JPH0439883B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for detecting the position of an outer welded portion of an electric resistance welded pipe.

[Prior art and its problems]

ERW pipes are made by passing steel strips through a group of forming rolls, forming the steel strips upward into a circular shape so that their seam ends face each other, and then folding the seam ends of the raw pipe formed into a circle in this way. The base pipe is adjusted by welding the seam ends together under pressure using a squeeze roll while heating, and the surplus of the weld bead of the base pipe thus adjusted is cut off with a cutting tool. Manufactured continuously.

The electric resistance welded tube manufactured in this way is transported to the flaw detection device installed downstream of the production line described above, and the flaw detection device detects defects inside the weld after cutting off the excess material. Then, the ERW tube is transported to a heat treatment device provided downstream of the flaw detection device, as necessary, and is treated by the heat treatment device.
Heat treatment is continuously applied to the weld.

The center of the welded portion of the electric resistance welded ship is located approximately at the upper part of the electric resistance welded tube, but the center position of the welded portion shifts in the circumferential direction during the manufacturing process of the electric resistance welded tube. For this reason, in order to accurately perform the flaw detection and heat treatment of the weld defects described above, it is necessary to make these flaw detection and heat treatment devices follow the movement of the weld. need to be detected accurately.

A conventional method for detecting the center position of a welded portion in an electric resistance welded pipe is disclosed in Japanese Patent Laid-Open No. 58-37550 (hereinafter referred to as prior art). The principle of the method for detecting the center position of a welded part according to this prior art will be explained with reference to FIGS. 8 and 9.

During manufacture of the electric resistance welded pipe 1, the excess weld bead of the raw pipe is cut with a cutting tool at a temperature of approximately 1200°C, so the surface of the welded portion 2 rapidly oxidizes. Therefore, the reflectance of the surface of the welded portion 2 is lower than that of the surface of the base material portion 1' adjacent thereto.
Focusing on this point, as shown in Fig. 8, the electric resistance welded pipe 1
A light receiver 4 is placed above the welding part 2 of the light receiver 4.
A pair of floodlights 3 are placed on both sides of the weld zone 2 and the base metal portion 1' in its vicinity by the pair of floodlights 3.
The surface of the welded part 2 and the base metal part 1' is irradiated with light.
The brightness of the surface of the welded part 2 is detected by the light receiver 4, and the center position of the welded part 2 is detected based on the brightness signal thus detected.

That is, since the brightness level of the surface of the base metal part 1' is higher than the brightness level of the surface of the welding part 2, the brightness signal detected by the light receiver 4 is as shown in FIG. 9A. It becomes a waveform. Therefore, a threshold level of a predetermined magnitude is set for the luminance signal, and the luminance signal is binarized as shown in FIG.
Based on the valued luminance signal, the central position L of the welded portion 2 in the width direction is calculated by the calculator 5 using the following formula.

L=l ₁ +l ₂ /2 ...(1) However, l ₁ : Dimension based on the time until the first fall of the binarized luminance signal, l ₂ : Second rise of the binarized luminance signal Dimensions based on time.

However, the above-mentioned prior art has the following problems.

(1) If heat treatment is applied to the welded part 2 of the ERW pipe 1 after cutting the weld bead, the surface of the welded part 2 will of course
The surfaces of the base material portion 1' in the vicinity are oxidized, and the reflectance of these surfaces is therefore reduced.
The brightness level of the surface of the base metal part 1' near the weld is as follows:
The difference between the luminance level of the surface of the welded part 2 and the luminance level of the surface of the welded part 2 becomes smaller. As a result, the center position of the welded portion 2 cannot be detected accurately.

(2) During pipe making,
If scratches are caused by a squeeze roll or the like, the reflectance of the surface of the base material 1' will partially change.
The waveform of the reflected luminance signal obtained by the light receiver 4 is disturbed. As a result, the position of the welded portion 2 cannot be detected accurately.

Therefore, even if heat treatment is applied to the welded part 2, and
There is a need for a method for detecting the position of the outer surface weld of an electric resistance welded pipe, which can always accurately detect the center position of the weld 2 even if there are flaws on the surface of the base metal 1' near the weld. However, such a method has not yet been proposed.

[Purpose of the invention]

Therefore, an object of the present invention is to always accurately detect the center position of the weld even if the weld is heat-treated and even if there are flaws on the surface of the base metal near the weld. An object of the present invention is to provide a method for detecting the position of an outer welded portion of an electric resistance welded pipe.

