Arc welding method

Abstract

To perform welding smoothly in an arc welding method in which pulsed arc welding and short circuit transfer arc welding are switched alternately.SOLUTION: An arc welding method is provided in which a period (period from time t1 to t2) during which pulsed arc welding is performed with a welding wire feeding speed Fw as a first feeding speed and a period (period from time t3 to t4) during which short circuit transfer arc welding is performed with the feeding speed Fw as a second feeding speed are switched alternately to perform welding, and in which a transition period (period from time t2 to t3) is provided between the period of pulsed arc welding and the period of short circuit transfer arc welding, and in the transition period, the first feed speed is switched to the second feed speed. In the arc welding method, time from a start of the transition period until a first short circuit occurs during the period of short circuit transition arc welding (period from time t2 to t31) is detected, and a time length of the transition period (period from time t2 to t3) is controlled on the basis of the time of short-circuit occurrence during the transition period.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an arc welding method in which welding is performed by alternately switching between a period in which pulse arc welding is performed and a period in which short-circuit transfer arc welding is performed. [Background technology]

[0002] A welding method is used in which a welding wire is fed and a period of pulse arc welding and a period of short circuit transfer arc welding are alternately switched (for example, see Patent Document 1). In this case, the switching frequency is about 0.1 to 10 Hz. With this welding method, a beautiful scale-like bead can be formed. Furthermore, with this welding method, the heat input to the base material can be controlled by adjusting the ratio between the period of pulse arc welding and the period of short circuit transfer arc welding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-313179 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology, when switching between pulse arc welding and short circuit transfer arc welding, the droplet transfer form changes, which causes spattering and makes the welding state unstable.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide an arc welding method capable of smoothly switching between pulse arc welding and short circuit transfer arc welding. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the invention of claim 1 comprises: welding is performed by alternately switching between a period in which the welding wire is fed at a first feed speed and pulse arc welding is performed and a period in which the welding wire is fed at a second feed speed and short circuit transfer arc welding is performed; a transition period is provided between a period of the pulse arc welding and a period of the short circuit transfer arc welding, and the feed speed is changed from the first feed speed to the second feed speed with a slope during the transition period, Detecting a transition short circuit occurrence time from a start point of the transition period to a time when a short circuit first occurs during the short circuit transfer arc welding period; controlling a time length of the transition period based on the transition short circuit occurrence time; When the transition short circuit occurrence time is equal to or longer than a reference time, the length of the transition period is controlled to be shortened. The present invention relates to an arc welding method.

[0008] Claim 2 The invention is welding is performed by alternately switching between a period in which the welding wire is fed at a first feed speed and pulse arc welding is performed and a period in which the welding wire is fed at a second feed speed and short circuit transfer arc welding is performed; a transition period is provided between a period of the pulse arc welding and a period of the short circuit transfer arc welding, and the feed speed is changed from the first feed speed to the second feed speed with a slope during the transition period, Detecting a transition short circuit occurrence time from a start point of the transition period to a time when a short circuit first occurs during the short circuit transfer arc welding period; controlling the length of the transition period so that the transition short circuit occurrence time becomes equal to a reference time; The present invention relates to an arc welding method.

[0009] Claim 3 The invention is Calculating a moving average value of the transition short circuit occurrence time; and controlling the length of the transition period by using the moving average value instead of the transition short circuit occurrence time. Characterized by Claims 1-2 1 is an arc welding method according to any one of claims 1 to 9. Effect of the Invention

[0010] According to the present invention, switching between pulse arc welding and short circuit transfer arc welding can be smoothly performed. [Brief description of the drawings]

[0011] [Figure 1]1 is a block diagram of a welding power source for carrying out an arc welding method according to an embodiment of the present invention. [Diagram 2] 2 is a timing chart of each signal in the welding power source of FIG. 1 illustrating the arc welding method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] 1 is a block diagram of a welding power source for carrying out an arc welding method according to an embodiment of the present invention. Each block will be described below with reference to the diagram.

