DeIects and DiscontinuitiesDeIect A Ilaw or Ilaws that by nature or accumulated eIIect render a part or product unable to meet minimum applicable acceptance standards or speciIications. The term designates reiectability.Discontinuity An interruption oI the typical structure oI a material, such as a lack oI homogeneity in its mechanical, metallurgical, or physical characteristics. A discontinuity is not necessarily a deIect.eld Joint Discontinuities Misalignment (hi-lo) Undercut Underfill Concavity or Convexity Excessive reinforcement Improper reinforcement Overlap Burn-through Incomplete or Insufficient Penetration Incomplete Fusion Surface irregularity Overlap Arc Strikes Inclusions Slag agon tracks Tungsten Spatter Arc Craters Cracks Longitudinal Transverse Crater Throat Toe Root Underbead and Heat-aIIected zone Hot Cold or delayed Base Metal Discontinuities Lamellar tearing Laminations and Delaminations Laps and Seams Porosity UniIormly Scattered Cluster Linear Piping Heat-affected zone microstructure alteration Base Plate laminations Size or dimensionsMisalignment (hi-lo) Definition: Amount a ioint is out oI alignment at the root Cause: Carelessness. Also due to ioining diIIerent thicknesses (transition thickness) Prevention: orkmanship. Transition angles not to exceed 2.5 to 1. Repair: Grinding. CareIul on surIace Iinish and direction oI grind marks. Inside oI Pipe /Tube diIIicult.isalignmentUndercut Definition: A groove cut at the toe oI the weld and leIt unIilled. Cause: High amperage, electrode angle, long arc length, rust Prevention: Set machine on scrap metal. Clean metal beIore welding. Repair: eld with smaller electrode, sometimes must be low hydrogen with preheat. Sometimes must gouge Iirst.Undercut(cont......)Undercut typically has an allowable limit. DiIIerent codes and standards vary greatly in the allowable amount.Plate - the lesser oI 1/32 or 5 (typ.)Under CutInsuIIicient Fill or Under Iill DeIinition: The weld surIace is below the adiacent surIaces oI the base metal Cause: Improper welding techniques Prevention: Apply proper welding techniques Ior the weld type and position. Use stripper beads beIore the cover pass. Repair: Simply weld to Iill. ay require preparation by grinding. Under IillInsuIIicient Fill on the Root Side(suckback) DeIinition: The weld surIace is below the adiacent surIaces oI the base metal at the weld root. Cause: Typically improper ioint preparation or excessive weld pool heat. Prevention: Correct cause. (see next slide) Repair: Backweld to Iill. ay requireremoval oI weld section by grinding Ior access to the ioint root. Cause Ior InsuIIicient Fill at the RootSome liquids, like water or molten steel, try to cover as much surIace area oI whatever they are in contact with as possible.elding a root pass too wide can also cause the bead to sag (overhead position).Removing a root pass by grinding1. Recreate the groove geometry as closely as possible.2. Use a saw or die grinder and 1/16 - 1/8 cut oII wheel to recreate root opening. Remember repairs are sometimes required to be made with a smaller electrode.3. Open the groove angle. Be careIul to leave the proper root Iace dimension. 4. Feather the start and stop to blend smoothly into and out oI the existing weld.xcessive Concavity or Convexity Definition: Concavity or convexity oI a Iillet weld which exceeds the speciIied allowable limits Cause: Amperage and travel speed Prevention: Observe proper parameters and techniques. Repair: Grind oII or weld on. ust blend smoothly into the base metal. ConcavityRoot ConcavityConvexityReinIorcement xcessive InsuIIicient Improper contourFace ReinIorcementRoot ReinIorcementThe amount oI a groove weld which extends beyond the surIace oI the platexcessive ReinIorcement DeIinition: SpeciIically deIined by the standard. Typically, ReinIorcement should be Ilush to 1/16(pipe) or Ilush to 1/8 (plate or structural shapes). Cause: Travel speed too slow, amperage too low Prevention: Set amperage and travel speed on scrap plate. Repair: Remove excessive reinIorcement and Ieather the weld toes to a smooth transition to the base plate.xcessive Penetration DeIinition: SpeciIically deIined by the standard. Typically, UnderIill may be up to 5 oI metal thickness not to exceed 1/32 as long as the thickness is made up in the opposite reinIorcement. Not applied to Iillet welds. Cause: On root reinIorcement - Too little Iiller metal will cause thinning oI the Iiller metal. In OH position, too hot or too wide will cause drooping oI the open root puddle. Prevention: Use proper welding technique. Use backing or consumable inserts. Use back weld or backing. Repair: Possibly simply increase the Iace reinIorcement. II backwelding is not possible, must