Svetskommissionen
How to examine a weld,
review of weld defects, and
why they occur
SS-EN ISO 17637:2017
Non-destructive testing of welds – Visual testing of
fusionwelded joints
• Replaces SS-EN ISO 17637:2011 and SS-EN 970.
• The illuminance at the surface shall be a minimum of
350 lx. However, 500 lx is recommended.
• Remote inspection using mirrors, boroscopes, fibre optic
cables or cameras shall be considered when the access
for testing is not possible or when specified by an
application standard.
SS-EN ISO 17637:2017
• Visual testing of welds and the evaluation of results for
final acceptance shall be performed by qualified and
capable personnel. It is recommended that the
personnel performing indirect visual testing is qualified
according to ISO 9712 or at an appropriate level in the
relevant industry sector.
• The examiner shall have access to the necessary
inspection and production documentation required.
• Undergo an annual test of visual acuity according to EN
ISO 9712.
SS-EN ISO 17637:2017
For direct inspection, the access shall be sufficient to place the eye within 600 mm of
the surface to be examined and at an angle not less than 30°.
Source: Figure 1, ISO 17637:2017
SS-EN ISO 17637:2017
Visual testing:
• Prior to welding
• During welding
• After completion of the weld
• Final testing shall be done after eventual heat treatment
Examples of test equipment:
Multi-purpose weld gauge, caliper, mirror, flashlight, Tape Measure,
magnifying glass, flashlight, camera.
SS-EN ISO 17637:2017
Visual testing prior to welding:
• Verify the shape and dimensions of the weld preparation.
• Check the cleanliness of the fusion faces and adjacent surfaces.
• Check the surface treatment so that it has been carried out in accordance
with the requirements.
• Verify that the parts to be welded are correctly fixed in relation to each
other.
SS-EN ISO 17637:2017
Visual testing during welding:
• Check that each run or layer of weld metal is cleaned before it is covered
by a further run.
• Verify that here are no visible imperfections, e.g. cracks or cavities.
• Check the transition between the runs, between the weld and the parent
metal before welding the next run.
• Verify that the depth and shape of gouging is in accordance with the WPS.
• Verify that any necessary repairs/remedial action conforms to the original
requirements of the WPS.
SS-EN ISO 17637:2017
Visual testing after completion of the weld:
Check that the weld meet the requirements according to the application or product
standard e.g. ISO 5817.
Cleaning and dressing
• Check that all slag has been removed to avoid imperfections being obscured.
• Verify that there are no tool impressions or blow marks.
• When weld dressing is required, ensure that overheating of the joint due to
grinding, grinding marks, and an uneven finish are avoided.
• Verify that fillet welds and butt welds to be dressed flush, the transition of joint
merges smoothly with the parent metal without under flushing.
SS-EN ISO 17637:2017
Profile and dimensions
• Check the profile of the weld face and the height of any excess weld metal so that
it meets the requirements.
• Ensure the surface of the weld is regular and also that the weld shows an even
and satisfactory visual appearance.
• Ensure that the weld width is consistent over the whole of the joint and that it
meets the requirements.
SS-EN ISO 17637:2017
Weld root and surfaces
• Verify for single-sided butt welds, the penetration, root concavity and any burnthrough or shrinkage grooves are within the requirements.
• Verify that any undercut is within the requirements.
• Check after imperfections such as cracks or porosity, in the weld surface or heat
affected zones comply with the requirements.
• Verify any attachments temporarily welded to the object to facilitate production or
assembly and which are prejudicial to the function of the object or the ability to
examine it are removed so that the object is not damaged; the area where the
attachment was fixed shall be checked to ensure freedom of cracks.
• Check that any arc strikes are within the requirements.
SS-EN ISO 5817:2014
Welding – Fusion-welded joints in steel, nickel, titanium and their
alloys (beam welding excluded) – Quality levels for imperfections
• It is covering all types of steel, nickel, titanium and their alloys. It
applies to material thickness ≥ 0,5 mm.
• It contains fusion weld imperfections based on the designations
given in ISO 6520-1. ISO 6520-1 gives the classification of
geometric imperfections in metallic materials.
SS-EN ISO 5817:2014
The version EN ISO 5817:2014 superseeds EN ISO 5817:2007 and
previous releases.
