Uploaded byGaurav Singh Rajput
Visual Inspection of Welding Process
The document discusses visual inspection of welds, including terminology for different types of welds and weld features. It provides checklists for welding procedures before, during, and after welding. Common welding defects such as lack of fusion, undercut, and porosity are described along with their potential causes. Visual inspection procedures and features to examine in butt and fillet welds are also outlined.
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Visual Inspection of Welding Process
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- 2. Terminology Butt Joints • SquareEdged, Open and Closed • Single Vee, Butt and Bevel • Double Vee, Butt and Bevel
- 3. Terminology Fillet Joints • Tee• Lap • Corner
- 4. Terminology Butt Weld Features 1 2 34 5 6 7 8 9 10
- 5.
- 6. Visual Inspection Procedures •What is the nature of the product? • What operating conditions will be present? • What is the quality of welding required? • Is there a code or standard available to inspect the welds against
- 7. Welding Checklist • Documentation •Materials • Weld preparations • Fit up for welding • Welding equipment Before Welding Commences
- 8. Welding Checklist • Correctparameters • WPS at the work place • Inter run cleanliness and quality • Interpass temperature • Consumable control • Maintenance of preheat • Process control NDE regime • Weld records and maintenance of weld maps During Welding
- 9. Welding Checklist • Visualinspection and records • NDE • PWHT • Final testing • Cleaning, painting, preservation, packing • Final documentation Welding Completion
- 10. How Do ICarry Out a Visual Inspection? • What is the nature of the product? • What operating conditions will be present? • What is the quality of welding required? • Is there a code or standard available to inspect the welds against
- 11. Features to Consider Buttwelds - Size Excess weld metal height Root penetration Root bead width Weld cap width
- 12. Features to Consider Filletwelds - Size Minimum and maximum leg length size Minimum design throat thickness
- 13. Features to Consider Buttwelds - Profile
- 14. Features to Consider Filletwelds - Size
- 15. Features to Consider Buttwelds - Toe Blend
- 16. Features to Consider Filletwelds - Toe Blend
- 17. Features to Consider Buttwelds - Weld Width
- 18. Welding Defects • Incompleteroot penetration
- 19. Welding Defects • Rootconcavity
- 20. Welding Defects • Lackof fusion
- 21. Welding Defects • Undercut Causes •Excessive welding current • Welding speed too high • Incorrect electrode angle • Excessive weave • Electrode too large
- 22. Welding Defects • IncompletelyFilled Groove Causes • Insufficient weld metal deposited • Improper welding technique
- 23. Welding Defects • BurnThrough Causes • Excessive amperage during welding of root • Excessive root grinding • Improper welding technique
- 24. A Weld :Definitions • A union between pieces of metal at faces rendered plastic or liquid by heat,pressure or both. BS 499 • A continuous defect surrounded by parent material NASA
- 25. Welds • An idealweld must give a strong bond between materials with the interfaces disappearing To achieve this • Smooth,flat or matching surfaces • Surfaces shall be free from contaminants • Metals shall be free from impurities • Metals shall have identical crystalline structures
- 26. Welding • A unionbetween pieces of metal at faces rendered plastic or liquid by heat,pressure or both. BS 499 • Ultrasonics • Electron beam • Friction • Electric resistance • Electric arc Possible energy sources
- 27. Electric Arc Welding Power supply Workpiece Electrod e Clamp(Earth)
- 28. Electric Arc Welding •Electric discharge produced between cathode and anode by a potential difference (40 to 60 volts) • Discharge ionises air and produces -ve electrons and +ve ions • Electrons impact upon anode, ions upon cathode • Impact of particles converts kinetic energy to heat (7000o C) and light • Amperage controls number of ions and electrons, Voltage controls their velocity
- 29. Electric Arc Welding ArcWelding Processes • Manual metal arc • Tungsten Inert Gas • Metal Inert Gas • Submerged Arc Differences between them • Methods of shielding the arc • Consumable or Non-consumable electrode • Degree of automation
