JPH05288706A - Monitoring system of defect of metal member - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a defect monitoring system capable of highly accurately detecting both crack generation and temperature rise of a metal member. [Structure] A voltage is supplied from a high frequency power source 2 to the point P ₀ of the metal member 1 with at least two different frequencies, and a plurality of measurement points P _i (i = 1, 2, ...) Are supplied to the phase difference measuring device 33.
Amplitude ratio measuring device 3 which measures the phase difference between voltage and current at
At 4, the amplitude ratio between the voltage amplitude and the current amplitude at point P _i is measured. Based on the phase difference from the phase difference measuring device 33, the crack determining device 35 determines the presence or absence of a crack between the points P ₀ and P _i and the size thereof. In the temperature determining device 36, the R component due to the crack between the points P ₀ and P _i is determined based on the phase difference for each frequency from the phase difference measuring device, and the point P is determined based on the amplitude ratio from the amplitude ratio measuring device. _The temperature-dependent R component is determined by obtaining the difference between the measured R component and the crack-dependent R component between ₀ and P _i ,
Based on this, the temperature between points P ₀ and P _i is determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nondestructive defect detection system for monitoring abnormalities of metal members, and more particularly, for monitoring the occurrence of cracks and abnormal temperature rise due to fatigue of metal members in a furnace body such as a converter. Defect detection system.

[0002]

2. Description of the Related Art As a device for detecting cracks nondestructively, a crack is detected by supplying an electric current to a subject (metal member or a metal member coated with a non-conductive film) and detecting a potential difference caused thereby. A so-called 4-terminal method has been proposed (Japanese Patent Laid-Open No. 2-293657).
(See Japanese Patent Laid-Open No. 2-122753). In this method, crack detection is configured based on the change in the electrical resistance of the subject due to the occurrence of cracks.

Further, as a device for detecting the temperature of a metal member, a device for detecting the temperature by a four-terminal method in which a current is supplied to the metal member to detect a potential difference (Japanese Patent Laid-Open No. 56-12542).
(See Japanese Patent Laid-Open Publication No. JP-A-51-242), which detects temperature by measuring the change in impedance of a coil wound around a metal member (JP-A-51)
-78377 and 54-88293) are proposed.

[0004]

In all of the above-mentioned conventional techniques, only one of crack detection and temperature detection can be detected, but neither of them can be detected. Further, in crack detection, the temperature at the time of detection becomes a large error factor and becomes a factor that hinders the quantification of cracks.On the other hand, in temperature detection, the presence of cracks or the like in the metal member also causes impedance. Since the components change, there is a problem that an error occurs in the detected temperature depending on the surface condition such as cracks.

Therefore, it is awaited that a system capable of both crack detection and temperature detection of a metal member can be obtained by the same system, and that a highly accurate detection result can be obtained by eliminating each detection error. Was there.

Therefore, an object of the present invention is to provide a defect detection system capable of detecting both crack generation and temperature rise of a metal member with high accuracy.

[0007]

In order to achieve the above-mentioned object, in the defect monitoring system of the present invention, (a) a high frequency power source for supplying a voltage by switching a frequency to a metal member in a plurality of ways, and (b) Phase difference measuring means for comparing the voltage phase and the current phase at a plurality of measurement points of the metal member and measuring the phase difference in each case where the frequency of the power source is switched to a plurality of ways, and (c) the metal member. The amplitude ratio measuring means for comparing the voltage amplitude and the current amplitude at a plurality of measurement points of (1) to measure the amplitude ratio, which is the value of the ratio, and (d) the phase difference obtained by the phase difference measuring means. Based on
Based on the phase difference obtained by (e) the phase difference measuring means, a crack judging means for judging the presence or absence of a crack and its size between the power supplying point and each measuring point, and the power supplying point and each measuring point. While determining the L and C components between and, based on the amplitude ratio obtained by the amplitude ratio measuring means, to determine the total R component between the above, further, by referring to the crack pattern table stored in advance, The crack dependent R component is determined based on the obtained L and C components, the difference between the total R component and the crack dependent R component is calculated to determine the temperature dependent R component, and based on that, the power supply point and each The present invention is characterized in that it is composed of a temperature judging means for judging the temperature between the measuring point and the crack, the size thereof, and the temperature of the metal member with high accuracy.

