JP2001047202A - Production of grain oriented silicon steel sheet excellent in magnetic characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel sheet excellent in magnetic characteristics by giving electromagnetic stirring to molten steel at the unsolidified part when the molten steel having a specified composition is continuously cast. SOLUTION: This molten steel contains, by wt.%, 0.03-0.10 C, 2.5-4.5 Si, 0.005-0.050 Bi and the other inhibiter elements. Desirably, a steel slab obtd. by continuously casting the molten steel which contains, by wt.%, 0.03-0.10 C, 2.5-4.5 Si, 0.005-0.050 Bi and 0.05-1.5 Mn, and as the main inhibiter elements, 0.01-0.04 S and/or Se, 0.015-0.05 sol. Al and 0.005-0.015 N, and as the inhibiter reinforcing elements, one or more kinds selected among 0.05-0.5 Cu, 0.05-0.5 Sn, 0.005-0.10 Sb, 0.005-0.10 Mo and 0.001-0.01 B, is heated at >=1350 deg.C and applied with annealing, pickling and cold-rolling, and applied further, with decarburize-annealing which is also primary recrystallization, secondary recrystallization and purifying treatment. In the continuous casting, the electromagnetic stirring is applied to the molten steel at the unsolidified part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties and suitable for use in an iron core of a transformer or a generator.

[0002]

2. Description of the Related Art A product containing Si and having a crystal orientation of $ 1
Oriented electrical steel sheets oriented in the 10 ° <001> direction are widely used as various iron core materials in the commercial frequency range because of their excellent soft magnetic properties. As a characteristic required for an electrical steel sheet, it is important that the iron loss value represented by W _17/50 (W / kg), which is a loss when magnetized to 1.7 T at a frequency of 50 Hz, is low. The iron loss of the core of the generator and transformer is W
_The use of a material having a low value of _17/50 can significantly reduce the use of the material, and therefore the development of a material having a low iron loss has been strongly demanded year by year.

[0003] Generally, to reduce iron loss of a material, a method of increasing the content of Si, which is effective in reducing eddy current loss, to increase electric resistance, a method of reducing the thickness of a steel sheet, and a crystal grain size of a product Are known, and a method of increasing the degree of integration of crystal orientations to improve the magnetic flux density is known. this house,
There is a limit to the method of increasing the Si content because excessively containing Si deteriorates the rollability and workability, and the method of further reducing the thickness of the steel sheet and the method of reducing the crystal grain size are not limited. , Leading to extreme manufacturing costs,
Not preferred.

[0004] Methods for improving the remaining magnetic flux density have been well studied so far, and the special feature thereof is to select a kind of precipitate called an inhibitor that controls secondary recrystallization and to carry out a morphology control technique associated therewith. It is not an exaggeration to say. Inhibitor control largely depends on the uniform fine dispersion in the hot rolling process, but the fact is that the condition that always controls the morphology first is always selected in other processes.

By the way, MnS, MnSe, AlN and the like have been put to practical use as typical inhibitors so far. In particular, when AlN is used as the main inhibitor, {110} <is set by increasing the rolling reduction to 80% or more in the cold rolling process.
A texture suitable for secondary recrystallization of the 001> orientation can be obtained, and as a result, a high magnetic flux density is industrially realized. Recently, for the purpose of further strengthening the inhibitor function, for example, Japanese Patent Publication No. 60-48886 discloses Cu in steel.
JP-A-2-115319 discloses a method of adding Sb and Mo, respectively.

Further, Japanese Patent Publication No. 62-45285 discloses a method of reducing S or Se of a raw material and performing a nitriding treatment in an intermediate step. According to this method, it is possible to omit the high-temperature heating of the slab, which is indispensable for controlling the inhibitor, so that there is an advantage that various defects caused by the conventional high-temperature heating can be fundamentally solved.

[0007] In addition, Japanese Patent Publication No. 57-41526 discloses that the crystal structure of a slab is improved by using electromagnetic stirring at the stage of producing a continuous cast slab, and the slab grain growth is caused by high temperature heating in the next process. However, it is a fact that such a high-temperature slab heating is becoming a category of unnecessary technology. As described above, the magnetic properties of grain-oriented electrical steel sheets have been greatly improved, but transformer manufacturers are increasingly demanding improvements as global environmental protection has increased.

On the other hand, as disclosed in JP-A-51-41624, Bi has long been known as an element which is extremely effective in enhancing the function of an inhibitor. However, although this effect is excellent, Bi has the following disadvantages: (1) unstable secondary recrystallization and unstable magnetic properties; and (2) no formation of a forsterite film unique to grain-oriented electrical steel sheets. is there. For example, JP-A-8-232019 discloses that
A technique for controlling the amount of oxygen after decarburizing annealing and improving the coating by adding a specific compound to the annealing separator has been disclosed, but since there are many unsolved parts, the direction containing Bi At present, production of conductive electrical steel sheets has not yet been carried out industrially.

[0009]

SUMMARY OF THE INVENTION The present invention has been developed in view of the above situation, and has been developed in the case of manufacturing a grain-oriented electrical steel sheet containing the above-mentioned known inhibitors, especially Al, N and Bi. Excellent magnetic properties, eliminating the instability of secondary recrystallization, achieving extremely high magnetic flux density, and thus extremely low core loss, and effectively eliminating the inherent coating property defects inherent in Bi-added steel. It is an object of the present invention to propose an advantageous method of manufacturing a conductive electrical steel sheet.

