Tandem arc welding control method

Abstract

The present invention provides a tandem arc welding control method that can stabilize the formation of the molten pool and weld bead even during high-speed welding. [Solution] This is a tandem arc welding control method comprising a first step and a second step. In the first step, the base material 16 is arc-welded while the leading welding torch 6A is moved along the first welding line Lw1. In the second step, the base material 16 is arc-welded while the trailing welding torch 6B is moved along the second welding line Lw2. The relative positions of the leading welding torch 6A and the trailing welding torch 6B are controlled so that the first welding line Lw1 is separated by a first distance P in a direction perpendicular to the second welding line Lw2. In the second step, the welding current Aw input to the trailing welding wire 9B is controlled so that the welding is lower heat input than in the first step.

Description

Technical Field

[0001] The present disclosure relates to a tandem arc welding control method.

Background Art

[0002] Conventionally, tandem arc welding is known as a technique for increasing the speed and deposition rate of consumable electrode arc welding. In tandem arc welding, one of two welding torches holding welding wires is advanced along the welding line and the other is retarded. Further, an arc is generated between each of the two welding wires and the base material, which is the object to be welded, to perform welding. The welding line is a virtual line along the planned welding location on the base material.

[0003] Further, Patent Document 1 discloses an example in which, in a tandem arc welding method, the welding process performed using the leading welding torch and the welding process performed using the trailing welding torch are different processes. For example, there is a disclosure that it is possible to perform pulse welding using the leading welding torch and cold metal transfer welding involving forward and backward movement of the welding wire using the trailing welding torch.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, usually, when performing tandem arc welding, while each of the arcs generated between the two welding wires and the base material moves along the same welding line, the base material is welded.

[0006] However, in this case, insufficient penetration of the base metal may result in the weld bead formed on the base metal being narrower than the desired width. Furthermore, the edges of the weld bead may become wavy, forming discontinuous, bumpy beads, also known as humping beads.

[0007] Furthermore, in actual welding, disturbances often occur, such as the position of the welding wire tip deviating from the target position, or the shape and dimensions of the base material deviating from the design values. However, when two welding wires move along the same weld line while welding the base material, such disturbances can cause the shape of the weld bead formed on the base material to deteriorate. Moreover, the aforementioned fluctuations in the width and deterioration of the shape of the weld bead become particularly noticeable in high-speed welding.

[0008] This disclosure has been made in view of the above, and its purpose is to provide a tandem arc welding control method that can stably form a molten pool even during high-speed welding, and can also stabilize the formation of a weld bead by the subsequent solidification of the molten metal. [Means for solving the problem]

[0009] To achieve the above objective, the tandem arc welding control method according to the present disclosure comprises at least: a first step of generating an arc between the leading welding wire and the base material while moving a leading welding torch holding a leading welding wire along a first welding line, thereby arc welding the base material; and a second step of continuing from the first step of generating the arc between the trailing welding wire and the base material while moving a trailing welding torch holding a trailing welding wire along a second welding line, thereby arc welding the base material, wherein the first welding line is separated from the second welding line by a first distance in a direction parallel to and perpendicular to the second welding line. The relative positions of the preceding welding torch and the following welding torch are controlled, and in the second step, the welding output input to the preceding welding wire and the following welding wire is controlled so that the base material is arc-welded with a lower heat input than in the first step. [Effects of the Invention]

[0010] According to this disclosure, a stable molten pool can be formed even during high-speed welding. Furthermore, the formation of the weld bead can be stabilized. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of a tandem arc welding system according to an embodiment. [Figure 2A] This diagram shows the positions of the leading and trailing welding torches in horizontal welding, viewed from the X direction. [Figure 2B] This diagram shows the positions of the leading and trailing welding torches in horizontal welding, viewed from the Y direction. [Figure 3A] This is a time chart showing various output waveforms during pre-welding. [Figure 3B] This is a time chart showing various output waveforms during subsequent welding. [Figure 4] This is a schematic diagram illustrating how a weld bead is formed during tandem arc welding. [Figure 5] This figure shows the relationship between the first distance, the distance between electrodes, and the appearance quality of the weld bead. [Figure 6] This figure shows the relationship between welding speed, electrode distance, and the appearance quality of the weld bead. [Figure 7A] This diagram shows the positions of the preceding and succeeding welding torches in the comparative example, viewed from the X direction. [Figure 7B] This diagram shows the positions of the preceding and succeeding welding torches in the comparative example, viewed from the Y direction. [Figure 8] This is a schematic diagram showing how a weld bead is formed in tandem arc welding, as shown in the comparative example. [Figure 9] This is a schematic diagram showing another example of a welding torch. [Figure 10A] This is a schematic diagram showing an example of a preceding welding torch and a succeeding welding torch related to a modified example. [Figure 10B]It is a schematic diagram showing another example of the leading welding torch and the trailing welding torch according to the modified example.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described based on the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0013] (Embodiment) [Configuration of Tandem Arc Welding System] FIG. 1 is a schematic configuration diagram of a tandem arc welding system according to an embodiment. As shown in FIG. 1, the tandem arc welding system 24 includes a leading arc welding device 23A and a trailing arc welding device 23B, and during tandem arc welding, the leading arc welding device 23A and the trailing arc welding device 23B operate in联动 with each other.

