° C.
Since the size and distribution of the precipitates change, it is also important to control the rate of temperature rise. That is, if the heating rate is lower than 5 ° C./s, coarse precipitation is likely to occur, and if the heating rate is higher than 25 ° C./s, B
The precipitation amount of N becomes insufficient.

Although there is no particular requirement for the cooling conditions after annealing, the quenching treatment increases the solid solution C in the steel, improves the primary recrystallization texture, and combines with the quenching treatment to reduce the low temperature. Since the treatment for retaining and precipitating fine carbide further improves the primary recrystallization texture, these treatments are effective when applied to the present invention. Further, performing decarburization of the surface layer of the steel sheet during annealing can obtain more preferable results.

Secondly, as an essential condition for effectively utilizing the technique of precipitating fine BN in the process of raising the temperature of hot-rolled sheet annealing, BN is not precipitated as much as possible in the hot rolling step. If BN precipitates in the hot rolling step, a large amount of BN that has already precipitated as precipitation nuclei is precipitated as a precipitation nucleus in the temperature rising process of hot-rolled sheet annealing, so that a small number of coarse precipitated BN is formed and the suppressing power is reduced. Will deteriorate.

In the hot rolling step, there are three points for preventing the precipitation of BN. One of the points is that BN is present in the steel in a supersaturated solid solution state at a high hot rolling end temperature. Since it is known that the precipitation temperature of BN changes depending on the Si content and the B content, it is important to change the hot rolling end temperature in accordance with these contents. If the hot rolling end temperature is low, BN
Precipitates. In the above experiment, the product of coil symbol B-2 re-dissolved and re-precipitated with hot rolled sheet annealing at a high temperature, aside from coil symbol B with hot rolled sheet annealing at a low temperature
In the case of the product of -1, a small number of coarse BNs are precipitated, the suppressing power is reduced, and the secondary recrystallization is poor, so that the magnetic properties are deteriorated.

Another point is that the cooling of the steel sheet after the completion of hot rolling is rapidly cooled. That is, the rapid cooling makes it possible to freeze B in the steel in a supersaturated state. Conversely, when the cooling rate is low, BN tends to precipitate in the cooling process. The cooling rate required to prevent the precipitation of BN is 20 ° C./s or more.

One remaining point is that the coil winding temperature after the completion of hot rolling is lowered. Since the coil is kept close to the winding temperature for a long time, if the temperature is high, the BN is also increased.
Is caused. In order to prevent the precipitation of BN, it is essential that the coil winding temperature be 670 ° C. or lower.

Next, an experiment was conducted to investigate an appropriate range of the hot rolling end temperature. Except that the content of Si and B were intentionally changed, various 250 mm thick slabs for grain-oriented electrical steel sheets having almost the same composition as in the above experiment were used, except that the hot rolling end temperature was changed. Is the coil symbol A-1 in the above experiment.
Under the same conditions as above, each product was manufactured, and the value of the magnetic flux density B ₈ / B _s (B _s is the saturation magnetic flux density) of each obtained product was examined.

FIG. 1 is a graph showing the effects of the contents of Si and B of the material and the hot rolling end temperature on the magnetic flux density B ₈ / B _s . From FIG. 1, the hot-rolling end temperature for obtaining an extremely high value of B ₈ / B _s of 0.95 or more is expressed by Si
Formula 745 + 35 where (%) is represented by X and B (ppm) is represented by Y
It requires a value of X + 3Y or more and a temperature of 950 ° C. or more,
It is also found that the temperature needs to be 900 + 35X + 3Y or less and 1150 ° C. or less. When the hot-rolling end temperature is lower than the above range, BN is mostly precipitated during the hot-rolling process, and when the temperature is high, BN is rolled in a high-temperature region, and the width of the band structure of the hot-rolled sheet increases, and The reason is that they hinder the growth of recrystallization.

Third, the crystal grain size of the secondary recrystallized grains is reduced by lowering the annealing temperature of the hot-rolled sheet. The reason for this is not clear, but by lowering the annealing temperature, the amount of γ transformation is reduced and the crystal grain size before rolling is substantially increased, and the nucleation frequency of (110) grains in the primary recrystallized structure of rolling is reduced. It is speculated that this may have been due to an increase in

It is a well-known phenomenon that when the number of (110) grains increases in the primary recrystallized structure, the secondary recrystallized grains become finer. In this case, however, the magnetic flux density is reduced as compared with the conventional case. This was always the case. However, in the present invention, it is presumed that the effect of suppressing the strong inhibitor was obtained, and at the same time, the effect of improving the magnetic flux density was obtained at the same time as the secondary recrystallized grains were refined.

