JP2002069532A - Method for producing bidirectionally oriented silicon steel sheet having high magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To industrially stably produce a bidirectioanlly oriented silicon steel sheet having high magnetic flux density, in the method for producing a bidirectionally oriented silicon steel sheet in which [100]<;001>; orientation is developed by a cross cold rolling method, by suppressing the development of [110] suborientation deteriorating its magnetic properties. SOLUTION: In this method for producing a bidirectionally oriented silicon steel sheet, a silicon steel hot rolled sheet containing, by mass, 0.8 to 6.7% Si, <=0.085% C, 0.021 to 0.048% acid soluble Al and <=0.012% N, and the balance Fe with inevitable impurities is subjected to cold rolling at a draft of 40 to 80% in a direction identical with that in hot rolling, is further subjected to cold rolling at a draft of 30 to 70% in a direction crossing the above cold rolling direction and is then subjected to decaruburizing annealing, thereafter, a separation agent for annealing is applied thereto, and finish annealing for secondary recrystallization and purification is performed. In the crystal grain structure after the decarburizing annealing, the ratio of I[111]/I[211] is controlled to <=1, and moreover, the content of oxygen in an oxidized layer in the steel sheet is controlled to <=2.3 g/m2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a so-called bidirectional electromagnetic steel sheet in which crystal grains are accumulated in a {100} <001> (Cube) orientation with a Miller index. This steel sheet has an easy axis of magnetization (<001> axis) in the rolling direction and a direction perpendicular to the rolling direction, and has excellent magnetic properties in these directions. It is advantageous to use it as an iron core material of a device that needs to flow magnetic flux in two directions, for example, a large generator, as compared with a unidirectional magnetic steel sheet. In the field of miniature stationary devices, non-oriented electrical steel sheets that do not have a high degree of integration of easy axes are generally used, but by using bi-directional electrical steel sheets, miniaturization and higher efficiency can be achieved. There is a possibility.

[0002]

2. Description of the Related Art A bidirectional electrical steel sheet is required to have an excitation property and an iron loss property as magnetic properties. As an index representing the excitation characteristic, a magnetic flux density at a magnetic field strength of 800 A / m: B
8 is usually used. As an index representing iron loss characteristics, the steel sheet 1 when magnetized to 1.7 T at a frequency of 50 Hz is used.
Iron loss per kg: W17 / 50 is used. Magnetic flux density:
B8 is the largest controlling factor of iron loss characteristics, and the magnetic flux density: B
8 The higher the value, the better the iron loss characteristics. Magnetic flux density: B8
In order to increase the crystallinity, it is important to make the crystal orientation highly uniform.

The following two methods are mainly disclosed as a method for producing such a bidirectional magnetic steel sheet. One is to perform high temperature annealing in an atmosphere containing a polar gas, for example, hydrogen sulfide, as disclosed in Japanese Patent Publication No. 377-1110, and to form {100} <001> oriented grains using surface energy. It is a method of growing preferentially. However, this method is not suitable for a mass production process because the surface cleanliness of the steel sheet needs to be highly controlled.

As another method, as disclosed in Japanese Patent Publication No. 35-2657, after cold rolling is performed in the same direction as hot rolling, cold rolling is performed in a direction crossing the cold rolling. Rolling, then short-time annealing and high-temperature annealing at 900 to 1300 ° C, so that {100} <001> oriented grains are preferentially grown by secondary recrystallization, so-called “cross cold rolling method”.
It is. In order to control the secondary recrystallization, it is necessary to adjust the primary recrystallization structure before the secondary recrystallization and to adjust a fine precipitate called an inhibitor. Regarding the technique for adjusting the primary recrystallization structure and the technique for adjusting fine precipitates called inhibitors, {110} <001>
There is the following knowledge about the manufacturing technology of the grain-oriented electrical steel sheet that develops the orientation.

