JPH07258802A - Grain oriented silicon steel sheet having high magnetic flux density and low iron loss and its production - Google Patents

Abstract

PURPOSE:To produce a grain oriented silicon steel sheet capable of forming a primary film and also providing stable Goss-oriented secondary-recrystallized grains. CONSTITUTION:This steel sheet is a grain oriented silicon steel sheet having a composition where 0.001-0.50% of elements having >=70kcal/mol activation energy, such as Hf and Bi, are contained in iron containing 1-7% Si. The primary-recrystallized grain size of this sheet is regulated to 5-35mum, and the standard deviation value is 10-70% of the above. An antimony type compound is added by 0.05-5.0% to magnesia, and the average temp. rise rate from 800'C to the maximum ultimate temp. at the time of secondary recrystallization annealing is regulated to (0.1 to 80) deg.C/hr, and also the bearing between sheets at the time of secondary recrystallization annealing is regulated to <=0.3kg/mm<2>. At this time, when a boron type compound is used instead of antimony type compound, the temp. rise rate from 800 deg.C to the maximum ultimate temp. is regulated to (5 to 400) deg.C/hr. By this method, a magnetic flux density of >=1.92T can be stably obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon steel sheet excellent in surface coating and magnetic properties and a method for producing the same.

[0002]

2. Description of the Related Art In manufacturing a silicon steel sheet having excellent magnetic properties for a transformer or the like, the insulating property and the magnetic property required for improving the performance of the transformer are improved by applying tension to the surface of the steel plate, and the adhesion with the steel plate is improved. It is very important to form a good primary coating. In the usual technique, magnesium oxide (MgS) called magnesia is applied to the steel sheet after primary annealing accompanied by decarburization.
(O) fine powder of water is applied as a slurry, dried as necessary, and then fired in the secondary recrystallization annealing step, and forsterite (Mg
A ceramic-like insulating coating called ₂ SiO ₄ ) is formed. This is effective in giving tension to the steel sheet and improving the magnetic property, especially the characteristic value called iron loss, which governs the efficiency of the transformer. Moreover, this state of forsterite formation is called the GOSS orientation of the steel sheet in the secondary recrystallization annealing, which is {110 to the steel sheet longitudinal direction (rolling direction) which is essential for improving the magnetic permeability and the magnetic flux density. }
It is well known that it also plays an important role in growing slightly coarse secondary recrystallized grains having a [001] crystal orientation.

That is, even if an attempt is made to carry out secondary recrystallization during the temperature rising process of secondary recrystallization annealing without forming a sufficiently dense film, fine nitrides and sulfides called inhibitors in the steel sheet remain as they are. Or, it disassembles and falls out of the steel plate quickly. For this reason, the GOSS oriented grains are preferentially grown during the temperature rise, and the inhibitor effect of the role of suppressing the growth of other oriented grains cannot be exhibited. This is commonly called fine grain, and secondary recrystallization of the GOSS oriented grains is performed. This results in a steel sheet with extremely poor magnetic properties in which grain growth does not occur partially or entirely. It should be noted that titanium oxide (TiO ₂ or the like) or another compound may be added to this MgO to form a denser primary coating.

In practice, however, it is not easy to stably produce a sufficient primary coating film and secondary recrystallization structure even with the above technical knowledge, and in particular, various secondary recrystallization annealing conditions are industrially necessary. Although it may be changed, it is not easy in this case to form a sufficient primary coating and to generate a secondary recrystallization having a sufficiently proper orientation. One of the reasons for this is that the elucidation in the manufacturing process regarding the formation of the primary coating and the formation of an appropriate precipitate in the secondary recrystallization process called an inhibitor is not yet sufficient.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, stably forming a primary coating on the surface of silicon steel during secondary recrystallization, and magnetic flux density B before magnetic domain control. ₈ ≧ 1.92T (tesla) and iron loss W _17/50
The present invention provides a grain-oriented silicon steel sheet having secondary recrystallized grains in which GOSS orientation is integrated, and a method for producing the same, capable of constantly producing ≤ 1.10 w / kg.

[0006]

The gist of the present invention is as follows. (1) Si: 1 to 7% and a steel containing at least one kind of elements having an activation energy Q of diffusion in iron of 70 kcal / mol or more in a total amount of 0.001% or more and 0.50% or less , Hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing in the production of grain-oriented electrical steel sheet as the basic process, in the magnesia applied before the secondary recrystallization annealing compound of antimony-based 0.05 to 5.0% is added, the average value of the measurement of the primary recrystallized grain size (cross-sectional grain size) is 5 to 35 μ, and the standard deviation value of each grain size is 10 to 70% of the average value.
And 800 in secondary recrystallization annealing
Average heating rate from ℃ to the highest temperature
The surface pressure between the plates in the secondary recrystallization annealing is set to 80 ° C.
A method for producing a high magnetic flux density low iron loss unidirectional electrical steel sheet characterized by being set to 3 kg / mm ² or less.

