JP3333798B2 - Grain-oriented electrical steel sheet with low iron loss - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-loss magnetic steel sheet suitable for use in iron cores of transformers and other electric equipment.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are used as cores for transformers and other electrical equipment, and have excellent magnetic properties.
Above all, low iron loss is required. The iron loss can be generally represented by the sum of the hysteresis loss and the eddy current loss, and the hysteresis loss is determined by using an inhibitor having a strong suppressing force to change the crystal direction to the Goss orientation, that is, (11).
0) It has been greatly reduced by highly integrating in the <001> direction, by reducing impurity elements which cause generation of a pinning factor at the time of domain wall movement when magnetized, and the like. On the other hand, regarding eddy current loss, increasing the Si content to increase the electrical resistance, reducing the thickness of the steel sheet,
The reduction has been attempted by forming a film having a different thermal expansion coefficient from that of the base steel on the surface of the steel base steel to impart tension to the base steel, reducing the magnetic domain width by refining crystal grains, and the like.

[0003] In order to further reduce eddy current loss, a method has been developed in which a magnetic pole is introduced in a direction substantially perpendicular to the rolling direction of the steel sheet to subdivide the 180-degree magnetic domain. (Japanese Patent Publication No. 57-2252), a method of irradiating a plasma flame (Japanese Patent Application Laid-Open No. 62-96617) and the like, and a heat-resistant magnetic domain subdivision method include forming grooves in a steel sheet after secondary recrystallization by mechanical processing. (Japanese Patent Publication No. 50-35679) and a method of introducing a linear notch in a direction perpendicular to the rolling direction before finish annealing (Japanese Patent Publication No. 3-69968).

Japanese Patent Application Laid-Open No. 54-40223 discloses a method for reducing eddy current loss by appropriately controlling the inclination angle of a crystal from a rolled surface in the [001] direction.

[0005]

As described above, conventionally, in order to reduce the hysteresis loss, integration of the crystal orientation in the Goss orientation and to reduce eddy current loss, the magnetic domain width in the rolling direction has to be reduced. Although mainly aimed at, it is no longer possible to expect a significant improvement in iron loss by using these methods alone.

The present invention advantageously satisfies the above requirement for reduction of iron loss, and newly focuses on non-uniformity of magnetic flux density distribution in a steel sheet as a factor of iron loss of a grain-oriented electrical steel sheet.
An object of the present invention is to propose a grain-oriented electrical steel sheet which reduces such non-uniformity by defining the shape of the secondary recrystallization, and as a result, achieves a lower iron loss than ever before.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a silicon-containing steel sheet which has been subjected to a final finish annealing, wherein an Al component is contained in an undercoat on the steel sheet surface in an amount of 0.1 to 0.7 g / m ² and a Ti component is contained in a 0.1 to 0.8 g / m m ² and containing an average aspect ratio of the length of the rolling direction of the secondary recrystallized grains length and sheet width direction is 0.10 to 0.95, and magnetizing force
800 magnetic flux density B ₈ in A / m is less oriented electrical steel sheet iron loss, characterized in that at least 1.89 T.

Here, the average aspect ratio is expressed by the following equation:
(1) or Equation (2).

(Equation 1)

As described above, the iron loss of the grain-oriented electrical steel sheet is as follows.
Hysteresis loss and eddy current loss can be divided into two types. In the former, the amount of the impurity element that hinders the domain wall movement and the crystal orientation [0
01] in the rolling direction, and the latter is determined by the sheet thickness, the specific resistance, and the magnetic domain width. These factors show a good correspondence with the magnetic properties of the steel sheet if the local magnetic flux density distribution in the steel sheet is uniform, and iron loss can be reduced only by controlling these factors.

However, in an actual polycrystalline steel sheet, particularly a steel sheet having a large crystal grain such as a grain-oriented electrical steel sheet, the magnetic flux density in the excited state is unevenly distributed. Focusing on this point, in addition to the previously known iron loss determinant described above, the inventors have found that local non-uniformity of magnetic flux density in the steel sheet is one factor that deteriorates the iron loss of the electromagnetic steel sheet. Revealed that there is. Therefore, when the nonuniformity of the local magnetic flux density distribution is reduced, in particular, when the nonuniformity r of the local magnetic flux density distribution defined by the following equation (3) is 0.15 or less, it is particularly excellent. The result is a steel sheet with magnetic properties. Based on this finding, the present inventors have clarified that the uniformity of the magnetic flux density distribution can be controlled by optimizing the shape of the secondary recrystallized grains, and have reached the present invention.

