AC arc welding method

Abstract

The present invention involves causing a welding device to execute: a current-raising step in which a welding current is increased, according to a first slope (S1), from a negative value to a second current value (I2) that is 0.6-0.9 (inclusive) times a prescribed positive first current value (I1), and then is increased from the second current value (I2) to the first current value (I1) according to a second slope (S2) ranging from 60 μA / μs to 600 mA / μs (inclusive), the second slope (S2) being less than the first slope (S1); and a current-lowering step in which the welding current is reduced, according to a third slope (S3), from a positive value to a fourth current value (I4) that is 0.6-0.9 (inclusive) times a prescribed negative third current value (I3), and then is reduced from the fourth current value (I4) to the third current value (I3) according to a fourth slope (S4) of -60 μA / μS to -600 mA / μs (inclusive), the fourth slope (S4) being greater than the third slope (S3).

Description

[Technical Field]

[0001] The present disclosure relates to an AC arc welding method for performing welding by generating an arc between an electrode and a base metal using an AC welding current. [Background technology]

[0002] Patent Document 1 discloses an AC arc welding method in which an AC welding current is used to generate an arc between an electrode and a base metal to perform welding. In this AC arc welding method, the waveform of the welding current is a square-wave AC current with a pulse superimposed on it, so that the directionality of the arc can be maintained even if the time ratio of the electrode negative period is reduced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2689752 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the welding current waveform is a waveform in which a pulse is superimposed on a square wave AC, so when the welding current rises from a negative value to a positive value, the welding current increases rapidly, generating a high-pitched operating noise and increasing the burden on the worker.Furthermore, when the welding current falls from a positive value to a negative value, the welding current also decreases rapidly, causing the same problem.

[0005] Furthermore, if the waveform of the welding current is made sinusoidal in order to suppress the generation of high-pitched working noise, the melting of the base material slows down, and working efficiency deteriorates.

[0006] The present disclosure has been made in consideration of the above points, and its object is to reduce the working noise while suppressing a deterioration in welding work efficiency. [Means for solving the problem]

[0007] A first aspect of the present disclosure is an AC arc welding method for welding by generating an arc between an electrode and a base metal using an AC welding current, characterized in that the method executes at least one of a current ramp-up step in which the welding current is increased at a first slope from a negative value to a second current value that is 0.6 to 0.9 times a predetermined positive first current value, and then increased from the second current value to the first current value at a second slope of 60 μA / μs to 600 mA / μs that is smaller than the first slope over a first ramp period; and a current ramp-down step in which the welding current is decreased at a third slope from a positive value to a fourth current value that is 0.6 to 0.9 times a predetermined negative third current value, and then decreased from the fourth current value to the third current value at a fourth slope of -60 μA / μs to -600 mA / μs that is larger than the third slope over a second ramp period.

[0008] According to this aspect, when the current ramp-up step is performed, when the welding current is increased from a negative value to the first current value, the welding current is increased at a second gradient of 600 mA / μs or less from the time the welding current reaches the second current value until it reaches the first current value, thereby reducing the operating noise compared to when the welding current is increased at a gradient exceeding 600 mA / μs.

[0009] Furthermore, when the current ramp-up step is performed, when the welding current is increased from a negative value to the first current value, the welding current is increased at a first gradient greater than the second gradient until the welding current reaches the second current value. This allows the base material to melt faster and improves work efficiency compared to when the welding current is increased at the second gradient.

[0010] Furthermore, when the current ramp-up step is performed, the second current value is set to 0.6 times the first current value or more, which makes it possible to melt the base material faster, improve work efficiency, and shorten the period when the welding current is low, making it less likely for the arc to break, compared to when the second current value is set to less than 0.6 times the first current value. Furthermore, the second current value is set to 0.9 times the first current value or less, which makes it possible to lengthen the period when the work noise is low, compared to when the second current value is greater than 0.9 times the first current value.

[0011] On the other hand, when the current reduction step is performed, when the welding current is reduced from a positive value to the third current value, the welding current is reduced at a fourth slope of -600 mA / μs or more from the time when the welding current reaches the fourth current value until when the welding current reaches the third current value, thereby reducing the operating noise compared to when the welding current is increased at a slope of less than -600 mA / μs.

