AWS Filler Metals & Consumables 2 — Questions and Answers
Question 1: Which shielding gas mixture is most commonly used for GMAW of carbon steel to balance arc stability, spatter reduction, and penetration?
- 75% Argon / 25% CO₂ (C25) (Correct answer)
- 100% Argon
- 100% CO₂
- 50% Argon / 50% Helium
Correct answer: 75% Argon / 25% CO₂ (C25)
A 75% Ar / 25% CO₂ mixture (C25) is the industry standard for carbon steel GMAW because it provides excellent arc stability, reduced spatter, and good weld bead profile.
Question 2: In self-shielded flux-cored arc welding (FCAW-S), where does the shielding of the weld pool come from?
- Decomposition of flux compounds within the wire core (Correct answer)
- An external cylinder of inert shielding gas
- A granular flux pre-placed on the joint surface
- The base metal's natural oxide layer
Correct answer: Decomposition of flux compounds within the wire core
In FCAW-S, the flux ingredients packed inside the hollow tubular wire decompose under welding heat to generate shielding gases and slag that protect the molten pool without any external gas supply.
Question 3: In the AWS FCAW electrode classification E71T-1C, what does the 'T' designate?
- Tubular (flux-cored) electrode construction (Correct answer)
- Tensile strength modifier
- Titanium-bearing flux system
- Two-pass maximum application
Correct answer: Tubular (flux-cored) electrode construction
The 'T' in FCAW electrode classifications designates that the electrode is tubular (flux-cored), distinguishing it from solid wire electrodes used in GMAW.
Question 4: For GTAW (TIG) welding of Type 304 austenitic stainless steel, which filler metal is most commonly specified?
- ER308L (Correct answer)
- ER316L
- ER309L
- ER70S-6
Correct answer: ER308L
ER308L is the standard filler for Type 304 stainless; the 'L' (low carbon) designation minimizes sensitization and carbide precipitation in the heat-affected zone.
Question 5: AWS A5.20 covers filler metals used in which welding process?
- Flux-cored arc welding (FCAW) of carbon steel (Correct answer)
- Submerged arc welding (SAW) of carbon steel
- Gas metal arc welding (GMAW) of carbon steel
- Shielded metal arc welding (SMAW) of carbon steel
Correct answer: Flux-cored arc welding (FCAW) of carbon steel
AWS A5.20 is the specification for Carbon Steel Electrodes for Flux-Cored Arc Welding, classifying both gas-shielded (FCAW-G) and self-shielded (FCAW-S) tubular electrodes.
Question 6: Which filler metal is most commonly recommended for GMAW or GTAW of 6XXX-series aluminum alloys?
- ER4043 (Correct answer)
- ER5356
- ER308L
- ER70S-6
Correct answer: ER4043
ER4043 (aluminum-silicon filler) is widely preferred for 6XXX-series aluminum because it provides excellent crack resistance, good fluidity, and a bright weld appearance.
Question 7: What is the primary advantage of the higher silicon (Si) and manganese (Mn) content in ER70S-6 compared to ER70S-3?
- They act as deoxidizers, enabling sound welds on lightly rusted or mill-scaled surfaces (Correct answer)
- They significantly increase the tensile strength of the weld deposit
- They lower the required preheat temperature for thick base metal
- They replace the need for external shielding gas in some applications
Correct answer: They act as deoxidizers, enabling sound welds on lightly rusted or mill-scaled surfaces
The elevated Si and Mn in ER70S-6 act as powerful deoxidizers, combining with oxygen in the weld pool to produce sound, porosity-free welds even on base metal with light rust or mill scale.
AWS Filler Metals & Consumables 2
Which shielding gas mixture is most commonly used for GMAW of carbon steel to balance arc stability, spatter reduction, and penetration?