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impact of the failure of the welded
structure,
• the possibility of routine operational
inspection and control.
10.1. Approval procedures
The procedures are either contractual
between client and supplier
or self-regulated by the fabricator.
Welders must be certified
and qualified in accordance with
EN ISO 9606-2. Welding procedure
specification must be in
accordance with EN ISO 15609-
1, EN ISO 15612, EN ISO 15613
and EN ISO15614-2.
Test specimens must be submitted
for tensile or bending tests.
Bending tests are important
because they:
• detect bonding that is hard to
identify in non-destructive testing,
• help achieve a good balance
of parameters with a view to preventing
these defects.
The type of inspection carried
out on welded joints will naturally
depend on the work rate of
the weldments.
In the fabrication shop it is possible
to perform the following
non-destructive tests (NDT) in
addition to visual inspection:
• dye penetration tests are valuable
for detecting leaks and
emergent cracks,
• weld shape tests (geometrical
shape),
• radiography, used to detect
internal defects (porosity, cracks,
inclusions) in butt joints,
• ultrasonic tests
It may also be prudent to perform
some destructive tests on
reference specimens.
An inspection plan must be
made containing:
• extent of inspection before
welding
• extent of inspection and NDT
• NDT methods to be used
• acceptance criteria (quality level)
in accordance with EN ISO 10042
10.2. Inspecting welded joints
123
EUROPEAN ALUMINIUM ASSOCIATION
Weld defects and quality levels
are given in EN ISO 10042.
Guidance for choice of quality
level is given in EN 1090-3.
An international nomenclature of
defects has been established and
is given in EN ISO 6520-1 which
lists 6 groups of imperfections:
• Group 100: Cracks
• Group 200: Cavities and
wormholes
• Group 300: Solid inclusions
• Group 400: Lack of fusion and
penetration
• Group 500: Defects of shape
• Group 600: Sundry defects
LISTS SOME COMMON WELD DEFECTS AND THEIR CAUSES
TABLE VIII.4
N° Type of Defect Likely Cause Photos of Imperfections
101 Cracks Base alloy unsuitable
Poor choice of filler metal
Incorrect welding sequence
Excessive clamping
Sudden cooling
104 Crater cracks Pass finished with sudden arc cutoff
2012 Irregular wormholes Work inadequately degreased
Work and/or filler wire dirty or wet
Insufficient protection by inert gas
(low gas flow or leak in the system)
Pass begun on cold component
High arc voltage
Weld cooled too quickly
2014 Aligned wormholes Incomplete penetration (double pass)
Temperature gradient between
backing and work too abrupt
Excessive gap between edges of the joint
300 Solid inclusions Dirty metal (oxides, brush hairs)
303 Oxide inclusions Poor gas shielding
Metal stored in poor conditions
Castings
Defect 104
Defect
2012
Defect 101
10.3. Weld defects & approval criteria
124
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER VIII WELDING 124 | 125
N° Type of Defect Likely Cause Photos of Imperfections
3041 Tungsten inclusions Electrode diameter too small
(TIG) Poor handling by welder
Excessive current density
Poor quality of tungsten electrode
402 Incomplete penetration Inadequate cleaning (presence of oxide)
Incorrect bevel preparation on thick work
(too tight, excessive shoulder)
Gap between workpieces too small
(or incon-sistent)
Low current, especially at the start
of the seam
Welding speed too fast
High arc voltage
4011 Lack of fusion High arc voltage
on edges Low current, especially at the start
of the seam
Work cold (difference in thickness
between materials to be welded)
502 Excessive thickness Poor power control
(poor U/I match)
Welding speed too slow
Poor edge preparation on thick work
Insufficient starting current
507 Misalignment Work positioned incorrectly
Incorrect welding sequence
508 Angle defect Excessive welding power
Incorrect welding sequence
509 Collapse Wire speed too fast
Torch speed too slow
Poor torch guidance
602 Splatter (or beads) Incorrect arc control
Problem in electrical contact to ground
Defect 402
Defect 502
Defect 507
Defect 402
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