Multi-layer welding method

Abstract

To make a welding action efficient in a multi-layer welding method performed by performing electrification with a welding current having a pulse waveform.SOLUTION: In a multi-layer welding method, a welding wire is fed, and arc-welding is performed by performing electrification with a welding current Iw having a pulse waveform in which electrification of a peak current Ip in a peak period Tp and a base current Ib in a base period Tb is set to one pulse cycle. In the multi-layer welding method, when the top player of a bevel of a base material 2 is welded, the parameters Tp and Ip of the pulse waveform are set to a one pulse cycle multi-droplet transfer condition.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a multi-layer welding method for arc welding by passing a welding current having a pulse waveform. [Background technology]

[0002] Pulse arc welding, which is performed while feeding a welding wire, is widely used to weld various metals. In this pulse arc welding, a rising transition current that rises from a base current to a peak current is passed during the rise period, a peak current is passed during the peak period, a falling transition current that falls from the peak current to a base current is passed during the fall period, and a base current is passed during the base period, and these welding current passes are repeated as one pulse period to perform welding. In addition, the arc length is maintained at an appropriate value by feedback controlling the pulse period so that the average value of the welding voltage is equal to the welding voltage setting value.

[0003] In pulse arc welding, the parameters of the pulse waveform of the welding current are set so that one droplet is transferred per pulse period in order to improve the welding condition. The invention of Patent Document 1 discloses a method for automatically setting the parameters of the pulse waveform so that one droplet is transferred per pulse period under various welding conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-67674 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a multi-layer welding method in which a pulsed welding current is applied, when welding upper layers other than the first layer, the bead width is narrow, so multiple welding steps must be repeated, resulting in poor work efficiency.

[0006] Therefore, an object of the present invention is to improve the efficiency of the welding action in a multi-layer welding method in which a welding current having a pulse waveform is applied. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the invention of claim 1 comprises: 1. A multi-layer welding method for arc welding by feeding a welding wire and passing a welding current having a pulse waveform in which a peak current during a peak period and a base current during a base period constitute one pulse cycle, comprising: When welding the top layer, the parameters of the pulse waveform are set to a one-pulse-cycle multiple droplet transfer condition. The multi-layer welding method is characterized by the above.

[0008] The invention of claim 2 is as follows: When welding an upper layer other than the first layer, the parameters of the pulse waveform are set to the one-pulse-cycle multiple droplet transfer condition. 2. The multi-layer welding method according to claim 1,

[0009] The invention of claim 3 is as follows: When welding the first layer, the parameters of the pulse waveform are set to a one-pulse-period, one-droplet transfer condition. 3. The multi-layer welding method according to claim 1, wherein the first and second layers are welded together.

[0010] The invention of claim 4 is as follows: The parameters of the pulse waveform are the peak duration and the peak current. 3. The multi-layer welding method according to claim 1, wherein the first and second layers are welded together. Effect of the Invention

[0011] According to the multi-layer welding method of the present invention, the efficiency of welding work can be improved. [Brief description of the drawings]

[0012] [Figure 1]1 is a block diagram of a welding device for carrying out a multi-layer welding method according to an embodiment of the present invention. [Diagram 2] 2 is a timing chart of each signal in the welding device of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] Fig. 1 is a block diagram of a welding device for carrying out a multi-layer welding method according to an embodiment of the present invention. The welding device is mainly composed of a welding power source PS, a robot control device RC, a robot (not shown), etc., all of which are enclosed by a dashed line. Each block will be described below with reference to the figure.

[0015] The welding power source PS is composed of the following blocks: The main power source circuit MC receives an AC commercial power source (not shown) such as a three-phase 200V, performs output control such as inverter control according to a drive signal Dv described below, and outputs a welding voltage Vw and welding current Iw suitable for welding. Although not shown, the main power source circuit MC includes a primary rectifier circuit that rectifies the AC commercial power source, a capacitor that smoothes the rectified DC, an inverter circuit that converts the smoothed DC into high-frequency AC according to the drive signal Dv, an inverter transformer that steps down the high-frequency AC to a voltage value suitable for welding, and a secondary rectifier circuit that rectifies the stepped-down high-frequency AC.

