JP2019085632A - Grain-oriented electrical steel sheet and production method for the same - Google Patents

Abstract

To provide a method for achieving mirror formation at a high level without deterioration due to hysteresis loss while maintaining a high magnetic flux density.SOLUTION: A production method of a grain-oriented electrical steel sheet comprises a series of steps of: forming a cold rolled sheet having a final thickness by single cold rolling or multiple cold rolling with intermediate annealing of a steel material composed of C: 0.02-0.08% or less, Si: 2.5-4.5% and Mn: 0.03-0.30%, and the balance Fe with inevitable impurities; performing decarburization annealing which also serves as a primary recrystallization; and applying annealing separation agent thereto, followed by finish annealing. The oxygen basis weight is 0.8 g/mor less and the residual C content is 150 ppm or less on a surface of the steel sheet after the decarburization annealing. The finish annealing is carried out under a pressure of 10 Pa or less at a temperature of 500°C or more.SELECTED DRAWING: Figure 1

Description

The present invention is used as an iron core material of a large motor or generator, has no undercoat (glass coating) mainly composed of forsterite (Mg ₂ SiO ₄ ), has a low core loss and a high magnetic flux density The present invention relates to a method of manufacturing a magnetic steel sheet.

  Since a grain-oriented electrical steel sheet is mainly used as a core material of a transformer, it is strongly demanded that the magnetic properties be excellent, in particular that the iron loss be low. For this reason, the grain-oriented electrical steel sheet is subjected to decarburizing annealing that also serves as primary recrystallization annealing on a cold-rolled Si-containing steel sheet, and after applying an annealing separator containing MgO as a main ingredient, secondary annealing in finish annealing It is produced by a method in which the crystal grains are highly aligned to the {110} <001> orientation (so-called Goth orientation). Since the above-mentioned finish annealing requires about 10 days by combining the secondary recrystallization and the purification treatment for raising the temperature to a maximum temperature of about 1200 ° C., it is usually carried out by batch annealing carried out in a coiled state. There is.

During the final annealing, a subscale of SiO ₂ as a main component formed on the steel sheet surface during decarburization annealing, and annealing separating agent to a main agent the coated MgO on the steel sheet surface after decarburization annealing, MgO + SiO ₂ → A reaction of Mg ₂ SiO ₄ is caused to form a vitreous forsterite film on the surface of the steel sheet.

  Since the coating is hard, when the electromagnetic steel sheet is slitted by shearing or punched and formed into a core, the mold is abraded easily, so the mold is frequently polished or replaced I needed it. For this reason, improving the punchability of the die has also been an important issue of the grain-oriented electrical steel sheet.

  Furthermore, in recent years, the need to improve the magnetic properties has further increased, but in order to solve this, the method of smoothing the film-base iron interface and eliminating the pinning of the domain wall movement due to the rough surface has been intensively studied. ing. Specifically, it is necessary not to form the forsterite film as much as possible, and many methods therefor have been proposed.

For example, in Patent Document 1, a method of adding a chloride in the annealing separator is also used, and in Patent Document 2, after suppressing the oxygen per unit area after decarburizing annealing to a low level, the main agent of the annealing separator is used. Methods using Al ₂ O ₃ are disclosed respectively. Further, Patent Document 3 discloses a method of forming a low thermal expansion coating during finish annealing and peeling off the film by the stress acting between the base iron and the film.

Japanese Patent Application Laid-Open No. 09-49027 Japanese Patent Application Publication No. 08-269558 JP 10-8141 A

  However, according to the method described in Patent Document 1, although the film peels off in the low temperature region of finish annealing, the film formation reaction occurs again after the chloride ions are released outside the system in the high temperature region thereafter, so a sufficient mirror surface The problem was that no In addition, since the inhibitor components in the steel such as AlN and MnS are degraded by the influence of chloride, there is a problem that the secondary recrystallization behavior is changed and a high magnetic flux density can not be obtained. Furthermore, harmful chlorine gas is discharged at the time of finish annealing, which causes problems such as damage to gas piping and furnace body and an increase in processing cost for discarding the gas.

