JPH08269562A - Grain-oriented silicon steel sheet reduced in magnetostriction and its production - Google Patents

Abstract

PURPOSE: To provide a product prepared by reducing magnetostriction in a grain-oriented silicon steel sheet after finish annealing and its production. CONSTITUTION: A magnetostriction value (peak-peak) is reduced at <=1.8T magnetic flux density by allowing internal microstrain to remain in a grain- oriented silicon steel sheet. The volume of 90deg magnetic domain at a magnetic flux density of 0T is increased by applying internal microstrain, and further, by decreasing the change in volume of 90deg magnetic domain at <=1.8T magnetic flux density in an alternating magnetic field, a magnetostriction value lower by >=5% as compared with the case after stress relief annealing can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented silicon steel sheet used for an iron core or a magnetic shield of an electromagnetic application device such as a transformer and a method for producing the same, and more particularly to a grain-oriented silicon steel sheet. By reducing the magnetostriction, it is intended to reduce the noise and vibration of the device due to the magnetostriction.

[0002]

2. Description of the Related Art Grain-oriented silicon steel sheets are used for iron cores or magnetic shields of electromagnetically applied equipment such as transformers, and it has been demanded that they have excellent magnetic properties, and especially low iron loss. By the way, as for the grain-oriented silicon steel sheet, a slab containing 2 to 4% of Si is hot-rolled, cold-rolled, intermediate-annealed, decarburized-annealed,
It is manufactured by processing by a process such as finish annealing. Since the finish annealing is performed in a coil shape, the steel sheet after the finish annealing has a coil set. Since the grain-oriented silicon steel sheet is used by being laminated as an iron core of electromagnetic application equipment such as a transformer, it is important that its shape property is good, and correction and lateral strain of the coil set during the finish annealing, It is necessary to carry out straightening of the shape, such as so-called flattening. If the cooling strain during finish annealing and large internal strain such as during coil set straightening remain in the grain-oriented silicon steel product, iron loss deteriorates, so it is necessary to reduce the internal strain during continuous annealing after the finish annealing. . From this point of view, as disclosed in JP-A-61-159529 and JP-A-61-174329, it has been an important item in manufacturing to completely release internal strain from the standpoint of reducing iron loss. It has been.

On the other hand, along with the heightening of environmental problems, there has been a demand for reducing noise and vibration of electromagnetically applied equipment such as transformers, and a grain-oriented silicon steel sheet used for the iron core and magnetic shield of these equipment. Low noise and low iron loss
Materials suitable for vibration have come to be demanded.

The magnitude of magnetostriction of the grain-oriented silicon steel sheet is very small, on the order of 10 ^-6 , but the noise from the iron core etc.
Most noticed as a cause of vibration. As a method of reducing the magnetostriction, a metallurgical method such as increasing the Si content and highly aligning the secondary recrystallized grains in the (110) [001] orientation, and applying tension to the steel sheet by a tension coating are known. ing. In addition, it is considered that the magnetostriction of grain-oriented silicon steel sheet increases only if the internal strain remains, and it is an important item in manufacturing to thoroughly release the internal strain, as in the above-mentioned reduction of iron loss. Came.

The magnitude of magnetostriction is very small as described above, and it is difficult to measure the magnetostriction of grain-oriented silicon steel sheet products. For this reason, research on magnetostriction has not progressed as much as iron loss. The problem with this measurement is
The development of the high-precision magnetostriction measuring method disclosed in Japanese Patent No. 085849 facilitated the development and enabled detailed analysis of the magnetostriction phenomenon.

[0006]

It has been considered that the magnetostriction of grain oriented silicon steel products is most reduced by completely releasing the internal strain by annealing. However, the present inventors have found that As a result of detailed investigation of the relation between the internal strain and the internal strain, it was found that the magnetic strain becomes the smallest when a small internal strain is left under the excitation condition of medium to low magnetic flux density.

[0007]

The present invention has been made on the basis of this finding, and the gist thereof is to leave a small amount of internal strain in the grain-oriented silicon steel sheet after finish annealing and thereby obtain a medium to low level. It is a method of realizing a grain-oriented electrical steel sheet product having a low magnetostriction in the magnetic flux density and a method of leaving a small amount of internal strain.

