JPH0668133B2 - Method for producing unidirectional silicon steel sheet with excellent magnetic properties - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a unidirectional silicon steel sheet having excellent magnetic properties, and is intended to advantageously improve the magnetic flux density even in the magnetic properties. .

(Prior art) The characteristics required of unidirectional silicon steel sheets mainly used as iron core materials for transformers and electric motors are that the magnetic flux density obtained at a constant magnetizing force is high and that a constant magnetic flux density is given. That is, the iron loss is low. Usually, magnetic flux density B ₈ (T: Tesla) and magnetic flux density 1.70 T at a magnetizing force of 800 A / m and iron loss W _17/50 (W / Kg) at a frequency of 50 Hz are adopted as _{typical values} .

In order to improve the magnetic characteristics including both of these characteristics,
Much research has been conducted to date, and in particular, significant improvements have been achieved in each of the components of the material, hot and cold rolling methods, heat treatment methods, and the like.

Conventional unidirectional silicon steel sheet is usually Si: 2.5-4.5wt%
Low carbon steels containing (hereinafter simply expressed as%) contain trace amounts of Mn, S, Se,
After hot-rolling a material to which an inhibitor-forming element such as Sb, Al, Sn, N and B is added, the cold-rolled steel sheet is decarburized through one or two or more cold rollings with intermediate annealing. The secondary recrystallized grains are highly integrated in the {110} <001> orientation by performing the primary recrystallization annealing that also serves as the secondary recrystallization treatment in the final finish annealing step, and by the subsequent annealing annealing. Good magnetic properties are obtained by removing impurities in the steel sheet.

At this time, as the orientation of secondary recrystallized grains accumulates in {110} <001>, the magnetic flux density of the steel sheet becomes higher, but on the other hand, it becomes easy to become huge secondary grains, the magnetic domain width in the grains increases, and the vortex flow increases. The iron loss characteristics tended to deteriorate due to the increase in loss. Therefore, various efforts have been made to reduce the size of the secondary grains. For example, in Japanese Patent Laid-Open No. Sho 60-89521, recrystallization promoting regions and ground zones are alternately provided to increase the nucleation of the secondary grains. 2 by stopping growth
A method has been proposed in which the secondary grain is made finer to improve the iron loss. However, in recent years, with the establishment of a magnetic domain subdivision technique (for example, Japanese Patent Laid-Open No. 58-26410) by introducing a physical local strain, it has become possible to obtain a low iron loss without particularly refining secondary grains. , The direction of technological development is tilted toward the improvement of magnetic flux density.

In this regard, Japanese Patent Publication No. 58-50295 discloses a method of obtaining a high magnetic flux density by applying a temperature gradient in one direction during secondary recrystallization and selectively growing secondary grains in the {110} <001> orientation. Has been done. This method utilizes a phenomenon peculiar to secondary recrystallization in which the secondary grain nucleation rate is high at a relatively high temperature, while the grain growth rate is high at a low temperature. By heating while giving a temperature gradient, huge grains are grown to improve the directionality of the entire steel sheet.

(Problems to be Solved by the Invention) However, since the above method has not been devised for the 2 o'clock grain that occurs first, the characteristics of the entire plate depend on the orientation of the secondary grain that initially occurs. That is, it was largely influenced by chance, that is, it was a problem that a high B ₁₀ value was not always obtained.

The present invention advantageously solves the above problem by first nucleating {110} <001>, that is, Goss-oriented grains with high probability, and then preferentially growing secondary grains of this orientation. Accordingly, it is an object of the present invention to propose an advantageous method capable of stably producing secondary grain orientations highly aligned with the Goss orientation and thus stably producing a high magnetic flux density unidirectional silicon steel sheet.

(Means for Solving Problems) From the above viewpoints, the inventors systematically proceeded with research on nucleation and grain growth.

