JPH04340403A - Seam part position detector for seam welded steel pipe - Google Patents

Abstract

PURPOSE:To enable miniaturization, lower cost production and higher detection accuracy for a seam part position detector of seam welded steel pipes. CONSTITUTION:The surface of a seam welded steel pipe P is irradiated with light from a projector 51 and a part irradiated is imaged two-dimensionally by a TV camera 52. A two-dimensional image picked-up by the TV camera 52 is binary coded being separated into a seam part and other parts with a binary coding processing section 501. A seam part position judging section 503 determines the position of the seam part of the seam welded steel pipe P two dimensionally based on the binary coded two-dimensional images.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the position of a seam in an electric resistance welded steel pipe.

0002

[Prior Art] Generally, electric resistance welded steel pipes are made by passing a steel band through a group of forming rolls and bending it into a cylindrical shape with opposite edge portions.
This is passed between squeeze rolls while heating the both side edge portions by applying a current to the end faces of the both side edge portions, and the both side edge portions are butt welded, and a bead is formed at the welded portion (hereinafter referred to as the seam portion). It is manufactured by cutting and removing it and shaping it with sizer rolls.

[0003] In electric resistance welded steel pipes manufactured in this manner, defects are likely to occur at the seam portions, so the seam portions are subjected to ultrasonic flaw detection for quality control. Generally, the seam portion is easily displaced, so when performing the ultrasonic flaw detection, the position of the seam portion is detected and the ultrasonic flaw detection is performed on the detected seam portion.

Conventionally, the following three methods have been disclosed as methods for detecting the position of the seam of an electric resistance welded steel pipe. The first conventional seam position detection method (Japanese Unexamined Patent Publication No. 2-17041) utilizes the fact that the temperature of the seam is locally high in the temperature distribution of the electric resistance welded steel pipe immediately after welding. That is, the temperature distribution of the electric resistance welded steel pipe immediately after welding is measured, and the portion of this temperature distribution exceeding a predetermined temperature is detected as the position of the seam portion.

[0005] In the second conventional seam position detection method (Japanese Unexamined Patent Publication No. 58-41347), transverse ultrasonic waves are generated in the ERW steel pipe using an electromagnetic ultrasonic oscillator, and the transverse waves propagated in the ERW steel pipe are detected. The position of the seam was detected by measuring the amount of attenuation of ultrasonic waves.

[0006] In the conventional third seam position detection method (Japanese Unexamined Patent Publication No. 1-302103), two light projectors installed across the seam of an ERW steel pipe detect the seam, including the seam. Light is irradiated at different positions on the surface of an ERW steel pipe from diagonal directions, each irradiation position is simultaneously imaged with one television camera, and the light that exists in each of the two viewing areas corresponding to each irradiation position is detected. For more than one scanning line, the luminance signals on these scanning lines are individually binarized to obtain two position signals representing the one-dimensional position of the seam in the circumferential direction of the ERW steel pipe. The portion where the position signals matched was detected as the true seam position in the circumferential direction of the ERW steel pipe.

[0007]

[Problem to be solved by the invention] However, the above-mentioned first problem
The seam position detection method cannot detect the seam unless the seam is at a high temperature. There was a problem that it could not be applied to seam position detection in flaw detection.

Furthermore, in the second seam position detection method described above, the electromagnetic ultrasonic oscillator for generating transverse ultrasonic waves is large and expensive, and the apparatus for performing ultrasonic flaw detection for quality control is required. The problem was that it was difficult to incorporate into the

Furthermore, in the third seam position detection method described above, the signal processing method for the image taken by the television camera is complicated, and the seam position detection result can be obtained one-dimensionally. Therefore, there was a problem of poor measurement accuracy.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a seam position detection device for electric resistance welded steel pipes, which is small and inexpensive, and has good measurement accuracy. .

[0011]

[Means for Solving the Problems] A seam position detection device for an ERW steel pipe according to the present invention includes means for irradiating light onto the surface of an ERW steel pipe, and two-dimensional imaging of the portion irradiated by the means. and an imaging means for detecting the position of a seam in an ERW steel pipe based on the imaging result of the imaging means, wherein the two-dimensional image taken by the imaging means is divided into the seam and other parts. The present invention is characterized by comprising means for converting into a value, and means for two-dimensionally determining the position of a seam in an electric resistance welded steel pipe based on a two-dimensional image binarized by the means.

