JP3382804B2 - Manufacturing method of grain-oriented electrical steel sheet with excellent glass coating - 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 producing a grain-oriented electrical steel sheet having an excellent glass film in which an oxide film is controlled during decarburization annealing to final finish annealing in the production of grain-oriented electrical steel sheet.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are generally used as iron core materials for transformers and other electrical equipment, and are required to have excellent magnetic excitation characteristics and iron loss characteristics. In order to obtain good magnetic characteristics, the axis of easy magnetization <
It is important to highly align the 001> axis in the rolling direction.
Further, the plate thickness, crystal grain size, and crystal grain size, as well as film forming conditions, are important because they have a great influence on the magnetic properties. The crystal orientation was greatly improved by a method characterized by final cold rolling under high pressure using AlN or AlN or MnS as an inhibitor, and at present, magnetic flux densities close to theoretical values are manufactured. Came.

Further, in recent years, iron loss characteristics have been improved to a considerable level by the progress of the technology for thinning the plate thickness and the high Si steel, and the development of the technology for increasing the tensile strength of the glass film and the insulating film. When the grain-oriented electrical steel sheet is used in a consumer's house, it is the film characteristic that is important together with the magnetic characteristic. This is because the film characteristics affect not only the insulating property of the transformer core, but also the building factor and the magnetic strain and strain sensitivity that cause noise. In this way, the film performance of grain-oriented electrical steel sheets has a great influence on product properties, and in the process of film formation, it has an important role in the control of inhibitor in steel and film tension in the case of glass film. However, in the case of an insulating film, it has an important role in terms of denseness and film tension.

Therefore, in order to obtain a grain-oriented electrical steel sheet having a high magnetic flux density and a low iron loss, it is necessary to strictly control the quantity, quality, forming speed, etc. as the forming conditions of these in the manufacturing process. is important. In general, grain-oriented electrical steel sheets are surface-treated with a two-layer film consisting of a glass film (forsterite + spinel) formed by final finish annealing and an insulating film. The former uses a forsterite film (Mg ₂ SiO ₄ ) formed by the reaction between the annealing separator MgO and the oxide film mainly composed of SiO ₂ generated during decarburization annealing, and uses Al as a steel component as in the present invention. In case of doing, Al ₂ O ₃
It is composed of an oxide component produced by the addition of other annealing separator additives, and a compound having a spinel structure by these. This glass film has the effect of improving the insulating property, iron loss, magnetostriction, etc. depending on the formation state and the tension effect.
On the other hand, depending on the formation state, magnetic flux density, iron loss, space factor,
Adhesion, processability, and product appearance are degraded. Further, when AlN is used as an inhibitor as in the present invention as in the present invention, the formation timing, formation rate, formation amount, etc., of N from the atmospheric gas into the steel at the interface of the steel sheet, denitrification of N, and AlN. And the stability of the inhibitor AlN is greatly affected. For this reason, it is important to realize an appropriate glass film formation reaction in order to obtain a product having both film properties and magnetic properties.

A number of proposals have been made for techniques for improving the glass film and magnetic properties depending on the conditions under which the decarburizing annealing oxide film is formed. In Japanese Patent Laid-Open No. 59-185725, in the decarburization annealing step of a high magnetic flux density grain-oriented electrical steel sheet, the steel sheet oxygen amount after decarburization annealing is -2500X + 1163 ≦ Y ≦.
-2500 + 1413 (however, X; thickness of steel plate (mm),
Y: oxygen content (ppm) of the steel plate is controlled within a range given by the formula. According to the present invention, the characteristics of high magnetic flux density and low iron loss can be obtained by controlling the oxygen content of the oxide film formed by decarburization annealing in a specific range. The impact on is stated. JP-A-8-157971 discloses that Mn: 0.02 to 0.15%, Se: 0.005 as an inhibitor-forming component.
~ 0.06%, Al: 0.010 to 0.06% and N:
In the decarburization annealing step of the grain-oriented electrical steel sheet material containing 0.0030 to 0.0120%, the amount of oxide on the surface of the steel sheet before decarburization annealing is adjusted to 0.02 to 0.10 g / m ² in terms of oxygen basis weight. , Subsequent decarburization annealing, the steel plate surface temperature is 500 ~ 750
In the process of being at a temperature of 0 ° C, the hydrogen partial pressure of the atmospheric gas is 0.5 to 0.
8 have been proposed to control each. In the present invention, the Fe-Si-O content is controlled by controlling the amount of oxides of the steel sheet before decarburization annealing and controlling the oxidizability during and after the temperature rise.
The difference in the quality of the oxides of the system, that is, the difference in the substance, controls the reaction between the base iron and the atmosphere to stabilize the secondary recrystallization and improve the magnetic properties. Also, JP-A-8-1439
In Japanese Patent Publication No. 64, cold rolling is performed by tandem rolling using a rolling roll of 300 to 400 mm, and the ratio of water vapor partial pressure to hydrogen partial pressure in the temperature rising process and soaking process of decarburization annealing is adjusted to increase the temperature. By setting PH ₂ O / PH ₂ in the warming process to be lower than that in the soaking process, it was conventionally difficult to obtain excellent magnetic properties. Roll diameter 300 mm
The above-described single rolling method by tandem rolling can be applied. This enables efficient production of grain-oriented electrical steel sheets with excellent magnetic properties. Further, as a similar method, Japanese Patent Laid-Open No. 6-336616 discloses
By setting the degree of oxidation PH ₂ O / PH ₂ in the soaking process of decarburization annealing to be less than 0.7 and setting it to be lower than the degree of oxidation soaking process in the temperature raising process, Methods have been proposed for obtaining a uniform glass film over the width.
However, the technology for improving the glass film and magnetic properties by controlling the oxide film and atmosphere gas of these decarburization annealing is for stabilizing the oxygen content of the oxide film and the inhibitor.
It is hard to say that it is still sufficient in terms of stable reaction control of the glass film during coil annealing and control of the film quality.

