Power source, welding system, and control method

Abstract

To achieve excellent robustness in feeding control welding.SOLUTION: A power source having a function of performing feeding control to alternately switch feeding speed between a forward feeding period and a reverse feeding period includes a waveform control table linear arithmetic section. The waveform control table linear arithmetic section includes a condition related to at least welding current as a condition to be determined for each prefixed setting condition. When a wire position phase which has the position of a welding wire as a reference when switching from the reverse feeding period to the forward feeding period is defined as 0deg as the condition related to the welding current, the power source has a table which is set so that an average value I 90 to 180 deg_ave of the welding current in periods T90 to 180 deg when the wire position phase is 90 deg to 180 deg is larger than a set welding current value Iset and an average value I 180 to 270 deg_ave of the welding current in periods T180 to 270 deg when the wire position phase is 180 deg to 270 deg is smaller than the set welding current value Iset.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a power supply, a welding system and a control method. [Background technology]

[0002] Fillet welding is one of the construction methods used in gas shielded arc welding, and is used in a variety of industries, including welding overlapping thin steel plates (hereinafter also referred to as "lap fillet welding") and welding steel plates perpendicular to each other in a T-shape. In fillet welding, the accuracy of the steel plate fixing, workability, and assembly accuracy can cause deviations in the welding target position and gaps (gaps) between the steel plates. Due to these deviations in the target position and the presence of gaps, there have traditionally been problems such as poor bridging due to burn-through that falls into the gap and poor bead shape.

[0003] In order to solve the above problems, for example, Patent Document 1 discloses a wire for MAG welding of thin steel plates containing, by mass%, C: 0.04-0.15%, Si: 0.75-1.00%, Mn: 1.00-2.00%, Cr: 0.35-0.80%, with the remainder being Fe and unavoidable impurities.

[0004] Patent Document 2 discloses a gas-shielded arc welding method for thin steel plate having a thickness of 0.5 to 1.2 mm, which uses a wire having a wire diameter of 0.5 to 0.9 mm and containing, by mass, C: 0.02 to 0.10%, Si: 0.7 to 2.0%, Mn: 0.5 to 3.0%, P≦0.020%, S: 0.005 to 0.020%, with the balance being Fe and unavoidable impurities, and applies pulses with a peak current (Ip): 300 to 450 A, a base current (Ib): 20 to 100 A, and where the relationship between the peak current (Ip) and the peak time (Tp) satisfies a predetermined formula (1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-170970 A [Patent Document 2] JP 2001-321946 A Summary of the Invention [Problem to be solved by the invention]

[0006] As disclosed in Patent Document 1 and Patent Document 2, conventionally, MAG welding and pulse MAG welding have been used to widen the bead width of welding. However, in recent years, the use of feed control welding, which has been increasing due to the advantages of welding workability such as reduced spatter, has not been able to solve the above problem. Feed control welding is a method of welding by alternately switching the feed speed of the welding wire between a forward feed period and a reverse feed period. Generally, it is based on a short circuit transition that generates a short circuit period and an arc period, so it is suitable for low heat input welding. However, in welding where the welding target position is shifted or a gap occurs between the steel plates, the penetration is shallow and the bead width does not increase, so that poor bead shape and burn through into the gap are likely to occur. In particular, the larger the gap or the shift in the welding target position is, the more prominent the problems of poor bead shape and bridging become, and it can be said that the robustness is very poor. Therefore, in feed control welding, which has excellent welding workability, robustness equivalent to or greater than that of conventional MAG welding and pulse MAG welding is desired.

[0007] Therefore, an object of the present invention is to provide a power source, a welding system, and a control method that can achieve excellent robustness in feed control welding. [Means for solving the problem]

[0008] The present invention comprises the following configurations. (1) A power source having a function of performing feed control to alternately switch the feed speed between a forward feed period and a reverse feed period, The power supply includes a waveform control table linear calculation unit, the waveform control table linear calculation unit includes at least a condition related to a welding current as a condition to be determined for each of the predetermined setting conditions, The condition relating to the welding current is When the wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, the average value I90-180deg_ave of the welding current in a period T90-180deg in which the wire position phase is 90deg-180deg is greater than the set welding current value Iset, and, A power source comprising at least a table in which an average value I180-270deg_ave of the welding current in a period T180-270deg in which the wire position phase is 180deg-270deg is set to be smaller than a set welding current value Iset.

[0009] (2) A welding system having a feed control function for alternately switching a feed speed between a forward feed period and a reverse feed period, The welding system includes a waveform control table linear calculation unit, the waveform control table linear calculation unit includes at least a condition related to a welding current as a condition to be determined for each of the predetermined setting conditions, The condition relating to the welding current is When the wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, the average value I90-180deg_ave of the welding current in a period T90-180deg in which the wire position phase is 90deg-180deg is greater than the set welding current value Iset, and, A welding system comprising at least a table in which an average value I180-270deg_ave of the welding current in a period T180-270deg in which the wire position phase is 180deg-270deg is set to be smaller than a set welding current value Iset.

[0010] (3) A control method using a power source having a function of performing feed control to alternately switch the feed speed between a forward feed period and a reverse feed period, The power supply includes a waveform control table linear calculation unit, the waveform control table linear calculation unit includes at least a condition related to a welding current as a condition to be determined for each of the predetermined setting conditions, The condition relating to the welding current is When the wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, the average value I90-180deg_ave of the welding current in a period T90-180deg in which the wire position phase is 90deg-180deg is greater than the set welding current value Iset, and, A control method comprising: at least a table in which an average value I180-270deg_ave of the welding current in a period T180-270deg in which the wire position phase is 180deg-270deg is set to be smaller than a set welding current value Iset. Effect of the Invention

[0011] According to the present invention, excellent robustness can be achieved in feed control welding. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a welding system according to this embodiment. [Diagram 2] FIG. 2 is a block diagram showing a schematic configuration relating to control of a welding power source, a welding control device, and a servo amplifier in this embodiment. [Diagram 3] FIG. 3 is a graph illustrating the relationship between the wire feed speed, the wire tip position, and the current detection signal in this embodiment. [Figure 4] FIG. 4 is a diagram showing the compositions of two wires used in the examples. [Diagram 5]FIG. 5 is a diagram showing two welding methods used in the examples. [Figure 6] FIG. 6 is a graph showing the welding current and the wire feed speed when the wire feed control method A is used as the welding method. [Figure 7] FIG. 7 is a graph showing the welding current and the wire feed speed when wire feed control method B is used as the welding method. [Figure 8] FIG. 8 is a diagram showing welding conditions and actual measurement data when feed control method A, feed control method B, and pulse MAG welding as a comparative example are respectively used. [Figure 9A] FIG. 9A is a diagram showing the results of the target deviation test based on the welding conditions and the measured data in the case of Test No. 1. [Figure 9B] FIG. 9B is a diagram showing the results of the misalignment test based on the welding conditions and the measured data in the case of Test No. 2. [Figure 9C] FIG. 9C is a diagram showing the results of the misalignment test based on the welding conditions and the measured data in the case of Test No. 3. [Figure 9D] FIG. 9D is a diagram showing the results of the misalignment test based on the welding conditions and the measured data in the case of Test No. 4. [Figure 9E] FIG. 9E is a diagram showing the results of the misalignment test based on the welding conditions and the measured data in the case of Test No. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of a power source, a welding system, and a control method according to the present invention will be described in detail with reference to the drawings. Note that this embodiment is an example of a case where a welding robot is used, and the power source, the welding system, and the control method according to the present invention are not limited to the configuration of this embodiment. For example, an automatic welding device using a cart instead of a welding robot body may be applied, or a portable small welding robot may be applied.

[0014] The feed control method may be of a type in which the feed speed of the welding wire is alternately switched between a forward feed period and a reverse feed period, and welding is performed based on a short circuit transition form that generates a short circuit period and an arc period (hereinafter, also referred to as a "short circuit type feed control method"), or of a type in which the feed speed of the welding wire is alternately switched between a forward feed period and a reverse feed period, and welding is performed based on a globule transition form that suppresses the occurrence of a short circuit period (hereinafter, also referred to as a "short circuit suppression type feed control method"). There is no particular restriction on the welding method of the present invention, but in this embodiment, the system configuration of the short circuit suppression type feed control method will be described as an example. Furthermore, in this embodiment, lap fillet welding will be described as an example of fillet welding.

[0015] 1 is a schematic diagram showing an example of the configuration of a welding system according to this embodiment. Welding system 50 includes welding robot 110, welding control device 120, welding power source 140, controller 150, push motor 180 that feeds welding wire 100, servo motor 170, servo amplifier 160 that controls servo motor 170, and wire buffer 190. Push motor 180 feeds welding wire 100.

[0016] Welding power source 140 is connected to welding robot 110 via a positive power cable (not shown) so as to pass current through welding wire 100, which is a consumable electrode, and is connected to workpiece (hereinafter also referred to as "base material") 200 via a negative power cable (not shown). This connection is for the case where welding is performed with reverse polarity; when welding is performed with positive polarity, the polarity of welding power source 140 can be reversed.

