This document discusses various welding defects such as slag inclusion, undercut, porosity, incomplete fusion, overlap, underfill, spatter, excessive convexity, incomplete penetration, and excessive penetration. It provides the causes and ways to prevent or repair each defect. Nondestructive and destructive testing methods for inspecting welds are also summarized, including visual inspection, ultrasonic testing, radiographic testing, dye penetrant testing, magnetic particle testing, and mechanical tests.

1. WELDING DEFECTSWELDING DEFECTS
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M SIVAKUMAR

2. Types of defects
Slag Inclusion
Undercut
Porosity
Incomplete fusion
Overlap
Underfill
Spatter
Excessive Convexity
Incomplete Penetration
Excessive Penetration
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3. Slag Inclusion
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Slag is the waste material created and bits of this solid material can
become incorporated into weld. Bits of flux and rust can be counted
as slag.
Cause:- Low amperage, improper techniques, slow travel rate
Prevention:- Increase amperage, increase travel rate
Repair:- Remove by grinding or other mechanical process

4. UNDERCUT
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Undercutting is an extremely common welding defect. It happens when
your base metal is burned away at one of the toes of a weld. portion of
base metal melted away
Cause:- High amperage, wrong electrode angle, long arc length,
electrode is too large for the base metal
Prevention:- clean metal before welding
Repair:- Weld with smaller electrode, sometimes must be low hydrogen
with preheat.

5. POROSITY
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In this defect, air bubbles or gases are present in the weld zone
Cause:- inclusion of atmospheric gases, sulfur in weld metal, or surface
contaminants
Prevention:- slower speed to allow gases time to escape

6. INCOMPLETE FUSION
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A weld bead in which fusion has not occurred throughout entire cross
section of joint
Cause:- Low amperage, fast travel speed, short arc gap, lack of preheat,
electrode too small, unclean base metal
Prevention:- Eliminate the potential causes
Repair:- Remove & reweld, being careful to completely remove the
defective area.

7. Cracks
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It is a discontinuity in the metal that significantly reduces strength
Cause:- low ductility of weld, solidification shrinkage
Prevention:-
When finishing move back the electrode to fill up the crack, Increase
crater fill time by power source.

8. OVERLAP
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Weld metal spills beyond joint onto part surface but no fusion occurs
Cause:- Improper welding technique, steep electrode angle, fast travel
speed
Prevention:- Overlap is a contour problem. Proper welding technique
will prevent this problem

9. UNDERFILL
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Depression in weld below adjacent base metal surface
Cause:- Improper welding techniques
Prevention:- Apply proper welding techniques for the weld type &
position. Use stripper beads before the cover pass.
Repair:- Simply weld to fill. May require preparation by grinding.

10. SPATTER
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Small particles of metal that attach themselves to the surface of the
material
Cause:- High arc power, Damp electrodes
Prevention:- Reduce arc power, reduce arc length, use dry electrodes
Repair:- Remove by mechanical process

11. INCOMPLETE PENETRATION
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Incomplete penetration happens when your filler metal and base metal
aren’t joined properly, and the result is a gap or a crack of some sort.
Cause:- Low amperage, low preheat, tight root opening, fast travel speed,
short arc length
Prevention:- Correct the contributing factors.
Repair:- Back gauge and back weld

12. EXCESSIVE PENETRATION
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13. EXCESSIVE CONVEXITY
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Cause:- Amperage & travel speed
Prevention:- Observe proper parameters & techniques
Repair:- Must blend smoothly into the base metal

14. EXCESSIVE CONCAVITY
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Cause:- Amperage & travel speed
Prevention:- Observe proper parameters & techniques
Repair:- Must blend smoothly into the base metal

15. Arc blow
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Arc deflection as a result of magnetic effects into the opposite direction of
the earth lead clamp.
Arc deflection as a result of magnetic effects in the direction of heavy part of
work piece especially at corner and edges.
Remedies:
Use AC electrode where possible.
Try welding away from earth clamp connection. Try splitting the earth clamp
and correct to both side of the joint.

16. Fusion Weld Zone
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17. Weldability
• Capacity of a metal or combination of metals to be welded into a
suitable structure, and for the resulting weld joint(s) to possess
the required metallurgical properties to perform satisfactorily in
intended service
• Good weldability characterized by:
• Absence of weld defects
• Strength, ductility, and toughness in welded joint
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18. Inspection and Testing Methods
• Visual inspection
• Nondestructive evaluation
• Destructive testing
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19. Visual Inspection
• Most widely used welding inspection method
• Human inspector visually examines for:
• Cracks, cavities, incomplete fusion, and other surface
defects
• Limitations:
• Only surface defects are detectable
• Welding inspector must also decide if additional tests
are warranted
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20. Nondestructive Evaluation (NDE) Tests
• Ultrasonic testing - high frequency sound waves through
specimen to detect cracks and inclusions
• Radiographic testing - x rays or gamma radiation provide‑
photograph of internal flaws
• Dye penetrant and fluorescent penetrant tests‑ ‑ - to detect small
cracks and cavities at part surface
• Magnetic particle testing – iron filings sprinkled on surface reveal
subsurface defects by distorting magnetic field in part
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21. Destructive Testing
Tests in which weld is destroyed either during testing or to prepare
test specimen
• Mechanical tests - purpose is similar to conventional testing
methods such as tensile tests, shear tests, etc
• Metallurgical tests - preparation of metallurgical specimens (e.g.,
photomicrographs) of weldment to examine metallic structure,
defects, extent and condition of heat affected zone, and similar
phenomena
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22. Mechanical Tests in Welding
• (a) Tension-shear test, (b) fillet break test, (c) tension-shear of
spot weld, and (d) peel test for spot weld
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