JPH0610050A - Production of grain-oriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet excellent in magnetic properties by subjecting the rolled sheet of a silicon steel containing specific amounts of C, Si, Mn, S, and Se to decarburizing annealing, specific heat treatment, secondary recrystallization treatment, and purification annealing. CONSTITUTION:A slab of a silicon steel having a composition containing, by weight, 0.020-0.080% C, 2.5-4.0% Si, 0.03-0.15% Mn, and 0.008-0.100% S and/or Se is hot-rolled, cold-rolled once or cold-rolled twice while process-annealed between the cold rolling stages, and finished to the final sheet thickness. Then decarburizing annealing is applied to the steel sheet and a separation agent at annealing, composed essentially of MgO, is applied, and secondary recrystallization treatment is carried out at 800-920 deg.C. Subsequently purification annealing is applied to the steel sheet, by which a grain-oriented steel sheet is obtained. At this time, prior to the secondary recrystallization treatment, the steel sheet is held at 650-800 deg.C for 5-20hr in an atmosphere consisting of 25-75% dry H2 and the balance N2. By this method, Goss-oriented secondary- recrystallized grains can be increased in the integration degree and refined, and iron loss value can be remarkably reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to propose a method for producing a grain-oriented silicon steel sheet having a low iron loss value and a high magnetic flux density, which is suitable mainly for an iron core of a power transformer. is there. Generally, as a means for reducing iron loss, in addition to increasing the Si content, reducing the product plate thickness, etc., the crystal grain integration degree of the (110) [001] orientation in the secondary recrystallized grains, that is, the Goss orientation It is known to increase the grain size and to reduce the secondary recrystallized grains. Of the above,
In particular, to increase the degree of accumulation of secondary recrystallized grains in the Goss direction,
It is also effective and effective in improving the magnetic flux density.

[0002]

2. Description of the Related Art As a method for producing a silicon steel sheet having a high degree of accumulation of secondary recrystallized grains of Goss orientation, Japanese Patent Publication No. 51-1346.
No. 9 discloses a final finish annealing for the purpose of secondary recrystallization, purification, etc. performed after decarburization annealing after final cold rolling, in which secondary recrystallized grains are formed in a temperature range of 800 ° C. to 920 ° C. A method for obtaining a silicon steel sheet having excellent magnetic properties by sufficiently growing it is disclosed. However, this method certainly has the effect of increasing the degree of accumulation of the secondary recrystallized grains in the Goss orientation, but has the disadvantage that the secondary recrystallized grains become coarse and the target low iron loss value cannot be obtained. is there.

Further, in Japanese Patent Laid-Open No. 60-67625, the purpose is to supplement the inhibitor function in the steel which is insufficient before the secondary recrystallization treatment in the final finish annealing performed after decarburization annealing after the final cold rolling. In particular, S or Se or a compound thereof is added to the annealing separator in advance, and further 2
There is a disclosure of a method in which the atmosphere of the secondary recrystallization annealing is changed to an inert gas. This method aims at sufficiently exhibiting the inhibitor function in the steel, and although it is expected that the magnetic properties will be recovered to some extent in the case of a steel sheet with a poor secondary recrystallization, a steel sheet with a sufficient inhibitory force by the inhibitor is obtained. In this case, the secondary recrystallized grains are remarkably coarsened, and the iron loss value is rather deteriorated.

[0004]

SUMMARY OF THE INVENTION The present invention drastically improves the disadvantage of the above-mentioned prior art, that is, the disadvantage that the iron loss value is deteriorated due to the coarsening of the secondary recrystallized grains. Further increase the degree of crystal grain accumulation, and further 2
It is an object of the present invention to propose a method for producing a unidirectional silicon steel sheet which makes it possible to reduce the iron loss value remarkably by refining the secondary recrystallized grains.

[0005]

The inventors of the present invention have noticed that the drawback of the prior art lies in the coarsening of the secondary recrystallized grains, and a method for suppressing the coarsening of the secondary recrystallized grains. As a result of various studies, the usefulness of the method of performing the pretreatment before the secondary recrystallization annealing was found. That is, before the secondary recrystallization annealing, H ₂ : 25 to 75% between 650 ℃ and 800 ℃, the balance is N ₂ before
Atmosphere for 5 to 20 hours, or between 650 and 800 ° C
H _2: 25~75%, the balance by heating at Noborinetsu rate of 3 to 20 ° C. / h in an atmosphere of N _2, easily Goss orientation without lowering the function of the inhibitor MnS, such MnSe in the steel It has been found that it is possible to increase the degree of integration and refine the secondary recrystallized grains, and to manufacture a unidirectional silicon steel sheet having excellent magnetic properties. This invention
It is based on the above findings.

