TEE JOINTS                                                                                                                                                     [ PRINT ]

Tee joints are used when one part must be joined to the center of another part forming a "T". Like the other types of weld, there are several ways that this joint can be prepared and welded, each with their own benefits and disadvantages. Most methods of welding tee joints involve welding the two joints between the parts, with either a high or low energy density beam. Like the other weld types, there are fundamental differences in the processes used with these two types of weld.

When a tee joint is welded with either a high or low energy density system, the process usually involves first placing and clamping the parts in the necessary configuration. If necessary, the parts may be tack welded together to make welding the final joint easer. This can, however, case complications in the final weld, which will be elaborated on later. From here, the processes begin to diverge.

In the case of low energy density welding, such a GTAW and PAW, the joint is made by making a weld bead on one, or usually both, sides of the vertical plate. This is usually done with filler wire, as there is no non-critical area for the volume of the weld bead to come from, as there is in some other weld types. This method forms a very strong weld, usually with minimal distortion. However, it is not nearly as strong as the base metal. In this case, there are relatively few problems associated with spot welding before the final weld.

There are more options for welding tee joints with high energy density devices, such as the laser and electron beam. One option is to weld in a manner similar to that used in low energy density processes, along the joint. However, rather than simply welding on the surface, the beam penetrates deep into the piece, making a weld that can be comparable in strength to the base metal. Unfortunately, this method tends to case more distortion of the workpiece than low energy density methods. Welding both sides of the joint can help to correct this distortion, as well as strengthen the weld.

The second option when welding tee joints with a high energy density beam is to weld through the top of the "T" and into the perpendicular. This can be faster and easer, as it does not require that the joint be followed exactly, but tends to be far weaker than a weld from the side. This method also reduces distortion and is particularly well suited for welding a relatively thick piece to a thin plate, as the beam easily melts the thin plate that it must weld through but does not heat the second plate excessively.

As mentioned earlier, preparatory spot welding can cause severe complications in high energy density beam welding. When the spot weld is created, it usually adds material other than that of the two parts being joined. This foreign material may be included as inclusions in the weld, may evaporate under the intense heat of the beam and form porosities, or may combine metallurgicaly with the base metal and prevent it form crystallizing properly.