JP3154935B2 - Manufacturing method of low iron loss mirror-oriented unidirectional electrical steel sheet with high magnetic flux density - 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 electrical steel sheet mainly used as an iron core of a transformer or other electric equipment. In particular, {110}
<001> B, which is a highly developed Goss direction
A method for producing iron-added high magnetic flux density grain-oriented electrical steel sheets and improving the core loss characteristics industrially at low cost by effectively introducing a method for producing a surface-oriented electrical steel sheet and a means for mirror-polishing the surface and a means for subdividing magnetic domains. Pertains to the method.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is mainly used as a soft magnetic material for core materials of transformers and other electric equipment, and must have good magnetic properties such as excitation properties and iron loss properties. No. As an index indicating the excitation characteristics, usually, a magnetic flux density B ₈ (magnetic flux density at a magnetic field strength of 800 A / m) is used. As an index indicating the iron loss characteristics,
W _17/50 (iron loss per unit weight when magnetized to 1.7 T at 50 Hz) is used.

[0003] The grain-oriented electrical steel sheet contains 0.8 to 4.
8%, secondary recrystallization occurs in the final annealing step at a temperature of 900 ° C. or more in the final stage of the manufacturing process. Obtained by developing tissue. Among them, the magnetic flux density B ₈ those with more excellent excitation characteristics 1.88T is called high flux density grain-oriented electrical steel sheet.

[0004] As a typical method for producing a high magnetic flux density electromagnetic steel sheet, Japanese Patent Publication No. 40-15644 and Japanese Patent Publication No. 51-1
No. 3469 and the like. It can be said that the high magnetic flux density unidirectional electrical steel sheet currently produced on a worldwide scale is produced based on the above two patents. However, the magnetic flux density B _{8 of the} product based on the above patent is 1.88 T to at most 1.
It is about 95T, for example, only showing a value of about 95% of the saturation magnetic flux density of 3% Si steel of 2.03T.
In recent years, social demands for energy savings and resource savings have become increasingly severe, and demands for reduction of iron loss and improvement of magnetic properties of the grain-oriented electrical steel sheets have also become fierce.

Generally, the magnetic flux density B ₈ increases and the crystal grains of the product tend to increase. Even if B ₈ is increased by using a high magnetic flux density magnetic steel sheet, the magnetic domain width increases by 180 °. And the expectation of further improvement in iron loss is not desired in metallurgy. From this viewpoint, a magnetic domain control technique such as laser irradiation has been proposed as a technical technique for reducing iron loss in Japanese Patent Publication No. 57-2252 and Japanese Patent Publication No. 58-59.
No. 68, JP-A-58-26405 and the like. In addition, since the reduction of iron loss by this method is caused by strain introduced by laser irradiation, it cannot be used for a wound core transformer that requires strain relief annealing after forming into a transformer. Kosho 6
JP-A-2-53579, JP-B-63-44804, JP-B-04-48847 and the like, introduce a groove by, for example, a gear-type roll after finish annealing,
A method is disclosed in which fine grains are formed by applying processing strain to subdivide magnetic domains.

However, the method of forming a groove on the surface of a steel sheet by machining a gear-type roll or the like involves the necessity of crushing a surface ceramic layer called a primary film (glass film) of a grain-oriented electrical steel sheet. Wear is high, which causes a problem in manufacturing cost.

On the other hand, when the movement of the magnetic domains of the steel sheet subjected to the magnetic domain refining treatment was observed in detail, it was found that some of the statically subdivided magnetic domains did not move. In order to further reduce the iron loss value of grain-oriented electrical steel sheets, in addition to the magnetic domain refining technology according to the above method, a technology that eliminates factors that hinder the movement of magnetic domains (magnetic domain activation technology)
Need to be introduced. In other words, it is effective to remove the glass coating or the like on the steel sheet surface, which is a major factor that hinders the movement of the magnetic domains, and to make the surface mirror-finished.

As a means for achieving this, a method of removing the glass coating by pickling or the like after finish annealing and then performing chemical polishing or electrolytic polishing to mirror-finish the surface is disclosed in, for example, Japanese Patent Application Laid-Open No. 64-64.
No. 83620 is disclosed. However, methods such as chemical polishing and electrolytic polishing are capable of processing small sample materials at the laboratory level, but for industrial scale operation, chemical concentration control, temperature control, and provision of pollution equipment are required. However, there is a major problem in this respect, and the production cost is increased by adding such a step, so that it has not yet been put to practical use.

[0009] On the other hand, the present applicant has developed a method for mirror-finishing the surface of a steel sheet on an industrial scale at low cost (for example, JP-A-5-033052 and JP-A-6-093335). These are to remove oxygen generated on the steel sheet surface during decarburization annealing, or to regulate the oxygen amount by controlling the atmosphere of decarburization annealing, then apply alumina as an annealing separator on the steel sheet surface and perform finish annealing, The purpose is to achieve both the mirror finishing of the steel sheet surface and the formation of secondary recrystallization with a high magnetic flux density.

