Rig Fab Educational Services
Welder’s Handbook
Incorrect Shape Cont’d.
Underfill
Underfill
A concave root surface is a depression in the weld extending below the surface of the adjacent base metal caused by an underfill in the root pass of a weld, Concave root surface is detected by RT. If considered a defect, the surface may be suitably prepared or cleaned and additional weld metal added. Concave Root Surface reduces the cross-sectional area of the weld below the amount required in the design. Underfill tends to occur primarily in the flat position in filler welding and in the 5G and 6G pipe groove welding positions. Underfill creates a region susceptible to structural failure from insufficient cross section to support the load. Underfill is detected by VT. A discontinuity in which the weld face or root surface extends below the adjacent surface of the base metal. Underfill
Melt through is also called burn through. It is a discontinuity that occurs in butt welds when the arc melts through the bottom of the weld. Melt-through is different than melt-thru, which is visible root reinforcement produced in a joint that is welded from one side. Melt through is detected by RT as a region of excessive thickness in the region of the weld root. Melt Through
19
Made with FlippingBook Ebook Creator