Pulse arc welding control method

Abstract

To prevent arc breakage due to magnetic blow and stably maintain a welding state in consumable electrode pulse arc welding.SOLUTION: In a pulse arc welding control method that feeds a welding wire and performs welding by repeating a peak period Tp for outputting peak current Ip and peak voltage and a base period Tb for outputting base current Ib and base voltage Vb, the base current Ib is oscillated within a current range of 100 A or less, and with an amplitude of 40 A or more and a frequency of 300 Hz or more. Magnetic blow is discriminated (Hd) on the basis of rise in the base voltage Vb when arcing, and after discriminating (Hd) magnetic blow, oscillation of the base current Ib is started.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a countermeasure against magnetic blow in consumable electrode pulsed arc welding. [Background technology]

[0002] In consumable electrode pulsed arc welding, welding is performed by repeatedly feeding the welding wire and outputting a peak current and a peak voltage during a peak period, and outputting a base current and a base voltage during a base period. The peak current is set to a large current value of about 500A, which is equal to or greater than the critical current value, and the welding wire is melted to form and transfer droplets. The base current is set to about 40A, which is less than the critical current value, and the welding wire is hardly melted. When the welding current value exceeds the critical current value, the droplet transfer state becomes a spray transfer state. In pulsed arc welding, it is important to maintain a one-pulse-cycle one-droplet transfer state, in which one droplet is transferred by passing one peak current, in order to obtain a high-quality weld bead with little spatter.

[0003] In pulse arc welding of steel and the like, a magnetic field is formed around the arc generating part by the welding current passing through the base material, and the arc is often subjected to a force from this magnetic field and deformed. This condition is generally called magnetic blow or arc blow. When the magnetic blow condition becomes severe, the arc is significantly deformed and the arc length becomes very long, making it impossible to maintain the arc, resulting in arc interruption. When arc interruption occurs, the welding quality deteriorates. For this reason, countermeasures against magnetic blow are a major issue in pulse arc welding.

[0004] In the invention of Patent Document 1, when the rate of increase of the base voltage during the generation of an arc during the base period is detected to be equal to or greater than a reference rate of increase, it is determined that a magnetic blow has occurred, and control for dealing with the magnetic blow is performed by rapidly increasing the base current to 200 A or more. Magnetic blow occurs during the base period when the rigidity of the arc is weakened due to a small current value. When the arc length is lengthened due to magnetic blow, the arc voltage (base voltage) increases, and this is utilized to determine the occurrence of magnetic blow. Furthermore, when the base current is increased, the rigidity of the arc increases, making it possible to suppress deformation of the arc even when a force is applied from the magnetic field. As a result, arc interruption can be prevented. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-268081 A Summary of the Invention [Problem to be solved by the invention]

[0006] Increasing the base current to 200A or more as in the conventional magnetic blow countermeasures can prevent arc interruption. However, increasing the base current to a high current value of 200A or more promotes melting of the welding wire and the formation of droplets. As a result, the one-pulse-cycle one-droplet transfer state is not achieved, and there is a problem that the welding state is inferior to a good state.

[0007] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a pulse arc welding control method capable of preventing arc interruption due to magnetic blow and maintaining a good welding condition. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a pulse arc welding control method for feeding a welding wire and welding by repeating a peak period in which a peak current and a peak voltage are output and a base period in which a base current and a base voltage are output, comprising: The base current is oscillated at a current range of 100 A or less, an amplitude of 40 A or more, and a frequency of 300 Hz or more. Let, a magnetic arc blow is determined based on an increase in the base voltage when an arc is generated, and the oscillation of the base current is started after the magnetic arc blow is determined; an average value of the base current when the base current is vibrating is equal to a value of the base current when the base current is not vibrating; The present invention relates to a pulse arc welding control method. Effect of the Invention

[0011] According to the present invention, in consumable electrode pulsed arc welding, arc interruption due to magnetic blow can be prevented and a good welded state can be maintained. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a welding power source for carrying out a pulse arc welding control method according to a first embodiment of the present invention. [Diagram 2] 2 is a timing chart of each signal in the welding power source of FIG. 1, illustrating a pulse arc welding control method according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0014] 1 is a block diagram of a welding power source for carrying out a pulse arc welding control method according to an embodiment of the present invention. Each block will be described below with reference to the diagram.

[0015] The main power supply circuit MC receives a commercial power supply (not shown) such as 3-phase 200V as input, performs output control such as inverter control according to a current error amplification signal Ei, which will be described later, and outputs an output voltage suitable for welding.

[0016] The reactor WL smoothes the output of the main power supply circuit MC.