Although the method described in Patent Document 2 uses Al ₂ O ₃ to suppress the above reaction, in fact, Al ₂ O ₃ reacts with the internal SiO ₂ to form a thin film, and thus a sufficient mirror surface is obtained. reduction is can not be obtained, the hysteresis loss has occurred deteriorates fine Al ₂ O ₃ precipitated in the steel. Furthermore, the dew point of the annealing atmosphere must be lowered in order to reduce the amount of oxygen per unit area at the time of decarburization annealing, but at that time the decarburization also becomes defective and C remains to the final product, which causes the magnetic properties There was also a problem of aging deterioration.

  The method described in Patent Document 3 has a problem that the unevenness of the film remains as it is on the surface of the ground iron and the hysteresis loss is not sufficiently improved since the film is once peeled off and the film is peeled off.

  Besides these, many methods for mirror formation have been proposed, but it is difficult to say that all the problems such as the deterioration of the hysteresis loss and the remaining of the thin film as described above have been sufficiently solved. . In addition, from the recent increase in environmental concerns, in order to further improve the magnetic properties, techniques have been developed to incorporate various additive elements into the steel, and the use and discharge of harmful substances are being made with stricter environmental regulations. In order to be strictly regulated or to promote energy saving, the amount of use of high-grade electromagnetic steel sheets is increased, and it is therefore necessary to process a large number of lots, so that the finish annealing coil becomes large and nonuniformity in the coil increases. Environmental change has occurred. Under such conditions, it is more difficult in the prior art to achieve both mirror formation and high magnetic flux density over the entire length of the coil.

  The present invention has been made in view of the above-described circumstances, and proposes a method for achieving a high-level mirror finish without deterioration due to hysteresis loss while maintaining a high magnetic flux density.

First, an experiment that led to the development of the present invention will be described.
<Experiment 1>
A steel containing S: 0.06 mass%, Si: 3.4 mass%, Mn: 0.07 mass%, Al: 0.03 mass%, N: 0.007 mass% and Se: 0.02 mass% is melted, and a steel slab is cast by a continuous casting method. And then hot rolled to make a 2.2 mm thick hot rolled sheet, subjected to hot rolled sheet annealing at 1050 ° C. × 60 seconds, and then primary cold rolled to form an intermediate sheet thickness After being subjected to an intermediate annealing at 1100 ° C. for 80 seconds, the cold rolled sheet having a final thickness of 0.23 mm was obtained by warm rolling at 200 ° C.
Was then subjected to decarburization annealing _{50vol% H 2 -50vol% N 2} , PH 2 O / PH 2 holds 820 ° C. × 100 seconds under a humid atmosphere of 0.35. The amount of oxygen per unit area after decarburizing annealing at this time was 0.78 g / m ² , and the amount of residual C was 90 ppm.
Then, cordierite as annealing separator, using _{2MgO · 2Al 2 O 3 · 5SiO} 2, which applied to the surface of the steel sheet in a slurry, after drying, the temperature was raised up to 1200 ° C. at 20 ° C. / h Finish annealing for 5 hours. At this time, the atmosphere for finish annealing was adjusted by reducing the pressure after purging with N ₂ gas at normal temperature, and changing the atmospheric pressure from 10 ⁵ Pa to 0.01 Pa in a temperature range of 500 ° C. to 1200 ° C. The amount of oxygen per area (both sides of the steel plate), the amount of residual C and the magnetic flux density of the steel plate after finish annealing thus obtained were measured. The measurement results are shown in FIGS.

  As can be seen from FIG. 1, as the atmosphere pressure of finish annealing is lowered, the amount of oxygen per unit area after finish annealing is reduced to become mirror-like, and as shown in FIG. 2, decarburization is also improved. In particular, if the pressure is lower than 10 Pa, as shown in FIG. 1, the per-area oxygen coverage decreases to a satisfactory level as a filmless mirror material, and as shown in FIG. . As a result, as shown in FIG. 3, the magnetic flux density is also improved by setting the atmospheric pressure to 10 Pa or less.