[0005] The inhibitor has the function of suppressing the growth of general orientation grains in the primary recrystallized structure and preferentially growing only specific orientation grains. As typical precipitates, M.P. F. Littmann (Japanese Patent Publication No. 30-365)
No. 1) and J.I. E. FIG. May & D. Turnbull
(Trans. Met. Soc. AIM 212 (19
(1983) p769 and others used MnS and Taguchi et al.
No. 15644) discloses AlN and Imanaka et al.
No. 13469) discloses MnSe. Basically, a method is employed in which these precipitates are completely dissolved in slab heating before hot rolling, and then finely precipitated in hot rolling and a subsequent annealing step. In order to completely dissolve these precipitates, it is necessary to heat at a high temperature of 1350 to 1400 ° C or more.

In recent years, Komatsu et al. (Japanese Patent Publication No. 62-45285) discloses a method of manufacturing by low-temperature slab heating without heating by high-temperature slab heating.
A method using Si) N as an inhibitor is disclosed. However, knowledge on the adjustment of the primary recrystallized structure before the secondary recrystallization has not been disclosed much, and the present inventors have disclosed, for example, Japanese Patent Publication No. 8-32929 and Japanese Patent Application Laid-Open No. 9-256.
No. 051 discloses its importance.

On the other hand, AlN disclosed by Taguchi et al. As an inhibitor in the manufacturing technology of a bidirectional magnetic steel sheet is $ 1.
Japanese Patent Publication No. 35-2657 discloses that it is effective to preferentially grow grains having a <001><001> orientation, and (Al, Si) N disclosed by Komatsu et al.
It is disclosed in Japanese Patent Publication No. Hei 6-99752 that it is effective for preferential growth of 00 ° <001> orientation grains, but there is almost no knowledge about adjustment of the primary recrystallized grain structure before secondary recrystallization.

[0008] As described above, although the bidirectional electrical steel sheet is an ideal material having two easy axes oriented in the plane of the steel sheet, it has not been industrially manufactured to date. This is because the above-mentioned manufacturing method is difficult to perform industrially, but the expected degree of integration in the {100} <001> orientation cannot be obtained stably.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a bi-directional electrical steel sheet in which the {100} <001> orientation is developed by secondary recrystallization based on the above "cross cold rolling method". The present invention discloses a method for manufacturing a grain-oriented electrical steel sheet having high magnetic flux density and excellent magnetic properties by controlling the grain structure after decarburizing annealing.

[0010]

The gist of the present invention is as follows. (1) Mass: Si: 0.8 to 6.7%, C: 0.085% or less, Acid-soluble Al: 0.01 to 0.048%, N: 0.012% or less, balance Fe And a hot rolled silicon steel sheet comprising unavoidable impurities is cold rolled in the same direction as hot rolling at a rolling reduction of 40 to 80%, and further, at a rolling reduction of 30 to 70% in a direction crossing the cold rolling direction. Cold rolling, then after decarburizing annealing, in the method of manufacturing a bidirectional electrical steel sheet to apply an annealing separator, and to perform finish annealing for the purpose of secondary recrystallization and purification, the crystal grains after decarburizing annealing A two-way electromagnetic having a high magnetic flux density, wherein the ratio of I [111] / I [211] is set to 1 or less in the structure and the oxygen content of the oxide layer of the steel sheet is set to 2.3 g / m ² or less. Steel plate manufacturing method. (2) The method for producing a bidirectional electrical steel sheet having a high magnetic flux density according to the above (1), wherein 0.02 to 0.2% of Sn is added by mass. Here, I [111] and I [211] represent the diffraction intensity values measured at a plate thickness of 1/2 layer by X-ray diffraction measurement, and the {111} and {211} planes respectively correspond to the plate surface. The ratio of grains that are parallel is evaluated.

