JPH07103947A - Measuring apparatus for crystal grain - Google Patents

Abstract

PURPOSE:To detect an abnormality with high accuracy irrespective of a fluctuation in a detected sheet thickness by a method wherein the flaw-detection frequency of ultrasonic waves is changed so as to obtain a resonance frequency according to the sheet thickness. CONSTITUTION:A personal computer 32 sets a flaw-detection reference frequency and a reference voltage according to coil information on an input sheet thickness or the like, and it sends them to a peak-frequency detection circuit 34 and a function generator 36. The generator 36 generates an electric signal at a frequency and a reference voltage which are set by a peak frequency detection circuit 34, and ultrasonic waves are incident on a steel plate 10 by the use of transmission probe 22A and they are received by a reception probe 22B. The received ultrasonic waves are input to a gate peak detector 42, and an abnormal particle is detected when the level of an extracted peak voltage is at a prescribed value or lower. At this time, a flaw-detection frequency shift circuit 44 shifts a flaw-detection frequency when an input peak voltage has a shape corresponding to a normal part. Then, the circuit 34 changes the flaw-detection frequency on the basis of the relationship between a sheet thickness (d)[m] and a resonance frequency (f)[Hz] when a sheet-thickness fluctuation width is at DELTAd, it finds a peak frequency at which a sound pressure becomes maximum, and it sends the peak frequency to the generator 36. Thereby, it is possible to obtain the resonance frequency according to the sheet thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention sends and receives ultrasonic waves to and from a strip-shaped test material in which normal grains having a uniform crystal orientation and abnormal grains not having a uniform crystal orientation coexist, and the crystal orientation of each crystal in the test material is used. The difference in ultrasonic wave propagation speed is converted into the difference in amplitude by utilizing the resonance phenomenon due to multiple reflection interference in the test material, and the abnormal particles in the test material are detected from the amplitude attenuation when the abnormal particles occur. The present invention relates to a crystal grain measuring device for detecting, and more particularly, to a crystal grain measuring device which is suitable for use in detecting an abnormality in the crystal grain direction of a grain-oriented silicon steel sheet and does not cause an error due to plate thickness variation.

[0002]

2. Description of the Related Art Grained silicon steel sheets having excellent electromagnetic characteristics in the rolling direction have been manufactured for the purpose of application to a core of a step-up transformer for alternating current. In this grain-oriented silicon steel sheet, the secondary recrystallization orientation in the rolling direction is aligned with <100> (Goss orientation) to significantly improve the magnetism.

As the number of crystal grains closer to the Goss orientation increases,
Although it is a grain-oriented silicon steel sheet with excellent electromagnetic characteristics,
In the actual manufacturing process, it is not always possible to make only crystal grains close to the Goss orientation, and if secondary recrystallization is insufficient due to changes in manufacturing conditions or disturbance, crystal grains that are greatly deviated from the Goss orientation, so-called abnormal Grain is created,
The magnetic properties deteriorate and the quality fails.

FIG. 1 shows a schematic view of a product steel plate 10 having these abnormal grains 10A. Normal grain 10B close to Goss direction
Has a large grain size of several mm to several tens of mm, but in the abnormal grain 10A, the grain size is generally several mm or less, and the orientation of the crystal grains is random. As shown in FIG. Distributed over a long period of time.

As a device for detecting abnormal grains of such grain-oriented silicon steel sheet, the applicant has already disclosed in Japanese Patent Laid-Open No. 1-229962.
In No. 5, the difference in ultrasonic wave propagation velocity between normal grains and abnormal grains is converted into a difference in amplitude using the resonance phenomenon due to multiple reflection interference in the steel sheet, and the amplitude attenuation amount when abnormal grains occur We have proposed a crystal grain orientation distribution measuring device for grain-oriented silicon steel sheets that detects grains.

As shown in the principle of the transmission type in FIG. 2, this measuring apparatus uses resonance because the elastic coefficient differs depending on the crystal orientation and the ultrasonic propagation velocity in the plate thickness direction differs between normal grains and abnormal grains. Then, the difference in the propagation velocity is converted into the difference in the amplitude, and the abnormal particle is judged from the attenuation amount of the signal. That is, in the case of normal grains, the ultrasonic wave resonates under the resonance condition 2d = λ (d is the plate thickness, λ is the wavelength of the ultrasonic wave), and as shown in FIG. While ultrasonic waves with a large amplitude are incident on the ultrasonic probe 22B, the ultrasonic wave does not resonate at the site where abnormal particles are present, as shown in FIG. , The amplitude decreases, and this difference is used to detect abnormal grains. In FIG. 2, 22A is an ultrasonic probe on the transmission side.

Further, Japanese Patent Application Laid-Open No. 51-29187 also discloses a crystal grain size determination method for determining the size of crystal grains of a silicon steel sheet by ultrasonic waves.

