Arc welding control method

Abstract

In a first step of an arc welding control method according to the present disclosure, a welding current Aw is varied between a peak current Ip and a base current Ib at intervals Tf in a main welding period Th while alternately repeating forward feeding and reverse feeding of a welding wire 21, so that molten droplets are separated from the tip end of the welding wire 21 and transferred to a base material 25. In a second step, the welding current Aw is applied to the welding wire 21 in an arc end period Te following the main welding period Th, and the welding wire 21 and the base material 25 are short-circuited while alternately repeating forward feeding and reverse feeding of the welding wire 21 to cause short-circuiting transfer of molten droplets formed at the tip end of the welding wire 21 to the base material 25.

Description

Arc welding control method

[0001] The present disclosure relates to a method for controlling arc welding.

[0002] In consumable electrode arc welding, an arc is generated between a welding wire (a consumable electrode) and the base metal to be welded, and the base metal is welded. During the final stage of arc welding (also known as the arc-end period), the welding wire slows down along the weld line and eventually stops. However, because the welding current itself remains constant, the arc generated during the arc-end period has the same arc length and arc force as during other periods. Therefore, in a crater formed near the end point of the weld, a crater may shrink and form a shrinkage hole. The formation of a crater or shrinkage hole can result in a poor weld. In particular, a welding method known as pulse welding alternately passes a peak current and a base current, which is lower than the peak current, through the welding wire. Pulse welding ensures sufficient heat input to the base metal, allowing droplets to detach from the welding wire and transfer to the base metal during or immediately after the peak current period. Meanwhile, during the peak current period, the arc length is long and the arc force is strong. This makes the aforementioned crater and shrinkage hole more likely to occur.

[0003] Therefore, Patent Document 1 proposes a method for controlling the wire feed speed by periodically repeating forward and reverse feed of the welding wire during the arc end period of pulse welding, thereby short-circuiting and transferring droplets formed at the tip of the welding wire to the base metal. This method can suppress the formation of crater depressions near the welding end point of the weld during the arc end period. This eliminates or reduces the need for post-processing (crater post-processing), which is the work of repairing large depressions in craters near the welding end point of the weld. Furthermore, it can prevent products from being shipped with large depressions remaining. Furthermore, it can suppress the generation of spatter during the arc end period.

[0004] Furthermore, Patent Document 2 discloses a configuration in which a detachment detection unit is provided to detect droplets detaching from the tip of a welding wire in pulse welding in which a peak current and a base current having a lower current value are periodically passed through the welding wire. In this case, if the detachment detection unit does not detect droplets detaching during the reverse feeding of the welding wire, the welding wire is fed forward at a constant speed after the end of the reverse feeding period. Also, if the detachment detection unit detects droplets detaching while the welding wire is fed forward at a constant speed, forward and reverse feeding of the welding wire is periodically repeated.

[0005] Alternatively, if the detachment detection unit detects the detachment of a droplet during the forward feeding period of the welding wire between the time when the command value for the welding wire feed speed becomes maximum and the time when the period switches to the reverse feeding period, the welding wire is fed forward at a constant speed at the time when the reverse feeding is switched to the forward feeding. Also, if the detachment detection unit detects the detachment of a droplet while the welding wire is being fed forward at a constant speed, the forward feeding and reverse feeding of the welding wire are cyclically repeated.

[0006] This prevents droplets from dropping onto the base material at undesired times during welding, thereby preventing spatter from occurring.

[0007] Patent No. 5978465 Patent No. 7041034

[0008] In pulse welding, the fluctuating frequency of the welding current can be synchronized with the generation and detachment of droplets, allowing for smooth droplet transfer. Generally, pulse welding is widely used in consumable electrode arc welding such as MIG welding (Metal Inert Gas Welding) and MAG welding (Metal Active Gas Welding).

[0009] On the other hand, in consumable electrode arc welding, a method is generally used in which a shielding gas that has low reactivity with molten metal is sprayed onto the welding point of the base material to prevent the molten base material or welding wire from reacting with the air around the base material. ２ (carbon dioxide gas) is often used. ２ is available at a lower cost than inert gases such as argon. ２By using this, the arc tends to concentrate, which allows for deeper penetration into the base material.

[0010] However, CO as a shielding gas ２ When using CO , the arc reaction force becomes large, making it difficult for droplets to drop (detach). Therefore, when performing pulse welding in which the welding wire is fed at a constant speed in MIG welding or MAG welding, ２ The method of using as a shielding gas has not been adopted.

[0011] The present disclosure has been made in consideration of the above points, and its purpose is to provide an arc welding control method that can stably form a molten pool on the base material before and after switching between the main welding period and the arc end period, and that can suppress the occurrence of crater depressions and the like near the welding end point at the welding location.

[0012] In order to achieve the above object, an arc welding control method according to the present disclosure is an arc welding control method for performing welding by generating an arc between a welding wire that is a consumable electrode and a base metal, the method comprising at least a first step of, during a main welding period, fluctuating a welding current flowing through the welding wire at a predetermined cycle while alternately repeating forward and reverse feed of the welding wire, thereby causing the droplet to detach from the tip of the welding wire and transfer to the base metal; and a second step of, during an arc end period provided after the main welding period, flowing a welding current through the welding wire and alternately repeating forward and reverse feed of the welding wire, thereby short-circuiting the welding wire and the base metal, thereby short-circuiting the droplet formed at the tip of the welding wire and transferring it to the base metal. the arc end period is a period from the end of the main welding period until an average feed speed of the welding wire becomes zero, the cycle includes a peak current period in which a peak current flows through the welding wire and a base current period following the peak current period in which a base current flows through the welding wire, the current value of the base current is lower than the current value of the peak current, and the welding current is varied at a predetermined cycle while alternately feeding the welding wire forward and backward to cause the droplets to be separated and transferred, and the average feed speed during the main welding period in which the welding current is varied at a predetermined cycle while alternately feeding the welding wire forward and backward to cause the droplets to be short-circuit transferred is equal to or higher than the average feed speed at the start of the arc end period in which the welding wire is fed forward and backward to cause the droplets to be short-circuit transferred.

[0013] According to the present disclosure, a molten pool can be stably formed on the base material before and after switching between the main welding period and the arc end period. In addition, the amount of spatter is suppressed, and a welded portion can be formed in which the size of a crater is small near the welding end point and further, there is no depression in the crater portion.

[0014] Fig. 1 is a schematic diagram of an arc welding apparatus according to embodiment 1. Fig. 2 is a schematic diagram of another arc welding apparatus according to embodiment 1. Fig. 3 is a diagram showing waveforms of a welding current, a welding voltage, and a wire feed speed. Fig. 4 is a diagram showing waveforms of a welding current, a welding voltage, and a wire feed speed according to embodiment 2. Fig. 5 is a diagram showing waveforms of a welding current, a welding voltage, and a wire feed speed according to embodiment 3. Fig. 6 is a diagram showing waveforms of a welding current, a welding voltage, and a wire feed speed according to embodiment 4. Fig. 7 is a diagram showing waveforms of a welding current, a welding voltage, and a wire feed speed according to embodiment 5.