(2) Si: steel containing 1 to 7% and a total of one or more elements having an activation energy Q of diffusion in iron of 70 kcal / mol or more of 0.001% or more and 0.50% or less. Average value of the measurement of primary recrystallized grain size (cross-sectional grain size) in the production of grain-oriented electrical steel sheet with the basic steps of melting, hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing Is 5 to 35 μm, and the standard deviation value of the respective grain sizes is 10 to 70% of the average value, and the boron-based, strontium-barium-based boron is contained in the magnesia applied before the secondary recrystallization annealing. System, charcoal / nitride system, sulfide system, chloride system, total of 0.05-5.0%
The average temperature rising rate from 800 ° C to the highest temperature reached in the secondary recrystallization annealing was 5 to 400 ° C per hour, and the interplanar surface pressure was 0.3 kg / mm ^{2 in the} secondary recrystallization annealing. A method for producing a high magnetic flux density low iron loss grain-oriented electrical steel sheet characterized by the following. (3) Activation energy Q in (1) and (2) above
Hf, Bi, W, Nb, C with an element of 70 kcal / mol or more
Method of specifying o, Ni, Cu, Mo. (4) Activation energy Q in (1) and (2) above
Should be specified as Hf, Bi, W of elements with a value of 80 kcal / mol or more. (5) Hf, Bi, W, Nb, Co, Ni, and C in a steel sheet including a primary coating containing forsterite as a main component.
A total of one or more elements of u and Mo is 0.003 to 0.
A high magnetic flux density low iron loss unidirectional electrical steel sheet containing 30% and having a magnetic flux density B ₈ of 1.92 T (tesla) or more and an iron loss W _17/50 of 1.10 w / kg or less. (6) In the steel sheet including the primary coating containing forsterite as a main component, 0.003 to 0.30% of one or more elements of Hf, Bi, and W are contained in total, and the magnetic flux density B ₈ is ≥1.92T (tesla) and iron loss W _17/50 is 1.1
High magnetic flux density of less than 0 w / kg, low iron loss, grain-oriented electrical steel sheet.

The present invention will be described in detail below. Secondary recrystallization of grain-oriented silicon steel sheet is called GOSS orientation {11
It is essential that grains having a 0} <001> orientation are sufficiently grown during secondary recrystallization annealing (also called finish annealing).
This is to coarsely recrystallize only certain grains in the primary recrystallization annealing (hereinafter referred to as primary annealing) plate. At this time, fine precipitates such as AlN called an inhibitor are sufficient before finish annealing. It is well known that it is technically necessary to make it. And AlN, Si
_{When 3} N ₄ or the like is used, N necessary for this purpose is added during steel melting, after primary annealing, or during other steps. In the latter case, there is a method in which a facility for performing a nitriding reaction is installed inside or in close proximity to a part of the facility for primary annealing that also normally functions as a decarburizing reaction, and the nitriding reaction is performed after the primary annealing or in parallel with it.

In the case of steel having a sufficiently low carbon content at the time of steel melting, it is more important than the decarburizing function to change the oxide layer of the surface layer after the primary annealing so that the oxide layer has an advantageous shape for film formation.
In this way, the so-called MgO powder mainly composed of MgO is applied to the surface of the steel sheet in a slurry form on the steel sheet to which nitrogen is added in the step before or after the primary annealing, and the film is formed in the finish annealing step and the secondary re-annealing is performed. One method is to generate crystals, and the following experiment was conducted in connection with this primary film formation.

Table 1 shows the results of a finish annealing pull-out experiment in which a MgO powder was applied in a slurry form to a 3% Si steel sheet after the primary annealing and nitriding and the secondary recrystallization annealing was performed. Here, the powders are referred to as Sb-based and B-based, respectively. Here, a small amount of TiO ₂ (5%) and Sb ₂ (SO ₄ ) ₃ (0.2%), TiO ₂ (5%) and Na are included in the MgO powder, respectively. ₂ B ₄ O ₇ (0.3%) was added to promote the formation of forsterite. Secondary recrystallization annealing was performed halfway by the method shown in FIG. 1 and a so-called pull-out experiment was performed at each temperature. GDS analysis (Glow Discharge Optical Emission Sp
ectrometry: glow discharge emission spectroscopy), and Table 1 shows the results of investigating from which extraction temperature forsterite, that is, the Mg peak appears. Here, the temperature in () is determined to have appeared in the middle of the measured temperature. What is clear from the results in Table 1 is that forsterite is formed at a lower temperature in the Sb system than in the B system.

[0011]

[Table 1]

[0012] Forsterite is formed by reacting MgO with surface-enriched Si in the steel sheet, and 2MgO + SiO ₂ → M
It is generally considered that the reaction of g ₂ SiO ₄ has occurred. By the way, how can the manufacturing process of silicon steel sheets and the properties of these steel sheets be controlled?
I examined the point. If the causal relationship between the formation process of the primary coating film and the various properties of the silicon steel sheet is clarified as described above, naturally it can be industrially reflected in the production.

As can be seen from the experimental results in Table 1, when a small amount of Sb-based compound is added to MgO, the melting of MgO is performed at a relatively low temperature, so that the temperature rising rate of the secondary recrystallization annealing is relatively high. The smaller the size, the faster the production of forsterite is promoted and the easier it is to form an excellent primary coating. The antimony (Sb) -based compound means not only Sb ₂ (SO ₄ ) ₃ used in this experiment but other compounds containing Sb. On the other hand, even with the same low melting point compound, B
When a small amount of a system-based compound is added to MgO, the melting of MgO is performed at a relatively higher temperature than that of the Sb-based compound. Therefore, for example, it is faster to make the temperature rising rate of the secondary recrystallization annealing faster. Promotes the production of stellite. The boron (B) -based compound is not only a Na-based compound, but also a compound containing Ca, Mg, etc. instead of Na or boric acid (H ₃ BO).
₃ ) Also means sodium borate.

Further, strontium / barium type, carbon / nitride type, sulfide type, and chloride type have the same action as boron type in that they are higher melting point type than antimony type. These compounds will be collectively called non-antimony compounds. It should be noted that, although oxides such as TiO ₂ are usually added to MgO to facilitate the high temperature reaction, the effects of the above additives of the present invention are exhibited regardless of the amount of the oxide added. Even if an oxide is added to MgO, it can be regarded as a part of the base material by calling it a plane. As described above, according to the present invention, the primary coating, which is an important controlling factor for the properties of the silicon steel sheet, can be controlled to some extent freely by elucidating its composition distribution and combining it with a manufacturing method having a correlation therewith.

