JPH0387314A - Production of grain-oriented silicon steel sheet reduced in iron loss - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet with low iron loss at a low treatment cost by carrying out the fractionization of the width of magnetic domain of a grain-oriented silicon steel sheet hy means of the formation of fine grooves alone, without recourse to the application of strain. CONSTITUTION:Etching is applied to the surface of a grain-oriented silicon steel sheet after final finish annealing or a grain-oriented silicon steel sheet with low core loss consisting of tertiary recrystallized grains of >= about 10mm by using an etchant consisting of ethyl alcohol, nitric acid, etc., by which fine grooves where space between grooves, groove width, and groove depth are regulated to 2-10mm, 20-30mu, and 3-4mu, respectively, are formed into linear or dashed-line state in a direction having an angle of 45-90 deg. with respect to the rolling direction. Subsequently, an insulation coating solution, such as phosphate and chromate, is applied to the above steel sheet and baked at >= about 350 deg.C, by which an insulation coating is formed. By this method, the grain-oriented silicon steel sheet free from deterioration in characteristics even if subjected to stress relief annealing and reduced in iron loss can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing grain-oriented silicon steel sheets with extremely low core loss, and in particular, to magnetic domain subdivision that does not lose the core loss improvement effect even after heat treatment. The present invention relates to a method for manufacturing grain-oriented silicon steel sheets with low core loss using a chemical conversion method.

[Conventional technology]

Grain-oriented silicon steel sheets are electrical steel sheets that are widely used as core materials for transformers and the like. There is a need to reduce iron loss from the perspective of saving energy in electrical equipment or suppressing temperature rises due to heat generation.

In order to reduce iron loss, the crystal orientation is changed to (110) (001
) to achieve a high level of alignment, reduce the plate thickness, and 3i
It is effective to increase the specific resistance of the m-plate by increasing the content.

For example, in the invention described in Japanese Patent Application No. 62-3270, a commercially available grain-oriented silicon steel sheet is cold-rolled and heat-treated in a vacuum at a temperature of 200°C or higher in order to make the sheet thinner and to have a highly oriented crystal orientation. Therefore, a method has been proposed for obtaining grain-oriented silicon steel sheets with extremely low iron loss, which are composed of tertiary recrystallized grains with a grain size of 10 mm or more. However, if the crystal grains are large, the magnetic domain width becomes large and there is a tendency that the core loss in the high frequency region cannot be reduced.

On the other hand, as a method to reduce iron loss by subdividing magnetic domains,
There is a method (Japanese Patent Publication No. 585968) in which a small ball is pressed onto the surface of a grain-oriented silicon steel sheet after final finish annealing to form a recess with a depth of 3 μm or less to impart a linear microstrain. Furthermore, in Japanese Patent Publication No. 58-26406 and Japanese Patent Publication No. 58-26410, laser irradiation is used to form traces on the surface of a grain-oriented silicon steel sheet after final finish annealing to give local minute strain and reduce iron loss. A method is proposed. However, the silicon steel sheet with low iron loss obtained as described above also has
For example, there is a problem in that the iron loss improvement effect is lost due to strain relief annealing at 800° C. or higher during manufacturing of the wound core.

In order to solve the above-mentioned loss of iron loss improvement effect due to annealing,
There is a method in which a dotted or broken line machining strain is applied to a steel plate that has been finish annealed or treated with an insulating coating, and then heat treated at 750°C or higher to generate fine crystal grains and subdivide the magnetic domains (Japanese Patent Publication No. 6253579). )Proposed.

Furthermore, there is a proposal to solve the above-mentioned loss of the iron loss improvement effect due to annealing by forming a foreign material different from the steel composition or steel structure of the finish-annealed grain-oriented silicon steel sheet.

For example, a method of embedding metal powder etc. in the cold rolling process (Japanese Patent Publication No. 63-31527), a method of forming foreign matter by heat treatment after applying a specific element (Japanese Patent Publication No. 63-195)
67, Japanese Patent Publication No. 63-30968), and a method of forming an interstitial material different from the composition and structure of steel by heat treatment after electroplating (Japanese Patent Publication No. 63-19568, Japanese Patent Publication No. 63-1982).
No. 19569).

[Problem to be solved by the invention]

Although the above proposed method does not have the problem that the iron loss improvement effect disappears due to strain relief annealing, it is difficult to obtain the same iron loss reduction effect as laser irradiation, or it requires heat treatment etc. to produce grain-oriented silicon steel sheets. There is a problem in that the cost is high.

The purpose of the present invention is to propose a magnetic domain refining method that does not lose the iron loss improvement effect even when subjected to heat treatment, for example, stress relief annealing at 800°C or higher, and which has a low processing cost, thereby producing grain-oriented silicon steel sheets with low iron loss. This is what we are trying to provide.

