JPH11347742A - Superposed arc welding method for aluminum work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve welding quality and the efficiency of welding work by stably and efficiently forming a hole in an upside work and a molten pool in a downside work, in a method wherein arc welding is executed to a vertically superposed aluminum work by the use of a plasma arc welding torch. SOLUTION: Before a hole 6 is formed in an upside work 1, a plasma arc (a) is made incident on the upside work 1 with a polarity ratio which enlarges a reverse polarity ratio more than a straight polarity ratio, and an oxide film 1a of the upside work 1 is removed. Also, after the hole is formed, the plasma arc (a) is made incident on the downside work 2 through the hole 6 with the same polarity ratio as the above described one, and an oxide film 2a of the downside work 2 is removed. The hole in the upside work 1 and a molten pool 7 in the downside work 2 are formed with the reverse polarity ratio lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for arc welding of aluminum-based workpieces in which an overlapped portion of a workpiece made of an aluminum-based material which is overlapped vertically is arc-welded using a plasma arc welding torch.

[0002]

2. Description of the Related Art Conventionally, when an overlapped portion of a vertically superposed work is arc-welded, a plasma arc is incident on an upper work, a hole is formed in the upper work, and the above-mentioned work is formed on the lower work. A plasma arc is incident through the hole to form a molten pool in the lower work, and then a filler material is fed to fill the molten pool and the hole.

[0003]

By the way, a work made of an aluminum-based material is oxidized even in the air, and the surface of the work is made of Al.
_An oxide film composed of ₂ O ₃ is formed. Since this oxide film has a higher melting point than the base material of the work, it is difficult to stably perform drilling of the upper work and melting of the lower work after the drilling.

By the way, when a plasma arc is incident on a work with a reverse polarity using a torch electrode as an anode and a work as a cathode, thermal electrons are emitted from an oxide film serving as a cathode point, and a cleaning action for removing the oxide film is obtained. Therefore,
By performing arc welding with a polarity ratio that is greater than the polarity of the positive polarity, the oxide film is removed, and the upper workpiece is drilled and the lower workpiece after drilling is melted stably. And the welding quality is improved.

However, in the case of an aluminum-based work, when the ratio of the reverse polarity is increased, the penetration becomes shallow, and the efficiency of drilling and the formation of a molten pool deteriorates. Therefore, the current situation is to increase the ratio of the positive polarity to increase the efficiency of the welding operation.

SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for arc welding of aluminum-based workpieces, which removes an oxide film to improve welding quality and improves the efficiency of welding work. Is an issue.

[0007]

Means for Solving the Problems In order to solve the above problems,
The present invention is a method of arc welding a superimposed portion of a work made of an aluminum-based material which is superimposed on a top work using a plasma arc welding torch. A drilling step for drilling a hole, a plasma arc incident on the lower work through the hole to form a molten pool on the lower work, and a welding material fed into the plasma arc. In the step of performing a molten pool and a hole filling step of filling the hole, before the drilling step, a plasma arc is incident on the upper work at a polarity ratio having a larger reverse polarity ratio than the positive polarity, A first cleaning step of removing the oxide film of the work is performed, and prior to the molten pool forming step, the lower side is formed at a polarity ratio having a larger reverse polarity ratio than the positive polarity. A plasma arc is incident on the workpiece through the hole to perform a second cleaning step of removing an oxide film on the lower workpiece, and the hole is drilled at a polarity ratio lower than that of each of the cleaning steps. Step and the molten pool forming step are performed.

According to the present invention, the oxide films on the upper and lower works are removed by the first and second cleaning steps, so that the upper work is perforated and the lower work after the perforation is melted. It can be performed stably. In addition, in the drilling process and the weld pool forming process, the ratio of the reverse polarity is reduced, so that the drilling and the weld pool forming efficiency are improved, thus improving the welding quality and improving the efficiency of the welding operation. Can be planned.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows two workpieces 1 and 2 made of an aluminum-based material such as aluminum or an aluminum alloy superimposed one on top of the other. 4 shows a step of performing arc welding using the same.

As an arc power source, an AC power source having one pole connected to a torch electrode and the other pole connected to a work is used. The AC power source has a positive polarity using the torch electrode as a cathode and a reverse polarity using the torch electrode as an anode. The ratio can be changed.
Further, the plasma arc welding torch 3 is provided with a wire supply tube 4 from which a filler material 5 made of a wire-like aluminum material is fed into the plasma arc a.

