Weld Defects

Fillet weld seldom require 100% penetration

They do, however require enough to penetrate past intersection of the two pieces being welded . The welding symbol often specifies a leg size and weld size large enough to ensure adequate penetration. Poor penetration on a fillet weld cannot be inspected visually.

Slag inclusions

are caused when slag is trapped during a multiple-pass weld. Slag must be completely removed after each weld pass to prevent slag inclusions.

Porosity

can be seen on the surface of some welds. Some porosity can be beneath the surface and not visible on a completed weld. Welding with a long arc or improper electrode motion can cause porosity.

Welds that are too Wide/Narrow

have too much build up, are under-filled, or butt joints that do not have complete penetration can be found by visual inspection. The weld face should be consistent and not sag. The weld bead should be convex.

Complete 100% penetration

is generally required only on a weld with a groove-type joint. A weld bead with 100 penetration will show a small, uniform bead like bump on the root side of the weld.

Udercut

occurs when the base metal at the weld toe are is melted but is not filled with filler metal. This causes a weak area in the weldment.

Overlap

occurs when the weld toe is not fused into the base metal