JP3336142B2 - Manufacturing method of grain-oriented silicon steel sheet with excellent magnetic properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented silicon steel sheet having excellent magnetic properties, and more particularly to an advantageous improvement in magnetic flux density.

[0002]

BACKGROUND ART oriented silicon steel sheet, intended to be used as a core, such as transformers and generators, the magnetic properties, represented by the value B ₈ in the magnetic field strength of the magnetic flux density (800 A / m Is high and the core loss (indicated by the 50 Hz alternating iron loss value W _17/50 at a maximum magnetic flux density of _{1.7 T} ) is required. Efforts to reduce iron loss in this type of material have been vigorously pursued, including (1) reducing the thickness of the steel sheet, (2) increasing the Si content, and (3) reducing the grain size of the final product. As a result of improvements such as reduction, materials with an iron loss of 0.90 W / kg at W _17/50 can be obtained. However, it is not easy to reduce iron loss more than the current situation. The reason is that if the thickness of the steel sheet is made thinner than the current state, secondary recrystallization failure described later is caused and iron loss deteriorates conversely, and if the Si content is increased, cold rolling becomes difficult, and the crystal grain size is further increased. This is because, if the average particle diameter is reduced to 4 to 8 mm or more, the secondary recrystallization also becomes defective, resulting in deterioration of iron loss.

However, in recent years, a so-called magnetic domain segmentation technique for locally introducing strain or forming a groove on the surface of a steel sheet has been developed, thereby making it possible to greatly reduce iron loss. In other words, in the case of the iron loss material of 0.90 W / kg at W17 / ₅₀ described above, the iron loss can be reduced to 0.80 W / kg by introducing an appropriate local strain to the steel sheet surface with a plasma jet or the like. It became. In order to obtain an excellent iron loss material by such a method, unlike the conventional case, it is not necessary to reduce the crystal grain size of the final product, and it depends exclusively on the plate thickness, the Si content and the magnetic flux density. At present, increasing the Si content further is limited by the workability, so improving iron loss depends on solving the technical problem of how to improve the magnetic flux density of thin materials. ing.

[0004] In order to improve the magnetic flux density of a grain-oriented silicon steel sheet, it is necessary to highly integrate the crystal grain orientation of the product in a (110) [001] orientation, a so-called Goss orientation.
Goss-oriented crystal grains of a grain-oriented silicon steel sheet are obtained by a secondary recrystallization phenomenon in final finish annealing. In this secondary recrystallization, it is necessary to grow only crystal grains close to the (110) [001] direction to suppress the growth of crystal grains in other directions, that is, to perform so-called selective growth. It is necessary to add an inhibitor (inhibitor) for suppressing the growth of crystal grains in the orientation. This inhibitor forms a precipitated dispersed phase in the steel, and functions as an inhibitory action on grain growth.

As the inhibitor, the stronger the inhibitory action, the stronger the selective growth effect and the material having a high magnetic flux density can be obtained. Therefore, many studies have been made on this point. The result was AlN. That is, as disclosed in Japanese Patent Publication No. 46-23820, in an Al-containing steel sheet, the annealing before final cold rolling is performed as a quenching treatment, and the rolling reduction of the final cold rolling is 80 to 95.
%, As shown in Example 5, with a plate thickness of 0.35 mm, B ₁₀ : 1.981T (B ₈
In this case, a material having a high magnetic flux density of about 1.95 T) is obtained. However, when the thickness of the steel sheet is reduced,
The above technique has a problem that a high magnetic flux density cannot be obtained. That is, it becomes the core of the secondary recrystallized grains (110).
[001] The grains of the orientation are not present uniformly in the thickness direction but near the surface layer of the thickness. However, when the thickness is reduced, the influence of the atmosphere at the time of final finish annealing is reduced. Therefore, secondary recrystallization becomes unstable, and stabilization of magnetic properties has been an urgent issue.

