WELD DISCOUNTINUITESS

1. 1 1
Causes of welding discontinuities
Base metal, joint design
Welder skill, improper supervision
Welding consumables and shielding gases

2. 1 2
As per ISO 6520-1987 Welding discontinuities
are divided in following six groups
Group Designated Defect
1 Cracks
2 Cavities
3 Solid Inclusions
4 Lack of Fusion &
penetration
5 Imperfect Shape
6 Miscellaneous defects

3. 1 3

4. 1 4
Weld Discontinuities
1. Crater cracks
2. Face cracks
3. HAZ cracks
4. Longitudinal cracks
5. Root cracks
6. Transverse cracks
7. Under bead cracks
8. Lamination
9.Misalignment
10.Concavity
11.Excess Cap
12-Overlap
13. Slag inclusion
14. Lack of fusion
15. Lack of penetration
16. Porosity
17. Undercut/Under fill
18. Spatter
19. Tungsten inclusion
20. Arc strike
21. Burn through
22.Mechanical Damage

5. CRACKS
• Crack is a tight linear separation of metal that
can be very short to very long indications
• Cracks are grouped as hot or cold cracks.
• Hot cracks usually occur as the metal solidifies
at elevated temperatures.
• Cold cracks occur after the metal has cooled to
ambient temperatures ( delayed cracks).

6. 1 6

8. Solidification Crack
W = Bead Width
P = Bead Depth
W
P P
W
W/P>1 W/P<1
That is W/P

9. Longitudinal Crack

10. 1 10
Center Line Crack
A longitudinal crack located in the weld throat area

11. 1 11
Transverse Crack

12. 1 12
Crater Crack
Joint Line Crater
*
Crater crack is generally in the shape of a star in the
center of the terminated weld bead.It is a hot crack

13. 1 13
Causes Remedies
Highly restrained joint Preheat, Stress relief, welding sequence change
Excessive dilution Change welding current & speed, use DC-, buttering
Defective electrodes or
flux
Use new electrodes or flux, check baking cycle
Poor fit up Reduce root opening, build up edges
Small weld bead Increase electrode size, raise welding current,
reduce speed
High S in base metal Use low-S filler
Crater cracking Fill crater before extinguishing arc
Angular distortion Change to balanced welding
Causes & Remedies- Weld Cracking

14. 1 14
Porosity appears often as dark round irregular spots in clusters or
rows. Sometimes it is elongated and may have an appearance of a
tail. This is the result of gas attempting to escape while the metal is
still in a liquid state & is called wormhole porosity. All porosity is
indeed a void will have a darker density than the surrounding.
Cavities

15. 1 15
•Gas pore _ singular.
•Blowhole _ singular.
•Scattered Porosity.
•Cluster Porosity.
•Linear Porosity.
•Piping.
• Worm holes.
Cavities
Fine Severe

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Cluster porosity is caused when electrodes are contaminated with
moisture or hydrocarbon. It appears like regular porosity in a film
but the indications will be grouped close together.
Cavities

17. 1 17
Cavities

18. 1 18
Causes & Remedies of Porosity
Causes Remedies
Excessive H2,N2,O2 in
welding atmosphere
Use low-H2 electrodes, high deoxider fillers,
increase shielding gas flow
High solidification rate Use preheat or increase heat input
Dirty base metal Clean joint face and adjacent surfaces
Improper arc length.
Welding current or
electrode manipulation
Change welding conditions or techniques
Galvanized steel Use E6010 electrodes and volatilize zinc ahead of
weld pool
Excessive moisture in
electrode
Check baking and storing of electrodes, Preheat
base metal

19. 1 19
Slag Inclusions are the nonmetallic solid materials trapped in
weld or between the weld and base metal. In a radiograph, dark,
jagged asymmetrical shapes within the weld or along the weld joint
areas are indicative of slag inclusions.
Solid Inclusions

20. 1 20
Tungsten inclusions. Tungsten is a brittle and dense material
used as an electrode in tungsten inert gas welding. If an incorrect
welding procedures & skill is performed, then only the tungsten gets
trapped. Radiographically, tungsten is more dense than aluminum
or steel; therefore, it shows as a lighter area with a distinct outline
on the radiograph
Solid Inclusions

21. 1 21
Oxide inclusions are usually visible on the surface of a weld mtal
(especially aluminum). Oxide inclusions are less dense than the surr
-ounding metals and, thus it appears as dark irregular shaped discon
-tinuity in radiograph. This is also referred as puckering in ISO.
Solid Inclusions

22. 1 22
Lack of Fusion and Penetration
Lack of side wall fusion is a condition where the weld metal does
not fuse with the base metal. Appearance on radiograph is usually a
darker line or lines oriented in the direction of the weld seam along
the weld joining area.

23. 1 23
Lack of interrun fusion is a condition where the weld metal does
not fuse with the base metal or the previous weld bead (interpass
cold lap). The arc does not melt the base metal and causes the
molten puddle to flow into the base metal without the proper
bonding.
Lack of Fusion and Penetration

24. 1 24
Imperfect
Undercut is an erosion of the base metal next to the toe of the weld
face. It appears in radiograph as a dark irregular line on outer edge
of the weld.
Imperfect Shape

25. 1 25
Root undercut is an erosion of the base metal next to the root of the
weld. It appears in radiographic images as a dark irregular line offset
from the centerline of the weldment. Undercutting is not as straight
edged as LOP because it does not follow the straight edge
Imperfect Shape

26. 1 26
Imperfect Shape

27. 1 27
Root concavity or suck back is a condition where the weld metal
has contracted as it cools down & has been drawn up into the root of
the weld. On a film it appears similar to the lack of root penetration
but the line has irregular wide edges and placed in the middle.
Imperfect Shape

28. 1 28
Excessive reinforcement is an area of a weld added in excess of
that specified by the drawings and codes. The appearance on a
radiograph is a localized & less darker area. A visual examination
will easily determine if the weld reinforcement is in excess.
Imperfect Shape

29. 1 29
Underfilling is an area where the deposited weld metal is less than
the required thickness. It is easy to determine by RT films, because
the image density in the area of inadequacy will be darker than the
surrounding image density.
Imperfect Shape

30. 1 30
Imperfect Shape

31. 1 31
Imperfect Shape

32. 1 32
Imperfect Shape

33. 1 33
Imperfect Shape

34. 1 34
Imperfect Shape

35. 1 35
Misalignment: The radiographic image is a noticeable difference in
density between the two mismatched pieces. The difference in
density is caused by the difference in material thickness. The dark,
straight line is caused by failure of the weld metal to fuse with the
land area.
Imperfect Shape

36. 1 36
Distortion:
Imperfect Shape

37. 1 37
Burn through (icicles) results when too much heat causes weld to
pierce through. Lumps of weld metal sag through the seam creating
a thick globular condition on the root face. On a radiograph, burn
through appears as dark spots surrounded by light globular areas.
Whiskers are the short lengths of electrode wire, visible on
the top or bottom surfaces of the weld or contained within the
weld. On radiograph they appear as light, "wire like" indications.

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Miscellaneous discontinuities

39. 1 39
Lamellar Tearing:

40. 1 40
Miscellaneous discontinuities
Arc Strike
Spatters
Torn Surface
Grinding Marks
Chipping Marks
Underflushing
Poor Start