remove and reweld.InsuIIicient ReinIorcement DeIinition: hen the weld exhibits less than a 1350transition angle at the weld toe. Cause: Poor welding technique Prevention: Use proper techniques. A weave or whip motion can oIten eliminate the problem. Repair: The weld Iace must be Ieathered into the base plate.1350Improper eld ContourOverlap DeIinition: hen the Iace oI the weld extends beyond the toe oI the weld Cause: Improper welding technique. Typically, electrode angles and travel speed. Prevention: Overlap is a contour problem. Proper welding technique will prevent this problem. Repair: Overlap must be removed to blend smoothly into the base metal. Be careIul oI deep grind marks that run transverse to the load. Also be careIul oI Iusion discontinuities hidden by grinding. Use NDT to be sure.OverlapOverlap is measured with a square edge such as a 6 rule. No amount oI overlap is typically allowed.Burn-through (non-standard) DeIinition: hen an undesirable open hole has been completely melted through the base metal. The hole may or may not be leIt open. Cause: xcessive heat input. Prevention: Reduce heat input by increasing travel speed, use oI a heat sink, or by reducing welding parameters. Repair: ill be deIined by standards. Filling may suIIice. Otherwise, removal and rewelding may be required. Some standards may require special Iiller metal and/or PHT.Incomplete or InsuIIicient Penetration DeIinition: hen the weld metal does not extend to the required depth into the ioint root Cause: Low amperage, low preheat, tight root opening, Iast travel speed, short arc length. Prevention: Correct the contributing Iactor(s). Repair: Back gouge and back weld or remove and reweld.ICPIncomplete Fusion DeIinition: here weld metal does not Iorm a cohesive bond with the base metal. Cause: Low amperage, steep electrode angles, Iast travel speed, short arc gap, lack oI preheat, electrode too small, unclean base metal, arc oII seam. Prevention: liminate the potential causes. Repair: remove and reweld, being careIul to completely remove the deIective area. This is sometimes extremely diIIicult to Iind.Lack oI Side all FusionArc Strike DeIinition: A localized coalescence outside the weld zone. Cause: Carelessness Prevention: In diIIicult areas, adiacent areas can be protected using Iire blankets. Repair: here applicable, arc strikes must be sanded smooth and tested Ior cracks. II Iound, they must be remove and repaired using a qualiIied repair procedure and inspected as any other weld.Arc Strikeeld Spatter,:808 !70;03943High aic povoi Roduco aic povoiMagnolic aic lIov Roduco aic Ionglh oi svilch lo AC povoiIncoiiocl sollings foi CMAW piocossModifv oIocliicaI sollings (lul lo caiofuI lo nainlain fuII fusionDanp oIocliodos Uso div oIocliodosInclusions Slag agontracks Tungsten DeIinition: Slag entrapped within the weld Cause: Low amperage, improper technique, Trying to weld in an area that is too tight.Slow travel in Vertical Down Prevention: Increase amperage or preheat, grind out tight areas to gain access to bottom oI ioint. Repair: Remove by grinding. Reweld.Slag InclusionSlag Inclusion DeIinition: Slang term Ior a groove leIt at the toe oI a root pass which becomes Iilled with slag and is trapped in the weld. Cause: The contour oI the root pass is too high, or the weld toe is not bonded to the base metal Prevention: Use proper technique to deposit the weld root. Repair: Best repaired beIore applying the hot pass. CareIully grind the root pass Iace Ilat. be careIul not to gouge other areas on the weldment.agon Tracks (non-standard) DeIinition: A tungsten particle embedded in a weld. (Typically GTA only) Cause: Tungsten electrode too small, amperage too high, AC balance on , Upslope too high, electrode tip not snipped, electrode dipped into the weld pool or touched with the Iill rod, electrode split. Prevention: liminate the cause Repair: Grind out and reweldTungsten InclusionInclusions Iix when you see it. otherwise grind out & Iixhiskers Unsightly Inhibits material Ilow in piping Are inclusions Can break oII in pipes and damage equipment downlineSpatter DeIinition: Small particles oI weld metal expelled Irom the welding operation which adhere to the base metal surIace. Cause: Long arc length, severe electrode angles, high amperages. Prevention: Correct the cause. Base metal can be protected with coverings or hi-temp paints. Repair: Remove by grinding or sanding. Sometimes must be tested as iI it were a weld.Arc Craters DeIinition: A depression leIt at the termination oI the weld where the weld pool is leIt unIilled. Cause: Improper weld termination techniques Prevention: Repair: II no cracks exist, simply Iill in the crater. Generally welding Irom beyond