JP2000144251A - Manufacture of grain oriented silicon steel having stress relief annealing resistance and low core loss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To show the optimum instruction of manufacture according to application magnetic flux density and to manufacture a steel sheet from deterioration in core loss due to stress relief annealing by regulating B8 deterioration before and after the formation of grooves in a steel sheet to a specific value when the design magnetic flux density of a transformer for which the steel sheet is used is set at a specific value. SOLUTION: Core loss is improved by physically forming grooves in a finish annealed steel sheet to fractionize a magnetic domain. When the design magnetic flux density of a transformer is >=1.7 T, B8 deterioration before and after the formation of the grooves in the steel is 0.03-0.06 T. It is preferable that B8 deterioration becomes 0.04-0.06 T when the design magnetic flux density of the transformer is 1.4-<1.7 T and that B8 deterioration becomes 0.04-0.06 T when the design magnetic flux density becomes <1.4 T. A fixed relationship is held between the amount of B8 deterioration and core loss after the magnetic domain fractionization, and the depth of the grooves is regulated as a means of regulating B8 deterioration. Core loss characteristic after stress relief annealing treatment is regulated so that most suitable core loss can be obtained according to the applied magnetic flux density, and the energy loss of the transformer can be reduced.

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 low-iron-loss unidirectional magnetic steel sheet which is used for a transformer core or the like and whose iron loss does not deteriorate after strain relief annealing.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets currently in practical use are easily magnetized in the rolling direction of the steel sheet, and are mainly used for electrical equipment such as transformers. When a magnetic domain is refined by introducing local strain or forming a groove in the steel sheet, eddy current flowing in the cross section of the steel sheet is reduced, and generation of heat energy is suppressed, so that iron loss is reduced. Thereby, the energy loss of the electric device can be reduced.

[0003] However, the above-described magnetic domain segmentation effect is lost in a usual method when a strain relief annealing at about 800 ° C is performed after a steel sheet is assembled as a winding transformer in a customer.

As a method of subdividing magnetic domains which does not disappear by the strain relief annealing, a method of forming a physical groove is effective. For example, Japanese Patent Application Laid-Open No. 60-211012 discloses a method in which a groove is formed on a cold rolled sheet by a roll with a projection. A method for controlling the secondary recrystallization by forming a steel sheet is disclosed, and JP-A-61-117218 discloses that a steel sheet after finish annealing is subjected to heat treatment by forming a groove with an appropriate load and interval. A method for periodically forming fine crystal grains is disclosed.

[0005] Incidentally, the above-described grain-oriented electrical steel sheet having physical grooves formed therein has a reduced magnetic permeability or B8 (magnetic field 8) due to a decrease in cross-sectional area due to the grooves and fine grains generated immediately below the grooves.
It is known that the magnetic flux density at 00 A / m) deteriorates. If the magnetic flux density is high, the transformer can be downsized by increasing the design magnetic flux density of the transformer. Therefore,
Conventionally, steel plates have also been manufactured in consideration of being used at a higher design magnetic flux density.

[0006]

As described above, various methods have been disclosed for a strain-relieving annealed low iron loss unidirectional electrical steel sheet having no deterioration in iron loss due to strain relief annealing. Various production methods have been proposed. However, in such a manufacturing method, there is no example in which simple manufacturing conditions are used and optimum conditions are shown according to the magnetic flux density to be used, and it cannot be said that the method is industrially excellent.

In the present invention, by using manufacturing conditions that are simpler than in the prior art, the shape and spacing of the grooves are not defined under detailed constant conditions, but an optimum manufacturing guideline is provided according to the magnetic flux density used. An object of the present invention is to provide a method for producing a strain-relieving annealed low iron loss unidirectional electrical steel sheet having no iron loss deterioration due to annealing.

