SAW Transmission & Drivetrain Systems 2 — Questions and Answers
Question 1: When applying SAW to rebuild worn drive shaft journals, which parameter most directly controls heat input to minimize distortion?
- Travel speed (Correct answer)
- Flux depth
- Wire diameter
- Contact tip distance
Correct answer: Travel speed
Travel speed is the primary control for heat input per unit length, and faster travel reduces total heat delivered to the journal.
Question 2: A transmission housing weld made with SAW shows porosity concentrated at weld start locations. The most likely cause is:
- Insufficient preheat
- Contaminated flux at run-on tabs (Correct answer)
- Excessive wire feed speed
- High arc voltage
Correct answer: Contaminated flux at run-on tabs
Flux at run-on tabs can absorb moisture or contaminants, releasing gas into the first molten pool and causing start porosity.
Question 3: SAW overlays on ring gear blanks require low dilution to preserve hardfacing alloy composition. Which technique best achieves this?
- Increase arc voltage
- Use electrode negative (DCEN) polarity (Correct answer)
- Decrease travel speed
- Increase wire diameter
Correct answer: Use electrode negative (DCEN) polarity
DCEN polarity concentrates more heat at the wire tip, producing shallower penetration and lower dilution of the base metal.
Question 4: A differential carrier housing requires a circumferential SAW weld. The correct torch positioning for a horizontal rotating fixture is:
- Directly at the 12 o'clock position
- Slightly past 12 o'clock in the direction of rotation
- At the 3 o'clock position
- Slightly before 12 o'clock against rotation (Correct answer)
Correct answer: Slightly before 12 o'clock against rotation
Positioning the torch slightly behind top-dead-center against rotation lets gravity help pool control and prevents the molten metal from running ahead of the arc.
Question 5: Which flux characteristic is most critical when SAW welding high-carbon drivetrain shafts to avoid hydrogen cracking?
- High basicity index (Correct answer)
- Low basicity index
- Fine granule size
- High SiO2 content
Correct answer: High basicity index
A high basicity index flux produces lower weld metal hydrogen levels, reducing the risk of hydrogen-induced cracking in high-carbon steels.
Question 6: When SAW is used to weld heavy-wall axle tube sections, which preheat factor is most important for crack prevention?
- Base metal carbon equivalent (Correct answer)
- Ambient humidity
- Flux brand
- Wire spool weight
Correct answer: Base metal carbon equivalent
Carbon equivalent (CE) of the axle steel determines hardenability and therefore the minimum preheat temperature needed to avoid cold cracking.
Question 7: After SAW rebuild of a transmission input shaft, which post-weld practice is most important before machining?
- Flux removal by wire brushing only
- Stress relief heat treatment (Correct answer)
- Rapid water quench
- Immediate grinding without delay
Correct answer: Stress relief heat treatment
Stress relief heat treatment reduces residual stresses from the weld deposit, preventing distortion or cracking during subsequent machining operations.
SAW Transmission & Drivetrain Systems 2
When applying SAW to rebuild worn drive shaft journals, which parameter most directly controls heat input to minimize distortion?