JPS6362317B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a consumable wire welding device using an arc generally called a spray transfer arc, and is based on the idea of performing feedback control to simplify welding condition settings and improve welding quality in response to condition fluctuations. The aim is to achieve uniformity.

Traditionally, spray transfer arc welding has been widely used as a welding method with excellent welding quality such as bead appearance due to less spatter, and a typical method is metal inert gas arc welding (hereinafter referred to as metal inert gas arc welding).
(abbreviated as MIG) or pulsed MIG, which uses a sprayed pulsed current and has a wide range of application.
Welding methods are widely known. However, such spray transferred arc has the disadvantage that arc concentration is inferior to carbon dioxide arc welding, and welding efficiency in joint shapes such as lap fillet welding and horizontal fillet welding is significantly reduced. In order to alleviate this basic drawback, welding operators usually set arc length conditions that are extremely short, that is, conditions that include some short circuits, but the margin for setting such conditions is In pulse MIG welding, which is extremely narrow and requires skill in setting conditions, and there are many factors for setting conditions, it is extremely difficult to set the conditions, which is one of the causes of a decrease in welding work efficiency. By the way, a normal spray transfer arc becomes a complete spray arc if the voltage is sufficient, and there is no problem with the stability of the arc.
As mentioned above, such a spray arc greatly reduces the welding speed when performing fillet welding, and has a narrow range of application. When the voltage is gradually lowered from such a complete spray state, short circuits begin to occur.First of all, short circuits of 1 msec or less, which can be described as extremely short instantaneous short circuits, begin, and then the voltage When the voltage is lowered, a clear short circuit occurs with a short circuit time of 1 to 3 msec, and depending on the voltage drop, a long short circuit of 3 msec or more can also occur. As the short-circuit time increases in this way, it becomes possible to increase the welding speed as in carbon dioxide gas welding, but on the other hand, spatter occurs more frequently, which impairs the advantages of spray arc. Therefore, the desirable short circuit time is 1 msec or less, then 1 to 3 msec.
This results in a mixed state with clear short circuits. Since a long short circuit of 3 msec or more impedes the characteristics of the spray arc as described above, it is necessary to avoid this condition. Also, from the point of view of welding quality,
In a completely sprayed state where no short circuit occurs, the arc length is too long and not only the welding speed but also tends to cause defects such as blowholes, which has the drawback that it is not practical. If the time exceeds 3 msec, it will cause unevenness in the penetration shape, and this condition is also unfavorable as welding conditions. Therefore, considering the welding quality, it can be said that the condition of mixed short circuits is optimal, and it can be said that this optimal condition is selected based on experience in actual work. Another important characteristic is that the relationship between weldability and short-circuit condition does not depend on the welding material. As described above, there is a close relationship between the occurrence of short circuits in spray arc and appropriate welding conditions, and it can be said that the number of short circuits per unit time is effective as a detection factor for welding conditions. In other words, the conventional method of controlling welding conditions using arc voltage or arc current is affected by various factors such as the shape of the joint and the welding posture.
Since an extremely wide variety of condition tables are required, the current state is that displaying standard welding conditions is not actually useful. The present invention was made in view of the practical problems of conventional spray transfer arc welding as described above, and its purpose is to use the number of short circuits as a detection factor to adjust welding conditions based on feedback control. The purpose is to simplify the settings and to homogenize welding quality.

Hereinafter, the present invention will be explained based on the figures.
As shown in the figure, an input terminal 1 which receives a short-circuit state as a short-circuit signal based on an arc voltage is connected to a short-circuit time discriminator 2 which distinguishes the short-circuit time. This short-circuit time discriminator 2 detects short-circuit signals with a short-circuit time of 1 msec or less, from 1 to
It distinguishes between 3 msec and 3 msec or more, and inputs each short circuit signal to counters 3, 4, and 5. Each counter 3,
4 and 5 count the number of short circuits within a certain period of time,
If the number of short circuits of 1 msec or less is less than a predetermined number, the counter 3 gives a constant arc voltage reduction signal to the output setting unit 6 that sets the arc voltage, and the counter 4 counts the number of short circuits of 1 to 3 msec. However, a constant arc voltage increase signal is given to the output setting section 6 only when the number of short circuits is equal to or greater than a predetermined value. Further, the counter 5, which counts the occurrence of a short circuit of 3 msec or more, immediately gives an arc voltage increase signal to the output setting section 6 in the same way as the counter 4 upon one detection, and the arc voltage is significantly increased. It is basically possible to implement the present invention using the above control system configuration, but since the output signals of the counters 4 and 5 both give arc voltage increase signals to the output setting section 6, the arc voltage can be increased at the same time. If the signal is applied to the output control section 6, it may result in over-control. Therefore, as shown in FIG. 2, a selection element 8 is provided between the counters 4, 5 and the output setting section 6, so that the counter 5 reaches a steady state when the arc is started in order to quickly set the initial conditions. It is preferable to limit the function to a certain period of time.
Note that 7 is an output end.

