JP2009006368A - Gas shielding and arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the welding efficiency of tandem arc welding by increasing a welding current without causing arc interference with respect to a welding method in which a plurality of welding torches are synchronously moved that are juxtaposed so that torch tip ends are in a forward and backward relation relative to the advancing direction (welding direction) of the torches. <P>SOLUTION: The gas shielded arc welding, particularly desirably, CO<SB>2</SB>gas shielded arc welding is performed in a manner that, in a plane including an advancing direction B of torches, the front torch 2f in the advancing direction of two torches arranged in a truncated chevron is right-angled, at least in the tip end axial line, to the torch advancing direction B, or that the tip end axial line of the front torch 2f is inclined in the direction forward in the torch advancing direction in the tip end side (base material side). Since at least the tip end axial line of the front torch 2f and the rear torch 2r is in the truncated chevron, the axial line of the rear torch 2r is more inclined, in the tip end side, than the front torch 2f in the direction forward in the torch advancing direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a welding method in which a plurality of welding torches arranged in parallel so that the front end of the torch is in a front-rear relationship with the traveling direction (welding direction) of the torch are synchronously moved.

  In order to improve the welding quality by controlling the current value and the wire feed speed given to multiple welding torches, the main purpose is to improve the productivity of welding work by increasing the moving speed of the welding torch. Arc welding (hereinafter referred to as “tandem welding”) performed by synchronously moving the front and rear of the torch tips in a state where the front-rear relationship is kept constant is known as shown in Patent Documents 1 to 3.

  In tandem welding, welding is performed with two torches that move synchronously. Therefore, more molten metal can be melted into the base metal with a single movement of the torch compared to single welding with one torch. By adopting tandem welding for gas shielded arc welding, which is relatively high per se, efficient high-speed welding can be realized.

  In tandem welding, it is necessary to make the torch tip approach so that the two welding wires fed from the tip of the two torches form one molten pool. The arc column is disturbed and the welding quality is degraded. Also, if the current passed through each of the front and rear torches is about the same as that when welding with a single torch, arc interference is likely to occur and the thermal load becomes excessive, which also degrades the welding quality. . Since the front torch located in front of the traveling direction of the torch becomes a torch forming a molten pool, the current value is made larger than that of the rear torch. That is, in the conventional tandem arc welding, the current flowing through the front torch is made lower than that in the case of the single torch, and the current passed through the rear torch is made lower than that. For this reason, even if two torches are used, the improvement in welding efficiency is usually only about a few percent.

  As described above, in tandem arc welding, for example, the front and rear torches need to be close to each other at intervals of about 20 mm so that the wire ends of the torches form one molten pool, but the torch body is thicker than that. Must be bent in a direction approaching each other (see Patent Document 2), or the entire torch must be arranged in an inverted C shape so that the tip side approaches. The apex angle of the tip of the torch at this time, in fact, the inverted half-shape of the welding wire is about 10 to 30 degrees.

The angle of the torch tip with respect to the torch traveling direction when welding with one torch is usually a right angle. Also in the case of performing tandem welding, conventionally, welding is performed such that the center line C of the two torches 2f and 2r is perpendicular to the torch traveling direction B, as shown in FIG. Accordingly, at this time, the front torch 2f is inclined in a direction in which the torch tip side is retracted with respect to the traveling direction, and the rear torch 2r is inclined in a direction in which the torch tip side is advanced with respect to the traveling direction. When the two torches 2f and 2r are arranged symmetrically with respect to the center line C of the inverted C shape at the tip, when the center line C is perpendicular to the traveling direction B of the torches, the tips of both torches The distance g from the base material to the base material becomes the same. That is, conventionally, the two torches 2f and 2r are arranged symmetrically with respect to the center line C that is equidistant from both axes, and the center line C is perpendicular to the traveling direction B of the torch. We were welding.
JP 2004-314104 A Japanese Patent Laying-Open No. 2005-81376 Japanese Patent Laid-Open No. 2005-219095

  As described above, in tandem welding, arc interference occurs when the current value of the front and rear torches is increased. Therefore, welding must be performed at a current value lower than that in the case of single welding. Despite the use, there has been a problem that the improvement in welding speed is limited to about several tens of percent.

