JP2000034521A - Production of grain oriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel sheet in which secondary recrystallization is stabilized and excellent in magnetic permeability and iron loss by optimumly controlling the average cooling rate after the completion of the hot rolling of a Bi- added silicon slab, the atmosphere in decarburizing annealing and the content of oxygen in the surface of the final finish annealed steel sheet respectively. SOLUTION: The compsn. of steel is composed of, by weight, 0.03 to 0.10% C, 2.0 to 5.0% S, 0.04 to 0.15% Mn, one or two kinds of S and Se by 0.01 to 0.03%, 0.015 to 0.035% solAl, 0.0050 to 0.010% N, 0.001 to 0.07% Bi, and the balance Fe. This silicon slab is heated to >=1,300 deg.C and is subjected to hot rolling. The average cooling rate till the passage of 5 sec directly after the completion of the hot rolling is controlled to 30 to 120 deg.C/sec. PH20/PH2 in the atmosphere in the soaking stage in decarburizing annealing is controlled to 0.45 to 0.70. Moreover, the content of oxygen in the surface of the final finish annealed steel sheet is controlled to <=1.5 g/m2 per side. Or, furthermore, as for a separation agent for annealing for final finish annealing, the amt. of TiO2 to be added to 100 pts.wt. MgO is controlled to <=10 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet which is suitable for use as an iron core of a transformer or other electric equipment.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets used as core materials for transformers, generators and rotating machines are required to have high magnetic flux density and low iron loss as the most important characteristics. To date, various measures have been taken to reduce the iron loss of grain-oriented electrical steel sheets. Among them, the crystal orientation must be highly integrated in the {110} <001> orientation called the Goss orientation. Is one of the most important development goals. This is because the crystal orientation <001>, which is the direction of the axis of easy magnetization of the iron crystal, is highly integrated in the rolling direction, so that the magnetizing force required for the magnetization in the rolling direction is reduced.
This is because as a result of the decrease in the coercive force, the hysteresis loss decreases, and thus the iron loss decreases.

[0003] In addition, aligning the crystal orientation with the Goss orientation greatly contributes to the reduction of noise when magnetized, which is an important required characteristic of grain-oriented electrical steel sheets. That is, as a cause of noise generated from a transformer, it is known that there is a magnetostrictive vibration or an electromagnetic vibration of an iron core material, but the degree of integration of a crystal orientation in a Goss orientation is improved, which causes a magnetostrictive vibration. At the same time as the generation of 90 ° magnetic domains is suppressed, the exciting current is reduced to suppress the electromagnetic vibration, and as a result, noise is reduced.

As described above, it can be said that it is the most important task for the grain-oriented electrical steel sheet to integrate the crystal orientation <001> in the rolling direction. Here, as an index of the degree of integration of the crystal orientation, B ₈ (magnetic flux density at a magnetization force of 800 A / m)
In many cases it is used, therefore, the development of the grain-oriented electrical steel sheet is promoted to improve the B ₈ as a major goal. In addition, typical values of iron loss include an exciting magnetic flux density of 1.7 T,
W _17/50, which is an energy loss at an excitation frequency of 50 Hz, is typically used.

[0005] The secondary recrystallized grain structure of such a grain-oriented electrical steel sheet is formed through a phenomenon called secondary recrystallization during final finish annealing. The product having the desired magnetic properties has been obtained by huge growth.

In order to effectively promote the accumulation of the secondary recrystallized grains, a precipitation-dispersed phase called an inhibitor which selectively inhibits the growth of the primary recrystallized grains is uniformly and appropriately sized in steel. It is important to form with. The presence of this inhibitor suppresses the normal grain growth of the primary recrystallized grains, maintains the state of fine primary grains up to high temperatures during finish annealing, and increases the selectivity for the growth of crystal grains with good orientation. Accumulation of oriented crystal grains is increased, and a high magnetic flux density is realized. It is generally considered that the stronger the inhibitor and the stronger the ability to suppress normal grain growth, the higher the degree of orientation accumulation.

[0007] Such inhibitors include MnS, M
Substances with low solubility in steel, such as nSe, Cu _2-x S, Cu _2-x Se, and AlN, are used. For example, JP-B-33-4710 and JP-B-40-15644 disclose Al in the material.
Is disclosed, in which the final cold rolling reduction is set to a high pressure of 81 to 95% and annealing is performed before final cold rolling to precipitate AlN, which is a strong inhibitor.

[0008] In addition to the above inhibitor components,
It is known that the addition of Sn, As, Bi, Sb, B, Pb, Mo, Te, V, Ge, etc. is effective for improving the degree of secondary crystal orientation. . Among these additional inhibitor components, P, As, Sb, and Bi, which are classified as Group 5B elements in the periodic table, segregate on the crystal grain boundaries to form the main inhibitors MnS, MnSe, and Cu. _{2-x S, Cu 2-} x Se, in cooperation with AlN or the like to enhance the normal grain growth inhibiting force, is known to enhance the magnetic properties. Among these components, Bi is particularly promising as a component for enhancing the ability to suppress normal grain growth due to the grain boundary segregation effect, since Bi has particularly low solubility in iron.

As a technique for improving the magnetic properties by adding Bi, there are JP-B-51-29496 and JP-B-54-32.
The technology disclosed in Japanese Patent Publication No. 412 is known.
Also, Japanese Patent Publication No. 62-56924 and Japanese Patent No. 2872
No. 404 and Japanese Patent Publication No. 7-62176 disclose AlN
A method is described in which Bi, MnSe, MnS, etc., and Bi are added to steel in a complex manner. In these technologies, it is true that Bi
However, it has not yet established proper manufacturing conditions for Bi-added materials, and is not sufficient to stably obtain grain-oriented electrical steel sheets with high magnetic properties. there were.