[0006] In order to solve these problems associated with the reduction in sheet thickness, Japanese Patent Publication No. Sho 62-56925 discloses that in the cold rolling of steel containing Al twice, cooling during intermediate annealing is allowed to cool to room temperature by air. A technique comprising cooling at a faster rate, further performing pickling sufficiently until the scale of the steel sheet is completely removed, and performing at least one pass aging between the passes in the final cold rolling. ing. However, even with this technique, the stabilization of magnetic properties is not sufficiently satisfactory, and stable production of thin grain silicon steel sheets could not be expected at all.

[0007]

SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned circumstances, and advantageously solves the deterioration of magnetic properties accompanying the production of thin-oriented silicon steel sheets in industrial production, and achieves stable production. It is an object of the present invention to propose a new method for manufacturing a grain-oriented silicon steel sheet that can obtain a material having a high magnetic flux density.

[0008]

Means for Solving the Problems Now, the inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, while carrying out weak decarburization in the intermediate annealing, the temperature of the steel sheet at the time of starting pickling. Further, it has been found that the intended purpose can be advantageously achieved by specifying the temperature and the immersion time of the aqueous acid solution. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. C: 0.050 to 0.100 wt%, Si: 2.0 to 5.5 wt%, A
l: A slab for grain-oriented silicon steel containing 0.005 to 0.040 wt% is subjected to hot rolling, then cold rolling once or twice with intermediate annealing, then decarburizing annealing and final finishing annealing In producing a grain-oriented silicon steel sheet by a series of processes, C is 0.005 to 0.015 at the time of annealing before final cold rolling.
wt% decarburized and at least 900 when cooled
Average cooling rate from ℃ to pickling start temperature: more than 10 ℃ / s
After cooling at a high speed, pickling is started when the temperature of the steel sheet is 70-170 ° C, and a short-time pickling treatment is performed for 3-60 seconds in an aqueous acid solution at 60 ° C or higher. Manufacturing method of excellent oriented silicon steel sheet.

[0010] 2. C: 0.050 to 0.100 wt%, Si: 2.0 to
5.5 wt%, Al: 0.005 to 0.040 wt%
After hot rolling the slab for silicon steel, perform one or intermediate annealing.
Cold rolling twice, then decarburizing annealing and final
Through a series of finish annealing processes,
In manufacturing , C was set to 0.0 at the time of annealing before final cold rolling.
05 to 0.015 wt%
At least 10 ° C from 900 ° C to the cooling stop point between 200 and 400 ° C
/ S or more, and cool for 15 to 300 seconds.
Hold or keep the temperature below 1.0 ℃ / s from the cooling stop point.
After cooling at a speed, pickling is performed when the steel plate temperature is 70 to 170 ° C.
Start in a short time for 3 to 60 seconds in an aqueous acid solution at 60 ° C or higher.
Excellent magnetic properties characterized by performing pickling treatment
A method for manufacturing oriented silicon steel sheets.

3. In the above item 1 or 2, hot rolling
After, before cold rolling, it is characterized by performing hot rolled sheet annealing
A method for producing grain-oriented silicon steel sheets with excellent magnetic properties.

Hereinafter, the present invention will be described specifically. First, a description will be given of experimental results on which the present invention is based. The materials used in the experiment contained C, Si and Al as essential components. Here, C is an element useful for improving the structure in hot rolling and cold rolling, and Si is an element useful for increasing electric resistance and improving iron loss.
Al improves the secondary recrystallized grain orientation as an inhibitor component,
That is, it is an element useful for improving the magnetic flux density.

Experiment 1 C: 0.065 wt%, Si: 3.35 wt%, Mn: 0.075 wt%, Al:
After the hot rolling, a directional silicon steel slab containing 0.025 wt%, Se: 0.018 wt% and Sb: 0.025 wt% is subjected to hot-rolled sheet annealing at 1000 ° C. for 1 minute, and then the first time. The sheet was cold-rolled to a thickness of 1.40 mm, annealed at 1100 ° C. for 60 seconds as intermediate annealing, and then cooled to room temperature at a cooling rate of 40 ° C./s using mist water. At this time, an ammonia decomposition gas of N ₂ : 25% and H ₂ : 75% was used as an atmosphere gas for the intermediate annealing, and the atmosphere at the time of temperature rise was changed to a dew point (dp) of 10 ° C., 25 ° C.
The surface layer of the steel sheet was decarburized in a wet hydrogen-nitrogen atmosphere at 35 ° C, 45 ° C, 50 ° C and 70 ° C. The amounts of decarburization by this intermediate annealing were 0.002% (dp: 10 ° C) and 0.004% (dp:
25 ° C), 0.006% (dp: 35 ° C), 0.010% (dp: 45 ° C)
, 0.015% (dp: 50 ° C) and 0.021% (dp: 70 ° C). The steel sheet after the intermediate annealing was pickled with a 15% HCl aqueous solution, and then subjected to a second cold rolling to a final thickness of 0.20 mm. After that, a groove having a width of 0.1 mm, a depth of 20 μm in a direction of 80 ° from the rolling direction, a depth of 20 μm, and a spacing of 5 mm was formed, and a Si compound was electrodeposited on the surface of the steel plate by electrolytic degreasing.
Decarburization annealing was performed at 0 ° C. for 2 minutes. Next, 5 wt% of TiO ₂
%, Sr (OH) ₂ .8H ₂ O, 2 wt%, and an annealing separator containing MgO as a main component was applied, and then a final finish annealing was performed at 1200 ° C.

FIG. 1 shows the results of an investigation on the relationship between the magnetic properties of the steel sheet thus obtained and the amount of decarburization in the intermediate annealing. As shown in the figure, 0.005 to 0.015 during intermediate annealing
When decarburized by about wt%, excellent magnetic properties were obtained.
When the texture after decarburization annealing was examined, the (110) [001] strength was increased in the steel sheet having good magnetism, and improvement of the texture was recognized.

Experiment 2 Next, the pickling conditions performed after the intermediate annealing were investigated. Usually, pickling is performed after cooling to room temperature, but in this experiment, the steel sheet during cooling was pickled and its effect on magnetism was examined. Nine steel sheets were prepared from the same material as in Experiment 1 and subjected to the first cold rolling to a thickness of 1.40 mm, and an intermediate annealing was performed at 1100 ° C. for 60 seconds in a hydrogen-nitrogen atmosphere. And mist water at an average cooling rate of 40 ° C./s. At this time, as atmosphere gas, N ₂ : 25%, H ₂ : 75
% Ammonia decomposed gas to reduce the atmospheric dew point
At 45 ° C, weak decarburization of 0.011 wt% was performed. During subsequent cooling, for each steel plate, the plate temperature was 300 ℃, 250 ℃,
After cooling to 200 ° C., 170 ° C., 140 ° C., 100 ° C., 70 ° C., 50 ° C. and room temperature, the surface was removed by immersion in a 15% HCl aqueous solution at 80 ° C. for 20 seconds, followed by washing with water. Thereafter, cold rolling, decarburizing annealing, application of an annealing separator, and final finish annealing were performed under the same conditions as in Experiment 1.

FIG. 2 shows the results of a study on the relationship between the magnetic properties of the steel sheet thus obtained and the temperature of the steel sheet at the start of pickling after intermediate annealing. As shown in the figure, a remarkable improvement in magnetic properties was observed when the temperature of the pickling-starting steel sheet was between 70 and 170 ° C.

Although the reason why the magnetic properties are improved by the above-mentioned treatment has not been clearly elucidated yet, in the case of pickling from a high temperature, the texture after cold rolling and decarburizing annealing in the next step. Is remarkably observed, and this effect is characteristically observed only in a steel sheet in which a predetermined amount of C is weakly decarburized. This is probably due to the promotion of precipitation of C which forms a solid solution in the steel. It is presumed that.

