JPH08297104A - Strain evaluating method for grain oriented electromagnetic steel plate - Google Patents

Abstract

PURPOSE: To quantitatively evaluate the strain in a steel plate by feeding parallel X-rays to the steel plate while diffracting the X-rays with a monocrystal of Si, measuring a diffraction intensity curve, and obtaining the half-value width. CONSTITUTION: Parallel X-rays having the divergence angle 100sec or below are fed to a steel plate, a diffraction intensity curve is measured, and the internal strain of a material is evaluated by the half-value width. X-rays are fed to a monocrystal to be diffracted, and the diffracted X-rays with good parallelism are used as parallel X-rays fed to the steel plate for evaluation. The rolling direction of the steel plate is used as the rotation axis when the diffraction intensity curve is measured. The half-value width must be kept at 100sec or below to keep the magnetic strain of the grain oriented electromagnetic steel plate at the preferable range of 5×10<-6> or below. The internal strain at the level corresponding to the dispersion of the magnetic characteristic of the grain oriented electromagnetic steel plate can be quantitatively evaluated, and the control of operating conditions for manufacture and the quality control of products can be conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating internal strain of a material of grain-oriented electrical steel sheet which is mainly used as an iron core of transformers and other electric devices.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are used as magnetic iron cores in many electric devices. The grain-oriented electrical steel sheet is Si
Of 0.8 to 4.8% and the crystal grain orientation of the product is {11
0} <001> is a highly integrated steel plate. Its magnetic characteristics are required to have low magnetostriction and iron loss. It is known that these soft magnetic properties are greatly affected by the internal strain of the material, but the evaluation method has not been established. For example, IEEE Trans. MAG (1974) p.
123 to 127: Fig. 7 shows that the magnetostriction characteristic is more sensitive to the internal strain, but the internal strain has not been quantitatively evaluated, and the dislocation distribution is observed by the etch pits. Only.

[0003]

It is known that the magnetic properties (magnetostriction, iron loss, etc.) of grain-oriented electrical steel sheets are greatly affected by the internal strain of the material. Therefore, if the internal strain can be quantitatively evaluated, it becomes possible to control the operating conditions of manufacturing and the quality of the product. An object of the present invention is a quantitative evaluation method of internal strain of grain-oriented electrical steel sheet which has never been established.

[0004]

Means for Solving the Problems The present invention is to solve the above problems, and in a strain evaluation method for a grain-oriented electrical steel sheet containing 0.8 to 4.8% by weight of Si, a divergence angle of 100
It is a strain evaluation method for a grain-oriented electrical steel sheet, characterized in that a parallel X-ray of a second or less is incident on a steel sheet, a diffraction strength curve is measured, and the half-width thereof is used to evaluate the internal strain of the material. Further, here, X-rays are made incident on a single crystal to be diffracted, and the diffraction lines with good parallelism are used as parallel X-rays made incident on the steel sheet for evaluation. The axis of rotation for measuring the diffraction intensity curve is It is also characterized in that the rolling direction of the steel sheet is used.

[0005]

The present inventor considered that the X-ray diffraction intensity curve is used for the measurement of internal strain as a basic premise, and evaluated the correspondence with the magnetic characteristic level of the grain-oriented electrical steel sheet product, which is currently a problem. As a result, it is not possible to evaluate grain-oriented electrical steel sheets with an X-ray diffraction apparatus normally used for steel materials,
It has been found that in order to evaluate the internal strain of the grain-oriented electrical steel sheet, it is necessary to enhance the angular resolution of incident X-rays and detect the difference with a half width on the order of 100 seconds or less. The details will be described below.

The present inventor first evaluated the crystal perfection of grain-oriented electrical steel sheet products. It is known that grain-oriented electrical steel sheets are polycrystals having an average orientation dispersion of several degrees, but as a result of detailed investigation of each single crystal grain, they are divided into subgrains of the order of 0.1 degree. It was found that (J. Mat. Eng. 13 (1991) p.113-
118). In addition to this finding, the relationship between the dispersion of these subgrains, the crystal perfection of each subgrain, and the like, and magnetostriction (particularly important among magnetic properties) was investigated. As a result, it was found that the half width of the diffraction intensity curve of each subgrain is closely related to the magnetostrictive property.

