JPH02117777A - MIG welding method for aluminum and its alloys - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an improved MIG welding process for aluminum and its alloys.

Conventional MIG welding of aluminum and its alloys tends to cause weld metal cracks and pores, as well as weld distortion and puckering as weld defects. Therefore, in addition to preventing weld metal cracking and porosity, it is necessary to prevent welding distortion.

Conventionally, known methods for preventing the occurrence of welding strain include reducing welding heat input as much as possible, limiting interpass temperature, and applying reverse strain. However, these preventive measures pose problems in terms of work efficiency.

Furthermore, if welding is performed without taking measures to prevent welding strain, it is necessary to carry out strain relief work after welding, which has the disadvantage of increasing the number of work steps.

On the other hand, puckering occurs as a defect specific to welding aluminum and its alloys. This puckering is described, for example, in Light Metal Welding vol22 (1984) 111 & 11.
As described in 9゜P395 to P407, this occurs when the welding current is too large or there is insufficient shielding, but to prevent this, measures such as suppressing the welding current and increasing the shielding gas flow rate are taken. ing.

However, if these measures are taken, the wire melting rate will inevitably decrease and the amount of shielding gas used will increase, which is uneconomical.

Problems to be Solved by the Invention As mentioned above, welding strain and puckering occur in the MIG welding method for aluminum and its alloys.

In order to eliminate the above-mentioned problems, it is an object of the present invention to provide a MIG welding method for aluminum and its alloys that prevents welding distortion and puckering.

Means for Solving the Problems In order to achieve the above object, the present inventors have intensively studied conventional techniques for preventing the occurrence of welding distortion, and have found that it is important to reduce the temperature of the weld molten pool. I discovered that.

That is, the higher the temperature of the molten pool, the greater the shrinkage during cooling and the greater the welding strain.

In addition, as a result of considering the puckering phenomenon of welding defects, the present inventors found that the mechanism of puckering is not only the pushing of the molten metal to the outside by the arc force described in the cited document, but also the surface of the molten pool. This is thought to be due to the effect of oxides formed on the surface.

As a result of the above studies, we have found that welding distortion can be suppressed by inserting a cold wire into the molten pool of MIG welding and controlling the molten pool temperature to a low temperature.

Furthermore, regarding the puckering phenomenon, we have found that it is effective to increase the amount of molten metal by inserting a cold wire into the molten pool.

Based on these findings, we extensively investigated specific welding conditions and came to the conclusion that the following conditions are appropriate.

Leading wire: Aluminum cold wire Trailing wire: Aluminum electrode wire Cold wire insertion angle (retreat angle): 20 to 70 degrees Electrode wire insertion angle (advance angle): 5 to 40 degrees Cold wire target position: Melting on the welding direction side IkebataHere, the reason why the electrode wire is set at an advancing angle is to prevent impurities such as oxides generated in the molten pool from being mixed into the weld metal, and the reason why the electrode wire is set at a receding angle is to prevent the cold wire from being mixed into the weld metal. This is because when inserted into the molten pool, it has good fluidity, and it is easy to form molten metal, and it is possible to form a good weld metal with a small excess height.

If the cold wire insertion angle is less than 20 degrees, if the wire feeding speed during insertion is high, the wire will pass through the molten pool and directly hit the base material, and if the wire feeding speed is small, the wire will not enter the molten pool. First, the droplets scatter outside the molten pool.

Moreover, if the wire feeding speed exceeds 70 degrees, the wire may be slightly broken, making the arc and molten pool unstable. If the wire feeding speed is small, the droplets will not enter the molten pool and the molten pool will melt. Scattered outside the pond. Therefore, 20-7
The range was 0 degrees.

If the electrode wire insertion angle is less than 5 degrees, there is a risk that impurities such as oxides formed on the surface of the molten pool will be present in the weld metal, and if it exceeds 40 degrees, the arc force will prevent the insertion of the cold wire. Since this would be difficult, the temperature was set at 5 to 40 degrees.

The reason why the cold wire is inserted into the end of the molten pool on the side in the welding direction is to ensure smooth melting and to stabilize the arc column. If you aim for the center of the molten pool or the outside of the molten pool, large droplets will form outside the molten pool, and the droplets will only enter the molten pool intermittently, making the formation of the arc column and molten pool unstable. Therefore, high quality weld metal cannot be obtained.

The reason why the ratio of the cold wire supply amount to the electrode wire supply amount was set to 0.2 to 1.3 was because if it was less than 0.2, the droplet could not be stably inserted into the molten pool, and if it exceeded 1 or 3. In this case, the bead shape becomes unstable.

The temperature of the molten pool can be lowered by inserting a cold wire at the end of the molten pool formed by the arc of the working electrode wire. At the same time, the amount of molten metal also increases.

