JPS5915748B2 - Inert gas consumable electrode arc welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high current inert gas consumable electrode arc welding method for aluminum alloys using a consumable electrode with a large diameter of 2.4 llLm or more.

In inert gas consumable electrode arc welding (hereinafter referred to as MIG welding) of aluminum alloy, the diameter is 1.211.6,
In the case of normal MIG welding that uses a relatively small diameter consumable electrode such as a 2.4-meter, a DC welding power source with constant voltage characteristics is used to feed the consumable electrode at a constant speed. There is. in this case. The action of keeping the arc length constant is mainly due to the self-control action of the welding power source, which has constant voltage characteristics. On the other hand, in order to weld aluminum alloy thick plates with high efficiency, the diameter is 2.4,
3. A large welding current of 400 A or more using a large diameter wire such as 2, 4, O, 4.8, 5.6 mwL as a consumable electrode,
A 0MIG welding method has been developed and put into practical use. Second
The figure shows the tip of a consumable electrode 1 and a molten pool 3 formed on a workpiece 2 in a high-current MIG welding method.
As shown in the figure, in high-current MIG welding, a high current is inevitably used15. enters the molten pool and the arc force blows up the molten metal, and this molten metal is covered with oxides and nitrides and is layered in a wrinkled manner, causing the arc 20 to become rough and welding impossible, a so-called puckering phenomenon. It's coming. Therefore, in the high-current MIG welding method, the welding current to be used must be limited to a current that causes the puckering phenomenon or less. In order to increase this kind of puckering limit current by 25%, in the high current MIG welding method that has been developed and put into practical use, external characteristics that indicate the relationship between the output current value and the output voltage value at the output terminal of the welding power source are A method using a DC welding power source with drooping characteristics close to constant voltage characteristics 30, in which the output voltage value decreases by 10 to 30 V when the output current value increases by 50 A, has been put into practical use. The term "apparent arc length" is used herein to mean the shortest distance between the tip of the consumable electrode and the surface of the workpiece, as shown by Lo in FIG.

In the figure, the actual arc length is the distance La between the electrode tip P and the actual arc generation point Q (cathode point), as shown by the broken line. In the normal MIG welding method, if the welding current is held constant, the apparent arc length and arc voltage are approximately proportional as shown in curve 1 in Figure 1, so the appropriate arc length is It can be set by adjusting the arc voltage. Further, the arc generation states at points a and b on curve 1 in FIG. 1 are as shown in FIGS. 3 a and b, respectively. On the other hand, large current MIG
Regarding the welding method. As shown by the curve in FIG. 1, the arc voltage remains constant at approximately 30° even if the apparent arc length changes. The arcing conditions at points c and d on this curve are as shown in Figure 3 c and d. In this case, the appropriate value for the apparent arc length is -27!17! from experience. L~+2m7! It is said that L. Figure 3 c to d
As shown in Figure 2, the arc voltage remains approximately constant even when the apparent arc length increases. It is not possible to determine the arc voltage that corresponds to the appropriate value of the apparent arc length. Therefore, in the high current MIG arc welding method, the arc length cannot be adjusted by the arc voltage.
The arc length must be adjusted by adjusting the electrode feed rate to adjust the apparent arc length. By the way, in high current MIG welding method 17C, when the arc length is shortened, the arc itself has a self-control action that rapidly increases the melting rate per unit current, so welding power sources with drooping characteristics or characteristics close to constant current There is a stable point of the arc even if . Therefore, the external characteristic showing the relationship between the output current value and the output voltage value at the output terminal of the welding power source was made into a drooping characteristic that is close to a constant voltage characteristic in which the output voltage value decreases by 10 to 30 V when the output current value increases by 50 A. Attempts have been made to further increase the puckering limit current using a DC welding power source, but this has not been put to practical use because it is difficult to set appropriate welding conditions. The reason for this is that in the normal MIG welding method that uses a welding power source with constant voltage characteristics, the welding voltage can be adjusted by the voltage regulator of the welding power source, and the welding current is determined separately from the welding voltage by the feed rate of the consumable electrode. It is easy to set the welding voltage and welding current because the welding voltage and welding current can be adjusted by On the other hand, when the output current value increases by 50A with conventional external characteristics, the output voltage value increases by 10 to 30A.
When setting the apparent arc length and welding current in the MIG welding method that uses the droop characteristic that V decreases,
Since the feed speed regulator of the consumable electrode and the output current regulator of the welding power source must be set in relation to each other, there is a drawback that each cannot be adjusted independently. An object of the present invention is to provide a high-current MIG welding method that allows for easy setting of appropriate welding conditions and that allows the limit current for puckering to be raised above the limit value of this type of welding method that has been put into practical use in the past. It's about making suggestions. The welding method of the present invention is. Large current MI with welding current of 400A or more
In the G welding method, a DC welding power source is used in which the external characteristic indicating the relationship between the output current value and the output voltage value at the output terminal of the welding power source is a nearly constant current characteristic in which the output voltage value decreases by 50 V or more when the output current value increases by 50 A. It is characterized by its use.