As a result, if the inhibitory force due to the texture or the inhibitor in the plate surface of the steel sheet is changed and grain growth is performed while giving a temperature gradient from the region with stronger inhibitory force, {110} 〈0
01> It was found that secondary grains with excellent orientation are generated and grow. Further, it was also found that the temperature T _{SR at} which the secondary recrystallization starts is low in such a region where the suppression force is strong.

The present invention is based on the above findings.

That is, according to the present invention, a silicon steel-containing slab is hot-rolled and then cold-rolled once or twice or more with intermediate annealing to obtain a final plate thickness, followed by decarburization / primary recrystallization annealing. After applying the annealing separator on the steel plate surface,
In producing a unidirectional silicon steel sheet by a series of steps of performing secondary recrystallization annealing and then purifying annealing, in the annealing separating agent applying step, S is added to the annealing separating agent.
And Se and at least one selected from those compounds are contained, and a region where the S and / or Se concentration in the separating agent continuously changes is provided from one end to the other end of the steel sheet. The difference in the concentration between the beginning and the end is set to 0.01% or more, or a region where the concentration of S and / or Se in the separating agent is set to 0.01% or more is formed stepwise, or by one or both means. A gradient or means is given to the secondary recrystallization starting temperature across the width direction or the longitudinal direction, and then, under the temperature gradient larger than the gradient of the secondary recrystallization starting temperature, the steel sheet end portion having a low secondary recrystallization starting temperature Is a method for producing a unidirectional silicon steel sheet having excellent magnetic properties, which is characterized by performing a gradient annealing for starting secondary recrystallization.

The present invention will be specifically described below.

First, regarding the starting material of the present invention, the components of conventionally known unidirectional silicon steel sheets, for example, C: 0.005 to 0.15%, S
i: 0.1 to 7.0% and Mn: 0.002 to 0.15%,
S: 0.005-0.05% as an inhibitor-forming component, Se:
0.005-0.05%, Te: 0.003-0.03%, Sb: 0.005-0.05
%, Sn: 0.03 to 0.5%, Cu: 0.02 to 0.3%, Mo: 0.005 to
0.05%, B: 0.0003 to 0.0040%, N: 0.001 to 0.01%, A
Any material containing at least one selected from l: 0.005 to 0.05% and Nb: 0.001 to 0.05% is advantageously suitable.

These materials are conventionally known steel-making methods, for example, steelmaking in a converter, an electric furnace, and further slab, sheet bar or directly thin steel sheet by an ingot-segmentation method, continuous casting method, roll quenching method, or the like, If necessary, it is made into a silicon steel sheet by hot rolling, warm rolling or cold rolling. Then, if necessary, homogenizing annealing is performed, and further, one or more rollings with intermediate annealing are performed to finish the final sheet thickness. The homogenizing annealing and the intermediate annealing are intended for the recrystallization treatment for homogenizing the crystal structure after rolling, and are usually carried out at 800 to 1200 ° C. for 30 seconds to 10 minutes. The finish thickness is 0.50mm or less, but 2
The present invention is particularly effective at a thin finish thickness of 0.23 mm or less at which secondary recrystallization becomes unstable.

Next, it is annealed in wet hydrogen at 700 to 900 ° C. for 1 to 15 minutes to remove C in the steel, and at the time of the next annealing, a primary recrystallization grain having a Goss orientation is achieved. Recrystallized texture is formed. If the starting material is an extremely low C material, decarburization annealing is unnecessary.

Then, an annealing separator is applied. At this time, at least one selected from S and Se and their compounds is contained in the annealing separator, and when this annealing separator is applied, from one end of the steel sheet. A region where the concentration of S and / or Se in the separating agent changes continuously is provided to the other end, and the concentration difference between the beginning and the end of the region is set to 0.01% or more, or the concentration difference in the separating agent is gradually increased. S and / or
By forming a region where the Se concentration is 0.01% or more,
In other words, S in the separating agent is continuously and / or stepwise.
And / or a region where the concentration of Se differs by 0.01 or more (in the case of continuous, it means that the concentration difference between the beginning and the end of the region is 0.01% or more. The same applies hereinafter) is formed in the width direction or the longitudinal direction of the steel sheet. Therefore, it is important to give a gradient or step to the secondary recrystallization starting temperature.