That is, the present invention is C: 0.020 to 0.08.
0 wt%, Si: 2.5 to 4.0 wt%, Mn: 0.03 to 0.15 wt%, and 0.008 to 0.100 wt% of one or two of S and Se.
The contained silicon steel slab is hot-rolled, then cold-rolled once or cold-rolled twice with intermediate annealing to finish to the final thickness, then decarburized and annealed. In the method for producing a unidirectional silicon steel sheet, after applying an annealing separator as a main component, performing a secondary recrystallization treatment in a temperature range of 800 ° C to 920 ° C, and then performing a purification annealing, the above secondary recrystallization prior to treatment, a dry H _2: 25 to 75%, in an atmosphere of balance N _2,
This is a method (first invention) for producing a unidirectional silicon steel sheet having excellent magnetic properties, which is characterized by holding at a temperature in the range of 650 to 800 ° C for 5 to 20 hours.

The present invention also provides C: 0.020 to 0.080 wt.
%, Si: 2.5 to 4.0 wt%, Mn: 0.03 to 0.15 wt%,
And a silicon steel slab containing 0.008 to 0.100 wt% of one or two of S and Se is hot-rolled, and then subjected to one cold rolling or two cold rolling with intermediate annealing, and finally. After finishing the plate thickness, decarburization annealing is applied, then an annealing separator containing MgO as a main component is applied, and then secondary recrystallization treatment is performed in the temperature range of 800 ° C to 920 ° C, followed by purification annealing. In the method for producing a unidirectional silicon steel sheet, prior to the secondary recrystallization treatment, dry H ₂ : 25 to 75%, the balance of N ₂ is 650
A method for producing a unidirectional silicon steel sheet having excellent magnetic properties (second invention), which comprises heating a temperature range of ℃ to 800 ℃ at a heating rate of 3 to 20 ℃ / h.

[0008]

The present invention will be described in detail below based on the experimental results. As the test material, steels having the same composition were used, and the processes under the same conditions described below were performed from slab rolling to decarburization annealing. C: 0.
045 wt%, Si: 3.30 wt%, Mn: 0.087 wt%, S: 0.026
A 200 mm thick slab made of silicon steel with a composition containing wt% is heated at a temperature of 1380 ° C for 1 hour and then hot rolled to a thickness of 2.
A 0 mm hot rolled sheet was used. Then, this hot-rolled sheet is annealed at 900 ° C for 2 minutes, then pickled and then cold-rolled to a thickness of 0.60 mm, and further subjected to an intermediate annealing at a temperature of 950 ° C for 2 minutes, and finally. Cold rolling was performed to a thickness of 0.23 mm. The cold-rolled sheet was degreased and then 830 in a wet hydrogen atmosphere.
After decarburization annealing at 3 ° C. for 3 minutes, an annealing separator containing MgO 2 as a main component was applied.

Using a sample coated with this annealing separator, 1
As a conventional process, one sample was subjected to a secondary annealing treatment in a dry N ₂ atmosphere at 840 ° C. for 40 h in a conventional finish annealing process, then switched to dry H ₂ and subjected to purification annealing at 1200 ° C. for 5 h. For other samples, prior to the secondary recrystallization retention treatment, various temperatures between 500 ℃ and 850 ℃ were soaked for 3 hours, 5 hours, 10 hours, 20 hours, and 30 hours, and dry H ₂ : 50%. , Dry N ₂ : 50% atmosphere retention treatment,
Then, after the secondary recrystallization retention treatment in a dry N ₂ atmosphere at 840 ° C. for 40 hours, it was switched to dry H ₂ and subjected to purification annealing at 1200 ° C. for 5 hours.

The results of examining the magnetic characteristics of the respective samples subjected to the above-mentioned respective conditions are shown in FIG.
And 3 hours in relation to the retention temperature prior to the secondary recrystallization annealing
Soaking (▽ mark), 5h soaking (△ mark), 10h soaking (○ mark),
Shown for 20 h soaking (□) and 30 h soaking (◇).