At the time of welding, first, as shown in FIG. 1A, a plasma arc a is incident on the upper work 1 at a polarity ratio in which the ratio of the reverse polarity is greater than the positive polarity, for example, 66%. And the oxide film 1a of the upper work 1
Is performed in the first cleaning step.

Next, as shown in FIG. 1B, a plasma arc a is incident on the upper work 1 at a polarity ratio lower than that of the first cleaning step, for example, at a reverse polarity ratio of 50%. Then, a drilling step for drilling a hole 6 in the upper work 1 is performed. This drilling process is performed stably because the oxide film 1a of the upper work 1 has been removed in the immediately preceding cleaning process, and further, by lowering the reverse polarity ratio, the work base material made of an aluminum-based material is melted. And the hole 6 is efficiently drilled. As shown in FIG. 2, the first cleaning step and the drilling step are performed with a relatively large flow rate of the operating gas supplied to the plasma arc welding torch 3 and a relatively small arc current.

Next, as shown in FIG. 1C, the hole 6 is passed through the lower work 2 at a polarity ratio with an increased reverse polarity ratio, for example, the same reverse polarity ratio of 66% as in the first cleaning step. A second cleaning step is performed in which the plasma arc a is incident and the oxide film 2a of the lower work 2 is removed. Incidentally, in the second cleaning step, the flow rate of the operating gas is reduced and the arc current is increased in comparison with the drilling step.

Next, as shown in FIG. 1 (D), the lower work has a polarity ratio lower than that of the second cleaning process, for example, 50% reverse polarity ratio similar to that of the drilling process. A plasma arc a is incident on the workpiece 2 through the hole 6, and a molten pool forming step of forming a molten pool 7 on the lower work 2 is performed. In this case, the oxide film 2a of the lower work 2 is removed in the immediately preceding cleaning step, and the base material of the work melts well due to a decrease in the reverse polarity ratio, so that the molten pool 7 is formed stably and efficiently. Is done. In the molten pool forming step, the plasma arc welding torch 3 is displaced upward so that the molten metal in the molten pool 7 is not blown off by the plasma flow, and the flow rate of the working gas is made lower than that in the second cleaning step.

Next, as shown in FIG. 1 (E), the filler metal 5 is fed into the plasma arc a, and the molten metal 8 which is melted as droplets from the filler metal 5 melts into the molten pool 7 and the hole 6. Perform a hole filling process to fill In the filling process, both the flow rate of the working gas and the arc current are reduced as compared with the molten pool forming process.

Finally, as shown in FIG. 1 (F), the plasma arc welding torch 3 is further displaced upward, the flow rate of the working gas and the arc current are further reduced, and the molten metal 8 filled is preheated. Crater processing for preventing solidification cracking due to the rapid cooling is performed.

[0017]

As is apparent from the above description, according to the present invention, the drilling of the upper workpiece and the formation of the molten pool in the lower workpiece can be performed stably and efficiently, and the welding quality can be improved. And the efficiency of welding work can be improved.

[Brief description of the drawings]

1A to 1F are process diagrams showing a welding operation procedure according to the present invention.

FIG. 2 is a time chart showing changes in torch height, arc current, working gas flow rate, and reverse polarity ratio during welding work.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Upper work 2 Lower work 1a, 2a Oxide film 3 Plasma arc welding torch 5 Filler material 6 Hole 7 Weld pool

Continued on the front page (72) Inventor Kimitsutoshi Fujishita 1-10-1, Shinsayama, Sayama City, Saitama Prefecture Inside Honda Engineering Co., Ltd. (72) Inventor Yasunari Wakisaka 1-10-1, Shinsayama, Sayama City, Saitama Prefecture Honda Engineering Inside the corporation

Claims (1)

[Claims] 1. A method for arc welding a superimposed portion of a work made of an aluminum-based material, which is superimposed on an upper work, using a plasma arc welding torch. A drilling step of drilling a hole in the workpiece, a plasma arc incident on the lower workpiece through the hole, and a molten pool forming step of forming a molten pool in the lower workpiece, and a filler material is fed into the plasma arc. In the step of performing the molten pool and the hole filling step of filling the hole, before the drilling step, a plasma arc is incident on the upper workpiece at a polarity ratio having a larger reverse polarity ratio than the positive polarity, A first cleaning step of removing an oxide film on the upper work is performed, and before the molten pool forming step, a polarity ratio in which the polarity of the polarity opposite to the positive polarity is increased. A plasma arc is incident on the lower work through the hole to perform a second cleaning step of removing an oxide film of the lower work, and the polarity ratio is lower than that of each of these cleaning steps. And performing the drilling step and the molten pool forming step.