JPH0329503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc control method that performs stabilization control such as heating an electrode in advance at the start of welding in order to stabilize the arc start.

An arc is generated between an arc electrode and a workpiece, and welding or fusing is performed using the arc. If a non-consumable electrode such as tungsten is used for the arc electrode, the arc will be stable when the electrode becomes red hot due to arc heat.
It is known to be unstable until it becomes red-hot. In order to generate an arc stably,
At the time of arc start, the voltage applied to the electrode and the workpiece is made higher than the steady voltage.
In addition, when using a consumable electrode, in order to smoothly melt the consumable electrode due to arc heat and proceed with stable welding, it is necessary to keep the electrode feeding speed low at the time of arc start, or use a non-consumable electrode. A high voltage is applied between the electrode and the workpiece in the same way as in the case of (Hereinafter, stabilizing the arc start will be referred to as stabilization control.) A conventional DC arc welding method in which the arc start is stabilized will be explained with reference to FIG. This DC arc welding method is an example in which a consumable wire electrode is fed toward a workpiece and an arc is generated between the wire electrode and the workpiece. First, welding is started at time _t1 , and the wire feeding speed at that time is set to a low speed _S1 (approximately 1 to 2 m/min). (hereinafter referred to as wire slowdown control) On the other hand, the output voltage becomes arc start in a state where a high output voltage V ₁ (hereinafter referred to as hot start) is applied.
This prevents shock when the wire short-circuits to the base metal, and a large short-circuit current flows, resulting in an instantaneous transition to an arc. At the same time as the arc occurs or outside a certain period of time, the output voltage changes to the welding condition setting voltage V ₂ ,
The wire feeding speed is also controlled to be switched to the welding condition setting speed _S2 . If controlled in this way, the arc start will be stable and good, but each time the arc is started, the wire slowdown control _S1 and the hot start control _V1 will work as shown in FIG. However, in the case of welding work in which tack welding is performed rapidly and continuously, that is, when a high voltage is applied due to a hot start from the welding end time t ₃ to the next arc start time t ₄ in Fig. 1, or when the wire slow If the wire is slow due to down, the wire will burn up violently at the start of the arc, and sometimes welding (punback) will occur between the inside of the torch and the wire, resulting in failure to form an equal spacing pool, or it may take a long time to form the welding pool. This causes problems such as poor welding and poor workability. Therefore, this hot start and wire slowdown control contributes to stabilizing the arc start when the wire tip is in a cooled state, but it has the opposite effect when starting the arc during continuous tack welding. There were some negative effects.

The object of the present invention is to provide an arc start control method that performs arc start stabilization control such as wire slowdown control and hot start control, and which changes the control according to the arc start condition to always obtain a stable arc start. To provide a control method.

In order to achieve the above object, the present invention performs stabilization control at the time of arc start by measuring the arc interruption time when starting the arc again after stopping the arc that has occurred once, and determining whether the arc interruption time is a predetermined length. If it is within the range, the arc is generated without performing the above stabilization control. Specifically, for example, if the arc is restarted within a certain period of time (approximately 0.5 seconds) after welding is completed, the wire slowdown control and hot start control are canceled to eliminate arc start errors and ensure that the arc is always started. It is characterized by making it possible to stabilize.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a time chart explaining the procedure of the arc welding method according to the present invention. In this figure, the same reference numerals as in FIG. 1 indicate the same parts, and similarly to FIG. 1, this figure shows an example in which the present invention is applied to a DC arc welding device using a consumable electrode. Any welding in the middle of the welding process (hereinafter referred to as the first welding for convenience), such as when tack welding is repeated and repeated, or when multiple workpieces are lined up and welded one after another (hereinafter referred to as the first welding for convenience) and the next welding. When welding, the control operation from the first arc start (time t ₁ ) to the end of welding (time t ₃ ) is the same as that shown in FIG. 1.

In the control method of the present invention, the time from the welding end time _t3 to the next arc start time _t4 is a predetermined time (approximately
0.5sec) and determines whether the wire slowdown control or hot start control is to be performed or not.

By doing this, if the time from time t ₃ to t ₄ is within the predetermined time, that is, if the wire tip is still hot and the wire is easily melted, wire slowdown control S and hot start control are activated. By not performing stabilization control such as V ₁ ,
The arc burns up when the arc starts, and it takes time for the arc to stabilize. Furthermore, defects in the formation of the weld pool can be eliminated, arc start is stable, and the efficiency of welding work can be improved.

The time from time t ₃ to t ₄ is a predetermined time (approximately 0.5 sec)
If it is longer, the tip of the wire will also be in a cooled state, so that stabilization control such as wire slowdown control, hot start control, etc. can be performed at the time of arc start to stabilize the arc start as before.

Next, a control device for carrying out the above control method will be explained in detail with reference to FIG.

