CAUSES | CORRECTIVE ACTION | |
A. POROSITY | ||
1. | Contamination of work piece | Clean Joint area |
2. | Excessive moisture pickup in Electrode covering | Follow manufacturer’s recommended rebaking procedure. |
3. | Moisture on work surfaces | Use preheating/warm up work piece. |
4. | High Sulphur content of | Use basic coated base metal electrodes. |
5. | a) A long arc length b) Excessive current c)Higher travel speed | Change Welding parameters and technique. |
6. | High solidification rate | · Use preheat · Increase heat input. |
B. INCLUSIONS | ||
1. | Improper cleaning procedure | Clean work surfaces and each Weld run thoroughly. Wherever necessary use power wires brush, grinders, chisel to ensure through removal of slag. |
2. | Improper welding technique a) Long arc length b) High travel speed c) Slag flooding ahead of welding arc. | Improve welding technique. Reposition work to prevent loss of slag control wherever possible Restrict weaving to minimum |
3. | Narrow, inaccessible joints | Increase groove angle. |
C. INCOMPLETE FUSION | ||
1. | Improper joint design | Increase includes angle of groove joint. Change the groove design to 'J' or a 'U' type |
2. | Presence of slag or oxide film | Clean weld surfaces prior to welding. |
3. | Incorrect electrode position and operating current | Maintain proper electrode position and current. |
4. | Improper manipulation of arc | Use correct manipulation techniques to melt the joint faces properly. |
D. INADEQUATE PENETRATION | ||
1. | Improper joint preparation. a) Excessively thick root face. b) Insufficient root opening c) Bridging of root opening | Use proper joint geometry. Reduce root face height. Use wider root opening. |
2. | Electrode diameter too large | Use smaller electrode in root. Increase root opening. |
3. | Inadequate current | Follow correct welding current and technique. |
E. CRACKS | ||
1. | High rigidity of joint | Use preheating Relieve residual stresses minimises shrinkage stresses, using backstep or block welding sequences. |
2. | Poor joint fit up | Adjust root opening all alignment. |
3. | Higher carbon content of weld metal and/or hardenable base material | Use proper electrode. Use buttering layers wherever necessary. |
4. | Too small a weld bead | Decrease travel speed to increase cross section of bead. Increase electrode size. |
5. | High sulphur content in base level of sulphur of weldmetal element like Mn. | Use filler with high level of sulphur fixing element like Min. |
6. | Hot cracking | Reduce the heat input. Minimum joint restraints. |
7. | Cracking at the crater | Filling up the crater before withdrawing the electrode. Use taper poer control device. Use back step welding technique. |
8. | High hardenablity | Preheat the job. Post weld heat treatment without cooling to room temperature. |
9. | Hydrogen induced cracking/Delayed cracking | Use low hydrogen welding electrode. Use suitable preheat and post weldheat treatment. |
10. | Presence of brittle phases in the micro-structure of the base material | Soften the material before welding |
11. | Low ductility of the base material | Use preheat Anneal the base metal. Use ductile weldmetal. |
12. | High residual stresses | Redesign the weldmetal and reduce restraints. Change welding sequence. Use intermediate stress-relief heat treatment. |
13. | Excessive dilution | Change welding current. Use buttering technique wherever possible. |
Reference:
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