The biggest change from version 2007 to 2014 is that Annex C has
been added giving additional requirements on quality levels in order to
meet the fatigue class (FAT) requirement.
SS-EN ISO 5817:2014
The standard is divided into 4 different parts.
• Part 1 - Surface imperfections
• Part 2 - Internal imperfections
• Part 3 - Imperfections in joint geometry
• Part 4 - Multiple imperfections
Part 1 and Part 3 shall be used during visual testing.
SS-EN ISO 5817:2014
The standard is divided into 3 different quality levels, B, C and D.
B has the highest requirements.
It applies to material thickness ≥ 0,5 mm.
The quality levels are divided into two different dimensions:
• t = 0,5 - 3 mm
• t = >3 mm
SS-EN ISO 5817:2014
What is an imperfection? - Discontinuity in the weld or a deviation from the
intended geometry. Lack of continuity.
Short imperfections
• Weld length is more than 100 mm: Imperfections whose total length is not
greater than 25 mm in the 100 mm of the weld which contains the greatest
number of imperfections.
• Weld length is less than 100 mm: imperfections whose total length is not
greater than 25 % of the length of the weld
Systematic imperfections
• Imperfections that are repeatedly distributed in the weld over the weld
length to be examined, the size of a single imperfection being within the
specified limits
SS-EN ISO 5817:2014
Smooth weld transition
• Even surface with no irregularities or sharpness at the transition between
the weld bead and the parent material
SS-EN ISO 10042:2005
Arc-welded joints in aluminium and its alloys – Quality levels for
imperfections
• It is covering arc-welded joints in aluminium and its alloys. It applies to
material thickness ≥ 0,5 mm.
• It contains fusion weld imperfections based on the designations given in
ISO 6520-1.
• The standard is divided into 4 different parts. Part 1 and Part 3 shall be
used during visual testing
• The standard is divided into 3 different quality levels, B, C and D. B has
the highest requirements.
SS-ISO 6520-1
Classification of geometric imperfections in
metallic materials
• The standard serves as the basis for a precise
classification and description of weld
imperfections.
• The types of imperfections are defined with
explanations and illustrations.
Crack
What is a crack?
Imperfection produced by a local rupture in the solid state which can
arise from the effect of cooling or stresses.
Crack (100) - Solidification crack
Crack (100) - Solidification crack
Cause:
Prevention:
• Generated under high temperatures about 1200
• Widht / Depth ratio ≥ 1-1,5
°C…under influence of shrinkage stresses.
• Solidification cracking is associated with
impurities, particularly sulfur and phosphorus.
• Solidification cracks can be deep and can
seriously reduce the efficiency of a joint.
• Manganese / Sulfur ≥ 20
• Reduce parent material in weld.
• UCS: Units of Crack Susceptibility.
UCS: 230C+190S+75P+45Nb-12,3Si-5,4Mn-1
• UCS less than = 10 high resistance.
UCS above = 30 low resistance.
Crack (100) - Hydrogen crack
Crack (100) - Hydrogen crack
Cause:
Prevention:
• Three conditions for hydrogen cracks to occur:
• Use preheat temperature.
1. Stress
• Carbon equivalent (CE) important factor.
2. Hydrogen
• Use filler metal with low hydrogen content.
3. Hardened zone
• Use welding plan
• Generated under temperatures below 200°C
• Wait with NDT (Non Destructive Testing).
They can occur after 16-72 hours.
Crack (100)
Limits for imperfections for quality levels
Remarks:
D
C
B
> 0,5 mm
Not permitted
Not permitted
Not permitted
Pore
What is a pore?
Gas cavity of essentially spherical form.
Pore
Cause of pores:
Prevention of pores:
• Moisture in the filler metal or on joint surfaces.
• Avoid moisture and impurities in the filler
• Inadequate shielding gas flow.
• Excessive shielding gas flow. This can cause
aspiration of air into the gas stream.
• Severely clogged gas nozzle or damaged gas
supply system (leaking hoses, fittings, etc.)
• An excessive wind in the welding area. This
can blow away the gas shield. Eg open ports.
• Primer.
metal and joint surfaces.
• Check the gas supply at regular intervals.
• Avoid turbulence of gas flow, check
welding electric parameters.
• Reduce thickness of primer.
Surface pore (2017)
Limits for imperfections for quality levels
Remarks:
Only short imperfections are allowed.
