JPS6333177A - Consumable electrode type dc welding method - Google Patents

Abstract

PURPOSE:To smoothly execute the droplet transfer of a DC are in such a way as water flows, by allowing the high frequency current of a specific frequency to be conducted to a consumable electrode, melting the electrode from the outside surface by its surface effect, and also, forming its tip to a pencil shape. CONSTITUTION:By consumable electrode type DC welding, an arc 2 is generated between a consumable electrode 1 and a welding base material 3 under the integument of a sealing gas flow 7 by applying a DC voltage to a feeding chip 4, and a droplet 14 is transferred to the base material 3 from the electrode 1. In such case, between a DC welding power source and the electrode 1, a semiconductor element for an output control is inserted, and by bringing it to an electric conduction control by the frequency of 0.5-1,000kHz, a high frequency welding current 6 is allowed to flow between the electrode 1 and the base material 3. The high frequency current 6 melts the electrode 1 from the outside surface by its surface effect, and by forming the tip of the electrode 1 to a pencil shape, the droplet 14 is transferred to a fine particle shape. In such way, the droplet transfer can be executed smoothly in such a way as water flows.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to consumable electrode type direct current welding in which droplets of molten metal are transferred between a consumable electrode and a welding base material.

[Conventional technology]

In conventional arc welding, in which droplets of weld metal are transferred between a consumable electrode and the base metal, the consumable electrode and base metal are connected to a DC welding power source with constant voltage characteristics, and the consumable electrode is fed at a constant speed. The droplets are transferred from the consumable electrode to the base material as shown in FIG. In FIG. 4, 1 is a consumable electrode, 14 is a droplet formed at the tip of the consumable electrode, 3 is a welding base material, and 2 is an arc.

4(a) shows a state in which an arc is generated from the tip of the consumable electrode 1, and FIG. 4(b) shows a state in which the tip of the consumable electrode 1 is melted by the arc and a droplet 14 grows. Figure 4(c) shows a short circuit state in which the droplet 14 has melted with the welding base metal 3, and Figure 4(d) shows the droplet 14 moving toward the welding base metal 3 side and constricting the droplet 14. Figure 4 (e) shows the state when the short circuit is broken and arc 2 is generated, and Figure 4 (f) shows the state when the constricted droplet 14 is broken and spatter 15 is generated. show. During welding, (a) to (f) in Figure 4
The process is repeated.

It has been reported that spatter occurs the moment a droplet grows large at the tip of the consumable electrode and short-circuits with the welding base metal, and that the droplet becomes spatter from the tip of the consumable electrode due to electromagnetic pinching force. . In particular, at the moment when the droplet from the consumable electrode 1 short-circuits with the welding base material 3, as shown in FIG.
The welding voltage becomes an extremely low value, and conversely, the welding current reaches its maximum like a surge waveform. The energy at this time blows off the droplet at the tip of the consumable electrode l, resulting in spatter.

As described above, with the conventional consumable electrode feeding method of a DC welding power source, a lot of spatter is generated, the welding efficiency is reduced, and it is necessary to remove the attached spatter. This has caused problems such as adhesion to the shield nozzle of the welding torch, obstructing the flow of shielding gas and causing defects in the weld.

In order to improve these problems, the output voltage of the DC welding power source is lowered before and after the droplets short-circuit to the welding base metal.
A method of reducing the amount of spatter generated or a method of reducing the amount of spatter generated by controlling the welding current output has been proposed. For example, JP-A-60-1
No. 30469, Japanese Patent Application Laid-open No. 145277/1983,
JP-A-60-145278, JP-A-60-133
This method has been proposed in Publication No. 977, etc.

In addition, low frequency pulses (1
0 to 300H2), repeating spray transition and globular transition (short circuit transition) within the set frequency range, and making the average welding output voltage equal to that during short circuit transition, reducing spatter generation and improving welding workability. Suggestions for improving the system are also used.

[Problem that the invention seeks to solve]

However, the method of lowering the DC welding voltage before and after a short circuit or controlling it to a required value is complicated in terms of electrical circuits, and the short circuit time is 3 to 10 (msec) per time, so the output of the DC welding power source The need for quick response requires, for example, an inverter power supply using transistors and a corresponding control circuit, which tends to make the system even more complicated.