The decrease in output voltage value with respect to the increase in output current value is 50V/
When setting the welding current to 50A or more, the welding current setting is determined only by the output current regulator of the welding power source, regardless of the output voltage, so the apparent arc length is determined by the consumable electrode feed speed regulator, regardless of the welding current. It can only be adjusted by Therefore, since the welding current and the apparent arc length can be adjusted independently, it is easy to set appropriate conditions. Next, looking at the limiting current that causes puckering, when the output current value that has been put into practical use increases by 50A, the output voltage value increases by 10A.
In welding power sources with drooping characteristics close to constant voltage characteristics where the voltage drops by 30 to 30, electrode diameters of 2.4, 3.2, 4.0, 4.
For 8mm. The limiting currents for occurrence of puckering are 550, 620, 680, and 700 A, respectively. In the welding power source of the welding method of the present invention, which has a substantially constant current characteristic in which the output voltage value decreases by 50 or more when the output current value increases by 50 A, electrode diameters of 2.4, 3.2, 4.0, 4. 81tm
However, the limiting current for puckering occurrence is 58, respectively.
0,680,750,800A). It was possible to increase the limiting current compared to the conventional method.

In addition, in the welding power source with substantially constant current characteristics according to the welding method of the present invention, there is almost no change in welding current due to fluctuations in the power supply voltage, and the puckering phenomenon does not occur even when used relatively close to the puckering generation limit current. .

When the output current is 400A or more, the output current value is 50A or more.
A substantially constant current characteristic in which the output voltage value decreases by 50 V or more as A increases can be easily obtained using a thyristor type welding power source. According to the welding method of the present invention, it is easy to set appropriate welding conditions, and the limiting current for occurrence of puckering is high, so high-efficiency, large-current MIG welding can be performed. The actual benefits are great.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the apparent arc length and arc voltage in the ordinary MIG welding method and the high current MIG welding method when the welding current is held constant, and Figure 2 is a diagram showing the relationship between the apparent arc length and the arc voltage in the high current MIG welding method. Explanatory diagram showing the tip of the electrode and the molten pool. 3A to 3D are explanatory diagrams showing the state near the tip of the consumable electrode at points a to d on curves 1 and 1 in FIG. 1, respectively. 1...Consumable electrode. 2... object to be welded, 3... molten pool.

Claims (1)

[Claims] 1 External characteristics showing the relationship between the output current value and output voltage value at the output terminal of the welding power source in the high current inert gas consumable electrode arc welding method for aluminum alloy using a large diameter consumable electrode with a diameter of 2.4 mm or more The output current value is 5
An inert gas consumable electrode arc welding method characterized in that a consumable electrode is fed at a constant speed using a DC welding power source with a substantially constant current characteristic in which the output voltage value decreases by 50 V or more when the output voltage increases by 0 A.