JP2006247695A - Tandem torch welding method and torch polarity switching apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a technique for avoiding arc interference of a tandem torch, in which two or more torches are attached to a welding robot, to prevent occurrence of weld defects due to arc interference, and to perform the most suitable welding to various welding styles including multi-layer welding, in which a tandem torch is reciprocated, single torch welding, in which one torch comprising a tandem is retreated, or even an operation, in which one pool welding is switched with two pool by varying a torch interval. <P>SOLUTION: In the tandem torch welding method using a DC welding power source, two of the DC welding power sources are used and then, the polarity of the electrodes for the two torches arranged in parallel is reversed when the advancing direction of the torch is reversed, so that an electrode on the plus side relative to a workpiece is connected to the torch in the front in the advancing direction while an electrode on the minus side relative to the workpiece is connected to the torch in the rear in the advancing direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a welding method for a tandem torch in which two or more torches are mounted on a welding robot in welding a workpiece by a welding robot, and to a technique for avoiding arc interference between two adjacent torches.

  Welding by a tandem torch that is performed by attaching two or more torches to a welding robot and simultaneously operating them is known. Since welding with a tandem torch can increase the welding speed, there is an advantage that welding of a large workpiece having a long welding line can be performed in a short time. However, tandem torches cannot weld narrow or winding areas.

  In order to solve this problem, a technique of welding one of the tandem torches in the middle of welding to weld a narrow part or a winding part is proposed in the following Patent Document 1 relating to the applicant of this application.

  In the technique proposed in this document, in a welding head having a plurality of welding torches or a plurality of torches including a welding torch and a fusing torch, one of the torches is provided so as to be movable forward and backward. When welding a detail or a narrow part with a welding head provided with a plurality of welding torches, the welding is performed with one welding torch advanced. When welding a wide part at a high speed, welding is performed by setting a plurality of welding torches at the same position and operating all the welding torches.

  An example of the welding method described in the above document will be described with reference to FIG. In the example of the figure, there is a step 4a having a height H that interferes with the torch and a narrow portion K at the welding start position (a) and the end position (f). At the welding start position (a), the front torch 2a, which is the front side in the movement direction indicated by the arrow M in the figure, is retracted, and the welding head 1 is tilted clockwise in the figure, so that the rear torch is the rear side in the movement direction. The tip of 2b is brought close to the stepped portion 4a of the workpiece 4, and welding is started.

  Then, when the welding head moves to a distance where the interference between the front torch 2a and the step 4a is eliminated (position (b)), the front torch 2a is advanced, the inclination of the welding head is returned, and the arc of the front torch is started. It is set as the state which welds with both torches 2a and 2b. Then, at the timing at which the welding head 1 moves by the distance W between the front torch 2a and the tip of the rear torch 2b after starting the arc of the front torch 2a, the moving speed of the welding head 1 is increased and welding in a flat section L is performed. At high speed.

  Then, when approaching the narrowed portion K at the end of the weld line, the welding head 1 is decelerated, and after the deceleration operation is completed, the arc of the rear torch 2b is stopped at the timing moved by the interval W. The torch 2b is retracted, and the welding head 1 is tilted counterclockwise in the figure. In this state, it moves to the welding end (f).

  When the first layer welding is thus completed, the second layer welding is started from the position shown in FIG. That is, the welding head 1 starts moving in the reverse direction without stopping the arc of the leading torch 2a, and the welding to the point (a) is performed while the leading torch 2a and the trailing torch 2b advance and retreat in the same order as described above. I do. The above operation is repeated a predetermined number of times to weld a desired layer.

  In tandem torch welding, there are a case where one pool is formed by bringing the tips of two torches close to each other, and a case where two pools are formed with a gap between the tips. The present applicant specializes in a technique that can change the interval of the welding torch in the direction along the welding line of the work of the tandem torch so that both of the welding forming the 1 pool and the welding forming the 2 pool can be handled. This is proposed in Japanese Patent Application No. 2003-315600.

