Arc-welding method

Abstract

To provide an arc-welding method which can stabilize alignment at an edge of a bead when performing a short-circuit welding.SOLUTION: An arc-welding method is given in which a welding wire 18 is moved along a weldment section at a prescribed speed. A weld bead 30 is, while alternately repeating a first period T1 where welding-current flows in the welding wire 18 and a second period T2 where welding-current does not flow therein, formed in a base material 17 along the weldment section. The first period T1 includes: an arc period TA when arc 19 is generated between the welding wire 18 and the base material 17; and a short-circuit period TS when the welding wire 18 and the base material 17 are short-circuited following the arc period TA. The first period T1 alternately repeats forward feed and reverse feed of the welding wire 18 in which an extrusion length LEX1 of the welding wire 18 from an edge of a tip 21 is 3 mm or more and 10 mm or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a consumable electrode arc welding method. [Background technology]

[0002] Consumable electrode MIG welding and MAG welding are becoming increasingly popular in the welding of bicycles, motorcycles, and other vehicles, in order to achieve beautiful scale-like weld beads and improve productivity. In consumable electrode MIG welding and MAG welding, an electric current is passed through a welding wire, which serves as an electrode, and the arc heat generated between the welding wire and the base material, which serves as the welding object, is used to melt the welding wire while welding, which allows for high welding efficiency and fast welding speeds.

[0003] In consumable electrode MIG welding and MAG welding, methods have been proposed to control the bead shape by varying the heat input to the base metal, a typical example being pulse welding. Pulse welding is commonly used because it allows droplet transfer while keeping the average current below the critical current by alternately passing a peak current higher than the critical current that detaches droplets from the welding wire and a base current lower than the critical current that maintains the arc. Furthermore, because one droplet is transferred during one peak current, it is also called one pulse, one drop.

[0004] For example, Patent Document 1 discloses a method of superimposing a second peak current, whose current value is lower than the peak current, on the base current during a base period when the base current flows through the welding wire at a second pulse frequency higher than the first pulse frequency at which the peak current flows. This method maintains a low time integral of the current flowing through the welding wire during the base period, thereby periodically strengthening the arc force during the base period. This prevents a decrease in arc directionality and ensures stable heat input to a predetermined position on the base metal relative to the welding direction. As a result, unevenness of the bead edge around the weld bead is suppressed, the bead edge is stabilized, the weld bead width is stabilized, and the appearance is improved. Furthermore, during the second peak period when the second peak current flows, the arc is irradiated onto the surface of the base metal with a stronger arc force than during the period when the base current flows. This decomposes and cleans the oxide film on the surface of the base metal made of aluminum or an aluminum-based alloy (hereinafter referred to as an aluminum-based material). In other words, a kind of cleaning action is performed, making it possible to prevent smut from adhering to the surface of the base material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 110786 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the base metal has become thinner, and there has been a demand for arc welding to be performed on the base metal with even lower heat input. Short-circuit welding is known as an arc welding method with even lower heat input than pulse welding. In short-circuit welding, while a welding current is flowing through the welding wire, the welding wire is alternately fed forward and backward, thereby alternately generating a period in which an arc is generated between the base metal and the welding wire and a period in which the base metal and the welding wire are short-circuited.

[0007] However, the inventors of the present invention have found that in short-circuit welding, simply adjusting the welding current and the welding wire feed speed may result in uneven bead edges around the periphery of the weld bead.

[0008] The present disclosure has been made in view of the above points, and an object of the present disclosure is to provide an arc welding method that can stabilize the alignment of bead edges in short-circuit welding. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, an arc welding method according to the present disclosure is an arc welding method in which a welding wire is moved along a welding section of a base metal at a predetermined speed, and a first period in which a predetermined welding current flows through the welding wire and a second period in which the welding current does not flow through the welding wire are alternately repeated to form a weld bead on the base metal along the welding section, wherein the first period includes an arc period in which an arc is generated between the welding wire and the base metal, and a short-circuit period following the arc period in which the welding wire and the base metal are short-circuited, and during the first period, forward and reverse feed of the welding wire is alternately repeated, and a protruding length of the welding wire from a tip of a tip that holds the welding wire is 3 mm or more and 10 mm or less. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to stabilize the alignment of the bead edge in short circuit welding. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of an arc welding device according to an embodiment; [Figure 2] FIG. 1 is a schematic diagram for explaining short-circuit stitch welding. [Figure 3] 4A to 4C are diagrams showing various output waveforms during arc welding according to an embodiment. [Figure 4]FIG. 10 is a diagram showing time waveforms of various command values ​​in a first period. [Figure 5A] 10A and 10B are schematic diagrams for explaining the state of the welding wire when the extension length is within an appropriate range. [Figure 5B] FIG. 10 is a schematic plan view of a weld bead formed on a base material when the protrusion length is within an appropriate range. [Figure 6A] 10A and 10B are schematic diagrams for explaining the state of the welding wire when the extension length is longer than the appropriate range. [Figure 6B] 10 is a schematic plan view of a weld bead formed on a base material when the extension length is longer than the appropriate range. FIG. [Figure 7A] 10A and 10B are schematic diagrams illustrating the operation of the welding wire and the generation of an arc when the extension length is within an appropriate range. [Figure 7B] 10A and 10B are schematic diagrams illustrating the operation of the welding wire and the generation of an arc when the extension length is shorter than the appropriate range. [Figure 8A] 10 is a schematic diagram showing an arc generation state when the extension length is longer than the appropriate range. FIG. [Figure 8B] FIG. 2 is a schematic diagram showing the relationship between the base material-tip distance and the protrusion length. [Figure 8C] 8B is a schematic plan view of a weld bead formed on a base material and an arc irradiated region in the state shown in FIG. 8A. FIG. [Figure 9A] FIG. 10 is a schematic diagram showing an arc generation state when the extension length is within an appropriate range. [Figure 9B] 9B is a schematic plan view of a weld bead formed on a base material and an arc irradiated region in the state shown in FIG. 9A. FIG. [Figure 10A] 10 is a schematic diagram showing the positional relationship between the base material, the torch, and the welding wire when both the extension length and the tip extension length are outside the appropriate ranges. FIG. [Figure 10B] 10 is a schematic diagram showing the positional relationship between the base material, the torch, and the welding wire when the tip protrusion length is outside the appropriate range. FIG. [Figure 10C] FIG. 10 is a schematic diagram showing the positional relationship between the base material, the torch, and the welding wire when both the extension length and the tip extension length are within the appropriate range. [Figure 11A] FIG. 10 is a diagram showing the time waveforms of various command values ​​when the minimum value of the reverse feed speed is −12 m / min. [Figure 11B] FIG. 10 is a diagram showing the time waveforms of various command values ​​when the minimum value of the reverse feed speed is −2 m / min. [Figure 12A] 11B is a photograph showing a weld bead formed on a base material under the conditions shown in FIG. 11A. [Figure 12B] 12B is a schematic diagram of the weld bead shown in FIG. 12A as viewed from the direction of arrow A. FIG. [Figure 13A] 11C is a photograph showing a weld bead formed on a base material under the conditions shown in FIG. 11B. [Figure 13B] 13B is a schematic diagram of the weld bead shown in FIG. 13A as viewed from the direction of arrow A. FIG. [Figure 14] 5A and 5B are schematic diagrams showing changes in the state of the welding wire during an arc period. [Figure 15A] FIG. 10 is a diagram showing the extension length of the welding wire during reverse feeding. [Figure 15B] FIG. 10 is a diagram showing the extension length of the welding wire during forward feeding. [Figure 16] FIG. 10 is a diagram showing the relationship between the welding state, the extension length, and the reverse feed distance. [Figure 17] FIG. 10 is a schematic diagram for explaining the time it takes for the forward transport speed to reach its maximum value after the short circuit is released. [Figure 18A] FIG. 10 is a diagram showing time waveforms of various command values ​​before adjusting the short circuit period in the first period. [Figure 18B] 10A and 10B are diagrams showing time waveforms of various command values ​​after adjusting the short circuit period in the first period. [Figure 19A] FIG. 10 is a diagram showing time waveforms of various command values ​​before adjusting the bending point current in the first period. [Figure 19B] FIG. 10 is a diagram showing the time waveforms of various command values ​​after adjusting the bending point current in the first period. [Figure 20] 10A and 10B are diagrams showing various output waveforms during arc welding according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present embodiment will be described in detail below with reference to the drawings. The following description of the preferred embodiment is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0013] (Embodiment) [1: Configuration of arc welding equipment] 1 is a schematic diagram of an arc welding apparatus according to this embodiment. Arc welding apparatus 16 welds base material 17 using welding wire 18, which is a consumable electrode.

