JPS63145902A - Eddy current type eccentricity measuring apparatus - Google Patents

Abstract

PURPOSE:To enable measurement of material to be inspected even at a high temperature, by electrically rotating a high frequency detection frequency using a rotary magnetic field caused by a low frequency to induce an eddy current. CONSTITUTION:A low frequency 3-phase AC from a 3-phase AC generator 2 is applied to balanced modulators 6a-6c to be modulated in balance by an output of a high frequency AC generator 5 and the results are applied into a rotary magnetic field generator 1 through respective phase amplifiers 7a-7c. An eddy current detection sensor 17 arranged on the inner wall of the generator 1 detects an eddy current generated around the radial direction of material to be inspected passed therethrough. One end of the sensor 17 is earthed while the other end thereof is connected to a phase detector 9 through an amplifier 8 to cancel the residual output thereof with a zero adjustment circuit 10. An output of a single-phase AC oscillator 3 phase shifted 11 is used as reference wave to phase defect 12 outputs produced subsequently. Thus, any material can be inspected only if it is conductive and the apparatus thus obtained is applicable to steel material with the magnetic property thereof lost at a high temperature or a nonmagnetic metal body.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an eccentricity measuring device using electromagnetic effects,
In particular, it relates to a device that instantaneously measures the eccentricity of a hot or cold cylindrical tube or round bar that moves in the longitudinal direction without contact.

[Conventional technology]

In eddy current flaw detection and ultrasonic flaw detection of pipes, round bars, etc., in order to perform accurate flaw detection, part of the detection sensor and the test material are aligned while the test material is moving in the longitudinal direction. This is very important.

For example, in the case of a small diameter pipe penetrating eddy current flaw detection device, the air gap (difference between the detection coil radius and the small diameter pipe radius) is usually 2 to 7.
However, in order to increase the reliability of flaw detection, for example to keep the sensitivity difference between the top, bottom, left and right sides of the bottom position within 3 dB, the amount of air gap variation should be approximately 1/10 of the air gap setting value. That is, it is necessary to align the center to 0.2 to 0.7 points.

In addition, in a rotating probe eddy current flaw detection device, the air gap setting value is 0.2 to 0.5 l, but ideally it is 1/20 of the air gap in order to reduce the difference in sensitivity between the top, bottom, left and right sides. , that is, it is preferable to align the centers to 10 to 25 μm.

To check the alignment accuracy of these flaw detection devices, in the case of penetrating eddy current flaw detection devices, inductive judgment is performed by investigating the reproducibility of flaw detection sensitivity, and in the case of rotary probe eddy current flaw detection devices, measurement is performed using a gap sensor.

It is also known to measure eccentricity using an ultrasonic sensor, as proposed in Japanese Patent Laid-Open No. 61-181908.

Furthermore, in the field of steel bars and wire rods, the establishment of "in-line high-performance controlled rolling" technology that controls cooling during rolling to create materials with various useful properties is becoming increasingly important.

Controlled rolling is performed by cooling troughs installed between rolling mills. Cooling in the cooling trough is performed by passing the material through the center of the trough and spraying water evenly from the circumferential direction of the material. If the material is eccentric in the trough, the cooling water will be applied unevenly, and the surface temperature of the material will vary around the circumference and in the direction, resulting in so-called cooling unevenness. For this reason, it is important to accurately align the material to the center of the trough. Conventionally, this centering has been carried out using numerical values determined from the nominal dimensions of the materials, and due to the low centering accuracy, the cooling unevenness has sometimes reached 50 to 80°C.

[Problem that the invention seeks to solve]

As mentioned above, there is no effective measuring method for checking the alignment accuracy with a penetrating eddy current flaw detector, and the gap sensor of a rotating probe eddy current flaw detector cannot confirm alignment accuracy (11. The error is large.

(2) If the gap between the material to be tested and the sensor becomes large, measurements cannot be made.

(3) Online monitoring of eccentricity and automatic processing of measurement data require complicated equipment.

There are drawbacks such as.

Furthermore, the method using an ultrasonic sensor has the problem that measurement cannot be performed when the material to be tested is at a high temperature. Furthermore, there is no effective means for measuring the alignment accuracy of cooling trough equipment, and eccentricity of several nanometers cannot be avoided.