Smooth transition is required.
D
C
B
Short imperfections 0,5-3 mm
Short imperfections > 3 mm
BW: d ≤ 0,3 s
FW: d ≤ 0,3 a
Not permitted
Not permitted
BW: d ≤ 0,3 s
(but max 3 mm)
FW: d ≤ 0,3 a
(but max 3 mm)
BW: d ≤ 0,2 s
(but max 2 mm)
FW: d ≤ 0,2 a
(but max 2 mm)
Not permitted
End crater pipe / crater crack
What is end crater pipe?
Open crater with a hole reducing the cross-section of the weld.
What is crater crack?
Crack in the crater at the end of a weld.
End crater pipe / crater crack
Cause:
Prevention:
• Lack of welder skill due too high current.
• Use correct crater filling technique
• Depth can be up to half of the weld hight.
• Use slope downs.
End crater pipe (2025)
Limits for imperfections for quality levels
Remarks:
D
C
B
Short imperfections 0,5-3 mm
Short imperfections > 3 mm
h ≤ 0,2 t
Not permitted
Not permitted
h ≤ 0,2 t,
but max. 2 mm
h ≤ 0,1 t,
but max. 1 mm
Not permitted
Crater crack (104)
Limits for imperfections for quality levels
Remarks:
D
C
B
> 0,5 mm
Not permitted
Not permitted
Not permitted
Sagging / Incompletely filled groove
What is sagging?
Weld metal collapse due to gravity.
What is incompletely filled groove?
Longitudinal continuous or intermittent channel in the surface of a weld
due to insufficient deposition of weld filler material.
Sagging (509), Incompletely filled groove (511)
Cause:
Prevention:
• Insufficient filler metal
• Adjust parameters.
• Current or wire feed too low
• Teach welder.
• Too high travel speed.
Sagging (509), Incompletely filled groove (511)
Limits for imperfections for quality levels
Remarks:
Only short imperfections are allowed.
Smooth transition is required.
D
C
B
Short imperfections 0,5-3 mm
Short imperfections > 3 mm
h ≤ 0,25 t
h ≤ 0,1 t
Not permitted
h ≤ 0,25 t
but max. 2 mm
h ≤ 0,1 t
but max.1 mm
h ≤ 0,05 t
but max. 0,5 mm
Excess penetration
What is excess penetration?
Reinforcement of the butt weld on the root side is too large.
Excess penetration
Cause:
Prevention:
• Joint gap is too large.
• Verify that joint-fit-up is according to WPS.
• Root face too small.
• Train welder.
• Heat input is too high.
Excess penetration (504)
Limits for imperfections for quality levels
Remarks:
D
C
B
0,5-3 mm
> 3 mm
h ≤ 1 mm + 0,6 b
h ≤ 1 mm + 0,3 b
h ≤ 1 mm + 0,1 b
h ≤ 1 mm + 1,0 b,
but max. 5 mm
h ≤ 1 mm + 0,6 b,
but max. 4 mm
h ≤ 1 mm + 0,2 b,
but max. 3 mm
Lack of fusion
What is lack of fusion?
Lack of union between the weld metal and the parent material or
between the successive layers of weld metal.
Lack of fusion
Cause:
Prevention:
• Too narrow joint preparation.
• Use a sufficiently wide joint preparation.
• Incorrect welding parameters.
• Adjust welding parameters (increase current
or travel speed).
• Molten metal flowing ahead of arc.
• Improve electrode angle and work position.
• Arc length too long.
• Sharp edges between weld strings.
• Insufficient cleaning.
Lack of fusion (401)
Limits for imperfections for quality levels
Remarks:
Also referred to as “cold laps”.
D
C
B
> 0,5 mm
Not permitted
Not permitted
Not permitted
Undercut
What is undercut?
Irregular groove at a toe of a run in the parent material or in previously
deposited weld metal.
Undercut
Cause:
Prevention:
• Travel speed is too high.
• Decrease the travel speed.
• Too high voltage.
• Decrease the arc voltage and/or current.
• Welding arc is too long.
• Maintain the correct arc length.
• High welding current.
• Deposit an additional weld bead.
• Grind a radius in the load direction.
Continuous undercut (5011), Intermittent undercut (5012)
Limits for imperfections for quality levels
Remarks:
Only short imperfections are allowed for 0,5-3 mm.