[0017] In addition, the welding power source 140 and the push motor 180 for feeding the welding wire 100 are connected by a signal line, so that the feed speed of the welding wire can be controlled. In the feed control of this embodiment, the push motor 180 rotates only in the forward direction, and the servo motor 170, which will be described later, is switched between the forward and reverse directions.

[0018] The welding robot 110 is equipped with a welding torch 111 as an end effector. The welding torch 111 has an energization mechanism, i.e., a welding tip, that energizes the welding wire 100. An arc is generated from the tip of the welding wire 100 when energized from the welding tip, and the generated heat welds the workpiece 200 that is the object of welding. The welding tip is also generally referred to as a contact tip.

[0019] The welding torch 111 includes a shielding gas nozzle that is a mechanism for ejecting the shielding gas. The shielding gas is not particularly limited, but in view of the characteristics of the control used in this embodiment, it is preferable that the gas composition has a globular transition form, and specifically, it is preferable that at least one gas among carbon dioxide gas, nitrogen gas, hydrogen gas, and oxygen gas, which have a high potential gradient, is included. In addition, from the viewpoint of versatility, in the case of a mixed gas with argon gas (hereinafter also referred to as "Ar gas"), a system in which at least 10% by volume of carbon dioxide gas is mixed is more preferable, a system in which 90% by volume of carbon dioxide gas is mixed is even more preferable, and it is even more preferable to use carbon dioxide gas alone. The shielding gas is supplied from a shielding gas supply device (not shown).

[0020] Servo motor 170 is provided near welding torch 111. Servo amplifier 160 connected to servo motor 170 controls servo motor 170. In this embodiment, welding torch 111 is configured independent of servo motor 170, but welding torch 111 may be configured to include servo motor 170 (also referred to as servo torch). Servo motor 170 switches between forward and reverse rotation directions based on a forward / reverse feed command to control feed. In addition, servo amplifier 160 enables high-speed calculation processing and has forward / reverse feed command generation unit 161, which will be described in detail later.

[0021] A wire buffer 190 is disposed between the push motor 180 and the servo motor 170. Because the push motor 180 feeds only in the forward direction and the servo motor 170 feeds in both the forward and reverse directions, the feed directions of the push motor 180 and the servo motor 170 may differ, creating a situation in which a large load is likely to be placed on the wire within the feed path. To enable appropriate feed control even in such a feed system situation, a wire buffer is provided to suppress buckling of the wire.

[0022] The welding wire 100 used in this embodiment is not particularly limited. For example, either a solid wire that does not contain flux or a flux-cored wire that contains flux may be used. The material of the welding wire 100 is also not limited. For example, the material may be mild steel, stainless steel, aluminum, or titanium, and the wire surface may be plated with Cu or the like. The diameter of the welding wire 100 is also not limited. In this embodiment, the upper limit of the diameter is preferably 1.6 mm and the lower limit is preferably 0.8 mm. Thus, the type and composition of the welding wire are not limited, but a wire composition that is particularly suitable for the welding method according to this embodiment will be described later.

[0023] In this embodiment, the specific configuration of workpiece 200 is not particularly important, and welding conditions such as joint shape, welding posture, and groove shape are also not particularly important. Welding control device 120 mainly controls the operation of welding robot 110. Therefore, welding control device 120 may be referred to as a robot controller. Welding control device 120 holds teaching data that predetermines the operation pattern, welding start position, welding end position, welding conditions, weaving operation, etc. of welding robot 110, and instructs welding robot 110 to control the operation of welding robot 110. Also, welding control device 120 provides welding conditions such as welding current, welding voltage, and feed speed during welding work to welding power source 140 according to the teaching data.

[0024] As shown in FIG. 1, welding system 50 of the present embodiment has a configuration in which welding control device 120 is independent from welding power source 140. However, welding control device 120 may be provided within welding power source 140.

[0025] Controller 150 is connected to welding control device 120, and creates or displays a program for operating welding robot 110, inputs teaching data, and the like. Information input to controller 150 by a user is provided to welding control device 120. Controller 150 may also have a function for manually operating welding robot 110. Note that the connection between controller 150 and welding control device 120 may be wired or wireless.

[0026] In response to a command from welding control device 120, welding power source 140 supplies power to welding wire 100 and workpiece 200, thereby generating an arc between welding wire 100 and workpiece 200. In addition, in response to a command from welding control device 120, welding power source 140 outputs a control signal for push motor 180.

[0027] Next, the functional configuration of welding system 50 according to this embodiment will be described in detail with reference to Fig. 2 and Fig. 3. Fig. 2 is a block diagram showing a schematic configuration relating to the control of welding power source 140, welding control device 120, and servo amplifier 160 in this embodiment. Fig. 3 is a graph illustrating the relationship among the wire feed speed, the wire tip position, and the current detection signal in this embodiment.

[0028] Welding power source 140 is connected to welding control device 120 via digital communication, and welding control device 120 is connected to servo amplifier 160 via digital communication. That is, servo amplifier 160, welding control device 120, and welding power source 140, which are digitally connected, are connected in a line configuration in this order. This can be interpreted as a state in which servo amplifier 160 and welding power source 140 are indirectly connected by digital communication. Note that servo amplifier 160, welding power source 140, and welding control device 120 may also be connected in a line configuration in this order. This can be interpreted as a state in which servo amplifier 160 and welding power source 140 are directly connected by digital communication.

[0029] In this embodiment, communication between welding power source 140 and welding control device 120 is via CAN (Controller Area Network), which is an industrial field network, and communication between welding control device 120 and servo amplifier 160 is via EtherCAT (Ethernet for Control Automation Technology) (registered trademark), which is an industrial field network, but this is not limited to these.

[0030] (Functional configuration of welding power source) The control system 141 of the welding power source 140 is executed, for example, through the execution of a program by the welding control device 120 or a computer (not shown). The control system 141 of the welding power source 140 includes a current setting unit 36. The current setting unit 36 ​​in this embodiment has a function of setting various current values ​​that define the welding current flowing through the welding wire 100 according to processes such as arc start and welding determined in the welding sequence unit, and a function of setting the start time and end time of each period of the current control. The current setting unit 36 ​​has a target current setting unit 36A, a wire tip position conversion unit 36B, and a voltage setting unit 36C. The target current setting unit 36A has a function of setting the start time and end time of each period of the peak period Dap, the fall period Ddwn, the base period Db, and the rise period Dup related to the current control. The wire tip position conversion unit 36B has a function of obtaining information on the tip position of the welding wire 100.

[0031] The various condition settings may be determined based on, for example, setting values ​​input in advance by an operator, a waveform control table prepared in advance, a database of welding conditions, etc. The setting values, table, database, etc. may be stored in any of the components of welding system 50. The setting values, table, database, etc. may be stored in welding control device 120, welding power source 140, etc.

[0032] The various condition settings for the peak period Dap, the falling period Ddwn, the base period Db, and the rising period Dup related to the current non-suppression period TIP (the sum of the Dup and Dap periods in this embodiment) and the current suppression period TIB (the sum of the Ddwn and Db periods in this embodiment) may be determined by the waveform control table linear calculation unit 37 based on a waveform control table prepared in advance. The various condition settings here refer to the condition settings of the current value, time, phase, etc. in this embodiment.

[0033] In the case of the short circuit suppression type feed control method applied in this embodiment shown in FIG. 3, the welding current shows a pulse waveform in which the welding current is alternately repeated between a current non-suppression period TIP and a current suppression period TIB based on a phase related to the wire tip position (hereinafter also referred to as "wire position phase"). In this embodiment, the timings of the peak period Dap, the falling period Ddwn, the base period Db, and the rising period Dup are controlled based on the wire position phase of 0 to 360 deg (0 to 2π), where 0 deg is the closest to the tip side and 180 deg is the closest to the base metal side. At least the welding current may be switched between a current suppression period TIB and a current non-suppression period TIP according to the feed speed phase described later.

[0034] Based on the setting value of the average feed rate Favg in the welding condition information stored by the control system unit 141, the set current value Ip (hereinafter also referred to as the "peak current Ip") of the peak period Dap in the current non-suppression period TIP and the set current value Ib (hereinafter also referred to as the "base current Ib") of the base period Db in the current suppression period TIB calculated by the waveform control table linear calculation unit 37 are set in the current setting unit 36.

[0035] In the case of the short circuit suppression type feed control method of this embodiment, the welding current is basically controlled by two values, the peak current Ip and the base current Ib. Therefore, the start time of the base period Db represents the time when the base current Ib starts, that is, the base current start time. Moreover, the end time of the base period Db represents the time when the base current Ib ends, that is, the base current end time. The start time of the base period Db, the end time of the base period Db, the period (time) of the falling period Ddwn, and the period (time) of the rising period Dup are calculated by the waveform control table linear calculation unit 37. The start time of the peak period Dap may be expressed as the peak current start time, and the end time of the peak period Dap may be expressed as the peak current end time. As shown in FIG. 3, the timing of the peak current end time is preferably determined by the set period d1 when the wire position phase is set to 0°, and the timing of the peak current start time is preferably determined by the set period d2 when the peak current end time is set to start. This setting period may be set by phase. For example, if d1 is set to 190° and d2 is set to 120°, the peak current ends when the wire position phase is 190° (d1) and starts when the wire position phase is 310° (d1 + d2).