In the cold rolling step, a one-time cold rolling method in which a hot-rolled sheet is annealed and then a single cold-rolling is performed, and a hot-rolled sheet is annealed and then a first cold-rolling is performed. The second cold rolling method in which annealing is performed and then the second cold rolling is performed, or the second cold rolling is performed after the first cold rolling and the intermediate annealing after the first cold rolling is omitted. Any of the two cold rolling methods in which cold rolling is performed can be employed. In the first annealing (hot-rolled sheet annealing or intermediate annealing) performed in this cold rolling step, BN is precipitated during the temperature raising process, and attention is paid to prevent Ostwald growth, re-solid solution and re-precipitation of the precipitated BN. That is, Ostwald growth of BN precipitated in the second annealing (intermediate annealing) in the case of performing hot-rolled sheet annealing and intermediate annealing,
It is important to take care to prevent re-dissolution and re-precipitation.

The rolling reduction of the cold rolling requires that the rolling reduction of the final rolling be 80 to 95% as conventionally known. When the rolling reduction in the final rolling is less than 80%, the crystal structure for growing nuclei in secondary recrystallized grains having excellent orientation is insufficient, leading to a decrease in magnetic flux density. The density of the nuclei of the secondary recrystallization is reduced, and secondary recrystallization is likely to be defective.

Experiment 2 As Experiment 2, an investigation was made on the final finish annealing conditions. C: 0.08%, Si: 3.38%, Mn: 0.07%, Al: 0.008
%, Se: 0.020%, Sb: 0.035%, B: 0.0025% and N: 0.008%, the balance being substantially Fe and 10 slabs for a 250 mm thick grain-oriented electrical steel sheet, each at a temperature of 1420 ° C. After finishing the rough rolling at a temperature of 1270 ° C. and a plate thickness of 45 mm, finishing the finishing rolling at a temperature of 1020 ° C. and a plate thickness of 2.2 mm, a large amount of cooling water was injected to 65 ° C. / s, and wound on a coil at a temperature of 550 ° C.

These hot-rolled sheets were heated at a heating rate of 9.5 ° C./s, subjected to hot-rolled sheet annealing at 1080 ° C. for 30 seconds, pickled, and pickled at 120 to 190 ° C. by a Sendzima rolling mill. The steel sheet was warm-rolled in a temperature range, finished to a final cold-rolled sheet thickness: 0.30 mm, and after degreasing, each was subjected to decarburization and primary recrystallization annealing at 850 ° C. for 2 minutes.

Next, after applying an annealing separator shown in Table 2 to each of these decarburized annealed sheets, the final finish annealing was performed at a temperature increasing rate of 30 ° C./s to a temperature of 1180 ° C. A heat pattern that keeps the temperature for a while and then cools down.
The test was performed in an N ₂ atmosphere up to a temperature of ° C., and thereafter in an atmosphere shown in Table 2.

[0041]

[Table 2]

Then, after removing the unreacted annealing separator for each steel sheet, an insulating coating mainly containing magnesium phosphate containing 50% of colloidal silica was applied, and the product was baked at a temperature of 800 ° C. did.

From each of the products thus obtained, a test piece of Epstein size having a long side extending in the rolling direction along the direction perpendicular to the rolling direction was cut out, subjected to strain relief annealing at a temperature of 800 ° C. for 3 hours, and then subjected to 1.7 T for 1.7 T. Iron loss in magnetic flux density (
W _17/50 ) and magnetic flux density (B ₈ ) were measured, and the average crystal grain size of each product was also measured. Table 3 summarizes the measurement results.

[0044]

[Table 3]

As is evident from Table 3, the magnetic properties of the products of the condition symbols A and B, which were treated in the final finish annealing to a high temperature in an atmosphere of plain N _2, were deteriorated. In addition, as components to be contained in the annealing separator, Ca, B and Ti
Can be understood to be a component that is advantageous for further improving the magnetic properties. This is due to the SiO ₂ formed on the surface of the steel sheet during decarburization annealing.
And MgO, which is the main component of the annealing separator, react during the final annealing to form a coating mainly composed of forsterite (Mg ₂ SiO ₄ ) on the steel sheet surface.
It is thought that by adding components such as and Ti, these nitrides or oxides are formed in the coating to enhance the strengthening effect of the coating and increase the tensile effect of the coating, resulting in improved magnetic properties. Can be

The atmosphere of the final finish annealing plays an important role in the formation of oxides and nitrides in such a film, and by increasing the reducibility particularly in the middle to late stages of the annealing,
It is presumed that a better effect was obtained.

