JPH0417755B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a two-electrode narrow gap welding method for welding joints of thick plates.

[Conventional technology]

As is well known, as a highly efficient method for welding joints of thick plates, there is a method of narrowing the groove width and performing one pass welding for each layer, which is called a narrow gap welding method. Furthermore, as a method for further increasing the efficiency of the narrow gap welding method, a two-electrode method in which two welding torches are arranged in parallel, one behind the other, can be considered, and it is expected that the efficiency will be approximately doubled.

[Problem that the invention seeks to solve]

However, according to the narrow gap welding method described above, the gap between the welding torch and the groove wall is usually 2 to 5 mm.
Because of its small size, workers can constantly monitor the welding situation.
It was necessary to adjust the torch position (up and down, left and right, and tilt) with high precision.

On the other hand, in the case of the two-electrode method, this monitoring and adjustment is more frequent, so the adjustment requires a high level of skill.Moreover, since the monitoring requires one's attention, it is mentally taxing and only experienced workers can handle it. Nakatsuta. Therefore, although this two-electrode method is extremely effective as a highly efficient welding method for thick-walled structures, the range of application is limited due to the lack of skilled workers, etc., and it has not been fully utilized.

The present invention has been made in view of the above circumstances, and enables one person to manage multiple joints by automating weld line tracing in thick-walled welded structures such as pressure vessels, thereby significantly improving efficiency and reducing costs. The purpose is to provide a two-electrode narrow gap welding method.

[Means for solving problems]

The present invention captures an image of the welded part of the preceding welding torch with a TV camera, processes the image to control the welding torch position to follow the appropriate position, and detects arc light at the top of the groove and focuses on the arc point. By controlling the welding torch angle, the leading welding torch is properly positioned within the narrow gap, and the position of the trailing welding torch is delayed for a certain period of time, so that the trailing welding torch is moved forward with the control signal used to correct the position of the leading welding torch. It is designed to imitate the welding torch of

[Effect]

First, a TV camera images the welded area of the preceding welding torch, and the image is processed to calculate the groove width, wire position, and wire protrusion length, and detect any deviation of the preceding welding torch within the groove. Next, this information is input to the control device, compared with a preset reference value, and a correction signal is issued to the drive system of the preceding welding torch to always keep the preceding welding torch 3a in the appropriate position (up, down,
(in terms of left, right, and angle). Next, the position of the preceding welding torch is memorized for a certain period of time, and when welding has progressed by the distance between both torches, the trailing welding torch is followed. By doing so, the position control of the leading and trailing welding torches necessary for welding deep and narrow die grooves can be completely automated, and the quality of thick plate multilayer welds can be improved and costs can be reduced.

In the present invention, a method of detecting arc light to follow (control) the welding torch angle is as follows. This will be explained with reference to FIGS. 3 and 4.

Narrow groove welding is aimed at narrow and deep grooves, and in FIG. 3, the gap between the welding torch 41 and the groove wall is approximately several mm. It is essential to proceed with welding while maintaining these conditions. but,
The groove may be deformed due to assembly errors or heat shrinkage during welding,
It may fall over as shown by the broken line in the figure. At this time,
Among the detection sensors 42a and 42b arranged on both sides of the welding torch 41 to detect arc light, the detection sensor 42a is blocked from light by the upper part of the groove, and the light reception signal changes from "bright" to "dark".

Therefore, the following angle control is performed so that the light reception signals of both detection sensors 42a and 42b become "bright". That is, welding arc point 43 in FIG.
In order to change the attitude (angle) of the welding torch 41 around , the movement distance L ₁ of the welding torch portion that connects the first motor 44a to the motor 44a via the transmission shaft 45a, and the movement distance L 1 of the welding torch portion that connects the first motor 44a to the motor 44a via the transmission shaft 45a, and
The welding torch is controlled so that the moving distance of the welding torch portion connected via the transmission shaft 45b is _L2 . More specifically, the moving speed of the first motor 44a and the moving speed of the second motor 44b are controlled to be L ₁ :L ₂ .

As described above, the arc light is detected and the welding torch angle is followed.

〔Example〕

Hereinafter, a case in which an embodiment of the present invention is applied to a thick-walled cylindrical circumferential joint will be described with reference to FIGS. 1 and 2a and 2b. Here, FIG. 1 shows an automatic torch position tracing method and a welding control method according to the present invention. Further, FIG. 2a is a front view partially showing FIG. 1, and FIG. 2b is a side view of FIG. 1a. Note that the attached letter a in the member number indicates a component of the preceding welding torch, and the attached letter b indicates a component of the trailing welding torch.