[0010] These techniques are suitable mainly for lowering the cost of manufacturing magnetic domain control materials for wound iron core transformers, because the wear of gear rolls and the like is small when machining the steel sheet surface for magnetic domain refining treatment. ing. For example, Japanese Patent Laid-Open No. 7-2589
No. 45 discloses that when a ceramic film is not present on the steel sheet surface after the finish annealing as in the related art, the life of the gear roll is increased by 5 times or more.

However, with the maturation of peripheral technologies such as magnetic domain control and mirror finishing, it becomes easy to reduce iron loss using a high magnetic flux density electromagnetic steel sheet, and it is further necessary to aim for ultra-low iron loss electromagnetic steel sheet. A material having a high magnetic flux density is expected as an essential condition. On the other hand, the present inventors have found that by including Bi in the molten steel of the grain-oriented electrical steel sheet, the magnetic flux density can be reduced by industrial means from the level of the conventional high magnetic flux density unidirectional magnetic steel sheet to the ultra-high magnetic flux density. JP-A-6-8814 and JP-A-6-8814 disclose a method for increasing the level of grain-oriented electrical steel sheets.
88173.

For the first time, the magnetic flux density B ₈ is 1.
Ultra high magnetic flux density unidirectional magnetic steel sheets exceeding 96T can be produced relatively stably on a factory scale. The present invention is not merely a combination of the conventional method of manufacturing an ultra-high magnetic flux density unidirectional magnetic steel sheet by the Bi addition method and the method of manufacturing a low iron loss unidirectional magnetic steel sheet by a mirror finishing technique, but also the disadvantages in industrialization of the former and the stability of the latter. It provides a very effective way of solving the facilitation.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a conventional Bi
By organically combining the addition technology and the mirror finishing technology, it is possible to stably manufacture ultra-high magnetic flux density unidirectional mirror-oriented magnetic steel sheet material with extremely high magnetic flux density on a factory scale, and furthermore develop a magnetic domain control technology. By combining
It is an object of the present invention to produce an ultra-low iron loss mirror-oriented electrical steel sheet having extremely low iron loss at low cost.

[0014]

The features of the present invention are as follows. (1) C: 0.02 to 0.1% by weight, Si: 2.
0 to 4.8%, acid-soluble Al: 0.012 to 0.050
%, N: 0.030 to 0.0150%, Bi: 0.00
Of molten steel containing 0.55 to 0.03%, the balance being Fe and unavoidable impurities, hot rolling, and then 6%.
Cold rolling is performed once or twice or more including intermediate strong annealing of 5 to 95% to obtain a final sheet thickness. After decarburizing annealing, nitriding is performed or not. In the method for producing a grain-oriented electrical steel sheet comprising a step of performing recrystallization finish annealing, decarburizing annealing is performed in an atmosphere gas having an oxidation degree in which Fe-based oxides are not formed, or an oxide generated by decarburizing annealing is subjected to acid treatment. A method for producing a mirror-oriented unidirectional magnetic steel sheet having a high magnetic flux density, wherein after removing by washing, alumina is applied as an annealing separating agent so that the surface of the steel sheet after finish annealing is made into a mirror state.

(2) A method for producing a specular grain-oriented electrical steel sheet having a low iron loss, wherein a magnetic domain refinement treatment is performed by introducing local distortion into the steel sheet according to the above (1). (3) A grain-oriented electrical steel sheet having a low iron loss, in which after forming a tension film by a coating treatment on the steel sheet according to the above (1), a magnetic domain refinement treatment is performed by introducing local strain. Manufacturing method.

(4) The steel sheet described in (1) above is perpendicular to the rolling direction or at an interval of 45 degrees within a range of 45 degrees from the perpendicular.
Forming continuous, discontinuous or point-like local grooves in the range of 10 to 300 μm in width and 10 to 300 μm in depth and 5 to 50 μm in depth, together with forming a tension film by coating treatment to subdivide magnetic domains. A method for producing a mirror-oriented electrical steel sheet having a low iron loss, characterized by comprising:

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The present inventors have disclosed JP-A-6-8814 and JP-A-6-8814.
As disclosed in Japanese Patent No. 88173, etc., by conducting experiments in a laboratory, Bi is added to and contained in a material for a grain-oriented electrical steel sheet having aluminum nitride as a main inhibitor, so that a commercially available high magnetic flux density is obtained. B of electrical steel sheet
₈ = 1.95T or more, far exceeding 1.93T,
An ultra-high magnetic flux density unidirectional magnetic steel sheet of 2T was obtained. Thereafter, the magnetic flux density B ₈ of the steel sheet was carried out factory tests in coil form so as to stably produced on an industrial scale a so-called ultra-high magnetic flux density grain-oriented electrical steel sheet described above 1.95 T, the magnetization of the manufacturing conditions and product A close examination of the properties and properties of the primary coating revealed that there were problems in some cases.

