FCAW (Flux-Cored Arc Welding — ISO 4063 Process 136/114) is an arc welding method using a continuously fed flux-cored tubular electrode that combines the advantages of MAG and SMAW. The flux inside the wire functions both as a shielding gas source and as an alloying medium.
FCAW is preferred in structural steel fabrication, particularly in site conditions where high deposition rate and wind tolerance are required.
FCAW Wire Types
| Type | Shielding Gas | Weld Quality | Application |
|---|---|---|---|
| Rutile Flux-Cored (E7XT-1) | CO₂ or Ar+CO₂ | Good bead appearance, easy slag removal | General structural steel, all positions |
| Basic Flux-Cored (E7XT-5) | CO₂ or Ar+CO₂ | High toughness (low temperature) | Critical structures, dynamic loads, low temperature |
| Metal-Cored (E70T-9) | Ar+CO₂ mandatory | Very clean, minimal slag | High-speed applications, robotic |
| Self-Shielded (E71T-11) | None (self-shielded) | Moderate — more spatter | Field, open air, gas transport impossible |
Parameter Optimisation
Key parameters and typical values for FCAW:
- Current: 150–400 A (depending on wire diameter and type)
- Voltage: 22–36 V
- CTWD (Contact Tip-to-Work Distance): 15–25 mm — 15–20 mm for rutile; 20–25 mm for basic
- Travel Speed: 20–50 cm/min
- Shielding Gas (gas-shielded): 75% Ar + 25% CO₂ or 100% CO₂
CTWD effect: In FCAW, increasing CTWD raises resistive preheating and changes melting behaviour. A longer CTWD is the nominal working point compared to MAG — this is normal and expected.
Comparison with MAG and Selection Criteria
Situations where FCAW outperforms MAG (process 135):
- Site environments with wind speed > 2 m/s (especially self-shielded FCAW)
- When thick section (> 15 mm) and high deposition rate are the priority
- When rutile wire provides better slag support than MAG for positional welds
- When Charpy values must be guaranteed with basic wire for critical high-toughness structures
MAG (process 135) is preferred for thin plate, indoor use, robotic applications and where clean bead appearance is critical.
FCAW Applications in Structural Steel
At ArmaWeld, FCAW is used in structural steel projects under EN 1090 EXC2/3, particularly for site assembly welds and fillet welds. The wires used are certified rutile and basic flux-cored wires compliant with EN ISO 17632. An approved WPS is available for every FCAW application; heat input (kJ/mm) is recorded in the weld log. Basic flux-cored wire is particularly preferred for bridge and industrial structural steel projects to meet high toughness requirements.
Your Structural Steel Welding Project
Discuss with our technical team the best choice between MAG, FCAW or SAW; we will prepare a quote with process recommendation and WPS scope.
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