[0010]

Means for Solving the Problems In order to eliminate the instability of the secondary recrystallization described above, the present inventors have carefully studied the effect of the inhibitor Bi on the secondary recrystallization, and as a result, It was newly found that the uniform dispersibility of Bi in the casting slab stage was extremely important. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. C: 0.03 to 0.10 wt%, Si: 2.5 to 4.5 wt% and B
i: In a method for producing a grain-oriented electrical steel sheet comprising 0.005 to 0.050 wt% and molten steel containing other known inhibitor elements, formed into a slab by continuous casting and combining hot rolling, cold rolling and heat treatment. A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, wherein electromagnetic stirring is applied to molten steel in an unsolidified portion during continuous casting.

2. C: 0.03 to 0.10 wt%, Si: 2.5 to 4.5
wt%, Mn: 0.05 to 1.5 wt% and Bi: 0.005 to 0.050 wt
%, And S and / or as the main inhibitor element
Or Se: 0.010 to 0.040 wt%, sol.Al: 0.015 to 0.05
0 wt% and N: 0.005 to 0.015 wt%, and Cu: 0.05 to 0.5 wt%, Sn:
0.05 to 0.5 wt%, Sb: 0.005 to 0.10 wt% Mo: 0.005 to 0.
Molten steel containing one or more selected from 10 wt% and B: 0.001 to 0.01 wt% is made into a slab by continuous casting, and the steel slab is heated to 1350 ° C. or more, and then hot-rolled. Hot-rolled sheet, if necessary, hot-rolled sheet annealing, and after pickling, cold rolling is performed once or twice or more including intermediate annealing to obtain a final sheet thickness, and then primary recrystallization is performed. Decarburization annealing is also performed, followed by applying an annealing separator containing MgO as a main component, followed by final finish annealing.
In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of performing a subsequent recrystallization and purification treatment, in the continuous casting, the magnetic direction is excellent in magnetic properties characterized by applying electromagnetic stirring to molten steel in an unsolidified portion. Manufacturing method of electrical steel sheet.

3. C: 0.03 to 0.10 wt%, Si: 2.5 to 4.5
wt%, Mn: 0.05 to 1.5 wt% and Bi: 0.005 to 0.050 wt
% And S and / or Se as a main inhibitor element: less than 0.010 wt%, sol.Al: 0.015 to 0.050 wt%
And N: 0.005 to 0.015 wt%, and Cu: 0.05 to 0.5 wt%, Sn: 0.05 to 0.05% as an inhibitor reinforcing element.
0.5 wt%, Sb: 0.005 to 0.10 wt% Mo: 0.005 to 0.10 wt%
And B: molten steel containing one or more selected from 0.001 to 0.01 wt% is made into a slab by continuous casting, and then the steel slab is heated to 1250 ° C. or less, and then hot-rolled by hot rolling. A rolled sheet was subjected to hot-rolled sheet annealing as needed, and after pickling, cold rolling was performed once or twice or more including intermediate annealing to obtain a final sheet thickness, which also served as primary recrystallization. After decarburizing annealing, and then applying an annealing separator containing MgO as a main component, a secondary recrystallization and purification treatment is performed by final finish annealing.
Perform nitriding at any stage before the start of the next recrystallization,
A method for producing a grain-oriented electrical steel sheet, comprising a series of steps, wherein electromagnetic stirring is applied to molten steel in an unsolidified portion during continuous casting.

4. In the above 1, 2 or 3, the method for producing a grain-oriented electrical steel sheet having excellent magnetic properties is characterized in that the direction of application of the stirring force of the electromagnetic stirring is an alternating direction.

[0015] 5. In the above 1, 2, 3, or 4, the production of grain-oriented electrical steel sheets having excellent magnetic properties, characterized by further containing Cr: 0.05 to 0.50 wt% in the steel in order to produce a good forsterite film. Method.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The results of experiments which led to the present invention will be described below. Experiment 1 This experiment was performed to clarify the effect of Bi on secondary recrystallization. C: 0.06wt% (hereinafter simply abbreviated as%), Si: 3.25%,
Mn: 0.07%, S: 0.004%, Al: 0.027% and N: 0.
0090% based on molten steel containing Bi
Steel in various ranges was converted into a slab by continuous casting, heated to 1150 ° C, and then hot-rolled.
After forming a hot-rolled sheet of 2.2 mm thickness, it was subjected to hot-rolled sheet annealing at 950 ° C for 1 minute, quenching, pickling, cold-rolling to a 1.6 mm thickness by a tandem rolling mill, and Minute intermediate annealing, quenching, cold rolling including 200 ° C warm rolling is performed by a reverse rolling mill with a roll diameter of 80 mm.
Finished 0.22mm thick. Then, after performing decarburizing annealing at 840 ° C. for 2 minutes, the N content was 2% in an atmosphere of NH _3.
Nitrogen treatment until the concentration reaches 00 ppm, then apply an annealing separator mainly composed of MgO.
The temperature was raised to 10 ° C. at a rate of 10 ° C./h, and then finish annealing was performed in an atmosphere of nitrogen: 25% and hydrogen: 75% up to 1200 ° C. at a rate of 30 ° C./h. When the magnetic properties of the product sheets thus obtained were compared, no clear effect of the amount of added Bi on the magnetic flux density was observed.

