JP2005179745A - Method for producing bi-directional silicon steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bi-directional silicon steel sheet where the degree of accumulation in the ä100}<001> orientation is improved with secondary recrystallization. <P>SOLUTION: Regarding a primary recrystallized texture, the existing ratio of the orientation which has the orientation difference of 20 to 45° from the ä110}<001> orientation and has no coincidence relation with ä110}<001> orientation is reduced to ≤70% and the existence ratio of the orientation which has the orientation difference of 20 to 45° from ä100}<001> orientation and has no coincidence relation with ä100}<001> orientation is increased to ≥70%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a bi-directional electrical steel sheet having a high degree of {100} <001> orientation integration.

The magnetic properties of electrical steel sheets are affected by the crystal orientation, and it is known that the easy magnetization axis <001> of crystal grains is parallel to the steel sheet surface, which is necessary for obtaining excellent magnetic characteristics. It has been.
Usually, electrical steel sheets are roughly classified into non-oriented electrical steel sheets and directional electrical steel sheets. Non-oriented electrical steel sheets have a weak texture development and the ratio of crystal grains whose <001> axis is parallel to the plate surface is smaller than that of directional electrical steel sheets. Cannot be obtained.

On the other hand, the grain oriented electrical steel sheet has a high accumulation of <001> in the rolling direction by preferentially growing {110} <001> oriented grains by secondary recrystallization. Therefore, when magnetized in the rolling direction, it exhibits excellent magnetic properties, and is suitable for use as a core material for transformers.
However, since the <111> axis, which is the most difficult to magnetize, is also included in the plate surface, the magnetic properties are extremely poor when magnetized in this direction. For this reason, when good magnetic properties are required in all directions within the surface, such as a core material of a motor or a generator, good magnetic properties cannot be obtained even if a unidirectional electrical steel sheet is used.

  If an electromagnetic steel sheet having a crystal structure whose {100} plane is parallel to the rolling surface can be produced with respect to these electromagnetic steel plates, there are many <100> axes and <111> axes in the rolling surface. Therefore, it is extremely advantageous in terms of magnetic characteristics. In particular, the {100} <uvw> structure in which the rolled surface is {100} and the direction of the <001> axis is random eliminates the magnetic property anisotropy in the surface, and is ideal as a material for motors. is there.

  Attempts to develop the {100} <uvw> structure as described above have been made for a long time. For example, Patent Literature 1, Patent Literature 2 and Patent Literature 3 disclose a technique for developing a {100} structure by improving the manufacturing method of a non-oriented electrical steel sheet. However, with these techniques, a {100} structure with a high degree of integration has not been obtained, and the improvement in magnetic properties has been insufficient. The reason for this is considered to be that there is a limit to highly increasing the degree of integration in a specific orientation by primary recrystallization.

On the other hand, a method for producing a so-called bi-directional electrical steel sheet in which a {100} <001> structure is developed by secondary recrystallization has long been studied.
For example, in Patent Document 4, after cold rolling in one direction, further cold rolling is performed in a direction crossing this direction, and short-time annealing and high-temperature annealing at 900 to 1300 ° C. are performed. , {100} <001> oriented grains are secondarily recrystallized using an inhibitor. In Patent Document 5, after cold rolling at a reduction rate of 50 to 90% in a direction perpendicular to the hot rolling direction, annealing for the purpose of primary recrystallization is performed, followed by secondary recrystallization and purification. There has been proposed a method of subjecting {100} <001> oriented grains to secondary recrystallization using AlN by subjecting to final finishing annealing.
However, in these techniques, since cross rolling with extremely low productivity is indispensable, it has not yet been industrially mass-produced.