[0012] Furthermore, when the current reduction step is performed, when the welding current is reduced from a positive value to the third current value, the welding current is reduced at a third gradient that is smaller than the fourth gradient until the welding current reaches the fourth current value, making it less likely that the arc will break compared to when the welding current is reduced at the fourth gradient.

[0013] Furthermore, when the current reduction step is performed, the fourth current value is set to 0.6 times the third current value or less, which shortens the period during which the absolute value of the welding current is small compared to when the fourth current value is greater than 0.6 times the third current value, making it less likely that arc interruption will occur. Furthermore, the fourth current value is set to 0.9 times the third current value or more, which lengthens the period during which the work noise is low compared to when the fourth current value is less than 0.9 times the third current value.

[0014] A second aspect of the present disclosure is an AC arc welding method for welding by generating an arc between an electrode and a base metal using an AC welding current, the method comprising: a first peak current application step for applying the welding current to a current value that is 1.15 to 1.6 times a predetermined positive set current value only during a first pulse period; and a first base current application step for applying the welding current to a current value that is 0.6 to 0.9 times the set current value only during a second pulse period, the first peak current application step being performed at least twice during the period from when the welding current is increased from a negative value to a positive value until when the welding current is decreased to the negative value again. a second peak current applying step of applying the welding current to a current value in the range of −1.2 to −1.8 times the set current value only for a third pulse period, and a second base current applying step of applying the welding current to a current value in the range of −0.6 to −0.9 times the set current value only for a fourth pulse period, each of which is alternately performed once during the time period from when the welding current is decreased from a positive value to a negative value until when the welding current is increased to the next positive value.

[0015] According to this embodiment, the first peak current application step provides the filler rod with more heat for melting the filler rod, and the increased electromagnetic pinch force improves the output directivity of the arc, promoting smooth droplet transfer, thereby increasing the melting rate compared to when the welding current is always set to a set current value. Furthermore, even if the welding current is made higher than the set current value in the first peak current application step, the welding current is made lower than the set current value in the first base current application step, so the effective value of the welding current during the first pulse current application step can be made closer to the set current value.

[0016] Furthermore, when the second pulse current applying step is performed, the output directivity of the arc is improved by increasing the electromagnetic pinch force in the second peak current applying step, and the cleaning action can be promoted compared to when the welding current is always set to the set current value. Furthermore, even if the welding current is set to less than -1 times the set current value in the second peak current applying step, the welding current is set to more than -1 times the set current value in the second base current applying step, so the effective value of the welding current during the second pulse current applying step can be made closer to -1 times the set current value.

[0017] Furthermore, since the first peak current application step and the first base current application step are performed two or more times, the melting rate can be increased more effectively than when they are performed only once.

[0018] Furthermore, because the second peak current application step and the second base current application step are each performed only once, the third pulse period can be longer than when they are performed two or more times. Therefore, the period during which cleaning is performed at a current value smaller than -1 times the set current value can be longer, allowing oxides on the base metal surface to be thoroughly removed. Even when the period during which the welding current is set to a negative value is set to a small percentage (less than 50% of one cycle), the third pulse period and the fourth pulse period can be longer than when the second peak current application step and the second base current application step are each performed two or more times. This prevents the third pulse period and the fourth pulse period from being too short, making control difficult. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to reduce the working noise while suppressing a deterioration in the welding work efficiency. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a welding device. [Figure 2] FIG. 2 is a circuit diagram of a welding power source. [Figure 3] FIG. 3 is a diagram showing the waveform of a welding current during arc welding. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0022] 1 shows a welding device 1. This welding device 1 includes a welding torch 10 and a welding power source 20. This welding device 1 is an AC TIG welding device in which the welding torch 10 is a non-consumable electrode torch.

[0023] Welding torch 10 has a nozzle 11 that sprays shielding gas SG supplied from a gas supply device (not shown). A roughly cylindrical collet 12 is disposed inside nozzle 11 so as to align with the spray direction of nozzle 11. A rod-shaped tungsten electrode TE is fixed inside collet 12.