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0016] First Embodiment [Configuration of Arc Welding Apparatus] FIG. 1 is a schematic diagram of an arc welding apparatus according to a first embodiment, and FIG. 2 is a schematic diagram of another arc welding apparatus.

[0017] As shown in FIG. 1 , the arc welding device 30 includes a primary rectifier 2, a switching unit 3, a transformer 4, a secondary rectifier 5 and a DCL 6, a driver 7, a welding voltage detector 8, a welding current detector 9, a short circuit / arc detector 10, a short circuit controller 11, an arc controller 12, and a wire feed speed controller 13. The primary rectifier 2 rectifies the power input from the input power source 1. The switching unit 3 converts the output of the primary rectifier 2 into AC. The transformer 4 transforms the output of the switching unit 3. The secondary rectifier 5 and the DCL 6 rectify the output of the transformer 4. The driver 7 controls the switching unit 3. The welding voltage detector 8 detects the welding voltage. The welding current detector 9 detects the welding current. The short circuit / arc detector 10 detects whether the welding state is a short circuit state or an arc state based on at least one of the output of the welding voltage detector 8 and the output of the welding current detector 9. The short circuit control unit 11 controls the welding output when a short circuit occurs. The arc control unit 12 controls the welding output when an arc occurs. The wire feed speed control unit 13 controls the wire feed speed according to the set current.

[0018] Welding wire 21, which is a consumable electrode stored in wire storage unit 20, is fed by wire feed motor 22. Electric power is supplied to welding wire 21 via tip 23 provided on welding torch 26. An arc 24 is generated between welding wire 21 and base metal 25, which is the workpiece to be welded, to perform welding. Welding torch 26 is attached to and moved by manipulator 18, which constitutes, for example, an industrial robot.

[0019] In addition to the general components arranged in the welding power supply 14, the arc welding apparatus 30 also includes a manipulator 18 that constitutes an industrial robot, and a robot control device 16 that controls the manipulator 18. A wire feed speed corresponding to a set current from a welding condition setting unit 15 in the robot control device 16 is sent as a speed signal from a wire feed speed control unit 13 to a wire feed motor 22. The wire feed speed output from the wire feed speed control unit 13 is also sent as a speed signal to a short circuit control unit 11 or an arc control unit 12, thereby controlling the welding output in a short circuit state or an arc state. The welding condition setting unit 15 is used to set welding conditions such as a set current and a set voltage.

[0020] The short circuit control unit 11 outputs a short circuit current in response to a short circuit determination signal from the short circuit / arc detection unit 10, and performs control to melt the tip of the welding wire 21 and promote release of the short circuit. In addition, the arc control unit 12 outputs a high current immediately after release of the short circuit in order to form a molten droplet at the tip of the welding wire 21 while ensuring the arc length, and then controls the current and voltage to transition to a low current so that a short circuit can easily occur.

[0021] Each of the components constituting the arc welding device 30 shown in FIG. 1 may be configured independently, or a plurality of components may be combined to form a single device.

[0022] Arc welding apparatus 30 further includes an industrial robot including manipulator 18 and robot controller 16 that controls the operation of manipulator 18, and welding power supply 14. The industrial robot includes welding condition setting unit 15. Welding power supply 14 may also include switching unit 3, drive unit 7, welding current detection unit 9, welding voltage detection unit 8, short circuit / arc detection unit 10, short circuit control unit 11, arc control unit 12, and wire feed speed control unit 13.

[0023] 2, the welding power supply 14 may be provided within the robot control device 17. With this configuration, the arc welding device can be made even more compact.

[0024] [Outline of Arc Welding Control Method] Fig. 3 is a diagram showing waveforms of the welding current, welding voltage, and wire feed speed. In this embodiment, the base material 25 is mild steel, and the material of the welding wire 21 is also mild steel. The shielding gas sprayed onto the base material 25 during welding is CO ２ However, the materials of the base metal 25 and the welding wire 21, and the type of the shielding gas are not particularly limited to these.

[0025] Although not shown, a main welding period Th shown in Fig. 3 starts after a predetermined time has elapsed since the switch of welding torch 26 was turned on. Main welding period Th is a period during which a welded portion (not shown), such as a weld bead, is substantially formed on base material 25.

[0026] 3 , during the main welding period Th, the wire feed speed control unit 13 and the wire feed motor 22 control the feeding operation of the welding wire 21 so that the welding wire 21 is fed forward and reversely at a predetermined cycle (hereinafter referred to as the wire feed cycle). In the following description, the feed speed of the welding wire 21 is referred to as the wire feed speed Wf. When the wire feed speed Wf is a positive value, the welding wire 21 is fed forward, and the tip of the welding wire 21 moves toward the base material 25. When the wire feed speed Wf is a negative value, the welding wire 21 is fed backward, and the tip of the welding wire 21 moves away from the base material 25. The average feed speed, which is the time average value of the wire feed speed Wf, increases over time, and the average feed speed during the main welding period Th is a constant value (=Wfh).

[0027] Furthermore, the arc control unit 12 controls the welding current Aw flowing through the welding wire 21 to fluctuate periodically. Specifically, after a base current Ib flows through the welding wire 21, a peak current Ip having a current value higher than the base current Ib flows through the welding wire 21. The period during which the peak current Ip flows through the welding wire 21 is called a peak current period Tp, and the period during which the base current Ib flows through the welding wire 21 is called a base current period Tb. The sum of the peak current period Tp and the subsequent base current period Tb corresponds to a fluctuation period Tf of the welding current Aw (hereinafter simply referred to as period Tf). Furthermore, the reciprocal of the period Tf corresponds to a fluctuation frequency Fa of the welding current Aw.

[0028] Specifically, a peak current period Tp during which a peak current Ip flows and a base current period Tb during which a base current Ib flows are alternately repeated. In this embodiment, immediately after the peak current period Tp, a droplet formed at the tip of the welding wire 21 is detached by inertial force and transferred to the base material 25.

[0029] Furthermore, the period Tf corresponds to the aforementioned wire feed period during the actual welding period Th. During the actual welding period Th, the maximum value of the forward feed speed of the welding wire 21 during one period Tf is referred to as the second forward feed speed Wff2, and the maximum value of the reverse feed speed is referred to as the second reverse feed speed Wfg2. In the following description, the maximum reverse feed speed refers to the case where the absolute value of the reverse feed speed is the maximum value. In other words, it is the value at which the speed at which the welding wire 21 is reversed is the fastest. In the following description, the reverse feed speeds are compared in terms of their absolute values. Furthermore, the acceleration of the welding wire 21 during forward feed is referred to as the forward feed acceleration Aff, and the acceleration of the welding wire 21 during reverse feed is referred to as the reverse feed acceleration Afg.