Thereafter, Patent Document 6 discloses a technique for developing {100} <001> orientation by a method of reducing impurities in steel and performing secondary recrystallization without using an inhibitor.
However, in this method, since the {110} <001> orientation also grows, it does not become a complete bi-directional electrical steel sheet, and a structure in which the {100} <001> orientation and the {110} <001> orientation coexist. I had to be.
In some small electrical appliances, electrical steel sheets with a mixed {100} <001> orientation and {110} <001> orientation have better iron loss characteristics in actual machines than complete bi-directional electrical steel sheets. In some cases, however, the electromagnetic steel sheet having such a mixed structure has a problem that its application is narrowly limited.

As described above, many studies on secondary recrystallization of silicon steel have been conducted so far. However, the {110} <001> orientation is overwhelmingly easier to grow than other orientations. So far, a technique for preferentially growing directions other than the {110} <001> direction has not been established.
Comparing the {110} <001> orientation with the {100} <001> orientation, the former has the <001> axis in the rolling direction, but the rolling perpendicular direction becomes the <011> axis, and this orientation is easily magnetized. The property is inferior to the <001> axis. On the other hand, the latter is the <001> axis that is easily magnetized in both the rolling direction and the direction perpendicular to the rolling direction. When used as an iron core material of an EI type core, which is one of typical examples of transformers, it goes without saying that the latter is more advantageous because the magnetic flux flows in both the rolling direction and the direction perpendicular to the rolling direction. In addition, the {110} <001> orientation includes the <111> axis that is most difficult to magnetize in the plate surface, but there is also an advantage that the {100} <001> orientation is not included. Further, since the {100} <001> orientation has {100} planes aligned on the plate surface, it goes without saying that it is also advantageous for the motor.
Therefore, it is very beneficial to stably recrystallize the {100} <001> orientation, but in the prior art, grains grown by secondary recrystallization are overwhelmingly {110} <001>. There is a property limited to the vicinity of the azimuth, and so far, no industrially producible production method for secondary recrystallization of the {100} <001> azimuth has been found.

Japanese Patent Publication No.51-942 Japanese Patent Publication No.57-14411 JP-A-5-5126 Japanese Patent Publication No. 35-2657 JP-A-4-362132 JP 2001-158950 A

  The present invention has been developed in view of the above situation, and proposes an advantageous manufacturing method of a bidirectional electrical steel sheet in which {100} <001> orientation integration degree is effectively improved by secondary recrystallization. With the goal.

  Conventionally, it has been reported that precipitates called inhibitors play an important role in secondary recrystallization. That is, when the secondary recrystallization is caused in the final finish annealing, the inhibitor pinches the movement of the grain boundary on the grain boundary and suppresses the normal grain growth of the primary recrystallized grain, but {110} < It has been reported that the grain boundaries surrounding the 001> orientation can be preferentially unpinned and can grow to a selected extent.

By the way, as a result of intensive studies on the mechanism of the secondary recrystallization, the inventors have found that, in the secondary recrystallization, in addition to the presence of an inhibitor, an orientation difference angle (a lattice of adjacent crystals is superimposed) in the primary recrystallization structure. The minimum rotation angle required for the above is important, and the grain boundary with this misorientation angle of 20-45 ° (high energy grain boundary) has been found to play an important role in the development of secondary recrystallization. Reported in Acta Material Volume 45.
That is, according to the study by the inventors, a high energy grain boundary having a misorientation angle of 20 to 45 ° has a higher moving speed than other grain boundaries, and in general, the {110} <001> orientation is different from other grain boundaries. Since the probability of being surrounded by a high energy grain boundary with a misorientation angle of 20 to 45 ° is higher than the orientation, it has been found that growth proceeds preferentially.

Therefore, the inventors controlled the primary recrystallization structure to preferentially recrystallize the {100} <001> orientation, and the orientation difference angle from the {100} <001> orientation was 20 to 45. Attempted to increase the degree of crystal grains.
That is, various investigations were made on the steel components, rolling conditions, annealing conditions, etc., the primary recrystallization texture was changed, and the secondary recrystallization behavior in the final finish annealing thereafter was investigated in detail.
As a result, in the primary recrystallization texture, it was possible to increase the crystal grains whose misorientation angle from the {100} <001> orientation to 20 to 45 ° to some extent, but the orientation from the {110} <001> orientation. Since crystal grains with a difference angle of 20 to 45 ° are also generated with a considerable frequency, both the {100} <001> and {110} <001> orientations are secondarily recrystallized after the final finish annealing. A bi-directional electrical steel sheet could not be obtained.

