JPS6352991B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a consumable electrode type DC arc welding method in which arc starting is performed using high frequency and high voltage.

A DC arc welding device used in the conventional DC arc welding method is shown in FIG.
In the figure, 1 is a welding power source, 2 is a consumable electrode (hereinafter referred to as a wire), 3 is a contact chip for supplying power to the wire 2, 4 is an arc, and 5 is a workpiece placed opposite to the wire 2 (hereinafter referred to as a wire). 6 is a feed roller that feeds the wire 2 toward the base material 5, 7 is a wire feeding electric motor (hereinafter referred to as motor) that drives the feed roller 6, and 8 is a chip 3. A high frequency generator is connected in parallel to the welding power source 1 between the base metals 5, 9 is a welding start switch, and 10 is an electromagnetic contactor (hereinafter referred to as a relay) that becomes operational by turning on the welding start switch. ,
11 is a relay that becomes operational when it detects that current has flowed to the output side of welding power source 1; 12 is relay 1;
0 normally open contact, 13 normally open contact of relay 11, 1
Reference numeral 4 denotes a relay that becomes operational when both normally open contacts 12 and 13 become closed;
3 and relay 14 are connected in series. 15 is a variable resistor for setting the rotation speed (wire feeding speed) of the motor 7, 16 is a normally open contact of the relay 10, 17 is also a normally open contact of the relay 10, 18 is a normally closed contact of the relay 11, 19 is a normally open contact of the relay 14.

Next, a DC arc welding method using this conventional device will be explained.

First, when the welding start switch 9 is turned on, the relay 10 becomes operational. Along with this, the normally open contact 16 of the relay becomes closed, and the welding power source 1
Voltage is output to the output terminal of. However, wire 2
Since arc 4 is not generated between and base metal 5,
The output end of the power source 1 is in an open circuit state, and no welding current flows. Therefore, relay 11 becomes inactive. Here, the normally open contact 17 of the relay 10 and the normally closed contact 18 of the relay 11 are both in a closed state, the high frequency generator 8 is in an operating state, a high frequency high voltage is applied between the wire 2 and the base material 5, and the wire The insulation between the base material 2 and the base material 5 is broken, and an arc 4 is generated. As a result, the output end of the welding power source 1 becomes closed, and welding current begins to flow.

Therefore, the relay 11 is activated. When the relay 11 is in the operating state, the normally open contact 13 of the relay 11 is in the closed state, so the relay 14 is in the operating state, the normally open contact 19 of the relay 14 is in the closed state, the motor 7 rotates, and the wire 2 is connected. It is fed toward the base material 5. In addition, the normally closed contact 1 of the relay 11
8 becomes open, the operation of the high frequency generator 8 is stopped. Then, normal welding begins,
This conventional device was designed to reduce spatter at the start of welding.

Incidentally, DC arc welding using the conventional apparatus shown in FIG. 1 is shown in the time chart of FIG. 3.

In such a conventional device, an arc start is caused by high frequency and high voltage with the wire 2 initially stopped.
An arc is started using high frequency and high voltage while the wire is separated from the base material 5, and before the wire 2 is fed, the wire 2 is
After the tip of the wire is sufficiently melted, the wire 2 is fed to ensure reliable welding.

By the way, since the conventional DC arc welding method is performed as described above, if the distance between the wire 2 and the base metal 5 is long, the insulation between the wire 2 and the base metal 5 cannot be destroyed with the general high frequency generator 8. This means that arc activation will not occur. Therefore, either cut the tip of the wire 2 to make it sharper, or shorten the distance between the wire 2 and the base material 5 to facilitate dielectric breakdown between the wire 2 and the base material 5 due to high frequency and high voltage. I had to do it. Moreover, even if the distance between the wire 2 and the base material 5 is shortened,
The dielectric breakdown time between the wire 2 and the base material 5 due to high frequency and high voltage varies; in some cases, the dielectric breakdown occurs in a short time, and in other cases, the dielectric breakdown occurs for several seconds or more. Therefore, when welding is started while moving the wire 2 along the base material 5, ie, a so-called running start, there is a problem that the welding starting position is not stable.

This invention was made in order to eliminate the drawbacks of the conventional method as described above, and the wire is always fed toward the workpiece a predetermined time after the welding start switch is turned on. It is an object of the present invention to provide a DC arc welding method that allows the arc to start without fail after a predetermined period of time.

