AC arc welding method

Abstract

The present disclosure provides an alternating current arc welding method, in which a welding device executes a current rising step and a current falling step. In the current rising step, the welding current is increased from a negative value to a second current value (I2) which is more than 0.6 times and less than 0.9 times of a given positive first current value (I1) at a first slope (S1). Next, the welding current is increased from the second current value (I2) to the first current value (I1) at a second slope (S2) which is more than 60 μA / μs and less than 600 mA / μs and smaller than the first slope (S1). In the current falling step, the welding current is decreased from a positive value to a fourth current value (I4) which is less than 0.6 times and more than 0.9 times of a given negative third current value (I3) at a third slope (S3). Next, the welding current is decreased from the fourth current value (I4) to the third current value (I3) at a fourth slope (S4) which is less than -60 μA / μs and more than -600 mA / μs and larger than the third slope (S3).

Description

Technical Field

[0001] The present disclosure relates to an alternating current arc welding method in which an arc is generated between an electrode and a base material by an alternating welding current for welding. Background Art

[0002] In Patent Document 1, an alternating current arc welding method is disclosed in which an arc is generated between an electrode and a base material by an alternating welding current. In this alternating current arc welding method, by setting the waveform of the welding current to a waveform in which a pulse is superimposed on a rectangular wave alternating current, the directivity of the arc can be maintained even when the time ratio during the negative electrode period is reduced.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent No. 2689752 Gazette Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, in Patent Document 1, since the waveform of the welding current is set to a waveform in which a pulse is superimposed on a rectangular wave alternating current, when the welding current rises from a negative value to a positive value, due to the rapid increase in the welding current, a high operating noise will be generated, and the burden on the operator becomes large. In addition, when the welding current drops from a positive value to a negative value, the same problem will also occur due to the rapid decrease in the welding current.

[0008] In addition, if the waveform of the welding current is set to a sine wave in order to suppress the generation of high operating noise, the melting of the base material becomes slow and the working efficiency deteriorates.

[0009] The present disclosure has been completed in view of this point, and its object is to reduce the operating noise while suppressing the deterioration of the working efficiency of welding.

[0010] Technical Means for Solving the Problems

[0011] The first aspect of the present disclosure is an alternating current arc welding method in which an arc is generated between an electrode and a base material by an alternating welding current, characterized in that at least one of a current increase step and a current decrease step is performed. In the current increase step, the welding current is increased from a negative value to a second current value that is 0.6 times or more and 0.9 times or less of a given positive first current value at a first slope. Next, from this second current value, it is increased to the first current value at a second slope that is 60 μA / μs or more and 600 mA / μs or less and smaller than the first slope over a first inclination period. In the current decrease step, the welding current is decreased from a positive value to a fourth current value that is 0.6 times or less and 0.9 times or more of a given negative third current value at a third slope. Next, from this fourth current value, it is decreased to the third current value at a fourth slope that is -60 μA / μs or less and -600 mA / μs or more and larger than the third slope over a second inclination period.

[0012] According to this aspect, in the case of performing the current increase step, when increasing the welding current from a negative value to the first current value, during the period from when the welding current reaches the second current value to when it reaches the first current value, the welding current is increased at a second slope of 600 mA / μs or less. Therefore, compared with the case of increasing at a slope exceeding 600 mA / μs, the operation noise can be reduced.

[0013] Furthermore, in the case of performing the current increase step, when increasing the welding current from a negative value to the first current value, until the welding current reaches the second current value, the welding current is increased at a first slope that is larger than the second slope. Therefore, compared with the case of increasing at the second slope, the melting of the base material can be accelerated and the operation efficiency can be improved.

[0014] Furthermore, in the case of performing the current increase step, the second current value is set to be 0.6 times or more of the first current value. Therefore, compared with the case of setting the second current value to be less than 0.6 times of the first current value, the melting of the base material can be accelerated, the operation efficiency can be improved, and the period with a small welding current can be shortened, making it less likely to cause arc interruption. In addition, the second current value is set to be 0.9 times or less of the first current value. Therefore, compared with the case of making the second current value greater than 0.9 times of the first current value, the period during which the operation noise becomes low can be extended.