Various investigations were conducted on the processing conditions in each step, and it was found that the presence or absence of the application of electromagnetic stirring during continuous casting had a strong effect on the magnetic flux density. In a method that does not require high-temperature slab heating, secondary recrystallization failure due to the slab structure after high-temperature heating is unlikely to occur.
It is expected that this has some influence on the magnetic properties.

Therefore, the relationship between the Bi content and the magnetic flux density when electromagnetic stirring was applied was investigated. The results obtained are shown in FIG. As shown in the figure, it was found that an extremely high magnetic flux density could be obtained in the range of 0.005 ≦ Bi ≦ 0.050% under the application of electromagnetic stirring. On the other hand, when the Bi content exceeds 0.050%, the magnetic flux density deteriorates as compared with the conventional material, and when the Bi content is less than 0.005%, it is only about the same as the conventional material.

When electromagnetic stirring is used to reduce the segregation of the center of the slab, it is common to apply one direction in which the stirring force increases, but the effect on the electromagnetic characteristics is more in the alternating direction. It turned out to be big.

Based on the above results, when the existence form of Bi was examined for slabs and hot-rolled sheets, it was found that the size of the Bi phase in the steel tended to be smaller as the Bi content was smaller and larger as the Bi content was larger. There was found. Even more surprisingly, it has been found that the size of the Bi phase becomes extremely small and is uniformly dispersed by the application of the magnetic stirring.

The reason for this is not clear, but Bi is hardly dissolved in the parent phase and has a higher specific gravity than iron, so that it is expected that aggregation and sedimentation are likely to occur during continuous casting.
At this time, it is considered that although the agglomeration rate is proportional to the concentration of Bi, when a stirring force acts on the molten steel, the tendency is suppressed. In any case, it was revealed that in the region of 0.005% or more where Bi exerts the inhibitor function effectively, Bi can be uniformly dispersed by applying magnetic stirring, and the magnetic properties are improved. As a result, the instability of the secondary recrystallization due to the conventional Bi addition has been eliminated, and the magnetic properties can be stabilized.

Experiment 2 Next, a intensive study was conducted on how to improve the forsterite film formation defect, which is another defect of the Bi-added material, and it was found that the addition of Cr to steel was extremely effective. It has been found. Hereinafter, the experimental results in the case where the amount of Cr added and that of Bi are added in combination will be described. C: 0.06%, Si: 3.30%, Mn: 0.08%, Se: 0.021%,
Sb: 0.025%, Bi: 0.025%, Al: 0.025% and N:
Based on molten steel containing 0.0085%, this base steel
Lab ingots with Cr added to 0.02, 0.05, 0.10, 0.2 and 0.5% were prepared. Next, the steel ingot was forged into a sheet bar having a thickness of 50 mm, heated to 1420 ° C., and then hot-rolled into a hot-rolled sheet having a thickness of 2.2 mm. Then, hot rolled sheet annealing at 950 ° C for 2 minutes
After pickling, it was cold-rolled to a thickness of 1.5 mm. Continue at 1050 ° C,
After 1 minute of intermediate annealing, a cold rolled sheet having a thickness of 0.22 mm is formed by cold rolling including warm rolling at 250 ° C., and then decarburized annealing is performed at 840 ° C. for 2 minutes, followed by annealing mainly containing MgO. After applying the separating agent, the temperature is raised to 850 ° C at a rate of 10 ° C / h in a nitrogen atmosphere, and then 1200 ° C in an atmosphere of 25% nitrogen and 75% hydrogen.
Finish annealing was performed by heating to 30 ° C. at a rate of 30 ° C./h.
Table 1 shows the results obtained by examining the magnetic properties and coating properties of the product sheet thus obtained. The coating properties were evaluated by applying a magnesium phosphate containing 50% colloidal silica as a coating agent, baking the coating at 850 ° C., and then winding the coating on a round bar to evaluate the peeling limit diameter of the coating.

[0023]

[Table 1]

As is clear from the table, 0.05 to 0.50%
It has been found that the addition of Cr does not impair the effect of improving the magnetic flux density of Bi, and the addition of 0.05% or more of Cr negates the effect of suppressing the formation of Bi and forms a good film. In addition, the formation of a good film brings about the effect of imparting tension to the steel sheet, and thus greatly contributes to the improvement of iron loss.

Although the effect of Cr as described above has not been clearly elucidated, it has been found that in the case of a steel material to which Cr has been added, the form of SiO ₂ formed on the surface layer of the decarburized annealed sheet has changed. Was confirmed.

Next, in the method for manufacturing a grain-oriented electrical steel sheet according to the present invention, constituent elements necessary for obtaining intended effects, and their preferred ranges and functions will be described in detail. First, the component composition range of the material will be described. C: If the C content exceeds 0.10%, the amount of γ transformation becomes excessive, the uniformity of the distribution of inhibitors such as MnSe and MnS precipitated during hot rolling is hindered, and the load of decarburization annealing also increases, resulting in decarburization. Defects are more likely to occur. On the other hand, if it is less than 0.03%, the effect of improving the structure cannot be obtained, and the secondary recrystallization becomes incomplete, and the magnetic properties are similarly deteriorated. Therefore, the C content was limited to the range of 0.03 to 0.10%.