[0006]

SUMMARY OF THE INVENTION The present invention has an extremely uniform glass film during coil annealing of grain-oriented electrical steel sheets,
At the same time, it is an object to provide a grain-oriented electrical steel sheet having good magnetic properties.

[0007]

The method for producing a grain-oriented electrical steel sheet having a uniform glass film and good magnetic properties of the present invention is characterized by decarburization annealing, an annealing separator and subsequent finish annealing. . The final cold rolled material is decarburized and annealed in a continuous line. By this decarburization annealing, primary recrystallization, removal of C, and formation of an oxide film for forming a glass film on the surface of the steel sheet are performed. In the present invention,
First of all, the degree of oxidation of the atmospheric gas during this decarburization annealing
0.15 over the entire region of the PH ₂ O / PH ₂ from raising the temperature to the soaking
It is annealed while controlling the firelite production region to 0.59, and decarburization annealing with an oxidation degree higher than this is not suitable. At this time, the amount of iron oxide produced is converted into FeO of 0.05 to
Anneal to 1.0 g / m ² . However, the value of the amount of iron oxide is obtained by quantifying the value of Fe obtained by dissolving only the oxide film, and is represented by g / m ² value. As a result, the SiO ₂ layer, which is the main component of the oxide film, becomes dense, and iron oxide having a firelite structure is appropriately formed on the surface layer portion. As a result, the reactivity in forming the glass film is excellent, the oxidation resistance,
An oxide film having excellent reduction resistance and nitriding resistance is formed.

In the present invention, the oxide film is controlled as described above.
Therefore, as the decarburizing annealing condition, a temperature of 800 to 875 ° C is used.
In degrees, N₂+ H₂PH under the atmosphere₂O / PH₂, Soaking
Balance time, heating speed, stripping speed, gas amount, etc.
Anneal. At this time, as described above, the decarburization annealing temperature rise to the soaking
0.15-0.59 phis over the entire area until the end
Control in the jarlite generation area, or more preferable conditions
As the region above 650 ° C or the temperature rise,
Atmospheric gas oxidation degree in (less than 30% of total soaking time)
Lower than the degree of oxidation in the soaking zone or the rest of the soaking zone
Anneal. This makes it more excellent in finish annealing.
Atmosphere resistance of the oxide film is achieved. Then the invention
In the case of material conditions, preferably in the latter half of the tropical or cooling process
Atmosphere gas N₂+ H₂PH when using₂O /
PH₂ 0.001-0.15, N ₂When using gas
Has a dew point of −20 ° C. to + 47 ° C. and S on thermochemical equilibrium.
iO₂Annealing is performed in the production area. This allows the oxide film
Oxide film surface layer with the amount of Fe oxide inside kept properly
At the same time the inner layer SiO₂Layers are densified and finish firing later
For oxide film that is hard to cause additional oxidation, reduction, and nitriding in blunt
Modification is performed.

The application of such decarburization annealing conditions exerts a great effect particularly in the case of the production by the strip nitriding process using the low temperature slab heating material as in the second aspect of the present invention. As a method of manufacturing the grain-oriented electrical steel sheet in this case, C: 0.021 to 0.075 as a steel component.
%, Si: 2.5 to 4.5%, Mn: 0.05 to 0.4
5%, S ≦ 0.014%, Al: 0.010 to 0.04
0%, N: 0.0030 to 0.130%, Sn: 0.0
After heating a slab containing 3 to 0.50% and the balance Fe and unavoidable impurities to a temperature below 1280 ° C.,
After hot-rolling, if necessary, hot-rolled sheet annealing, then cold rolling one or more times with intermediate annealing between them to obtain the final sheet thickness, and decarburization annealing to steel sheet that has undergone nitriding in strip running state. The basic process is to apply an annealing separator and then perform high temperature finish annealing.

When such components and basic steps are used, 2
The secondary recrystallization temperature is as high as around 1100 ° C, and inhibitors (Al, Si) via the film state during the glass film formation process
This is because the control of N is important, and controlling the reactivity and quality of the oxide film has a great influence not only on the glass film but also on the magnetic properties. According to the oxide film formation and modification conditions of the present invention, such a problem does not occur.