Experiment 3 Since the above effects are expected to be affected by the bath temperature and the residence time in the pickling bath, a third experiment was performed using the bath temperature of the pickling solution and the pickling bath. The residence time was varied and the effect was investigated. Using the same material as in Experiment 2, it was divided into a large number and subjected to intermediate annealing under the same conditions as in Experiment 2, and upon cooling, when the steel plate temperature reached 150 ° C, the bath temperatures were 30 ° C and 40 ° C, respectively. 1,2,3,5,1 in a 15% pickling bath at 50, 60, 70, 80 and 90 ° C
It was immersed for 0, 40, 60, 80, 110 and 150 seconds and then washed with water. Thereafter, cold rolling, decarburizing annealing, application of an annealing separator, and final finish annealing were performed under the same conditions as in Experiment 1.

FIG. 3 shows the results obtained by examining the relationship between the iron loss characteristics of the steel sheet thus obtained and the pickling conditions. As shown in the figure, it has been found that good magnetic properties can be obtained by performing short-time pickling for 3 to 60 seconds with an aqueous acid solution at a liquid temperature of 60 ° C. or higher.

The effect of improving the magnetic properties by changing the pickling conditions is not only the effect of the above-mentioned precipitation of carbides, but also the surface of the steel sheet after pickling due to the high temperature reaction of the steel sheet with the acid bath at a high temperature. Was found to be involved. That is, it is considered that when the surface of the ground iron of the steel sheet after pickling exhibits a certain range of roughness, the frictional force of the cold rolling in the next step is increased, and the effect of improving the texture is obtained. Note that such effects can be obtained irrespective of the acid concentration to some extent.

Experiment 4 Next, an experiment conducted on cooling conditions effective for further enhancing the effect of the present invention will be described. Regarding the precipitation of carbides in the above-mentioned acid bath, it is expected that the faster the cooling, the greater the amount of dissolved C before precipitation and the higher the precipitation effect. Therefore, as a fourth experiment, using the same material as in Experiment 1, and under the same intermediate annealing conditions as in Experiment 2, the average cooling rate from 900 ° C. was 2.1 ° C./s, 4.5 ° C./s, 10.2 ° C./s, 15.7 ° C.
C./s, 23.8 / s and 32.4 / s, cooled to 150 150C and then placed in 80% 18% HCl aqueous solution.
Soaked for 20 seconds. Thereafter, cold rolling, decarburizing annealing, application of an annealing separator, and final finish annealing were performed under the same conditions as in Experiment 1.

FIG. 4 shows the results of a study on the relationship between the magnetic properties of the steel sheet thus obtained and the average cooling rate after the intermediate annealing. As is clear from the figure, it was found that when the average cooling rate after the intermediate annealing was 10 ° C./s or more, the magnetic properties were stably improved.

Experiment 5 Further, as a method of effectively roughening the surface of the steel sheet after pickling, a method of maintaining the temperature at a constant temperature or slowly cooling it during cooling can be considered. That is, it is expected that the surface of the steel sheet is further oxidized by such a treatment, and the unevenness of the steel sheet surface after the pickling is further increased. Therefore, in order to confirm this effect, in Experiment 5, the same material as in Experiment 1 was used, and under the same intermediate annealing conditions as in Experiment 2, the temperature was rapidly cooled from the soaking temperature to 350 ° C. at an average cooling rate of 30 ° C./s. Stopped. This 350
2, 5, 10, 15, 60, 100, 200, 3
Hold for 00,500 seconds, then add 1%
It was immersed in acid for 0 seconds and washed. Thereafter, cold rolling, decarburizing annealing, application of an annealing separator, and final finish annealing were performed under the same conditions as in Experiment 1.

The magnetic properties of the steel sheet thus obtained and 350 ° C
FIG. 5 shows the result of investigation on the relationship with the holding time in the above. As is clear from the figure, it was found that the magnetic properties were stably improved by quenching after the intermediate annealing, stopping the cooling at 350 ° C. during the cooling, and maintaining this temperature for 15 to 300 seconds.