[0014] The power supply main circuit MC receives a commercial AC power supply (not shown) such as a three-phase 200V power supply, performs output control by inverter control in accordance with a drive signal Dv described below, and outputs a welding current Iw and a welding voltage Vw. Although not shown, the power supply main circuit MC includes a primary rectifier circuit that rectifies the AC commercial power supply, a capacitor that smoothes the rectified DC, an inverter circuit that converts the smoothed DC into high-frequency AC in accordance with the drive signal Dv, a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for arc welding, a secondary rectifier circuit that rectifies the stepped-down high-frequency AC, and a reactor that smoothes the rectified DC.

[0015] The welding wire 1 is fed through the welding torch 4 by the rotation of a feed roll 5 coupled to a feed motor WM described later, and an arc 3 is generated between the welding wire 1 and the base metal 2. A welding voltage Vw is applied between the welding wire 1 and the base metal 2, and a welding current Iw flows between the welding wire 1 and the base metal 2.

[0016] The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The average voltage detection circuit VAD receives the voltage detection signal Vd and outputs an average voltage detection signal Vad. The average voltage detection signal Vad is calculated by passing the voltage detection signal Vd through a low-pass filter. The voltage error amplifier circuit EV amplifies the error between the voltage detection signal Vd and a welding voltage setting signal Vr (described later) and outputs a voltage error amplifier signal Ev.

[0017] The average voltage error amplifier circuit EVA amplifies the error between a welding voltage setting signal Vr (described later) and the average voltage detection signal Vad, and outputs an average voltage error amplified signal Eva. The pulse period timer circuit TFC receives the average voltage error amplified signal Eva, performs voltage / frequency conversion on the average voltage error amplified signal Eva, and outputs a pulse period signal Tf that becomes a high level for a short time every pulse period. The peak period timer circuit TPC receives the pulse period signal Tf, and outputs a peak period signal Tpc that becomes a high level during a predetermined peak period every time the pulse period signal Tf changes to a high level for a short time and then becomes a low level. When the peak period signal Tpc is at a high level, it is a peak period, and when it is at a low level, it is a base period.

[0018] The pulse arc welding period setting circuit T1R outputs a predetermined pulse arc welding period setting signal T1r. The first feed rate setting circuit F1R outputs a first feed rate setting signal F1r for setting the feed rate during the pulse arc welding period. The first welding voltage setting circuit V1R outputs a first welding voltage setting signal V1r for setting the welding voltage Vw during the pulse arc welding period.

[0019] The short circuit transfer arc welding period setting circuit T2R outputs a predetermined short circuit transfer arc welding period setting signal T2r. The second feed rate setting circuit F2R outputs a second feed rate setting signal F2r for setting the feed rate during the short circuit transfer arc welding period. The second welding voltage setting circuit V2R outputs a second welding voltage setting signal V2r for setting the welding voltage Vw during the short circuit transfer arc welding period.

[0020] The short circuit determination circuit SD receives the voltage detection signal Vd as input, and when this value is less than a predetermined short circuit determination value (approximately 10 V), it determines that the device is in a short circuit period and outputs a short circuit determination signal Sd that goes to a High level, and when this value is equal to or greater than this value, it determines that the device is in an arc period and outputs a Low level short circuit determination signal Sd.

[0021] The transition short-circuit occurrence time detection circuit TD receives as input a timer signal Tm (described later) and the above-mentioned short circuit discrimination signal Sd, detects the transition short-circuit occurrence time from the point at which the timer signal Tm changes to 2 (first transition period) to the point at which the short circuit discrimination signal Sd first changes to a High level (short circuit period), and outputs a transition short-circuit occurrence time detection signal Td.

[0022] The transition short circuit occurrence time moving average calculation circuit TDA receives the transition short circuit occurrence time detection signal Td, calculates a moving average, and outputs a transition short circuit occurrence time moving average calculation signal Tda. The number of times the moving average is calculated is about several to several tens of times.

[0023] The reference time setting circuit TDR outputs a predetermined reference time setting signal Tdr which is a target value for the transition short circuit occurrence time.

