JPH0678905B2 - Clad material thickness measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an apparatus for measuring the thickness of a clad material using ultrasonic waves.

[Prior art]

The clad material has a laminated structure consisting of a base material made of different metals and a laminated material, and is used to increase the material strength, to withstand use in a special atmosphere, to be used as a corrosion allowance or lining allowance, etc. It is used for the purpose. Therefore, the thickness of the laminated material is an important factor in guaranteeing the performance as a clad material, and in order to measure this, development of a measuring device using eddy current by magnetic means or electromagnetic induction method has been attempted. .

By the way, in the magnetic thickness measuring device, it is useless when the mating material and the base material are both non-magnetic or magnetic, and the electromagnetic induction method cannot be applied to materials having the same electromagnetic properties. Also, there is a big drawback that the observation and measurement on the cut surface cannot be guaranteed as a whole.

Further, the total thickness, the base material thickness, and the laminated material thickness must be combined with the total thickness measurement by ultrasonic waves, and two types of measuring devices are required, and the cost of the entire device is high.

On the other hand, ultrasonic thickness measurement has the following drawbacks. That is, at the laminated interface between the base material and the laminated material, the two are metallurgically bonded, and no reflected wave can be obtained at this interface except for a very large difference in acoustic impedance between the two. For this reason, the present inventor has proposed a device for solving the above-mentioned problems in the use of ultrasonic waves in Japanese Utility Model Publication No. 55-137305. This is to clarify the reflected wave by selectively extracting a portion of the received signal including the reflected wave at the laminated interface, and subjecting only this portion to differential signal processing different from the other portions.

[Problems to be solved by the invention]

By the way, in the above-mentioned device by the present inventor, since the signal extraction of the reflected wave at the laminated interface also detects the noise signal at the same time, it is not possible to accurately extract only the reflected wave, or even if the differential is added to the high frequency waveform, S / N It became clear that problems such as the ratio not improving occur and affect the accuracy of subsequent signal processing.

The present invention has been made in view of such circumstances, and in order to improve the above-mentioned problems, a received signal is amplified by a wide band amplifier and a narrow band amplifier, and a portion including a reflected wave at a laminated interface is narrowed. To provide a wall thickness measuring device for a clad material capable of clarifying the reflected wave and accurately measuring the wall thickness of a laminated material or a base material by adopting a structure in which a S / N ratio is taken out by a band amplifier. With the goal.

[Means for solving problems]

An apparatus for measuring the thickness of a clad material according to the present invention is an apparatus for ultrasonically measuring the total thickness of a clad material having a laminated structure of a base material and a laminated material and the thickness of the base material or the laminated material. A wideband amplifier for amplifying an ultrasonic reflected wave received by the ultrasonic probe, and a specific low-frequency narrowband signal of the ultrasonic reflected wave received by the ultrasonic probe. A narrow band amplifier, a differentiator for differentiating an output signal of the narrow band amplifier to output a threshold value of a differential waveform, information about the total thickness from the output of the wide band amplifier, and an output of the narrow band amplifier and It further comprises means for extracting information about the base material thickness or the laminated material thickness from the output of the differentiator, and calculating the required thickness based on the extraction result.

[Action]

The reflected ultrasonic wave received by the ultrasonic probe is amplified by a wide band amplifier and a narrow band amplifier, respectively, and information regarding the total thickness is extracted in relation to the output of the wide band amplifier.
The threshold value of the differential waveform is output from the differentiator that differentiates the output signal of the narrow band amplifier. Information about the base material thickness or the laminated material thickness is extracted in relation to the output of the narrow band amplifier and the threshold value output from the differentiator. Based on these extraction results, the total thickness of the clad material and the base material thickness or the combined material thickness are calculated.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to the drawings illustrating the embodiments.

