GMAW/FCAW (MIG/Flux Core) — Welder (456A) Practice Questions

Free GMAW/FCAW (MIG/Flux Core) practice questions

1. 1.GMAW shielding gas for carbon steel is typically:

   • A.Pure argon
   • B.75% Argon / 25% CO₂ (C25) or 100% CO₂✓
   • C.Pure helium
   • D.Pure nitrogen

   Why: C25 (75/25): good penetration, low spatter, smooth arc. 100% CO₂: deeper penetration, more spatter, lower cost. Pure argon is for aluminum/stainless (with GTAW).

2. 2.Spray transfer (GMAW) produces:

   • A.High spatter
   • B.A smooth, high-deposition stream of fine droplets — used for thick material in flat/horizontal only✓
   • C.Low penetration
   • D.Cold welds

   Why: Spray: above transition voltage/current, small droplets spray across the arc. High deposition, deep penetration, excellent appearance. Limited to flat/horizontal (high heat).

3. 3.Bird-nesting (tangled wire) in the GMAW gun is caused by:

   • A.Perfect settings
   • B.Excessive drive roll pressure, worn liner, wrong liner size, or kink in the cable✓
   • C.Too little wire feed
   • D.Too much gas

   Why: Bird-nesting: wire tangles at the drive rolls. Causes: too much pressure (feeds faster than tip allows), worn/wrong liner, clogged tip, kink in cable. Reduces to waste.

4. 4.Dual-shield FCAW (FCAW-G) uses:

   • A.No shielding
   • B.Both flux core AND external shielding gas (typically 75/25 or 100% CO₂)✓
   • C.Only flux
   • D.Only gas

   Why: FCAW-G: flux core + external gas. Better weld quality than self-shielded, higher deposition than GMAW. Popular for structural steel, heavy fabrication, and shipbuilding.

5. 5.Voltage in GMAW controls:

   • A.Current
   • B.Arc length and bead width — higher voltage = longer arc = wider, flatter bead✓
   • C.Wire feed speed
   • D.Gas flow

   Why: In CV systems: voltage controls arc length. Higher V = longer arc = wider/flatter bead. Too high = excessive spatter, undercut. Too low = stubbing, narrow bead.

6. 6.Globular transfer mode in GMAW is generally:

   • A.Preferred
   • B.Undesirable — large irregular drops transfer across the arc causing high spatter✓
   • C.The best mode
   • D.Used for aluminum

   Why: Globular: large drops form, grow, and fall by gravity. High spatter, poor appearance. Occurs between short-circuit and spray voltage ranges. Avoided in practice.

7. 7.FCAW electrodes classified as E71T-1 are:

   • A.Self-shielded
   • B.Gas-shielded flux core wire, all position (1), for use with CO₂ or 75/25 mixed gas✓
   • C.Solid wire
   • D.TIG wire

   Why: E71T-1: E=electrode, 7=70ksi, 1=all position, T=tubular (flux core), 1=classification (gas-shielded, CO₂ or mixed). High deposition, all positions, requires external gas.

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