Hereinafter, description will be made based on the experimental results. The present inventors have made {100} <001 based on the “cross cold rolling method”.
> (Cube) orientation by secondary recrystallization, a method for producing a bidirectional electrical steel sheet, wherein {100} <0
The major factor that deteriorates the degree of integration in the <01> orientation is Cu
The so-called Goss orientation system, such as {110} <001> or {110} <110>, which develops as a secondary orientation of the secondary recrystallized structure together with the be orientation, is caused by these orientations. It was shown to develop from the thick central part and the thick surface part (for example, Japanese Patent Publication No. 7-3354).
No. 6).

[0012] It has been found that the texture of matrix grains has a great effect on the preferential development of the Cube orientation and the Goss system orientation as secondary recrystallization orientations. For the Cube orientation, there is a corresponding orientation relationship of # 6
The 32 ° orientation is important for developing the Cube orientation.

[0013] The texture of the primary recrystallized matrix produced by the cross cold rolling method is {2} near {632}.
Since there are peaks in the directions from 11 ° to {311} to {310}, control of these peaks is substantially important.
As typical values of the peak values, {211}, {311},
The evaluation can be performed using a measured value such as {310} or a total value of the plurality of measured values. Here C
Evaluation was performed using a {211} diffraction intensity value (I [211]) measured by X-ray diffraction measurement as a matrix for growing secondary recrystallized grains having a ube orientation. Also, Gos
For the s-system orientation, it is considered that the grains grow by eating the grains of the {111} orientation in the matrix, so the {111} diffraction intensity value (I [111]) measured by X-ray diffraction measurement
The evaluation was performed using. The measurement was performed at the center of the sheet thickness where the Cube orientation developed (the sheet thickness 1/2 thickness position).

As a result of a detailed study of the development behavior of these primary recrystallization textures in the decarburization annealing step, methods for controlling the primary recrystallization texture include, for example, the heating rate, soaking temperature, It has been clarified that it can be controlled by adjusting the annealing cycle conditions of decarburization annealing such as soaking time. At the same time, while controlling the primary recrystallization texture, the oxidation degree (P H ₂ O / P H ₂ ) and the annealing time of the atmosphere gas were adjusted so that the oxygen content of the steel sheet was 2.3 g / m ² or less. Controlling can be achieved with AlN or (Al, Si)
It was found to be important in utilizing N inhibitors.

FIG. 1 shows the influence of the primary recrystallization texture (I [111] / I [211]) and the oxygen content of the steel sheet on the magnetic flux density B8 of the product. Here, Si: 3.2%,
C: 0.05%, acid-soluble Al: 0.027%, N:
A silicon steel slab containing 0.008%, Mn: 0.1%, and S: 0.007% was heated to 1150 ° C. and hot-rolled to a thickness of 1.8 mm. This hot-rolled sheet is heated to 1100 ° C
And cold-rolled to 0.81 mm in the same direction as hot rolling, and then cold-rolled to a final thickness of 0.39 mm in a direction orthogonal to the cold rolling direction. Then, after heating to 810 ° C at a heating rate of 5 ° C / sec to 100 ° C / sec, it was cooled to room temperature.

Next, heating is performed at a heating rate of 15 ° C./sec.
After annealing at 90 ° C. to 850 ° C. for 2 minutes with an atmosphere gas having an oxidation degree (PH ₂ O / P H ₂ ) in the range of 0.33 to 0.70, annealing at 750 ° C. for 30 seconds in an ammonia-containing atmosphere. Then, the amount of nitrogen in the steel sheet was set to 0.02%. Then MgO
After applying an annealing separating agent containing as a main component, finish annealing was performed at 1200 ° C. for 20 hours. As a result, as shown in FIG. 1, when the oxygen content of the steel sheet is 2.3 g / m ² or less, the secondary recrystallized structure develops stably, and I [111] / I [211 ) And a magnetic flux density B8 of 1.90 T or more can be stably manufactured.