Therefore, the inventors further examined whether there is a factor that greatly affects the grain boundary movement other than the orientation difference angle.
The reason why the grain boundary with a misorientation angle of 20 to 45 ° is easy to move is considered as follows.
Grain boundaries with misorientation angles of 20 to 45 ° are high energy grain boundaries, and the free space within the grain boundaries has a large and messy structure. Grain boundary diffusion is a phenomenon in which atoms move through the grain boundary. Therefore, a high energy grain boundary having a large free space in the grain boundary has a faster grain boundary diffusion than other grain boundaries. Accordingly, there is a difference in moving speed between the high energy grain boundaries and other grain boundaries.
However, even if the misorientation angle is in the range of 20 to 45 °, if the two crystal grains sandwiching the grain boundary are in a corresponding orientation relationship, the consistency is good and the free space in the grain boundary is disturbed. Will be less.
The inventors paid attention to this character and came to have an idea that “a grain boundary having a misorientation angle of 20 to 45 ° and not having a corresponding orientation relationship is likely to move”.

Note that the corresponding orientation relationship means that when two adjacent crystal lattices are extended and overlapped and translated to match a pair of lattice points, 1 / Σ of the lattice points coincides with the lattice point of the adjacent crystal The degree of coincidence is expressed by a Σ value. A matching grid point is referred to as a corresponding grid point, and the Σ value is the reciprocal of the corresponding grid point density. Σ is an integer of 3, 5, 7, 9, 11, 13, 17... The smaller the Σ value, the higher the degree of lattice matching. Even if it is not in a strict correspondence relationship, Brandon considers that it has a characteristic as a correspondence direction if the deviation from the correspondence relationship is within 15 ° / Σ ^1/2 . When two adjacent crystal grains are in a corresponding orientation relationship, the boundary is a corresponding grain boundary.

Now, in the primary recrystallization texture obtained by rolling and annealing, the orientations that are easy to develop can be roughly divided into two. One peak appears in the vicinity of {554} <225>. The other peak is likely to shift depending on the conditions, but appears on a rotation sequence that goes to approximately {410} <001> to {12 4 1} <014> to {411} <148>. Here, the former is called the M direction, and the latter is called the S direction.
The peak position in the M direction is almost {554} <225> and does not change much depending on the conditions. This {554} <225> azimuth is 29.5 ° from the {110} <001> azimuth and 53.4 ° from the {100} <001> azimuth. Therefore, an increase in the M orientation in the primary recrystallization texture has an advantageous effect on secondary recrystallization in the {110} <001> orientation.

  On the other hand, the peak position of the S orientation is easily shifted depending on the conditions as described above. The {410} <001> orientation is 31.0 ° from the {110} <001> orientation and 14 ° from the {100} <001> orientation, which is advantageous for secondary recrystallization in the {110} <001> orientation. Yes, this is a disadvantageous orientation for secondary recrystallization in {100} <001> orientation. The {12 4 1} <014> orientation is 29.5 ° from the {110} <001> orientation and 23.6 ° from the {100} <001> orientation, and the secondary recrystallization of the {110} <001> orientation Is also advantageous for secondary recrystallization in the {100} <001> orientation. The {411} <148> azimuth is 38.9 ° from the {110} <001> azimuth and 32.0 ° from the {100} <001> azimuth. Considering only the azimuth difference angle, this is also {110} < It can be said that this is an advantageous orientation for both secondary recrystallization of the 001> orientation and secondary recrystallization of the {100} <001> orientation.

