JP2013185902A - Method and device for measuring crystal orientation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for measuring a crystal orientation, which can easily measure the crystal orientation of a coarse crystal grain of a grain-oriented electrical steel sheet in production in a short period.SOLUTION: A controller 4 simultaneously applies both a DC magnetic field A and an AC magnetic field including a component B orthogonal to the DC magnetic field to a steel sheet 5, measures an output signal proportional to the magnitude of internal energy of the steel sheet 5, and calculates a crystal orientation of the steel sheet 5 on the basis of a measured value of the output signal. Therefore, the crystal orientation of a coarse crystal grain of a grain-oriented electrical steel sheet in production can be easily measured in a short period.

Description

  The present invention relates to a crystal orientation measuring method and a crystal orientation measuring apparatus for nondestructively measuring the crystal orientation of crystal grains of a steel sheet.

  The crystal orientation and texture of the crystal grains of the steel sheet are important indicators of product characteristics. In general, the measurement of crystal orientation is performed using a diffraction phenomenon, focusing on the fact that atoms are regularly arranged. Examples of the crystal orientation measurement method include X-ray pole figure method using X-ray diffraction phenomenon, X-ray Laue method, Kossel line method using characteristic X-ray by electron beam, and backscattered electron beam using electron beam A diffraction method (EBSD) or the like is known. In these measurement methods, the crystal orientation is measured from the direction of diffraction satisfying the Bragg diffraction condition with the lattice spacing of crystal grains being known.

  In general, X-ray diffraction and X-ray Laue methods measure an area of several millimeters, whereas TEM / A is a measurement method that analyzes and measures Kikuchi lines observed with an EBSD or a transmission electron microscope (TEM). In the Kikuchi line method, a region of several nm can be measured. Therefore, EBSD and the TEM / Kikuchi line method are used for analysis of textures caused by plastic deformation of metals.

  A micro facet pit method is known as a method for measuring crystal orientation without using a diffraction phenomenon. This micro facet pit method makes use of the fact that the corrosion rate varies depending on the crystal orientation, and corrodes the crystal grains under appropriate conditions to create corrosion holes composed of specific crystal planes and observe the direction. Thus, the crystal orientation is measured.

  By the way, the grain-oriented electrical steel sheet has coarse crystal grains of about several millimeters to several centimeters and exhibits a special crystal orientation called a GOSS orientation. Since the GOSS orientation is excellent in magnetic properties, control of the crystal orientation of the grain-oriented electrical steel sheet is important in determining the product characteristics. Therefore, a technique for measuring the crystal orientation in a non-destructive manner during production (online) of a grain-oriented electrical steel sheet is desired.

  Patent Document 1 describes a technique for measuring a change in crystal orientation of a grain-oriented electrical steel sheet using ultrasonic waves. In this method, an ultrasonic burst wave is incident and subjected to multiple reflection, thereby detecting a change in sound velocity due to a change in crystal orientation and detecting a degree of deviation from the target crystal orientation. Patent Document 2 describes a technique for discriminating a secondary recrystallization failure portion and a healthy portion of a grain-oriented electrical steel sheet using magnetism. These techniques measure a region of several mm to several cm, and it is difficult to measure a region of several μm. Therefore, it is necessary to limit an application, for example, when detecting a defective portion of a crystal orientation of a grain-oriented electrical steel sheet.

Japanese Patent Laid-Open No. 1-229962 JP 2010-54254 A

  Measurement of crystal orientation using the diffraction phenomenon is highly accurate but takes time and cost. For example, the time taken per measurement point is about 30 minutes for the X-ray Laue method and about 15 minutes for the Kossel pattern method. In general, the diffraction pattern obtained as a result of the measurement is analyzed by a computer, but there is a possibility that the accuracy may be deteriorated due to an error factor such as an incident direction.

  In this respect, the EBSD method has improved the time and accuracy required with the recent improvement in computer performance, but the problem remains that the apparatus is expensive and large. Moreover, since the EBSD method irradiates the measurement object with an electron beam, measurement in a vacuum is indispensable, and it is difficult to use a directional electrical steel sheet that is traveling during manufacture as the measurement object.

  In the EBSD method and the TEM / Kikuchi method, a sample of several mm square to several cm square is usually taken, the surface is polished, and measurement is performed in a vacuum. Therefore, the EBSD method and the TEM / Kikuchi method substantially measure the measurement object while destroying the measurement object.

  Although measurement using ultrasonic waves, including the technique described in Patent Document 1, is performed nondestructively, it is extremely sensitive to changes in the plate thickness and the inclination of the measurement object, and quantitative measurement of crystal orientation is not possible. Have difficulty. Further, according to the technique described in Patent Document 2, although it is possible to measure the presence / absence of a crystal orientation deviation from the reference rolling direction, it is difficult to quantitatively measure the deviation amount.