[0014] The leading arc welding device 23A includes a leading robot controller 1A, a leading welding power source 2A, a leading welding robot 3A, a leading wire feeding device 4A, a leading feeding liner 5A, a leading welding torch 6A, and a leading welding wire storage unit 9C. The leading arc welding device 23A also includes two leading current cables 10A, 10A and a leading control cable 14A.

[0015] It should be noted that the term "联动" in the original text is not a common English expression. It might be a misspelling or a technical term specific to the original language. Here, I translated it as "联动" as it is not clear what the exact intended English term should be. If there is more context or if it is a known technical term with a specific English equivalent, a more accurate translation can be provided.The lead robot controller 1A includes one or more CPUs (Central Processing Units), a communication unit, and ICs (Integrated Circuits) or LSIs (Large Scale Integrations) (not shown) that drive multiple motors provided on the lead welding robot 3A. The lead robot controller 1A is connected to the lead welding robot 3A via a lead control cable 14A so as to be able to communicate, and controls the operation of the lead welding robot 3A according to a predetermined teaching program. The teaching program includes the trajectory of the lead welding robot 3A's tip and the welding speed S, which is the speed at which it moves. The welding speed S corresponds to the movement speed of the lead welding torch 6A along the first welding line Lw1 (see Figure 2B), which will be described later. The welding speed S also corresponds to the movement speed of the trailing welding torch 6B along the second welding line Lw2 (see Figure 2B), which will be described later.

[0016] The lead welding power supply 2A is electrically connected to the lead welding tip 8A via the lead current cable 10A. The lead welding power supply 2A is also electrically connected to the base material 16 via the lead current cable 10A. In this embodiment, the lead current cable 10A connected to the negative terminal of the lead welding power supply 2A is connected to the lower plate 12 of the base material 16. The lead current cable 10A connected to the positive terminal of the lead welding power supply 2A is electrically connected to the lead welding tip 8A via wiring (not shown) provided on the lead welding robot 3A.

[0017] Based on the input average current and average voltage, the lead welding power supply 2A supplies welding output to the lead welding wire 9A, which is held in the lead welding tip 8A and is feedable toward the base material. Specifically, the lead welding power supply 2A supplies welding current Aw to the lead welding wire 9A via the lead current cable 10A and the lead welding tip 8A.

[0018] In this specification, the average current is the average value of the welding current Aw over the entire period during which the leading bead 21 or trailing bead 22 is formed on the base material 16. Similarly, the average voltage is the average value of the welding voltage Vw over the entire period during which the leading bead 21 or trailing bead 22 is formed on the base material 16.

[0019] Alternatively, a welding program may be input to the lead welding power supply 2A to control the welding output supplied to the lead welding wire 9A. In this case, the average current and average voltage mentioned above are pre-set in the welding program. The teaching program mentioned above may also be incorporated into the welding program. Although not shown, the lead welding power supply 2A has a control terminal, and a command to feed the lead welding wire 9A is sent from the control terminal to the lead welding wire feeder 4A via a control cable (not shown).

[0020] The lead welding robot 3A is an articulated robot that holds a lead welding torch 6A at its tip. In response to commands from the lead robot controller 1A, the lead welding robot 3A moves the tip of the lead welding torch 6A along the first welding line Lw1 (see Figure 2B). The first welding line Lw1 is a virtual line along the planned welding location on the base material 16 by the lead welding torch 6A. By moving the lead welding torch 6A along the first welding line Lw1 and applying a welding current Aw to the lead welding wire 9A, a lead bead 21 is formed on the base material 16.

[0021] The lead wire feeder 4A feeds the lead welding wire 9A toward the base material 16 in response to a control command from the lead welding power supply 2A. The lead welding wire 9A stored in the lead welding wire storage section 9C is introduced to the lead welding torch 6A via the lead wire feeder 4A. The lead welding wire 9A introduced from the lead wire feeder 4A to the lead welding torch 6A is protected by a cylindrical lead wire feeder liner 5A.

[0022] The lead welding torch 6A holds a lead welding tip 8A inside. A lead welding wire 9A is also held so as to be able to be fed to the lead welding tip 8A. A lead nozzle 7A is provided at the tip of the lead welding torch 6A, and a portion of the lead welding tip 8A protrudes from the lead nozzle 7A. The lead nozzle 7A is connected to a shielding gas pipe (not shown), and shielding gas flows from the lead nozzle 7A toward the base metal 16 during arc welding. The shielding gas isolates the molten metal formed on the base metal 16 during arc welding from the atmosphere, preventing the molten metal from reacting with the atmosphere.

