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Welding Week 4 > Weld Defects > Flashcards

Weld Defects Flashcards

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1
Q

What is a defect?

A

A flaw(s) by nature or by accumulated effect, render a pile or product unable to meet minimum acceptance standards/specifications.

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2
Q

What is a discontinuity?

A

An interruption of the typical structure of a material.

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3
Q

Is a discontinuity a defect?

A

Not, if it meets standards.

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4
Q

What am I? Amount a joint is out of alignment at the root.

A

Misalignment (hi-lo)

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5
Q

What is the cause, prevention and repair of a misalignment?

A

Cause: Carelessness/ joining different thicknesses

Prevention: Workmanship/ Transition angle not exceeding 2.5 to 1

Repair: Grinding

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6
Q

What am I? A groove cut at the toe of the weld and left unfilled.

A

Undercut

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7
Q

What is the cause, prevention and repair of a undercut?

A

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.

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8
Q

_____ 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.

A

Undercut

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9
Q

What am I? The weld surface is below the adjacent surfaces of the base metal.

A

Insufficient Fill or Under Fill (groove weld)

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10
Q

What is the cause, prevention, and repair for insufficient fill or under fill?

A

Cause: Improper welding techniques

Prevention: Proper welding technique for weld type/ position. Use stripper beads before the cover pass.

Repair: Simply weld to fill.

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11
Q

What am I? The weld surface is below the adjacent surfaces of the base metal at the weld root.

A

Insufficient Fill on the Root Side/ AKA: Suckback

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12
Q

What is the cause, prevent and repair for Insufficient fill on the root side (suckback)?

A

Cause: Improper joint preparation/ excessive weld pool heat

Prevention: Correct cause.

Repair: Backweld to fill.

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13
Q

What are other causes for insufficient fill at the root?

A

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.

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14
Q

What are the 4 steps to removing a root pass by grinding?

A
  1. Recreate groove geometry
  2. recreate root opening with saw/ die grider and 1/16- 1/8” cut off wheel
  3. Open groove angle
  4. Feather start and stop smoothly
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15
Q

What am I? Concavity or convexity of a fillet weld which exceeds the specified allowable limits.

A

Excessive concavity or convexity (fillet weld)

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16
Q

What is the cause, prevent and repair for excessive concavity or convexity?

A

Cause: amperage/travel speed

Prevention: Observe proper parameters/techniques

Repair: Grind off or weld on.

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17
Q

What am I? The amount of a groove weld which extends beyond the surface.

A

Reinforcement (can be face and root)

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18
Q

To prevent excessive reinforcement by standard, reinforcement should be flush to ____ (pipe) or flush ___ on plate or structural shapes.

A

1/16” pipe or 1/8” plate

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19
Q

What is the cause, prevent and repair for excessive reinforcement?

A

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.

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20
Q

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.

A

5%, not exceeding 1/32”

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21
Q

What is the cause, prevent and repair for Insufficient reinforcement.

A

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

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22
Q

What am I? When the weld exhibits less than a 135 degree transition angle at the weld toe.

A

Improper welding contour

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23
Q

What is the cause, prevent and repair for improper weld contour?

A

Cause: poor welding technique.

Prevention: use proper technique. Weave or whip motion.

Repair: Weld face must be feather into the base plate.

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24
Q

What am I? When the face of the weld extends beyond the toe of the weld.

A

Overlap

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25
Q

What is the cause, prevent and repair for overlap?

A

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

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26
Q

_____ is measured with a square edge such as 6” rule. No amount of ____ is typically allowed.

A

Overlap

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27
Q

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.

A

Burn-through

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28
Q

What is the cause, prevent and repair for burn-through?

A

Cause: excessive heat

Prevention: reduce heat by increasing travel speed, use of heat sink, or reducing welding parameters

Repair: Filling may suffice.

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29
Q

What am I? When the weld metal does not extend to the required depth into the joint root.

A

Incomplete/insufficient penetration

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30
Q

What is the cause, prevent and repair for incomplete or insufficient penetration?

A

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.

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31
Q

What am I? Where the weld metal does not form a cohesive bond with the base metal.

A

Incomplete Fusion

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32
Q

What is the cause, prevent and repair for incomplete fusion?

A

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,.

33
Q

What am I? A localized coalescence outside the weld zone.

A

Arc Strike

34
Q

What is the cause, prevent and repair for arc strike?

A

cause: carelessness

Prevention: adjacent areas can be protected using fire blankets

Repair: must be sanded smooth and tested for cracks

35
Q

What are the causes for weld spatter?

A

high arc, magnetic arc blow, incorrect setting for gmaw, damp electrodes.

