1. WELDING INSPECTION AND QUALITY CONTROL
TASK # 2:
FLAWS/DISCONTINUITIES / DEFECTS
WHY IS IT IMPORTANT FOR YOU TO LEARN THIS SKILL?
UPON COMPLETION OF THIS MODULE YOU WILL BE ABLE TO:
DIFFERENTIATE FLAWS, DISCONTINUITIES AND DEFECTS.
DEFINE THE MAJOR CLASSIFICATION OF WELD DEFECTS
IDENTIFY DEFECTS, ITS CAUSES AND ITS REMEDIES
ACCEPTANCE STANDARDS

2. Discontinuity
All Welds have flaws.
Another name for a flaw is a discontinuity
Discontinuities are interruptions in the normal crystalline structure (or grain) of the metal.
Discontinuities are NOT always defects
Defect
A flaw or flaws that by nature or accumulated effect render a part or product unable to meet minimum applicable acceptance standards or specifications. The term designates rejectability.

3. Acceptance Standards CODE requirements Users standards
Sample of Codes and Standards
AWS – American Welding Society
API – American Petroleum Institute
ASME – American Society of Mechanical Engineers
ABS – American Bureau of Shipping

4. The purpose of welding inspections is to locate and determine the size of any discontinuities
Discontinuities that are too large or repeated too often within the weld become defects
Defects will compromise the welds overall strength

5. What are some common defects?
CLASSIFICATION SYSTEM AND TYPES
DRAWING AND DIMENSIONAL
STRUCTURAL DISCONTINUITIES IN WELDS
PROPERTIES(Mechanical and Chemical) of weld metal and or base metal.
Dimensional
1. Warpage-Longitudinal Distortion-Angular

6. b. Causes of warpage / distortion – 1
b. Causes of warpage / distortion – 1. shrinkage of weld metal and overheating of joint, 2. faulty preparation 3. faulty clamping or weak tacking c. Controlling methods 1. proper bead sequence 2. correct preparation 3. intermittent welding 4. correct clamping, proper tack size, prewarp d. Correction method – straightening operation, heating, removal of welds and subsequent re-welding e. Effects 1. builds stress 2. failure to meet design dimensions

7. Joint Preparation Correct Bevel Angle Correct Root Gap
Correct Root Face
Proper Tack Weld
Proper Alignment

8. 2. failure to issue proper instructions
2. Incorrect Joint Preparation
a. Types
1. bevel angle
2. groove angle
3. root opening or root gap
4. root face
b. Causes
1. improper methods used
2. failure to issue proper instructions
3. failure to follow instructions
4. use of improper symbols
c. Controlling methods
1. use proper instructions
2. use of correct symbols
3. use correct techniques
d. Corrections methods
1. prepare again using proper methods
e. Effects–warpage/trapped slag/incomplete fusion/improper bead shape

12. Concavity
Fillet weld
Corner joint

13. Convexity
Fillet weld
Corner joint

14. Excessive Concavity or Convexity
Incorrect weld size
Excessive Concavity or Convexity
Types
1. excessive convexity/incorrect length
2. excessive concavity / excessive root reinforcement
Causes
1. improper welding technique
2. failure to follow instruction
3. insufficient or excessive welding current
Controlling Methods
1. use proper technique
2. follow instruction
d. Correction Methods
1. removal of welds and subsequent welding
Effects
1. notch effect
2. concentration of stress under load
3. insufficient throat thickness

15. EXCESSIVE CONVEXITY

16. EXCESSIVE CONCAVITY

17. EXCESSIVE WELD REINFORCEMENT
Incorrect weld profile
EXCESSIVE WELD REINFORCEMENT
Tie end

18. Excessive Face Reinforcement

19. Excessive Root Reinforcement
Insufficient penetration
Burn through
Narrow root gap

20. 4. Incorrect Weld Profile
Type
1. excessive root reinforcement
2. excessive face reinforcement
Causes
1. slow travel speed
2. excessive heat
3. incorrect root face
4. improper electrode angle
c. Controlling methods
1. increase travel speed
2. reduce heat
3. use correct preparation
4. use correct electrode angle
d. Correction methods
1. removal of excessive reinforcement
2. possible removal of welds and subsequent re-welding
Effects – concentration of stress under load/notch effect

