JPH02249965A - Method and device for automatic flaw detection for seam part - Google Patents

Abstract

PURPOSE:To correct a marking line detector to a position corresponding exactly to a marking line even if the size of an object inspection body is changed by moving an optical marking line detector in accordance with an object in a device for inspecting the seam part of an electric resistance welded tube. CONSTITUTION:Together with a first holding body 10 for holding a marking line detector 11, a position change is executed in accordance with the size change. In this case, since their absolute positions are unknown, a first positioning device 15 fixed to ground is provided separately, and by this positioning device 15, a first holding body 10 moves and its abutting position becomes a reference position, the holding body 10 is moved by a prescribed distance L1 from this reference position, and at that time, the present marking line M is detected. Subsequently, a deflection distance (x) from the marking line M which is to exist unless a size change is executed is detected optically, and when the holding body 10 is moved by the distance (x) portion and the position of the detector 11 is corrected, the detector 11 can be positioned to a normal position corresponding to the marking line M. Consequently, an ultrasonic flaw detector 2 which follows it up also comes to follow up, based on the normal position as a reference, therefore, the flaw detection accuracy is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic flaw detection method and apparatus for a seam portion such as a seam portion of an electric resistance welded pipe.

[Conventional technology]

In the production line of ERW pipes, ultrasonic flaw detection is carried out to ensure the quality of the seams.

In this case, in order to further improve flaw detection accuracy, an automatic tracking method is adopted in which the ultrasonic flaw detector automatically traces along the seam portion. Conventionally, the following two methods have been used as this tracking method.

(1) An optical detector, such as an image sensor, is installed on the seam to detect the position of the seam based on the difference in the distribution of reflected light between the seam and the base material. Based on this, an ultrasonic flaw detector is installed. A method to follow.

(2) With respect to the optically detected seam position, a marking line is placed in the longitudinal direction of the tube at a constant deviation position in the circumferential direction, and using this marking line as a reference, the ultrasonic flaw detector is used in the same manner as in (1) above. A method to follow.

[Problem to be solved by the invention]

However, in the method (1) above, the seam can be sufficiently detected immediately after welding based on the difference in the distribution of reflected light between the cut surface and the base metal, but it is not possible to detect the seam immediately after welding. If you try to do so, the material change between the seam part and the base material part is not clear and followability is poor.

In this respect, the method (2) is superior because it does not have this risk, but if the marking line is applied on or near the seam, the marking line will be burned by annealing (local heating of the seam), so the seam It is necessary to space them further apart.

However, by spacing the marking line sufficiently far from the seam, new problems arise. In other words, Fig. 6 (
A marking line detector 11 consisting of a CCD camera or the like held on a first segment 10 serving as a common first holding body detects marking lines Ma or Mb of tubes A or B having various outer diameters, such as al. , when detecting the marking line Ma or Mb, the curvature of the first segment is the same even though the curvatures of the tubes A and B are different, so the position where the marking line detector 11 detects the marking line Ma or Mb is determined by the error of the angle occurs. As a result, as the position output signal of the marking line detector 11, an error X occurs as shown in However, positional deviation occurs, making it impossible to perform accurate flaw detection.

On the other hand, when marking lines are applied to a target pipe using a spray gun, etc., it is difficult to accurately reposition the gun in response to the size change of the target pipe, and some errors may occur. . This is also a factor that reduces the accuracy of ultrasonic flaw detection.

SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to provide an automatic flaw detection method for a seam portion and an apparatus therefor, which can correct a marking line detector to a position that accurately corresponds to the marking line even if the size of the object to be inspected is changed. It is in.

[Means to solve the problem]

In order to solve the above-mentioned problems, the method of the present invention includes a marking line detector that optically looks at the marking line applied to the object to be inspected in parallel to the seam at a position spaced apart from the seam in the circumferential direction; a first holding body for holding the first holding body, a first driving means for moving the first holding body in the circumferential direction together with the marking line detector, and a first movement amount detector for detecting the amount of movement by the first driving means. , a marking line tracking system comprising: a first positioner fixed to the ground that detects a circumferential movement position of at least one of the first holding body and the marking line detector; The first holding body is moved until the first positioning device detects its movement, and then the first holding body is moved in the circumferential direction a predetermined distance from this detected position by the first driving means, and at the position after this movement. , optically detecting the positional deviation of the current marking line viewed by the marking line detector from the reference marking line, and moving the first holding body in the circumferential direction by the first driving means in order to correct the positional deviation. It is characterized by:

The device of the present invention also includes a marking line detector that optically looks at marking lines applied to the object to be inspected parallel to the seam at a position spaced apart from the seam in the circumferential direction, and a first holder for holding the marking line detector. a first driving means for moving the first holding body in the circumferential direction together with the marking line detector; a first movement amount detector for detecting the amount of movement by the first driving means; and the first holding body. and a first positioning device fixed to the ground that detects the movement position of at least one of the marking line detectors in the circumferential direction; An ultrasonic flaw detector that performs sonic flaw detection, a second holding body that holds the same, a second driving means that moves the second holding body in the circumferential direction together with the ultrasonic flaw detector, and an amount of movement by the second driving means and a second positioning device fixed to the ground that detects the circumferential movement position of at least one of the second holding body and the ultrasonic flaw detector. That is.