First, FIGS. 2a and 2b will be explained. 1a and 1b in the figure are base materials as thick-walled structures, and a backing metal 2 is provided on the back side. The base material 1
A leading welding torch 3a and a trailing welding torch 3b are provided between a and 1b. Welding wires 4a and 4b are provided at the tips of the preceding welding torch 3a and the trailing welding torch 3b, respectively. These welding wires 4a, 4b are connected to feed rollers 5a, 4b, respectively.
5b. In addition, 6a, 6 in the figure
b denotes a leading welding torch 3a and a trailing welding torch 3, respectively.
7a and 7b are welded metals produced by the same torches 3a and 3b, respectively.

Next, FIG. 1 will be explained. Note that the same members as those in FIGS. 2a and 2b are given the same reference numerals and their explanations will be omitted. Further, only the drive system on the preceding welding torch side will be described here. 8a in the figure is a shield box. This shield box 8a is provided with arc light detection sensors 9, 9, each of which has a built-in light-receiving element that constantly receives arc light on both sides of the torch on the upper surface of the groove and inside the groove and outputs a light-receiving signal using the photoelectric effect. ing. These sensors 9 have a narrow entrance path for receiving straight light and a function of emitting gas from this path for cooling and preventing the adhesion of welding fumes and the like. Preliminary welding torch 6a on this shield box 8a
Drive motors 12a, 13a are connected to the drive motors 12a, 13a via transmission shafts 10a, 11a. Here, one transmission shaft 10a is for tracing the torch 6a left and right (in the groove width direction), and the other transmission shaft 11
A is for tracing the inclination angle of the torch 6a.
The drive motors 12a, 13a are housed in a box 14a. On this box 14a is a torch 6.
A driving motor 16a is provided via a transmission shaft 15a for vertical copying.

Near the preceding welding torch 3a, there is an industrial TV camera 17 for imaging the welded part by the torch 3a.
is provided. This TV camera 17 is equipped with a suitable filter that can distinguish between the arc 6a, the molten pool, the welding wire 4a, and the groove wall, and its field of view is fixed on the welding area and is adapted to work in conjunction with the torch 3a. . An image processing device 19 is connected to the TV camera 17 via a cable 18 for transmitting TV signals. This device 19 binarizes the image of the welded part taken by the TV camera 17 (by setting an appropriate reference value, processes the brightness distribution of the arc light into binary values of bright and dark), and converts the resulting 2 Valued image
It works to calculate the groove width, wire position, and wire protrusion length from the TV scanning line signal.

A control device 21 having the following two functions is connected to the image processing device 19 via a cable 20 that transmits calculated data. This device 21 is composed of a microcomputer and an input/output interface, and compares information on the groove width, wire position, and wire protrusion length output from the image processing device 19 with preset reference values to determine the torch position (up, down, It has a function of always controlling the left and right sides to a constant condition, and a function of following the welding torch angle to correct the deviation of the preceding welding torch 3a at the upper end of the groove by judging the signals from the arc light detection sensors 9, 9. here,
Detailing the determination of the signals from the sensors 9, 9, when one of the sensors 9, 9 installed on both sides of the torch no longer receives arc light, the advance welding torch 3a is moved in the direction in which it receives the arc light. However, the torch 3a rotates in an arc around the arc point.

22 in the figure is the arc light detection sensor 9, 9
This is an amplifier connected via a cable 23 for transmitting a light reception signal. This amplifier 22 amplifies the transmitted weak light reception signal (current) and converts it into a voltage signal. Amplifier 22 and the control device 2
1 are connected by a cable 24 that transmits the amplified signal. The control device 21 and the drive motors 12a, 13a are connected by a cable 25 that transmits a welding torch left/right scanning signal and a welding torch angle scanning signal. The control device 21 and the drive motor 16a are connected by a cable 26 that transmits welding torch up and down tracing signals. A delay copying control device 28 is connected to the control device 21 via a cable 27 that transmits the groove width signal outputted from the image processing device 19, the welding torch outputted from the control device 21, and the left/right and angle scanning signals. It is connected. This device 28 first controls the welding speed from information on the groove width, and then changes the position (vertical, horizontal, angular) of the preceding welding torch 3a for a certain period of time (distance between the preceding welding torch 3a and the following welding torch 3b). divided by the welding speed), and the trailing welding torch 3b
Outputs a delayed copying control signal to. To explain in detail the control of the welding speed, the groove width between the preceding welding torch 3a and the trailing welding torch 3b is updated and stored in memory according to the progress of welding, and the average groove width during this period is calculated. The calculated average groove width is compared with a preset reference value, and if there is a difference, a differential voltage is generated and a command signal for an appropriate welding speed is output. To give an example of input/output timing, groove width data is captured every 5 mm of welding progress, and welding speed control signals are output every 20 mm of welding length (approximately every 3 seconds).