In this way, it is advantageous for secondary recrystallization of {100} <001> orientation and disadvantageous growth for secondary recrystallization of {110} <001> orientation. It turns out that it is difficult to think only from.
In fact, conventionally, even if a bi-directional electrical steel sheet is manufactured by secondary recrystallization, only {110} <001> orientation and {100} <001> orientation are mixed.

However, when attention is paid to the corresponding azimuth relationship in addition to the azimuth difference angle, the {411} <148> azimuth is exactly Σ9 from the {110} <001> azimuth. Therefore, the {411} <148> orientation is advantageous for secondary recrystallization in the {100} <001> orientation, but is considered to be a disadvantageous orientation for secondary recrystallization in the {110} <001> orientation. Can do.
Of the above-mentioned azimuths, the {110} <001> azimuth and the {100} <001> azimuth have a corresponding azimuth relationship when evaluated according to the Brandon standard, and {411} <148> azimuth and {110} Only a combination of <001> orientations.

Therefore, the inventors in the primary recrystallization texture,
(a) Decrease the strength of the M direction,
(b) By controlling the peak position of the S orientation to the {411} <148> orientation and focusing on increasing its strength, and properly combining the rolling conditions and annealing conditions, the {100} <001> orientation Succeeded in the development of secondary recrystallization that preferentially grows.

As for the behavior of the corresponding grain boundary during secondary recrystallization, as reported in CAMP-ISIJ vol.14 (2001) P.1188 to 1191, “Σ9 corresponding grain boundary promotes selective growth”. Conventionally, it has been reported that the corresponding grain boundary moves more easily than other grain boundaries.
However, contrary to these reports, the present invention clarifies the nature that the corresponding grain boundary is difficult to move, and based on this new knowledge, has led to the completion of a novel method for producing a bidirectional electrical steel sheet. It was.

That is, the gist configuration of the present invention is as follows.
1. The silicon steel slab is hot-rolled and subjected to hot-rolled sheet annealing as necessary, and then the final sheet thickness is obtained by one or more cold rollings sandwiching the intermediate annealing, and then after the primary recrystallization annealing, In producing a bi-directional electrical steel sheet by a final finishing annealing process for secondary recrystallization,
In the primary recrystallized texture, the abundance ratio of orientations having an orientation difference of 20 to 45 ° from the {110} <001> orientation and not corresponding to the {110} <001> orientation is 70% or less. And reducing the presence ratio of azimuths having a azimuth difference of 20 to 45 ° from {100} <001> azimuth and not having a corresponding azimuth relationship with {100} <001> azimuth to 70% or more. A method for producing a bi-directional electrical steel sheet, which is characterized.

2. The silicon steel slab is hot-rolled and subjected to rolling sheet annealing as necessary, and then the final sheet thickness is obtained by cold rolling at least once with one or two intermediate sandwiches, and then after the primary recrystallization annealing, In producing a bi-directional electrical steel sheet by a final finishing annealing process for subsequent recrystallization,
In the primary recrystallization texture, the {554} <225> orientation accumulation degree is reduced to 6 or less in the random intensity ratio, and the {411} <148> orientation accumulation degree is increased to 7 or more in the random intensity ratio. A method for producing a bi-directional electrical steel sheet, which is characterized.

  According to the present invention, it is possible to stably obtain a bi-directional electrical steel sheet in which the crystal orientation is highly integrated in the {100} <001> orientation.

The present invention will be specifically described below.
First, the suitable raw material component in this invention is demonstrated. Unless otherwise specified, “%” in relation to ingredients means mass%.
C: 0.003 to 0.1%
C is preferably added in the range of 0.003% to 0.1% for improving the structure. However, if C is contained in the product, the iron loss deteriorates due to aging. Therefore, it is necessary to decarburize to 0.0050% or less in the process of making the product.

Si: 2.0 to 4.5%
Si has the function of improving iron loss by increasing the electric resistance. To that end, it is necessary to contain 2.0% or more. However, if it exceeds 4.5%, cold rolling becomes extremely difficult. It is preferable to be about ~ 4.5%.