As is apparent from FIG. 1, the magnetic properties are remarkably high under the condition that the method of the present invention is applied and dry H ₂ : 50% is maintained for 5 to 20 hours between 650 ° C. and 800 ° C. as compared with the conventional process. When the holding temperature is improved and the holding temperature is low, the soaking time is long, and when it is high, the soaking time is short, and the most suitable magnetic properties are obtained under the conditions of 750 ° C and 10 h. It was

Next, 650 ° C. to 800 ° C. before secondary recrystallization annealing
The results of experiments in which the ratio of dry H ₂ was changed in the atmosphere during the same treatment will be described for examples in which the heating was performed at various heating rates. Using a sample that was subjected to the above-mentioned experiment and a series of steps until the components and the annealing separator were applied under the same conditions, one sample was used as a conventional step in the normal annealing at finish 840 ℃,
40h Dry after dry recrystallization retention treatment in N ₂ atmosphere
It was switched to H ₂ and subjected to purification annealing at 1200 ° C for 5 hours. Also,
For other samples, 650 prior to secondary recrystallization retention treatment
Heat up to 800 ℃ at various heating rates of 1.5 ℃ / h to 40 ℃ / h and change the atmosphere between dry H ₂ and dry H ₂ 25%.
-Dry N ₂ 75%, Dry H ₂ 50% -Dry N ₂ 50
%, Dry H ₂ 75% -Dry N ₂ 25% and Dry N
Treatment in each atmosphere of ₂ and then 840 ℃, 40h
After the secondary recrystallization was completed by the secondary recrystallization retention treatment in dry N ₂ , it was switched to dry H ₂ and subjected to purification annealing at 1200 ° C. for 5 hours.

The results of examining the magnetic characteristics of the respective samples subjected to the above-mentioned respective conditions are shown in FIG.
And, in relation to the temperature rising rate prior to the secondary recrystallization annealing, dry H ₂ atmosphere (▽ mark), dry H ₂ 25% -dry N ₂ 75
% Atmosphere (△ mark), dry H ₂ 50% -dry N ₂ 50% atmosphere (○ mark), dry H ₂ 75% -dry N ₂ 25% atmosphere (□ mark) and dry N ₂ atmosphere (◇ mark) Show in case.

As is apparent from FIG. 2, the temperature rising rate between 650 ° C. and 800 ° C. is within the range of 3-20 ° C./s, which is the condition of the present invention, and the atmosphere is further increased, as compared with the magnetic characteristics in the conventional process. Dry H
₂ 25 to 75%, the remainder being good magnetic characteristics can be obtained than the conventional process when treated under the condition of dry N _2, Noborinetsu among them the most preferred conditions are 650 ° C. to 800 ° C. between the 12.5 ° C. / h ,dry
This is a treatment in an atmosphere of H ₂ 50% and dry N ₂ 50%. It should be noted that although the level of magnetic characteristics tends to be slightly lower than that of the experimental example of the retention treatment shown in FIG. 1, the magnetic characteristics are significantly improved as compared with the conventional process.

In order to investigate in detail the reason why the magnetic properties are improved by the pretreatment prior to the secondary recrystallization treatment according to the present invention as described above, in the experiment shown in FIG. Dry H ₂ 50, which is the preferred condition of the invention
Samples that had been subjected to the retention treatment at 750 ° C. for 10 hours in a% -dry N ₂ 50% atmosphere were taken out just before the secondary recrystallization treatment, and the sample surface was analyzed by EPMA after removing MgO. The results of this EPMA survey are shown in Table 1.

[0016]

[Table 1]

As is apparent from Table 1, the sample treated in the conventional process contains a larger amount of each of Mn, S, Si and oxygen than the sample treated under the conditions of the present invention. It is clear that the sample No. 1 has reduced Mn, S, Si, and oxygen on the surface compared with the sample in the conventional process.

From the above experiment, the conventional process conditions are as follows:
After decarburization annealing in the manufacturing process of grain-oriented silicon steel, MgO
With the process of the final annealing after coating and drying a slurry state, since significantly oxidizing increases going dehydration of MgO in the inter finish annealing initial _{300 ~600 ℃, SiO 2, Fe} 2 SiO
₄ through the oxide layer of the steel sheet surface layer composed mainly of Mn in the steel,
It is considered that the inhibitor component of S is concentrated on the sub-scale surface layer, and as a result, the inhibitory force in steel is significantly reduced. On the other hand, it is considered that those treated under the conditions of the present invention are improved in magnetic properties by suppressing the oxidation of the surface layer and thus suppressing the concentration of the inhibitor component of Mn and S.