An object of the present invention is to provide a device for measuring the amount of eccentricity in a moving state of a test material such as a hot or cold cylindrical tube or round bar moving in the longitudinal direction, which can also measure non-magnetic materials. The object of the present invention is to solve the above-mentioned problems and provide a simple eccentricity measuring device that is capable of constant measurement and monitoring, recording of measured values, and monitoring of eccentricity.

[Means for solving problems]

The present invention relates to a power supply circuit that outputs low-frequency multiphase alternating current that is balanced and modulated independently for each phase using high-frequency alternating current, and a hollow cylindrical rotating magnetic field that is excited by the low-frequency multiphase alternating current and passes through a test material. an eddy current detection sensor disposed in a ring shape in the circumferential direction along the cylindrical inner wall of the rotating magnetic field generator; a detector that detects the phase of the output voltage of the eddy current detection sensor using high-frequency alternating current; It is characterized by comprising a zero adjustment circuit that cancels the unbalanced output voltage of the detector from the detected output voltage, and a detector that performs phase detection of the output voltage of the zero adjustment circuit using low frequency alternating current. .

Hereinafter, the content of the present invention will be explained in detail based on the drawings.

FIG. 1 shows an embodiment of the present invention. In this figure, 1 is a rotating magnetic field generator, which has a winding 13. as shown in FIG. Iron core 1
4. Cylindrical outer support 15. has an inner insulating inner cylinder 16;
A ring-shaped eddy current detection sensor 17 is installed inside the inner insulating inner cylinder 16.
is accommodated. In this example, the winding 13 is composed of three sets of coils spaced apart by 2π/3, and is formed so as to be excited by low frequency three-phase alternating current to generate a rotating magnetic field.

The three-phase AC generator 2 is a single-phase low-frequency AC oscillator 3°240
It consists of a 120" phase shift circuit 4a and a 120" phase shift circuit 4b.
Generates phase current. The frequency used is 10-1.0OOHz
It is. These are applied to balanced modulators 6a, 6b, 5c and balanced modulated at a frequency of 10 to 1.000 KHz, which is much higher than the three-phase AC outputted by high frequency AC generator 5. These three-phase balanced modulated waves are applied to the rotating magnetic field generator 1 via the sum term width filters 7a, 7b, and 7C. In this way, the density distribution of the high frequency magnetic flux generated by the high frequency AC generator 5 rotates at a speed determined by the frequency of the low frequency three-phase AC.

The eddy current detection sensor 17 may be any sensor as long as it can detect eddy currents generated centering in the radial direction of the material to be tested. For example, as shown in FIG. It is formed from a wound coil,
It consists of two coils divided in the longitudinal direction of the material to be tested, and connected so that one winding direction is opposite to the other. A indicates the material to be tested.

As shown in FIG. 1, one end of the eddy current detection sensor 17 is grounded, and the other end is connected to the amplifier 8. The output of this amplifier is input to a phase detector 9, and phase-detected using the output of the high-frequency AC generator 5 as a reference wave. Ideally, the output voltage of the detection coil would be zero when there is no object to be detected, but in reality, due to the unevenness of the detection sensors, there is a residual output, which becomes noise, so this residual output signal is combined with the rotating magnetic field. This is canceled out by a zero adjustment circuit 10 that generates a sine wave with the same period and variable amplitude and phase. The output of this zero adjustment circuit is input to the phase detector eL device 12, and phase-detected using the output of the low-frequency AC oscillator 3 phase-shifted by the phase shift circuit 11 as a reference wave. The phase shift circuit 11 is connected to the eddy current detection sensor 1
It has a function of adjusting so that the moving direction of the material to be inspected in 7 and the output (v=β, 2 + , , 2 ) after the phase detector 12 are in the same direction on a two-dimensional plane.

FIG. 4 shows an example of eccentricity measurement by the apparatus of the present invention.

In this case, as shown in FIG. 4(a), a known test material is placed in advance, its radius is r, and the eccentricity is Δr.

Assuming that the direction of eccentricity is φ, the phase shift l-circuit 11 shown in FIG.
v = f)] 777 animals - 1 = v cosφ, ■y =
v sinφ) may be adjusted in the same direction.