Similarly, JP-A-6-88171, JP-A-6-88172, JP-A-6-88173, JP-A-6-88174, etc. add Bi to an Al-based inhibitor. Thus, it is stated that the magnetic flux density can be greatly improved, but the effect itself of adding Bi has not only been known in the past but also has not been able to stably bring out the effect of improving the magnetic properties.

Japanese Patent Application Laid-Open No. 6-158169 discloses a method for stabilizing the magnetic properties of a material to which Bi is added. In addition, a production method in which the decarburization annealing subsequent stage is set to a reducing atmosphere is disclosed, but the decarburization annealing conditions in this technique are mainly intended to stabilize the film formation, and to the material to which Bi is added. However, it cannot be said that optimal conditions have been established.

Further, as to the finish annealing separator, Japanese Patent Application Laid-Open No. 8-253819 discloses a technique in which the coating amount per one side of a steel sheet is 5 g / m ² or more. This technique aims at improving the coating by improving the flowability between the coil layers, and does not have an effect of stabilizing the magnetic characteristics. Further, according to the research results of the inventors, it is expected that merely increasing the application amount of the separating agent will promote instability of magnetic properties.

Regarding the technique of using a low-activity substance as an annealing separator of the Bi additive, Japanese Patent Application Laid-Open No. 6-256849 discloses a method of applying a substance having low reactivity with SiO ₂ after a nitriding treatment step. However, in this technique, Bi plays only the role of preventing the decomposition of the inhibitor during the finish annealing which is peculiar to the mirror-finished material including the nitriding treatment step. Japanese Patent Application Laid-Open No. 7-173544 discloses a method of manufacturing a mirror-oriented grain-oriented electrical steel sheet in which an annealing separator containing a chlorine compound of a metal is applied to a material to which Bi is added. Also, in Bi, the main purpose of Bi added to steel is mainly to obtain a mirror surface, and if the decarburizing annealing conditions are not controlled, sufficient magnetic properties cannot be stably obtained.

Japanese Patent Application Laid-Open No. 9-202924 discloses that decarburizing annealing is performed in an atmosphere in which iron-based oxides are not generated, or after removing oxides on the surface of a decarburized annealing plate,
A method of applying alumina as an annealing separator is described, and alumina is used as an annealing separator in order to obtain good magnetic properties without being affected by the flow of Bi gas between coil layers during finish annealing. By using this technique, the amount of oxygen on the surface of the final finish annealing plate as intended in the present invention is reduced by the alumina separating agent, and although the magnetic properties are stabilized to some extent, the decarburizing annealing condition is advantageous only for mirror finishing. Secondary recrystallization is not completely stable because
When alumina is used as the annealing separator, it is difficult to remove impurities from the steel, and the hysteresis loss is deteriorated.

[0015]

Although the addition of Bi is a very promising method for improving the magnetic properties of grain-oriented electrical steel sheets, secondary recrystallization defects are likely to occur due to various factors, and high magnetic properties can be obtained. Is difficult to obtain in a stable manner. An object of the present invention is to stabilize secondary recrystallization of a grain-oriented electrical steel sheet to which Bi is added, and to produce a grain-oriented electrical steel sheet having excellent magnetic permeability and iron loss.

[0016]

[Means for Solving the Problems] As a result of the inventors' research,
It was concluded that it was important to optimize the decarburization annealing and finish annealing conditions for the Bi-added materials, as well as the manufacturing conditions for the upper steps such as hot rolling. In addition, it has been found that when the forsterite film is excessively formed during the finish annealing, the magnetic properties of the material to which Bi is added easily deteriorate. From this, the inventors conducted research to solve the above-mentioned problems, and found that the Bi-added material can stably produce a grain-oriented electrical steel sheet with a high magnetic flux density by limiting the formation of forsterite during finish annealing. The present invention was found to be possible.

According to the present invention based on the above findings, C: 0.03
~ 0.10wt%, Si: 2.0 ~ 5.0wt%, Mn: 0.04-0.15wt
%, S and Se, one or two selected from: 0.01 to 0.2.
03 wt%, sol.Al: 0.015-0.035 wt% and N: 0.0050-
After heating a silicon steel slab containing 0.010 wt% and containing Bi: 0.001 to 0.07 wt% to a temperature of 1300 ° C. or more, hot rolling is performed, and then annealing and cold rolling are combined. In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of decarburizing annealing and then final finishing annealing after the final sheet thickness, the average cooling rate from immediately after the end of hot rolling to 5 seconds after the end of hot rolling is 30 to 120 ° C. / controls seconds, a P _H20 / P _H2 in the atmosphere of the soaking process in decarburization annealing and 0.45 to 0.70, further, per side oxygen content of the final finish annealing plate surface 1.5 g / m
This is a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by being ² or less.

Further, the present invention relates to a method for producing C: 0.03 to 0.10 wt%,
Si: 2.0 to 5.0 wt%, Mn: 0.04 to 0.15 wt%, one or two selected from S and Se: 0.01 to 0.03 wt%, sol.A
l: A silicon steel slab containing 0.015 to 0.035 wt% and N: 0.0050 to 0.010 wt% and containing Bi: 0.001 to 0.07 wt% is heated to a temperature of 1300 ° C. or more, and then hot-rolled. Next, in a method for manufacturing a grain-oriented electrical steel sheet comprising a series of steps of performing a final sheet thickness by combining an annealing treatment and a cold rolling treatment and then performing a decarburizing annealing and a final finishing annealing, 5 seconds immediately after the end of hot rolling. Average cooling rate after 30
Controls to to 120 ° C. / sec, a P _H20 / P _H2 in the atmosphere of the soaking process in decarburization annealing and 0.45 to 0.70, further, Ti for MgO 100 parts by weight per annealing separator for final annealing
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the amount of O ₂ added is controlled to 10 parts by weight or less and the hydration of MgO is controlled so as to satisfy the condition of the following formula (1). . Y ≦ −3X + 15 ----- (1) where, X: hydrated amount of MgO (wt%) Y: coated amount of separating agent per one side of steel sheet after coating and drying (g /
m ² )