That is, variations in the magnetization characteristics for each coil position and peeled portions of the primary film were found inside the coil. In order to solve this problem, the finish-annealed coil was developed, and the positional relationship between the secondary recrystallization structure and the state of formation of the primary film was examined in detail. while recrystallization structure hardly ultra-high magnetic flux density equiaxed grains manner is obtained, the secondary recrystallized grains has good primary coating also exhibited stretch particle is characteristic of Bi additive in the portion of the coil end portion, B ₈ It turned out that 1.95 T or more was obtained stably.

By the way, in order to realize an ultra-high magnetic flux density, the Bi content in the steel must be a certain amount or more. On the other hand, it is necessary to vaporize and remove the Bi in the steel from the surface of the steel plate during the finishing / purification annealing. is there. For example, in the case of a laboratory-scale plate-like small test piece, it is easy to remove Bi during finish annealing. However, in the case of manufacturing on a factory scale, it is premised that the steel sheet wound in a coil shape is annealed in a box-shaped finish annealing furnace, so that gas permeability is particularly poor inside the coil,
It becomes difficult to remove Bi from steel, and it is difficult to obtain an ultra-high magnetic flux density.

Further, it was presumed that a good primary film was hardly obtained because Bi vapor concentrated between the steel sheets had an adverse effect on the formation of the primary film. Conversely, since the gas permeability is relatively good at the coil end, it is easy to obtain an ultra-high magnetic flux density.
The primary film is presumed to be good because the vapor also does not concentrate. That is, it is difficult to remove Bi particularly at the center of the coil by annealing with a coil foam on a factory scale, and Bi remaining between steel sheets is presumed to be harmful to the formation of a primary film. Conducted the following experiment in order to quantitatively grasp the influence of gas permeability between the plates during the secondary recrystallization finishing annealing by adding Bi.

C: 0.05%, Si: 3.25%, M
n: 0.10%, S: 0.007%, P: 0.025
%, Acid-soluble Al: 0.029%, N: 0.007%,
Cr: Silicon steel containing 0.12% is melted, and the Bi content is set to 0, 0.007%, 0.013%, and 0.025%. Heating,
Immediately after extraction, hot-rolled to a thickness of 2.3 mm, and water-cooled after hot-rolling.
It was kept at 50 ° C. Thereafter, the hot-rolled sheet was annealed at a temperature of 1120 ° C. for 30 seconds, then at 900 ° C. for 90 seconds, air-cooled to 750 ° C., and quenched into 80 ° C. water.

Next, it is pickled and then 250 mm on the way to 0.23 mm.
The sample was cold rolled by aging at 5 ° C. 5 times. Subsequently, in a mixed gas of nitrogen and hydrogen, the oxidation degree is 0.40 (PH ₂ O).
/ PH ₂ ) by adjusting the introduced steam and decarburizing
Next, recrystallization annealing was performed, and subsequently, nitriding annealing was performed in an NH ₃ atmosphere so that the N content became 200 ppm. After applying an annealing separator containing MgO as a main component, secondary recrystallization finish annealing was performed.

To see the effect of gas permeability between the plates,
A sample in which about 50 sheets of 0 mm × 500 mm steel sheets are stacked is packed in an iron thin film and inserted into a furnace. Then, a gas in a wet hydrogen atmosphere having a nitrogen partial pressure of 25% is introduced, and the flow rate is set to 1, 5, 10, and 1
The temperature was raised to 1200 ° C. at 15 ° C./hr with 5 Nm ³ / min, followed by 2 hours at 1200 ° C. in a dry hydrogen atmosphere.
A zero-hour purification annealing was performed. At this time, the furnace volume of the annealing furnace was 0.06 m ³ . Status and relationship between the magnetic flux density B ₈ of the primary coating obtained steel sheet and furnace Flow rate of introduced gas shown in FIG.

As a result, the ultra-high magnetic flux density unidirectional electrical steel sheet to which Bi is added is higher than that of the conventional high magnetic flux density unidirectional electrical steel sheet using aluminum nitride as a main inhibitor.
It was found that if the gas permeability during the finish annealing was poor, the primary coating was adversely affected, and it was difficult to obtain a high magnetic flux density. Although the present inventors have not explained the mechanism of the primary film peeling and the deterioration of B ₈ , when Bi in the steel evaporates from the surface after diffusing to the surface during the finish / purification annealing, the Bi vapor is mixed with the base iron. It is presumed that the primary film peels from the ground iron because it expands at the interface of the primary film.

On the other hand, when the primary coating peels off, A
It is presumed that this affects the formation of l ₂ O ₃ and the behavior of nitrogen, which affects the inhibitor behavior mainly of AlN, and changes the secondary recrystallization process. In order to solve these problems, for example, the flow rate of gas introduced into the annealing furnace in the factory may be increased, but the furnace volume of the box-type annealing equipment on the factory scale is usually about 30 m ³ , and it is simply calculated. However, an introduction gas of 500 times the introduction gas flow rate of the laboratory annealing furnace for steam is required.