[0030] During the main welding period Th, the arc end period Te begins at time P1 when an arc end signal is input from the welding condition setting unit 15 to the wire feed speed control unit 13. During the arc end period Te, the feeding operation of the welding wire 21 is controlled so that the maximum value of the reverse feed speed in one wire feed cycle is constant, while the maximum value of the forward feed speed decreases with each wire feed cycle. Therefore, the average feed speed Wfe during the arc end period Te decreases as time passes from the average feed speed Wfh during the main welding period Th, in other words, as the number of repetitions of forward and reverse feed of the welding wire 21 increases. The maximum value of the reverse feed speed in one wire feed cycle during the arc end period Te is referred to as the first reverse feed speed Wfg, and the maximum value of the forward feed speed is referred to as the first forward feed speed Wff. The first reverse feed speed Wfg during the arc end period Te is controlled to be smaller than the second reverse feed speed Wfg2 during the main welding period Th. That is, the amount of reverse feed of the welding wire 21 during the arc end period Te is smaller than the amount of reverse feed of the welding wire 21 during the main welding period Th.

[0031] Furthermore, from or immediately before the start point P1 of the arc end period Te, the welding current Aw decreases and, when it reaches the base current Ib, the welding current Aw is maintained at the base current Ib for a predetermined period until point P2. When the welding voltage Vw falls below the arc determination level voltage Va (also referred to as the voltage threshold Va), from point P2, the control of the welding output is switched from the arc control unit 12 to the short circuit control unit 11.

[0032] From time P2, welding wire 21 is periodically fed forward and backward a plurality of times, whereby welding wire 21 is short-circuited with base material 25 at a constant cycle, and the short-circuit release from base material 25 is repeated. As the welding current Aw flows and the welding wire 21 is heated, a droplet ( is formed at the tip of the welding wire 21, and the droplet is transferred to the base metal 25 when the welding wire 21 is short-circuited with the base metal 25. In addition, during the period from when the short circuit is released to when the next short circuit occurs, an arc 24 is generated between the welding wire 21 and the base metal 25. When the welding wire 21 and the base metal 25 are short-circuited, the welding current Aw increases, and when the welding wire 21 separates from the base metal 25 and the arc 24 begins to be generated, the welding current Aw decreases. In addition, the welding voltage Vw increases in response to the generation of the arc 24, and when the welding wire 21 and the base metal 25 are short-circuited, the welding voltage Vw decreases to zero or near zero. In response to the feeding operation of the welding wire 21, the welding current Aw and the welding voltage Vw periodically repeat the changes described above.

[0033] The set current is a moving average value of the welding current Aw over time, which is preset for each period of arc welding. The average feed rate Wfe during the arc end period Te is determined corresponding to the set current. Furthermore, the welding voltage Vw at the time of generation of the arc 24 during the arc end period Te and the peak values ​​of the welding current Aw before and after short circuit release also decrease over time.

[0034] At time P3 when the average feed speed Wfe becomes zero, the arc end period Te ends and the burn back period Tbb begins. In other words, the arc end period Te is the period from time P1 when the arc end signal is input to time P3 when the average feed speed Wfe becomes zero.

[0035] During the burnback period Tbb, the welding torch 26 remains stationary, while the welding wire 21 is fed backward at a constant speed, in this case, a first reverse feed speed Wfg, and a constant burnback current IE is passed through the welding wire 21. By doing so, during the burnback period Tbb, an arc 24 is generated between the welding wire 21 and the base metal 25, causing the welding wire 21 to burn up and form a molten metal ball at its tip. At time P4, when the formation of the metal ball is completed, the burnback period Tbb ends, and both the welding current Aw and the welding voltage Vw become zero. By providing the burnback period Tbb, adhesion between the welding wire 21 and the base metal 25 can be prevented. Furthermore, adhesion between the welding wire 21 and the tip 23 can be prevented. Furthermore, since a sufficient distance can be maintained between the welding wire 21 and the base metal 25, the arc can be reliably started when the next arc welding operation is initiated.

[0036] The forward feed speed (Wf) during forward feed, the reverse feed speed (Wf) during reverse feed, the wire feed cycle (Wf) during alternate forward and reverse feed, and the frequency (its reciprocal) are set independently for the arc-end period Te and the main welding period Th. The ratio of the forward feed amount to the reverse feed amount of the welding wire 21 during forward feed and the speed ratio are also set independently for the arc-end period Te and the main welding period Th. The speed ratio during the arc-end period Te is the absolute value of the ratio of the first forward feed speed Wff to the first reverse feed speed Wfg, based on the average feed speed Wfe. The speed ratio during the main welding period Th is the absolute value of the ratio of the second forward feed speed Wff2 to the second reverse feed speed Wfg2, based on the average feed speed Wfh.

[0037] During the arc end period Te, these values ​​are optimized to stabilize the repetition cycle in which the welding wire 21 is short-circuited with the base metal 25 and then an arc 24 is generated between the base metal 25 and the tip of the welding wire 21. On the other hand, during the main welding period Th, these values ​​are optimized to allow a droplet formed at the tip of the welding wire 21 to be detached by inertial force and transferred to the base metal 25. In FIG. 3 , the first reverse feed speed Wfg, which is the maximum value of the reverse feed speed of the welding wire 21 during the arc end period Te, is constant, and the maximum value Wfg of the reverse feed speed is the same during both the arc end period Te and the burn back period Tbb. This makes the short-circuit state of the welding wire 21 more stable when the reverse feed speed is at its maximum value. Furthermore, the release of the short circuit of the welding wire 21 is more stable. Note that the maximum value Wfg of the reverse feed speed of the welding wire 21 need not be constant and may gradually change as long as it does not adversely affect the release of the short circuit.

[0038] Basically, the average feeding speed Wfe during the arc-end period Te decreases, and the maximum value of the reverse feeding speed (first reverse feeding speed) Wfg also decreases. Note that the maximum value of the reverse feeding speed Wfg during the arc-end period Te does not necessarily have to be the same as the maximum value of the reverse feeding speed during the burn-back period Tbb.

[0039] In the arc end period Te, the speed ratio is set to 1, that is, the first reverse feed speed Wfg and the first forward feed speed Wff are set to be equal with respect to the average feed speed Wfe. Similarly, in the main welding period Th, the second reverse feed speed Wfg2 and the second forward feed speed Wff2 are set to be equal with respect to the average feed speed Wfh. However, this is not particularly limited. Taking into consideration the burning of the welding wire 21, etc., the speed ratio may be set in the range of 1 to 4 in each period. For example, in the main welding period Th, the ratio of the second reverse feed speed Wfg2 and the second forward feed speed Wff2 may be set to 1:4 with respect to the average feed speed Wfh.