In the present invention, the silicon steel slab is composed of Sn:
0.02-0.5 wt%, Ni: 0.05-0.5 wt%, Cr: 0.05-0.5
wt% and Ge: one or two selected from 0.001 to 0.1 wt%
The inclusion of more than one species is advantageous for obtaining better magnetic properties.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the experiment leading to the present invention will be described below. As main components, C: 0.06 wt%, Si: 3.2 wt%
%, Mn: 0.07 wt%, Se: 0.02 wt%, S: 0.005 wt%, A
l: A steel ingot containing 0.022 wt%, N: 0.0085 wt%, and Bi containing 0 wt% and 0.035 wt%, respectively, is heated to 1400 ° C., held for 30 minutes, and then hot-rolled to 2.4 mm. The thickness was set. At this time, the average cooling rate of the hot-rolled sheet from immediately after the completion of the hot rolling to after 5 seconds was 70 ° C./sec. Then 1000 ℃
A hot rolled sheet was annealed for 30 seconds, pickled, and then subjected to primary cold rolling to a thickness of 1.8 mm. Subsequently, an intermediate annealing at 1100 ° C. × 1 minute was performed, and this was pickled and then subjected to secondary cold rolling to obtain a 0.23
mm. Subsequently, the temperature of the soaking process is 850 ° C,
Decarburizing annealing was performed at 850 ° C. for 100 seconds at P _H20 / P _H2 = 0.60 in the soaking process.

Subsequently, these materials were coated with an annealing separator containing MgO as a main component in various amounts in a slurry state, and then subjected to finish annealing at a maximum temperature of 1200 ° C. × 5 hours. Here, the annealing separator changes the hydration of MgO from 0.5 to 5.
0 wt% was changed, and 100 parts by weight of these MgO (excluding the weight of hydration water) to which 10 parts by weight of TiO ₂ was added was used. Per 2
It was varied in the range of 1212 g / m ² . The MgO hydration was determined by turbidizing MgO in pure water at 20 ° C for 1 hour,
After drying for 1 minute at
The weight is measured at the value of heating at 60 ° C. for 60 minutes, and the weight reduction ratio before and after heating is referred to. That is, after hydration
Assuming that the weight after drying for 1 minute is w ₁ and the weight after drying at 1000 ° C. for 60 minutes is w ₂ , the hydration amount is defined by the following formula (2). Hydration amount = (w ₁ −w ₂ ) / w ₁ × 100 (%) --- (2) From the finish annealed plate obtained by the above process, a test piece (width
30 mm, 280 mm) and eight were collected length, the magnetic flux density was measured B ₈ by Epstein test method. Further, the oxygen amount σ (per one side of the steel sheet) on the surface of the finish annealed sheet was measured.

Here, σ is subtracted from the oxygen amount obtained when the final finish-annealed sheet is chemically analyzed in a state where the surface coating is attached to the final finish-annealed sheet, when the surface coating is removed and the analysis is performed only with the base iron,
It was determined by converting to the oxygen basis weight of one side of the steel sheet.

The hydration of MgO in FIG 1, showing the coating amount of the annealing separator and (per side) the relationship between the final finishing annealed sheet of the magnetic flux density B _8. From Figure 1, ₈ or more values B 1.96T by properly controlling the hydration of the coating amount of MgO in the annealing separator was found to be obtained stably. Figure 2 is a graph showing the relationship between the surface oxygen amount σ and the magnetic flux density B ₈ of final annealing plates per side result in FIG. In FIG. 2, B _{8 of} the Bi-added material is defined by σ, and it is important to control σ to 1.5 g / m ² or less in order to stably obtain high B _8. It was revealed. On the other hand, when the steel ingot without added Bi, sigma is 1.5 ~2.5 g / m ² of about B ₈ is high in the range, magnetic deterioration when outside this region is moderate. From the above, when stably obtaining high magnetic properties in a material to which Bi is added, the application amount of the annealing separator and the hydration amount of MgO are controlled within the preferred ranges shown in FIG. It was found that it was important to limit the amount of oxygen σ on the surface of the finish annealed plate to 1.5 g / m ² or less.

Subsequently, the oxidizing property of the decarburizing annealing atmosphere (P _H20 /
The relationship between P _H2 ) and magnetic properties was examined. The result is shown in FIG. In this study, the oxygen content σ
Is adjusted to two levels of 1.0 g / m ² and 1.8 g / m ² ,
10 parts by weight of TiO ₂ was added to 100 parts by weight of MgO in the annealing separator. The average cooling rate immediately after the end of hot rolling (5 seconds) was set at two levels of 20 ° C./s and 50 ° C./s.

In FIG. 3, σ = 1.0 g / m^Two, Average cold immediately after hot rolling
If the reject speed = 50 ° C / s, P_H20/ P _H2Is in the range of 0.45 to 0.70
Extremely high B around₈Is obtained stably. In contrast
And σ = 1.8 g / m^TwoOr average cooling immediately after hot rolling
When the speed is 20 ° C / s, P_{H2 0}/ P_H2 0.45 to 0.70 range
However, sufficient characteristics have not been obtained. Therefore,
Average cooling rate immediately after hot rolling, atmosphere of decarburizing annealing, finish
When the oxygen content on the surface of the blunt plate satisfies the specified conditions,
Stable product with high magnetic flux density
Was revealed.

Subsequently, the components of the annealing separator were examined. FIG. 4 shows the relationship between the amount of TiO ₂ added in the annealing separator and B ₈ . In this study, the application amount of the annealing separator was 6.5 g / m ² per one side, and the hydration amount was 2.5 wt%. From this Figure 4, the TiO ₂ amount added to the annealing separator can be high B ₈ to 10 parts by weight or less per 100 parts by weight of MgO was found to be stably obtained. Since the oxygen source in the annealing separator by an increase of the TiO ₂ is increased, sigma is reduced by the TiO ₂ amount limit, it said to have improved orientation integration degree of the secondary recrystallized grains.

