JP2004292834A - Method for producing grain-oriented silicon steel sheet excellent in coating characteristics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new producing method for grain-oriented silicon steel sheet with which uniform forsterite coating film excellent in stickiness having no defect can be obtained over on the whole width and the whole length of a coil and further, the excellent magnetic characteristic can be obtained by uniformly controlling quality of subscale formed at decarburizing annealing. <P>SOLUTION: When a grain-oriented silicon steel sheet is produced with a series of processes, with which after hot-rolling to a silicon-containing steel slab, cold-rolling at one time or two or more times interposing intermediate annealing, is applied and successively, after decarburize-annealing, annealing parting agent is coated on the surface of the steel sheet and the last finish-annealing is applied, an atmospheric oxidizing degree (P[H<SB>2</SB>O]/P[H<SB>2</SB>]) in the soaking process at the decarburize-annealing is regulated to in the range of 0.40-0.60 and further, on the surface of the steel sheet after decarburize-annealing, SiO<SB>2</SB>production ratio in the oxide produced on the surface layer, is regulated to ≤ 60%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４９】
同表から明らかなように、この発明に従う条件にて製造した発明例はいずれも、良好な被膜特性および磁気特性を示している。
【００５０】
【発明の効果】
この発明によれば、脱炭焼鈍後の鋼板表面におけるＳｉＯ_２生成比率を所定の値以下とし、さらに脱炭焼鈍の均熱過程における雰囲気酸化度（Ｐ［Ｈ_２Ｏ］／Ｐ［Ｈ_２］）を適切に制御することによって、被膜特性に優れた方向性電磁鋼板を安定して得ることができる。
【図面の簡単な説明】
【図１】ＦＴ−ＩＲ法によるＳｉＯ_２生成比率の算出要領を示した図である。
【図２】被膜外観とＳｉＯ_２生成比率との関係を示す図である。
【図３】脱炭焼鈍昇温過程の雰囲気酸化度とＳｉＯ_２生成比率との関係を示した図である。
【図４】ＳｉＯ_２生成比率および均熱過程の雰囲気酸化度が被膜外観に及ぼす影響を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a grain-oriented electrical steel sheet suitable for use in applications such as transformers and iron cores of other electrical equipment, and particularly by controlling the generation state of subscales in decarburization annealing, in particular, coating properties. It is intended to improve the above.
[0002]
[Prior art]
The grain-oriented electrical steel sheet is mainly used as a core material for transformers or rotating equipment, and as magnetic properties, it is required to have a high magnetic flux density and a small iron loss and magnetostriction.
In particular, recently, there is an increasing need for grain-oriented electrical steel sheets with excellent magnetic properties from the viewpoints of energy saving and resource saving.
[0003]
In order to obtain a grain-oriented electrical steel sheet having excellent magnetic properties, it is important to obtain a secondary recrystallized structure highly integrated in the (110) [001] orientation, so-called Goth orientation.
This grain-oriented electrical steel sheet is obtained by hot rolling a steel slab containing an inhibitor necessary for secondary recrystallization, such as MnS, MnSe, AlN, BN, etc. after heating and, if necessary, performing hot-rolled sheet annealing. The final sheet thickness is obtained by cold rolling at least once with intermediate or intermediate annealing, and after decarburization annealing, an annealing separator mainly composed of MgO is applied to the steel sheet, followed by final finish annealing. Manufactured by.
[0004]
And, on the surface of this grain-oriented electrical steel sheet, except for special cases, an insulating film mainly composed of forsterite (Mg ₂ SiO ₄ ) (hereinafter simply referred to as forsterite film) is formed. It is common. This forsterite film contributes not only to electrical insulation of the surface but also to improvement of iron loss and magnetostriction by imparting tensile stress generated due to its low thermal expansion property to the steel sheet.