[0008]

SUMMARY OF THE INVENTION The gist of the present invention is to have excellent low iron loss obtainability after strain relief annealing,
An object of the present invention is to provide a strain-relieving annealed low iron loss unidirectional electrical steel sheet which has no production loss due to strain-relieving annealing and shows a production guideline for obtaining an optimum iron loss according to a used magnetic flux density.

The specific means of the present invention are as follows.

(1) In a method for improving iron loss in which magnetic grooves are formed by physically forming grooves in a unidirectional electrical steel sheet which has been subjected to finish annealing, the design magnetic flux density of a transformer using the steel sheet is 1.7 T or more. The B8 deterioration before and after the formation of the groove in the steel sheet is set to 0.03T to 0.06T, wherein the iron in the strain-relieving annealed low iron loss unidirectional electrical steel sheet has no iron loss deterioration due to the strain-relieving annealing. Loss improvement method.

(2) In a method for improving iron loss, in which a magnetic groove is physically formed in a finish-annealed grain-oriented electrical steel sheet, the magnetic flux is refined, and the design magnetic flux density of a transformer using the steel sheet is less than 1.7 T; When 1.4T or more, the B8 deterioration before and after the formation of the groove in the steel sheet is set to 0.04T to 0.06T. To improve iron loss of conductive electrical steel sheets.

(3) In a method for improving iron loss in which magnetic grooves are formed by physically forming grooves in a grain-oriented electrical steel sheet that has been subjected to finish annealing, the design magnetic flux density of a transformer using the steel sheet is less than 1.4T. The B8 deterioration before and after the formation of the groove in the steel sheet is 0.05T to 0.09T, wherein the strain-relieving annealed low iron loss unidirectional magnetic steel sheet has no iron loss deterioration due to the strain-relieving annealing. Loss improvement method. (4) The method according to any one of the above (1) to (3), wherein the depth of the groove is adjusted as a method of adjusting the B8 deterioration.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on experimental results.

The present inventors have conducted various studies on the width, depth, and interval of the grooves formed on the surface of the steel sheet, the fine grains formed immediately below the grooves, and the iron loss characteristics after strain relief annealing. Of B
8 It has been found that there is a certain relationship between the deterioration amount and the iron loss. The details will be described below based on experimental results.

A 0.23 mm-thick grain-oriented electrical steel sheet having a finish of annealed and having a B8 of about 1.93 T is selected, and a cutting die is pressed in a direction perpendicular to the rolling direction. Samples were prepared with various intervals and depths of the grooves.

After the steel sheet was finally subjected to strain relief annealing at 800 ° C., B = B
Iron loss was evaluated under the conditions of 1.3, 1.5, and 1.7T.

FIG. 1 shows B8 and B = 1.3T iron loss (W1
3/50). This magnetic flux density range (1.4T>
In B), the optimum value of iron loss was obtained when B8 was 1.84 to 1.88, and the amount of B8 deterioration before and after groove formation was 0.05T to 0.09T.

FIG. 2 shows B8 and B = 1.5T iron loss (W1
5/50). This magnetic flux density range (1.7T>
In the case of (B ≧ 1.4T), B8 was 1.87 to 1.89, and thus the B8 deterioration before and after the groove formation was 0.04T to 0.06T, and the optimum value of iron loss was obtained.

FIG. 3 shows B8 and B = 1.7 T of iron loss (W1
7/50). This magnetic flux density range (B ≧ 1.7
In T), the optimum value of iron loss was obtained when B8 was 1.87 to 1.90, and thus the amount of B8 deterioration before and after groove formation was 0.03T-0.06T.

Table 1 shows the amount of B8 degradation at each groove interval and groove depth. Table 1 shows that the B8 deterioration amount gradually increases with the groove depth irrespective of the groove interval, and this indicates that the desired B8 deterioration amount can be controlled by the groove depth. Therefore, as a method of adjusting the B8 deterioration, adjusting the depth of the groove, preferably 5 to 5
It is necessary to adjust the depth of the groove according to the design magnetic flux density of the transformer used in the range of 25 μm.

