JP2015096268A - Arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deepen the penetration of a welding start portion and a stationary welding portion and to improve the bead appearance in a spray transfer welding.SOLUTION: When the completion of a transient state Tk is determined during an arc start time, the oscillation of a welding current Iw is started. The oscillation of the welding current Iw is the repetition of the energization of a first welding current Iw1 during a first period T1, a second welding current Iw2 during a second period T2, and a third welding current Iw3 during a third period T3. Since the welding current Iw is not oscillated during a transient state Tk, the bead appearance can be improved. Then, during the first period T1 the molten metal just below the wire is made to a thinner state, during the second period T2 the arc is concentrated just below the wire, during the third period T3 a molten pool is heated concentrically, and then the molten pool is made to be moderated. Thereby, the penetration of a welding start portion and a stationary welding portion can be deepened and thus the bead appearance is improved.

Description

  The present invention relates to an arc welding method in which a welding wire is fed, a welding current is vibrated, and welding is performed in a spray transfer mode.

  Mag welding using solid wire with shield gas as mixed gas of argon gas and carbon dioxide gas, arc welding using flux cored wire with carbon dioxide gas as shield gas, and flux cored wire for self shield without using shield gas For self-shielded arc welding, etc., the droplet transfer mode is the spray transfer mode. In the spray transfer mode, the tip of the welding wire is melted by the arc heat to become fine particles and transfer to the molten pool. In the spray transfer mode, the droplet does not transfer by a short circuit but transfers by free fall.

  For arc welding in the spray transfer mode (hereinafter referred to as spray transfer welding), a welding power source having a constant voltage characteristic is used, and the welding wire is fed at a constant speed. Spray transfer welding is characterized by low spatter generation and good bead appearance. On the other hand, in spray transfer welding, the arc length is longer than in short-circuit transfer welding, and the arc spreads, so that the penetration becomes shallow. This point may cause a problem in welding quality depending on the workpiece. Hereinafter, the spray transfer welding of a prior art is demonstrated with reference to drawings.

  FIG. 3 is a voltage / current waveform diagram in general spray transfer welding. FIG. 4A shows the time change of the voltage setting signal Er for setting the output value of the constant voltage characteristic of the welding power source, and FIG. 4B shows the welding voltage Vw applied between the welding wire and the base material. (C) shows the time change of the welding current Iw for energizing the arc. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 6A, the voltage setting signal Er is set to a constant value. As shown in FIG. 5B, the welding voltage Vw slightly fluctuates up and down, but has a substantially constant value. As shown in FIG. 5C, the welding current Iw also varies slightly up and down, but is a substantially constant value. An instantaneous value of the welding voltage Vw is set by the voltage setting signal Er. The average value of the welding current Iw is set by the feeding speed of the welding wire.

  In the invention of Patent Document 1, in spray transfer welding and globule transfer welding, the welding current is changed within a current amplitude of 20 A to 100 A by periodically changing the output voltage of the welding power source at a frequency of 100 Hz to 600 Hz. Let them weld. Thus, in the invention of Patent Document 1, in spray transfer welding and globule transfer welding, fluctuations in arc length can be suppressed and droplet transfer can be made regular and finer, thus improving the stability of the welded state. Can be made.

JP 2007-229775 A

  Therefore, an object of the present invention is to provide an arc welding method capable of deepening the penetration of the welding start portion and the steady weld portion and improving the bead appearance in spray transfer welding.

In order to solve the above-described problems, the invention of claim 1
In the arc welding method in which the welding wire is fed, the welding current is vibrated, and welding is performed by the spray transfer mode,
Starting the vibration of the welding current from the time when it was determined that the transient state at the time of arc start was finished and transitioned to a steady state,
The vibration of the welding current is a repetition of energization of the first welding current Iw1 during the first period, the second welding current Iw2 during the second period, and the third welding current Iw3 during the third period, and 0 <Iw2 <Iw3 <Iw1.
This is an arc welding method characterized by the above.

