JPS649911B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a consumable electrode type arc welding device, in particular a pulsed arc current I applied to a DC arc current (hereinafter referred to as background current) supplied between a wire electrode and a base metal. The present invention relates to a welding method in which a wire electrode (hereinafter referred to as a pulsed current) is superimposed and melted by the electromagnetic contraction force caused by the pulsed current is made into fine particles and transferred to a base material (spray transfer) for welding.

FIG. 1 is a block diagram of this type of device according to the prior art. In the figure, 1 is a DC power supply circuit, 2 is a group of switches such as power transistors, and 3 is a group of switches 2.
4 is an auxiliary power supply circuit that supplies arc sustaining current (background current);
51, 52 are flywheel diodes, 61,
62 is a reactor, 7 is a welding wire winding frame, 8 is a motor that feeds the welding wire in the direction of arrow A, 9 is a welding torch, and 12 is for detecting the arc voltage Va between the wire electrode 10 and the base metal 11. Voltage detector, 1
4 is an average voltage converter that converts the arc voltage Va detected by the voltage detector 12 into an average voltage a (hereinafter referred to as welding voltage), and 15 is an operation panel that converts the arc voltage Va detected by the voltage detector 12 into an average voltage a (hereinafter referred to as welding voltage).
It has a welding current setting device 16a for setting Io, and a welding voltage setting device 16b for setting a reference welding voltage o.

The control circuit 3 also includes a pulse frequency setter 17 that receives a reference welding current Io and sends out a pulse current frequency signal f [=F ₁ (Io)], and a pulse frequency setter 17 that receives a reference welding current Io and sends out a pulse current frequency signal f [=F 1 (Io)]. The pulse peak current setting device 18 that sets the peak value Ip of
While setting the comparator 19 that outputs Vs (=o-a) and the reference pulse width τo of the pulse current,
A pulse width setter 20 receives the difference signal Vs, calculates the correction signal τs, and sends out the corrected pulse width signal τ(τo+τs), and receives the pulse frequency command signal f, the peak value signal Ip, and the pulse width signal τ. A switch command device 22 operates to control the conduction of the switch element group 2 and supply a pulse current having a commanded peak value and pulse width at a frequency f, and a reference welding current signal Io.
In response to this current value, a welding wire feed speed signal V [F ₂ = (Io)] suitable for this current value is sent out to the feed motor 8.
and a wire feed speed control device 21 that drives the wire feed speed control device 21.

Next, the operation of the conventional welding machine shown in FIG. 1 will be explained. In the above configuration, the pulse peak value Ip and the pulse width τo are set in advance by the pulse peak current value setting device 18 and the pulse width setting device 20 according to the material, diameter and shielding gas of the wire electrode, and then, Welding current and welding voltage that match welding conditions such as the plate thickness of base material 11 are adjusted using welding current setting device 16a and welding voltage setting device 16b. With this setting operation, this welding machine uses the reference welding current signal Io to adjust the pulse frequency f [=F ₁
(Io)] and wire feeding speed V [F ₂ (Io)] are determined,
Welding is performed. Further, the arc voltage Va is detected by the voltage detector 12, and this arc voltage Va
is input to the average voltage converter 14, and the welding voltage a
is converted to This a and the reference welding voltage o are compared, and according to the difference signal Vs, the pulse width τ
is corrected. By performing such feedback control, a constant welding voltage (a=
o) Welding is controlled to be performed while maintaining

Since the pulse arc welding machine according to the prior art is configured as described above, the welding current setting device 16a
It is necessary to maintain a predetermined function between the pulse frequency f and the wire feeding speed V by adjusting the dial. In order to satisfy this relationship between f and v, the pulse frequency setter 17 and wire feed speed controller 21 in the control circuit set the functions F ₁ (Io) and F ₂ in advance.
(Io) is determined and the reference welding current signal (Io) is input to each of 17 and 21 to determine f and v. Therefore, the control circuit 3 becomes a very complicated circuit, which increases the manufacturing cost. Furthermore, if variations occur in the wire feeding speed due to frictional resistance of the cable that feeds the wire electrode, the function between the pulse frequency f and the wire feeding speed v may deviate from a predetermined function, and such a situation There was a problem that good spray transfer could not be obtained.

This invention was made with the aim of eliminating the above-mentioned drawbacks, and the distance l between the wire electrode and the base material, which can be fed at a constant speed, is determined based on the arc voltage Va detected by the voltage detector 12. According to the determined result, the arc current is increased or decreased to form a pulsed arc current waveform and a background arc current.

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 2, 161b is a background voltage setting device for setting the minimum background voltage V _BO (minimum voltage), and 191 is the minimum background voltage.
A comparator that compares and determines V _BO and arc voltage Va,
23 is a critical arc voltage setting circuit that sets the critical arc voltage (maximum voltage) Vc, and 24 is a comparator that compares and determines the critical arc voltage Vc and arc voltage Va. 3 and 4 are explanatory diagrams of the welding state of the welding machine to which this invention is applied, and FIG. 3a shows the spray transfer state when the wire feeding speed is set to v [m/min]. Figure 4b shows the arc voltage waveform, Figure 4c shows the arc current waveform, Figure 4a shows the spray transfer state when the wire feeding speed is 2V [m/min], and Figure 4b shows the arc The voltage waveform is shown in the same figure c.
represent the arc current waveforms, respectively. Note that the broken line in the arc voltage waveform indicates the minimum voltage V _BO and the maximum voltage Vc, lo indicates the minimum arc length, and lc indicates the maximum arc length after droplet transfer.