Further, when the cooling stop temperature range suitable for obtaining such an effect was examined, it was found that the cooling stop temperature was preferably in the range of 200 to 400 ° C. That is, if the cooling stop temperature is less than 200 ° C, the temperature for oxidation of the steel sheet is not sufficient, while 400 ° C
If the amount exceeds the limit, the oxidation becomes excessive, so that there is a disadvantage that an excessive scale remains even after the pickling. Also, holding at the cooling stop temperature has the same effect as slow cooling treatment,
In this case, it was also investigated that the cooling rate should be slow cooling of 1.0 ° C./s or less.

As described above, the present invention provides a process for producing a grain-oriented silicon steel sheet containing a predetermined amount of C, Si, and Al, by decarburizing a predetermined amount of C during annealing before final cold rolling, and During the cooling of such annealing, by performing a short-time pickling treatment with a high-temperature acid aqueous solution at a time when the steel sheet temperature is high, one is to promote the precipitation of carbides in the steel, and the other is It is intended to improve the properties of the surface, to provide an effect of improving the texture during rolling, and finally to improve the magnetic properties of the product.

[0027]

The reason why the material components are limited to the above-mentioned composition range in the present invention will be described below. C: 0.050 to 0.100 wt% C is an element useful for improving the structure in hot rolling and cold rolling, but if the content is less than 0.050 wt%, the intended carbide precipitation effect intended by the present invention can be sufficiently obtained. 0.100 wt
%, The carbon content is limited to the range of 0.050 to 0.100 wt%, because decarburization is poor and magnetic properties are deteriorated.

Si: 2.0 to 5.5 wt% Si is an important component for increasing the electrical resistance of the product and reducing the eddy current loss. However, if it is less than 2.0 wt%, it is transformed during the final finish annealing to change the crystal orientation. Losing disadvantage, while 5.5wt
%, The cold rollability deteriorates.
Limited to the range of 5.5 wt%.

Al: 0.005 to 0.040 wt% Al precipitates as AlN in the steel and is essential to fulfill the function as an inhibitor.
A content of at least 05 wt% is necessary, but if it exceeds 0.040 wt%, AlN becomes coarse and the suppressing power decreases.
It was made to contain in the range of -0.040 wt%.

In addition, if necessary, Mn can be contained up to 2.5 wt% and Mo up to 0.05 wt% in order to enhance the hot rolling property. In addition, S, S
It is possible to add e, Ge, P, V, Sn, Sb, Bi, B, N and the like. For this purpose, S, Se, Ge, P,
0.005 to 0.040 wt% for V and N, 0.005 to 0.2 wt% for Sn and Sb, and 0.0003 to 0.0100 for Bi and B.
About wt% is appropriate. Note that N can be added during the manufacturing process.

Next, a manufacturing method according to the present invention will be described. The directional silicon steel slab which is the preferred component is cast by a conventionally used steelmaking method, re-rolled if necessary, and then hot-rolled into a hot-rolled steel sheet. Such a hot-rolled steel sheet has a final thickness by cold rolling once or twice with intermediate annealing. The term “annealing before final cold rolling”, which is the subject of the present invention, means that the cold rolling is performed only once. Is hot-rolled sheet annealing, and when cold rolling is performed twice, it is intermediate annealing.

In the annealing before the final cold rolling, C
Decarburization in the range of 0.005 to 0.015 wt% is one of the essential requirements of the present invention. That is, by slightly removing C from the steel sheet, it is possible to reduce coarse carbides precipitated during hot rolling and increase solid solution C. For this purpose, as shown in Fig. 1 above, decarburization must be at least 0.005 wt% or more. Conversely, if it exceeds 0.015 wt%, the amount of C excessively solidifies and the crystal structure of the steel sheet is reduced. The effect of C to make finer is deteriorated. So the decarburization amount of C is 0.005 ~
The texture was improved to 0.015 wt%.