(Equation 2)

In the following, various experiments on the shape of the above-mentioned secondary recrystallized grains and the results thereof performed by the inventors to complete the present invention will be described. A steel slab containing 3.3% of Si is hot-rolled, subjected to two cold-rollings with intermediate annealing to obtain a final sheet thickness, decarburized, subjected to primary recrystallization annealing, and then to secondary recrystallization. In producing a unidirectional silicon steel sheet by a series of steps of crystal annealing and then purification annealing, 0 to 10% of Al ₂ O ₃ is added to the steel sheet surface after decarburizing annealing,
Various steel sheets coated with MgO slurry containing various amounts of TiO ₂ in the range of 0 to 15% and SnO ₂ in the range of 0 to 10% were subjected to 0 ° C / cm, 5 ° C / cm, 10 ° C / The secondary recrystallization was completed by raising the temperature while giving a temperature gradient of each condition of cm 2, 20 ° C./cm, 30 ° C./cm and 40 ° C./cm 2, and then purification annealing was performed at 1200 ° C. for 10 hours. .

As a result, due to the temperature gradient in the sheet width direction during the secondary recrystallization annealing and the addition of SnO ₂ into MgO, the secondary recrystallized grains having a long shape in the direction perpendicular to the rolling direction in the plane of the steel sheet. A steel plate was obtained.

Next, the steel sheet (plate thickness 0.23 mm) obtained as described above was sheared into a specimen having a length of 280 mm in the rolling direction and a width of 100 mm in a direction perpendicular to the rolling direction. iron loss W _{1 7/50} piece (maximum magnetic flux density 1.7 T, the loss at a frequency 50 Hz) were measured by veneer magnetic tester. Further, the average magnetic domain width of each specimen in the demagnetized state was determined by magnetic domain observation.

As a result, Al and
Containing no Ti is the magnetic domain width of the average is wide and 0.40～0.50Mm, also less than 0.1 g / m ² of Al, the steel sheet containing the base in the coating is less than 0.1 g / m ² of Ti has a magnetic domain width 0.30 It was rather wide with ~ 0.40mm. On the other hand, those containing 0.1 g / m ² or more of Al and 0.1 g / m ² or more of Ti in the undercoat film have an average magnetic domain width of 0.30 or more.
It was narrow, less than mm. No change in the magnetic domain width due to the addition of SnO ₂ to MgO was observed.

Next, the pickling macroetchin was added to each of the above-mentioned specimens.
At 2 o'clock to reveal the recrystallized structure and roll each crystal grain
Average length L in direction_i, The average length in the direction perpendicular to the rolling direction
Sa C _iIs measured, and the average as
Pect ratio a₁I asked. Where L_i,C_iIs the pressure
Draw a straight line every 5 mm in the direction perpendicular to the rolling direction and rolling direction.
Calculated as the average of the length of the part that intersects with each crystal grain
Was. Temperature gradient in plate width direction and average aspect ratio a₁Relationship with
The person in charge, SnO_TwoThe results are shown in FIG. Figure 1 shows
Thus, as the temperature gradient in the plate width direction increases, a₁of
The maximum value is smaller. Also SnO_TwoIs large.
Secondary recrystallized grains grow in the width direction of the plate, and have a small aspect ratio.
A steel sheet with a specific ratio is obtained.

FIG. 2 is a graph showing the relationship between the average aspect ratio a ₁ and the aforementioned iron loss W _17/50 . FIG. 2 shows the results for the average magnetic domain width at three levels and the Al and Ti contents in the undercoat. That, Al, with ^steel sheet ² containing 0.50 g / m in the base film is Ti, 0.15 to 0.20 mm
Although narrow magnetic domain width of is obtained, this time, in particular average aspect ratio a ₁ is when the range of 0.10 to 0.95 is very good iron loss value is obtained. Thus, in a state in which the magnetic domain width is subdivided, if the average aspect ratio a ₁ is within the compliance range, the magnetic domain width, the average aspect ratio of more than expected by the respective effects, that there is iron loss reducing effect I understand.