The decarburized and annealed steel sheet is then subjected to continuous nitriding treatment in the same line or another line while the coil is running. The optimum nitriding amount at that time is 150 to 300 ppm
Is treated as. After that, as an annealing separator, BET:
Mg of 15 to 40 m ² / g and hydration water content of 1.5 to 3.5%
O: With respect to 100 parts by weight, with respect to the amount of iron oxide in the oxide film after decarburization annealing, one or two or more of Fe and Cl compounds is used as total F and / or Cl, -200X + 400≤H≤-600X + 950 (H Halogen element content (ppm) X; Iron oxide content in oxide film (Fe
The second characteristic is that an annealing separator represented by g / m ² ) and 0.05 ≦ X ≦ 1.0) is used as O.

At this time, other additives such as oxides, sulfates, borates, etc. are added as required, and the slurry is applied to the steel sheet, dried, and then wound into a coil. Then a final annealing of 20 hours at a temperature of 1200 ° C. is carried out,
Secondary recrystallization, glass film formation, and purification are performed. The third feature of the present invention resides in the atmospheric gas conditions at the time of temperature rise at this time. In the present invention, the finish annealing temperature rising process 500 to 9
The N ₂ ratio of the atmosphere gas up to 00 ° C. is 50% or less,
In addition, the degree of oxidation PH ₂ O / PH ₂ is maintained in the fayalite formation region in thermochemical equilibrium. Such conditions are performed by controlling the hydration water content of the coil at the time of finish annealing, the application amount of the annealing separating agent, the amount of atmospheric gas, the temperature rising conditions and the like. As a result, additional oxidation and reduction of the oxide film do not occur until the glass film is formed during the final annealing, and additional nitriding, etc. is controlled, and the above-mentioned decarburizing annealing and annealing separating agent additives etc. are fully effective. To form a very uniform and excellent glass film.

The glass sheet-coated steel sheet thus obtained is subjected to insulation coating treatment and heat flattening at 800 to 900 ° C. in a continuous line. As described above, in the grain-oriented electrical steel sheet, the tension of the coating is effective for improving the iron loss characteristic and the magnetostrictive characteristic. Therefore, for example, a phosphate-colloidal silica-based tension-imparting coating agent as described in JP-B-53-28375 is applied and baked. Further, when further improving the iron loss, before or after the heat flattening treatment, a depth of 1 to 30 μm and an interval of 2 to 15 mm in the rolling direction by laser, tooth roll, press roll, scribing, local etching, etc. On the other hand, a point-shaped or linear strain or groove forming process is performed in the direction of 45 ° to 90 °.

The present inventors performed grain nitriding electrical steel sheet using AlN, MnS as an inhibitor or strip nitriding after decarburization annealing to form an inhibitor mainly composed of (Al, Si) N, an annealing separator and a final finish annealing. In order to obtain a good quality glass film and magnetic properties, control of the quality of the oxide film during decarburization annealing, reactivity of the annealing separator, and control of the atmospheric oxidation degree at the time of temperature increase during finish annealing are well balanced in a specific range. They found that control was important.

That is, if these process conditions are made appropriate, the extremely excellent reactivity and denseness of the oxide film can be stably obtained, and in each part of the coil during the finish annealing temperature rising process, which is important in coil annealing. The uniform reaction of the glass film formation, the additional oxidation and reduction of the oxide film, and the additional nitridation from the atmospheric gas are prevented, and the uniform film formation is performed over the entire length and width of the coil during the glass film formation. In addition, this also keeps the inhibitor AlN component stable up to high temperatures. Also,
In the case of the strip nitriding process, the quality and quantity are kept stable and the secondary recrystallization is kept stable until the effective AlN is changed in the high temperature region. As a result, the development of a technique that can provide excellent magnetic properties has been achieved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the reasons for limiting the construction technique of the present invention will be described. The features of the present invention are decarburization annealing conditions, an annealing separator, and final finishing annealing conditions. First, the decarburization annealing conditions are performed at 800 to 875 ° C., and the oxidation degree PH ₂ O / PH ₂ of the atmospheric gas at the time of temperature rising and soaking is 0.15 to 0 as shown in FIG. Due to the thermochemical equilibrium of 0.59, it is important to control the formation of firelite.

In particular, in the step of changing (Al, Si) N to AlN in the vicinity of 950 ° C. when the temperature is raised in the finish annealing process as an inhibitor as in the present invention, the surface sealing property is increased in the finish annealing temperature rising process. And improve the glass film reactivity,
The key to achieving both good glass film and secondary recrystallization is to use an oxide film layer having excellent oxidation resistance, reduction resistance, and nitriding resistance. The method proposed as a conventional method for controlling the atmosphere of decarburization annealing is not suitable for the present invention because the atmosphere gas condition is mainly in the region where the degree of oxidation is considerably high.

The degree of oxidation of the atmospheric gas PH ₂ O / PH ₂ is 0.1
When it is less than 5, decarburization is deteriorated and it is difficult to secure the amount of the Fe-based oxide of the present invention, and it is industrially difficult to obtain the required amount of oxidation, so that it is limited. On the other hand, if it exceeds 0.59, the atmosphere becomes a FeO generation region in the soaking zone 800 to 875 ° C., and a low-grade Fe-based oxide (FeO) is generated on the surface, which is harmful to the glass film formation and Oxide film reforming treatment, nitriding treatment, reduction by finish annealing temperature rise process,
A metal-like iron exposed portion is generated on the surface layer portion, and the atmosphere resistance is impaired, so that a good glass film or magnetism cannot be obtained.

