JP3147290B2 - Processing method of unidirectional silicon steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a grain-oriented silicon steel sheet suitable for use as an iron core of a small transformer, and more particularly to a method for processing a trouble such as occurrence of surface breakage and deterioration of electromagnetic characteristics. The present invention relates to a method for processing a grain-oriented silicon steel sheet that has been eliminated.

[0002]

2. Description of the Related Art A magnetic steel sheet used as an iron core of a transformer includes a directional silicon steel sheet and a non-oriented silicon steel sheet. Conventionally, small transformers often do not require strict electromagnetic characteristics, and non-oriented silicon steel sheets have been mainly used in terms of cost. However, recently, there has been a strong demand for small transformers to be improved in performance and to be reduced in size and weight, and oriented silicon steel sheets having excellent magnetic properties have been used.

[0003] In the case of a wound iron core, the steel plate is subjected to bending, but in the case of a small transformer, the bending radius is necessarily small. When a directional silicon steel sheet is used for a small transformer,
The frequency of occurrence of surface breakage during bending increases. When the surface breaks, the subsequent transformer manufacturing process is hindered, and the electromagnetic characteristics are also deteriorated, which is a problem.

On the other hand, in the case of using an iron core such as an EI type transformer, the steel sheet is punched. Generally, the steel sheet is passed through a leveler before the punching processing to correct the shape and / or control the tension. It is carried out. However, in the case of a directional silicon steel sheet, when the steel sheet passes through a leveler, there is a problem that the steel sheet is broken and punching cannot be performed.

[0005] Regarding the bending of a silicon steel sheet, for example, Japanese Patent Application Laid-Open No. 6-179977 proposes a method of improving the bending of a steel sheet by controlling the precipitation form of nitrides in the steel sheet. However, this technique can improve the bending that occurs when the steel sheet is bent slowly and repeatedly, but cannot improve the surface bending that occurs when the steel sheet is bent rapidly.

[0006]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems, and proposes a method for processing a grain-oriented silicon steel sheet which can prevent the occurrence of surface breakage even at a high speed processing at a strain rate of 0.01 / sec or more. The purpose is to:

[0007]

Means for Solving the Problems The present inventors have conducted a detailed investigation on the surface breaks occurring when high-speed processing of grain-oriented silicon steel sheets. It was found that the problem was not due to interfacial cracking due to precipitates but to twinning deformation. Twin deformation is a deformation that occurs when the crystal is deformed under stress by changing the arrangement of the atoms in mirror symmetry with the twin plane as a boundary, and the deformation mode is different from the slip deformation due to the generation and movement of dislocations It is a deformation.

Further, the present inventors have investigated in detail the cause of twin deformation without slip deformation during high-speed bending, and as a result, the generation and movement of dislocations that cause slip deformation due to fine precipitates and the like have been found. It has been found that this is the case where the deformation is suppressed and twin deformation is more likely to occur instead of slip deformation. In order to increase the mobility of dislocations and to suppress twinning deformation, the present inventors have found that it is effective to impart a slight plastic strain to the material before product processing as preliminary strain in advance. Was found.

Next, the experimental results on which the present invention is based will be described. A 300 × 280 mm test piece was sampled from a directional silicon steel sheet product sheet having a sheet thickness of 0.20 mm, and pre-strained. Pre-strain processing is to change the amount of strain by wrapping a test piece around a round bar with a different diameter, wrapping it around a round bar, then releasing,
The flexural curvature after opening was measured and defined as the applied plastic strain. The number of repetitions of the same condition was set to 10. A test piece to which no preliminary strain was applied was also prepared. Then, for half of the test pieces, a curve
It was bent to mmφ. After the bending, the presence or absence of surface breaks was investigated, and the occurrence of surface breaks was determined. For the remaining specimens,
After flattening, performing a strain relief annealing at 850 ° C. for 1 hour in a nitrogen atmosphere, measuring the iron loss W _17/50 , determining the rate of decrease in iron loss with respect to the pre-strained _untested specimen, and determining the iron loss deterioration rate. . The result is shown in FIG.

From FIG. 1, by applying a preliminary strain,
It can be seen that the incidence of surface breaks decreases, and particularly when plastic strain with a plastic strain amount of 0.0002 or more is applied, the occurrence of surface breaks decreases significantly to zero. If the amount of plastic strain exceeds 0.01, the iron loss deterioration rate becomes 10% or more, and the degree of iron loss deterioration increases. Furthermore, the present inventors have studied the effect of the strain rate when applying the preliminary strain. A 300 × 280 mm test piece was sampled from a 0.20 mm thick directional silicon steel product sheet, and the diameter was 60 mm.
The time when winding the test piece around the φ round bar, that is, changing the strain rate and winding, applying a pre-strain of 0.0033 plastic strain, investigating the presence or absence of surface breakage due to pre-strain processing, I asked. The number of repetitions of the same condition was set to 10.
The result is shown in FIG.