[0036] Moreover, the wire tip position conversion unit 36B determines the wire tip position based on the phase synchronization signal and the phase delay correction amount signal from the servo amplifier 160. In this embodiment, the wire tip position may be expressed using angles of 0 to 2π as the wire position phase as described above, and the forward feed start position is defined as 0 as shown in Fig. 3.

[0037] The phase delay correction amount signal is output from phase delay correction unit 38. Phase delay correction unit 38 has a database in which the error between the actual forward / reverse feed operation of servo motor 170 and the forward / reverse feed command of servo amplifier 160 is pre-determined as the phase delay correction amount for each of various welding conditions. For example, when the various welding conditions are a wire forward / reverse frequency Tf that is a frequency when a forward feed period and a reverse feed period are set as one cycle, the phase delay correction amount is determined based on the database in accordance with the value of the wire forward / reverse frequency to be used, and is output from phase delay correction unit 38 as the phase delay correction amount signal.

[0038] The main power supply circuit of welding power supply 140 is composed of a three-phase AC power supply (hereinafter also referred to as the “AC power supply”) 1, a primary side rectifier 2, a smoothing capacitor 3, a switching element 4, a transformer 5, a secondary side rectifier 6, and a reactor 7.

[0039] AC power input from an AC power source 1 is full-wave rectified by a primary side rectifier 2, and further smoothed by a smoothing capacitor 3 to be converted into DC power. Next, the DC power is converted into high-frequency AC power by inverter control using a switching element 4, and then converted into secondary power via a transformer 5. The AC output of the transformer 5 is full-wave rectified by a secondary side rectifier 6, and further smoothed by a reactor 7. The output current of the reactor 7 is provided to the welding tip as an output from the main power supply circuit, and is passed through a welding wire 100 serving as a consumable electrode.

[0040] The welding wire 100 is fed by the push motor 180 and the servo motor 170, and an arc is generated between the welding wire 100 and the base material 200. A forward feed period during which the tip of the welding wire 100 is moved toward the base material 200 is referred to as a forward feed period TP. A reverse feed period during which the tip of the welding wire 100 is moved in a direction opposite to the direction in which the base material 200 is located is referred to as a reverse feed period TN. In this embodiment, the servo motor 170 feeds the welding wire 100 periodically, with the forward feed period TP and the reverse feed period TN forming one cycle. Note that the "tip of the welding wire" here generally refers to the tip of the wire when the presence of droplets hanging down from the tip of the wire is ignored. In other words, the wire melted by the arc is immediately considered to have been transferred to the base material.

[0041] The feeding of the welding wire 100 by the push motor 180 is controlled by a control signal based on the push feeder control unit 39. The average value of the feeding speed is approximately the same as the melting speed. In this embodiment, the feeding of the welding wire 100 by the push motor 180 is also controlled by the welding power source 140.

[0042] Further, push feeder control unit 39 performs control according to the state of wire buffer 190. In this embodiment, wire buffer 190 is provided with a wire play portion (a gap portion into which the wire can escape when the wire slackens due to the influence of feeding between the motors) so that a large load is not applied to the wire on the feeding path between push motor 180 and servo motor 170, and the amount of slack in the wire is detected by an absolute encoder built into wire buffer 190 in terms of a rotation angle. The detected value is converted into an analog signal by serial-to-analog conversion unit 191, and an electrical angle is calculated by an electrical angle calculation unit. The calculated electrical angle is input to A / D input unit 40 of the welding power source.

[0043] A difference signal obtained by calculating the difference between the electrical angle from the A / D input unit 40 and a reference value of the electrical angle preset in the electrical angle adjustment unit 41 is input to the push feeder control unit 39. Based on this difference signal, the push feeder control unit 39 controls the push motor 180 so as to obtain an appropriate buffer amount of wire, thereby performing interference control to prevent a large load from being placed on the feed system. Note that, although the above-mentioned interference control is performed in this embodiment, the present invention is not limited to this. Also, although an absolute encoder built into the wire buffer 190 is used in this embodiment, the present invention is not limited to this. For example, a rotation angle sensor may be used, in which case the serial-to-analog conversion unit 191 may not be provided.

[0044] A voltage setting signal Vap, which is a target value of a voltage to be applied between a contact tip (not shown), a current passing position of the welding wire 100, and the base material 200, is given as a voltage command to a voltage setting section 36C of the current setting section 36. Based on the voltage setting signal Vap, the current setting section 36 controls the welding current in each period such as a peak period Dap so that the length of the arc (hereinafter also referred to as "arc length") is constant.

[0045] The voltage detection signal Vo obtained by the voltage detection unit is an actual measurement value. In this embodiment, the voltage detection signal Vo passes through a low-pass filter LPF, passes through a separation detection unit 33, and is input to the current setting unit 36 ​​as a separation detection signal DTR. Note that a voltage comparison unit may be provided to amplify the difference between the voltage setting signal Vap and the voltage detection signal Vo, and output the amplified voltage error signal to the current setting unit 36.

[0046] The current error amplifier 34 amplifies the difference between the current setting signal CCset given as a target value by the current setting unit 36 ​​and the current detection signal Io detected by the current detection unit 31, and outputs it as a current error amplified signal Ed to the inverter drive unit 30. The inverter drive unit 30 corrects the drive signal Ec to the switching element 4 using the current error amplified signal Ed.

[0047] A detachment detection signal DTR, which is a signal for detecting detachment of a droplet from the tip of the welding wire 100, is also input to the current setting unit 36. The detachment detection signal DTR is output from the detachment detection unit 33. The detachment detection unit 33 monitors a change in the voltage detection signal Vo output by the voltage detection unit 32, and detects the detachment of a droplet from the welding wire 100 from the change. Note that the detachment detection unit 33 is an example of a detection means.

[0048] The detachment detection unit 33 detects the detachment of a droplet by, for example, comparing a value obtained by differentiating or second-order differentiating the voltage detection signal Vo passed through the LPF with a detection threshold value. The detection threshold value is stored in advance in a storage unit (not shown). The detachment detection unit 33 may generate the detachment detection signal DTR based on a change in resistance value calculated from the voltage detection signal Vo and the current detection signal Io, which are actual measured values.

[0049] An average feed speed Favg of the welding wire 100 being fed is provided to waveform control table linear calculation unit 37. Average feed speed Favg is stored in advance in feed setting data unit 35. Note that, although feed setting data unit 35 is provided in welding power source 140 in this embodiment, various pieces of information relating to the feed settings may be stored in welding control device 120, and the various pieces of information may be output from welding control device 120 to welding power source 140.

[0050] Based on the given average feed speed Favg, the waveform control table linear calculation unit 37 determines values ​​of the peak current Ip, the base current Ib, the time t1 when the base current Ib starts, and the time t2 when the base current Ib ends, and outputs these to the current setting unit 36. Since the values ​​of the wire position phase, time, and cycle cyc can be mutually converted as described above, the setting value of the base start phase, etc. may be converted into a value of time or cycle cyc, and the converted value may be output to the current setting unit 36.

[0051] 2, the average feed speed Favg is input to the waveform control table linear calculation unit 37, but a value related to the average feed speed Favg may be input as a set value to the waveform control table linear calculation unit 37, which may then use the set value as the average feed speed Favg. For example, if a database of average feed speeds Favg and average current values ​​that enable optimal welding for the average feed speed Favg is stored in a storage unit (not shown), the average current value may be used as the set value, and the set value may be used as the average feed speed Favg.

[0052] The feed setting data unit 35 may store set values ​​such as the wire amplitude Wf, the wire forward / reverse frequency Sf, and the wire forward / reverse cycle Tf in addition to the average feed speed Favg. The wire amplitude Wf, the wire forward / reverse frequency Sf, and the wire forward / reverse cycle Tf may be determined based on the input average feed speed Favg. The feed setting data unit 35 may store set values ​​other than these as feed setting data. In this embodiment, the value of the wire amplitude Wf ​​refers to the wave height Wh shown in Fig. 3. In other words, the set value of the wire amplitude Wf ​​is set to be the same as the wave height Wh.

[0053] In this embodiment, a period in which the feed speed is higher than the average feed speed Favg is defined as a forward feed period, and a period in which the feed speed is lower than the average feed speed Favg is defined as a reverse feed period, resulting in feed in which forward feed periods and reverse feed periods alternate (hereinafter, abbreviated as "amplitude feed"). Note that a period in which the feed speed is lower than the average feed speed Favg refers to a feed speed lower than the average feed speed Favg, and includes a negative feed speed, i.e., a speed at which the wire tip moves in the opposite direction to the position of the base material 200. The wire amplitude Wf ​​gives the range of change relative to the average feed speed Favg, and the wire forward / reverse cycle Tf gives the time of change in the wire amplitude, which is a repetition unit. The wire forward / reverse frequency Sf is the reciprocal of the wire forward / reverse cycle Tf.