Si: Si is an element useful for increasing electric resistance and reducing iron loss. For this purpose, it is necessary to contain 2.5% or more. However, if it exceeds 4.5%, the workability deteriorates, and it becomes extremely difficult to manufacture and process the product. Therefore, the Si content is limited to the range of 2.5 to 4.5%.

Mn; Mn is also a useful element for increasing electric resistance and improving hot workability at the time of production. At least 0.05% content is required for this purpose,
If it exceeds 1.5%, γ transformation is induced to cause deterioration of magnetic properties, so the Mn content is limited to the range of 0.05 to 1.5%.

Se, S; Se, S as an inhibitor component
Is preferably contained alone or in combination, and these precipitate as Mn compounds or Cu compounds in steel.
In the case of normal high-temperature slab heating, 0.010% or more is required in either case of single addition or combined use in order to maintain the effect of suppressing normal grain growth. It is harmful because it cannot be dissolved to form a coarse precipitate. Therefore, the content of S and / or Se in the case of high-temperature slab heating is set in the range of 0.010 to 0.040%. At this time, Mn / (Se
If (+ S) is smaller than 2.5, grain boundary cracks and edge roughness increase significantly during hot rolling, so that Mn / (Se + S) ≧ 2.5 is practically preferable. On the other hand, when the slab heating at a high temperature is omitted, the smaller the content of Se and S, the lower the solid solution temperature, so that it works well. Therefore, the content in this case should be 0.010% or less.

Al, N: When the final cold rolling reduction is 80% or more, the secondary recrystallization temperature becomes extremely high. Therefore, in addition to the above-mentioned elements, the steel contains an inhibitor component which is stable at a high temperature. It is necessary and essential to include Al and N as inhibitor components. Al is 0.015 to 0.050%
Must be included. This is because the Al content is 0.015
%, The amount of precipitated AlN is insufficient, and
This is because secondary recrystallization cannot be obtained, while if it exceeds 0.050%, it becomes difficult to uniformly disperse the particles in a size that functions as an inhibitor. N is 0.0
It is necessary to contain more than 05%. However, 0.015%
If N is exceeded, it gasifies in the steel and causes defects such as blisters. Therefore, N should be contained in the range of 0.005 to 0.015%.

Bi: addition of Bi, which is one of the features of the present invention,
In addition, when Bi is added less than 0.005%, the expected effect cannot be obtained when added in combination with Cr. On the other hand, when Bi exceeds 0.050%, uniform dispersion becomes difficult, so Bi is 0.005 to 0.050%.
In the range described above. The Bi additive material has not been put into practical use until now because a defect of suppressing the forsterite film was inevitable. The forsterite film is formed by a solid-phase reaction between MgO in the annealing separator and SiO ₂ formed on the surface of the decarburized annealed sheet. It has been known. Bi strongly suppresses the oxidation reaction and greatly changes the form of SiO ₂ formed on the decarburized annealed sheet. Therefore, it is expected that it was difficult to form a coating by extension of the conventional technique.

Cr: In this case, a film can be formed for the first time by adding Cr in combination. The reason is that Cr has the effect of counteracting the oxidation suppression effect of Bi and has the effect of favorably improving the SiO ₂ morphology of the decarburized annealed plate, or has the effect of accelerating the forsterite formation reaction, or both. It is thought to be. If the effect is less than 0.05%, the effect is not sufficient, while if it exceeds 0.50%, the effect reaches saturation and the cost increases, so the Cr content is limited to the range of 0.05 to 0.50%.

Cu, Sn, Sb, Mo, B; Cu, Sn, Sb, Mo, and B are all known inhibitors and have an auxiliary function of enhancing the suppressing power. Is preferred. Suitable contents for this are 0.05 to 0.5% for Cu and Sn and 0.005 to 0.10 for Sb and Mo.
% And B are 0.001 to 0.01%.

As for other additive elements, for example, Ni,
Since the addition of Co or the like has the effect of improving the surface properties of the steel sheet, it is advantageous to appropriately include it.

A slab is manufactured by continuous casting from molten steel adjusted to the above-mentioned preferable component composition. At this time, in order to suppress the agglomeration of Bi due to solidification of the molten steel, a flow accompanied by forcible movement by electromagnetic stirring is performed. It is very important to impart the molten steel to the molten steel. Frequency: 1
~ 10Hz, magnetic field strength: 0.05 ~ 0.1T, pole pitch: 100
A range of about 700 mm is preferable.

If the Bi phase dispersed in the molten steel is solidified and settled during continuous casting, uniform dispersion of Bi cannot be obtained, so that secondary recrystallization in a good orientation is not stabilized and causes a variation as a whole. As a result, the effect of adding Bi cannot be obtained. The reason is that Bi is hardly dissolved in molten steel, so it exists in a dispersed state as a single phase, and since it has a higher specific gravity than molten steel, it is expected that remarkable aggregation and sedimentation are likely to occur,
It is considered that Bi is non-uniform during rapid solidification of molten steel by continuous casting.