[0005]
In general, grain oriented electrical steel sheets have a glassy coating on the forsterite coating, which is very thin and transparent, so the forsterite coating determines the final appearance of the product. . Therefore, the quality of the appearance greatly affects the product value. For example, a film having a film in which part of the iron is partially exposed is regarded as inappropriate as a product, and the effect of the film properties on the product yield is extremely large.
[0006]
Accordingly, the formed forsterite coating is required to have a uniform appearance and no defects, and to have excellent adhesion so that the coating is not difficult to peel in shearing, punching, bending, or the like. Furthermore, the surface is smooth, and it is required to have a high space factor when laminated as an iron core.
[0007]
The forsterite film is formed in the final finish annealing, but the film formation behavior affects the inhibitor effect by MnS, MnSe, AlN, etc. in the steel, and is an essential process for obtaining excellent magnetic properties. It also affects the secondary recrystallization itself.
In addition, the formed forsterite film contributes to the improvement of the magnetic properties of the steel sheet by sucking up an inhibitor component that becomes unnecessary after the secondary recrystallization is completed and purifying the steel.
Therefore, controlling the formation process of this forsterite film to produce the film uniformly is extremely important in obtaining a grain-oriented electrical steel sheet having excellent magnetic properties.
[0008]
A forsterite film having a great influence on product quality is generally formed by the following process.
First, a final cold-rolled sheet for grain-oriented electrical steel sheets that has been cold-rolled to a desired final sheet thickness is continuously annealed at a temperature of 700 to 900 ° C. in wet hydrogen. By this annealing (decarburization annealing), the structure after cold rolling is primary recrystallized so that proper secondary recrystallization occurs in the final finish annealing, and the magnetic properties of the product are prevented from aging deterioration. Carbon contained in the steel in an amount of about 0.01 to 0.10 mass% is reduced to about 0.003 mass% or less.
At the same time, a subscale containing SiO ₂ is generated on the steel sheet surface layer by oxidation of Si in the steel.
[0009]
Then, after applying an annealing separator mainly composed of MgO on the steel sheet, it is wound in a coil shape, and in a reducing or non-oxidizing atmosphere, a final finish annealing that combines secondary recrystallization annealing and purification annealing Is performed at a temperature of about 1200 ° C. at maximum, thereby forming a forsterite film mainly according to a solid phase reaction represented by the following reaction formula.
2MgO + SiO ₂ → Mg ₂ SiO ₄
[0010]
This forsterite coating is a ceramic coating in which fine crystals with a diameter of around 1 μm are densely accumulated. As described above, the subscale containing SiO ₂ formed on the steel sheet surface in decarburization annealing is used as one raw material. Since it is generated on the steel sheet, the type, amount, and distribution of this subscale are related to the nucleation and grain growth behavior of forsterite, and also to the grain boundaries of the coated crystal grains and the strength of the grains themselves. Also affects the coating quality after finish annealing.
[0011]
Further, as the other raw material of forsterite coating, the annealing separator composed mainly of MgO is to be applied to the steel sheet as a slurry suspended in water, after drying was also physically adsorbed H ₂ O Is partly hydrated and changed to Mg (OH) ₂ . For this reason, during the finish annealing, H ₂ O continues to be released in a small amount up to about 800 ° C. The surface of the steel sheet is oxidized during finish annealing by this H ₂ O. This oxidation also affects the formation behavior of forsterite and also affects the inhibitor effect. If this additional oxidation amount is large, it causes deterioration of magnetic properties. The ease of oxidation by H ₂ O released by magnesia is also greatly influenced by the physical properties of the subscale formed by decarburization annealing. In particular, when the plate thickness is reduced, the influence of the surface is relatively increased. Therefore, controlling the quality of the subscale formed during decarburization annealing is extremely important for obtaining excellent magnetic properties.
[0012]
As described above, controlling the quality of the subscale formed on the steel sheet surface layer during decarburization annealing makes it possible to form an excellent forsterite film uniformly at an appropriate temperature, and normal secondary recrystallization. Therefore, it is an indispensable technique for producing a grain-oriented electrical steel sheet, and is one of the important control items when producing grain-oriented electrical steel sheets.