Further, in the method of applying low frequency pulses, if the welding materials and welding conditions are different, the set frequency must be adjusted each time, and a satisfactory result cannot be obtained.

In view of the above problems, it is an object of the present invention to use a relatively simple electric circuit to make droplets into fine particles for smooth droplet transfer and to keep the amount of spatter generated to a minimum.

[Means for solving problems]

In the present invention, in consumable electrode direct current welding in which an arc is generated between the consumable electrode and the base material and droplets are transferred from the consumable electrode to the base metal, a high frequency current of 0.5 K) + 2-1000 KIIZ is applied to the consumable electrode. When electricity is applied, the skin effect melts the consumable electrode from its outer surface, making its tip shaped like a pencil.

[Effect]

According to this, since the tip of the consumable electrode is formed into a pencil shape, the droplets become fine particles, stably flow down like flowing water, and transfer to the welding base material. As a result, the generation of spatter is extremely small, and even if one spatter is generated, the particle size of the spatter is small, so the heat capacity is low and it does not adhere to the surrounding welding base material, the nozzle of the welding torch, the tip, etc., and therefore welding workability and gas shielding properties are improved. resolved. Since there is no need to perform voltage control at microscopic timing, such as lowering the DC welding voltage before and after a short circuit or controlling it to a required value, the power supply circuit configuration is simplified.

The present invention will be explained in detail below.

FIG. 1 shows an example of the configuration of a consumable electrode type DC welding power supply device embodying the present invention. The DC welding power supply control device 16 converts the AC output from the transformer 11 for current magnetic amplification into DC (pulsating current) using the rectifier 12, smoothes it using the reactor 18, and converts the AC output from the transformer 11 for current magnetic amplification into DC (pulsating current), and converts the AC output from the transformer 11 for current magnetic amplification into DC (pulsating current).
Power is supplied to the power supply chip 4 through the power supply chip 4. The output control semiconductor element 13 is connected to a high frequency oscillation controller 19. The conduction is controlled at a frequency of 0.5 KH2 to 1000 KH2 (7), and a voltage having a waveform as shown in FIG. 2 is output.

The wire feeding device 17 transports the consumable electrode l onto a wire reel lO.
The wire is pulled out and fed to the base material 3 by a wire feed roller 8 directly connected to a wire feed motor 9.

The consumable electrode 1 is supplied with a high frequency voltage (
(Fig. 2) is supplied with electricity, and this high-frequency voltage generates an arc 2 between the consumable electrode 1 and the base metal 3, and the consumable electrode is melted by the arc 2 and welded to the weld base metal 3 as molten metal.

Next, the effect of applying the above-mentioned high frequency voltage will be explained. FIG. 3 shows an example of transfer of weld metal droplets 14 between the consumable electrode 1 and the weld base metal 3. The power supply chip 4 is supplied with a high frequency voltage as shown in FIG. 2, which is applied to the consumable electrode 1 and generates an arc 2.
A high frequency welding current 6 flows between the consumable electrode 1 and the base material 3. Since the high frequency welding current 6 is 0.5 to 1000 (K) 12), it flows intensively to the surface of the consumable electrode 1 due to the skin effect.
Near the arc 2, the outer surface tends to be melted, and as a result, the tip of the consumable electrode 1 becomes pencil-shaped. Due to this pencil shape, the droplets 14 become small particles and stably transfer to the welding base material 3. 5 is a gas nozzle, and 7 indicates a path of shielding gas.

In the present invention, as described above, by supplying high-frequency voltage to the consumable electrode, a high-frequency welding current is concentrated on the outer surface of the consumable electrode, and the consumable electrode is melted from the surface to form a pencil-shaped tip. The droplets become fine particles and stably flow down from the consumable electrode like flowing water and transfer to the welding base metal. As a result, spatter is extremely rare, and even if spatter is generated, its particle size is small, so it has a low heat capacity and does not adhere to the surrounding welding base metal, welding torch nozzle, tip, etc., which improves welding workability and gas shielding properties. Ta.