In this decarburization annealing step, as a preferable range, the degree of oxidation is lower than that of the soaking zone or the remaining soaking zone in the temperature range of 650 ° C. or more before annealing, or in the region of 650 ° C. or more and within 30% of soaking zone before annealing. It is better to let it do it. In this case, an effect of improving the denseness of the oxide film and a good decarburizing property can be obtained. The control of the degree of oxidation of the atmospheric gas at the time of temperature rise is set to 650 ° C. or higher because the oxidation of the steel sheet hardly progresses below this temperature and no influence is observed. Further, when the decrease in the degree of oxidation in the soaking zone reaches 30% or more of the total soaking zone, it affects the subsequent control of oxidation and decarburization depending on the setting conditions of the degree of oxidation, and the iron oxidation of the present invention It is limited because it becomes difficult to secure the amount of material and it has an adverse effect on the glass film formation. When making a difference in the atmospheric oxidation degree between the front-stage area and the rear-stage area, an atmosphere gas partition device is provided in the furnace to make a sharp difference, or the degree of oxidation of the atmosphere gas is inclined by controlling the dew point of the introduced gas, the amount of gas, etc. The method of attaching.

In the case of the components and process conditions of the present invention, modification of the oxide film surface and / or prevention of alteration can be prevented by controlling the oxidation degree of the atmospheric gas up to 500 ° C. in the subsequent stage of decarburization annealing or in the cooling process. Done. Thereby, the oxidation resistance, reduction resistance, and nitriding resistance of the oxide film are improved, and an excellent glass film is obtained. In this case, when H ₂ + N ₂ gas is used as the atmosphere gas, PH ₂ O / PH ₂ is controlled to 0.001 to 0.15. If it is less than 0.001, the reduction of the surface proceeds too much and the reactivity decreases, which is not preferable.
On the other hand, if it exceeds 0.15, the surface is not sufficiently modified, additional oxidation is caused during the cooling process, the sealing property of the oxide film is deteriorated, and the glass forming reaction is not uniform in the coil, which is not preferable. Within the range of 0.001 to 0.105, the densification of the outermost layer of the oxide film and the inner layer SiO ₂ film is promoted, the amount of Fe oxide is also kept stable, and a stable atmosphere sealing effect and uniform glass film formation are formed. The effect of is obtained.

In the present invention in which decarburization annealing is performed in this manner, the amount of Fe oxide after decarburization annealing is 0.05 to 1.0 g /
m ² . In the case of the present invention, the degree of oxidation of the decarburizing and annealing atmosphere gas is in the firelite generation region, and the Fe oxide is mainly the one brought by Fe ₂ SiO ₄ . If it is less than 0.05 g / m ² , the reactivity of the oxide film is insufficient and the uniformity and thickness of the glass film formation are affected. on the other hand,
If it exceeds 1.0 g / m ² , defects such as metallic spots, scales, and blackening peculiar to reduction of peroxide are likely to occur, so that it is limited.

Next, when the low temperature slab heating material is processed by the strip nitriding process, the components of the starting slab are C: 0.021 to 0.075% by weight and Si: 2.5 to.
4.5%, Mn: 0.05 to 0.45%, S: ≤ 0.0
14%, acid-soluble Al: 0.010 to 0.040%, N:
0.0030 to 0.0130%, Sn: 0.03 to 0.
It contains 50% and the balance is Fe and inevitable impurities.

When the content of C is less than 0.021%, the secondary recrystallization becomes unstable, and even when the secondary recrystallization is performed, the magnetic flux density of the product is as low as about 1.80 Tesla at B _8. It On the other hand, if it exceeds 0.075%, it takes a long time in the decarburizing step, and particularly under the decarburizing annealing atmosphere conditions of the present invention, the productivity is impaired. The specific resistance of Si varies depending on its content. If it is less than 2.5%, a good iron loss value cannot be obtained. On the other hand, if it exceeds 4.5%, cracks and fractures frequently occur during cold rolling, making stable cold rolling operation impossible.

One of the characteristics of the component of the second invention is that S is 0.
It is to be 014% or less. In the conventional known technique, for example, the technique disclosed in Japanese Examined Patent Publication No. 47-25220, S is an element that forms a precipitate necessary for causing secondary recrystallization as MnS. There is a range of the amount of S that exerts the most effect, and it was defined as the amount of MnS that can be solid-dissolved in the slab heating step performed prior to hot rolling. However, in recent studies, (Al, Si) N has been used as a precipitate necessary for secondary recrystallization.
In a method for producing a one-way electrical steel sheet using a low temperature slab heating using S, S was found to promote secondary recrystallization failure when a slab containing a large amount of Si in a raw material was heated at a low temperature and hot rolled. If the Si content in the material is 4.5% or less, 0.014% or less, preferably 0.0070% or less, no secondary recrystallization failure occurs at all.

