JPH0411303B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic vertical welding apparatus for a workpiece whose plate thickness increases in the direction of welding progress.

(Prior art) When performing butt welding of shaped steel whose plate thickness changes in the welding direction as shown in Fig. 6 a, b, c, while oscillating the wire in the plate thickness direction, the plate In order to obtain sufficient penetration of the thick surface area, it is necessary to weld the oscillation width as much as possible to the plate thickness. However, it is difficult to manually adjust the oscillation width during welding when the thickness of the workpiece changes, and this is particularly true for electrogas or When performing electroslag welding, it is difficult to identify the location where the plate thickness changes from the outside. Therefore, if the oscillation width is increased before the plate thickness changes, there is a risk that the torch will come into contact with the metal and be damaged. On the other hand, if the oscillation width is increased too late, there is a risk that it will melt near the plate thickness surface and cause insufficient damage. There are some problems.

As a means to solve the above problems, JP-A-52-
As described in Publication No. 69838, a technique has been proposed in which the optimal oscillation width corresponding to the height position of the torch tip or arc point is set in advance in a memory mechanism, and the oscillation width of the torch is adjusted using the signal to perform welding. ing. By the way, the proposed technique falls within the range of mechanical tracing techniques in which the oscillation width is adjusted by using a trajectory plate on which the movement trajectory of the wire tip is recorded or by making a tracing roller follow the material to be welded.
The structure around the welding torch becomes complicated, and depending on the shape of the structure around the object to be welded, it may be difficult to provide the trajectory plate near the weld line.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned problems, and the present invention does not provide a detection device around the welding torch or near the welding line. It is an object of the present invention to provide an automatic welding device that is relatively free from limitations and can accurately detect changes in plate thickness and adjust the oscillation width of a torch.

(Means for Solving the Problems) The gist of the present invention is to provide a vertical automatic welding device for welding a workpiece whose thickness increases in the direction of welding progress by oscillating a wire in the direction of the thickness. , a relay that opens and closes depending on the current level in conjunction with the welding ammeter pointer, and a welding torch that is raised so that the wire protrudes at a constant length at high speed when the relay is open and at low speed when closed. a clock for measuring the closing time of the relay, a comparator for comparing the closing time with a preset reference time, and a welding torch oscillation width adjustment motor when the closing time exceeds the reference time. There is provided a vertical automatic welding device characterized by having a control circuit for starting the vertical welding device.

The present invention will be described in detail below with reference to embodiments shown in the drawings.

(Operations and Examples) FIG. 1 is an explanatory diagram of an electroslag welding method, which is an example of a method to which the present invention is applied. In the figure, reference numeral 1 denotes a workpiece whose plate thickness increases in the direction of welding progress, and the workpiece 1 is surrounded by copper dowels 2 and 3 on the front and back to form a groove. 4 is already solidified weld metal, 5 is molten metal in an unsolidified state, and 6 is slag deposited on the top of molten metal 5. The wire 8 fed through the welding torch 7 is in the slag 6. It melts and becomes molten metal. Here, the length of the wire from the tip of the welding torch 7 to the upper end of the molten slag 6 is defined as the wire protrusion length.
The welding torch 7 is operated by a torch lifting mechanism (not shown) consisting of a holding roller for holding the welding torch 7, a lifting drive roller and a guide roller connected to a lifting motor via a speed reducer. Alternatively, the lifting mechanism may be a mechanism in which the clamp is raised and lowered by the rotation of an electric motor, and furthermore, it may be fixed to a slider 19 shown in FIG. 4 via a clamp 20.
Arrow 9 indicates the oscillation direction of wire 8. The oscillation width of the wire 8 must be selected to be an appropriate size corresponding to the plate thickness, and welding is performed by changing it as shown in FIG. 2 b ₁ to _{b 7} in accordance with the welding direction.

On the other hand, the welding torch 7 is raised as welding progresses, and the raising speed is automatically controlled and determined to keep the welding current substantially constant. In other words, when welding by feeding the wire at a constant speed using a DC power source with constant voltage characteristics as the welding current supply source, there is a correlation between the wire protrusion length and the welding current, so the welding current is kept approximately constant. If the control is performed, the length of the wire protrusion is maintained substantially constant, and the welding torch 7 can be raised in synchronization with the progress of welding.