[0016] The reactor WL is inserted between the positive output of the main power supply circuit MC and the welding torch 4, and smoothes the output of the main power supply circuit MC.

[0017] The feed motor WM is driven to rotate by a feed control signal Fc, which will be described later. The welding wire 1 is fed at a feed speed Fw through the welding torch 4 by the rotation of a feed roll 5 coupled to the feed motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. The base material 2 is a thick plate with a groove formed therein, and a first layer and an upper layer are welded in a multi-layer manner. The feed motor WM and the welding torch 4 are mounted on a robot (not shown). A welding voltage Vw is applied between a power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw flows.

[0018] The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The welding voltage averaging circuit VAV averages the welding voltage detection signal Vd (by passing it through a low-pass filter) and outputs a welding voltage average value signal Vav. The welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr. The voltage error amplification circuit EV amplifies the error between the welding voltage setting signal Vr(+) and the welding voltage average value signal Vav(-) and outputs a voltage error amplification signal Ev.

[0019] The V / F converter VF receives the voltage error amplified signal Ev, converts it into a period corresponding to the voltage error amplified signal Ev, and outputs a pulse period signal Tf, which is a trigger signal that goes to high level for a short period of time every period. The period during which this pulse period signal Tf goes to high level for a short period of time constitutes one pulse period.

[0020] The rising period setting circuit TUR outputs a predetermined rising period setting signal Tur. The falling period setting circuit TKR outputs a predetermined falling period setting signal Tkr. The base current setting circuit IBR outputs a predetermined base current setting signal Ibr.

[0021] The pulse waveform parameter setting circuit PR receives the first layer signal Lr from the robot control device RC (described later) as input. When the first layer signal Lr is at a high level (first layer), a peak period setting signal Tpr and a peak current setting signal Ipr are outputted so as to achieve a one droplet transfer state per one pulse period. When the initial layer signal Lr is at a low level (an upper layer other than the initial layer), a peak period setting signal Tpr and a peak current setting signal Ipr that are preset to achieve a multi-droplet transfer state in one pulse period are output.

[0022] The welding current setting circuit IR receives as inputs the pulse period signal Tf, the rise period setting signal Tur, the peak period setting signal Tpr, the fall period setting signal Tkr, the peak current setting signal Ipr and the base current setting signal Ibr, and performs the following processing each time the pulse period signal Tf changes to a high level for a short period of time, to output the welding current setting signal Ir. 1) During the period determined by the rise period setting signal Tur, a welding current setting signal Ir that rises from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr is output. 2) Subsequently, during the period determined by the peak period setting signal Tpr, the peak current setting signal Ipr is output as the welding current setting signal Ir. 3) Subsequently, during a period determined by the falling period setting signal Tkr, the welding current setting signal Ir is output, which decreases from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr. 4) Subsequently, during the period until the pulse period signal Tf again becomes high level for a short period of time, the base current setting signal Ibr is output as the welding current setting signal Ir.

[0023] The welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The current error amplifier circuit EI amplifies the error between the welding current setting signal Ir(+) and the welding current detection signal Id(-) and outputs a current error amplified signal Ei. The drive circuit DV receives the current error amplified signal Ei and a start signal On from a robot control device RC (described later) as inputs, and performs PWM modulation control based on the current error amplified signal Ei when the start signal On is at a high level (welding starts) and outputs a drive signal Dv for driving the inverter circuit in the main power supply circuit MC, but does not output the drive signal Dv when the start signal On is at a low level (welding stops).

[0024] The feed speed setting circuit FR outputs a predetermined feed speed setting signal Fr. The feed control circuit FC receives the feed speed setting signal Fr and an activation signal On from a robot control device RC (described later) as inputs, and outputs a feed control signal Fc to the feed motor WM for feeding the welding wire 1 at the value of the feed speed setting signal Fr when the activation signal On is at a High level (welding start), and outputs a feed control signal Fc to the feed motor WM for stopping feeding when the activation signal On is at a Low level.

[0025] The robot control device RC moves a robot (not shown) according to a pre-taught work program, outputs a start signal On to command the start or stop of welding, and outputs a first layer signal Lr that becomes a high level when welding the first layer.

