JPH07258739A - Production of grain oriented magnetic steel sheet having low iron loss - Google Patents

Abstract

PURPOSE:To produce the grain oriented magnetic steel sheet having low iron loss by forming linear groove in the direction intersecting to rolling direction on the surface of grain oriented magnetic steel sheet of finish annealed and introducing the prescribed linear infinitesimal rolling strain. CONSTITUTION:On the surface of cold rolled sheet of the grain oriented magnetic steel containing about 3.2% Si, a linear groove extending in the direction intersecting to rolling direction is formed, subjecting to decarburization annealing and finish annealing. In the steel sheet, an infinitesimal rolling strain of interval (11)mm is introduced as satisfying 5<=12.(11)<1/2=100. At this time, the linear groove is preferably of 30-300mum width, 10-70mum depth, 1-30mum interval, having the intersecting angle to the rolling direction of <=30 deg. to right angle direction. Also, the infinitesimal rolling strain is preferably imparted by pressing at a bearing of 10-70kg/mm<2> with the roll which has a linear protrusion of 50-500mum width, 10-70mum depth, 1-30mum interval, 30 deg. angle to the rolling direction.

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 grain-oriented electrical steel sheet having a low iron loss, which is suitable for use in an iron core of a transformer or other electrical equipment.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used as iron core materials for transformers and other electrical equipment and are required to have low energy loss, that is, iron loss. Therefore, conventionally, in order to reduce iron loss, the crystal orientation was set to (110)
Various measures have been taken, such as highly aligning with the (001) orientation, increasing the Si content to increase the electrical resistance of the steel sheet, reducing impurities, and further reducing the sheet thickness. As a result, for steel sheets with a thickness of _{0.23 mm} or less, iron loss W _17/50 (magnetic flux density: 1.7 T, 50 Hz) of 0.9 W / kg or less can be obtained. However, with such a metallurgical method, it has been impossible to expect further significant improvement in iron loss.

In recent years, various methods for artificially subdividing magnetic domains have been tried as means for overcoming the above problems and achieving a low iron loss. Among them, as a method which is currently industrialized, a method of irradiating a laser on the steel sheet surface after finish annealing as disclosed in JP-B-57-2252, and JP-A-62-96617. There is a method of radiating a plasma flame as disclosed. All of these methods attempt to subdivide a 180 ° magnetic domain by a locally high dislocation density region introduced by a laser or a plasma flame, and thereby reduce iron loss. However, in the steel sheet thus obtained, the high dislocation density region disappears by heat treatment at a high temperature such as strain relief annealing, leading to deterioration of iron loss. It had the drawback that it could not be used for.

On the other hand, as a technique capable of strain relief annealing, for example, Japanese Patent Publication No. Sho 62-54873 discloses a steel sheet that has been subjected to finish annealing after the insulating coating is locally removed by a laser or mechanical means, and then pickling or A method of forming a linear groove in the coating removal portion by a mechanical means such as a knife, and then forming a phosphoric acid-based tension-applying coating so as to fill the groove is also disclosed in JP-B-62-53579. , 90 to 22 on finish annealed steel plate
A method has been proposed in which a groove having a depth of more than 5 μm is formed in a base metal portion with a load of about 0 kg / mm ² and then heat treatment is performed at a temperature of 750 ° C. or higher. Further, Japanese Patent Publication No. 3-69968 proposes a method of introducing linear notches after the final cold rolling in a direction substantially perpendicular to the rolling direction of the steel sheet. In each of the steel sheets obtained as described above, one of the factors is that the magnetic domain is subdivided by the magnetic poles generated in the vicinity of the linear groove formed on the surface, and the low iron loss is achieved. It is believed that.

[0005]

According to the above method,
A low iron loss material capable of strain relief annealing has come to be obtained, but according to a close examination thereafter, the iron loss of such a steel sheet is found to be the wire disclosed in Japanese Examined Patent Publication No. 57-2252. It was found that it may be slightly inferior to a steel sheet having a high dislocation density region like a shape. Therefore, when the inventors investigated this point, they presumed that the cause of the iron loss deterioration was due to the difference in the amount of magnetic poles introduced. Therefore, based on this assumption, as a result of repeated experiments and studies on further improvement of the iron loss characteristics, it is possible to introduce a linear microrolling strain under a certain condition into the steel sheet with linear grooves. , We have found that it is extremely effective in achieving the intended purpose.
The present invention is based on the above findings.