[0024] The first transition period setting circuit TER receives as input the transition short circuit occurrence time detection signal Td, the transition short circuit occurrence time moving average calculation signal Tda, and the reference time setting signal Tdr, performs the following processing, and outputs a first transition period setting signal Ter. 1) When the value of the transition short-circuit occurrence time detection signal Td is equal to or greater than the value of the reference time setting signal Tdr, a first transition period setting signal T1r that is shorter than the current first transition period setting value by a predetermined value is output. 2) The value of the first transition period setting signal T1r is feedback-controlled so that the transition short-circuit occurrence time detection signal Td becomes equal to the value of the reference time setting signal Tdr. 3) The transition short circuit occurrence time moving average calculation signal Tda is used in place of the transition short circuit occurrence time detection signal Td used in the above 1) and 2).

[0025] The second transition period setting circuit TSR outputs a predetermined second transition period setting signal Tsr.

[0026] The timer circuit TM receives as input the pulse arc welding period setting signal T1r, the first transition period setting signal Ter, the short circuit transfer arc welding period setting signal T2r and the second transition period setting signal Tsr, performs the following processing, and outputs a timer signal Tm. 1) During the pulse arc welding period determined by the pulse arc welding period setting signal T1r, a timer signal Tm=1 is output. 2) Subsequently, during the first transition period determined by the first transition period setting signal Ter, a timer signal Tm=2 is output. 3) Subsequently, during the short-circuit transfer arc welding period determined by the short-circuit transfer arc welding period setting signal T2r, a timer signal Tm=3 is output. 4) Subsequently, during the second transition period determined by the second transition period setting signal Tsr, the timer signal Tm=4 is output. 5) Repeat steps 1) to 4) above.

[0027] The feed speed setting circuit FR receives the first feed speed setting signal F1r, the second feed speed setting signal F2r, and the timer signal Tm as inputs, performs the following processing, and outputs a feed speed setting signal Fr. 1) When the timer signal Tm=1 (pulse arc welding period), the first feed speed setting signal F1r is output as the feed speed setting signal Fr. 2) When the timer signal Tm=2 (first transition period), a feed speed setting signal Fr that changes along a slope from the first feed speed setting signal F1r to the second feed speed setting signal F2r is output. 3) When the timer signal Tm=3 (short circuit transfer arc welding period), the second feed speed setting signal F2r is output as the feed speed setting signal Fr. 4) When the timer signal Tm=4 (second transition period), a feed speed setting signal Fr that changes along a slope from the second feed speed setting signal F2r to the first feed speed setting signal F1r is output.

[0028] The feed control circuit FC receives the feed speed setting signal Fr and outputs a feed control signal Fc to the feed motor WM for feeding the welding wire 1 at a feed speed Fw determined by the feed speed setting signal Fr. The feed motor WM feeds the welding wire 1 in accordance with the feed control signal Fc.

[0029] The welding voltage setting circuit VR receives the first welding voltage setting signal V1r, the second welding voltage setting signal V2r, and the timer signal Tm as inputs, performs the following processing, and outputs the welding voltage setting signal Vr. 1) When the timer signal Tm=1 (pulse arc welding period), the first welding voltage setting signal V1r is output as the welding voltage setting signal Vr. 2) When the timer signal Tm=2 (first transition period), a welding voltage setting signal Vr that changes along a slope from the first welding voltage setting signal V1r to the second welding voltage setting signal V2r is output. 3) When the timer signal Tm=3 (short-circuit transfer arc welding period), the second welding voltage setting signal V2r is output as the welding voltage setting signal Vr. 4) When the timer signal Tm=4 (second transition period), a welding voltage setting signal Vr that changes with a slope from the second welding voltage setting signal V2r to the first welding voltage setting signal V1r is output.

[0030] The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr, and the base current setting circuit IBR outputs a predetermined base current setting signal Ibr.

[0031] The current control setting circuit ICR receives the peak current setting signal Ipr, the base current setting signal Ibr, and the peak period signal Tpc as inputs, and outputs the peak current setting signal Ipr as the current control setting signal Icr when the peak period signal Tpc is at a high level (peak period), and outputs the base current setting signal Ibr as the current control setting signal Icr when the peak period signal Tpc is at a low level.