The present invention has been completed as a result of intensive studies based on these experiments and investigations.

Next, with respect to the component composition and the production method of the grain-oriented electrical steel sheet of the present invention, the requirements for obtaining the effects of the present invention, the range thereof, and the operation will be described in detail. First, the component composition will be described.

C: 0.025 to 0.095% If the content of C exceeds 0.095%, the amount of γ transformation becomes excessive, the distribution of Al during hot rolling becomes uneven, and the rise of hot-rolled sheet annealing and intermediate annealing increases. The uniformity of distribution of BN precipitated during the temperature process is impaired, and the load of decarburization annealing is increased, so that poor decarburization is likely to occur. On the other hand, if it is less than 0.025%, the effect of improving the structure cannot be obtained, and the secondary recrystallization becomes incomplete and the magnetic properties deteriorate. Therefore, its content is in the range of 0.025 to 0.095%.

Si: 1.5 to 7.0% Si is an essential component for increasing electric resistance and reducing iron loss. For this purpose, it is necessary to contain 1.5% or more. If it is contained, the processability deteriorates, and it becomes extremely difficult to manufacture and process the product. Therefore, its content is in the range of 1.5 to 7.0%.

Mn: 0.03 to 2.5% Mn is an important component because it increases the electric resistance and improves the hot workability at the time of manufacturing like Si. For this purpose, it is necessary to contain 0.03% or more.
%, Magnetic properties are deteriorated by inducing γ transformation. Therefore, its content is in the range of 0.03 to 2.5%.

In addition to these components, an inhibitor for inducing secondary recrystallization is required in the steel, and it is necessary to contain B and N as inhibitor components.

B: 0.0008% to 0.0085% If the B content is less than 0.0008%, the amount of BN precipitated in the process of increasing the temperature of hot-rolled sheet annealing or intermediate annealing is insufficient, and good secondary recrystallization can be obtained. Can not. On the other hand, when the content exceeds 0.0085%, the precipitation temperature of BN becomes high, and in normal hot rolling, B
The precipitation of N cannot be suppressed. Therefore,
Its content is in the range of 0.0008 to 0.0085%.

N: 0.0030 to 0.0100% When the content of N is less than 0.0030%, the amount of BN precipitated during the heating process of hot-rolled sheet annealing or intermediate annealing is insufficient, and good secondary recrystallization can be obtained. If it is not possible, on the contrary, if it exceeds 0.0100%, defects such as blisters will be caused in the steel. Therefore, the content is in the range of 0.0030 to 0.0100%.

Further, in addition to these components, a small amount of S
And / or Se must be contained.

One or two of S or Se: 0.003 to 0.040% S and / or Se precipitate as Mn compounds or Cu compounds in steel, but these have almost no action as inhibitors. In addition, it functions as nuclei for precipitation of BN precipitated during the temperature rising process of hot-rolled sheet annealing. Since a small amount of precipitates is sufficient for the formation of nuclei for fine and high-density dispersion, 0.003% or more of each alone or in combination of both is sufficient for the expression of this function. On the other hand, if it is contained excessively, it will not be harmful because the excess will only coarsely precipitate, but if it exceeds 0.040%, it will precipitate at grain boundaries and impede the workability during hot rolling. . Therefore, the total content in the case of each alone or in the case of a combination of both is in the range of 0.003 to 0.040%.

Further, Sb, Sn, Bi, Te, Ge, P, Pb, Zn,
Since In, Cr, and the like have an auxiliary function of reinforcing the inhibitory power as inhibitors, they are preferably added to steel as needed. Their preferred contents are each in the range of 0.0010 to 0.30%. For other additive components, for example, N
Since i, Co, Mo, and the like have an effect of improving the surface properties of the steel sheet, they can be appropriately contained.

Next, the manufacturing method of the present invention will be described. The slab for a grain-oriented electrical steel sheet adjusted to the above component composition can be manufactured by any conventionally known method.

The slab is subjected to ordinary slab heating and then hot-rolled to form a hot-rolled sheet coil. At this time, it is important that the slab heating temperature be 1350 ° C. or higher. one of. This slab heating temperature is 13
When the temperature is lower than 50 ° C., the solid solution of the inhibitor is not sufficient, and a fine and uniform dispersed precipitation state of BN in the subsequent annealing step cannot be obtained. In the hot rolling, a known technique such as a thickness reduction process or a width reduction process for homogenizing the structure before and after the slab heating can be added as needed.

