identification of weld discountinuitie 2
TRANSCRIPT
-
8/7/2019 Identification of Weld Discountinuitie 2
1/40
1 1
Causes - welding discontinuities
Base metal, joint design
Welder skill, improper supervision
Welding consumables and shielding gases
-
8/7/2019 Identification of Weld Discountinuitie 2
2/40
1 2
As per ISO 6520-1987 Welding discontinuitiesare divided in following six groups
Group Designated Defect
1 Cracks2 Cavities
3 Solid Inclusions
4 Lack of Fusion &penetration
5 Imperfect Shape
6 Miscellaneous defects
-
8/7/2019 Identification of Weld Discountinuitie 2
3/40
1 3
-
8/7/2019 Identification of Weld Discountinuitie 2
4/40
1 4
Weld Discontinuities
1. Crater cracks2. Face cracks3. HAZ cracks4. Longitudinal cracks
5. Root cracks6. Transverse cracks7. Under bead cracks8. Lamination
9.Misalignment10.Concavity11.Excess Cap
12-Overlap13. Slag inclusion14. Lack of fusion15. Lack of penetration
16. Porosity17. Undercut/Under fill18. Spatter19. Tungsten inclusion
20. Arc strike21. Burn through22.Mechanical Damage
-
8/7/2019 Identification of Weld Discountinuitie 2
5/40
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).
-
8/7/2019 Identification of Weld Discountinuitie 2
6/40
1 6
-
8/7/2019 Identification of Weld Discountinuitie 2
7/40
-
8/7/2019 Identification of Weld Discountinuitie 2
8/40
Solidification Crack
W = Bead Width
P = Bead Depth
W
PP
W
W/P>1 W/P
-
8/7/2019 Identification of Weld Discountinuitie 2
9/40
Longitudinal Crack
-
8/7/2019 Identification of Weld Discountinuitie 2
10/40
1 10
Center Line Crack
A longitudinal crack located in the weld throat area
-
8/7/2019 Identification of Weld Discountinuitie 2
11/40
1 11
Transverse Crack
-
8/7/2019 Identification of Weld Discountinuitie 2
12/40
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
-
8/7/2019 Identification of Weld Discountinuitie 2
13/40
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, reducespeed
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
-
8/7/2019 Identification of Weld Discountinuitie 2
14/40
1 14
Porosity appears often as dark round irregular spots in clusters orrows. 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
-
8/7/2019 Identification of Weld Discountinuitie 2
15/40
1 15
Gas pore _ singular.
Blowhole _ singular.
Scattered Porosity.
Cluster Porosity.
Linear Porosity.
Piping.
Worm holes.
Cavities
Fine Severe
-
8/7/2019 Identification of Weld Discountinuitie 2
16/40
1 16
Cluster porosity is caused when electrodes are contaminated withmoisture or hydrocarbon. It appears like regular porosity in a filmbut the indications will be grouped close together.
Cavities
-
8/7/2019 Identification of Weld Discountinuitie 2
17/40
1 17
Cavities
-
8/7/2019 Identification of Weld Discountinuitie 2
18/40
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
-
8/7/2019 Identification of Weld Discountinuitie 2
19/40
1 19
Slag Inclusions are the nonmetallic solid materials trapped inweld 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
-
8/7/2019 Identification of Weld Discountinuitie 2
20/40
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
-
8/7/2019 Identification of Weld Discountinuitie 2
21/40
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
-
8/7/2019 Identification of Weld Discountinuitie 2
22/40
1 22
Lack of Fusion and Penetration
Lack of side wall fusion is a condition where the weld metal doesnot 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.
-
8/7/2019 Identification of Weld Discountinuitie 2
23/40
1 23
Lack of interrun fusion is a condition where the weld metal doesnot 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
-
8/7/2019 Identification of Weld Discountinuitie 2
24/40
1 24
Imperfect
Undercut is an erosion of the base metal next to the toe of the weldface. It appears in radiograph as a dark irregular line on outer edge
of the weld.
Imperfect Shape
-
8/7/2019 Identification of Weld Discountinuitie 2
25/40
1 25
Root undercut is an erosion of the base metal next to the root of theweld. 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
-
8/7/2019 Identification of Weld Discountinuitie 2
26/40
1 26
Imperfect Shape
-
8/7/2019 Identification of Weld Discountinuitie 2
27/40
1 27
Root concavity or suck backis a condition where the weld metalhas 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
-
8/7/2019 Identification of Weld Discountinuitie 2
28/40
1 28
Excessive reinforcement is an area of a weld added in excess ofthat 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
-
8/7/2019 Identification of Weld Discountinuitie 2
29/40
-
8/7/2019 Identification of Weld Discountinuitie 2
30/40
1 30
Imperfect Shape
-
8/7/2019 Identification of Weld Discountinuitie 2
31/40
1 31
Imperfect Shape
-
8/7/2019 Identification of Weld Discountinuitie 2
32/40
1 32
Imperfect Shape
-
8/7/2019 Identification of Weld Discountinuitie 2
33/40
1 33
Imperfect Shape
-
8/7/2019 Identification of Weld Discountinuitie 2
34/40
1 34
Imperfect Shape
-
8/7/2019 Identification of Weld Discountinuitie 2
35/40
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
-
8/7/2019 Identification of Weld Discountinuitie 2
36/40
1 36
Distortion:
Imperfect Shape
-
8/7/2019 Identification of Weld Discountinuitie 2
37/40
1 37
Burn through (icicles) results when too much heat causes weld topierce 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 onthe top or bottom surfaces of the weld or contained within the
weld. On radiograph they appear as light, "wire like" indications.
-
8/7/2019 Identification of Weld Discountinuitie 2
38/40
1 38
Miscellaneous discontinuities
-
8/7/2019 Identification of Weld Discountinuitie 2
39/40
1 39
Lamellar Tearing:
-
8/7/2019 Identification of Weld Discountinuitie 2
40/40
1 40
Miscellaneous discontinuities
Arc Strike
Spatters
Torn SurfaceGrinding Marks
Chipping Marks
Underflushing
Poor Start