[0054] The average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Sf, and wire forward / reverse cycle Tf stored in the feed setting data unit 35 are input from the digital communication unit 42 to the digital communication unit 122 of the welding control device 120. In this embodiment, the communication of these feed setting data is performed by CAN communication.

[0055] The welding sequence unit processes each task in the order of idle, gas flow, arc start, welding in progress, and anti-stick based on the teaching data and on the gas ON and arc start signals output from welding control device 120. In the welding in progress task, control is performed mainly by current setting unit 36 ​​described above. In Fig. 2, the welding condition information held by welding control device 120 is shown enclosed by a dashed line even within welding power source 140 for the sake of convenience.

[0056] (Functional configuration of welding control device) As described above, feed setting data such as average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Sf, and wire forward / reverse cycle Tf are input to digital communication unit 122 of welding control device 120 from feed setting data unit 35 of welding power source 140 via CAN communication. Welding control device 120 has digital communication unit 123 for outputting the feed setting data to digital communication unit 162 of servo amplifier 160. In this embodiment, digital communication unit 123 of welding control device 120 and digital communication unit 162 of servo amplifier 160 are connected via EtherCAT (registered trademark) communication.

[0057] In addition, welding control device 120 stores various welding condition information such as the timing of gas and arc start (welding ON), voltage, and average feed speed settings, and outputs signals for gas ON, arc start, voltage command, and feed command to welding power source 140 based on a program created to operate welding robot 110.

[0058] (Servo amplifier functional configuration) Feeding setting data such as average feeding speed Favg, wire amplitude Wf, wire forward / reverse frequency Sf, and wire forward / reverse cycle Tf are input to a digital communication unit 162 of the servo amplifier 160 via EtherCAT (registered trademark) communication. A forward / reverse feed command generating unit 161 of the servo amplifier 160 generates a feed command for forward feeding or reverse feeding based on the setting information input via digital communication, i.e., the feeding setting data. More specifically, the forward / reverse feed command generating unit 161 of the servo amplifier 160 calculates an amplitude feed speed Ff from the wire amplitude Wf ​​and the wire forward / reverse cycle Tf, and calculates a feed speed command signal Fw based on this amplitude feed speed Ff and the average feed speed Favg.

[0059] In this embodiment, the feed speed command signal Fw is expressed by the following equation. Fw=Ff+Favg...Formula (A)

[0060] Further, the forward / reverse feed command generating unit 161 may detect at which wire position phase of the amplitude feed the detachment has occurred, based on the detachment detection signal DTR provided by the detachment detection unit 33. However, the feed speed command signal Fw expressed by the formula (A) is only used when the detachment of a droplet from the tip of the welding wire 100 is detected within an expected period. When the detachment of a droplet is not detected within the expected period, the forward / reverse feed command generating unit 161 may switch the feed speed command signal Fw to a constant speed feed control. For example, the forward / reverse feed command generating unit 161 switches the feed speed command signal Fw to feeding at an average feed speed Favg. The switching from feeding at the average feed speed Favg to the feed control expressed by the formula (A) is determined according to the timing at which the detachment of a droplet is detected.

[0061] The servo amplifier performs inverter control of the servo motor 170 based on the feed speed command signal Fw in a forward / reverse feed command generating unit 161. Also, a synchronization signal generating unit 163 of the servo amplifier 160 outputs a phase synchronization signal to the welding power source 140. This phase synchronization signal is generated based on the feed speed command signal Fw.

[0062] Note that welding power source 140 and synchronization signal generating unit 163 of servo amplifier 160 may be connected at least via an analog input / output. In this case, a synchronization signal is input from servo amplifier 160 to welding power source 140 via an analog input / output. By transmitting feeding setting data such as average feeding speed Favg, wire amplitude Wf, wire forward / reverse frequency Sf, and wire forward / reverse cycle Tf by digital communication, while transmitting the synchronization signal by analog communication, it is possible to efficiently use digital communication and analog communication depending on the application.

[0063] Here, the phase related to the feed speed command signal Fw (hereinafter also referred to as "feed speed phase") is 0 deg at the start of forward feed, 180 deg (π) at the end of forward feed and the start of reverse feed, and 360 deg (2π) at the end of reverse feed. In this embodiment, the phase synchronization signal is a feed speed phase synchronization signal and a wire position phase synchronization signal. The feed speed phase synchronization signal is a synchronization signal that is ON during the forward feed period (position from 0 to π) and OFF during the reverse feed period (position from π to 2π). On the other hand, the wire position phase synchronization signal is a synchronization signal that is ON during a period (position from 0.5π to 1.5π) when the wire is fed forward or backward and approaches the base material 200 side from the center position of the wave height, and is OFF during a period (position from 1.5π to 0.5π) when the wire is fed forward or backward and approaches the tip side from the center position of the wire amplitude. Based on this phase synchronization signal and the above-mentioned phase delay correction amount, the tip position of welding wire 100, that is, the wire position phase, is determined by wire-tip-position conversion unit 36B in welding power source 140.

[0064] (Welding method) Next, a welding method according to the present embodiment will be described. The welding method according to the present embodiment is based on the technical idea of ​​locally increasing the arc pressure at a specific wire position phase in the wire feed control method, thereby expanding the molten pool, thereby obtaining penetration and a wide bead width.

[0065] In the feed control method, the wire tip is closest to the molten pool when the wire tip is switched from forward feed to reverse feed. When the wire tip is close to the molten pool, the arc length is shortened, and the arc pressure on the molten pool increases instantaneously. Therefore, the wire position phase that locally increases the arc pressure is before and after the wire tip is switched from forward feed to reverse feed, that is, the wire position phase of 90 degrees (0.5π) to 270 degrees (1.5π), and if the welding current is further increased during this period, the effect of expanding the molten pool is increased. However, such control may result in excessive expansion of the molten pool, which may cause burn-through or sagging of the molten part due to the influence of gravity, resulting in poor cross-linking. In addition, the arc pressure that pushes up the droplets is high even during the reverse feed period in which the droplets are detached. This hinders droplet detachment during the reverse feed period, which makes the droplet transfer unstable and may cause spattering. Therefore, in the welding method according to this embodiment, in the local range of the wire position phase between 90 degrees (0.5π) and 180 degrees (1.5π), the welding current is increased significantly to expand the molten pool and ensure penetration and a wide bead width, and in the range between 180 degrees (π) and 270 degrees (1.5π), the welding current is decreased significantly and a cooling period is provided to prevent burn-through, dripping of the molten part due to the influence of gravity, and failure to separate the droplets. This ensures robustness in fillet welding. The welding current between the wire position phases will be described in detail below.

[0066] (Wire position phase 90deg~180deg: above average current) The period from 90deg to 180deg of the wire position phase is the period for expanding the penetration and bead width, and the average value of the welding current during this period is I 90~180deg_ave is the average current value I ave The average welding current value I ave is the set welding current value I set Therefore, in this embodiment, I ave ≒I set The average current value I 90~180deg_ave The average current value I setBy setting the current value to the value above, the penetration and bead width can be increased in the wire feed control method. In order to increase the penetration and bead width further, the wire position phase is set to 90° to 180° during the period T 90~180deg The average value of the welding current in 90~180deg_ave and the set welding current value I set (≒Average welding current I ave ), which is the ratio of (I 90~180deg_ave ) / (I set ) is preferably 1.10 or more.

[0067] (Wire position phase 180deg~270deg: below average current) The period from 180° to 270° of the wire position phase is a cooling period in which the welding current is significantly reduced. The average value of the welding current during this period is I 180~270deg_ave is the average current value I ave The average welding current value I ave is the set welding current value I set Therefore, in this embodiment, I ave ≒I set The average current value I 180~270deg_ave The average current value I set By setting the current value below, in the feed control method, the dripping of the molten part due to the influence of burn-through and gravity and failure of droplet detachment can be prevented. In addition, in order to increase the penetration and bead width, the welding wire position is set to 180° to 270° during the period T 180~270deg The average value of the welding current in 180~270deg_ave and the set welding current value I set (≒Average welding current I ave ), which is the ratio of (I 180~270deg_ave ) / (I set ) is preferably 0.90 or less.

[0068] ((I 180~270deg_ave ) / (I 90~180deg_ave )≦0.50) As described above, by setting the average current or more during the wire position phase period of 90° to 180° and the average current or less during the wire position phase period of 180° to 270°, robustness in fillet welding can be ensured. This robustness is favorable the greater the difference between the average current during the wire position phase period of 90° to 180° and the average current during the wire position phase period of 180° to 270°. Specifically, during the period T when the welding wire position is 90° to 180°, 90~180deg The average value of the welding current in 90~180deg_ave and the period T when the welding wire position is 180° to 270° 180~270deg The average value of the welding current in 180~270deg_ave The ratio of (I 180~270deg_ave ) / (I 90~180deg_ave From the viewpoint of the stability of droplet transfer, the lower limit of this ratio should be set to 0.10 or more.