Smooth transition is required.
This is not regarded as a systematic imperfection.
D
C
B
0,5-3 mm
> 3 mm
h ≤ 0,2 t
h ≤ 0,1 t
Not permitted
h ≤ 0,2 t,
but max. 1 mm
h ≤ 0,1 t,
but max. 0,5 mm
h ≤ 0,05 t,
but max. 0,5 mm
Overlap
What is overlap?
Excessive weld metal covering the parent material surface but not
fused to it.
Overlap
Cause:
Prevention:
• Poor manipulation of the electrode or welding
• Teach welder.
gun.
• Reduce current or increase welding speed.
• Weld pool is large.
• Cleaning of the parent material before
• Oxides on the metal surface prevent the weld
welding.
metal fusing with the parent metal.
Overlap (506)
Limits for imperfections for quality levels
Remarks:
D
C
B
> 0,5 mm
h ≤ 0,2 b
Not permitted
Not permitted
Root concavity
What is root concavity?
Shallow groove due to shrinkage of a butt weld at the root.
Root concavity
Cause:
Prevention:
• Root gap either too small or, in some cases, too
• Verify that joint-fit-up is according to WPS.
large.
• Excessively high welding speeds.
• Melting of the root pass by the second pass.
• Verify the parameters and that they are being
followed.
Root concavity (515)
Limits for imperfections for quality levels
Remarks:
Only short imperfections are allowed.
Smooth transition is required.
D
C
B
Short imperfections 0,5-3 mm
Short imperfections > 3 mm
h ≤ 0,2 mm + 0,1 t
h ≤ 0,1 t
Not permitted
h ≤ 0,1 t,
but max.1 mm
h ≤ 0,05 t,
but max. 0,5 mm
(short Imperfections
doesn’t apply)
h ≤ 0,2 t,
but max. 2 mm
Incorrect weld toe
What is incorrect weld toe?
Too small an angle between the plane of the parent material surface
and a plane tangential to the weld-run surface at the toe of the weld.
Incorrect weld toe
Cause:
Prevention:
• See excess penetration, excess weld metal and
• See excess penetration, excess weld metal
excessive convexity.
and excessive convexity..
Incorrect weld toe (505)
Limits for imperfections for quality levels
Remarks:
D
C
B
> 0,5 mm
Butt welds α ≥ 90°
Butt welds α ≥ 110°
Butt welds α ≥ 150°
Fillet welds α ≥ 90°
Fillet welds α ≥ 100°
Fillet welds α ≥ 110°
Linear misalignment
What is linear misalignment?
Misalignment between two welded pieces such that they are not in the
same required parallel plane, even though their surface planes are
parallel.
Linear misalignment
Cause:
Prevention:
• Poor component fit-up before welding.
• Be careful about the fitting, especially when
• Tacks that break during welding.
there is variations in the shape and thickness.
• Add more tack welds.
Linear misalignment (507)
Limits for imperfections for quality levels
Plates and longitudinal welds 0,5-3 mm och ≥ 3 mm
D
C
B
h ≤ 0,2 mm + 0,25 t
h ≤ 0,2 mm + 0,15 t
h ≤ 0,2 mm + 0,1 t
h ≤ 0,25 t
but max. 5 mm
h ≤ 0,15 t,
but max. 4 mm
h ≤ 0,1 t,
but max. 3 mm
Circumferential welds ≥ 0,5 mm
D
h ≤ 0,5 t,
but max. 4 mm
C
h ≤ 0,5 t,
but max. 3 mm
B
h ≤ 0,5 t,
but max. 2 mm
Incomplete root penetration
What is incomplete root penetration?
One or both fusion faces of the root are not melted.
Incomplete root penetration
Cause:
Prevention:
• Excessive thick root face.
• Increase arc power or decrease travel speed.
• Insufficient root gap.
• Be careful with tack welding.
• Low heat input.
• Add fixation plates.
• Electrode to large (low current density).
• Suitable welding sequence due to creep.
• Vertical down welding.
• Failure with grinding or gouging operation
before welding from the other side.
Incomplete root penetration (4021)
Limits for imperfections for quality levels
Remarks:
Only short imperfections are allowed.