[0015] On the other hand, in the case of performing the current decrease step, when decreasing the welding current from a positive value to the third current value, during the period from when the welding current reaches the fourth current value to when it reaches the third current value, the welding current is decreased at a fourth slope of -600 mA / μs or more. Therefore, compared with the case of decreasing at a slope less than -600 mA / μs, the operation noise can be reduced.

[0016] In addition, in the case of performing the current decrease step, when reducing the welding current from a positive value to the third current value, until the welding current reaches the fourth current value, the welding current is reduced at a third slope smaller than the fourth slope. Therefore, compared with the case of reducing at the fourth slope, it is less likely to cause arc interruption.

[0017] In addition, in the case of performing the current decrease step, the fourth current value is set to be 0.6 times or less of the third current value. Therefore, compared with the case where the fourth current value is greater than 0.6 times of the third current value, the period during which the absolute value of the welding current is small can be shortened, and arc interruption is less likely to occur. In addition, the fourth current value is set to be 0.9 times or more of the third current value. Therefore, compared with the case where the fourth current value is set to be less than 0.9 times of the third current value, the period during which the operation sound becomes low can be extended.

[0018] The second aspect of the present disclosure is an alternating current arc welding method in which an arc is generated between an electrode and a base material by an alternating current welding current, characterized in that a first pulse current application step and a second pulse current application step are performed. In the first pulse current application step, during the period when the welding current rises from a negative value to a positive value and then drops to a negative value, the first peak current application step and the first base current application step are alternately performed two or more times. In the first peak current application step, the welding current is set to be 1.15 times or more and 1.6 times or less of a given positive set current value during the first pulse period. In the first base current application step, the welding current is set to be 0.6 times or more and 0.9 times or less of the set current value during the second pulse period. In the second pulse current application step, during the period when the welding current drops from a positive value to a negative value and then rises to a positive value, the second peak current application step and the second base current application step are each alternately performed once. In the second peak current application step, the welding current is set to be -1.2 times or less and -1.8 times or more of the set current value during the third pulse period. In the second base current application step, the welding current is set to be -0.6 times or less and -0.9 times or more of the set current value during the fourth pulse period.

[0019] According to this method, in the first peak current application step, more heat for melting the filler wire is imparted to the filler wire, and the output directivity of the arc is improved by increasing the electromagnetic constriction force, which can promote the smooth transfer of molten droplets. Therefore, compared with the case where the welding current is always set to the set current value, the melting speed can be increased. In addition, even if the welding current is made greater than the set current value in the first peak current application step, since the welding current is made less than the set current value in the first base current application step, the effective value of the welding current during the execution of the first pulse current application step can be made close to the set current value.

[0020] In addition, in the case of executing the second pulse current application step, in the second peak current application step, the output directivity of the arc is improved by increasing the electromagnetic constriction force, and the cleaning effect can be promoted compared with the case where the welding current is always set to the set current value. In addition, even if the welding current is made less than -1 times the set current value in the second peak current application step, since the welding current is made greater than -1 times the set current value in the second base current application step, the effective value of the welding current during the execution of the second pulse current application step can be made close to -1 times the set current value.

[0021] In addition, the first peak current application step and the first base current application step are executed more than twice. Therefore, compared with the case of executing only once, the melting speed can be increased more effectively.

[0022] In addition, the second peak current application step and the second base current application step are each executed only once. Therefore, compared with the case of executing more than twice, the third pulse period can be extended. Thus, the period of cleaning with a current value smaller than -1 times the set current value can be extended, and thus the oxides on the surface of the base material can be reliably removed. In addition, even when the period during which the welding current is set to a negative value is set to a small ratio of less than 50% of one cycle, compared with the case where the second peak current application step and the second base current application step are each executed more than twice, the third pulse period and the fourth pulse period can be extended, and thus it is also possible to prevent the third pulse period and the fourth pulse period from being too short to be controlled.

[0023] Advantages of the Invention

[0024] According to the present disclosure, it is possible to reduce the operation noise while suppressing the deterioration of the welding operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a diagram showing a schematic configuration of a welding apparatus.

[0026] Figure 2 is a circuit diagram of a welding power source.

[0027] Figure 3 It is a diagram showing the waveform of the welding current during arc welding. Detailed implementation

[0028] Hereinafter, embodiments of the present disclosure will be described based on the drawings.