  As means for avoiding arc interference, a method of increasing the distance (between the poles) d between the welding points P1 and P2 of the front and rear torches, and a method of applying a magnetic field in a direction in which the front and rear arc columns are separated from each other to the torch tip are conceivable. However, the former method makes it difficult to form a single weld pool by the front and rear arcs, increases the minimum radius that can be welded, reduces the number of products or welding points that can be tandemly welded, and makes the entire weld As a result, there is a problem that the welding efficiency is lowered. In the latter method, an electromagnet is provided at the tip of the torch, and the energization of the electromagnet must be controlled. Therefore, there is a problem that the equipment cost and operation cost of the welding apparatus are increased.

  This invention improves the welding efficiency of tandem arc welding by increasing the welding current without causing arc interference in the tandem arc welding in which a plurality of torches are moved synchronously. The challenge is to make it happen.

  In the present invention, at least the tip of two torches (front torch) 2f on the front side in the direction of travel of the two torches arranged in a reverse C-shape (V shape with the lower end separated) in the plane including the direction of travel B of the torch. Gas shielded arc welding in which the axis is perpendicular to the torch traveling direction B, or the tip axis of the front torch 2f is inclined in a direction in which the tip side (base material side) is forward of the torch traveling direction, Particularly preferably, the above-mentioned problems are solved by performing carbon dioxide gas welding.

  Since the axes of at least the front end portions of the front torch 2f and the rear torch 2r have an inverted C shape, the axis of the rear torch 2r is further inclined from the front torch 2f in the direction in which the front end side is forward of the torch traveling direction. It will be. The preferred inclination angles (advance angles) of these axes with respect to the axis perpendicular to the direction of travel of the torch are the forward angle θf of the front torch being 5 to 20 degrees and the forward angle θr of the rear torch being 15 to 50 degrees.

  Further, in the method of the present invention, the rear torch 2r is set at a position slightly retracted from the symmetrical position of the front torch 2f with respect to the center line C of the front and rear torches in order to make the welding gap g of the front and rear torches the same. Therefore, the conventional welding head (see FIG. 6) in which the rear torch 2r is provided at the symmetrical position of the front torch 2f with respect to the center line C of the front and rear torches is simply tilted as a whole. Welding is not possible.

  In the arc welding method according to the first aspect of the present application, a plurality of torches are arranged so that the front ends of the torches are in a front-to-back relationship with respect to the traveling direction of the torches so that the front ends thereof form an inverted letter C. In the arc welding method in which a current larger than the rear torch is passed through the front torch in the traveling direction and the front and rear torches move synchronously while maintaining their mutual positional relationship, at least the front end of the front torch is the torch at the front end side. The gas shielded arc welding method is characterized in that the two torches are moved synchronously while being inclined in a direction toward the traveling direction.

  The invention according to claim 2 of the present application is characterized in that, in the gas shielded arc welding method provided with the above means, an angle of inclination in the direction at least at the tip of the front torch is 5 to 20 degrees. Is.

  It has been shown in Patent Documents 1 to 3 that it is possible to weld a narrow welding spot with one torch by advancing and retracting one of the two welding torches. It is also possible in the arc welding method of the present invention to make it possible to switch between single welding and tandem welding in the manner shown. In this case, what is different from the conventional structures shown in Patent Documents 1 to 3 is that when the tandem welding state in which the tips of both torches are aligned, the tips of the front and rear torches are at the same position (with respect to the center line C) in the conventional method. In contrast, in the method of the present invention, the leading end of the rear torch is set at a position where the leading end of the rear torch recedes from the symmetrical position of the front torch with respect to the center line C of both torches. Is done.

  In the experiment in which carbon dioxide welding was performed by the method of the present invention, the forward angle θf of the front torch was 7.5 to 17.5 degrees, and the forward angle θr of the rear torch was optimal within the range of 27.5 to 37.5 degrees. When inclined, the current value of the front torch is increased by about 10% compared to the conventional method, and even if the current value of the rear torch is increased by about 50%, arc interference does not occur, and the total current value is about 2.5%. I was able to make it bigger. As a result, the welding efficiency of tandem arc welding can be made 1.5 times or more that of single welding, and the welding efficiency can be greatly improved without increasing the equipment cost and running cost.