The invention of claim 2 determines that the transient state has ended by determining that a predetermined period has elapsed since the welding current started energization.
The arc welding method according to claim 1, wherein:

According to a third aspect of the present invention, it is determined that the transient state has ended, by determining that the absolute value of the change rate of the welding voltage has become less than a predetermined reference value since the welding current has started energization. Do,
The arc welding method according to claim 1, wherein:

  According to the present invention, when the transient state at the time of arc start ends, vibration of the welding current starts. Since the welding current is not vibrated during the transient state, it is possible to suppress deterioration of the welding quality at the welding start portion. In addition, by vibrating the welding current during the steady state, the following effects can be obtained. During the first period, a large arc pressure acts on the molten pool, the molten pool has a concave shape that is recessed immediately below the wire, and the molten metal immediately below the wire is in a thin state. Subsequently, during the second period, the arc shape is deflated, and the arc is concentrated in a portion where the molten metal immediately below the wire is in a thin state. Subsequently, during the third period, the depressed portion of the molten pool is concentrated and heated by the arc in the first half, and since the arc pressure is constant in the second half, the depressed portion of the molten pool disappears and the state becomes calm. In the present invention, by repeating these first period to third period after the transient state at the time of arc start is completed, in the spray transfer welding, the penetration of the welding start part and the steady welding part is deepened and the quality is improved. Can be achieved.

It is a block diagram of the welding power supply for enforcing the arc welding method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding power supply of FIG. 1 for demonstrating the arc welding method which concerns on Embodiment 1 of this invention. It is a voltage / current waveform diagram in general spray transfer welding.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 is a block diagram of a welding power source for performing the arc welding method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as a three-phase 200V, performs output control by inverter control using a drive signal Dv described later, and outputs an output voltage E. Although not shown, this power main circuit PM is a primary rectifier circuit that rectifies commercial power, a capacitor that smoothes the rectified direct current, and an inverter circuit that converts the smoothed direct current into high frequency alternating current according to the drive signal Dv. A high-frequency transformer that steps down the high-frequency alternating current to a voltage value suitable for arc welding, and a secondary rectifier circuit that rectifies the stepped-down high-frequency alternating current. The reactor WL smoothes the output voltage E and outputs a welding voltage Vw.

  The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 coupled to the feed motor WM, and the arc 3 is generated between the base metal 2 and welding is performed. 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 is passed through the arc 3.

  The welding start circuit ST outputs a welding start signal St that becomes High level when it becomes a start command and becomes Low level when it becomes a stop command. This welding start circuit ST corresponds to a torch switch (not shown) attached to the welding torch 4 and outputs a welding start signal St that becomes High level / Low level corresponding to on / off. In the case of a welding apparatus using a robot, this circuit is built in the robot controller.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current energization determination circuit CD receives the current detection signal Id and, when this value is equal to or greater than a predetermined current determination value, determines that the welding current Iw is energized and becomes a high level current energization determination signal. Cd is output. This current discrimination value is set to about 10 A, for example.

  The hot start current setting circuit IHR outputs a predetermined hot start current setting signal Ihr. The hot start period setting signal THR outputs a predetermined hot start period setting signal Thr.

  The hot start period timer circuit TH receives the hot start period setting signal Thr and the current energization determination signal Cd, and is a period determined by the hot start period setting signal Thr from the time when the current energization determination signal Cd changes to the High level. Only a hot start period signal Ths that is at a high level is output.

  The current error amplification circuit EI amplifies an error between the hot start current setting signal Ihr (+) and the current detection signal Id (−) and outputs a current error amplification signal Ei.

  The voltage setting circuit ER outputs a predetermined voltage setting signal Er. The voltage increase value setting circuit EUR outputs a predetermined voltage increase value setting signal Eur. The voltage decrease value setting circuit EDR outputs a predetermined voltage decrease value setting signal Edr.

  The first period setting circuit T1R outputs a predetermined first period setting signal T1r. The second period setting circuit T2R outputs a predetermined second period setting signal T2r. The third period setting circuit T3R outputs a predetermined third period setting signal T3r.