Now, it is necessary to touch on the method of manufacturing a silicon steel sheet. As described above, the silicon steel sheet to which the present invention is applicable contains Al as necessary, and contains AlN or Si ₃ N
It is possible that ₄ is part of the major inhibitor.
Of course, in addition to Si and Al, the pseudo-inhibitor element of the present invention described below and Mn, S, Se, Sb, B, Ti and S
The addition of other additive elements such as n, V, Cr and P to improve the magnetic characteristics does not change the basics of the present invention. By the way, steels using AlN or Si ₃ N ₄ as an inhibitor are known, and the technique of the present invention can be applied to any of them. However, with this alone, B ₈ ≧ 1.92T and W _17/50 ≦ 1.10 w / kg before performing the target magnetic domain control of the present invention.
Is difficult to achieve in a stable manner. That is, some of the main ideas of the present invention are as follows.

G is produced by secondary recrystallization of a conventional unidirectional electrical steel sheet.
In order to obtain a sharp OSS orientation, it is known to precipitate a precipitate called an inhibitor in iron before or during secondary recrystallization. It is generally said that this is because crystal grains having a GOSS orientation preferentially grow so as to suppress the growth of crystal grains in other orientations. In fact, unidirectional electrical steel sheets represented by AlN, MnS, MnSe, etc. use these precipitates to produce excellent magnetic steel sheets. However, it is difficult to stably produce the steel sheet having the above-mentioned characteristics of the present invention under any conditions by such a method alone. It is considered that the reason is that these precipitates basically decompose at a high temperature, for example, 1000 ° C. or higher. Therefore, it is considered that even if grain growth is performed under the inhibitor-free condition at grain growth of 1000 ° C. or higher, the grain growth may slightly deviate from the GOSS direction.

In order to deal with such a situation, firstly 10
It can be seen that the precipitates that exist stably at 00 ° C or higher are extremely important. Unfortunately, conventional knowledge has not found a suitable technology. The reason is that, for example, Ti forms a compound that is stable even at high temperatures, such as TiN, and oxides of other elements are stable even at relatively high temperatures, for example, 1200 ° C. or higher. However, the number of these compounds is not large enough to evenly cover the grain boundaries of crystal grains,
The function as an inhibitor cannot be expected. Even if a large amount is added to increase the amount, the secondary recrystallization annealing (also referred to as finish annealing), which also has the purpose of purification this time, does not sufficiently escape and remains and deteriorates the iron loss of the product. On the other hand, if the inhibitor strength remains unchanged at 1000 ° C or higher and remains stubborn,
It is conceivable that secondary recrystallized grains that have grown slightly up to 000 ° C. and are slightly deviated from the GOSS orientation may remain in the product as they are without correcting the trajectory.

The present invention has found breakthrough technical knowledge in order to overcome the situation of the conventional knowledge. The present invention was focused on from the viewpoint that there is a substance that suppresses grain boundary migration without being bound by the conventional concept of precipitates. As a result, it is easy to segregate at grain boundaries and 1000
It came to the point that there is an element that remains relatively even at high temperatures above ℃, and that gradually disappears from the steel sheet surface when the temperature becomes higher. As a result, we focused on the element that has a large diffusion activation energy Q (kcal / mol) after entering iron. The reason is as follows. The so-called diffusion coefficient D is expressed by an equation. D = D ₀ exp (−Q / RT) …………………………………… where D: diffusion constant, D ₀ : constant, R: gas constant, T:
Absolute temperature This formula becomes the formula when the logarithm is taken. InD = InD ₀ + (-Q / RT) …………………………………………

That is, the diffusion constant D shows that the larger the activation energy Q is, the smaller it is at high temperature, that is, the diffusion requires a long time. This means that if this equation holds even at high temperatures, elements with large Q (high diffusion energy elements) are stable even at high temperatures. It is predicted that such elements may themselves have potential as inhibitors. As a result, according to the present invention, it was revealed that when Q is 70 kcal / mol or more, the effect of the element itself as an inhibitor (hereinafter referred to as a pseudo-inhibitor effect in the present invention) is recognized. On the other hand, the addition of this element having a large Q is not always sufficient, and the magnetic flux density B ₈ ≧ 1.92T and the iron loss W _17/50 ≦ 1.10 w / kg before the target magnetic domain control of the present invention.
It has been revealed that it is difficult to manufacture a grain-oriented electrical steel sheet that satisfies the above requirements. The reason is as follows.

As described above, in the case of the grain-oriented electrical steel sheet, if the primary coating containing forsterite as a main component cannot be sufficiently formed, the inhibitor will escape, and not only the secondary recrystallization having the aligned GOSS orientation will not grow sufficiently. Iron loss due to the tension of the primary coating is not sufficiently improved, and a product with good magnetic properties cannot be obtained. On the other hand, there are more important conditions for the present invention to use the pseudo-inhibitor which is based on the characteristics of the diffusion constant of the element as described above. This is because pseudo-inhibitor elements such as Hf and Bi that appear on the surface during retention or cooling after the completion of secondary recrystallization react with other elements present on the surface to form a compound, and the form of the surface coating generated with care. This is a phenomenon that erodes stellite and the like, and these primary coatings do not sufficiently remain or do not exist at all. Therefore, the surface pressure between the plates of the coil during the secondary recrystallization needs to be 0.3 kg / mm ² or less. Above this, Hf, Bi, etc. do not sufficiently escape from the surface into the atmosphere, and the primary coating is not sufficiently formed.