[Means to solve the problem]

The present invention is achieved by forming linear grooves by etching (chemical polishing) on the surface of a grain-oriented silicon steel sheet after final finish annealing or a low-loss grain-oriented silicon steel sheet consisting of tertiary recrystallized grains of 10 mm or more. , which attempts to reduce the iron loss of the silicon steel plate.

The decrease in iron loss due to the formation of grooves is thought to be due to the fact that the presence of grooves on the surface of the steel sheet increases static magnetic energy, and the reversal of magnetic domains that occur to cancel this increase results in fragmentation of the magnetic domains.

In the prior art, forming linear depressions by pressing a small ball or forming traces by laser irradiation both give minute distortions. In contrast, in the present invention, the grooves are formed by an etching method and are not dependent on the application of strain, so the effect of improving core loss is not lost by annealing. It also exhibits the effect of reducing iron loss on silicon steel sheets with large crystal grains.

The grooves are formed by the etching method of the present invention preferably before the application of the insulating film, using ethyl alcohol, nitric acid, or the like as a corrosive liquid at an angle of 45 to 45 to the rolling direction of the silicon steel sheet.
Linear or broken line in 90 degree direction, groove spacing 2 to 1
0mm, groove width 20-30μm, groove depth 3-4μm
It is carried out in the range of m. Next, the steel plate is treated with phosphoric acid, phosphates such as aluminum phosphate, magnesium phosphate, zinc phosphate, calcium phosphate, chromates such as chromic acid and magnesium chromate, dichromates, colloidal silica, etc. An insulating coating solution containing one or more species is applied and baked at a temperature of 350° C. or higher to form an insulating coating.

The silicon steel sheet to which the method of the present invention is applied is a grain-oriented silicon steel sheet that has been finish annealed or, in the case of a tertiary recrystallized grain growth copper electrode, a steel sheet that has been heat-treated for tertiary recrystallization. It is not necessary to specify the composition and manufacturing conditions up to final annealing. Preferably, the treatment is applied to a steel plate before the insulation coating is applied. However, even after applying the insulation coating, physical
It is only necessary to remove the film by a chemical method, and there is no limitation to this method.

In addition to the above-mentioned ethyl alcohol and nitric acid, as the etching solution, water and nitric acid, hydrofluoric acid and sulfuric acid, hydrochloric acid and nitric acid, water and hydrochloric acid, ethyl alcohol and picric acid, etc. are used depending on the processing speed.

Figure 1 shows (a) a photograph of the magnetic domain before groove formation using a scanning electron microscope, and (b) a photograph of the magnetic domain after groove formation, clearly showing how the magnetic domains have been subdivided by the application of the present invention. It is shown.

In addition, 1 in the figure is the domain wall, 2 is the magnetic domain width, 3 is the grain boundary, and 4 is the magnetic domain width.
is a groove formed by etching.

〔Example〕

The description will proceed according to specific experiments that led to the above invention. In the experiment, a grain-oriented silicon steel plate was used before being coated with an insulating coating made of tertiary recrystallized grains. Its characteristics are iron tMW+tzs. (
Iron loss at 1, 77, 50Hz) = 0.55W/Kg
, magnetic flux density Bs (magnetic flux density at 800 A/m)
-1,947, plate thickness 0.071 mm oriented silicon t! f
4 plates were annealed for strain relief at 800° C. for 30 minutes.

Using 1O% nitric acid water as an etching solution, the groove width of each sample was varied in the range of 20 to 590 μm, and grooves were formed in a direction 90 degrees to the rolling direction with a groove depth of 5 μm to evaluate the effect of groove width. It was investigated.

FIG. 2 shows the relationship between the groove width and the number of domain walls. Curve A in the diagram
simulates the tension applied to a steel plate by applying and baking an insulating coating, and when a tension of 4 kg/mm2 is applied to the sample, curve B shows the relationship between the groove width and the number of domain walls when no tension is applied. From this experiment, the number of domain walls is the largest when the groove width is 20 to 30 μm, that is, the interval between the domain walls and the domain width is the smallest. If the groove width is wider than 20 mm, the influence of the groove will be reduced, which is not preferable.

Next, the groove width of the sample was fixed at 25 μm, and the groove depth was set to 0.5 μm.
Grooves were formed by the same etching method in a direction 90 degrees to the rolling direction, and experiments were conducted to examine the effect of groove depth. FIG. 3 shows the relationship between the groove depth and the number of domain walls. Curve C in the figure shows the relationship between the groove width and the number of domain walls when a tension of 4 kg/mm2 is applied as in Fig. 2, and the curve shows the relationship between the groove width and the number of domain walls when no tension is applied.