  In order to clarify this cause, the chemical composition was analyzed about the sample finished annealing by atmospheric pressure 0.01 Pa and atmospheric pressure. The results at this time are shown in Table 1. At atmospheric pressure, N is rather high compared to the original component. C, Al and O decrease, but their weight loss is small. On the other hand, under the reduced pressure conditions, all of C, N and Al are 10 ppm or less, and O is also significantly reduced. Therefore, it can be said that the decrease in the concentration of these impurities is the main cause for the improvement of the magnetic characteristics and the realization of the mirror surface by the removal of the surface film.

The present inventors consider as follows the cause of the decrease in impurity concentration as described above.
First, nitrogen is rather increased at atmospheric pressure, presumably because the purged N ₂ gas infiltrated into the steel during finish annealing. However, depressurization suppresses the infiltration of these, and further depressurization causes the steel to volatilize and escape from the steel. The oxides formed by the decarburization annealing are similarly volatilized under reduced pressure and desorbed from the surface. At the same time, at low pressure, decarburization reaction is promoted, decarburization reaction occurs, and C is reduced. By these, mirrorization and purification are compatible.

In order to cause such surface reactions, it is essential that the annealing separator be a non-reactive substance. If it is something like MgO used conventionally, it will become an obstacle of denitrification and decarburization by forming Mg ₂ SiO ₄ on the surface. Non-reactive separating agents include, for example, materials such as silicates and aluminates. By using these, a film is not formed on the surface, and a decrease in the diffusion rate of C, Al or the like in steel can be suppressed. Furthermore, in combination with finish annealing under reduced pressure, purification is achieved as a result of these elements being easily discharged to the surface.
The present invention is based on the above experimental results, and the summary thereof is as follows.

1. In mass%,
C: 0.02 to 0.08% or less,
Si: 2.5 to 4.5% and
Mn: 0.03 to 0.30%
A steel material having the composition of the balance Fe and the inevitable impurities, and made into a final thickness cold-rolled sheet by cold rolling once or twice or more with intermediate annealing interposed, and decarburizing that doubles as primary recrystallization. A method for producing a grain oriented electrical steel sheet comprising a series of steps of applying annealing separators after annealing and finish annealing, wherein the coated amount of oxygen on the steel sheet surface after decarburizing annealing is 0.8 g / m ² or less And while making residual C amount into 150 ppm or less, the manufacturing method of the directionality electromagnetic steel sheet which performs the said finish annealing in the atmosphere whose pressure in 500 degreeC or more is 10 Pa or less.
Here, the oxygen coverage is the sum of the oxygen coverage on both the front and back sides of the steel sheet.

2. The annealing separator is at least 50% of one or more of Mg, Al, Mn, Zr, Ca, and Sr, or Mg, Fe, Ca, Mn, Ni, Zr, Co The method for producing a grain-oriented electrical steel sheet according to 1 above, which is any one or more aluminates and composite oxides thereof.

3. In addition to the above-mentioned component composition, the above-mentioned steel material is further in mass%,
Al: 0.010 to 0.040% and N: 0.003 to 0.012%
The manufacturing method of the directionality electromagnetic steel sheet as described in said 1 or 2 containing B.

4. In addition to the above-mentioned component composition, the above-mentioned steel material is further in mass%,
Se: 0.003 to 0.030% and S: 0.002 to 0.030%
The manufacturing method of the grain-oriented electrical steel sheet of said 1, 2 or 3 containing any 1 type or 2 types of.

5. In addition to the above-mentioned component composition, the above-mentioned steel material is further in mass%,
Ni: 0.01 to 1.50%,
Cr: 0.01 to 0.50%,
Cu: 0.01 to 0.50%,
P: 0.005 to 0.20%,
Sb: 0.005 to 0.20%,
Sn: 0.005 to 0.50%,
Bi: 0.005 to 0.10%,
Mo: 0.005 to 0.10%,
B: 0.0002 to 0.0025%,
Te: 0.0005 to 0.010%,
Nb: 0.001 to 0.010%,
V: 0.001 to 0.010%,
Ti: 0.001 to 0.010% and
Ta: 0.001 to 0.010%
The manufacturing method of the directionality electromagnetic steel sheet in any one of said 1-4 containing 1 type (s) or 2 or more types selected from among them.

6. The method for producing a grain-oriented electrical steel sheet according to any one of 1 to 5, wherein the surface area of the steel sheet after the finish annealing is 0.5 g / m ² or less and the residual C amount is 40 ppm or less.