This imposes a burden on equipment costs and is difficult from the viewpoint of cost per unit, etc., that is, in order to stably produce ultra-high magnetic flux density unidirectional magnetic steel sheets on an industrial scale by adding Bi. Found that the application of a mirror finishing technique that does not rely on the formation of a primary film may be effective.

Hereinafter, the results of the experiment which led to the present invention will be described. The present inventors performed the following experiment in order to quantitatively grasp the influence of the temperature gradient during the secondary recrystallization finishing annealing due to the addition of Bi. C: 0.05%, Si: 3.25%, M
n: 0.10%, S: 0.007%, P: 0.025
%, Acid-soluble Al: 0.029%, N: 0.007%,
Cr: Silicon steel containing 0.12% is melted, and the Bi content is reduced to 0%, 0.007%, 0.013%, 0.025%.
After dispensing and casting into slabs, each was heated to 1150 ° C., immediately after extraction, hot-rolled to a thickness of 2.3 mm, cooled with hot water, and kept at 550 ° C.

Thereafter, the hot-rolled sheet was annealed at a temperature of 1120 ° C. for 30 seconds and subsequently at 900 ° C. for 90 seconds, air-cooled to 750 ° C., and rapidly cooled in 80 ° C. water. Next, it was pickled and cold rolled with aging treatment at 250 ° C. five times in the middle to 0.23 mm. Subsequently, in a mixed gas of nitrogen and hydrogen,
6 and the oxygen content of the steel sheet is 20
Perform decarburization and primary recrystallization annealing so that it becomes 0 ppm or less,
Subsequently, nitriding annealing was performed in an NH ₃ atmosphere so that the N content became 200 ppm.

After applying an annealing separator mainly composed of Al ₂ O ₃ , a second recrystallization finish annealing was performed. In the same manner as in the above experiment, a sample in which about 50 100 mm × 500 mm steel sheets were stacked was packed in an iron thin film, inserted into the furnace, a dry nitrogen atmosphere was introduced into the furnace, and the flow rate was set to 1, 5, 10 , 15,
The temperature was raised to 1200 ° C. at 15 ° C./hr with Nm ³ / min, followed by purification annealing at 1200 ° C. for 20 hours. Oxygen of the steel sheet obtained as furnace Flow rate of introduced gas and shows the relationship between the magnetic flux density B ₈ in FIG.

As is apparent from FIG. 2, by applying the mirror finishing technique, the magnetic flux density was not affected by the gas flow rate during the finish annealing, and the effect of improving the magnetic flux density by adding Bi was stably obtained. As described above, since the secondary recrystallization process is not easily affected by the gas permeability variation in the position inside the coil, being not affected by the gas flow rate during the finish annealing is advantageous in the production by the finish annealing using the coil foam on a factory scale. It indicates that there is. In addition, in FIG. 2, since the amount of oxygen adhering to the mirror-finished steel sheet in a small amount decreases along with the amount of Bi added, it is expected that the addition of Bi has an effect of promoting mirror polishing.

Further, the present inventors performed strain relief annealing on the sample obtained in FIG. 2 at a temperature of 850 ° C. for 2 hours, and then performed a laser irradiation process at 5 mm intervals in a direction perpendicular to the rolling direction to obtain a magnetic domain. Tried to control. The magnetic flux density B ₈ of the material (before magnetic domain control) and the iron loss W after magnetic domain control of the obtained sample
FIG. 3 shows the _17/50 relationship.

The following can be seen from FIG. First, by adjusting the Bi content of 0.007% or perform Bi added to 0.025%, the magnetic flux density B ₈ is expressed more ultra-high magnetic flux density grain-oriented electrical steel sheet 1.96T, also the magnetic domain control In combination with the above, an ultra-low iron loss electromagnetic steel sheet can be obtained. Also, B ₈ and W
_The straight line indicating the _17/50 relationship decreases with the addition of Bi, and it can be seen that the iron loss of the Bi-added material is further improved from the iron loss expected from the improvement of the magnetic flux density.

This is presumed to be due to the effect of adding Bi as described above with reference to FIG.
The present invention is not merely a combination of the conventional method of manufacturing an ultra-high magnetic flux density unidirectional magnetic steel sheet by the Bi addition method and the method of manufacturing a low iron loss unidirectional magnetic steel sheet by a mirror finishing technique, but also the disadvantages in industrialization of the former and the stability of the latter. It provides a very effective way of solving the facilitation.

Next, the components necessary for the present invention and the reasons for limiting them will be described. In the present invention, the components contained in the material are, by weight, C: 0.02 to 0.1%, Si:
0 to 4.8%, acid-soluble Al: 0.012 to 0.050
%, N: 0.030 to 0.0150%, Bi: 0.00
0.05 to 0.03%, the balance being Fe and unavoidable impurities, and these are essential components and the other components are not limited.