Note that the waveform of the high-frequency output voltage is not limited to the rectangular pulse shown in FIG. 2, but may be other waveforms such as a sine wave or a sawtooth wave. In addition, as long as it contains a high-frequency current component sufficient to make the tip of the consumable electrode pencil-shaped, the steady DC component (
For example, the current corresponding to E8 in FIG. 2 may be included.

Note that the high frequency requires adjustment depending on the length of the power cable. For example, increasing the frequency will increase the impedance (especially reactance) of the power cable.
As the value increases, the output tends to decrease. Therefore, it is necessary to use the power cable as short as possible.

〔Example〕

The fluctuation states of the welding voltage waveform and welding current waveform during droplet short-circuit transition in which short-circuiting and arcing are repeated in the conventional method are as follows.
+wm), and welding conditions 30 (V), 200 (A)
When set to , the fluctuation range of the waveform shown in Figure 5 is 10 to 3
2 (V) and 100-250 (A), indicating an extremely unstable arc state.

According to the present invention, when the high frequency is set to 10 (KH2) and the peak voltage is 50 (V) under the same conditions as above, the waveform state shown in FIG. 6 is obtained, and an extremely stable arc state is created, which causes the nozzle of the welding torch to The amount of spatter deposited on the chip was reduced to about 173 to 1/2 compared to the conventional method.

〔Effect of the invention〕

As explained above, in the present invention, a high frequency voltage is supplied to the consumable electrode and the consumable electrode is shaped like a pencil due to its skin effect, so that droplet transfer resembles flowing water.
As a result, spatter was reduced, shielding properties were stabilized, welding defects were eliminated, and welding workability was improved. In particular, as the welding industry has recently progressed to automatic welding, computer-controlled robot welding, and automatic welding systems, noise generated from unstable welding arcs can cause malfunctions in automatic control electronic equipment, causing entire welding lines to be shut down. This reduces the causes of welding defects, making it possible to stabilize automatic welding and improve and uniformize the quality of welded joints.

As described above, the present invention provides a consumable electrode DC welding method that is extremely industrially valuable.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the configuration of a control device for carrying out the consumable electrode type DC welding power supply control method of the present invention, and FIG. 2 is a waveform diagram showing the high frequency voltage applied to the consumable electrode 1 shown in FIG. 1. , FIG. 3 is a sectional view showing a mode in which droplets transfer between the consumable electrode 1 and the welding base material 3 in the welding apparatus shown in FIG. 1. Figures 4 (a) to (f) are conventional side views showing the process of droplet transfer from the consumable electrode to the welding base metal, and Figure 5 is the welding voltage waveform when using a conventional DC welding power source. FIG. 3 is a waveform diagram showing a welding current waveform. FIG. 6 is a waveform diagram showing a high frequency welding voltage waveform and a high frequency welding current waveform in one embodiment of the present invention. 1: Consumable electrode 2: Arc 3: Welding base material 4: Power supply tip 5: Gas nozzle 6: High frequency welding current 7: Shielding gas path 8: Wire feed roller 9: Wire feed motor 10: Wire reel ll Nidor Lance 12: Rectifier 13: Semiconductor element for output control 14: Melt haze 15 Varnish batter 16: DC welding power supply control device 17: Wire feeding bag [18: Reactor 19: High frequency oscillation control 1 Peek throat hate Kue ward 37 Child 4 ■ (a) (b) (C) Black 5 Figure 6

Claims (2)

[Claims] (1) In consumable electrode direct current welding, which generates an arc between the consumable electrode and the base material and transfers droplets from the consumable electrode to the base metal, a high frequency current of 0.5KHZ to 1000KHZ is applied to the consumable electrode. A consumable electrode direct current welding method characterized by melting the consumable electrode from its outer surface due to its skin effect, making the tip of the consumable electrode pencil-shaped. (2) The consumable electrode type DC welding method according to claim 1, wherein a semiconductor element is inserted between the consumable electrode and the welding DC power source, and the semiconductor element is energized for high frequency conduction.