According to the present invention, it is possible to manufacture a grain-oriented electrical steel sheet having a low core loss and a high magnetic flux density without having an undercoat film mainly composed of forsterite (Mg ₂ SiO ₄ ).

It is a figure which shows the relationship between the atmosphere pressure of finish-annealing, and an oxygen area weight. It is a figure which shows the relationship between the atmosphere pressure of finish annealing, and the amount of residual C. It is a figure which shows the relationship between the atmospheric pressure of finish annealing, and a magnetic flux density.

Next, the method for producing the grain-oriented electrical steel sheet of the present invention will be described.
First, component compositions of a steel material which is a starting material for producing a grain-oriented electrical steel sheet according to the present invention will be described in order. In addition, "%" display regarding the component composition shown below means "mass%" unless otherwise indicated.
C: 0.02 to 0.08%
If the content of C is less than 0.02%, the grain boundary strengthening effect of C is lost, and defects such as cracks in the slab occur, which cause problems in production. On the other hand, when it exceeds 0.08%, it becomes difficult to reduce to 0.005% or less where magnetic aging does not occur after final finish annealing. Therefore, C is preferably in the range of 0.02 to 0.08%. More preferably, it is in the range of 0.025 to 0.075%.

Si: 2.5 to 4.5%
Si is an element necessary to increase the specific resistance of steel and to reduce iron loss. This effect is not sufficient if it is less than 2.5%, while if it exceeds 4.5%, the processability is reduced and it becomes difficult to produce by rolling. Therefore, Si is made into 2.5 to 4.5% of range. Preferably, it is in the range of 2.8 to 4.0%.

Mn: 0.03 to 0.30%
Mn is an element necessary to improve the hot workability of steel. This effect is not sufficient if it is less than 0.03%, while if it exceeds 0.3%, the magnetic flux density of the product plate will be reduced. Therefore, Mn is in the range of 0.03 to 0.30%. Preferably, it is in the range of 0.04 to 0.20%.
Containing the above components, the balance is Fe and unavoidable impurities.

In the present invention, in addition to the above-described basic component composition, Al and N, or Al and N, and S and / or Se can also be contained in order to reinforce the grain growth suppressing power.
Al: 0.010 to 0.040%
Al is used as an inhibitor constituent element. When it is used, if it is less than 0.010%, the inhibitor effect is not sufficiently obtained, while if it exceeds 0.040%, the secondary recrystallization becomes unstable and the magnetic characteristics are largely dispersed. Therefore, it is preferable to make Al into 0.010 to 0.040%. More preferably, it is 0.015 to 0.030%.

N: 0.003 to 0.012%
N is an element which constitutes AlN of the inhibitor together with Al. If it exceeds 0.012%, surface defects such as blisters and holes occur, so the content is made smaller. The lower limit may be 0.003% or more in any of the cases where the nitrification treatment is performed or not performed in the middle of the manufacturing process. If it is less than this, even if the renitrification treatment is performed, the inhibitor inhibitory power is insufficient.
There is also a method which does not use AlN as an inhibitor, but in this case, it is necessary to suppress Al to less than 100 ppm and nitrogen to less than 50 ppm.
Besides this, it is also possible to use S or Se.

S: 0.002 to 0.030% or Se: 0.003 to 0.030%
S and Se can be used as an element which comprises inhibitors, such as MnSe and MnS, with above-mentioned Mn. The composite precipitation of these precipitates and AlN makes it possible to exert the suppressing power stably even at high temperatures of secondary recrystallization annealing. If S is less than 0.002% and Se is less than 0.003%, the suppressing power is insufficient and secondary recrystallization defects occur. Also, if S exceeds 0.03% or Se exceeds 0.03%, surface defects such as baldness occur. Therefore, it is in this range.

  In addition to the above components in the grain-oriented electrical steel sheet of the present invention, Ni: 0.01 to 1.50%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0.20%, for the purpose of further improving the magnetic properties. Sb: 0.005 to 0.20%, Sn: 0.005 to 0.50%, Bi: 0.005 to 0.10%, Mo: 0.005 to 0.10%, B: 0.0002 to 0.0025%, Te: 0.0005 to 0.010%, Nb: 0.001 to 0.010%, V One or more selected from 0.001 to 0.010%, Ti: 0.001 to 0.010%, and Ta: 0.001 to 0.010% may be appropriately added.