As is well known, the linear secondary recrystallization failure caused by the coarse and non-uniform crystal structure of the slab after high temperature heating is caused by the slab crystal grain size. It has been effective to apply electromagnetic stirring to an appropriate position for the purpose of making the particles uniform and fine. In this regard, when high-temperature heating of the slab is not required, there is no point in using electromagnetic stirring for the purpose of controlling the slab structure. However, in Bi-added steels, it is extremely effective to newly prevent the aggregation and sedimentation of the Bi phase to improve the magnetic properties.Therefore, it is extremely useful to use electromagnetic stirring for this purpose.
It is clear that such an effect on the Bi phase acts similarly even in the case of a composition requiring high-temperature heating.

Further, the position where the electromagnetic stirring is applied is not from the viewpoint of controlling the crystal grain size of the slab, but the aggregation and the Bi phase.
It is determined from the viewpoint of suppressing sedimentation. From this point of view, such as electromagnetic stirring of the mold or electromagnetic stirring of the strand, the closer to the meniscus is more suitable, but if too close, the risk of breakout due to fluctuations in the molten steel surface and the thinned solidified shell thickness increases, It is desirable that the solidified shell thickness is at least 1/20 of the slab thickness at the developed position.

Further, as to the direction in which the electromagnetic stirring is applied, it is more effective to apply the electromagnetic stirring in an alternating direction in which the stirring direction changes periodically, rather than in one direction for the purpose of reducing center segregation. The reason for this is that when the stirring direction is changed, aggregation of the Bi phase is more difficult to occur.

In the hot rolling step, usually after slab heating,
A hot-rolled coil is formed by hot rolling. At this time, when MnS or MnSe is contained as an inhibitor and slab heating at a high temperature is required, the slab heating temperature needs to be 1350 ° C. or higher. This is because if the slab heating temperature is less than 1350 ° C, the solid solution of the inhibitor will not be sufficient and Mn (Se +
S), because a fine and uniform dispersed precipitation state of AlN cannot be obtained. On the other hand, when components that require a high temperature for solution treatment, such as Se and S, are limited and slab heating at a high temperature is omitted, the slab heating temperature is set at 1250 ° C. where grain growth does not occur after heating.
The following conditions are important conditions for homogenizing the hot-rolled structure and improving the magnetic properties. In addition, at the time of hot rolling, it is possible to add a known technique such as a thickness reduction process or a width reduction process for homogenizing the structure before and after slab heating as needed.

In the cold rolling step, a so-called one-time cold rolling method in which the final thickness is obtained by one cold rolling after the hot rolled sheet annealing,
In addition, any of the so-called two-time cold-rolling method in which the first cold-rolling, the intermediate annealing, and the cold-rolling a plurality of times after the hot-rolled sheet annealing is performed as necessary can be employed. Regarding the rolling reduction of the cold rolling, the rolling of the first rolling of the two-time cold rolling method is set to 15 to 60% as conventionally known. If the rolling reduction is less than 15%, the mechanism of rolling recrystallization does not work and the crystal structure cannot be homogenized, while if it exceeds 60%, the texture is accumulated and the effect of the second rolling is reduced. This is because it cannot be obtained. The rolling reduction in the final rolling is 80-90.
% Is desirable. When the rolling reduction exceeds 90%, secondary recrystallization becomes difficult.
This is because the orientation of the next recrystallized grain cannot be obtained and the magnetic flux density of the product deteriorates.

For hot rolled sheet annealing or intermediate annealing,
If the annealing temperature is excessively low, the frequency of the (110) grains serving as nuclei for secondary recrystallization in the recrystallized structure after rolling is insufficient, and a secondary recrystallized structure with a good orientation cannot be obtained.
In order to obtain the strength of (110) grains, it is necessary to coarsen the crystal structure after annealing of the hot-rolled sheet to a certain size or more. For this purpose, it is preferable to heat to a temperature of 900 ° C. or more. Regarding the upper limit of the annealing temperature, Mn (Se
+ S), since it is important not to re-dissolve AlN or to grow Ostwald, it is preferable to set the temperature to 1200 ° C. or lower.
Further, the cooling process of the annealing is not particularly limited, but a quenching treatment is performed from the viewpoint of increasing the solute C in the steel after annealing, or a quenching low temperature for precipitating fine carbide in the steel. Performing the holding process is effective in improving the magnetic properties of the product. A known means for increasing the oxidizing property of the annealing atmosphere and decarburizing the surface layer of the steel sheet is also effective.

Further, the final cold rolling is carried out in a known manner.
Warm rolling at ~ 350 ° C or 10 ~ 100 ° C at 350 ° C
The aging treatment between passes for up to 60 minutes is useful for improving the texture of the primary recrystallization, and therefore, the adoption of the present invention also provides more preferable results. In addition, after the final cold rolling, it is also advantageous to perform a process of providing a linear groove on the surface of the steel sheet for magnetic domain refining as is known.

The steel sheet having the final thickness as described above is
After performing decarburization and primary recrystallization annealing by a known method,
After applying an annealing separator containing MgO as a main component to the steel sheet surface, it is subjected to final finish annealing.At that time, adding a Ti compound or including Ca or B in the annealing separator is
There is an effect of further improving the magnetic characteristics, and a favorable result can be obtained.

