JPS5915743B2 - Arc welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for accurately controlling the movement of a torch by the arc itself without using a groove position detector in automatic welding that progresses along the weld line direction of a weld joint. The present invention relates to an arc welding method in which welding conditions are controlled in accordance with the following motion.

In order to achieve unmanned automatic welding, a detection sensor and the detection A sensor-based torch position/O position adjustment mechanism is required.

Conventionally, this type of detection sensor has various types, such as contact type differential transformer type, potentiometer type, or limit switch type, or non-contact type electromagnetic type or optical position detection type. sensor is used.

However, in any case, in addition to the torch, a unique device called a sensor is installed near the torch, so a certain distance is required between the detection position and the control target position due to dimensional restrictions. Only an extremely complicated control method with limited accuracy has been put into practical use, in which the torch position is controlled by giving a time difference corresponding to the above-mentioned interval size to the output of the sensor. Therefore, the inventor
We previously developed a technology that improved the problems in the prior art described above and filed a patent application as Japanese Patent Application No. 583506. In the welding process,
A mechanism for moving the torch in the axial direction is provided to compensate the arc characteristics between the torch and the base metal for changes in wire protrusion length or arc length, and the amount of torch movement is constantly monitored to determine the axial displacement or position of the torch. is used for copying control.

According to this method, stable welding is possible without requiring a separate scanning sensor. That is, in the arc welding method of this prior invention, a direct current constant current power source is used as a welding power source, and the movement of the torch is controlled in the axial direction by the above-mentioned moving mechanism so as to maintain a set arc voltage. It is. Then, while moving the torch at a predetermined speed in the welding progress direction along the groove line of the base metal, the reciprocating motion By setting the direction change point to the point where the displacement or position in the direction of the torch axis becomes a predetermined value, the arc always reciprocates within the groove width due to the slope of the groove surface, performing a tracing operation, In addition, the arc welding force is maintained so that the height from the root to the toe of the welded joint is always kept constant. In addition, in this case, if the groove line is no longer parallel to the welding direction, or the width of the tip changes, etc., every half cycle of the reciprocating motion
Although the welding cross-sectional area changes, in this prior invention, a signal corresponding to the groove cross-sectional area is obtained for each cycle by time-integrating the change in the amount of movement of the torch in the axial direction for each half cycle. be able to. Separately, by differentiating the above-mentioned interval distance change for each cycle, a signal corresponding to the toe-to-toe distance can be obtained for each cycle. Furthermore, by using these signals for each cycle, the set values of various welding conditions such as welding current, torch movement speed, filler wire feeding speed, etc. are corrected and controlled using separately determined algorithms. This ensures that the desired welding and proper back bead formation in the case of single-sided welding are always achieved. However, while implementing this prior invention, the following problems were found.

In other words, the relative distance between the direction of torch movement and the groove in the direction of the torch axis may change due to deformation of the base material during welding, bending of the welding wheel rail, or malfunction in the initial position setting of the base material and torch. As a result, the reversal operation of the torch swing direction at the groove portion was not performed at the desired depth of the groove from the base material surface, resulting in a situation where the bead height was not constant. This invention solves the problems of the prior invention described above, and even if the relative distance between the torch moving direction and the bevel in the torch axial direction changes, the torch can be oscillated appropriately at the desired bevel. The present invention provides an arc welding method that enables dynamic reversal, in which the torch is moved toward and away from the base material so as to maintain the arc characteristics constant, and while the arc length is maintained constant. In an arc welding method in which welding is performed while the torch progresses while swinging in the width direction, the position or displacement of the torch in the axial direction is determined using a value indicating the surface position of the base plate in the swing direction of the torch as a reference value. The present invention is characterized in that the direction of swing of the torch is changed when the value reaches a predetermined value with respect to the reference value.

Next, the arc welding method of the present invention will be explained with reference to the drawings.

In FIG. 1, 1 and 1'' are objects to be welded, and 6 is an opening formed between objects 1 and 1' to be welded, consisting of opposing inclined surfaces 4 and 4' that widen toward the top and a bottom surface 5. 2 is a welding electrode inserted substantially perpendicularly into the groove 6; 3 is a welding torch through which the welding electrode 2 is passed; It may be a delivered consumable welding electrode or a non-consumable welding electrode.

A welding current is supplied to the welding electrode 2 to generate an arc between the tip of the welding electrode 2 and the groove portion 6, and the objects to be welded 1 and 1' are welded together by the arc heat. Bevel part 6
The welded portion is shielded from the atmosphere by a shielding gas ejected from the tip of the torch 3 or a separately provided nozzle (not shown). The torch 3 descends along the slope 4 from point A on one inclined surface 4 to point B on the bottom surface 5 in the width direction of the groove 6, as shown by the two-dot chain line in FIG. Then, it moves from point B along the bottom surface 5 to point C, and then rises from point C along the other inclined surface 4' to reach point D.

