4. • GEOMETRIC IMPERFECTIONS
• Geometric imperfections refer to certain weld
characteristics such as fit-up and weld bead
shape as determined by visual inspection.
1)Misalignment
This type of geometric defect is generally
caused by a setup/fit up problem, or trying to
join plates of different thickness.
5. 2)Overlap
• The protrusion of weld metal beyond the weld toe or weld root. It is
caused by poor welding techniques and can generally be overcome by an
improved weld procedure. The overlap can be repaired by grinding off
excess weld metal and surface grinding smoothly to the base metal.
3)Undercutting
• Undercutting is one of the more severe welding defects. It is essentially an
unfilled groove along the edge of the weld. The causes are usually
associated with incorrect electrode angles, incorrect weaving technique,
excessive current and travel speed.
6. • 4) Concave and Convex Welds
• Misshaped welds are caused by a combination of incorrect
electrode current and speed. Excessive concavity (lack of
reinforcement), results in insufficient throat thickness in
relation to the nominated weld size. Excessive convexity
results in poor weld contour.
7. 5) Cracking
• Cracking Cracks and planar discontinuities are some of the
most dangerous especially if they are subject to fatigue loading
conditions.
• Cracks can occur in the weld itself, the base metal, or the heat
affected zone (HAZ).
• Cracking is commonly caused by a cooling problem, the
elements in the weld cooling at different rates.
8. • INCLUSIONS
• Inclusions are generated by extraneous material such as slag,
tungsten, sulfide and oxide inclusions becoming part of the
weld. .
• These defects are often associated with undercut, incomplete
penetration and lack of fusion in welds.
• Insufficient cleaning between multi-pass welds and incorrect
current and electrode manipulation can leave slag and unfused
sections along the weld joint.
• Slag inclusions not only reduce cross sectional area strength of
the joint but may serve as an initiation point for serious
cracking.
• This defect can only be repaired by grinding down or gouging
out and re-welding
9. • POROSITY
• Porosity is a collective name describing cavities or pores caused by
gas and non-metallic material entrapment in molten metal during
solidification.
• Porosity can be classified as uniformly scattered, clustered, linear,
or piping.
• Uniformly scattered porosity can be caused by moist or dirty base or
filler metal. It can be caused by improper welding technique
• Clustered porosity is likely to result form improper arc starting or
breaking, or periodic loss of shielding gas coverage
• Linear porosity aligns along the boundary of a joint and is directly
related to contamination in the base metal, weld metal or both.
10. • INCOMPLETE FUSION
• Poor joint design and poor edge preparation are the most
common causes of incomplete fusion.
• If the heat input is too low during welding, the molten puddle
may not fuse into the base material. Lack of fusion can also be
caused by incorrect work and travel angles.
• Incomplete fusion cannot be detected without the use of a
nondestructive testing method other than visual.
11. • WELD SPATTER
• Metal drops expelled from the weld that stick to the
surrounding surfaces.
• Spatter can be minimized by correcting weld conditions
and should be eliminated by grinding when present.
12. • INCORRECT WELD PROFILE
• Incorrect weld profile is a weld that does not meet the requirements for size
or contour.
• Overlap is the bulging or protruding portion of a weld that extends beyond
the toe, face, or root.
• Insufficient throat or underfill is a weld face or root that is depressed or
extends below the adjacent base metal surfaces.
13. • LAMELLAR TEARING
• Lamellar tearing is a type of defect that is most likely to occur
below a welded joint at points of high stress concentration.
• It is created by non-metallic inclusions being rolled into
• the hot plate metal during fabrication. These tears occur when
weld metal is deposited on the surface of a joint where there is
high restrain.
14. • WELD DAMAGE
• They are caused by using excessive force using a
chipping hammer, careless handling of welding
electrode holder and arc manipulation.
• These imperfections can cause cracking in HAZ,
leading to stress concentration.
• CRATER
• These are visually inspect able depressions that
indicate improper weld terminations, usually with
presence of radial cracks.
17. CONCLUSIONS
• Welding defects can greatly affect weld
performance longevity
• Detection techniques must be sensitive enough
to detect harmful discontinuities.
• It is necessary to repair that are considered
detrimental to the structural integrity of the
weld structure.