[0014] In this embodiment, the welding wire 18 is made of hard aluminum (A5183-WY) with a wire diameter of 1.2 mm, and the base material 17 is made of aluminum. However, the base material 17 may be an alloy mainly made of aluminum. The shielding gas sprayed onto the base material 17 contains 80% or more of Ar (argon) gas.

[0015] As shown in FIG. 1 , welding wire 18 is held by welding tip 21 (hereinafter simply referred to as tip 21), and tip 21 is held by torch 20. As torch 20 moves at a constant speed, the tip of welding wire 18 also moves at the same speed along a predetermined welding section. A nozzle 20A is provided at the tip of torch 20. Nozzle 20A is provided with a shielding gas outlet hole (not shown). The tip of tip 21 protrudes outward from the tip of nozzle 20A, that is, toward base material 17. As will be described in detail later, the tip of tip 21 may be flush with the tip of nozzle 20A.

[0016] Arc welding device 16 has a main transformer 2, a primary side rectifier 3, a switching unit 4, a DCL (reactor) 5, a secondary side rectifier 6, a welding current detector 7, a welding voltage detector 8, a control switching unit 9, an output controller 10, and a wire feed speed controller 13. Arc welding device 16 also has a robot controller (not shown) that controls the operation of a robot (not shown) that holds torch 20.

[0017] The control switching unit 9, the output control unit 10, and the wire feed speed control unit 13 are each configured with one or more CPUs (Central Processing Units). Alternatively, the control switching unit 9, the output control unit 10, and the wire feed speed control unit 13 are each configured with one or more MCUs (Micro Control Units). The control switching unit 9, the output control unit 10, and the wire feed speed control unit 13 may be configured with the same CPU or MCU.

[0018] Output control unit 10 has a short-circuit welding control unit 11 and a pulse welding control unit 12. Wire feed speed control unit 13 has a wire feed speed detection unit 14 and a calculation unit 15. Primary side rectification unit 3 rectifies the input voltage input from an input power source (three-phase AC power source) 1 external to arc welding device 16. Switching unit 4 controls the output of primary side rectification unit 3 to an output suitable for welding. Main transformer 2 converts the output of switching unit 4 into an output suitable for welding.

[0019] Secondary side rectifier 6 rectifies the output of main transformer 2. DCL (reactor) 5 smoothes the output of secondary side rectifier 6 to a current suitable for welding. Welding current detector 7 detects welding current I flowing through welding wire 18. Welding voltage detector 8 detects welding voltage V applied between welding wire 18 and base material 17.

[0020] Control switching unit 9 is a switching unit that outputs the timing for switching from short circuit welding control to pulse welding control to output control unit 10. Control switching unit 9 has a timing function, and measures a predetermined time set by welding condition setting unit 23, and outputs the timing for switching control to output control unit 10 and wire feed speed control unit 13.

[0021] The output control unit 10 controls the welding output by outputting a control signal to the switching unit 4. The short circuit welding control unit 11 controls short circuit welding when the control switching unit 9 commands short circuit welding. The pulse welding control unit 12 controls pulse welding when the control switching unit 9 commands pulse welding.

[0022] The output control unit 10 calculates the average current I S The welding current I is controlled so that the average current I S is the moving average value of the welding current I over a predetermined period.

[0023] Wire feed speed control unit 13 controls wire feed unit 22 to control feed speed W of welding wire 18 (hereinafter simply referred to as feed speed W). Wire feed speed detection unit 14 detects feed speed W. Based on a signal from wire feed speed detection unit 14, calculation unit 15 calculates an integrated amount of the feed amount of welding wire 18 and controls feed speed W. Specifically, calculation unit 15 compares a command value and a detected value of feed speed W to determine the difference, and performs feedback control based on the integrated amount of the difference so as to match the actual feed speed W to the command value.

[0024] A wire feeder 22 and a welding condition setting unit 23 are connected to the arc welding device 16. The welding condition setting unit 23 is used to set welding conditions for the arc welding device 16. The welding condition setting unit 23 also has a short-circuit welding setting unit 24, a pulse welding setting unit 25, and a cooling period setting unit 26. The wire feeder 22 controls the feeding of the welding wire 18 based on a signal from the wire feed speed control unit 13. A welding program, which describes the welding output control procedure and the feeding procedure of the welding wire 18 during short-circuit welding and pulse welding, is stored in a memory unit (not shown) provided in the arc welding device 16.

[0025] When a torch SW (switch) (not shown) is turned ON, the welding output of arc welding device 16 is supplied to welding wire 18 via tip 21. Then, the welding output output from arc welding device 16 generates arc 19 between welding wire 18 and base material 17, or the tip of molten welding wire 18 comes into contact with base material 17, thereby performing arc welding.

[0026] When actually performing arc welding, if only short-circuit welding, which will be described later, is performed, the control switching unit 9, pulse welding setting unit 25, and cooling period setting unit 26 may be omitted.