FIG. 2 shows that the strain rate at which the preliminary strain is applied is 0.01
It can be seen that when the rate exceeds / sec, the occurrence of surface breakage increases.
The present invention has been made based on the above findings. That is, the present invention is a method for processing a unidirectional silicon steel sheet, in which a product processing such as bending and punching is performed on the unidirectional silicon steel sheet.
/ sec or less is applied at a strain rate or less, is a method for processing a unidirectional silicon steel sheet that prevents the occurrence of surface breaks characterized by performing the product processing, the preliminary strain is a plastic strain of 0.0002 to 0.01. Preferably, there is.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When a grain-oriented silicon steel sheet is processed into an iron core such as a transformer, a bending process is performed on a wound iron core and a punching process is performed on a stacked iron core. In the present invention, a mild plastic strain is preliminarily applied to a steel sheet as a pre-strain before processing these products. By giving this preliminary strain, slip deformation occurs even when severe deformation is applied to the grain-oriented silicon steel sheet during product processing, and twins do not occur, so that the occurrence of surface breakage can be prevented.

The strain rate at the time of adding the preliminary strain is 0.01 / sec.
The following is assumed. When the strain rate exceeds 0.01 / sec, the possibility of twinning increases in the grain-oriented silicon steel sheet, and the effect of pre-straining is reduced because pre-straining does not lead to an increase in dislocation density due to slip deformation. Decrease. The preliminary distortion to be added is
Preferably, the plastic strain is 0.0002 or more and 0.01 or less. If the preliminary strain is less than 0.0002, the effect of preventing the occurrence of surface breakage is slightly reduced. Further, in the case of a plastic strain having a preliminary strain of more than 0.01, release of the applied strain becomes insufficient even after the strain relief annealing, and the electromagnetic properties of the product are slightly deteriorated.

The method of applying the pre-strain may be any method such as bending or tensioning, and is not particularly limited. However, it is preferable that the strain is continuously applied by passing through a bending roll, assuming the case of a coil. In the present invention, the product processing is
It is particularly suitable for a bending process that satisfies 2R / t <300 (R: radius of curvature, t: plate thickness). When severe bending such as 2R / t of less than 300 is required, the occurrence of surface breakage can be prevented by applying a pre-strain before processing the product, especially since the frequency of surface breakage is high.

[0015]

【Example】

Example 1 A directional silicon steel product steel strip having a thickness of 0.20 mm and a width of 55 mm was formed into a wound iron core by a processing apparatus suitable for carrying out the present invention shown in FIG. The steel strip 1 paid off from the coil 2 wound on the payoff reel 7 is passed through a tension pad 3 to a preliminary strain applying device 4 comprising two bending rolls 4a.
After pre-straining was performed, the take-up reel 5 was used as the take-up core 5. The pre-strain amount and the strain rate shown in Table 1 were changed by changing the roll diameter of the bending roll 4a and the feeding speed of the steel strip. Unwind the wound iron core and make it 10cm in the longitudinal direction.
The number of breaks per unit was investigated. In addition, to wound iron core
An iron loss value was measured by performing a strain relief annealing at 850 ° C. for 1 hour. Table 1 shows the results.

[0016]

[Table 1]

Further, a rolled iron core was produced from a directional silicon steel product steel strip having the same dimensions by using a processing apparatus shown in FIG. Longitudinal direction as in the example
The number of surface breaks per 10 cm and the iron loss value after strain relief annealing were investigated. The examples of the present invention within the scope of the present invention have a lower number of surface breaks as compared with the comparative example, can prevent the occurrence of surface breaks, and have less deterioration of iron loss values.

(Example 2) As a preliminary strain is applied to a directional silicon steel product steel strip having a thickness of 0.20 mm and a width of 55 mm, a plastic strain of 0.005 is applied by a bending roll at a strain rate of 0.005 / sec, and the shape is corrected by a leveler. Then, punching was performed to produce an E-shaped iron core. By applying the preliminary strain, there was no occurrence of surface breakage during leveler correction. On the other hand, in the conventional example having no preliminary strain, the surface was broken at the time of leveler correction, and punching was difficult.

[0019]

According to the present invention, even when a grain-oriented silicon steel sheet is processed at high speed, the occurrence of surface breakage can be prevented, and the deterioration of the magnetic characteristics is also small. Further, according to the present invention, it is possible to improve the production efficiency by preventing the occurrence of trouble in the production process,
A remarkable effect is obtained that the grain-oriented silicon steel sheet can be advantageously applied as a material for a small transformer.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the occurrence rate of surface breakage, the iron loss deterioration rate, and the amount of plastic strain applied in preliminary strain processing.

FIG. 2 is a graph showing the relationship between the occurrence rate of surface breaking and the strain rate at the time of applying preliminary strain.

FIG. 3 is a schematic side view of a wound iron core processing apparatus suitable for carrying out the present invention.

FIG. 4 is a schematic side view of a conventional wound iron core processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel strip 2 Coil 3 Tension pad 4 Prestraining device 4a Bending roll 5 Take-up reel 6 Iron core 7 Payoff reel

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01F 41/00-41/12 H01F 1/00-1/117

Claims (2)

(57) [Claims] 1. A method for processing a unidirectional silicon steel sheet, wherein a product processing such as bending and punching is performed on the unidirectional silicon steel sheet, wherein a preliminary strain of 0.01% / sec.
A method for processing a unidirectional silicon steel sheet in which surface breakage is prevented, wherein the processing is performed after the application at the following strain rate. 2. The method according to claim 1, wherein the preliminary strain is a plastic strain of 0.0002 to 0.01.