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

Question 1

What type of power source characteristic is used for GMAW (MIG) welding?

Accepted Answer

Constant voltage (CV)

Answer

Constant current (CC)

Answer

Pulsed current only

Answer

AC transformer

Question 2

What is the function of the shielding gas in GMAW welding?

Accepted Answer

Protects the weld pool from atmospheric oxygen and nitrogen, affects arc characteristics and bead profile

Answer

Cools the contact tip to prevent burnback

Answer

Carries the electrode wire to the weld pool

Answer

Provides the ionization path for arc initiation only

Question 3

Which shielding gas mixture is most commonly used for GMAW on carbon steel in Canada?

Accepted Answer

75% Argon / 25% CO2 (C25)

Answer

100% CO2

Answer

100% Argon

Answer

50% Argon / 50% Helium

Question 4

What is 'wire burnback' in GMAW and what causes it?

Accepted Answer

The wire fuses to the contact tip; caused by the wire feed stopping while the arc is still active

Answer

Excessive spatter that clogs the gas nozzle

Answer

Porosity from shielding gas interruption

Answer

Electrode wire breaking inside the conduit liner

Question 5

In GMAW short-circuit transfer mode, what happens during the 'short circuit' phase of metal transfer?

Accepted Answer

The wire touches the weld pool, current surges, and surface tension pulls molten metal from the wire into the pool

Answer

A droplet of metal detaches freely in the arc without touching the pool

Answer

The wire is vaporized by a high-energy pulse

Answer

Metal is transferred by explosive electromagnetic forces

Question 6

What shielding gas is recommended for GMAW welding of aluminum?

Accepted Answer

100% Argon

Answer

75% Argon / 25% CO2

Answer

100% CO2

Answer

100% Helium