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Welding defects
- 1. 1 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Welding Imperfections Course notes section reference 3 TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Weld Defect ClassificationWeld Defect Classification Defects can be grouped under three main classifications Planar Defects: linear from at least one dimension • Cracks • Lack of fusion Linear Volumetric Defects: Linear in length with volume • Slag lines • lack of fusion with associated slag • Piping. Non-planar defects: rounded indications without significat length • Slag inclusions • Gas pores/blow holes. • Other matallic and non-matallic inclusions
- 2. 2 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Defects which may be detected by visual inspection can be grouped under the following headings Cracks Solid inclusions Surface and profiles Misalignment (set-up irregularities) Gas pores and porosity Lack of fusion Mechanical damage Parent material damage Miscellaneous Faults in Fusion WeldsFaults in Fusion Welds TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers CracksCracks
- 3. 3 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Classified by Shape Longitudinal Transverse Branched Chevron Classified by Position HAZ Centreline Crater Fusion zone Parent metal Cracks that may occur in welded materials are caused generally by many factors and may be classified by shape and position, cracks are classed as planar. CracksCracks TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Longitudinal parent metal crack Longitudinal weld metal crack Lamellar tearing Transverse weld metal crack CracksCracks
- 4. 4 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Transverse crack Longitudinal crack TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers InclusionsInclusions
- 5. 5 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Root piping Cluster porosityGas pore Blow hole Herringbone porosity Loss of gas shield Damp electrodes Contamination Arc length too large Damaged electrode flux Moisture on parent material Welding current too low Gas pore <1.5mm Blow hole.>1.6mm Gas CavitiesGas Cavities TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Root piping Porosity Gas CavitiesGas Cavities
- 6. 6 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Cluster porosity Herringbone porosity TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Slag originates from welding flux MAG and TIG welding process produce silica inclusions Slag is caused by inadequate cleaning Other inclusions include tungsten and copper inclusions from the TIG and MAG welding process Slag inclusions are defined as a non-metallic inclusion caused by some welding process Slag inclusions Parallel slag lines Lack of interun fusion + slag Lack of sidewall fusion with associated slag Solid InclusionsSolid Inclusions
- 7. 7 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Solid InclusionsSolid Inclusions Lack of interun fusion + slag Lack of sidewall fusion + slag TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Elongated slag linesInterpass slag inclusions
- 8. 8 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Lack of FusionLack of Fusion TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Incomplete filled groove + Lack of sidewall fusion 1 2 1. Lack of sidewall fusion 2. Lack of inter-run fusion Poor welder skill Incorrect electrode manipulation Arc blow Incorrect welding current/voltage Incorrect travel speed Incorrect inter-run cleaning Lack of FusionLack of Fusion
- 9. 9 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Lack of FusionLack of Fusion Lack of sidewall fusion + incomplete filled groove TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers An imperfection at the toe or root of a weld caused by metal flowing on to the surface of the parent metal without fusing to it Contamination Slow travel speed Incorrect welding technique Current too low OverlapOverlap
- 10. 10 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Toe OverlapToe Overlap Fillet weldFillet weld Toe OverlapToe Overlap Butt weldButt weld OverlapOverlap TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Lack of root fusion Incomplete root penetration Low Amps/volts Large Root face Small Root Gap Fast Travel Speed Incorrect Electrode Angle Contamination Arc blow Weld Root DefectsWeld Root Defects
- 11. 11 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Lack of root fusion Incomplete root Penetration Weld Root DefectsWeld Root Defects TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Lack of root penetration Lack of root fusion
- 12. 12 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Surface & ProfileSurface & Profile TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Incomplete filled groove Poor cap profile Excessive cap height Poor cap profiles and excessive cap reinforcements may lead to stress concentration points at the weld toes and will also contribute to overall poor toe blend Weld Profile DefectsWeld Profile Defects