The present inventors have found that when the heating rate of the decarburizing annealing is increased or the dew point of the atmosphere is increased, the secondary recrystallization becomes unstable in some of the samples, and the cause is investigated. In order to do so, a detailed survey was conducted. As a result, it was found that when the heating rate was first increased, the amount of surface oxidation of the steel sheet after decarburizing annealing increased, despite the short oven time combining the heating time and soaking time. Was. this is,
It is considered that the initial oxidation state in the heating process of the steel sheet changed depending on the heating rate, which affected the oxidation behavior in the subsequent soaking process. Also, when the degree of oxidation of the atmosphere gas is increased, the amount of surface oxidation increases.

The effect of this surface oxide layer on secondary recrystallization was examined. When a large amount of surface oxide was formed, (Al, S) was found in the secondary recrystallization temperature range of the finish annealing.
i) It was elucidated that the N inhibitor rapidly decomposed and the secondary recrystallization became unstable. When a large amount of surface oxide is formed, the decomposition rate of the (Al, Si) N inhibitor is increased because the removal of N by the modification of the surface oxide layer or the oxidation of Al by the surface oxide is promoted. Is estimated. The cause of the instability of the secondary recrystallization is not the influence of the primary recrystallization structure but the effect of the inhibitor. Therefore, by controlling the temperature in the tropical zone and the degree of oxidation of the atmosphere gas during the decarburization annealing, and adjusting the primary recrystallized grain structure, the oxygen content of the surface oxide layer is limited to a range of 2.3 g / m ² or less. It is presumed that by doing so, the decomposition of the (Al, Si) N inhibitor was suppressed, and the secondary recrystallization was stabilized.

[0019]

Next, an embodiment of the present invention will be described. As the components of the steel of the present invention, Si: 0.8 to 6.7
%, C: 0.085% or less, acid-soluble Al: 0.01 to
0.048%, N: 0.012% or less is required. S
As for i, when the amount of addition is increased, the electric resistance increases and the iron loss characteristics are improved. However, if it exceeds 4.8%, cracks are likely to occur during rolling and cold rolling becomes difficult. However, since rolling can be performed by warm rolling, the upper limit is 6.7% which is effective in improving soft magnetic properties. And On the other hand, if it is less than 0.8%, γ transformation occurs at the time of finish annealing, and the crystal orientation is impaired.

C is an element effective in controlling the primary recrystallization structure, but has an adverse effect on the magnetic properties, so that it is necessary to decarbonize before the final annealing. If C is more than 0.085%, the decarburization annealing time will be long and productivity will be impaired.

In the present invention, acid-soluble Al is an essential element for bonding with N to function as AlN or (Al, Si) N as an inhibitor. The limited range is 0.01 to 0.048% at which the secondary recrystallization is stabilized.

If N exceeds 0.012%, pores in a steel sheet called blisters are generated during cold rolling. In addition, MnS, MnSe, Cu ₂ S and the like, which are effective inhibitors in the production of a grain-oriented electrical steel sheet, may be used in combination in a known range and used to stabilize the secondary recrystallization. It is valid.

Further, Sn is the value of # 11 after the above decarburization annealing.
It is an element effective for improving the texture such as 1} and {411} and stably producing a product having a high magnetic flux density. As shown in Example 5 described later, Sn is 0.02 to 0.2%.
It is desirable to add. Below this lower limit, the texture improving effect is small, and a substantial magnetic flux density improving effect cannot be obtained. If the upper limit is exceeded, nitriding into the steel sheet becomes difficult, and secondary recrystallization may become unstable.

In addition, trace amounts of Cu, Sb, Mo, Bi,
The inclusion of Ti or the like in steel does not impair the gist of the present invention.