[0008]

FIG. 1 is a block diagram of an embodiment in which the present invention is applied to the defect monitoring of a converter, in which 1 is a test object which is the iron shell of the converter and 2 is a signal transmitting side. And a variable high frequency power supply for supplying one end of the power supply to the point P ₀ of the subject 1,
3 is a signal receiving side, and the measurement point P _i of the subject 1 (i =
1, 2, ..., N) are sequentially switched to connect the other end of the power supply, and the crack / temperature detection unit that performs crack detection and temperature detection based on the signal at that time is used to estimate the life of the converter. The converter life estimation unit 5 is an alarm generation unit.

The crack / temperature detecting section 3 includes a cable compensator 31 for impedance matching between the cables connected to P _i at each measurement point of the subject 1, a waveform shaper 32 for removing noise, and a supply. Based on the information from the phase difference measuring device 33 that measures the phase difference between the voltage and the current of the power source, the amplitude ratio measuring device 34 that measures the voltage amplitude ratio of the power source, the presence or absence of cracks and the size (length) A crack determiner 35 for determining temperature, width, and depth), and a temperature determiner 36 for determining temperature based on information from the measuring devices 33 and 34.

Before describing the operation of the above embodiment in detail,
The principle of the present invention will be described with reference to FIGS.

When the subject 1 which is a metal member is healthy (for example, when new), as shown in FIG. 2A, a common point of high frequency power supply (frequency f ₀ , voltage) is established at a point P ₀ on the surface of the subject. V ₀ , phase ψ ₀ ) is connected, the other end is sequentially switched to each of the measurement points P _{1 to} P ₄ , a current is passed, and the healthy voltage and phase detected at each of the measurement points P _{1 to} P ₄ are represented by ( V ₁ , ψ ₁ ) to (V ₄ ,
ψ ₄ ).

As the usage period of the subject 1 becomes longer,
Although a high temperature may locally occur or a crack may occur, for example, it is assumed that the crack Q and the high temperature portion H occur at the position shown in FIG. 2B. In such a state, the high frequency power source (f ₀ , V ₀ , ψ ₀ ) is applied to the point P ₀ as described above.
Is supplied to detect the voltage and phase at each of the measurement points P _{1 to} P ₄ . Make each detection result healthy (')
Shall be attached.

When the temperature of the subject 1 becomes high, the electric conductivity σ becomes small [especially when the temperature is higher than a predetermined temperature, σ∝1 /
There is a relation of T ⁴ (T is temperature)], so that the electric resistance becomes small. In the case of FIG. 2B, the high temperature portion H is at the power supply point P.
Since it is sandwiched between ₀ and the measurement point P ₂ , the voltage V ₂ ′ at the measurement point P ₂ becomes smaller than the voltage V ₂ at the normal time,
The voltage swing ratio V ₂ '/ V ₂ can be considered as a function of temperature.

On the other hand, even if the material is heated to a high temperature, the reactance components L and C are hardly affected, and the phase ψ hardly changes. Therefore, in the signal at the measurement point P ₂ , ψ ₂ = ψ ₂ ′.

As is clear from the above, by monitoring the voltage amplitude V at each measuring point, the temperature between the transmitting side, that is, the high frequency power supply point and the receiving side, that is, each measuring point can be known.

When a crack is formed, the impedance components R, L and C generally change greatly,
Among them, the C component changes particularly greatly, so that the change of the phase ψ becomes large. In the case of FIG. 2B, the crack Q is sandwiched between the power supply point P ₀ and the measurement point P ₁ , so the measurement point P
Signal phase [psi ₁ 'in _1, varies greatly from the phase [psi ₁ during normal.

Therefore, by monitoring the change in phase at each measurement point, it is possible to know whether or not a crack has occurred.