[0026] Fig. 2 is a timing chart of each signal in the welding device of Fig. 1. Fig. 2(A) shows the change over time of the welding current Iw, and Fig. 2(B) shows the change over time of the welding voltage Vw. The operation of each signal will be explained below with reference to Fig.

[0027] The feed speed Fw (not shown) is fed at a predetermined constant speed during welding. In the pulse period Tf from time t1 to t2, during the rise period Tu, as shown in FIG. 1A, an upward transition current Iu that rises from the base current Ib to the peak current Ip is applied between the welding wire and the base metal, and as shown in FIG. 1B, an upward transition voltage that rises from the base voltage Vb to the peak voltage Vp is applied between the welding wire and the base metal. During the following peak period Tp, as shown in FIG. 1A, a peak current Ip with a large current value equal to or greater than the critical value is applied to transfer droplets from the welding wire, and as shown in FIG. 1B, a peak voltage Vp proportional to the arc length is applied. During the following fall period Tk, as shown in FIG. 1A, a downward transition current Ik that falls from the peak current Ip to the base current Ib is applied, and as shown in FIG. 1B, a downward transition voltage that falls from the peak voltage Vp to the base voltage Vb is applied. During the subsequent base period Tb, as shown in FIG. 1(A), a base current Ib of a small current value less than the critical value is passed to prevent droplets from forming, and as shown in FIG. 1(B), a base voltage Vb proportional to the arc length is applied. The arc length becomes longer during the peak period Tp and shorter during the base period Tb. The rise period tu is set by the rise period setting signal Tur in FIG. 1. The peak period tp is set by the peak period setting signal Tpr in FIG. 1. The fall period tk is set by the fall period setting signal Tkr in FIG. 1. The peak current Ip is set by the peak current setting signal Ipr in FIG. 1. The base current Ib is set by the base current setting signal Ipr in FIG. 1.

[0028] The pulse period Tf is feedback controlled (frequency modulation controlled) so that the value of the welding voltage average value signal Vav in Fig. 1 becomes equal to the predetermined value of the welding voltage setting signal Vr in Fig. 1. For this reason, the rise period Tu, peak period Tp, fall period Tk, peak current Ip and base current Ib are set to predetermined values, and the base period Tb (pulse period Tf) is determined by feedback control so that the average value of the welding voltage Vw becomes equal to the predetermined welding voltage setting value.

[0029] The rise time Tu, fall time Tk and base current Ib are fixed to predetermined values ​​when welding the first and upper layers of the groove, for example, Tu=1 ms, Tk=1 ms and Ib=50A.

[0030] The number of droplets transferred during one pulse period Tf varies depending on the combination of the peak duration Tp and peak current Ip. The peak duration Tp and peak current Ip are set by the pulse waveform parameter setting circuit PR in FIG. 1 as follows: 1) When the first layer signal Lr input from the robot control device RC in Fig. 1 is at a high level (first layer), the peak period Tp and peak current Ip are set so that one droplet is transferred per pulse period. For example, Tp = 1.2 ms and Ip = 450 A. 2) When the initial layer signal Lr input from the robot control device RC in Fig. 1 is at a low level (an upper layer other than the initial layer), the peak period Tp and peak current Ip are set so that multiple droplets are transferred in one pulse period. For example, Tp = 2.4 ms and Ip = 500 A. 3) In particular, when welding the uppermost layer, it is preferable to set the peak period Tp and peak current Ip so as to achieve a state in which multiple droplets are transferred in one pulse period.

[0031] The same applies to the pulse period Tf from time t2 to t3.

[0032] The above is the case where the output control is frequency modulation control, and the pulse period Tf is feedback controlled. In this case, the peak period Tp and the peak current Ip become the pulse waveform parameters for setting the droplet transfer state. Also, when the output control is pulse width modulation control, the peak period Tp is feedback controlled. In this case, the pulse period Tf and the peak current Ip become the pulse waveform parameters for setting the droplet transfer state. Furthermore, when the output control is current modulation control, the peak current Ip and the base current Ib are feedback controlled. In this case, the pulse period Tf and the peak period Tp become the pulse waveform parameters for setting the droplet transfer state.

