JP2006043736A - Consumable electrode gas shielded arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain satisfactory welding quality by improving the controllability of arc length when the arc length is set to be high in a consumable electrode gas shielded arc welding using a welding source having constant current properties, . <P>SOLUTION: In the consumable electrode gas shielded arc welding method, welding voltage Vw between a base metal and a welding wire is set by the set value Vs of the welding voltage; the welding voltage Vw under welding is detected; the detected value Vd of the welding voltage is subjected to moving averaging to calculate the average value Vra in the movement of the welding voltage; at this time, when the set value Vs of the welding voltage is less than a beforehand decided standard value of high arc length, the average value Vra in the movement of the welding voltage is decided as the control set value Vs of the welding voltage; at the time when the set value Vs of the welding voltage is higher than the standard value of high arc length, the set value Vs of the welding voltage is decided as the control set value Vsc of the welding voltage; and the welding current values Isc, Iw by constant current properties are changed in such a manner that the detected value Vd of the welding voltage is made almost equal to the control set value Vsc of the welding voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a consumable electrode gas shielded arc welding method for improving arc controllability using a welding power source having a constant current characteristic.

The following conventional techniques are described in Patent Document 1 and Japanese Patent Application No. 2004-088631.
FIG. 10 is a diagram showing the relationship between the melting characteristics L1 of the welding wire and the external characteristics CC1 and CC2 of the welding power source in aluminum MIG welding. In the figure, the horizontal axis represents the welding current Iw energized to the arc, and the vertical axis represents the arc length La. The melting characteristic L1 was measured by measuring the relationship between the welding current Iw and the arc length La when the welding wire feed speed was set to a predetermined constant value and the welding voltage Vw between the welding wire and the base metal was changed. Is. At the point Q1, the arc length La is about 2 mm, and at each point on the melting characteristic L1 lower than this, the droplet transfer form becomes a short-circuit transfer form. At point Q2, the arc length La is about 6 mm, and at each point on the melting characteristic L1 above this point, the droplet transfer form becomes a spray transfer form. At each point between points Q1 and Q2, the droplet transfer form is a mesospray transfer form. In this mesospray transfer mode, the droplets are transferred to the spray while a short time of 1 ms or less occurs. Considering welding quality such as spatter, bead appearance, blow hole, etc., the arc length La that is frequently used in practice is about 2 to 5 mm. Therefore, in the range of the arc length La that is frequently used in practice, the droplet transfer form is a mesospray transfer form. However, it may be used with a higher arc length than the mesospray transfer configuration.

  By the way, the arc length La is determined by the balance between the welding wire feeding speed and the melting speed. The melting rate is substantially proportional to the value of the welding current Iw. Since the melting characteristic L1 is when the feeding speed is constant, the value of the welding current Iw is determined so that the melting speed and the feeding speed are equal for each arc length. In the melting characteristic L1, the welding current value at the point Q2 with an arc length La = 6 mm is larger than the welding current value at the point Q1 with an arc length La = 2 mm. , The specific melting amount) becomes smaller. That is, in the mesospray transfer mode, the specific melting amount decreases in inverse proportion to the arc length La. For this reason, when the welding current Iw is a constant value (when using a welding power source having a constant current characteristic), disturbances such as fluctuations in the feeding speed, fluctuations in the distance between the power supply tip and the base material (hereinafter simply referred to as disturbances) ), The arc length La is controlled so that the arc length La becomes shorter because the specific melting amount becomes smaller and the melting speed becomes slower when the arc length La becomes transiently longer. On the contrary, when the arc length La is shortened due to a disturbance, the specific melting amount is increased and the melting rate is increased, so that the arc length La is controlled to become longer. This action of restoring the variation in arc length is called “arc-specific self-control action”.

