456A MIG/FCAW (GMAW & Flux-Cored Arc Welding) 3

Question 1

What is the correct procedure when porosity is found in a GMAW weld due to suspected shielding gas loss?

Accepted Answer

Check gas flow rate, hose connections, and nozzle for blockage; test on scrap before resuming production welding

Answer

When porosity indicates shielding gas issues, the welder must systematically check: flow rate (typically 15–20 L/min for C25), hose connections for leaks, nozzle cleanliness, and draft/wind conditions. Testing on scrap confirms the fix before resuming production welding to avoid rejectable welds.

Question 2

What is the minimum recommended shielding gas flow rate for GMAW carbon steel welding (C25) to ensure adequate coverage?

Accepted Answer

15–20 L/min (30–40 CFH)

Answer

A flow rate of 15–20 L/min (approximately 30–40 CFH) is the standard range for GMAW with C25 shielding gas. Too low a flow rate provides inadequate protection; too high a flow rate causes turbulence that can draw in atmospheric air, both resulting in porosity.

Question 3

What is 'lack of fusion' (LOF) in GMAW and what typically causes it?

Accepted Answer

Weld metal that does not bond to the base metal or previous pass; caused by insufficient heat input or improper technique

Answer

Lack of fusion occurs when the weld metal and base metal (or adjacent weld passes) are in contact but not metallurgically bonded. Causes include too low an amperage/voltage, too fast a travel speed, improper electrode angle directing the arc away from the fusion face, or a dirty/oxidized base metal surface.

Question 4

When welding with an E71T-1C flux-cored electrode, what does the 'C' suffix indicate?

Accepted Answer

CO2 shielding gas is required

Answer

In the AWS A5.20 (and CSA equivalent) flux-cored electrode classification, the 'C' suffix on FCAW electrodes (e.g., E71T-1C) indicates that pure CO2 shielding gas is required. An 'M' suffix indicates mixed gas (Ar/CO2). Some electrodes are rated for both (C/M).

Question 5

What is the main advantage of FCAW-G over SMAW for structural welding?

Accepted Answer

Higher deposition rate and continuous wire feed allowing longer welds without stopping to change electrodes

Answer

FCAW-G offers significantly higher deposition rates than SMAW (up to 4–5× faster) and uses continuous wire so the welder does not need to stop to change electrodes. This increases productivity, reduces labour costs, and is why FCAW-G has largely replaced SMAW in structural fabrication shops.

Red Seal Welder 456A Practice Test

Red Seal Welder 456A Practice Test

456A MIG/FCAW (GMAW & Flux-Cored Arc Welding) 3