Mn: 0.03-2.5%
Mn, like Si, has an effect of improving iron loss by increasing electrical resistance, and is also a useful component in terms of improving hot workability during production. For this purpose, it is necessary to contain 0.03%, but if it exceeds 2.5%, it induces γ transformation and deteriorates the magnetic properties, so Mn should be about 0.03 to 2.5%. Is preferred.

The elements other than the above are not particularly limited, but basically, the higher the purity, the more the difference in mobility due to the grain boundary character (whether or not the orientation difference angle corresponds to the corresponding grain boundary) becomes obvious. Suitable for Since the present invention is a technique for secondary recrystallization of the {100} <001> orientation using the difference in mobility due to the grain boundary character, it is basically unnecessary to add an inhibitor element.
In addition, the addition of an inhibitor is not necessarily harmful. However, the addition of the inhibitor tends to favor the secondary recrystallization in the {110} <001> orientation, although the mechanism is not clear. In particular, Se, S, O, and N all inhibit the expression of secondary recrystallization in the {100} <001> orientation, and remain in the ground iron to deteriorate the iron loss, so it is reduced to 0.005% or less. It is preferable to do.

  However, Sb, Sn and Bi are easy to segregate at the grain boundary and have the effect of making the difference in mobility due to the grain boundary character more obvious, so may be added as appropriate. In that case, mechanical properties such as the bend characteristics of the product will deteriorate if added excessively, so Sb is 0.001% or more and less than 0.1%, Sn is 0.001% or more and less than 0.1%, Bi is 0.0005% or more and less than 0.05% It is preferable to set the degree.

Further, although the mechanism is not clear, the addition of a small amount of Al favors stable secondary recrystallization in the {100} <001> orientation. Therefore, Al is preferably added in the range of 0.0010% to 0.020%.
In the present invention, since N is reduced as much as possible, the secondary recrystallization mechanism is fundamentally different from the conventional manufacturing method in which AlN functions as an inhibitor and performs secondary recrystallization.

  In addition, Cu, Mo, Cr, and the like have an advantageous effect on the improvement of magnetic properties, and can be contained as appropriate. In that case, in order to obtain the effect of improving magnetic characteristics, it is preferable to add Cu: 0.01 to 1.50%, Mo: 0.005 to 0.50%, Cr: 0.01 to 1.50%. When the addition amount is less than the above range, there is no effect of improving the magnetic properties, whereas when the addition amount is large, secondary recrystallization does not develop, leading to deterioration of the magnetic properties.

Next, the manufacturing process of the present invention will be described.
The molten steel adjusted to the above preferred component composition is made into a slab by a normal ingot-bundling method or a continuous casting method. Alternatively, a thin cast piece having a thickness of 100 mm or less may be directly produced by using a direct casting method.
Next, the slab is heated and hot rolled. Since the present invention does not require a solid solution-precipitation type inhibitor, the slab heating temperature may be about ordinary steel, and the slab heating temperature is preferably about 1250 ° C. or less for energy saving. In addition, the direct rolling method which uses for a hot rolling immediately after casting, without being heated can also be applied suitably.

  The hot-rolled sheet is subjected to hot-rolled sheet annealing as necessary, and then subjected to cold rolling twice or more with intermediate or intermediate annealing to obtain a final sheet thickness. This cold rolling may be performed at room temperature, but warm rolling in which the temperature is raised to a temperature of 100 ° C. or higher and rolling is more preferable from the viewpoint of texture control. Further, so-called inter-pass aging treatment in which a temperature range of 150 ° C. or higher is maintained for at least 1 minute between cold rolling passes can also be suitably used in the present invention.

  Next, the final cold rolled sheet is subjected to annealing for primary recrystallization and decarburization. In addition, this annealing reduces the C content to 0.005% or less, preferably 0.003% or less, in which magnetic aging does not occur. Note that the technique of increasing Si by a siliconization method after final cold rolling or after annealing for primary recrystallization and decarburization can also be suitably applied to the present invention as a method of reducing iron loss.