In the present invention, (Al, Si) N is used as a precipitate necessary for secondary recrystallization. Therefore, in order to secure the minimum necessary AlN generated at a high temperature near 950 ° C., 0.010% or more of acid-soluble Al and 0.0030% or more of N are required. However, acid-soluble Al is 0.04
If it exceeds 0%, AlN during hot rolling becomes unsuitable and the secondary recrystallization becomes unstable, so it is limited to 0.010 to 0.040%. On the other hand, the content of N is 0.0130%
If it exceeds 0.1, cracks on the surface of the steel sheet called blister occur, and the grain size of primary recrystallization cannot be adjusted.
It is limited to 0030 to 0.0130%.

If Mn is less than 0.05%, secondary recrystallization is not possible.
Be stable. However, when the number increases, B ₈Value is high but
Adding more than the fixed amount is disadvantageous in terms of cost. For this reason,
It is limited to 0.05 to 0.45%. Release these ingredients
The characteristics of the present invention used as the material are decarburization annealing conditions and annealing separation.
Agent, final finish annealing conditions.

Next, as the annealing separator used in the present invention, BET: 15-40 m ² / g, hydrated water content: 1.5-
3.5% MgO: 100% by weight, with one or more F and Cl compounds as total F and / or Cl, based on the amount of Fe oxide in the oxide film, -200X + 400 ≦ H ≦
Add so that the relational expression is −600 × + 950. Although the present invention is based on making the decarboxylated film highly reactive and densified, the annealing separator also has an important role. Mg
When the BET of O is less than 15 m ² / g, the glass film formation tends to shift to the high temperature side, and the finish annealing tends to be affected by the oxidation and nitriding of the coil outer periphery and the edge portion.
On the other hand, when it exceeds 40 m ² / g, it becomes difficult to control the water content of hydration in the field coating line, which may cause nonuniformity of the glass film in the coil. If the hydrated water content is less than 1.5%, the degree of oxidation between the plates will be insufficient, and the glass film in the coil, especially near the coldest point during coil annealing heating, will be thinned, which is limited. On the other hand, if it exceeds 3.5%, the atmospheric gas at the time of temperature rise during finish annealing becomes peroxidized, causing additional oxidative oxidation on the outer circumference of the coil and the edge portion to increase glass film defects. Furthermore, it is limited due to weakening of the inhibitor via this additional oxidation, which leads to deterioration of the magnetic properties.

As the reaction accelerator added to MgO which is the main component of the annealing separator, the F and Cl compounds are added within the range shown in FIG. The amount of F and Cl is based on M
The total amount of gO and additives is −200X + 400 ≦ H ≦ −600X + 950 (H; halogen element amount (ppm) X; iron oxide amount in oxide film (Fe
O must be added as O in balance with the Fe oxide represented by g / m ² ) and 0.05 ≦ X ≦ 1.0). If the amounts of F and Cl are less than this range, the effect of improving the stability of the glass film cannot be obtained. On the other hand, if it exceeds this range, defects such as dot-like metal spots and scales called shimofuri occur. Further, in an extreme case, a tendency of thinning occurs on the entire surface.

Next, as the atmosphere gas in the finish annealing, N of the atmosphere gas at a temperature rise of 500 to 900 ° C. is used.
_It is preferable that the ratio of ₂ is 50% or less and that the oxidation degree in each temperature range is maintained in the fayalite formation region in terms of thermochemical equilibrium.
In the present invention, as an inhibitor in steel, (Al, Si)
N is used, but the amount, quality, and the glass film formation state are affected by the oxidation, nitriding, and denitrification during finish annealing. Particularly, when the temperature is raised to 500 ° C. or higher, it is a region where the quality of the oxide film is changed from the above phenomenon,
If the degree of participation of the atmospheric gas up to 900 ° C. where the glass film forming reaction becomes active is controlled in the fayalite formation region due to thermochemical equilibrium, the oxide film surface does not change and the glass film formation is kept stable. At the time of temperature rise, the atmosphere from 500 to 900 ° C is on the dry side (SiO ₂
In the production region), the surface layer is reduced over a long period of temperature rise, and the reactivity decreases. As a result, film defects on the outer circumference of the coil and the edge portion increase. Further, denitrification may be accelerated and secondary recrystallization failure may occur. On the other hand, in the oxidation side (FeO generation area) from the firelite generation area, excessive oxidation occurs before the glass film is formed at the time of temperature rise, and film defects due to overoxidation occur frequently in the coil outer peripheral portion and the edge portion, and secondary recrystallization occurs. Is not preferable because it causes non-uniformity.