By the way, when a crack occurs, the resistance component of that portion also changes greatly as described above.
The detection voltage at the measurement point also changes. That is, the change in voltage at the measurement point is the sum of the one that depends on the temperature and the one that depends on the occurrence of cracks. Therefore, simply monitoring the voltage causes an error in the temperature determination.

Therefore, in the present invention, the frequency f ₀ of the power supply is changed for temperature detection, the actually measured R, L, C components are determined from the information obtained at the measurement points for each frequency, and the obtained L and C are obtained. From the components, the crack pattern table is referred to detect the crack-dependent R component that depends only on the crack, and the temperature is detected based on the crack-dependent R component and the actually measured R component.

That is, when the L component and the C component are obtained, various crack patterns (type of crack, depth, length,
The crack-dependent R component is determined by the crack pattern table (see FIG. 3) that is preset and stored based on the (width), and the difference between this R component and the measured R component obtained from the measurement result at the measurement point is calculated. By doing so, a temperature-dependent R component that is irrelevant to cracks and that depends only on temperature can be obtained. The temperature is determined based on this temperature-dependent R component.

Thus, the crack generation and the temperature rise can be detected at the same time without any error.

Returning to FIG. 1, the operation of the embodiment of the present invention will be described.

A predetermined frequency f ₀ , voltage V ₀ , and phase ψ ₀ are supplied from the high-frequency power source 2 to a point P ₀ of the subject 1, and each measurement point P _i (i = 1, 2) from the point P _0. , ..., N), a current flows. The signal from each measurement point is supplied to the phase difference measuring device 33 and the amplitude ratio measuring device 34 via the cable compensator 31 and the waveform shaper 32.

The high frequency power source 2 is also connected to the measuring devices 33 and 34, and the phase difference measuring device 33 causes the phase ψ _i of the signal at each measuring point to be changed when the power source frequency is changed in plural ways. 'Is detected, and the result is supplied to the crack determiner 35 and the temperature determiner 36. Further, the amplitude ratio measuring device 34 also measures the detection voltage V _i ′ and the detection current A _i ′ for each frequency, and the result is the temperature determination device 36.
Entered in.

The crack determiner 35 detects whether or not a crack has occurred between the power supply point P ₀ and each measurement point P _i based on the input phase difference (ψ _i −ψ ₀ ). Furthermore, the size (length, width, depth) of the crack that has occurred is estimated. In this case, the estimation is executed in consideration of the normal phase. The crack information from the determiner 35 is supplied to the furnace life estimator 4.

In the temperature determiner 36, the reactance component between the power supply point P ₀ and each measurement point P _i is calculated based on the phase difference (for each power supply frequency) input from the phase difference measuring device 33. , I.e., determining the L and C components,
The resistance component, that is, the actually measured R component is determined based on the amplitude ratio (V _i '/ V ₀ ) from the amplitude ratio measuring device 34. And
The crack-dependent R component is determined from the obtained L and C components by referring to the crack pattern table. After that, the determiner 36
Determines the temperature-dependent R component by subtracting the crack-dependent R component from the measured R component, and based on that, estimates the temperature between the power supply point P ₀ and each measurement point P _i . This temperature information is supplied to the furnace life estimator 4.

In the furnace life estimator 4, the decision devices 35 and 36 are used.
The life of the converter is estimated based on the crack information and the temperature information from, and when it is determined that there is an unacceptable level of crack or temperature rise, the alarm device 5 issues an alarm.

The results of an experiment using another embodiment having such a configuration will be described.