With such a crystal grain measuring device, it is possible to perform nondestructive on-line measurement of abnormal grains of a silicon steel sheet.

[0009]

However, particularly in the case of the crystal grain measuring apparatus disclosed in the former Japanese Patent Laid-Open No. 1-229962, when the plate thickness d of the steel plate 10 changes, the wavelength λ of the ultrasonic wave remains constant. However, since the resonance condition is not satisfied and the signal level observed by the ultrasonic probe 22B on the receiving side is attenuated even with normal particles, it may be difficult to distinguish it from abnormal particles. Had.

The present invention has been made to solve the above-mentioned conventional problems, and can satisfy the resonance condition even if the plate thickness of the material to be tested changes, and therefore abnormal particles can be accurately detected. An object is to provide a crystal grain measuring device capable of detecting.

[0011]

According to the present invention, ultrasonic waves are transmitted and received to and from a test material in which normal grains having a uniform crystal orientation and abnormal grains having a non-uniform crystal orientation coexist, and the crystal orientation of each crystal in the test material is used. The difference in ultrasonic wave propagation speed is converted into the difference in amplitude by utilizing the resonance phenomenon due to multiple reflection interference in the test material, and the abnormal particles in the test material are detected from the amplitude attenuation when the abnormal particles occur. In the crystal grain measuring device for detecting, means for detecting the plate thickness of the test material,
The above object is achieved by providing a means for changing the flaw detection frequency of ultrasonic waves so that the resonance frequency can be obtained according to the detected plate thickness.

Further, the plate thickness detecting means uses the ultrasonic waves for detecting abnormal grains and detects the plate thickness from the ultrasonic wave propagation time in the test material.

Further, the plate thickness detecting means uses the ultrasonic wave for detecting abnormal particles, and the flaw detection frequency of the ultrasonic wave is changed in the normal portion to determine the peak frequency at which the peak level of the received signal becomes maximum. Then, the peak frequency is used as the flaw detection frequency.

[0014]

In the present invention, the plate thickness of the material to be tested is detected, and the resonance frequency is obtained according to the detected plate thickness.
Since the ultrasonic inspection frequency is dynamically changed, the resonance condition can always be satisfied even if the plate thickness changes. Therefore, the signal level in the normal portion is not attenuated by the change in the plate thickness, and the abnormal grain can be detected with high accuracy even if the plate thickness changes.

When the ultrasonic wave for detecting abnormal particles is used to detect the plate thickness from the ultrasonic wave propagation time in the test material, a separate plate thickness detecting means is unnecessary, The configuration is simple.

Similarly, an ultrasonic wave for detecting abnormal particles is used, and the flaw detection frequency of the ultrasonic wave is changed in the normal portion to obtain the peak frequency at which the peak level of the received signal is maximum,
When the peak frequency is used as the flaw detection frequency, it is possible to accurately detect and set the flaw detection frequency (resonance frequency) satisfying the resonance condition.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

This embodiment is constructed as shown in FIG. 3, and coil information such as plate thickness and width is supplied from a host process computer 30 to a personal computer (personal computer) 32 of a crystal grain measuring apparatus. The personal computer 32 is
A reference value of a flaw detection frequency (hereinafter referred to as a reference frequency) and an amplitude of a flaw detection signal (hereinafter referred to as a reference voltage) according to coil information provided from the host process computer 30.
And the length (referred to as coil length) of the steel plate 10 is measured from the amount of movement of the steel plate 10.

The flaw detection reference frequency and reference voltage set by the personal computer 32 are sent to the peak frequency detection circuit 34 and the function generator 36, respectively. The function generator 36 uses the frequency set from the peak frequency detection circuit 34,
Moreover, an electric signal having a reference voltage (amplitude) set by the personal computer 32 is generated and input to the transmission amplifier 38. The transmission amplifier 38 amplifies the output of the function generator 36, sends the output to the transmission probe 22, and makes the ultrasonic wave incident on the steel plate 10.

The ultrasonic wave transmitted through the steel plate 10 is received by the reception probe 22B, and is input to the gate peak detector 42 via the reception amplifier 40. This gate peak detector 4
In accordance with the level of the peak voltage extracted by separating the noise component and the like in 2, abnormal particles are detected when the level is below a predetermined value.

On the other hand, the peak voltage output from the gate peak detector 42 is input to the flaw detection frequency shift circuit 44. The flaw detection frequency shift circuit 44 is provided, for example, in the personal computer 3
2 operates according to the timing signal input from the data sampling timing determination circuit 46 at each predetermined sampling timing according to the coil length measured in 2,
When the peak voltage input from the gate peak detector 42 has a predetermined shape corresponding to the normal portion, the flaw detection frequency is shifted.