The pickling after annealing of the weakly decarburized steel sheet in the above range is performed in an aqueous acid solution at a steel sheet temperature of 70 to 170 ° C. and a liquid temperature of 60 ° C. or higher for a short time of 3 to 60 seconds. Is the second essential requirement of the present invention. In other words, synergistically with the above-mentioned weak decarburization, the effect of carbide precipitation in the steel is obtained in one part. An improvement effect is obtained. In order to obtain this effect, it is essential to set the temperature of the pickling start steel sheet between 70 and 170 ° C. as shown in FIG.
If the temperature is lower than ℃, sufficient precipitation of carbides and the effect of increasing the roughness of the steel sheet surface cannot be obtained. On the other hand, if the temperature exceeds 170 ° C, the steel sheet surface becomes excessively rough and the texture deteriorates.

It is necessary that the temperature of the aqueous acid solution be 60 ° C. or higher. This is because, when the temperature is lower than 60 ° C., the steel sheet is cooled and the above-described action of increasing the roughness of the steel sheet surface and the precipitation of carbide cannot be obtained, and the effect of improving the texture is poor. Further, the pickling time in the aqueous acid solution is 3 to 60.
It must be between seconds. Because if it is shorter than this time, even the external scale such as FeO and Fe ₂ O ₃ will not be removed by pickling, while if longer than this, the steel sheet surface will be excessively rough and the effect of improving the texture will be reduced. It is. Note that the pickled steel sheet is washed with water and subjected to final cold rolling in the next step.
Also, there is no difference in the effect of the present invention even if the high temperature is sent to the next step without cooling.

By the way, according to the study by the inventors, it has been found that in the annealing treatment before the final rolling as described above, if the cooling treatment after the soaking is modified, the magnetic properties can be further improved. Was. That is, it has been found that the effect of the present invention can be more stably obtained by setting the average cooling rate to 10 ° C./s or more at the time of cooling after the annealing until the start of pickling. It is considered that the reason for this is that increasing the cooling rate promotes the increase of solid solution C, and further enhances the carbide precipitation action in the acid aqueous solution. Speed: It is necessary to perform at 10 ° C / s or more. Here, the controlled cooling as described above needs to be started at least at 900 ° C. This is because the temperature at which γ grains present in steel start α transformation is about 900 ° C. From this temperature,
This is because the amount of C soluble in the steel is drastically reduced, and the driving force for carbide precipitation is increased.

Further, as a method of effectively roughening the surface of the steel sheet after the pickling, a method of heating and holding the steel sheet at a constant temperature or cooling slowly after heating after the annealing is considered. That is, by such a process, the steel sheet surface is further oxidized,
The unevenness of the steel sheet surface after pickling increases. For this purpose, as described above, the cooling stop temperature of the quenching process at an average cooling rate of 10 ° C./s or more is set to 200 to 400 ° C., and heating is maintained at this stop temperature for a certain period of time, or from this temperature. What is necessary is just to heat and gradually cool. Here, the cooling stop temperature is 200
If the temperature is lower than ℃, the temperature for oxidation of the steel sheet is not enough.
If the temperature exceeds 400 ° C., the oxidation proceeds excessively, and an excessive scale remains even after pickling, thereby deteriorating the texture.
The heating and holding from the cooling stop point is 1.0
The same is true for slow cooling at a temperature of not more than ° C / s, and the time required for such treatment is appropriately 15 to 300 seconds. That is, 15
If it is shorter than 2 seconds, the effect of cooling stop will not be sufficient, while 3
If the time is longer than 00 seconds, the surface oxidation proceeds, and an excessive scale remains even after the acid washing, and conversely, the texture is deteriorated.

After such annealing, final cold rolling is performed.
This final cold rolling may be any known rolling method. That is, of course, normal cold rolling, 150-35
Warm rolling between 0 ° C. may be performed, and furthermore, in such warm rolling, aging treatment can be performed for each rolling pass. After the final cold rolling, decarburization annealing is performed, then an annealing separator is applied, and then final finish annealing is performed at a temperature of about 1200 ° C. to obtain a final product. In addition, if necessary, an insulating coating may be applied, and a flattening process may be performed to obtain a product.