  Generally, a welding power source having constant voltage characteristics is used for consumable electrode gas shielded arc welding including aluminum MIG welding. This is because the arc length La is detected by the welding voltage Vw by utilizing the fact that the arc length La is proportional to the welding voltage Vw, and a constant voltage is set so that the detected value matches the target value (welding voltage set value). The arc length is controlled by controlling. When the welding conditions such as the material of the aluminum wire, the diameter, the type of the shielding gas, etc. are determined and the feeding speed is set, the melting characteristic L1 is determined. For this purpose, the constant voltage characteristic may be set so as to obtain a desired arc length. However, aluminum MIG welding has a property that the melting characteristic L1 changes depending on the state of the oxide film of the base material. In MIG welding, welding is performed while removing (cleaning action) the base oxide film with an arc. The cleaning state of the oxide film is greatly affected by fluctuations in the condition of the surface of the base material, the temperature of the base material, the shielding state of the shielding gas, and the like. Moreover, the cleaning state changes every time during welding.

  When the cleaning state changes, the melting characteristic L1 changes. This is because the arc shape changes due to the change in the cleaning state, the heat input from the arc to the welding wire changes, and the melting rate changes. In order to set the arc length La to a desired value of 4 mm when the melting characteristic is L1, the constant voltage characteristic is set. When the melting characteristic L1 changes in this state, it is necessary to change the setting of the constant voltage characteristic in order to maintain the arc length La at 4 mm. That is, in aluminum MIG welding, the setting of the constant voltage characteristic has to be corrected in order to maintain the arc length at a desired value every time the cleaning state changes. As described above, since the cleaning state also changes during welding, it is necessary to change the setting of the constant voltage characteristic during welding. For this reason, it has been practiced in the field that the welding operator manually adjusts the constant voltage characteristic while visually confirming the variation in the arc length due to the variation in the cleaning state. However, this method has a problem that automation is difficult and the arc length cannot be accurately maintained at a desired value.

  In order to solve the above-described problems, aluminum MIG welding with constant current characteristics shown in the figure has been conventionally performed. As described above, when the melting characteristic is expressed with the welding current Iw on the horizontal axis and the welding voltage Vw on the vertical axis, the melting characteristic changes depending on the cleaning state. However, as shown in the figure, when the melting characteristics are expressed with the welding current Iw on the horizontal axis and the arc length La on the vertical axis, the melting characteristics remain almost L1 even when the cleaning state changes. Therefore, if the constant current characteristic CC1 is set so that the arc length La has a desired value of 4 mm, the operating point becomes P1 and the arc length La can be controlled to a desired value. In this case, even if the cleaning state changes, the melting characteristic remains L1, so the operating point P1 is also maintained and the arc length La = 4 mm is maintained. The conventional technology described below is based on the arc length control based on the constant current characteristics and the control for suppressing the fluctuation of the arc length due to disturbance.

  When a disturbance occurs in the steady arc state at the operating point P1 and the arc length La becomes transiently long, the operating point moves from P1 to P2. In the prior art, the welding voltage Vw and the welding voltage moving average value Vra are detected, and the welding current value Iw based on the constant current characteristic is changed according to these voltage error amplification values ΔV = G · (Vra−Vw). Here, G is a predetermined amplification factor. That is, Iw2 = Iw1 + ΔV. The welding current Iw1 is a current value of the constant current characteristic CC1. When the arc length La becomes longer due to disturbance, the welding voltage Vw becomes larger than the welding voltage moving average value Vra, and the voltage error amplification value ΔV <0. As a result, Iw2 <Iw1, and the constant current characteristic changes to CC2. In response to this, the operating point moves from P2 to P3. Since the welding current decreases when the operating point becomes P3, the melting rate is slowed down, and the arc length La is controlled to be shortened. That is, the fluctuation of the arc length La due to the disturbance is detected by the voltage error amplification value ΔV, and the constant current characteristic is changed to make the self-control action by the external characteristic work. As described above, the self-control action based on the external characteristics has better transient response of the arc length control and the arc length fluctuation width is smaller than the self-control action inherent to the arc.

