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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