In this hot rolling, the following four requirements are indispensable. First, the cumulative rolling reduction in finish rolling is to be in the range of 85 to 99%. This is because if the cumulative rolling reduction is less than 85%, the interval of the band structure in the hot-rolled sheet becomes large and it becomes harmful to the secondary recrystallization, and if it exceeds 99%, recrystallized grains are present in the hot-rolled sheet. And the BN dispersed precipitation state in the cold rolling step becomes coarse.

Second, the finishing rolling temperature: T (° C.) is set to 95
Temperature range from 0 ° C to 1150 ° C and Si (%):
X and B (ppm): It is necessary to make the range satisfying the following formula (1) according to Y. 745 + 35X + 3Y≤T≤900 + 35X + 3Y --- (1) This is because if the finishing rolling temperature is lower than the above lower limit, BN will precipitate during rolling, and the BN fine uniformity in hot-rolled sheet annealing and intermediate annealing Precipitates cannot be obtained, and desired magnetic properties cannot be obtained. On the other hand, when the value exceeds the upper limit, rolling is performed in a high-temperature region, the density of defects in the steel is reduced, and high-density precipitation of ultra-fine sulfides and selenides which are nuclei of BN precipitation is suppressed, and BN fineness This is because uniform dispersion is hindered and magnetic properties deteriorate.

Third, it is necessary to rapidly cool at a cooling rate of 20 ° C./s or more after hot rolling is completed. That is, quenching suppresses the precipitation of BN from the supersaturated state, and increases the driving force for BN precipitation during the temperature rise process in hot-rolled sheet annealing or intermediate annealing.

Fourth, the coil winding temperature must be 670 ° C. or less. This is because if the winding temperature exceeds 670 ° C., BN is precipitated from the supersaturated state, and the inhibitory power of the inhibitor is deteriorated, so that desired magnetic properties cannot be obtained.

In the cold rolling step, a one-time cold rolling method after hot-rolled sheet annealing, a two-time cold rolling method with hot-rolled sheet annealing followed by an intermediate annealing, or an intermediate annealing without hot-rolled sheet annealing is sandwiched. 2
Any of the cold rolling methods can be adopted. In the first annealing (hot-rolled sheet annealing or intermediate annealing) in the cold rolling step, a fine precipitation treatment of BN, which is the essence of the present invention, is performed in the temperature raising step, and the subsequent annealing step and the second annealing (intermediate step) In annealing, it is extremely important to take care to prevent Ostwald ripening of the deposited BN and re-solid solution / precipitation.

In the first cold rolling method and the second cold rolling method in which the first annealing is performed in the cold rolling step, that is, the hot rolling sheet annealing, the hot rolling sheet annealing and the hot rolling sheet annealing are omitted. In the twice cold rolling method, BN
In order to finely precipitate
Is required to be in the range of 5 to 25 ° C./s. This is because if the heating rate is less than 5 ° C./s, the precipitates are coarsely deposited, and a strong inhibitory force as an inhibitor cannot be obtained. Conversely, if the temperature exceeds 25 ° C./s, the amount of the deposited precipitates is insufficient. This is also because it becomes impossible to obtain a strong inhibitory force as an inhibitor.

Further, it is necessary that the annealing be performed at a temperature of 900 to 1150 ° C. for a holding time of 150 seconds or less.
That is, if the annealing temperature is excessively low, the strength of the (110) grains serving as nuclei for secondary recrystallization in the recrystallized structure after rolling is insufficient, and a secondary recrystallized structure having a good orientation cannot be obtained. In order to obtain sufficient strength of the (110) grains, it is necessary that the crystal structure after annealing is coarsened to a certain size or more. For this purpose, annealing at a temperature of 900 ° C. or more is indispensable. Also, regarding the upper limit of the annealing temperature,
The most important point is not to grow Ostwald or re-dissolve the BN finely precipitated during the heating process.
For this purpose, set the annealing temperature to 1150 ° C or less and set the holding time
It must be less than 150 seconds. As described above, the present invention is characterized by lowering the annealing temperature. Thus, it becomes possible to increase the strength of the (110) grains in the structure of the primary recrystallized grains. Secondary recrystallization of a fine grain structure can be obtained.

Further, regarding the cooling process of the annealing,
Although not particularly required, quenching treatment to increase solid solution C in the steel after annealing, quenching treatment to precipitate fine carbide in the steel, and subsequent low-temperature holding treatment Doing so is effective because it improves the magnetic properties of the product. Here, the quenching process is a process of blowing a gas and / or a liquid as a cooling medium onto a steel sheet so as to have a cooling rate faster than natural cooling, for example, blowing N ₂ gas, or spraying mist water or jet water. This is the process of cooling the sprayed steel plate.