Next, the method for producing the grain-oriented electrical steel sheet of the present invention will be described.
After the steel having the above-described composition is melted in a conventional refining process, a steel material (slab) may be manufactured by a conventionally known ingot-slab rolling method or continuous casting method, or directly Thin cast pieces having a thickness of 100 mm or less may be produced by a casting method. The above-mentioned slab is heated to about 1350 ° C. and subjected to hot rolling according to a conventional method. In the case of thin cast pieces, hot rolling may be performed, or hot rolling may be omitted and the process may proceed to the subsequent steps.

  Next, the hot-rolled sheet obtained by hot rolling is subjected to hot-rolled sheet annealing as required. It is preferable to make the annealing temperature of this hot-rolled sheet annealing into the range of 800-1150 degreeC, in order to acquire a favorable magnetic characteristic. That is, if the temperature is less than 800 ° C., the band structure formed by hot rolling remains, making it difficult to obtain a primary recrystallization structure of sized grains, which may inhibit the development of secondary recrystallization. On the other hand, if the temperature exceeds 1150 ° C., the grain size after hot-rolled sheet annealing becomes too coarse, and there is also a possibility that it may be difficult to obtain a primary recrystallized structure of sized grains.

  The hot-rolled sheet (or the thin cast strip) after hot rolling or after hot-rolled sheet annealing is cold-rolled to a final thickness by two or more cold-rollings that sandwich one cold rolling or intermediate annealing. It will be a board. It is preferable to make the annealing temperature of the said intermediate annealing into the range of 900-1200 degreeC. If the temperature is less than 900 ° C., recrystallized grains after intermediate annealing become finer, and Goss nuclei in the primary recrystallized structure tend to be reduced, and the magnetic specification of the product plate tends to be lowered. On the other hand, if the temperature exceeds 1200 ° C., as in the case of hot-rolled sheet annealing, the crystal grains become too coarse, and it becomes difficult to obtain a primary recrystallized structure of sized grains.

  In addition, cold rolling (final cold rolling) to be the final plate thickness is performed by raising the steel plate temperature during cold rolling to 100 ° C. to 300 ° C., or 100 to 300 ° C. in the middle of cold rolling The application of one or more aging treatments at temperature is effective to improve the primary recrystallization texture and improve the magnetic properties.

Thereafter, the cold-rolled sheet having the final thickness is subjected to decarburization annealing which also serves as primary recrystallization annealing. The temperature is in the range of 700 ° C. to 900 ° C., and the time is in the range of 30 to 300 seconds. If the temperature of decarburization annealing is less than 700 ° C., or if the same time is less than 30 seconds, the primary recrystallized grain size is too small and the magnetic properties deteriorate, while if it exceeds 900 ° C. or exceeds 300 seconds, the primary grain size Becomes too large, and the magnetic properties also deteriorate.
In addition, pH ₂ O / pH ₂ in the atmosphere of decarburization annealing is about 0.1 to 0.4 in general. This is because, as described below, the amount of residual C and the amount of coated oxygen are optimized. If pH ₂ O / pH ₂ is lower than 0.1, the amount of residual C becomes too high, and if it is higher than 0.4, there is a fear that the coated amount of oxygen becomes too high.

  Here, in the steel sheet after decarburization annealing, it is necessary to adjust the amount of oxygen per unit area and the amount of residual C in an appropriate range. Even when the decarburization annealing is performed under the same atmosphere conditions, the amount of oxygen coverage and the amount of residual C after decarburization annealing differ depending on the material components and the sheet passing conditions before decarburization annealing.

First, the oxygen coverage after decarburization annealing is 0.8 g / m ² or less. If the weight per unit area of oxygen exceeds 0.8 g / m ² , oxygen remains even if the oxygen is volatilized and removed during finish annealing, which results in formation of a small amount of film, so this range is taken. In addition, the amount of residual C is 150 ppm or less. Because if this range is exceeded, it is not enough how C volatilizes and is removed during finish annealing, C remains on the product plate, and iron loss is deteriorated by magnetic aging during use in a transformer etc. It is for.