Highly accumulated here due to subsequent tilt annealing {110}
To obtain the <001> texture, the secondary recrystallization start temperature T
The T _SR at the steel plate edge where the _SR is low needs to be lower than the other regions by 10 ° C. or more, and therefore the concentration of S and / or Se at the steel plate edge is 0.01% lower than that at the other regions.
It is necessary to make it darker.

In order to adjust the Se concentration of S, an annealing separator containing MgO as a main component is applied, and before drying, at least one selected from S and Se and their compounds is applied in the width direction or the longitudinal direction. It can be easily achieved by a method such as continuous and / or stepwise spraying according to the desired concentration.

Then, a secondary recrystallization annealing is performed. This secondary recrystallization annealing is performed from the edge of the steel sheet having a low T _SR under a temperature gradient larger than the gradient of T _SR given as described above. Slanted annealing is started. The temperature gradient in such gradient annealing is preferably 2 ° C. or more per unit length of 1 cm.

Then, in dry hydrogen atmosphere, 1100-1250 ℃, 5-25h
Degree of annealing is applied.

Note that the finish annealing as described above is industrially carried out as a type that processes a coiled steel strip, but it is a continuous type in which one or more steel plates (including cut plates) are continuously annealed. Have been proposed, and either type can be used in the present invention.

Further, in providing the temperature gradient, it is possible to easily achieve it by providing a zone having a temperature gradient in the furnace, and the direction of applying the temperature gradient can be the width direction of the steel sheet, the length direction or any other direction. May be

Although it is possible to effectively improve the magnetic properties by performing such a series of treatments, in the present invention, the magnetic properties can be more improved by forming a tension-imparting ultra-thin film on the surface of the steel sheet after purification annealing. Further improvement can be achieved.

In order to form such an ultra-thin film, first, after removing the non-metallic substances on the steel sheet surface after the annealing annealing, the smoothness of the steel sheet surface is subjected to scientific polishing or electrolytic polishing with a center line average roughness Ra of 0.
4 μm or less. The reason is that if the roughness is higher than this, the effect of improving the iron loss cannot be expected even by the subsequent application of the ultrathin coating.

Then, Ti, Nb, S are deposited by a vapor deposition method such as CVD method or PVD method (ion plating or ion implantation).
i, V, Cr, Al, Mn, B, Ni, Co, Mo, Zr, Ta, Hf, W nitride and /
Alternatively, the surface of the steel sheet is strongly coated with an ultrathin coating mainly composed of at least one selected from carbides, oxides of Al, Si, Mn, Mg, Zn and Ti.

In addition to the above listed materials,
Any material having a low coefficient of thermal expansion and firmly adhering to the steel sheet may be used.

Further, if necessary, a tension-imparting low thermal expansion top coat insulating film is preferably formed according to a conventional method, and a magnetic domain subdivision technique such as laser irradiation, plasma jet irradiation, electric discharge machining, scribing method and ballpoint pen processing method is applied.

(Operation) When heating the steel sheet while applying large temperature gradient than the slope of the T _SR from low T _SR regions, first end portion of the steel sheet increases to T _SR a temperature above the orientation with good grain small amount nucleation Then 2
Next, a recrystallized region is formed. Between such a secondary recrystallization region and not yet reached the T _SR region, a region where the primary recrystallized structure and a secondary recrystallized structure are mixed in a narrow range results. Then, as the temperature of the steel sheet rises, such a region will continue to move to pyrometry, and along with that, the secondary recrystallization region will expand and grain growth will occur.