[0069] (Wire forward / reverse frequency: 50~150) The wire forward / reverse frequency is preferably in the range of 50 to 150. By setting the wire forward / reverse frequency to 150 or less, the period T 90~180deg The average value of the welding current in 90~180deg_ave and the period T when the wire position phase is 180deg to 270deg 180~270deg The average value of the welding current in 180~270deg_ave On the other hand, by setting the value to 50 or more, the stability of the droplet transfer can be maintained.

[0070] (Wire amplitude: 3.3~6.3) The wire amplitude is preferably in the range of 3.3 to 6.3. By setting the wire amplitude to 3.3 or more, the stability of the droplet transfer can be maintained. On the other hand, by setting the wire amplitude to 6.3 or less, during the period when the wire position phase is 90 degrees to 180 degrees, the wire tip approaches the molten pool more while preventing short circuiting, and the arc pressure increases, so that a deeper penetration and a wider bead width can be obtained.

[0071] (Welding wire) In the feed control method, when forward or reverse feed is performed, there are wire position phases where the wire is fed at an excessively high feed rate and there are wire position phases where the feed rate is zero, and a large speed fluctuation occurs within one cycle in which forward and reverse feed is performed. This speed fluctuation is particularly noticeable in the short-circuit suppression type feed control. Specifically, in this embodiment, when the wire position phase is 90 degrees, the feed rate is the maximum speed during forward feed, and is zero around 180 degrees, and furthermore, at 270 degrees, the feed rate is the maximum speed during reverse feed, and is zero just before 360 ​​degrees. As described above, between the wire position phases of 90 degrees and 180 degrees, a strong arc pressure is used to push the molten pool and at the same time, it has the effect of widening the width of the molten pool, but during this period, the feed rate goes from the maximum speed during forward feed to zero, and the inertial force acts on the droplets formed at the wire tip, making it easy for the droplets to detach or swing at an unintended timing. If the droplets detach at unintended times, such as during the normal feed period, the timing of droplet transfer becomes unstable, which may result in increased spatter and poor bead shape. In addition, if the droplets oscillate, the arc deflects according to the movement of the oscillating droplets, so the position where the molten pool is pushed by the arc pressure fluctuates and is not concentrated at one point, making it impossible to obtain good penetration and bead width. Therefore, it is preferable to prevent droplets from detaching or oscillating even if excessive inertial force is applied.

[0072] In general, in order to prevent droplets from detaching or swaying at unintended timing, the welding wire may be designed to control the physical properties during melting, such as by increasing the viscosity of the droplets. However, controlling the physical properties during melting limits the composition, and the applicable wire composition is also limited. Therefore, in the welding method according to the present embodiment, it is preferable to use a welding wire that can prevent droplets from detaching or swaying even when an excessive inertial force acts without considering the physical properties of the droplets. In response to this, the inventors have found that by applying a welding wire containing a trace amount of strong deoxidizing elements such as Ti, Al, Mg, Zr, and oxygen as a welding wire suitable for the welding method according to the present embodiment, droplets can be prevented from detaching or swaying even when an excessive inertial force acts, without controlling the physical properties of the droplets by the composition. This is due to the fact that the welding wire is melted by the arc, and strong deoxidizing elements such as Ti, Al, Mg, Zr, and oxygen in the wire combine with each other to form an oxide film of the strong deoxidizing elements on the droplet surface. This oxide film has a high interfacial tension with the surrounding gas and acts to reduce the surface area of ​​the droplet itself, so that at the initial droplet weight when the droplet begins to grow, the droplet is less likely to detach and oscillation is suppressed.

[0073] Here, the strong deoxidizing element contained in the wire naturally has a high affinity with oxygen, and if the element is not an element whose oxide has a high melting point, an oxide film will not form on the droplet surface, so the strong deoxidizing element added to the welding wire is preferably an element selected from Ti, Al, Mg, and Zr. Note that although there is no problem with the type of welding wire, a metal-based flux-cored wire is preferably used from the viewpoint of ease of controlling the amount of oxygen in the wire.

[0074] Hereinafter, the form of the welding wire that is most suitable for the welding method according to the present embodiment will be described in detail. In the following description, the amount of each component in the wire is defined as the content relative to the total mass of the wire.

[0075] (C: 0.20% by mass or less (including 0% by mass)) C has a deoxidizing effect and is an ingredient that has the effect of enhancing the mechanical performance of the weld metal. The content of C may be appropriately adjusted according to the strength of the application, and in the welding method according to the present embodiment, it is not necessary to contain C if the strength can be ensured by other elements. That is, it may be 0 mass%. However, since C has a deoxidizing effect when contained, in order to stably form an oxide film on the droplet surface, it is preferable to set the content to 0.20 mass% or less. Furthermore, in the application of lap fillet welding of 440 to 980 MPa class steel sheets applied to automobile suspension parts, it is more preferable to determine the content so that the MIX value described later falls within an appropriate range.

[0076] (Si: 1.00% by mass or less (including 0% by mass)) Si is a deoxidizer and is a component that has the effect of enhancing the mechanical performance of the weld metal. The content of Si may be adjusted appropriately according to the strength of the application, and in the welding method according to the present embodiment, it may not be contained if the strength can be ensured by other elements. That is, it may be 0 mass%. However, the melting point of Si oxide is 1710°C, and when Si combines with oxygen in the molten pool to generate an oxide, it may be in a molten state on the molten pool surface. Since the molten oxide has a very high viscosity, it becomes a factor that inhibits deep penetration and expansion of the bead width between 90 degrees and 180 degrees of the wire position phase. In addition, if the oxide of Si remains as slag on the weld bead, it becomes impossible to form an electrodeposition coating film. Therefore, the lower the content of Si, the more preferable it is, and it is preferably 1.00 mass% or less, more preferably 0.50 mass% or less, and even more preferably 0.20 mass% or less. In particular, by limiting the Si content to 0.50 mass% or less, the increase in viscosity of the molten pool can be suppressed, resulting in good robustness, and furthermore, the composition of the slag formed on the weld bead changes, resulting in a thin slag with good adhesion that can form an electrodeposition coating. In addition to reducing the Si content, it is even more preferable for the MIX value, which will be described later, to be within an appropriate range in applications for lap fillet welding of 440 to 980 MPa class steel sheets used in automobile suspension parts.

[0077] (Mn:1.30~2.40% by mass) Mn, like Si, is a deoxidizer and is a component that has the effect of enhancing the mechanical performance of the weld metal. The content of Mn may be adjusted appropriately depending on the strength of the application, and in the welding method according to this embodiment, it is not necessary to contain Mn if the strength can be ensured by other elements. That is, it may be 0 mass%. In the case of suppressing the above-mentioned Si content, it is preferable to supplement it with the Mn content, and if it is contained in the range of 1.30 to 2.40 mass%, it is preferable as a means of balancing the mechanical performance without impairing the effect of this embodiment. Furthermore, in the application of lap fillet welding of 440 to 980 MPa class steel plates applied to automobile suspension parts, it is more preferable to determine the content so that the MIX value described later falls within an appropriate range.

[0078] (P:0.025 mass% (including 0 mass%)) P is an element related to the cracking tendency of the weld metal, and the lower the P content in the weld metal, the better the cracking resistance, so in the welding method according to the present embodiment, it is not necessary to contain P. In other words, it may be 0 mass %. From the viewpoint of cracking resistance, the P content in the wire is preferably 0.025 mass % or less.

[0079] (S:0.030 mass% (including 0 mass%)) S is a component that reduces the surface tension of the molten metal. The lower the surface tension, the more the droplet detachment tends to be promoted. Therefore, in the present invention, in order to prevent droplet detachment between the wire positions of 90 degrees and 180 degrees, the S content is preferably 0.030 mass% or less. From the viewpoint of preventing droplet detachment, it is not particularly necessary to contain S (0 mass% is also acceptable), but on the other hand, since an appropriate amount of S affects the physical properties of the molten pool surface and has the effect of improving the fit of the weld bead, it is more preferable to contain 0.001 mass%.

[0080] (Cu: 0.50% by mass or less (including 0% by mass)) Cu is a component that has the effect of enhancing the mechanical performance of the weld metal. The content of Cu may be appropriately adjusted according to the strength of the application, and in the welding method according to the present embodiment, Cu may not be contained if the strength can be ensured by other elements. That is, it may be 0 mass%. Cu may also be added to the welding wire as a plating, and the total content in the wire and the plating amount is preferably 0.50 mass% or less. This is because by suppressing it to 0.50 mass% or less, a balance is achieved with other elements that enhance the mechanical performance, and the weld metal does not have excessive strength. Furthermore, in the application of lap fillet welding of 440 to 980 MPa class steel sheets applied to automobile suspension parts, it is more preferable to determine the content so that the MIX value described later falls within an appropriate range.