In order to bring the oxygen coverage and the residual C amount in the above-described range in the steel sheet after decarburizing annealing, the method of adjusting the atmosphere pH ₂ O / pH ₂ of the above decarburizing annealing is the simplest.

  Then, an annealing separator is applied, and at this time, as a main agent of the annealing separator, that is, 50% or more of the annealing separator, Mg, Al, Mn, Zr, Ca, and Sr any one or more of It is important to use any one or more aluminates of silicate, Mg, Fe, Ca, Mn, Ni, Zr, Co, and complex oxides thereof. By using these, film formation is not performed and uniform film elimination is realized. Furthermore, it is also possible to use additives for this.

  Additives include oxides such as Li, Na, K, Ca, Sr, Ba, Sb, Ti, B, Sn, Ni, Fe or Mg, hydroxides, sulfates, carbonates, nitrates, borates Any of chloride, sulfide and the like can be used. These may be added not only singly but also in combination. The addition amount is 0.5 to 15%. If the amount is less than this range, there is no effect, and if the amount is too large, the film may be formed thin because these become reaction sources. The balance of the above additives is preferably the main agent described above.

After applying the above-mentioned annealing separator to a steel plate, finish annealing is performed in the state which wound up the steel plate in the shape of a coil.
It is preferable to carry out the temperature of finish annealing at 800 ° C. or higher in order to develop secondary recrystallization. Further, in order to complete the secondary recrystallization, it is preferable to carry out at about 1050 ° C. or higher, and further, at 1100 ° C. or higher for purification.

It is extremely important to perform this finish annealing in an atmosphere under reduced pressure. That is, in order to reduce both the amount of oxygen per area and the amount of residual C of the steel sheet after finish annealing and to obtain excellent magnetic properties, as shown in FIGS. 1 and 2 above, the pressure of finish annealing at 500 ° C. or higher It is important to carry out in an atmosphere of 10 Pa or less. By performing finish annealing in such an atmosphere, a steel plate having an oxygen coverage of not more than 0.5 g / m ² and a residual C content of not more than 40 ppm can be obtained.

Here, the target for adjustment of oxygen coverage of the steel sheet after finish annealing: 0.5 g / m ² or less and residual carbon content: 40 ppm or less is the coating target, first, when the oxygen coverage is over 0.5 g / m ² , the coating The reason is that there is a problem that sufficient film elimination can not be achieved. On the other hand, if the amount of residual C exceeds 40 ppm, carbides are precipitated during use in a transformer, resulting in deterioration of iron loss due to magnetic aging.

  Furthermore, by performing finish annealing in an atmosphere under reduced pressure, a secondary recrystallized structure highly accumulated in the Goss orientation can be obtained simultaneously. Although the cause is not sufficiently understood, it is considered that recrystallization using a surface energy as a driving force is occurring by annealing in vacuum.

In the final annealing, although the atmospheric pressure may temporarily exceed 10 Pa due to the annealing separator and the volatilization gas for purification, it is desirable if the average atmospheric pressure at 500 ° C. or higher in the final annealing is 10 Pa or less. It is possible to achieve the property. On the other hand, the lower limit is not particularly limited, but the equipment cost is increased as the degree of vacuum is increased, and therefore, the lower limit is preferably 10 ⁻⁴ Pa or more.

  After the finish annealing, water washing, brushing, pickling and the like are performed to remove the unreacted annealing separator attached to the steel sheet surface. Then, a coating is applied and flattening annealing is performed. The temperature at this time is 800 ° C. to 900 ° C. If this temperature is lower than 800 ° C., the yield is lowered due to insufficient shape correction ability, and if it is carried out at a temperature higher than 900 ° C., the steel plate creeps and the iron loss is deteriorated. Is preferred.