As described above, since Goss-oriented grains are likely to be generated from the region where the S and Se concentrations are high and the suppressing force is strong, if the heat is raised under the temperature gradient as described above, it will be compared to the case of normal uniform heat raising. Then, the Goss-oriented grains can be generated more reliably, and the first crystal-oriented grains are smoothly transferred to the high temperature side, which is also advantageous in obtaining large secondary grains.

Through this growth, the temperature in the boundary region between the primary recrystallization and the secondary recrystallization is kept relatively constant.

According to the experiments conducted by the inventors, the improvement of B ₁₀ is _{achieved when} the temperature difference between T _SR at the initial nucleation site of the secondary recrystallized grain and the delayed portion is 10 ° C or more and the temperature gradient is 2 ° C / cm or more. It was found that a remarkable effect was seen.

When the secondary recrystallization is advanced while applying a temperature gradient,
The temperature at which secondary recrystallization occurs is not constant depending on the type of steel sheet and the heating conditions, and its temperature range cannot be limited. For example, in the case of grain-oriented silicon steel sheets with MnSe and Sb as inhibitors, 850-950 In the present invention, a temperature gradient may be provided in this boundary region. Before and after that, the treatment conditions conventionally employed may be adopted, and of course, the temperature gradient may be provided. .

Thus, it has become possible to stably obtain a unidirectional silicon steel sheet having excellent magnetic properties, particularly magnetic flux density.

(Example) Example 1 C: 0.045%, Si: 3.30%, Mn: 0.080%, S: 0.003
%, Se: 0.025% and Sb: 0.025%, and the balance of the composition is essentially Fe.
After annealing at 2 ° C. for 2 minutes, it was pickled and cold rolled to a thickness of 0.75 mm, followed by intermediate annealing at 950 ° C. for 2 minutes to give a final sheet thickness of 0.30 mm. Then, after degreasing, 835 in wet hydrogen
After decarburization annealing at 4 ℃ for 4 minutes, apply an annealing separator containing MgO as the main component, dry it, and then perform secondary recrystallization in a Box-type finishing annealing furnace at 840 ℃ in a H ₂ atmosphere for 30 hours. Annealing,
Then, annealing was performed at 1200 ° C. for 10 hours.

In the annealing separating agent applying step described above, immediately after the annealing separating agent containing MgO as a main component is applied, S in the separating agent is immediately applied.
Magnesium sulfate was sprayed so that the concentration was 0% at one end in the plate width direction and 5.0% at the other end so that the concentration continuously changed in the plate width direction. After drying, it was held for 20 hours and the secondary recrystallization start temperature T _SR in the coil width direction was examined. One end was 895 ° C, the center was 875 ° C, and the other end was 860 ° C. A Box-type finishing annealing furnace, in which the temperature gradient from one end to the other end of the steel plate was adjusted to 3 ° C per cm, 800
The temperature is gradually heated up to 900 ℃ at 3 ℃ / h, then 1200 ℃, 10
A final finish anneal of time was applied.

The results of examining the magnetic property B ₁₀ value of the product plate thus obtained are shown below.

For comparison, the results of the survey on the product sheet manufactured by the usual process without spraying magnesium sulfate are also shown.

B ₁₀ (T) Example 1.956 Comparative Example 1.908 Example 2 C: 0.054%, Si: 3.28%, Mn: 0.087%, S: 0.028
%, Sol Al: 0.033% and N: 0.0080%, a 2.4 mm thick hot-rolled sheet having a composition of 1000 ° C. for 2 minutes was annealed.
After pickling, finishing cold rolling to 0.27 mm thickness, degreasing,
Then, after decarburization annealing in wet hydrogen, an annealing separating agent containing MgO as a main component is applied, followed by drying and heating to 1200 ° C in a H ₂ atmosphere at a heating rate of 20 ° C / h, and then 10 A time-holding finish annealing was performed.