[0024] Welding power source 20 generates arc A by applying an AC voltage between tungsten electrode TE of welding torch 10 and base metal W.

[0025] Using this welding device 1, an operator can generate an arc A between the tungsten electrode TE and the base material W to form a molten pool P on the base material W, and then insert a filler rod R into this molten pool P to form a weld bead.

[0026] In detail, as shown in FIG. 2, welding power source 20 includes a first rectifying and smoothing circuit 21, a first inverter circuit 22, a first transformer 23, a second rectifying and smoothing circuit 24, first and second reactors 25, 26, a second inverter circuit 27, and a control device 30.

[0027] The first rectifying and smoothing circuit 21 converts input AC power input from the commercial power supply 2 into DC power and outputs it.

[0028] The first inverter circuit 22 is, for example, a single-phase full-bridge PWM control inverter and includes four switching elements (not shown). The first inverter circuit 22 switches these four switching elements in response to a switching signal SG1 output by the control device 30, thereby converting the DC power output by the first rectifying and smoothing circuit 21 into AC power and outputting it. Here, the output voltage of the first inverter circuit 22 is referred to as a first AC voltage. Note that the first inverter circuit 22 may be an inverter circuit with another configuration, such as a half-bridge inverter.

[0029] The first transformer 23 converts the first AC voltage output by the first inverter circuit 22 into a second AC voltage and outputs the second AC voltage. The first transformer 23 has a first primary coil 23a and a first secondary coil 23b. The first AC voltage output by the first inverter circuit 22 is applied to the first primary coil 23a. The voltage of the first secondary coil 23b becomes the second AC voltage.

[0030] The second rectifying and smoothing circuit 24 converts the second AC voltage output by the first transformer 23 into a first DC voltage and outputs it from a positive output terminal 24a and a negative output terminal 24b. The second rectifying and smoothing circuit 24 is a diode bridge circuit consisting of four diodes 24c.

[0031] The second inverter circuit 27 is a single-phase half-bridge inverter circuit. The second inverter circuit 27 includes first and second input terminals 271 and 272, and an upper arm switching element 273 and a lower arm switching element 274 connected in series between the first and second input terminals 271 and 272. A polarity switching signal SG2 output by the control device 30 is input to the upper arm switching element 273, while an inverted signal of the polarity switching signal SG2 is input to the lower arm switching element 274. A first input terminal 271 of the second inverter circuit 27 is connected to the positive output terminal 24a of the second rectifying and smoothing circuit 24 via a first reactor 25. A second input terminal 272 of the second inverter circuit 27 is connected to the negative output terminal 24b of the second rectifying and smoothing circuit 24 via a second reactor 26. An output terminal 275 of the second inverter circuit 27 is connected to the workpiece W.

[0032] Therefore, with the upper arm switching element 273 turned on and the lower arm switching element 274 turned off, the second inverter circuit 27 sets the base metal W at a higher potential than the tungsten electrode TE, while with the upper arm switching element 273 turned off and the lower arm switching element 274 turned on, the second inverter circuit 27 sets the base metal W at a lower potential than the tungsten electrode TE. When a pulse signal that switches between high and low levels at a predetermined cycle is input to the second inverter circuit 27 as the polarity switching signal SG2, the second inverter circuit 27 periodically switches the polarity of the AC voltage applied between the base metal W and the tungsten electrode TE between an EN (electrode negative) polarity where the tungsten electrode TE is at a lower potential than the base metal W, and an EP (electrode positive) polarity where the tungsten electrode TE is at a higher potential than the base metal W. This causes an AC welding current to flow between the base metal W and the tungsten electrode TE.