[0013]
Now, regarding decarburization annealing of grain-oriented electrical steel sheets, for example, as disclosed in Patent Document 1, a method for controlling the oxygen content of a steel sheet after decarburization annealing, as disclosed in Patent Document 2 Further, a method in which the oxidation degree of the atmosphere is 0.15 or more in the front region of the decarburization annealing and the oxidation degree is 0.75 or less and lower than that in the front region in the subsequent rear region, Patent Document 3 and Patent Document 4 The method of performing heat treatment at 860 to 1050 ° C. in a non-oxidizing atmosphere after decarburization annealing as shown in FIG. 5, cooling after decarburization annealing as disclosed in Patent Document 5 is 750 ° C. or less. In the temperature region, the cooling is performed with the degree of oxidation being 0.008 or less, and the atmospheric oxidation degree (P [H ₂ O] / P [H ₂ ]) in the soaking process as disclosed in Patent Document 6 is 0. Less than 70 and atmospheric oxidation in the temperature rising process A method of setting the temperature (P [H ₂ O] / P [H ₂ ]) to a value lower than that of the soaking process, and a method of defining the heating rate and the annealing atmosphere as disclosed in Patent Document 7, Etc. are known.
[0014]
[Patent Document 1]
JP 59-185725 A [Patent Document 2]
Japanese Patent Publication No.57-1575 [Patent Document 3]
JP-A-2-240215 [Patent Document 4]
Japanese Patent Publication No.54-24686 [Patent Document 5]
Japanese Patent Publication No. 3-57167 [Patent Document 6]
JP-A-6-336616 [Patent Document 7]
JP-A-7-278668 [0015]
[Problems to be solved by the invention]
However, although all of the above-mentioned methods are recognized to have certain effects, they are not always sufficient, and the quality of the subscale formed during decarburization annealing still varies, and the resulting magnetic properties May not be stable. In other words, there is still room for improvement in order to stably produce products having excellent quality and further improve yield.
[0016]
The present invention has been developed in view of the above-mentioned actual situation, and the quality of the subscale formed at the time of decarburization annealing is uniformly controlled to provide a uniform and excellent adhesiveness with no defects over the entire width and length of the coil. It is an object of the present invention to propose a novel method for producing a grain-oriented electrical steel sheet capable of obtaining a stellite film and thus obtaining excellent magnetic properties.
[0017]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the inventors evaluated the quality of the subscale formed after decarburization annealing, and examined the influence on the quality of the forsterite film formed after finish annealing.
As a result, it was investigated that the SiO ₂ production ratio on the steel sheet surface after decarburization annealing has a great influence on the appearance of the forsterite film after finish annealing, and the present invention has been completed.
[0018]
That is, in the present invention, after hot-rolling a silicon-containing steel slab, it is subjected to one or more cold rollings sandwiching intermediate annealing, and after decarburization annealing, an annealing separator is applied to the steel sheet surface. Then, when producing a grain-oriented electrical steel sheet through a series of processes for final finishing annealing,
The atmospheric oxidation degree (P [H ₂ O] / P [H ₂ ]) in the soaking process in the decarburization annealing is set to a range of 0.40 to 0.60, and the steel sheet surface after the decarburization annealing is formed on the surface layer. A method for producing a grain-oriented electrical steel sheet having excellent coating properties, characterized in that the SiO ₂ production ratio in the produced oxide is 60% or less.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The elucidation process of the present invention will be described below.
Now, the inventors have investigated the quality of the subscale in the decarburized annealed plate corresponding to the product having deteriorated magnetic properties using various measuring means. In this investigation process, for samples with a deteriorated appearance of the final product forsterite film, the steel plate surface after decarburization annealing is determined by the surface reflection infrared absorption spectrum method (Fourier Transform Infra Red: FT-IR method). Thus, it became clear that the deterioration of the appearance of the forsterite film of the final product can be accurately determined.