[0029] Figure 1 The welding device 1 is shown. The welding device 1 includes a torch 10 and a welding power source 20. The welding device 1 is an AC TIG welding device in which the torch 10 is a non-consumable electrode type torch.

[0030] The torch 10 has a nozzle 11 that ejects a shielding gas SG supplied from a gas supply device (not shown). Inside the nozzle 11, a substantially cylindrical chuck 12 is disposed along the ejection direction of the nozzle 11. Inside the chuck 12, a rod-shaped tungsten electrode TE is fixed.

[0031] The welding power source 20 generates an arc A by applying an alternating voltage between the tungsten electrode TE of the torch 10 and the base material W.

[0032] An operator generates an arc A between the tungsten electrode TE and the base material W through the welding device 1, thereby forming a molten pool P in the base material W, and a weld bead can be formed by inserting a filler wire R into the molten pool P.

[0033] Specifically, as Figure 2 shown, the 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.

[0034] The first rectifying and smoothing circuit 21 converts the input AC power input from the commercial power supply 2 into DC power and outputs it.

[0035] The first inverter circuit 22 is, for example, a single-phase full-bridge type PWM control inverter and includes four switching elements (not shown). The first inverter circuit 22 converts the DC power output by the first rectifying and smoothing circuit 21 into AC power and outputs it by switching these four switching elements according to a switching signal SG1 output by the control device 30. Here, the output voltage of the first inverter circuit 22 is set as the first AC voltage. In addition, as the first inverter circuit 22, an inverter circuit having another structure such as a half-bridge type inverter can also be used.

[0036] The first transformer 23 changes the first AC voltage output from the first inverter circuit 22 to a second AC voltage and outputs it. The first transformer 23 has a first primary coil 23a and a first secondary coil 23b. The first AC voltage output from 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.

[0037] The second rectifying and smoothing circuit 24 converts the second AC voltage output from the first transformer 23 into a first DC voltage and outputs it from the positive output terminal 24a and the negative output terminal 24b. The second rectifying and smoothing circuit 24 is a diode bridge circuit including four diodes 24c.

[0038] The second inverter circuit 27 is a single-phase half-bridge type inverter circuit. The second inverter circuit 27 includes first and second input terminals 271, 272, and an upper-branch switching element 273 and a lower-branch switching element 274 that are connected in series between the first and second input terminals 271, 272. The polarity switching signal SG2 output from the control device 30 is input to the upper-branch switching element 273. On the other hand, a signal obtained by inverting the polarity switching signal SG2 is input to the lower-branch switching element 274. The 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 the first reactor 25. The 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 the second reactor 26. The output terminal 275 of the second inverter circuit 27 is connected to the base material W.

[0039] Therefore, in a state where the upper-branch switching element 273 is turned on and the lower-branch switching element 274 is turned off, the second inverter circuit 27 makes the base material W have a higher potential than the tungsten electrode TE. On the other hand, in a state where the upper-branch switching element 273 is turned off and the lower-branch switching element 274 is turned on, the second inverter circuit 27 makes the base material W have a lower potential than the tungsten electrode TE. If a pulse signal that is switched between a high level and a low level at a given period 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 material W and the tungsten electrode TE to an EN (electrode negative) polarity in which the tungsten electrode TE has a lower potential than the base material W and an EP (electrode positive) polarity in which the tungsten electrode TE has a higher potential than the base material W. As a result, an alternating welding current flows between the base material W and the tungsten electrode TE.

[0040] The control device 30 controls the welding current I. For the control device 30, a given positive first current value I1 is input by the user using an input unit (not shown) and set as the set current value. 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 outputs a polarity switching signal SG2 for switching the polarity of the alternating voltage applied between the electrode TE and the base material W. The control of the welding current I by the control device 30 is performed by the output of the switching signal SG1 and the polarity switching signal SG2. The frequency of the polarity switching signal SG2, that is, the frequency of the welding current, is set to be 10 Hz or more and 400 Hz or less.

[0041] Hereinafter, with reference to Figure 3 the control of the welding current for one cycle T by the control device 30 when welding is performed by the alternating current arc welding method according to the embodiment of the present disclosure will be described.