[0032] 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 control setting signal Icr and the current detection signal Id and outputs a current error amplification signal Ei.

[0033] The welding method switching circuit SM receives the above current error amplified signal Ei, the above voltage error amplified signal Ev and the above timer signal Tm as inputs, and outputs the current error amplified signal Ei as the error amplified signal Ea when the timer signal Tm = 1, 2 or 4, and outputs the voltage error amplified signal Ev as the error amplified signal Ea when the timer signal Tm = 3. As a result, pulse arc welding is performed during the first transition period, pulse arc welding period and second transition period, and short-circuit transfer arc welding is performed during the short-circuit transfer arc welding period.

[0034] The drive circuit DV performs pulse width modulation control based on the error amplified signal Ea, and outputs a drive signal Dv for driving the inverter circuit of the main power supply circuit MC.

[0035] Fig. 2 is a timing chart of each signal in the welding power source of Fig. 1, which shows the arc welding method according to the embodiment of the present invention. Fig. 2(A) shows the time change of the feed speed Fw, Fig. 2(B) shows the time change of the short circuit determination signal Sd, Fig. 2(C) shows the time change of the welding current Iw, and Fig. 2(D) shows the time change of the welding voltage Vw. The operation will be described below with reference to the figures.

[0036] The period from time t1 to t2 is a pulse arc welding period, the period from time t2 to t3 is a first transition period, the period from time t3 to t4 is a short circuit transfer arc welding period, and the period from time t4 to t5 is a second transition period. The pulse arc welding period is set by the pulse arc welding period setting signal T1r in FIG. 1. The first transition period is set by the first transition period setting signal Ter in FIG. 1. The short circuit transfer arc welding period is set by the short circuit transfer arc welding period setting signal T2r in FIG. 1. The second transition period is set by the second transition period setting signal Tsr in FIG. 1. In this figure, the welding power source in FIG. 1 is output controlled so that the second transition period, the pulse arc welding period, and the first transition period are pulse arc welding. The welding power source in FIG. 1 may be output controlled so that the second transition period and / or the first transition period are short circuit transfer arc welding.

[0037] (1) Operation during pulse arc welding from time t1 to t2 As shown in FIG. 1(A), the feed speed Fw becomes the first feed speed, and is set by the first feed speed setting signal F1r in FIG. 1. During this period, as shown in FIG. 1(C), a peak current and a base current are applied with a plurality of pulse periods, and as shown in FIG. 1(D), a peak voltage and a base voltage are applied. The pulse period is controlled so that the average value of the welding voltage Vw is equal to the value of the first welding voltage setting signal V1r in FIG. 1. The peak current is set to, for example, 450A. The base current is set to, for example, 50A. Since almost no short circuit occurs during this period, as shown in FIG. 1(B), the short circuit discrimination signal Sd remains at a low level (arc period).

[0038] (2) Operation in the first transition period from time t2 to t3 As shown in FIG. 1(A), the feed speed Fw changes with a slope from the first feed speed set by the first feed speed setting signal F1r in FIG. 1 to the second feed speed set by the second feed speed setting signal F2r in FIG. 1. F1r>F2r. The welding voltage setting signal Vr in FIG. 1 changes with a slope from the first welding voltage setting signal V1r in FIG. 1 to the second welding voltage setting signal V2r in FIG. 1. V1r>V2r. Pulse arc welding is also performed during this period. This period is a transition period from pulse arc welding to short circuit transfer arc welding. The reason why the feed speed Fw and the welding voltage setting signal Vr are switched with a slope is to make the transition from pulse arc welding to short circuit transfer arc welding smooth. Since almost no short circuit occurs during this period, the short circuit discrimination signal Sd remains at a low level (arc period) as shown in FIG. 1(B).