[0006]

That is, the present invention provides a finish-annealed unidirectional electrical steel sheet having a linear groove extending in a direction intersecting the rolling direction on the surface thereof, in the rolling direction of the linear groove. Is defined as l ₁ (mm), a linear micro-rolling strain is introduced below the interval satisfying the following formula: l ₂ (mm), also in a direction intersecting the rolling direction. This is a method for producing a grain-oriented electrical steel sheet with low iron loss. Note 5 ≦ l ₂ · (l ₁ ) ^1/2 ≦ 100

In the present invention, the shape of the linear groove formed in the finish-annealed grain-oriented electrical steel sheet has a width of 30 to 300 μm.
m 2, depth: 10 to 70 μm, interval: 1 to 30 mm, crossing angle with rolling direction: it is preferable to be within 30 ° with respect to the direction perpendicular to the rolling direction.

In the present invention, when the micro rolling strain is introduced, the linear projection width: 50 to 500 μm, the projection height: 10
It is desirable to use a roll having linear projections of up to 100 μm and an angle of 30 ° with the roll axis, and press the roll with linear projections against a steel plate at a surface pressure of 10 to 70 kg / mm ² .

The present invention will be specifically described below. First, the experimental results that are the basis of the present invention will be described. Hot-rolled 3.2% silicon steel sheet containing MnSe and AlN as inhibitors was cold rolled twice with intermediate annealing.
After rolling to a thickness of 23 mm, after applying an etching resist by gravure offset printing, electrolytic etching was performed to form linear grooves having a width of 180 μm and a depth of 18 μm in a direction perpendicular to the rolling direction. At this time, by changing the pattern of the gravure roll, the spacing between the linear grooves can be reduced.
Variously changed from 0.7 mm to 100 mm. The electrolytic etching was carried out in a 20% NaCl electrolytic bath at a current density of 20 A / dm ² , and the etching time was controlled so that the groove depth was kept constant at 18 μm even if the groove width was slightly changed. . After the groove forming treatment as described above, decarburization annealing and then final finishing annealing were performed, and further topcoat coating treatment was performed to obtain a product.

Epstein test pieces were cut out from the product plate thus obtained, and the magnetic properties after stress relief annealing were investigated. The obtained results are shown in FIG. 1 in relation to the interval between the linear grooves and the iron loss W _17/50 . As is clear from the figure, the iron loss of the steel sheet which has been subjected to the groove forming treatment is smaller than that of the untreated steel sheet.

The result shown in FIG. 1 is almost the same as the conventional result disclosed in Japanese Patent Publication No. 3-69968. Next, the inventors of the present invention changed the magnetic properties when a minute rolling strain was introduced into a steel sheet by a roll with protrusions for a product in which linear grooves were formed at an interval: 1 to 30 mm in which a particularly low iron loss was obtained. Was investigated. A roll having linear projections parallel to the roll axis direction as shown in FIG. 2 was used to introduce the micro rolling strain. Protrusion height is 50 μm, protrusion width is 200 μm
And a load of 20 kg / mm ² was applied. At this time, the distance between the linear protrusions was changed from 1 mm to 100 mm. A linear high dislocation density part was observed over the width of 300 μm in the pressed part of the linear projection of the steel sheet. Width from product thus obtained: 150 m
m, length: 280 mm sample is taken, single plate magnetic tester (S
When the magnetic properties were measured by (ST), a product having a lower iron loss and a product having a lower iron loss were obtained by roll rolling with protrusions as compared with the case of only grooves.

Therefore, as a result of careful analysis of the obtained measurement results, the inventors have determined that the spacing between the linear grooves in the rolling direction is l ₁
(mm), and the linear projection interval of the roll with protrusions (interval of minute rolling strain) is l ₂ (mm), as shown in FIG. 3, l ₂ · (l ₁ )
It was newly found that when ^1/2 is 5 or more and 100 or less, the iron loss is remarkably reduced as compared with the conventional one. Where l ₂
When (l ₁ ) ^1/2 is smaller than 5, the iron loss is rather deteriorated as compared with the case where only the groove is formed. The reason is that the amount of magnetic poles introduced by the formation of the high dislocation density portion is too large, On the contrary, it is considered that the history loss is increased. Also, l ₂ · (l ₁ )
^{When 1/2} is larger than 100, the amount of magnetic poles generated is small, so that the effect of conspicuously improving iron loss cannot be obtained. that's all,
As mentioned above, the spacing between the linear grooves in the rolling direction is l ₁ (mm)
And an interval satisfying 5 ≦ l ₂ · (l ₁ ) ^1/2 ≦ 100:
It was clarified that by introducing a linear microrolling strain of l ₂ (mm) into the steel sheet, the iron loss can be further reduced as compared with the conventional case.