  Furthermore, since the crystal orientation of the grain-oriented electrical steel sheet and the iron loss are strongly related to each other, it is possible to estimate the crystal orientation by measuring the iron loss. However, since there are many factors affecting the iron loss in addition to the crystal orientation, the crystal orientation cannot be estimated by measuring the iron loss alone.

  The present invention has been made in view of the above, and provides a crystal orientation measuring method and a crystal orientation measuring apparatus that can easily and quickly measure the crystal orientation of coarse crystal grains of a grain-oriented electrical steel sheet being manufactured. The purpose is to do.

  In order to solve the above-described problems and achieve the object, the crystal orientation measurement method according to the present invention applies a DC magnetic field and an AC magnetic field containing a component orthogonal to the DC magnetic field to the steel sheet at the same time, Measuring the output signal proportional to the magnitude of the internal energy of the steel sheet, and calculating the crystal orientation of the steel sheet based on the measured value of the output signal.

  Further, the crystal orientation measuring method according to the present invention is based on the above-mentioned invention, the step of rotating the steel sheet with respect to the direction of the DC magnetic field and storing the output signal for each rotation angle, and the output for each rotation angle. And a step of calculating a specific crystal orientation.

  The crystal orientation measuring method according to the present invention is characterized in that, in the above invention, the specific crystal orientation is a direction of an easy axis of magnetization of a steel plate and a direction of a hard axis of magnetization.

  Further, the crystal orientation measuring apparatus according to the present invention simultaneously applies a DC magnetic field and an AC magnetic field including a component orthogonal to the DC magnetic field to the steel sheet, and outputs an output signal proportional to the magnitude of the internal energy of the steel sheet. And means for measuring and means for calculating the crystal orientation of the steel sheet based on the measured value of the output signal.

  According to the present invention, the crystal orientation of coarse crystal grains of a grain-oriented electrical steel sheet can be measured easily and in a short time.

FIG. 1 is a perspective view showing a schematic configuration of a crystal orientation measuring apparatus according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the principle of the present invention. FIG. 3 is a flowchart showing the crystal orientation measurement processing procedure of the present embodiment. FIG. 4 is a diagram for explaining the crystal orientation measurement processing of the present embodiment. FIG. 5 is a diagram for explaining the crystal orientation measurement processing of the present embodiment. FIG. 6 is a diagram showing the results of the crystal orientation measurement process of the present embodiment. FIG. 7 is a diagram showing a result of comparison between the crystal orientation measurement method of the present embodiment and the EBSD method.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. Moreover, in description of drawing, the same code | symbol is attached | subjected and shown to the same part.

  First, a schematic configuration of the crystal orientation measuring apparatus 1 of the present embodiment will be described with reference to FIG. As shown in FIG. 1, the crystal orientation measuring device 1 includes an AC magnetizing device 2, a DC electromagnet 3, and a control device 4. The AC magnetizing apparatus 2 is configured by winding an excitation coil 22 and a detection coil 23 around a U-shaped core 21 such as a ferrite or electromagnetic steel sheet laminated core. The AC magnetizing device 2 and the DC electromagnet 3 are arranged close to the steel plate 5 so that the AC magnetic field generated by the AC magnetizing device 2 has a component B orthogonal to the DC magnetic field A generated by the DC electromagnet 3. The control device 4 is realized using a memory that stores a processing program and the like, a CPU that executes the processing program, and the like, and controls the AC magnetizing device 2 and the DC electromagnet 3 to execute a crystal orientation measurement process described later.

  In the present embodiment, the DC electromagnet 3 is disposed outside the AC magnetizing device 2, but the present invention is not limited to this. The AC magnetizing device 2 and the DC electromagnet 3 may be opposed to each other with the steel plate 5 interposed therebetween. Further, the core 21 of the AC magnetizing apparatus 2 may be I-type or E-type. The excitation coil 22 and the detection coil 23 may be wound around different cores 21. The DC electromagnet 3 may be a permanent magnet.

  Here, with reference to FIG. 2, the principle of the crystal orientation measurement process of the present embodiment will be described. Ferromagnetic crystals such as grain-oriented electrical steel sheets are easily magnetized depending on the crystal orientation. The direction that is easy to magnetize is called the easy axis of magnetization, and this is the [100] direction in the case of a cubic crystal such as iron. The direction of spontaneous magnetization when no external magnetic field is applied is the direction x1 of the easy magnetization axis. On the other hand, the direction in which magnetization is difficult is called a magnetization difficult axis, and in iron, the [111] direction corresponds to this. The angle formed by the [100] direction and the [111] direction is 54.7 °. That is, for iron, the angle formed by the direction x1 of the easy axis and the direction x2 of the hard axis is 54.7 °.