[0042] First, at time tA, the control device 30 executes the following current rising step, that is, the welding current is increased from a negative value to a second current value I2 which is (1 - α) times the positive first current value I1 at a first slope S1 of 1.7 A / μs, and then, from this second current value I2, it is increased to the first current value I1 through a first inclination period SPE1 at a second slope S2 which is more than 60 μA / μs and less than 600 mA / μs and smaller than the first slope S1. The α is set to be 0.1 or more and 0.4 or less. Therefore, the second current value I2 becomes 0.6 times or more and 0.9 times or less of the first current value I1.

[0043] In this way, in the current rising step, the welding current is increased from the second current value I2 to the first current value I1 at the second slope S2 of 600 mA / μs or less. Therefore, compared with the case where the slope is increased by more than 600 mA / μs, the operation noise can be reduced and a softer feeling can be brought to the operator.

[0044] In addition, the second slope S2 is set to be 60 μA / μs or more. Therefore, compared with the case where it is set to be less than 60 μA / μs, the melting of the base material W can be accelerated.

[0045] In addition, in the current rising step, the welding current is increased from a negative value to the second current value I2 at the first slope S1 of 1 A / μs or more. Therefore, compared with the case where it is increased at the second slope S2, the melting of the base material W can be accelerated and the operation efficiency can be improved.

[0046] In addition, since the second current value I2 is set to be 0.6 times or more of the first current value I1, compared with the case where the second current value I2 is set to be less than 0.6 times of the first current value I1, the melting of the base material W can be accelerated, the working efficiency can be improved, the period with a small welding current can be shortened, and arc interruption is less likely to occur. In addition, since the second current value I2 is set to be 0.9 times or less of the first current value I1, compared with the case where the second current value I2 is made greater than 0.9 times of the first current value I1, the period during which the working sound becomes low can be extended.

[0047] Next, from time tB, the control device 30 executes the following first pulsed current application step, that is, the first peak current application step and the first base current application step are alternately executed 2 times in sequence. In the first peak current application step, the welding current is increased to the first peak current value P1 which is (1 + α / 2 + β) times of the first current value I1 and is the first peak current value P1 during the first pulse period PPE1. In the first base current application step, the welding current is decreased to the first base current value B1 which is (1 - β) times of the first current value I1 and is the first base current value B1 during the second pulse period PPE2. The above β is set to be 0.1 or more and 0.4 or less. Therefore, the first peak current value P1 becomes 1.15 times or more and 1.6 times or less of the first current value I1, and the first base current value B1 becomes 0.6 times or more and 0.9 times or less of the first current value I1.

[0048] In the above first peak current application step, by setting the welding current to the first peak current value P1 which is larger than the first current value I1, more heat for melting the filler wire R can be imparted to the filler wire R, and the output directivity of the arc A can be improved by increasing the electromagnetic constriction force, promoting the smooth transfer of the molten droplets. Therefore, compared with the case where the welding current is always set to the set current value (the first current value I1), the melting speed can be increased. In addition, in the first base current application step, the welding current is set to the first base current value B1 which is smaller than the first current value I1, so that the effective value of the welding current during the execution of the first pulsed current application step can be made close to the set current value.

[0049] In addition, since the above β is set to be 0.1 or more, compared with the case where it is set to be less than 0.1, the melting speed can be effectively increased. In addition, since the above β is set to be 0.4 or less, compared with the case where it is set to be greater than 0.4, it is possible to suppress the arc A from becoming too strong in the first peak current application step, slow down the self-consumption of the tungsten electrode TE, and reduce the burden on the operator.

[0050] Then, at time tC, the control device 30 increases the welding current from the first base current value B1 to the first current value I1. Then, the control device 30 executes the following current reduction step, that is, the welding current is reduced from the first current value I1 at a slope of -1 times the second slope S2, that is, at a slope -S2 of not less than -60 μA / μs and not more than -600 mA / μs, within a reduction period DPE that is not less than 0.35 times and not more than 0.95 times the first slope period SPE1. Next, at time tD immediately after the control device 30 executes the current reduction step, the welding current is a positive rising current value RI that is not less than 1.0 times and not more than 1.65 times the first current value I1 within a rising period RPE that is not less than 0.05 times and not more than 0.65 times the first slope period SPE1.