[0017] Welding wire 1 is fed through welding torch 4 by the rotation of a feed roll 5 connected to a wire feed motor (not shown), and an arc 3 is generated between the welding wire 1 and base metal 2. A welding voltage Vw is applied between a power feed tip (not shown) in welding torch 4 and base metal 2, and a welding current Iw flows.

[0018] The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The voltage averaging circuit VAV averages the voltage detection signal Vd and outputs a voltage average signal Vav. The voltage setting circuit VR outputs a voltage setting signal Vr of a desired value.

[0019] The voltage error amplifier circuit EV amplifies the error between the voltage setting signal Vr and the voltage average signal Vav, and outputs the voltage error amplified signal Ev. The V / F converter VF outputs a pulse frequency signal Tf having a frequency according to the voltage error amplified signal Ev. This pulse frequency signal Tf is a signal that determines the frequency whose one period is the peak period and the base period.

[0020] The peak period timer circuit TTP outputs a peak period signal Ttp that is at a high level only for a predetermined peak period Tp for each frequency of the pulse frequency signal Tf. Therefore, this peak period signal Ttp is a signal that is at a high level during the peak period Tp and at a low level during the base period.

[0021] The arc determination circuit AD receives the voltage detection signal Vd and determines whether an arc has occurred based on the voltage detection signal Vd, and outputs an arc determination signal Ad that goes to a High level.

[0022] The base voltage rising state detection circuit DV receives the peak period signal Ttp, the arc discrimination signal Ad, and the voltage detection signal Vd as inputs, detects the rising state of the voltage detection signal Vd (base voltage) when the peak period signal Ttp is at a low level (base period Tb) and the arc discrimination signal Ad is at a high level (arc occurring state), and outputs a base voltage rising state detection signal Dv. The base voltage rising state detection signal Dv is calculated, for example, as follows. 1) The rate of rise (differential value) of the voltage detection signal Vd when an arc is generated during the base period 2) The rise (difference) of the voltage detection signal Vd from a predetermined reference base voltage value during an arc generation state during the base period 3) Absolute value of voltage detection signal Vd when arcing occurs during the base period

[0023] The magnetic blow countermeasure mode selection circuit MS is a switch or the like provided on the front panel of the welding power source, and outputs a magnetic blow countermeasure mode selection signal Ms that goes to a High level when the welding operator determines that the workpiece is prone to magnetic blow and selects the "magnetic blow countermeasure mode" and goes to a Low level when the welding operator selects the "normal mode."

[0024] The magnetic blow detection circuit HB receives the magnetic blow countermeasure mode selection signal Ms, the base voltage rise state detection signal Dv, and the peak period signal Ttp as inputs, performs one of the following processes 1) to 3), and outputs a magnetic blow detection signal Hd. Process 1) When the magnetic blast countermeasure mode selection signal Ms is at a high level (magnetic blast countermeasure mode), a magnetic blast determination signal Hd that is always at a high level is output. Process 2) When the magnetic blast countermeasure mode selection signal Ms is at a low level (normal mode), if the value of the base voltage rise state detection signal Dv becomes equal to or greater than a predetermined reference value, the magnetic blast discrimination signal Hd is set to a high level, and if the peak period signal Ttp then becomes a high level, the magnetic blast discrimination signal Hd is reset to a low level. Process 3) When the magnetic blow countermeasure mode selection signal Ms is at a low level (normal mode), if the value of the base voltage rise state detection signal Dv becomes equal to or exceeds a predetermined reference value, a magnetic blow discrimination signal Hd is output, which is set to a high level and then reset to a low level when welding is completed.

[0025] The normal base current setting circuit IBSR outputs a normal base current setting signal Ibsr for setting a predetermined normal value of the base current. The setting range of the normal base current setting signal Ibsr is about 20 to 50A.

[0026] The oscillating base current setting circuit IBBR outputs an oscillating base current setting signal Ibbr that periodically oscillates with a waveform such as a square wave, a triangular wave, a sine wave, etc. The oscillating base current setting signal Ibbr oscillates with an amplitude of 40 A or more and a frequency of 300 Hz or more in a current range of 100 A or less. The average value of the oscillating base current setting signal Ibbr is preferably set to be equal to the value of the above-mentioned normal base current setting signal Ibsr.

[0027] The base current setting circuit IBR receives as input the magnetic blow detection signal Hd, the normal base current setting signal Ibsr, and the vibration base current setting signal Ibbr, and outputs a base current setting signal Ibr which becomes the normal base current setting signal Ibsr when the magnetic blow detection signal Hd is at a low level, and which becomes the vibration base current setting signal Ibbr when the magnetic blow detection signal Hd is at a high level.