  The transient period determination circuit TKD receives the current energization determination signal Cd as described above, and changes to the High level when a predetermined initial period Ts elapses from when the current energization determination signal Cd changes to the High level (energization). A transient period discrimination signal Tkd is output.

The voltage control setting circuit ECR includes the voltage setting signal Er, the voltage increase value setting signal Eur, the voltage decrease value setting signal Edr, the first period setting signal T1r, the second period setting signal T2r, With the third period setting signal T3r and the transient period determination signal Tkd as inputs, the following processing is performed to output the voltage control setting signal Ecr.
1) Ecr = Er is output during the initial period Ts when the transient period determination signal Tkd is at the low level. Therefore, during the initial period Ts, the voltage control setting signal Ecr has a constant value.
2) When the transient period determination signal Tkd becomes High level, the voltage control setting signal Ecr is changed to an oscillating waveform by repeating the following processes 3) to 5).
3) Ecr = Er + Eur is output during the first period T1 determined by the first period setting signal T1r.
4) Subsequently, Ecr = Er-Edr is output during the second period T2 determined by the second period setting signal T2r.
5) Subsequently, Ecr = Er is output during the third period T3 determined by the third period setting signal T3r.

  The output voltage detection circuit ED detects the output voltage E and outputs an output voltage detection signal Ed. The voltage error amplification circuit EV amplifies an error between the voltage control setting signal Ecr (+) and the output voltage detection signal Ed (−), and outputs a voltage error amplification signal Ev.

  The external characteristic switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, and the hot start period signal Ths, and when the hot start period signal Ths is at a high level, the current error amplification signal Ei. Is output as the error amplification signal Ea, and when it is at the Low level, the voltage error amplification signal Ev is output as the error amplification signal Ea. The drive circuit DV receives the error amplification signal Ea and the welding start signal St. When the welding start signal St is at a high level, the drive circuit DV performs pulse width modulation control based on the error amplification signal Ea, and generates the drive signal Dv. Output. As a result, when the welding start signal St becomes high level, the constant voltage characteristic is obtained and the output of the welding voltage Vw is started. When the welding current Iw starts energization, constant current characteristics are obtained, and the hot start current Ih is energized during the hot start period Th. When this period ends, the constant voltage characteristic is obtained. When the transition period determination signal Tkd becomes a high level, the welding voltage Vw and the welding current Iw become vibration waveforms.

  The feeding speed setting circuit FR outputs a predetermined feeding speed setting signal Fr. The feed speed control setting circuit FCR receives the feed speed setting signal Fr, the welding start signal St and the current energization determination signal Cd, and inputs a predetermined slow-down feed when the welding start signal St becomes a high level. When the current energization determination signal Cd becomes High level, the feed speed setting value becomes a value determined by the feed speed setting signal Fr, and when the welding start signal St becomes Low level, the feed speed control setting signal Fcr that becomes 0 is output.

  The feed control circuit FC receives the feed speed control setting signal Fcr as an input, and feeds a feed control signal Fc for feeding the welding wire 1 at a feed speed corresponding to this value to the feed motor WM. Output.

  FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1 for explaining the arc welding method according to the first embodiment of the present invention. (A) shows the time change of the welding start signal St, (B) shows the time change of the voltage control setting signal Ecr, (C) shows the time change of the welding voltage Vw, (D) shows the time change of the welding current Iw, (E) shows the time change of the feeding speed Fw, (F) shows the time change of the current energization determination signal Cd, (G) ) Shows a time change of the transient period discrimination signal Tkd. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 5B, the voltage control setting signal Ecr is a constant value set by the voltage setting signal Er because the transient period determination signal Tkd shown in FIG. The vibration waveform is not superimposed.

  At time t1, when the welding start signal St changes to a high level (start command) as shown in FIG. 5A, the welding power source is activated and starts outputting. At this time, since the welding wire 1 and the base material 2 are separated from each other and are in an unloaded state, the welding voltage Vw becomes an unloaded voltage value of about 80 V as shown in FIG. At the same time, since the feeding is started, the feeding speed Fw becomes a predetermined slow-down feeding speed, which is a slow speed, as shown in FIG. As shown in FIG. 4D, the welding current Iw is not energized.