[0023] The configuration and function of the trailing arc welding device 23B are the same as those of the leading arc welding device 23A. Furthermore, the configuration and function of each component of the trailing arc welding device 23B are also the same as those of each component of the leading arc welding device 23A.

[0024] In other words, the trailing arc welding device 23B comprises a trailing robot controller 1B, a trailing welding power supply 2B, a trailing welding robot 3B, a trailing wire feeder 4B, a trailing wire feeder liner 5B, a trailing welding torch 6B, and a trailing welding wire storage unit 9D. The trailing arc welding device 23B also comprises two trailing current cables 10B, 10B and a trailing control cable 14B.

[0025] The trailing welding torch 6B holds a trailing welding tip 8B inside. A trailing welding wire 9B is also held so as to be able to be fed to the trailing welding tip 8B. A trailing nozzle 7B is provided at the tip of the trailing welding torch 6B, and a portion of the trailing welding tip 8B protrudes from the trailing nozzle 7B. The trailing nozzle 7B is connected to a shielding gas pipe (not shown), and during arc welding, shielding gas flows from the trailing nozzle 7B towards the base metal 16.

[0026] In response to commands from the trailing robot controller 1B, the trailing welding robot 3B moves the tip of the trailing welding torch 6B along the second welding line Lw2 (see Figure 2B).

[0027] Based on the input average current, average voltage, or welding program, the trailing welding power supply 2B supplies welding output to the trailing welding wire 9B held in the trailing welding tip 8B so as to be feedable toward the base material. Specifically, the trailing welding power supply 2B supplies welding current Aw to the trailing welding wire 9B via the trailing current cable 10B and the trailing welding tip 8B.

[0028] The second welding line Lw2 is a virtual line along the planned welding location on the base material 16 by the trailing welding torch 6B. By moving the trailing welding torch 6B along the second welding line Lw2 and applying a welding current Aw to the trailing welding wire 9B, a trailing bead 22 is formed on the base material 16.

[0029] However, as will be described later, the arc welding performed by the leading welding torch 6A (hereinafter sometimes referred to as leading welding) and the arc welding performed by the trailing welding torch 6B (hereinafter sometimes referred to as trailing welding) have different heat inputs to the base material 16. Also, the second welding line Lw2 is in a different position from the first welding line Lw1. Accordingly, the leading welding torch 6A and the trailing welding torch 6B are positioned such that their relative positions before the start of welding satisfy a predetermined relationship. Furthermore, the leading bead 21 formed by leading welding and the trailing bead 22 formed by trailing welding are collectively referred to as the welding bead 20.

[0030] Furthermore, the lead robot controller 1A and the trailing robot controller 1B are configured to communicate with each other via a communication cable 13.

[0031] [Tandem Arc Welding Method] <Initial position setting of the leading and trailing welding torches> Figure 2A shows the positions of the leading and trailing welding torches in horizontal welding, viewed from the X direction. Figure 2B shows the positions of the leading and trailing welding torches in horizontal welding, viewed from the Y direction.

[0032] In the following explanation, the vertical direction will be referred to as the Z direction, the direction in which the upper plate 11 and lower plate 12 are superimposed as shown in Figure 2A will be referred to as the Y direction, and the directions perpendicular to the Y and Z directions will be referred to as the X direction. Furthermore, in the Z direction, the side on which the upper plate 11 is located will be referred to as the top or upper side, and the side on which the lower plate 12 is located will be referred to as the bottom or lower side. In the Y direction, the side on which the upper plate 11 is located will be referred to as the rear or rear, and the side on which the lower plate 12 is located will be referred to as the front or front side.

[0033] Furthermore, in this specification, "parallel" or "orthogonal" means that the assembly tolerances and manufacturing tolerances of each component of the tandem arc welding system 24, as well as the manufacturing tolerances of the base material 16, are included in the meaning of "parallel" or "orthogonal." It does not mean that the comparison objects are strictly parallel or orthogonal to each other.

[0034] As shown in Figure 2A, the base material 16 in this embodiment is a fillet joint in which a part of the upper plate 11 and a part of the lower plate 12 are overlapped in the Y direction. Furthermore, the front surfaces of the upper plate 11 and the lower plate 12, which are the welding surfaces of the base material 16, are parallel to the Z direction. In other words, the tandem arc welding in this embodiment is a horizontal welding performed in a horizontal position.

[0035] Furthermore, the materials of the upper plate 11, lower plate 12, leading welding wire 9A, and trailing welding wire 9B are all mild steel. However, these materials are not particularly limited; for example, the materials of the upper plate 11 and lower plate 12 may be high-tensile steel. Also, the plate thickness of the upper plate 11 and lower plate 12 is 3.2 mm each, but these plate thicknesses are not particularly limited. Also, the wire diameter of the leading welding wire 9A and trailing welding wire 9B is 1.2 mm each, but these wire diameters are not particularly limited.

