JPS6261779A - Tig arc welding method for aluminum base metal - Google Patents

Abstract

PURPOSE:To remove the surface oxidized substance disusing a pretreating stage and to deepen the penetration of a base metal by passing either one part of the DC reversed polarity arc current with the base metal as the negative pole or AC arc current and the DC positive polarity arc current with the base metal as the positive pole alternately between torch and base metal. CONSTITUTION:The surface oxidized film 7 of a base metal 3 is removed by the AC arc current I, (welding time T1) passed from AC power source 9 and shallow penetration is simultaneously made. The penetration is then deepened by the concentration of the arc 4 of the DC positive polarity arc current I2 (welding time T2) from DC power source 8 on the part where the oxidized film 7 is removed. The welding of the whole part to be welded is performed by repeating the alternate passing of the current I1, I2 by switching the power sources 8, 9 with a controller 10. And the current I1 can obtain the same effect as the DC reversed polarity current with the base metal as the negative pole, but the heating at the electrode side becomes large and the electrode life is made shorter compared to the case of AC.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to TIG (Tungsten IG) non-consumable electrode type arc welding using aluminum as a base material.
rtGas) welding method.

[Prior art]

FIG. 3 is a side view showing TIG welding using an aluminum base material as a positive electrode. 1 is a welding torch, 2 is a tungsten electrode of the welding torch 1, 3 is an aluminum base material, 4 is an arc, 5 is an argon gas, and 6 is a molten pool. However, although the aluminum base material 3 has the advantage that the penetration of the molten pool 6 is concentrated and deep due to its positive polarity, there is a problem that an oxide film 7 is formed on the surface. This oxide film 7 has a high melting point and obstructs screw engagement with molten metal from the outside, so it is necessary to remove it by a cleaning action.

Conventionally, the oxide film 7 has been cleaned by using reverse polarity DC or AC (not shown) with the aluminum base material 3 as the negative electrode, as shown in FIG. 4, and the oxide 7 is removed by the arc 4. Or, recently, as shown in Figure 5, the AC waveform (
A method using a current with an increased positive polarity component at a commercial frequency of 50 or 60 cycles has been proposed.

(Problem to be solved by the invention) However, in TIG welding using DC reverse polarity or AC, the arc 4 spreads and the weld penetration 6 of the aluminum base material 3 occurs.
There was a problem that the electrode became shallow (Fig. 4) and the electrode life was short. In addition, in the latter method (Fig. 5), the penetration of the aluminum base material 3 is deep to some extent, but the reverse polarity component is small, so the arc is likely to break and the removal of surface oxides is likely to be insufficient. There was a problem.

In addition, in order to obtain deep penetration, there is a method in which surface oxides are removed by pretreatment such as wire brushing, cutting, or cleaning, and then welding is performed using direct current with positive polarity (Figure 3). This method requires a separate pretreatment step, which poses a problem in that it is time-consuming.

An object of the present invention is to provide a TIG welding method for an aluminum base material that can remove surface oxides without requiring a pretreatment step and that can achieve deep penetration into the aluminum base material.

[Means and effects for solving the problem] The present invention provides an electric current between the welding torch and the aluminum base material, either an AC arc current or a DC reverse polarity arc current with the aluminum base metal side as the negative pole, and an electric current between the welding torch and the aluminum base material. By alternately flowing a DC positive arc current with the positive pole on the side, the DC positive arc current penetrates deeply into the aluminum base material.

Surface oxides are mainly removed using AC arc current, etc.
By alternately repeating these two arc currents, deep penetration is ensured while removing surface oxides.

〔Example〕

FIG. 1 is a diagram showing an arc current pattern according to the present invention. After flowing the AC arc current I for T1 hours, the DC positive polarity arc current 2 is caused to flow for 12 hours.

Then, these surface currents are passed alternately. In order to completely remove surface oxides, it is recommended that the current application time of the AC arc current be 0.1 seconds or more.
Since this time also depends on the size of the electric current, it is necessary to set it appropriately. Moreover, the depth of penetration can be adjusted by appropriately setting the DC positive polarity component process 2 and the energization time T2.

FIG. 2 is a diagram showing an example of a circuit of the welding method according to the present invention. Controller 10 for switching between DC power supply 8 and AC power supply 9
The configuration is such that it can be switched with . Arc starting and stopping and SWI
The switching is synchronized.

Next, the operation of the above embodiment will be explained. The surface oxide film 7 of the aluminum base material 3 is removed by the alternating current arc current t (current application time T) from the alternating current power source 9, and at the same time shallow penetration is achieved. Next, DC positive polarity arc current L (current conduction time T
2), the arc 4 concentrates on the portion where the oxide film 7 has been removed, resulting in deep penetration. The entire part to be welded is welded by repeating this surface current I welding process 2.

In the above embodiment, the case where an alternating current arc current is used as the current for removing the oxide film 7 is shown, but the same effect can be obtained by using a direct current reverse polarity arc current with the aluminum base material as the negative electrode.

However, in this case, heat generation on the electrode side increases and the electrode life becomes shorter than when using alternating current.

〔Effect of the invention〕

According to the present invention, since the current for removing the surface oxide film (alternating current arc current, etc.) and the current for deepening the penetration (direct current positive arc current) are alternately passed, the pretreatment process for wire brushing, etc. Surface oxides can be removed without the need for oxidation, and penetration into the aluminum base material can be deepened.

Furthermore, since this is a welding method in which there is a large amount of direct current with a positive polarity component rather than a welding method in which an alternating current is constantly passed, the life of the tungsten electrode can be extended.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a pattern of arc current according to the present invention,
FIG. 2 is a diagram showing an example of a circuit of the welding method according to the present invention,
Figure 3 is a side view showing conventional TIG welding using an aluminum base material as a positive electrode, and Figure 4 is a side view showing conventional TIG welding using a DC reverse polarity arc current using an aluminum base metal as a negative electrode. FIG. 5 shows current pattern diagrams showing other conventional examples. 1... Welding torch, 3... Aluminum base material, 7.
...Oxide.

Claims (1)

[Claims] The feature is that either an alternating current arc current or a direct current reverse polarity arc current with the aluminum base material as the negative electrode, and a direct current positive polarity arc current with the aluminum base material as the positive electrode are alternately passed between the welding torch and the aluminum base material. TIG welding method for aluminum base material.