According to the present invention, in the range of 650 ° C to 800 ° C,
Hold for 20 hours, or 3 to 20 ℃ / h in the range of 650 ℃ to 800 ℃.
Based on experimental facts, the reason for limiting the heating to a dry H ₂ atmosphere of 25 to 75% and the balance N ₂ is as follows.

First, when the above treatment is performed at less than 650 ° C., MgO
This is because the dehydration of (3) is not completed, which causes a problem of acceleration of oxidation, and at a temperature of more than 800 ° C, the problem also occurs because it rather promotes coarsening of the inhibitor.

When the holding time between 650 ° C. and 800 ° C. is as short as less than 5 h, the effect of suppressing the surface layer concentration of Mn, S is low, and
When the time is longer than h, the inhibitor is coarsened and the concentration of Mn and S in the surface layer is disadvantageously increased. Therefore, the range is limited to 5 to 20 h.

Regarding the rate of temperature rise, if the heating is slower than 3 ° C./h, the residence time within 650 ° C. to 800 ° C. will be remarkably long, and the inhibitor in steel will become coarse and the surface concentration of Mn and S will increase. In the case of relatively rapid heating that is liable to occur and is faster than 20 ° C / h, the effect of suppressing the surface layer concentration of Mn and S is low and the effect is thin, as in the case of soaking for a short time. Limited to h range.

Further, the atmosphere was defined as dry H ₂ 25% to 75% and the balance dry N ₂ is that in the case of N ₂ —H ₂ atmosphere exceeding 75%, the concentration of Mn, S, Si and oxygen components on the surface is high. In order to further promote chemical conversion, and also to promote de-S and Se even when H ₂ exceeds 75% and inhibit the inhibitor function, the atmosphere was limited to dry H ₂ 25 to 75% and the balance dry N ₂ atmosphere.

Next, the steel component composition in the present invention will be explained. C: When C is less than 0.020 wt%, the texture after decarburization annealing is damaged and the magnetic properties are deteriorated.
If it is contained in a large amount exceeding 80 wt%, decarburization by continuous annealing becomes difficult and the magnetic properties of the final product are deteriorated. Therefore, the C content is limited to 0.020 to 0.080 wt%. Si: When Si is less than 2.5 wt%, it is difficult to obtain the iron loss as low as expected in the present invention, while when it is more than 4.0 wt%, it becomes brittle and deteriorates cold workability, which causes deterioration of cold workability. Since it becomes difficult to perform dynamic rolling, the Si content was limited to the range of 2.5 to 4.0 wt%. Mn: Mn combines with S and Se to form an inhibitor of MnS and MnSe, and suppresses the growth of grains other than the (110) 001 orientation in the secondary recrystallization process. Although it is an element necessary to sufficiently develop secondary recrystallized grains,
If the content is less than 0.03 wt%, the above inhibitor formation amount is not sufficient, while if it exceeds 0.15 wt%, MnS and MnSe are formed.
Mn is 0.03 to 0.15 because it becomes difficult to disperse them in a preferable state as an inhibitor under industrially possible slab heating conditions.
It was limited to the wt% range. S and / or Se: Both S and Se are useful components for developing secondary recrystallized grains as an inhibitor, but if they are out of the above-mentioned proper ranges, sufficient effects cannot be obtained. Therefore, S and Se must be contained in the range of 0.008 to 0.100 wt% whether used alone or in combination. It should be noted that addition of grain boundary segregation type elements such as Sb, As, Bi, Pb and Sn is also effective as a component for assisting the inhibitor effect. All of them have no addition effect at less than 0.010 wt%, and deteriorate the magnetic properties and impair cold rolling at more than 0.200 wt%. Therefore, each of these components alone or in combination has a content of 0.010 to 0.200. A wt% range is preferred.