FIG. 1 shows the full width at half maximum of a diffraction strength curve and a magnetostrictive characteristic of a grain-oriented electrical steel sheet product having a sheet thickness of 0.35 mm. From FIG. 1, it can be seen that the difference in magnetostrictive properties, which is a problem in grain-oriented electrical steel sheets, can be sufficiently evaluated by the half width of the diffraction strength curve. From FIG. 1, in order to set the magnetostriction of the grain-oriented electrical steel sheet to not more than 5 × 10 ^−6, which is a preferable range, the half-value width is 10
It can be seen that the time needs to be 0 seconds or less.

FIG. 2 shows the measuring system used in the present invention. In the figure, 1 is a path of X-rays, 2 is a Si single crystal, 3 is a sample, 4 is a detector (scintillation counter or the like), 5 is a sample, and a rotation axis of the detector. A rotor target type generator using a Mo target was used as the X-ray source, and the {620} asymmetrical reflection of the Si single crystal 2 was used to reduce the angular divergence of the incident X-ray to about 3 seconds. This X-ray with excellent parallelism is made incident on the sample 3 and the sample and the detector are respectively separated by θ.
Then, the diffraction intensity curve was measured by rotating 2θ. As the magnetostrictive property, a measured value at a maximum magnetic flux density of 1.9 T under application of compressive stress (0.3 kg / mm ² ) was used.

From the above results, in order to evaluate the internal strain of the grain-oriented electrical steel sheet, diffraction was performed with an accuracy capable of measuring the half width of 100 seconds or less by controlling the angular dispersion of incident X-rays and the rotation of the sample. It turns out that it is necessary to configure a system for measuring the intensity curve. In particular, it is not necessary to limit the method for controlling the angular dispersion of incident X-rays, but Si, Ge, Fe
A method in which a single crystal having a high degree of perfection, such as -Si, is incident and diffracted and the diffraction line having good parallelism is used as the incident line of the sample is effective for downsizing the apparatus system.

Further, the grain-oriented electrical steel sheet is usually finish-annealed in a coil shape, and at that time, the crystal orientation is controlled by utilizing the secondary recrystallization phenomenon. In that case, due to the influence of the coil set, the sub-grain of the grain-oriented electrical steel sheet introduces angular dispersion with the axis of rotation perpendicular to the rolling direction. Therefore, when azimuth control is performed in such a coiled form,
It is necessary to measure the diffraction strength curve with the rolling direction that is not affected by the coil set as the axis of rotation. That is, in FIG. 2, the rotation axis 5 of the sample 3 may be rotated in the rolling direction.

[0011]

[Examples] Grain-oriented electrical steel sheet products after finish annealing (0.3
(1) 500 ° C. as strain relief annealing
(2) Annealed at 700 ° C. and (3) 800 ° C. for 1 hour, and the magnetostrictive characteristics and the diffraction strength curve were measured. The results are shown in Table 1, and the internal strain is lowered and the half width is reduced by increasing the annealing temperature. This improves the magnetostrictive characteristics,
That is, the magnetostriction becomes small, and it is in a preferable range at an annealing temperature of 700 ° C or higher.

[0012]

[Table 1]

[0013]

The magnetic characteristics (magnetostriction, iron loss, etc.) of grain-oriented electrical steel sheets are greatly affected by the internal strain of the material. According to the method of the present invention, it becomes possible to quantitatively evaluate the internal strain of a level corresponding to the variation in the magnetic characteristics of the grain-oriented electrical steel sheet.
This makes it possible to control the operating conditions of manufacturing and the quality of products.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the full width at half maximum of the diffraction strength curve of a grain-oriented electrical steel sheet measured by the method of the present invention and the magnetostrictive characteristic.

FIG. 2 is a diagram showing an example of the configuration of a measurement system.

[Explanation of symbols]

 1 X-ray path 2 Si single crystal 3 Sample 4 Detector 5 Rotation axis

Claims (3)

[Claims] 1. In a strain evaluation method of a grain-oriented electrical steel sheet containing 0.8 to 4.8% by weight of Si, a parallel X-ray with a divergence angle of 100 seconds or less is incident on the steel sheet to measure a diffraction intensity curve. , A method for evaluating the strain of grain-oriented electrical steel sheets, characterized in that the internal strain of the material is evaluated by its half width. 2. The grain-oriented electrical steel sheet according to claim 1, wherein X-rays are incident on a single crystal to be diffracted, and the diffraction lines having good parallelism are used as parallel X-rays incident on the steel sheet. Strain evaluation method. 3. The strain evaluation method for a grain-oriented electrical steel sheet according to claim 1, wherein the axis of rotation when measuring the diffraction strength curve is the rolling direction of the steel sheet.