the crater back into the crater.Cracks Longitudinal Transverse Crater Throat Toe Root Underbead and Heat-aIIected zone Hot Cold or delayed DeIinition: A crack running in the direction oI the weld axis. ay be Iound in the weld or base metal. Cause: Preheat or Iast cooling problem. Also caused by shrinkage stresses in high constraint areas. Prevention: eld toward areas oI less constraint. Also preheat to even out the cooling rates. Repair: Remove and reweldLongitudinal Crack DeIinition: A crack running into or inside a weld, transverse to the weld axis direction. Cause: eld metal hardness problem Prevention: Repair:Transverse Crack DeIinition: A crack, generally in the shape oI an 'X which is Iound in a crater. Crater cracks are hot cracks. Cause: The center oI the weld pool becomes solid beIore the outside oI the weld pool, pulling the center apart during cooling Prevention: Use crater Iill, Iill the crater at weld termination and/or preheat to even out the cooling oI the puddle Repair:Crater Crack DeIinition: A longitudinal crack located in the weld throat area. Cause: Transverse Stresses, probably Irom shrinkage. Indicates inadequate Iiller metal selection or welding procedure. ay be due to crater crack propagation. Prevention: Correct initial cause. Increasing preheat may prevent it. be sure not to leave a crater. Use a more ductile Iiller material. Repair: Remove and reweld using appropriate procedure. Be sure to correct initial problem Iirst.Throat Crack DeIinition: A crack in the base metal beginning at the toe oI the weld Cause: Transverse shrinkage stresses. Indicates a HAZ brittleness problem. Prevention: Increase preheat iI possible, or use a more ductile Iiller material. Repair: Toe CrackToe Crack DeIinition: A crack in the weld at the weld root. Cause: Transverse shrinkage stresses. Same as a throat crack. Prevention: Same as a throat crack Repair:Root CrackRoot Crack DeIinition: A crack in the unmelted parent metal oI the HAZ. Cause:Hydrogen embrittlement Prevention: Use Lo/Hi electrodes and/or preheat Repair: (only Iound using NDT).Remove and reweld.Underbead Crack DeIinition: A crack in the weld that occurs during solidiIication. Cause: icro stresses Irom weld metal shrinkage pulling apart weld metal as it cools Irom liquid to solid temp. Prevention: Preheat or use a low tensil Iiller material. Repair:Hot Crack DeIinition: A crack that occurs aIter the metal has completely solidiIied Cause: Shrinkage, Highly restrained welds, Discontinuities Prevention: Preheat, weld toward areas oI less constraint, use a more ductile weld metal Repair: Remove and reweld, correct problem Iirst, preheat may be necessary.Cold CrackCold Crack or eld etal Hydrogen CrackRepairs to Cracks Determine the cause Correct the problem Take precautions to prevent reoccurrence Generally required to repair using a smaller electrodeBase Metal Discontinuities Lamellar tearing Laminations and Delaminations Laps and SeamsLamellar TearingLaminationsBase etal Discontinuityay require repair prior to weldingFormed during the milling processLamination eIIects can be reduced by ioint design:Laps and SeamsA mill-induced discontinuity in which results Irom a lump oI metal being squeezed over into the surIace oI the material. II beyond acceptable limits, must be removed and repaired or discarded.Porosity Single Pore UniIormly Scattered Cluster Linear PipingPorositySingle Pore Separated by at least their own diameter along the axis oI the weldUniIormly Scattered Porosity Typically iudged by diameter and proximity to a start or stop oIten caused by low amperage or short arc gap or an unshielded weld startCluster Porosity Typically viewed as a single large discontinuityLinear Porosity being linear greatly aIIects the severity oI this discontinuityPiping Porosity Generally has special allowable limitsPorosity preheat will help eliminate may need an electrode with more deoxidizers Use run-on/run-oII taps restart on top oI previous weld and grind oII lumpHeat-aIIected zone microstructure alteration add drawing oI HAZ oI groove weld with leaders to: grain reIinement grain growth hardened areas soItened areas precipitate suseptable areas.Size or dimension II it renders the part unusable, it is a deIect. II it is outside the allowable limit, it renders the part unusable. Things don`t have to be perIect, iust within the acceptable tolerance. orking to perIection is too time consuming and costlyHammer marks Stress risers Unsightly UnnecessaryRPAIR TCHNIQUS ay involve: diIIerent process diIIerent procedure diIIerent preheat/PHT diIIerent electrode smaller electrodeOnly repair defects. Discontinuities are by definitionacceptable. Repair is therefore unnecessary and not cost effective.