[0036] Typically, in the base material 16 shown in Figures 2A and 2B, arc welding is performed along the intersection line between the rear end on the upper surface of the lower plate 12 and the front surface of the upper plate 11 (see Figures 7A and 7B). This intersection line corresponds to the second welding line Lw2 shown in Figure 2B. On the other hand, as shown in Figures 2A and 2B, the first welding line Lw1 in the pre-weld is parallel to the second welding line Lw2, but is located at a distance P above the second welding line Lw2 in the Z direction. Furthermore, before performing tandem arc welding, the relative positions of the pre-weld torch 6A and the trailing welding torch 6B are adjusted so that the tip of the pre-weld wire 9A is positioned forward of the tip of the trailing welding wire 9B by a distance L (hereinafter referred to as the electrode distance L) in the welding direction, in this case the X direction. This adjustment is performed by the pre-weld robot 3A and / or the trailing welding robot 3B. The electrode distance L is the distance between the tip of the leading welding wire 9A and the tip of the trailing welding wire 9B, and is the distance along the direction parallel to the first welding line Lw1, which in this embodiment is the X direction.

[0037] <Regarding the difference in output waveforms between pre-welding and post-welding> Figure 3A is a time chart showing various output waveforms during pre-welding. Figure 3B is a time chart showing various output waveforms during post-welding.

[0038] As shown in Figure 3A, during pre-welding, the base material 16, particularly the upper plate 11, is arc-welded by alternating between arc period Ta1 and short-circuit period Ts1. During arc period Ta1, a base current of Ib is passed through the pre-welding wire 9A, followed by a peak current of Ip (>Ib). During arc period Ta1, when an arc 15 is generated between the pre-welding wire 9A and the upper plate 11 during the period when the base current is flowing (see Figure 4), droplets (not shown) begin to form at the tip of the pre-welding wire 9A. During the period when the peak current is flowing, the pre-welding wire As the Ya9A flames up, the arc length increases and the molten droplets grow. During the arc period Ta1, the time variation of the welding current Aw is similar to that of known pulsed welding.

[0039] During the short-circuit period Ts1, base current flows through the lead welding wire 9A, while the arc length shortens, causing the tip of the lead welding wire 9A to contact the upper plate 11 and short-circuit. At this time, molten droplets transfer to the upper plate 11. In this embodiment, the average voltage set for the lead welding power supply 2A is set low to periodically generate the short-circuit period Ts1.

[0040] Furthermore, during pre-welding, the operation of the pre-welding wire feeder 4A is controlled so that the feed speed of the pre-welding wire 9A (hereinafter referred to as the wire feed speed Wf) is a positive constant value (=Wf1). When the wire feed speed Wf is a positive value, it is a forward feed operation in which the pre-welding wire 9A or the trailing welding wire 9B is fed toward the base material 16, and when it is a negative value, it is a reverse feed operation in which the pre-welding wire 9A or the trailing welding wire 9B is fed toward the base material 16.

[0041] As shown in Figure 3B, during trailing welding, the base metal 16, particularly the lower plate 12, is arc-welded by alternating between arc welding periods Ta2 and short-circuit welding periods Ts2. However, unlike during leading welding, during trailing welding, the trailing wire feeder 4B feeds the trailing welding wire 9B by periodically alternating between forward and reverse feeding. The time-averaged value of the wire feed speed Wf during trailing welding is set to a positive value (=Wf2). In other words, the method used for trailing welding is the known short-circuit welding method.

[0042] In trailing welding, an arc 15 is generated between the tip of the trailing welding wire 9B and the base metal 16 during the arc period Ta2, and molten droplets are formed on the tip of the trailing welding wire 9B, similar to the preceding welding. Also, in the short-circuit period Ts2, the tip of the trailing welding wire 9B comes into contact with the lower plate 12, causing a short circuit, and the molten droplets mainly migrate to the lower plate 12, similar to the preceding welding. However, in preceding welding, a peak current is applied to the trailing welding wire 9A during the arc period Ta1, resulting in a higher heat input than in trailing welding.

[0043] <Regarding the results of tandem arc welding> Figure 4 is a schematic diagram showing how a weld bead is formed in tandem arc welding.

[0044] As shown in Figure 3A, when the lead welding wire 9A is fed toward the upper plate 11 and a welding current Aw is passed through the lead welding wire 9A, an arc 15 is generated between the tip of the lead welding wire 9A and the upper plate 11. As mentioned above, the first welding line Lw1 is set to be above the second welding line Lw2, that is, the intersection line between the rear end on the upper surface of the lower plate 12 and the front surface of the upper plate 11 by a distance P.

[0045] Therefore, in the pre-welding process, penetration in the upper plate 11 is ensured, as shown on the left side of Figure 4. In the example shown in Figure 4, the penetration depth in the upper plate 11 is D. Furthermore, since the pre-welding is a high-heat-input arc welding process including pulse welding, deep penetration can be stably formed in the upper plate 11, and the width of the pre-weld bead 21 can be widened.

