In the context of fusion welding, the welding imperfection that can be encountered during inspections are classified and described in the standard EN ISO 6520-1.
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Classification of types of defects
The standard EN ISO 6520-1 classifies and lists about a hundred imperfections in welding seams. Here is an example:
The various types of defects in welding seams are classified by the standard into 6 groups:
1
Cracks
2
Cavities
3
Solid inclusions
4
Lack of fusion and penetration
5
Shape and dimensional imperfections
6
Miscellaneous imperfections
Complete list of imperfections
| Group | Reference | Name | Description | Visual |
|---|---|---|---|---|
| 1 | 100 | Crack | An imperfection produced by a local rupture locale à rétat solide en arise from the effect of cooling or stresses | |
| 1 | 1001 | Microcrak | A crack only visible under the microscope | |
| 1 | 101 | Longitudinal crack | A crack essentially parallel to the axis of the weld |
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| 1 | 1011 | Longitudinal crack | A crack essentially parallel to the axis of the weld in the weld metal |
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| 1 | 1012 | Longitudinal crack | A crack essentially parallel to the axis of the weld at the wetd junction |
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| 1 | 1013 | Longitudinal crack | A crack essentially parallel to the axis of the weld in the heat affected zone |
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| 1 | 1014 | Longitudinal crack | A crack essentially parallel to the axis of the weld in the parent metal |
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| 1 | 102 | Transverse crack | A crack essentially transverse to the axis of the weld |
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| 1 | 1021 | Transverse crack | A crack essentially transverse to the axis of the weld in the weld metal |
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| 1 | 1023 | Transverse crack | A crack essentially transverse to the axis of the weld in the heat affected zone |
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| 1 | 1024 | Transverse crack | A crack essentially transverse to the axis of the in the parent metal |
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| 1 | 103 | Radiating crack | Cracks radiating from a common point NOTE - Small cracks of this type are called ‘star cracks' |
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| 1 | 1031 | Radiating crack | Cracks radiating from a common point in the weld metal |
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| 1 | 1033 | Radiating crack | Cracks radiating from a common point in the heat-affected zone |
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| 1 | 1034 | Radiating crack | Cracks radiating from a common point in the parent metal | |
| 1 | 1045 | Crater crack | A crack in the crater at the end of a weld which longitudinal |
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| 1 | 1046 | Crater crack | A crack in the crater at the end of a weld which transverse |
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| 1 | 1047 | Crater crack | A crack in the crater at the end of a weld which radiating (star cracking) |
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| 1 | 105 | Group of disconnected cracks | Group of disconnected cracks in any direction |
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| 1 | 1051 | Group of disconnected cracks | Group of disconnected cracks in any direction in the weld metal |
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| 1 | 1053 | Group of disconnected cracks | Group of disconnected cracks in any direction in the heat affected zone |
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| 1 | 1054 | Group of disconnected cracks | Group of disconnected cracks in any direction in the parent metal |
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| 1 | 106 | Branching cracks | A group of connected cracks originating from a common crack and distinguishable from a group of disconnected cracks (105) and from radiating cracks (103) |
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| 1 | 1061 | Branching cracks | A group of connected cracks originating from a common crack and distinguishable from a group of disconnected cracks (105) and from radiating cracks (103) in the weld metal |
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| 1 | 1063 | Branching cracks | A group of connected cracks originating from a common crack and distinguishable from a group of disconnected cracks (105) and from radiating cracks (103) in the heat affected zone |
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| 1 | 1064 | Branching cracks | A group of connected cracks originating from a common crack and distinguishable from a group of disconnected cracks (105) and from radiating cracks (103) in the parent metal |
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| 2 | 200 | Cavity | Cavity | |
| 2 | 2011 | Gas pore | A gas cavity of essentially spherical form |
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| 2 | 2012 | Uniformly distibruted porosity | A number of gas pores distributed in a substantially uniform manner throughout the weld metal; not to be confused with linear porosity (2014) and clustered porosity (2013) |
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| 2 | 2013 | Clustered (localized) porosity | A group of gas pores having a random geometric distribution |
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| 2 | 2014 | Linear porosity | A row of gas pores situated parallel to the axis of the weld |
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| 2 | 2015 | Elongated cavity | A large non-spherical cavity with its major dimension approximately parallel to the axis of the weld |
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| 2 | 2016 | Worm-hole | A tubular cavity in weld metal caused by release of gas. The shape and position of worm-holes are determined by the mode of solidification and the sources of the gas. Generally they are grouped in clusters and distributed in a herringbone formation. Sorne worm-holes may break the surface of the weld |
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| 2 | 2017 | Surface pore | A gas pore which breaks the surface of the weld |
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| 2 | 2018 | Surface porosity | Porosity appearing at the surface of the weld; single or multiple gas cavities that break the surface of the weld | |
| 2 | 2021 | Interdendritic shrinkage | Elongated shrinkage cavity that can contain entrapped gas, formed between dendrites during cooling. Such an imperfection is generally found perpendicular to the weld face |
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| 2 | 2024 | Crater pipe | Shrinkage cavity at the end of a weld run and not eliminated before or during subsequent weld runs |
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| 2 | 2025 | End crater pipe | Open crater with a hole reducing the cross-section of the weld |
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| 2 | 203 | Micro-shrinkage | Shrinkage cavity visible only under the microscope | |
| 2 | 2031 | Interdendritic microshrinkage | Elongated micro-shrinkage formed between dendrites during cooling following the boundaries of grains | |
| 2 | 2032 | Transgranular microshrinkage | Elongated micro-shrinkage cavity crossing grains during solidification | |
| 3 | 300 | Solid inclusions | Solid foreign substances entrapped in the weld metal | |
| 3 | 3011 | Slag inclusion | Solid inclusion in the form of slag linear |
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| 3 | 3012 | Slag inclusion | Solid inclusion in the form of slag isolated |
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| 3 | 3013 | Slag inclusion | Solid inclusion in the form of slag clustered |
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| 3 | 3021 | Flux inclusion | Solid inclusion in the form of flux linear |
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| 3 | 3022 | Flux inclusion | Solid inclusion in the form of flux isolated |
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| 3 | 3023 | Flux inclusion | Solid inclusion in the form of flux clustered |
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| 3 | 3031 | Oxide inclusion | Solid inclusion in the form of oxide linear | |
| 3 | 3032 | Oxide inclusion | Solid inclusion in the form of oxide isolated | |
| 3 | 3033 | Oxide inclusion | Solid inclusion in the form of oxide clustered | |
| 3 | 3034 | Puckering | In certain cases, especially in aluminium alloys, gross oxide film enfoldment can occur due to a combination of unsatisfactory protection from atmospheric contamination and turbulence in the weld pool | |
| 3 | 3041 | Metal inclusion | Solid inclusion of tungsten |
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| 3 | 3042 | Metal inclusion | Solid inclusion of copper |
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| 3 | 3043 | Metal inclusion | Solid inclusion of other metal |
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| 4 | 400 | Lack of fusion and penetration | Lack of fusion and penetration | |
| 4 | 4011 | Lack of fusion | Lack of side-wall fusion |
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| 4 | 4012 | Lack of fusion | Lack of inter-run fusion |
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| 4 | 4013 | Lack of fusion | Lack of root fusion | |
| 4 | 4014 | Lack of fusion | Micro-lack of fusion |
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| 4 | 402 | Incomplete penetration (lack of penetration) | Difference between the actual and the nominal penetration |
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| 4 | 4021 | Incomplete root penetration | One or both fusion faces of the root are not melted |
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| 4 | 403 | Spiking | Extremely non-uniform penetration occurring in electron-beam and laser welding giving a sawtooth appearance. This can include cavities, cracks, shrinkages, etc |
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| 5 | 500 | Imperfect shape | Imperfect shape of the external surfaces of the weld or defective joint geometry | |
| 5 | 5011 | continuous undercut | Undercut of significant length without interruption |
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| 5 | 5012 | Intermittent undercut | Short length of undercut, intermittent along the weld |
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| 5 | 5013 | Shrinkage grooves | Undercuts visible on each side of the root run |
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| 5 | 5014 | Inter-run undercut (interpass undercut) | Undercut in the longitudinal direction between weld runs |
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| 5 | 5015 | Local intermittent undercut | Short undercuts, irregularly spaced, on the side or on the surface of the weld runs |
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| 5 | 502 | Excess weld metal | Reinforcement of the butt weld on the face is too large |
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| 5 | 503 | Excessive convexity | Reinforcement of the fillet is too large |
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| 5 | 5041 | Local excessive penetration | Reinforcement of the butt weld on the root side is too large : local excessive penetration |
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| 5 | 5042 | Continuous excessive penetration | Reinforcement of the butt weld on the root side is too large : continuous excessive penetration |
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| 5 | 5043 | Excessive melt-through | Reinforcement of the butt weld on the root side is too large : excessive melt-through |