As a basic production method, a production method using (Al, Si) N as a main inhibitor by Komatsu et al. (For example, Japanese Patent Publication No. 62-45285) or a main inhibitor using AlN and MnS by Taguchi / Sakakura et al. (For example, Japanese Patent Publication No. 40-15644)
Should be applied.

C is a γ-region open type element, and is an important element that forms a texture that is advantageous for secondary recrystallization due to the α → γ transformation or the presence of solute C in the steps from hot rolling to decarburizing annealing. It is. If C is less than 0.02%, α → γ transformation does not occur, which is not preferable. On the other hand, if it exceeds 0.1%, a load is applied to the decarburization annealing step, and the cost is increased.

Si is an important element for increasing electric resistance and reducing iron loss. If the content exceeds 4.8%, the material is easily cracked during cold rolling, and cannot be rolled. On the other hand, if it is less than 2.0%, the eddy current loss of the product increases, and the α → γ transformation occurs at the time of finish annealing, and the directionality of the crystal is impaired.

Acid-soluble Al combines with N to form AlN and is a main inhibitor constituent element for producing high magnetic flux density unidirectional magnetic steel sheets. If it is less than 0.012%, the amount is insufficient, and the inhibitor strength is insufficient. On the other hand, 0.050
%, AlN becomes coarse, and as a result, the inhibitor strength decreases, so that secondary recrystallization does not occur.

N contained in the material forms nitrides such as Si and Al, and has an effect particularly as an inhibitor of the primary recrystallization when low-temperature slab heating is assumed. The N content is determined from the heat history of the process and the necessary primary annealing temperature from the viewpoint of controlling the primary recrystallized grain size. On the other hand, in the case where AlN is finely dispersed in the previous stage by high-temperature slab heating, it is necessary to consider the conditions of the secondary recrystallization annealing. 0.030%
If it is less, the cost of the smelting stage will increase due to denitrification,
If the content exceeds 0.0150%, a defect called a blister occurs, so the content is set in the range of 0.030% to 0.0150%. As other inhibitor constituent elements, Mn, S,
Se, V, N, B, Nb, Sn, Cu, Ti, Zr, T
a, Mo, Sn and the like can be added in combination.

Bi is an element necessary for obtaining an ultra-high-speed density, and the effective content of Bi is in the range of 0.0005 to 0.03%. If it is less than 0.0005%, the effect is slight, and if it exceeds 0.03%, the effect of improving the magnetic flux density is saturated and a crack occurs at the end of the hot rolled sheet, so the upper limit is limited to 0.03%.

Next, the manufacturing process conditions will be described. The material for an ultra-high magnetic flux density grain-oriented electrical steel sheet whose components have been adjusted as described above can be used as the material of the present invention regardless of any ordinary melting method or ingot making method. Next, the magnetic steel sheet material is rolled into a hot-rolled coil by ordinary hot rolling.

A production method using (Al, Si) N as a main inhibitor by Komatsu et al. (For example, JP-B-62-452)
No. 85) from the viewpoint of securing the temperature during hot rolling.
1280 over 100 ° C and no complete solution of AlN
After performing heating at a temperature of not more than ℃, hot rolling is performed. A production method using AlN and MnS as main inhibitors by Taguchi and Sakakura (for example, Japanese Patent Publication No. 40-15644).
In Japanese Unexamined Patent Publication (Kokai) No. H11-260, hot rolling may be performed after heating at a temperature of 1300 ° C. or higher at which complete solution is formed.

Subsequently, the final sheet thickness is obtained by one-stage cold rolling or a plurality of stages of cold rolling including intermediate annealing. However, since a unidirectional magnetic steel sheet having a high magnetic flux density is obtained, the rolling rate of the final cold rolling is reduced. (In the case of one-stage cold rolling, the rolling ratio thereof) is preferably a strong reduction of 65 to 95%. The rolling rates of stages other than the final rolling need not be particularly defined. Further, in order to strengthen AlN, annealing and cooling may be performed before final cold rolling. Annealing is performed in a temperature range of 750 to 1200 ° C. for 30 seconds to 30 minutes, and this annealing is effective for enhancing the magnetic properties of the product. It is advisable to decide whether or not to take into account the desired product characteristic level and cost.

The cold-rolled sheet rolled to the final product thickness is subjected to primary recrystallization annealing and a wet atmosphere of hydrogen or a mixed atmosphere of hydrogen and nitrogen for the purpose of removing carbon contained in steel.
Decarburization annealing is performed in a temperature range of 30C for 30 seconds to 30 minutes. In this decarburization annealing, Fe-based oxides (Fe ₂ SiO ₄ ,
One of the points of the present invention is that annealing is performed at a degree of oxidation that does not form FeO or the like, and alumina is applied as an annealing separator. For example, decarburization annealing is usually performed 80
In the temperature range of 0 ° C. to 850 ° C., by adjusting the degree of oxidation of the atmospheric gas (PH ₂ O / PH ₂ ) <0.15, the generation of Fe-based oxides can be suppressed.