FIG. 1 is a schematic diagram showing a wall thickness measuring device according to the present invention (hereinafter referred to as a device of the present invention) together with a clad material to be measured. Now, assuming that a clad steel pipe or the like having a laminated material on the inner surface is the clad material C to be measured, the ultrasonic probe 1 is used so as to face the base material C ₁ side on the outer peripheral side. For the purpose of the present invention, the probe 1 should be a beam converging type because it is necessary to effectively extract the reflected wave (hereinafter referred to as interface echo) at the laminated interface between the base material C ₁ and the laminated material C _2. A shock wave type is used to improve resolution. Reference numeral 1a is a shoe for interposing a contact medium such as water or oil between the base material C ₁ and the probe 1, and is fitted to the probe 1. The dissipative contact medium is replenished from the liquid supply port 1b.

The specifications of the probe 1 and the shoe 1a are selected so that the focus of the ultrasonic beam is located at the interface between the base material and the laminated material in consideration of the approximate thickness of the base material C ₁ which is known in advance. I'll do it.

A pulse oscillating circuit 2 is connected to the probe 1 as in the conventional device, and the oscillator in the probe 1 vertically emits an ultrasonic wave by the pulse oscillating circuit 2. Then, the reflected waves from the surface, the interface and the back surface of the laminated material C ₂ are captured by the probe 1 and enter the receiving circuit. The device of the present invention is characterized by this receiving circuit. That is, the signal obtained by the acoustic-electric conversion action of the transducer of the probe 1 is amplified by the preamplifier 4 and then input to the wideband amplifier 5 and the narrowband amplifier 6.

The broadband amplifier 5 faithfully amplifies the original waveform as shown in FIG. Here, T is the oscillation wave from the probe 1, S is the base material
The reflected wave from the surface of C ₁ (hereinafter referred to as surface echo), I is the reflected wave from the boundary surface between the base material C ₁ and the laminated material C ₂ (hereinafter referred to as boundary surface echo), and B is the laminated material C ₂ Waveforms of reflected waves from the back surface (hereinafter referred to as bottom surface echoes) are shown, and the difference in size between the surface echo S and the boundary surface echo I is, for example, S45C (base material), SUS304 (composite material) having a total thickness of 10 mm. ) In the clad material, the boundary surface echo I is extremely small with respect to the surface echo S, and the S / N ratio is poor. The ultrasonic waves are scattered and attenuated by the crystal grain boundaries due to the propagation in the material, and the scattered waves are noise echoes. This depends on the frequency, and the high frequency component is attenuated as the ultrasonic wave propagates, and the center frequency shifts to the low frequency side. Therefore, by using the narrow band amplifier 6, a specific signal, that is, a high frequency component is scattered as noise echo and attenuated,
Among the signals whose center frequency has shifted to the low frequency side, it is effective to amplify the narrow band frequency signal in which the boundary surface echo I is detected with a good S / N ratio.

The output signal (a) of the wide band amplifier 5 is input to the comparator 7, which then oscillates as shown in FIG. 2 (a).
A threshold level V _TH1 (one-dot chain line in the figure) which is slightly lower than the peaks of T, surface echo S and bottom echo B is set, and a signal (b) exceeding this V _TH1 is output to the logic circuit 10. The logic circuit 10 rises shortly before the time when the surface echo S is output, and rises shortly after the time when the surface echo S is output, and then the gate signal G1 that rises shortly before the time when the bottom surface echo B is output. After the output of the bottom echo B, the gate signal G2 which falls shortly after being output is set in advance in synchronization with the oscillation wave T based on the ultrasonic wave propagation speed.
The timing gate TG1 between S and B is formed, and the logic circuit 12
Output to.