Subsequently, a search was made for component elements to obtain more stable and excellent magnetic properties. As a result, C: 0.03
~ 0.10wt%, Si: 2.0 ~ 5.0wt%, Mn: 0.04-0.15wt
%, S and Se, one or two selected from: 0.01 to 0.2.
03 wt%, sol.Al: 0.015-0.035 wt% and N: 0.0050-
A more stable high magnetic flux by adding one or more of Sn, Ni, Cr and Ge to a basic component containing 0.010 wt% and Bi: 0.001 to 0.07 wt%. It was found that a product with a high density was obtained. In FIG. 5, C:
0.06wt%, Si: 3.3wt%, Mn: 0.07wt%, Se: 0.02wt
%, Sol.Al: 0.03wt%, N: 0.0090wt%, Bi: 0.030wt%
%: Sn: 0.1 wt%, Ni: 0.1 wt%, Cr:
0.1 wt%, Ge: 0.1 wt % of showing the relationship between σ and B ₈ in the case where each added alone. In FIG. 5, as in FIG. 2, B ₈ rapidly deteriorates with an increase in σ, but when Sn, Ni, Cr or Ge is added as a steel component, σ exceeds 1.5 g / m ² . B ₈ even if is obtained good magnetic properties exceeding 1.96T. When σ is 1.5 g / m ² or less, B ₈
Extremely good magnetic properties of 1.97T or more are obtained.

As described above, it is not clear why a higher magnetic flux density can be stably obtained by adding one or more of Sn, Ni, Cr, and Ge, but these components are hardened in steel. It is a component that exerts an inhibitory effect in a dissolved state, and is considered to have an effect of enhancing the grain growth suppressing effect of Bi concentrated on the grain boundary. In addition, the effect of suppressing the disappearance of Bi from the surface by concentrating on the surface layer of the steel sheet is also estimated. By these effects, it is considered that a higher magnetic flux density is realized by the Bi-containing material, and good magnetic properties can be obtained even when σ is 1.5 g / m ² or more.

From the above results, the amount of the applied annealing separator, Mg
It is clear that extremely good magnetic properties can be obtained by controlling the amount of O hydration and the amount of TiO ₂ added to appropriate ranges, and further defining the cooling rate immediately after the end of hot rolling and the atmosphere for decarburizing annealing. Invented the invention.

Hereinafter, the reason for limiting the component composition of the raw material to the above range in the present invention will be described. (C: 0.03 to 0.10 wt%) C is a component useful for improving the hot-rolled structure by utilizing transformation, and is also a component useful for generating Goss-oriented crystal grains, and effectively exhibits such an effect. In order to achieve this, a content of 0.03 wt% or more is required.
If the content exceeds 0.10 wt%, decarburization failure occurs even by decarburization annealing, so C was limited to the range of 0.03 to 0.10 wt%. (Si: 2.0 to 5.0 wt%) Si is a component necessary to increase electric resistance to reduce iron loss and to stabilize the iron BCC structure to enable high-temperature heat treatment. Although wt% is required, cold rolling is difficult if the content exceeds 5.0 wt%, so the content was limited to 2.0 to 5.0 wt%.

(Mn: 0.04 to 0.15 wt%) Mn not only effectively contributes to the improvement of hot brittleness of steel but also precipitates such as MnS and MnSe when S and Se are mixed. It forms and acts as an inhibitor (inhibitor). When the content of Mn is less than 0.04 wt%, the above effect is insufficient. On the other hand, when the content of Mn exceeds 0.15 wt%, the particle size of precipitates such as MnSe becomes coarse and the effect as an inhibitor is lost. is 0.
Limited to the range of 04 to 0.15 wt%. (S and / or Se: 0.01 to 0.03 wt%) S or Se is Mn or
Cu combine with MnSe, useful components exhibiting MnS, Cu _2-x Se, to form a Cu _2-x S The effect of inhibitors as a dispersed second phase in the steel. The total content of these S and Se is 0.01 wt%
If less than 0.04% by weight, on the other hand, if it exceeds 0.04% by weight, not only incomplete solid solution at the time of slab heating but also a defect on the product surface may be caused. Was also limited to the range of 0.01 to 0.03 wt%.

(Sol. Al: 0.015 to 0.035 wt%) Al is a useful component that forms AlN in steel and acts as an inhibitor as a dispersed second phase, but if the added amount is less than 0.015 wt%. On the other hand, if the precipitation exceeds 0.035 wt%, AlN precipitates coarsely and loses its effect as an inhibitor.
Limited to the range of 5 wt%. (N: 0.0050 to 0.010 wt%) N is also a component necessary for forming AlN, like Al. If the addition amount is less than 0.0050 wt%, the precipitation of AlN is insufficient, and if the addition amount exceeds 0.010 wt%, blisters and the like occur during slab heating.
It was limited to the range of 50 to 0.010 wt%.

(Bi: 0.001 to 0.070 wt%) Bi concentrates preferentially at the grain boundaries of the primary recrystallized grains, lowers the mobility of the grain boundaries during annealing, raises the secondary recrystallization temperature, and increases the magnetic flux. It has the effect of increasing the density. Such effects are similar to Sb, As, etc., but Bi has a particularly low solubility in iron and a very low melting point of 271 ° C., so it has a higher segregation effect at grain boundaries than Sb, As. it is conceivable that. For this reason, it is considered that the effect of imparting a normal grain growth suppressing force is high, and it effectively acts to improve the degree of orientation accumulation. Also, Bi is a grain boundary segregation-type inhibitory-strengthening component, like Sb, etc., so that the magnetic properties of grain-oriented electrical steel sheets using an inhibitor system such as MnSe, MnS or AlN + (MnSe, MnS) Is considered to have the effect of uniformly improving If the content of Bi is less than 0.001 wt%, the effect of suppressing normal grain growth due to the above-described grain boundary segregation is not exhibited.
001 wt% or more. Further, Bi has a very low solubility in iron, so it is difficult to add Bi in an amount exceeding 0.07% by weight. Therefore, the upper limit of the addition amount is set to 0.07% by weight.