From this experimental result, the number of domain walls increases at a depth of 3 to 4 μm. The number of domain walls decreases both when it is shallower than 3 μm and when it is deeper than 4 μm, and the optimal range is at a depth of 3 to 4 μm.
It turned out to be μm.

Furthermore, in order to investigate the effect of the groove spacing, the groove width was 25 μm, the groove depth was 3.5 μm, and the distance between the grooves was varied in the range of 0.5 to 20 mm for each sample in the direction 90 degrees to the rolling direction. A groove was formed.

Figure 4 shows the relationship between the groove spacing of each sample and the iron loss measurement results of the sample. Curve F in Figure 9 shows the iron loss measurement when a tension of 4 kg/mm'' is applied, and curve E shows the iron loss measurement without tension. It shows the iron loss measurement value in the case of no tension, tension 4 kg g 7
In the case of mm2, the iron loss is low in all cases between 2 and 10 mm. If it is less than 2 mm, there will be no groove and the number of domain walls will not increase, and if it is more than IQ mm, a region will be created where the influence of groove formation will be small, so both are not preferable. Comparing the iron loss before and after groove formation from this figure, after groove formation,
Iron loss is reduced by 8-19%, and the energy-saving effect when applied to products is immeasurable.

Regarding the influence of the groove direction, the groove width was 25 μm, the groove depth was 3.5 μm, and the angle with the rolling direction was set at 2 for each sample.
Grooves were formed by varying the angle between 0 and 90 degrees, and the effects were examined.

FIG. 5 shows the relationship between the angle formed by the grooves of each sample with the rolling direction and the number of domain walls. Curve G in the figure has a tension of 4K as in Figure 2.
Curve H shows the relationship between the angle and the number of domain walls when no tension is applied when g/mm2 is applied.

From this, the number of domain walls increases at an angle of 45 degrees or more,
In order to significantly improve the magnetic domain width, it is necessary to set the angle to 45 to 90 degrees.

The present invention will be described in detail below based on the case where the present invention is applied to a grain-oriented silicon steel sheet comprising tertiary recrystallized grains.

Iron loss according to JIS regulations is W+7/S. ≦1.05W
/kg, if East density B8≧1.89T, provisional 1! J-0
, 3 mm commercially available grain-oriented silicon steel plate was removed by pickling.

Next, the plate thickness was 100 μm by cold rolling at a reduction rate of 67%.
Roll until. Thereafter, the temperature was raised to 1200°C under a vacuum of 2 x 10-' Torr and maintained for 7 hours.
Iron loss W19/il+ = by the method based on No. 2-3270
0.49 w/kg (tension 4kg, 7mm” applied), magnetic flux density Bs=1.977, plate thickness t=0.071
mm, number of domain walls 4/mm (tension 4 kg/mm2 applied)
A grain-oriented silicon steel sheet consisting of tertiary recrystallized grains was obtained.

After coating the surface of this steel plate with vinyl resin and drying it at room temperature, use a 35 μm tip scriber to pierce it at 5 mm intervals.
The resin was removed in a linear manner. Next, 10% nitric acid water was dropped onto the surface to etch the part where the resin had been removed, and after 10 seconds, it was washed with water. Thereafter, it was immersed in acetone to dissolve and remove the vinyl resin.

After forming grooves with a width of 40 μm, a depth of 2.5 μm, an interval of 5 mm, and an angle of 90 degrees to the rolling direction using the above method, the tension applied to the steel plate due to the insulation coating was simulated, and a tension of 4 kg/mm was applied to the sample. The iron loss was measured with the applied state at a frequency of 50 Hz and the excitation magnetic flux density varied from 0.5 T to 1.7 T. The measurement results are shown in Figure 6. The iron loss at 1.7 T was 0.
．． It was confirmed that it could be reduced to 35w/kg.

Similarly, with a tension of 4 kg/mm, W,
7. . ,W,ya. . , magnetic flux density B, and number of domain walls were measured. Furthermore, an insulating film made of colloidal silica and aluminum phosphate was applied to this sample, and baked at 500° C. for 2 minutes. Thereafter, strain relief annealing was performed at 800° C. for 30 minutes, and iron loss, magnetic flux density, and number of domain walls were measured. Table 1 shows the iron loss WI715° before and after groove formation, film application, and strain relief annealing.

WS/400, magnetic flux density B8, and domain wall number measurement results are shown.

As is clear from this table, there is no change in the magnetic flux density, but the number of domain walls increases by about 7 times, and accordingly the iron loss increases by W, 7. . Approximately 30%, W574°.