The peak frequency detection circuit 34 detects the peak level of the received signal from the waveform as shown in FIG. 4 when the flaw detection frequency shift circuit 44 shifts the flaw detection frequency f by, for example, the half width method. Detects the peak frequency at which is maximum. That is, the relationship between the plate thickness d (m) and the resonance frequency f (Hz) is expressed by the following formula based on the measurement principle.

F = v / 2d (1)

Here, v is the speed of sound (m / s) of ultrasonic waves.

Therefore, when the thickness variation width is Δd, the flaw detection frequency is changed within the following range, for example, every 0.1% of the set frequency, and the peak frequency at which the sound pressure is maximized is obtained.

Upper frequency limit fmax = v / 2 (d−Δd) (2) Lower frequency limit fmax = v / 2 (d + Δd) (3)

The detected peak frequency is set in the function generator 36 so that the peak frequency becomes the flaw detection frequency. A frequency upper / lower limit setting device 48 is connected to the peak frequency detection circuit 34, and the flaw detection frequency is
It is restricted so that it does not exceed the preset upper and lower limits.

The shift of the flaw detection frequency and the detection of the peak frequency are performed, for example, at a normal grain portion by installing a sensor on the looper entrance side of the coil line and stopping the line for each predetermined length or for each coil. You can When the probe is provided with a plurality of channels, it is more preferable to perform it for each channel.

In the present embodiment, ultrasonic waves for detecting abnormal grains are used, and the crystal grain measuring device is switched to a plate thickness meter at appropriate intervals to measure the resonance frequency in the normal portion. Since this is done, the measurement can always be performed at the frequency corresponding to the plate thickness.

The method of detecting the plate thickness d of the steel plate 10 and changing the flaw detection frequency of the ultrasonic wave so as to obtain the resonance frequency is not limited to this. For example, from the ultrasonic wave propagation time in the steel plate 10, It is also possible to detect the plate thickness and calculate and change the flaw detection frequency of the ultrasonic wave so as to satisfy the detection resonance condition according to the detected plate thickness. Further, the plate thickness detecting means is not limited to the one using ultrasonic waves.

Although ultrasonic waves transmitted through the steel plate are detected in the above embodiment, the receiving probe 22B is arranged on the same side as the transmitting probe 22A and is reflected by the bottom surface of the steel plate 10. It is obvious that the present invention can be similarly applied to the reflection type crystal grain measuring device for detecting the generated ultrasonic waves.

[0032]

As described above, according to the present invention,
Since the ultrasonic flaw detection frequency is changed according to the plate thickness variation, the resonance condition can always be satisfied, and highly accurate abnormal grain detection can be performed regardless of the plate thickness variation. In particular, by using both the crystal grain detection and the plate thickness measurement, there is a space saving effect in a continuous processing line and a significant reduction in equipment cost.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a silicon steel sheet containing abnormal grains, which is an example of a measurement target of the present invention.

FIG. 2 is a sectional view showing the measurement principle of crystal grains.

FIG. 3 is a block diagram showing a configuration of an embodiment of a crystal grain measuring device according to the present invention.

FIG. 4 is a diagram showing a peak frequency detecting method in the embodiment.

[Explanation of symbols]

 10 ... Steel plate 22A, 22B ... Ultrasonic probe 34 ... Peak frequency detection circuit 36 ... Function generator 42 ... Gate peak detector 44 ... Flaw detection frequency shift circuit 46 ... Data sampling timing determination circuit 48 ... Frequency upper / lower limit setting device

Claims (3)

[Claims] 1. An ultrasonic wave is transmitted to and received from a test material in which normal grains having a uniform crystal orientation and abnormal grains not having a uniform crystal orientation are mixed, and the difference in the ultrasonic wave propagation velocity due to the crystal orientation of each crystal in the test material is calculated. Converted to a difference in amplitude using the resonance phenomenon due to multiple reflection interference in the test material, from the amount of amplitude attenuation when abnormal particles occur, in the crystal grain measuring device to detect abnormal particles in the test material, A crystal grain characterized by comprising a means for detecting the plate thickness of the material to be inspected, and a means for changing the flaw detection frequency of the ultrasonic wave so that the resonance frequency can be obtained according to the detected plate thickness. measuring device. 2. The plate thickness detecting means according to claim 1,
A crystal grain measuring device for detecting a plate thickness from an ultrasonic wave propagation time in a test material by using the ultrasonic wave for detecting abnormal grains. 3. The plate thickness detecting means according to claim 1,
Using the ultrasonic wave for abnormal particle detection, by changing the flaw detection frequency of the ultrasonic wave in a normal part, the peak level of the peak level of the received signal is obtained, and the peak frequency is used as the flaw detection frequency. A crystal grain measuring device.