From another point of view, the rate of temperature rise during secondary recrystallization is naturally a very important factor. This combination, so to speak, constitutes another important technical element of the present invention. The diffusion amount of the pseudo-inhibitor element, which is still stable even at 1000 ° C. or higher, changes depending on the heating rate. For example, in the case of Bi, it was revealed in the present invention that the diffusion formula is expressed as follows. D = 3.9 × 10 ³ exp (−85,000 / RT) …………………… (where Q of Bi is 85 kcal / mol)

Based on this, when the temperature rise rate of the secondary recrystallization annealing (finish annealing) is changed as shown in FIG. 2, the diffusion amount (movement amount) of Bi at that time is calculated from the equation. 3, the diffusion movement amount increases as the heating rate decreases. On the other hand, the formula is a diffusion formula of As in iron. D = 4.3 × exp (−52,500 / RT) ……………………

In the case of As, the relationship between the rate of temperature rise and the amount of diffusion movement is also represented as shown in FIG. That is, it can be seen from this that As has a smaller activation energy Q of 52.5 kcal / mol than Bi, the diffusion transfer amount is much larger at any heating rate, and the inhibitor function is much weaker. In both cases, the smaller the heating rate is, the larger the diffusion movement amount is. Then, as long as the secondary recrystallization is performed in the thermal activation process, there is competition with self-diffusion specific to the iron (Fe) element. The activation energy Q of Fe self-diffusion is 6
The value is around 0 kcal, which is smaller than the Q (≧ 70 kcal / mol) of the pseudo-inhibitor element of the present invention. This indicates that the driving force for the self-grain growth of the secondary recrystallized grains based on the self-diffusion of Fe is larger than the driving force for the diffusion movement of the pseudo-inhibitor element. It is considered that this is the reason why the pseudo-inhibitor element is, as a brake, a kind of drag effect as an inhibitor of secondary recrystallization. Therefore, the drag effect is 60 kcal / m of activation energy of iron self-diffusion.
If the element is 70 kcal / mol or more, which is larger than the ol value,
Naturally, a drug effect can be expected. B as this element
i, Hf, W, Nb, Co, Ni, Cu, Mo.

On the other hand, it was found that at 80 kcal / mol or more, this drag effect is further enhanced, and a high magnetic flux density unidirectional electrical steel sheet having a sharper secondary recrystallized structure in the GOSS direction can be obtained. Hf and B for elements above 80 kcal / mol
i and W. What is particularly important in the present invention is the relationship with the temperature rising rate of finish annealing. That is, when the temperature rising rate is high, the self-diffusion activation energy Q is smaller than the diffusion Q of the pseudo-inhibitor element of the present invention. That is, the driving force for iron grain growth is far greater than the driving force for pseudo-inhibitor.

However, as shown in FIG. 3, when the heating rate is high, the migration amount of the pseudo-inhibitor is reduced (the remaining amount is increased), so that the inhibitor effect is strengthened accordingly. Balance with the sudden increase in driving force of. On the other hand, when the heating rate is low, the opposite phenomenon occurs, and in this case as well, the grain growth and the inhibitor strength are well balanced. It is considered that the self-adjusting action of this pseudo-inhibitor element contributes to the formation of sharp secondary recrystallization of GOSS in an industrially stable manner with respect to the fluctuation of the heating rate. Especially the activation energy Q of diffusion is 80kc
It was found that the elements Hf, Bi, and W of al / mol or more exert this effect sufficiently, and that a grain-oriented electrical steel sheet having an extremely sharp magnetic flux density in the GOSS direction is obtained.

Naturally, the self-diffusion energy of iron (6
Activation energy Q of diffusion larger than 0 kcal / mol)
Nb, Co, Ni, C of other elements with a value of 70 kcal / mol or more
Elements such as u and Mo have similar effects, although to a lesser extent. Further, even if Q is in the order of 60 kcal / mol, V, Cr, and P close to 70 kcal / mol can be expected to have an auxiliary effect, but they are not essential in the present invention. Therefore, the temperature rising rate of finish annealing is rather determined by the requirement that the formation of the primary coating can follow it, and from this point, the following restrictions occur. When an Sb-based additive such as Sb ₂ (SO ₄ ) _3- based additive is added to magnesia, a good primary coating is likely to be formed at a relatively low temperature rising rate of finish annealing and from a low temperature. On the other hand, when a boron-based additive is added, it is easy to form a primary coating at a relatively high temperature and at a relatively high temperature rising rate.

Further important points of the constituent elements of the present invention are the following technical findings. It is difficult to stably obtain a secondary recrystallized structure having a sufficiently sharp GOSS orientation only by adding an element having an activation energy Q of diffusion of 70 kcal / mol or more which brings about the pseudo-inhibitor effect of the present invention. FIG. 4 shows 3.20 containing 0.025% of the pseudo-inhibitor element Bi.
% Of the average grain size and standard deviation of the cross-sectional structure of the crystal grain size after primary recrystallization annealing obtained by an image analyzer of the% Si steel and the magnetic flux density B _{8 of the} product It shows the relationship. Here, the method of obtaining the standard deviation of the particle diameter is expressed by an equation. Standard deviation: σn = ((ΣX ² − (ΣX) ² / n)) / n) ^1/2 ... where X: each crystal grain size n: number of crystal grains

In the present invention, the standard deviation is divided by the average particle size, multiplied by 100, and expressed as a percentage (%), which is an important index in the present invention as the ratio of the standard deviation to the average particle size. Treated as one of. As is clear from this, it can be seen that there is an optimum range of the ratio of the average particle diameter of the primary particle diameter in the cross section and the standard deviation to the average particle diameter that can stably obtain a high magnetic flux density. The reason for this is not clear, but it is considered as follows. That is, this is also considered to be related to the activation energy for diffusion of the pseudo-inhibitor element. The average value of the primary recrystallized grain size corresponds to the magnitude of the grain boundary energy of the primary grain size. The smaller the grain size, the larger the grain boundary area, and therefore the larger the grain boundary energy.