As an example, the inner diameter of the eddy current detection sensor is 6011φ,
Test material non-magnetic stainless steel round steel (SU
A case in which the method is applied to step S304) will be described. The measured value (v V) of the amount of eccentricity is shown in Fig. 4(b). Similarly, the inner diameter of the detection sensor is 60φ, the amount of eccentricity is constant at 2.5111, and the outer diameter of the eddy current test material is 15. Crane φ, 20mmφ, 25
FIG. 4(C) shows the measured value (vV) when the voltage is changed to φ. From these results, the measured value (vV) and eccentricity (Δr
), the material to be tested (r) has a relationship of VOCΔr−r.

In other words, Δr −r cosφ■ y= Δr −r
It can be seen that it can be expressed as r −r sinφ. Therefore, the radius r of the material to be inspected is known, and by measuring vx and V with the device of the present invention, the amount of eccentricity (Δr) and the direction of eccentricity (φ) can be known. In addition, the frequency for generating the rotating magnetic field in this case is 60
Hz, and the high frequency alternating current used was 32 KHz. FIG. 5 is an output example of an eccentricity monitor configured using the device of the present invention, which allows the amount and direction of eccentricity to be output simply and continuously. In addition, this data is obtained by inserting a test material with an outer diameter of 15 φ into a detection sensor with an inner diameter of 60 φ, with an eccentricity of 511 mm, and changing the direction of eccentricity (φ) while maintaining an eccentricity of 5 φ. The output voltages vX and vy at each (φ) are changed from 0° to 360° at 10° intervals.

This was recorded directly with a Y recorder. B indicates the display point. In the above description of the present invention, it has been described that three-phase alternating current is used to generate a rotating magnetic field, but the present invention is not limited to this (it may be any polyphase alternating current that forms a rotating magnetic field).

〔Effect of the invention〕

As is clear from the above explanation, the eccentricity measuring device of the present invention utilizes electromagnetic effects, and the excitation magnetic field is electrically rotated and can be rotated at high speed. Furthermore, it is possible to easily construct a two-dimensional eccentricity monitor that can be measured even when the specimen is moved at high speed in the longitudinal direction and has good accuracy.

In the case of the present invention, the high-frequency detection frequency is electrically rotated by a rotating magnetic field caused by a low frequency, and the overcurrent induced by this is used, so the material to be tested is a conductive object. It can be used for steel materials and non-magnetic metal materials that have lost their magnetism at high temperatures.

The amount of eccentricity detected in this manner can be used for correcting misalignment of various flaw detection devices, and is useful for improving the precision of flaw detection performed online. It can also be used to correct misalignment in a cooling trough that performs online cooling in a rolling line.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a configuration example of the present invention, Fig. 2 is an explanation of a rotating magnetic field generator, (8) is an end view, and (8) is a side view.
FIG. 3 is an explanatory diagram of the detection sensor according to the present invention (al
4(a) is a front view, FIG. 4(b) is a side sectional view, FIG. (C) is a chart showing the output of the detection sensor in the example, and FIG. 5 is a chart showing an example of the output of the two-dimensional eccentric monitor. 1: Rotating magnetic field generator, 2: 3-phase AC generator, 3: Low frequency AC generator, 4a, 4b: Phase shift circuit, 5:
High frequency alternating current generator, 6a, 6b. 6C: Balanced modulator, ? a, 7b, 1c: each phase amplifier,
8: Amplifier, 9: Phase detector, 10: Zero decay circuit,
11: Phase shift circuit, 12: Phase detector, 13
: Winding, Work 4: Iron core, 15: Cylindrical outer support,
16; Inner insulation inner cylinder, 17: Eddy current detection sensor

Claims (1)

[Claims] A power supply circuit that outputs low-frequency multiphase alternating current that is balanced and modulated independently for each phase using high-frequency alternating current; a rotating magnetic field generator, an eddy current detection sensor disposed in a ring shape in the circumferential direction along the cylindrical inner wall of the rotating magnetic field generator, and a detector that detects the phase of the output voltage of the eddy current detection sensor using high frequency alternating current; It is characterized by comprising a zero adjustment circuit that cancels the unbalanced output voltage of the eddy current detection sensor from the phase detection output voltage, and a detector that performs phase detection of the output voltage of the zero adjustment circuit using low frequency alternating current. Eddy current eccentricity measuring device.