On the other hand, in the narrow band amplifier 6, the signal of the narrow band frequency in which the boundary surface echo I is detected with a good S / N ratio among the signals whose center frequency is shifted to the low frequency side is shown in FIG. The boundary surface echo I is amplified to a predetermined level as shown in FIG. As a result, the surface echo S and the bottom surface echo B, which are larger than the boundary surface echo I, are saturated. Although the noise echo N is amplified, it is attenuated over time. The output signal of the narrow band amplifier 6 is input to the comparator 8 and the differentiator 9. The differentiator 9 has a time constant set on the basis of the approximate thickness and material of the clad material, and differentiates the signal from the narrow band amplifier 6 to obtain a differential waveform threshold V _TH2 (two in the figure). The dotted chain line) is output to the comparator 8. The comparator 8 compares the signal directly input from the narrow band amplifier 6 with the threshold V _TH2 input from the differentiator 9, and outputs a signal (d) exceeding this threshold V _TH2 to the logic circuit 11. To do. The V _TH2 is set by the differentiator 9 in order to prevent the scattered wave, that is, the noise echo N, from being included in the grain boundary described above, which means that the intensity of the scattered wave is attenuated with time. Is based on what you do. This improves the S / N ratio when detecting the interface echo I. The logic circuit 11 synchronizes the gate signal G3, which rises slightly before the time when the interface echo I is output, and then falls slightly after the output of the interface echo I, with the oscillation wave T in advance in the same manner as G1 and G2 described above. By setting based on the sound wave propagation velocity, a timing gate TG2 between the oscillation wave T and the interface echo I is formed, and the timing gate TG2 is output to the logic circuit 12.

The logic circuit 12 is based on the timing gate TG1 between S and B, that is, the full thickness gate, and the timing gate TG2 between T and I, that is, the interface gate, from the overlapping portion to the base material thickness gate TG3 between S and I. And the total material thickness gate TG1 and the base material thickness gate TG3 form a combined material thickness gate TG4 between I and B.

Then, each output signal of TG1, TG3, and TG4 is output to the thickness conversion circuit 13 including a time analog conversion circuit. The thickness conversion circuit 13 outputs analog signals corresponding to the total wall thickness, the base material thickness and the laminated material thickness from the respective input signals TG1, TG3 and TG4.

The thickness measurement by the device of the present invention configured as described above is performed by exposing the probe 1 to the object to be measured so that the shoe 1a is in contact therewith as in the conventional case. The ultrasonic waves emitted by the probe 1 are also captured by the probe 1 and processed by the reception system circuit having the above-described configuration, and the total thickness gate TG1 and the narrow band amplifier 6 from the output of the wide band amplifier 5 are processed. The interface gate TG2 is obtained from each output, and the base metal thickness gate TG3 and the laminated material thickness TG4 are obtained by the logic circuit 12, and each gate output is converted to the thickness by the thickness conversion circuit 13, and the total thickness of the clad material C and the base material thickness are obtained. And the thickness of the laminated material is calculated.

〔effect〕

In the thickness measuring device for the clad material according to the present invention, the reflected wave at the interface between the base material and the laminated material is amplified by the narrow band amplifier, and the output of the narrow band amplifier is compared with the differential waveform to perform the interface echo. Since I is obtained, the interface echo I can be detected with a good S / N ratio without being affected by noise due to scattering in the crystal grain boundaries, and based on this, the total thickness of the cladding material, the base material thickness and the composite material It is possible to accurately determine the thickness. Since the device of the present invention uses ultrasonic waves, it can be applied even if the clad material C is a non-magnetic material, and the measurement of the entire length and the entire surface of the sample can be performed online by scanning. , There are many places where the present invention contributes to the improvement of quality control technology for clad steel, etc.,
The present invention has excellent effects.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a block diagram of the device of the present invention, and FIG. 2 is a signal waveform diagram of each part. 1 ... Ultrasonic probe, 2 ... Pulse oscillating circuit, 5 ... Wideband amplifier, 6 ... Narrowband amplifier, 9 ... Differentiator, 10,1
1,12 ... Logic circuit

Claims (1)

[Claims] 1. An apparatus for ultrasonically measuring the total thickness of a clad material having a laminated structure of a base material and a laminated material and the thickness of the base material or the laminated material, the ultrasonic probe and the ultrasonic probe. A wideband amplifier for amplifying an ultrasonic reflected wave received by a child, a narrowband amplifier for amplifying a specific low frequency narrowband signal of the ultrasonic reflected wave received by the ultrasonic probe, and the narrowband amplifier A differentiator for differentiating the output signal of the amplifier to output a threshold value of the differential waveform; information about the total thickness from the output of the wideband amplifier; and a base material from the output of the narrowband amplifier and the output of the differentiator. A device for measuring the thickness of a clad material, comprising: means for extracting information about the thickness or the thickness of the laminated material, and calculating a required thickness based on the extraction result.