(Sn: 0.02 to 0.5 wt%, Ni: 0.05 to 0.5 wt%
%, Cr: 0.05-0.5 wt%, Ge: 0.001-0.1 wt%) In addition to the above components, Sn: 0.02-0.5 wt%, Ni: 0.05-
0.5 wt%, Cr: 0.05 to 0.5 wt% and Ge: 0.001 to 0.1 wt
% Of one or more selected from by adding to the steel, it is possible to obtain a higher B ₈ stably. It is presumed that the reason for this is that the effect of inhibiting the normal grain growth of Bi is further enhanced by the presence of the solid solution type inhibitor component as described above. Such effects are achieved by the equivalent amount of the annealing separator, the hydration amount of MgO, the decarburizing annealing atmosphere,
It is effective only when all the hot rolling conditions are satisfied to prevent deterioration of the Bi inhibitor effect. When the added amount of these components is below the above range, the effect of strengthening the inhibitory power of Bi is not exhibited, and when the added amount is above the above range, the effect is saturated and the saturation magnetic flux density decreases and the surface properties deteriorate. Therefore, the range is limited to the above range.

In addition, Sb, A
The addition of s, Mo, Cu, P, B, Te, V, Nb, etc., alone or in combination, is effective for further improving magnetic properties. Sb and As have the effect of segregating at the grain boundaries to increase the inhibitory force, like Bi, and are desirably added in the range of 0.001 to 0.10 wt%. Mo has the effect of sharpening the nuclei of secondary recrystallized grains to the Goss orientation, and the effect is remarkable in the range of 0.001 to 0.20 wt%. Cu, like Mn, is a component that combines with Se and S to form precipitates and increase the suppressing power.
The effect is remarkable in the range of 0.01 to 0.30 wt%. P is Sb
As in the above, it is a component that segregates at the grain boundaries to increase the suppression power,
If it is less than 0.010 wt%, the effect of addition is poor, while 0.030 wt%
Exceeding this will destabilize the magnetic properties and surface properties,
Preferably, the content is 0.010 to 0.030 wt%. Also, B,
Te, V, and Nb have the function of further increasing the ability to suppress normal grain growth by forming precipitates such as BN, MnTe, VN, NbN, and NbC in the steel. For B, 0.0010 to 0.010 wt% V, Nb, and Te are desirably added in the range of 0.005 to 0.10 wt%.

Next, the main manufacturing steps of the present invention will be described. According to the production method of the present invention, when hot rolling the grain-oriented electrical steel sheet slab material containing Bi, the average cooling rate for 5 seconds after the end of the rolling is set in the range of 30 to 120 ° C./sec. P _H20 / P _H2 in the soaking process was set to 0.45 to 0.70, and the oxygen content of the surface of the finished annealed plate was set to 1.5 g /
By setting it to m ² or less, it is intended to stably obtain a product having excellent magnetic properties. Another object of the present invention is to obtain a product having good magnetic properties by appropriately controlling the amount of the annealing separator used in the final finish annealing and the hydration amount of MgO. The above-mentioned limited range is based on the experimental results shown in FIGS.

The reason why a desired effect can be obtained by limiting the manufacturing conditions to the above range is not necessarily clear, but is presumed as follows. First, regarding the hot rolling conditions, if the cooling rate during hot rolling is not sufficient,
It is considered that Bi and AlN do not disperse evenly, which leads to deterioration and non-uniformity of the suppressing power of the material, so that the magnetic properties become unstable. Therefore, the average cooling rate immediately after hot rolling (5 seconds) needs to be 30 ° C./second or more. On the other hand, the cooling rate
If the temperature exceeds 120 ° C / sec, the shape of the steel strip is likely to be defective, so the upper limit is set to 120 ° C / sec.

Next, the conditions of the decarburizing atmosphere will be described. According to the inventors' research, it has been clarified that Bi-added materials are liable to cause magnetic deterioration due to deterioration of the inhibitor of the sheet thickness surface layer during finish annealing.
As shown in the above, by keeping P _H20 / P _H2 in the soaking process of decarburizing annealing high to some extent, the oxide layer (SiO ₂ , Fe ₂ SiO ₄ ) on the surface of the decarburized annealed plate is sufficiently formed, and the surface layer It is considered that the secondary recrystallization becomes stable because the oxidation of the inhibitors (AlN, Bi) is suppressed. Here, the reason why the magnetic flux density decreases again when P _H20 / P _H2 becomes too high is that if the surface oxidation of the decarburized annealed plate progresses excessively, the uniformity of the surface oxide layer is reduced and the protection against the atmosphere is reduced. Is thought to be because Therefore, from the viewpoint of preventing the deterioration of the inhibitor during the finish annealing and ensuring the uniformity of the surface oxide layer of the decarburized annealed sheet, it is considered necessary to set P _H20 / P _H2 to 0.45 to 0.70.

Next, the appropriate range of the oxygen content on the surface of the finish annealed plate will be described. Although Bi-added materials are considered to be susceptible to the decomposition of inhibitors during finish annealing as described above, as a method to prevent this, it is not enough to ensure the oxidizing properties of the decarburizing annealing atmosphere . Decomposition of Bi in the surface layer of the sheet thickness due to surface oxidation during finish annealing causes secondary recrystallization failure.To suppress this, the surface oxygen content σ per one side of the finish annealed sheet is 1.5
It is effective to set it to g / m ² or less. In order to improve the magnetic properties by lowering the surface oxygen content of the final annealing plate of Bi-added material, the amount of moisture introduced between the layers of the final annealing coil by reducing the amount of the separating agent applied and the amount of MgO hydrated It is effective to reduce the amount, and therefore, it is effective that the annealing separator satisfies the condition of the above formula (1). Further, when the Sn in the steel, Ni, Cr, is Bi inhibitor effect of the addition of such Ge enhanced, better even when the surface oxygen content of the final finishing annealed sheet exceeds 1.5 g / m ² Magnetic characteristics can be obtained. In order to reduce the surface oxygen content σ of the final finish annealed sheet, Al ₂ O ₃ , SiO ₂ , CaO, Sb ₂ O ₃ , CaCl ₃
And the like can be effectively or stably mixed.