However, if the degree of oxidation is too low, the decarburization rate will be low, which is not desirable from an industrial point of view. Taking these both into consideration, the degree of oxidation of the atmospheric gas (PH ₂ O / PH ₂ ): 0.0 in the temperature range of 750 to 900 ° C.
It is preferable to anneal in the range of 1 to 0.15. The annealing temperature is determined mainly from the viewpoint of obtaining an optimum primary recrystallized grain size.

When it is necessary to strengthen the (Al, Si) N inhibitor in the decarburized annealed sheet, or when (Al, S
i) In a production method using N as a main inhibitor (for example, Japanese Patent Publication No. 62-45285), a nitriding treatment is performed. The method of the nitriding treatment is not particularly limited, and there is a method of performing the nitriding treatment in an atmosphere gas having a nitriding ability such as ammonia. Nitrogen may be nitrided in an amount of 0.005% or more, desirably the equivalent of Al in steel as a total nitrogen amount.

When these decarburized annealed sheets are wound around a coil form, alumina as an annealing separating agent is dry-coated with a water slurry or an electrostatic coating method. When applying with a water slurry, it is preferable to adopt, for example, a method disclosed in JP-A-7-62427.

The alumina annealing separator is extremely effective when producing a Bi-added ultra-high magnetic flux density unidirectional magnetic steel sheet on a factory scale by using a coal foam. The present invention provides an ultra-high magnetic flux density by the conventional Bi-adding method. This is an extremely effective combination of iron reduction and iron loss by mirror surface finishing technology by alumina coating. This coil is finish-annealed to perform secondary recrystallization and purification of nitride. Secondary recrystallization is disclosed in
As disclosed in Japanese Patent No. 58929, performing at a predetermined temperature range by means such as holding at a constant temperature is effective in increasing the magnetic flux density.

After the completion of the secondary recrystallization, 100% hydrogen is applied to purify impurities such as nitrides and smoothen the surface.
Anneal at a temperature of 0 ° C. or higher. After the final annealing, the excess annealing separating agent is continuously removed, and then continuous tension annealing for correcting coil winding and the like is performed, and at the same time, an insulating film coating is applied and baked. At this time, if necessary, the steel sheet is subjected to magnetic domain refining treatment such as laser irradiation, mechanical groove formation, and tension film coating. In the present invention, since the magnetic flux density is increased by adding Bi and the secondary recrystallized grain size is largely controlled, the magnetic domain refining treatment is effective from the viewpoint of improving iron loss characteristics. There is no particular limitation on the method of magnetic domain subdivision.

In the case where magnetic domain subdivision is performed by introducing local distortion, for example, a method of irradiating a laser beam described in Japanese Patent Publication No. 57-2252 or the like,
A method for performing plasma flame irradiation described in Japanese Patent No. 51511 and Japanese Patent Publication No. 6-45824 may be used.

In the case where magnetic domains are subdivided by forming local grooves, a gear roll method (for example, Japanese Patent Publication No. 4-48847) is used.
Publication) and a mold pressing method (for example, Japanese Patent Publication No. 6-63037).
JP-A-5-69284 and resist ink etching method (JP-B-46673, JP-B-3-69968). A method using chemical etching or electrolytic etching may be employed.
The grooves formed in the steel sheet are perpendicular to the rolling direction or within a range of 45 degrees from the perpendicular, and the interval is preferably 2 to 10 mm from the viewpoint of reducing iron loss.

The shape of the groove may be continuous, discontinuous or point-like. The width and depth of the groove are 10 to 30 respectively.
The ranges of 0 μm and 5 to 50 μm are preferable from the viewpoint of reducing iron loss. When the width of the groove is reduced, the groove tends to be a starting point when bending with a small radius of curvature. In addition, if the width of the groove is increased, the magnetic flux density decreases. Similarly, if the depth of the groove is too large, the magnetic flux density will decrease.

As the tension coating, for example, a coating liquid mainly composed of colloidal silica and aluminum phosphate disclosed in JP-A-48-39338;
A method of baking a coating solution mainly containing colloidal silica and magnesium phosphate according to JP-A-79442 or a coating solution mainly containing alumina sol and boric acid according to JP-A-6-65754 is adopted. Good.

[0054]

【Example】

(Example 1) C: 0.05%, Si: 3.3%, Mn:
0.1%, S: 0.01%, acid-soluble Al: 0.03
%, N: 0.008%, as basic components (A: Bi added) Bi: 0.01% and (B: conventional method) Bi: 0%
After smelting a level of silicon steel and dispensing it into
The material was heated to 200 ° C. and hot-rolled to a sheet thickness of 2.3 mm immediately after the extraction. Thereafter, it was pickled and cold rolled to 0.23 mm. This cold-rolled sheet was annealed at a temperature of 830 ° C. for 100 seconds in a mixed gas of nitrogen and hydrogen at a degree of oxidation (C: mirror surface) of 0.1 and (D: conventional method) of 0.44 for primary recrystallization. . Then, by annealing in an ammonia atmosphere, the amount of nitrogen was increased to 0.02% to strengthen the inhibitor.