[0021]

[Table 1] The mechanism by which the low iron loss condition is obtained by defining the B8 deterioration amount according to the present invention is not necessarily clear, but is considered as follows. Due to the groove formation, magnetic domain segmentation occurs and iron loss is reduced. On the other hand, if the B8 deterioration amount is too large, the magnetic permeability of the steel sheet decreases and the sectional area substantially decreases, and the passing magnetic flux relatively increases to increase iron loss. It is considered that an optimum value appears due to a balance between these two conflicting phenomena, and a certain optimum B8 deterioration amount is determined.

Based on the above-mentioned knowledge, it has excellent low iron loss yieldability even after strain relief annealing, has a production guideline for obtaining an optimal iron loss according to the magnetic flux density used, and has resistance to iron loss due to strain relief annealing. The production method of strain relief annealing low iron loss unidirectional electrical steel sheet was clarified.

Hereinafter, embodiments will be described.

[0024]

EXAMPLE A sharp marking needle was run perpendicularly to the rolling direction on a 0.23 mm-thick grain-oriented electrical steel sheet having been subjected to finish annealing to form grooves having variously varied groove intervals and depths. . Finally, strain relief annealing was performed at 800 ° C. to evaluate iron loss. Table 2 shows the results.

[0025]

[Table 2]

[0026]

As described above, by forming a groove with the B8 deterioration amount described in the present invention as a guide, the iron loss characteristics of a grain-oriented electrical steel sheet after a strain relief annealing treatment can be reduced. An optimum iron loss can be obtained in accordance with the used magnetic flux density, and its industrial significance is extremely large from the viewpoint of transformer energy loss.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between B8 after a groove is formed at B = 1.3T and iron loss at each magnetic flux density.

FIG. 2 is a diagram illustrating a relationship between B8 after a groove is formed at B = 1.5T and iron loss at each magnetic flux density.

FIG. 3 is a diagram showing a relationship between B8 after a groove is formed at B = 1.7T and iron loss at each magnetic flux density.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Masao Matsuo 1-1, Hibata-cho, Tobata-ku, Kitakyushu-city, Fukuoka Prefecture Inside Nippon Steel Corporation Yawata Works (72) Inventor: Kimihiko Sugiyama Tobata-ku, Kitakyushu-shi, Fukuoka Town 1-1 Shin-Nippon Steel Corporation Yawata Works F-term (reference) 4K033 AA02 PA06 5E041 AA02 AA11 CA02 HB00 HB11 NN15

Claims (4)

[Claims] In a method for improving core loss by physically forming grooves in a finish-annealed grain-oriented electrical steel sheet to reduce magnetic domains, the design magnetic flux density of a transformer using a steel sheet is 1.7.
When the temperature is T or more, the B8 deterioration before and after the groove is formed in the steel sheet is set to 0.03T to 0.06T. Iron loss improvement method for steel sheet. 2. In a method for improving iron loss, in which a groove is physically formed in a finish-annealed unidirectional magnetic steel sheet to reduce magnetic domains, the design magnetic flux density of a transformer using a steel sheet is set to 1.7.
When less than T and 1.4 T or more, the B8 deterioration before and after the formation of grooves in the steel sheet is set to 0.04 T to 0.06 T. A method for improving iron loss of unidirectional magnetic steel sheets. 3. A method for iron loss improvement in which magnetic grooves are formed by physically forming grooves in a finish-annealed unidirectional electrical steel sheet, wherein a design magnetic flux density of a transformer using the steel sheet is 1.4.
When less than T, the B8 deterioration before and after the groove is formed in the steel sheet is set to 0.05T to 0.09T. Iron loss improvement method for steel sheet. 4. The strain relief method according to claim 1, wherein the depth of the groove is adjusted as a method of adjusting the B8 deterioration. Method for improving iron loss of annealed low iron loss unidirectional electrical steel sheet.