[0020]
That is, according to this FT-IR method, it is possible to evaluate the existence state of substances in the outermost layer of the steel sheet. For example, as shown in FIG. 1, SiO ₂ and other oxides (Fe ₂ SiO ₄ : Firelite, etc.), if the SiO ₂ peak is a and the other oxide peak is b,
a / (a + b) × 100 (%)
Thus, the production ratio of SiO ₂ can be obtained.
[0021]
FIG. 2 shows the film appearance pass rate of the final product with respect to the SiO ₂ production ratio thus obtained. Here, the coating film appearance pass rate means that the coating film appearance defect portion in the entire coil length is 10% or less of the entire coil length.
From the results shown in FIG. 2, it can be seen that the coating appearance can be accurately predicted from the determination result by the FT-IR method. In particular, the pass rate of the coating appearance jumps dramatically by setting the generation ratio of SiO ₂ to 60% or less. It can be seen that this is improved.
[0022]
Next, the factors affecting the SiO ₂ production ratio were investigated. As a result, the degree of atmospheric oxidation (P [H ₂ O] / P [H ₂ ]) in the temperature rising process during decarburization annealing, that is, hydrogen in the atmosphere It was found that the influence of the partial pressure of water vapor on the partial pressure was large.
[0023]
Hereinafter, the experiment that has led to this finding will be described.
C: 0.045 mass%, Si: 3.05 mass%, Mn: 0.068 mass% and Se: 0.019 mass%, with the balance being a silicon steel slab having a composition of Fe and inevitable impurities, A cold-rolled sheet having a thickness of 0.23 mm was obtained by cold rolling and then cold-rolling twice with intermediate annealing. Next, when performing decarburization annealing, the atmospheric oxidation degree (P [H ₂ O] / P [H ₂ ]) in the temperature raising process was changed variously. The atmosphere oxidation degree in the soaking process was set to 0.5.
[0024]
FIG. 3 shows the results of investigating the relationship between the SiO ₂ production ratio and the degree of atmospheric oxidation (P [H ₂ O] / P [H ₂ ]) in the temperature raising process in the decarburized annealed plate thus obtained. . From FIG. 3, when the SiO ₂ production ratio is S and the atmospheric oxidation degree (P [H ₂ O] / P [H ₂ ]) in the temperature rising process is y,
S≈−109.1y + 96.1
It was found that there is a correlation.
Therefore, the SiO ₂ production ratio can be controlled by the degree of atmospheric oxidation during the temperature raising process. In addition, although said relational expression, especially a coefficient change with the raw material components and process history of a steel plate, what is necessary is just to determine a relational expression each time as needed.
[0025]
As described above, the SiO ₂ production ratio was controlled to 60% or less, and the coating appearance was remarkably improved. However, there were some cases where the coating appearance deteriorated in some products.
Thus, further investigation on decarburization annealing revealed that the degree of atmospheric oxidation during the soaking process had an effect. That is, FIG. 4 shows the effect of the SiO ₂ production ratio and the atmospheric oxidation degree in the soaking process on the appearance of the coating film, with the SiO ₂ production ratio being 60% or less and further the atmospheric oxidation degree in the soaking process. It has been clarified that the film deterioration on the product plate can be prevented by regulating (P [H ₂ O] / P [H ₂ ]) in the range of 0.40 to 0.60.
In addition, the pass rate of the coating | film | coat external appearance shown in this FIG. 4 is evaluated similarly to what was shown in FIG.
[0026]
Here, regarding the degree of atmospheric oxidation in the soaking process (P [H ₂ O] / P [H ₂ ]), the height did not particularly affect the SiO ₂ production ratio.