The above-mentioned silicon steel slab is obtained by smelting steel in a converter or an electric furnace, subjecting the molten steel to vacuum degassing if necessary, and then subjecting the steel to continuous casting or ingot casting followed by slab rolling. . Thereafter, slab heating is performed prior to hot rolling. Regarding slab heating, as in the production method of Taguchi et al. (Japanese Patent Publication No. 40-15644), 13
A method in which an inhibitor such as AlN is dissolved in a solid solution by heating at a temperature of 50 to 1400 ° C. or higher and finely precipitated during hot rolling or subsequent cooling of annealing, or Komatsu et al.
As disclosed in Japanese Patent Application Laid-Open No. 2-45285, any of the methods using a slab heating temperature of 1280 ° C. or lower and using (Al, Si) N precipitated by nitriding treatment in a subsequent step as an inhibitor may be used. .

The above-mentioned hot-rolled sheet is usually subjected to short-time annealing at 900 to 1200 ° C. for 30 seconds to 30 minutes in order to enhance magnetic properties. Thereafter, cold rolling is performed once or twice or more after annealing to obtain a final thickness. It is advisable to decide whether or not to take into account the desired product characteristic level and cost. Thereafter, rolling is performed in the same direction as the hot rolling at a rolling reduction of 40 to 80%, and a rolling reduction of 30 in the direction crossing the cold rolling direction.
Cold roll at ~ 70%.

The steel sheet after cold rolling is subjected to decarburizing annealing in a humid atmosphere in order to remove C contained in the steel. At this time, the ratio of I [111] / I [211] in the grain structure after decarburizing annealing was set to 1 or less, and the oxygen content of the oxide layer of the steel sheet was set to 2.3 g / m 2.
By adjusting the value to ² or less, a product having a high magnetic flux density can be stably manufactured. As a method of controlling the primary recrystallization texture after this decarburization annealing, for example, it is controlled by adjusting the annealing cycle conditions of the decarburization annealing such as the heating rate in the decarburization annealing step, the soaking temperature, and the soaking time. You. At this time, while controlling the primary recrystallization texture, the oxidation degree (P H ₂ O / P H ₂ ) and the annealing time of the atmosphere gas are controlled so that the oxygen content of the steel sheet is 2.3 g / m ² or less. That is the point of the present invention.

The heating rate of the decarburizing annealing is a large factor for controlling the primary recrystallization texture ({111}, {211}), and is preferably about 15 ° C./sec or more. The temperature range that needs to be heated at this heating rate is a temperature range of at least 600 ° C to 750 to 900 ° C. At 600 ° C or higher, primary recrystallization starts and the texture starts to change.
It is necessary to perform heating at a predetermined heating rate from a temperature of 600 ° C. or less. The reason why the effect is not exhibited when the upper limit temperature is less than 750 ° C. is that primary recrystallization is not completed below 750 ° C., and it is necessary to complete recrystallization in order to obtain a desired primary recrystallization texture. That's why. 900 ° C
It is considered that when the sample was heated to an excessive temperature, a transformed structure was generated in a part of the sample, and the structure at the time of completion of the subsequent decarburization annealing became a mixed grain structure.

The method of controlling the heating rate of the decarburization annealing is not particularly limited. For a heating rate of about 100 ° C./sec or less, a conventional decarburization method using a radiant tube or the like using radiant heat is used. Equipment converted from annealing equipment,
For a heating rate of 100 ° C./sec or more, it is effective to apply a new method using a high-energy heat source such as laser or plasma, an induction heating, an electric heating device, or the like. In addition, it is also possible to combine a method using a new energy source such as a new laser or plasma, a method using an induction heating, a current heating device, etc., to the conventional decarburization annealing equipment using a radiant tube using normal radiant heat. It is.

As for the soaking temperature, it is usually 770-90.
Perform at 0 ° C. From the viewpoint of controlling the texture, for example, as disclosed in Japanese Patent Publication No. 8-32929, in a temperature range in which the distribution of the grain structure does not become non-uniform, it is preferable to perform the grain growth by annealing at a high temperature. It is also effective to increase the temperature after the soaking for the purpose of grain adjustment after decarburizing before the soaking. If the heating rate in the heating stage is increased, oxidation during soaking is promoted, so it is necessary to control the degree of atmospheric oxidation or soaking time to control the oxygen content within a certain range. is there.