Next, the reasons for limiting the amount of TiO ₂ added in the annealing separator will be described. It is known that by adding an appropriate amount of TiO ₂ to the separating agent, the film formation during the finish annealing is promoted and the appearance of the product is improved. Usually, 10 to 15 wt% of TiO 2 based on 100 parts by weight of MgO is known. ₂ is often added. Although TiO ₂ contributes to the film formation as an oxygen source in the separating agent, as described above, when the film is excessively formed with the material to which Bi is added, the magnetic property is deteriorated as described above. Therefore, the TiO ₂ loading in the separating agent, as shown in FIG. 4
It must be limited to 10 parts by weight or less based on 100 parts by weight of MgO. It is effective to add a compound such as Sr, Sb, B, Zr, Nb, or Cr, which is a conventionally known auxiliary agent, to the annealing separator described above to improve the film properties.

The above-mentioned effects can sufficiently improve the magnetism even when the hot-rolled sheet annealing and the intermediate annealing are omitted.
The presence or absence of the hot-rolled sheet annealing or the intermediate annealing step is not particularly limited.
Therefore, in the present invention, in the case where the final sheet thickness is obtained by performing the hot-rolled sheet annealing and then performing the cold rolling two or more times including the intermediate annealing, the hot-rolled sheet annealing is not performed and the two or more times including the intermediate annealing is performed. In any case, such as a case where the final sheet thickness is obtained by cold rolling or a case where the final sheet thickness is obtained by performing one cold rolling after performing hot-rolled sheet annealing. In the method of the present invention, the average cooling rate immediately after the completion of hot rolling, the atmosphere of decarburizing annealing, and the amount of oxygen (or the amount of separating agent applied, the amount of MgO hydrated, and the amount of TiO ₂ added) on the surface of the finished annealed sheet are properly adjusted. The processing may be performed in accordance with conventionally known conditions except for the control described above.

Further, a laser beam disclosed in Japanese Patent Publication No. 57-2252 and a plasma disclosed in Japanese Patent Application Laid-Open No. 62-96617 are applied to grain-oriented electrical steel sheets produced under the above manufacturing conditions. The method of introducing linear strain by flame or the like, or the introduction of a linear notch in a direction substantially perpendicular to the rolling direction before the finish annealing disclosed in Japanese Patent Publication No. 3-69968, requires iron loss. It is extremely important in reducing the amount of noise, and can be effectively applied in the present invention. Further, after the surface of the finish-annealed sheet obtained by the method of the present invention is mirror-finished, by forming a tension coating artificially or by combining this with the magnetic domain refining treatment, extremely low iron loss can be obtained. It is possible to obtain the material.

[0043]

EXAMPLES (Example 1) C: 0.060 wt%, Si: 3.30 wt%
%, Mn: 0.070 wt%, Al: 0.020 wt%, N: 0.0075 wt%
%, Sb: 0.040 wt%, Se: 0.020 wt%, Mo: 0.020 wt%
And S: 0.001 wt%, Bi is 0 wt%,
A silicon steel slab containing 0.001 wt%, 0.030 wt%, and 0.060 wt%, with the balance being mainly Fe, was heated by induction heating at 1400 ° C for 60 minutes and then hot-rolled to a hot-rolled sheet thickness of 2.5 mm. . At this time, the cooling rate for 5 seconds immediately after the end of the final pass of the hot rolling was set at 50 ° C./sec. After this, 950 ℃
Hot-rolled sheet annealing for 1 minute, then pickling, primary cold rolling to a thickness of 1.6 mm, intermediate annealing at 1050 ° C for 1 minute, pickling, secondary cold rolling The final thickness was 0.23 mm by rolling. A P _H20 / P _H2 of the soaking process 0.40 (dew point 56.5
° C, H ₂ : N ₂ = 50: 50), 0.55 (dew point 62.0 ° C, H ₂ : N ₂ = 50: 5
Decarburization annealing was performed at 850 ° C for 100 seconds at two levels of 0). Then, using MgO with a hydration of 3.0 wt%, a separating agent containing 10 parts by weight of TiO ₂ added to the MgO was applied to the surface of the steel sheet.
The coating was performed at two levels of coating amounts of 4.0 g / m ² and 8.0 g / m ² .
Thereafter, a final finish annealing at a maximum temperature of 1200 ° C. × 5 hours was performed. The surface oxygen content of the final annealed sheet thus obtained was measured. Subsequently, after applying an insulating tension coating containing colloidal silica as a main component, an angle of 90 ° formed with the rolling direction by a plasma flame and linear strain regions introduced at intervals of 7 mm with respect to the rolling direction to obtain a product. . From the product obtained as described above, Epstein test piece 50
0 g corresponding cut out, the magnetic flux density was measured B ₈ and iron loss W _17/50 by Epstein test method. Table 1 shows the magnetic properties of the obtained products. It can be seen that extremely high magnetic flux density B ₈ product is obtained in the grain-oriented electrical steel sheet produced by conditions compatible with the present invention.