In the case of the present invention, the pseudo-inhibitor element is naturally segregated at the grain boundaries of the primary recrystallized grains, and also suppresses grain growth during the grain growth process. Therefore, if the average grain size is too large, the grain boundary energy is too weak, and grain growth is not sufficiently performed in finish annealing, resulting in a so-called fine grain structure, which is extremely poor in magnetism. On the other hand, if the average value of the primary grain size is too small, the grain boundary energy is too large and grains in any orientation are likely to grow, and secondary recrystallized structures in dispersed orientations are likely to be formed and the magnetism is not stably increased. This is the reason why the optimum range of the average grain size of the primary recrystallized structure exists.

On the other hand, when the large grains and the small grains are mixedly present, the concentration of the pseudo-inhibitor element segregated at the grain boundaries is locally different, and the pseudo-inhibitor element is diffused during the growth process of the primary recrystallized grains in the finish annealing. The absolute amount of movement is partially different. Therefore, due to the imbalance between the so-called iron self-diffusion-based grain growth driving force and the local variability of the inhibitor effect due to the local ubiquity of the migration amount of the pseudo-inhibitor element, grain growth of secondary recrystallization occurs. And the inhibitor effect are inconsistent with each other, and the inhibitor strength is gradually weakened uniformly with the growth of the secondary recrystallized grains, which causes a deviation from the basic idea of the present invention of preferential growth of GOSS. It seems that stability is not seen.

On the other hand, if the standard deviation of the primary particle diameter is less than 10% with respect to the average particle diameter, the magnetism deteriorates again. The reason for this is not clear, but the following can be considered. That is, if the grain size control property of the primary structure becomes too good, grains in any orientation have uniform and relatively uniform grain boundary energies, and it is conceivable that the growth priority of the GOSS oriented grains is lost. Now, in order to further exert the characteristics of the present invention, the following manufacturing method is most suitable.

That is, in the steel containing 1 to 7% of Si, if necessary, Al is contained in an amount of 0.1% or less when the steel is melted.
When Si ₃ N ₄ etc. is used as an inhibitor, N is forced into steel through direct nitriding reaction during or after decarburization annealing during steel melting in the silicon steel sheet manufacturing process or during primary annealing after cold rolling. It is characterized in that N is contained in the steel of 60 to 400 ppm before the secondary recrystallization annealing by a method such as a method of selectively adding it. In the present invention, at least 1% of Si is necessary for forming forsterite as described above. On the other hand, 7
If it exceeds%, the workability is extremely deteriorated and it is not suitable for industrial production.

Al is effective in forming an AlN inhibitor. However, if it exceeds 0.1%, the amount of Al ₂ O ₃ produced increases, impairing the cleanliness of sound steel, and adversely affecting the magnetic properties. N is indispensable for forming AlN and Si ₃ N ₄ inhibitors. In the present invention, when these inhibitors are used, a minimum of 60 ppm is required after primary annealing, that is, before the initiation of secondary recrystallization of finish annealing. is there. On the other hand, if it exceeds 400 ppm, Al and Si are eaten too much, which is not preferable. In the present invention, the other elements are not particularly characteristic as compared with the conventional steel, but the following restrictions are preferable.

C needs to be sufficiently low during steel melting or sufficiently low during decarburization annealing of primary annealing, and is preferably 0.03% or less at the start of secondary recrystallization annealing. If Mn is 0.5% or less, it reacts with S to form a MnS inhibitor. If it is 0.15% or less, it is preferable for further improving the magnetic flux density. O is Al if 0.05% or less after steel is melted
_It is preferable for cleanliness without making too much ₂ O ₃ . Hf,
The elements of Bi, W, Nb, Co, Ni, Cu and Mo have an activation energy of diffusion of 70 kcal / mol or more in iron and have the effect of improving the magnetic flux density and reducing the iron loss due to the above-mentioned pseudo-inhibitor effect. For that purpose, the total of one or more of them must be at least 0.001% at the time of steel melting. On the other hand, 0.
If it exceeds 50%, hot brittleness becomes severe and hot rolling becomes extremely difficult. It is considered that this is not related to the large activation energy at high temperature. V, Cr, and P are not essential elements in the present invention, but an auxiliary effect on the pseudo-inhibitor element is recognized as described above. In this case, if the total of one or more kinds does not include 0.02% or more, there is no auxiliary effect, while if over 0.30%, the primary film formation becomes insufficient. Although Sn is not an essential element in the present invention, it is effective in reducing iron loss, and in that case, 0.02% or more is necessary. On the other hand, if it exceeds 0.20%, the primary coating cannot be sufficiently formed.

Next, the production method of the present invention other than the chemical components will be described. Continuous casting method, ingot-agglomeration and rolling method, or thin slab continuous method for omitting hot rolling step, in which steel is tapped in a converter or electric furnace, and a refining step is added as necessary to adjust the composition. A slab having a thickness of 30 to 400 mm (50 mm or less in the thin slab continuous casting method) is formed by a casting method or the like. Here, 30 mm is the lower limit of productivity, and 400 mm is the upper limit for preventing abnormal distribution of Al ₂ O ₃ etc. due to center segregation. Further, 50 mm is the upper limit for suppressing the generation of coarse particles due to the low cooling rate in the thin slab continuous casting method.