  The above-described method described with reference to FIG. 3 is welding in which one torch tip is formed close to the torch tip, but when welding is performed by connecting a DC power source of the same polarity to two welding torches with the torch tip close to each other. The magnetic action called magnetic blowing causes the two welding arcs to deviate in the direction in which they approach, causing arc interference. If arc interference occurs, there is a risk of undercutting, insufficient penetration, beat width irregularity, beat cracking, blow holes, and other welding defects.

In order to avoid arc interference caused by magnetic blowing, it is effective to drive one of the torches with an AC power supply. If the polarities of the two arcs are reversed, the magnetic blowing can cause the arc to deviate. It has been reported.
JP 2004-314104 A

  In this invention, in tandem torch welding using a DC power source, the occurrence of defective welding due to arc interference is prevented, and multilayer welding in which the tandem torch is reciprocated along the workpiece welding line, or one of the tandem torches is retracted. In various types of tandem torch welding, such as single torch welding performed in addition, and switching between 1 pool welding and 2 pool welding by changing the torch interval, welding is performed with the polarity most suitable for each type. The challenge is to make it happen.

  The tandem torch welding method according to the first aspect of the present invention that solves the above-described problem is a tandem torch welding method using a DC welding power source, wherein two DC welding power sources are used, and the torch on the front side in the traveling direction has a plus side relative to the workpiece. Of the electrode to be applied to the two torches arranged in parallel when the traveling direction of the torch is reversed so that the negative electrode with respect to the workpiece is connected to the torch on the rear side in the traveling direction. The polarity is reversed.

  The tandem torch welding method according to claim 2 of the present application is the tandem torch welding method using a tandem torch provided with an advancing / retreating device for retreating one of the welding torches with respect to the other. When the front torch moves backward, the rear torch moves in the single welding state by the distance W between the tandem torches, and then the positive electrode with respect to the workpiece is connected to the rear torch in the traveling direction. The tandem torch welding method according to claim 1, wherein the polarity of the electrode applied to the torch on the rear side in the traveling direction is reversed so as to shift to single torch welding.

  The above-described welding method of the present invention provides a welding power source and a workpiece by means of a robot controller for controlling the welding robot by providing a polarity switching device between the welding power source, the workpiece and the torch, and a signal of a tandem interface for controlling the tandem torch. And switching the connection with the torch.

  Accordingly, the torch polarity switching device for tandem torch welding according to the invention of claim 3 of the present application includes two DC welding power sources and a switching device, and the switching device is connected to each welding power source. The switching device has two pairs of input terminals, a first terminal and a second terminal, a work connection terminal, and the switching device in which the traveling direction of the tandem torch is reversed. Sometimes, one pair of + terminals is connected to the first torch connection terminal, the other pair of − terminals is connected to the second torch connection terminal, and the remaining − terminal and + terminal are connected to the work connection terminal. In one connection mode, one pair of-terminals is connected to the first torch connection terminal, the other pair of + terminals is connected to the second torch connection terminal, and the remaining + terminals and-terminals are connected to the work connection terminals. The second connection mode is switched.

  In the method of the present invention, when the movement direction of the tandem torch is switched, the polarity of the front torch in the new movement direction becomes a positive pole with respect to the workpiece, and the polarity of the rear torch becomes a negative pole with respect to the workpiece. Switching is performed. That is, according to the method of claim 1 of the present application, regardless of the direction of movement of the tandem torch, the torch forward in the moving direction becomes the + pole with respect to the workpiece, and the rear torch becomes the -pole with respect to the workpiece. When welding is performed in a state and tandem torch welding is performed with the torch tip approaching, the tip of the torch has a reverse polarity, and arc interference can be avoided.

  In the invention of claim 2, the forward torch in the traveling direction is used to switch to single torch welding when performing tandem torch welding with the torch forward in the traveling direction as the + pole and the rear torch as the -pole with respect to the workpiece. When retreating, the polarity of the remaining rear torch is switched from the negative pole to the positive pole for welding. By performing this switching, it is possible to ensure an appropriate polarity during single torch welding. When the tandem torch welding is retracted from the torch at the rear in the traveling direction to switch to the single torch welding, the polarity of the remaining single torch is originally a + pole, so that it is not necessary to switch the polarity.