The present invention will be described in detail below. First, the magnetostriction phenomenon will be described. The present inventor investigated the magnetostriction phenomenon in detail and studied a method of controlling the magnetostriction. The magnetostriction phenomenon of not only the grain-oriented silicon steel sheet but also the ferromagnetic substance largely depends on the change of the magnetic domain structure during the magnetization process. 3% as physical property value
Although the magnetostriction constant of silicon steel is about 3 × 10 ⁻⁵ , the magnetostriction value of a normal grain oriented silicon steel sheet product is often 1/10 or less. This is because the secondary recrystallized grains forming the grain-oriented silicon steel sheet are extremely highly aligned with the (110) [001] orientation, so that the 180 degree magnetic domain in which the spontaneous magnetization direction is substantially parallel to the rolling direction is the steel plate volume. This is because it occupies a major part. In this 180 degree domain, the direction of spontaneous magnetization is <00.
1) It is an aggregate structure of stripe-shaped magnetic domains facing the axis and alternately facing the opposite directions, but each magnetic domain extends in the spontaneous magnetization direction by a ratio of magnetostriction constant × 3/2. When it is excited and the magnetic flux passes, the adjacent 180
The boundaries between the degrees magnetic domains, that is, the 180 degree domain walls move,
If there is no change in the total volume of the 0 degree magnetic domain, the elongation of the steel sheet due to the excitation, that is, the magnetostriction becomes zero.

However, in an actual grain-oriented silicon steel sheet, a 90-degree magnetic domain structure is included in addition to the 180-degree magnetic domain in the portion where the crystal orientation is largely displaced from the (110) [001] orientation or the portion where the internal strain is large. . Since there is no elongation in the rolling direction in the 90 degree domain, 90
When the volume of the magnetic domain increases or decreases, the elongation of the steel sheet in the rolling direction decreases or increases, and as a result, magnetostriction occurs.

<001> in the spontaneous magnetization direction of the 180 degree magnetic domain
When the crystal axis forms an angle β with the surface of the steel sheet, magnetic poles are generated on the front surface and the back surface of the steel sheet. A 90 degree magnetic domain in which spontaneous magnetization is oriented in the <100> crystal axis or the <010> crystal axis direction is generated in the steel sheet in a direction of canceling the magnetostatic energy created by the front and back magnetic poles, and a dagger called a lancet magnetic domain is formed on the steel sheet surface. Shaped 180 degree magnetic domains appear. When a large internal strain remains in the steel sheet, a large amount of 90-degree magnetic domains are generated in the steel sheet due to the work-induced magnetic anisotropy, and the surface of the steel sheet is so-called maize magnetic domain, or thin in the direction perpendicular to the rolling direction. A magnetic domain structure appears in which the extended 180 degree magnetic domains are arranged finely and densely in the rolling direction.

The reduction of magnetostriction of grain-oriented silicon steel sheet will be described with reference to FIG. FIG. 1 shows an example of a magnetostrictive loop in the case where a 0.23 m thick grain-oriented silicon steel sheet Hi-B which has been subjected to strain relief annealing to release internal strain is excited at a frequency of 50 Hz and a magnetic flux density of 1.7 T. Shows. The vertical axis of FIG. 1 represents the change in length of the steel sheet in the rolling direction, and the horizontal axis represents the magnetic flux density for excitation.
In FIG. 1, o-, which is used as an evaluation index of the magnetostrictive characteristic,
The definitions of the peak value and the peak-peak value are shown. Figure 2
In addition, o-peak in 0.35 mm grain-oriented silicon steel sheet
An example of the relationship between the magnetic flux density and the magnetic flux density of the peak-peak value is shown, but at low to medium magnetic flux densities of about 1.8 T or less, op
The absolute value of the eak value and the peak-peak value are close to each other, but at 1.9T, the peak-peak value is o-.
It becomes larger than the absolute value of the peak value. This is because at a magnetic flux density of approximately 1.8 T or higher, the shape of the magnetostrictive loop collapses due to a change in magnetic domain structure. In the present invention, the magnetostriction value is evaluated by the peak-peak value from the idea that it is the magnetostriction amplitude that leads to noise such as the iron core.

To consider a method for reducing magnetostriction, FIG.
We attempted to explain the magnetostrictive loop in Fig. 3 by the change of the magnetic domain structure during the magnetization process. In FIG. 1, when the magnetic flux density increases from zero to positive or negative, the o-peak value becomes a negative value and the length in the rolling direction of the steel sheet shrinks. This is due to the magnetostatic energy of the front and back of the steel sheet and the 90 degree magnetic domain. Can be explained in relation to. When the magnetic flux density in the steel sheet increases positively or negatively, the 180 degree magnetic domain width in the direction in which the magnetic flux passes becomes wider and the magnetic domain width in the opposite direction becomes narrower. Since the signs of the magnetic poles on the surface of the steel sheet are opposite to each other across the domain wall, the magnetostatic energy between the front and back surfaces is reduced near the domain wall. However, when the domain wall spacing increases and the surface area away from the domain walls increases, the magnetostatic energy between the front and back surfaces increases at this portion, and as described above, the 90 ° domain volume increases so as to cancel this magnetostatic energy. Will shrink in the rolling direction.