Next, in order to determine the conditions under which the iron loss reduction effect can be obtained, the effect of Al,
The effect of Ti content was investigated in more detail. That is,
The average aspect ratio of the sample of the secondary recrystallized grains shape of a ₁ is 0.1 to 0.95, Al in the base coat, with variously changing the Ti component amount, were investigated on the iron loss W _17/50. The result is shown in FIG. From FIG. 3, Al, each base in the coating amount of Ti 0.1~0.7 g / m ^2, when the 0.1 ~0.8 g / m ^2, W
_It can be seen that excellent magnetic properties with _17/50 less than 0.80 W / kg were obtained.

As described above, when the Al and Ti are contained in the base film in predetermined amounts, the magnetic domain refining effect appears and the iron loss reducing effect is obtained. The reason is that Al ₂ O ₃ and / or MgO · Al ₂ O
_{It is considered that 3} and TiO ₂ and / or MgO.TiO ₂ were formed in the coating and the tensile effect of the underlying coating was enhanced.

From the above experimental results, it was found that
By specifying the Al component amount and the Ti component amount, and increasing the shape of the secondary recrystallization in the direction perpendicular to the rolling direction, it became clear that an extremely low iron loss can be obtained. is there. In all the experiments, the total amount of Sn in SnO ₂ added to MgO was diffused and homogenized in the steel.

[0020]

In the grain-oriented electrical steel sheet according to the present invention, the reason why a group of crystal grains long in the direction perpendicular to the rolling direction gives good magnetic properties is determined in detail by measuring the distribution of local magnetic properties of the steel sheet. Analyzed.

The inventors measured the local magnetic flux density distribution of steel sheets having different average aspect ratios obtained by experiments using a method called a “probe method”. Here, the "probe method" is a non-destructive measurement of the local magnetic flux density similar to that of a search coil by bringing two needles arranged in a direction perpendicular to the magnetization direction of the steel sheet into contact with the base iron part. It is a method that can be. The measurement shows that the maximum magnetic flux density
The component in the rolling direction of the magnetic flux passing through a 10 mm width in a direction perpendicular to the rolling direction of the steel sheet when excited to 1.7 T was performed. The measurement points are set at 10 mm intervals in the rolling direction and the direction perpendicular to the rolling direction, respectively,
The measurement was performed at approximately 200 points in the center of the steel sheet in the rolling direction.
From the numerical values thus obtained, the magnetic flux density distribution in the local region was quantified according to the above equation (3).

FIG. 4 shows an average magnetic domain width of 0.10 mm to 0.20 mm.
Is the relationship between the average aspect ratio a _{1 of the} sample and the nonuniformity r of the local magnetic flux density distribution. FIG. 4 shows a relationship that r increases as the average aspect ratio a ₁ increases. Thus, a ₁ is reduced, local magnetic flux density by a long grain in a direction perpendicular to the rolling direction becomes uniform, it can be seen that the low iron loss can be obtained.

Considering the mechanism of the influence of the average aspect ratio on the local magnetic flux density distribution, it is as follows. FIG. 5 schematically shows the flow of magnetic flux of a steel sheet composed of two crystal grains. FIG. 5 (A) is a model of a crystal grain having a large average aspect ratio, and FIG. This is a model of a small crystal grain. Since the magnetic flux tends to pass through a grain boundary or an edge of a steel sheet having a difference in α angle (rotation angle in the plane of the crystal orientation [001]) at which a magnetic pole can be generated, the magnetic flux has an α angle for each grain. If there is a difference between
A portion where the magnetic flux hardly flows as shown by hatching occurs. Simply, it can be said that the greater the proportion of such a portion in the steel sheet, the more unevenly the local magnetic flux density is distributed in the steel sheet.

Here, comparing FIGS. 5A and 5B, FIG. 5B having a smaller average aspect ratio has a smaller portion of the magnetic flux than FIG. 5A having a larger average aspect ratio. The area is smaller. Moreover, such an effect becomes more remarkable when the number of grain boundaries extending in a direction perpendicular to the rolling direction as shown in FIG. Therefore, if the average value of the crystal orientations is the same, it can be said that the smaller the average aspect ratio is, the more uniformly the magnetic flux density in the steel sheet under excitation is improved, and the more the iron loss characteristics are improved.