[0027] [2: Overview of arc welding methods] 2 is a schematic diagram for explaining short-circuit stitch welding. In the following description, the thickness direction of base material 17, which is a plate material, may be referred to as the Z direction. The welding direction, which is the direction in which torch 20 is moved linearly relative to base material 17, may be referred to as the Y direction. The Y direction is also the longitudinal direction of scale-like weld bead 30 (see FIG. 5B; hereinafter simply referred to as weld bead 30) formed on base material 17. The direction perpendicular to the Y direction and the Z direction may be referred to as the X direction.

[0028] In this specification, "orthogonal," "parallel," or "same" means that the two objects are orthogonal, parallel, or the same, taking into account the assembly tolerances and processing tolerances of the arc welding device 16 and its components, as well as the processing tolerances of the base material 17 and processing tolerances during arc welding. It does not mean that the objects being compared are orthogonal, parallel, or the same in the strict sense.

[0029] As shown in Fig. 2, short-circuit welding in this embodiment is performed by either passing a welding current through welding wire 18 to generate an arc, or by bringing welding wire 18 into contact with the surface of base metal 17 while a welding current is flowing. The period during which a welding current flows through welding wire 18 is referred to as a first period T1. As will be described later, first period T1 is also referred to as an arc period T2 during which an arc 19 is generated between welding wire 18 and base metal 17. A and arc period T A Subsequently, a short-circuit period T S and includes.

[0030] Following first period T1, a period is provided in which no welding current flows through welding wire 18. This period is referred to as second period T2. That is, in short-circuit welding in this embodiment, first period T1 and second period T2 are alternately repeated to form weld bead 30 on base material 17. This method is sometimes referred to as short-circuit stitch welding.

[0031] In the short-circuit stitch welding of this embodiment, unlike general stitch welding in which welding is performed while torch 20 is stopped and then torch 20 is moved to the next teaching point after welding is stopped, torch 20 is continuously moved along a predetermined weld line (see FIG. 5B) so that the welding speed is kept constant. Note that the welding speed does not have to be constant throughout the entire welding portion of base material 17. For example, the welding speed may be changed in areas where the thickness of base material 17 changes.

[0032] Fig. 3 is a diagram showing various output waveforms during arc welding according to the embodiment, Fig. 4 is a diagram showing time waveforms of various command values ​​in a first period.

[0033] FIG. 3 shows the time variations of the wire feed rate W, welding voltage V, welding current I, and droplet transfer state D at the tip of the welding wire 18 during arc welding.

[0034] 2 and 3, the set current, which is the moving average value of the welding current flowing through welding wire 18, is set to 110 A. However, the set current is not particularly limited to this value and is changed appropriately depending on the materials of base metal 17 and welding wire 18, the thickness of base metal 17, the wire diameter of welding wire 18, etc. In this embodiment, the set current is set in the range of 50 A or more and 220 A or less.

[0035] First, the torch SW is operated, and feeding of the welding wire 18 is started at a feed rate W1 from the time when the torch SW signal is turned ON, that is, from the time Wst when the welding start command is issued. Then, from the time Wst when the welding start command is issued, or from the time Ed when the welding start command is issued and the occurrence of a short circuit between the welding wire 18 and the base material 17 is detected, the welding output is controlled by the short circuit welding control unit 11 under the conditions set by the short circuit welding setting unit 24, and short circuit stitch welding is performed between the welding wire 18 and the base material 17. In this case, as shown in FIG. 4 , in the first period T1, the arc period T A (See (a) of droplet transfer state D in Figure 3) and short circuit period T S (See (b) of droplet transfer state D in FIG. 3) are alternately repeated. As shown in FIG. 3, during the first period T1, the feed speed W periodically changes from a positive value to a negative value and from a negative value to a positive value. When the feed speed W is a positive value, it is called forward feed or a forward feed state, and when it is a negative value, it is called reverse feed or a reverse feed state. In other words, during the first period T1, the welding wire 18 moves while periodically repeating forward feed and reverse feed relative to the base material 17.

[0036] At the end of the first period T1, the torch SW signal is turned OFF, starting the second period T2. As described above, during the second period T2, no welding current I flows through the welding wire 18, and welding of the base material 17 stops. As shown in FIG. 3, the outputs of the welding current I and welding voltage V become zero, and the feed speed W also becomes zero. However, the torch 20 advances at a constant welding speed along the welding direction. The first period T1 and the subsequent second period T2 constitute one welding cycle, and by sequentially repeating this welding cycle, a scale-like weld bead 30 is formed on the base material 17.

[0037] In the first period T1, as shown in FIG. A and short circuit period T S are alternately repeated. Arc period T A During the short circuit period T , a speed command is input from wire feed speed control unit 13 to wire feed unit 22 so that welding wire 18 mainly moves forward. S In this case, a speed command is input from wire feed speed control unit 13 to wire feed unit 22 so that welding wire 18 moves from forward feed to reverse feed and then transitions to forward feed operation.

[0038] [3: Knowledge that led to this disclosure] Fig. 5A is a schematic diagram for explaining the state of a welding wire when the extension length is within an appropriate range. Fig. 5B is a schematic plan view of a weld bead formed on a base material when the extension length is within the appropriate range. Fig. 6A is a schematic diagram for explaining the state of a welding wire when the extension length is longer than the appropriate range. Fig. 6B is a schematic plan view of a weld bead formed on a base material when the extension length is longer than the appropriate range.

[0039] As shown in Figure 5A, the protrusion length L EX1 is the length of the welding wire 18 protruding from the tip of the tip 21, and in the example shown in FIG. 5A, it is the length along the Z direction from the tip of the tip 21 to the tip of the welding wire 18. EX1 If is a positive value, the welding wire 18 protrudes from the tip 21 toward the base material 17. EX1 If is a negative value, the tip of the welding wire 18 remains inside the tip 21.

[0040] Projection length L EX1 When is within the appropriate range, as shown in Fig. 5B, weld bead 30 is formed along the weld line in base material 17, i.e., along the Y direction. Except for both ends, the width of weld bead 30 in the X direction is constant along the longitudinal direction of weld bead 30. In addition, the pitch (= P) of the scale-like portions in weld bead 30 is kept constant along the longitudinal direction of weld bead 30.

[0041] On the other hand, according to the study by the inventors of the present application, the protruding length L EX1 It was found that when the length of the weld bead 30 is longer than the appropriate range, the bending of the welding wire 18 protruding from the tip 21 has a large effect, as shown in FIG. 6A. Furthermore, in the case shown in FIG. 6A, when the weld bead 30 is formed on the base material 17 by the method shown in FIGS. 2 and 3, the weld bead 30 is formed to bend in a direction intersecting the longitudinal direction, in this case, along the X direction, as shown in FIG. 6B. In this case, both ends of the weld bead 30 in the X direction, in other words, the edge of the weld bead 30, will not be aligned along the Y direction. In addition, the pitches P1, P2, ... P of the scale-like portions n However, this varies across the length of weld bead 30. If this occurs, not only will the appearance of weld bead 30 be marred, but there is also the risk of poor welding.

