To create strong tubular joints when brazing, it is very important that the joint have enough surface area inside the joint, i.e., between the faying surfaces, so that the molten brazing filler metal (BFM) can flow into and through the joint by capillary action.
Figure 1 shows a typical tubular joint, in which the inside, faying surfaces are parallel (gap-clearance is exaggerated for illustration purposes) and the two tubes have an overlap distance that meets the normal brazing requirement of 3T-6T overlap, where “T” is the wall thickness of the tube with the thinner wall thickness. However, when the joint design isn’t a straight tubular joint, but is, instead, a T-joint where the two tubes are perpendicular to each other, such as shown in Fig. 2, then how are those two tubes to be brazed together effectively?