[0033] The effects of this embodiment will be described below. According to this embodiment, in the multi-layer welding method, when welding the top layer, the parameters of the pulse waveform of the welding current are set to the one-pulse-cycle multiple droplet transfer condition. When the one-pulse-cycle multiple droplet transfer state is reached, the arc assumes a widened shape, and the bead width formed becomes wider. For this reason, when the top layer is welded in the one-pulse-cycle multiple droplet transfer state, the bead width becomes wider, and the number of welding repetitions can be reduced. As a result, in this embodiment, the efficiency of multi-layer welding work can be improved.

[0034] More preferably, according to this embodiment, when welding an upper layer other than the initial layer, the pulse waveform parameters are set to the one-pulse-cycle multiple droplet transfer condition. When an upper layer other than the initial layer is welded in the one-pulse-cycle multiple droplet transfer condition, the bead width becomes wider and the number of welding repetitions can be reduced. As a result, this embodiment can improve the efficiency of multi-layer welding work.

[0035] More preferably, according to this embodiment, when welding the first layer, the pulse waveform parameters are set to a one-pulse-period, one-droplet-transfer condition. When the one-pulse-period, one-droplet-transfer state is reached, the arc has a narrowed shape, and deep penetration can be obtained. When welding the first layer, it is important from the viewpoint of weld quality to form deep penetration. For this reason, when the first layer is welded in the one-pulse-period, one-droplet-transfer state, a sound bead with deep penetration can be formed.

[0036] More preferably, according to this embodiment, the parameters of the pulse waveform are the peak duration and the peak current. Depending on the combination of the peak duration and the peak current, the droplet transfer state can be a multiple droplet transfer state per pulse cycle or a one droplet transfer state per pulse cycle. This makes it possible to optimize the droplet transfer state according to the layer to be welded. [Explanation of symbols]

[0037] 1 Welding wire 2 Base material 3. Arc 4. Welding torch 5 Feeding roll DV driver circuit Dv drive signal EI Current Error Amplifier Circuit Ei Current error amplification signal EV voltage error amplifier circuit Ev Voltage error amplified signal FC feed control circuit Fc feed control signal FR feed speed setting circuit Fr feed speed setting signal Fw Feed speed Ib Base current IBR base current setting circuit Ibr Base current setting signal ID Welding current detection circuit Id Welding current detection signal Ik falling transition current Ip Peak current Ipr Peak current setting signal IR welding current setting circuit Ir Welding current setting signal Iu rising transition current Iw Welding current MC power supply main circuit On Start signal PR pulse waveform parameter setting circuit PS Welding Power Source RC robot controller Tb Base period Tf Pulse period (signal) TKR Falling period setting circuit Tkr Falling period setting signal Tp peak period Tpr Peak period setting signal Tu Rise Period TUR Rising period setting circuit Tur Rising period setting signal VAV Welding voltage averaging circuit Vav Welding voltage average value signal Vb Base voltage VD Welding voltage detection circuit Vd Welding voltage detection signal VF V / F converter Vp Peak voltage VR welding voltage setting circuit Vr Welding voltage setting signal Vw welding voltage WL Reactor WM Feed motor

Claims

1. 1. A multi-layer welding method for arc welding by feeding a welding wire and passing a welding current having a pulse waveform in which a peak current during a peak period and a base current during a base period constitute one pulse cycle, comprising: When welding the top layer, the parameters of the pulse waveform are set to a one-pulse-cycle multiple droplet transfer condition. A multi-layer welding method comprising the steps of:

2. When welding an upper layer other than the first layer, the parameters of the pulse waveform are set to the one-pulse-cycle multiple droplet transfer condition. The multi-layer welding method according to claim 1 .

3. When welding the first layer, the parameters of the pulse waveform are set to a one-pulse-period, one-droplet-transfer condition.

3. The multi-layer welding method according to claim 1 or 2.

4. The parameters of the pulse waveform are the peak duration and the peak current.

3. The multi-layer welding method according to claim 1 or 2.

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