After applying the annealing separating agent containing MgO as a main component in the above-mentioned annealing separating agent applying step, immediately after the S separating agent in the separating agent is applied.
The density is 0% when the width of the board is 1000 mm and the width of the edge is 100 mm. The remaining 1/2 of the width of 900 mm is 1.50% and the remaining edge is 450 mm.
Strontium sulfate was sprayed so as to change stepwise at 3.5% and then dried.

In order to examine T _{SR in the} coil width direction, a 20-hour retention annealing was performed.
90 ° C, the central part with 1.50% S content was 1040 ° C and the other end with 3.5% S content was 1005 ° C, so the S content in the separating agent was 3.5%.
With the end of the as the lower part, with a hearth heater installed type, a Box-type finishing annealing furnace having a temperature gradient of 5 ° C. per 1 cm, heats up to 1200 ° C. in a H ₂ atmosphere at a heating rate of 20 ° C./h, Then, finish annealing was performed for 10 hours.

The results of examining the magnetic property B ₁₀ value of the product plate thus obtained are shown below. For comparison, the results of investigations on product plates obtained according to the usual method are also shown.

B ₁₀ (T) Example 1.988 Comparative Example 1.933 Example 3 C: 0.046%, Si: 3.43%, Mn: 0.082%, S: 0.018
%, Se: 0.026%, Sb: 0.018% and Sn: 0.035%, a 2.0 mm thick hot-rolled sheet was annealed at 935 ° C. for 2 minutes, pickled, and cold-rolled to 0.60 mm in thickness. After that, 950 ℃, 2
After the intermediate annealing for a minute, the product was finished and cold rolled to a final plate thickness of 0.23 mm. Next, after degreasing, decarburization annealing in wet hydrogen, applying an annealing separator containing MgO as the main component, and drying, then in an H ₂ atmosphere.
The temperature is raised from 800 to 900 ℃ at a rate of 5 ℃ / h, then to 1200 ℃.
Finish annealing was performed for 10 hours.

Immediately after applying the annealing separating agent containing MgO as the main component in the above-mentioned annealing separating agent applying step, iron sulfide and selenium anhydride were immediately added, and S + Se amount was 0% at the end in the plate width direction, and 1 / in the plate width direction.
The concentration is continuously increased and sprayed over 3 parts, and the amount of S + Se in 1/3 part is 1%, and S over the plate width direction 1/3 to 2/3.
+ Se was set to 1%, the concentration was continuously increased from the remaining plate width 2/3 to the other end to make the amount of S + Se at the other end 3.5%, and then immediately dried. When the secondary recrystallization starting temperature after holding for 20 hours was investigated, the edge of S + Se in the separating agent was 0%, 900 ° C, the center was 878 ° C, and the amount of S + Se was 3.5%.
Since the other end of the steel plate was 865 ° C, the temperature gradient from the one end to the other end of the steel plate was 3.5 ° C per cm in the finishing annealing furnace. It was heated at a temperature rate and then subjected to finish annealing in dry hydrogen at 1200 ° C for 10 hours.

The results of examining the magnetic properties B ₁₀ of the product plate thus obtained are shown below in comparison with those obtained by the conventional method.

B ₁₀ (T) Example 1.968 Comparative Example 1.913 Example 4 C: 0.054%, Si: 3.28%, Mn: 0.087%, S: 0.028
%, Sn: 0.038%, solAl: 0.033% and N: 0.0080%
The hot-rolled sheet with a thickness of 2.0 mm containing 10
After annealing in minutes, pickling, then cold rolling to a thickness of 0.19 mm, degreasing, decarburization in wet hydrogen, primary recrystallization annealing, and then applying an annealing separator containing MgO as a main component, 30 ° C / up to 950 ° C
h, after heating from 950 ℃ to 1100 ℃ at a heating rate of 5 ℃ / h,
Annealing annealing was performed at 1200 ° C for 10 hours in a hydrogen atmosphere.