  Next, when the cleaning state changes in the steady arc state at the operating point P1, the welding voltage Vw changes. However, the changing speed of the cleaning state is slower than the changing speed due to the above disturbance. For example, the fluctuation speed due to the disturbance is about several ms to several tens of ms, while the fluctuation speed of the cleaning state is about several tens ms to several hundred ms. Therefore, the moving average period for calculating the welding voltage moving average value Vra is set longer than the fluctuation speed of the disturbance and shorter than the fluctuation speed of the cleaning state. As a result, when a gradual change in the cleaning state occurs, Vw≈Vra, and the constant current characteristic remains CC1. For this reason, the arc length La remains at a desired value even when the cleaning state varies. On the other hand, when a disturbance occurs, Va ≠ Vra as described above, and the constant current characteristic changes transiently from CC1 to CC2 and the like, and the self-control action by the external characteristic works. When returning to the steady arc state, the constant current characteristic returns to CC1.

Japanese Patent No. 2993174

  FIG. 11 is a diagram showing the relationship between the melting characteristic L1 and the constant current characteristic CC3 when the arc length La is set to be more than 6 mm in FIG. 10 described above. In the figure, as described above, the range of arc length La of about 2 to 6 mm is the mesospray transition region, and within this range, the arc-specific self-control action works, and the arc is controlled against the variation of the cleaning state. The length La can be maintained at an appropriate value. However, when the Q2 point exceeds 6 mm, the melting characteristic L1 becomes substantially vertical, and therefore it is difficult to set the arc length La to, for example, 6.5 mm even if the constant current characteristic CC3 is adjusted. Usually, it is often used in the mesospray transition region, but depending on the weld joint, welding position, welding speed, etc., it may be used outside the mesospray transition region. In such a case, it has been difficult for the prior art to set the arc length outside the mesospray transition region.

  Furthermore, even in the mesospray transition region, the arc-specific self-control action does not stop with the Q2 point as a boundary value. Since the arc length is slightly shorter than the above-mentioned boundary value, the effect of the arc-specific self-control action gradually decreases, and the boundary value hardly works. This area is referred to as a transition area. In this transition region, since the arc-specific self-control action is weakened, there is a problem that as the arc length is set closer to the boundary value Q2, the variation in the arc length gradually increases with the change in the cleaning state.

  In the present invention, the arc length can be accurately set to a range exceeding the mesospray transition region or a desired value in the transition region, and fluctuations in the arc length due to the cleaning state and disturbance can be suppressed. A consumable electrode gas shield arc welding method is provided.

In order to solve the above-described problem, the first invention is a consumable electrode that feeds a welding wire at a predetermined speed, and conducts welding by applying a predetermined welding current to the arc by a constant current characteristic of a welding power source. In the gas shielded arc welding method,
The welding voltage between the base metal and the welding wire is set by the welding voltage setting value, the welding voltage during welding is detected, the welding voltage moving average value is calculated by moving the welding voltage detection value, and the welding voltage setting is performed. When the value is less than a predetermined high arc length reference value, the welding voltage moving average value is set as a welding voltage control set value, and when the welding voltage set value is equal to or higher than the high arc length reference value, the welding voltage set value is set. A consumable electrode gas shielded arc welding method characterized in that the welding current control value is changed, and the welding current value according to the constant current characteristic is changed so that the welding voltage detection value is substantially equal to the welding voltage control setting value. It is.

  Further, in the second invention, when the welding voltage set value is less than the intermediate arc length reference value set in advance to a value smaller than the high arc length reference value, the welding voltage moving average value is set to the welding voltage control set value. And when the welding voltage set value is not less than the intermediate arc length reference value and less than the high arc length reference value, the welding voltage moving average value and the welding voltage set value are mixed by a predetermined mixing function. The consumable according to the first aspect, wherein the welding voltage control set value is used, and when the welding voltage set value is greater than or equal to the high arc length reference value, the welding voltage set value is used as the welding voltage control set value. This is an electrode gas shield arc welding method.

  Further, the third invention is consumable electrode pulse arc welding in which the consumable electrode gas shield arc welding repeats energization of a peak current during a peak period and energization of a base current during a base period as a pulse period, and the welding current value Is a welding current average value for each pulse period, the welding voltage value is a welding voltage average value for each pulse period, and at least one or more of the peak period, the peak current, the base period, or the base current The consumable electrode gas shielded arc welding method according to the first or second invention, wherein the welding current average value for each pulse period is changed by changing.