These steel sheets are then coated with (C: mirror-finished) alumina (Al ₂ O ₃ ) and (D: conventional method) magnesia (MgO) with a water slurry, and then laminated to form a steel sheet having a low gas flow rate. Finish annealing was performed on the base. After forming grooves with a width of 50 μm and a depth of 15 μm on these samples in a direction of 10 degrees from the direction perpendicular to the rolling direction with a gear roll, a coating liquid mainly containing colloidal silica and phosphate was applied. Bake at 850 ° C. for 2 minutes. After measuring the magnetic properties of these samples, strain relief annealing was further performed at 800 ° C. for 4 hours. Table 1 shows the magnetic properties of the obtained products.

[0056]

[Table 1]

Example 2 Si: 3.3% by weight, M
n: 0.1%, C: 0.05%, S: 0.007%, acid-soluble Al: 0.03%, N: 0.008%, Sn:
0.05% as a basic component, (A: Bi added) Bi:
Melting two levels of silicon steel of 0.01% and (B: conventional method) Bi: 0%, dispensing and casting each to a slab, heating to 1200 ° C., and immediately after extraction to 2.3 mm sheet thickness. Hot rolled.
The cold-rolled sheet which was pickled and cold rolled to 1.4 mm was annealed at a temperature of 1120 ° C. for 30 seconds and at 900 ° C. for 90 seconds, air-cooled to 750 ° C., quenched in water at 80 ° C., and finally cooled to a final thickness of 0.1 mm. Cold rolled to 15 mm. The degree of oxidation of this cold-rolled sheet in a mixed gas of nitrogen and hydrogen (C: mirror polishing method) 0.06, and (D: conventional method)
It was annealed at a temperature of 830 ° C. at 0.44 for 70 seconds to perform primary recrystallization. Then, by annealing in an ammonia atmosphere, the amount of nitrogen was increased to 0.025% to strengthen the inhibitor.

These steel sheets were then subjected to (C: mirror finishing)
After applying alumina (Al ₂ O ₃ ) and (D: conventional method) magnesia (MgO) with a water slurry, a steel sheet is laminated,
Finish annealing was performed under a low gas flow rate. After forming a groove having a width of 30 μm and a depth of 10 μm in a direction perpendicular to the rolling direction on the sample after the finish annealing by a photoetching method, a coating solution containing alumina sol and boric acid as main components is applied. Bake at 870 ° C. for 2 minutes. After measuring the magnetic properties of these samples, strain relief annealing was further performed at 800 ° C. for 4 hours. Table 2 shows the magnetic properties of the obtained products.

[0059]

[Table 2]

(Example 3) Si: 3.3% by weight, M
n: 0.07%, C: 0.07%, Se: 0.025
%, Acid-soluble Al: 0.028%, N: 0.008%,
Sb: 0.1% as a basic component, (A: Bi added) B
i: 0.01% and (B: conventional method) Bi-level silicon steels of 2% were melted, each of which was dispensed and cast into a slab, and then 1350
C., immediately after the extraction, hot-rolled to a thickness of 2.3 mm, and immediately cooled with water to room temperature. 1100 ° C
And then pickled, and cold rolled with aging treatment at 250 ° C. five times on the way to a final sheet thickness of 0.27 mm. This cold rolled sheet was oxidized in a mixed gas of nitrogen and hydrogen (A:
(Method of the present invention) 0.06 and (B: Conventional method) 0.44 to 8
Annealed at a temperature of 50 ° C. for 120 seconds for primary recrystallization.

These steel sheets were then subjected to (A: the method of the present invention)
After applying alumina (Al ₂ O ₃ ) and (B: conventional method) magnesia (MgO) with a water slurry, steel sheets were laminated and pressed in the thickness direction at 20 kg / mm ² , followed by finish annealing. These samples were coated with a coating solution containing colloidal silica and phosphate as main components and baked at 850 ° C. for 2 minutes. Thereafter, the surface of the steel sheet was irradiated with laser at intervals of 5 mm in a direction perpendicular to the rolling direction. Table 3 shows the magnetic properties of the obtained products.