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| 5 | 5051 | Incorrect weld toe angle | Too small an angle (α) between the plane of the parent material surface and a plane tangential to the weldrun surface at the toe of the weld |
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| 5 | 5052 | Incorrect weld toe radius | Too small a radius (r) at the toe of the weld |
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| 5 | 5061 | Toe overlap | Toe overlap at the weld toe |
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| 5 | 5062 | Root overlap | Root overlap at the weld root |
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| 5 | 5071 | Linear misalignment between plates | Pieces are plates |
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| 5 | 5072 | Linear misalignment between tubes | Pieces are tubes |
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| 5 | 508 | Angular misalignment | Misalignment between two welded pieces such that their surface planes are not parallel or at the intended angle |
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| 5 | 5091 | Sagging in the horizontal position | Sagging in the horizontal position |
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| 5 | 5092 | Sagging in the flat or overhead position | Sagging in the flat or overhead position |
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| 5 | 5093 | Sagging in a fillet weld | Sagging in a fillet weld |
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| 5 | 5094 | Sagging (melting) at the edge of the weld | Sagging (melting) at the edge of the weld |
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| 5 | 510 | Burn-through | Collapse of the weld pool resulting in a hole in the weld |
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| 5 | 511 | Incompletely filled groove | Longitudinal continuous or intermittent channel in the surface of a weld due to insufficient deposition of weld filler material |
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| 5 | 512 | Excessive asymmetry of fillet weld (excessive unequal leg length) | Explanation not necessary |
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| 5 | 513 | Irregular width | Excessive variation in width of the weld | |
| 5 | 514 | Irregular surface | Excessive surface roughness | |
| 5 | 515 | Root concavity | Shallow groove due to shrinkage of a butt weld at the root (see also 5013) |
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| 5 | 516 | Root porosity | Spongy formation at the root of a weld due to bubbling of the weld metal at the moment of solidification | |
| 5 | 517 | Poor restart | Local surface irregularity at a weld restart |
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| 5 | 5171 | Poor restart in the capping run | Poor restart in the capping run |
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| 5 | 5172 | Poor restart in the root run | Poor restart in the root run |
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| 5 | 520 | Excessive distortion | Dimensional deviation due to shrinkage and distortion of welds | |
| 5 | 5211 | Excessive weld thickness | Weld thickness is too large |
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| 5 | 5212 | Excessive weld width | Weld width is too large |
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| 5 | 5213 | Insufficient throat thickness | Actual throat thickness of the fillet weld is too small |
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| 5 | 5214 | Excessive throat thickness | Actual throat thickness of the fillet weld is too large |
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| 6 | 600 | Miscellaneous imperfections | All imperfections which cannot be included in groups 1 to 5 | |
| 6 | 601 | Arc strike 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 | |
| 6 | 602 | Spatter | Globules of weld metal or filler metal expelled during welding and adhering to the surface of parent material or solidified weld metal | |
| 6 | 6021 | Tungsten spatter | Particles of tungsten transferred from the electrode to the surface of parent material or solidified weld metal | |
| 6 | 603 | Torn surface | Surface damage due to the removal by fracture of temporary welded attachments | |
| 6 | 604 | Grinding mark | Local damage due to grinding | |
| 6 | 605 | Chipping mark | Local damage due to use of a chisel or other tools | |
| 6 | 606 | Underflushing | Reduction in the thickness of the workpiece due to excessive grinding | |
| 6 | 607 | Tack weld imperfection | Imperfection resulting from defective tack welding | |
| 6 | 6071 | Tack weld imperfection | Broken run or no penetration | |
| 6 | 6072 | Tack weld imperfection | Defective tack has been overwelded | |
| 6 | 608 | Misalignment of opposite runs | Difference between the centrelines of two runs made from opposite sides of the joint |
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| 6 | 610 | Temper colours (visible oxide film) | Lightly oxidized surface in the weld zone, e.g. in stainless steels | |
| 6 | 6101 | Discolouration | Visibly tinted surface layers in the weld metal and heataffected zone caused by the weld heat and/or by lack of protection, e.g. in titanium | |
| 6 | 613 | Scaled surface | Heavily oxidized surface in the weld zone | |
| 6 | 614 | Flux residue | Flux residue that is not sufficiently removed from the surface | |
| 6 | 615 | Slag residue | Adherent slag that is not sufficiently removed from the surface of the weld | |
| 6 | 617 | Incorrect root gap for fillet welds | Excessive or insufficient gap between the parts to be joined |
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| 6 | 618 | Swelling | Imperfection due to a burning on welded joints in light alloys resulting from a prolonged holding time in the solidification stage |
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What are the acceptance criteria for defects to consider for visual inspection of weld beads?
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