  In addition, since the mirror-coated steel plate which does not have a film is obtained according to this invention, it is effective in depositing a ceramic film by methods, such as PVD and CVD, after that. It is also possible to subject the pretreatment such as PVD and CVD to electrolytic etching, chemical polishing and mechanical polishing. After these ceramic coatings are applied, conventional tension coatings can also be applied. Furthermore, in order to further reduce iron loss, it is also possible to perform magnetic domain refinement processing. As a processing method, a method of forming a groove in the final product plate, introducing a thermal strain or impact strain in a linear or point shape by laser irradiation or electron beam irradiation, as generally practiced, final It is possible to use a method of forming a groove by performing etching on the surface of the steel plate in an intermediate step, such as a steel plate cold-rolled to a plate thickness. By combining the mirror formation of the present invention and these magnetic domain refining methods, it is possible to significantly reduce iron loss.

C: 0.070%, Si: 3.43%, Mn: 0.08%, Se: 0.02%, Al: 0.02%, N: 0.007%, P: 0.02%, Sn: 0.05% and Bi: 0.02%, the balance being Fe and A steel slab consisting of unavoidable impurities is manufactured by a continuous casting method, heated to a temperature of 1350 ° C., and then hot-rolled to form a hot-rolled sheet having a thickness of 2.4 mm, hot-rolled sheet annealing at 1000 ° C. × 50 seconds And then perform an intermediate annealing at 1100 ° C for 20 seconds to obtain an intermediate plate thickness of 1.8 mm by primary cold rolling, and then finish the cold rolled sheet with a final plate thickness of 0.23 mm by secondary cold rolling. It was decarburized and annealed. Decarburization annealing was conducted held _{50vol% H 2 -50vol% N 2} , 840 ℃ × 100 seconds under a humid atmosphere with a dew point of 35 ° C.. The surface weight of oxygen on both sides of the steel plate at this time was 0.5 g / m ² , and the amount of C was 60 ppm.

  Subsequently, it was made into a slurry form using the annealing separator of A to I of Table 2 as an annealing separator, and it apply | coated and dried on the steel plate surface. Furthermore, finish annealing with a purification treatment at 1200 ° C. for 10 hours was applied. The pressure was adjusted so that the atmospheric pressure during finish annealing was 0.008 Pa on average at 500 ° C. or more until the purification temperature range. Thereafter, the unreacted separating agent is removed, a coating is applied, and flattening annealing is performed at 850 ° C. × 20 s under a furnace tension of 13.7 MPa to obtain a final product.

  The appearance of the film of the steel plate thus obtained, the surface area of oxygen after finish annealing, and the magnetic flux density are shown in Table 2. The steel sheet surface is uniformly mirror-polished and high magnetic properties are obtained regardless of which annealing separator is used.

Continuous casting of steel slab containing C: 0.06%, Si: 3.40%, Mn: 0.07%, Se: 0.02%, Cu: 0.06%, Sb: 0.03% and Cr: 0.03% and the balance Fe and unavoidable impurities And heated to a temperature of 1400 ° C and hot rolled to a hot-rolled sheet with a thickness of 2.4 mm, subjected to hot-rolled sheet annealing at 900 ° C for 50 seconds, and then by primary cold rolling The intermediate plate thickness was 1.5 mm, and after intermediate annealing at 1000 ° C. for 20 seconds, secondary cold rolling was performed to finish a cold-rolled plate having a final plate thickness of 0.20 mm and decarburizing annealing. In the decarburization annealing is maintained for 840 ° C. × 100 seconds, the atmosphere by performing with various changing the dew point at _{50vol% H 2 -50vol% N 2} , oxygen basis weight after decarburization annealing, various modifications residual C amount did.

Subsequently, the powder of A of Table 2 was made into a slurry form as an annealing separator, and it apply | coated and dried on the steel plate surface. Furthermore, finish annealing with a purification treatment at 1200 ° C. for 10 hours was applied. The atmosphere pressure of finish annealing was 0.002 Pa in an average of 500 ° C. or more and 1200 ° C.
Thereafter, the unreacted separating agent is removed, a coating is applied, and flattening annealing is performed at 850 ° C. for 20 seconds to obtain a final product.
The appearance of the film at this time, the amount of oxygen per unit area (both sides of the steel plate) after finish annealing, the amount of residual C and the magnetic flux density are shown in Table 3. By optimizing the amount of oxygen coverage and the amount of residual C after decarburization annealing, even more uniform film absence and high magnetic properties are obtained.