As the nitriding treatment, a method of annealing in an atmosphere containing a gas having a nitriding ability such as ammonia, MnN
And the like, for example, by adding a powder having a nitriding ability to the annealing separator during the final annealing. Then, after applying an annealing separator containing magnesia as a main component, finish annealing is performed, and {100} <001> oriented grains are preferentially grown by secondary recrystallization. In that case, Tokuhei 8-329
Controlling the secondary recrystallization temperature by separating the secondary recrystallization and purification by the method disclosed in Japanese Patent No. 29 is effective in increasing the magnetic flux density of the product.

[0032]

[Example 1] Si: 3.2%, C: 0.05
%, Acid-soluble Al: 0.027%, N: 0.008%,
A silicon steel slab containing Mn: 0.1% and S: 0.007% was heated at 1150 ° C. and hot-rolled to a sheet thickness of 1.8 mm. The hot-rolled sheet was annealed at 1100 ° C., cold-rolled to 0.81 mm in the same direction as the hot-rolling, and then cold-rolled to a final sheet thickness of 0.39 mm in a direction perpendicular to the cold-rolling direction. . Thereafter, at a heating rate of 15 ° C./sec, 810 ° C.
After heating to 810 ° C., decarburization annealing was performed at an atmosphere oxidation degree of 0.52 at 810 ° C. for 150 to 600 seconds. Thereafter, the steel sheet was annealed at 750 ° C. for 30 seconds in an ammonia-containing atmosphere to reduce the amount of nitrogen in the steel sheet to 0.019%. After applying an annealing separator containing MgO as a main component, finish annealing was performed at 1200 ° C. for 20 hours. Table 1 shows the characteristic values of the products. It can be seen that when the oxygen content of the steel sheet increased to 2.35 g / m ² , the magnetic properties were deteriorated.

[0033]

[Table 1]

Example 2 The cold-rolled sheet used in Example 1 was
In a mixed gas of nitrogen and hydrogen having an oxidation degree of 0.033,
Heating rate (1) 3 ° C / sec, (2) 20 ° C / sec, (3) 1
It was heated to 810 ° C. at a rate of 00 ° C./sec, and was annealed at 810 ° C. for 150 seconds for primary recrystallization. Thereafter, the steel sheet was annealed at 750 ° C. for 30 seconds in an ammonia-containing atmosphere, and the amount of nitrogen in the steel sheet was reduced to 0.021% by changing the ammonia content. After applying an annealing separator containing magnesia as a main component to these steel sheets, finish annealing was performed. Finish annealing is 1
Up to 200 ° C., at a heating rate of 15 ° C./hr in an atmosphere gas of N ₂ : 25% + H ₂ : 75%,
₂ Switching to 100% and annealing for 20 hours. As shown in Table 2, it can be seen that as the heating rate increases, I [111] / I [211] decreases and the magnetic flux density increases.

[0035]

[Table 2]

Example 3 The cold rolled sheet used in Example 1 was
In a mixed gas of nitrogen and hydrogen having an oxidation degree of 0.033,
Heating to 770 ° C to 850 ° C at a heating rate of 20 ° C / sec,
Annealing was performed for 210 seconds at each temperature to perform primary recrystallization. Then 7
Annealing was performed at 50 ° C. for 30 seconds in an ammonia-containing atmosphere to reduce the amount of nitrogen in the steel sheet to 0.020%. After applying an annealing separator containing magnesia as a main component to these steel sheets, finish annealing was performed. Finish annealing is N ₂ up to 1200 ° C:
The heating was performed at a heating rate of 15 ° C./hr in an atmosphere gas of 25% + H ₂ : 75%, and switching to H ₂ 100% was performed at 1200 ° C. for 20 hours. As shown in Table 3, as the soaking temperature increases, I [111] / I [211] decreases and the magnetic flux density increases.