21. 5. Incorrect Final Dimension
Types
1. Too long / Too short
Causes
1. incorrect tolerance on drawings or specifications
2. shrinkage of welds
3. incorrect joint preparation
c. Controlling methods
1. inspect for correct dimensions or tolerances prior to fabrication
d. Correction methods
1. possible removal of welds and subsequent re-welding
e. Effects
1. will change dimensions of entire product

22. Structural Discontinuities
Porosity
Slag inclusion
Tungsten Inclusion
Poor penetration
Undercut
Cracks
Lack of Fusion
Burn Through
Rollover or “Cold Lap”

23. Structural Discontinuities in Weld
POROSITY- Gas entrapment

24. Sample of Defective Welds
Porosity would likely to occur at starting the weld, Tie Ins.
Over reinforcement

25. Sample of Defective Welds
A. Porosity
Causes:
1.Welding speed too rapid
2.Current too low
3.High sulphur or other impurities
4.Faulty electrodes

26. Porosity
Types
1. uniformly scattered porosity
2. cluster porosity
3. linear porosity
b. Causes
1. dirt, grease, rust, oil, moisture on base metal
2. excessive current
3. moisture in shielding gas
4. moisture in filler metals
c. Controlling methods
1. clean base metal properly
2. dry base metal and/or filler materials
3. proper welding technique
d. Corrective methods
1. removal of defective area and subsequent re-welding
e. Effect
depending on nature and type can propagate into a crack

27. 2. Slag Inclusions
Type
1. slag at root of joint
2. slag at bond area
3. scattered slag inclusions
b. Causes
1. improper joint preparation
2. improper cleaning of welds
3. improper techniques – wrong current setting
- wrong travel or speed
c. Controlling methods
1. proper joint preparation
2. proper cleaning before welding another bead
3. use proper technique – adjust current setting,
- adjust travel or speed
d. Corrective methods
1. removal of defective area and subsequent re-welding
e. Effect – weld is weak and cause cracking

28. Sample of Defective Welds
B. Slag Inclusion
Causes:
1.Joint design: sharp V-shaped recess
2.High viscosity of molten metal, rapid chilling, too low a weld temperature
Slag are not complete remove before depositing another bead.

30. 3. Tungsten Inclusions
Type
1. Scattered inclusions
b. Causes
1. touching the electrode to the work or molten weld metal
2. incorrect current type and or current setting
3. incorrect type and or size of tungsten electrode
c. Controlling methods
1. use proper welding technique
2. use correct type and current setting
3. use correct type and size of tungsten electrode
d. Correction method
1. removal of defective area and subsequent re-welding
e. Effects
1. creates brittle area
2. can cause cracking
Note: can be seen as white image in x-ray film.

31. 4. Incomplete Fusion
Type
1. incomplete fusion at the root of the weld or adjacent layers of weld metal
b. Causes
1. inadequate amount of heat (low current setting)
2. incorrect electrode angle
3. travel speed too fast
4. incorrect joint preparation
c. Controlling Methods
1. increase amount of heat (increase current setting)
2. reduce travel speed
3. use correct electrode angle
4. use proper joint preparation
d. Correction methods
1. possible back gouge and re-weld
2. removal of defective area and subsequent re-welding
e. Effect – weak joint and can cause cracking

32. 4. Incomplete fusion at the root of the weld
Corner edge of the joint is not melted

33. 4. INCOMPLETE FUSION at adjacent of the weld

34. 5. Incomplete joint penetration
Type
1. lack of complete fill at the root of the joint / either butt joint or tee joint.
b. Causes
1. groove design not suited for the process
2. root face dimension is too great (thick)
3. root opening is too small
4. fast travel speed
5. insufficient welding current
c. Controlling methods
1. use proper joint design
2. reduce travel speed
3. increase current setting
d. Correction method
1. possible back gouge and re-weld
2. removal of defective area and subsequent re-welding
e. Effects – notch effect possible start cracks

35. Inadequate joint penetration

36. Defective Root Penetration
Lack of penetration:
Causes:
1.Too long arc
2.Wrong fit-up or root gap
3. Low current rating
4. Faulty electrode size
5. Wrong travel speed

37. Defective Root Penetration
keyhole
Keyhole = root gap + 1/16” on both sides is the recommended size.
Burn Through / Melt through

38. Defective Root Penetration
Lack of Penetration In tie ins

39. Insufficient Fill on the Root Side (suckback)
Definition: The weld surface is below the adjacent surfaces of the base metal at the weld root.
Cause: Typically improper joint preparation or excessive weld pool heat.
Prevention: Correct cause.
Repair: Backweld to fill. May requireremoval of weld section by grinding for access to the joint root.