[0046] Next, as shown in Figure 3B, when the trailing welding wire 9B is fed toward the base metal 16 and a welding current Aw is passed through the trailing welding wire 9B, an arc 15 is generated mainly between the tip of the trailing welding wire 9B and the lower plate 12. The tip of the trailing welding wire 9B is controlled to move along the second weld line Lw2. In this case, the base metal 16, including the lower plate 12, melts due to the arc 15 so as to build up onto the leading bead 21, and after solidification, the trailing bead 22 is formed. As a result, the upper plate 11 and the lower plate 12 are reliably bridged, and a weld bead 20 including the leading bead 21 and the trailing bead 22 is formed on the base metal 16. In the example shown in Figure 4, the weld bead 20 The width in the Z direction is W. Also, as mentioned above, trailing welding is a welding method with lower heat input than trailing welding. For this reason, in the horizontal welding shown in this embodiment, the sagging of the weld bead 20 can be suppressed.

[0047] Furthermore, the inventors of this application have found that the first distance P, the distance L between electrodes, and the welding speed S affect the appearance of the weld bead 20. This will be explained below.

[0048] Figure 5 shows the relationship between the first distance and the distance between electrodes and the quality of the weld bead's appearance. Figure 6 shows the relationship between the welding speed and the distance between electrodes and the quality of the weld bead's appearance.

[0049] First, by varying the first distance P and the electrode-to-electrode distance L, it was found that when the base material 16 shown in Figures 2A and 2B was tandem arc welded, there were conditions under which the appearance of the weld bead 20 was good and conditions under which it was poor. Specifically, as shown in Figure 5, the optimal condition (◎) for the best appearance of the weld bead 20 was when the first distance P was 1.5 mm and the electrode-to-electrode distance L was 10 mm. Furthermore, around this condition, within the range of first distance P = 1.5 mm ± 0.5 mm and electrode-to-electrode distance L = 10 mm ± 5 mm, the appearance of the weld bead 20 was either good (〇) or the bead shape was uneven (△) but not considered poor. On the other hand, around the optimal condition, when the first distance P and electrode-to-electrode distance L exceeded the aforementioned ranges, the appearance of the weld bead 20 was poor (×). In the example shown in Figure 5, the welding speed S was 3.0 m / min.

[0050] Furthermore, as shown in Figure 6, it was found that the appearance of the weld bead 20 is appropriate when the electrode distance L and the welding speed S satisfy a predetermined relationship. Specifically, L=L C = 3.3 × S ···(1) Focusing on cases where this occurs, L d = 3.3 × S - 5 ≤ L ≤ L u = 3.33 × S + 5 ... (2) It was found that the appearance of the weld bead 20 is appropriate within the range that satisfies the given conditions. In other words, it was found that the electrode distance L needs to be set according to the welding speed S so as to satisfy the relationship shown in equation (2). It was also found that the relative distance between the leading welding torch 6A and the trailing welding torch 6B needs to be controlled so as to satisfy the relationship shown in equation (2). In order to maintain this relative distance so as to satisfy the relationship shown in equation (2), the positions of the leading welding robot 3A and / or the trailing welding robot 3B are controlled by commands from the leading robot controller 1A and / or the trailing robot controller 1B.

[0051] [Effects, etc.] As described above, the tandem arc welding control method according to this embodiment comprises at least the following first and second steps.

[0052] In the first step, the leading welding torch 6A, which holds the leading welding wire 9A, is moved along the first welding line Lw1, and an arc 15 is generated between the leading welding wire 9A and the base material 16 to arc weld the base material 16.

[0053] In the second step, following the first step, the trailing welding torch 6B, which holds the trailing welding wire 9B, is moved along the second welding line Lw2, and an arc 15 is generated between the trailing welding wire 9B and the base material 16 to arc weld the base material 16.

[0054] The relative positions of the leading welding torch 6A and the trailing welding torch 6B are controlled such that the first welding line Lw1 is parallel to and perpendicular to the second welding line Lw2, and in this embodiment, is separated by a first distance P along the Z direction.

[0055] In the second step, the welding output, specifically the welding current Aw, input to the leading welding wire 9A and the trailing welding wire 9B is controlled so that the base material 16 is arc-welded with a lower heat input than in the first step.

[0056] According to this embodiment, even during high-speed welding, the penetration into the base material 16 can be stabilized. That is, a molten pool can be stably formed on the base material 16. Further, the formation of the weld bead 20 can be stabilized. This will be further described below.

[0057] FIG. 7A is a view of the positions of the leading welding torch and the trailing welding torch according to the comparative example as seen from the X direction. FIG. 7B is a view of the positions of the leading welding torch and the trailing welding torch according to the comparative example as seen from the Y direction. FIG. 8 is a schematic diagram showing how a weld bead is formed in the tandem arc welding according to the comparative example.

[0058] FIG. 7A corresponds to FIG. 2A, FIG. 7B corresponds to FIG. 2B, and FIG. 8 corresponds to FIG. 4, respectively. However, the tandem arc welding of the comparative example is different from the tandem arc welding of this embodiment shown in FIGS. 2A, 2B, and FIG. 4 in that the first welding line Lw1 overlaps the second welding line Lw2. Note that the heat input amounts of the leading welding and the trailing welding are the same.