[0013]

The function of linear grooves and micro rolling strain introduced in the present invention will be described. First, the width of the linear groove is 30-30
It is desirable that the depth is 0 μm and the depth is 10 to 70 μm in order to reduce iron loss. This is because if the groove width and depth are too small, the amount of magnetic poles generated is small and a sufficient domain refinement effect cannot be obtained, while if too large, the magnetic flux density is significantly reduced. Further, it is preferable that the introduction angle of the groove is within 30 ° with respect to the direction perpendicular to the rolling direction. This is because the magnetic domain refining effect sharply diminishes above 30 °.
Further, particularly good results are obtained when the groove introduction interval is 30 mm or less. However, if the introduction interval is smaller than 1 mm, the magnetic pole generation amount becomes too large and the hysteresis loss increases. Therefore, it is preferable that the introduction interval of the groove be in the range of 1 to 30 mm. .

Next, the microrolling strain will be described. A roll with linear projections is particularly advantageously suited as a strain imparting means. Regarding the shape of the protrusion, the tip may be sharp, rounded, or flat, but the tip is preferably round from the viewpoint of durability and effect. The width of the linear protrusions is preferably about 50 to 500 μm. The reason for this is that if the thickness is 50 μm or less, the effect is small because the microstrain region is narrow, while if it is 500 μm or more, the strain amount is too large and the hysteresis loss is deteriorated. Further, the height of the protrusion is not particularly limited, but about 10 to 100 μm is practically suitable. Furthermore, as described above, the spacing between the protrusions is 5 ≦ l ₂ · (l
₁ ) It is an essential condition that the interval satisfying ^1/2 ≦ 100: l ₂ (mm). Further, the angle of the linear protrusions is most preferably parallel to the roll axial direction, but may intersect with each other as long as the angle is within 30 ° from the axial direction. The surface pressure applied during rolling is preferably about 10 to 70 kg / mm ² . This is because when the surface pressure is less than 10 kg / mm ^{2, the} effect of introducing micro strain is poor, while when it exceeds 70 kg / mm ² , the amount of strain is too large and the hysteresis loss is deteriorated. In addition,
The positional relationship between the linear groove and the micro rolling strain introduction portion is not particularly limited. That is, the groove and the strain introducing portion may be at the same position, there may be a strain introducing portion between the grooves, or both may intersect, and both are formed on the same surface or both surfaces. It has been confirmed that it does not matter. Further, as the micro-rolling strain introduction means, the above-mentioned roll with protrusions is particularly advantageous, but in addition, a method of applying a reduction from the steel wire arranged at intervals on the steel plate can also be used. .

Next, the manufacturing process of the grain-oriented electrical steel sheet according to the present invention will be described. First, a slab for grain-oriented electrical steel sheets is hot-rolled, then hot-rolled sheet is annealed as necessary, and then cold rolled one or more times with intermediate annealing to obtain a final product sheet thickness, and then After decarburization annealing and then final finishing annealing, a topcoat is usually applied to obtain a product. The introduction time of the linear groove may be before or after the final finish annealing. Examples of the method of forming the groove include a method of locally etching, a method of scribing with a blade or the like, a method of rolling with a roll having protrusions, and the like. The most desirable method is a method in which after the final cold rolling, an etching resist is attached to the steel sheet by printing or the like, and then a groove is formed by a treatment such as electrolytic etching. After that, a micro rolling strain is introduced into the steel sheet according to the above-mentioned point. The steel sheet obtained in this manner exhibits excellent performance as a material for a laminated core that does not particularly require strain relief annealing, but even when used as a material for a wound core that requires strain relief annealing, it is a conventional material. Demonstrate performance equivalent to.

[0016]

【Example】

Example 1 A hot-rolled sheet of 3.3% silicon steel containing MnSe, Sb, and AlN as an inhibitor was cold-rolled twice with intermediate annealing to a thickness of 0.23 mm, and then an etching resist was applied by gravure offset printing. After that, by performing electrolytic etching and resist stripping in alkaline solution, a linear groove with a width of 160 μm and a depth of 18 μm is 3 mm so that it forms an angle of 10 ° from the direction perpendicular to the rolling direction. Pitch (l ₁
= 3). Then, decarburization annealing and final finishing annealing were performed, and then a top coat was applied. After that, high dislocation density portions were locally formed on the obtained steel sheet by rolling with protrusions. As a roll with protrusions,
Projection height: A roll having a linear projection of 20 μm parallel to the roll axis direction was used, and a load of 30 kg / mm ² was applied. At this time, the distance between the linear protrusions was changed from 1 mm to 100 mm.
From the product plate thus obtained, width: 150 mm, length: 280
Table 1 shows the results of magnetic properties measured by a single-plate magnetic tester (SST) by taking a specimen of mm. In addition, Table 1 also shows, as a comparison, the results of investigations on a steel sheet having only grooves not subjected to the projection roll rolling treatment and a steel sheet only subjected to the projection roll rolling.

