Weld Defects Flashcards
What is a defect?
A flaw(s) by nature or by accumulated effect, render a pile or product unable to meet minimum acceptance standards/specifications.
What is a discontinuity?
An interruption of the typical structure of a material.
Is a discontinuity a defect?
Not, if it meets standards.
What am I? Amount a joint is out of alignment at the root.
Misalignment (hi-lo)
What is the cause, prevention and repair of a misalignment?
Cause: Carelessness/ joining different thicknesses
Prevention: Workmanship/ Transition angle not exceeding 2.5 to 1
Repair: Grinding
What am I? A groove cut at the toe of the weld and left unfilled.
Undercut
What is the cause, prevention and repair of a undercut?
Cause: High amperage, electrode angle, long arc length, rust
Prevention: set machine on scrap metal to correct parameter/ clean metal before welding
Repair: Weld with smaller electrode.
_____ typically has an allowable limit. On a plate, it is normally the lesser of 0.8 mm or 5%. Anything deeper than 1 mm must be repaired.
Undercut
What am I? The weld surface is below the adjacent surfaces of the base metal.
Insufficient Fill or Under Fill (groove weld)
What is the cause, prevention, and repair for insufficient fill or under fill?
Cause: Improper welding techniques
Prevention: Proper welding technique for weld type/ position. Use stripper beads before the cover pass.
Repair: Simply weld to fill.
What am I? The weld surface is below the adjacent surfaces of the base metal at the weld root.
Insufficient Fill on the Root Side/ AKA: Suckback
What is the cause, prevent and repair for Insufficient fill on the root side (suckback)?
Cause: Improper joint preparation/ excessive weld pool heat
Prevention: Correct cause.
Repair: Backweld to fill.
What are other causes for insufficient fill at the root?
Welding a root pass too wide can cause the bead to sag (overhead position), or some liquids like water/molten steel, try to cover as much surface area possible.
What are the 4 steps to removing a root pass by grinding?
- Recreate groove geometry
- recreate root opening with saw/ die grider and 1/16- 1/8” cut off wheel
- Open groove angle
- Feather start and stop smoothly
What am I? Concavity or convexity of a fillet weld which exceeds the specified allowable limits.
Excessive concavity or convexity (fillet weld)
What is the cause, prevent and repair for excessive concavity or convexity?
Cause: amperage/travel speed
Prevention: Observe proper parameters/techniques
Repair: Grind off or weld on.
What am I? The amount of a groove weld which extends beyond the surface.
Reinforcement (can be face and root)
To prevent excessive reinforcement by standard, reinforcement should be flush to ____ (pipe) or flush ___ on plate or structural shapes.
1/16” pipe or 1/8” plate
What is the cause, prevent and repair for excessive reinforcement?
Cause: Travel speed and amperage too low.
Prevention: Set amperage and travel speed on scrap plate
Repair: Remove excessive reinforcement and feather the weld toes to a smooth transition.
To prevent insufficient reinforcement, under fill may be up to ___ of metal thickness, not exceeding ____ as long as the thickness is made up in the opposite reinforcement.
5%, not exceeding 1/32”
What is the cause, prevent and repair for Insufficient reinforcement.
Cause: on root: too little filler metal will cause thinning of filler metal. In Oh position: too hot/too wide will cause dropping of open root puddle.
Prevention: proper welding technique. use backing/ consumable inserts. Backwelding
Repair: Increase face reinforment
What am I? When the weld exhibits less than a 135 degree transition angle at the weld toe.
Improper welding contour
What is the cause, prevent and repair for improper weld contour?
Cause: poor welding technique.
Prevention: use proper technique. Weave or whip motion.
Repair: Weld face must be feather into the base plate.
What am I? When the face of the weld extends beyond the toe of the weld.
Overlap
What is the cause, prevent and repair for overlap?
Cause: improper weld technique, electrode angles and travel speed.
Prevention: contour problem, so proper welding technique
Repair: blend smoothly into base. no grid marks that run transverse to load. Careful of fusion discontinuities hidden, use NDT
_____ is measured with a square edge such as 6” rule. No amount of ____ is typically allowed.
Overlap
What am I? When an undesirable open hole has been completely melted through the base metal. The hole may or may not be left open.
Burn-through
What is the cause, prevent and repair for burn-through?
Cause: excessive heat
Prevention: reduce heat by increasing travel speed, use of heat sink, or reducing welding parameters
Repair: Filling may suffice.
What am I? When the weld metal does not extend to the required depth into the joint root.
Incomplete/insufficient penetration
What is the cause, prevent and repair for incomplete or insufficient penetration?
Cause: Low amp, low preheat, tight root opening, fast travel speed short arc length
Prevention: correct contributing factors
Repair: back gouge and back weld or remove and reweld.
What am I? Where the weld metal does not form a cohesive bond with the base metal.
Incomplete Fusion
What is the cause, prevent and repair for incomplete fusion?
Cause: low amp, steep electrode angles, fast travel speed, short arc gap, lack of preheat, electrode too small, unclean base metal, arc off seam.
Prevention: Eliminate the potential causes.
Repair: Remove and re-weld,.
What am I? A localized coalescence outside the weld zone.
Arc Strike
What is the cause, prevent and repair for arc strike?
cause: carelessness
Prevention: adjacent areas can be protected using fire blankets
Repair: must be sanded smooth and tested for cracks
What are the causes for weld spatter?
high arc, magnetic arc blow, incorrect setting for gmaw, damp electrodes.
what are the preventions to weld spatter?
reduce arc, reduce arc length/ switch to ac power, modify electrical settings, use dry electrodes.