Further, a known means for increasing the oxidizing property of the annealing atmosphere and decarburizing the surface layer of the steel sheet also works effectively. The amount of decarburization in hot-rolled sheet annealing and intermediate annealing before this final cold rolling is
It is better to be in the range of 0.005 to 0.025%. Due to such decarburization treatment, the C content of the surface layer of the steel sheet is reduced, and the amount of γ transformation during annealing is reduced, so that the inhibitory force of the inhibitor on the surface layer of the sheet thickness at which nuclei for secondary recrystallization is generated is enhanced, Preferred secondary recrystallization can be obtained. To obtain this effect, the C content of the steel sheet is preferably reduced by 0.005% or more. However, if the content is reduced beyond 0.025%, the primary recrystallized structure is deteriorated, which is not preferable.

The second annealing (intermediate annealing) of the cold rolling twice after the hot-rolled sheet annealing is the same as the first annealing for maintaining the state of finely precipitated BN and adjusting the crystal structure. Annealing at a temperature in the range of 900 to 1150 ° C for 150 seconds or less.

Regarding the rolling reduction of the cold rolling, it is necessary that the rolling reduction of the final cold rolling be in the range of 80 to 95% as conventionally known. This is because when the rolling reduction exceeds 95%, secondary recrystallization becomes difficult, and when the rolling reduction is less than 80%, a good orientation of secondary recrystallized grains cannot be obtained, and the magnetic flux density of the product deteriorates.

The rolling reduction in the first rolling of the two-time cold rolling is in the range of 15 to 60%. If the rolling reduction is less than 15%, the mechanism of rolling recrystallization does not work and the crystal structure cannot be homogenized. Conversely, if it exceeds 60%, the crystal structure is integrated and the second rolling is performed. This is because the effect of (1) cannot be obtained.

Further, in the final cold rolling, it is possible to carry out warm rolling in a temperature range of 90 to 350 ° C. in a known manner, or to pass in a time range of 10 to 60 minutes at a temperature range of 100 to 300 ° C. Performing the intermediate aging treatment has the effect of improving the primary recrystallized texture and more preferable results are obtained, and therefore, it is significant to apply the present invention to the present invention.

After the final cold rolling, a linear groove may be provided on the surface of the steel sheet for magnetic domain refinement as is known.

The steel sheet having the final cold-rolled thickness obtained by the above method is subjected to primary recrystallization annealing by a known method,
An annealing separator containing O 2 as a main component is applied to the steel sheet surface and then subjected to final finish annealing.Adding a Ti compound or adding Ca or B to the annealing separator further improves the magnetic properties It is preferable because it has an effect.

In the final finish annealing, a small amount of
H from at least 900 ° C _TwoAtmosphere containing
It is necessary to raise the temperature inside. That is, N
_TwoAnnealing in the atmosphere, during the final annealing
Nitriding progresses, crystal grains with poor orientation recrystallize secondarily, and magnetic flux density increases
Deterioration of degree. Therefore, the final finish annealing atmosphere is
H at least over 900 ° C_TwoThrough
Is necessary. Also, H_TwoAtmosphere including
Means that Ti, Ca and
And plays an important role in the formation of oxides and nitrides such as B
For this purpose, from the middle stage of annealing at a temperature of 900 ℃ or more
It is important to enhance the reducibility especially in the latter period
it is conceivable that.

After the final annealing, after removing the unreacted annealing separating agent, an insulating coating is applied to the surface of the steel sheet to obtain a product. If necessary, the surface of the steel sheet may be mirror-finished before coating. In addition, a tension coating may be used as the insulating coating, and the coating baking process may also serve as a planarization process.

Further, in order to reduce iron loss, the steel sheet after the secondary recrystallization is subjected to a plasma jet or laser irradiation as a well-known magnetic domain refining treatment, or a linear dent is formed by a projection roll. Or other processing can be performed.

[0078]

【Example】

Example 1 C: 0.08%, Si: 3.32%, Mn: 0.07%, Al: 0.008%,
S: 0.003%, Sb: 0.02%, Se: 0.015%, B: 0.0035
% And N: 0.008%, the remainder being a slab having a composition consisting of Fe and unavoidable impurities, heated to a temperature of 1420 ° C. to obtain a sheet bar having a rolling end temperature of 1230 ° C. and a sheet thickness of 45 mm. After finishing the rolling at a rolling end temperature of 1020 ° C. and a thickness of 2.2 mm, the cooling water is sprayed at 25 ° C.
/ S and cooled at a temperature of 600 ° C. into a coil to obtain a hot-rolled coil.