[0033] The control device 30 controls the welding current I. A predetermined positive first current value I1 is input to the control device 30 by the user using input means (not shown) and set as the set current value. More specifically, based on the measured value of the welding current I input from a current sensor (not shown), the control device 30 outputs a switching signal SG1 to the first inverter circuit 22 by PWM control so that the effective value of the welding current I becomes the set current value, and also outputs a polarity switching signal SG2 that switches the polarity of the AC voltage applied between the electrode TE and the base metal W. The control of the welding current I by the control device 30 is performed by outputting the switching signal SG1 and the polarity switching signal SG2. The frequency of the polarity switching signal SG2, i.e., the frequency of the welding current, is set to be equal to or greater than 10 Hz and equal to or less than 400 Hz.

[0034] Hereinafter, with reference to FIG. 3, the control of the welding current for one cycle T by the control device 30 when welding is performed by the AC arc welding method according to the embodiment of the present disclosure will be described.

[0035] First, at timing tA, control device 30 increases the welding current from a negative value to a second current value I2, which is (1-α) times the positive first current value I1, at a first gradient S1 of 1.7 A / μs. Next, control device 30 executes a current ramp-up step in which control device 30 increases the welding current from the second current value I2 to the first current value I1 at a second gradient S2 of 60 μA / μs to 600 mA / μs, which is smaller than the first gradient S1, over a first gradient period SPE1. α is set to a value between 0.1 and 0.4. Therefore, second current value I2 is between 0.6 and 0.9 times the first current value I1.

[0036] In this way, in the current ramp-up step, the welding current is increased from the second current value I2 to the first current value I1 at the second gradient S2 of 600 mA / μs or less, so that the working noise is lower and a softer sensation is given to the worker compared to when the welding current is increased at a gradient exceeding 600 mA / μs.

[0037] Furthermore, since the second slope S2 is set to 60 μA / μs or more, the base material W can be melted faster than when the second slope S2 is set to less than 60 μA / μs.

[0038] In addition, in the current ramp-up step, the welding current is increased from a negative value to the second current value I2 at a first gradient S1 of 1 A / μs or more, which allows the base material W to melt faster and improves work efficiency compared to when the welding current is increased at a second gradient S2.

[0039] Furthermore, since the second current value I2 is set to 0.6 times or more the first current value I1, the base metal W melts faster, improving work efficiency, and shortening the period when the welding current is low, making it less likely for the arc to break, compared to when the second current value I2 is set to less than 0.6 times the first current value I1. Furthermore, since the second current value I2 is set to 0.9 times or less the first current value I1, the period when the work noise is low can be lengthened, compared to when the second current value I2 is set to more than 0.9 times the first current value I1.

[0040] Next, starting from timing tB, control device 30 executes a first peak current application step in which the welding current is increased to a first peak current value P1, which is (1 + α / 2 + β) times the first current value I1, and maintained at this first peak current value P1 for a first pulse period PPE1. Another first pulse current application step in which the welding current is decreased to a first base current value B1, which is (1 - β) times the first current value I1, and maintained at this first base current value B1 for a second pulse period PPE2 is executed alternately twice. β is set to a value between 0.1 and 0.4. Therefore, first peak current value P1 is between 1.15 and 1.6 times the first current value I1, and first base current value B1 is between 0.6 and 0.9 times the first current value I1.

[0041] In the first peak current application step, the welding current is set to a first peak current value P1 greater than the first current value I1, thereby providing more heat to the filler rod R to melt it, and increasing the electromagnetic pinch force to improve the output directivity of the arc A and promote smooth droplet transfer. This increases the melting rate compared to when the welding current is always set to a set current value (first current value I1). In addition, in the first base current application step, the welding current is set to a first base current value B1 less than the first current value I1, so the effective value of the welding current during the first pulse current application step can be brought closer to the set current value.

[0042] Furthermore, because β is set to 0.1 or more, the melting rate can be increased more effectively than when β is set to less than 0.1. Furthermore, because β is set to 0.4 or less, the arc A is prevented from becoming too strong in the first peak current application step, which slows down wear on the tungsten electrode TE and reduces the burden on the operator, compared to when β is set to more than 0.4.