On the other hand, the degree of atmospheric oxidation in the temperature rising process described above affects the oxide formed in the initial stage. When the SiO ₂ production ratio is lowered by this control, Excessive concentration and internal oxide deficiency are suppressed, and a uniform and dense oxide is formed. This oxide suppresses nitriding and oxidation during finish annealing, resulting in improved coating characteristics on the product plate. It seems that it was done. That is, the degree of atmospheric oxidation during the temperature rising process is dominant in the oxide distribution form.
[0027]
In this respect, the degree of atmospheric oxidation in the soaking process is dominant with respect to the amount of oxide formed. If the degree of atmospheric oxidation is too low, the subscale necessary for film formation is insufficient, resulting in poor film formation. If it is too high, a subscale is excessively formed, and the forsterite formation reaction at the time of finish annealing proceeds locally to cause a point-like film defect.
[0028]
Next, the preferred component composition of the grain-oriented electrical steel sheet targeted by the present invention will be described. As the raw material silicon-containing steel, any conventionally known component composition can be used, but the representative composition is as follows.
C: 0.02-0.10 mass%
C is a useful component for improving the crystal structure by utilizing the α-γ transformation during hot rolling, but a good primary recrystallized structure is obtained if the content is less than 0.02 mass%. On the other hand, if it exceeds 0.10 mass%, decarburization becomes difficult and poor decarburization is caused, leading to deterioration of magnetic properties. Therefore, it is preferable to be about 0.02 to 0.10 mass%.
[0029]
Si: 2.0 to 4.5 mass%
Si is an important component for increasing the electrical resistance of the product and reducing eddy current loss. However, if the content is less than 2.0 mass%, the crystal orientation is impaired by the α-γ transformation during the final finish annealing. On the other hand, if it exceeds 4.5 mass%, a problem occurs in the cold rolling property. About 0.5 mass% is preferable.
[0030]
Mn: 0.05 to 0.2 mass%, Se and / or S: 0.01 to 0.04 mass%
Mn and Se and S function as inhibitors MnSe and MnS, but if the amount of Mn is less than 0.05 mass% and the amount of Se or S is less than 0.01 mass%, the inhibitor function is insufficient, while Mn If the amount exceeds 0.2 mass% and the amount of Se or S exceeds 0.04 mass%, the temperature required for slab heating becomes too high to be practical, so Mn is 0.05 to 0.00. 2 mass%, and Se and S are preferably about 0.01 to 0.04 mass%, either alone or in combination.
[0031]
Sb: 0.005 to 0.05 mass%
Sb functions as an auxiliary inhibitor and is an element useful for improving magnetic properties. However, if the content is less than 0.005 mass%, the effect of addition is poor. On the other hand, if the content exceeds 0.05 mass%, the decarburization property is deteriorated, and therefore it is preferable to be about 0.005 to 0.05 mass%.
[0032]
The basic components have been described above. However, in the present invention, the following elements can be appropriately contained.
Cu: 0.05-0.20 mass%
Cu is an element effective for improving and stabilizing the magnetic properties. When Cu is added, the inhibitor changes from MnSe or MnS to CuSe or CuS. However, if the content is less than 0.05 mass%, it will not function sufficiently as an inhibitor. On the other hand, if it exceeds 0.20 mass%, pickling and brittleness during hot rolling deteriorate, so 0.05-0. It is preferable to be about 20 mass%.
[0033]
Cr: 0.05-0.30 mass%
When Cr content is less than 0.05 mass%, the effect of addition is poor. On the other hand, when it exceeds 0.30 mass%, a good primary recrystallized structure cannot be obtained. Therefore, Cr is contained at about 0.05 to 0.30 mass%. Is preferred.
[0034]
Sn: 0.03-0.30 mass%, Ge: 0.03-0.30 mass%
When Sn and Ge content is less than 0.03 mass%, the effect of addition is poor. On the other hand, when the content exceeds 0.30 mass%, a good primary recrystallized structure cannot be obtained, so 0.02 to 0.30 mass%, respectively. It is preferable to make it contain in a grade.