[0042] Welding wire 18 is held in wire feeder 22 in a state where it is wound around a reel (not shown), or is held in a wound state in a storage pack (not shown). Therefore, welding wire 18 is supplied to torch 20 in a bent state. It is thought that the reason the position of weld bead 30 varies in the X direction is because the welding wire 18 protruding from the tip of tip 21 is bent significantly, causing the tip of welding wire 18 to swing in the X direction during welding.

[0043] [4: Adjusting various parameters] Therefore, the inventors of the present application have determined that the extension length L EX1 The appropriate range of the protrusion length L EX1 We also investigated other issues that may arise when setting the value of the parameter to the appropriate range, and how to adjust various parameters to resolve these issues. These will be explained in more detail below.

[0044] [4-1: Adjusting the protrusion length] Fig. 7A is a schematic diagram showing the movement of the welding wire and the generation of an arc when the extension length is within the appropriate range, and Fig. 7B is a schematic diagram showing the movement of the welding wire and the generation of an arc when the extension length is shorter than the appropriate range.

[0045] Fig. 8A is a schematic diagram showing the state of arc generation when the extension length is longer than the appropriate range. Fig. 8B is a schematic diagram showing the relationship between the base metal-tip distance and extension length. Fig. 8C is a schematic plan view of the weld bead and arc irradiated area formed on the base metal in the state shown in Fig. 8A. Fig. 9A is a schematic diagram showing the state of arc generation when the extension length is within the appropriate range. Fig. 9B is a schematic plan view of the weld bead and arc irradiated area formed on the base metal in the state shown in Fig. 9A.

[0046] Extension length L of welding wire 18 EX1 is within the appropriate range. For example, as shown in FIG. 7A, the protrusion length L EX1 is 5 mm, the tip of the welding wire 18 always protrudes outward from the tip of the tip 21 during the first period T1, even while the welding wire 18 is being fed backward. EX1 If the protrusion length L is shorter than the appropriate range, for example, as shown in FIG. EX1 is 2 mm, the tip of the welding wire 18 will enter the inside of the tip 21 during the reverse feeding operation of the welding wire 18 in the first period T1. As a result, the welding wire 18 and the tip 21 will be welded together.

[0047] In addition, the extension length L of the welding wire 18 EX1 is longer than the appropriate range, for example, as shown in FIG. 6B, EX1 If the distance is 15 mm, as described above, the alignment of the edges of the weld bead 30 will not be stable and the pitch of the scale-like portions will also vary.

[0048] 8B, in a state where no arc 19 is being generated, the distance h between the end of tip 21 and the surface of base material 17 (hereinafter referred to as base material-tip distance h) is adjusted. For example, when teaching the movement trajectory of torch 20 held by a welding robot (not shown) relative to base material 17, the distance h (hereinafter referred to as base material-tip distance h) is adjusted so that the distance is the same as extension length LEX1 of welding wire 18 or so that welding wire 18 is close to the surface of base material 17.

[0049] 8A, during actual welding, arc 19 is generated between welding wire 18 and base metal 17. In this case, as shown in FIG. 8C, weld bead 30 may be formed extending beyond the arc irradiated area where arc 19 irradiates base metal 17 in the X direction (the width direction of the weld bead). As a result, smut may remain around weld bead 30. Smut is fine metal oxide that is formed when a portion of a molten metal droplet detached from the tip of welding wire 18 evaporates due to arc heat, oxidizes, solidifies, and adheres to the surface of base metal 17 outside the area where the shielding gas is sprayed.

[0050] Inside the arc irradiated area, smut is cleaned and removed by the arc heat, and adhesion to base metal 17 is suppressed. However, as shown in FIG. 8C , when weld bead 30 is formed protruding outside the arc irradiated area, smut may remain around the protruding portion of weld bead 30. When base metal 17 and welding wire 18 are made of an aluminum-based material, smut is likely to remain on the surface of base metal 17. Furthermore, in this case, because smut is black, adhesion of smut detracts from the appearance of the welded portion.

[0051] On the other hand, the protruding length L EX1 is within the appropriate range of this embodiment, an arc 19 is also generated between the tip 21 and the base material 17, as shown in Fig. 9A. In this case as well, the following relationship holds.

[0052] Projection length L EX1 <Base metal-tip distance h ≒ arc length LARC 9B, the arc irradiated area is wider in the X direction than in the case shown in FIG. 8C, and arc 19 is irradiated to base material 17, including an area that is a predetermined distance away in the X direction from the edge of weld bead 30. This suppresses the adhesion of smut around weld bead 30.

[0053] As described above, the extension length L of the welding wire 18 EX1 It has been found that if the extension length L is shorter than the appropriate range, the welding wire 18 may penetrate into the tip 21 during welding and may be welded to the tip 21. EX1 If the length of the tip 21 is longer than the appropriate range, the bending of the welding wire 18 protruding from the tip of the tip 21 will be large, causing the tip of the welding wire 18 to swing in the X direction during welding, and the position of the edge of the weld bead 30 to vary in the X direction. As a result, not only will the appearance of the weld bead 30 be impaired, but there is also a risk of poor welding.

[0054] Therefore, as a result of the investigation conducted by the inventors of the present application, it was found that the extension length L of the welding wire 18 under the above-mentioned welding conditions EX1 It was found that the appropriate range of the protrusion length L is 3 mm or more and 10 mm or less. EX1 value, for example, shorter than 15 mm.

[0055] Projection length L EX1 By setting the protruding length L of the welding wire 18 within this appropriate range, the influence of bending of the welding wire 18 protruding from the end of the tip 21 can be suppressed, and the alignment of the weld bead 30 can be stabilized. As a result, the appearance of the weld bead 30 can be improved, and the occurrence of welding defects can be suppressed. EX1 However, it has been found that the above-mentioned effects can be more significantly achieved when the distance is preferably 5 mm or more and 8 mm or less.

[0056] If you want to expand the cleaning area, the protrusion length L EX1By setting the extension length L to 5 mm or less, the arc 19 is generated not only from the tip of the welding wire 18 but also from the tip 21, and the irradiation area of ​​the arc 19 on the base material 17 is relatively expanded, thereby further improving the cleaning effect of the arc 19. This allows the cleaning width of the surface of the base material 17 by the arc 19 to be expanded, and smut adhesion can be suppressed. EX1 By setting the cleaning width of the arc 19 to 5 mm or less, for example, the cleaning width of the surface of the base material 17 by the arc 19 can be improved by about 120%.

