JPS6016308B2 - Welding method for edge joints - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a method for welding edge joints when welding products with edge joints made of thin plates, such as machine parts and containers, using a non-consumable electrode type arc. be.

Compared to conventional welding, plasma welding has faster welding speeds, higher efficiency, precision welding with less heat influence and distortion, deep penetration due to the keyhole effect, and uniform underwaves. Because it has excellent features such as a beautiful bead appearance with no spatter, it can be applied to a wide range of fields from thin plates to thick plates, and is also suitable for automatic welding of mass-produced products.

However, most of these are butt welds, and other welding contacts are not widely used. For example, welding of special products having several overlapping edge joints has hardly been put to practical use. When a product is made by stacking sheets formed one by one by press working, gaps or misalignments are likely to occur between the sheets at the joint. Furthermore, these gaps and misalignments have a significant adverse effect on welding and cause welding beads to sag, so they must be taken into consideration when welding. The present invention solves these problems and provides a welding method for edge joints that performs welding without causing weld bead sagging and in which the edge joint portion has a uniformly rounded penetration. It is something to do.

In the present invention, the inner thin plate sandwiched between the thin plates on both sides is made into a convex shape that protrudes from the outside within a range that does not exceed the thickness of the thin plate, and then the edge joint is placed in a downward position using a non-consumable electrode type arc. Alternatively, welding is performed in an upright position.

Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows
This shows an example in which the plates with a thickness of 1.2 mm are press-formed and then assembled by welding.
Plasma welding is performed in a downward position.
In the figure, 1 is a welding torch, and 2 is a jet flame (also called an arc flame) of plasma gas generated from the welding torch 1. 3 is the edge joint part of the thin plate, and the thin plate 3a
, 3b, and 3c are superimposed.

When the welding torch 1 is positioned above the hem joint 3 and a plasma arc is generated in the direction of the hem joint 3, the arc flame 2 splits to both sides of the hem joint 3, so that the molten part can be cut out. In addition, since the outer plate surfaces on both sides are heated, wetting of the molten metal with good wettability and uniformly rounded penetration can be obtained (4 is the welded part).

Next, we will discuss the shape of the edge joint and its welding results according to examples.In the case of a two-ply joint, the gaps and misalignments between the plates are limited to a predetermined shape, but when three or more sheets are stacked, There are various joint shapes. For example, 3
Examples of the staggered (protruding) shape of stacked sheets include the types shown in FIG. 2. It should be noted that there are also left-right reversed shapes of c and d, but they are not shown here because the welding results in the downward position are the same. When welding a concave edge joint as shown in a in the figure, a stable molten pool cannot be obtained and the bead swells, resulting in welding defects. On the other hand, when welding a convex edge joint as shown in b, the jet flame of the plasma arc is split evenly to both sides of the edge joint to be welded, melting the central inner plate protrusion. At the same time, the outer plate surfaces on both sides are sufficiently heated and melted, so that a rounded and good bead is formed. In addition, there are cases where one of the outer panels and the inner panel protrude as shown in c, and there are cases where each panel protrudes irregularly as shown in d, but according to the experimental results, only one of the outer panels on both sides sticks out. When the plates are ejected, the inner plate in contact with the outer plate should have at least the same length or longer protrusion length than the outer plate, so that the jet flame of the plasma arc acts to stroke the molten part, and the inner plate is in contact with the outer plate. It has been found that since the outer plate of the weld can be heated, the molten pool can be stably formed without spilling out, good penetration can be obtained, and welding speed can be increased. Figure 3 shows the shape of an edge joint when both misalignment (protrusion) and gap occur, and typical examples of convex and concave shapes are shown separately before and after welding. be. In case 1, where the center inner plate protrudes beyond the outer plates on both sides, even if there is a gap (in this case, the gap is less than 0.3 ribs, and if it is larger than this, welding will not be possible). .) 1' where good welding results were obtained. On the other hand, in the case of the concave joint No. 2, the inner plate in the center is recessed from the outer plates on both sides, so the heat is reflected and cannot be heated sufficiently.
Moreover, because the gap is expanded by the thickness of the plate, the surface tension of the molten metal causes only the tip of each plate to become rounded, and the joint solidifies without being joined.
. In order to successfully weld the edge joint of stacked plates in this way, it is necessary to prevent the shape from becoming concave, and the inner plate sandwiched between the outer plates on both sides should protrude from the outside. It is effective to form the edge joint in this manner.