[0044]

[Table 1]

Example 2 C: 0.065 wt%, Si: 3.40 wt
%, Mn: 0.065 wt%, Cu: 0.05 wt%, Al: 0.022 wt%,
N: 0.0082 wt%, Mo: 0.02 wt%, Se: 0.016 wt%, S:
0.009 wt% and 0.045 wt% Bi, with the balance being mainly
A silicon steel slab made of Fe was heated by induction heating at 1400 ° C. for 60 minutes, and then hot-rolled to a hot-rolled sheet thickness of 2.5 mm. At this time, the cooling rate for 5 seconds immediately after the end of the final pass of hot rolling was set at 20 ° C / sec, 30 ° C / sec, 60 ° C / sec, and 100 ° C / sec.
Four levels of seconds. Thereafter, the sheet is annealed at 950 ° C. for 1 minute, then pickled, and subjected to primary cold rolling to a thickness of 1.
After the thickness was reduced to 6 mm, the steel sheet was subjected to intermediate annealing at 1050 ° C. for 1 minute, then pickled, and subjected to secondary cold rolling to a final thickness of 0.23 mm.
Subsequently, a P _H20 / P _H2 of the soaking process 0.40 (dew point 62.3 ° C.,
H ₂ : N ₂ = 70: 30) and 0.50 (dew point 66.1 ° C, H ₂ : N ₂ = 70: 30)
At 2 levels, subjected to decarburization annealing of 850 ° C. × 100 seconds, and thereafter, an annealing separating agent consisting only of hydrated amount 0.8 wt% of MgO in the coating amount per surface 4.0 g / m ² coated After that, a final finish annealing at a maximum temperature of 1200 ° C. × 5 hours was performed. The surface oxygen content of the final finish annealed sheet thus obtained was measured. Subsequently, the coil after the final annealing is washed with hydrochloric acid and acid, and then the surface of the steel plate is mirror-polished by electropolishing in a NaCl bath. Was applied, and a linear strain region having an angle of 85 ° with the rolling direction was introduced by plasma flame at intervals of 5 mm with respect to the rolling direction to obtain a product. From the product obtained as above, an Epstein test piece equivalent to 500 g was cut out, and the magnetic flux density B ₈ and the iron loss W _{17/50 were determined} by the Epstein test method.
Was measured. Table 2 shows the magnetic properties of the obtained products. A product having extremely excellent magnetic properties has been stably obtained in a grain-oriented electrical steel sheet manufactured under conditions compatible with the present invention.

[0046]

[Table 2]

(Example 3) C: 0.065 wt%, Si: 3.30 wt%
%, Mn: 0.065 wt%, Cu: 0.05 wt%, Al: 0.025 wt%,
N: 0.0075wt%, Mo: 0.02wt%, Se: 0.015wt%, S:
A silicon steel slab containing 0.010 wt% and Bi at 0 wt% and 0.020 wt%, respectively,
After heating by induction heating at 60 ° C. for 60 minutes, a hot-rolled sheet thickness of 2.5 mm was obtained by hot rolling. At this time, the cooling rate for 5 seconds immediately after the end of the final pass of the hot rolling was set at 60 ° C./sec. Thereafter, without hot-rolled sheet annealing, pickling treatment, primary cold rolling to a thickness of 1.6 mm, intermediate annealing at 1050 ° C. for 1 minute, then pickling, secondary The final thickness was 0.27 mm by cold rolling. Subsequently, the resist etching was used to make an angle of 85 ° with the rolling direction, a gap of 3.0 mm in the rolling direction, and a width of 100 mm.
After forming a groove having a depth of 25 μm and a depth of 25 μm, decarburization annealing was performed at 850 ° C. for 100 seconds. At this time, P _H20 / P _{H2 in the} soaking process
Annealing was performed at 0.35 (dew point 64.3 ° C., H ₂ : N ₂ = 90: 10) or 0.45 (dew point 49.5 ° C., H ₂ : N ₂ = 30: 70). Thereafter, an annealing separator containing MgO ₂ having a hydration amount of 3.0 wt% as a main component and adding 7 parts by weight and 12 parts by weight of TiO ₂ with respect to 100 parts by weight of MgO to 4.0 g / m ² per side was applied. After applying a final finish annealing at a maximum temperature of 1200 ° C. × 5 hours, an insulating coating mainly composed of colloidal silica was applied to obtain a product. Cut out Epstein test piece 500 g equivalent of the obtained product by the above steps, the magnetic flux density was measured B ₈ and iron loss W _17/50 by Epstein test method. Table 3 shows the magnetic properties of the obtained products. A product having extremely excellent magnetic properties has been stably obtained in a grain-oriented electrical steel sheet manufactured under conditions suitable for the present invention.

[0048]

[Table 3]

Example 4 C: 0.060 wt%, Si: 3.25 wt
%, Mn: 0.072 wt%, Al: 0.020 wt%, N: 0.0075 wt%
%, Sb: 0.030 wt%, Mo: 0.020 wt%, Se: 0.020 wt%
%, S: 0.001 wt% and Bi: 0 wt% or 0.030 wt%
Containing silicon steel slab with the balance being mainly Fe
After heating by induction heating at 1400 ° C. for 60 minutes, a hot-rolled sheet was 2.3 mm in thickness by hot rolling. At this time, the average cooling rate for 5 seconds immediately after the end of the final pass of the hot rolling was 70 ° C./sec. Thereafter, hot-rolled sheet annealing was performed at 1050 ° C. for 1 minute, followed by pickling and cold rolling to a final sheet thickness of 0.27 mm.
After that, by resist etching, an angle of 10 ° with the rolling direction, a distance of 3.0 mm in the rolling direction, a width of 100 μm, a depth of 25 μm
m grooves were formed. Subsequently, P _H20 / P _H2 = 0.6 in the heating process
Decarburization annealing was performed at 870 ° C. for 80 seconds at 0 (dew point: 54.6 ° C., H ₂ : N ₂ = 30: 70). Subsequently, the hydration amount of 2.0 wt% and 4.0 wt%
% MgO, 100 parts by weight of MgO, 6.0 parts by weight of TiO ₂ and ₂ parts by weight of SnO ₂ were added to the annealing separator at 6.0 g / side of the steel sheet.
After applying with an application amount of m ² , the maximum temperature reached 1200 ° C x 5
A final finish anneal for hours was performed. Thereafter, an insulating coating containing colloidal silica as a main component was applied to obtain a product. Cut out Epstein test piece 500 g equivalent from the resulting product as described above, the magnetic flux density was measured B ₈ and iron loss W _17/50 by Epstein test method. Table 4 shows the magnetic properties of the obtained products. A product having extremely excellent magnetic properties has been stably obtained in a grain-oriented electrical steel sheet manufactured under conditions suitable for the present invention.