  According to the first aspect of the invention, the welding current is changed by the welding voltage moving average value Vra when the arc length is less than the high arc length reference value Vth, and the welding voltage set value Vs is used when the arc length is higher than the high arc length reference value Vth. By changing the welding current, the arc length can be accurately set to a desired value for both low and high values. Furthermore, the arc length variation can be suppressed against disturbance and cleaning state variation. In particular, even when the arc length is in a high range exceeding the mesospray transition region, the arc length can be accurately set to a desired value.

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the welding voltage moving average value in the intermediate arc length range of the transition region that is greater than the intermediate arc length reference value Vtm and less than the high arc length reference value Vth. The welding current is changed by a welding voltage control set value Vsc obtained by appropriately mixing Vra and the welding voltage set value Vs. For this reason, the arc length controllability in the intermediate arc length range is further improved.

  According to the third aspect, the effects of the first and second aspects can be achieved in pulse arc 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 carrying out the consumable electrode gas shield arc welding method according to the first embodiment. Hereinafter, each block will be described with reference to FIG.

  The main power supply circuit MC receives a commercial AC power supply (three-phase 200 V, etc.) as an input, performs output control by inverter control, chopper control, etc. according to a current error amplification signal Ei described later, and outputs a welding current Iw and a welding voltage Vw. The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 of the wire feeding device, and an arc 3 is generated between the welding wire 1 and the base material 2.

  The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The welding voltage moving average value calculation circuit VRA averages the welding voltage detection signal Vd and outputs a welding voltage moving average value signal Vra. The welding voltage setting circuit VS outputs a welding voltage setting signal Vs having a desired value. The welding voltage setting switching circuit SWV switches to the a side when the value of the welding voltage setting signal Vs is less than the predetermined high arc length reference value Vth, and sets the welding voltage moving average value signal Vra to the welding voltage control setting. When it is equal to or higher than the high arc length reference value Vth, it is switched to the b side and the welding voltage setting signal Vs is output as the welding voltage control setting signal Vsc. The operation of this circuit will be described later. The voltage error amplification circuit EV amplifies an error between the welding voltage control setting signal Vsc and the welding voltage detection signal Vd and outputs a voltage error amplification signal ΔV = G · (Vsc−Vd). Here, G is a predetermined amplification factor.

  The current setting circuit IS outputs a predetermined current setting signal Is. The adder circuit AD adds the current setting signal Is and the voltage error amplification signal ΔV, and outputs a current control setting signal Isc = Is + ΔV. The current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The current error amplification circuit EI amplifies an error between the current control setting signal Isc and the welding current detection signal Id and outputs a current error amplification signal Ei. By this circuit, a constant current characteristic determined by the current control setting signal Isc is formed. In the steady arc state of the voltage error amplification signal ΔV = 0, Isc = Is, and thus a constant current characteristic determined by the current setting signal Is is formed.

  When the welding voltage control setting signal Vsc is the welding voltage moving average value signal Vra (when Vs <Vth), the conventional consumable electrode gas shield arc welding method described above with reference to FIG. 10 is performed. That is, for a rapid arc length variation due to disturbance, the constant current characteristic is changed by the voltage error amplification signal ΔV to suppress the arc length variation. For a gradual arc length variation such as a cleaning state, Vra≈Vd and the voltage error amplification signal ΔV≈0, so that the constant current characteristic by the welding current setting signal Is does not change, and the arc-specific self-control action Therefore, the fluctuation of the arc length is suppressed.

  On the other hand, when the welding voltage control setting signal Vsc is the welding voltage setting signal Vs (when Vs ≧ Vth), consumable electrode gas shield arc welding with constant voltage characteristics is performed. That is, when the arc length becomes longer than the mesospray transition region, the variation range of the arc length due to the variation of the cleaning state becomes small. Therefore, it is less necessary to consider the variation in the arc length due to the variation in the cleaning state. For this reason, since the arc length is substantially proportional to the welding voltage Vw, the arc length is set to a desired value by the welding voltage setting signal Vs, and the constant voltage characteristic is formed by the voltage error amplification signal ΔV to control the arc length. can do.