Next, the manufacturing method of the present invention will be described in the order of steps. The silicon steel material adjusted to the above component composition is usually heated to a high temperature of 1250 ° C. or higher, and then a hot rolled mother board having a plate thickness of 1.2 to 4.5 mm is prepared by a known method. If necessary, perform annealing in the temperature range of 800 to 1100 ° C, pickle it, and then perform one cold rolling, or perform two or more cold rollings with annealing in the temperature range of 750 to 1100 ° C to obtain the final product. Thickness 0.15
A cold rolled sheet of about 0.35 mm is finished, but the cold rolling rate when finishing to the final sheet thickness by this cold rolling is preferably in the range of 40 to 80%. After degreasing this final cold-rolled sheet, in a wet hydrogen atmosphere
Decarburization annealing is performed in the temperature range of 750 to 900 ℃ and the amount of C is 0.003wt.
% Or less. After that, apply an annealing separator containing MgO as the main component, and then dry at 650 to 800 ° C in finish annealing.
H ₂ 25 to 75% balance Dry 5 to 20 hours in N ₂ atmosphere or treated at a heating rate of 3 to 20 ° C / h and then 800 to 92 in dry N ₂
After completing the secondary recrystallization in the temperature range of 0 ° C, dry H
Switch to ₂ and perform purification annealing at a high temperature of 1000 ° C or higher. Finally, an insulating coating is applied to obtain a unidirectional silicon steel sheet product.

By manufacturing by such a treatment process, it becomes possible to stably manufacture a unidirectional silicon steel sheet having excellent magnetic properties stably at a low cost without newly requiring capital investment. . In the present invention, the temperature is maintained between 650 and 800 ° C prior to the secondary recrystallization annealing in a dry H ₂ 25 to 75% balance dry N ₂ atmosphere for 5 to 20 hours, and 3 to 20 ° C / h.
It may be performed in combination with the heat treatment.

[0027]

EXAMPLES Example 1 C: 0.04 wt%, Si: 3.29 wt%, Mn: 0.082 wt%, Se: 0.
A 200 mm thick silicon steel slab having a composition containing 027 wt% was heated at a temperature of 1380 ° C for 1 hour, hot-rolled to a thickness of 2.0 mm, annealed at a temperature of 920 ° C for 3 minutes, and then acid-treated. Washed, 0.60
After cold rolling to mm thickness, intermediate annealing at 950 ℃ for 2 minutes, final cold rolling to 0.23 mm thickness, degreasing and decarburization in wet hydrogen at 830 ℃ for 3 minutes. It was annealed. As a comparative example of the conventional method, one coil was dry N ₂ coated with an annealing separator containing MgO as a main component after decarburization annealing.
35 hours at 845 ° C followed by dry H ₂
After that, the product was annealed for 10 hours at a temperature of 1200 ° C. The other one coil is a suitable example according to the method of the present invention. After decarburization annealing, an annealing separating agent containing MgO as a main component is applied, and then finish annealing is performed at 750 ° C. for 10 hours and dry H ₂ 50%-
After treatment in a dry N ₂ 50%, switching to dry N _2, 84
Following a 35 hour hold at a temperature of 5 ° C, the finish was annealed by switching to dry H ₂ and holding at a temperature of 1200 ° C for 10 hours. The magnetic properties of these products are shown in Table 2.

[0028]

[Table 2]

As is apparent from this table, it is understood that the magnetic properties of the examples of the present invention are remarkably excellent.

Example 2 C: 0.048 wt%, Si: 3.37 wt%, Mn: 0.085 wt%, Se:
A 200 mm thick slab of silicon steel with a composition containing 0.023 wt%, S: 0.023 wt% and Sb: 0.030 wt% was heated at a temperature of 1380 ° C for 1 hour, and then hot rolled to a thickness of 1.8 mm, and 900 After annealing at a temperature of ℃ for 3 minutes, pickling, cold rolling to 0.58 mm thickness,
After intermediate annealing for 2 minutes at a temperature of 970 ° C., final cold rolling to a thickness of 0.18 mm, degreasing, and decarburization annealing for 3 minutes at a temperature of 820 ° C. in wet hydrogen. One of the coils, as a comparative example by the conventional method, was coated with an annealing separation agent containing MgO as the main component after decarburization annealing, and was subjected to 35 at a temperature of 850 ° C in dry N _2.
Subsequent to the time retention, switching to dry H ₂ was performed and the final annealing was performed at a temperature of 1200 ° C for 10 hours retention. The other one coil is
As a suitable example according to the method of the present invention, after the decarburization annealing, after applying the annealing separating agent containing MgO as a main component, in the finish annealing, 650
Dry H ₂ 50% -at a heating rate of 12.5 ° C / h between ℃ and 800 ° C
After processing in an atmosphere of dry N ₂ 50%, switch to dry N ₂ and hold for 35 hours at a temperature of 850 ℃, then switch to dry H ₂ and finish annealing with a hold for 10 hours at a temperature of 1200 ℃. gave. The magnetic properties of these products are shown in Table 3.