[0030]

【Example】

(Example 1) C: 0.076% by weight, Si: 3.25
%, Mn: 0.06%, acid-soluble Al: 0.028%,
S: 0.024%, N: 0.0080%, Cu: 0.0
8%, Sn: 0.12%, the balance is Fe and the unavoidable impurities are high magnetic flux density grain-oriented electrical steel sheet material slab 135
It heated at 0 degreeC and hot-rolled, and it set it as the hot-rolled board of 2.3 mm. Then, it was annealed at 1120 ° C. for 2 minutes, pickled and cold rolled to a final plate thickness of 0.22 mm. Then 1 at 830 ° C
Decarburization annealing was performed in a furnace in which the dew point was changed and the degree of oxidation was controlled as shown in Table 1 in N ₂ 25% + H ₂ 75% for 20 seconds. At this time, at a temperature of 830 ° C. in the latter part of the decarburization annealing,
Annealing was performed for 0 seconds in the same atmosphere with an oxidation degree of 0.10. The amount of iron oxide in the oxide film at this time is as shown in Table 1. BET: 18 m ² as an annealing separator on this coil
/ G, hydrated water content: 2.5% MgO: 100 parts by weight, TiO: 2 5 parts by weight and total F and Cl by NaF and FeCl2: F: 200 ppm, Cl:
The annealing separator slurry adjusted to 350 ppm was applied and dried at a rate of 7 g / m ² per side, and then wound up,
Finish annealing of 20 hours was performed at a temperature of 1200 ° C. Then, 30% colloidal silica as an insulating film agent: 10
0 ml + 50% Al primary phosphate: 70 ml + CrO: 3
A treatment agent consisting of 9 g was applied so that the weight after baking was 5 g / m ² , and baking treatment was performed at a temperature of 850 ° C. for 30 seconds to obtain a product. Table 2 shows the results of the glass film and the magnetic properties in this test.

[0031]

[Table 1]

[0032]

[Table 2]

As a result of this test, in the present inventions 1 to 4, the components of the oxide film surface layer after decarburization annealing were Fe ₂ SiO ₄ and SiO ₂ , and FeO was detected most strongly in all of Comparative Examples 1.2. The SiO ₂ component was weak. Further, the amount of iron oxide in the oxide was also detected in many cases in the comparative example,
In the present invention, it was as low as 0.08 to 0.26, and it was confirmed that the composition and the composition ratio were considerably different.

In the case of the material of the present invention, the glass film after finish annealing was a grayish black uniform glass film from the outer circumference to the inner circumference of the coil, and the magnetic properties were good. On the other hand, in the comparative example, many metal spot-like or scale-like defects were found in the outer peripheral portion and the edge portion of the coil, and there were many variations in the analysis result of the film amount, which was unstable due to additional oxidation or reduction. I understood. Also, the magnetic properties were considerably inferior to those of the present invention. (Example 2) C: 0.055% by weight, Si: 3.30
%, Mn: 0.11%, acid-soluble Al: 0.030%,
S: 0.0068%, N: 0.0071%, Sn: 0.
A material consisting of 035% and the balance Fe and unavoidable impurities was slab heated at 1150 ° C. and hot rolled to 2.6 mm.
Annealed at 20 ° C for 2 minutes, pickled, cold rolled, final plate thickness 0.2
It was set to 9 mm. Then, at a temperature of 830 ° C. for 130 seconds,
Decarburization annealing was performed in a furnace in which the dew point was changed and the degree of oxidation was controlled as shown in Table 3 in N ₂ : 25% + H ₂ : 75%. At this time, it was annealed at a temperature of 830 ° C. for 10 seconds in the latter region of the decarburization annealing with the oxidation degree of the atmosphere being 0.0020. Then, a nitriding treatment was performed in an atmosphere of N ₂ : 25% + H ₂ : 75% + NH ₃ so that the steel sheet N content was 200 ppm. The amount of iron oxide in the oxide film at this time is as shown in Table 3. BET: 22 m ² / as an annealing separator on this coil
g, hydrated water content: 1.8% MgO: 100 parts by weight, TiO: 2 5 parts by weight and total F and Cl by HCl and HF: F: 200 ppm, Cl: 250
The annealing separator slurry adjusted to be ppm is applied and dried at a rate of 7 g / m ² per side, and then wound up to 120
A finish annealing of 20 hours was performed at a temperature of 0 ° C. afterwards,
30% colloidal silica 100 ml + as insulating film agent
A treatment agent consisting of 50% Al primary phosphate: 70 ml + CrO: 9 g was applied so that the weight after baking was 5 g / m ² , and the product was baked at a temperature of 850 ° C. for 30 seconds. Table 4 shows the results of the glass film and magnetic properties in this test.

[0035]

[Table 3]

[0036]

[Table 4]

