JPS63275951A - Probe for detecting flaw in metal - Google Patents

Abstract

PURPOSE:To improve detecting ability even for linear defects in the circumferential direction in a metal pipe, by slanting the winding directions of test coils with respect to the circumferential direction of the metal pipe to be checked. CONSTITUTION:Test coils 2a and 2b are obliquely wound with respect to the main body of a probe in the adjacent pattern. The probe 1 is moved in a metal pipe to be checked. A checking part 2 is a bridge circuit, which is constituted so as to include the test coils 2a and 2b. The bridge circuit 2 is excited with high frequency from an oscillator 3. The output signal of the checking part 2 undergoes phase detection with phase detectors 4a and 4b. The results are displayed on the screen of a CRT tube 5 as Lissajous waveforms. Defects, which are present in the metal pipe, are detected based on the change in waveforms. Meanwhile, the phase angles of the signals are obtained based on the signal from the detectors 4a and 4b in an operating part 6. The depths of cracks 4 in the circumferential directions and other flaws are operated and recorded in a recorder 7.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an eddy current flaw detection device for metal tubes for detecting defects such as scratches and cracks occurring in metal tubes, and particularly relates to an eddy current flaw detection device of this type with improved measurement accuracy. This invention relates to a metal flaw detection probe for a device.

[Prior Art] In conventional eddy current flaw detection equipment, a test coil through which a high-frequency current is passed is inserted and moved inside a metal tube, and changes in eddy current caused by flaws (hereinafter referred to as defects) in the metal tube are electrically detected. INI+ is set.

First, since this change in eddy current (change in impedance) is minute, it is increased by a detector and an amplifier and converted into a voltage. This method is called the amplitude method and evaluates the defect by displaying the shape and depth of the defect with a single signal.

Furthermore, whether the defects that occur in the metal tube are on the inner or outer surface, and how deep are the defects?
As an eddy current flaw detection device for metal tubes that can accurately and quickly measure, a device that can distinguish between internal and external defects and detect the defect depth from the phase of the defect signal has been proposed. (Gan Sho 57-185696).

[Problems to be solved by the invention] By the way, cracks that occur in brass pipes such as BSTF materials generally occur in the circumferential direction of the pipe and are often small in volume.
Even with an eddy current flaw detector with high measurement accuracy, it is difficult to detect such cracks in the tube circumferential direction due to the induced current generated in the circumferential direction of the coil.

That is, as shown in FIG. 4, in the conventional probe 1', the direction of the induced current in the coils 2'a and 2°b coincides with the direction of the crack 11 in the metal tube.

Due to this division, the overcurrent does not change,
Therefore, the crack 11 will not be detected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a metal flaw detection probe that overcomes these conventional problems and has improved ability to detect linear defects in the circumferential direction of metal tubes.

[Means for Solving the Problems] In order to achieve the above object, the metal frame wound probe of the present invention consists of a probe body and a test coil wound around the probe body. In the metal frame flaw probe that moves and detects changes in eddy current caused by defects in the metal tube using the test coil, the winding direction of the test coil is oblique to the circumferential direction of the metal tube. It is characterized by the presence of

[Function] As shown in FIG. 1, the metal frame wound probe of the present invention has a test coil 2a, a
Since the winding direction (arrow B) of the test coils 2b is inclined, the induced current i of the test coils 2a and 2b is generated across the crack 11 in the circumferential direction.

As a result, the induced current i changes due to the crack 11,
This change is detected as a change in the impedance of the test coils 2a, 2b.

[Embodiment] Hereinafter, an embodiment of the present invention using a probe for inspection of gold marks will be described with reference to the drawings.

As shown in FIG. 2, the eddy current flaw detection apparatus of the present invention includes test coils 2a, 2b, a detection section 2, an oscillator 3, and a phase detection circuit 4a.
, 4b, an image display device @5, an arithmetic processing section 6, and a recorder 7. That is, the test coils 2a, 2b are as shown in FIG.
As shown in a), the probes 1 are each wound obliquely around the probe body 1a adjacent to each other, and are movable in the axial direction within the metal tube 10 to be inspected, so that there are no scratches or dents in the metal tube 10. Changes in eddy current caused by this are detected as changes in impedance. The detection unit 2 is a bridge circuit including test coils 2a and 2b, and is excited by a high frequency from an oscillator 3. The two phase detection circuits 4a and 4b perform phase detection on the output signal of the detection section 2 using two control signals having different phases. two phase detection circuits 4a,
The output of 4b is displayed on the screen of the cathode ray tube 5 as a Lissajous waveform. This Lissajous waveform changes in response to the change in the phase of the output signal of the detection section 2 due to a defect present in the metal tube (FIG. 3(a)).

The third waveform of the surge waveform corresponding to the typical defect pattern
It is shown in figure (b). The circumferential split of the metal tube is imaged on the cathode ray tube 5 as a surge waveform as shown in FIG. 3(b) [phase].

The arithmetic processing unit 6 electrically reads the amplitude of the signals from the phase detectors 4a and 4b similar to those input to the cathode ray tube 5, determines the phase angle, and determines circumferential cracks and other flaws. Depth of CPU (Central Processing Unit)
[Effects of the Invention]As is clear from the above embodiments, the metal-frame wound probe of the present invention has a test coil tilted obliquely with respect to the circumferential direction of the metal tube. The provision of such a sensor makes it possible to reliably detect linear defects such as minute cracks in the circumferential direction of the metal tube. It goes without saying that defects other than the cotton-like defects described above can also be detected.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the metal frame wound probe of the present invention, and FIG.
The figure is a block diagram of the eddy current flaw detection device, FIG.
b) is a diagram showing a typical defect pattern and a corresponding surge waveform, and FIG. 4 is a diagram showing a conventional metal frame flaw probe. l...Metal flaw detection probe la...Probe body 2a, 2b...Test coil 10...Metal tube 11... ...Cracked (Defect) Agent Patent Attorney Moritani - Pheasant Procedural Amendment (Own) 1. Indication of the case Japanese Patent Application No. 112193/1982 2 Name of the invention Total bending flaw detection probe 3 Person making the amendment Relationship to the case Patent applicant (588) Mitsui Petrochemical Industries, Ltd. (and 1 other person) 4
, Agent 〒103 5. Detailed description of the invention column and drawing 6 in the specification subject to amendment, Contents of the amendment (1) "Inside the metal pipe" on page 3, line 4 of the specification has been changed to "metal pipe 10".
``Inside,'' corrected. (2) "Figure 3 (a)" in the 5th line from the bottom of page 4 is corrected to "Figure 1." (3) Figures 1, 2, 3 (a) and 4 of the drawings will be corrected as shown in the attached sheet. Fig. 1 1] Fig. 2 Fig. 3 Fig. 4 Fig. 1'

Claims (1)

[Claims] A metal flaw detection probe consisting of a probe body and a test coil wound around the probe body, which moves in the axial direction within a metal tube and detects changes in eddy current caused by defects in the metal tube using the test coil. . A probe for metal flaw detection, wherein the winding direction of the test coil is oblique to the circumferential direction of the metal tube.