Which statement about GMAW transfer modes is correct?

• A. Only short circuit and spray are possible.
• B. Globular transfer uses the same voltage as short circuit
• C. The three recognized transfer modes are short circuit, globular, and spray.
• D. All transfer modes require the same heat input.

Answer: (C)

In GMAW, how metal is transferred from the filler wire to the work is described by transfer modes, which depend on the arc voltage and current, wire size, shielding gas, and other welding conditions. The three classic modes describe distinct droplet behavior and heat input.

Short-circuit transfer happens at lower arc voltage where the wire tip repeatedly makes contact with the work and then transfers a small molten drop during a short circuit. This mode is forgiving for thin materials and welding in multiple positions with lower heat input.

Globular transfer uses higher current so larger molten droplets form and detach, producing a more spattery arc and less controlled metal transfer. It tends to be less suitable for quality welds on thin parts due to spatter and potential porosity.

Spray transfer operates at high current and voltage, ejecting many tiny droplets in a smooth spray across the arc, giving deep penetration and high deposition rates. It requires adequate shielding gas and is used for higher-speed welds on thicker sections.

These describe the main, recognized transfer modes in many curricula, though variations like pulsed spray exist as modulation of spray. The other statements are not accurate because they misstate the number of modes, or compare voltage or heat input across modes that actually differ.