  FIG. 2 is a characteristic diagram for explaining the operating principle of the consumable electrode gas shield arc welding method according to Embodiment 1 of the present invention. In aluminum MIG welding, the figure shows the relationship between the arc length La shown on the horizontal axis and the welding current Iw and welding voltage Vw shown on the vertical axis when the feeding speed is fixed to a predetermined value. Hereinafter, a description will be given with reference to FIG.

  As described above, in the mesospray transition region where the arc length is about 2 to 6 mm, the arc length La can be set by changing the welding current Iw (constant current characteristic). In particular, when the arc length is less than about 4 mm, the inclination of the characteristic of the welding current Iw is steep, so that the controllability of the arc length is excellent. As the arc length approaches 6 mm, the inclination becomes gentler and the controllability of the arc length becomes weaker. When the arc length exceeds 6 mm, the inclination becomes substantially horizontal, and the controllability of the arc length is almost lost.

  On the other hand, when the arc length La exceeds 6 mm, the welding voltage Vw becomes a characteristic substantially proportional to the arc length La as described above. This is because the arc length La is less affected by the change in the cleaning state. As the arc length becomes shorter than 6 mm, the width of the welding voltage Vw having the same arc length La increases. This is because if the arc length La is short, the arc length La is greatly influenced by a slight change in the cleaning state, and as a result, the welding voltage Vw changes. That is, when the arc length La is short, the change width of the welding voltage Vw with respect to the arc length La becomes large, and the controllability of the arc length is weak. When the arc length La becomes longer, the welding voltage Vw and the arc length La show a proportional relationship, and the controllability of the arc length becomes better.

  Therefore, in the first embodiment, a high arc length such as 5 mm or 6 mm is set in advance, and the welding voltage set value Vs is compared with a value corresponding to the high arc length (high arc length reference value Vth), and Vs < When Vth, arc length controllability by the welding current Iw is used, and when Vs ≧ Vth, arc length controllability by the welding voltage Vw is used. This utilizes the fact that the parameter having controllability differs depending on the length of the arc length La.

[Embodiment 2]
In Embodiment 2 of the present invention, welding voltage control set value Vsc is calculated by mixing welding voltage moving average value Vra and welding voltage set value Vs by a predetermined mixing function Vsc = fm (Vra, Vs). Details will be described below.

  FIG. 3 is a block diagram of a welding power source for carrying out the consumable electrode gas shield arc welding method according to the second embodiment. In the figure, the same blocks as those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from those in FIG. 1 will be described.

The mixing function circuit FM presets an intermediate arc length reference value Vtm having a smaller value in addition to the high arc length reference value Vth,
(1) When the welding voltage setting signal Vs is less than the intermediate arc length reference value Vtm, the welding voltage moving average value signal Vra is output as the welding voltage control setting signal Vsc,
(2) When the welding voltage setting signal Vs is not less than the intermediate arc length reference value Vtm and less than the high arc length reference value Vth, the welding voltage moving average value signal Vra and the welding voltage setting signal Vs are previously set. Mixed by a predetermined mixing function fm and output as the welding voltage control setting signal Vsc,
(3) When the welding voltage setting signal Vs is equal to or higher than the high arc length reference value Vth, the welding voltage setting signal Vs is output as the welding voltage control setting signal Vsc. The mixing function fm will be described later with reference to FIGS.

  In FIG. 2 described above, the range where the arc length La is about 2 to 6 mm is a mesospray transition region. For example, the value of the welding voltage setting signal Vs corresponding to La = 6 mm is set as the high arc length reference value Vth, and La = 3 mm. The value of the corresponding welding voltage setting signal Vs is preset as the intermediate arc length reference value Vtm. In the case of an arc length less than the above-mentioned intermediate arc length reference value Vtm, the welding current Iw has a strong correlation with the arc length, so the conventional control using the welding voltage moving average value signal Vra and the welding current setting signal Is is performed. Since the welding voltage Vw and the arc length have a strong correlation when the arc length is equal to or higher than the high arc length reference value Vth, constant voltage control using the welding voltage setting signal Vs is performed. For the arc length between the intermediate arc length reference value Vtm and the high arc length reference value Vth, the welding voltage moving average value signal Vra and the welding voltage setting signal Vs are mixed and the above two controls are used together.