[Summary of the invention]

In the present invention, a left side floodlight and a right side floodlight are arranged above a horizontally moving electric resistance welded tube, and the left side floodlight illuminates the welded portion of the electric resistance welded tube and the surface of a base material in the vicinity thereof diagonally in the upper left direction. irradiate the surface with light from the right side using the right side projector, and measure the brightness of the surface with a light receiver disposed between the left side projector and the right side projector, and In the method for detecting the position of the welded part on the outer surface of an ERW pipe, the method comprises detecting the position of the welded part based on the brightness signal measured in this way, , and the left side brightness of the surface due to the irradiated light from the left side projector and the right side brightness of the surface due to the irradiated light from the right side projector are measured by the light receiver, and the thus measured The level of the left side brightness signal and the level of the right side brightness signal are compared for each position on the circumferential surface of the ERW tube, and the lower level is selected for each position on the surface as the brightness signal. The present invention is characterized in that only the brightness signal of the surface of the welded part is extracted by combining, and the position of the welded part is detected based on the thus extracted surface brightness of the welded part. It is something.

[Structure of the invention]

The inventors of the present application have conducted extensive research in order to solve the above-mentioned problems. As a result, we obtained the following knowledge. In other words, even if the weld is heat-treated, and even if there are flaws on the surface of the base metal near the weld, in order to always accurately detect the center position of the weld, it is necessary to It is sufficient to extract only the brightness signal of the surface of the welded part from the brightness signal of the surface of the base metal part.

This invention was made based on the above-mentioned knowledge. The principle of this invention will be explained below with reference to the drawings.

In FIG. 1, the left side emitter 3A and the right side emitter 3B are arranged on both sides of the receiver 4 installed directly above the welded part 2 of the ERW pipe 1.
Light is irradiated onto the surfaces of base material portions 1'A and 1'B in the vicinity thereof. Left side floodlight 3A and right side floodlight 3
B is an angle (θ) in which the irradiation direction of the light is perpendicular to the axis of the ERW tube 1 and with respect to a straight line l that passes through the center of the welded portion 2 in the width direction and extends in the radial direction of the ERW tube 1.
They are arranged on both sides of the light receiver 4 so as to be tilted by a certain amount. Left side floodlight 3A and right side floodlight 3B
The irradiation light from the base metal part 1'A near the welding part
It is specularly reflected on the surface of base material 1'A, 1'B, as shown in FIG.
In this case, only the light specularly reflected by the surfaces of the base metal parts 1''A and 1''B at positions slightly away from the welding part 2 directly enters the light receiver 4.

Therefore, the left side floodlight 3A and the right side floodlight 3B
When light is simultaneously irradiated on the surface of the welded part 2 of the ERW pipe 1 and the base material parts 1'A and 1'B in the vicinity thereof,
A luminance signal having three peaks as shown in FIG. 2B is obtained from the light receiver 4.

As shown in Fig. 2B, the brightness level of the surfaces of the base metal parts 1''A and 1''B located slightly away from the welding part 2 is highest due to the irradiation from the left side floodlight 3A and the right side floodlight 3B. This is because the light is specularly reflected on the surfaces of the base material portions 1''A and 1''B and directly enters the light receiver 4. The brightness level of the surface of the welded part 2 is the same as that of the base metal parts 1'A, 1'B on both sides, that is, the base metal parts 1''A, 1''B.
The base metal parts 1'A and 1'B are closer to the welding part 2 compared to
The brightness level of the welded part 2 is higher than that of the surface of
This is because the surface of the weld bead is cut off by a cutting tool, so it becomes a diffusely reflecting surface, and the diffusely reflected light thereby enters the light receiver 4.

In the prior art described above, the reason why the luminance signal obtained by the light receiver 4 does not have the waveform shown in FIG. , 1''B, the irradiation light from the projector 3, which is diametrically opposed to the surface of the base metal parts 1'A and 1'B, which is closer to the welding part 2, directly enters the receiver 4.

As described above, by irradiating light from the left side floodlight 3A and the right side floodlight 3B onto the welding part 2 of the electric resistance sewing machine 1 and the surfaces of the base metal parts 1'A and 1'B in the vicinity thereof, welding can be performed. Although the brightness signal of the surface of the welded portion 2 can be obtained, it is necessary to extract only the brightness signal of the surface of the welded portion 2 from other brightness signals.

Next, this extraction method will be explained. As shown in FIG. 3A, the light irradiated from the left side emitter 3A to the surface of the welding part 2 is diffusely reflected on the surface of the welding part 2 and enters the light receiver 4, and as shown in FIG. 3B, The light irradiated onto the surface of the welding part 2 from the right side projector 3B is diffusely reflected on the surface of the welding part 2 and enters the light receiver 4.