As shown in FIG. 1, a hysteresis phenomenon is generally observed in the magnetostrictive loop. This is because the 90-degree domain wall, which is the boundary between the 90-degree domain and the 180-degree domain, is interacted with the magnetic field. It can be explained by thinking.
In the domain wall, the spin of the iron atom rotates from the spin of one domain that sandwiches the domain wall to the spin of the other domain. Therefore, when a 180 ° domain wall receives a magnetic field in the rolling direction, a force acts to move the magnetostriction in the direction of increasing the domain width in the direction of the magnetic field.
In the 0 degree domain wall, a force to move the 90 degree domain wall acts in the direction of reducing the volume of the 90 degree domain. Furthermore, it is considered that the magnetostrictive loop exhibits hysteresis due to the hysteresis between the magnetic field and the magnetic flux density. Also, the magnetic flux density is about 1.8T.
Since the magnetic field strength increases remarkably when the above is reached, the 90 ° domain volume contracts rapidly and the steel sheet expands, resulting in magnetostrictive o-pe.
The ak value increases rapidly. When the o-peak value changes from a negative value to a positive value during one cycle of magnetic flux change (50 Hz in FIG. 1), the peak-peak value is the o-peak value.
The value will be larger than the absolute value.

Based on the above knowledge, the cause of magnetostriction at a magnetic flux density of approximately 1.8 T or higher, where the magnetic field strength is relatively weak, is as follows.
It can be said that there is an increase in the volume of the 90-degree magnetic domain in the period of the magnetic flux, that is, an increase from the 90-degree magnetic domain volume at the zero magnetic flux density to the 90-degree magnetic domain volume at the maximum magnetic flux density. The following two methods were considered as methods for reducing the volume increase of the 90-degree magnetic domain. One is a method of reducing the 90-degree magnetic domain volume at the maximum magnetic flux density, which is a metallurgical method of highly aligning the crystal orientation to (110) [001] and a surface tension on the steel sheet by the film tension to induce magnetic anisotropy. This is a method of making it difficult to generate a 90-degree magnetic domain having a vertical component on the steel plate surface due to the property. This method is the same as the method conventionally used to reduce iron loss. The other is a method of increasing the volume of a 90 degree magnetic domain at a magnetic flux density of zero, which is according to the present invention.

As a method of increasing the volume of 90 degree magnetic domains at a zero magnetic flux density, a method of applying compressive stress to a grain-oriented silicon steel sheet was first examined. FIG. 3 shows a case where a compressive stress is applied in the rolling direction of a grain-oriented silicon steel sheet Hi-B having a thickness of 0.27 mm,
This is an example of measuring a change in magnetostriction value at a frequency of 50 Hz and a magnetic flux density of 1.7 T. O-pea with increasing compressive force
The k value changed to a positive value, and became a positive value at 0.2 kg / mm ² , and when a compressive stress was further applied, it rapidly became a large positive value. At the same time, the peak-peak value was a minimum at 0.2 kg / mm ² . However, when the compressive stress is removed, it returns to the original magnetostrictive value, and it is difficult to continuously apply the compressive stress to the product, which is not practical.

Therefore, in the present invention, as a method of improving the magnetostriction of the product, a method of leaving a small internal strain in the steel sheet was found. In the flattening annealing in the manufacturing process of the grain-oriented silicon steel sheet described above, a test was performed by changing the annealing temperature, the line tension and the line speed, and the magnetostriction was observed in the low to medium magnetic flux density while the internal strain remained. It may be small in some cases, and upon strain relief annealing, the magnetostriction o-peak value increased to a negative value, and the magnetostriction value (peak-peak) increased. At this time, the magnetostriction value at high magnetic flux density (1.9 T) was sometimes small before stress relief annealing, but in many cases it was smaller after stress relief annealing. When the internal strain remains, tension acts in the direction of the 90 degree magnetic domain, so even when the magnetic flux density is zero, that is, the magnetic domain width of the 180 degree magnetic domain is equally narrow and the magnetostatic energy between the front and back surfaces is low, it is efficient. It is considered that 90-degree magnetic domains are likely to occur. However, at a high magnetic flux density, the interaction between the strong magnetic field and the domain wall described above causes
It is considered that the magnetostriction is still large because the 0 degree magnetic domain is compressed.