  Also, since the arc of the front torch is stabilized and the arc interference is mitigated, the weld pool formed by the arc of the front torch is stabilized, which stabilizes the arc of the rear torch and the beat surface is smooth. The effect becomes. As a result, in the conventional multi-layer welding by tandem welding, the last beat can be performed by tandem welding up to the last beat, and the welding efficiency can be improved in this respect. There is an effect.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing an example of a torch mounting structure, FIG. 2 is an enlarged side view of a tip portion of a torch performing fillet welding by the method of the present invention, and FIG. 3 is an enlarged front view thereof. In FIG. 1, 11 is an arm tip of the welding robot, 12 is a tilt portion attached to the arm tip so as to be swingable about an axis in a direction perpendicular to the plane of FIG. 1, and 13 is a central axis 14 at the tip of the tilt portion. The wrist flange is mounted so as to be able to rotate around, and the wrist flange is a member on the welding robot side.

  15 is a mounting plate fixed to the wrist flange 13 with a bolt 16, 17 is a shock sensor mounted with the body side fixed to the tip of the mounting plate, and 18 is a torch mounting plate fixed to a rod 17a of the shock sensor. It is. The shock sensor 17 is provided to absorb the shock when the torch collides with a workpiece or the like due to a teaching mistake with respect to the welding robot, to prevent the torch from being damaged and to stop the welding robot urgently. . The above structure is general.

  The torch 2 is attached to the torch mounting plate 18 via the individual advance / retreat device 3, the centering device 4 and the tilting device 5. Although only one torch 2 is shown in FIG. 1, two torches are mounted in a reverse letter C shape when viewed from the front in the front-rear direction of the plane of FIG. 1 (see FIG. 3). The individual advancing / retreating device 3 retracts one of the two torches 2 in the axial direction, and includes a slide holder 22 and an advancing / retreating cylinder 23 that advance and retract each of the two torches in the axial direction. The individual advancing / retreating device 3 is provided so that welding can be performed with only one torch (single welding) at the start or end of welding, or when welding a narrow place or a bent place. It is.

  The centering device 4 is provided to move one torch for performing single welding to the center position of the two torches at the time of tandem welding. In tandem welding, as shown in FIG. 3, the tips of the two torches 2f and 2r are arranged with a distance d between them to avoid arc interference. In this state, when one torch is moved backward to shift to single welding, the center of welding is shifted by 1/2 of the distance d. Therefore, in order to avoid this problem, when one torch is retracted, the torch remaining in the centering device 4 is moved to the torch side retracted by 1/2 of the distance d, and the retracted torch is returned to the tandem. When returning to welding, it moves to the opposite side so that the welding center does not change between tandem welding and single welding.

  The centering device 4 includes a shift bracket 20 guided by a circular arc guide 19 in the direction perpendicular to the paper surface of FIG. 1, and two shift cylinders 26 for reciprocating the shift bracket 20 along the circular arc guide 19 in the direction perpendicular to the paper surface of FIG. It has. The two shift cylinders 26 are provided so that the remaining torch can be moved to the welding center when any of the front and rear torches is retracted. The individual advance / retreat apparatus 3 described above is attached to the shift bracket 20.

  The tilting device 5 has a structure in which the tilting plate 28 to which the centering device 4 is mounted is fixed to the torch mounting plate 18 by tilting around the tilting axis 29 perpendicular to the surface on which the two torches 2f and 2r are arranged. In this structure, the inclined plate 28 is fixed to the torch mounting plate 18 with a bolt or the like in a state tilted in the left-right direction (left-right direction as viewed from the left direction in FIG. 1) in front view.

  FIG. 2 shows a state where the first plate 31 provided with the groove 34 having a groove angle of 35 degrees is fillet welded to the second plate 32 using the two torches mounted with the above structure. Yes. The two torches 2 (2f, 2r) are inclined with respect to the second plate 32 at an angle that is ½ of the groove angle. This tilting is performed by tilting the wrist of the welding robot. In addition, 33 of FIG. 2 is a backing money.