A steel ingot having various components shown in Table 4 was heated to a temperature of 1350 ° C. and hot-rolled to form a hot-rolled sheet having a thickness of 2.4 mm and subjected to hot-rolled sheet annealing at 1000 ° C. × 50 seconds After that, an intermediate plate thickness of 1.8 mm is obtained by primary cold rolling, and after intermediate annealing at 1100 ° C. for 20 seconds, secondary cold rolling is performed to finish a cold rolled sheet having a final thickness of 0.27 mm and decarburization. Annealed. Decarburization annealing changes the _{50vol% H 2 -50vol% N 2} , oxygen basis weight and the residual C amount after decarburization annealing by adjusting the dew point in the range of 40 ℃ ~55 ℃, 840 ℃ in humidified atmosphere It went by holding for 100 seconds.

Subsequently, the powder of I of Table 2 was made into a slurry form as an annealing separator, and it apply | coated and dried on the steel plate surface. Furthermore, finish annealing with a purification treatment at 1200 ° C. for 10 hours was applied. The atmosphere for finish annealing was performed under reduced pressure so that the average atmospheric pressure from 500 ° C. to 1200 ° C. was 0.0001 Pa. Thereafter, the unreacted separating agent is removed, a coating is applied, and flattening annealing is performed at 850 ° C. for 20 seconds to obtain a final product.
The appearance of the film at this time, the amount of oxygen per unit area after finishing annealing (both sides of the steel plate), the amount of residual C and the magnetic flux density are shown in Table 4. When the oxygen coverage after decarburization annealing is within the range of the present invention, more uniform film absence and high magnetic properties are obtained.

Claims (6)

In mass%,
C: 0.02 to 0.08% or less,
Si: 2.5 to 4.5% and
Mn: 0.03 to 0.30%
A steel material having the composition of the balance Fe and the inevitable impurities, and made into a final thickness cold-rolled sheet by cold rolling once or twice or more with intermediate annealing interposed, and decarburizing that doubles as primary recrystallization. A method for producing a grain oriented electrical steel sheet comprising a series of steps of applying annealing separators after annealing and finish annealing, wherein the coated amount of oxygen on the steel sheet surface after decarburizing annealing is 0.8 g / m ² or less And while making residual C amount into 150 ppm or less, the manufacturing method of the directionality electromagnetic steel sheet which performs the said finish annealing in the atmosphere whose pressure in 500 degreeC or more is 10 Pa or less.   The annealing separator is at least 50% of one or more of Mg, Al, Zr, Mn, Ca and Sr, one or more of Mg, Fe, Ca, Mn, Ni, Zr, Co The method for producing a grain-oriented electrical steel sheet according to claim 1, which is any one or more kinds of aluminates and composite oxides thereof. In addition to the above-mentioned component composition, the above-mentioned steel material is further in mass%,
Al: 0.010 to 0.040% and N: 0.003 to 0.012%
The manufacturing method of the directionality electromagnetic steel sheet of Claim 1 or 2 containing B. In addition to the above-mentioned component composition, the above-mentioned steel material is further in mass%,
Se: 0.003 to 0.030% and S: 0.002 to 0.030%
The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 3 containing any one or two of them. In addition to the above-mentioned component composition, the above-mentioned steel material is further in mass%,
Ni: 0.01 to 1.50%,
Cr: 0.01 to 0.50%,
Cu: 0.01 to 0.50%,
P: 0.005 to 0.20%,
Sb: 0.005 to 0.20%,
Sn: 0.005 to 0.50%,
Bi: 0.005 to 0.10%,
Mo: 0.005 to 0.10%,
B: 0.0002 to 0.0025%,
Te: 0.0005 to 0.010%,
Nb: 0.001 to 0.010%,
V: 0.001 to 0.010%,
Ti: 0.001 to 0.010% and
Ta: 0.001 to 0.010%
The manufacturing method of the directionality electromagnetic steel sheet in any one of Claim 1 to 4 containing 1 type (s) or 2 or more types selected from them. The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 5, wherein the surface area of the steel sheet after the finish annealing is 0.5 g / m ² or less and the residual C amount is 40 ppm or less.

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