SAW Advanced Diagnostics & Troubleshooting 3 — Questions and Answers
Question 1: A SAW operator notices that the arc voltage meter reads normal but depth of penetration is much shallower than the WPS requires. Which condition is most likely?
- Excessive flux particle size
- Electrode extension (stickout) is too long (Correct answer)
- Travel speed is too slow
- Base metal is preheated above specified range
Correct answer: Electrode extension (stickout) is too long
Excessive electrode extension increases resistance heating in the wire, reducing the arc energy available for penetration despite a normal voltage reading at the power source.
Question 2: Weld metal oxygen content is found to be excessively high on a SAW procedure qualification test. Which flux parameter should be reviewed?
- Flux basicity index (BI) (Correct answer)
- Flux mesh size
- Flux bulk density
- Flux color consistency
Correct answer: Flux basicity index (BI)
A low basicity index (acidic flux) transfers more oxygen to the weld metal; selecting a higher-BI flux reduces weld metal oxygen content.
Question 3: During SAW of a thick plate, radiographic inspection shows a planar lack-of-fusion indication at the weld root after a double-sided procedure. The most likely cause is:
- Insufficient back-gouge depth to remove the initial root pass (Correct answer)
- Incorrect flux type
- Excessive preheat on the second side
- Electrode diameter too large
Correct answer: Insufficient back-gouge depth to remove the initial root pass
If back-gouging does not reach sound metal, residual root defects remain unfused when the second-side SAW passes are deposited.
Question 4: A SAW power source trips on overtemperature repeatedly during a long production run. The cooling fan is functioning. What is the most logical next diagnostic step?
- Check duty cycle against the actual arc-on time percentage (Correct answer)
- Increase wire feed speed to complete welds faster
- Switch to a smaller diameter wire
- Reduce flux depth
Correct answer: Check duty cycle against the actual arc-on time percentage
If arc-on time exceeds the power source rated duty cycle, internal components overheat; reducing arc-on time or using a higher-rated machine resolves the issue.
Question 5: Slag inclusions are found at the inter-run boundaries of a multi-pass SAW weld. What corrective action is most appropriate?
- Increase travel speed on subsequent passes
- Improve inter-pass slag removal and ensure bead profile is flat before next pass (Correct answer)
- Reduce voltage to narrow bead width
- Use a coarser flux mesh
Correct answer: Improve inter-pass slag removal and ensure bead profile is flat before next pass
Residual slag trapped in bead valleys or undercuts is covered by the next pass, creating slag inclusions; thorough removal and flat bead profiles prevent entrapment.
Question 6: A SAW wire feeder displays a 'wire slip' alarm intermittently, and the amperage fluctuates. After confirming the wire spool is free-turning, what is the next item to inspect?
- Drive roll condition and tension setting (Correct answer)
- Contact tip bore diameter
- Flux hopper agitator
- Power source output cables
Correct answer: Drive roll condition and tension setting
Worn, mismatched, or improperly tensioned drive rolls cause intermittent wire slip that produces current fluctuations and unstable arc conditions.
Question 7: A weld made on HY-80 steel using SAW fails a Charpy impact test at the required temperature. The WPS-specified flux and wire were used correctly. What metallurgical factor should be investigated?
- Interpass temperature exceeding the maximum allowed value (Correct answer)
- Insufficient flux depth during welding
- Contact tip setback distance
- Wire cast and helix
Correct answer: Interpass temperature exceeding the maximum allowed value
Excessively high interpass temperatures coarsen the heat-affected zone and weld metal microstructure, significantly reducing Charpy impact toughness in quenched-and-tempered steels.
SAW Advanced Diagnostics & Troubleshooting 3
A SAW operator notices that the arc voltage meter reads normal but depth of penetration is much shallower than the WPS requires.
Which condition is most likely?