In claim 1 of the present invention, the magnetic flux density is 1.8.
Although it is limited to T or less, the reason is that even in the state where the magnetostriction is 1.8 T or less and the minimum magnetostriction, the magnetostriction may be larger than the case where the strain is released at 1.8 T or more.
Since the design magnetic flux density of iron cores and the like for which grain-oriented silicon steel sheets are used is often 1.8T or less, it is effective for these applications to minimize the magnetostriction value of 1.8T or less for noise reduction. is there. Further, the reason why the change in magnetostriction is 5% as compared with the case where the internal strain is released by annealing or the like is that a significant difference is taken in consideration of the magnetostriction measurement accuracy.

As a method of manufacturing the product of claim 1,
It does not particularly matter as long as it is a method of leaving a minute internal strain in the steel sheet, but considering the advantages in cost and strain control in the manufacturing process, the method of leaving strain in the above-described flattening annealing (claim 2 ), A method of introducing strain by means such as bending, pulling, rolling, pressing, shot projection after flattening annealing (claim 3), and then performing annealing for adjusting excessive internal strain ( Claim 4) is preferred.

[0019]

As described above, the present invention increases the volume of the 90-degree magnetic domain at the zero magnetic flux density by allowing the internal strain to remain in the grain-oriented silicon steel sheet. Magnetostriction value (peak
-Peak) is reduced.

[0020]

EXAMPLES Next, examples will be described. Example 1 A coil-shaped finish-annealed grain-oriented silicon steel sheet having a thickness of 0.30 mm was coated with an insulating film and flattened in a laboratory annealing furnace. At this time, the internal strain was left by limiting the furnace temperature to 800 ° C. or lower. Table 1 shows the magnetostriction value of this material and the magnetostriction value of the material after strain relief annealing at 850 ° C. for 4 hours. As a comparative example, the magnetostriction value of the material treated under the annealing condition in which the furnace temperature is 850 ° C. and almost no internal strain remains is shown.

[0021]

[Table 1]

Example 2 A grain-oriented silicon steel sheet having a thickness of 0.35 mm after the flattening annealing was 850
It was placed in a furnace at a temperature of 0 ° C., a tension of 1 kg / mm ² was applied, and then it was air-cooled outside the furnace to introduce an internal strain. About this material, 8
The magnetostriction was measured after annealing at a furnace temperature of 00 ° C, and then 8
Annealing was repeated while raising the furnace temperature to 50 ° C. and 900 ° C., and the magnetostriction after each annealing was measured. FIG. 4 shows the results.

[0023]

As can be seen from the above examples, according to the present invention, a small internal strain is left in the grain-oriented silicon steel sheet, so that the magnetostriction is 5% as compared with the case where the internal strain is released by stress relief annealing. The above effect was shown to be reduced.

[Brief description of drawings]

FIG. 1 shows an example of a magnetostrictive loop of a grain-oriented silicon steel sheet.

FIG. 2 shows an example of magnetostrictive excitation characteristics of a grain-oriented silicon steel sheet.

FIG. 3 shows changes in magnetostriction when a compressive stress is applied to a grain-oriented silicon steel sheet.

FIG. 4 shows a change in magnetostriction due to a change in annealing temperature of a grain-oriented silicon steel sheet having internal strain.

Claims (4)

[Claims] 1. A magnetostriction value in the rolling direction at a magnetic flux density of 1.8 T or less is 5% more than that when the internal strain is released by annealing etc. by leaving a minute internal strain remaining in the grain-oriented silicon steel sheet after finish annealing. A grain-oriented silicon steel sheet having a low magnetostriction characterized by being smaller than the above. 2. The directionality according to claim 1, wherein in the method for producing a grain-oriented silicon steel sheet, which comprises annealing in a coil state and then performing flattening annealing, a minute internal strain is left in such flattening annealing. Manufacturing method of silicon steel sheet. 3. The direction according to claim 1, wherein the flattened and annealed grain-oriented silicon steel sheet is subjected to bending, stretching, rolling, pressing or shot projection to leave a small internal strain in the steel sheet. For manufacturing a high-quality silicon steel sheet. 4. The residual internal strain amount is adjusted by performing bending, pulling, rolling, pressing, or shot projection processing on the grain-oriented silicon steel sheet that has been flattened and annealed, and then performing annealing. Item 1. A method for producing a grain-oriented silicon steel sheet according to Item 1.