[0031]

[Table 3]

As is apparent from this table, the magnetic properties of the conforming example of the present invention are remarkably excellent.

Example 3 C: 0.045 wt%, Si: 3.28 wt%, Mn: 0.082 wt%, S:
200m with composition containing 0.028 wt% and As: 0.022 wt%
After heating a m-thick silicon steel slab at a temperature of 1380 ° C for 1 hour, hot rolling it to a thickness of 3.0 mm, annealing it at a temperature of 950 ° C for 2 minutes, pickling it, and cold rolling it to a thickness of 1.00 mm, 3 at a temperature of 910 ° C
After intermediate annealing for 1 minute, final cold rolling to a thickness of 0.30 mm, degreasing, and decarburizing annealing in wet hydrogen at a temperature of 820 ° C. for 3 minutes. As a comparative example of the conventional method, one coil was coated with a separating agent containing MgO as a main component after decarburization annealing,
After holding for 50 hours at a temperature of 830 ° C in dry N ₂ , the temperature was switched to dry H ₂ and finish annealing was performed for 10 hours at a temperature of 1200 ° C. As another example of conformity with the method of the present invention, the other one coil is applied with an annealing separating agent containing MgO as a main component after decarburization annealing, and then subjected to finish annealing at 700 ° C. for 12.5 h, dry H ₂ 35% -dry N ₂ After treatment at 65%, switch to dry N ₂ and continue to dry at 50 ° C for 50 hours.
It was switched to H ₂ and subjected to a finish annealing that was held for 10 hours at a temperature of 1200 ° C. The magnetic properties of these products are shown in Table 4.

[0034]

[Table 4]

As is apparent from this table, the magnetic properties of the conforming example of the present invention are remarkably excellent.

Example 4 C: 0.045 wt%, Si: 3.29 wt%, Mn: 0.082 wt%, S:
A 200 mm thick silicon steel slab having a composition containing 0.021 wt%, Sb: 0.026 wt%, Bi: 0.015 wt% was heated at a temperature of 1380 ° C for 1 hour, and then hot rolled to a thickness of 2.7 mm, and 1000 It was annealed at a temperature of 0 ° C for 2 minutes, pickled, immediately cold-rolled to a final thickness of 0.27 mm, degreased, and then decarburized and annealed at a temperature of 820 ° C for 3 minutes in wet hydrogen. One of the coils, as a comparative example by the conventional method, was decarburized and annealed with a MgO-based annealing separator, and then switched to dry H ₂ for 40 hours at 840 ° C in dry N _2. 10 at 1200 ℃
Finish annealing of time retention was given. The other one coil is, as a conforming example of the method of the present invention, after decarburization annealing, after applying an annealing separating agent containing MgO as a main component, in finishing annealing, 650 ° C to 80 ° C.
Dry H ₂ 60% -Dry N at a heating rate of 15 ° C / h between 0 ° C
After treatment with ₂ 40% atmosphere, it was subjected to finish annealing temperature at 10 hours retention of subsequently 1200 ° C. is switched to a dry H ₂ to retention of 40 hours at a temperature of 840 ° C. in a dry N _2. Table 5 shows the magnetic properties of these products.

[0037]

[Table 5]

As is apparent from this table, the magnetic properties of the conforming example of the present invention are remarkably excellent.

Example 5 C: 0.045 wt%, Si: 3.25 wt%, Mn: 0.080 wt%, S:
0.022 wt%, Se: 0.020 wt%, Sb: 0.031 wt%, Pb: 0.
A 200 mm thick silicon steel slab with a composition containing 025 wt% was heated at a temperature of 1415 ° C for 20 minutes, hot-rolled to a thickness of 2.2 mm, annealed at 1000 ° C for 1 minute, and then pickled to 0.64. After intermediate cold rolling to a thickness of mm, annealing at 950 ° C. for 1.5 minutes, finishing cold rolling to a thickness of 0.23 mm, degreasing, and decarburization annealing at 830 ° C. for 2 minutes in wet hydrogen. As a comparative example of the conventional method, one coil was applied with an annealing separator containing MgO as a main component after decarburization annealing, and then subjected to secondary recrystallization annealing in dry N ₂ at a temperature of 845 ° C. for 40 hours, followed by dry H _After switching to ₂ , the product was annealed for 10 hours at a temperature of 1200 ° C. As another example of the application of the method of the present invention, another coil was subjected to decarburization annealing, and after applying an annealing separating agent containing MgO as a main component, it was subjected to finish annealing at a temperature of 775 ° C. for 7.5 seconds.
Time Dry H ₂ 35% -Dry N ₂ 65% After annealing in an atmosphere, switch to dry N ₂ at a temperature of 845 ° C and hold for 40 hours to maintain secondary recrystallization, then switch to dry H ₂ at a temperature of 1200 ° C. Purification annealing was performed for 10 hours. Table 6 shows the magnetic properties of these products.