An example of the mixing function fm is shown in the following equation.
Vsc = Vra · (100−α) / 100 + Vs · α / 100 (1) where α is the mixing ratio [%]. 4 and 5 are examples of the relationship between the mixing ratio α and the welding voltage setting signal Vs. Both figures show a case where an aluminum alloy wire having a diameter of 1.2 mm is used in aluminum MIG welding. FIG. 4 shows the case where the average welding current is 50 A, and FIG. 5 shows the case where the average welding current is 150 A. The mixing rate α is determined by the values of the welding current setting signal Is (average welding current) and the welding voltage setting signal Vs. Then, the welding voltage control setting signal Vsc is calculated by the above equation (1).

[Embodiment 3]
The third embodiment of the present invention is a case where consumable electrode pulse arc welding is used as the consumable electrode gas shield arc welding in the first embodiment. FIG. 6 shows current / voltage waveforms of pulse arc welding. FIG. 4A shows the time change of the welding current instantaneous value iw, and FIG. 4B shows the time change of the welding voltage instantaneous value vw. During the peak period Tp from time t1 to t2, as shown in FIG. 4A, a large current peak current Ip is applied to transfer the droplet, and welding is performed as shown in FIG. A peak voltage Vp is applied between the wire and the base material. During the base period Tb from time t2 to t3, as shown in FIG. 6A, the base current Ib having a small current value is energized so as not to melt the welding wire, and as shown in FIG. A base voltage Vb is applied between the wire and the base material. A pulse period Tf is formed from the peak period Tp and the base period Tb. In pulse arc welding, the so-called 1-pulse 1-droplet transfer is generally performed in which one droplet transfers to the base material at each pulse period Tf. Therefore, the arc length La changes greatly every pulse period Tf. For this reason, as welding current Iw and welding voltage Vw in Embodiment 1 described above, it is necessary to use welding current average value Iwa for each pulse period Tf and welding voltage average value Vwa for each pulse period Tf in Embodiment 3. is there. That is, in the third embodiment, the constant current characteristic is formed so that the above-described pulse cycle welding current average value Iwa becomes a constant value. The welding voltage moving average value Vra is calculated by moving average the above-mentioned pulse period welding voltage average value Vwa. Therefore, the voltage error amplification value ΔV = G · (Vra−Vwa). In FIG. 5A, when the peak period Tp, peak current Ip, base period Tb, and base current Ib are set, the pulse cycle welding current average value Iwa is set to a predetermined value. Therefore, in order to change the pulse period welding current average value Iwa, at least one of the peak period Tp, peak current Ip, base period Tb, or base current Ib may be changed. Other than the above, the second embodiment is the same as the first embodiment.

  FIG. 7 is a block diagram of a welding power source for carrying out the consumable electrode gas shield arc welding method according to the third embodiment. In the figure, the same blocks as those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from those in FIG. 1 will be described.

  The pulse cycle welding voltage average value calculation circuit VWA calculates an average value of the welding voltage detection signal Vd, which has detected the welding voltage instantaneous value vw, for each pulse cycle Tf, and outputs a pulse cycle welding voltage average value signal Vwa. The welding voltage moving average value calculation circuit VRA moves and averages the pulse period welding voltage average value signal Vwa and outputs a welding voltage moving average value signal Vra. The voltage error amplification circuit EV amplifies an error between the welding voltage control setting signal Vsc and the pulse period welding voltage average value signal Vwa, and outputs a voltage error amplification signal ΔV = G · (Vra−Vwa). Here, G is a predetermined amplification factor.