[0028] The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr, which is set to about 400 to 600 A depending on the diameter, material, feed speed, etc. of the welding wire.

[0029] The current setting circuit IR receives the base current setting signal Ibr, the peak current setting signal Ipr, and the peak period signal Ttp as inputs, and outputs the peak current setting signal Ipr as the current setting signal Ir when the peak period signal Ttp is at a high level, and outputs the base current setting signal Ibr as the current setting signal Ir when the peak period signal Ttp is at a low level.

[0030] The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current error amplifier circuit EI amplifies the error between the current setting signal Ir and the current detection signal Id and outputs a current error amplified signal Ei.

[0031] Fig. 2 is a timing chart of each signal in the welding power source of Fig. 1, which illustrates a pulse arc welding control method according to an embodiment of the present invention. Fig. 2(A) illustrates the change over time of the welding current Iw, Fig. 2(B) illustrates the change over time of the welding voltage Vw, and Fig. 2(C) illustrates the change over time of the magnetic blow discrimination signal Hd. The operation of each signal will be explained below with reference to the figures.

[0032] The figure shows two periods of waveforms, with the occurrence of magnetic flux loss being detected during the first period.

[0033] (1) Operational explanation of the first cycle During a predetermined peak period Tp from time t1 to t2, as shown in FIG. 1(A), a predetermined peak current Ip is applied, and as shown in FIG. 1(B), a peak voltage proportional to the arc length is applied. The peak current Ip is set by a peak current setting signal Ipr in FIG. 1. During the peak period Tp, the tip of the welding wire is melted and a droplet is formed, and the droplet transfers to the molten pool around the time when the peak period Tp ends (one droplet transfer state per pulse period). The peak period Tp and the peak current Ip are set so as to achieve this one droplet transfer state per pulse period.

[0034] The period from time t2 to t3 is the base period Tb. The period from time t1 to t3 is one pulse period. The pulse period (pulse frequency) is feedback controlled (frequency modulation controlled) so that the average value of the welding voltage Vw is equal to the value of the voltage setting signal Vr in Figure 1. This maintains the average value of the arc length at an appropriate value.

[0035] During the period from t2 to t21 in the base period Tb, no magnetic blow occurs, so a predetermined normal base current flows as shown in Fig. 1(A), and a substantially constant normal base voltage Vb is applied as shown in Fig. 1(B). The normal base current is set by the normal base current setting signal Ibsr in Fig. 1.

[0036] At time t21, the arc is deformed due to the occurrence of magnetic blow, and the arc length gradually becomes longer than in the normal state. For this reason, as shown in FIG. 1B, the base voltage Vb rises from time t21, and at time t22, the rising state reaches a predetermined reference value or more. The rising state of the base voltage Vb is detected by the base voltage rising state detection signal Dv of FIG. 1. When the rising state of the base voltage Vb reaches the reference value or more, as shown in FIG. 1C, the magnetic blow discrimination signal Hd changes to a high level. In response to this, as shown in FIG. 1A, the base current Ib switches from a constant normal base current to a rectangular wave oscillating base current Ibb. The oscillating base current Ibb is set by the oscillating base current setting signal Ibbr of FIG. 1. The oscillating base current Ibb oscillates with an amplitude of 40 A or more and a frequency of 300 Hz or more in a current range of 100 A or less. For this reason, the rigidity of the arc increases, and the deformation of the arc due to magnetic blow can be suppressed. The reason why the vibration base current Ibb is set to 100 A or less is to suppress the growth of droplets and maintain a state of one droplet transfer per pulse period. Here, in order to more reliably maintain a state of one droplet transfer per pulse period, it is preferable to set the average value of the vibration base current Ibb to be equal to the value of the normal base current. Also, the reason why the vibration base current Ibb is oscillated with an amplitude of 40 A or more and a frequency of 300 Hz or more is to generate arc rigidity that can resist the deformation of the arc caused by magnetic blow. Then, after time t22, the deformation of the arc is suppressed, and the rising state of the base voltage Vb returns to the normal value, as shown in FIG. 1B.

[0037] The magnetic blow detection signal Hd goes high in level in one of the following three cases. Process 1) When the welding operator selects the "magnetic blow countermeasure mode" by the magnetic blow countermeasure mode selection signal Ms in Fig. 1, the magnetic blow discrimination signal Hd is always at a high level. In this case, the base current Ib is always the vibration base current Ibb, regardless of the rising state of the base voltage Vb. When the welding operator determines that the workpiece is in a state where magnetic blow is very likely to occur, he can select the "magnetic blow countermeasure mode." This makes it possible to reliably suppress arc deformation due to magnetic blow and prevent arc interruption, without having to determine magnetic blow based on the rising state of the base voltage Vb. On the other hand, this has the disadvantage that the noise from the arc becomes louder, since the base current Ib is always the vibration base current Ibb.