As shown in FIG. 4A, the light irradiated from the left side projector 3A onto the surfaces of the base metal parts 1'A, 1'B near the welding part 2 However, only the light that has been specularly reflected on the surface of the base material portion 1″A enters the light receiver 4.As shown in FIG. The light irradiated onto the surfaces of the base metal parts 1'A and 1'B is specularly reflected by the surfaces of the base metal parts 1'A and 1'B, but the light of the base metal parts 1''B is reflected on the light receiver 4. Only the light that is specularly reflected by the surface enters.

As shown in FIG. 5A, the light irradiated from the left side projector 3A to the flaws 6A, 6B on the surfaces of the base metal parts 1'A, 1'B near the welding part 2,
However, only the light that was specularly reflected on the surface of the left flaw 6A enters the light receiver 4. As shown in FIG.
However, only the light that was specularly reflected on the surface of the right flaw 6B enters the light receiver 4. Notch-shaped flaws 6A caused by squeeze rolls, etc.
6B has an exposed metal surface and is mirror-like, so the irradiated light from the left and right projectors 3A, 3B is regularly reflected by the flaws 6A, 6B.

As is clear from the above, on the surface of the welded part 2, the left and right floodlights 3A, 3B
The irradiated light from any of these is diffusely reflected and enters the light receiver 4. On the other hand, on the surfaces of the base material parts 1'A, 1'B, only the irradiated light from either the left or right emitters 3A, 3B is directly opposite to the light receiver 4.
does not enter.

Therefore, the left side floodlight 3A and the right side floodlight 3B
Welding part 2 and base metal part 1' in the vicinity alternately from
A, 1'B surfaces are irradiated with light, and the level of the left side luminance signal due to the irradiated light from the left side projector 3A and the level of the right side brightness signal due to the irradiated light from the right side projector 3B are thus obtained. By comparing each position in the circumferential direction of the ERW tube 1, selecting the lower signal level at each position, and combining it as a brightness signal, it is possible to extract only the brightness signal of the surface of the welded part 2. can.

In this way, when only the brightness signal of the surface of the welded part 2 is extracted, a predetermined threshold level is set for the brightness signal and the brightness signal is binarized. The center position of the welded portion 2 in the width direction can be detected based on the brightness signal.

As shown in FIG. 6A, when there is a flaw 6A on the surface of the left side base material 1'A of the welded part 2 of the ERW tube 1, the waveform of the left side brightness signal due to the irradiated light from the left side projector 3A. is shown in FIG. B, and the waveform of the right brightness signal due to the light emitted from the right floodlight 3B is shown in FIG. The waveform of the luminance signal obtained by selecting and synthesizing the lower signal level at each position is shown in figure D, and figure E is shown in figure D.
2 shows the waveform of the minimum value of the binarized luminance signal.
The center position L of the welded portion 2 is calculated from the equation below from E in the figure.

L= _l3 + _l4 /2...(2) However, _l3 : Dimension based on the time to the rise of the binarized luminance signal, _l4 : Dimension based on the time to the fall of the binarized luminance signal. Dimensions.

Next, an embodiment in which the present invention is applied to an automatic weld follower for an electric resistance welded pipe will be described with reference to the block diagram of FIG.

In FIG. 7, the pedestal 7 is freely moved along a rail 8 curved with the same curvature as the electric resistance welded pipe 1 by a tracing motor 9. A light receiver 4 is mounted on the mount 7.
and a left emitter 3A placed on both sides of the receiver 4.
and a right side floodlight 3B are attached.
The left and right floodlights 3A and 3B are alternately blinked at predetermined time intervals by a blinking control circuit 10.

An analog signal of the left side luminance of the surface of the welding part 2 and the base material parts 1'A and 1'B in the vicinity thereof, which is generated by the irradiation light from the left side emitter 3A arranged on the left side of the light receiver 4, is sent to the A/D converter 11. is converted into a digital signal by Similarly, the analog signal of the right side brightness of the surface of the welding part 2 and the base metal parts 1'A and 1'B in the vicinity thereof by the irradiation light from the right side emitter 3B arranged on the right side of the light receiver 4 is A /D converter 11 converts the signal into a digital signal.

The left and right luminance signals converted into digital signals in this manner are alternately stored in the left storage circuit 12 and the right storage circuit 13 according to commands from the blinking control circuit 10.

The left and right brightness signals stored by the left and right storage circuits 12 and 13 are compared by the brightness signal detection circuit 14, and only the brightness signal of the surface of the welded part 2 is extracted.

The luminance signal of the surface of the welded part 2 extracted in this way is binarized by the center position calculation circuit 15 based on a preset threshold level, and The center position is calculated.