In the final finish annealing, it is desirable to increase the temperature in an atmosphere containing H ₂ from at least 900 ° C. during the temperature increase. In other words, the H ₂ atmosphere plays an important role in the formation of oxides and nitrides in the film formed during final finish annealing, and enhances the reducibility especially in the middle to late stages of annealing at 900 ° C or higher. It is effective. After the final finish annealing, after removing the unreacted separating agent, the surface of the steel sheet is coated with an insulating coating to make the product, but if necessary, the steel sheet surface may be mirror-finished before coating, or A tension coating may be used as the coating. Furthermore, the coating baking process of the coating may also serve as the flattening process. In addition, in order to obtain an iron loss reduction effect on the steel sheet after the secondary recrystallization, a known domain refining treatment, that is, plasma jet or laser irradiation is applied to a linear region, or a linear concave region is provided by a projection roll. Can be performed.

[0046]

EXAMPLES Example 1 C: 0.07%, Si: 3.30%, Mn: 0.065%, Se: 0.018
%, Sb: 0.045%, Al: 0.025%, N: 0.0088%, Bi:
0.020%, Cr: 0.20%, Cu: 0.10% and Mo: 0.012%
When the molten steel having a composition of Fe and unavoidable impurities was formed into a slab by continuous casting, electromagnetic stirring was applied to the molten steel in the mold under various conditions. Then
The obtained continuous cast slab was heated to 1400 ° C. in an induction heating furnace, and hot-rolled into a hot-rolled sheet having a thickness of 2.6 mm.
C. and wound on a coil. Then, the temperature was raised to 1150 ° C,
Soaking time: After hot-rolled sheet annealing for 90 seconds, quenched at 25 ° C / s, pickled, 0.35 by a combination of cold rolling and 200 ° C warm rolling
A cold rolled sheet having a thickness of mm was finished by one rolling. Then, after degreasing, decarburizing annealing was performed at 850 ° C for 4 minutes.
After applying an annealing separator containing 2% of SrSO ₄ and 5% of TiO ₂ to the steel sheet surface, the final finishing annealing is performed until 850 ° C with N ₂
Temperature rises at a rate of 30 ° C / h in 25% from 850 ° C to 1050 ° C
In a mixed atmosphere of N ₂ and 75% H ₂ , the temperature was raised at a rate of 12.5 ° C./h,
Then, the temperature was raised to 1200 ° C. at a rate of 25 ° C./h in H ₂ and 1200 ° C.
, And then cooled down to 600 ° C in H ₂ ,
Was subjected to a process of lowering the temperature in an Ar atmosphere. Then, after removing the unreacted annealing separating agent, magnesium phosphate containing 50% colloidal silica was applied as a tension coating, and baked at 850 ° C. to obtain a product. Table 2 shows the results obtained by examining the magnetic properties and coating properties of the product sheet thus obtained.

[0047]

[Table 2]

As shown in the table, according to the present invention, Bi and
In the case of containing Cr in a complex and applying electromagnetic stirring at the time of continuous casting, both good magnetic properties and coating properties are obtained.

Example 2 C: 0.08%, Si: 3.35%, Mn: 0.075%, Se: 0.020
%, Sb: 0.025%, Al: 0.025%, N: 0.0095% and
Bi: Contain 0.030%, the balance is molten steel with the composition of Fe and unavoidable impurities.
Magnetic stirring was applied to the molten steel in the mold under various conditions. Next, the obtained steel slab is subjected to 13 heating in an induction heating furnace.
The sheet was heated to 80 ° C., hot-rolled into a hot-rolled sheet having a thickness of 2.6 mm, and then wound around a coil at 500 ° C. Then, the temperature was raised to 1150 ° C, soaking time: after annealing the hot-rolled sheet for 90 seconds, quenched at 25 ° C / s, pickled, and 0.30 mm thick by a combination of cold rolling and 200 ° C warm rolling. Was finished by one rolling. Next, after degreasing, decarburizing annealing is performed at 850 ° C. for 3 minutes, and then an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, and then as final finishing annealing in N _{2 to} 850 ° C. 30 ℃ / h
Temperature from 850 ° C to 1050 ° C with 25% N ₂ and 75% H ₂
The temperature was raised at a rate of 12.5 ° C. / h in a mixed atmosphere of, then the temperature was raised to 1200 ° C. at a rate of 25 ° C. / h in H _2, then held for 8 hours at 1200 ° C., in H ₂ up to 600 ° C. Temperature from 600 ℃ to Ar
A process of lowering the temperature in an atmosphere was performed. As in this example, Bi
On the other hand, for steel containing no Cr, the formation of the forsterite film is insufficient, so after the final finish annealing, the unreacted annealing separating agent is removed, followed by washing with hydrochloric acid and then magnesium dichromate and A semi-organic coat mainly composed of an emulsion resin was baked at 300 ° C, making it a magnetic shield material with good workability. Table 3 shows the results of examining the magnetic flux density and the magnetic permeability of the product plate thus obtained.

[0050]

[Table 3]

As shown in the table, when Bi is contained in an appropriate amount and electromagnetic stirring is applied during continuous casting according to the present invention, both good magnetic flux density and magnetic permeability can be obtained. Was.