To explain in more detail how to automatically raise the welding torch, first, set a speed H higher than the welding speed expected based on experience, a lower speed L, and a reference welding current value S, and then start welding. If the current becomes higher than the reference value S, the welding torch 7 is raised at a speed H, and if the welding current becomes lower than the reference value S, the welding torch 7 is raised at a lower speed L. Switching between the welding speeds H and L is performed in conjunction with the pointer of the welding ammeter, using a signal from a relay that opens and closes depending on the level of the welding current. To give an example and explain in detail, if the welding speed (the rising speed of the surface of slag 6) is faster than the rising speed of the welding torch due to some factor, then the wire protrusion length is gradually becomes shorter as the period progresses. Therefore, as the protruding length of the wire is reduced, the electrical resistance of the wire is reduced, and the welding current is thereby changed according to Ohm's law I=E/R (I: current, E: voltage,
R: resistance). When the increased welding current exceeds the reference welding current value S, the signal is switched by the relay 11 and the welding torch rises at speed H. Next, when the torch rising speed is at speed H, the welding torch rising speed becomes faster than the welding speed, so the wire protrusion length gradually increases as welding progresses. Therefore, the welding current decreases for the same reason as mentioned above due to the increase in the electrical resistance of the wire due to the increase in the protruding length of the wire. When the reduced welding current falls below the reference welding current value S, the signal is switched by the relay 11 and the welding torch rise speed becomes the speed L. If the welding current is controlled to be kept substantially constant in this manner, the welding torch is automatically raised while the wire protrusion length is also kept substantially constant. When using the above-mentioned automatic control method to weld a workpiece whose plate thickness increases while keeping the two preset welding torch rising speeds H and L fixed, the times of the speeds H and L will change as the plate thickness gradually increases. The ratio will change. To explain in detail, as the plate thickness increases, the groove cross-sectional area increases,
If welding is continued without changing the welding conditions, the amount of wire supplied is constant, so the time it takes to form the weld metal 4, in other words, the welding speed, slows down. That is, weld metal 4, weld metal 5, and
Since the rise of the slag 6 is slow, the change in welding current is slow compared to when the groove cross-sectional area is narrow, and the change in wire protrusion length is also slow. Therefore, as explained above, after the welding speed is switched to speed L, the time required for the wire protrusion length to gradually become shorter and the welding current to exceed the reference welding current value S is determined by the groove cross-sectional area. It will be longer than when it is narrow. Conversely, when the welding speed is switched to speed H, the welding torch rises faster than the welding speed, and the groove cross-sectional area increases and the welding speed slows down, so the wire protrusion length immediately increases and the standard welding current below the value S. In other words, by controlling the welding current to be approximately constant, the wire protrusion length is controlled to be approximately constant, and as the plate thickness of the workpiece increases, the groove cross-sectional area increases and the average welding speed decreases. is delayed. Therefore, the time ratio between the welding speeds H and L automatically increases with the speed L. FIG. 3 schematically shows how the time ratio changes and the welding current changes. In FIG. 3, the horizontal axis shows the elapsed time of welding, the lower vertical axis shows how the torch ascending speeds H and L are switched, and the upper vertical axis shows the welding current fluctuation. As shown in the figure, the torch rising speed is switched in response to fluctuations in the welding current, and the time ratio of the above speeds H and L changes from TH1/TL1 to TH2/TL2 as welding progresses (gradual increase in plate thickness). The torch is rising at a low rising speed L for a long time.

That is, if the wire is fed at a constant speed, the welding speed will decrease as the plate thickness increases, so by changing the time ratio of the torch rising speeds H and L, the average speed of the torch rising is made smaller. The welding speed is controlled to match the welding speed.

Focusing on the control configuration and welding phenomenon as described above, it is possible to conversely detect a change in plate thickness by observing and measuring the operation time of the torch rising speed H or L.

The operation of the apparatus of the present invention, which has been achieved from the above point of view, will be explained with reference to the example of the apparatus shown in FIGS. 4 and 5. In FIG. 5, 10 is a welding ammeter, 11 is a relay that opens and closes depending on the level of welding current in conjunction with the pointer of the welding ammeter 10, 12 is a clock that measures the closing time of the relay, and 13 is a comparator. The measured value of the closing time is compared with the set value 14 of the reference time, and a start signal is issued to the oscillation width adjustment motor drive circuit 15. 16 is an oscillation width adjustment motor, and 17 is an encoder for detecting the amount of rotation of the motor 16, which returns the amount of rotation of the motor 16 to the reference time setting value and increases the set time by one step. The opening/closing signal of the relay 11 is input to the torch raising mechanism 18 to raise the torch at a speed H or L.