0012

[Operation] In the present invention, the surface of the ERW steel pipe irradiated with light is imaged two-dimensionally, and the imaged two-dimensional image is binarized into the seam portion and other portions. , the binarized two-dimensional image shows a two-dimensional image of the seam portion. By converting the position of such a two-dimensional image of the seam into coordinates on the two-dimensional image, the position of the seam in the electric resistance welded steel pipe can be determined with high accuracy.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically explained below based on drawings showing embodiments thereof. FIG. 1 is a schematic diagram showing a production line for electric resistance welded steel pipes to which a seam position detection device for electric resistance welded steel pipes according to the present invention (hereinafter referred to as the device of the present invention) is applied.

In the figure, 1 is a forming roll for forming an open pipe O by bending a steel band B into a cylindrical shape.On the downstream side of the line of the forming roll group 1, both edges of the open pipe O are abutted. A welder 2 for welding the ERW steel pipe P, a water cooling tank 3 for cooling the ERW steel pipe P that has been butt welded, a sizer roll group 4 for shaping the ERW steel pipe P, and a position of the seam of the ERW steel pipe P. A seam position detection device 5 for detecting the position, and a cut-off machine 6 for cutting the electric resistance welded steel pipe P into a predetermined length.
are arranged in this order.

In the production line for electric resistance welded steel pipes constructed as described above, the steel strip B is fed in the direction from the upstream side of the line to the downstream side of the line, as indicated by the white arrow in the figure. The steel B is passed through a forming roll group 1, and an open pipe O is formed which is bent into a cylindrical shape with opposite edge portions thereof. Then, in the welder 2, current is applied to both edge portions of the open pipe O, and the edge portions of the open pipe O are butt-welded to become an electric resistance welded steel pipe P while being heated and melted by resistance heat. The electric resistance welded steel pipe P that has been butt-welded in this manner is cooled in a water cooling tank 3, and beads on the inside and outside of the pipe are cut by a cutting device (not shown).

[0016] Then, the electric resistance welded steel pipe P is placed in the sizer roll group 4.
The position of the seam portion is detected by the seam portion position detection device 5 while the outer diameter fluctuation is suppressed, and the detected seam portion is tested by an ultrasonic flaw detection device (not shown). Thereafter, the electric resistance welded steel pipe P is shaped to a predetermined outer diameter by a group of sizer rolls 4, and cut into a predetermined length by a cut-off machine 6.

Next, the configuration of the seam position detection device 5 will be explained. FIG. 2 is a block diagram showing the configuration of the seam position detection device 5. As shown in FIG. Above the ERW steel pipe P, a light projector 51 that irradiates light onto the surface of the ERW steel pipe P from an oblique direction and a television camera 52 that captures an image of the surface of the ERW steel pipe P illuminated by the light projector 51 are arranged. It is set up. TV camera 5
The second imaging signal is provided to a signal processing device 50 that performs signal processing such as image processing to determine the position of the seam portion. Furthermore, the data representing the position of the seam determined by the signal processing device 50 is given to the ultrasonic flaw detection device as a control output for controlling the ultrasonic flaw detection device.

The signal processing device 50 includes a binarization processing unit 501 that binarizes an image captured by a television camera 52 according to its luminance, and a threshold value that stores a luminance threshold for the binarization. It is comprised of a storage unit 502 and a seam position determination unit 503 that determines the position of the seam of the electric resistance welded steel pipe P from the binarized image.

Next, the operation of the seam position detection device 5 constructed as described above will be explained. TV camera 52
The imaging signal is given to a binarization processing section 501 in the signal processing device 50. The binarization processing unit 501 is given a luminance threshold value for binarization from the threshold storage unit 502 in advance, and the binarization processing unit 501
The image of the electric resistance welded steel pipe P captured by the television camera 52 is binarized into a seam portion and other portions based on the brightness and the threshold value.

FIG. 3 is a schematic diagram showing an image binarized by the binarization processing section 501. 7 in the figure represents an imaging area of the television camera 52, and a seam portion 71 is displayed within this imaging area 7 by the binarization. Also,
72 is a window representing the detection area of the position of the seam portion 71. As shown in FIG. 3, this window 72 displays the coordinates (x1, y
1 ), ( x1 , y2 ), ( x2 , y1
), (x2, y2).

