AWS AWS Welding Processes & Equipment 4 — Questions and Answers
Question 1: In flux-cored arc welding (FCAW), what is the primary difference between FCAW-S and FCAW-G?
- FCAW-S uses a solid wire while FCAW-G uses a tubular wire
- FCAW-S is self-shielded requiring no external gas while FCAW-G requires external shielding gas (Correct answer)
- FCAW-S operates on DC while FCAW-G operates on AC
- FCAW-S is used only for stainless steel while FCAW-G is used for carbon steel
Correct answer: FCAW-S is self-shielded requiring no external gas while FCAW-G requires external shielding gas
FCAW-S (self-shielded) generates its own shielding from flux compounds inside the tubular wire, while FCAW-G (gas-shielded) requires an external shielding gas supply.
Question 2: Which welding process uses a non-consumable tungsten electrode and is best suited for welding thin aluminum sections?
- SMAW
- GMAW
- GTAW (Correct answer)
- SAW
Correct answer: GTAW
Gas tungsten arc welding (GTAW/TIG) uses a non-consumable tungsten electrode and provides precise heat control ideal for thin aluminum.
Question 3: What is the purpose of a contactor in a welding power source?
- To regulate the shielding gas flow rate
- To energize the welding output terminals only when the arc is struck or the torch trigger is pressed (Correct answer)
- To cool the welding torch during extended use
- To convert AC to DC current
Correct answer: To energize the welding output terminals only when the arc is struck or the torch trigger is pressed
A contactor is a high-current switch that keeps the welding output terminals de-energized until the welder initiates an arc, improving operator safety.
Question 4: During submerged arc welding (SAW), what function does the granular flux serve?
- It acts as the consumable electrode that melts into the weld pool
- It shields the arc and weld pool from atmospheric contamination and can add alloying elements (Correct answer)
- It preheats the base metal prior to welding
- It provides the electrical path between the workpiece and the power supply
Correct answer: It shields the arc and weld pool from atmospheric contamination and can add alloying elements
In SAW, the granular flux completely covers the arc and molten pool, protecting it from the atmosphere and potentially contributing alloying elements to the weld.
Question 5: A welding power source rated at 300A/32V with a 60% duty cycle can be used continuously at rated output for how many minutes out of every 10-minute period?
- 3 minutes
- 4 minutes
- 6 minutes (Correct answer)
- 8 minutes
Correct answer: 6 minutes
A 60% duty cycle means the machine can operate at rated output for 60% of a 10-minute period, which equals 6 minutes on and 4 minutes off.
Question 6: In plasma arc welding (PAW), what distinguishes the 'keyhole' technique from conventional fusion welding?
- The keyhole technique uses lower current to avoid burn-through on thin materials
- A high-velocity plasma jet penetrates completely through the base metal, creating a hole that is progressively filled as the torch advances (Correct answer)
- The keyhole technique requires the use of filler metal on every pass
- The keyhole technique is performed without any shielding gas
Correct answer: A high-velocity plasma jet penetrates completely through the base metal, creating a hole that is progressively filled as the torch advances
In keyhole PAW, the constricted plasma arc fully penetrates the joint, and surface tension holds the molten metal as the keyhole moves forward, enabling full-penetration single-pass welds.
Question 7: Which shielding gas or gas mixture is most commonly recommended for GMAW of carbon steel to achieve a good balance of penetration, bead appearance, and arc stability?
- 100% argon
- 100% CO2
- 75% argon / 25% CO2 (Correct answer)
- 50% helium / 50% argon
Correct answer: 75% argon / 25% CO2
A 75% Ar / 25% CO2 blend (C25) is the industry standard for carbon steel GMAW, balancing CO2's penetration and cost with argon's arc stability and reduced spatter.
AWS AWS Welding Processes & Equipment 4
In flux-cored arc welding (FCAW), what is the primary difference between FCAW-S and FCAW-G?