A plurality of calculation results of the center position of the welded portion 2 by the center position calculation circuit 15 are collected by the average value calculation circuit 16, and the average value thereof is calculated.

The calculation result of the center position of the welded part 2 averaged in this way is processed by the deviation calculation circuit 17 as follows.
A signal that is compared with a preset reference value and whose deviation becomes zero is sent to the copying motor 9.

As a result, even if the position of the welded portion 2 of the electric resistance welded pipe 1 shifts in the circumferential direction during pipe production, the pedestal 7 always follows the movement. Therefore, by connecting the frame 7 and, for example, a flaw detection device, the welded portion 2 can be accurately detected at all times.

〔Effect of the invention〕

As explained above, according to the present invention, the center position of the weld can always be accurately detected regardless of the brightness state of the surface of the weld and the base material in the vicinity. Useful effects are produced.

[Brief explanation of drawings]

Figure 1 is a front view showing the principle of this invention, Figure 2 is a front view showing the principle of this invention.
Figure A is a front view showing the state in which the irradiated light from the left and right side floodlights is regularly reflected on the surfaces of base metal parts 1''A and 1''B, and Figure B is a front view showing the welded part and its vicinity from the left and right side floodlights. Figure 3A is a graph showing the relationship between the brightness when light is irradiated onto the surface of the base material and the circumferential position of the ERW tube. Figure 4B is a front view showing the state, and Figure 4A is a front view showing the state in which the irradiated light from the right side floodlight is diffusely reflected on the surface of the welded part.
is a front view showing a state in which the irradiated light from the left side projector is regularly reflected on the surface of the left side base material part, and Figure B shows a state in which the irradiated light from the right side projector is regularly reflected on the surface of the right side base material part. Front view, Figure 5A is a front view showing the state in which the irradiated light from the left side projector is specularly reflected on the surface of the flaw on the left side base material, and Figure 5B shows the state where the irradiated light from the right side projector is reflected on the right side base material. Figure 6A is a front view showing a state in which the irradiated light from the left and right side floodlights is reflected on the surface of an ERW tube with a flaw on the left side base material. Figure, same B
The figure is a graph showing the relationship between the left side brightness and the position in the circumferential direction of the ERW pipe. The figure C is a graph showing the relationship between the right side brightness and the position in the circumferential direction of the ERW pipe. The figure D is a graph showing the relationship between the right side brightness and the circumferential position of the ERW pipe. Fig. 7 is a graph showing the relationship between the brightness of the welded part and the position in the circumferential direction of the ERW pipe. A block diagram of an embodiment applied to an automatic tracking device, FIG. 8 is a front view showing the principle of the prior art, and FIG. A graph showing the relationship between the brightness of the surface and the position in the circumferential direction of the ERW tube,
Figure B is a graph showing binarized luminance. In the drawings, 1... ERW pipe, 2... Welded part, 1'... Base metal part,
1'A...Left side base metal part, 1'B...Right side base metal part, 3
... Emitter, 3A... Left emitter, 3B... Right emitter, 4... Receiver, 5... Arithmetic unit, 6A, 6
B...Flaw, 7... Frame, 8... Rail, 9... Copying motor, 10... Flashing control circuit, 11... A/
D converter, 12... Left memory circuit, 13... Right memory circuit, 14... Luminance signal detection circuit, 15...
Center position calculation circuit, 16...Average value calculation circuit, 1
7... Deviation calculation circuit.

Claims (1)

[Scope of Claims] 1. A left side floodlight and a right side floodlight are arranged above a horizontally moving electric resistance welded tube, and the left side floodlight illuminates the welded portion of the electric resistance welded tube and the surface of the base material in its vicinity. Light is irradiated diagonally from the upper left, the right side emitter irradiates the surface diagonally from the upper right, and the brightness of the surface is measured by a light receiver placed between the left side emitter and the right side emitter. and, in the method for detecting the position of the welded part on the outer surface of an electric resistance welded pipe, the method comprises detecting the position of the welded part based on the luminance signal measured in this way. Light is irradiated alternately from the projector, and the left side brightness of the surface due to the irradiation light from the left side projector and the right side brightness of the surface due to the irradiation light from the right side projector are measured by the light receiver, and in this way, Comparing the measured level of the left side luminance signal and the level of the right side luminance signal for each position on the circumferential surface of the ERW tube, and selecting the lower level for each position on the surface, By combining the luminance signals as a luminance signal, only the luminance signal of the surface of the welding part is extracted, and the position of the welding part is detected based on the surface luminance of the welding part extracted in this way. A method for detecting the position of the outer welded part of an ERW pipe.