When the local magnetic flux density distribution is non-uniform, the iron loss characteristic deteriorates because, when the magnetic flux density is non-uniformly distributed inside the steel sheet, the local distortion of the magnetic flux waveform increases and the eddy current loss increases. It is considered that the increase in iron loss deteriorates the total iron loss.

From the above, according to the present invention, since the uniformity of the magnetic flux density in the steel sheet is sufficiently maintained by setting the average aspect ratio to 0.95 or less, a grain-oriented electrical steel sheet having low iron loss can be obtained. I can say.

In the above experiment, the above equation (1) was used.
For the lengths of RD (rolling direction) and TD (direction perpendicular to the rolling direction) of each grain, a method using an average length was adopted. However, in equation (1), not only the average length of each grain but also the maximum length. A method using a length may be used. Also, not only equation (1),
The average aspect ratio can be similarly obtained by calculating the average aspect ratio from the average particle lengths in the RD and TD directions as in the above equation (2). In this case, the average aspect ratio can be obtained in a range where the average aspect ratio is smaller than 0.95. Thus, a steel sheet having good iron loss characteristics can be obtained.

FIGS. 6 and 7 show the relationship between the average aspect ratio defined by the equation (2) and the average aspect ratio a ₁ calculated by using the average length of each grain in the RD and TD directions in the equation (1). Is shown. Note that a ₃ and a ₄ shown in FIGS. 6 and 7 are derived from the following equations (4) and (5) according to the equation (2).

(Equation 3)

In FIGS. 6 and 7, the range of a ₁ from 0.1 to 0.95 also corresponds to a ₃ and a _{4 from} 0.1 to 0.95.
It can be seen that similar results can be obtained by defining the aspect ratio as in (5). Here, as a method of calculating the average length of the crystal grain length in the RD and TD directions of the equation (2), R
Draw a straight line in a mesh shape in the D and TD directions, count the number of grain boundaries that intersect with this, count the number of grain boundaries, calculate the average aspect ratio, and measure the maximum value of the length of each grain in the RD and TD directions,
There is a method of obtaining <L> and <C> from these simple averages.

From the above description, in the grain-oriented electrical steel sheet of the present invention, the aspect ratio a is limited to the range of 0.1 to 0.95. When the aspect ratio is less than 0.1 (for example, when there is no grain boundary in the direction perpendicular to the rolling direction), the effect of correcting the direction of the domain wall in the rolling direction is lost due to the magnetic pole generated at the grain boundary. It is considered that the iron loss deteriorated as shown in FIG. In this sense, it is preferable that some crystal grain boundaries exist in the direction perpendicular to the rolling direction, and the lower limit of the aspect ratio needs to be 0.1. Conversely, 0.
If it is larger than 95, the magnetic flux density becomes non-uniform and iron loss deteriorates. A more preferred range is from 0.15 to 0.80.

In addition to this average aspect ratio,
It is necessary to regulate the content of Al and Ti.
When the content is less than 0.1 g / m ² , a sufficient magnetic domain refining effect cannot be obtained, and when it exceeds 0.7 g / m ² , the formation of a base coat is inhibited. Therefore, the Al content is in the range of 0.1 to 0.7 g / m ² . Similarly, if the Ti content is less than 0.1 g / m ^2,
If a sufficient magnetic domain refining effect cannot be obtained, and if it exceeds 0.8 g / m ² , Ti penetrates into the steel to deteriorate iron loss. Therefore, the Ti content is in the range of 0.1 to 0.8 g / m ² . More preferred range is Al, Ti each 0.30~0.7 g / m ^2, 0.4~0.
8 g / m ² .

Further, in the steel sheet as B ₈ is smaller than 1.89 T, an aspect ratio such as the rate is large the present invention occupied by the hysteresis loss, since the iron loss reducing effect is buried wins by optimizing the magnetic domain width, B ₈ is limited to more than 1.89 T.