As a result of this test, P in the soaking zone of the present invention was obtained.
When H ₂ O / PH ₂ was decarburized and annealed at 0.41 and 0.52, a uniform and good glass film was formed over the entire width from the outer circumference to the inner circumference of the coil. Also, the film adhesion was good, and it was confirmed from the measurement results of the glass film amount that no additional oxidation was performed during the finish annealing. Further, in terms of magnetic characteristics, the outermost part of the coil was very good, and the same results as those of the inner part were obtained. On the other hand, when the PH ₂ O / PH ₂ in the soaking zone of the comparative example is 0.77, scale-like defects frequently occur on the outer circumference of the glass coil, and the coating thickness is extremely close to the coldest spot on the inner circumference. The result was thin. In this case, in all cases, the magnetism of the outer peripheral portion of the coil was considerably inferior to the condition of the present invention. FIG. 3 and FIG. 4 are finish annealing of the steel sheet after the application of the annealing separating agent of the present invention 2 and the comparative example 1 by controlling the dew point of the temperature rising atmosphere, and a pull-out test was conducted in the temperature rising process. It is the result of investigating the change of. In the case of the material of the present invention, it was confirmed that the additional oxidation and the additional nitridation during the finishing temperature rising process were small, and the material was stable to the atmospheric gas. (Example 3) The same material slab as in Example 1 was hot-rolled to obtain a hot-rolled sheet having a plate thickness of 2.3 mm. After that, the same treatment as in Example 1 was performed to obtain a cold-rolled sheet having a final sheet thickness of 0.225 mm. Then, the present invention 4 of Example 1 and the atmospheric conditions of Comparative Example 2 were set to 8
After decarburization annealing at a temperature of 30 ° C. for 110 seconds and oxide temperature modification treatment at a temperature of 830 ° C. for 15 seconds with PH ₂ O / PH ₂ = 0.003, nitriding annealing is performed so that the nitriding amount is 210 ppm, The annealing separator slurry having the composition shown in FIG.
Coating and drying at g / m ² and 20H at 1200 ℃
Final finishing annealing of r was performed. After that, an insulating film agent was treated in the same manner as in Example 1 to obtain a final product. Table 6 shows the results of the glass film and the magnetic properties in this test.

[0038]

[Table 5]

[0039]

[Table 6]

As a result, when the decarburizing annealing of the present invention was carried out and the annealing separating agent in which the amount of halogen elements was adjusted to 300 ppm and 600 ppm was used, the glass coating and the magnetic properties were extremely excellent over the entire coil length and the entire surface. was gotten. On the other hand, in the comparative example in which the soothing atmosphere of decarburization annealing is PH ₂ O / PH ₂ of 0.77, even if the annealing separating agent of the present invention is used, the scale-like defects on the outer peripheral portion of the coil and the thinning tendency on the inner peripheral portion of the coil tend to occur. The appearance of the glass film was rather poor and the magnetic properties were also poor. Further, when the amount of halogen element in the annealing separator was as large as 1100 ppm, the glass film was inferior in any decarburizing annealing, and particularly when the decarburizing annealing of the comparative example was performed, severe film defects frequently occurred. . (Example 4) The same decarburization annealing, surface modification and nitriding treatments as those of the present invention 2 of Example 2 and Comparative Example 2 were similarly coated with the annealing separating agent, dried and wound on the coil. I took it. Then, as shown in Table 7, during the temperature rise in the final annealing, 9
After changing the temperature of PH ₂ O / PH ₂ up to 00 ° C and raising the temperature, 1200
Annealing was performed for 20 hours at a temperature of ° C. After that, an insulating film agent was treated in the same manner as in Examples 1 and 2 to obtain a final product.
Table 8 shows the results of the glass film and magnetic properties in this test.

[0041]

[Table 7]

[0042]

[Table 8]

As a result of this test, when the decarburization-annealed material of the present invention was used, a coil having a film with uniform adhesion and good adhesion was obtained under any finish annealing condition, and the magnetic characteristics were good.
In particular, superior film properties and magnetic properties were obtained when the atmosphere gas oxidation degree at a temperature of 500 to 900 ° C. was controlled in an atmosphere of a firelite generation region of 0.20 to 0.35. On the other hand, in the case of the decarburization annealing of the comparative example, the coating on the outer peripheral portion of the coil was non-uniform because of frequent occurrence of scale-like and exposed portions of the metal surface, and the magnetic properties were also poor. In particular, the degree of oxidation of the finish annealing atmosphere gas is 0.10 to 0.25 or 0.
When an atmospheric condition deviating from the firelite production range of 25 to 0.55 was generated, an extremely nonuniform glass film was formed.

[0044]

According to the present invention, an extremely tight and highly reactive oxide film is formed by decarburization annealing, and the glass film formation is further promoted with the halogen compound of the annealing separator. As a result, a glass film excellent in oxidation resistance, reduction resistance, nitriding resistance and the like during finish annealing is formed, and in coil annealing, excellent film characteristics and magnetic characteristics are obtained over the entire length and width.

[Brief description of drawings]

FIG. 1 is a diagram showing an oxidation degree in a decarburizing annealing step in the present invention.

FIG. 2 is a diagram showing a range of an iron oxide amount of a decarburized annealing oxide film and a halogen element content in an annealing separator in the present invention.

FIG. 3 is a diagram showing changes in glass film formation, additional oxidation amount, and steel plate oxygen amount during a finish annealing temperature rising process.