[0043] At timing tC, control device 30 increases the welding current from first base current value B1 to first current value I1. Control device 30 then executes a current reduction step in which the welding current is reduced from first current value I1 at a slope -1 times second slope S2, i.e., a slope -S2 of -60 μA / μs or less and -600 mA / μs or more, over a reduction period DPE of 0.35 to 0.95 times the first ramp period SPE1. Next, at timing tD immediately after the current reduction step, control device 30 sets the welding current to a positive ramp-up current value RI of 1.0 to 1.65 times the first current value I1 over a ramp-up period RPE of 0.05 to 0.65 times the first ramp period SPE1.

[0044] During the first slope period SPE1 and the decrease period DPE, the welding current is set to be smaller than the first current value I1. Therefore, even if the welding current is set to be larger than the first current value I1 in the first peak current application step, the effective value of the welding current during the period when the welding current is positive can be made to approach the set current value (first current value I1).

[0045] Then, at timing tE, control device 30 reduces the welding current. Specifically, control device 30 reduces the welding current from the positive ramp-up current value RI to a fourth current value I4, which is (1-γ) times the negative third current value I3, at a third slope S3 of -1.7 A / μs. Next, control device 30 executes a current reduction step in which control device 30 reduces the welding current from the fourth current value I4 to the third current value I3 at a fourth slope S4 of -60 μA / μs or less and -600 mA / μs or more, which is greater than the third slope S3, over a second slope period SPE2. The third current value I3 is -1 times the first current value I1 (the set current value). γ is set to a value between 0.1 and 0.4. Therefore, the fourth current value I4 is between 0.6 and 0.9 times the third current value I3.

[0046] In this way, a current decrease step is executed between the execution of the current increase step and the next time the welding current is decreased to a negative value, and the welding current is temporarily increased to the increase current value RI just before the welding current is decreased from a positive value to a negative value.

[0047] In this way, immediately after the current reduction step is performed, the welding current is temporarily increased from a current value lower than the set current value (first current value I1) to a start-up current value RI that is 1.0 to 1.65 times the first current value I1. Therefore, compared to when the welding current is decreased to a negative value immediately after the current reduction step is performed, the third slope S3 is steeper (smaller), making it less likely that an arc will break.

[0048] Immediately after the current decreasing step, the welding current may be decreased to a negative value rather than being increased to the initial current value RI. In this case, the decrease period DPE may be set to 0.95 to 1 times the first slope period SPE1.

[0049] In addition, in the current reduction step, the welding current is reduced from the fourth current value I4 to the third current value I3 at a fourth slope S4 of -600 mA / μs or more, so that the working noise is lower and a softer feeling is given to the worker compared to when the welding current is increased at a slope of less than -600 mA / μs.

[0050] Furthermore, since the fourth slope S4 is set to -60 μA / μs or less, arc interruption is less likely to occur compared to when the slope exceeds -60 μA / μs.

[0051] In addition, in the current reduction step, the welding current is reduced from a positive value to the fourth current value I4 at a third gradient S3 of -1 A / μs or less, making arc interruption less likely to occur compared to when the welding current is reduced at the fourth gradient S4.

[0052] Furthermore, since the fourth current value I4 is set to 0.6 to 0.9 times the third current value I3, the period during which the absolute value of the welding current is small is shortened, making arc interruption less likely to occur, compared to when the fourth current value I4 is set to more than 0.6 times the third current value I3. Furthermore, the period during which the working noise is low can be lengthened, compared to when the fourth current value I4 is set to less than 0.9 times the third current value I3.

[0053] Next, starting from timing tF, control device 30 executes a second pulse current application step in which the welding current is decreased to a second peak current value P2, which is (1 + γ + σ) times the third current value I3, and maintained at this second peak current value P2 for a third pulse period PPE3, and a second pulse current application step in which the welding current is increased to a second base current value B2, which is (1 - σ) times the third current value I3, and maintained at this second base current value B2 for a fourth pulse period PPE4, alternately executing these steps only once. σ is set to a value between 0.1 and 0.4. Therefore, second peak current value P2 is between 1.2 and 1.8 times the third current value I3, i.e., between -1.2 and -1.8 times the set current value (first current value I1). The second base current value B2 is 0.6 to 0.9 times the third current value I3, that is, −0.6 to −0.9 times the set current value (first current value I1).