An embodiment of the method of the invention will be described below with reference to the drawings. FIG. 2 shows a DC arc welding apparatus used in a method according to an embodiment of the present invention, and the same or corresponding parts as in FIG. 1 are given the same reference numerals. In FIG. 2, 20 is a normally open contact of the relay 10, 21 is a timer that is activated after a predetermined time period when the normally open contact 20 is closed, and 22 is a timer 21 connected in parallel to the normally open contact 13. It is a normally open contact with a time limit.

Next, the method of this embodiment will be explained.

First, when the welding start switch 9 is turned on, the relay 10 becomes operational, and as explained in the conventional device shown in FIG. A high frequency and high voltage is applied between them, the insulation between the wire 2 and the base metal 5 is broken, an arc 4 is generated, and a welding current flows.
Then, as the welding current flows, relay 1
1 is turned on, wire 2 is fed, and normal welding begins. On the other hand, since the normally open contact 20 of the relay 10 is brought into a closed state, the timer 21 is brought into operation after a predetermined time period. Therefore, timer 2
Since normally open contact 22 of relay 10 becomes closed after a predetermined time period, relay 14 closes normally open contact 1 of relay 10 even if normally open contact 13 of current detection relay 11 is open.
If wire 2 is in the closed circuit state, it will be in the operating state after a predetermined time period, the normally open contact 19 of the relay 14 will be in the closed circuit state, and the wire 2 will be fed toward the base material 5. If the insulation between the wire 2 and the base metal 5 is destroyed by the high frequency and high voltage within the time set by the timer 21 in this way, arc starting will be performed as before, and the arc will be started within the time set by the timer 21. If the insulation between the wire 2 and the base material 5 is not broken, the wire 2 is fed toward the base material 5 to shorten the distance between the wire and the base material and facilitate dielectric breakdown.
Note that if the dielectric breakdown still does not occur, the wire 2 and the base metal 5 are short-circuited, a large short-circuit current flows, the tip of the wire is scattered, and at the same time an arc 4 is generated and welding is started. Generally, the distance between the wire 2 and the base material 5 is 5 mm below, and the wire feeding speed is 1 m/min or more, so 0.3 seconds after the wire feeding starts (5 ÷ 1000/60 = 0.3) Within this time, the tip of the wire 2 and the base material 5 become short-circuited.

As described above, according to the method of this embodiment, the arc start will always occur after the time limit set by the timer 21, so that the dispersion in the time until the arc start, which was a drawback of the conventional method, can be avoided. Now I can almost eliminate it.

Therefore, when performing the above-mentioned running start, there is an effect that the welding start position can be stabilized.

In addition, the time limit set by the timer 21 is such that the arc start by high frequency and high voltage is almost completely completed.
In addition, it is good if the time it takes for welding work to start arcing does not feel long, and generally 0.5~
Approximately 2 seconds is appropriate.

Incidentally, the operation of DC arc welding using the apparatus shown in FIG. 2 is shown in the time chart of FIG. 4.

In the above embodiment, the high frequency generator 8 is not built into the welding power source 1, but the high frequency generator 8 may be built into the welding power source 1. Moreover, although the high frequency high voltage is connected in parallel with the output voltage of the welding power source 1, it may be connected in series.

As described above, according to the method of the present invention, if arc start does not occur within a predetermined time after high frequency high voltage is applied between the wire and the base material,
Since the wire is fed toward the workpiece, the distance between the wire and the base metal is shortened, and insulation breakdown due to high frequency and high voltage is facilitated, and the arc is always started within a predetermined time after the welding start switch is turned on. There is an effect that can be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a DC arc welding device used in a conventional method, FIG. 2 is a block diagram showing a DC arc welding device used in an embodiment method of the present invention, and FIG. 3 is a conventional welding device similar to that shown in FIG. FIG. 4 is a time chart of a sequence according to an embodiment of the method of the present invention. In the drawings, the same or corresponding parts are given the same reference numerals.

Claims (1)

[Claims] 1. In a direct current arc welding method in which arc starting is performed by applying high frequency high voltage between a consumable electrode and a workpiece that are arranged opposite to each other through a predetermined gap, arc starting due to the high frequency high voltage does not occur for a predetermined period of time. A direct current arc welding method characterized in that the consumable electrode is fed toward a workpiece by detecting the above.