  When performing tandem torch welding with a wide interval between two torches, such as welding that forms two pools, there is no risk of arc interference. I do. When tandem torch welding is performed with the torch at the rear in the traveling direction being positive, when the torch at the front in the traveling direction is retracted, the switching device is switched to a state in which both torches are both positive and the traveling direction. What is necessary is just to cut off the power supply circuit to the front torch.

  According to the present invention, there is an effect that it is possible to prevent occurrence of arc interference during tandem torch welding performed by bringing the torch tips close to each other. Furthermore, according to the present invention, when one of the tandem torches is retracted and switched to the single torch, single torch welding with an appropriate polarity can always be performed, and the tandem torch welding is performed by widening the interval between the torch tips. Even when performing the above, there is an effect that proper welding is performed with both the torch polarities being positive.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an entire welding apparatus for performing welding according to the method of the present invention, wherein 3 is a welding robot, 4 is a work, 5 is a positioner that supports the work 4 and changes its posture when necessary, and 6 is welding. A robot controller for controlling the movement of the robot 3 and the positioner 5; 7a and 7b are DC welding power supplies; 8 is a polarity switching device of the present invention; 2a and 2b are two torches attached to the tip of an arm 9 of the robot 3; 10 is a tandem interface for controlling the advance and retreat of the two torches 2a and 2b and the torch interval, and 11a and 11b are power supplies to the torch when one of the torches is retracted according to a command from the tandem interface 10. It is a switch that shuts off. Although 12a and 12b are search units, they are not directly related to the invention of the present application, and the cables connected from the polarity switching device 8 to the switches 11a and 11b are directly connected in the search units 12a and 12b. You can think about it.

  For each of the welding power sources 7a and 7b, the polarity switching device 8 is connected to the workpiece 4 via the positioner 5 and two pairs of input terminals 14a and 14b and 15a and 15b for connecting the positive electrode and the negative electrode. A set of two work connection terminals 16 and two torch connection terminals 17a and 17b connected to each of the two torches 2a and 2b are provided.

  The polarity switching device 8 includes two double-switching switches Sa and Sb that are electromagnetically operated. As shown in FIG. 2A, the two switching switches Sa and Sb are both tilted to the right side in the drawing. In the standard connection mode, the two + side input terminals 14a and 14b are both connected to the two torch connection terminals 17a and 17b, and the two − side input terminals 15a and 15b are both connected to the work connection terminal 16. Therefore, the two torches 2a and 2b are both positive with respect to the workpiece 4. On the other hand, as shown in FIG. 2B, when the left changeover switch Sb is switched to the left side in the drawing, the input terminal 14b connected to the positive pole of the welding power source 7b is connected to the work terminal 16, and the welding is performed. Since the terminal 15b connected to the negative pole of the power supply is connected to the left torch terminal 17b in the figure, one of the two welding torches 2a has a reverse polarity and the other 2b has a positive polarity. Further, as shown in FIG. 2C, when the right changeover switch Sa falls to the left in the state where the left changeover switch Sb is tilted to the right, the positive pole of the welding power source 17 a is connected to the work terminal 16. Since the negative electrode of the welding power source is connected to the torch terminal 17a, the polarities of the two welding torches 2a and 2b are opposite to those in the case of FIG.

  The changeover switches Sa and Sb are switched by a command from the tandem interface 10. That is, when welding is performed with a wide interval between the two torches 2a and 2b, or when single torch welding is performed with one of the two welding torches 2a and 2b retracted, both torches 2a are used. 2b is connected to the positive poles of the respective welding power sources 7a and 7b, and the tip of the two welding torches 2a and 2b is brought close to each other to perform tandem torch welding. Depending on the moving direction of the welding torch from the robot controller 6, the mode is switched to (b) or (c) in FIG.