[0040] In the present embodiment, the welding wire 21 is periodically fed and reversed at a constant frequency and speed amplitude set for each of the arc-end period Te and the main welding period Th. However, this is not limiting. The welding wire 21 may be non-periodic. For example, the welding wire 21 may be fed forward during the arc-end period Te, and then switched to reverse feeding when the short-circuit / arc detection unit 10 detects a short circuit between the welding wire 21 and the base material 25. In this case, the forward feeding operation may be switched to after a predetermined time has elapsed since the start of reverse feeding. Furthermore, during the main welding period Th, the short-circuit / arc detection unit 10 may cause a peak current Ip to flow through the welding wire 21 when the welding voltage Vw falls below the voltage threshold Va, and then cause a base current Ib to flow after a predetermined time has elapsed. While the base current Ib is flowing, the peak current Ip may be caused to flow through the welding wire 21 for a predetermined time when the welding voltage Vw drops to the voltage threshold Va.

[0041] [Effects, etc.] As described above, the arc welding control method according to the present embodiment is a method for controlling arc welding in which arc 24 is generated between welding wire 21, which is a consumable electrode, and base material 25 to perform welding, and includes at least a first step and a second step described below.

[0042] In the first step, during the actual welding period Th, the welding wire 21 is alternately fed forward and backward while the welding current Aw is varied at a predetermined period Tf, causing droplets to detach from the tip of the welding wire 21 and transfer to the base material 25.

[0043] In the second step, during the arc end period Te provided after the main welding period Th, a welding current Aw is passed through the welding wire 21, and the welding wire 21 is alternately fed forward and backward, thereby short-circuiting the welding wire 21 and the base material 25, thereby short-circuiting the droplet formed at the tip of the welding wire 21 and transferring it to the base material 25.

[0044] The arc end period Te is the period from the end point (first point) P1 of the main welding period Th to the point P3 at which the average feed speed Wfe of the welding wire 21 becomes zero.

[0045] The period Tf includes a peak current period Tp during which a peak current Ip flows through the welding wire 21, and a base current period Tb following the peak current period Tp during which a base current Ib flows through the welding wire 21. The current value of the base current Ib is lower than the current value of the peak current Ip.

[0046] The average feed speed Wfh during the main welding period Th is the same as the average feed speed Wfe at the start point P3 of the arc end period Te.

[0047] In this embodiment, so-called pulse welding is performed during the main welding period Th, in which a peak current Ip and a base current Ib are alternately passed through the welding wire 21. In addition, by alternately feeding the welding wire 21 forward and backward at a predetermined frequency and speed amplitude, it is possible to smoothly detach a droplet formed at the tip of the welding wire 21. The frequency during the main welding period Th is the reciprocal of a cycle Tf, which is the sum of the peak current period Tp and the base current period Tb.

[0048] According to this embodiment, during the main welding period Th, the welding wire 21 is alternately fed forward and backward, so that the droplets grown at the tip of the welding wire 21 are subjected to vibration in the direction of gravity, causing the droplets to fall. ２ By using this, even when the droplets are difficult to separate due to the arc reaction force, the welding can be reliably transferred to the base material 25 for each period Tf. This allows, for example, the width and height of the weld bead formed on the base material 25 to be constant along its length.

[0049] Furthermore, according to this embodiment, an arc-end period Te is provided following the main welding period Th. During the arc-end period Te, the wire feed speed Wf is controlled so that the welding wire 21 alternates between forward and reverse feed at a predetermined frequency and speed amplitude, repeatedly short-circuiting the droplets to the base material 25. This reduces the amount of spatter and allows for the formation of a small, dent-free crater at the welded portion. In particular, the molten pool can be stably grown and formed in the base material 25 before and after switching from the main welding period Th to the arc-end period Te, thereby suppressing the generation of spatter during the arc-end period Te. These features eliminate or reduce post-processing, which involves repairing large dents. Furthermore, it is possible to prevent products from being shipped with large dents remaining.

[0050] The first reverse feed speed Wfg during the arc end period Te is controlled to be constant. The first forward feed speed Wff during the arc end period Te is controlled to decrease as the number of repetitions of forward and reverse feed of the welding wire 21 increases. The second reverse feed speed Wfg2 during the main welding period Th is controlled to be larger than the first reverse feed speed Wfg during the arc end period Te. The second forward feed speed Wff2 during the main welding period Th is controlled to be larger than the first forward feed speed Wff during the arc end period Te.

[0051] By doing so, the average feed speed Wfe can be decreased over time during the arc end period Te. As a result, at the end point P1 of the main welding period Th, the average feed speed Wfe during the arc end period Te and the average feed speed Wfh during the main welding period Th can be made the same, allowing for a smooth transition of the feeding operation of the welding wire 21. Furthermore, the second forward feed speed Wff2 during the main welding period Th in which droplets are detached and transferred is set to be higher than the first forward feed speed Wff during the arc end period Te in which droplets are short-circuit transferred. Furthermore, the second reverse feed speed Wfg2 during the main welding period Th is set to be higher than the first reverse feed speed Wfg during the arc end period Te. By doing so, the average feed speed Wfh can be increased to a desired value, and the feed amount of the welding wire 21 corresponding to the welding current Aw can be ensured during the main welding period Th in which droplets are detached and transferred.

[0052] Furthermore, the welding current Aw is reduced immediately after the start of the arc end period Te or immediately before the end of the main welding period Th so that the base current Ib flows through the welding wire 21. During the main welding period Th, the welding voltage between the welding wire 21 and the base metal 25 gradually decreases, and after it falls below a predetermined voltage threshold Va, the welding current Aw is reduced immediately after the start of the arc end period Te or immediately before the end of the main welding period Th. After the welding current Aw is maintained at the base current Ib for a predetermined period, it is preferable to short-circuit the welding wire 21 and the base metal 25 by alternately feeding the welding wire 21 forward and backward multiple times. During the main welding period Th, the feeding speed of the welding wire 21 is increased by alternately feeding the welding wire 21 forward and backward, and the arc length is shortened, compared to when the feeding speed of the welding wire 21, i.e., the wire feeding speed Wf, is constant. Therefore, the welding voltage Vw is gradually reduced while the welding current Aw is maintained at the base current Ib for a predetermined period.

[0053] In this way, the arc 24 can be stabilized, and droplets can grow at the tip of the welding wire 21. This ensures that droplets are transferred to the base metal 25 at the time when the welding wire 21 and the base metal 25 are first short-circuited. In addition, by detecting that the arc 24 is in a stable state, the welding state can be reliably transitioned to the arc end period Te.

[0054] Also, around the end of the main welding period Th, a peak current Ip flows through the welding wire 21. From this state, the welding current Aw is reduced in one or more stages to transition to the base current Ib. In this way, the arc 24 can be stabilized at the beginning of the arc end period Te, and the welding state can be smoothly transitioned to a short-circuit transition state between the welding wire 21 and the base material 25.