D
C
B
> 0,5 mm
h ≤ 0,2 t
but max. 2 mm
Not permitted
Not permitted
Excess weld metal / Excessive convexity
What is excess weld metal?
Reinforcement of the butt weld on the face is too large.
What is excessive convexity?
Reinforcement of the fillet is too large.
Excess weld metal / Excessive convexity
Cause:
Prevention:
• Poor technique.
• Teach welder.
• Deposition of large volumes of 'cold' weld
• Adjust parameters on WPS.
metal.
Excess weld metal, butt weld (502)
Excessive convexity, fillet weld (503)
Limits for imperfections for quality levels
Butt weld ≥ 0,5
Remarks:
Smooth transition is required.
D
h ≤ 1 mm + 0,25 b,
but max. 10 mm
C
h ≤ 1 mm + 0,15 b,
but max. 7 mm
B
h ≤ 1 mm + 0,1 b,
but max. 5 mm
Fillet weld ≥ 0,5
D
h ≤ 1 mm + 0,25 b,
but max. 5 mm
C
B
h ≤ 1 mm + 0,15 b,
but max. 4 mm
h ≤ 1 mm + 0,1 b, but
max. 3 mm
Excessive asymmetry of fillet weld
What is excessive asymmetry of fillet weld?
Unequal leg length.
z2
z1
Excessive asymmetry of fillet weld
Cause:
Prevention:
• Incorrect electrode position or gravity pulling
• Adjust electrode position.
the molten pool towards one face of the joint.
Excessive asymmetry of fillet weld (512)
Limits for imperfections for quality levels
Remarks:
In cases where an asymmetric fillet weld has not
been prescribed.
D
C
B
> 0,5 mm
h ≤ 2 mm + 0,2 a
h ≤ 2 mm + 0,15 a
h ≤ 1,5 mm + 0,15 a
Incorrect root gap for fillet welds
What is incorrect root gap for fillet welds?
Excessive or insufficient gap between the parts to be joined.
Incorrect root gap for fillet welds
Cause:
Prevention:
• Poor workshop practice
• Verify the gap before welding
• Poor dimensioning and tolerance dimensions
on drawings
• May increase the risk of cracking.
Incorrect root gap for fillet welds (617)
Limits for imperfections for quality levels
Remarks:
Gaps exceeding the appropriate limit may, in certain cases, be
compensated for by a corresponding increase in the throat
thickness.
D
C
B
Short imperfections 0,5-3 mm
Short imperfections > 3 mm
h ≤ 0,5 mm + 0,1 a
h ≤ 0,3 mm + 0,1 a
h ≤ 0,2 mm + 0,1 a
h ≤ 1 mm + 0,3 a,
but max. 4 mm
h ≤ 0,5 mm + 0,2 a,
but max. 3 mm
h ≤ 0,5 mm + 0,1 a,
but max. 2 mm
Stray arc
What is stray arc?
Local damage to the surface of the parent material adjacent to the
weld, resulting from arcing or striking the arc outside the joint
preparation.
Stray arc
Cause:
Prevention:
• Poor access to work.
• Improve access.
• Accidental contact of electrode or welding
• Check current return clamp.
torch.
• Check insulation on electrode holder and
• Loose current return clamp or missing
torch.
insulation on electrode holder or torch.
• Most common for Manual metal arc welding
(111).
• Fast cooling creating small hard spots which
may contain cracks.
Stray arc (601)
Limits for imperfections for quality levels
Remarks:
D
C
B
> 0,5 mm
Permitted, if the
properties of the
parent metal are not
affected.
Not permitted
Not permitted
Spatter
What is spatter?
Globules of weld metal or filler metal expelled during welding and
adhering to the surface of parent material or solidified weld metal.
Spatter
Cause:
Prevention:
• Short or long welding arc
• Modify electrical settings
• Cleanliness of the base material surface
• Ensure
• Selection of gas (CO2 welding yields more)
• Reduce arc length
• Welding at a wrong angle
• Imbalance between voltage and amperage
• Incorrect wire feed speed
• Magnetic arc blow.
Spatter (602)
Limits for imperfections for quality levels
Remarks:
D
C
B
> 0,5 mm
Acceptance depends
on application, e.g.
material, corrosion
protection
Acceptance depends
on application, e.g.
material, corrosion
protection
Acceptance depends
on application, e.g.
material, corrosion
protection