[0081] (Ni: 1.00% by mass or less (including 0% by mass)) Ni is a component that has the effect of enhancing the mechanical performance of the weld metal. The Ni content may be adjusted appropriately depending on the strength of the application, and in the welding method according to the present embodiment, if the strength can be ensured by other elements, it may not be contained. That is, it may be 0 mass%. By suppressing the Ni content to 1.00 mass% or less, a balance with other elements that enhance mechanical performance is achieved, and the weld metal does not have excessive strength, so it is preferable to set the Ni content to 1.00 mass% or less. Furthermore, in the application of lap fillet welding of 440 to 980 MPa class steel plates applied to automobile suspension parts, it is more preferable to determine the content so that the MIX value described later falls within an appropriate range.

[0082] (Cr: 1.00% by mass or less (including 0% by mass)) Cr is a component that has the effect of enhancing the mechanical performance of the weld metal. The Cr content may be appropriately adjusted depending on the strength of the application, and in the welding method according to the present embodiment, if the strength can be ensured by other elements, it may not be contained. That is, it may be 0 mass%. By suppressing the Cr content to 1.00 mass% or less, a balance with other elements that enhance mechanical performance is achieved, and the weld metal does not have excessive strength, so it is preferable to set the Cr content to 1.00 mass% or less. Furthermore, in the application of lap fillet welding of 440 to 980 MPa class steel plates applied to automobile suspension parts, it is more preferable to determine the content so that the MIX value described later falls within an appropriate range.

[0083] (Mo: 1.00% by mass or less (including 0% by mass)) Mo is a component that has the effect of enhancing the mechanical performance of the weld metal. The content of Mo may be appropriately adjusted depending on the strength of the application, and in the welding method according to the present embodiment, if the strength can be ensured by other elements, it is not necessary to contain Mo. That is, it may be 0 mass%. By suppressing the Mo content to 1.00 mass% or less, a balance with other elements that enhance mechanical performance is achieved, and the weld metal does not have excessive strength, so it is preferable to set the Mo content to 1.00 mass% or less. Furthermore, in the application of lap fillet welding of 440 to 980 MPa class steel plates applied to automobile suspension parts, it is more preferable to determine the content so that the MIX value described later falls within an appropriate range.

[0084] (V: 0.50% by mass or less (including 0% by mass)) V is a component that has the effect of enhancing the mechanical performance of the weld metal. The content of V may be appropriately adjusted depending on the strength of the application, and in the welding method according to the present embodiment, if the strength can be ensured by other elements, it may not be contained. That is, it may be 0 mass%. By suppressing the V content to 0.50 mass% or less, a balance with other elements that enhance mechanical performance is achieved, and the weld metal does not have excessive strength, so it is preferable to set the V content to 0.50 mass% or less. Furthermore, in the application of lap fillet welding of 440 to 980 MPa class steel plates applied to automobile suspension parts, it is more preferable to determine the content so that the MIX value described later falls within an appropriate range.

[0085] (B: 0.010% by mass or less (including 0% by mass)) B is a component that has the effect of enhancing the mechanical performance of the weld metal. The content of B may be appropriately adjusted depending on the strength of the application, and in the welding method according to the present embodiment, if the strength can be ensured by other elements, it is not necessary to contain B. That is, it may be 0 mass%. By suppressing the B content to 0.010 mass% or less, a balance with other elements that enhance mechanical performance is achieved, and the weld metal does not have excessive strength, so it is preferable to set the B content to 0.010 mass% or less. Furthermore, in the application of lap fillet welding of 440 to 980 MPa class steel plates applied to automobile suspension parts, it is more preferable to determine the content so that the MIX value described later falls within an appropriate range.

[0086] (Total amount of Ti, Al, Mg, and Zr: 0.001 to 0.450 mass%) ((Ti+Al+Mg+Zr) / O:0.5~150) Ti, Al, Mg, and Zr are strong deoxidizing elements that have a very high affinity with O (oxygen), and the melting points of these oxides are higher than the melting point of iron. When at least one of Ti, Al, Mg, and Zr and O (oxygen), which will be described later, is contained in the welding wire, an oxide film is formed on the surface of the droplet when the droplet is formed at the tip of the welding wire. The formation of this oxide film makes it difficult for the shape of the droplet to change even if the feed speed changes locally depending on the wire position and an inertial force is applied to the droplet, so that the fluctuation of the droplet and the detachment of the droplet at an unintended wire position phase can be suppressed. The total content of the strong deoxidizing elements (Ti, Al, Mg, and Zr) that fully exerts the above-mentioned effect is preferably 0.001 mass% or more, more preferably 0.050 mass% or more, and even more preferably 0.150 mass% or more. In addition, when the contents of Ti, Al, Mg, and Zr are excessive, the amount of slag on the weld bead increases, and the slag composition also changes depending on the contents of Ti, Al, Mg, and Zr, so in the application of lap fillet welding of 440 to 980 MPa steel plates applied to automobile suspension parts, from the viewpoint of bead appearance and electrocoatability, it is preferable to suppress the total amount of Ti, Al, Mg, and Zr to 0.450 mass% or less, and more preferably to suppress it to 0.380 mass% or less. In addition, when droplets are formed at the tip of the welding wire, the relationship between Ti, Al, Mg, and Zr and O (oxygen) suitable for forming an oxide film on the droplet surface is preferably a value calculated from (Ti+Al+Mg+Zr / )O in the range of 0.5 to 150, and more preferably in the range of 0.5 to 75.0.

[0087] (O:0.0010~0.0100% by mass) By including O together with the above-mentioned strong deoxidizing elements, an oxide film can be formed on the surface of the droplets when the droplets are formed at the tip of the welding wire, and the droplets can be prevented from swinging and from detaching from unintended wire positions. In the welding method according to the present embodiment, the content of O effective for preventing the droplets from swinging and from detaching from unintended wire positions is preferably 0.0010% by mass or more, and more preferably 0.0015% by mass or more. Moreover, if O is excessively contained in the wire, the amount of slag on the weld bead increases, which may affect the bead appearance, so the content is preferably 0.0100% by mass or less, more preferably 0.0080% by mass or less, and even more preferably 0.0050% by mass or less.

[0088] (N: 0.0300% by mass or less) N is a component that has the effect of enhancing the mechanical performance of the weld metal. The N content can be adjusted appropriately depending on the strength of the application, and in the welding method according to the present embodiment, N does not need to be contained if the strength can be ensured by other elements. In other words, it may be 0 mass%. By suppressing the N content to 0.0300 mass% or less, a balance is achieved with other elements that enhance mechanical performance, and the weld metal does not have excessive strength, so it is preferable to keep the N content to 0.0300 mass% or less.

[0089] (0.35≦MIX value≦1.40) The MIX value is C+Si / 24+Mn / 6+Ni / 40+Cr / 5+Mo / 4+V / 4+Cu / 13. When improving robustness by suppressing the increase in viscosity of the molten pool and improving electrodeposition paintability by controlling the slag composition, it is necessary to keep the Si content below 0.50 mass%, so it is necessary to compensate for the mechanical performance with other elements by reducing the Si content, but it is preferable to balance the other elements so that the MIX value is in the range of 0.35 to 1.40.

[0090] (Ti:0.030~0.250% by mass) (Al:0.001~0.300% by mass) As the strong deoxidizing element contained, Ti and Al are preferably selected. The oxides of Mg and Zr have melting points of 2500°C or higher, and the lower the temperature, the higher the affinity with oxygen, so a thick oxide film is formed on the entire droplet. Therefore, a thick oxide film is formed on the upper part of the droplet, which is relatively low in temperature, i.e., near the boundary between the droplet and the wire, and this may hinder the formation of a constriction at the droplet detachment position in the latter half of the reverse wire feed (270° to 360°), and the droplet may not detach. On the other hand, the melting points of Ti and Al oxides are 2100°C or lower, and compared with Mg and Zr, the oxide film is not thick, and it is difficult for an oxide film to form near the boundary between the droplet and the wire. Therefore, in the latter half of the reverse wire feed, a constriction occurs at the boundary between the wire and the droplet, and the droplet detaches. Therefore, it is preferable that Ti and Al are contained as strong deoxidizing elements, the Ti content is preferably contained in the range of 0.030 to 0.250 mass%, the Al content is preferably contained in the range of 0.001 to 0.300 mass%, and more preferably in the range of 0.001 to 0.200 mass%. The Al content is more preferably contained in excess of 0.10 mass%. The above effect is promoted when the ratio of the Ti content to the Al content (Ti / Al) is 0.3 to 20. Furthermore, from the viewpoint of further improving the electrodeposition coating property, when the Si content is suppressed to 0.5 mass% or less and the slag composition formed on the weld bead is controlled, the ratio of the Ti content to the Al content (Ti / Al) is even more preferably 0.4 to 13.0, and even more preferably 0.4 to 3.0.