[0035]
Ni: 0.03-0.50 mass%
When the content of Ni is less than 0.03 mass%, the effect of addition is poor. On the other hand, when the Ni content exceeds 0.50 mass%, the hot strength decreases. Therefore, it is preferable that Ni be about 0.03 to 0.50 mass%.
[0036]
P: 0.002 to 0.30 mass%
When P is less than 0.002 mass%, the effect of addition is poor. On the other hand, when it exceeds 0.30 mass%, a good primary recrystallized structure cannot be obtained. Therefore, P is preferably about 0.002 to 0.30 mass%. .
[0037]
Nb: 0.003-0.10 mass%, V: 0.003-0.10 mass%
If Nb and V are both less than 0.003 mass%, the effect of addition is poor. On the other hand, if the content exceeds 0.10 mass%, decarburization deteriorates. It is preferable to contain.
[0038]
Mo: 0.005-0.10 mass%
Furthermore, Mo can be added to improve surface properties. However, if the content is less than 0.005 mass%, the effect of addition is poor. On the other hand, if the content exceeds 0.10 mass%, the decarburization property deteriorates, so it is preferable to set the content to about 0.05 to 0.10%.
[0039]
Next, preferred production conditions of the present invention will be specifically described.
First, the molten steel adjusted to the above-mentioned suitable component composition according to a conventionally used steelmaking method is cast by a continuous casting method or an ingot-making method, and a slab is sandwiched between pieces as necessary, and then 1250 to 1450 ° C. After performing the slab heating in the temperature range, hot rolling is performed. Next, after performing hot-rolled sheet annealing as necessary, a cold-rolled sheet having a final thickness is obtained by cold rolling at least once with one or intermediate sandwiches interposed therebetween.
[0040]
Next, decarburization annealing is performed. In this invention, first, the SiO ₂ generation ratio in the surface portion of the steel sheet after decarburization annealing is set to 60% or less. This SiO ₂ production ratio has a high correlation with the degree of atmospheric oxidation (P [H ₂ O] / P [H ₂ ]) in the temperature rising process in the decarburization annealing as described above, and the SiO ₂ production ratio is 60 It is preferable to adjust the degree of atmospheric oxidation during the temperature raising process so that the ratio is not more than%.
[0041]
In addition, as described above, obtaining the correlation between the SiO ₂ production ratio and the atmospheric oxidation degree in the temperature rising process as a relational expression in advance is simple in order to make the SiO ₂ production ratio 60% or less. At that time, since the relational expression varies depending on the component composition of the material and the process history before decarburization annealing, it is preferable to obtain the relational expression according to the steel type and the process conditions.
[0042]
In this decarburization annealing, the upper and lower limits of the atmospheric oxidation degree (P [H ₂ O] / P [H ₂ ]) in the soaking process must be limited to the range of 0.40 to 0.60. There is.
This is because if the degree of atmospheric oxidation in the soaking process is less than 0.40, the amount of subscale decreases, the amount of forsterite film formed becomes insufficient, and film formation defects such as thin films occur. On the other hand, if it exceeds 0.60, a subscale is excessively formed, the forsterite formation reaction at the time of finish annealing proceeds locally, and a point-like film defect occurs.
[0043]
The steel sheet surface that has been subjected to decarburization annealing as described above is coated with an annealing separator mainly composed of magnesia in a slurry state, and then dried.
Further, for the purpose of further improving the coating properties and magnetic properties, an oxide such as TiO ₂ , SnO ₂ , Fe ₂ O ₂ and CaO, a sulfide such as MgSO ₄ and SnSO _{4 in} the annealing separator, or One or two or more selected from Sr compounds such as SrSO ₄ and Sr (OH) ₂ .8H ₂ O may be added alone or in combination.
[0044]
Then, after the final finish annealing which also serves as secondary recrystallization annealing and purification annealing, a phosphate-based insulating coating, preferably an insulating coating having a tension, is applied to obtain a product. The secondary recrystallization annealing may be either a method in which the temperature is raised after performing a holding annealing for 20 to 70 hours at a certain temperature within a range of 750 to 900 ° C. during annealing, or a method in which annealing is performed without holding.