  Thereafter, an annealing separator is applied as necessary, and then final finish annealing is performed. As the annealing separator, a slurry of a refractory powder such as silica, alumina, magnesia, or a colloidal solution is suitable. In addition, a method of adhering these refractory powders to a steel sheet by dry coating such as electrostatic coating is more preferable because moisture is not included in the final finish annealing atmosphere. Furthermore, a method of sandwiching a steel plate whose surface is coated with these refractories by thermal spraying or the like can also be applied. The final finish annealing is performed by heating to a temperature range of 800 ° C. or higher for secondary recrystallization in the {100} <001> orientation. Furthermore, when a base coating such as a forsterite coating is required, there is no problem in raising the temperature to about 1200 ° C.

In addition, when laminating | stacking and using a steel plate, it is effective to give an insulating coating to the steel plate surface after said final finishing annealing. The type of insulating coating is not particularly limited, but any known insulating coating is suitable. For example, a coating solution containing phosphate-chromic acid-colloidal silica described in JP-A-50-79442 and JP-A-48-39338 is applied to a steel plate and baked at about 800 ° C. The method is preferred. This insulating film may be a multilayer film composed of two or more kinds of films, or may be a film in which a resin or the like is mixed depending on the application. Furthermore, an insulating coating mainly composed of a phosphate that imparts tension is also effective in reducing iron loss and noise.
In addition, after the final finish annealing, it is possible to perform flattening annealing so as to adjust the shape of the steel sheet. At this time, it is also possible to perform the flattening annealing that doubles the baking of the insulating film.

In the present invention, it is most important to control the primary recrystallization texture so that the {100} <001> orientation preferentially undergoes secondary recrystallization in the final finish annealing.
Here, the primary recrystallization texture for preferential secondary recrystallization of the {100} <001> orientation is:
(A) Reducing the abundance ratio of azimuths having a azimuth difference of 20 to 45 ° from {110} <001> azimuth and not having a corresponding azimuth relationship with {110} <001> azimuth to 70% or less, and { 100} <001> is a structure having an azimuth difference of 20 to 45 ° from the azimuth and having an abundance ratio of azimuths not corresponding to the {100} <001> azimuth to 70% or more, preferably ,
(B) It is a structure in which the degree of accumulation in the {411} <148> orientation is increased to 7 or more in the random intensity ratio and the degree of accumulation in the {554} <225> direction is reduced to 6 or less in the random intensity ratio.

In order to control the primary recrystallized texture having the crystal orientation as described above, it is important to optimize the steel components, hot rolling conditions, cold rolling conditions, annealing conditions, and the like. Since the texture changes depending on the rolling mill and annealing furnace used, it is important to adjust the operation parameters so that the primary recrystallization texture satisfies the above-mentioned conditions.
For example, for rolling conditions:
(1) By increasing the rolling reduction in the final cold rolling (preferably 80% or more), the peak position of the S orientation can be brought close to {411} <148>. In this case, the intensity of the {554} <225> orientation also increases.
(2) Also, the method of increasing the rolling temperature to cause dynamic strain aging, so-called warm rolling, has the effect of reducing the degree of integration of {554} <225> orientations. However, in this case, the peak position in the S direction is slightly deviated from {411} <148>.

Therefore, it is necessary to control the rolling reduction and the rolling temperature in combination. For example, a suitable primary recrystallization aggregate is obtained by performing warm rolling at 150 to 300 ° C. in one pass or more of the final cold rolling and appropriately controlling the final cold rolling reduction within a range of 85 to 90%. It can be an organization.
In addition, a method of maintaining static aging in a temperature range of 150 ° C. or higher between rolling passes for 1 minute or longer brings about a texture change similar to that of warm rolling. preferable.