  When a DC magnetic field is applied to such a ferromagnetic crystal, the magnetization direction of the crystal becomes a direction obtained by combining the direction A of the external magnetic field (DC magnetic field) and the direction of spontaneous magnetization, and the internal energy of the crystal changes. When the direction A of the direct current magnetic field coincides with the direction of spontaneous magnetization, that is, the direction x1 of the easy axis, the internal energy becomes minimum, and when the direction A of the direct current magnetic field coincides with the direction of the hard axis x2, the internal energy becomes It becomes maximum.

  Next, when a DC magnetic field A and an AC magnetic field having a component B orthogonal to the DC magnetic field are applied to such a ferromagnetic crystal, the direction of the external magnetic field received by the crystal is the direction of the DC magnetic field A and the AC magnetic field. It becomes a vector sum with the direction and fluctuates by an alternating magnetic field. At that time, the stability (internal energy) of the magnetization of the crystal changes depending on the relationship between the crystal orientation and the direction of the DC magnetic field. When the direction X of the DC magnetic field coincides with the direction x1 of the easy axis, the internal energy becomes minimum, and the stability of the magnetization of the crystal is increased. On the other hand, when the direction A of the direct current magnetic field coincides with the direction x2 of the hard axis, the internal energy becomes maximum, and the stability of magnetization of the crystal is lowered. Therefore, in the present embodiment, the stability of the magnetization of the crystal due to the change in the external magnetic field is detected as an electric signal, and the crystal orientation is calculated based on this.

  Hereinafter, the crystal orientation measurement processing procedure by the crystal orientation measuring apparatus 1 will be described with reference to the flowchart of FIG. The flowchart in FIG. 3 starts, for example, at a timing when an instruction input for crystal orientation measurement is input by the operator, and the crystal orientation measurement processing proceeds to processing in step S1.

  In the process of step S <b> 1, the control device 4 energizes the AC magnetizing device 2 and the DC electromagnet 3, and applies a DC magnetic field and an AC magnetic field to the steel plate 5 simultaneously. The alternating magnetic field applied at this time includes a component orthogonal to the direct magnetic field. Thereby, the process of step S1 is completed and the crystal orientation measurement process proceeds to the process of step S2.

  In the process of step S2, the control device 4 acquires the output signal of the detection coil 23 and stores it in the memory. At this time, as shown in FIG. 4, the control device 4 rotates the steel plate 5 in the direction of the arrow C while bringing the steel plate 5 close to the AC magnetizing device 2 and the DC electromagnet 3, and measures the output signal acquired at every predetermined angle. Store as a value. The control device 4 performs an effective value process or an amplitude calculation process on the output signal to obtain a measured value. In addition, this output signal is proportional to the magnitude | size of the internal energy of the steel plate 5 by an external magnetic field and spontaneous magnetization. Thereby, the process of step S2 is completed, and the crystal orientation measurement process proceeds to the process of step S3. In the process of step S2, the steel plate 5 may be fixed and the AC magnetizing device 2 and the DC electromagnet 3 may be rotated.

  In the process of step S3, the control device 4 acquires information on the angle at which the measured value stored in the memory is maximized. Thereby, the process of step S3 is completed, and the crystal orientation measurement process proceeds to the process of step S4.

  FIG. 5 shows measured values of output signals for each rotation angle with respect to the AC magnetizing apparatus 2 and the DC electromagnet 3 of the steel plate 5 obtained according to the present embodiment. The case where the rolling direction of the steel plate 5 and the direction A of the DC magnetic field coincide with each other is defined as 0 °. Here, the steel plate 5 is manufactured so that the rolling direction and the easy magnetization axis direction substantially coincide with each other by component adjustment or recrystallization treatment in the manufacturing process. Therefore, the direction of the easy axis is approximately 0 °. As shown in FIG. 5, the measured value is minimal in the direction of the easy axis of magnetization. In addition, the angle at which the measured value is maximum is the direction of the hard axis.

  In the process of step S4, the control device 4 calculates the direction of the hard magnetization axis and the direction of the easy magnetization axis based on the angle at which the measurement value acquired in step S3 is maximized. As described above, the angle at which the measured value is maximized is the direction of the hard axis. Further, the direction of the easy magnetization axis that forms an angle of 54.7 ° with the hard magnetization axis can be calculated from the direction of the hard magnetization axis. Thereby, the process of step S4 is completed and a series of crystal orientation measurement processes are complete | finished.