[Effect]

Also in the present invention, the position of the marking line is detected by looking at the marking line with a marking line detector. At that time, when there is a change in the size of the target object to be inspected, such as a tube, as mentioned above,
This causes a detection error (angle θ or position X) of the marking line.

Therefore, in the present invention, the position of the marking line detector is changed together with the first holding body that holds the marking line detector in response to the size change. At this time, since their absolute positions are unknown, a first positioning device fixed to the ground is separately provided, and the first holder is moved by this first positioning device, and the abutting position is set as the reference position,
Moving the first holding body a predetermined distance from this reference position,
At that time, the current marking line is detected, the deviation distance X from the reference marking line that would have been if there had been no size change is detected optically, the first holder is moved by this deviation distance X, and the marking line is By correcting the position of the detector, the marking line detector can be positioned at a regular position corresponding to the current marking line. As a result, the ultrasonic flaw detector that follows this also follows with the regular position as a reference, which improves the flaw detection accuracy.

On the other hand, if the ultrasonic flaw detection system is also positioned in the same way as the marking line tracking system, calibration can be performed after changing the size, and the flaw detection accuracy will be further improved.

[Specific structure of the invention]

The present invention will be further explained in detail below.

In FIGS. 1 to 4, a steel pipe 1 as an object to be inspected is placed above the steel pipe 1 at intervals (for example, 500 mm) in the longitudinal direction.
), a first segment 10 and a second segment 20 are arranged. Each of these segments 10.20 includes a camera box 12 that accommodates a marking line detector 11, and a flaw detector box 2 that accommodates an ultrasonic flaw detector 21.
2 is fixed.

A first driving means 13 is provided for moving the first segment 10 in the circumferential direction so that the marking line detector 11 looks at the marking line M at a normal position. The first drive means 13 is formed by a drive gear 13b connected to the output shaft of a drive motor 13a meshing with a gear 10a formed on the outer peripheral surface of the first segment 10. moreover,
In order to detect the amount of movement of the first segment 10 by the first driving means 13, a rotary encoder 14 as a first movement amount detector is disposed in contact with the outer peripheral surface of the first segment 10. In order to detect the marking line M more clearly, the camera box 12 is equipped with an illumination lamp 15.
is installed.

On the other hand, the seam S tracking system of the ultrasonic flaw detector 21 is similarly provided with a second drive means 23 and a rotary encoder 24 as a second movement amount detector. As shown in FIG. 1, the ultrasonic flaw detectors 21 are provided in pairs on both sides of the seam S.

Referring to FIG. 1, the output signal from the marking line detector 11 is taken into a marking line detection circuit 3o, and the detection signal is input to a main processing unit (CPU) 31. On the other hand, the rotary encoder 14.
The position feedback signals of 24 are each taken into the servo control circuit 32, and together with the signal from the main processing unit 31, the position feedback signals of the motors 13a, 23aj, m are used as position control signals of the first and second segments 10.20.
It is now possible to output a te. 33 is a position indicator of the ultrasonic flaw detector 21.

Furthermore, a first limit switch 15 as a first positioner and a second limit switch as a second positioner are placed at appropriate positions in the movement range of the first and second segments 10.20.
A limit switch 25 is fixed to the ground.

With the device configured in this manner, when calibration is required such as when changing the size of the pipe 1, referring also to FIG. Move the first segment 10 until it comes into contact with the first limit switch 15, and
When the limit switch 15 is turned on, the servo control circuit 32 uses that position as a reference point for position correction,
The first driving means 13 moves the first segment 10 in the opposite direction by a distance L1. This distance L1 is the distance L0 on the first segment 10 corresponding to the marking line M reference position from the seam S center to the marking line M reference position, for example, 50III11. Calculate it in advance by subtracting it from the known distance.

In this manner, the marking line M is optically detected by the marking line detector 11 at the position where the first segment 10 has returned. In this detection result, if a positional deviation X of the marking line M is observed as shown in Fig. 4,
For the time being, the main processing unit 1f32 calculates the amount of positional deviation
Temporarily store it in the memory of.