36
Q

what are the preventions to weld spatter?

A

reduce arc, reduce arc length/ switch to ac power, modify electrical settings, use dry electrodes.

37
Q

What are 3 types of inclusions?

A

slag, wagon tracks, tungsten

38
Q

What am I? Slag entrapped within the weld.

A

Slag inclusion

39
Q

What is the cause, prevent and repair for slag inclusion?

A

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

40
Q

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.

A

Wagon Tracks

41
Q

What is the cause, prevent and repair for wagon tracks?

A

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.

42
Q

What am I? A tungsten particle embedded in a weld, typically GTAW only.

A

Tungsten Inclusion

43
Q

What is the cause, prevent and repair for tungsten inclusion?

A

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

44
Q

What am I? Inhibits material flow in piping and are inclusions.

A

Whiskers

45
Q

What am I? small particles of weld metal expelled from the welding operation which adhere to the base metal surface.

A

spatter

46
Q

What is the cause, prevent and repair for spatter?

A

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.

47
Q

What am I? A depression left at the termination of the weld where the weld pool is left unfilled.

A

Arc Craters

48
Q

What is the cause and repair for arc craters?

A

cause: improper weld termination technique
repair: if no cracks - fill in crater.

49
Q

Name the 9 types of cracks.

A

Longitudinal, transverse, crater, throat, toe, root, underbead/HAZ, hot, cold/delayed

50
Q

What am I? A crack running in the direction of the weld axis.

A

Longitudinal Crack

51
Q

What is the cause, prevent and repair for longitudinal Crack?

A

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

52
Q

What am I? A crack running into or inside a weld, transverse to the weld axis direction.

A

Transverse Crack

53
Q

What is the cause, prevent and repair for transverse crack?

A

Cause: weld metal hardness

Prevention: Minimize head input and monitor inter pass temp max 200 c

repair dependent on spec and material

54
Q

What am I? A crack, generally in a shape of an X which is found in a crater? (they are also hot cracks)

A

Crater Crack

55
Q

What is the cause, prevent and repair for crater crack?

A

Cause: center of weld pool becomes solid before the outside of the weld pool, pulling the center apart during cooling.

Prevention, use crater fill

56
Q

What am I? A longitudinal crack located in the weld throat area.

A

Throat crack

57
Q

What is the cause, prevent and repair for throat crack?

A

cause: transverse stresses, probably from shrinkage. Inadequate filler or weld procedure.

Prevention: correct cause. Increase preheat.

Repair: remove reweld

58
Q

What am I? A crack in the base metal beginning a the toe of the weld.

A

Toe Crack

59
Q

What is the cause, prevent and repair for toe crack?

A

Cause: transverse shrinkage stresses, haz brittleness.

Prevent: increase preheat, use more ductile filler.

60
Q

What am I? A crack in the weld at the weld root.

A

Root Crack

61
Q

What is the cause, prevent and repair for root crack?

A

Cause: Transverse shrinkage stresses.

Prevention: same as throat crack

62
Q

What am I? A crack in the unmelted parent metal of the HAZ.

A

Underbead crack

63
Q

What is the cause, prevent and repair for underbead crack?

A

Cause: hydrogen embrittlement

Prevention: use lo/hi electrodes and/or preheat

Prepair: Found only using NDT remove and reweld.

64
Q

What am I? A crack in the weld that occurs during solidification.

A

hot crack

65
Q

What is the cause, prevent and repair for hot crack?

A

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.

66
Q

What am I? A crack that occurs after the metal has completely solidified.

A

cold crack

67
Q

What is the cause, prevent and repair for cold crack?

A

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.

68
Q

What are the 3 base metal discontinuities?

A

Lamellar tearing, lamination and delaminations, laps/seams

69
Q

What is formed during the milling process, may require repair prior to welding, and is a base metal discontinuity?

A

Laminations

70
Q

How can lamination effects be reduced?

A

By joint design

71
Q

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.

A

Laps and seams

72
Q

What are the 5 types of porosity?

A

Single pore, uniformly scattered, cluster, linear, piping

73
Q

What am I? Separated by at lead their own diameter along the axis of the weld.

A

single pore

74
Q

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

A

uniformly scattered porosity

75
Q

What am I? Typically viewed as a single large discontinuity.

A

cluster porosity

76
Q

What am I? Being linear greatly affects the severity of this discontinuity.

A

linear porosity

77
Q

Only repair _____.

A

defects

78
Q

_____ are by definition acceptable.

A

Discontinuities

79
Q

_______ is therefore unnecessary and not cost effective.

A

Repair

Welding Week 4 (10 decks)

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