As shown in FIG. 4, the subject 1 which is a steel plate.
In addition, four kinds of cracks K _{1 to} K ₄ are artificially formed by electric discharge machining, and high-frequency power sources 2 ₁ to 2 ₄ having a current source configuration are connected to the points P _{1 to} P ₅ on the surface of the subject and the detection unit. 3 _{1 to} 3 ₄ were connected. The distance between each point was 100 mm, and a crack was formed in the middle. The length l, width w, and depth d of the crack used in the experiment are as follows (represented by l × w × d,
Units are mm): Case 1 (only the length is changed) K ₁ ; 5 × 0.1 × 0.5 K ₂ ; 10 × 0.1 × 0.5 K ₃ ; 50 × 0.1 × 0. 5 K ₄ ; 100 × 0.1 × 0.5 Case 2 (only the width is changed) K ₁ ; 50 × 0.1 × 0.5 K ₂ ; 50 × 0.2 × 0.5 K ₃ ; 50 × 1.0 × 0.5 K ₄ ; 50 × 2.0 × 0.5 Case 3 (only the depth is changed) K ₁ ; 50 × 0.1 × 0.5 K ₂ ; 50 × 0.1 × 1 0.0 K ₃ ; 50 × 0.1 × 2.0 K ₄ ; 50 × 0.1 × 5.0 Further, such a steel plate is heated from the lower surface by a burner for 10 minutes after the temperature reaches a target value. It was held and various measurements were performed.

The results of these measurements are shown in FIGS.

FIG. 5 shows that, with respect to the crack of K ₂ in case 1 described above, the power supply frequency was changed and the temperature target value was 25 ° C.
The results of measuring the voltage amplitude ratio are shown at 100 ° C. and 300 ° C. The k / attenuation ratio at a frequency of 50 KHz and a temperature of 25 ° C. was set to “1”.

FIG. 6 shows the results of measuring the phase difference in each of the above cases 1 to 3 using a 50 KHz current source and a constant temperature.

From FIG. 5, the frequency of the current source is 50 to 70K.
It can be seen that the amplitude ratio greatly changes depending on the temperature in the range of Hz. Basically, the higher the frequency for crack measurement, the higher the accuracy, and the lower the frequency for temperature measurement, the higher the accuracy. It is appropriate to use. However, since the detection of the phase difference is delicate, it is considered better to use the highest possible frequency.

The cable compensator 31 in the embodiment shown in FIG. 1 is not necessary if the above-mentioned arrangement is adopted, that is, if the power supply line and the measurement line are separate and have the same terminal pair.

[0035]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to detect cracks in metal body members of various kinds and their sizes, and to detect the temperature with the same system, not limited to the iron shell of the converter. In addition, it is possible to eliminate mutual interference and obtain a detection result with less error. Therefore, it is possible to monitor the occurrence of cracks in the metal member subjected to the heat load and the defects due to the temperature rise with high accuracy, and it can be used for abnormality diagnosis.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining the principle of the present invention.

FIG. 3 is an explanatory diagram showing a crack pattern table used in the present invention.

FIG. 4 is an explanatory diagram for explaining another embodiment of the present invention and an experiment using the embodiment.

5 is obtained as a result of an experiment using the embodiment of FIG.
6 is a graph showing an amplitude ratio related to temperature and power supply frequency.

6 is obtained as a result of an experiment using the embodiment of FIG.
It is a graph which shows the phase difference related to the size of a crack.

Claims (2)

[Claims] 1. In a defect detection system for detecting an abnormality of a metal member, a high frequency power supply for supplying a current to the metal member by switching a plurality of frequencies, and a phase difference for measuring a phase between a voltage and a current of the power supply. Measuring means, amplitude measuring means for measuring the magnitude of the amplitude of the current and voltage of the power supply, L component and C component are obtained from the phase difference obtained by the phase difference measuring means, and the L component A crack determination unit that determines the presence or absence of a crack in the metal member between the power supply points based on the C component, and determines the size of the crack from the amount of change between the L component and the C component for each frequency, and the amplitude measurement unit. A temperature determination means for determining the R component from the obtained current value and voltage value, correcting the R component based on the size of the crack previously determined, and determining the temperature of the metal member. Defect detection and monitoring system for metal parts Temu. 2. A defect detection system for detecting an abnormality of a metal member, wherein a plurality of measuring ends are connected to the surface of the metal member at intervals.
The defect detection and monitoring system for a metal member, wherein the measurement system according to claim 1 is connected through a switch for switching a pair of combinations of the measurement ends.