As a result, welding distortion and puckering are prevented from occurring.

Example (Example 1) The welding method according to the present invention will be explained based on FIG.

Electrode wire (1) made of aluminum or its alloy
is the trailing wire in the welding direction, and the electrode wire (1
) is the leading wire, and the electrode wire (1) is inserted into the molten pool ( 3) MIG by placing it at the front end and keeping the feed rate ratio of cold wire and electrode wire in the range of 0.2 to 1.3.
Perform welding.

Note that (4) in the figure is the base metal, and (5) is the weld metal.

Now, using aluminum electrode wire and aluminum cold wire, welding current is 300-500 Amp.

Welding was performed by changing the heat input under the conditions of a welding speed of ioo cm/min, and changes in the molten pool temperature were investigated. The result is
Figure 2 shows a comparison with the conventional welding method using only aluminum electrode wires.

From FIG. 2, it can be seen that according to the method of the present invention, the molten pool temperature is significantly lower than that of the conventional method, and is lower than that of the conventional method even when the heat input exceeds 70 J/cra.

(Example 2) The appropriate condition range was investigated by changing the cold wire insertion angle θ], the electrode wire insertion angle θ2, the cold wire target position, and the ratio r of the cold wire supply amount to the electrode wire supply amount. The results are shown in Table 1.

The welding current was 300 Amp, and the welding speed was 700 Amp.
cm/win, shielding gas flow rate is Ar gas 25 (1
/min.

From Table 1 above, the insertion angle θ1 of the electrode wire (1) is 5~
Sample mlO,15 where the insertion angle of the cold wire (2) deviates from 40 degrees, and sample N where the insertion angle θ2 of the cold wire (2) deviates from 20 to 70 degrees.
nl, 2. 8. No. 9 has poor weld bead formation in all cases. In addition, sample tkL16.17, in which the target position of the cold wire is outside the molten ground edge, and sample tkL18.2B, in which the supply amount ratio of cold wire and electrode wire is outside of 0.2 to 1.3, both cause weld beads. is poorly formed. It can also be seen that the weld bead formation is good in all of the samples obtained by implementing the present invention.

(Example 3) Using the MIG welding method of the present invention and the conventional MIG welding method, downward fillet welding (equal leg length 7 mm) of a T-shaped joint of A 5083 material with a plate thickness of 70 W + m and a length of 1 m was performed as shown in Table 2. The welding was carried out under the welding conditions shown below.

Table 2 below shows the molten pool temperature and welding strain in this welding. The results are shown in Table 3. From these results, it can be seen that according to the implementation of the present invention, the molten pool temperature is lower than that of the conventional method, and the melt strain is also reduced.

Note that the temperature of the molten pool was measured using an infrared radiation thermometer.

(Example 4) Since puckering occurs when the welding current is excessively high, welding was carried out using the present invention method and the conventional method under the welding conditions shown in Table 4, and the puckering generation currents were compared. The results are shown in Figure 3.”The amount of cold wire melting was 45
From the results shown in Table 4 and Figure 3 for welding at a/min. 6, it can be seen that this method allows for a larger melting amount than the conventional method, and puckering is less likely to occur even at 1 min.

In addition, we conducted a radiographic examination of the welded part and a tensile test of the weld metal using the method of this invention, but the results were similar to those of the conventional method.

Effects of the Invention This invention suppresses welding distortion by inserting a cold wire into the molten pool under certain conditions to lower the temperature of the molten pool to a minimum and increase the amount of molten metal. can be prevented. Therefore, it is possible to improve the efficiency of MrG welding of aluminum and its alloy.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the positions of the electrode wire A and the cold wire when carrying out the present invention, and Fig. 2 (secondary heat input and Graph showing the relationship between δ and molten pool humidity, 3rd [; q is a diagram that does not show the area where puckering occurs during G welding 1 and 1 by this invention method and the conventional method. 1... Electrode wire 2... Call biwa 1' layer 3... Molten pool 4... Base metal 5... Weld metal θ14 θ2... Insertion angle , Association)

Claims (1)

[Claims] 1. In MIG welding of aluminum and its alloys, M
A MIG welding method for aluminum and its alloys, which comprises inserting an IG welding electrode wire and a cold wire having substantially the same composition as the electrode wire under the following conditions. Conditions Leading wire: Aluminum cold wire Trailing wire: Aluminum electrode wire Cold wire insertion angle (backward angle): 20 to 70 degrees Electrode wire insertion angle (advance angle): 5 to 40 degrees Cold wire target position: On the welding direction side Molten pool end (cold wire supply amount g/min)/(electrode wire supply amount g/min) = 0.2 to 1.3