[0017]

[Table 1]

As shown in Table 1, when the groove spacing is l ₁ (mm), the spacing l ₂ (mm) which satisfies 5 ≦ l ₂ · (l ₁ ) ^1/2 ≦ 100
The steel sheet to which a linear micro-rolling strain was introduced by using a roll with protrusions under the condition showed an excellent iron loss value not only in the case of only the groove but also in the case of performing only rolling with the protrusion. In addition, when these steel sheets were subjected to stress relief annealing in N _{2 for} 3 hours at 800 ° C, the steel sheet was only rolled with protrusions (No. 8).
Has deteriorated iron loss up to 0.87 W / kg, but grooved steel plate (N
o.2-5) was 0.72W / kg at most.

Example 2 A hot-rolled sheet of 3.2% silicon steel containing MnSe, Sb, and AlN as an inhibitor was processed according to a conventional method to give a steel sheet having a thickness of 0.18 mm. A groove with a width of 180 μm and a depth of 15 μm was obtained by linearly removing the insulating coating from the finished annealed steel plate using an ultrasonic vibrator and then pickling it in 30% HNO ₃ solution. Are formed at 4 mm intervals (l ₁ = 4) in the direction perpendicular to the rolling direction, and then the top coat is applied again.
Baking for 3 min at ℃ After that, a high dislocation density portion was locally formed by roll rolling with protrusions. As the roll with protrusions, a roll having linear protrusions having a protrusion height of 30 μm and parallel to the roll axis direction was used, and a load of 25 kg / mm ² was applied. At this time, the distance between the linear protrusions was changed from 1 mm to 80 mm. Table 2 shows the results of magnetic properties measured by SST, in which sample pieces having a width of 150 mm and a length of 280 mm were sampled from the product plate thus obtained. In addition, Table 2 also shows, as a comparison, the results of investigations on a steel sheet having only grooves not subjected to the projection roll rolling treatment and a steel sheet only subjected to the projection roll rolling.

[0020]

[Table 2]

As shown in Table 2, when the groove spacing is l ₁ (mm), the spacing l ₂ (mm) which satisfies 5 ≦ l ₂ · (l ₁ ) ^1/2 ≦ 100
The steel sheet introduced with a linear micro-rolling strain using a roll with protrusions underneath shows a superior iron loss value not only to a steel plate with only grooves but also to a steel plate only subjected to roll rolling with protrusions. It was When these steel sheets were subjected to stress relief annealing in N _{2 for} 3 hours at 800 ° C, the steel sheets were only rolled with protrusions (N
The iron loss deteriorated to 0.82 W / kg in o.16), but was 0.71 W / kg at most in the grooved steel sheets (No. 10 to 13).

[0022]

As described above, according to the present invention, a finish-annealed unidirectional electrical steel sheet having linear grooves extending on the surface in a direction substantially perpendicular to the rolling direction can be formed into a fine linear alloy under predetermined conditions. By introducing rolling strain, it is possible to significantly improve the iron loss characteristics as compared with the conventional one, which in turn greatly contributes to the efficiency improvement of the transformer.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the distance between linear grooves and iron loss W _17/50 .

FIG. 2 is a view showing the outer appearance of a roll with protrusions.

FIG. 3 is a graph showing the relationship between l ₂ · (l ₁ ) ^1/2 and iron loss W _17/50 .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kunihiro Senda, 1st Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture, Technical Research Division, Kawasaki Steel Co., Ltd. (72) Michio Komatsubara 1st Kawasaki-cho, Chuo-ku, Chiba (72) Inventor Kazuhiro Suzuki, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Iron & Steel Co., Ltd.

Claims (3)

[Claims] 1. A finish-annealed grain-oriented electrical steel sheet having linear grooves extending in a direction intersecting with the rolling direction on the surface thereof, and the spacing between the linear grooves in the rolling direction is l ₁ (mm). In this case, a unidirectional electrical steel sheet with low iron loss, characterized in that a linear microrolling strain is introduced under an interval satisfying the following formula: l ₂ (mm) in a direction that also intersects the rolling direction. Manufacturing method. Note 5 ≦ l ₂ · (l ₁ ) ^1/2 ≦ 100 2. The linear groove according to claim 1, wherein the width is 30 to
300 μm, depth: 10 to 70 μm, interval: 1 to 30 mm, angle of intersection with rolling direction: a method for producing a unidirectional electrical steel sheet with low iron loss, which is within 30 ° with respect to the direction perpendicular to the rolling direction. 3. The microrolling strain applying means according to claim 1 or 2, wherein the linear projection width is 50 to 500 μm, and the projection height is:
It is a roll that has linear protrusions with an angle of 10 to 100 μm and the axis of the roll: within 30 ° .The roll with linear protrusions should be pressed against a steel plate at a surface pressure of 10 to 70 kg / mm ^2. A method for producing a grain-oriented electrical steel sheet having low iron loss.