[0091] In the latter half of reverse feeding of the wire, in order to stably separate the wire by inertia force, the maximum feed speed during reverse feeding is preferably 50 m / min or more. On the other hand, in the welding method according to the present embodiment, in the latter half of forward feeding (90 deg to 180 deg), it is necessary to obtain penetration and a wide bead width by applying a high current instantaneously and increasing the arc pressure on the molten pool, so that the maximum feed speed during forward feeding must necessarily be equal to or close to the maximum feed speed during reverse feeding. However, the higher the maximum speed on the forward feed side, the higher the possibility of the droplets swinging and detaching in the latter half of forward feeding (90 deg to 180 deg). In the present embodiment, by containing the above-mentioned Al and Ti and controlling the oxide film, it is possible to prevent the droplets swinging and detaching in the latter half of forward feeding (90 deg to 180 deg) and promote detachment in the latter half of reverse feeding. Specifically, the distribution of strong deoxidizing elements is preferably (Ti+Al) / (Ti+Al+Mg+Zr)>0.5, and more preferably the value of (Ti+Al) / (Ti+Al+Mg+Zr) is 0.95 or more. It is even more preferable that the contents of Mg and Zr are equal to or less than the contents of unavoidable impurities, and that the alloy is composed only of Ti and Al.

[0092] (Balance: Fe and unavoidable impurities) The remainder of the wire preferably used in this embodiment is Fe and unavoidable impurities. Examples of the unavoidable impurities include Nb, Li, Sn, Sb, Bi, and As. The content of each of these unavoidable impurities is preferably 0.0100 mass% or less, and more preferably 0.0050 mass% or less, based on the total mass of the wire. The total content of these unavoidable impurities is preferably 0.0200 mass% or less, based on the total mass of the wire. EXAMPLES

[0093] The present embodiment will be described in more detail below with reference to examples. However, the present invention is not limited to these examples, and modifications can be made within the scope of the invention, and all such modifications are included in the technical scope of the invention.

[0094] (Welding wire) FIG. 4 is a diagram showing the compositions of two wires used in the examples. In the examples, two types of wires, Wire A and Wire B, were used. The components contained in each wire are as shown in FIG. 4. Note that all values ​​in FIG. 4 indicate mass %. The remainder other than the wire components shown in FIG. 4 is Fe and unavoidable impurities.

[0095] (Welding control method) 5 is a diagram showing two welding methods used in the examples. In the examples, two types of welding methods were used: feed control method A and feed control method B. In addition, general pulse MAG welding was used as a comparative example.

[0096] The feed control method A is a short circuit suppression type method, with a wire frequency of 70 Hz and a wave height of 5 mm (amplitude ±2.5 mm). The timing of switching the current control is fixed at the wire position. The wire position for peak current switching is 157 deg, and the wire position for base current switching is 350 deg (see Figure 6).

[0097] The feed control method B is a short circuit type method. The wire frequency varies according to the short circuit period. The wire amplitude also varies. The timing for switching the current control is when a short circuit is detected.

[0098] (Welding conditions) The welding conditions were set as follows: Steel plate: 200mm length x 50mm width x 2.3mm thickness, SPH440 steel plate Welding position: horizontal lap fillet welding Shielding gas: 100% CO2 gas by volume, 80% Ar + 20% CO2 gas by volume ·Average current: 200~250A Average voltage: 19~27V Wire feed rate: 7.0m / min Welding speed: 100cm / min Welding length: 150mm

[0099] (Evaluation Results) Fig. 6 is a graph of the welding current and the feed speed when the welding method is the feed control method A. Fig. 7 is a graph of the welding current and the feed speed when the welding method is the feed control method B. In both graphs, the horizontal axis indicates the wire position phase. The vertical axis indicates the welding current in amperes (A) and the feed speed in m / min (mpm).

[0100] Fig. 8 is a diagram showing welding conditions and actual measurement data when feed control method A, feed control method B, and pulse MAG welding as a comparative example are respectively used. Figs. 9A to 9E are diagrams showing the results of a target deviation test based on the welding conditions and actual measurement data shown in Fig. 8.

[0101] First, the welding conditions are described. Test Nos. 1 and 2 use the feed control method A. Test Nos. 3 and 4 use the feed control method B. Test No. 5 uses pulse MAG welding. Regarding the type of wire, Test No. 2 uses Wire B, and Test Nos. 1 and 3-5 use Wire A. Regarding the shielding gas, Test Nos. 1-3 used 100 vol.% CO2 gas (referred to as CO2 in FIG. 8 and hereafter), and Test Nos. 4-5 used 80 vol.% Ar+20 vol.% CO2 gas (referred to as Ar-CO2 in FIG. 8 and hereafter). The welding speed was 100 cm / min in all tests. The feed speed was 7 m / min in all tests.

[0102] Next, the actual measurement data will be described. For each test number, the average current and average voltage values ​​are shown in Figure 8. For test numbers 1 to 4, the average current in a given period and the average voltage in a given period are shown in Figure 8. In addition, for test numbers 1 to 4, the ratio of the average current was also calculated based on the above-mentioned actual measurement values, and is shown in Figure 8.

[0103] As shown in Figures 9A to 9E, trials were conducted for each test number at multiple target positions. The gap width and target position (amount of deviation of the target position) values ​​at that time, and whether the welding result was good (good welding results are indicated by a circle in Figures 9A to 9E) or poor (poor welding results are indicated by a cross in Figures 9A to 9E) are shown as test results. The target position (amount of deviation of the target position) is the amount of deviation when the axis is perpendicular to the weld line and a value of 0 is the normal target position. Negative values ​​(-1 to -5) indicate a deviation in the direction of the upper plate, and positive values ​​(1 to 5) indicate a deviation in the opposite direction.

[0104] Furthermore, the test results, indicated by circles (○) and crosses (×), were plotted on a target deviation tolerance graph. The horizontal axis of the target deviation tolerance graph is the target position (mm), and the vertical axis is the gap width (mm). In the target deviation tolerance graph, the allowable range is indicated by a dashed line. The allowable range is indicated as a rectangle that is inside the region that is formed by connecting the plotted points where the test results are ○. It can be said that the larger the area of ​​the dashed line region, the higher the robustness. This is because, as described above, the larger the deviation or gap of the welding target position, the more pronounced the problems of poor bead shape and bridging become, while inside the dashed line region, the probability of obtaining good welding results is high, and the larger the area of ​​the dashed line region, the better the welding results can be obtained even if the target position is deviated more significantly or the gap width is larger.

[0105] 9A to 9E, it can be seen that the area of ​​the dashed line region is larger and more robust in the case of feed control method A than in the case of feed control method B. It can also be seen that when the same feed control method A is used, the area of ​​the dashed line region is larger and more robust in the case of wire A than in the case of wire B.

[0106] The present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these are included in the scope of protection sought.

[0107] As described above, the present specification discloses the following:

[0108] (1) A fillet welding method using a feed control method in which the feed speed is alternately switched between a forward feed period and a reverse feed period, In the feeding control method, When the wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, The wire position phase is in the range of 90° to 180°. 90~180deg The average value of the welding current in 90~180deg_ave The set welding current value I set Larger than and, The wire position phase is in the range of 180° to 270°. 180~270deg The average value of the welding current in 180~270deg_ave The set welding current value I set The fillet welding method according to claim 1, wherein the welding distance is smaller than or equal to the welding distance. According to this fillet welding method, excellent robustness can be achieved even when a feed control welding method is applied.

[0109] (2) The method for controlling the feeding includes setting a wire frequency when a forward feeding period and a reverse feeding period are one cycle to a predetermined value, 2. The fillet welding method according to claim 1, wherein at least the welding current is switched between a current suppression period and a current non-suppression period in response to the wire position phase or the wire feed speed phase. According to this fillet welding method, excellent robustness can be achieved even in the case of a short circuit suppression type feed control method.

[0110] (3) A period T during which the wire position phase is 90° to 180°90~180deg The average value of the welding current in 90~180deg_ave and the set welding current value I set is the ratio of (I 90~180deg_ave ) / (I set ) is 1.10 or more. This fillet welding method allows for greater penetration and wider bead width.

[0111] (4) A period T during which the wire position phase is 180° to 270° 180~270deg The average value of the welding current in 180~270deg_ave and the set welding current value I set is the ratio of (I 180~270deg_ave ) / (I set ) is 0.90 or less. This fillet welding method allows for greater penetration and wider bead width.

[0112] (5) A period T during which the wire position phase is 90° to 180° 90~180deg The average value of the welding current in 90~180deg_ave and the wire position phase is in the range of 180° to 270° T 180~270deg The average value of the welding current in 180~270deg_ave is the ratio of (I 180~270deg_ave ) / (I 90~180deg_ave ) is 0.5 or less. This fillet welding method ensures high robustness.

[0113] (6) The welding wire has a mass of: O: Contains 0.0010 to 0.0100 mass%, Further containing at least one of Ti, Al, Mg, and Zr; Contains Ti, Al, Mg, and Zr in a total amount of 0.001 to 0.450 mass%; A fillet welding method according to any one of (1) to (5), characterized in that According to this fillet welding method, when droplets are formed at the tip of the welding wire, an oxide coating is formed on the surface of the droplets. This causes the feed speed to change locally depending on the wire position. Even if the droplets are subjected to inertial forces, the shape of the droplets is less likely to change, thereby suppressing droplet oscillation and droplet detachment from unintended wire positions.