[0059] In this case, as shown in FIG. 8, during the leading welding, since the arc 15 hits the corner portion formed by the upper surface of the lower plate 12 and the front surface of the upper plate 11, the penetration of the base material 16 becomes shallower than in the case shown in FIG. 4. That is, the penetration depth D' of the base material 16 shown in FIG. 8 is shallower than the penetration depth D shown in FIG. 4. In this state, since the leading bead 21 is formed in the corner portion, the width of the leading bead 21 shown in FIG. 8 along the Z direction is also narrower than the width of the leading bead 21 shown in FIG. 4 along the Z direction.

[0060] In this case, if the trailing welding is performed following the leading welding, since the arc 15 hits along the narrow leading bead 21, the molten metal is piled up on the leading bead 21, and the width W' (<W) of the weld bead 20 including the trailing bead 22 along the Z direction does not widen, and a convex bead shape with a large bulge is formed. In particular, in high-speed welding where the welding speed S exceeds 1.0 m / min, this tendency becomes significant. Also, in high-speed welding, the above-described humping bead is likely to be formed.

[0061] On the other hand, according to this embodiment, the first welding line Lw1 is separated from the second welding line Lw2 by a first distance P, and the preceding welding is performed as arc welding with a higher heat input than the succeeding welding. By doing so, even in high-speed welding, the width W of the weld bead 20 along the Z direction can be widened, and the formation of humping beads and the like can be suppressed. In addition, a molten pool can be stably formed in the base material 16, and deep penetration can be obtained. Furthermore, the upper plate 11 and the lower plate 12 can be reliably bridged by the succeeding welding, and a margin of error in the weld bead 20 can be ensured even if there is a misalignment of the welding wire tip or a deviation from the design values ​​of the shape and dimensions of the base material.

[0062] In the first step, pulse welding is performed, and in the second step, it is preferable to perform short-circuit welding by alternately feeding the trailing welding wire 9B forward and backward.

[0063] Specifically, in the first step, it is preferable to apply a base current to the leading welding wire 9A at a predetermined cycle, and then apply a peak current with a higher current value than the base current following the base current. In the second step, it is preferable to alternately feed the trailing welding wire 9B forward and backward to short-circuit the trailing welding wire 9B to the base material 16, and then generate an arc between the trailing welding wire 9B and the base material 16.

[0064] By making the first step pulse welding, the heat input to the base material 16 during arc welding can be increased. Furthermore, the width of the arc 15 that contacts the base metal 16 can be widened, and consequently, the width W of the weld bead 20 can be widened. Also, by making the second step a short-circuit welding, the heat input of the subsequent welding can be lower than that of the preceding welding. This suppresses excessive heat input to the base metal 16, and allows the molten metal formed on the base metal 16 in the second step to be appropriately shared with the molten metal formed on the base metal 16 in the first step. As a result, the molten metal formed on the base metal 16 in the second step is properly deposited on the preceding bead 21, and the appearance of the weld bead 20 can be maintained in good condition.

[0065] Furthermore, the first distance P is preferably in the range of 1.5 mm ± 0.5 mm, in other words, 1.0 mm or more and 2.0 mm or less. When the first distance P is within this range, a weld bead 20 with a good appearance can be formed.

[0066] Furthermore, it is preferable to control the relative positions of the leading welding torch 6A and the trailing welding torch 6B such that the distance L between electrodes increases as the welding speed S increases.

[0067] in particular, 3.33 × S - 5 ≤ L ≤ 3.33 × S + 5 ... (2) It is preferable to control the relative positions of the leading welding torch 6A and the trailing welding torch 6B so as to satisfy the relationship shown. When the electrode distance L is within this range, a weld bead 20 with a good appearance can be formed.

[0068] Also, L = 3.33 × S ... (1) It is more preferable to control the relative positions of the leading welding torch 6A and the trailing welding torch 6B so as to satisfy the relationship shown. When the electrode distance L is within this range, a weld bead 20 with a better appearance can be formed.

[0069] Furthermore, it is preferable that the average current flowing through the trailing welding wire 9B is smaller than the average current flowing through the leading welding wire 9A. By doing so, the heat input to the base material 16 in trailing welding can be easily reduced compared to the heat input in leading welding.

[0070] Furthermore, in the first step, it is preferable that the pulse welding period includes a period during which the lead welding wire 9A and the base material 16 are short-circuited. By short-circuiting the transfer of molten droplets from the lead welding wire 9A to the base material 16, it is possible to suppress the unevenness of the shape of the lead bead 21. In addition, it is possible to suppress the generation of spatter during welding. As a result, deterioration of the shape of the weld bead 20 can be suppressed, and a weld bead 20 with a good appearance can be obtained.

[0071] In this embodiment, the average voltage in pulse welding is set low to cause a periodic short-circuit period Ts2 to occur. However, this is not limited to this, and for example, as shown in Figure 3B, a period for controlling the wire feed speed Wf and welding current Aw may be provided after the arc period Ta1.