Next, a method for manufacturing a grain-oriented electrical steel sheet according to the present invention will be described. First, regarding the component composition range of the magnetic steel sheet, any of the conventionally known component-based magnetic steel sheets can be used as the grain-oriented magnetic steel sheet of the present invention without any particular limitation. The typical components and their contents are as follows. C is 0.02-0.10wt%, Si
Is preferably about 2.0 to 4.5 wt%. Further, there are MnS, MnSe-based and AlN-based inviters, and any one of them can be used or used in combination. For MnS and MnSe systems, Mn:
0.02 to 0.20 wt% and at least one of S and Se are used alone or in a total amount of about 0.010 to 0.040 wt%. In the case of AlN system, Al: 0.010 to 0.065 wt%, N:
It is contained in the range of 0.001 to 0.0150 wt%. Further, if necessary, Sb: 0.01 to 0.20 wt%, Cu: 0.02 to 0.20 wt%,
Mo: 0.01 to 0.05 wt%, Sn: 0.01 to 0.30 wt%, Ge: 0.005
To 0.30 wt%, Ni: 0.01 to 0.20 wt%.

If the content of C is less than 0.02 wt%, a good primary recrystallized structure cannot be obtained. If the content exceeds 0.10 wt%, decarburization becomes poor and the magnetic properties deteriorate, so that about 0.02 to 0.10 wt% is preferable. . Si is a component necessary to increase the electrical resistance of the product and reduce eddy current loss. If the content is less than 2.0 wt%, the crystal orientation is impaired by α-γ transformation during final finish annealing,
If the content exceeds 4.5 wt%, a problem occurs in cold rolling.
About 4.5 wt% is preferable.

One or two of Mn and S and Se function as an inhibitor. When the amount of Mn is less than 0.02 wt% or when S and Se are used alone or less than 0.010 wt% in total, the inhibitor function is not obtained. Insufficient and Mn content is 0.20
If the content of Sn and S exceeds 0.1% by weight or the total amount of S and Se exceeds 0.040% by weight, the temperature required for slab heating becomes too high to be practical, so that Mn is 0.02 to 0.20% by weight, S and Se. One or two of the above may be used alone or as a total of 0.010 to 0.04
About 0 wt%.

In the case of an AlN-based inviter, in order to obtain a good iron loss, Al is 0.010 to 0.065 wt% and N is 0.010 to 0.010 wt%.
It is desirable to be in the range of 0.150 wt%. If the content exceeds the upper limit of each of Al and N, AlN becomes coarse and the inhibitory power is lost, and if the content is lower than the lower limit, the amount of AlN as an inviter becomes insufficient.

In order to further improve the magnetic flux density, it is possible to add Sb and / or Cu. Sb is 0.20wt
%, The decarburization property deteriorates, and if it is less than 0.01 wt%, there is no effect, so 0.01 to 0.20 wt% is preferable. Cu is 0.20wt%
If the content exceeds 0.01%, the acid washability deteriorates, and if the content is less than 0.01% by weight, there is no effect. Mo may be added to improve the surface properties. If the amount of Mo exceeds 0.05 wt%, the decarburization property deteriorates, and if it is less than 0.01 wt%, there is no effect, so the range of 0.01 to 0.05 wt% is preferable.

In addition, Sn, Ge, and Ni can be added alone or in combination to improve iron loss. Sn is 0.
If the content exceeds 30% by weight, embrittlement occurs, and if the content is less than 0.01% by weight, there is no effect, so 0.01 to 0.30% by weight is preferable. Ge
If the content exceeds 0.30 wt%, a good primary recrystallization structure cannot be obtained, and if the content is less than 0.005 wt%, there is no effect.
005 to 0.30 wt% is preferred. If the content of Ni exceeds 0.20 wt%, the hot strength decreases, and if the content is less than 0.01 wt%, there is no effect, so 0.01 to 0.20 wt% is preferable.

After preparing a molten steel containing the above-described components, the molten steel is cast by a continuous casting method or an ingot casting method according to a conventional method, and if necessary, a slab is obtained through a slab rolling process. After hot-rolling after heating to about 1500 ° C, hot-rolled sheet annealing as necessary, cold-rolled sheet of final thickness by cold rolling one or more times with intermediate annealing And

After the final cold rolling, in a wet hydrogen atmosphere,
Perform decarburizing annealing at 1000 ° C for about 1 to 10 minutes, apply an annealing separator (for example, one containing MgO as a main component) to the steel sheet surface, and then perform secondary recrystallization and purification at 1200 ° C for 5 hours or more. Perform annealing. Thereafter, if necessary, a tension coating such as colloidal silica is applied on the undercoating to obtain a product.