  When the welding wire 1 comes into contact with the base material 2 at time t2, the welding voltage Vw becomes a short circuit voltage value for a short period of time as shown in FIG. To do. Thereafter, the welding voltage Vw gradually increases and converges to a steady value at time t4. The period from time t2 to t4 is the transition period Tk.

  At the same time, when the welding wire 1 comes into contact with the base material 2, the welding current Iw starts energization at time t2 as shown in FIG. 4D, and during the hot start period Th up to time t3, the hot start current value Ih. It becomes. The hot start current Ih is set to about 400 to 600 A, and the hot start period Th is set to about 5 to 10 ms. By energizing the hot start current Ih which is a large current value, the arc 3 can be quickly started when the welding wire 1 comes into contact with the base material 2, and the arc length can be quickly converged to an appropriate value. Can do. After time t3, the welding current Iw gradually decreases until time t4.

  At time t2, since the welding current Iw starts energization, the current energization determination signal Cd changes to the high level as shown in FIG. In response to this, as shown in FIG. 5E, the feeding speed Fw increases with an inclination, and converges to a steady value set by the feeding speed setting signal Fr slightly after time t3.

  At time t4 when a predetermined initial period Ts elapses from time t2 when the current energization determination signal Cd shown in FIG. 5F changes to the high level, as shown in FIG. 5G, the transient period determination signal Tkd is It changes to High level. This initial period Ts is set in advance so as to substantially coincide with the transition period Tk at the time of arc start. Therefore, the period from time t2 to t4 is the transition period Tk and also the initial period Ts. The initial period Ts is set to about 200 to 500 ms.

  Further, during the transition period Tk, as shown in FIG. 3C, the welding voltage Vw rises and becomes a substantially constant value when the transition period Tk ends. Using this, the rate of change of the welding voltage Vw (differential ground dVw / dt) is detected, and it is determined that the absolute value of this rate of change is less than a predetermined reference value, and the transition period Tk ends. You may make it discriminate | determine. In this case, the transient period discrimination circuit TKD in FIG. 1 may be configured as follows. The transient period determination circuit TKD receives the current application determination signal Cd and the welding voltage Vw, calculates the rate of change of the welding voltage Vw when the current application determination signal Cd becomes high level, and the absolute value of this change rate is determined in advance. When it becomes less than the reference value, a transition period determination signal Tkd that changes to a high level is output.

  When the transition period determination signal Tkd changes to High level at time t4, the voltage control setting signal Ecr becomes a waveform that periodically oscillates by the voltage control setting circuit ECR in FIG. During the first predetermined period T1 from t4 to t5, the voltage setting signal Er is added to the voltage increase value setting signal Eur. During the second predetermined period T2 from time t5 to t6, the voltage is set from the voltage setting signal Er. The value is obtained by subtracting the decrease value setting signal Edr, and becomes the value of the voltage setting signal Er during a predetermined third period T3 from time t6 to t7. The voltage control setting signal Ecr has a vibration waveform that is repeated with the time t4 to t7 as one cycle. Here, Er> 0, Eur> 0, Edr> 0, Ecr> 0.

  As shown in FIG. 6C, the welding voltage Vw is set by the voltage control setting signal Ecr, so that it has a vibration waveform, and during the first period T1 from time t4 to t5, the inclination is inclined from the third welding voltage value Vw3. And increases to a substantially constant first welding voltage value Vw1, and during the second period T2 from time t5 to t6, the first welding voltage value Vw1 decreases with a slope and decreases to a substantially constant first value. 2 welding voltage value Vw2, and during the third period T3 from time t6 to t7, the second welding voltage value Vw2 increases from the second welding voltage value Vw2 with an inclination to become a substantially constant third welding voltage value Vw3. The first welding voltage value Vw1 is set by Er + Eur, the second welding voltage value Vw2 is set by Er-Edr, and the third welding voltage value Vw3 is set by Er.