[0050]

[Table 4]

Example 5 A silicon steel slab containing the components shown in Table 5 with the balance being mainly Fe was heated by induction heating at 1400 ° C. for 60 minutes and then 2.5 mm by hot rolling.
Hot-rolled sheet thickness. At this time, the cooling rate for 5 seconds immediately after the end of the final pass of the hot rolling was set at 50 ° C./sec. After this, 95
After hot-rolled sheet annealing at 0 ° C for 1 minute, pickling treatment, primary cold rolling to a thickness of 1.6 mm, intermediate annealing at 1050 ° C for 1 minute, and pickling 0, by secondary cold rolling.
The final thickness was 23 mm. P _H20 / P _H2 = 0.50 in soaking process
Decarburization annealing was performed at 850 ° C. for 100 seconds (dew point 66.1 ° C., H ₂ : N ₂ = 70: 30). After this, the hydration amount of 2.0 wt% and 4.0 wt%
5 g of TiO ₂ added to 100 g of MgO adjusted to 100 g of MgO and applied at a coating amount of 5.0 g / m ² per steel sheet surface, and finally finished at a maximum temperature of 1200 ° C for 5 hours Annealed. Subsequently, an insulating coating containing colloidal silica as a main component was applied, and then a linear strain region was introduced at an angle of 80 ° to the rolling direction by a plasma flame at intervals of 7 mm with respect to the rolling direction to obtain a product. From the product obtained as above, an Epstein test piece equivalent to 500 g was cut out, and the magnetic flux density B ₈ and the iron loss W _{17/50 were determined} by the Epstein test method.
Was measured.

[0052]

[Table 5]

Table 6 shows the magnetic properties of the obtained products. A product having extremely excellent magnetic properties has been stably obtained in a grain-oriented electrical steel sheet manufactured under conditions suitable for the present invention. Of these, Sn, Ni, Cr, 5D addition of Ge in the range of the present invention, 5F, 5L, 5M, 5N , 5O, 5P, in 5Q, B ₈ is 1.99T
As described above, a product having extremely excellent magnetic properties with W _17/50 of 0.63 W / kg or less has been obtained.

[0054]

[Table 6]

[0055]

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

[Brief description of the drawings]

[1] the amount of hydration of MgO, is a diagram showing the relationship between the magnetic flux density B ₈ and after final annealing annealing separator coating amount.

Fig. 2 Oxygen content and magnetic flux density B _{8 on the} surface of the final annealed sheet
FIG.

Fig. 3 _PH20 / _PH2 and magnetic flux density during soaking process in decarburizing annealing
Is a diagram showing the relationship between B _8.

FIG. 4 is a graph showing the relationship between the amount of TiO ₂ added in an annealing separator and the amount of oxygen on the surface of a final finish annealing plate.

FIG. 5 is a diagram showing the relationship between the basis weight of oxygen σ and the magnetic flux density B ₈ of the final finish annealed sheet when Sn, Ni, Cr, and Ge are added to steel.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshito Takamiya 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Inside Kawasaki Steel Corporation Mizushima Works

Claims (3)

[Claims] 1. C: 0.03 to 0.10 wt%, Si: 2.0 to 5.0 wt%, Mn: 0.04 to 0.15 wt%, One or two selected from S and Se: 0.01 to 0.03 wt
%, Sol.Al: 0.015 to 0.035 wt%, N: 0.0050 to 0.010 wt%, and Bi: 0.001 to 0.07 wt%. In the method for producing a grain-oriented electrical steel sheet, which comprises a series of steps of performing cold rolling, followed by a combination of annealing treatment and cold rolling treatment to obtain a final sheet thickness, followed by decarburizing annealing, and then final finishing annealing. Average cooling rate from immediately after to 5 seconds after 30-120
° C. / controlled in seconds, a P _H20 / P _H2 in the atmosphere of the soaking process in decarburization annealing and 0.45 to 0.70, further, the oxygen content of the final annealing sheet surface per one surface 1.5 g / m ² or less A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties. 2. C: 0.03 to 0.10 wt%, Si: 2.0 to 5.0 wt%, Mn: 0.04 to 0.15 wt%, one or two selected from S and Se: 0.01 to 0.03 wt
%, Sol.Al: 0.015 to 0.035 wt%, N: 0.0050 to 0.010 wt%, and Bi: 0.001 to 0.07 wt%. In the method for producing a grain-oriented electrical steel sheet, which comprises a series of steps of performing cold rolling, followed by a combination of annealing treatment and cold rolling treatment to obtain a final sheet thickness, followed by decarburizing annealing, and then final finishing annealing. Average cooling rate from immediately after to 5 seconds after 30-120
° C. / controlled in seconds, a P _H20 / P _H2 in the atmosphere of the soaking process in decarburization annealing and 0.45 to 0.70, further, the TiO ₂ amount for MgO 100 parts by weight per annealing separator for final annealing A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, comprising controlling the hydration amount of MgO to 10 parts by weight or less and satisfying the condition of the following formula (1). Y ≦ −3X + 15 ----- (1) where, X: hydrated amount of MgO (wt%) Y: coated amount of separating agent per one side of steel sheet after coating and drying (g /
m ² ) 3. The silicon steel slab is one or two selected from the group consisting of: Sn: 0.02 to 0.5 wt%, Ni: 0.05 to 0.5 wt%, Cr: 0.05 to 0.5 wt%, and Ge: 0.001 to 0.1 wt%. The method for producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 1 or 2, comprising the above.