[0057] [4-2: Adjusting the tip protrusion length] As described above, in order to suppress bending of the weld bead 30, align the edges of the weld bead 30, and improve the appearance, the extension length L of the welding wire 18 is set to EX1 It is preferable to set the protrusion length L to 3 mm or more and 10 mm or less, preferably 5 mm or more and 8 mm or less. EX1 It turns out that shortening the time frame can create other challenges.

[0058] Fig. 10A is a schematic diagram showing the positional relationship between the base material, the torch, and the welding wire when both the extension length and the tip extension length are outside the appropriate ranges. Fig. 10B is a schematic diagram showing the positional relationship between the base material, the torch, and the welding wire when the tip extension length is outside the appropriate ranges. Fig. 10C is a schematic diagram showing the positional relationship between the base material, the torch, and the welding wire when both the extension length and the tip extension length are within the appropriate ranges.

[0059] As shown in FIG. 10A, when the base material 17 is a T-shaped joint, the protrusion length L EX1 is a normal value, for example, about 15 mm, there is a sufficient distance between the nozzle 20A and the base material 17, and there is little risk that the nozzle 20A will interfere with the base material 17. In the example shown in FIG. 10A, the tip protrusion length L EX2 is set to -4 mm. Here, the side where the tip of the tip 21 protrudes outward from the tip of the nozzle 20A is positive (+), and the side where it goes inward is negative (-). Also, the tip protrusion length L EX2The tip protrusion length L is the distance from the tip of the nozzle 20A to the tip of the tip 21. EX2 When the tip protrusion length L is a negative value, the tip end of the tip 21 is recessed into the nozzle 20A, as shown in FIG. EX2 When is a positive value, the tip of the tip 21 protrudes outward from the nozzle 20A.

[0060] On the other hand, as shown in FIG. 10B, the extension length L EX1 is set to an appropriate value (for example, 3 mm to 10 mm), the distance from the tip of nozzle 20A to the tip of welding wire 18 becomes shorter than in the case shown in Fig. 10A. In this case, there is a risk of interference between nozzle 20A and base material 17, such as the tip of nozzle 20A coming into contact with base material 17, as shown in Fig. 10B.

[0061] As a result of the investigations conducted by the inventors of the present invention, it was found that such interference can be prevented by making the tip 21 protrude outward from the tip of the nozzle 20A, as shown in FIG. EX2 It is preferable that the value of is a positive value and is not more than +5 mm. However, the tip protrusion length L EX2 In this case, interference between the nozzle 20A and the base material 17 can be suppressed. EX2 If the distance exceeds 5 mm, the distance between the tip of nozzle 20A and base material 17 becomes too long, weakening the effect of spraying shielding gas to prevent contact between the atmosphere and the molten metal. In other words, contact with the atmosphere may cause bubbles to form in the molten metal, potentially resulting in poor welding of weld bead 30.

[0062] In other words, the tip protrusion length L EX2 By setting the gap between 0 mm and 5 mm, interference between the nozzle 20A and the base material 17 can be suppressed, and contact between the air and the molten metal can be prevented, thereby suppressing the occurrence of welding defects.

[0063] [4-3: Adjusting the reverse speed] FIG. 11A is a diagram showing the time waveforms of various command values ​​when the minimum value of the reverse feed speed is -12 m / min. FIG. 11B is a diagram showing the time waveforms of various command values ​​when the minimum value of the reverse feed speed is -2 m / min. FIG. 12A is a photograph showing a weld bead formed on a base material under the conditions shown in FIG. 11A. FIG. 12B is a schematic diagram of the weld bead shown in FIG. 12A as viewed from the direction of arrow A. FIG. 13A is a photograph showing a weld bead formed on a base material under the conditions shown in FIG. 11B. FIG. 13B is a schematic diagram of the weld bead shown in FIG. 13A as viewed from the direction of arrow A.

[0064] Projection length L EX1 If the length is shorter than the appropriate range, the tip of the welding wire 18 will enter the inside of the tip 21, and the welding wire 18 will be welded to the tip 21 during welding, as described above.

[0065] However, the protruding length L EX1 Even if the reverse feed speed of the welding wire 18 is set within the appropriate range, welding between the welding wire 18 and the tip 21 may occur. For example, this may occur if the reverse feed speed of the welding wire 18 is not adjusted appropriately. This will be explained further.

[0066] In the example shown in FIG. 11A, the maximum value W F is set to 12 m / min, and the minimum value W B On the other hand, in the example shown in FIG. 11B, the maximum value W F is set to 12 m / min, and the minimum value W B is set to -2m / min.

[0067] When weld bead 30 was formed on base material 17 under the conditions shown in Fig. 11A, weld bead 30 had stable edge alignment and a good appearance without any curves, as shown in Fig. 12A. Furthermore, weld bead 30 was formed with a good balance between the width in the X direction and the height in the Z direction, as shown in Fig. 12B.

[0068] On the other hand, when weld bead 30 was formed on base material 17 under the conditions shown in Fig. 11B, weld bead 30 had a narrower width in the X direction and larger unevenness at its top, as shown in Fig. 13B. Also, as shown in Fig. 13B, weld bead 30 had a narrower width in the X direction and a higher height in the Z direction, forming a convex shape, compared to the example shown in Fig. 12B.

[0069] As a result of considering the cause of this, the minimum value W of the feed speed W during reverse feed was B When the absolute value of becomes smaller than the appropriate range, the lifting speed of the welding wire 18 becomes slower. As a result, the time required to open the short circuit between the welding wire 18 and the base material 17 becomes longer. In addition, the arc period T A Therefore, the arc 19 is not irradiated onto the base material 17, and the time required for the base material 17 to cool naturally becomes longer.

[0070] As a result, the width of weld bead 30 in the X direction is narrowed. In addition, because it takes time to pull up welding wire 18, it takes a long time to release the short circuit between welding wire 18 and base material 17, and the tip of welding wire 18 is pulled for a long time in a state where it is quasi-welded to the surface of base material 17, resulting in a convex shape with a high height in the Z direction. When this happens, not only is the appearance of weld bead 30 marred, but there is also a risk of poor welding.

[0071] On the other hand, the minimum value W B is smaller than the appropriate range, in other words, the minimum value W B If the absolute value of becomes larger than the appropriate range, the tip of welding wire 18 may be pulled in during welding, and welding wire 18 may be welded to tip 21.

[0072] As a result of the investigation by the inventors of the present application, under the above-mentioned welding conditions, the minimum value W B It was found that the optimum range for this is between -12m / min and -3m / min.

[0073] Minimum value of feeding speed W BSetting this within the appropriate range can prevent welding between tip 21 and welding wire 18. In addition, the width of weld bead 30 in the X direction can be prevented from becoming narrower and the height in the Z direction can be prevented from becoming higher than necessary, thereby improving the appearance of weld bead 30.