  The base period setting circuit TBS outputs a predetermined base period setting signal Tbs. The subtraction circuit SB subtracts the voltage error amplification signal ΔV from the base period setting signal Tbs, and outputs a base period control setting signal Tbsc = Tbs−ΔV. The peak period setting circuit TPS outputs a predetermined peak period setting signal Tps. The timer circuit TM becomes High level during the period determined by the peak period setting signal Tps, and becomes Low level during the period determined by the subsequent base period control setting signal Tbsc. Thereafter, the timer circuit Tm repeats this operation. Output. That is, when the timer signal Tm is at a high level, it is a peak period, and when it is at a low level, it is a base period. The peak current setting circuit IPS outputs a predetermined peak current setting signal Ips. The base current setting circuit IBS outputs a predetermined base current setting signal Ibs. The switching circuit SW switches to the a side when the timer signal Tm is at the high level and outputs the peak current setting signal Ips as the welding current control setting signal Isc, and switches to the b side when the timer signal Tm is at the low level. The base current setting signal Ibs is output as a welding current control setting signal Isc. The welding current instantaneous value iw described above with reference to FIG. 6 corresponding to the welding current control setting signal Isc is energized.

  In the figure, since the voltage error amplification signal ΔV = 0 when in the steady arc state, Tbsc = Tbs. Therefore, a current determined by the peak current setting signal Ips is energized during the period determined by the peak period setting signal Tps, and a current determined by the base current setting signal Ibs is energized during the period determined by the base period setting signal Tbs. Therefore, the base period setting signal Tbs shown in the figure corresponds to the welding current setting signal Is shown in FIG.

  When a disturbance occurs in the steady arc state and the arc length La becomes transiently long, the voltage error amplification signal ΔV> 0. Therefore, Tbsc <Tbs, and the base period is shorter than the steady arc state. As a result, the pulse cycle welding current average value Iwa becomes small, and the fluctuation of the arc length La is suppressed by acting a self-control action by the external characteristics.

  In the above description, the base period Tb is varied to change the pulse period welding current average value Iwa. In addition to this, when the peak period Tp is varied, Tp = Tps + ΔV may be set. Similarly, when the base current Ib is varied, Ib = Ibs + ΔV. Further, when the peak current Ip is varied, Ip = Ips + ΔV may be set.

  When the value of the welding voltage setting signal Vs becomes equal to or higher than the high arc length reference value Vth, the welding voltage control setting signal Vsc = Vs. For this reason, constant voltage control is performed so that the pulse cycle welding voltage average value signal Vwa = Vs. As a result, it is possible to control the arc length in a range exceeding the mesospray transition region.

[Embodiment 4]
The fourth embodiment of the present invention uses the consumable electrode pulse arc welding described in the third embodiment as the consumable electrode gas shielded arc welding in the second embodiment. FIG. 8 is a block diagram of a welding power source for carrying out the consumable electrode gas shield arc welding method according to the fourth embodiment. In this figure, the mixed function circuit FM described in FIG. 3 is incorporated in the block diagram described in FIG. Therefore, description of each block is the same as each block of FIG.7 and FIG.3.

  Although the above has described aluminum MIG welding, it can also be applied to MIG welding of magnesium or the like in which an oxide film is formed on the base material.

[effect]
FIG. 9 is an upper limit voltage comparison diagram showing an example of the effect of the present invention. In the figure, in MIG welding using an aluminum wire having a diameter of 1.2 mm, the maximum value (upper limit voltage) of the welding voltage capable of stable welding with respect to the average welding current shown on the horizontal axis is measured. Since the upper limit voltage is substantially proportional to the arc length, the figure shows that the maximum arc length that enables stable welding is measured. As is clear from the figure, the upper limit voltage of the present invention is about 2V larger than that of the prior art. From this result, it can be seen that the present invention can be stably controlled to a higher arc length range. This is because the controllability of the arc length is secured by gradually switching from the constant current control to the constant voltage control in the high arc length range.