1 is a welding start signal generation circuit, which is a switch or sequence control device (not shown) operated by the operator.
It is. 2 is a hot start circuit which outputs a voltage lower than that of the reference setting circuit 3; The reference setting circuit 3 includes a variable resistor (not shown) that divides the voltage into a desired voltage. Reference numeral 4 denotes an output bias circuit configured such that the output voltage is reduced when the output of the hot start circuit 2 is applied. Reference numeral 5 denotes a firing phase control circuit for the thyristor circuit 6, which controls the phase according to the magnitude of the output voltage from the output bypass circuit 4. The output of the thyristor circuit 6 is applied to the consumable wire electrode W. 7 is a wire speed setting circuit 8 which is a reference wire slowdown circuit.
outputs a higher voltage than the Reference numeral 9 denotes an output bias circuit, which may have the same configuration as the output bias circuit 4.
A control circuit 10 controls the rotational speed of the wire feeding motor 11, and controls the rotational speed of the wire feeding motor 11 according to the magnitude of the output from the output bias circuit 9. A wire electrode feeding roll L is connected to an output shaft (not shown) of the wire feeding motor 11, and the wire feeding speed is adjusted according to the rotation speed of the roll L.
Reference numeral 12 denotes a time circuit, which is set when the current signal from the welding current detection circuit 13 stops and is reset by a signal from the welding start signal generation circuit 1. The timer is composed of an integrating circuit and a switching circuit. A time circuit 12 applies the output of the hot start circuit 2 to the output bias circuit 4 in response to a signal from the welding start signal generating circuit 1. The output of this output bias circuit is a low voltage similar to the output from the hot start circuit 2, and at this time the output of the thyristor circuit 6 is a high voltage. When applied to the output bias circuit 9 of the wire slowdown circuit 7 at the same time, the output of the output bias circuit 9 is at a high voltage and the control circuit 1
0 causes the motor 11 to rotate at a low speed. When the wire electrode is fed by the motor 11 via the feed roll L and the arc is ignited, the current detector 13 detects the arc current and applies a detection signal to the time circuit 12. When the current detection signal is input to the time circuit 12, the output from the hot start circuit 2 is stopped and the output from the reference setting circuit 3 is transferred to the output bias circuit 4.
Since the voltage is applied to the ignition phase control circuit 5 via the thyristor circuit 6, the output voltage of the thyristor circuit 6 is changed to a steady low voltage. Similarly, the output of the wire slowdown circuit 7 is stopped by a signal from the time circuit 12, and the output of the wire speed setting circuit 8 is applied to the bias circuit 9, so that the control circuit 10 causes the motor 11 to rotate at high speed.

When this welding is once completed and the next welding is started, the timer or integral circuit of the time circuit 12 is set because the first welding current has stopped, and is reset after a predetermined period of time. While the timer or integral circuit is set, when a signal to start the next welding is input from the welding start signal generation circuit 1, the outputs of the reference setting circuit 3 and wire speed setting circuit 8 are changed to the output bias by the switching circuit. Applied to circuits 4 and 9. At this time, hot start circuit 2
And there is no output from the wire slowdown circuit 7. Therefore, the welding voltage is a steady low voltage, and the wire feeding speed is a steady high speed state (no stabilization control is performed). Furthermore, when a signal is received from the start signal generation circuit 1 after the timer or integrator is reset, welding is started at a high welding voltage and a low wire feeding speed.

As described above, the present invention cancels stabilization controls such as arc start hot start control and wire slowdown control when the next welding starts within a predetermined time (approximately 0.5 seconds) after the first welding ends. In tack welding, etc., where arc starts and stops are frequently performed, there is no arc start failure or bead formation failure, and a stable and clean bead can be formed, and the arc start is easy and the welding work is simple. Furthermore, since the time required for the arc to stabilize is short, work efficiency is improved.

In the description of one embodiment of the present invention, the outputs from the welding start signal generation circuit 1 and the reference setting circuit 3 are switched using the time circuit 12, but the present invention is not limited to this. The signal from the signal generation circuit 1 and the signal from the reference setting circuit 3 can also be selectively switched by a signal from the current detector 13 or a signal from a timer. In short, it goes without saying that the circuit configuration can be changed as necessary as long as it is configured to allow sequential operation or control operation such that a plurality of set levels can be selectively taken out using a signal that takes arc occurrence and its time into account.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional control operation at arc start. FIG. 2 is an explanatory diagram of the control operation at the time of arc start showing one embodiment of the present invention, and FIG. 3 is a block diagram showing one embodiment of the present invention. 1...Welding start signal signal generation circuit, 2...Hot start circuit, 3...Reference setting circuit, 4...Output bias circuit, 5...Phase control circuit, 6...Thyristor circuit, 7...Wire slowdown circuit,
8... Wire speed setting circuit, 9... Output bias circuit, 10... Control circuit, 11... Wire feeding motor, 12... Time circuit.

Claims (1)

[Claims] 1. In an arc control method that repeatedly generates and stops an arc, stabilizing the generation of the arc at the time of arc start, measuring the arc interruption time when starting the arc again after stopping the generated arc, and calculating the interruption time of the arc. An arc control method characterized in that an arc is generated without performing the above-mentioned stabilization control if the length is within a predetermined length.