[0074] [4-4: Adjusting the ratio of the welding wire reverse feed distance to the extension length] Fig. 14 is a schematic diagram showing changes in the state of the welding wire during the arc period. Fig. 15A is a diagram showing the extension length of the welding wire during reverse feeding. Fig. 15B is a diagram showing the extension length of the welding wire during forward feeding. Fig. 16 is a diagram showing the relationship between the welding state and the extension length and reverse feeding distance.

[0075] Projection length L EX1 and the minimum value of the feed speed W B Even if the value is set within the appropriate range, welding may occur between the welding wire 18 and the tip 21. This will be further explained.

[0076] As shown in Figure 14, the arc period T A In the example, the welding wire 18 is fed in the reverse direction to release the short circuit between the welding wire 18 and the base material 17, and then the welding wire 18 is switched from the reverse feeding operation to the forward feeding operation, and the welding wire 18 and the base material 17 are short-circuited again.

[0077] After the short circuit is released when welding wire 18 is fed in the reverse direction before being fed in the forward direction in accordance with the feed speed command, arc 19 is generated between welding wire 18 and base material 17, and the tip of welding wire 18 is in a molten state. In other words, when welding wire 18 is fed in the reverse direction, welding wire 18 is being pulled up while melting. In other words, welding wire 18 is being pulled up while burning.

[0078] The length of the melted portion 18 of the welding wire 18 at this time varies depending on the value of the welding current. When the set current is in the range described above, ie, 50 A or more and 220 A or less, the length (melted length) L1 of the melted portion 18a of the welding wire 18 during the reverse feeding operation of the welding wire 18 is about 3 mm (see FIG. 15A). Also, the reverse feeding distance L2 of the welding wire 18 during the reverse feeding (the return distance of the welding wire 18 during the reverse feeding) is about 1 mm (see FIG. 15A). The extension length L EX1 If the set value of is 5 mm, the protrusion amount L3 of welding wire 18 at the start of the forward feeding operation will be about 1 mm (see FIG. 15B).

[0079] Projection length L EX1 If the set value of the extension length L is longer than the sum of the melting length L1 and the reverse feed distance L2 shown in FIG. 15A, the welding wire 18 will not penetrate into the tip 21, and welding between the welding wire 18 and the tip 21 will not occur. EX1 It was found that there is an appropriate range for the ratio of the reverse feed distance L2 to the

[0080] As shown in Figure 16, the protrusion length L EX1 When the ratio of the reverse feed distance L2 to the extension length L was 30%, the welding result, i.e., the appearance of the weld bead 30, was poor (NG). Also, welding between the welding wire 18 and the tip 21 occurred. EX1 When the ratio of reverse feed distance L2 to tip 21 was 16% and 20%, the appearance of weld bead 30 was good, and no welding between welding wire 18 and tip 21 occurred.

[0081] As a result of further investigation by the inventors of the present application, it was found that the protruding length L EX1It has been found that the appropriate range for the ratio of reverse feed distance L2 to base metal 17 is 10% or more and 20% or less. If this ratio is less than 10%, the amount of heat input to base metal 17 will be insufficient, resulting in weld bead 30 having a convex shape as shown in FIGS. 13A and 13B. On the other hand, if this ratio exceeds 20%, welding between welding wire 18 and tip 21 will occur, as described above. By feeding welding wire 18 so that this ratio is 10% or more and 20% or less, welding between welding wire 18 and tip 21 can be prevented, and the appearance of weld bead 30 can be improved.

[0082] [4-5: Adjustment of the time from when the short circuit is released until the welding wire forward speed reaches its maximum value] There are other measures to prevent welding between the welding wire 18 and the tip 21 in addition to those described above. For example, welding between the welding wire 18 and the tip 21 can also be prevented by setting the time T from when the short circuit between the welding wire 18 and the base material 17 is released until the forward feed speed of the welding wire reaches its maximum value within an appropriate range. This will be further described with reference to the drawings.

[0083] FIG. 17 is a schematic diagram for explaining the time T required for the forward transport speed to reach its maximum value after the short circuit is released.

[0084] As shown in FIG. 17, in the first period T1, the short-circuit period T S In this case, the welding wire 18 is moved from the forward feed operation to the reverse feed operation, and the reverse feed speed command value reaches the minimum value W B At this point, the arc period T A The arc period T A In this case, the welding wire 18 is moved from the reverse feed operation to the forward feed operation, and the forward feed speed command value reaches the maximum value W F When this happens, the short circuit period T S When the period during which the feeding operation of the welding wire 18 transitions from forward feeding to reverse feeding and then from reverse feeding to forward feeding is defined as one cycle, and the time change in the feed speed command value in that cycle is assumed to be a sine wave, the time phase of the sine wave can be regarded as the feed angle.

[0085] On the other hand, by adjusting the reverse feed speed command value, the feed angle is skipped discontinuously, and as shown by the dashed line in FIG. 17, the time from the end of reverse feed (t2) to the transition to forward feed operation, specifically the arrival time T, can be shortened.

[0086] For example, if the reverse feed speed command value is not adjusted, the time T from when the short circuit between welding wire 18 and base metal 17 is released until the forward feed speed of the welding wire reaches its maximum value is assumed to be 6 msec. In this case, the reverse feed distance L2 of welding wire 18 described above becomes too large, and there is a risk that welding wire 18 will penetrate into tip 21 and be welded to tip 21.

[0087] Therefore, the backward feed speed command value is adjusted to immediately shorten the arrival time T to 3 msec.

[0088] By shortening the arrival time T, welding wire 18 starts forward feeding immediately after the short circuit is released, so that reverse feeding distance L2 can be reduced and welding between welding wire 18 and tip 21 can be suppressed.

[0089] Furthermore, as a result of further investigations by the inventors of the present application, it was found that the appropriate range for the arrival time T is 0 msec or more and 5 msec or less. If the arrival time T exceeds 5 msec, as described above, the reverse feed distance L2 of the welding wire 18 becomes too large, and there is a risk that the welding wire 18 may penetrate into the tip 21 and be welded to the tip 21.

[0090] In addition, the extension length L of the welding wire 18 EX1 By setting the ratio of the reverse feed distance L2 to the tip 21 within the appropriate range described above and further setting the arrival time T to be 0 msec or more and 5 msec or less, welding between the welding wire 18 and the tip 21 can be reliably prevented.

[0091] [4-6: Short-circuit period adjustment] 18A and 18B are diagrams showing the time waveforms of various command values ​​before and after adjusting the short circuit period in the first period.

[0092] As described above, the extension length L of the welding wire 18 EX1 By adjusting the reverse feed distance L2 of welding wire 18 relative to base metal 17, it is possible to prevent welding of welding wire 18 to tip 21. On the other hand, as already mentioned, if the amount of heat input to base metal 17 is insufficient, weld bead 30 will have a convex shape as shown in Figures 13A and 13B.