- 30. Zones in FusionWelds • Fusion Zone • Heat Affected Zone • Parent Material or Base Metal
- 31. Joint Design Butt Weld Corner Joint Lap Joint TJoint Edge Weld
- 32. Manual Metal Arc(MMA) Consumable electrode Flux coating Core wire Arc Evolved gas shield Parent metal Slag Weld metal
- 33. Manual Metal ArcWelding • Shielding provided by decomposition of flux covering • Electrode consumable • Manual process Welder controls • Arc length • Angle of electrode • Speed of travel • Amperage settings
- 34. Tungsten Inert Gas(TIG) Non-consumable tungsten electrode Arc Parent metal Weld metal Gas shield Filler wire Gas nozzle
- 35. Metal Inert Gas(MIG) Consumable electrode(filler wire) Arc Parent metal Weld metal Gas shield Gas nozzle Reel feed
- 36. Submerged Arc Consumable electrode Reel feed Fluxfeed Flux retrieval Parent metal Weld metal Slag
- 37. Electroslag Filler wire Molten flux Weldmetal Water cooled copper shoes
- 38. Welding Defects 4 CrackTypes • Solidification cracks • Hydrogen induced cracks • Lamellar tearing • Reheat cracks Cracks
- 39. Welding Defects Classified byShape • Longitudinal • Transverse • Branched • Chevron Cracks Classified by Position • HAZ • Centreline • Crater • Fusion zone • Parent metal
- 40. Welding Defects Solidification • Occursduring weld solidification process • Steels with high sulphur content (low ductility at elevated temperature) • Requires high tensile stress • Occur longitudinally down centre of weld • eg Crater cracking Cracks
- 41. Welding Defects Hydrogen Induced •Requires susceptible grain structure, stress and hydrogen • Hydrogen enters via welding arc • Hydrogen source - atmosphere or contamination of preparation or electrode • Moisture diffuses out into parent metal on cooling • Most likely in HAZ Cracks
- 42. Welding Defects Lamellar Tearing •Step like appearance • Occurs in parent material or HAZ • Only in rolled direction of the parent material • Associated with restrained joints subjected to through thickness stresses on corners, tees and fillets • Requires high sulphur or non-metallic inclusions Cracks
- 43. Welding Defects Re-Heat Cracking •Occurs mainly in HAZ of low alloy steels during post weld heat treatment or service at elevated temperatures • Occurs in areas of high stress and existing defects • Prevented by toe grinding, elimination of poor profile material selection and controlled post weld heat treatment Cracks
- 44. Welding Defects • Incompleteroot penetration Causes • Too large or small a root gap • Arc too long • Wrong polarity • Electrode too large for joint preparation • Incorrect electrode angle • Too fast a speed of travel for current
- 45. Welding Defects • Rootconcavity Causes • Root gap too large • Insufficient arc energy • Excessive back purge (TIG)
- 46. Welding Defects • Lackof fusion Causes • Contaminated weld preparation • Amperage too low • Amperage too high (welder increases speed of travel)
- 47. Welding Defects • Undercut Causes •Excessive welding current • Welding speed too high • Incorrect electrode angle • Excessive weave • Electrode too large
- 48. Welding Defects • IncompletelyFilled Groove Causes • Insufficient weld metal deposited • Improper welding technique
- 49. Welding Defects • Gaspores / Porosity Causes • Excessive moisture in flux or preparation • Contaminated preparation • Low welding current • Arc length too long • Damaged electrode flux • Removal of gas shield
- 50. Welding Defects • Inclusions- Slag Causes • Insufficient cleaning between passes • Contaminated weld preparation • Welding over irregular profile • Incorrect welding speed • Arc length too long
- 51. Welding Defects • Inclusions- Tungsten Causes • Contamination of weld during TIG welding process
- 52. Welding Defects • BurnThrough Causes • Excessive amperage during welding of root • Excessive root grinding • Improper welding technique
- 53. Welding Defects • ArcStrikes Causes • Electrode straying onto parent metal • Electrode holder with poor insulation • Poor contact of earth clamp • Spatter Causes • Excessive arc energy • Excessive arc length • Damp electrodes • Arc blow