The slab is reheated to 1000 to 1400 ° C. by gas heating, electric heating, etc., and then hot rolled to obtain a hot coil having a thickness of 10 mm or less. Here, 1000 ° C. is the lower limit of AlN melting, and 1400 ° C.
Is the upper limit of surface roughness and material deterioration. Further, 10 mm is an upper limit for obtaining a cold speed at which an appropriate precipitate is formed. In the thin slab continuous casting method, it is possible to directly form a coil, and for that purpose, it is preferably 10 mm or less. The hot coil thus produced is often annealed again at 800 to 1250 ° C. to improve the magnetism. 8 here
00 ° C. is the lower limit for re-dissolving inhibitor precipitates such as AlN, and 1250 ° C. is the upper limit for preventing coarsening of inhibitor precipitates such as AlN.

After this treatment step, the hot coil is pickled directly or batchwise and then cold rolled. Cold rolling is performed at a rolling reduction of 60 to 95%, 60% being the limit of recrystallization in the present invention, preferably 70% or more by primary annealing and increasing {111} [112] oriented grains, It is a lower limit for promoting the generation of GOSS oriented grains during secondary recrystallization annealing,
On the other hand, if the content exceeds 95%, secondary recrystallization annealing causes GOSS-oriented grains, which are called swinging GOSS grains, to rotate in the plane of the plate to produce grains unfavorable to the magnetic properties. Although the above is the case of manufacturing by the so-called single cold rolling method, when the cold rolling-annealing-cold rolling is performed by the double cold rolling method, the first rolling reduction is 10 to 80.
%, And the second rolling reduction is 50 to 95%. Where 10
% Is the minimum reduction ratio required for recrystallization, 80% and 95% are the upper limit reduction ratios for producing proper GOSS oriented grains during secondary recrystallization, and 50% is the primary annealing in the double cold rolling method. It is the lower limit of the reduction rate in which {111} [112] oriented grains are appropriately left.

It is also commonly called "interpass aging" and it is effective to improve the magnetic properties by heating the steel sheet in the range of 100 to 400 ° C by an appropriate method during the cold rolling. 10
If it is less than 0 ° C, the effect of aging is not obtained, while if it exceeds 400 ° C, dislocations are recovered. After that, the primary annealing is performed by either the single cold rolling method or the double cold rolling method, and it is effective to perform decarburization by this annealing. As described above, C is not preferable for the growth of secondary recrystallized grains, and if it remains as an impurity, it causes deterioration of iron loss. If C is lowered during melting of steel, not only the decarburization process is shortened, but also {111} [1
12] It is preferable because the number of oriented grains is also increased. By setting an appropriate dew point in this decarburization annealing step, the oxide layer necessary for the subsequent formation of the primary coating can be secured. Primary annealing temperature is 70
0-950 degreeC is preferable. Here, 700 ° C. is the lower limit temperature at which recrystallization is possible, and 950 ° C. is the upper limit temperature for suppressing the generation of coarse particles.

Further, in the case of positively utilizing AlN or N of Si ₃ N ₄ inhibitor, forcible addition is performed by a nitriding method or the like during melting of steel or during primary annealing, but
When performing during or immediately after the primary annealing, ammonia (NH
Nitriding is also performed by nitriding method such as ₃ ). In this case, the temperature of the nitriding method is preferably 600 to 950 ° C. Here, 600 ° C. is the lower limit of the nitriding reaction, while 950
C is the upper limit for suppressing the generation of coarse particles.

In the present invention, when the nitriding is performed after the primary recrystallization annealing, industrially, a partition is provided on the rear surface of the same furnace and the atmosphere is slightly changed according to need, and NH ₃ gas is flowed or it is brought close to it. Since it is carried out at the facility, nitriding is often performed in parallel with primary recrystallization. At this time, as described above, N
_The lower the partial pressure of ₂ is, the larger the amount of nitriding is, and the partial pressure ratio P N ₂ / P H ₂ of nitrogen and oxygen is preferably 0.5 or less. Primary annealing or the above nitriding method is performed, and then magnesium oxide (MgO as a main component; hereinafter referred to as MgO) powder is dissolved in water or an aqueous solution containing water as a main component to form a slurry, which is applied to a steel sheet. At this time, a trace amount of an appropriate compound may be added for the purpose of facilitating the melting of the MgO powder during the subsequent secondary recrystallization annealing and accelerating the forsterite formation reaction. When TiO ₂ is added, it is preferably 1 to 15%, but here, 1% is the lower limit for exerting the effect of promoting the forsterite reaction, and if it exceeds 15%, the amount of MgO decreases and the forsterite reaction does not proceed.

Antimony compounds such as Sb ₂ (SO ₄ ) ₃ are effective in melting MgO at a relatively low temperature, and when added, 0.05 to 5% is preferable. Here, 0.05% is the lower limit for causing the above-mentioned low-temperature melting, while if it exceeds 5%, it is too much to inactivate the original reaction of MgO forsterite. Boron-based compounds such as Na ₂ B ₄ O ₇ and strontium / barium-based, carbon / nitride-based, sulfide-based, and chloride-based compounds that have the same action as Mg have higher temperatures than antimony-based compounds.
It has the effect of melting O, and when it is added, it is 0.0
5 to 5% is preferable. Here, 0.05% is the lower limit for exhibiting the above-mentioned effect, while if it exceeds 5%, the original reaction of MgO forsterite is inactivated, which is not preferable. It should be noted that these compounds may be added in combination with each other.

However, when an antimony low temperature melting type compound and a boron or other relatively high temperature melting type compound are mixed and used, the effect is close to that of the high temperature melting type compound, but it contradicts the gist of the present invention. However, in that case, it is preferable to adopt the high temperature melting type temperature rising rate of the present invention. In addition,% of the compound added here is shown by the weight ratio when the weight of MgO is 100%. The secondary recrystallization annealing is preferably performed at the highest temperature reached of 1100 to 1300 ° C.
1100 ° C. is the lower limit temperature at which secondary recrystallization is performed,
On the other hand, if the temperature exceeds 1300 ° C., the crystal grains become too coarse, and the iron loss is deteriorated. Note that, as described above, the nitriding method in which N is additionally added from the atmosphere or the like may be performed at a relatively previous stage during the secondary recrystallization annealing.