[0038]

【Example】

Example 1 Steel slabs of A to K shown in Table 1 were hot-rolled into 2.0 mm-thick coils and then divided into two pieces. For one of the split coils, after subjecting the hot rolled sheet to annealing at 1000 ° C for 30 minutes,
After the first cold rolling to a thickness of 1.40mm,
Dew point: Intermediate annealing was performed at 1100 ° C for 60 seconds in a wet hydrogen-nitrogen atmosphere at 45 ° C. For subsequent cooling, use mist water to rapidly cool at an average cooling rate of 35 ° C / s. When the plate temperature is 100 ° C, immerse in an 80 ° C HCl aqueous solution for 20 seconds to perform pickling, and then brush. Washed and dried. At this time, the decarburization amount was 0.012 wt% for steel type A, 0.013 wt% for B, 0.006 wt% for C,
D is 0.008 wt%, E is 0.009 wt%, F is 0.006 wt%, G
Is 0.008 wt%, H is 0.009 wt%, I is 0.006 wt%, J is
0.006 wt% and K were 0.014 wt%. Then, after finishing to a final thickness of 0.20 mm by warm rolling at 150 ° C, the surface of the steel sheet is 80 μm deep and 20 μm wide and 100 μm wide in the rolling direction.
An inclined linear groove was formed at a pitch of 4 mm in the rolling direction. After that, decarburizing annealing in wet hydrogen at 850 ° C,
After applying the annealing separator, a final finish annealing was performed at 1200 ° C. Thereafter, a tension coating was applied and baked at 800 ° C. to serve as a flattening treatment, so that a suitable example was obtained. Table 2 shows the results of examining the magnetic properties of each of the obtained product plates.

On the other hand, the remaining split coils are subjected to hot rolling annealing at 1000 ° C. for 30 seconds and then to the first cold rolling to obtain 1.
Steel plate thickness of 40 mm, then 11 in dry hydrogen-nitrogen atmosphere
Intermediate annealing was performed at 00 ° C. for 60 seconds. At this time, after cooling to room temperature by quenching at an average cooling rate of 35 ° C./s using mist water, immersing in a 50 ° C. HCl aqueous solution for 30 seconds, pickling, then brush water washing and drying did. The decarburization amount of these steel sheets is 0.003 wt% for steel type A and 0.002 wt% for B
%, C is 0 wt%, D is 0.001 wt%, E is 0.001 wt%, F
Is 0 wt%, G is 0.001 wt%, H is 0.001 wt%, I is 0 wt%
%, J was 0 wt%, and K was 0.002 wt%. Then, under the same conditions as in the case of the above-mentioned conforming example, warm rolling, groove formation, decarburizing annealing, application of an annealing separator, final finish annealing, tension coating application, and flattening treatment were performed to obtain a comparative example. Table 2 also shows the results obtained by examining the magnetic properties of the products thus obtained.

[0040]

[Table 1]

[0041]

[Table 2]

As is evident from Table 2, when manufactured according to the present invention, a product plate excellent in magnetic flux density and iron loss as compared with the conventional method could be obtained.

Example 2 In Table 1, two steel slabs having the composition of steel type C were hot-rolled to a thickness of 2.30 mm. Then, one coil is
1150 ° C, 1 minute hot rolled sheet annealing, dew point: 40 ° C, H ₂ : 50%
Performed in an atmosphere of N ₂ balance (decarburization amount: 0.009 wt%)
After that, it was quenched with mist water at an average cooling rate of 40 ° C / s, and when the sheet temperature reached 250 ° C, it was heated and held for 60 seconds.
Then, when the plate temperature reaches 100 ° C, 18% HCl at 80 ° C
It was immersed in an aqueous solution for 10 seconds, pickled, washed with a brush, and dried. Then, the sheet was rolled to a sheet thickness of 0.30 mm by warm rolling at 250 ° C., degreased, decarburized, applied with an annealing separator, and then subjected to final finish annealing at 1200 ° C. for 5 hours. . Then, after removing the unreacted separating agent, a tension coating was performed, and a flattening treatment was performed at 800 ° C., so that a suitable example was obtained.