[0093] For example, in the example shown in FIG. 18A, the short-circuit period T S is 25 msec, but the short circuit period T S If the distance is too long, the amount of heat input to base material 17 will decrease, and there is a risk that weld bead 30 will have a convex shape.

[0094] Therefore, as shown in FIG. 18B, the short-circuit period T S By adjusting the welding output so that the welding time is short, it is possible to suppress a decrease in the amount of heat input to base material 17 and to make weld bead 30 have a good shape.

[0095] As a result of further investigation by the inventors of the present application, it was found that the short-circuit period T S The optimum range for the short circuit period T is between 3 msec and 10 msec. S If the short-circuit period T is less than 3 msec, the short-circuit period between the welding wire 18 and the base material 17 becomes too short, resulting in a micro-short circuit. As a result, the shape of the weld bead 30 becomes distorted and spatter is generated significantly. S If the short circuit period T exceeds 10 msec, the amount of heat input to base material 17 decreases, as described above, and weld bead 30 becomes convex. S However, by adjusting the welding output so that it is greater than or equal to 3 msec and less than or equal to 10 msec, it is possible to suppress the occurrence of micro-short circuits and therefore spatter, and also to prevent the shape of the weld bead 30 from becoming convex, thereby forming a weld bead 30 with a good shape.

[0096] [4-7: Adjustment of bending point current] 19A and 19B are diagrams showing the time waveforms of various command values ​​before and after adjusting the bending point current in the first period.

[0097] Short-circuit period T S The reduction in the amount of heat input to the base material 17 can be suppressed by a method other than adjusting the short circuit period T S The welding current I at point I rises with time from the start of the short circuit at a first gradient S1, and then changes to a second gradient S2 different from the first gradient S1. In this embodiment, S1>S2>0.

[0098] The point at which the time change of the welding current I changes from the first slope S1 to the second slope S2 is defined as the short-circuit current bending point, and the welding current I at this point is defined as the bending point current I F The bending point current I F By adjusting the value of , it is possible to suppress a decrease in the amount of heat input to the base material 17.

[0099] In the example shown in FIG. 19A, the minimum value of the reverse transport speed W B is set to -6 m / min. The bending current I F In this case, the amount of heat input to base material 17 was insufficient, resulting in a convex shape of weld bead 30. Therefore, while keeping the other parameters the same, the bending point current I F It was found that the shape of the weld bead 30 was improved by adjusting the welding current I so that the weld current I was 140 A.

[0100] As a result of further investigation by the inventors of the present application, the bending point current I F It has been found that the shape of the weld bead 30 can be improved by increasing the value of I from the value before adjustment by 50 A or more and within the range of the upper limit of the set value of the welding current I. In this case, the upper limit of the set value is, for example, 220 A. F If the increase is 0 A or more and less than 50 A, the insufficient amount of heat input to base material 17 cannot be completely resolved, and there is a risk that weld bead 30 will have a convex shape.

[0101] [5: Effects etc.] As described above, in the arc welding method according to this embodiment, welding wire 18 is moved at a predetermined speed along a welding section in base metal 17. Furthermore, a first period T1 during which a predetermined welding current flows through welding wire 18 and a second period T2 during which no welding current flows through welding wire 18 are alternately repeated to form weld bead 30 on base metal 17 along the welding section.

[0102] The first period T1 is an arc period T during which an arc 19 is generated between the welding wire 18 and the base material 17. A and arc period T A Subsequently, a short circuit period T S It includes:

[0103] In the first period T1, the welding wire 18 is alternately fed forward and backward, and the protruding length L of the welding wire 18 from the tip of the tip 21 holding the welding wire 18 is EX1 However, it is more than 3mm and less than 10mm.

[0104] According to this embodiment, it is possible to suppress the influence of bending of welding wire 18 protruding from the front end of tip 21, and to stabilize the alignment of weld bead 30. As a result, the appearance of weld bead 30 is improved, and the occurrence of welding defects can be suppressed.

[0105] The protruding length L of the welding wire 18 EX1 It is preferable that the thickness is 5 mm or more and 8 mm or less.

[0106] In addition, the protruding length L EX1 When the distance is set to 5 mm or less, the arc 19 is generated not only from the tip of the welding wire 18 but also from the tip 21, and the irradiation area of ​​the arc 19 on the base material 17 is relatively enlarged, thereby further enhancing the cleaning effect of the arc 19 between the tip 21 and the base material 17, and the cleaning width of the surface of the base material 17 by the arc 19 can be enlarged to, for example, about 120%, thereby suppressing the adhesion of smut.

[0107] Depending on the shape of the base material 17, the nozzle 20A provided at the tip of the torch 20 may collide with the base material 17, making it impossible to perform the desired welding. In order to prevent such interference between the torch 20 and the base material 17, the tip protrusion length L, which is the distance from the tip of the nozzle 20A to the tip of the tip 21, is set to 0. EX2 However, it is preferable that the thickness is 0 mm or more and 5 mm or less.

[0108] If the reverse feed speed of the welding wire 18 is too slow, the welding wire 18 may be welded to the tip 21 during the reverse feed of the welding wire 18. To prevent such a problem, the minimum value W B It is preferable to feed the welding wire 18 so that the welding wire 18 is fed at a rate of not less than -12 m / min and not more than -3 m / min.

[0109] In addition, the extension length L of the welding wire 18 EX1 The welding wire 18 may be fed so that the ratio of the reverse feed distance L2 of the welding wire 18 to the base metal 17 is 10% or more and 20% or less. Furthermore, it is preferable to feed the welding wire 18 so that the time from when the short circuit between the welding wire 18 and the base metal 17 is released until the forward feed speed of the welding wire 18 reaches its maximum value is 0 msec or more and 5 msec or less.

[0110] In addition, in order to prevent the shape of the weld bead 30 from becoming convex and to improve the shape of the weld bead 30, the short circuit period T S is preferably set to 3 msec or more and 10 msec or less.

[0111] In addition, the short-circuit period T S The welding current I at the inflection point I increases with time from the start of the short circuit at a first gradient S1, and then changes to a second gradient S2 different from the first gradient S1. In order to prevent the shape of the weld bead 30 from becoming convex and to improve the shape of the weld bead 30, the inflection point current I FThe bending point current I may be increased by 50 A or more from the value before adjustment and up to the upper limit of the set value of the welding current I. Here, the upper limit of the set value of the welding current I is, for example, 220 A. F is the value of the welding current I at the short-circuit current bending point, which is the point at which the time change of the welding current I changes from the first gradient S1 to the second gradient S2.

[0112] Furthermore, the arc welding method of this embodiment is particularly effective when the materials of welding wire 18 and base metal 17 are cooled and solidified immediately after melting. In this case, the edge of weld bead 30 can be clearly observed, and the scale-like appearance of weld bead 30 is good.