[0072] It is not essential to include a period of short-circuiting between the lead welding wire 9A and the base material 16 in the first step; pulse welding alone may be performed.

[0073] Furthermore, when the base material 16 is a fillet joint, the penetration depth is shallower and the width of the leading bead 21 and the weld bead 20 tends to be narrower compared to other types of joints. Therefore, the tandem arc control method of this embodiment, in which the first weld line Lw1 is separated from the second weld line Lw2 by a first distance P and the leading weld is an arc weld with a higher heat input than the trailing weld, is effective in forming a weld bead 20 with deep penetration and a good appearance in a fillet joint.

[0074] Furthermore, the tandem arc control method of this embodiment is particularly useful for application to horizontal welding. That is, in the first and second steps, the base material 16 is arc-welded in a horizontal position. At this time, the first welding line Lw1 is located above the second welding line Lw2.

[0075] According to this embodiment, by widening the width of the leading bead 21 and increasing the penetration depth during the leading weld, while using a lower heat input for the trailing weld than the leading weld, the sagging of the weld bead 20 can be reliably suppressed.

[0076] As shown in this embodiment, when tandem arc welding an upper plate 11 and a lower plate 12 made of the same material and composition, it is preferable that the material and composition of the leading welding wire 9A and the trailing welding wire 9B are the same as those of the upper plate 11 and the lower plate 12. In other words, it is preferable that the material and composition of the trailing welding wire 9B are the same as those of the leading welding wire 9A. In this embodiment, the wire diameter of the leading welding wire 9A is the same as that of the trailing welding wire 9B.

[0077] Furthermore, in this embodiment, the tandem arc welding system 24 is configured with two arc welding devices, namely a leading arc welding device 23A and a trailing arc welding device 23B, but the system is not limited to this. For example, as shown in Figure 9, a leading nozzle 7C, a leading welding tip 8A, a trailing nozzle 7D, and a trailing welding tip 8B may be provided on a single welding torch 6. Note that the leading welding wire 9A is held in a feedable manner in the leading welding tip 8A and the trailing welding wire 9B is held in a feedable manner in the trailing welding tip 8B, as is the case with the tandem arc welding system 24 shown in Figure 1.

[0078] The welding torch 6 shown in Figure 9 is provided with a first position adjustment mechanism 17A and a second position adjustment mechanism 17B. For example, suppose that a leading welding tip 8A and a trailing welding tip 8B are held in the welding torch 6 so as to be displaceable within a predetermined range in the Z and X directions, respectively. In this case, the first position adjustment mechanism 17A displaces the leading welding tip 8A and / or the trailing welding tip 8B in the Z direction to adjust the first distance P, that is, the distance along the Z direction between the tip of the leading welding wire 9A and the tip of the trailing welding wire 9B. The second position adjustment mechanism 17B displaces the leading welding tip 8A and / or the trailing welding tip 8B in the X direction to adjust the electrode distance L, that is, the distance along the X direction between the tip of the leading welding wire 9A and the tip of the trailing welding wire 9B.

[0079] In this case, either the leading robot controller 1A or the trailing robot controller 1B can be omitted. Also, either the leading welding robot 3A or the trailing welding robot 3B can be omitted. This simplifies the tandem arc welding system 24.

[0080] In this case, the leading welding tip 8A corresponds to the leading welding torch 6A, and the trailing welding tip 8B corresponds to the trailing welding torch 6B.

[0081] <Variation> Figure 10A is a schematic diagram showing an example of a preceding welding torch and a succeeding welding torch according to a modified example. Figure 10B is a schematic diagram showing another example of a preceding welding torch and a succeeding welding torch according to a modified example. For the sake of clarity, in Figures 10A and 10B, the same reference numerals are used for parts that are the same as in Embodiment 1, and detailed explanations are omitted.

[0082] In this embodiment, in order to create a difference in heat input between the preceding and succeeding welds, the preceding weld is pulsed welding and the succeeding weld is short-circuit welding. However, the method for creating the heat input difference is not particularly limited to this. do not have.

[0083] For example, as shown in Figure 10A, the wire protrusion length Lp2 of the trailing welding torch 6B may be longer than the wire protrusion length Lp1 of the leading welding torch 6A. Also, as shown in Figure 10B, the wire diameter d2 of the trailing welding wire 9B may be shorter than the wire diameter d1 of the leading welding wire 9A.

[0084] In either case, the subsequent welding can be performed using arc welding with a lower heat input than the preceding welding. In these cases, the welding method may be the same for both the preceding and succeeding welds, depending on the required heat input difference. For example, both may be short-circuit welding. Alternatively, as shown in the embodiment, the preceding welding may be pulse welding and the succeeding welding may be short-circuit welding.