In the above-mentioned annealing separating agent applying step, after applying the separating agent containing MgO as a main component, immediately selenium is applied at 2.0% in the plate width direction end portion, and the Se amount at 1/3 in the plate width direction is 1.0%. The concentration is continuously reduced so that 1/3 to 2/3 is 1.
0%, from the remaining 2/3 to the other plate width edge
The concentration was continuously reduced and sprayed so that the Se amount became 0%. Furthermore, magnesium sulfate has an S content of 2.0 in the longitudinal direction.
% To 0% at the length of the plate width, the concentration was continuously sprayed so as to decrease, and immediately dried.

When the secondary recrystallization start temperature was examined after holding for 20 hours, it was 98 when the total S + S amount in the width direction and the longitudinal direction was 4%.
7 ° C, 3% place is 1004 ° C, 2% place is 1023 ° C,
Since it was 1046 ° C at 1% and 1073 ° C at 0%, a finishing annealing furnace with a temperature gradient of 3 ° C from the edge of the steel plate to the other edge was operated at 950 ° C to 1100 ° C. ℃ /
The temperature is raised at a heating rate of h and then in a hydrogen atmosphere at 1200 ° C for 1
Finish annealing was performed for 0 h.

Magnetic properties B of the thus obtained unidirectional silicon steel sheet B
_The results of examining ₈ (T) are shown below.

For comparison, the results of investigations on product plates manufactured by a normal process in which Se and S are not dispersed are also shown.

B ₈ (T) Example 1.992 Comparative Example 1.933 Example 5 C: 0.040%, Si: 3.35%, Mn: 0.070%, Se: 0.020%
And 2.2 mm thick hot rolled sheet with a composition containing Sb: 0.025% are annealed at 950 ° C. for 2 minutes, pickled, intermediate cold rolled to a thickness of 0.60 mm, and annealed at 970 ° C. for 1.5 minutes. After cold rolling to 0.22 mm thickness, degreasing, decarburization in wet hydrogen, primary recrystallization annealing, then applying an annealing separator containing MgO as the main component and drying, and then between 820 and 925 ℃ After heating at a temperature rising rate of 2.5 ° C / h, annealing was performed at 1200 ° C for 10 hours in a hydrogen atmosphere. Then remove the oxide film by pickling and add 3% HF
After chemical polishing in H ₂ O ₂ solution to give a mirror finish,
A TiCl ₄ (70%) gas atmosphere was used for CVD to form a 0.8 μm thick TiN film on the surface of the steel sheet.

Immediately after applying the separating agent containing MgO as the main component in the above-mentioned annealing separating agent applying step, iron sulfide was immediately applied to the edge portion 1/4 in the width direction of 0
% In the width direction 2/4 to 0.75% and in the width direction 3/4 1.5%
Then, the remaining other end was sprayed stepwise so as to be 2.25% and then immediately dried.

When the secondary recrystallization start temperature after 20 hours retention was examined, the end 1/4 with S content of 0% in the separating agent was 903 ° C, 2/4 part was 888 ° C, 3 /
Since 4 parts were 873 ° C and the remaining other end was 858 ° C, it was a Box-type finishing annealing furnace adjusted to have a temperature gradient of 2.5 ° C per cm from the steel plate end to the other end, between 820 and 925 ° C. To
The temperature was raised at a heating rate of 2.5 ° C / h, and then annealing was performed at 1200 ° C for 10 hours in a hydrogen atmosphere.

Magnetic properties B of the thus obtained unidirectional silicon steel sheet B
_The results of examining ₈ (T) and w _10/50 (W / Kg) were as follows.

For comparison, the results of an investigation of a product plate manufactured by a normal process in which iron sulfide is not sprayed are also shown.