[0051] In the first slope period SPE1 and the reduction period DPE, the welding current is made less than the first current value I1. Therefore, even if the welding current is made greater than the first current value I1 in the first peak current application step, the effective value of the welding current within the period when the welding current is positive can be made close to the set current value (the first current value I1).

[0052] Then, at time tE, the control device 30 decreases the welding current. Specifically, the control device 30 executes the following current decrease step, that is, it decreases from the positive rising current value RI to the fourth current value I4 that is (1 - γ) times the negative third current value I3 at the third slope S3 of -1.7 A / μs. Next, from this fourth current value I4, it decreases to the third current value I3 through the second slope period SPE2 at a fourth slope S4 that is greater than the third slope S3 and is not less than -60 μA / μs and not more than -600 mA / μs. The third current value I3 is a value that is -1 times the first current value I1 (set current value). The above γ is set to be not less than 0.1 and not more than 0.4. Therefore, the fourth current value I4 becomes not more than 0.6 times and not less than 0.9 times the third current value I3.

[0053] In this way, the current reduction step is executed during the period from when the current increase step is executed until the welding current is next decreased to a negative value. Immediately before the welding current is decreased from a positive value to a negative value, the welding current temporarily rises to the rising current value RI.

[0054] In this way, immediately after the current reduction step is executed, the welding current is temporarily increased from a current value lower than the set current value (the first current value I1) to a rising current value RI that is not less than 1.0 times and not more than 1.65 times the first current value I1. Therefore, compared with the case where the welding current is decreased to a negative value immediately after the current reduction step is executed, the third slope S3 becomes steeper (smaller), and arc interruption is less likely to occur.

[0055] Alternatively, it can be set such that, immediately after the current reduction step is performed, the welding current is not temporarily increased to the rising current value RI, but instead the welding current is decreased to a negative value. In this case, the reduction period DPE can also be set to be 0.95 times or more and 1 time or less of the first slope period SPE1.

[0056] In addition, in the current decrease step, the welding current is decreased from the fourth current value I4 to the third current value I3 at a fourth slope S4 of -600 mA / μs or more. Therefore, compared with the case where the slope is increased at less than -600 mA / μs, the operating sound can be reduced, giving a softer feeling to the operator.

[0057] In addition, the fourth slope S4 is set to -60 μA / μs or less. Therefore, compared with the case where the slope is set to more than -60 μA / μs, arc interruption is less likely to occur.

[0058] In addition, in the current decrease step, the welding current is decreased from a positive value to the fourth current value I4 at a third slope S3 of -1 A / μs or less. Therefore, compared with the case where the welding current is decreased at the fourth slope S4, arc interruption is less likely to occur.

[0059] In addition, the fourth current value I4 is set to be 0.6 times or less and 0.9 times or more of the third current value I3. Therefore, compared with the case where the fourth current value I4 is made greater than 0.6 times the third current value I3, the period during which the absolute value of the welding current is small can be shortened, and arc interruption is less likely to occur. In addition, compared with the case where the fourth current value I4 is set to less than 0.9 times the third current value I3, the period during which the operating sound becomes low can be extended.

[0060] Next, from time tF, the control device 30 executes the following second pulse current application step, that is, the second peak current application step and the second base current application step are alternately executed once in sequence. In the second peak current application step, the welding current is decreased to a second peak current value P2 that is (1 + γ + qiao) times the third current value I3 and is the second peak current value P2 within the third pulse period PPE3. In the second base current application step, the welding current is increased to a second base current value B2 that is (1 - qiao) times the third current value I3 and is the second base current value B2 within the fourth pulse period PPE4. The above qiao is set to 0.1 to 0.4. Therefore, the second peak current value P2 becomes 1.2 times or less and 1.8 times or more of the third current value I3, that is, becomes -1.2 times or less and -1.8 times or more of the set current value (the first current value I1). The second base current value B2 becomes 0.6 times or less and 0.9 times or more of the third current value I3, that is, becomes -0.6 times or less and -0.9 times or more of the set current value (the first current value I1).