Next, a specific experimental example using the arc welding apparatus of this embodiment will be explained with reference to FIG.

Figure 3 shows the arc voltage and short-circuit time of 1 msec or less during spray transfer arc welding.
The relationship between the number of short circuits of 3 msec and 3 msec or more is shown experimentally. The shielding gas was a mixture of Ar and 20% CO ₂ , the wire was a regular commercially available MAG wire with a diameter of 1.2 mm, the welding current was 260 A, and the distance between the electrode base materials was 18 mm.

If the arc voltage is 30V or more, no short circuit will occur, but if the arc voltage is lowered to 30V or less, the short circuit time will decrease.
A short circuit of 1 msec or less occurs, and 1 to 29 V or less.
A short circuit of 3 msec occurs, and a short circuit of 3 msec or more occurs below 27V. The number of short circuits for each increases with decreasing arc voltage. According to our experiments, good welding results with less spatter were obtained when the arc voltage was 28V. When the arc voltage was 28V, the number of short circuits with a short circuit time of 1 msec or less was 10 times/second. Arc voltage is higher than 28V, short circuit time
If the number of short circuits of 1 msec or less is less than 10 times/sec, lower the arc voltage to the voltage (28V) at which the number of 1 msec short circuits is 10 times/sec.

When the arc voltage is 28V, the short circuit time is 1~
The number of short circuits for 3 msec was 4 times/second. The arc voltage is lower than 28V, and the number of short circuits of 1 to 3 msec is 4.
If the number of short circuits is more than 4 times/second, increase the arc voltage to a voltage (28V) at which the number of short circuits is 4 times/second.

Also, when the arc voltage is 28V, the short circuit time is
A short circuit of 3 msec or more does not occur, but the arc voltage
If the voltage is below 27V, a short circuit of 3msec or more will occur.
In this case, increase the arc voltage by 1V.

In this way, by counting the number of short circuits for each different short circuit time, the arc voltage can be adjusted to the optimum voltage.

As described above, the present invention simplifies the selection of conditions for the spray transfer arc based on feedback control, which has the advantage of making welding quality uniform.
The number of short circuits of each of these short circuits is counted to control the appropriate condition setting of the spray transfer arc.
Appropriate welding conditions are always selected simply by setting the wire feed speed, and setting conditions for pulsed MIG arcs in particular can be dramatically simplified, as well as being stable and unaffected by the welding material, joint shape, or welding position. It has the advantage of achieving high welding quality and increasing welding efficiency.

[Brief explanation of drawings]

Figures 1 and 2 are block diagrams of the circuit configuration for processing the number of short circuits according to the present invention, and Figure 3 shows the relationship between the arc voltage and the number of short circuits for each short circuit time when performing spray transfer arc welding. It is a characteristic diagram, and 1
2 is an input terminal, 2 is a short circuit time discriminator, 3, 4, and 5 are counters, 6 is an output setting section, 7 is an output terminal, 8 is a selection element, and 9 is a counter block.

Claims (1)

[Claims] 1. In a consumable wire welding device that uses a spray transferred arc, measure the short circuit time that occurs during welding and determine the short circuit time to be 1 msec or less, 1 to 3 msec,
means for dividing into 3 msec or more, a counter for counting the divided short circuit signals, and when the counting result (the number of short circuits) of the short circuit signals of 1 msec or less is below a predetermined value, a certain arc voltage reduction signal is generated. means for applying a constant arc voltage increase signal to the output setting section when the counting result (number of short circuits) of the short circuit signal of 1 to 3 msec is equal to or more than a predetermined value; When a short circuit signal count result (number of short circuits) is detected once, the apparatus includes means for supplying a constant arc voltage increase signal to an output setting section, and the output setting section has a function of setting a welding output. An arc welding device characterized by: