SAW Welding Techniques & Process Control 3 ā Questions and Answers
Question 1: What happens to weld bead convexity when arc voltage is set too low in SAW?
- The bead becomes flat and wide
- The bead becomes high and narrow (ropy) (Correct answer)
- Penetration increases dramatically
- Porosity increases near the toes
Correct answer: The bead becomes high and narrow (ropy)
Low arc voltage produces a short, constricted arc that deposits metal in a high, narrow, ropy bead shape.
Question 2: In SAW, what is 'electrode extension' (also called stick-out) and how does increasing it affect the process?
- Distance from contact tip to work; increasing it raises deposition rate via resistive heating (Correct answer)
- Distance from flux hopper to arc; increasing it deepens penetration
- Length of wire below flux surface; increasing it widens the bead
- Contact tip wear; increasing it reduces current
Correct answer: Distance from contact tip to work; increasing it raises deposition rate via resistive heating
Electrode extension is the wire length from contact tip to arc; longer stick-out increases resistive preheating, boosting deposition rate while reducing penetration.
Question 3: Which condition causes 'cold lapping' (lack of fusion at the toes) in SAW?
- Excessive arc voltage
- Insufficient current for the joint thickness (Correct answer)
- Too slow travel speed
- Excess flux depth
Correct answer: Insufficient current for the joint thickness
Insufficient welding current delivers too little heat to fuse the base metal at the weld toes, causing lack-of-fusion defects.
Question 4: What is the recommended action if porosity is found in an SAW weld and the flux was stored in a humid environment?
- Increase voltage to burn off moisture
- Re-dry the flux at the manufacturer's recommended temperature and time (Correct answer)
- Switch to a lower basicity flux
- Increase travel speed to reduce exposure time
Correct answer: Re-dry the flux at the manufacturer's recommended temperature and time
Absorbed moisture in flux releases hydrogen and steam during welding, causing porosity; re-drying at the correct temperature removes it.
Question 5: In SAW process control, what does a 'constant voltage' (CV) power source primarily regulate?
- Wire feed speed to maintain set amperage
- Arc voltage, allowing current to vary with arc length changes (Correct answer)
- Flux depth above the arc
- Travel speed based on arc feedback
Correct answer: Arc voltage, allowing current to vary with arc length changes
A CV power source maintains a preset voltage, and the arc self-regulates by drawing more or less current as arc length fluctuates.
Question 6: When making a circumferential weld on a pipe using SAW in the flat position, what technique prevents the molten pool from running ahead of the arc?
- Welding uphill on a steep incline
- Positioning the electrode slightly behind the pipe's top-center point (Correct answer)
- Using maximum flux depth
- Reducing arc voltage below 25 V
Correct answer: Positioning the electrode slightly behind the pipe's top-center point
Offsetting the electrode slightly back from the 12-o'clock position lets gravity keep the pool from flowing ahead and undermining the arc.
Question 7: What effect does using a finer-mesh flux granulation have on the SAW arc?
- Coarser beads with higher reinforcement
- Smoother arc with finer bead finish but reduced flux permeability (Correct answer)
- Greater penetration due to higher flux conductivity
- Increased travel speed capability
Correct answer: Smoother arc with finer bead finish but reduced flux permeability
Fine-mesh flux creates a denser, less permeable blanket that smooths the arc and bead surface but can trap gases if too tightly packed.
SAW Welding Techniques & Process Control 3
What happens to weld bead convexity when arc voltage is set too low in SAW?