Now, the temperature rising rate of the secondary recrystallization annealing is particularly important in the present invention. That is, it is necessary to change the temperature rising rate depending on the type of compound added to MgO. When an antimony-based compound is added to MgO, it is necessary that the average heating rate from 800 ° C. to the highest reached temperature is 0.1 to 80 ° C. per hour, which is relatively small. Here, 0.1 ° C./hour is the lower limit of the industrial heating rate, while as described above, MgO melts at a low temperature when an antimony-based compound is added, so that forsterite can be formed more quickly and reliably. It is necessary to set the temperature rise rate to 8
It is necessary to keep it at 0 ° C./hour or less. On the other hand, boron series,
In the case of strontium / barium system, carbon / nitride system, sulfide system and chloride system, the average heating rate is 5 to 400 per hour.
C is preferred. That is, since the melting of MgO occurs at a relatively high temperature when a high temperature melting type compound is added, a temperature rising rate of 5 ° C./hour or more is required in order to reach a high temperature quickly. Secondary recrystallization itself is not sufficiently performed in relation to the inhibitor.

Further, when the surface pressure between the plates of the coil during secondary recrystallization retention or cooling exceeds 0.3 kg / mm ² , pseudo-inhibitor elements such as Hf and Bi do not escape from the coil and form a compound, which corrodes forsterite. As a result, a sufficient primary coating cannot be formed. The above is an important part of the method for producing a silicon steel sheet according to the present invention, but industrially, for the purpose of further improving insulating properties and magnetic properties, a steel sheet is made of an organic or inorganic material such as a roll coater method, a colloid method or a zolgel method. To form a secondary film, and to control the magnetic domain by a non-contact type energy irradiation method such as mechanical, chemical or laser addition, and then to form a tertiary film to prevent dusting. Often involves steps.

[0045]

【Example】

Example 1 Steel having the chemical structure shown in Table 2 was melted in a 150 kg vacuum melting furnace. This was cast, heated and hot rolled to obtain a hot rolled sheet having a thickness of 1.8 mm. 1120 ℃ for some hot rolled sheets
It was annealed for 30 seconds. The hot-rolled sheet annealed material and the as-hot-rolled material were pickled and then cold rolled by applying a 90% reduction to give a final sheet thickness of 0.18 mm. During this cold rolling process, the material was subjected to interpass aging to keep the material at a temperature of 250 ° C. After that, wash the material with oil,
After performing primary recrystallization annealing which also serves as decarburization under the annealing conditions of Table 3 in an atmosphere of N ₂ : 25% + H ₂ : 75%, dew point: 60 ° C., the following annealing separator was applied.

(1) MgO + TiO ₂ (5%) + Sb ₂ (S
O ₄ ) ₃ (0.2%: Sb system), (0.02%: low Sb system),
(6.0%: High Sb system) (2) MgO + TiO ₂ (5%) + Na ₂ B ₄ O ₇ (0.3%:
B type), (0.03%: low B type), (7.0%: high B type) (3) MgO + MgSO ₄ (4%) + FeSO ₄ (0.1%) +
Na ₂ B ₄ O ₇ (0.5%) …… Sulfide system (4) MgO + SrCO ₃ (0.08%) + BaCl ₂ (0.5
%) + Ba (H) ₂ (0.1%) …… Strontium / barium system (5) MgO + V ₂ O ₅ (5%) + CrN (3%) …… Carbon / nitride system (6) MgO + MnO ₂ (0.2%) + TiO ₂ (8%) + Ti
Cl ₄ (0.5%) …… Chloride

The annealing separator is dissolved in water to form a slurry, which is applied to a steel sheet by a roll coater and then 350 ° C.
Dried in the oven. Then, in the finish annealing step,
The steel sheet was secondarily recrystallized by variously changing the temperature rising rate between 800 ° C. and the maximum reached temperature. After washing the annealed material with water,
A phosphoric acid type insulating film (secondary film) was applied and baked. N ₂ : 90% + H ₂ : 10% on the obtained silicon steel sheet
After performing stress relief annealing at 850 ° C. for 4 hours in the dry atmosphere, the film and macrostructure visual inspection, magnetic measurement, film tension measurement, and adhesion test were performed. The results are shown in Table 3.

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

The results of the visual inspection of the coating film are shown by ○: scale,
No marbling defect, △: Some marbling defect, ×
Mark: Scale and marbling defects were many, and the coating was not sufficiently formed. The scale means that the coating film is peeled off to some extent, and the marbling defect is a defect in which the coating film is peeled off in spots.
In addition, the results of the macrostructure visual inspection are indicated as ○: secondary recrystallized structure is sufficiently formed, △: fine grains are partially observed, ×: fine grains are observed on the entire surface Shown by way. The magnetic measurement was performed by an SST (Single Sheet Tester) test method for a single plate having a width of 60 mm and a length of 300 mm. The B ₈ value (magnetic flux density at 800 A / m [Gauss]) and W _17/50 (iron loss value at an alternating magnetic field of 1.7 Tesla at 50 Hz [w / kg]) were measured.

In the adhesion test, a steel plate was wound around a cylinder having a diameter of 20 mm, and the results are indicated as ◯: no cracks in the coating, Δ: fine cracks in the coating, x: cracks on almost the entire surface. It was evaluated by the display method. Further, the film tension was measured by a method in which the film on one surface of the steel sheet was removed, the warpage of the steel sheet at that time was measured, and the film tension was calculated. The larger the calculated value is, the larger the tension generated in the steel sheet due to the difference in thermal expansion coefficient between the coating and the base iron is, and thus the iron loss characteristics are greatly improved. The thinner the plate, the higher the film tension.

