AWS Welding Processes 3 — Questions and Answers
Question 1: What is the main difference between FCAW-G and FCAW-S?
- FCAW-G uses a solid wire while FCAW-S uses a flux-cored wire
- FCAW-G requires external shielding gas while FCAW-S is self-shielded by the core flux (Correct answer)
- FCAW-G operates on DC+ while FCAW-S requires AC current
- FCAW-G is used only on stainless steel while FCAW-S is for carbon steel only
Correct answer: FCAW-G requires external shielding gas while FCAW-S is self-shielded by the core flux
FCAW-G (gas-shielded) requires an external shielding gas supply, while FCAW-S (self-shielded) generates its own shielding from the flux core, making it usable without gas cylinders.
Question 2: In SMAW, what does the coating on a covered electrode primarily provide?
- Electrical insulation to prevent the welder from being shocked
- Shielding gas and slag to protect the molten weld metal from atmospheric contamination (Correct answer)
- Additional filler metal to increase deposition rates
- A flux that dissolves the base metal oxide before welding
Correct answer: Shielding gas and slag to protect the molten weld metal from atmospheric contamination
The electrode coating burns during welding to generate shielding gases and form a slag layer that protects the molten weld pool from oxygen and nitrogen in the atmosphere.
Question 3: Which electrode classification is a low-hydrogen SMAW electrode suitable for welding high-strength steels?
- E6010
- E6013
- E7018 (Correct answer)
- E6011
Correct answer: E7018
E7018 is a low-hydrogen iron powder electrode with a 70,000 psi minimum tensile strength, widely used for structural and high-strength steel applications.
Question 4: What polarity is typically used for GTAW on aluminum and why?
- DCEN (straight polarity), because it provides deeper penetration
- DCEP (reverse polarity), because it cleans the oxide layer from the aluminum surface
- AC, because it provides a cleaning action on positive half-cycles and penetration on negative half-cycles (Correct answer)
- Any polarity works equally well since aluminum conducts electricity uniformly
Correct answer: AC, because it provides a cleaning action on positive half-cycles and penetration on negative half-cycles
AC is used for GTAW on aluminum because the electrode-positive half-cycle provides a cathodic cleaning action that breaks up the refractory aluminum oxide, while the electrode-negative half-cycle provides penetration.
Question 5: Electroslag welding (ESW) is most appropriate for which application?
- Welding thin-gauge sheet metal in the flat position
- Joining very thick plates (over 1 inch) in the vertical position in a single pass (Correct answer)
- Making small tack welds on structural components
- Welding stainless steel pipe in the 5G position
Correct answer: Joining very thick plates (over 1 inch) in the vertical position in a single pass
ESW is designed for welding very thick plates vertically in a single pass using a molten slag bath and water-cooled copper shoes to contain the weld pool.
Question 6: What is 'pulsed GMAW' and what advantage does it offer?
- Welding with alternating current that pulses between positive and negative cycles
- A process that alternates between short-circuit and globular transfer modes automatically
- A mode that cycles between a high peak current (to transfer a droplet) and a low background current, enabling spray transfer at lower average heat input (Correct answer)
- GMAW performed with a pulsing wire feed speed to vary bead width
Correct answer: A mode that cycles between a high peak current (to transfer a droplet) and a low background current, enabling spray transfer at lower average heat input
Pulsed GMAW alternates between a high peak current to detach one droplet per pulse and a low background current, achieving spray-transfer quality at lower average heat input—ideal for thin materials or out-of-position work.
Question 7: Which statement correctly describes plasma arc welding (PAW) compared to GTAW?
- PAW uses a consumable electrode while GTAW uses a non-consumable tungsten
- PAW constricts the arc through a nozzle orifice to produce a higher energy density than GTAW (Correct answer)
- PAW always requires filler metal while GTAW can be autogenous
- PAW operates only on AC current while GTAW works on both AC and DC
Correct answer: PAW constricts the arc through a nozzle orifice to produce a higher energy density than GTAW
PAW forces the arc through a constricting orifice in the torch nozzle, creating a plasma column with much higher energy density than GTAW, enabling higher travel speeds and deeper penetration.
AWS Welding Processes 3
What is the main difference between FCAW-G and FCAW-S?