[0055] The current value of the base current Ib immediately after the start of the arc-end period Te or immediately before the end of the main welding period Th is preferably equal to or greater than 50 A and equal to or less than 200 A. By setting the current value of the base current Ib in this manner, it is possible to prevent the welding wire 21 from melting excessively and prevent the arc from interrupting.

[0056] In this embodiment, the wire feed speed Wf is controlled so that the time waveform becomes a sine wave during both the arc-end period Te and the main welding period Th, but this is not particularly limited thereto, and the feeding operation of the welding wire 21 may be controlled so that the time waveform becomes a trapezoidal wave. This control can also be applied to Embodiments 2 to 5 described later.

[0057] Furthermore, it is preferable that the arc end period Te ends and the burn back period Tbb starts at time P3 when the average feed rate Wfe becomes zero. It is preferable that the maximum value Wfg of the reverse feed rate during the arc end period Te is constant, and that the maximum value Wfg of the reverse feed rate during both the arc end period Te and the burn back period Tbb is the same. This stabilizes the state of the tip of the welding wire 21, thereby stabilizing the startability of welding when the next arc welding process is performed. In other words, good arc welding can be performed from the start of welding when the next arc welding process is performed.

[0058] (Embodiment 2) Fig. 4 is a diagram showing waveforms of the welding current, welding voltage, and wire feed speed according to embodiment 2. For ease of explanation, in Fig. 4 and the following drawings, the same parts as those in embodiment 1 are designated by the same reference numerals, and detailed explanations thereof will be omitted.

[0059] Among the various waveforms shown in Fig. 4, the time waveform of the peak current Ip during the main welding period Th differs from the time waveform of the peak current Ip of the first embodiment shown in Fig. 3. Specifically, as shown in Fig. 4, during the main welding period Th, the second peak current value Ip2, which is the current value of the peak current that finally flows through the welding wire 21, is controlled to be lower than the first peak current value Ip, which is the current value of the peak current that precedes it.

[0060] The second peak current value Ip2 is set to a value lower than the first peak current value Ip, ie, to be equal to or less than 350 A. The second peak current value Ip2 can be changed as appropriate depending on the period Tf, the material and diameter of the welding wire 21, the set current for the main welding period Th, and the like.

[0061] As described above, at the beginning of the arc end period Te, the base current Ib is passed through the welding wire 21 to grow droplets at the tip of the welding wire 21, enabling a smooth short-circuit transfer between the welding wire 21 and the base metal 25. However, if droplets of a certain size are formed at the tip of the welding wire 21 at the start point P1 of the arc end period Te, the droplets may detach before the short-circuit transfer begins. If this occurs, when the welding wire 21 and the base metal 25 are first short-circuited, it becomes difficult to release the short circuit because the tip of the welding wire 21 is free of droplets. To smoothly release the short circuit, the current value is reduced to the second peak current value Ip2 during the final peak current period Tp of the main welding period Th, thereby suppressing the detachment and growth of droplets. This allows droplets to remain at the tip of the welding wire 21 during the period when the base current Ib flows through the welding wire 21 at the beginning of the arc end period Te, enabling a smooth initial short-circuit release of the welding wire 25.

[0062] 4, the current value of the peak current Ip2 is set to the second peak current value Ip2 only in the cycle Tf immediately before the end of the main welding period Th, but this is not particularly limited. For example, the current value of the peak current in multiple cycles Tf immediately before the end of the main welding period Th may be set to the second peak current value Ip2. It is sufficient if, at the beginning of the arc end period Te, droplets remain at the tip of the welding wire 21 during the period when the base current Ib flows through the welding wire 21, thereby suppressing the occurrence of spatter or the like when the welding wire 21 is first short-circuited and released. In other words, one or multiple cycles Tf immediately before the end of the main welding period Th are defined as the first period. The second peak current value Ip2, which is the current value of the peak current in the first period, is controlled to be lower than the first peak current value Ip, which is the current value of the peak current in the main welding period Th that precedes the first period.

[0063] Furthermore, according to this embodiment, the same effects as those achieved by the method described in embodiment 1 can be achieved. That is, the detachment of droplets from the welding wire 21 during the main welding period Th can be stabilized. Furthermore, the amount of spatter is suppressed, and a welded portion with a small crater size and no crater depression near the welding end point can be formed. Because a molten pool can be stably formed in the base material 25 before and after switching from the main welding period Th to the arc end period Te, the generation of spatter during the arc end period Te can be suppressed. As a result, post-processing, which is the work of repairing large depressions, can be eliminated or reduced. Furthermore, it is possible to prevent products from being produced with large depressions remaining.

[0064] Third Embodiment FIG. 5 is a diagram showing waveforms of a welding current, a welding voltage, and a wire feed speed according to a third embodiment.

[0065] Among the various waveforms shown in Fig. 4, the time waveform of the peak current Ip in the main welding period Th is different from the time waveform of the peak current Ip shown in Fig. 4. Specifically, as shown in Fig. 5, in the main welding period Th, the second peak current period Tp2, which is the peak current period of the peak current Ip that last flows through the welding wire 21, is controlled to be shorter than the first peak current period Tp, which is the peak current period of the peak current Ip that precedes it.

[0066] The second peak current period Tp2 is set to be shorter than the first peak current period Tp by 50% or more and 80% or less, and can be changed as appropriate depending on the period Tf, the material and diameter of the welding wire 21, the set current for the main welding period Th, and the like.

[0067] As described in the second embodiment, if a droplet of a certain size is formed at the tip of the welding wire 21 at the start point P1 of the arc end period Te, the droplet may detach before the start of short-circuit transfer. In this case, when the short circuit is first released during the arc end period Te, spatter and other problems may occur. To prevent the occurrence of spatter and other problems, the second peak current period Tp2, in which the peak current Tp flows at the end of the main welding period Th, is made shorter than the preceding first peak current period Tp, thereby preventing the droplet from detaching and growing. This allows the droplet to remain at the tip of the welding wire 21 during the period in which the base current Ib flows through the welding wire 21 at the beginning of the arc end period Te, thereby preventing the occurrence of spatter and other problems when the welding wire 21 is first released from the short circuit.

[0068] 5, the peak current period is defined as the second peak current period Tp2 only in one cycle Tf immediately before the end of the main welding period Th, but this is not particularly limited. For example, the peak current period may be defined as the second peak current period Tp2 in multiple cycles Tf immediately before the end of the main welding period Th. It is sufficient that droplets remain at the tip of the welding wire 21 during the period when the base current Ib flows through the welding wire 21 at the beginning of the arc end period Te, thereby suppressing the occurrence of spatter or the like when the welding wire 21 is first short-circuited and released. In other words, the one or multiple cycles Tf immediately before the end of the main welding period Th are defined as the second period. The second peak current period Tp2, which is the period during which the peak current Ip flows in the second period, is controlled to be shorter than the first peak current period Tp, which is the period during which the peak current Ip flows in the main welding period Th before the second period.