[0037]

[Table 3]

Example 4 Si: 3.1%, C: 0.0
7%, acid-soluble Al: 0.027%, N: 0.007
%, Mn: 0.07%, S: 0.025%, Cu: 0.
135% silicon steel slab containing 0.7% Sn and 0.1% Sn
The sheet was heated at 0 ° C. and hot-rolled to a thickness of 2.3 mm. This hot-rolled sheet was annealed at 1100 ° C., cold-rolled to 1.1 mm in the same direction as the hot-rolling, and then cold-rolled to a final thickness of 0.5 mm in a direction orthogonal to the cold-rolling direction. .
Then, after heating to 830 ° C. at a heating rate of 3 ° C./sec to 100 ° C./sec, decarburizing annealing was performed at 830 ° C. for 210 seconds at an atmospheric oxidation degree of 0.59. The oxygen content of each steel sheet was 2.3 g / mm ² or less for each sample. After that, an annealing separator containing magnesia as a main component was applied,
Finish annealing was performed for 0 hours. As shown in Table 4, as the heating rate increases, I [111] / I [211] decreases and the magnetic flux density increases.

[0039]

[Table 4]

Example 5 Si: 3.1%, C: 0.0
7%, acid-soluble Al: 0.027%, N: 0.007
%, Mn: 0.07%, S: 0.025%, Cu: 0.
A silicon steel slab containing 07% and Sn: 0% to 0.3% was heated at 1350 ° C. and hot-rolled to a thickness of 2.3 mm. This hot-rolled sheet was annealed at 1100 ° C., cold-rolled to 1.1 mm in the same direction as the hot-rolling, and then cold-rolled to a final thickness of 0.5 mm in a direction orthogonal to the cold-rolling direction. . Thereafter, 830 at a heating rate of 3 ° C./sec to 100 ° C./sec.
After heating to ℃, decarburization annealing was performed at 830 ° C. for 210 seconds at an atmospheric oxidation degree of 0.59. The oxygen content of each steel sheet was 2.3 g / mm ² or less for each sample. Thereafter, an annealing separator containing magnesia as a main component was applied, followed by finish annealing at 1200 ° C. for 20 hours. As shown in Table 5, Sn
By adding preferably 0.02 to 0.2%
It can be seen that I [111] / I [211] decreases and the magnetic flux density increases.

[0041]

[Table 5]

[0042]

According to the present invention, by defining the primary recrystallization structure and the surface oxide layer, it is possible to industrially stably produce a bidirectional electrical steel sheet having a high magnetic flux density and excellent magnetic properties. .

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of the texture (I [111] / I [211] ratio) of the decarburized annealed sheet and the oxygen content of the decarburized annealed sheet on the magnetic flux density (B8) of the product.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/06 C22C 38/06 (72) Inventor Yukio Sasaki 20-1 Shintomi, Futtsu Nippon Steel Corporation F-term in the Technology Development Division (reference) 4E002 AA07 BC06 BC07 CB01 4K033 AA03 BA01 CA02 CA09 DA02 HA00 LA00 MA00 NA00 RA04 SA02 SA03 TA01

Claims (2)

[Claims] 1. A mass containing: Si: 0.8 to 6.7%, C: 0.085% or less, acid-soluble Al: 0.01 to 0.048%, N: 0.012% or less, A hot rolled silicon steel sheet consisting of the balance of Fe and unavoidable impurities is cold-rolled at a reduction of 40 to 80% in the same direction as hot rolling, and a reduction of 30 to 70 in a direction crossing the cold rolling direction. %, Followed by decarburizing annealing, then applying an annealing separator, and performing finish annealing for the purpose of secondary recrystallization and purification. A two-way high magnetic flux density characterized in that the ratio of I [111] / I [211] in the grain structure is 1 or less and the oxygen content of the oxide layer of the steel sheet is 2.3 g / m ² or less. Manufacturing method of conductive electrical steel sheet. 2. The method according to claim 1, wherein 0.02 to 0.2% of Sn is added by mass.