AWS Flux-Cored Arc Welding (FCAW) 5 — Questions and Answers
Question 1: What is the main advantage of using 75% Ar / 25% CO2 shielding gas instead of 100% CO2 for FCAW-G?
- Higher deposition rate
- Reduced spatter and smoother arc characteristics (Correct answer)
- Greater penetration depth
- Lower cost per cubic foot
Correct answer: Reduced spatter and smoother arc characteristics
Adding argon to CO2 shielding gas reduces spatter and produces a smoother, more stable arc, improving weld appearance and reducing cleanup time.
Question 2: Which AWS specification governs the classification of carbon steel flux-cored electrodes for FCAW?
- AWS A5.18
- AWS A5.20 (Correct answer)
- AWS A5.1
- AWS A5.36
Correct answer: AWS A5.20
AWS A5.20 is the specification that classifies carbon steel electrodes specifically for flux-cored arc welding.
Question 3: What defect is most likely to occur if the FCAW gun angle is too steep (pushing angle greater than 25°)?
- Undercut at the weld toes
- Excessive slag inclusions due to flux being pushed ahead of the arc (Correct answer)
- Incomplete fusion at the root
- Hydrogen cracking in the heat-affected zone
Correct answer: Excessive slag inclusions due to flux being pushed ahead of the arc
An excessively steep push angle drives molten flux ahead of the weld pool, where it can become entrapped in the solidifying weld metal as slag inclusions.
Question 4: When pre-qualifying a FCAW procedure under AWS D1.1, increasing the base metal thickness beyond the tested range typically requires:
- Only increasing the preheat temperature
- A new WPS supported by a new PQR at the increased thickness (Correct answer)
- Welder requalification only
- Simply updating the WPS without re-testing
Correct answer: A new WPS supported by a new PQR at the increased thickness
AWS D1.1 requires a new Procedure Qualification Record (PQR) with testing at the new thickness to support a revised WPS when essential variables change.
Question 5: Which condition distinguishes FCAW-S from FCAW-G regarding suitability for field welding?
- FCAW-S requires a constant-current power source
- FCAW-S needs no external gas cylinder, making it more portable for field use (Correct answer)
- FCAW-S always produces lower-strength welds
- FCAW-S is limited to flat position only
Correct answer: FCAW-S needs no external gas cylinder, making it more portable for field use
FCAW-S generates its own shielding from the flux core, eliminating the need to transport gas cylinders, which makes it highly practical for outdoor and field welding applications.
Question 6: A FCAW weld on A36 steel shows underfill (insufficient weld metal). Which corrective action is most appropriate?
- Increase travel speed
- Decrease wire feed speed
- Reduce travel speed or make additional weld passes (Correct answer)
- Increase voltage to spread the bead wider
Correct answer: Reduce travel speed or make additional weld passes
Slowing travel speed deposits more weld metal per unit length, and making additional passes builds up weld thickness to meet the required throat dimension.
Question 7: What is the purpose of the 'crater fill' function available on some FCAW power sources?
- To increase penetration at weld start
- To prevent crater cracking by gradually reducing heat input at weld termination (Correct answer)
- To preheat the base metal before welding
- To improve gas shielding coverage at the end of the weld
Correct answer: To prevent crater cracking by gradually reducing heat input at weld termination
Crater fill gradually reduces welding current and wire feed speed at the end of the weld, filling the crater and preventing crater cracks caused by rapid cooling stresses.
AWS Flux-Cored Arc Welding (FCAW) 5
What is the main advantage of using 75% Ar / 25% CO2 shielding gas instead of 100% CO2 for FCAW-G?