In this way, while the torch 3 moves along the groove surface of the welding part, the arc voltage or arc current of the arc generated between the tip of the welding electrode 2 and the groove part 6 is always maintained at a constant value. The torch 3 is moved up and down in the vertical direction, thus maintaining the distance between the tip of the welding electrode 2 and the groove 6 at a predetermined distance. The vertical position of the torch 3 that moves up and down the groove 6 is set at 1 in the width direction of the groove 6.
The voltage value is continuously detected for each movement. The detected voltage value is the voltage value that occurs when the welding electrode 2 rises to a position a predetermined distance H from the top of the groove 6, that is, the voltage value at the tip of the welding electrode 2 at A and D in FIG. When the voltage value indicative of the position matches, the moving direction of the torch 3 in the width direction of the groove portion 6 is reversed. FIG. 2 is a block diagram showing one embodiment of the present invention, in which the arc voltage of the arc generated between the tip of the welding electrode 2 and the groove 6 is always maintained at a constant value. An example in which the torch 3 is moved up and down in the vertical direction is shown.
In FIG. 2, a torch 3, which passes a welding electrode 2 inserted substantially vertically into a groove 6 formed between the workpieces 1 and 1', is connected to one of the workpieces 1 and 1'. The groove part 6 is moved by a cart (not shown) running on a rail (not shown) laid above the groove part 6 in parallel with the longitudinal direction of the groove part 6.
move in the longitudinal direction. 7 is a vertical screw rod for vertically moving the torch 3; 7' is a mounting member for the vertical screw rod 7; 8 is a vertical screw rod 7 installed at the upper end of the mounting member 7/; A support member 3'', which is a lifting motor for vertically moving the torch 3 and supports the torch 3, is screwed into a vertical threaded rod 7.

14 is a horizontal threaded rod for horizontally moving the torch 3, 14' is a mounting member for the horizontal threaded rod 14, and the mounting member 14' is fixed to the truck.

Reference numeral 15 denotes a horizontal movement motor installed at one end of the mounting member 14' for rotating the horizontal screw rod 14 and moving the torch 3 in the horizontal direction, and the mounting member 7 to which the vertical screw rod 7 is attached. '' is screwed into the horizontal threaded rod 14.

Therefore, the torch 3 is driven by the lifting motor 8 and the horizontal movement motor 15 to move the groove portion 6 in the vertical direction and the width direction. 10 is an arc voltage detector connected between the torch 3 and the workpiece 1, 11 is an arc voltage standard setter, and 12 is an arc voltage standard setter for the arc voltage value detected by the arc voltage detector 10. A differential amplifier 13 calculates the deviation from the arc voltage value set in advance by 11 and amplifies this deviation to a certain magnitude and outputs a deviation signal to a lifting motor controller to be described later. This is a lifting motor controller for controlling the driving of the lifting motor 8 and the reversal of the driving direction based on the deviation signal from the differential amplifier 12.

The arc voltage value detected by the arc voltage detector 10 is compared with the arc voltage preset by the arc voltage reference setter 11 by the differential amplifier 12. The differential amplifier 12 calculates the deviation of the detected arc voltage value from a preset arc voltage value, and outputs this deviation signal to the lifting motor controller 13. The controller 13 is
The lifting motor 8 is driven until the deviation signal becomes zero. In this way, the torch 3 moves the groove portion 6 in the width direction.
moves so that the distance between the tip of the welding electrode 2 and the groove 6 always maintains a predetermined distance. Reference numeral 9 indicates a potentiometer that continuously outputs, as a voltage value, a signal representing the vertical position of the torch 3 that moves up and down the groove portion 6; , a horizontal movement motor controller for reversing the rotation by a pulse sent from a comparator which will be described later, and 17 a speed setting device for setting the rotational speed of the horizontal movement motor 15.

Reference numeral 18 denotes a copying roller mounted on a truck so as to be able to move up and down via a spring or the like so as to constantly contact the surface of the workpiece 1'; 19 a support rod supporting the copying roller 18; 20; is a potentiometer for continuously outputting a signal indicating the vertical movement distance of the copying roller 18 as a voltage value.

The voltage value output from the potentiometer 20 is determined when the distance between the cart and the welded object 1'' is a preset distance, that is, when there is no vertical bend in the rail or the welded object 1/. is zero, increases as the distance increases, and decreases as the distance decreases.In other words, the potentiometer 20 measures the distance between the truck and the workpiece 1'. , continuously outputs a signal of the deviation from a preset distance as a voltage value.The voltage value output from the potentiometer 20 changes depending on the change in the distance between the cart and the workpiece 1'. 3 is equal to the voltage value output from the potentiometer 9 when the torch 3 moves up and down in the vertical direction.21 is for reversing the direction of movement of the torch 3 in the width direction of the groove 6;
This is a setting device for outputting a signal of a voltage value corresponding to a preset depth from the upper part of the groove portion 6 to a differential amplifier to be described later.