This hot-rolled sheet was heated to a temperature of 1100 ° C. at 15.5 ° C./s.
The steel sheet was annealed at a temperature rising rate of 30 ° C. and kept for 30 seconds, followed by pickling and cold rolling to a sheet thickness of 1.5 mm. Next, the cold-rolled sheet coil was divided into two equal parts, and subjected to intermediate annealing in an H ₂ atmosphere at a dew point of 40 ° C. to reduce the C content to 0.06%.
At this time, one coil is set at 1080 ° C.
・ Annealing condition for 50 seconds, 1200 for the other coil as a comparative example
An annealing condition of 50 ° C. for 50 seconds was set. These intermediate annealed sheets were each finished to a final cold-rolled sheet thickness: 0.22 mm by warm rolling at a steel sheet temperature of 220 ° C.

Thereafter, these cold-rolled sheets were degreased, and
After decarburization and primary recrystallization annealing at 0 ° C for 2 minutes,
After applying an annealing separator containing 5% of TiO ₂ to MgO containing 5% of Ca and 0.09% of B, the final finishing annealing is performed at a temperature of 800 ° C. in an N ₂ atmosphere at a temperature of 30 ° C./h. At a heating rate of 800 ° C in a mixed atmosphere of N ₂ : 25% and H ₂ : 75%
The temperature was raised to a temperature of 1050 ° C at a temperature rising rate of 12.5 ° C / h, and then heated to a temperature of 1200 ° C in a H ₂ atmosphere at a temperature rising rate of 25 ° C / h and held at this temperature for 6 hours. After that, the temperature dropped.
At this time, up to a temperature of 600 ° C. in an H ₂ atmosphere,
Each treatment was performed to lower the temperature in _two atmospheres.

After the final annealing, the unreacted annealing separator is removed, and then magnesium phosphate containing 50% of colloidal silica is applied as a tension coating to form a coating.
After baking at a temperature of 0 ° C., a plasma jet was applied at a pitch of 6 mm as a magnetic domain refining treatment to obtain each product.

The measurement results of the magnetic properties examined for these products are as follows. Magnetic density B ₈ (T) Iron loss W _17/50 (W / kg) Applicable example 1.964 0.678 Comparative example 1.902 0.938

As is apparent from the above results, the intermediate examples are out of the limited range of the present invention and are higher than the comparative examples, and the conforming examples of the present invention show extremely excellent magnetic properties.

Example 2 Each slab having various component compositions shown in Table 4 was
After heating to a temperature of 1430 ° C., after rough rolling at a temperature of 1250 ° C. on a sheet bar having a thickness of 50 mm, the finish rolling end temperature was set to 1000 ° C. for symbols I to VII and X, and symbol VIII,
XI, XII, and XIV steels are rolled to 1020 ° C, and the other steels are rolled to a thickness of 2.6 mm at 1100 ° C, jetted with water, and cooled at a cooling rate of 35 to 55 ° C / s. It was wound into a coil at a temperature of 550 ° C. to obtain a hot-rolled coil.

[0085]

[Table 4]

These hot-rolled sheets were pickled, cold-rolled to a thickness of 1.8 mm, and then heated to 1080 ° C. at a rate of 15 ° C./s for 50 seconds in an H ₂ atmosphere at a dew point of 50 ° C. After the holding intermediate annealing, the final cold-rolled sheet thickness: 0.26 mm was completed by warm rolling at a steel sheet temperature of 230 ° C. These cold-rolled sheets were degreased, decarburized at 850 ° C. for 2 minutes and subjected to primary recrystallization annealing, and then 8% TiO ₂ and 2% Sr (OH) ₂ were added to MgO. after winding the annealing separator to the coated shaped coil, as a final finish annealing, to a temperature of 850 ° C. in a N ₂ atmosphere 30 ° C. /
h, and the temperature was maintained at this temperature for 25 hours. Then, the temperature was raised from 850 ° C. to 15% in a mixed atmosphere of N ₂ : 25% and H ₂ : 75%.
° C. / at a Atsushi Nobori rate was raised to a temperature of 1200 ° C. of h, the temperature was lowered after 5 hours maintained in an H ₂ atmosphere in this temperature.

After removing the unreacted annealing separator, a tension coating containing 60% colloidal silica was applied and baked to obtain a product. Table 5 summarizes the measurement results of the magnetic properties investigated for these products.

