1.3 FCAW — Flux-Cored Arc Welding
Key Takeaways
- FCAW uses a tubular flux-cored wire electrode and operates on a constant voltage (CV) power source
- Two variants: FCAW-G (gas-shielded for shop) and FCAW-S (self-shielded for outdoor/field work)
- FCAW-S is the preferred process for field erection because it needs no external gas and resists wind
- Deposition rates of 8–25+ lbs/hr make FCAW the dominant process in structural and heavy fabrication
- Common wires: E71T-1 (gas-shielded, all-position) and E71T-8 (self-shielded, all-position)
- The "T" in wire classification means "tubular" — distinguishing flux-cored from solid ("S") wire
1.3 FCAW — Flux-Cored Arc Welding
Flux-Cored Arc Welding (FCAW) combines elements of both SMAW and GMAW. It uses a continuously fed tubular wire electrode filled with flux, operating on a constant voltage (CV) power source. FCAW is the dominant process in structural steel construction, shipbuilding, and heavy fabrication.
Two Variants of FCAW
| Variant | Designation | Shielding | Common Applications |
|---|---|---|---|
| FCAW-G (Gas-shielded) | Uses external shielding gas + flux core | CO₂ or Ar/CO₂ | Shop fabrication, structural steel |
| FCAW-S (Self-shielded) | Flux core provides all shielding — no gas needed | Self-shielded by flux decomposition | Field/outdoor work, windy conditions |
Why FCAW Dominates Structural Steel
FCAW combines the high deposition rates of GMAW with the all-position, outdoor capability of SMAW:
- Deposition rates: 8–25+ lbs/hr (much higher than SMAW)
- All-position welding with proper wire selection
- Self-shielded variant works in wind up to 35+ mph
- Deep penetration — effective on thick structural members
- Slag coverage provides good bead appearance and protects cooling weld
FCAW Wire Classification (AWS A5.20 — Carbon Steel)
Example: E71T-1C
| Character | Meaning |
|---|---|
| E | Electrode |
| 7 | Minimum tensile strength in ksi × 10 (70 ksi) |
| 1 | Usable positions (1 = all; 0 = flat/horizontal only) |
| T | Tubular (flux-cored) wire |
| 1 | Usability designator (operating characteristics) |
| C | Shielding gas (C = CO₂; M = mixed gas 75–80% Ar/25–20% CO₂) |
Common FCAW Electrodes:
| Electrode | Shielding | Positions | Key Features |
|---|---|---|---|
| E71T-1C/1M | Gas-shielded | All | Most common gas-shielded FCAW wire; smooth arc, good all-position |
| E70T-1C/1M | Gas-shielded | Flat/Horizontal | High deposition for flat/horizontal; structural, shipbuilding |
| E71T-8 | Self-shielded | All | All-position self-shielded; field erection, bridges |
| E70T-4 | Self-shielded | Flat/Horizontal | Very high deposition rates; heavy fabrication |
| E71T-9C/9M | Gas-shielded | All | Improved impact toughness; bridge and structural applications |
Self-Shielded vs. Gas-Shielded Comparison
| Factor | FCAW-G (Gas-Shielded) | FCAW-S (Self-Shielded) |
|---|---|---|
| Shielding | External gas + flux | Flux only |
| Wind tolerance | Moderate (similar to GMAW) | Excellent (35+ mph) |
| Penetration | Deep | Very deep |
| Bead appearance | Smooth, less spatter | Rougher, more spatter |
| Typical use | Shop fabrication | Field erection, outdoor |
| Slag | Present, usually easy to remove | Present, may be harder to remove |
| Fume generation | Moderate | Higher (more flux decomposition) |
| Typical wire | E71T-1 | E71T-8 |
FCAW-S Field Welding Considerations
Self-shielded FCAW is the preferred process for field erection of structural steel because:
- No gas cylinders or gas lines to transport and set up
- No wind screens needed
- Excellent penetration on thick members
- All-position capability
- Approved under AWS D1.1 for all structural applications
For the Exam: Know the difference between FCAW-G (gas-shielded) and FCAW-S (self-shielded). FCAW-S is the go-to process for outdoor field welding because it does not require external shielding gas. Also know that the "T" in the wire classification means "tubular."
Advantages and Limitations
| Advantages | Limitations |
|---|---|
| Very high deposition rates (8–25 lbs/hr) | Slag must be removed between passes |
| Self-shielded option for outdoor work | More fumes than GMAW (especially FCAW-S) |
| All-position capability | Wire can be more expensive than solid wire |
| Deep penetration | Equipment slightly more complex than SMAW |
| High productivity — less downtime | Proper storage of wire required (moisture pickup) |
| Good mechanical properties | Porosity risk if gas coverage lost (FCAW-G) |
What does the "T" stand for in the FCAW electrode classification E71T-1C?
Which FCAW variant is best suited for outdoor field welding in windy conditions?
What is the approximate deposition rate range for FCAW?