  FIG. 3 shows the angular relationship in the arrangement plane of the two torches 2f and 2r when viewed from the direction of the arrow A (front side) in FIG. In the example shown in the figure, the two torches 2f and 2r arranged in an inverted C shape with an apex angle of 20 degrees are such that the tip of the torch faces the torch traveling direction (arrow B direction, which is the left direction in FIG. 3). As a whole, it is attached with an inclination of 20 degrees. That is, the front torch 2f on the front side in the traveling direction of the torch is inclined by θf = 10 degrees in the direction in which the tip of the torch faces the traveling direction of the torch, and the rear torch 2r on the rear side in the traveling direction of the torch It is inclined by θr = 30 degrees in the direction facing the traveling direction of the torch.

  When the two torches 2f and 2r arranged in a reverse C-shape are inclined as a whole, the torch having the larger inclination angle in order to make the distance g from the tip of the two torches to the workpiece constant. The tip of 2r needs to be slightly retracted from the other side torch 2f. In the example of the figure, the distance d between the welding point P1 of the front torch 2f and the welding point P2 of the rear torch 2r is set to 18 mm, and the distance from each welding point to the tip of the torch is g = 30 mm. The axial positions of both torches 2f and 2r are moved back and forth. This axial front-rear relationship can be realized by shifting one of the advance / retreat cylinders 23 in the axial direction or by restricting one advance position of the advance / retreat cylinder 23 with a stopper.

  FIG. 4 shows a case where the tandem welding is performed by the above-described method of the present invention and a case where the center line C of the two torches is perpendicular to the torch traveling direction B as shown in FIG. FIG. 6 is a diagram in which the change in the welding voltage [V] and welding current [A] of the previous torch and the number of short circuits [times] are recorded with the elapsed time as the horizontal axis, and FIG. , (B) are of the conventional method. The welding conditions are a front torch current 340A, a rear torch current 230A, and a total current 570A. As is apparent from the figure, in the conventional method, the welding current fluctuates greatly due to the arc interference of the front and rear torches, and the welding voltage also fluctuates drastically. On the other hand, in the method of the present invention, it is understood that arc interference is avoided and stable welding is performed. In order to perform tandem welding without causing arc interference by the conventional method shown in FIG. 6, the front torch current 310A, the rear torch current 150A, and the total current 460A are the limits. On the other hand, according to the method of the present invention, the total current can be increased 1.24 times, and the welding efficiency of tandem welding can be increased to 50% or more of single welding.

  FIG. 5 shows that the forward angle of the front torch and the rear torch is maintained at 20 degrees, and the forward angle of the front torch is changed by 2.5 degrees from 2.5 degrees to 25 degrees. This shows the current stability (current value fluctuation range) and the results of the visual spatter amount, beat appearance and penetration evaluation, and the spatter amount, beat appearance and penetration evaluation and comprehensive judgment columns. “X” marked in “不可” means “not acceptable”, “Δ” means “good”, “◯” means “good”, and “◎” means particularly good. Conditions other than the advance angle of the torch are the same as those in the test of FIG. According to the results of this test, the forward torch forward angle of 7.5 to 17.5 degrees and the rear torch forward angle of 27.5 to 37.5 degrees are preferable, and the forward torch forward angle of 10 to 12.5 degrees is preferable. It can be seen that a forward angle of 30 to 32.5 degrees is particularly preferable.

Side view showing an example of a welding torch mounting structure Side view of the tip of the torch performing fillet welding Front view of the torch of FIG. 2 (viewed from the direction of arrow A in FIG. 2) Diagram showing the occurrence of arc interference between the method of the present invention and the conventional method The figure which shows the result of the evaluation test when changing the advancing angle of a torch by the method of this invention Front view of torch in conventional method

Explanation of symbols

2f front torch
2r Rear torch 3 Individual advance / retreat device 4 Centering device 5 Tilt device
13 Welding robot wrist flange
17 Shock sensor
18 Torch mounting plate B Torch travel direction θf Tilt angle of front torch θr Tilt angle of rear torch

Claims (2)

A plurality of torches are arranged so that the front ends of the torches are in a longitudinal relationship with respect to the traveling direction of the torches so that the front ends thereof form a reverse letter C. In the arc welding method in which the front and rear torches maintain their mutual positional relationship and move synchronously while flowing
A gas shielded arc welding method, wherein the two torches are synchronously moved by inclining at least the front end of the front torch in a direction in which the front end side faces the torch traveling direction.   The arc welding method according to claim 1, wherein the angle of inclination is 5 to 20 degrees.

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