[0088]

[Table 5]

As is clear from Table 5, all of the applicable examples of the present invention show good magnetic properties as compared with the comparative examples in which the component compositions are out of the limited range of the present invention.

Example 3 C: 0.075%, Si: 3.05%, Mn: 0.07%, Al: 0.012
%, S: 0.015%, Sb: 0.02%, B: 0.0010% and N: 0.0075%, with the balance being a slab (a) composed of Fe and unavoidable impurities, C: 0.078%, Si: 3.37
%, Mn: 0.07%, Al: 0.010%, S: 0.016%, Sb: 0.
A slab (b) having a composition of 02%, B: 0.0038% and N: 0.0077%, with the balance being Fe and unavoidable impurities;
C: 0.068%, Si: 3.49%, Mn: 0.07%, Al: 0.011
%, S: 0.0016%, Sb: 0.02%, B: 0.0043%, and N: 0.0075%, with the balance being slab (c) composed of Fe and unavoidable impurities and C: 0.074%, Si: 3.
23%, Mn: 0.07%, Al: 0.009%, S: 0.004%, Sb:
Slab containing 0.02%, B: 0.0022% and N: 0.0075%, with the balance being Fe and unavoidable impurities (d)
Each of the two is heated to a temperature of 1390 ℃, the thickness of the plate: 35mm
Rough rolling on sheet bar, finish rolling temperature 965 ℃
And 1055 ° C, rolled to a thickness of 2.2 mm,
Jet water is sprayed to rapidly cool at a cooling rate of 50 ° C / s.
It was wound into a coil at a temperature of 0 ° C. to form a hot rolled sheet.

Each of these hot-rolled sheets was subjected to hot-rolled sheet annealing at a heating rate of 15 ° C./s to 1100 ° C. and holding for 30 seconds, followed by pickling to make the intermediate sheet thickness: 1.5 mm. After cold rolling, intermediate annealing was performed. In this intermediate annealing, after holding at a temperature of 1080 ° C. for 60 seconds, mist water is sprayed and 40 ° C./s
Quenching was performed at a cooling rate of 350 ° C., and a precipitation treatment of carbide was carried out at a temperature of 350 ° C. for 30 seconds.

Thereafter, each steel sheet was subjected to an inter-pass aging treatment in a temperature range of 150 to 230 ° C. for a period of 10 to 30 minutes by a Sendzimer rolling mill, and a final cold-rolled sheet thickness: 0.22 mm, respectively.
Rolled. After degreasing these cold rolled sheets,
As a magnetic domain refining process, grooves with a width of 50 μm and a depth of 20 μm are provided linearly at a pitch of 4 mm at an angle of 15 degrees from the width direction of the steel sheet, and then decarburization and primary recrystallization annealing at 850 ° C. for 2 minutes. Alms,
7.5% MgO containing 0.22% Ca and 0.08% B
After applying an annealing separator containing TiO ₂ and 3% SnO ₂ and winding it into a coil, the final finishing annealing is performed in a N ₂ atmosphere to a temperature of 850 ° C. at a rate of 30 ° C./h. After heating and maintaining at this temperature for 25 hours, the temperature was raised to a temperature of 1150 ° C. in a mixed atmosphere of N ₂ : 25, H ₂ : 75% at a heating rate of 15 ° C./h,
After maintaining at this temperature for 5 hours in an H ₂ atmosphere, a treatment for lowering the temperature was performed.

After removing the unreacted annealing separator, a tension coating containing 50% of colloidal silica was applied and baked to obtain respective products. Table 6 summarizes the measurement results of the magnetic properties investigated for these products.

[0094]

[Table 6]

As is clear from Table 6, all of the applicable examples of the present invention in which the hot finish rolling temperature (T) satisfies 745 + 35X + 3Y ≦ T ≦ 900 + 35X + 3Y show extremely low iron loss.

Example 4 Five slabs each having the component composition of the symbol VII in Table 4 above were each heated to a temperature of 1400 ° C., roughly rolled into a sheet bar having a thickness of 50 mm, and finished at a finish rolling temperature of 1030 ° C. , Board thickness: 2.7m
m, and then jet water to 40 ° C
Quenched at a rate of 600 ° C./s and wound into a coil at a temperature of 600 ° C. to form hot rolled sheets.

These hot-rolled sheets were heated at a rate of 17 ° C./s for 11 hours.
After hot-rolled sheet annealing, which is heated to a temperature of 00 ° C and held for 60 seconds, is pickled, cold-rolled to a final cold-rolled sheet thickness of 0.30 mm, degreased, and 850 ° C for 2 minutes. , And primary recrystallization annealing.