It decreased by about 20%. Further, by applying the insulating film, the same iron loss reduction effect as applying a tension of 4 kg and 7 mm2 was obtained. Furthermore, this result is the iron loss measurement value after strain relief annealing, and no loss of the iron loss reduction effect due to strain relief annealing was observed.

Table 1 Next, an example in which the present invention is applied to a commercially available oriented silicon tone plate will be explained.

Iron PAW + tzs according to JIS regulations. ≦1.0
5 W/kg, Gt1 bundle density B1≧1.897, plate thickness 0
．． Using 3 mm commercially available grain-oriented silicon 11, the film was removed by pickling, and iron FIW, zse-1,02w/
kg (tension 1 kg/mm2 applied), magnetic flux density B,
= 1.917, plate thickness 0.28 mm, number of domain walls 6/mm (
A material with a tension of 1 kg/mm" was obtained. After this, a material with a width of 5
The sample was cut into pieces with a length of 100 mm and a length of 100 mm.

Next, as in the example of the grain-oriented silicon steel sheet made of tertiary recrystallized grains, etching was performed using nitric acid water to have the groove dimensions shown below.

As a result, after forming grooves with a width of 25 μm, a depth of 4 μm, and an interval of 7 mm at an angle of 90 degrees with the rolling direction, the sample was subjected to a tension of 1
kg/mm'' was applied, and the iron loss Wl'115°, magnetic flux density Bll, and number of domain walls were measured.After that, an insulating film made of colloidal silica and aluminum phosphate was applied, and
Baking was performed at 00°C for 2 minutes, and strain relief annealing was further performed at 800°C for 30 minutes, and the core loss, magnetic flux density, and number of domain walls were measured.

The results are shown in Table 2. The number of domain walls increases approximately three times, and the iron loss increases to W+? /So, the iron loss was reduced by 13%, and an improvement in iron loss was confirmed even in commercially available grain-oriented silicon steel sheets. Also, the improvement effect is not lost even with strain relief annealing. ll
I approved.

Table 2 4 [Effects of the Invention] Since the present invention has the above-described structure, there is no deterioration in properties even when strain relief annealing is performed, and it is possible to obtain a low-loss grain-oriented silicon steel sheet with low iron loss. can.

[Brief explanation of drawings]

Figures 1 (a) and (b) are magnetic domain photographs taken before and after groove formation using a scanning electron microscope, Figure 2 is a characteristic diagram showing the relationship between the groove depth and the number of domain walls, and Figure 3 is a graph showing the relationship between the groove depth and the number of domain walls. Fig. 4 is a characteristic diagram showing the relationship between the groove spacing and iron loss; Fig. 5 is a characteristic diagram showing the relationship between the groove angle with respect to the rolling direction and the number of domain walls; The figure is a characteristic diagram showing the relationship between excitation magnetic flux density and iron loss after groove formation. ■...Domain wall, 2...Magnetic domain width, 3...Liquid crystal grain boundary, 4...Groove. (b) Fig. 2 00 00 00 Groove width end m) Fig. 3 Fig. Groove depth (Pm) Fig. 4 Groove spacing (mm) Fig. 5 Angle with rolling direction (°) Fig. 6 Exciting magnetic flux density (T ) Procedural amendment (method) % formula % Indication of the case Patent Application No. 1-220254 Name of the invention Person amending the manufacturing method of low iron loss grain-oriented silicon steel plate Relationship to the case Applicant name (544) Babcock-Hitachi Co., Ltd. Company 4 Agent address: 1-6-13 Nishi-Shinbashi, Minato-ku, Tokyo 105-6 Number of claims increased by amendment 7 No column for brief explanation of drawings in the specification subject to amendment 1) Page 15 of the specification 6-5 lines from the bottom “Figure 1...
...Photograph" should be corrected to "Figure 1 (a) and (b) are microscopic photographs of the metal structure showing the state of the magnetic domains before and after groove formation.''that's all

Claims (4)

[Claims] (1) A method for reducing iron loss by subdividing the magnetic domain width of a grain-oriented silicon steel sheet, characterized in that the method subdivides the magnetic domain only by forming fine grooves without applying strain. A method for manufacturing a grain-oriented silicon steel plate with low iron loss. (2) A method for producing a low iron loss grain-oriented silicon steel sheet according to claim (1), wherein the method for forming the micro grooves is an etching method. (3) In claim (1), the dimensions of the fine grooves are width: 20 to 30 μm, depth: 3 to 4 μm, and pitch of the fine grooves: 2 to 10 mm. manufacturing method of silicon steel sheet. (4) A method for producing a low iron loss grain-oriented silicon steel sheet according to claim (1), wherein the fine grooves form an angle of 45 to 90 degrees with the rolling direction.