For annealing conditions,
(3) The primary recrystallization texture is greatly affected through the effect on the grain size before final cold rolling. Increasing the crystal grain size before the final cold rolling by increasing the annealing temperature before the final cold rolling for a long time has the effect of reducing the degree of integration of the {554} <225> orientation. Is too large, the peak position of the S orientation deviates from the {411} <148> orientation, so it is necessary to optimize to the optimum annealing conditions.
For example, controlling the annealing before the final cold rolling to 1050 to 1150 ° C and controlling the rolling temperature in the final cold rolling to 250 ° C or less, or controlling the annealing before the final cold rolling to 950 to 1050 ° C. By combining this with the control of the rolling temperature in the final cold rolling to 200 ° C. or higher, a suitable primary recrystallization texture can be obtained.

  In the present invention, it is important to control to the texture shown in the above (A) or (B) by performing at least one of the above-mentioned (1), (2) and (3). .

In Table 1, A: 2 slabs, B: 3 slabs, C: 3 slabs are prepared, A is 2.8 mm and 2.1 mm thick, B is 2.8 mm, 2.4 mm and 2.1 mm thickness and C were hot-rolled to 3.4 mm, 2.8 mm and 2.1 mm thickness, respectively. In the hot rolling, the A slab was heated to 1400 ° C. and then hot rolled, and the B and C slabs were heated to 1100 ° C. and hot rolled.
Then, hot-rolled sheet annealing was performed at 1100 ° C. for 60 seconds, pickling, and cold rolling at a time to a sheet thickness of 0.34 mm. The rolling reduction of cold rolling is 84% when using a 2.1 mm thick slab, 86% when using a 2.4 mm thick slab, 88% when using a 2.8 mm thick slab, and 3.4 mm thick 90% when the slab is used. Cold rolling was performed at 200 ° C for 2.4 mm and 2.8 mm thick slabs and at 300 ° C for 2.1 mm and 3.4 mm thick slabs.
After the cold rolling described above, degreasing treatment was performed, and then annealing for both primary recrystallization and decarburization was performed at 850 ° C. for 120 seconds. After annealing, the test piece was cut out and the texture near the surface layer was measured by X-ray pole figure method. In addition, a three-dimensional orientation distribution was obtained by calculation from the obtained X-ray pole figure data.

After annealing for primary recrystallization and decarburization, an annealing separator was applied, and then final finish annealing was performed. MgO was used as the annealing separator.
After the final finish annealing, after removing the unreacted separating agent, an insulating coating solution mainly composed of magnesium phosphate containing colloidal silica was applied and baked at 800 ° C. to obtain a product plate.
Table 2 shows the results of investigation on the iron loss W _{15/50 in} the rolling direction (L direction) and the rolling perpendicular direction (C direction) of each product plate thus obtained.

  As shown in Table 2, by controlling the primary recrystallization texture to the structure defined in the present invention, the {100} <001> orientation is preferentially recrystallized, and the L direction and the C direction A bi-directional electrical steel sheet with good iron loss could be obtained.

In the analysis of the primary recrystallization texture, Φ ₁ , Φ, and Φ ₂ were determined in increments of 5 ° for each of the three-dimensional orientation distributions in Bunge's Euler angle display.
The intensity of the {411} <148> orientation is as a random intensity ratio of (Φ ₁ , Φ, Φ ₂ ) = (20 °, 20 °, 45 °), while the intensity of the {554} <225> orientation is ( Φ ₁ , Φ, Φ ₂ ) = (90 °, 60 °, 45 °).
Further, the abundance ratio of orientation suitable for secondary recrystallization of {100} <001> orientation, that is, an orientation difference angle of 20 to 45 ° from {100} <001> orientation, and {100} <001> The existence ratio of azimuth that is not related to azimuth is determined. Similarly, the abundance ratio of orientation suitable for secondary recrystallization of {110} <001> orientation, that is, an orientation difference angle of 20 to 45 ° from {110} <001> orientation, and {110} <001 > The existence ratio of orientations not having a corresponding orientation relationship was also obtained. Corresponding orientation relations were subject to corresponding orientations with a Σ value of 19 or less, and the range of Brandon conditions was regarded as the corresponding orientation relation.