[0038] Process 2) When the welding operator selects the "normal mode" by the magnetic blow countermeasure mode selection signal Ms in FIG. 1, the magnetic blow discrimination signal Hd is set to a high level when the value of the base voltage rise state detection signal Dv in FIG. 1 becomes equal to or greater than a predetermined reference value, and is reset to a low level when the peak period signal Ttp in FIG. 1 becomes equal to or greater than a high level thereafter. That is, the magnetic blow discrimination signal Hd becomes a high level when the rise state of the base voltage Vb becomes equal to or greater than the reference value, and returns to a low level when the next period starts. In this case, the base current Ib is switched to the vibration base current Ibb only in the period in which the magnetic blow is detected, so that the deformation of the arc due to the magnetic blow can be suppressed and the arc interruption can be prevented. As a result, the noise due to the vibration base current Ibb is also suppressed. On the other hand, there is a weakness in that the magnetic blow must be detected reliably, and if the detection fails, the arc will be deformed.

[0039] Process 3) When the welding operator selects the "normal mode" by the magnetic blow countermeasure mode selection signal Ms in FIG. 1, the magnetic blow discrimination signal Hd is set to a high level when the value of the base voltage rise state detection signal Dv in FIG. 1 becomes equal to or greater than a predetermined reference value, and is reset to a low level when welding is completed thereafter. That is, the magnetic blow discrimination signal Hd becomes a high level when the rise state of the base voltage Vb becomes equal to or greater than a reference value, and returns to a low level when welding of the workpiece is completed. In this case, the base current Ib is switched to the vibration base current Ibb only in the period after the magnetic blow is detected, so that it is possible to suppress the deformation of the arc due to the magnetic blow and prevent arc interruption. As a result, since the current is switched to the vibration base current Ibb from the time when the magnetic blow is detected and thereafter, the noise is also limited. Furthermore, since once the magnetic blow is detected, the vibration base current Ibb remains until the welding is completed, it is possible to suppress the deformation of the arc and the occurrence of arc interruption even if the accuracy of the magnetic blow detection is somewhat poor.

[0040] (2) Operational explanation of the second cycle The operation during the peak period Tp from time t3 to t4 is the same as that from time t1 to t2. Moreover, since the figure shows the case of the above-mentioned process 3), during the base period Tb from time t4 to t5, as shown in FIG. 1A, the base current Ib becomes the vibration base current Ibb. Therefore, as shown in FIG. 1C, the magnetic blow discrimination signal Hd remains at a high level after time t22. [Explanation of symbols]

[0041] 1 Welding wire 2 Base material 3. Arc 4. Welding torch 5 Feeding roll AD Arc Discrimination Circuit Ad Arc discrimination signal DV base voltage rising detection circuit Dv Base voltage rising state detection signal EI Current Error Amplifier Circuit Ei Current error amplification signal EV voltage error amplifier circuit Ev Voltage error amplified signal HB magnetic blow detection circuit Hd magnetic blow detection signal Ib Base current Ibb Vibration base current IBBR Vibration base current setting circuit Ibbr Vibration base current setting signal IBR base current setting circuit Ibr Base current setting signal IBSR Normal base current setting circuit Ibsr Normal base current setting signal ID Current Detection Circuit Id Current detection signal Ip Peak current IPR Peak current setting circuit Ipr Peak current setting signal IR current setting circuit Ir Current setting signal Iw Welding current MC power supply main circuit MS Magnetic blowout prevention mode selection circuit Ms Magnetic blowout prevention mode selection signal Tb Base period Tf Pulse frequency signal Tp peak period TTP Peak Period Timer Circuit Ttp Peak Duration Signal VAV Voltage averaging circuit Vav Voltage average signal Vb Base voltage VD voltage detection circuit Vd Voltage detection signal VF V / F converter VR voltage setting circuit Vr Voltage setting signal Vw welding voltage WL Reactor

Claims

[Claim 1] 1. A pulse arc welding control method for feeding a welding wire and welding by repeating a peak period in which a peak current and a peak voltage are output and a base period in which a base current and a base voltage are output, The base current is oscillated in a current range of 100 A or less, with an amplitude of 40 A or more and a frequency of 300 Hz or more; a magnetic arc blow is determined based on an increase in the base voltage when an arc is generated, and the oscillation of the base current is started after the magnetic arc blow is determined; an average value of the base current when the base current is vibrating is equal to a value of the base current when the base current is not vibrating; A pulse arc welding control method comprising:

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