B ₈ (T) w _10/50 (W / Kg) Example 1.988 0.60 Comparative Example 1.902 0.89 Example 6 C: 0.054%, Si: 3.28%, Mn: 0.028%, solAl: 0.033
% And N: 0.0080%, a 2.4 mm thick hot-rolled sheet is annealed at 1000 ° C. for 2 minutes, pickled, and then 0.29
After cold rolling to mm thickness, degreasing, de-edgeing in wet hydrogen, primary recrystallization annealing, and then applying an annealing separator containing MgO as the main component, 27 ℃ / h up to 945 ℃, 945 ℃ After heating up to 1100 ° C. at a temperature rising rate of 5 ° C./h, annealing annealing was performed at 1200 ° C. for 10 hours in a hydrogen atmosphere, and after insulating coating, local strain was introduced by laser irradiation.

After applying the separating agent containing MgO as the main component in the above-mentioned annealing separating agent applying step, magnesium sulfate and strontium sulfate were immediately added to the coil so that the S content at one end was 0% and the other end was 4.5%. Sprayed to increase the concentration. Immediately after that, it was dried, and the temperature at which secondary recrystallization started after 20 hours of retention was examined.
Since the temperature was ℃ and the other end was 975 ℃, it was a Box-type finishing annealing furnace adjusted to have a temperature gradient of 4 ℃ from one end to the other end of the steel plate. The temperature was gradually increased at a heating rate of 1, and then annealing was performed at 1200 ° C. for 10 hours in a hydrogen atmosphere.

Magnetic properties B of the thus obtained unidirectional silicon steel sheet B
_The results of examining ₈ (T) and w _10/50 (W / Kg) were as follows.

In addition, for comparison, the results of an examination of a product plate manufactured by a normal process in which magnesium sulfide and strontium sulfate are not sprayed are also shown.

B ₈ (T) w _10/50 (W / Kg) Example 2.034 0.76 Comparative Example 1.941 0.99 (Effect of the Invention) Thus, according to the present invention, the secondary recrystallization annealing is performed in the production of the grain-oriented silicon steel sheet. When the annealing separator is applied in advance, at least one selected from S and Se and their compounds is added to the concentration of S and Se of 0.01 or more continuously and / or stepwise from one end of the steel sheet to the other. %, The primary recrystallization start temperature T
_When a gradient of 10 ° C or more is applied to _SR and the secondary recrystallization proceeds, the temperature gradient applied to the steel sheet from one end of the steel sheet is preferably 2 ° C / cm under a temperature gradient larger than T _SR.
By performing the gradient annealing as described above, it is possible to stably obtain a unidirectional silicon steel sheet having a remarkably high B ₁₀ value.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsumasa Kurosawa 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division (72) Yoshinori Kobayashi 1 Kawasaki-cho, Chiba-shi Kawasaki Steel Co., Ltd. Research headquarters

Claims (2)

[Claims] 1. A slab containing silicon steel is hot-rolled, and then cold-rolled once or twice or more with intermediate annealing to obtain a final plate thickness, followed by decarburization / primary recrystallization annealing. In order to manufacture a unidirectional silicon steel sheet by a series of steps in which the annealing separation agent is applied to the surface of the steel sheet, and then secondary recrystallization annealing and then purification annealing are performed, , S in the annealing separator
And Se and at least one selected from those compounds are contained, and a region where the S and / or Se concentration in the separating agent continuously changes is provided from one end to the other end of the steel sheet. The difference in concentration between the beginning and the end is set to 0.01% or more, or a region where the S and / or Se concentration in the separating agent is set to 0.01% or more is formed stepwise, either one or both means, A gradient or step is given to the secondary recrystallization start temperature across the width direction or the longitudinal direction, and then, under the temperature gradient larger than the gradient of the secondary recrystallization start temperature, the steel plate end portion having a low secondary recrystallization start temperature A method for producing a unidirectional silicon steel sheet having excellent magnetic properties, which comprises performing a gradient anneal for initiating secondary recrystallization. 2. The temperature gradient in the gradient annealing has a unit length of 1
The method according to claim 1, wherein the temperature is 2 ° C or more per cm.