For GMAW using 0.9 mm (0.035 in) mild steel wire with carbon dioxide shielding gas, which transfer modes are possible?

For GMAW using 0.9 mm (0.035 in) mild steel wire with carbon dioxide shielding gas, which transfer modes are possible?

• A. spray and globular
• B. globular and short circuiting
• C. short circuiting and pulse spray
• D. spray and pulse spray

Answer: (B)

In GMAW, the transfer mode depends on arc current, wire diameter, and shielding gas. A 0.035 in (0.9 mm) mild steel wire is small and doesn’t require the very high current that spray transfer needs. Pure CO2 shielding tends to destabilize spray modes more than argon-rich blends, so spray and pulsed spray aren’t practical with this setup. Instead, at these wire sizes and with CO2, you get transfer modes that occur at lower to moderate current: short-circuit transfer, where the wire tip meets the weld puddle and transfers metal in rapid, small bursts; and globular transfer, where larger molten droplets form and detach irregularly. These two modes are feasible here, while spray and pulsed spray are not.

In GMAW, the transfer mode depends on arc current, wire diameter, and shielding gas. A 0.035 in (0.9 mm) mild steel wire is small and doesn’t require the very high current that spray transfer needs. Pure CO2 shielding tends to destabilize spray modes more than argon-rich blends, so spray and pulsed spray aren’t practical with this setup. Instead, at these wire sizes and with CO2, you get transfer modes that occur at lower to moderate current: short-circuit transfer, where the wire tip meets the weld puddle and transfers metal in rapid, small bursts; and globular transfer, where larger molten droplets form and detach irregularly. These two modes are feasible here, while spray and pulsed spray are not.