In order to satisfy the average aspect ratio of the present invention, the grain-oriented electrical steel sheet as a product should be made of Sn as a secondary recrystallized grain growth inhibiting material immediately before decarburization annealing during such a manufacturing process.
SO ₄ or the like may be applied linearly in a direction perpendicular to the rolling direction (line spacing of about 5 to 50 mm), or SnO ₂ or the like may be added to the annealing separator as a secondary recrystallization grain growth inhibitor (addition amount). 3 to 15%
It is preferable to provide a temperature gradient in the sheet width direction during the secondary recrystallization annealing (about 0 to 50 ° C./cm). Also, in order to satisfy the Al and Ti contents in the steel sheet base coat, Al ₂ O ₃ or TiO ₂ is added to the annealing separator (the addition amount is Al ₂ O
₃ is about 5% or less, and TiO2 is about ₂ to 10%). It should be noted that Al is already contained as a component in the steel without being added to the annealing separator, and is sufficient because it becomes Al ₂ O ₃ in the coating in the purification annealing.

The grain-oriented electrical steel sheet of the present invention is not limited to one obtained by using such a manufacturing method, and the manufacturing method is not limited as long as the present invention is satisfied.

[0043]

【Example】

Example 1 C: 0.07 wt%, Si: 3.25 wt%, Mn: 0.07 wt%, S: 0.02
5 wt%, Al: 0.025 wt%, N: 0.007 wt%, Cu: 0.13 wt
%, Sb: 0.023 wt% silicon steel slab at 1430 ℃
And then hot-rolled to form a hot-rolled sheet with a thickness of 2.2 mm, annealed at 1000 ° C for 1 minute, and then cold-rolled to a thickness of 1.5 mm, and heated at 1100 ° C for 2 minutes. Intermediate annealing was performed, and a final thickness of 0.23 mm was obtained by cold rolling. Then 840 ° C., after decarburization annealing for 2 minutes, were introduced 5% uniform strain by pulling, the TiO ₂ 5%, wound up MgO addition of SnO ₂ 6% in the coating after the coil, plate 0 ° C / cm, 10 ° C / cm, 20 in width direction
The temperature was raised while giving a temperature gradient of 30 ° C./cm 2 to 30 ° C./cm 2 to complete the secondary recrystallization, followed by a purification annealing at 1200 ° C. for 10 hours. After this, unreacted MgO is removed and a tension coating is applied.
Baking was performed at 800 ° C. for 90 seconds in N ₂ .

[0044] In this way long the product obtained in the rolling direction of 280 mm, cut out as a test piece width 100mm in a direction perpendicular thereto, W _17/50 and B ₈ by veneer magnetic tester
Was measured. Further, the contents of Al and Ti in the undercoat film were analyzed. Thereafter, the tension coating and the forsterite film were removed with an acid, and the macrostructure was observed.
The average aspect ratio was calculated according to equation (1).

Table 1 shows the magnetic characteristics (W _17/50 , W _17/50 ) of the center ( _{medium winding} ) of each coil measured in the Epstein measurement frame.
B ₈ ) and average aspect ratio a ₁ , temperature gradient in the width direction at the time of secondary recrystallization annealing temperature rise 0 ° C./cm, 10 ° C./cm, 20 ° C.
/ cm, 30 ℃ / cm
The results for the highest and lowest a ₁ are shown.

[0046]

[Table 1]

In Table 1, the iron loss tends to be improved as the temperature gradient in the sheet width direction increases at the time of raising the temperature of the secondary recrystallization annealing. This is because the shape of the secondary recrystallization changes and the average aspect ratio is reduced. It can be seen that the effect is due to the reduction.