Next, the operation of the embodiment of this invention will be explained. First, a wire feeding speed and a minimum background voltage that meet the welding conditions for the thickness of the base material 11 are set using the welding current setting device 16a and the background voltage setting device 161b. Through this setting operation, the wire feeding speed v of this welding machine is determined based on the reference welding current signal Io. Thereby, the wire electrode 10 is sent to the welding torch 9, and the wire electrode 10
is shorted to the base material 11. The short circuit voltage is then detected by the voltage detector 12. This short circuit voltage is compared with _VBO in a comparator 191, and a command signal (ON command) for increasing the arc current is given to the switch command device 22. This action causes the short-circuited wire electrode 10 to become red-hot, and eventually the red-hot portion of the wire electrode 10 is burned out, starting a welding arc. When the welding arc starts, the increased arc current melts the tip of the wire electrode 10, forming a molten lump. This molten mass is
Due to the increased arc current, the wire grows faster than the feeding speed of the wire electrode 10, and eventually sprays onto the base material 11. Therefore, as the molten mass at the tip of the wire electrode 10 grows and eventually transfers to spray, the arc length l increases, and at the time of spray transfer, the arc length l becomes extremely extended, and this arc length l increases. Arc voltage according to go
Va becomes high.

Then, the arc voltage Va eventually reaches the maximum voltage Vc set by the critical arc voltage setting circuit 23, and the comparator 24 operates. When this comparator operates, it gives a command signal (OFF signal) to the switch command device 22 to reduce the arc current. In this way, the arc current decreases and only the back ground current I _B becomes sufficient to maintain the arc discharge.
The tip of the wire electrode 10 approaches the base material 11 again, and the arc voltage Va decreases as the arc length l decreases. In this way, the arc voltage Va becomes lower, and eventually the arc voltage Va becomes lower than the background voltage setting device 1.
The minimum voltage V _BO set by 61b is reached, and comparator 1
91 works. When this comparator operates, it gives a command signal (ON command) to the switch command device 22 to increase the arc current. As described above, as the arc voltage Va changes from the minimum voltage V _BO to the maximum voltage Vc, the arc current increases and decreases repeatedly to form a pulsed arc current, and this pulsed arc current causes spray transfer. , welding is performed.

In this way, in the apparatus of this embodiment, the pulse frequency (or in other words, the welding current) is automatically determined according to the wire feeding speed v. In addition, the minimum voltage V _BO is set by the background voltage setter 191b.
Any welding voltage can be selected by adjusting .

This invention provides a pulse arc welding machine that performs welding by supplying an arc sustaining current (background arc current) and a pulsed arc current that can be superimposed on the arc sustaining current (background arc current) between a wire electrode that is fed toward the base material and the base metal. , the arc voltage that changes depending on the distance between the wire electrode and the base metal, that is, the arc length, is detected, and when the arc voltage falls below a predetermined minimum voltage V _BO , a pulse of arc current is generated, After that, when the arc voltage exceeds a predetermined maximum voltage Vc, the arc current is controlled so that the arc current pulse falls, and by changing only the wire feeding speed, the arc current is automatically controlled. The optimum pulse frequency, that is, the welding current, can be obtained in order to obtain the optimum welding condition.The control system can be configured more simply, and the instability of spray transfer caused by fluctuations in the wire feeding speed can be reduced. This has the effect of eliminating this problem and making it possible to perform more stable welding.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of a pulse arc welding machine according to the prior art, Fig. 2 is a block diagram of an embodiment of the present invention, and Figs. FIG. 3 is a diagram showing a spray transition state, an arc voltage waveform, and an arc current waveform in FIG. In the figure, 1 is a DC power supply circuit, 2 is a switch element group, 3 is a control device, 4 is an auxiliary power supply, 51, 5
2 is a flywheel diode, 61 and 62 are DC reactors, 8 is a wire feeding motor, 9 is a welding torch, 10 is a wire electrode, 11 is a base material, 12 is a voltage detector, 13 is a current detector, and 14 is an average Voltage converter, 15 is an operation panel, 16a is a welding current setting device, 16b is a welding voltage setting device, 161b is a background voltage setting device, 17 is a pulse frequency setting device, 18 is a pulse peak current value setting device, 19,2
4, 191 is a comparator, 20 is a pulse width setter, 2
1 is a wire feed speed control device, 22 is a switch command device, and 23 is a critical current setting circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a welding method in which an arc sustaining current and a pulsed arc current superimposed on the arc sustaining current are supplied between the wire electrode and the base material, the wire electrode and the base material are The arc voltage during welding, which changes depending on the interval, is detected, and when the arc voltage falls below a predetermined minimum voltage, the pulse of the pulsed arc current is started, and then the arc voltage rises to the predetermined maximum voltage. A pulsed arc welding method characterized in that the pulse of the pulsed arc current is controlled to fall when the voltage exceeds the voltage.