JPS6026630B2 - Plasma keyhole welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma keyhole welding method that enables efficient welding of aluminum or the like without defects.

Conventionally, for example, "AC TI" was used for welding aluminum, etc.
A variety of methods are used, including the "G welding method" (welding is carried out by alternating current arc using tungsten as an electrode), the "DC MIG welding method" (using a metal wire as an electrode), and the "reverse polarity plasma post-melting method". Among the "reverse polarity plasma welding methods," the "plasma keyhole welding method" allows for penetration welding in one layer.
It is generally well known that the efficiency is extremely good. FIG. 1A shows a conventional "plasma keyhole welding method" of this kind, in which 1 is a reverse polarity plasma torch, 2 is a plasma arc, 3 is a welding wire, 4 is a feeding guide tube for this welding wire 3, 5 is a conduit tube, 6
1 is a welding base material, and 7 is a welding base material. The cross section of this welding base material 7 is as shown in FIG. 1B, and a keyhole 8 is formed.

The reverse polarity plasma torch 1 is configured to move in the direction of arrow A as shown in FIG. 1A, and the welding wire 3 is supplied from the front of the torch 1. The plasma arc 2 generated by the conventional "plasma keyhole welding method" configured as described above is constricted by a restraint/slip (not shown) placed at a predetermined position within the reverse polarity plasma torch 1. Because it is configured in
Compared to the above (AC TIG welding method), the energy density and arc pressure of the arc are higher, so the base material to be welded is penetrated by the arc, and generally "keyhole"
Since welding can be performed while forming a hole 8 called a hole 8, there is an advantage that complete penetration is possible with single-sided welding. Normally, when welding aluminum, the polarity is reversed, that is, the electrode side is "10" and the base metal side to be welded is "1", but even in the conventional plasma torch 1 shown in Fig. 1 mentioned above, , which are necessarily electrically connected to have opposite polarities, the plasma arc 2 generated from the plasma torch 1 against the base materials 6 and 7 to be welded has a high energy density and a high arc After melting the base materials 6 and 7 by the action of pressure and finally forming a penetrating keyhole (hole) with a diameter of several times the diameter, the plasma torch 1 is moved in the advancing direction,
The "plasma keyhole welding method" performs welding while maintaining the keyhole.

However, in this "plasma keyhole welding method", the metal molten in the keyhole 8 section hangs down somewhat toward the back side of the base materials 6 and 7 due to the influence of gravity, so that the surfaces of the base materials 6 and 7 are The neck tends to be concave.
Therefore, in order to replenish the recesses on the surfaces of the base materials 6 and 7, the welding wire 3 is supplied to the recesses from the front of the plasma torch 1 via the conduit tube 5 and the guide tube 4. . However, in such a conventional welding method, the welding wire 3 is supplied from the front of the plasma torch 1, so when the welding wire 3 is heated and melted by the plasma arc 2, it mixes with the molten metal of the base metal. After mixing, the metal moves to the vicinity of the keyhole 8, so the actual amount of melting increases, and the weight of the molten metal increases accordingly, making it even easier to sag, causing the welding wire 3 to sag. Even if the V supply amount is considerably increased, the surfaces of the base materials 6 and 7 tend to be dented.

Conventionally, in stainless steel or mild steel keyholes,
Because of its high viscosity, it is easy to hold the keyhole 8 even at high temperatures, and it does not sag slightly.However, light metals such as aluminum have particularly low viscosity at high temperatures and are extremely prone to sagging, so welding wire 3 is held in front of plasma torch 1. There was a problem with the method of supplying it. This invention has been made with attention to this point, and aims to eliminate the above-mentioned drawbacks by supplying the welding wire 3 from the rear of the plasma torch 1.

That is, FIG. 2A shows an embodiment of the present invention, in which 1 is a reverse polarity plasma torch, 2 is a plasma arc, and 3 is a reverse polarity plasma torch.
4 is a welding wire, 4 is a feeding guide tube for this weld bale wire 3, 5 is a conduit tube, 6 is an unwelded base material, and the cross section of this weld base 7 is as shown in FIG. 2B.

As shown in FIG. 2A, the reverse polarity plasma torch 1 is configured to move in the direction of arrow A, and the welding wire 3 is supplied from behind the torch 1. In the plasma keyhole welding method of the present invention, as described above, the welding wire 3 is supplied to the keyhole 8 from the rear of the reverse polarity plasma torch 1 that moves in a predetermined direction at a predetermined speed. 2, only the unwelded base metal 6 is melted first, and this molten metal moves around the keyhole (hole) and then mixes with the melted welding wire 3. Therefore, the welding wire 3 Even if the welding wire is supplied to the keyhole 8, unlike the conventional method described above (the method of supplying the welding wire from the front of the reverse polarity plasma torch), the molten pool does not tend to drip, and the welding wire ``Extra portion'' for the amount of 3.
Therefore, it is formed on the weld bead. In addition, when the welding wire 3 is supplied from the rear of the reverse polarity plasma torch 1 as in the present invention, the welding wire 3 is supplied from the front of the torch 1 as in the above-mentioned secondary method. Although the maximum possible welding groove amount of the welding wire 3 is smaller than that of the welding wire 3, the characteristic of the plasma keyhole welding method is that the welding wire 3 only needs to be supplied by the amount that the welding bead is recessed. The V supply amount of the welding wire 3 can be extremely small, which also contributes to reducing welding costs. As described above, according to the present invention, the welding wire 3 is inserted into the keyhole 8 from the rear of the reverse polarity plasma torch that moves in a predetermined direction at a predetermined speed. Even when keyhole welding is performed on low-quality aluminum or aluminum alloys, it has an excellent effect of preventing the occurrence of dents or the like on the surfaces of the base metals 6 and 7 due to dripping of molten metal.

In addition, although the above-mentioned embodiment described the case where the welding wire 3 is supplied to the keyhole 8 as an additive during welding, the same effect can be obtained even if a welding wire is used instead of the welding wire 3. For reference, the data of an experimental example in which the base material was 6 ribs in the above-mentioned example is as follows.

[Brief explanation of the drawing]

FIG. 1A is a side sectional view for explaining the conventional plasma hole welding method, FIG. 1B is a sectional view of the keyhole part,
FIG. 2A is a side sectional view for explaining one embodiment of the present invention, and FIG. 2B is a sectional view of the keyhole portion thereof. In the drawing, 1 is a reverse polarity plasma torch, 2 is a plasma arc, 3 is a welding wire, 6 and 7 are base materials, and 8 is a keyhole. Note that the same reference numerals in the figures indicate the same or corresponding parts. Heron
Figure 2

Claims (1)

[Claims] 1. Plasma keyhole welding, characterized in that a welding wire is supplied to the keyhole of the base material from the rear of a reverse polarity plasma torch that moves in a predetermined direction at a predetermined speed over the base metal. Method. 2. The plasma keyhole welding method according to claim 1, wherein aluminum or an aluminum alloy is used as the base material.