The delay copying control device 28 and the driving motors 12b and 13b on the trailing welding torch side are connected by a cable 29 that transmits left and right of the trailing welding torch 3b and a welding torch angle scanning signal.
In addition, the delay copying control device 28 and the drive motor 16b
They are connected by a cable 30 that transmits the up and down scanning signals of the torch 3b. The delay tracing control device 28 is connected to a welding speed controller 32 via a cable 31 for transmitting and receiving welding speed signals.
is connected. This controller 32 includes
A transmission mechanism 34 having a turning roller driving motor and a turning roller 35 are sequentially connected via a cable 33 that transmits a motor control signal.

Next, the effect will be explained. First, the welding part of the preceding welding torch 3a is imaged by the TV camera 17, this is binarized by the image processing device 19, the groove width, the wire position, and the wire protrusion length are calculated from this image, and the arc light Detection sensor 9, 9
Detects deviation of the preceding welding torch 3a in the groove. Next, this information is input to the control device 21, compared with a preset reference value, and a correction signal is issued to the drive system of the preceding welding torch 3a, so that the preceding welding torch 3a is always positioned at the appropriate position (vertical, horizontal, angular). (in terms of points). Next, the delayed tracing control device 28 memorizes the position of the preceding welding torch 3a for a certain period of time, and when the welding has progressed by the distance between both torches 3a and 3b (the variation in welding speed is corrected), the position of the preceding welding torch 3a is memorized. Follow the torch 3b. Here, this following means that the same signal as the correction signal given to the drive system of the preceding welding torch 3a is given to the drive system of the trailing welding torch 3b to correct the position of the trailing welding torch 3b.

According to the present invention, the preceding welding torch 3
The preceding welding torch 3a is detected by imaging the welding part a, by using the image processing method to trace the torch position (up, down, left and right), and by the arc light detection method to trace the torch angle.
By automating the tracing of the welding line and causing the trailing welding torch 3b to follow after a certain period of time, it is possible to automate the tracing of the welding line by both torches 3a and 3b. Therefore, the quality and efficiency of welding the base materials 1a and 1b can be improved, and multiple joints can be performed by one person, resulting in a significant cost reduction.

In the above embodiments, the case where the present invention is applied to a thick-walled cylindrical circumferential joint has been described, but the present invention is not limited to this, and similar functions and effects can be obtained also in longitudinal welding. In this case, the difference is that in the former case, welding is progressed by a turning roller, while in the latter case, it is carried out by a welding cart mounted on a welding torch. It has exactly the same action and effect.

In addition, the narrow gap welding method according to the present invention includes a method in which the arc is oscillated by applying a waveform bend to the wire by an appropriate method in order to prevent failure of fusion at the gap end, and a method in which the arc is oscillated by applying a waveform bend to the wire in order to prevent failure of fusion at the gap end. A method of swinging the arc using a real wire has already been proposed, but
Since the molten pool and arc conditions of the weld zone are basically the same, the present application can be applied to either of them.

〔Effect of the invention〕

As detailed above, according to the present invention, weld line tracing can be automated and multiple joints can be managed by one person, greatly improving efficiency and reducing costs, and can be applied to thick-walled welded structures such as pressure vessels. A two-electrode narrow gap welding method can be provided.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a two-electrode narrow gap welding method according to an embodiment of the present invention, Fig. 2a is a front view partially showing Fig. 1a, and Fig. 2b is a side view of Fig. 1a. FIG. 3 is an explanatory diagram of a method of controlling a welding torch by detecting an arc with a detection sensor, and FIG. 4 is an explanatory diagram of attitude control for changing the angle of the welding torch. 1a, 1b...Base metal, 3a...Advanced welding torch, 3
b... Trailing welding torch, 4a, 4b... Welding wire,
5a, 5b... feeding roller, 6a, 6b... arc,
7a, 7b...Welding metal, 8a, 8b...Shield box, 9...Sensor, 10a, 10b, 11a, 11
b, 15a, 15b...transmission shaft, 12a, 12b,
13a, 13b, 16a, 16b...Drive motor, 17...TV camera, 18, 20, 23, 2
4, 25, 26, 27, 29, 30, 31, 33
... cable, 19 ... image processing device, 21 ... control device, 22 ... amplifier, 28 ... delayed copying control device, 3
2...Controller, 34...Transmission mechanism, 35...Turning roller.

Claims (1)

[Claims] 1 Using a leading welding torch and a trailing welding torch 2
In the electrode type narrow gap welding method, the welded area of the preceding welding torch is imaged with a TV camera, and the image is processed to control the vertical and horizontal positions of the preceding welding torch to follow the appropriate position, and the arc is created at the top of the groove. By detecting light and controlling the welding torch angle around the arc point, the leading welding torch is appropriately positioned within the narrow gap, and the trailing welding torch's vertical, horizontal, and angular positions are delayed for a certain period of time to match the preceding welding torch. A two-electrode narrow gap welding method characterized by making the trailing welding torch follow the control signals used to correct the vertical, horizontal, and angular positions of the welding torch.