The image data binarized as described above is then given to the seam position determination section 503. The seam position determining unit 503 determines the position of the seam 71 using the method described below. FIG. 4 shows the seam part 71
FIG. When determining the position of the seam portion 71, first, four intersection points p, q, and
Coordinates of r, s (x3, y1), (x3, y
2 ), ( x4 , y1 ), ( x4 , y2
), and based on the obtained coordinates, find the intersections p, q, r, s
The area of the rectangle connecting the lines, that is, the area of the seam portion 71 within the window 72 is determined. Then, based on the obtained area, the center of gravity g of the seam portion 71 within the window 72 is determined.
The coordinates (x5, y3) of are determined, and this position is determined to be the center position of the seam portion 71.

The seam position determining section 503 supplies data representing the determined center position of the seam to the ultrasonic flaw detector as a control signal for controlling the ultrasonic flaw detector. The ultrasonic flaw detection device performs ultrasonic flaw detection on the seam based on data representing the center position of the seam given from the seam position determination unit 503 .

Next, the results obtained when the position of the seam of an electric resistance welded steel pipe is actually detected using the apparatus of the present invention as described above will be explained. The detection conditions in this case are that the ERW steel pipe is carbon steel with an outer diameter of 21.7 mm and a wall thickness of 2.5 mm, the pipe speed is 80 m/min, and the television camera is a high-speed shutter camera (1/1400 seconds). , the magnification was 3 times, and the illuminance of the projector was about 15,000 lx (irradiation angle of about 45 degrees).

FIG. 5 shows the amount of movement of the seam in the pipe circumferential direction and the detection error when the position of the seam of an ERW steel pipe is actually detected using the apparatus of the present invention under the conditions described above. This is a graph showing the relationship, with the vertical axis representing the measurement error and the horizontal axis representing the amount of movement of the seam portion in the circumferential direction. As is clear from Figure 5, the detection error is ±0.3mm.
It is within the range. Further, when the position of the seam portion was detected using a general conventional device under such conditions, the following detection error was obtained. As a representative example with the smallest detection error, in a device that implements the conventional first seam position detection method as described above, the detection error is ±1.5 mm.
As a representative example with the largest detection error, the detection error was within ±5.0 mm in a device implementing the conventional second seam position detection method as described above. As is clear from the above results, in the device of the present invention, the detection error was smaller and the detection accuracy was improved compared to the conventional device.

[0025]

Effects of the Invention As detailed above, in the device of the present invention, the surface of the ERW steel pipe irradiated with light is imaged two-dimensionally, and the imaged two-dimensional image shows the seam portion and other portions. Since it is binarized, the binarized two-dimensional image shows a two-dimensional image of the seam, and the position of such a two-dimensional image of the seam can be determined on the two-dimensional image. By converting into coordinates, the position of the seam in the ERW steel pipe can be determined with high accuracy, and the device includes a device that irradiates the surface of the ERW steel pipe with light, a device that images the irradiated portion, Since it is configured with a device that performs simple image processing, it has excellent effects such as being able to reduce the size of the device and reduce manufacturing costs.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a production line for ERW steel pipes to which a seam position detection device for ERW steel pipes according to the present invention is applied.

FIG. 2 is a block diagram showing the configuration of a seam position detection device.

FIG. 3 is a schematic diagram showing an image binarized by a binarization processing unit.

FIG. 4 is a schematic diagram illustrating a method of determining the position of a seam portion.

FIG. 5 is a graph showing the relationship between the amount of movement of the seam in the pipe circumferential direction and the detection error when the position of the seam of an electric resistance welded steel pipe is actually detected using the device of the present invention.

[Explanation of symbols]

51　Lighting device 52 TV camera 71 Seam part 501 Binarization processing unit 503 Seam position determination unit P ERW steel pipe

Claims (1)

[Claims] 1. A means for irradiating light onto the surface of an ERW steel pipe, and an imaging means for two-dimensionally imaging the area irradiated by the means, and based on the imaging result of the imaging means, the ERW steel pipe is A device for detecting the position of a seam portion, comprising means for binarizing a two-dimensional image captured by the imaging means into a seam portion and other parts, and a device based on the two-dimensional image binarized by the means. 1. A seam position detection device for an ERW steel pipe, comprising means for two-dimensionally determining the position of the seam in the ERW steel pipe.