As is clear from Table 3, a grain-oriented silicon steel sheet manufactured by using an annealing separator containing an Sb (antimony) -based compound has a low rate of temperature rise in the finish annealing step, and has a B-type composition. In the grain-oriented silicon steel sheet produced by using the annealing separator added with a compound such as the above, the temperature rising rate is relatively high, and the conditions defined in the present invention are satisfied. Among them, the primary recrystallization structure is in the present invention. All of the above products have good results of the above characteristic test.

Example 2 Steels having the chemical compositions shown in Tables 4 and 7 were melted in a converter,
A product having a thickness of 0.27 mm was manufactured under the manufacturing conditions shown in Tables 5 and 8. In addition, about the material of code | symbol 2-23, the nitriding process was given to the steel plate during temperature rising in the finish annealing process.
Regarding the materials 2-9 and 2-14 to 2-20, the steel sheets were nitrided in an atmosphere containing ammonia gas after the primary recrystallization annealing. Regarding the material indicated by the reference numeral 2-21, the steel sheet was nitrided in an atmosphere containing ammonia gas after the primary recrystallization annealing, and further, the steel sheet was nitrided during the temperature increase in the finish annealing step. The various compounds added to the annealing separator are the same as in Example 1.
The obtained product was subjected to various characteristics tests similar to those in Example 1. The results are shown in Tables 6 and 9. As is clear from Tables 6 and 9, those satisfying the conditions specified in the present invention have good results of the above characteristic tests.

[0055]

[Table 5]

[0056]

[Table 6]

[0057]

[Table 7]

[0058]

[Table 8]

[0059]

[Table 9]

[0060]

[Table 10]

[0061]

According to the present invention, it is possible to obtain a grain-oriented electrical steel sheet having excellent magnetic properties.

[Brief description of drawings]

1A, 1B, and 1C are charts showing finish annealing conditions.

FIG. 2 is a chart showing finish annealing rates.

FIG. 3 is a chart showing a relationship between a temperature rising rate and a diffusion movement amount.

FIG. 4 is a chart showing the relationship between the average value and standard deviation of primary particle diameters and magnetic measurement.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C23C 22/00 A H01F 1/16 (72) Inventor Shuichi Yamazaki 20-1 Shintomi, Futtsu-shi New Japan Technology Development Headquarters

Claims (6)

[Claims] 1. A steel containing 1: 1 to 7% of Si and a total of one or more elements having an activation energy Q of diffusion in iron of 70 kcal / mol or more of 0.001% to 0.50%. The average value of the measurement of the primary recrystallized grain size (cross-sectional grain size) in the production of grain-oriented electrical steel sheet, which is manufactured by hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing. 5
.About.35 .mu.m, and the standard deviation value of the respective grain sizes is 10 to 70% of the average value, and 0.0% of the antimony-based compound is added to the magnesia applied before the secondary recrystallization annealing.
Addition of 5-5.0%, and 800 ℃ in secondary recrystallization annealing
To the maximum temperature reached from 0.1 to 8 per hour
The surface pressure between the plates in the secondary recrystallization annealing is set to 0 ° C. and 0.3
A manufacturing method of a high magnetic flux density low iron loss unidirectional electrical steel sheet characterized by being set to kg / mm ² or less. 2. A steel containing 1: 1 to 7% of Si and one or more elements having an activation energy Q of diffusion in iron of 70 kcal / mol or more in a total amount of 0.001% to 0.50%. The average value of the measurement of the primary recrystallized grain size (cross-sectional grain size) in the production of grain-oriented electrical steel sheet, which is manufactured by hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing. 5
.About.35 .mu., And the standard deviation value of the respective grain sizes is 10 to 70% of the average value, and boron-based, strontium-barium-based, carbon-nitride is contained in magnesia to be applied before secondary recrystallization annealing. System, sulfide system, and chloride system, one or two or more of them are added in a total amount of 0.05 to 5.0%, and the average heating rate from 800 ° C to the maximum reached temperature in the secondary recrystallization annealing is A method for producing a high magnetic flux density low iron loss unidirectional electrical steel sheet, characterized in that the surface pressure between the sheets is set to 0.3 kg / mm ² or less by secondary recrystallization annealing at 5 to 400 ° C. per hour. 3. Hf, Bi, W, Nb, Co, Ni, C as an element having an activation energy Q of 70 kcal / mol or more.
3. The element according to claim 1, which is selected from the group of elements u and Mo.
A method for producing the described high magnetic flux density low iron loss unidirectional electrical steel sheet. 4. A high magnetic flux density, low iron loss unidirectional electromagnetic field according to claim 1, wherein the element having an activation energy Q of 80 kcal / mol or more is selected from the group of elements Hf, Bi and W. Steel plate manufacturing method. 5. Hf, Bi, W, Nb, Co, N in a steel sheet including a primary coating containing forsterite as a main component.
0.003 in total of one or more elements of i, Cu and Mo
˜0.30% and magnetic flux density B ₈ is 1.92T
(Tesla) or more and iron loss W _17/50 is 1.10 w / kg or less, high magnetic flux density low iron loss unidirectional electrical steel sheet. 6. A steel sheet including a primary coating containing forsterite as a main component contains 0.003 to 0.30% of one or more elements of Hf, Bi and W in total, and has a magnetic flux density B. ₈ is 1.92T (tesla) or more and iron loss W _17/50
Is 1.10 w / kg or less, high magnetic flux density low iron loss unidirectional electrical steel sheet.