[0040]

[Table 6]

As is apparent from this table, the magnetic properties of the conforming example of the present invention are remarkably improved.

[0042]

As described above, according to the present invention, 800 to 92 in the manufacturing process of the grain-oriented silicon steel sheet.
Prior to the secondary recrystallization treatment that completes the secondary recrystallization in the temperature range of 0 ° C, dry H ₂ 25% to 75% at 650 to 800 ° C,
Rest for 5 to 20 hours in N ₂ atmosphere or 3 to 20 ℃ / h
It is possible to obtain a unidirectional silicon steel sheet having good magnetic properties by processing at a heating rate of 1, and the industrial value is very large because of the growing need for energy saving and resource saving.

[Brief description of drawings]

FIG. 1 shows a conventional process manufactured by a conventional method and a secondary recrystallization pretreatment temperature range of 500 ° C. to 850 ° C. in an atmosphere of dry H ₂ 50% -dry N ₂ 50% for 3 hours, 5 hours, 10 hours, and 20 hours. , 30h
7 is a graph showing the magnetic characteristics of the examples retained in FIG.

FIG. 2 shows a conventional process produced by a conventional method and a secondary recrystallization pretreatment temperature of 650 to 800 ° C. at a heating rate of 1.5 to 40 ° C./h.
Therebetween treatment atmosphere dry H _2, dry H ₂ 25%: Dry N ₂ 75%, dry H ₂ 50%: Dry N ₂ 50%, dry H ₂ 75%: each a dry N ₂ 25% and a dry N ₂ It is a graph which shows and compares a magnetic property with the processed example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mr. Hiroshi Nishiike, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Iron & Steel Co., Ltd. Technical Research Division (72) Inventor Takahiro Suga 1 Kawasaki-cho, Chuo-ku, Chiba-shi Address: Kawasaki Steel Corporation Technical Research Division

Claims (2)

[Claims] 1. C: 0.020 to 0.080 wt%, Si: 2.5 to 4.
0 wt%, Mn: 0.03 to 0.15 wt%, and 1 of S and Se
After hot rolling a silicon steel slab containing 0.008 to 0.100 wt% of one or two kinds, and then performing one cold rolling or two cold rolling with intermediate annealing between them to finish the final plate thickness. , Decarburization annealing, then applying an annealing separator containing MgO as a main component, and then performing secondary recrystallization treatment in the temperature range of 800 ° C to 920 ° C, followed by purification annealing. Prior to the secondary recrystallization treatment described above, the method is characterized by holding in a temperature range of 650 to 800 ° C. for 5 to 20 hours in an atmosphere of dry H ₂ : 25 to 75% and the balance of N _2. A method for manufacturing a unidirectional silicon steel sheet having excellent magnetic properties. 2. C: 0.020 to 0.080 wt%, Si: 2.5 to 4.
0 wt%, Mn: 0.03 to 0.15 wt%, and 1 of S and Se
After hot rolling a silicon steel slab containing 0.008 to 0.100 wt% of one or two kinds, and then performing one cold rolling or two cold rolling with intermediate annealing between them to finish the final plate thickness. , Decarburization annealing, then applying an annealing separator containing MgO as a main component, and then performing secondary recrystallization treatment in the temperature range of 800 ° C to 920 ° C, followed by purification annealing. Prior to the secondary recrystallization treatment described above, the temperature range of 650 ° C to 800 ° C is 3 to 20 ° C in an atmosphere of dry H ₂ : 25 to 75% and the balance of N _2.
A method of manufacturing a unidirectional silicon steel sheet having excellent magnetic properties, which comprises heating at a heating rate of h.