[0069] Furthermore, according to this embodiment, the same effects as those achieved by the method described in embodiment 1 can be achieved. That is, the detachment of droplets from the welding wire 21 during the main welding period Th can be stabilized. Furthermore, the amount of spatter is suppressed, and a welded portion with a small crater size and no crater depression near the welding end point can be formed. Because a molten pool can be stably formed in the base material 25 before and after switching from the main welding period Th to the arc end period Te, the generation of spatter during the arc end period Te can be suppressed. As a result, post-processing, which is the work of repairing large depressions, can be eliminated or reduced. Furthermore, it is possible to prevent products from being produced with large depressions remaining.

[0070] (Embodiment 4) The end point of main welding period Th is not limited to the aforementioned time P1, but may be near time P1. Near time P1 may be, for example, a time around time P1 when wire feed speed Wf reaches a predetermined value Wfh, or a time around time P1 when wire feed speed Wf becomes zero. Alternatively, it may be a time after a predetermined first time has elapsed since time P1.

[0071] Alternatively, the end point of the main welding period Th may be set to the point after time P1 when the wire feed speed Wf reaches a predetermined speed threshold Ws.

[0072] If the end point of the main welding period Th is set to the point (P5) after point P1 when the wire feed speed Wf reaches a predetermined speed threshold Ws, it is preferable to set the second arc end period Te2 between the main welding period Th and the arc end period Te.

[0073] FIG. 6 is a diagram showing waveforms of the welding current, welding voltage, and wire feed speed according to the fourth embodiment. FIG. 6 differs from the various waveforms of the first embodiment shown in FIG. 3 in that a second arc end period Te2 is provided between the main welding period Th and the arc end period Te. In the example shown in FIG. 6, the second arc end period Te2 is the period from time P1 to time P5 when the wire feed speed Wf reaches the speed threshold Ws, and the arc end period Te is the period from time P5 to the aforementioned time P3. Note that the speed threshold Ws is a value lower than the average feed speed Wfh during the main welding period Th. In this case, the average feed speed Wfh during the main welding period Th is higher than the average feed speed Wfe at the start of the arc end period Te. Furthermore, after time P5, the welding torch 26 does not move in the welding direction along the weld line but stops at the position reached at time P5.

[0074] The time waveforms of the wire feed speed Wf, the welding voltage Vw, and the welding current Aw are similar between the second arc end period Te2 and the main welding period Th. In other words, during the second arc end period Te2, the welding current Aw flowing through the welding wire 21 may be varied in the cycle Tf while the welding wire 21 is alternately fed forward and backward, thereby causing a droplet to detach from the tip of the welding wire 21 and transfer to the base material 25.

[0075] The average feed speed in second arc end period Te2 is controlled to be lower than the average feed speed Wfh in main welding period Th and higher than the average feed speed Wfe in arc end period Te. In other words, the set current in second arc end period Te2 is controlled to be higher than the set current in arc end period Te and lower than the set current in main welding period Th.

[0076] If the difference between the set current during the main welding period Th and the set current during the arc end period Te is large, the set current during the arc end period Te must be increased, and the average feed rate Wfe must be set correspondingly high. However, if the average feed rate Wfe is set too high during the arc end period Te, where the short-circuit transition occurs, the welding wire 21 may plunge into the base material 25 during forward feed, or the welding wire 21 may suddenly break off after contacting the base material 25 during reverse feed. If this occurs, spatter is likely to occur. Furthermore, the crater depression near the welding end point at the welded portion becomes larger.

[0077] Therefore, as shown in this embodiment, a second arc end period Te2 is provided between main welding period Th and arc end period Te, and the set current and average feed rate in second arc end period Te2 are appropriately set. By doing so, even if there is a large difference between the set current in main welding period Th and the set current in arc end period Te, it is possible to suppress the generation of spatter and an increase in the size of the depression in the crater portion in the arc end period Te.

[0078] 6, it is preferable that the peak current and base current during second arc end period Te2 be reduced in a stepwise manner. This allows the amount of heat input to base metal 25 during second arc end period Te2 to be reduced in a stepwise manner, thereby preventing the appearance and shape of the weld from becoming non-uniform. Furthermore, arc 24 can be stabilized during second arc end period Te2 and the transition period from second arc end period Te2 to arc end period Te.

[0079] The stepwise decrease rates of the peak current, base current, average feed speed Wfe, etc. in the second arc end period Te2 may be the same as or different from those in the arc end period Te.

[0080] For example, by making the rate of decrease in the second arc end period Te2 lower than the rate of decrease in the arc end period Te, the decrease in the amount of heat input to the base material 25 when transitioning from the main welding period Th to the arc end period Te can be more mitigated, and the arc 24 can be more stabilized during the transition period from the main welding period Th to the second arc end period Te2 and the arc end period Te.

[0081] Furthermore, according to this embodiment, the same effects as those achieved by the method shown in embodiment 1 can be achieved. That is, the detachment of droplets from the welding wire 21 during the main welding period Th can be stabilized. Furthermore, the amount of spatter is suppressed, and a crater portion with a small size and no depression can be formed at the welded portion. Because a molten pool can be stably formed in the base material 25 before and after switching from the main welding period Th to the arc end period Te, the generation of spatter during the arc end period Te is suppressed. As a result, post-processing, which is the work of repairing large depressions, can be eliminated or reduced. Furthermore, it is possible to suppress the release of products with large depressions remaining.

[0082] (Embodiment 5) Figure 7 is a diagram showing waveforms of the welding current, welding voltage, and wire feed speed according to embodiment 5. Figure 6 differs from the various waveforms of embodiment 1 shown in Figure 2 in that a crater period Tc is provided between main welding period Th and arc end period Te. In the example shown in Figure 7, crater period Tc is the period from time P1 to time P6, and arc end period Te is the period from time P6 to the aforementioned time P3. Note that after time P2, welding torch 26 does not move in the welding direction along the weld line, but stops at the position reached at time P2.

[0083] As described above, a weld formed by arc welding often has a crater portion with a depression near the welding end point. Therefore, in the arc welding control method disclosed herein, an arc end period Te is provided to cause short-circuit transfer of droplets between welding wire 21 and base metal 25, thereby reducing the depression and the size of the crater portion.

[0084] However, depending on the welding conditions during the main welding period Th, the depression in the crater portion may become too large and may not be completely filled by the arc end period Te. In such cases, as shown in this embodiment, by providing a crater period Tc between the main welding period Th and the arc end period Te, the size and depression of the crater portion can be more effectively reduced.