  Ten slabs having the composition indicated by D in Table 1 are prepared, heated to 1150 ° C. and hot-rolled. The slabs (1) to (3) are formed into a 2.2 mm thick hot-rolled coil (4 The slabs () to (6) were rolled into a 3.1 mm thick hot rolled coil, and the slabs (7) to (10) were rolled into a 3.4 mm thick hot rolled coil. Subsequently, (1) to (3) were subjected to hot-rolled sheet annealing at 1100 ° C. for 60 seconds, and (4) to (10) were subjected to hot-rolled sheet annealing at 1000 ° C. for 60 seconds. After hot-rolled sheet annealing, pickling was performed, and cold rolling was performed once to a sheet thickness of 0.34 mm. The rolling reduction in cold rolling is 85% for (1) to (3), 89% for (4) to (6), and 90% for (7) to (10). Cold rolling is 300 ° C for (1) and (7), 250 ° C for (4) and (8), and for (2), (5), (9). It was carried out at 200 ° C, 150 ° C for (6) and (10), and 80 ° C for (3). In addition, (7) to (10) were subjected to an aging treatment of holding at 250 ° C. for 2 hours between cold rolling passes.

After cold rolling, after degreasing treatment, annealing was performed at 870 ° C for 120 seconds, which served as both primary recrystallization and decarburization. After annealing, the test piece was cut out and the texture near the surface layer was measured by X-ray pole figure method. In addition, a three-dimensional orientation distribution was obtained by calculation from the obtained X-ray pole figure data.
After annealing for primary recrystallization and decarburization, an annealing separator was applied to perform final finish annealing. MgO was used as the annealing separator.
After the final finish annealing, after removing the unreacted separating agent, an insulating coating solution mainly composed of magnesium phosphate containing colloidal silica was applied and baked at 800 ° C. to obtain a product plate.
Table 3 shows the results of investigation on the iron loss W _{15/50 in} the rolling direction (L direction) and the perpendicular direction (C direction) of each product plate thus obtained.
The analysis of the primary recrystallization texture is the same as in the case of Example 1.

  As is apparent from the table, by controlling the primary recrystallization texture to the structure defined in the present invention, the {100} <001> orientation is preferentially recrystallized, and the L direction and the C direction. A bi-directional electrical steel sheet with good iron loss was obtained.

Claims (2)

The silicon steel slab is hot-rolled and subjected to hot-rolled sheet annealing as necessary, and then the final sheet thickness is obtained by one or more cold rollings sandwiching the intermediate annealing, and then after the primary recrystallization annealing, In producing a bi-directional electrical steel sheet by a final finishing annealing process for secondary recrystallization,
In the primary recrystallized texture, the abundance ratio of orientations having an orientation difference of 20 to 45 ° from the {110} <001> orientation and not corresponding to the {110} <001> orientation is 70% or less. And reducing the presence ratio of azimuths having a azimuth difference of 20 to 45 ° from {100} <001> azimuth and not having a corresponding azimuth relationship with {100} <001> azimuth to 70% or more. A method for producing a bi-directional electrical steel sheet, which is characterized. The silicon steel slab is hot-rolled and subjected to rolling sheet annealing as necessary, and then the final sheet thickness is obtained by cold rolling at least once with one or two intermediate sandwiches, and then after the primary recrystallization annealing, In producing a bi-directional electrical steel sheet by a final finishing annealing process for subsequent recrystallization,
In the primary recrystallization texture, the {554} <225> orientation accumulation degree is reduced to 6 or less in the random intensity ratio, and the {411} <148> orientation accumulation degree is increased to 7 or more in the random intensity ratio. A method for producing a bi-directional electrical steel sheet, which is characterized.