It is a block diagram of the welding power supply which concerns on Embodiment 1 of this invention. It is a relationship figure of arc length La, welding current Iw, and welding voltage Vw for explaining the principle of operation of the consumable electrode gas shield arc welding method of the present invention. It is a block diagram of the welding power supply which concerns on Embodiment 2 of this invention. FIG. 10 is an example of a relationship diagram between a welding voltage setting signal Vs and a mixing rate α in the second embodiment. FIG. 10 is an example of a relationship diagram between a welding voltage setting signal Vs and a mixing rate α in the second embodiment. It is a current / voltage waveform diagram of pulse arc welding. It is a block diagram of the welding power supply which concerns on Embodiment 3 of this invention. It is a block diagram of the welding power supply which concerns on Embodiment 4 of this invention. It is a comparison figure of the upper limit voltage with respect to the average welding current which shows an example of an effect. It is a wire-melting characteristic figure which shows the consumable electrode gas-shield arc welding method by the constant current characteristic of a prior art. It is a wire-melting characteristic figure which shows the subject of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll AD Adder circuit CC1-CC3 Constant current characteristic EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit FM Mixing function circuit fm Mixing function Ib Base current IBS Base current setting circuit Ibs Base current setting signal ID Current detection circuit Id Welding current detection signal Ip Peak current IPS Peak current setting circuit Ips Peak current setting signal IS Welding current setting circuit Is Welding current setting signal Isc Welding current control setting signal Iw Welding current iw welding current instantaneous value Iwa pulse period welding current average value (signal)
L1 Melting characteristic La Arc length MC Power supply main circuit SB Subtraction circuit SW Switching circuit SWV Welding voltage setting switching circuit Tb Base period TBS Base period setting circuit Tbs Base period setting signal Tbsc Base period control setting signal Tf Pulse period TM Timer circuit Tm Timer signal Tp peak period TPS peak period setting circuit Tps peak period setting signal Vb base voltage VD welding voltage detection circuit Vd welding voltage detection signal Vp peak voltage VRA welding voltage moving average calculation circuit Vra welding voltage moving average (signal)
VS Welding voltage setting circuit Vs Welding voltage setting (value / signal)
Vsc Welding voltage control setting (value / signal)
Vth High arc length reference value Vtm Intermediate arc length reference value Vw Welding voltage vw Welding voltage instantaneous value VWA Pulse cycle welding voltage average value calculation circuit Vwa Pulse cycle welding voltage average value (value / signal)
α Mixing ratio ΔV Voltage error amplification (value / signal)

Claims (3)

In the consumable electrode gas shielded arc welding method of feeding a welding wire at a predetermined speed and welding by welding a predetermined welding current according to a constant current characteristic of a welding power source to the arc,
The welding voltage between the base metal and the welding wire is set by the welding voltage setting value, the welding voltage during welding is detected, the welding voltage moving average value is calculated by moving the welding voltage detection value, and the welding voltage setting is performed. When the value is less than a predetermined high arc length reference value, the welding voltage moving average value is set as a welding voltage control set value, and when the welding voltage set value is equal to or higher than the high arc length reference value, the welding voltage set value is set. A consumable electrode gas shielded arc welding method characterized in that the welding current control value is changed, and the welding current value according to the constant current characteristic is changed so that the welding voltage detection value is substantially equal to the welding voltage control setting value. .   When the welding voltage set value is less than the predetermined intermediate arc length reference value smaller than the high arc length reference value, the welding voltage moving average value is set as the welding voltage control set value, and the welding voltage set value is When the intermediate arc length reference value is equal to or greater than and less than the high arc length reference value, the welding voltage moving average value and the welding voltage set value are mixed by a predetermined mixing function as the welding voltage control set value, 2. The consumable electrode gas shielded arc welding method according to claim 1, wherein when the welding voltage set value is equal to or greater than the high arc length reference value, the welding voltage set value is set as the welding voltage control set value. The consumable electrode gas shielded arc welding is consumable electrode pulse arc welding in which energization of a peak current during a peak period and energization of a base current during a base period are repeated as a pulse period, and the welding current value is a welding current for each pulse period. Average value, the welding voltage value is a welding voltage average value for each pulse period, and at least one of the peak period or the peak current or the base period or the base current is changed for each pulse period. 3. The consumable electrode gas shielded arc welding method according to claim 1, wherein an average value of the welding current is changed.

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