Example 2 C: 0.069 wt%, Si: 3.31 wt%, Mn: 0.069 wt%, S:
0.023 wt%, Al: 0.021 wt%, N: 0.0083 wt%, Cu: 0.
A silicon steel slab containing 13 wt% and Sb: 0.023 wt% was subjected to cold rolling twice with intermediate annealing as in Example 1 to obtain 0.2%.
After rolling to 23 mm to obtain the final sheet thickness, SnSO ₄ powder is applied linearly with a width of 50 μm in a direction perpendicular to the rolling direction, followed by decarburization annealing, and MgO with 10% TiO ₂ added is applied. , Followed by final finish annealing. Thereafter, unreacted MgO was removed, and the tension coating was baked.

In the above steps, the intervals of the linear application of the SnSO ₄ powder were changed to 10 cm, 20 cm, 30 cm and 40 mm.
A seed product was obtained. In addition, using the same material, a product that was subjected to decarburizing annealing and final finishing annealing without applying SnSO ₄ powder was produced.

The magnetic properties of the steel sheet obtained as described above were measured using an Epstein measurement frame. After this, magnetizing force 10
After magnetizing to 000 A / m and degaussing at 50 Hz, magnetic domain observation using a magnetic colloid was performed to determine the average magnetic domain width of the steel sheet. Further, Al and Ti in the undercoating film were analyzed. Also, by macro etching, the secondary recrystallized grain structure is exposed,
To obtain an average aspect ratio of a _1. As a result, fine secondary recrystallized grains appear in the portion where the SnSO ₄ powder is applied,
Alternatively, in this portion, the grains that have undergone secondary recrystallized grain growth stop from the surroundings, forming crystal grain boundaries. W _17/50 ,
B ₈ average aspect ratio, the measurement results of the average magnetic domain width shown in Table 2.

[0051]

[Table 2]

Table 2 shows the results of the samples obtained by changing the application interval of the SnSO ₄ powder and having the same average magnetic domain width. When SnSO ₄ is applied in a linear form, fine grain groups and crystal grain boundaries extending in a direction perpendicular to the rolling direction are generated, and the magnetic domains generated in these are subdivided into magnetic domains, and as a result, iron loss is improved. Conceivable. However, since the samples described in Table 2 are samples having the same magnetic domain width, the influence of such magnetic domain segmentation has been eliminated. Accordingly, the results in Table 2 can be attributed to the fact that the average aspect ratio of the secondary recrystallized grains was reduced by the linear application of the SnSO ₄ powder, and the distribution of the magnetic flux was made uniform.

[0053]

According to the present invention, there is provided a grain-oriented electrical steel sheet having a low iron loss in which the contents of Al and Ti in a base coat and the shape of secondary recrystallized grains are optimized. A great deal of electric energy can be saved by using the iron core.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a temperature gradient in a sheet width direction during secondary recrystallization and an average aspect ratio of secondary recrystallized grains.

FIG. 2 is a graph showing a relationship between an average aspect ratio a ₁ and iron loss W _17/50 .

FIG. 3 _shows the relationship between the Al and Ti contents in the undercoat and the iron loss W _17/50 .
(0.1 ≦ a ₁ ≦ 0.95)

FIG. 4 is a graph showing a relationship between an average aspect ratio a ₁ and a magnetic flux density distribution nonuniformity r.

FIG. 5 is a diagram illustrating the relationship between the magnitude of the average aspect ratio and the uniformity of the magnetic flux density distribution.

FIG. 6 is a graph showing the relationship between the average aspect ratio a ₃ according to equation (1) and the average aspect ratio a ₁ according to equation (4).

FIG. 7 is a graph showing the relationship between the average aspect ratio a ₄ according to equation (1) and the average aspect ratio a ₂ according to equation (5).

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-17261 (JP, A) JP-A-6-73511 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 1/12-1/375

Claims (1)

(57) [Claims] 1. A silicon-containing steel sheet which has been subjected to final finish annealing, wherein an Al component is contained in a base coat on the steel sheet surface in an amount of 0.1 to 0.7 g / m ² ,
Containing 0.1 to 0.8 g / m ^{2 of} Ti component, and having an average aspect ratio of 0.10 between the length of the secondary recrystallized grains in the rolling direction and the length in the sheet width direction.
磁 束 0.95 and the magnetic flux density B at a magnetizing force of 800 A / m
_A grain-oriented electrical steel sheet having a low iron loss, wherein ₈ is 1.89T or more.