T-Joint with Intersection on Top
A typical T-joint is shown in Fig. 10-6. The joint must be very carefully prepared by beveling the edges so that a good fit-up is obtained. After the root bead is welded, additional filler beads are deposited to fill the joint and give it more strength.
On both sides, the weld is started at the lowest part of the joint. The tie-in of the beads is made at the two highest parts of the joint. While welding around the joint, it is important to maintain the correct electrode angles, which are shown in Fig. 10-6,
A slanted “loop” bead is used to weld the lowest part of the joint in order to prevent the puddle from drooping. The electrode should point slightly upward (see Fig. 10-6A) to allow the arc-force to assist in controlling the puddle. To allow the bottom of the joint to cool slightly, thereby reducing the tendency to droop, the electrode should pause momentarily at the top of the weld joint. This also provides additional metal at this part of the joint.
When the tendency of the puddle to droop decreases, the weave pattern is changed to a slant weave and the electrode pauses again at both edges of the weld. The slant pattern is continued until the bead reaches the top of the joint.
Fig. 10-7. Weave pattern for welding T-joint with intersecting pipe below
The procedure for welding the T-joint shown in Fig. 10-7 is similar to welding the previous T-joint, where the intersection is at the top of the horizontal pipe. First a root bead is welded, starting at the lowest part of the joint. This is followed by several additional beads that also start near the lowest part of the joint; however, all of these beads must overlap each other. A bead should never be started at the same place where the next lower bead was started.
Starting the filler bead in the lower region of the joint, a slanted “loop” weave is used since this portion of the joint is in the overhead position. A slight pause is made at the upper part of the joint when making this weave.
As the weld progresses around the joint, and when the molten metal loses its tendency to drip, the weave is changed to a modified slant weave pattern, as shown in Fig. 10-7. The electrode should pause at both edges of the joint when this pattern is started. This pattern is used until the layer is stopped at the top of the joint.
Fig. 10-8. Weave pattern for welding T-joint with intersecting pipe located at the side of the vertical pipe.