In this case, the protrusion length must be kept within a range that does not exceed the plate thickness; for example, in the above example, the plate thickness is 1.2
It is possible to extend it all the way to the sail, but if it goes beyond that, only the inner panels will be melted and the outer panels on both sides will be insufficiently melted.
A molten pool spanning three stacked plates cannot be formed, and the edge joints cannot be welded. Next, the board thickness is 1. The 4th example shows an example in which 4 pieces of Okamisaki plates are stacked on top of each other and welded in a downward position.
Explain according to the diagram. There are many more types of edge joint shapes than when three sheets are stacked (the shape with the left and right sides reversed is not shown here), but the welding result is 1. A good weld bead can be obtained with any shape in which the inner plate protrudes by more than one plate. In addition, when one of the outer panels on both sides protrudes, the inner panel adjacent to that outer panel must have the same length or a protruding length longer than the outer panel to form an edge joint. In this case, good welding results can be obtained. On the other hand, a type with a nearly concave shape is likely to cause welding defects such as humping during the welding process.
Furthermore, even when the number of stacked plates is increased, similar results will be obtained. In order to achieve uniformly rounded welding in the edge joint and to perform stable welding with a wide margin, the jet flame of the plasma arc must separate and exit on both sides of the edge joint to be welded. It is desirable to do so. For example, one way to meet this requirement is to select the nozzle diameter. It is best to weld using a nozzle with a diameter equal to or larger than the total thickness of the stacked plates (plate thickness x number of plates).

In addition, by slightly increasing the distance between the nozzle base materials, it is possible to spread the plasma arc, and the above requirements can be met. When welding in a downward position, the molten pool is mainly balanced by the surface tension of the molten metal without being affected by the effect of gravity, so the edge joint has a symmetrical penetration.

Similarly, even when welding in an upright position, the action of gravity is downward, so penetration is symmetrical. However, if the total thickness of the stacked plates is large or if the molten metal is made of a material with low surface tension, dripping of the molten pool is likely to occur.

For example, in the case of stainless steel, it is possible to weld both downward and vertical positions, but in the case of mild steel plates, although downward welding can be performed stably, in vertical welding, the total plate thickness is 3. If it is more than that, it may become unstable.
Note that slag or the like is formed on the surface of the bead. For example, if an oxidizing gas such as C02 or 02 is added to the Ar gas of the shielding gas so as to increase the surface tension of the molten pool, dripping of the molten pool can be reduced. Furthermore, if a wire with a deoxidizing effect is added at the same time, further improvement can be achieved. Although stainless steel and mild steel have been described as examples here, it goes without saying that the method of the present invention can also be applied to other alloy materials, non-ferrous metals, and dissimilar metal materials (FIG. 1).

Further, in this example, the experimental results using a plasma arc were shown, but as in the present invention, it is also possible to perform the experiment using a consumable electrode type arc such as a TIC arc after forming the edge joint part. is also possible. As described above, according to the present invention, the molten pool can be stably held without spilling out, and therefore uniform and well-rounded penetration without welding defects can be obtained, and the welding speed can be increased. can be achieved.

Particularly for small mass-produced products, automatic production can be performed by integrating press processing and welding lines, improving quality and reliability.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an embodiment of the present invention, Figure 2 is a diagram showing the shape of an edge joint of three stacked plates, and Figure 3 is an edge joint when the protrusion and gap of the plates are molded at the same time. FIG. 4 is a diagram showing an embodiment in which four sheets are stacked. 1...Torch, 2...Jet frame, 3...Thin plate. YFigure 2Figure 3Figure 4

Claims (1)

[Claims] 1 In a method in which three or more thin plates are overlapped so that the arc frame is divided into both sides and the edge joint is welded, a part or all of the inner thin plate sandwiched between the thin plates on both sides is A welding method for an edge joint, which is characterized in that the edge joint is made into a convex shape that protrudes from the outside within a range not exceeding , and then the edge joint is welded in a downward position or an upright position using a non-consumable electrode type arc.