SAW Advanced Diagnostics & Troubleshooting 2 — Questions and Answers
Question 1: A SAW bead shows a convex crown with sharp toes and no fusion at the edges. Which parameter change is most likely to correct this?
- Increase travel speed
- Decrease voltage
- Increase voltage (Correct answer)
- Reduce wire feed speed
Correct answer: Increase voltage
Increasing arc voltage widens and flattens the bead, improving toe wetting and fusion at the edges.
Question 2: Porosity is found exclusively on the start of every weld run in a production SAW operation. The most probable cause is:
- Excessive flux depth
- Flux moisture at the leading edge before arc stabilizes (Correct answer)
- Incorrect polarity
- High interpass temperature
Correct answer: Flux moisture at the leading edge before arc stabilizes
At arc start, flux has not yet been fully melted and degassed, trapping moisture-released hydrogen that causes start porosity.
Question 3: During tandem SAW, the trail wire arc becomes unstable and wanders. Which adjustment should be tried first?
- Increase lead wire voltage
- Reduce trail wire AC frequency
- Increase trail wire inductance setting (Correct answer)
- Switch trail wire to DCEP
Correct answer: Increase trail wire inductance setting
Increasing inductance on the trail wire dampens current fluctuations and stabilizes arc wandering in tandem configurations.
Question 4: A longitudinal crack appears in the weld metal centerline of a high-strength steel joint welded with SAW. This is most consistent with:
- Cold cracking from hydrogen
- Hot cracking due to high sulfur and high weld crown width-to-depth ratio (Correct answer)
- Lamellar tearing in base metal
- Solidification cracking from excessive preheat
Correct answer: Hot cracking due to high sulfur and high weld crown width-to-depth ratio
Centerline hot cracking results from low-melting sulfide films combined with a narrow, deep weld bead geometry that focuses stress at the centerline.
Question 5: A SAW procedure produces consistent undercut on the advancing side of a fillet weld made on a rotating cylinder. The best corrective action is:
- Increase wire feed speed
- Rotate the part so the weld puddle is slightly on the downhill slope (Correct answer)
- Reduce flux burden height
- Switch to AC power
Correct answer: Rotate the part so the weld puddle is slightly on the downhill slope
Repositioning the weld so gravity helps support the molten pool eliminates undercut caused by the puddle flowing away from the toe.
Question 6: Flux is being reclaimed and reused. New welds show increasing silicon and manganese content in the weld metal over successive passes. The root cause is:
- Excessive wire extension
- Slag inclusion from previous passes being melted into the flux (Correct answer)
- Flux is absorbing moisture
- Arc voltage is too low
Correct answer: Slag inclusion from previous passes being melted into the flux
Recycled slag mixed back into flux reintroduces silicon and manganese oxides that are reduced into the weld metal during subsequent arcs.
Question 7: On a butt joint, the SAW weld deposit is consistently off-center toward one side of the joint. The seam-tracking system shows no fault. What should be inspected first?
- Contact tip wear causing wire deflection (Correct answer)
- Flux hopper level
- Travel speed encoder calibration
- Shielding gas flow rate
Correct answer: Contact tip wear causing wire deflection
A worn or clogged contact tip can cause the wire to exit at an angle, deflecting the arc off-center even when the torch position appears correct.
SAW Advanced Diagnostics & Troubleshooting 2
A SAW bead shows a convex crown with sharp toes and no fusion at the edges.
Which parameter change is most likely to correct this?