- 13. 13 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Weld Profile DefectsWeld Profile Defects Poor Cap Profile & Poor Toe Blend TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Incomplete filled grooveExcess cap reinforcement
- 14. 14 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Poor stop/starts Weld Profile DefectsWeld Profile Defects TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Miscellaneous DefectsMiscellaneous Defects
- 15. 15 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Spatter Excessive current Damp electrodes Contamination Incorrect wire feed speed when welding with the MAG welding process Arc blow Miscellaneous DefectsMiscellaneous Defects TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Accidental striking of the arc onto the parent material Faulty electrode holder Poor cable insulation Poor return lead clamping Arc strike Miscellaneous DefectsMiscellaneous Defects
- 16. 16 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers An irregular groove at the toe of a weld run in the parent metal Excessive amps/volts Excessive travel speed Incorrect electrode angle Excessive weaving Incorrect welding technique Electrode too large Cap & Root UndercutCap & Root Undercut TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Intermittent Cap Undercut Cap UndercutCap Undercut
- 17. 17 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Cap undercutRoot undercut TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Shrinkage groove Insufficient weld metal deposited in the root pass Too fast a cooling rate during the application of the root bead pass Poor welding technique A shallow groove caused by contraction in the weld metal along each side of the penetration bead Weld Root DefectWeld Root Defect
- 18. 18 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Concave root Root gap too large Excessive back purge pressure during TIG welding Excessive root bead grinding before the application of the second pass A shallow groove, which may occur in the root of a butt weld Weld Root DefectWeld Root Defect TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Concave Root Weld Root DefectWeld Root Defect
- 19. 19 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Excessive root penetration Root faces too small Root gap too large Excessive amps/volts Slow travel speed Root penetration bead in excess in accordance with the relevant specification being used Weld Root DefectWeld Root Defect TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Weld Root DefectWeld Root Defect Excessive root penetration
- 20. 20 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Concave root Excess root penetration TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers High Amps/volts Small Root face Large Root Gap Slow Travel Speed Burn through A localized collapse of the weld pool due to excessive penetration resulting in a hole in the root run Weld Root DefectWeld Root Defect
- 21. 21 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Weld Root DefectWeld Root Defect Burn Through TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Loss or insufficient back purging gas Most commonly occurs when welding stainless steels Purging gases include argon, helium and occasionally nitrogen Oxidized Root (Root Coking)Oxidized Root (Root Coking)
- 22. 22 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Crater pipe Weld crater Crater PipeCrater Pipe TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Crater pipe is a shrinkage defect and not a gas defect, it has the appearance of a gas pore in the weld crater Too fast a cooling rate Deoxidization reactions and liquid to solid volume change Contamination Crater cracks (Star cracks) Crater pipe Crater PipeCrater Pipe
- 23. 23 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Mechanical DamageMechanical Damage TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Mechanical damage can be defined as any surface material damage cause during the manufacturing process. This can included damage caused by: Grinding Hammering Chiselling Chipping Breaking off welded attachments (torn surfaces) Using needle guns to compress weld capping runs Mechanical DamageMechanical Damage
- 24. 24 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Mechanical DamageMechanical Damage Mechanical Damage/Grinding Mark Chipping Marks TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers SetSet--up Irregularitiesup Irregularities
- 25. 25 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers A variation of leg lengths on a fillet weld Note: Unequal leg lengths on a fillet weld may be specified as part of the design, in which case it will not be considered as a defect. Unequal Leg LengthsUnequal Leg Lengths TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Plate/pipe Linear Misalignment (Hi-Lo) Angular Misalignment Linear misalignment is measured from the lowest plate to the highest point. Angular misalignment is measured in degrees SetSet--up Irregularitiesup Irregularities
- 26. 26 TECHNOLOGY Copyright © 2005TWI Ltd WI 3.1 M.Rogers Linear Misalignment SetSet--up Irregularitiesup Irregularities TECHNOLOGY Copyright © 2005 TWI Ltd WI 3.1 M.Rogers Linear Misalignment SetSet--up Irregularitiesup Irregularities