When performing multilayer welding on the groove 6, the reversal depth of the torch 3 differs for each welding pass, so the set voltage value differs for each pass. 22 was detected by potentiometer 20,
The sum of the voltage value corresponding to the deviation of the distance between the trolley and the workpiece 1' from a preset distance and the voltage value from the setting device 21 is calculated, and the value of this sum is set to a certain value. A differential amplifier 23 that amplifies the torch 3 when the voltage value continuously output from the potentiometer 9 matches the voltage value calculated by the differential amplifier 22. A comparator 24 outputs a reversal signal for reversing the direction of movement in the width direction of the groove 6 to the horizontal movement motor controller 16; This is a DC constant current power supply for use.

For each movement of the torch 3 in the width direction of the groove 6, the position of the torch 3 in the vertical direction is continuously detected by the potentiometer 9 as a voltage value (EY). This detected voltage value (EY) is sent to the comparator 23. Is the torch 3 the bevel for the potentiometer 9? 6, its bottom 5
The structure is such that a voltage value that increases as the voltage decreases toward the point is generated. As a result, the potentiometer 9 indicates that the torch 3 increases in height as it descends along one slope 4 of the groove 6 toward the bottom 5, and as it descends from the bottom 5 to the other slope 47. A voltage value that decreases as it increases is continuously sent to the comparator 23. on the other hand,
From the potentiometer 20, a voltage value (Ev
) is continuously output to the differential amplifier 22.

The differential amplifier 22 corresponds to the voltage value (EH) preset by the setting device 21 and the deviation of the distance between the truck and the workpiece 12 from the preset distance. The sum with the voltage value (Ev) is calculated, and this calculated voltage value (Ev) is calculated.
H+Ev) is output to the comparator 23 as a voltage value signal indicating the inverted position of the torch 3. Comparator 2
3 is a voltage value (Ev) indicating the position of the torch 3 in the vertical direction, which is continuously detected by the potentiometer 9 every time the torch 3 moves, and a voltage indicating the inverted position of the torch 3. The voltage value (EH+Ev) is compared with the voltage value (EH+Ev).
When EY) matches the voltage value (EH+Ev), an inversion signal for the moving direction of the torch 3 is output to the horizontal movement motor controller 16.

The horizontal movement motor controller 16 reverses the rotational direction of the horizontal movement motor 15 in response to the movement direction reversal signal. As a result, the direction of rotation of the horizontal threaded rod 14 is reversed,
As a result, the mounting member 7 screwed onto the horizontal threaded rod 14
By the action of ', the moving direction of the torch 3 in the width direction of the groove portion 6 is reversed. The groove portion 6 of the torch 3 mentioned above
The movement of the torch 3 in the width direction and the vertical direction, and the reversal of the direction of movement of the torch 3 in the width direction of the groove 6 are repeated 1, and thus the torch 3 moves between the tip of the welding electrode 2 and the groove 6. The tip of the welding electrode 2 follows the groove surface of the groove part 6 while always maintaining the distance between
The welding electrode 2 is moved back and forth in the width direction of the groove 6, and at the same time, the welding electrode 2 is moved in the longitudinal direction of the groove 6, so that the workpieces 1 and 1'' are moved in the longitudinal direction of the groove 6. Weld.

Thereafter, multilayer welding is performed within the groove portion 6 by the method described above, and welding of the objects 1 and 1' to be welded is completed. Next, according to the present invention, a part of the traveling rail of a welding machine truck, which is laid parallel to the groove 6' on the workpiece 1', is the workpiece 1' force tsubo surface ('c Nevertheless, the object to be welded 1/
An embodiment in which it is curved upward relative to the surface will be described with reference to FIGS. 1 and 2.

When the distance between the trolley running on the rail and the workpiece 1″ is a preset distance, the voltage of the signal output from the potentiometer 20 to the differential amplifier 22 The value (Ev) is zero.

Therefore, the voltage value (EH) preset by the setting device 21 is directly output to the comparator 23 as a voltage value signal indicating the inverted position of the torch 3. and,
When the voltage value (EY) of the signal indicating the position of the torch 3 outputted from the potentiometer 9 matches the voltage value of the signal indicating the inverted position of the torch 3, an inverted signal is sent from the comparator 23 to the horizontal movement motor controller. 16, and as a result,
The direction of movement of the torch 3 is reversed. On the other hand, when the truck reaches a rail curved upward relative to the object 1' to be welded, the distance between the truck and the object 1' to be welded becomes longer than the preset distance 5.