  If the angle at which the measured value is minimized in FIG. 5 can be specified, this may be used as the direction of the easy magnetization axis. Further, the direction of 54.7 ° from the direction of the specified easy axis of magnetization may be the direction of the hard axis of magnetization.

  The degree of freedom of measurement in the crystal orientation measurement process of the present embodiment is limited to the plane of the steel plate 5, and the measured crystal orientation is a projection of the easy axis or the hard axis to the plane of the steel plate. However, since the vertical crystal orientation of the steel sheet is determined by the manufacturing process and rarely changes greatly, the projection onto the plane of the steel sheet is sufficient.

  As described above, according to the crystal orientation measuring apparatus 1 of the present embodiment, the crystal orientation of coarse crystal grains of the grain-oriented electrical steel sheet being manufactured can be simplified simply by simultaneously applying a DC magnetic field and an AC magnetic field. And it can be measured in a short time.

  Further, the above embodiment is merely an example for carrying out the present invention, and the present invention is not limited to these, and various modifications according to specifications and the like are within the scope of the present invention. It is obvious from the above description that various other embodiments are possible within the scope of the present invention.

(Example)
In this example, the crystal orientation of the secondary recrystallized grains of the grain-oriented electrical steel sheet was measured. The grain-oriented electrical steel sheet to be measured has a polycrystalline structure with a crystal diameter of about several mm to 2 cm, and the plate thickness is about 0.3 mm. The AC magnetizing apparatus 2 used was 5 mm in the longitudinal direction and 10 mm in the width direction so that the crystal orientation of each crystal grain could be measured. The excitation frequency of the excitation coil 22 of the AC magnetizing apparatus 2 was 100 to 10 kHz. This excitation frequency is appropriately changed depending on the impedance of the exciting coil 22 and the thickness of the measurement target.

  If the excitation intensity of the DC electromagnet 3 is too strong, the fluctuation due to the AC magnetic field becomes relatively small, and the output difference between the hard axis and the easy axis decreases. On the other hand, if the excitation intensity of the DC electromagnet 3 is too weak, the behavior becomes unstable with respect to a change in angle. Therefore, the excitation intensity of the excitation coil 22 of the AC magnetizing apparatus 2 and the excitation intensity ratio between the AC magnetizing apparatus 2 and the DC electromagnet 3 are set to optimum values by experiments according to the measurement object.

  FIG. 6 shows the results of measuring the seven crystal grains of the grain-oriented electrical steel sheet to be measured with the rolling direction set to 0 °. As shown in FIG. 6, the maximum is in the vicinity of 54.7 ° which is the direction of the hard axis ([111] direction) as a whole, but the maximum angle is different for each crystal grain. It can be seen that the crystal orientations of the individual crystal grains are slightly shifted. This shift is considered to be caused by the manufacturing process.

  FIG. 7 shows the result of comparing the crystal orientation measurement method of the present embodiment with the EBSD method. With respect to the crystal grains of the grain-oriented electrical steel sheet to be measured, the angle formed by the rolling direction and the direction of the easy axis ([100] direction) is calculated and compared by each method. As shown in FIG. 7, the difference between the results of the two methods is within 2 °, which indicates that the crystal orientation measurement method of the present embodiment is effective.

DESCRIPTION OF SYMBOLS 1 Crystal orientation measuring apparatus 2 AC magnetizing apparatus 21 Core 22 Excitation coil 23 Detection coil 3 DC electromagnet 4 Control apparatus 5 Steel plate

Claims (4)

Applying a direct-current magnetic field and an alternating-current magnetic field containing a component orthogonal to the direct-current magnetic field to the steel sheet at the same time, and measuring an output signal proportional to the magnitude of the internal energy of the steel sheet;
Calculating the crystal orientation of the steel sheet based on the measured value of the output signal;
A crystal orientation measuring method comprising: Storing an output signal for each rotation angle by rotating the steel sheet relative to the direction of the DC magnetic field;
Calculating a specific crystal orientation based on the output for each rotation angle;
The crystal orientation measuring method according to claim 1, comprising:   The crystal orientation measuring method according to claim 2, wherein the specific crystal orientation is a direction of an easy axis of magnetization of a steel plate and a direction of a hard axis of magnetization. Means for simultaneously applying a DC magnetic field and an AC magnetic field containing a component orthogonal to the DC magnetic field to the steel sheet to measure an output signal proportional to the magnitude of the internal energy of the steel sheet;
Means for calculating the crystal orientation of the steel sheet based on the measured value of the output signal;
A crystal orientation measuring apparatus comprising:

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