[0054] In the second peak current applying step, the welding current is set to a second peak current value P2 that is smaller than the third current value I3, thereby increasing the electromagnetic pinch force and improving the output directivity of the arc A. Therefore, the cleaning action can be promoted more effectively than when the welding current is always set to the third current value I3 (-1 times the set current value). The second peak current value P2 is set independently of the first peak current value P1 depending on the required level of cleaning action. Furthermore, in the second base current applying step, the welding current is set to a second base current value B2 that is larger than the third current value I3, so the effective value of the welding current during the second pulse current applying step can approach -1 times the set current value.

[0055] At timing tG, control device 30 decreases the welding current from second base current value B2 to third current value I3. Control device 30 then executes a current increasing step in which the welding current is increased from third current value I3 at a slope of -1 times fourth slope S4, i.e., at a slope of 60 μA / μs to 600 mA / μs, for an increase period IPE of 0.35 to 0.95 times the second ramp period SPE2. Next, at timing tH immediately after the current increasing step, control device 30 sets the welding current to a fall current value FI of 1.0 to 1.65 times the third current value I3 for a fall period FPE of 0.05 to 0.65 times the second ramp period SPE2, and then repeats the operation from timing tA. That is, control device 30 increases the welding current from fall current value FI to a positive second current value I2 at a first slope S1 of 1.7 A / μs.

[0056] In this way, between the time when the current reduction step is executed and the time when the welding current is next increased to a positive value, the current increase step is executed, and the welding current is temporarily reduced to the reduction current value FI just before the welding current is increased from a negative value to a positive value.

[0057] In this way, immediately after the current increase step is performed, the welding current is temporarily reduced from a current value higher than -1 times the set current value to a reduction current value FI that is 1.0 to 1.65 times the third current value I3. Therefore, compared to when the welding current is increased to a positive value immediately after the current increase step is performed, the first slope S1 becomes steeper (larger), making it less likely that an arc will break.

[0058] Immediately after the current increasing step, the welding current may be increased to a positive value instead of being decreased to the decreasing current value FI. In this case, the increasing period IPE may be set to 0.95 to 1 times the second ramp period SPE2.

[0059] Furthermore, since the welding current is set to be greater than the third current value I3 during the second slope period SPE2 and the increase period IPE, even if the welding current is set to be less than the third current value I3 during the second peak current application step, the effective value of the welding current during the period when the welding current is negative can be made to approach -1 times the set current value (the third current value I3).

[0060] Here, the period from timing tA to the next timing tE, i.e., the period within one cycle T during which the polarity of the AC voltage applied between the base material W and the tungsten electrode TE is EN polarity, is called the EN (electrode negative) period Ten. Furthermore, the period from timing tE to the next timing tA, i.e., the period within one cycle T during which the polarity of the AC voltage applied between the base material W and the tungsten electrode TE is EP polarity, is called the EP (electrode positive) period Tep. The EN period Ten is set to 90 to 50% of one cycle T, and the EP period Tep is set to 10 to 50% of one cycle T. In the example of FIG. 3, the EN period Ten and the EP period Tep are each set to 50% of one cycle.

[0061] The first ramp period SPE1, each first pulse period PPE1, and each second pulse period PPE2 are set to about 1 / 6 of the EN period Ten. The sum of the decrease period DPE and the rise period RPE is also set to about 1 / 6 of the EN period Ten. Since the frequency of the welding current is set to 10 to 400 Hz, the first ramp period SPE1, each first pulse period PPE1, each second pulse period PPE2, and the sum of the decrease period DPE and the rise period RPE are each 200 μs or more and 15 ms or less.

[0062] The second ramp period SPE2, the third pulse period PPE3, and the fourth pulse period PPE4 are set to about 1 / 4 of the EP period Tep. The sum of the increase period IPE and the fall period FPE is also set to about 1 / 4 of the EP period Tep. Since the frequency of the welding current is set to 10 to 400 Hz, the second ramp period SPE2, the third pulse period PPE3, the fourth pulse period PPE4, and the sum of the increase period IPE and the fall period FPE are each 60 μs or more and 12.5 ms or less.

