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WELDMENT
DISCONTINUITYBy: JAMES F. PORTER, JR.
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WELDMENT
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DISCONTINUITY
An interruption of the typicalstructure of a material, such as a
lack of homogeneity in itsmechanical, metallurgical, orphysical characteristics.
A discontinuity is not necessarily adefect.
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DEFECT
A discontinuity or discontinuitiesthat by nature or accumulated
effect (for example, total cracklength) render a part or productunable to meet minimumapplicable acceptance standardsor specifications.
This term designates rejectability.
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WELDMENT DEFECTS
A. DEFECTIVE PROPERTIES
B. DIMENSIONAL DEFECTS
C. STRUCTURAL DEFECTS
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DEFECTIVE PROPERTIES
A. BASE METAL
B. WELD METAL
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DIMENSIONAL DEFECTS
A. DISTORTIONB. INCORRECT JOINT
PREPARATIONC. INCORRECT WELD SIZED. INCORRECT WELD PROFILEE. INCORRECT FINAL
DIMENSION
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AVOID OVERWELDING
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EDGE PREPARATION
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EDGE PREPARATION
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INTERMITTENT WELDING
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MINIMUM WELD PASS
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WELD NEAR NEUTRAL
AXIS
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BALANCE WELD
AROUND NEUTRAL AXIS
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PRE-SET PARTS
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BACKSTEP WELDING
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WELD SEQUENCE
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WELD SEQUENCE
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PRE-BENDING
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BACK-TO-BACK
CLAMPING
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Weld Profile/Size
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Weld Profile/Size
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Weld Profile/Size
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ACCEPTABLE
GROOVE WELD PROFILE
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ACCEPTABLE
GROOVE WELD PROFILE
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UNACCEPTABLE
GROOVE WELD PROFILE
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UNACCEPTABLE
GROOVE WELD PROFILE
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UNACCEPTABLE
GROOVE WELD PROFILE
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DESIRABLE FILLET
WELD PROFILE
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ACCEPTABLE
FILLET WELD PROFILE
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UNACCEPTABLE
FILLET WELD PROFILE
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UNACCEPTABLE
FILLET WELD PROFILE
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UNACCEPTABLE
FILLET WELD PROFILE
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STRUCTURAL DEFECTS
1. Porosity2. Slag Inclusion3. Tungsten Inclusion
4. Incomplete Fusion5. Undercut/Overlap6. Incomplete Penetration
7. Underfill8. Crack9. Distortion
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Porosity
Porosity gas pores formed by entrapped
gas during solidification of molten metalWorm-hole An elongated or tubularcavity formed by entrapped gas during thesolidification of molten metal.
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Porosity
CAUSES:
1. Inadequate cleaning
2. Moisture3. Inadequate shielding4. Damaged/contaminated flux5. Windy
6. Wrong polarity
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Slag Inclusion
nonmetallic solid material entrapped inweld metal or between weld metal andbase metal
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Slag Inclusion
CAUSES:
1.Inadequate cleaning
2.Improper electrode manipulation
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Incomplete Fusion
A weld discontinuity in which fusion didnot occur between weld metal and fusionfaces or adjoining weld beads.
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Incomplete Fusion
CAUSES:
1.Low current
2.Improper electrodemanipulation
3.Inadequate cleaning4.Inadequate preheating
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Incomplete Fusion at Weld Face
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Incomplete Fusion of Flare
Bevel Groove Welds
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Incomplete Fusion Between
Weld & Base Metal
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Undercut/Overlap
1.Undercut - A groove melted into the
base metal adjacent to the weld toe orweld root and left unfilled by weldmetal.
2.Overlap - The protrusion of weld metalbeyond the weld toe or weld root.
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Undercut/Overlap
CAUSES:
1.Undercut high current
- Improper electrodemanipulation2. Overlap - low current
Improper electrode
manipulation
Incomplete
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IncompletePenetration/Underfill
1.Underfill - A condition in which the weld faceor root surface extends below the adjacent
surface of the base metal.2.Incomplete Joint Penetration - A joint root
condition in a groove weld in which weldmetal does not extend through the joint
thickness
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Partial Penetration
Partial joint penetration groove weldsare commonly specified in lowly loaded
structures. Partial penetration joint abovewithout discontinuities is an acceptablecondition where appropriate.
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Incomplete Penetration
CAUSES:
1. Wrong edge preparation Included angle Root face Root gap or root opening
2. Large electrode3. Fast travel speed
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Crack
Fracture-type discontinuity characterized
by a sharp tip and high ratio of length andwidth to opening displacement. Above areseveral different representations of weldcracking.
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Crack
CAUSES:
1. Inadequate preheating2. Wrong electrode3. Too much restraint on joint
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Longitudinal Crack
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Transverse Crack
Th C k
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Throat Crack
T C k
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Toe Crack
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Closeup of Crater Cracksin Aluminum Weld
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Propagation of Crater Crackin Aluminum Weld
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Underbead Cracks
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Radiograph of Longitudinal Crack
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Radiograph of Transverse Crack