[0113] From this viewpoint, when performing arc welding using the arc welding method of the present embodiment, it is preferable that the materials of the welding wire 18 and the base material 17 are aluminum-based materials, or magnesium or alloys mainly containing magnesium (collectively referred to as magnesium-based materials).

[0114] Furthermore, because the arc welding method of this embodiment uses low-heat-input short-circuit stitch welding, even when the base material 17 is a thin plate, for example, when the base material 17 has a thickness of approximately 0.5 mm to 2 mm, a scale-like weld bead 30 with clearly defined waves can be formed on the base material 17.

[0115] <Modification> 20 is a diagram showing various output waveforms during arc welding according to a modified example. For ease of explanation, the same reference numerals are used to designate the same parts as in the embodiment, and detailed explanations thereof will be omitted.

[0116] In the arc welding method of this modification shown in FIG. 20, the first period T1 is a short-circuit stitch welding period T 1S and the subsequent pulse welding period T 1P The arc welding method of the present invention differs from the arc welding method of the embodiment in that it includes the steps of:

[0117] Short-circuit stitch welding period T 1S In the short-circuit period TS and arc period T A The above steps are alternately repeated a predetermined number of times to perform arc welding.

[0118] On the other hand, the short-circuit stitch welding period T 1S After this time, the control switching unit 9 switches to the short-circuit stitch welding period T 1S to pulse welding period T 1P Switch to pulse welding period T 1P In this case, the welding output is controlled by the pulse welding control unit 12 under the conditions set by the pulse welding setting unit 25. Specifically, the welding wire 18 is fed forward at a constant feed rate. Furthermore, a peak current and a base current, which is smaller in current value than the peak current, are alternately applied to the welding wire 18, thereby generating an arc 19 between the base material 17 and the welding wire 18, and pulse welding is performed from the pulse welding start time Pst1. During the pulse welding period T 1P During the pulse welding period T 1P At the end of the welding, the tip of the welding wire 18 is positioned at a predetermined distance from the base material 17.

[0119] Then, the pulse welding period T set in advance by the pulse welding setting unit 25 is 1P After this time, the control switching unit 9 switches to the pulse welding period T 1P Then, the period is switched to a second period T2 in which the welding current I is not applied to the welding wire 18.

[0120] This modification can achieve the same effects as the method described in the embodiment. That is, the effects of bending of the welding wire 18 protruding from the tip 21 can be suppressed, and the alignment of the weld bead 30 can be stabilized. As a result, the appearance of the weld bead 30 is improved, and the occurrence of welding defects can be suppressed. In addition, an arc 19 can be generated between the tip 21 and the base material 17, and the cleaning width of the surface of the base material 17 by the arc 19 can be expanded, suppressing the adhesion of smut.

[0121] According to this modification, short-circuit stitch welding and pulse welding are performed successively. 1P Immediately after this, a second period T2 is provided in which no welding current I is passed through the welding wire 18. This enhances the cooling effect at the welding point, increases the difference in heat input, and allows the formation of a clearly wavy, scale-like weld bead 30. Note that, during the second period T2, if the output of not only the welding current I but also the welding voltage V is set to zero, the heat input can be set to zero, thereby increasing the difference in heat input during welding. In other words, the wavy weld bead 30 can be made most clearly visible. On the other hand, if only the welding current I is set to zero and the welding voltage V is left applied during the second period T2, the no-load voltage V1 can be maintained, allowing the next arc start to be performed smoothly.

[0122] Also, the short-circuit stitch welding period T 1S and pulse welding period T 1P and the second period T2 are sequentially repeated, and a low heat input short-circuit stitch welding period T 1S and the high heat input pulse welding period T 1P and second period T2 during which the heat input is 0. In this way, the heat input to base material 17 can be controlled over a wide range, and the shape of weld bead 30 can be controlled more precisely. [Industrial Applicability]

[0123] The arc welding method of the present disclosure is useful in short-circuit welding because it can stabilize the alignment of the bead edge. [Explanation of symbols]

[0124] 1 Input power 2 Main transformer 3 Primary side rectifier 4 Switching section 5 DCL (reactor) 6 Secondary rectifier 7 Welding current detector 8 Welding voltage detector 9 Control switching unit 10 Output control section 11 Short circuit welding control unit 12 Pulse welding control unit 13 Wire feed speed control unit 14 Wire feed speed detector 15 Arithmetic section 16 Arc welding equipment 17 Base material 18 Welding wire 19 Arc 20 Torch 20A nozzle 21 Tip (welding tip) 22 Wire feeding section 23 Welding condition setting section 24 Short circuit welding setting section 25 Pulse welding setting section 26 Cooling period setting section 30 Weld Bead

Claims

1. 1. An arc welding method comprising: moving a welding wire along a welding section of a base metal at a predetermined speed; and alternately repeating a first period in which a predetermined welding current flows through the welding wire and a second period in which the welding current does not flow through the welding wire, thereby forming a weld bead on the base metal along the welding section, the first period includes an arc period in which an arc is generated between the welding wire and the base metal, and a short-circuit period subsequent to the arc period in which the welding wire and the base metal are short-circuited, During the first period, the welding wire is alternately fed forward and backward, 10. An arc welding method, comprising: a protruding length of the welding wire from the tip of a tip that holds the welding wire;

2. The arc welding method according to claim 1, An arc welding method characterized in that the extension length is preferably 5 mm or more and 8 mm or less.

3. The arc welding method according to claim 1, The arc welding method, wherein the minimum value of the reverse feed speed of the welding wire during the first period is −12 m / min or more and −3 m / min or less.

4. The arc welding method according to claim 1, An arc welding method, characterized in that a ratio of a reverse feed distance of the welding wire to the extension length is 10% or more and 20% or less.

5. The arc welding method according to claim 1, an arc welding method, characterized in that a time from when the short circuit between the welding wire and the base metal is released to when the forward feed speed of the welding wire reaches its maximum value is 0 msec or more and 5 msec or less.

6. The arc welding method according to claim 1, The arc welding method is characterized in that the short circuit period is 3 msec or more and 10 msec or less.

7. The arc welding method according to claim 1, the welding current during the short circuit period increases with time from a start point of the short circuit at a first gradient, and then changes to a second gradient different from the first gradient; a value of the welding current at a short-circuit current inflection point, which is a change point when the time change of the welding current changes from the first slope to the second slope, is increased from the value before adjustment by 50 A or more and not more than a set upper limit value of the welding current.

8. The arc welding method according to claim 1, the first period further includes a pulse welding period; the pulse welding period is provided after the short circuit period and the arc period are alternately repeated a predetermined number of times; the welding wire is fed at a constant feed rate during the pulse welding period, and a peak current and a base current are alternately passed through the welding wire, thereby performing pulse welding to generate an arc between the base metal and the welding wire.

9. The arc welding method according to any one of claims 1 to 8, 10. An arc welding method, wherein the welding wire and the base metal are made of an aluminum-based material or a magnesium-based material.

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