Example 3 C: 0.075%, Si: 3.35%, Mn: 0.070%, S: 0.004
%, Cu: 0.20%, Sn: 0.20%, Al: 0.028%, N: 0.00
Contains 70%, Bi: 0.025% and Cr: 0.25%, with the balance being
When molten steel having a composition of Fe and inevitable impurities was formed into a slab by continuous casting, electromagnetic stirring was applied to the molten steel in the mold under various conditions. Next, the obtained steel slab was heated to 1150 ° C., hot-rolled into a 2.4 mm thick hot rolled sheet, and then wound around a coil at 600 ° C. Then 95
The temperature was raised to 0 ° C, and the soaking time was 25 seconds after annealing the hot rolled sheet for 90 seconds.
After quenching at a rate of ° C./s, pickling and finishing the first cold rolling to an intermediate sheet thickness of 1.8 mm. Then, it was subjected to intermediate annealing at 1050 ° C for 60 seconds, quenched at 30 ° C / s, and then warm rolled at 250 ° C.
Finished to a final thickness of 27mm. Then, after degreasing, 8
After decarburizing annealing at 30 ° C. for 3 minutes, the N content was increased to 0.0180% by nitriding. Then 0.2% Ca
1.5% Sr (OH) ₂ in magnesia containing 0.05% B
%, 8% TiO ₂ added to the surface of the steel sheet, and then the final finish annealing is performed at up to 900 ° C in N ₂ at 30 ° C / h.
Temperature from 900 ℃ to 1050 ℃ 25% N ₂ and 75% H ₂
The temperature was raised at a rate of 12.5 ° C. / h in a mixed atmosphere of, then the temperature was raised to 1200 ° C. at a rate of 25 ° C. / h in H _2, it was kept 1200 ° C. Te 8 hours, in H ₂ up to 600 ° C. , And the temperature was lowered from 600 ° C. in an N ₂ atmosphere. After removing the unreacted annealing separating agent, aluminum phosphate containing 50% colloidal silica was applied as a tension coating, baked at 850 ° C, and a plasma jet was applied at 7.5 mm pitch as a domain refining process. The product was irradiated. Table 4 shows the results obtained by examining the magnetic properties of the product sheet thus obtained.

[0053]

[Table 4]

As is clear from the table, all the magnetic films obtained according to the present invention have good magnetic properties.

Example 4 When molten steel having the composition shown in Table 5 was formed into a slab by continuous casting, electromagnetic stirring was applied to the molten steel in the mold in an alternating direction. Next, the obtained slab was heated to 1430 ° C., then hot-rolled into a hot-rolled sheet having a thickness of 2.2 mm, and wound around a coil at 550 ° C. Then, the temperature was raised to 1000 ° C., soaking time: after annealing the hot-rolled sheet for 60 seconds, quenched at 20 ° C./s, pickled, and finished in an intermediate sheet thickness of 1.6 mm by the first cold rolling. . Then, the temperature is raised to 1100 ° C, after 60 seconds of intermediate annealing, quenched at 40 ° C / s, and 200 ° C warm rolling is performed in the second cold rolling including aging treatment at 300 ° C during rolling. As a result, a final thickness of 0.23 mm was obtained. Then, after degreasing, a magnetic domain refinement treatment was performed with a width of 50 μm: 20
μm grooves are formed in a line at an angle of 10 ° from the coil width direction at a pitch of 3 mm repeated in the coil longitudinal direction.
For 2 minutes. Then, after applying an annealing separator containing MgO, SrSO ₄ 2% and TiO ₂ 8%, to the steel sheet surface, the final finish annealing is performed at 30 ° C. in N ₂ up to 850 ° C.
temperature from 850 ° C to 1050 ° C with 25% N ₂ and 75%
The temperature was raised at a rate of 12.5 ° C. / h in a mixed atmosphere of H _2, then H ₂
The temperature was raised to 1200 ° C. at a rate of 25 ° C. / h at medium, after holding for 8 hours at 1200 ° C., the temperature was decreased in H ₂ to 600 ° C., N ₂ from 600 ° C.
A process of lowering the temperature in an atmosphere was performed. Then, after removing the unreacted annealing separating agent, magnesium phosphate containing 60% colloidal silica was applied as a tension coating, and baked at 840 ° C. to obtain a product. Table 6 shows the results obtained by examining the magnetic properties and coating properties of the product sheet thus obtained.

[0056]

[Table 5]

[0057]

[Table 6]

As shown in Table 6, when an appropriate amount of Bi is contained according to the present invention and electromagnetic stirring is applied during continuous casting, both excellent magnetic properties and coating properties are obtained. ing.

Example 5 When molten steel having the composition shown in Table 7 was formed into a slab by continuous casting, electromagnetic stirring was applied to the molten steel in the mold in an alternating direction. Next, the obtained slab was heated to 1400 ° C., then hot-rolled into a hot-rolled sheet having a thickness of 2.0 mm, and wound around a coil at 650 ° C. Then, the temperature was raised to 1000 ° C., soaking time: after annealing the hot-rolled sheet for 60 seconds, quenched at 20 ° C./s, pickled, and finished with an intermediate sheet thickness of 0.6 mm by the first cold rolling. Thereafter, the temperature was raised to 1000 ° C., after intermediate annealing for 60 seconds, rapidly cooled at 30 ° C./s, and 0.23% by the second cold rolling.
Finished to a final thickness of mm. Then, after the degreasing treatment, a magnetic domain subdivision treatment was performed with a width of 50 μm and a groove of 20 μm was formed in a line at an angle of 10 ° from the coil width direction at a pitch of 3 mm repeated in the longitudinal direction of the coil. For a minute. After that, 2% of SrSO ₄ and TiO ₂ were added to MgO.
After applying an annealing separator with 1.5% added to the steel sheet surface,
As final finish annealing, raise the temperature to 850 ° C at a rate of 30 ° C / h in N ₂ , hold at 850 ° C for 50 hours, then 12.5 ° C / h in H ₂ atmosphere
Then, the temperature was raised to 1200 ° C. at the rate described above, the temperature was maintained at 1200 ° C. for 8 hours, then the temperature was lowered to 600 ° C. in H ₂ , and the temperature was lowered from 600 ° C. in an N ₂ atmosphere. Then, after removing the unreacted annealing separating agent, aluminum phosphate containing 60% colloidal silica was applied as a tension coating, and baked at 800 ° C. to obtain a product. Table 8 shows the results obtained by examining the magnetic properties and coating properties of the product sheet thus obtained.