  As shown in FIG. 4D, the welding current Iw is determined by the welding voltage Vw and the arc load, and has a vibration waveform because the welding voltage Vw vibrates. During the first period T1 from time t4 to t5, The first welding current value Iw1 increases with an inclination from the three welding current values Iw3 to become a substantially constant first welding current value Iw1, and during the second period T2 from time t5 to t6, there is an inclination from the first welding current value Iw1. The second welding current value Iw2 decreases to a substantially constant second welding current value Iw2, and increases from the second welding current value Iw2 with an inclination during the third period T3 between times t6 and t7, and increases to a substantially constant third welding current value. Value Iw3. Here, 0 <Iw2 <Iw3 <Iw1.

  In the same figure, each inclination at the time of a period change becomes a value which becomes settled with the reactor WL of FIG. 1, and the total inductance value of a welding cable. If the voltage control setting signal Ecr is vibrated in a triangular wave shape or a sine wave shape, these inclinations can be set to desired values.

  Next, the effect of this Embodiment is demonstrated. In the present embodiment, the vibration of the welding current Iw is started when it is determined that the transition state (transition period Tk) at the time of arc start has ended and the state has shifted to the steady state. During the transient state, the weld pool is in the process of forming, so the welding state is not stable. For this reason, if the welding current Iw is vibrated during the transient state, the amount of spatter generated increases, the bead appearance deteriorates, and the weld quality at the welding start portion deteriorates. Therefore, the welding current Iw is oscillated after the transient state ends.

  The effects of oscillating the welding current Iw during the steady state are as follows. During the first period T1, since the welding current Iw becomes the first welding current value Iw1, which is the largest value, a large arc pressure acts on the molten pool, and the molten pool has a concave shape directly below the wire, The molten metal immediately below the wire becomes thin. During the second period T2, since the welding current Iw becomes the second welding current value Iw2, which is the smallest value, the arc shape is deflated, and the arc concentrates on the portion where the molten metal immediately below the wire is thin. It will be in the state. During the third period T3, the welding current Iw becomes a third welding current value Iw3 that is an intermediate value close to the welding current value determined by the feeding speed of the welding wire. By maintaining the third welding current value Iw3 at a substantially constant value, the recessed portion of the molten pool is concentratedly heated by the arc in the first half of the third period T3, and the arc pressure is constant in the second half, so that the molten pool is constant. It will be in a calm state with no hollow parts. If the molten pool is not in a calm state at the time of shifting to the first period T1, the shape immediately below the wire does not become a concave shape during the first period T1, but becomes a distorted shape, and the effect of deepening the penetration is obtained. Will be lost. Therefore, in order to ensure that the molten pool is in a calm state at the end of the third period T3, it is desirable that the third period T3 be set to a period longer than the first period T1 and the second period T2. By these functions and effects, a deep penetration shape can be stably formed.

  The first welding voltage value Vw1 (voltage increase value setting signal Eur) and the first period T1 (first period setting signal T1r) so that the molten pool can be deformed into a concave shape by the first welding current value Iw1. ) Is set. Further, the second welding voltage value Vw2 (voltage decrease value setting signal Edr) and the second period T2 (second period setting signal) are set so that the arc is deflated and concentrated immediately below the wire by the second welding current value Iw2. T2r) is set. Further, the third welding current value Iw3 and the third welding voltage value Vw3 (voltage setting signal Er) and the third period T3 (the third welding current value Iw3 are set so that the molten pool becomes calm after being concentrated and heated in the recessed portion. The third period setting signal T3r) is set. The constant current control is not performed so that the welding current Iw becomes the first welding current value Iw1 to the third welding current value Iw3 because constant voltage control is necessary to maintain the arc length at an appropriate value. Therefore, the welding current Iw is indirectly set. For this reason, the first welding current value Iw1 to the third welding current value Iw3 slightly vary depending on the arc load state.

