What are common visual weld defects and how can they be identified?

What are common visual weld defects and how can they be identified?

• A. Cracks, porosity, lack of fusion, undercut, convex/overly concave beads, misalignment; identified by visual inspection with proper lighting and measurement.
• B. Only minor color variation.
• C. Smooth uniform bead with no imperfections.
• D. Excessive gloss.

Answer: (A)

Visual inspection of a weld focuses on surface features that signal defects affecting strength and integrity. The most reliable visual defects you’ll look for include cracks, porosity, lack of fusion, undercut, and incorrect bead shape or alignment. Cracks appear as clear lines, either on the surface or through the bead, and can propagate under stress. Porosity shows up as small, round holes or gaps in the weld metal where gas was trapped during solidification. Lack of fusion means the weld hasn’t properly fused to the base metal or to a previous weld pass, leaving a visible gap or a step between metals. Undercut shows as a groove along the weld toe, weakening the joint by removing material from the base metal at the edge of the weld. Bead shape issues—being too convex (bulging out) or too concave (too shallow)—signal too much or too little filler material or improper heat/ travel speed, both of which can concentrate stress. Misalignment is evident when the joined pieces don’t sit flush, causing a discontinuity along the seam. To identify these defects, use proper lighting and clean the weld surface so you can see features clearly. Inspect from multiple angles, and if needed, measure bead width, height, and alignment against the joint geometry. While color variations or an exceptionally smooth, glossy finish might catch the eye, they don’t represent the common surface defects that compromise weld integrity, so they aren’t sufficient on their own to diagnose issues.

Visual inspection of a weld focuses on surface features that signal defects affecting strength and integrity. The most reliable visual defects you’ll look for include cracks, porosity, lack of fusion, undercut, and incorrect bead shape or alignment. Cracks appear as clear lines, either on the surface or through the bead, and can propagate under stress. Porosity shows up as small, round holes or gaps in the weld metal where gas was trapped during solidification. Lack of fusion means the weld hasn’t properly fused to the base metal or to a previous weld pass, leaving a visible gap or a step between metals. Undercut shows as a groove along the weld toe, weakening the joint by removing material from the base metal at the edge of the weld. Bead shape issues—being too convex (bulging out) or too concave (too shallow)—signal too much or too little filler material or improper heat/ travel speed, both of which can concentrate stress. Misalignment is evident when the joined pieces don’t sit flush, causing a discontinuity along the seam.

To identify these defects, use proper lighting and clean the weld surface so you can see features clearly. Inspect from multiple angles, and if needed, measure bead width, height, and alignment against the joint geometry. While color variations or an exceptionally smooth, glossy finish might catch the eye, they don’t represent the common surface defects that compromise weld integrity, so they aren’t sufficient on their own to diagnose issues.