until the lands (root faces) meet, controlling the overall
length dimension. See Figure 6-9.
Another weldment design is the butt joint with pre-
fabricated backing bar. The bar may be 1″ flat stock or
larger, depending on the thickness of the base material.
As the bar is assembled into the cylinder, tack welds are
placed on one edge. After assembly of the mating part,
the other side of the bar is tack welded. Since the weld
usually penetrates into the backing bar, the bar is not
removed after welding, Figure 6-10.
The major problem with this design is the fitup of
the bar to the back of the base material. Any area that
does not contact the back of the material will not con-
trol the heat flow, and penetration into the backing bar
may not occur. Specially designed joints are used for
controlling penetration into the joint where excessive
penetration could cause a problem with liquid flow. See
Figure 6-11.
Joining dissimilar metals often requires buttering—
depositing a material on one of the joint pieces to make
the joint materials metallurgically compatible with a
common filler material. See Figure 6-12.
50 Flux Cored Arc Welding Handbook
Figure 6-7. Applications for double welds.
Butt Bevel V
J U
Bevel and fillet Fillet Double fillet
Figure 6-8. Joggle-type joint.
Figure 6-9. Tubular butt joint with a built-in backing bar.
Figure 6-10. Plate butt weld with fabricated backing bar.
Figure 6-11. Controlled weld penetration joint.
Figure 6-12. Buttered weld joint face.