[0061] In the above-described second peak current application step, the welding current is set to a second peak current value P2 that is smaller than the third current value I3. As a result, the output directivity of the arc A can be improved by increasing the electromagnetic constriction force. Therefore, compared with the case where the welding current is always set to the third current value I3 ( - 1 times the set current value), the cleaning effect can be promoted. The second peak current value P2 is set independently of the first peak current value P1 according to the degree of the required cleaning effect. Further, in the second base current application step, the welding current is set to a second base current value B2 that is larger than the third current value I3. Therefore, the effective value of the welding current during the execution of the second pulse current application step can be made close to - 1 times the set current value.

[0062] Then, at time tG, the control device 30 causes the welding current to decrease from the second base current value B2 to the third current value I3. Then, the control device 30 executes the following current increase step, that is, the welding current is increased from the third current value I3 at a slope that is - 1 times the fourth slope S4, i.e., at a slope of 60 μA / μs or more and 600 mA / μs or less, within an increase period IPE that is 0.35 times or more and 0.95 times or less of the second slope period SPE2. Next, at time tH immediately after the control device 30 executes the current increase step, the welding current is set to a decrease current value FI that is 1.0 times or less and 1.65 times or more of the third current value I3 within a decrease period FPE that is 0.05 times or more and 0.65 times or less of the second slope period SPE2, and then the operation starting from time tA is repeated. That is, the control device 30 causes the welding current to rise from the decrease current value FI to a positive second current value I2 at a first slope S1 of 1.7 A / μs.

[0063] In this way, within the period from when the current decrease step is executed until the welding current is next increased to a positive value, the current increase step is executed, and immediately before the welding current is increased from a negative value to a positive value, the welding current is temporarily decreased to the decrease current value FI.

[0064] In this way, immediately after the current increase step is executed, the welding current is temporarily decreased from a current value higher than - 1 times the set current value to a decrease current value FI that is 1.0 times or less and 1.65 times or more of the third current value I3. Therefore, compared with the case where the welding current is increased to a positive value immediately after the current increase step is executed, the first slope S1 becomes steeper (larger), and arc interruption is less likely to occur.

[0065] Alternatively, it is also possible that, immediately after the current increase step is executed, instead of temporarily decreasing the welding current to the decrease current value FI, the welding current is increased to a positive value. In this case, the increase period IPE can also be set to 0.95 times or more and 1 time or less of the second slope period SPE2.

[0066] In addition, during the second slope period SPE2 and the increasing period IPE, the welding current is made greater than the third current value I3. Therefore, even if the welding current is made less than the third current value I3 in 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 close to -1 times the set current value (the third current value I3).

[0067] Here, the period from time tA to the next time tE, that is, the period during which the polarity of the alternating voltage applied between the base material W and the tungsten electrode TE in one cycle T becomes the EN polarity is referred to as the EN (electrode negative) period Ten. In addition, the period from time tE to the next time tA, that is, the period during which the polarity of the alternating voltage applied between the base material W and the tungsten electrode TE in one cycle T becomes the EP polarity is referred to as 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 Figure 3 the example of, the EN period Ten and the EP period Tep are each set to 50% of one cycle.

[0068] The first slope period SPE1, each first pulse period PPE1, and each second pulse period PPE2 are set to approximately 1 / 6 of the EN period Ten. The sum of the decreasing period DPE and the rising period RPE is also set to approximately 1 / 6 of the EN period Ten. The frequency of the welding current is set to 10 to 400 Hz, so the sum of the first slope period SPE1, each first pulse period PPE1, each second pulse period PPE2, the decreasing period DPE, and the rising period RPE each becomes 200 μs or more and 15 ms or less.

[0069] The second slope period SPE2, the third pulse period PPE3, and the fourth pulse period PPE4 are set to approximately 1 / 4 of the EP period Tep. The sum of the increasing period IPE and the falling period FPE is also set to approximately 1 / 4 of the EP period Tep. The frequency of the welding current is set to 10 to 400 Hz, so the sum of the second slope period SPE2, the third pulse period PPE3, the fourth pulse period PPE4, the increasing period IPE, and the falling period FPE each becomes 60 μs or more and 12.5 ms or less.

[0070] In the case where the frequency is 10 Hz to 600 Hz, the rising period RPE and the falling period FPE are set to 160 μs to 620 μs.

[0071] Therefore, according to the present embodiment, during the period from after the current rising step to the next time when the welding current is decreased to a negative value, the first peak current application step and the first base current application step are executed twice. Therefore, compared with the case of executing only once, the melting speed can be more effectively increased.