Thereafter, the final finish annealing was performed according to the application of the annealing separators A to E and the annealing atmosphere conditions shown in Table 2 above. Other conditions for the final finish annealing were as follows: the temperature was 400 ° C. in an N ₂ atmosphere, the temperature was raised to 1200 ° C. at a rate of 25 ° C./s, and the temperature was held at 1200 ° C. for 8 hours. Then the temperature dropped.

After the final annealing, the unreacted annealing separating agent is removed, aluminum phosphate containing 50% colloidal silica is applied and baked at a temperature of 800 ° C., and a plasma jet is applied as a magnetic domain refining treatment. Each product was irradiated linearly at a pitch of 7 mm. Table 7 summarizes the measurement results of the magnetic properties investigated for these products.

[0100]

[Table 7]

As is apparent from Table 7, all of the applicable examples of the present invention show extremely low iron loss.

[0102]

The present invention uses a material having a limited composition, specifies hot rolling conditions, hot-rolled sheet annealing conditions and intermediate annealing conditions, and finely precipitates BN precipitate nuclei by annealing before cold rolling. According to the present invention, it is possible to manufacture a high magnetic flux density oriented magnetic steel sheet having extremely low iron loss, which is advantageous in recent years for reducing iron loss of iron core materials. Can respond to.

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of the Si and B contents of a material and the hot rolling end temperature on the magnetic flux density B ₈ / B ₃ .

Claims (4)

[Claims] 1. C: 0.025-0.095 wt%, Si: 1.5-7.
A steel slab containing 0 wt%, Mn: 0.03 to 2.5 wt%, and one or two of S or Se: 0.003 to 0.040 wt% is heated as a raw material to a temperature of 1350 ° C. or more. After hot rolling, hot-rolled sheet annealing and then cold rolling once, or hot rolling and hot-rolled sheet annealing followed by double cold rolling with intermediate annealing, or after hot rolling After making the final cold-rolled sheet thickness by cold rolling of any of the two cold rolling methods sandwiching intermediate annealing, primary recrystallization annealing is performed,
Thereafter, in producing a grain-oriented electrical steel sheet by a series of steps of applying an annealing separator and then performing a final finish annealing, the composition of the material was determined to be B: 0.0008 as an inhibitor component.
~ 0.0085wt% and N: 0.0030 ~ 0.0100wt%, the finish rolling reduction rate of hot rolling is in the range of 85 ~ 99%, the finish rolling end temperature is in the range of 950 ~ 1150 ℃ and the material Si
Based on the relationship between the content and the B content, hot rolling is performed so as to satisfy the following formula (1), then rapidly cooled at a cooling rate of 20 ° C./s or more, and wound around a coil at a temperature of 670 ° C. or less. In both hot-rolled sheet annealing and intermediate annealing, the temperature is raised to a temperature of 800 ° C at a heating rate in the range of 5 to 25 ° C / s, and 900 to 1150 ° C.
Cold rolling should be performed under the condition that the holding time is not more than 150 seconds within the temperature range described above. 2. The first rolling is performed in a range of 15 to 60% by a cold rolling method twice, and then the second rolling after the intermediate annealing is performed in a rolling reduction: 80.
To a final cold-rolled sheet thickness, in the range of 95%, from the final finish annealing of heating the course of at least 900 ° C. or higher temperatures increasing the temperature in an atmosphere containing H _2, a sequential combination of A method for producing a high magnetic flux density grain-oriented electrical steel sheet having extremely low iron loss. [Note] 745 + 35X + 3Y≤T≤900 + 35X + 3Y ---- (1) T: Finish rolling end temperature (° C) X: Si (wt%) Y: B (wtppm) 2. The high magnetic flux with extremely low iron loss according to claim 1, wherein the cooling in the hot-rolled sheet annealing or intermediate annealing immediately before the final cold rolling is a quenching treatment for increasing the amount of solid solution C in the steel sheet. Method for producing density-oriented electrical steel sheet. 3. The high magnetic flux with extremely low iron loss according to claim 1 or 2, wherein decarburization of 0.005 to 0.025 wt% is performed by hot-rolled sheet annealing or intermediate annealing immediately before final cold rolling. Method for producing density-oriented electrical steel sheet. 4. The final cold rolling is performed at a temperature of 90 to 350 ° C. or at a temperature of 100 to 300 ° C.
4. The method for producing a high magnetic flux density grain-oriented electrical steel sheet having extremely low iron loss according to claim 1, wherein an inter-pass aging treatment is performed for a time range of 10 to 60 minutes.