[0062]

[Table 3]

(Example 4) C: 0.05%, Si: 3.
25%, Mn: 0.10%, S: 0.007%, P:
0.025%, acid-soluble Al: 0.029%, N: 0.
007%, Bi: 0.007%, and Cr: 0.12% are melted, cast into slabs, heated to 1150 ° C., and hot-rolled to 2.3 mm immediately after extraction. After hot rolling, it was cooled with water and wound up at 550 ° C. Then, the hot rolled sheet is
Annealed for 30 seconds at 900 ° C and 90 seconds at 900 ° C, 750 ° C
After air-cooling, the mixture was rapidly cooled in water at 80 ° C. Then after pickling,
Rolling was performed in 5 passes to 0.23 mm, and aging treatment was performed at 200 ° C. or more and 5 minutes or more on the way. Subsequently, decarburization and primary recrystallization annealing are performed in a mixed gas of nitrogen and hydrogen to obtain an oxidation degree of 0.1.
An atmosphere of 06 was performed at a temperature of 850 ° C. for 100 seconds, followed by nitriding annealing in an NH ₃ atmosphere so that the N content became 200 ppm.

The 5T coil to which the annealing separator containing alumina (Al ₂ O ₃ ) as a main component was applied was subjected to secondary recrystallization finish annealing in a box type annealing furnace. The temperature was raised to 1200 ° C. at a rate of 15 ° C./hr while flowing nitrogen into the furnace, and then purifying annealing was performed at 1200 ° C. for 75 hours while flowing hydrogen. Thereafter, while the coil was being developed in the continuous annealing line, the coil was inclined by 10 degrees from the direction perpendicular to the rolling direction to a width of 50 degrees.
After forming a groove in a tooth mold having a groove having a depth of 11 μm with a press, a coating liquid containing colloidal silica and phosphate as main components was applied and baked at 860 ° C. for 2 minutes. Sampling at five places of the obtained coil,
The measured Epstein value after annealing at 800 ° C. for 2 hours is:
1.97 T on average in magnetic flux density B ₈ and 0.6 in iron loss W _17/50
It was 1 W / kg.

[0065]

According to the present invention, the extremely high magnetic flux density achieved by the conventional Bi addition method and the low iron loss achieved by the mirror polishing technique using alumina coating are extremely effectively combined, so that the production is extremely stable and inexpensive in industrial production. In addition to obtaining a super magnetic flux density low unidirectional magnetic steel sheet, the iron loss characteristics after the magnetic domain refining treatment are extremely excellent, and it can be said that this is industrially extremely valuable.

[Brief description of the drawings]

[1] Figure showing the primary film-forming method (magnesia annealing separator agent), the finish annealing introducing gas flow rate and the magnetic flux density B ₈ and the relationship of the primary coating exfoliation area at the Bi content.

[FIG. 2] In the mirror polishing method (alumina annealing separating agent), the flow rate of the gas introduced into the finish annealing and the magnetic flux density B ₈ at each Bi content.
4 is a table showing the relationship between the steel sheet oxygen content.

FIG. 3 shows a relationship between a material magnetic flux density (before magnetic domain refining) B ₈ and a _core loss W _17/50 after magnetic domain refining when the sample obtained in FIG. 2 is subjected to magnetic domain refining treatment by laser irradiation. The chart shown.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shuichi Yamazaki 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Division (72) Inventor Norihito Abe 1 Fujimachi, Hirohata-ku, Himeji-shi Nippon Steel Corporation (56) References JP-A-7-118750 (JP, A) JP-A 5-279745 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21D8 / 12 C22C 38/00 303 C22C 38/06 H01F 1/16

Claims (4)

(57) [Claims] 1. C: 0.02-0.1% Si: 2.0-4.8%, acid-soluble Al: 0.012-0.050%, N: 0.030-0. 1150%, Bi: 0.0005-0.03%, the balance being cast from molten steel consisting of Fe and unavoidable impurities, hot-rolled, and then containing 65-95% final strong cold rolling1 One-way process consisting of performing a secondary recrystallization finish annealing with or without nitriding after performing cold rolling two or more times with or without intermediate annealing to obtain the final thickness and performing decarburizing annealing In the method for producing an electrical steel sheet, decarburizing annealing is performed in an atmosphere gas having an oxidation degree that does not form Fe-based oxides, or oxides generated by decarburizing annealing are removed by pickling, and then alumina is used as an annealing separator. By applying, the surface of steel sheet after finish annealing is mirror-like Method for producing a high specular grain-oriented electrical steel sheet magnetic flux density, characterized by a. 2. A method for producing a mirror-oriented unidirectional magnetic steel sheet having a low iron loss, wherein a magnetic domain refinement treatment is performed by introducing local distortion into the steel sheet according to claim 1. 3. A mirror surface unidirectional with low iron loss, wherein a magnetic domain refinement treatment is performed by introducing a local strain after forming a tension film by a coating process on the steel sheet according to claim 1. Manufacturing method of conductive electrical steel sheet. 4. The steel sheet according to claim 1, which is perpendicular to the rolling direction or at an interval of 2 to 10 m within a range of 45 degrees from the perpendicular.
m, forming a continuous, discontinuous or point-like local groove in a range of 10 to 300 μm in width and 5 to 50 μm in depth, and forming a domain film by forming a tension film by coating treatment. A method for producing a mirror-oriented unidirectional electrical steel sheet with low iron loss.