[0063] The rise period RPE and fall period FPE are set to 160 μs to 620 μs when the frequency is 10 Hz to 600 Hz.

[0064] Therefore, according to this embodiment, the first peak current application step and the first base current application step are performed twice between the time when the current rise step is performed and the time when the welding current is next reduced to a negative value, thereby more effectively increasing the melting rate than when they are performed only once.

[0065] Furthermore, since the second peak current application step and the second base current application step are each executed only once between the execution of the current reduction step and the next time the welding current is increased to a positive value, the third pulse period PPE3 during which the welding current is maintained at the second peak current value P2 can be lengthened compared to when these steps are executed two or more times. This lengthens the period during which cleaning is performed at the second peak current value P2, thereby thoroughly removing oxides from the surface of the base metal W. Even when the EP period Tep is set to a small percentage less than 50% of one cycle T, one third pulse period PPE3 and one fourth pulse period PPE4 can be lengthened compared to when the second peak current application step and the second base current application step are executed two or more times, preventing the third pulse period PPE3 and the fourth pulse period PPE4 from being too short and making control difficult.

[0066] In the above embodiment, each first pulse period PPE1 is set to about 1 / 6 of the EN period Ten, but it may be set to another ratio between 1 / 30 and 1 / 6.

[0067] Similarly, in the above embodiment, each second pulse period PPE2 is set to about 1 / 6 of the EN period Ten, but it may be set to another ratio between 1 / 6 and 3 / 10.

[0068] Furthermore, in the above embodiment, each third pulse period PPE3 is set to about 1 / 4 of the EP period Tep, but it may be set to another ratio between 1 / 20 and 1 / 4.

[0069] Similarly, in the above embodiment, each fourth pulse period PPE4 is set to about 1 / 4 of the EP period Tep, but it may be set to another ratio between 1 / 4 and 9 / 20.

[0070] In the above embodiment, the welding current is set to a common first peak current value P1 in the two first peak current application steps executed in the first pulse current application step, but the welding current may be set to different current values ​​as long as the current values ​​are 1.15 to 1.6 times the set current value.

[0071] Similarly, in the two first base current application steps executed in the first pulse current application step, the welding current is set to a common first base current value B1, but the current values ​​may be different from each other as long as they are between 0.6 and 0.9 times the set current value.

[0072] In the above embodiment, the control device 30 executes both the current rising step and the current falling step, and both the current falling step and the current rising step, but it may execute only the current rising step and the current falling step, without executing the current falling step and the current rising step. Also, it may execute only the current falling step and the current rising step, without executing the current rising step and the current falling step.

[0073] In addition, the control device 30 may execute only one of the steps of increasing the welding current to the start-up current value RI immediately after executing the current decrease step, and decreasing the welding current to the fall-down current value FI after executing the current increase step.

[0074] Furthermore, in the above embodiment, the control device 30 executes the first peak current application step and the first base current application step twice, but may execute them three or more times. [Industrial Applicability]

[0075] The AC arc welding method disclosed herein can reduce working noise while suppressing deterioration in welding efficiency, and is useful as an AC arc welding method in which welding is performed by generating an arc between an electrode and a base metal using an AC welding current. [Explanation of symbols]

[0076] W Base material TE Tungsten Electrode A Arc S1 First slope S2 Second slope S3 Third Slope S4 Fourth Slope I1 First current value (set current value) I2 Second current value I3 Third current value I4 Fourth current value P1 First peak current value B1 First base current value P2 Second peak current value B2 Second base current value RI start-up current value FI Falling Current Value SPE1 1st slope period SPE2 2nd slope period PPE1 First pulse period PPE2 Second pulse period PPE3 Third pulse period PPE4 4th pulse period