[0072] In addition, during the period from after the execution of the current decrease step to the subsequent increase of the welding current to a positive value, the second peak current application step and the second base current application step are each executed only once. Therefore, compared with the case of executing them more than twice, the third pulse period PPE3 during which the welding current is maintained at the second peak current value P2 can be extended. As a result, the period of cleaning with the second peak current value P2 can be extended, and thus the oxide on the surface of the base material W can be reliably removed. In addition, even when the EP period Tep is set to a small ratio less than 50% of one cycle T, compared with the case of executing the second peak current application step and the second base current application step more than twice, one third pulse period PPE3 and one fourth pulse period PPE4 can be extended. Therefore, it is also possible to prevent the third pulse period PPE3 and the fourth pulse period PPE4 from being too short to be controlled.

[0073] In addition, in the above-described embodiment, each first pulse period PPE1 is set to approximately 1 / 6 of the EN period Ten, but it may also be set to other ratios of 1 / 30 or more and 1 / 6 or less.

[0074] Similarly, in the above-described embodiment, each second pulse period PPE2 is set to approximately 1 / 6 of the EN period Ten, but it may also be set to other ratios of 1 / 6 or more and 3 / 10 or less.

[0075] In addition, in the above-described embodiment, each third pulse period PPE3 is set to approximately 1 / 4 of the EP period Tep, but it may also be set to other ratios of 1 / 20 or more and 1 / 4 or less.

[0076] Similarly, in the above-described embodiment, each fourth pulse period PPE4 is set to approximately 1 / 4 of the EP period Tep, but it may also be set to other ratios of 1 / 4 or more and 9 / 20 or less.

[0077] In addition, in the above-described embodiment, in the two first peak current application steps executed in the first pulse current application step, the welding current is set to the same first peak current value P1, but it may be a current value of 1.15 times or more and 1.6 times or less of the set current value, or may be set to different current values from each other.

[0078] Similarly, in the two first base current application steps executed in the first pulse current application step, the welding current is set to the same first base current value B1, but it may be a current value of 0.6 times or more and 0.9 times or less of the set current value, or may be set to different current values from each other.

[0079] In addition, in the above-described embodiment, the control device 30 executes both the current increase step and the current decrease step, as well as both the current reduction step and the current increase step. However, it is also possible to execute only the current increase step and the current reduction step without executing the current decrease step and the current increase step. In addition, it is also possible to execute only the current decrease step and the current increase step without executing the current increase step and the current reduction step.

[0080] In addition, it is also possible that the control device 30 executes only either the step of increasing the welding current to the rising current value RI immediately after executing the current reduction step or the step of decreasing the welding current to the falling current value FI after executing the current increase step.

[0081] In addition, in the above-described embodiment, the control device 30 executes the first peak current application step and the first base current application step twice, but it is also possible to execute them three or more times.

[0082] Industrial Applicability

[0083] PA228633D

[0084] The alternating current arc welding method of the present disclosure can reduce the operation noise while suppressing the deterioration of the welding operation efficiency, and is useful as an alternating current arc welding method for generating an arc between an electrode and a base material by an alternating welding current.

[0085] Reference Signs

[0086] W: Base material;

[0087] TE: Tungsten electrode;

[0088] A: Arc;

[0089] S1: First slope;

[0090] S2: Second slope;

[0091] S3: Third slope;

[0092] S4: Fourth slope;

[0093] I1: First current value (set current value);

[0094] I2: Second current value;

[0095] I3: Third current value;

[0096] I4: Fourth current value;

[0097] P1: First peak current value;

[0098] B1: First base current value;

[0099] P2: The second peak current value;

[0100] B2: The second base current value;

[0101] RI: The rising current value;

[0102] FI: The falling current value;

[0103] SPE1: The first slope period;

[0104] SPE2: The second slope period;

[0105] PPE1: The first pulse period;

[0106] PPE2: The second pulse period;

[0107] PPE3: The third pulse period;

[0108] PPE4: The fourth pulse period.