  Next, numerical examples will be given. This is a numerical example when a flux-cored wire for self-shielding (material: steel, diameter: 1.6 mm) is used as the welding wire and welding is performed at an average welding current of 250 A and an average welding voltage of 21 V. Ts = 300 ms, Er = 21 V, Eur = 10 V, Edr = 10 V, T1r = 2 ms, T2r = 4 ms, T3r = 5 ms. As a result, Vw1 = 31V, Vw2 = 11V, Vw3 = 21V, and Iw1 = 400A, Iw2 = 60A, and Iw3 = 250A.

  According to the first embodiment described above, the vibration of the welding current is started from the time when it is determined that the transient state at the time of arc start is finished and the state is shifted to the steady state, and the vibration of the welding current is in the first period. The first welding current Iw1, the second welding current Iw2 during the second period, and the third welding current Iw3 during the third period are repeatedly energized, and 0 <Iw2 <Iw3 <Iw1. When the transient state at the start of the arc is finished, the welding current starts to vibrate. Since the welding current is not vibrated during the transient state, it is possible to suppress deterioration of the welding quality at the welding start portion. In addition, by vibrating the welding current during the steady state, the following effects can be obtained. During the first period, a large arc pressure acts on the molten pool, the molten pool has a concave shape that is recessed immediately below the wire, and the molten metal immediately below the wire is in a thin state. Subsequently, during the second period, the arc shape is deflated, and the arc is concentrated in a portion where the molten metal immediately below the wire is in a thin state. Subsequently, during the third period, the depressed portion of the molten pool is concentrated and heated by the arc in the first half, and since the arc pressure is constant in the second half, the depressed portion of the molten pool disappears and the state becomes calm. In this embodiment, by repeating these first period to third period after the transient state at the time of arc start is completed, in the spray transfer welding, the penetration of the welding start part and the steady welding part is deepened and increased. Quality can be improved.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll CD Current energization discrimination circuit Cd Current energization discrimination signal DV Drive circuit Dv Drive signal E Output voltage Ea Error amplification signal ECR Voltage control setting circuit Ecr Voltage control setting signal ED Output Voltage detection circuit Ed Output voltage detection signal EDR Voltage decrease value setting circuit Edr Voltage decrease value setting signal EI Current error amplification circuit Ei Current error amplification signal ER Voltage setting circuit Er Voltage setting signal EUR Voltage increase value setting circuit Eur Voltage increase value setting signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feed control signal FCR Feed speed control setting circuit Fcr Feed speed control setting signal Fr Feed speed setting circuit Fr Feed speed setting signal Fw Feed speed ID current detection circuit Id current detection signal Ih hot start current IHR hot start current setting times Ihr hot start current setting signal Iw welding current Iw1 first welding current Iw2 second welding current Iw3 third welding current PM power main circuit ST welding start circuit St welding start signal SW external characteristic switching circuit T1 first period T1R first period setting Circuit T1r First period setting signal T2 Second period T2R Second period setting circuit T2r Second period setting signal T3 Third period T3R Third period setting circuit T3r Third period setting signal TH Hot start period timer circuit Th Hot start period Thr Hot start period setting signal Ths Hot start period signal Tk Transition period TKD Transition period determination circuit Tkd Transition period determination signal Ts Initial period Vw Welding voltage Vw1 First welding voltage value Vw2 Second welding voltage value Vw3 Third welding voltage value WL Reactor WM Feed motor

Claims (3)

In the arc welding method in which the welding wire is fed, the welding current is vibrated, and welding is performed by the spray transfer mode,
Starting the vibration of the welding current from the time when it was determined that the transient state at the time of arc start was finished and transitioned to a steady state,
The vibration of the welding current is a repetition of energization of the first welding current Iw1 during the first period, the second welding current Iw2 during the second period, and the third welding current Iw3 during the third period, and 0 <Iw2 <Iw3 <Iw1.
An arc welding method characterized by that. The determination that the transient state has ended is performed by determining that a predetermined period has elapsed since the welding current started energization.
The arc welding method according to claim 1. The determination that the transient state has ended is performed by determining that the absolute value of the change rate of the welding voltage is less than a predetermined reference value after the welding current starts energization.
The arc welding method according to claim 1.

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