[0039] (3) Operation during the short-circuit transfer arc welding period from time t3 to t4 As shown in FIG. 1(A), the feed speed Fw is the second feed speed set by the second feed speed setting signal F2r in FIG. 1. The welding voltage setting signal Vr in FIG. 1 is the second welding voltage setting signal V2r in FIG. 1. As shown in FIG. 1(C), the welding current Iw increases during the short circuit period and decreases during the arc period. As shown in FIG. 1(D), the welding voltage Vw has a short circuit voltage value of several volts during the short circuit period and an arc voltage value of several tens of volts during the arc period. As shown in FIG. 1(B), the short circuit determination signal Sd is at a high level during the short circuit period. The first short circuit occurs during this period at time t31. Therefore, the period from the start time t2 of the first transition period to time t31 is the transition short circuit occurrence time Td. The welding voltage Vw is constant-voltage controlled to be equal to the value of the second welding voltage setting signal V2r in FIG. 1.

[0040] (4) Operation in the second transition period from time t4 to t5 As shown in FIG. 1A, the feed speed Fw changes with a slope from the second feed speed set by the second feed speed setting signal F2r in FIG. 1 to the first feed speed set by the first feed speed setting signal F1r in FIG. 1. The welding voltage setting signal Vr in FIG. 1 changes with a slope from the second welding voltage setting signal V2r in FIG. 1 to the first welding voltage setting signal V1r in FIG. 1. Pulse arc welding is performed during this period. This period is a transition period from short circuit transfer arc welding to pulse arc welding. The reason why the feed speed Fw and the welding voltage setting signal Vr are switched with a slope is to make the transition from short circuit transfer arc welding to pulse arc welding smooth. Since almost no short circuit occurs during this period, the short circuit discrimination signal Sd remains at a low level (arc period) as shown in FIG. 1B.

[0041] Numerical examples of the above-mentioned parameters are shown below. Welding wire: mild steel solid wire, diameter 1.2mm Shielding gas: 20% argon gas + 80% carbon dioxide gas Pulse arc welding conditions: 1st feed speed 8m / min (welding current 200A), 1st welding voltage 27V Short circuit transfer arc welding conditions: Second feed speed 4m / min (welding current 100A), second welding voltage 17V Pulse arc welding period 500ms, first transition period (initial value) 50ms, short circuit transfer arc welding period 500ms, second transition period 70ms Reference time 70 ms

[0042] The effects of the above-described embodiment will now be described. (1) The transition short circuit occurrence time detection circuit TD in Figure 1 outputs the period from the start of the first transition period to the first occurrence of a short circuit during short circuit transfer arc welding (the period from times t2 to t31) as a transition short circuit occurrence time detection signal Td. (2) The first transition period setting circuit TER in FIG. 1 controls the value of the first transition period setting signal Ter so that the transition short-circuit occurrence time detection signal Td has an appropriate value. (3) Specifically, the initial value of the transition short-circuit occurrence detection signal Td is set to be longer than an appropriate value under most welding conditions, and when the transition short-circuit occurrence detection signal Td is equal to or greater than the value of a predetermined reference time setting signal Tdr during welding, the value of the first transition period setting signal Ter is controlled to be shorter. (4) Furthermore, the value of the first transition period setting signal Ter is controlled so that the value of the transition short-circuit occurrence time detection signal Td becomes equal to the value of a predetermined reference time setting signal Tdr. (5) Furthermore, the transition short-circuit occurrence time detection signal Td is moved to calculate a transition short-circuit occurrence time moving average calculation signal Tda, and the transition short-circuit occurrence time moving average calculation signal Tda is used instead of the transition short-circuit occurrence time detection signal Td to control the value of the first transition period setting signal Ter. In this way, the variation in the transition short-circuit occurrence time detection signal Td for each time can be averaged, thereby stabilizing the control. (6) The appropriate value of the transition short circuit occurrence time detection signal Td varies depending on various welding conditions such as the type of welding wire, the first feed speed, the second feed speed, the welding joint, and the welding speed. For this reason, it is difficult to calculate an appropriate value by experiment and set it in advance in response to all welding conditions. If the value of the transition short circuit occurrence time detection signal Td becomes shorter than the appropriate value, the change in the arc length is too steep, and the welding state is likely to become unstable. Conversely, if the value of the transition short circuit occurrence time detection signal Td becomes longer than the appropriate value, the time until the arc length converges to the appropriate value becomes longer, and the welding workability and bead appearance become worse. In contrast, in this embodiment, the first transition period is automatically adjusted so that the value of the transition short circuit occurrence time detection signal Td becomes the appropriate value regardless of the welding conditions. As a result, the transition state from pulse arc welding to short circuit transfer arc welding can be made smooth without being affected by the welding conditions. [Explanation of symbols]