Claims

1. An AC arc welding method for welding by generating an arc between an electrode and a base metal using an AC welding current, a current ramp-up step of increasing the welding current at a first gradient from a negative value to a second current value that is 0.6 to 0.9 times a predetermined positive first current value, and then increasing the welding current from the second current value to the first current value at a second gradient that is 60 μA / μs to 600 mA / μs smaller than the first gradient over a first ramp period; a current decreasing step of decreasing the welding current from a positive value at a third gradient to a fourth current value that is 0.6 to 0.9 times a predetermined negative third current value, and then decreasing the welding current from the fourth current value to the third current value at a fourth gradient that is greater than the third gradient and is −60 μA / μs to −600 mA / μs over a second gradient period; executing the current increasing step, and executing a current decreasing step of decreasing the welding current from the first current value at a gradient −1 times the second gradient for a period of 0.35 to 1 times the first gradient period, during a period from the execution of the current increasing step to the next decrease of the welding current to a negative value; performing at least one of: executing the current decreasing step; and, during the period from the execution of the current decreasing step until the next time the welding current is increased to a positive value, executing a current increasing step of increasing the welding current from the third current value at a gradient that is −1 times the fourth gradient for a period of 0.35 to 1 times the second gradient period; executing the current rising step and the current decreasing step, and immediately after executing the current decreasing step, setting the welding current to a rising current value that is 1.0 to 1.65 times the first current value for a period that is 0.05 to 0.65 times the first ramp period, and then decreasing the welding current from the rising current value to a negative value; the current decreasing step and the current increasing step are executed, and immediately after the current increasing step, the welding current is set to a decreasing current value that is 1.0 to 1.65 times the third current value for a period that is 0.05 to 0.65 times the second ramp period, and thereafter the welding current is increased from the decreasing current value to a positive value.

2. An AC arc welding method for welding by generating an arc between an electrode and a base metal using an AC welding current, comprising: a current ramp-up step of increasing the welding current at a first gradient from a negative value to a second current value that is 0.6 to 0.9 times a predetermined positive first current value, and then increasing the welding current from the second current value to the first current value at a second gradient that is 60 μA / μs to 600 mA / μs smaller than the first gradient over a first ramp period; a current decreasing step of decreasing the welding current from a positive value at a third gradient to a fourth current value that is 0.6 to 0.9 times a predetermined negative third current value, and then decreasing the welding current from the fourth current value to the third current value at a fourth gradient that is greater than the third gradient and is −60 μA / μs to −600 mA / μs over a second gradient period; performing the current rise step and alternately performing a first peak current application step of setting the welding current to a current value of 1.15 to 1.6 times the first current value only for a first pulse period, and a first base current application step of setting the welding current to a current value of 0.6 to 0.9 times the first current value only for a second pulse period, during a period from when the current rise step is performed until the welding current is next reduced to a negative value; and applying a second peak current to the welding current within a third pulse period, the second peak current being set to a current value not less than 1.2 times and not less than 1.8 times the third current value, and the second base current being set to a current value not less than 0.6 times and not less than 0.9 times the third current value, during a period from when the current is reduced to when the welding current is next increased to a positive value.

3. An AC arc welding method for welding by generating an arc between an electrode and a base metal using an AC welding current, a first pulse current applying step of alternately applying a first peak current to the welding current to a current value of 1.15 to 1.6 times a predetermined positive set current value only during a first pulse period and a first base current to the welding current to a current value of 0.6 to 0.9 times the set current value only during a second pulse period, the first peak current applying step being repeated two or more times during the period from when the welding current is increased from a negative value to a positive value until when the welding current is decreased to the negative value again; and a second pulse current application step in which the welding current is set to a current value in the range of −1.2 to −1.8 times the set current value only during a third pulse period, and the second peak current application step in which the welding current is set to a current value in the range of −0.6 to −0.9 times the set current value only during a fourth pulse period, are alternately performed once each during the time period from when the welding current is decreased from a positive value to a negative value until when the welding current is increased to the next positive value.

4. 4. The AC arc welding method according to claim 3, Immediately before the welding current is decreased from a positive value to a negative value, the welding current is increased from a current value lower than the set current value to a rise current value that is 1.0 to 1.65 times the set current value; and immediately before the welding current is raised from a negative value to a positive value, changing the welding current from a current value higher than -1 times the set current value to a falling current value that is -1.0 times or less and -1.65 times or more the set current value.

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