[0114] (7) The fillet welding method according to (6), characterized in that the Si contained in the welding wire is 0.50 mass% or less with respect to a total mass of the welding wire, and a value of C+Si / 24+Mn / 6+Ni / 40+Cr / 5+Mo / 4+V / 4+Cu / 13 is 0.35 to 1.40. According to this fillet welding method, by limiting the Si content to 0.50 mass% or less, the increase in viscosity of the molten pool can be suppressed, resulting in good robustness, and furthermore, the composition of the slag formed on the weld bead changes, resulting in a thin slag with good adhesion that can form an electrocoating film. In addition, it is necessary to compensate for the mechanical performance by using other elements by reducing the Si content, but by setting the MIX value in the above-mentioned range, it is possible to balance the other elements.

[0115] (8) relative to the total mass of the welding wire, Ti:0.030~0.250% by mass Al:0.001~0.300% by mass Contains The Ti / Al ratio is 0.3 to 20. The fillet welding method according to (7) above, According to this fillet welding method, the melting points of the oxides of Ti and Al are 2100°C or less, and compared with Mg and Zr, the oxide film is not thick and is difficult to form near the boundary between the droplet and the wire, so that a constriction occurs at the boundary between the wire and the droplet in the latter half of the reverse feed of the wire, and the droplet detaches. This effect is promoted by the Ti / Al ratio being 0.3 to 20.

[0116] (9) The feeding speed during reverse feeding when the wire position phase is 270 deg is 50 m / min or more, The fillet welding method according to (6), characterized in that the value of the formula (Ti+Al) / (Ti+Al+Mg+Zr), which is obtained by the contents of Ti, Al, Mg, and Zr contained in the welding wire, is 0.5 or more. According to this fillet welding method, the wire can be stably detached by inertial force in the latter half of reverse feed by setting the maximum feed speed during reverse feed to 50 m / min or more. In addition, by containing Al and Ti and controlling the oxide film, it is possible to prevent the droplet from swinging or detaching in the latter half of forward feed (90° to 180°) and to promote detachment in the latter half of reverse feed.

[0117] (10) A feed control method for a fillet welding method, which alternates a feed speed between a forward feed period and a reverse feed period, comprising the steps of: When the wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, The wire position phase is in the range of 90° to 180°. 90~180deg The average value of the welding current in 90~180deg_ave The set welding current value I set Larger than and, The wire position phase is in the range of 180° to 270°. 180~270deg The average value of the welding current in 180~270deg_ave The set welding current value I set The feed control method according to claim 1, wherein the feed control amount is smaller than the feed control amount. According to this feed control method, excellent robustness can be achieved even when applied to fillet welding.

[0118] (11) A power source that is applicable to a fillet welding method and has a function of performing feed control to alternately switch the feed speed between a forward feed period and a reverse feed period, In the feeding control, When the wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, The wire position phase is in the range of 90° to 180°. 90~180deg The average value of the welding current in 90~180deg_ave The set welding current value I set Larger than and, The wire position phase is in the range of 180° to 270°. 180~270deg The average value of the welding current in 180~270deg_ave The set welding current value I set The power supply is characterized in that it is smaller than According to this power supply, excellent robustness can be achieved even when a feed control welding method in which the power supply controls the feed is applied to fillet welding.

[0119] (12) A fillet welding system that employs a feed control method in which the feed speed is alternately switched between a forward feed period and a reverse feed period, In the feeding control method, When the wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, The wire position phase is in the range of 90° to 180°. 90~180deg The average value of the welding current in 90~180deg_ave The set welding current value I set Larger than and, The wire position phase is in the range of 180° to 270°. 180~270deg The average value of the welding current in 180~270deg_ave The set welding current value I set The fillet welding system according to claim 1, wherein the fillet welding distance is less than or equal to the distance between the fillet welding points. According to this fillet welding system, excellent robustness can be achieved even when a feed control welding method is applied. [Explanation of symbols]

[0120] 1 AC power supply 2 Primary rectifier 3. Smoothing capacitor 4 Switching elements 5. Transformer 6 Secondary rectifier 7 Reactor 30 Inverter drive unit 31 Current detection section 32 Voltage detection section 33 Detachment detection unit 34 Current error amplifier 35 Feed setting data section 36 Current setting section 36A target current setting section 36B Wire tip position change part 36C Voltage setting section 37 Waveform control table linear calculation section 38 Phase Delay Correction Unit 39 Push feeder control section 40 A / D input section 41 Electrical angle adjustment unit 42 Digital Communications Department 50 Welding System 100 Welding Wire 110 Welding Robot 111 Welding torch 120 Welding control device 122 Digital Communications Department 123 Digital Communications Department 140 Welding power source 141 Control Systems Department 150 Controller 160 Servo Amplifier 161 Forward / reverse feed command generation unit 162 Digital Communications Department 163 Synchronization signal generator 170 Servo Motor 180 Push Motor 190 Wire Buffer 191 Serial to Analog Converter 200 Work

Claims

1. A power source having a function of performing a feed control in which the feed speed is alternately switched between a forward feed period and a reverse feed period, The power supply includes a waveform control table linear calculation unit, the waveform control table linear calculation unit includes at least a condition related to a welding current as a condition to be determined for each of the predetermined setting conditions, The condition relating to the welding current is When a wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, an average value I90-180deg_ave of the welding current during a period T90-180deg in which the wire position phase is 90deg-180deg is greater than a set welding current value Iset; and, A power source comprising at least a table in which an average value I180-270deg_ave of a welding current in a period T180-270deg in which the wire position phase is 180deg-270deg is set to be smaller than a set welding current value Iset.

2. The conditions relating to the welding current are as follows:

2. The power supply of claim 1, including at least one of a peak current Ip, a base current Ib, a start of base current Ib, and an end of base current Ib.

3. The predetermined setting conditions are:

2. The power source according to claim 1, wherein the welding current is at least one of an average feed rate Favg and a set welding current value Iset.

4. The power source includes a delivery setting data section; 2. The power supply according to claim 1, wherein the feed setting data section has at least one of an average feed speed Favg, a wire amplitude Wf, a wire forward / reverse frequency Sf, and a wire forward / reverse period Tf as a set value.

5. The wire position phase is in the range of 90 deg to 180 deg. ９０～１８０ｄｅｇ The average value of the welding current in ９０～１８０ｄｅｇ＿ａｖｅ and the set welding current value I ｓｅｔ is the ratio of (I ９０～１８０ｄｅｇ＿ａｖｅ ) / (I ｓｅｔ 2. The power supply of claim 1, wherein the ratio of the capacitance of the first to the capacitance of the second electrode is 1.10 or greater.

6. The wire position phase is in the range of 180 deg to 270 deg. １８０～２７０ｄｅｇ The average value of the welding current in １８０～２７０ｄｅｇ＿ａｖｅ and the set welding current value I ｓｅｔ is the ratio of (I １８０～２７０ｄｅｇ＿ａｖｅ ) / (I ｓｅｔ 2. The power supply of claim 1, wherein the ΔT is less than or equal to 0.

90.

7. The wire position phase is in the range of 90 deg to 180 deg. ９０～１８０ｄｅｇ The average value of the welding current in ９０～１８０ｄｅｇ＿ａｖｅ and a period T in which the wire position phase is 180 deg to 270 deg. １８０～２７０ｄｅｇ The average value of the welding current in １８０～２７０ｄｅｇ＿ａｖｅ is the ratio of (I １８０～２７０ｄｅｇ＿ａｖｅ ) / (I ９０～１８０ｄｅｇ＿ａｖｅ 2. The power supply of claim 1, wherein:

8. A welding system having a function of performing feed control to alternately switch a feed speed between a forward feed period and a reverse feed period, The welding system includes a waveform control table linear calculation unit, the waveform control table linear calculation unit includes at least a condition related to a welding current as a condition to be determined for each of the predetermined setting conditions, The condition relating to the welding current is When a wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, an average value I90-180deg_ave of the welding current during a period T90-180deg in which the wire position phase is 90deg-180deg is greater than a set welding current value Iset; and, A welding system comprising at least a table in which an average value I180-270deg_ave of the welding current in a period T180-270deg in which the wire position phase is 180deg-270deg is set to be smaller than a set welding current value Iset.

9. A control method using a power source having a function of performing feed control to alternately switch a feed speed between a forward feed period and a reverse feed period, The power supply includes a waveform control table linear calculation unit, the waveform control table linear calculation unit includes at least a condition related to a welding current as a condition to be determined for each of the predetermined setting conditions, The condition relating to the welding current is When a wire position phase based on the position of the welding wire at the time of switching from the reverse feed period to the forward feed period is set to 0 deg, an average value I90-180deg_ave of the welding current during a period T90-180deg in which the wire position phase is 90deg-180deg is greater than a set welding current value Iset; and, The control method includes at least a table in which an average value I180-270deg_ave of the welding current during a period T180-270deg in which the wire position phase is 180deg-270deg is set to be smaller than a set welding current value Iset.

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