40. EXCESSIVE PENETRATION&INCOMPLETE PENETRATION

41. 6. Undercut
Types
1. side wall undercut
2. surface toe line undercut
b. Causes
1. excessive current (too high current)
2. too long arc length
3. magnetic arc blow (DC welding)
4. excessive travel speed (travel too fast)
5. incorrect electrode angle
c. Controlling methods
1. reduce current
2. adjust arc length
3. use AC welding
4. reduce travel speed
5. observe electrode angle

42. d. Correction methods
1. grinding or removal of defective area and subsequent re-welding.
e. Effects
1. reduces strength of the joint
2. can cause slag inclusion

43. Undercut
Definition: A groove cut at the toe of the weld and left unfilled.
Cause: High amperage, electrode angle, long arc length, rust
Prevention: Set machine on scrap metal. Clean metal before welding.
Repair: Weld with smaller electrode, sometimes must be low hydrogen with preheat. Sometimes must gouge first.

44. UNDERCUT

45. Undercut D. Undercutting Causes: 1.Current too high
2.Arc length too long
3.Improper manipulation of the electrode
4. Welding speed too rapid

46. Undercut typically has an allowable limit
Undercut typically has an allowable limit. Different codes and standards vary greatly in the allowable amount.
Plate - the lesser of 1/32” or 5% (typical)

47. 7. Cracks
Types
1. transverse and longitudinal weld cracks
2. crater cracks
3. base metal cracking
b. Causes
1. localized stress exceeds the ultimate strength of the material
2. lack of pre heat
3. poor crater fill technique
c. Controlling methods
1. use pre heating
2. use low hydrogen electrodes
3. sequence welds to balance shrinkage
4. use proper crater fill technique
5. avoid quenching and cooling conditions

48. d. Correction method
1. grinding / removal of defective area and subsequent re-welding
e. Effects
1. weld failure
2. cracks progress in length (increase of crack length)

49. Cracks

50. CRATER CRACKS
INSUFFICIENT FILLING AT THE END OF THE WELD

51. 8. Surface irregularities
Types
1. depressions
2. varying surface welds
3. varying reinforcement
4. non uniform weld ripples
5. spatter
b. Causes
1. inexperienced welder
2. restricted positioning while welding
c. Controlling methods
1. proper training of welders
2. workmanship samples
d. Correction methods
1. grinding or chipping before depositing succeeding welds
e. Effects
1. could result in slag entrapment or other discontinuities

52. OVERLAP

53. Insufficient Fill
Definition: The weld surface is below the adjacent surfaces of the base metal
Cause: Improper welding techniques
Prevention: Apply proper welding techniques for the weld type and position. Use stripper beads before the cover pass.
Repair: Simply weld to fill. May require preparation by grinding.

54. UNDERFILL

55. Surface Irregularities
SPATTER

56. POOR APPEARANCE
Crater
Incomplete Termination of Weldment

57. UNACCEPTABLE WELD PROFILES

58. Properties (Mechanical and Chemical) of Welded Metal and/or Base Metal
Tensile strength – ultimate strength of a material subjected to a tensile load
Yield strength – indication of maximum stress that can be developed in a material without with out plastic deformation.
Ductility – extent to which a material can sustain palstic deformation without rupture
Hardness – measure of a materials resistance to localized plastic deformation
Impact – energy required to fracture a part subjected to shock loading
Chemical Composition – the structure and properties of substances and of the changes they undergo.

59. How would you find these faults ?
TWO METHODS OF DETERMINING WELD FAULTS
1. Non Destructive Examination
2. DESTRUCTIVE TESTING

60. Standard Acceptability of welding defects:
1. Undercut should not exceed 1/32” inch(0.8mm) width and depth or must not exceed to 5% thickness from base metal.
2. No porosity shall exceed 1/16 inch (1.6mm) or in addition no square inch of weld metal shall exceed 1/16 inch(1.6mm) in greatest dimensions.
3. No gas pocket on square inch of weld metal area shall contain more than 6 gas pocket exceeding 1/16 inch (1.6mm) in greatest dimensions.
4. No slag inclusion shall exceed 1/8 inch (3.2mm) in every 6 inches of weld.

61. Florence-Darlington Technical College
Excerpts from:
Tim Turner
Elizabethtown Technical College
Wanda S. Benton
Florence-Darlington Technical College