[0043] 1 Welding wire 2 Base material 3. Arc 4. Welding torch 5 Feeding roll DV driver circuit Dv drive signal Ea Error amplification signal EI Current Error Amplifier Circuit Ei Current error amplification signal EV voltage error amplifier circuit Ev Voltage error amplified signal F1R 1st feed speed setting circuit F1r 1st feed speed setting signal F2R 2nd feed speed setting circuit F2r 2nd feed speed setting signal FC feed control circuit Fc feed control signal FR feed speed setting circuit Fr feed speed setting signal Fw Feed speed IBR base current setting circuit Ibr Base current setting signal ICR Current control setting circuit Icr Current control setting signal ID Current Detection Circuit Id Current detection signal IPR Peak current setting circuit Ipr Peak current setting signal Iw Welding current MC power supply main circuit SD Short circuit detection circuit Sd Short circuit detection signal SM Welding method switching circuit T1R Pulse arc welding period setting circuit T1r Pulse arc welding period setting signal T2R Short circuit transfer arc welding period setting circuit T2r Short circuit transfer arc welding period setting signal TD transition short circuit occurrence time detection circuit Td Transition short circuit occurrence time detection signal TDA Transition short circuit occurrence time moving average calculation circuit Tda Transition short circuit occurrence time moving average calculation signal TDR Transition short circuit occurrence time setting circuit Tdr Transition short circuit occurrence time setting signal TER 1st transition period setting circuit Ter 1st transition period setting signal TFC Pulse Period Timer Circuit Tf Pulse periodic signal TM timer circuit Tm Timer signal TPC Peak Period Timer Circuit Tpc Peak Period Signal TSR 2nd transition period setting circuit Tsr Second transition period setting signal V1R First welding voltage setting circuit V1r First welding voltage setting signal V2R Second welding voltage setting circuit V2r Second welding voltage setting signal VAD Average voltage detection circuit Vad Average voltage detection signal VD voltage detection circuit Vd Voltage detection signal VR welding voltage setting circuit Vr Welding voltage setting signal Vw welding voltage WM Feed motor

Claims

1. welding is performed by alternately switching between a period in which the welding wire is fed at a first feed speed and pulse arc welding is performed and a period in which the welding wire is fed at a second feed speed and short circuit transfer arc welding is performed; a transition period is provided between a period of the pulse arc welding and a period of the short circuit transfer arc welding, and the feed speed is changed from the first feed speed to the second feed speed with a slope during the transition period, Detecting a transition short circuit occurrence time from a start point of the transition period to a time when a short circuit first occurs during the short circuit transfer arc welding period; a control for controlling a length of the transition period based on the transition short-circuit occurrence time, and controlling the length of the transition period to be shorter when the transition short-circuit occurrence time is equal to or longer than a reference time; 1. An arc welding method comprising:

2. Welding is performed by alternating between a period in which a welding wire is fed at a first feed speed to perform pulse arc welding and a period in which the welding wire is fed at a second feed speed to perform short-circuit transfer arc welding; a transition period is provided between a period of the pulse arc welding and a period of the short circuit transfer arc welding, and the feed speed is changed from the first feed speed to the second feed speed with a slope during the transition period, Detecting a transition short circuit occurrence time from a start point of the transition period to a time when a short circuit first occurs during the short circuit transfer arc welding period; controlling the length of the transition period so that the transition short circuit occurrence time becomes equal to a reference time; 1. An arc welding method comprising:

3. Calculating a moving average value of the transition short circuit occurrence time, and controlling the length of the transition period by using the moving average value instead of the transition short circuit occurrence time.

3. The arc welding method according to claim 1, wherein the welding is performed in a manner similar to that described above.

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