Further, it is possible to perform a known magnetic domain refinement treatment after the final cold rolling, the final finish annealing, or the insulating coating, which is effective in further reducing the iron loss.
[0045]
【Example】
A steel slab containing C: 0.038 mass%, Si: 3.25 mass%, Mn: 0.071 mass%, Se: 0.020 mass% and Sb: 0.023 mass%, with the balance being Fe and inevitable impurities. After heating at 1400 ° C. for 20 minutes, a hot-rolled sheet having a thickness of 2.2 mm was formed by hot rolling. Then, after hot-rolled sheet annealing at 950 ° C. for 1 minute, a final sheet thickness of 0.23 mm was finished by cold rolling.
[0046]
Next, when performing decarburization annealing, the degree of atmospheric oxidation in the temperature raising process was set under various conditions, and the SiO ₂ generation ratio after decarburization annealing was changed. The atmosphere oxidation degree during the soaking process was also changed in the range of 0.20 to 0.80. Incidentally, SiO ₂ generation ratio was determined by the method using a FT-IR method.
Furthermore, an annealing separator mainly composed of magnesia is made into a slurry, applied to a decarburized annealing plate coil, dried, and then subjected to secondary recrystallization annealing at 850 ° C. for 50 hours in a nitrogen atmosphere, Next, the temperature was raised to 1180 ° C. at a rate of 30 ° C./h in an atmosphere of nitrogen: 20% and hydrogen: 80%, and then annealed at 1180 ° C. for 5 hours in a hydrogen atmosphere. Thereafter, an insulating coating composed mainly of magnesium phosphate and colloidal silica was applied.
[0047]
The magnetic characteristics (magnetic flux density B ₈ ) of each product coil thus obtained, the bending adhesion of the coating, and the coating appearance were investigated.
In addition, the bending adhesiveness of the film was evaluated by the minimum diameter at which the test piece was wound around a round bar having various diameters at intervals of 5 mm and the film did not peel off.
The obtained results are also shown in Table 1.
[0048]
[Table 1]

[0049]
As is apparent from the table, all of the inventive examples manufactured under the conditions according to the present invention show good film properties and magnetic properties.
[0050]
【The invention's effect】
According to this invention, the SiO ₂ production ratio on the steel sheet surface after decarburization annealing is set to a predetermined value or less, and the degree of atmospheric oxidation (P [H ₂ O] / P [H ₂ ]) in the soaking process of decarburization annealing. ) Is appropriately controlled, a grain-oriented electrical steel sheet having excellent coating properties can be stably obtained.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a calculation procedure of a SiO ₂ production ratio by an FT-IR method.
FIG. 2 is a diagram showing the relationship between the appearance of a film and the SiO ₂ production ratio.
FIG. 3 is a diagram showing the relationship between the degree of atmospheric oxidation and the SiO ₂ generation ratio in the decarburization annealing temperature raising process.
FIG. 4 is a graph showing the influence of the SiO ₂ production ratio and the degree of atmospheric oxidation in the soaking process on the appearance of the film.

Claims (1)

After hot rolling the silicon-containing steel slab, it is cold-rolled once or two times with intermediate annealing, and after decarburization annealing, an annealing separator is applied to the steel sheet surface, and then the final finish When manufacturing grain-oriented electrical steel sheets through a series of annealing processes,
The atmospheric oxidation degree (P [H ₂ O] / P [H ₂ ]) in the soaking process in the decarburization annealing is set to a range of 0.40 to 0.60, and the steel sheet surface after the decarburization annealing is formed on the surface layer. method for producing a grain-oriented electrical steel sheet having excellent coating properties, characterized in that the SiO ₂ generation ratio thereof in the resulting oxide and 60% or less.

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