[0085] During the crater period Tc, droplets are repeatedly short-circuited and transferred between the welding wire 21 and the base material 25, as in the arc-end period Te. This suppresses the generation of spatter. During the crater period Tc, the wire feed speed Wf is controlled to be lower than that during the main welding period Th. Specifically, during the crater period Tc, the reverse feed speed is controlled to be the same as the first reverse feed speed Wfg during the arc-end period Te. Meanwhile, the maximum value of the forward feed speed is constant, the same as during the main welding period Th, but is controlled to be lower than the second forward feed speed Wff2 during the main welding period Th. As a result, the average feed speed during the crater period Tc is constant but controlled to be lower than the average feed speed Wfh during the main welding period Th.

[0086] In the present embodiment, during the crater period Tc, the welding current Aw is applied to the welding wire 21, and the welding wire 21 is alternately fed forward and backward to short-circuit the welding wire 21 and the base material 25, thereby transferring the droplets formed at the tip of the welding wire 21 to the base material 25 via short-circuiting. However, this is not limiting, and for example, the welding current Aw may be applied to the welding wire 21 as in the actual welding period Th. In other words, during the crater period Tc, instead of short-circuiting transfer in which the welding wire 21 and the base material 25 are short-circuited to transfer the droplets formed at the tip of the welding wire 21 to the base material 25, the welding current Aw may be varied in a cycle Tf while the welding wire 21 is alternately fed forward and backward to cause the droplets to detach from the tip of the welding wire 21 and transfer to the base material 25.

[0087] By doing so, if the depression in the crater portion is large, it can be backfilled in a short time. In this case, it is preferable to set the set current in the crater period Tc smaller than the set current in the main welding period Th so that the heat input to the crater portion does not become too large. Therefore, the current value of the peak current in the crater period Tc is smaller than the current value Ip of the peak current in the main welding period Th. It is also preferable to set the current value of the base current in the crater period Tc smaller than the current value Ib of the base current in the main welding period Th, to the extent that arc interruption does not occur.

[0088] Furthermore, according to this embodiment, the same effects as those achieved by the method described in embodiment 1 can be achieved. That is, the detachment of droplets from the welding wire 21 during the main welding period Th can be stabilized. Furthermore, the amount of spatter is suppressed, and a welded portion with a small crater size and no crater depression can be formed. Because a molten pool can be stably formed on the base material 25 before and after switching from the main welding period Th to the arc end period Te, the generation of spatter during the arc end period Te is suppressed. As a result, post-processing, which is the work of repairing large depressions, can be eliminated or reduced. Furthermore, it is possible to prevent products from being produced with large depressions remaining.

[0089] Other Embodiments The components described in the first to fifth embodiments may be appropriately combined to form new embodiments. For example, in the second embodiment, the peak current period during which the second peak current Ip2 flows may be set shorter than the preceding peak current period during which the first peak current Ip flows, as described in the third embodiment. This reliably prevents droplets from detaching from the welding wire 21 before and after the transition from the main welding period Th to the arc end period Te.

[0090] In addition, in the second and third embodiments, examples have been shown in which the peak current value is made smaller than the previous peak current value or the peak current period is made shorter than the previous peak current period in one or more cycles Tf immediately before the end of the main welding period Th. However, methods other than these can also be used to suppress droplets from detaching from the welding wire 21 before and after switching from the main welding period Th to the arc end period Te, and to suppress the occurrence of spatters and the like when the short circuit is first released in the arc end period Te.

[0091] For example, in the example shown in FIG. 3 , the feeding operation of the welding wire 21 may be controlled so that in one or more cycles Tf immediately before the end of the main welding period Th, the reverse feed acceleration Afg during the reverse feed of the welding wire 21 is smaller than the reverse feed acceleration Afg during the previous main welding period Th.

[0092] That is, one or more cycles Tf immediately before the end of the main welding period Th are defined as the third period. The absolute value of the reverse feed acceleration Afg of the welding wire 21 during the third period is controlled to be smaller than the absolute value of the reverse feed acceleration Afg during the main welding period Th before the third period. Note that the first period, the second period, and / or the third period may be the same period or different periods.

[0093] This also makes it possible to prevent droplets from detaching from the welding wire 21 before and after switching from the main welding period Th to the arc end period Te, and to prevent spatters and the like from occurring when the first short circuit is released during the arc end period Te.

[0094] In addition, in this specification, CO２ However, the type of shielding gas used in the arc welding of the present disclosure is not particularly limited to this. ２ The shielding gas may be a mixed gas of CO ２ When the gas is mainly composed of CO, the arc reaction force is large, and as described above, droplets are difficult to detach in normal pulse welding. On the other hand, according to the arc welding control method disclosed herein, even when a shielding gas with a high arc reaction force is used, droplets can be stably detached from the welding wire 21 during the main welding period Th. ２ When the mixing ratio is 25% or more, the effects of the method of the present disclosure can be particularly exhibited.

[0095] However, the CO of the shielding gas ２ The mixing ratio of CO is not particularly limited to this. ２ The amount of argon gas may be increased. ２ The welding wire 21 and the base material 25 may be made of any gas that does not contain argon, helium, or other inert gas. The materials of the welding wire 21 and the base material 25 are not limited to mild steel.

[0096] CO ２ Even when a shielding gas with a high arc reaction force such as that described above is not used, droplets can be stabilized to detach from the welding wire 21 during the main welding period Th, and the shape of the crater can be restored during the arc end period Te at the end of welding, as described above. In particular, during the main welding period Th, by alternately feeding the welding wire 21 forward and backward, a force that shakes off the droplets, in addition to gravity, is applied to the droplets, and the droplets can be stably transferred to the base material 25 for each cycle Tf. Furthermore, because droplets can be detached even when the current value of the peak current Ip is low, the occurrence of spatter during the main welding period Th can be suppressed.

[0097] The arc welding control method disclosed herein is useful because it reduces the amount of spatter, reduces the size of the crater near the welding end point at the welding point, and allows the formation of a welding point that is free of crater depressions, and also reduces the generation of spatter during the arc end period.

[0098] REFERENCE SIGNS LIST 1 Input power supply 2 Primary rectifier 3 Switching unit 4 Transformer 5 Secondary rectifier 6 DCL 7 Drive unit 8 Welding voltage detector 9 Welding current detector 10 Short circuit / arc detector 11 Short circuit controller 12 Arc controller 13 Wire feed speed controller 14 Welding power supply 15 Welding condition setting unit 16 Robot controller 17 Robot controller 18 Manipulator 20 Wire storage unit 21 Welding wire 22 Wire feed motor 23 Tip 24 Arc 25 Base metal 26 Welding torch 30 Arc welding device Ip Peak current Ip2 Second peak current Ib Base current Ta Slow-down period Tbb Burn-back period Tc Crater period Te Arc end period Te2 Second arc end period Th Main welding period Tp Peak current period Tp2 Second peak current period Tb Base current period Tf Cycle Va Arc determination level voltage (voltage threshold) Wfa Slow-down speed Wfe Average feed speed during arc end period Wfh Average feed speed during main welding period Wff First forward feed speed Wff2 Second forward feed speed Wfg First reverse feed speed Wfg2 Second reverse feed speed