[0085] (Other embodiments) In this specification, the example of tandem arc welding being horizontal welding is given, but the invention is not limited to this, and the tandem arc welding control method of this embodiment can be applied to downward welding and upward welding as well. In these cases, too, the molten pool can be stably formed during high-speed welding, and the formation of the weld bead by the subsequent solidification of the molten metal can be stabilized. [Industrial applicability]

[0086] The tandem arc welding control method disclosed herein is useful because it can stably form a molten pool and a weld bead even during high-speed welding. [Explanation of symbols]

[0087] 1A Pre-release robot controller 1B Sequential Robot Controller 2A Pre-welding power supply 2B Trailing welding power source 3A Pre-launch welding robot 3B Sequential welding robot 4A Wire feeder for advance use 4B Trailing wire feeder 5A Advance Feed Liner 5B Rear-bound feeder liner 6A Pre-welding torch 6B Rear-facing welding torch 7A Pre-emptive nozzle 7B Rear Nozzle 7C Pre-emptive nozzle 7D Rear Nozzle 8A Pre-welding tip 8B Sequential welding tip 9A Pre-welding wire 9B Sequential welding wire 9C Pre-welding wire storage section 9D Rear welding wire storage section 10A Pre-emptive Current Cable 10B trailing current cable 11 Top plate 12 Lower plate 13 Communication Cable 14A Pre-emptive control cable 14B Trailing control cable 15 Arc 16 Base material 20 Weld beads 21 Leading Bead 22 Sequential bead 23A Pre-welding Arc Welding Equipment 23B Sequential Arc Welding Equipment 24 Tandem Arc Welding System

Claims

1. The first step involves moving a leading welding torch, which holds a leading welding wire, along the first welding line, while generating an arc between the leading welding wire and the base material, thereby arc welding the base material. The method further comprises, at least, the first step, followed by a second step in which a trailing welding torch holding a trailing welding wire is moved along a second welding line, and an arc is generated between the trailing welding wire and the base material to arc weld the base material, The relative positions of the leading welding torch and the trailing welding torch are controlled such that the first welding line is separated by a first distance in a direction parallel to and perpendicular to the second welding line. A tandem arc welding control method characterized in that, in the second step, the welding output input to the preceding welding wire and the following welding wire is controlled so that the base material is arc-welded with a lower heat input than in the first step. or, A tandem arc welding control method characterized in that, in the second step, the welding current flowing through the leading welding wire and the trailing welding wire is controlled so that the base material is arc-welded with a lower heat input than in the first step.

2. In the tandem arc welding control method according to claim 1, In the first step described above, pulse welding is performed. The tandem arc welding control method is characterized in that, in the second step, the forward and reverse feeding of the trailing welding wire is repeated alternately to perform short-circuit welding. or, In the first step, a base current is passed through the lead welding wire at a predetermined cycle, and a peak current with a higher current value than the base current is passed immediately following the base current. The tandem arc welding control method is characterized in that, in the second step, the forward and reverse feeding of the trailing welding wire is alternately repeated to short-circuit the trailing welding wire to the base material, and then the arc is generated between the trailing welding wire and the base material.

3. In the tandem arc welding control method according to claim 1, A tandem arc welding control method characterized in that the first distance is 1.0 mm or more and 2.0 mm or less.

4. In the tandem arc welding control method according to claim 1, The distance between the tip of the preceding welding wire and the tip of the following welding wire, along the direction parallel to the first welding line, is defined as the electrode distance L. When the moving speed of the leading welding torch along the first welding line and the moving speed of the trailing welding torch along the second welding line are defined as welding speeds S, A tandem arc welding control method characterized by controlling the relative positions of the leading welding torch and the trailing welding torch such that the distance L between electrodes increases as the welding speed S increases.

5. In the tandem arc welding control method described in claim 4, 3.33 × S - 5 ≤ L ≤ 3.33 × S + 5 A tandem arc welding control method characterized by controlling the relative positions of the leading welding torch and the trailing welding torch so as to satisfy the relationship shown.

6. In the tandem arc welding control method described in claim 5, L = 3.33 × S A tandem arc welding control method characterized by controlling the relative positions of the leading welding torch and the trailing welding torch so as to satisfy the relationship shown.

7. In the tandem arc welding control method according to claim 1, A tandem arc welding control method characterized in that the composition of the trailing welding wire is the same as the composition of the leading welding wire.

8. In the tandem arc welding control method according to claim 1, A tandem arc welding control method characterized in that the wire protrusion length in the trailing welding torch is longer than the wire protrusion length in the leading welding torch.

9. In the tandem arc welding control method according to claim 1, A tandem arc welding control method characterized by ensuring that the average current flowing through the trailing welding wire is smaller than the average current flowing through the leading welding wire.

10. In the tandem arc welding control method described in claim 2, The tandem arc welding control method is characterized in that the first step includes a period during which the leading welding wire and the base material are short-circuited.

11. In the tandem arc welding control method according to any one of claims 1 to 10, In the first and second steps described above, the base material is arc-welded in a lateral position. A tandem arc welding control method characterized in that the first welding line is located above the second welding line.

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