  The switching operation of the polarity switching device 8 will be described by taking the torch operation of FIG. 3 described above as an example. In the state of FIG. 3 (a) in which welding is started from the left end of the weld line, the polarity switching device 8 is switched to the state of FIG. 2 (a), and the power source of the retreating welding torch 2a is switched to the switch 11a. Is blocked by. Therefore, in this state, welding is performed in a state where the welding torch 2b is a positive pole. In the state of FIG. 3C where the welding torch subsequently moves to become a tandem torch, the torch 2a becomes the torch forward in the traveling direction, and the polarity switching device 8 is switched as shown in FIG. 2B. Thus, the front torch 2a in the traveling direction becomes a positive pole, and the rear torch 2b becomes a negative pole. Then, when the welding torch 2b moves backward toward the welding end on the right side, the power to the welding torch 2b is cut off by the switch 11b simultaneously with the backward movement. Therefore, in this state, the remaining one torch 2a becomes a positive pole and welding is performed.

  The traveling direction of the welding head 1 is reversed from the state in which the welding torch has reached the right end in FIG. 3, and the second layer welding is started. At the beginning of the second layer welding, the welding is performed in the same state as that at the end of the first layer welding, that is, the advanced one torch 2a becomes a positive pole, and the position shown in FIG. When switching to the tandem torch, the polarity switching device 8 is switched to the state of FIG. 2C, the welding torch 2b on the front side in the traveling direction is the + pole, and the welding torch 2a on the rear side is the-pole. The welding is done. When the welding torch 2a retreats at the position shown in FIG. 3 (c) approaching the left end of the weld line, the switch 11a is shut off, and the remaining torch 2b becomes a positive pole until the left end of the weld line. Welding is performed. In the welding of three or more layers, the third layer is performed in the same operation as the first layer, and the fourth layer is performed in the same operation as the second layer.

  As described above, according to the method of the present invention, when tandem torch welding is performed with the torch tip approaching, the torch on the front side in the moving direction is the + side with respect to the workpiece, and the rear torch is on the workpiece. When welding is performed in the state of being on the negative pole side and any one torch is retracted, single torch welding is performed in a state where the remaining torch is on the positive side. Further, when performing tandem torch welding with a wide torch interval W, such as welding forming two pools, both torches are welded with a positive pole.

The block diagram which shows the example of the apparatus which welds with the method of this invention The figure which shows the switching state of the polarity switching apparatus of FIG. Explanatory drawing which shows the example of the tandem torch welding accompanied by the backward movement operation | movement of one torch

Explanation of symbols

2a, 2b torch,
3 Welding robot 5 Positioner 6 Robot controller
7a, 7b DC welding power source 8 Polarity switching device 9 Robot arm
10 Tandem interface

Claims (3)

  In a tandem torch welding method using a DC welding power source, two DC welding power sources are used, a positive electrode with respect to the workpiece is connected to the front torch in the traveling direction, and a negative polarity with respect to the workpiece on the rear torch in the traveling direction. A tandem torch welding method characterized by reversing the polarity of electrodes applied to two torches arranged in parallel when the traveling direction of the torch is reversed so that the side electrode is connected.   In a tandem torch welding method using a tandem torch provided with an advancing / retracting device that retracts one of the welding torches with respect to the other, when the torch on the front side in the traveling direction is retracted, the torch on the rear side in the traveling direction is added to the workpiece. 2. The tandem torch welding method according to claim 1, wherein the single torch welding is performed by reversing the polarity of the electrode applied to the rear torch in the traveling direction so that the side electrode is connected.   Two DC welding power sources and a switching device, the switching device including two pairs of input terminals, a first terminal and a second terminal, connected to each welding power source. The switching device is configured to connect one pair of + terminals to the first torch connection terminal when the traveling direction of the tandem torch is reversed, and to connect the other pair. A first connection mode in which the-terminal of the first terminal is connected to the second torch connection terminal and the remaining-terminal and the + terminal are connected to the work connection terminal, and one pair of-terminals is connected to the first torch connection terminal and the other A tandem torch welding torch polarity switching device that switches the second connection mode in which the + terminal of the pair is connected to the second torch connection terminal and the remaining + terminal and-terminal are connected to the work connection terminal.

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