[0060]

[Table 7]

[0061]

[Table 8]

As shown in Table 8, all of those obtained according to the present invention have both excellent magnetic properties and coating properties.

[0063]

As described above, according to the present invention, the effect of improving the magnetic properties of Bi can be maximized without deteriorating the film properties, and as a result, a high magnetic flux density direction having extremely excellent iron loss properties can be obtained. Enables the production of conductive electrical steel sheets.

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of the presence or absence of electromagnetic stirring on molten steel and the Bi content on magnetic flux density.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C22C 38/02 C22C 38/02 38/60 38/60 H01F 1/16 H01F 1/16 B (72) Invention Person Kunihiro Senda 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. Inside the steelworks (72) Inventor Michio Komatsubara 1-chome, Kawasaki-dori, Mizushima, Kurashiki-shi, Okayama Pref. JA04 LA01 NA00 RA04 SA02 TA02 5E041 AA02 AA19 BC01 CA02 HB05 HB07 HB11 NN01 NN18

Claims (5)

[Claims] 1. A molten steel containing 0.03 to 0.10% by weight of C, 2.5 to 4.5% by weight of Si and 0.005 to 0.050% by weight of Bi and other known inhibitor elements is formed into a slab by continuous casting. In a method for producing a grain-oriented electrical steel sheet comprising a combination of hot rolling, cold rolling and heat treatment, a grain-oriented magnetic sheet excellent in magnetic properties characterized by applying electromagnetic stirring to molten steel in an unsolidified portion during continuous casting. Steel plate manufacturing method. 2. The composition contains 0.03 to 0.10% by weight of C, 2.5 to 4.5% by weight of Si, 0.05 to 1.5% by weight of Mn and 0.005 to 0.050% by weight of Bi, and contains S and / or as a main inhibitor element.
Se: 0.010 to 0.040 wt%, sol. Al: 0.015 to 0.050 wt% and N: 0.005 to 0.015
wt.%, and as inhibitor reinforcing elements, Cu: 0.05 to 0.5 wt%, Sn: 0.05 to 0.5 wt%, Sb: 0.005 to 0.10 wt% Mo: 0.005 to 0.10 wt% and B:
Molten steel containing one or more selected from 0.001 to 0.01 wt% is made into a slab by continuous casting, and this steel slab is heated to 1350 ° C or more, and then hot-rolled into a hot-rolled sheet. If necessary, hot-rolled sheet annealing is performed, and after pickling, cold rolling is performed once or twice or more including intermediate annealing to obtain a final sheet thickness, and then decarburization annealing combined with primary recrystallization And then apply an annealing separator mainly composed of MgO, and then perform a secondary recrystallization and purification treatment by final finish annealing. A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by applying electromagnetic stirring to molten steel in an unsolidified portion. 3. C: 0.03 to 0.10 wt%, Si: 2.5 to 4.5 wt%, Mn: 0.05 to 1.5 wt% and Bi: 0.005 to 0.050 wt%, and S and / or S as a main inhibitor element.
e: less than 0.010 wt%, sol.Al: 0.015 to 0.050 wt% and N: 0.005 to 0.015
wt.%, and as inhibitor reinforcing elements, Cu: 0.05 to 0.5 wt%, Sn: 0.05 to 0.5 wt%, Sb: 0.005 to 0.10 wt% Mo: 0.005 to 0.10 wt% and B:
Molten steel containing one or more selected from 0.001 to 0.01 wt% is made into a slab by continuous casting, and this steel slab is heated to 1250 ° C or less, and then hot-rolled into a hot-rolled sheet. If necessary, hot-rolled sheet annealing is performed, and after pickling, cold rolling is performed once or twice or more including intermediate annealing to obtain a final sheet thickness, and then decarburization annealing combined with primary recrystallization And then apply an annealing separator containing MgO as a main component, subject it to a secondary recrystallization and purification treatment by final finish annealing, and further to any of the processes from the end of hot rolling to the start of secondary recrystallization. In a method for producing a grain-oriented electrical steel sheet comprising a series of steps of performing a nitriding treatment in a stage, a grain-oriented electrical steel sheet having excellent magnetic properties characterized by imparting electromagnetic stirring to molten steel in an unsolidified portion during continuous casting. Manufacturing method. 4. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the direction of application of the stirring force of the electromagnetic stirring is an alternating direction. 5. The magnetic property according to claim 1, wherein the steel further contains Cr: 0.05 to 0.50 wt% in order to form a good forsterite film. Manufacturing method of grain-oriented electrical steel sheet.