FIG. 4 shows an example of an oscillating device according to the present invention. In FIG. 4, the welding torch 7 is connected to the slider 19.
The feed screw 22 is attached to the housing via a clamp 20, and is oscillated along a guide shaft 23 by a feed screw 22 which is rotated in forward and reverse directions by an oscillation motor 21. The oscillation width of the torch 7 is determined by the interval between the limit switches 24 and 25, and the interval is adjusted by rotating the feed screws 26 and 27 with the knob 28 or the motor 16.

Next, the operation of the apparatus of the present invention having the above configuration will be explained according to the welding procedure. The shape of the object to be welded will be explained with reference to a member whose plate thickness increases in one direction as shown in FIG.

When welding, first set the oscillation width appropriate for the plate thickness at the welding start point. The oscillation width is set by rotating the knob 28 and the motor 16, and the oscillation device is set so that the limit switch 25 on the side to be adjusted by the motor 16 is set to the side where the plate thickness increases.

When welding is started, the torch 7 rises as the relay 11 opens and closes, and each time the relay 11 opens and closes, the closing time is measured by the clock 12 and compared with the reference time setting value 14 by the comparator 13. However, here, relay 1
1 is closed, the torch is configured to rise at a low speed L.

At the beginning of welding when there is no change in the plate thickness, there is no change in the closing time of the relay 11, so no signal is output from the comparator 13 to the motor drive circuit 15, and therefore welding is performed with the oscillation width kept at the initial setting. As the welding progresses, as the plate thickness begins to increase, the welding speed decreases, the closing time of the relay 11 becomes longer, the average speed of torch rise also decreases, and welding is performed with the wire protrusion length being approximately constant. When the closing time of the relay 11 becomes longer than the reference time setting value, a signal is generated from the comparator 13, the motor 16 rotates, the limit switch 25 moves, the interval between the limit switches 24 and 25 is expanded, and the oscillation width is widened. By detecting the rotation amount of the motor 16 with the encoder 17 and performing feedback control that adds an increase proportional to the rotation amount to the reference time setting value, the closing time of the relay 11 is shorter than the reference time setting value. The motor 16 then stops. When the plate thickness further increases, the closing time of the relay 11 becomes longer than the reference time setting value again, the motor 16 starts, and the oscillation width increases.

By repeating the above operations, the oscillation width increases in accordance with the increase in plate thickness, and welding is performed.

Furthermore, when welding a workpiece as shown in FIG. The adjustment mechanism is not limited to that shown in FIG. 4, but any mechanism that is adjusted by motor drive can be implemented within the scope of the present invention.

(Effects of the Invention) As described above, according to the device of the present invention, an appropriate oscillation rate can be achieved for a workpiece whose plate thickness gradually increases without using mechanical tracing techniques such as a trajectory plate or a tracing roller as in the prior art. This greatly contributes to improving welding workability and realizing high-quality welds by making it possible to provide a wider width.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of electroslag welding, which is an example of a method to which the present invention is applied, Fig. 2 is a schematic diagram showing changes in the oscillation width of the torch, and Fig. 3 is a schematic diagram showing changes in the torch rising speed and welding current. 4 is a mechanical diagram of an example of an oscillating device, FIG. 5 is a block diagram showing the configuration and operation of the device of the present invention, and FIG. 6 a, b, and c show the shape of a workpiece to which the present invention is applied. It is a sectional view showing an example. 1... object to be welded, 2, 3... copper dowel, 4... weld metal, 5... molten metal, 6... slag, 7...
Welding torch, 8... wire, 9... oscillation direction, 10... ammeter, 11... relay, 12...
Clock, 13... Comparator, 14... Reference time setting value, 15... Motor drive circuit, 16... Oscillation width adjustment motor, 17... Encoder, 18...
Torch lifting mechanism, 19...Slider, 20...Clamp, 21...Oscillating motor, 22...
Feed screw, 23...Guide shaft, 24, 25...Limit switch, 26, 27...Feed screw for adjusting oscillation width, 28...Adjustment knob, H, L...
...Torch rising speed, _b1 to _b7 ...Oscillation width.

Claims (1)

[Claims] 1 A workpiece whose plate thickness increases in the direction of welding progress,
In vertical automatic welding equipment that welds by oscillating wire in the plate thickness direction, there is a relay that opens and closes depending on the current level in conjunction with the pointer of the welding ammeter, and when the relay is open it is fast and when it is closed it is a lifting mechanism that raises the welding torch at low speed so that the length of wire protrusion is approximately constant; a clock that measures the closing time of the relay; a comparator that compares the closing time with a preset reference time; A vertical automatic welding device characterized by having a control circuit that starts an oscillation width adjustment motor of a welding torch when a closing time exceeds a reference time.