Next, with the connection with the marking line tracking system once cut off, the second segment 20 is moved in the circumferential direction by the second driving means 23 in the tracking system of the ultrasonic flaw detector as well. is the second limit switch 25
When the second limit switch 25 is turned on, the servo control circuit 32 uses that position as a reference point for position correction, and the second drive means 23 moves the second segment 20 in the opposite direction by a distance. 7 minutes.

This distance L2 is preset based on the positional relationship between the seam portion S center and the second limit switch 25. This eliminates electrical and mechanical zero point positioning errors of the marking line detector 11.

Thereafter, in order to correct the previously memorized positional deviation X, the first driving means 13 moves the first Move segment 1o and mark line detector 1
Perform position correction in step 1.

Thereby, the visual field center of the marking line detector 11 comes to coincide with the center of the marking line M, and optical deviation can be eliminated.

Thus, after such calibration is completed, if the connection between the marking line tracking system and the ultrasonic flaw detection system is released, the ultrasonic flaw detector 21 automatically follows the marking line M. At this time, since the marking line detector 11 captures the marking line M at a regular position and provides a servo signal to the ultrasonic flaw detector 21, the flaw detection accuracy does not deteriorate.

Figure 5 shows a time flow chart of the method of the present invention.
It is unnecessary to explain it again since it is clear from the above explanation.

In the above example, the holders 10, 20, the drive means 13.2
3, and other modifications may also be adopted. The same applies to the positioner 15.25.

Furthermore, if the ultrasonic flaw detector 21 has substantially no positional error between the previous size and the next size, the calibration of the ultrasonic flaw detector 21 can be omitted.

〔Example〕

Figures 7 and 8 show changes in seam detection accuracy and manual intervention rate when tracking the seam between the conventional method and the method of the present invention under the conditions shown in Figure 3. We have shown the results of our investigation.

This clearly shows the advantages of adopting the present invention.

〔Effect of the invention〕

As described above, according to the present invention, even if the size of the object to be inspected is changed, the marking line detector can be corrected to a position that accurately corresponds to the marking line. Therefore, flaw detection accuracy is significantly improved.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the present invention, Fig. 2 is a perspective view of an automatic flaw detection device, Fig. 3 is a diagram of the positional relationship between the marking line detector and the marking line, and Fig. 4 is a positional deviation of the detected marking line. Figure 5 is a time flow chart of the method of the present invention, Figure 6 is a diagram of the principle of error generation in marking line detection during size change, Figures 7 and 8 are diagrams of the output waveform of the marking line detector.
The figure is a comparison graph between the present invention and a conventional example. 1... Object to be inspected (ERW pipe) 10... First segment 11... Marking line detector 13... First drive means 20... Second segment 21... Ultrasonic flaw detector 23... Second driving means 30... Marking line detection circuit 31... Main processing unit 32... Servo control circuit S... Seam portion M, Ma, Mb... Marking line diagram Diagram (video scratch) Y-axis curve diagram (α) (b)

Claims (2)

[Claims] (1) A marking line detector that optically looks at marking lines applied to the object to be inspected parallel to the seam at a position spaced apart from the seam in the circumferential direction; a first holder that holds the marking line; a first drive means for moving the first holding body in the circumferential direction together with the marking line detector; a first movement amount detector for detecting the amount of movement by the first driving means; and detection of the first holding body and the marking line. and a first positioning device fixed to the ground that detects a circumferential movement position of at least one of the marking line tracking systems, wherein the first positioning device is configured to position the first holding body in the circumferential direction by the first driving means. The first holding body is moved by the first driving means in the circumferential direction a predetermined distance from this detection position until the movement is detected by the marking line detector, and at the position after this movement, the current marking observed by the marking line detector is moved. An automatic flaw detection method for a seam portion, comprising optically detecting a positional deviation of a line from a reference marking line, and moving the first holding body in the circumferential direction by the first driving means to correct the positional deviation. . (2) a marking line detector that optically looks at marking lines applied to the object to be inspected parallel to the seam at a position spaced apart from the seam in the circumferential direction; a first holder that holds the marking line; a first drive means for moving the first holding body in the circumferential direction together with the marking line detector; a first movement amount detector for detecting the amount of movement by the first driving means; and detection of the first holding body and the marking line. a first positioning device fixed to the ground that detects the circumferential movement position of at least one of the marking line detectors; a sonic flaw detector, a second holder for holding the same, a second drive means for moving the second holder together with the ultrasonic flaw detector in the circumferential direction, and a second drive means for detecting the amount of movement by the second drive means. a second movement amount detector; and a second positioner fixed to the ground that detects the circumferential movement position of at least one of the second holding body and the ultrasonic flaw detector. Automatic flaw detection equipment.