What are 3 types of inclusions?
slag, wagon tracks, tungsten
What am I? Slag entrapped within the weld.
Slag inclusion
What is the cause, prevent and repair for slag inclusion?
cause: low amp, improper technique, trying to weld area that is too tight, slow travel in vertical Down.
Prevention: increase amperage or preheat, grind out tight areas to gain access to bottom of joint.
Repair: remove by grinding
What am I? Slang term for a groove left at the toe of a root pass which becomes filled with slag and is trapped in the weld.
Wagon Tracks
What is the cause, prevent and repair for wagon tracks?
Cause: contour of the root pass is too high, weld toe is not bonded to the base metal
prevention: use proper technique to deposit the weld root.
Repair: best before applying the hot pass. Grid root pass face flat.
What am I? A tungsten particle embedded in a weld, typically GTAW only.
Tungsten Inclusion
What is the cause, prevent and repair for tungsten inclusion?
Cause: tungsten electrode too small, amp too high, ac balance on +, up-slope too high, electrode tip not snipped, electrode dipped into weld pool or touched with the fill rod, electrode split
Prevention: eliminate the cause
repair: grin out and reweld
What am I? Inhibits material flow in piping and are inclusions.
Whiskers
What am I? small particles of weld metal expelled from the welding operation which adhere to the base metal surface.
spatter
What is the cause, prevent and repair for spatter?
cause: long arc length, severe electrode angles, high amp
prevention: base metal can be protected with coverings or hi-temp paints.
Repair: remove by grinding or sanding.
What am I? A depression left at the termination of the weld where the weld pool is left unfilled.
Arc Craters
What is the cause and repair for arc craters?
cause: improper weld termination technique
repair: if no cracks - fill in crater.
Name the 9 types of cracks.
Longitudinal, transverse, crater, throat, toe, root, underbead/HAZ, hot, cold/delayed
What am I? A crack running in the direction of the weld axis.
Longitudinal Crack
What is the cause, prevent and repair for longitudinal Crack?
Cause: preheat/fast cooling problem. also shrinkage stresses.
Prevention: weld toward areas of less constraint. Preheat to even out cooling rates.
Repair: remove and reweld
What am I? A crack running into or inside a weld, transverse to the weld axis direction.
Transverse Crack
What is the cause, prevent and repair for transverse crack?
Cause: weld metal hardness
Prevention: Minimize head input and monitor inter pass temp max 200 c
repair dependent on spec and material
What am I? A crack, generally in a shape of an X which is found in a crater? (they are also hot cracks)
Crater Crack
What is the cause, prevent and repair for crater crack?
Cause: center of weld pool becomes solid before the outside of the weld pool, pulling the center apart during cooling.
Prevention, use crater fill
What am I? A longitudinal crack located in the weld throat area.
Throat crack
What is the cause, prevent and repair for throat crack?
cause: transverse stresses, probably from shrinkage. Inadequate filler or weld procedure.
Prevention: correct cause. Increase preheat.
Repair: remove reweld
What am I? A crack in the base metal beginning a the toe of the weld.
Toe Crack
What is the cause, prevent and repair for toe crack?
Cause: transverse shrinkage stresses, haz brittleness.
Prevent: increase preheat, use more ductile filler.
What am I? A crack in the weld at the weld root.
Root Crack
What is the cause, prevent and repair for root crack?
Cause: Transverse shrinkage stresses.
Prevention: same as throat crack
What am I? A crack in the unmelted parent metal of the HAZ.
Underbead crack
What is the cause, prevent and repair for underbead crack?
Cause: hydrogen embrittlement
Prevention: use lo/hi electrodes and/or preheat
Prepair: Found only using NDT remove and reweld.
What am I? A crack in the weld that occurs during solidification.
hot crack
What is the cause, prevent and repair for hot crack?
Cause Micro stresses from weld metal shrinkage pulling apart weld metal as it cools from liquid to solid temp.
Prevention: preheat or use a low tensile filler material.
What am I? A crack that occurs after the metal has completely solidified.
cold crack
What is the cause, prevent and repair for cold crack?
Cause: shrinkage, highly restrained welds, discontinuities
Prevention: preheat, weld toward areas of less constraint, use a more ductile weld metal
Repair: remove and re weld.
What are the 3 base metal discontinuities?
Lamellar tearing, lamination and delaminations, laps/seams
What is formed during the milling process, may require repair prior to welding, and is a base metal discontinuity?
Laminations
How can lamination effects be reduced?
By joint design
What am I? A mill-induced discontinuity in which results from a lump of metal being squeezed over into the surface of the material. If beyond acceptable limits, but me removed and repaired/ discarded.
Laps and seams
What are the 5 types of porosity?
Single pore, uniformly scattered, cluster, linear, piping
What am I? Separated by at lead their own diameter along the axis of the weld.
single pore
What am I? Judged by diameter and proximity to a start or stop. Often caused by low amp or short arc gap or an unshielded weld start
uniformly scattered porosity
What am I? Typically viewed as a single large discontinuity.
cluster porosity
What am I? Being linear greatly affects the severity of this discontinuity.
linear porosity
Only repair _____.
defects
_____ are by definition acceptable.
Discontinuities
_______ is therefore unnecessary and not cost effective.
Repair