On the other hand, for the remaining hot-rolled coils, hot-rolled sheet annealing at 1150 ° C. for 1 minute was performed in a dry (H ₂ : 50%, N ₂ : 50%) atmosphere, and mist water was used for cooling. Average cooling rate: 40 ° C /
After cooling to room temperature as quenching of s, 18% HCl at 50 ° C
It was immersed in an aqueous solution for 30 seconds, pickled, and then washed with a brush and dried. Then, under the same conditions as in the above case,
Warm rolling, groove formation, decarburization annealing, application of an annealing separator, final finish annealing, tension coating application, and flattening treatment were performed to obtain a comparative example. The results of examining the magnetic properties of the product sheet thus obtained were as follows.

[0045]

[0046]

[0047]

As described above, according to the present invention, it is possible to stably produce a grain-oriented silicon steel sheet having remarkably excellent magnetic flux density and iron loss, and the effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of decarburization and the magnetic properties during intermediate annealing.

FIG. 2 is a graph showing the relationship between the temperature of a pickling start steel sheet after intermediate annealing and magnetic properties.

FIG. 3 is a graph showing the relationship between pickling time, pickling bath temperature, and iron loss characteristics.

FIG. 4 is a graph showing a relationship between an average cooling rate after intermediate annealing and magnetic properties.

FIG. 5 is a graph showing the relationship between the heating holding time at 350 ° C. and the magnetic properties during rapid cooling after intermediate annealing.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-192736 (JP, A) JP-A-6-192847 (JP, A) JP-A-5-202419 (JP, A) 56923 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 8/12

Claims (3)

(57) [Claims] (1) C: 0.050 to 0.100 wt%, Si: 2.0 to 5.
After hot rolling, a slab for oriented silicon steel containing 5 wt% and Al: 0.005 to 0.040 wt% is subjected to cold rolling once or twice with intermediate annealing, then decarburizing annealing and final In producing a grain-oriented silicon steel sheet by a series of steps of finish annealing, C is slightly decarburized by 0.005 to 0.015 wt% during annealing before final cold rolling, and at the time of cooling, the temperature is reduced from 900 ° C to at least 900 ° C.
Average cooling rate to washing start temperature: Cool at a rate of 10 ° C / s or more
After pickling, pickling is started when the temperature of the steel sheet is 70 to 170 ° C., and a short time pickling treatment is performed for 3 to 60 seconds in an acid aqueous solution of 60 ° C. or more, which is excellent in magnetic properties. Manufacturing method of grain-oriented silicon steel sheet. 2. C: 0.050-0.100 wt%, Si: 2.0-5.
After hot rolling, a slab for oriented silicon steel containing 5 wt% and Al: 0.005 to 0.040 wt% is subjected to cold rolling once or twice with intermediate annealing, then decarburizing annealing and final In producing a grain-oriented silicon steel sheet by a series of steps of finish annealing, C is slightly decarburized by 0.005 to 0.015 wt% during annealing before final cold rolling, and at the time of cooling, the temperature is reduced from 900 ° C to at least 900 ° C.
Cool at a rate of 10 ° C / s or more to the cooling stop point between 00 and 400 ° C.
And hold at the cooling stop for 15-300 seconds, or
Cooled at a rate of 1.0 ° C / s or less from the cooling stop point.
In addition , pickling is started when the temperature of the steel sheet is 70 to 170 ° C., and a short time pickling treatment is performed for 3 to 60 seconds in an acid aqueous solution of 60 ° C. or more, which has excellent magnetic properties. Manufacturing method of silicon steel sheet. 3. The hot rolling according to claim 1, wherein
After, before cold rolling, it is characterized by performing hot rolled sheet annealing
A method for producing grain-oriented silicon steel sheets with excellent magnetic properties.