CWI Welding Process Fundamentals 2 — Questions and Answers
Question 1: In GMAW, what is the primary function of the shielding gas?
- To preheat the base metal
- To protect the weld pool from atmospheric contamination (Correct answer)
- To increase wire feed speed
- To reduce spatter by cooling the arc
Correct answer: To protect the weld pool from atmospheric contamination
Shielding gas in GMAW surrounds the arc and weld pool to prevent oxidation and contamination from oxygen, nitrogen, and hydrogen in the atmosphere.
Question 2: Which GMAW transfer mode is best suited for welding thin sheet metal in all positions?
- Globular transfer
- Spray transfer
- Short-circuit transfer (Correct answer)
- Pulsed spray transfer
Correct answer: Short-circuit transfer
Short-circuit transfer uses low heat input and a small, fast-freezing weld pool, making it ideal for thin materials and out-of-position welding.
Question 3: What does the term 'duty cycle' mean for a welding power source?
- The number of welds completed per hour
- The percentage of a 10-minute period the machine can weld at a rated current (Correct answer)
- The ratio of arc-on time to electrode feed rate
- The maximum open-circuit voltage the machine can produce
Correct answer: The percentage of a 10-minute period the machine can weld at a rated current
Duty cycle is the percentage of a 10-minute interval during which a welding machine can operate at its rated output without overheating.
Question 4: In SAW (Submerged Arc Welding), what is the role of the flux?
- It serves as the primary filler metal
- It shields the arc, refines the weld metal, and can add alloying elements (Correct answer)
- It acts only as a preheating medium
- It replaces the need for a base metal
Correct answer: It shields the arc, refines the weld metal, and can add alloying elements
SAW flux covers the arc to prevent atmospheric contamination, stabilizes the arc, and can contribute alloying elements and remove impurities from the weld pool.
Question 5: What is the primary advantage of using a constant voltage (CV) power source for GMAW?
- It maintains a constant current regardless of arc length
- It self-corrects arc length by automatically adjusting current as wire feed rate varies (Correct answer)
- It eliminates the need for shielding gas
- It allows welding at higher travel speeds than SMAW
Correct answer: It self-corrects arc length by automatically adjusting current as wire feed rate varies
A CV power source maintains relatively constant voltage; when arc length changes, the machine adjusts amperage to restore the set voltage, providing self-regulation.
Question 6: Which of the following best describes the FCAW-S (self-shielded) process?
- Uses a solid wire electrode with external CO2 shielding
- Uses a flux-cored wire that generates its own shielding gases from core ingredients (Correct answer)
- Requires both flux and external shielding gas for all positions
- Uses a granular flux fed separately from the wire
Correct answer: Uses a flux-cored wire that generates its own shielding gases from core ingredients
FCAW-S uses a tubular wire filled with flux compounds that decompose in the arc to generate shielding gases and slag, eliminating the need for external gas.
Question 7: In GTAW, what is the purpose of high-frequency (HF) start?
- To increase travel speed
- To initiate the arc without the tungsten touching the base metal (Correct answer)
- To preheat the filler rod before welding
- To clean the oxide layer by reversing polarity
Correct answer: To initiate the arc without the tungsten touching the base metal
High-frequency start allows the GTAW arc to be initiated by jumping a spark across the gap, preventing tungsten contamination from contact starting.
CWI Welding Process Fundamentals 2
In GMAW, what is the primary function of the shielding gas?