Claims

1. A method for controlling arc welding in which an arc is generated between a welding wire that is a consumable electrode and a base metal to perform welding, comprising at least a first step of, during a main welding period, fluctuating a welding current flowing through the welding wire at a predetermined cycle while alternately feeding the welding wire forward and backward, thereby causing droplets to detach from the tip of the welding wire and transfer the droplets to the base metal; and a second step of, during an arc end period provided after the main welding period, causing a welding current to flow through the welding wire and short-circuiting the welding wire and the base metal while alternately feeding the welding wire forward and backward, thereby causing the droplets formed at the tip of the welding wire to short-circuit and transfer to the base metal, wherein the arc end period is the period from the end of the main welding period until the average feed rate of the welding wire becomes zero, and the cycle includes a peak current period in which a peak current flows through the welding wire and a base current period following the peak current period in which a base current flows through the welding wire, the current value of the base current being lower than the current value of the peak current, the welding current is varied at a predetermined cycle while alternately feeding the welding wire in a forward direction and a reverse direction, thereby causing the droplets to be separated and transferred; and the average feed speed during the main welding period, during which the welding current is varied at a predetermined cycle while alternately feeding the welding wire in a forward direction and a reverse direction, is equal to or higher than the average feed speed at the start of the arc end period, during which the welding wire is fed in a forward direction and a reverse direction and causing the droplets to be short-circuit transferred.

2. An arc welding control method according to claim 1, wherein the forward feed speed, which is the feed speed of the welding wire during forward feed, the reverse feed speed, which is the feed speed during reverse feed, the speed ratio, which is the absolute value of the ratio of the maximum value of the forward feed speed to the maximum value of the reverse feed speed, based on the average feed speed, and the frequency, which is the reciprocal of the wire feed cycle that alternately repeats the forward feed and the reverse feed, are set independently of each other in the arc end period and the main welding period.

3. An arc welding control method as defined in claim 2, wherein the reverse feed speed during the arc end period is controlled so that its maximum value is constant, the maximum value of the forward feed speed during the arc end period is controlled so that it becomes smaller as the number of repetitions of the forward feed and the reverse feed increases, the maximum value of the reverse feed speed during the main welding period is controlled so that it is greater than the maximum value of the reverse feed speed during the arc end period, and the maximum value of the forward feed speed during the main welding period is controlled so that it is greater than the maximum value of the forward feed speed during the arc end period.

4. An arc welding control method according to claim 1, characterized in that a second peak current value, which is the current value of the peak current in a first period including one or more cycles immediately before the end of the main welding period, is controlled to be lower than a first peak current value, which is the current value of the peak current in the main welding period before the first period.

5. The arc welding control method according to claim 4, wherein the second peak current value is controlled to be 350 A or less.

6. An arc welding control method according to claim 1, characterized in that a second peak current period, which is the peak current period in a second period including one or more cycles immediately before the end of the main welding period, is controlled to be shorter than a first peak current period, which is the peak current period in the main welding period before the second period.

7. The arc welding control method according to claim 6, wherein the second peak current period is controlled to be 50% or more and 80% or less of the first peak current period.

8. An arc welding control method according to claim 1, characterized in that the absolute value of the reverse feed acceleration of the welding wire during a third period including one or more of the cycles immediately before the end of the main welding period is controlled to be smaller than the absolute value of the reverse feed acceleration during the main welding period before the third period.

9. The arc welding control method according to claim 1, wherein the welding current is reduced immediately after the start of the arc end period or immediately before the end of the main welding period, so that the base current flows through the welding wire.

10. An arc welding control method as claimed in claim 9, characterized in that the welding voltage between the welding wire and the base metal gradually decreases and falls below a predetermined voltage threshold, and the welding current decreases immediately after the start of the arc end period or immediately before the end of the main welding period, and after the welding current has been maintained at the base current for a predetermined period, the welding wire and the base metal are short-circuited while alternately feeding the welding wire forward and backward.

11. The arc welding control method according to claim 9, wherein the welding current is reduced in one or more stages immediately after the start of the arc end period or immediately before the end of the main welding period, so that the base current flows through the welding wire.

12. The arc welding control method according to claim 9, wherein the current value of the base current flowing through the welding wire immediately after the start of the arc end period or immediately before the end of the main welding period is 50 A or more and 200 A or less.

13. An arc welding control method according to claim 1, wherein the end point of the main welding period is a first point in time when an arc end signal is input, or a point in the vicinity of the first point in time, or a point in time when a first time has elapsed since the first point in time.

14. An arc welding control method according to claim 13, wherein the vicinity of the first point in time is a point before or after the first point in time at which the welding wire feed speed becomes the average feed speed for the main welding period, or a point in time at which the feed speed becomes zero, or a point after the first point in time at which the welding wire feed speed reaches a predetermined speed threshold.

15. An arc welding control method according to claim 14, wherein, when the end point of the main welding period is a point after the first point in time when the feed speed of the welding wire reaches a predetermined speed threshold, a second arc end period is provided between the main welding period and the arc end period, the second arc end period is the period from the end point of the main welding period to the point at which the average feed speed reaches a predetermined speed threshold, and the arc end period is the period from when the average feed speed reaches the predetermined speed threshold to when it becomes zero, and during the second arc end period, the welding current flowing through the welding wire is varied in the cycle while the welding wire is alternately fed forward and backward, thereby causing the droplets to detach from the tip of the welding wire and transfer to the base metal, and during the second arc end period, the average feed speed is controlled to decrease over time.

16. An arc welding control method as claimed in claim 1, wherein a crater period starting from the end of the main welding period is provided between the main welding period and the arc end period, the arc end period being the period from the end of the crater period until the average feed rate becomes zero, and the average feed rate is controlled to be constant during the crater period.

17. An arc welding control method as set forth in claim 16, characterized in that during the crater period, the welding current flowing through the welding wire is varied in the cycle while the welding wire is alternately fed forward and backward, thereby causing the droplet to detach from the tip of the welding wire and transfer to the base material.

18. An arc welding control method as set forth in claim 16, characterized in that during the crater period, the welding current is passed through the welding wire, and the welding wire is fed alternately in forward and reverse directions while short-circuiting the welding wire and the base material, thereby causing the droplet formed at the tip of the welding wire to short-circuit and transfer to the base material.

19. An arc welding control method as defined in claim 1, wherein the arc end period ends and a burn back period begins when the average feed rate reaches zero, the burn back period continues until formation of a molten metal ball at the tip of the welding wire is completed, and the maximum value of the reverse feed rate during the arc end period is constant, and the maximum value of the reverse feed rate is the same during both the arc end period and the burn back period.

20. In the method for controlling arc welding according to any one of claims 1 to 19, the shielding gas blown onto the base metal during arc welding is CO ２ The arc welding control method is characterized in that the mixture ratio of the above gas is 25% or more.

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