FIG. 4 is a diagram showing changes in the nitrogen content of the steel sheet during the finish annealing temperature rising process.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshiyuki Ushigami Inventor Yoshiyuki Ushigami 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Co., Ltd. Technology Development Headquarters (72) Inventor Akira Sakita 1 Hibatacho, Tobata-ku, Kitakyushu, Fukuoka 1 -1 Inside Nippon Steel Co., Ltd. Yawata Works (72) Inventor Seio Mukai 1-1 Tobahata-cho, Tobata-ku, Kitakyushu, Kitakyushu 1-1 New Japan Works Ltd. Yawata Works (72) Inventor Masao Ono Fukuoka Prefecture 1-1 Hibatacho, Tobata-ku, Kitakyushu City New Nippon Steel Co., Ltd. Inside Yawata Works (72) Inventor Toru Tanaka 59 Nakatsura Plant Design Co., Ltd. (46), Nakahara 46, Tobata-ku, Kitakyushu City, Fukuoka Prefecture (56) References JP-A-4-183817 (JP, A) JP-A-3-211232 (JP, A) JP-A-4-218622 (JP, A) JP-A-6-336616 (JP, A) JP-A-8-143970 (JP , A) JP-A 8-143975 (JP, A) JP-A 55-58331 (JP, A) JP-A 54-33839 (JP, A) JP-A 62-156226 (JP, A) JP-A 62-33782 (JP, A) JP 55-65367 (JP, A) JP 7-62440 (JP, A) JP 57-1575 (JP, B1) JP 49-29409 (JP, B1) Yozo Kan, Development Trend of Low Iron Loss of Directional Electromagnetic Steel Sheet, Nishiyama Memorial Technical Lecture Text (Recent Progress of Soft Magnetic Materials), Japan Iron and Steel Institute, February 1, 1995, No. 155. 156 times (58) Fields surveyed (Int.Cl. ⁷ , DB name) C21D 9/46 501 C21D 8/12 C22C 38/00 303 C22C 38/06 H01F 1/16

Claims (5)

(57) [Claims] 1. A grain-oriented electrical steel sheet material is hot-rolled and cold-rolled once or two or more times with annealing to obtain a final sheet thickness, then decarburized and annealed, an annealing separator is applied, and high-temperature finish annealing is performed. In the method for producing a grain-oriented electrical steel sheet, which comprises performing insulating film treatment and heat flattening, the atmospheric gas oxidation degree P _H2O / P _H2 during decarburization annealing is set to 0.15 from the temperature rise to the end of soaking. To 0.59 in the firelite forming region, annealing is performed, and the iron oxide amount in the oxide film of the steel sheet after decarburization annealing is set to 0.05 to 1.0 g / m ² and finish firing is performed.
Atmosphere gas at 500 to 900 ° C.
N ₂ ratio of 50% or less and the degree of oxidation is fired
A method for producing a grain-oriented electrical steel sheet having an excellent glass film, which is characterized in that the temperature is maintained in the iron forming region . However, the value of the amount of iron oxide was obtained from the quantified value of Fe by dissolving only the oxide film, and was expressed in g / m ² value. 2. C: 0.021 to 0.075% by weight,
Si: 2.5-4.5%, Mn: 0.05-0.45
%, S: ≦ 0.014%, acid-soluble A1: 0.010-
0.040%, N: 0.0030 to 0.0130%, S
n: 0.03 to 0.50%, the balance consisting of Fe and inevitable impurities is heated at a temperature of less than 1280 ° C.,
Hot-rolled, cold rolled once or two times with annealing to obtain final plate thickness, then decarburized and annealed, strip nitriding annealed, annealed separating agent applied, high-temperature finish annealed, insulation coating agent In a method for producing a grain-oriented electrical steel sheet comprising treatment and heat flattening, an atmosphere gas oxidation degree P _H2O / P _H2 in decarburization annealing is 0.15 to 0.59 from a temperature rise to the end of soaking. In the firelite formation region of No. 3, and the amount of iron oxide in the oxide film of the steel sheet after decarburization annealing is set to 0.05 to 1.0 g / m ² and the finish annealing is performed.
N ₂ ratio of atmospheric gas at a temperature rise of 500 to 900 ° C.
To 50% or less and the degree of oxidation to the firelite formation region
A method for producing a grain-oriented electrical steel sheet having an excellent glass film, which is characterized by holding the temperature in a range and raising the temperature . 3. Annealing is performed at a temperature of 650 ° C. or higher during decarburization annealing or at an atmospheric oxidation degree of 650 ° C. or lower in the former stage of soaking (less than 30% of total soaking time) lower than that in the latter stage of soaking. The method for producing a grain-oriented electrical steel sheet having an excellent glass coating according to claim 1 or 2. 4. The atmosphere gas is N ₂ at the latter stage (less than 30% of the total soaking time) during soaking in decarburizing annealing and / or during cooling.
In the case of + H ₂ , P _H2O / P _H2 is 0.001 to 0.15,
When N ₂ is used as the atmosphere gas, the dew point is -20 ° C to 47 ° C.
The method for producing a grain-oriented electrical steel sheet having an excellent glass coating according to claim 1, 2 or 3, wherein the annealing is performed at a temperature of ℃ and as a SiO ₂ forming region. 5. BET: 15-40 as an annealing separator
m ² / g, hydrated water content: 1.5-3.5% MgO: 10
One part or two or more kinds of F and Cl compounds are added to 0 parts by weight as total F and / or Cl, and are added to firelite in the oxide film within a range represented by the following formula. The method for producing a grain-oriented electrical steel sheet having an excellent glass coating according to claim 1, 2, 3, or 4. −200x + 400 ≦ H ≦ −600x + 950 H; total halogen element amount (ppm), x: iron oxide amount in oxide film (g / m ² ), 0.05 ≦ x ≦ 1.0