As a result, the potentiometer 20 detects the truck and the workpiece 1'.
A signal of the voltage value (Ev) corresponding to the deviation (ΔL) of the distance from the distance (G), that is, a voltage value (Ev'') higher than 0V is output to the differential amplifier 22. In the differential amplifier 22, the sum of the voltage value (Ev″) and the voltage value (EH) preset by the setting device 21 is calculated, and the sum of the calculated voltage values ( EH+EV●
is output to the comparator 23 as a voltage value signal indicating the inverted position of the torch 3. Then, a voltage value (EY
'') matches the sum of the voltage values (EH+EV''), the comparator 23 outputs an inverted signal to the horizontal movement motor controller 16. As a result, the torch 3 moves the groove portion 6 in its longitudinal direction while accurately reversing at the preset reversing position despite the change in the distance between the cart and the workpiece 1″. Therefore, a bead of uniform height is formed in the groove portion 6 of the welded objects 1 and 1'', and welding is performed satisfactorily. In the above embodiment, the torch 3 rises by the distance (ΔL) together with the cart, but as described above, the distance between the tip of the electrode 2 and the groove portion 6 always maintains the predetermined distance (A). controlled to do so.

In other words, the torch 3 descends by the distance (ΔL). As a result, the voltage value (EY'') indicating the vertical position of the torch 3 output from the potentiometer 9 is the same as the voltage value (E
Y) becomes a higher value. The voltage value of the difference between the voltage value (EY″) and the voltage value (EY) is equal to the voltage value (Ev″) of the signal output from the electrometer 20. In the above-mentioned embodiment, a part of the rail on which the truck runs is the object to be welded 1''.
However, if a part of the rail is curved downward relative to the object to be welded 1'', or if the rail is curved straight above the object to be welded 1', Even if the workpiece 1'' is curved upward or downward, the torch 3 will be accurately reversed at a preset reversal position, as in the above-described embodiment.

Further, in the embodiment described above, the tip of the welding electrode 2 and the groove portion 6
As a means of maintaining a constant distance between the torch 3 and the welding power source, a constant current power source is used to detect the arc voltage, and the torch Although the position in the vertical direction is controlled, when welding with a consumable welding electrode, use a constant voltage power source and use arc current instead of arc voltage, so that the arc current value always remains at a predetermined value. The position of the torch 3 in the vertical direction may be controlled.

As explained above, according to the arc welding method of the present invention, even if the distance between the trolley to which the torch is attached and the workpiece changes, the reversal of the groove of the reciprocating torch can be prevented. This can be done accurately at a preset position from the top of the groove.

Therefore, it is possible to always form a bead of uniform height at the groove, resulting in good penetration and an extremely useful effect such as obtaining an excellent welded part without welding defects. It will be done.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the principle of the invention, and FIG. 2 is a block diagram of a control circuit showing an embodiment of the invention. In the figure, 1, 1'... work to be welded, 2...
...Welding electrode, 3...Torch, 3''...
...Supporting member, 4, 4'...Slanted surface, 5...
...Bottom surface, 6...Bevel, 7...Vertical threaded rod, 7'...Mounting member, 8...
Lifting motor, 9... Potentiometer, 10...
...Arc voltage detector, 11...Arc voltage reference setter, 12...Differential amplifier, 13...
...Motor controller for lifting, 14...Horizontal threaded rod, 14/...Mounting member, 15...Motor for horizontal movement, 16...Horizontal Movement motor controller, 17... Speed setting device, 18... Copying roller, 19... Support rod, 20...
Potentiometer, 21... Setting device, 22...
Differential amplifier, 23... Comparator, 24...
...DC constant current power supply.

Claims (1)

[Claims] 1 Along the longitudinal direction of the groove formed in the workpiece,
Welding the object to be welded by continuously moving a cart equipped with a welding torch and generating an arc between the welding electrode inserted through the welding torch and the groove,
While the trolley is moving, the torch is moved back and forth in the width direction of the groove, the arc voltage or arc current (E_V) of the arc is detected, and a preset value (E_O) of the value (E_V) is detected. The torch is moved in the vertical direction so that the deviation (E_O-E_V) becomes zero, and thus the distance between the electrode and the groove is calculated. A predetermined distance (l) is maintained, and the position of the torch in the vertical direction is detected as a voltage value (e_Y) displayed by a potentiometer for each movement of the torch in the width direction of the groove. , in an arc welding method in which the moving direction of the torch is reversed when the voltage value (e_Y) matches a predetermined voltage, the predetermined voltage value is equal to a preset voltage value (e_H), the cart and the welded object. The distance between the object and the preset distance (L
) is equal to the sum value (e_H+e_V) of the voltage value (e_V) corresponding to the deviation (ΔL) from ), the direction of movement of the torch is reversed.