Claims

1. An alternating current arc welding method, which performs welding by generating an arc between an electrode and a base material with an alternating welding current, and the alternating current arc welding method performs at least one of a current increasing step and a current decreasing step. In the current increasing step, the welding current is increased from a negative value to a second current value that is more than 0.6 times and less than 0.9 times a given positive first current value at a first slope. Next, from this second current value, it is increased to the first current value through a first inclination period at a second slope that is more than 60 μA / μs and less than 600 mA / μs and smaller than the first slope. In the current decreasing step, the welding current is decreased from a positive value to a fourth current value that is less than 0.6 times and more than 0.9 times a given negative third current value at a third slope. Next, from this fourth current value, it is decreased to the third current value through a second inclination period at a fourth slope that is less than -60 μA / μs and more than -600 mA / μs and larger than the third slope. The alternating current arc welding method performs at least one of the following: Performs the current increasing step, and alternately performs a first peak current application step and a first base current application step during the period from the execution of the current increasing step until the welding current is next decreased to a negative value. In the first peak current application step, the welding current is a current value that is more than 1.15 times and less than 1.6 times the first current value during a first pulse period. In the first base current application step, the welding current is a current value that is more than 0.6 times and less than 0.9 times the first current value during a second pulse period. Performs the current decreasing step, and alternately performs a second peak current application step and a second base current application step during the period from the execution of the current decreasing step until the welding current is next increased to a positive value. In the second peak current application step, the welding current is a current value that is less than 1.2 times and more than 1.8 times the third current value during a third pulse period. In the second base current application step, the welding current is a current value that is less than 0.6 times and more than 0.9 times the third current value during a fourth pulse period.

2. The alternating current arc welding method according to claim 1, wherein, it includes at least one of the following: Performs the current increasing step, and performs a current decreasing step during the period from the execution of this current increasing step until the welding current is next decreased to a negative value. In this current decreasing step, the welding current is decreased from the first current value at a slope that is -1 times the second slope during a period that is more than 0.35 times and less than 1 time the first inclination period. Perform the current decrease step, and perform a current increase step after performing the current decrease step and until the welding current next rises to a positive value. In this current increase step, increase the welding current from the third current value at a slope that is -1 times the fourth slope during a period that is 0.35 times or more and 1 time or less the second slope period.

3. The AC arc welding method according to claim 2, wherein, includes at least one of the following: Perform the current increase step and the current decrease step. Immediately after performing the current decrease step, make the welding current an increasing current value that is 1.0 times or more and 1.65 times or less the first current value during a period that is 0.05 times or more and 0.65 times or less the first slope period, and then decrease from this increasing current value to a negative value; Perform the current decrease step and the current increase step. Immediately after performing the current increase step, make the welding current a decreasing current value that is 1.0 times or less and 1.65 times or more the third current value during a period that is 0.05 times or more and 0.65 times or less the second slope period, and then increase from this decreasing current value to a positive value.

4. An AC arc welding method that performs welding by generating an arc between an electrode and a base material with an alternating current welding current. The AC arc welding method performs a first pulse current application step and a second pulse current application step. In the first pulse current application step, during the period in which the welding current rises from a negative value to a positive value and then decreases to a negative value, alternately perform the first peak current application step and the first base current application step two or more times. In the first peak current application step, make the welding current a current value that is 1.15 times or more and 1.6 times or less a given positive set current value during the first pulse period. In the first base current application step, make the welding current a current value that is 0.6 times or more and 0.9 times or less the set current value during the second pulse period. In the second pulse current application step, during the period in which the welding current decreases from a positive value to a negative value and then rises to a positive value, perform the second peak current application step and the second base current application step alternately once each. In the second peak current application step, make the welding current a current value that is -1.2 times or less and -1.8 times or more the set current value during the third pulse period. In the second base current application step, make the welding current a current value that is -0.6 times or less and -0.9 times or more the set current value during the fourth pulse period.

5. The AC arc welding method according to claim 4, wherein, includes at least one of the following: Before about to decrease from a positive value to a negative value, set the welding current from a current value lower than the set current value to an increasing current value that is 1.0 times or more and 1.65 times or less the set current value; Before the welding current is about to rise from a negative value to a positive value, the welding current is set to a decreasing current value that is less than or equal to -1.0 times and greater than or equal to -1.65 times the set current value, from a current value that is higher than -1 times the set current value.

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