FCAW · Flux-Cored Arc Welding
Flux-Cored Welding
Flux-cored welding feeds a tubular wire with flux inside, combining MIG's continuous feed with stick's slag shielding — available gas-shielded for quality or self-shielded for wind.
- FCAW
- DCEP for gas-shielded wires; DCEN for most self-shielded wires
- 70–450 A depending on wire size
- Flux only (self-shielded) or flux plus external gas (gas-shielded)
How flux-cored welding works
The electrode is a tube of mild steel filled with flux. As it melts, the flux does what a stick electrode's coating does: it generates shielding gas, deoxidises the puddle and forms a slag that covers the cooling weld. Gas-shielded wire adds an external gas for extra protection and toughness. Self-shielded wire relies on the flux alone, which is what lets it work outdoors.
At a glance
| AWS designation | FCAW — Flux-Cored Arc Welding |
|---|---|
| Also called | Flux core, FCAW, Dual shield, Gasless MIG, Innershield |
| Polarity | DCEP for gas-shielded wires; DCEN for most self-shielded wires |
| Typical amperage | 70–450 A depending on wire size |
| Typical voltage | 22–30 V |
| Positions | All positions with 71T wires; 70T flat-and-horizontal wires exist for high deposition |
| Deposition rate | The highest of the manual arc processes |
| Shielding | Flux only (self-shielded) or flux plus external gas (gas-shielded) |
| Skill level | Similar to MIG, with slag removal added |
Gas-shielded vs self-shielded
| Mode | Description | Typical use |
|---|---|---|
| FCAW-G (gas-shielded) | Uses CO2 or an argon/CO2 mix in addition to the flux. Smoother arc, better toughness, higher quality — and the choice for structural code work. Runs DCEP. | Indoor structural and production welding |
| FCAW-S (self-shielded) | No gas bottle at all. The flux generates everything the weld needs, so it works in wind. Runs DCEN, more spatter and smoke, generally lower toughness. | Outdoor, field and hobby welding |
Shielding gas selection
| Gas | Used for | Notes |
|---|---|---|
| 100% CO2 | Gas-shielded flux core | Deeper penetration, lower cost, more spatter. The traditional structural choice. |
| 75% Ar / 25% CO2 | Gas-shielded flux core | Smoother arc, less spatter, better out-of-position control, slightly higher tensile. |
| None | Self-shielded flux core | The flux provides all shielding. Adding gas does nothing useful. |
Starting settings
Starting points only — every machine, joint and position shifts them. Adjust by arc sound and bead profile.
| Wire | Thickness | Amps | Volts | Wfs |
|---|---|---|---|---|
| 0.030 in self-shielded | up to 1/8 in | 60–120 | 15–18 | 80–180 ipm |
| 0.035 in self-shielded | 1/8–1/4 in | 90–160 | 17–20 | 120–250 ipm |
| 0.045 in gas-shielded | 1/4–1/2 in | 180–280 | 24–28 | 250–400 ipm |
| 0.052 in gas-shielded | 3/8 in and up | 220–340 | 25–29 | 250–380 ipm |
| 1/16 in gas-shielded | 1/2 in and up | 280–450 | 26–32 | 200–350 ipm |
Advantages
- Highest deposition rate of the manual arc processes
- Self-shielded wire works outdoors where MIG cannot
- Deeper penetration than solid MIG wire at the same current
- Handles thicker plate in fewer passes
- All-position capability at high current thanks to the fast-freezing slag
Limitations
- Slag must be chipped between passes
- Produces noticeably more fume than solid wire, so ventilation matters
- Self-shielded wire has lower toughness and is usually thickness limited
- Gas-shielded wire still cannot be used in wind
- Wire is more expensive per pound than solid wire
Where it is used
- Structural steel fabrication and erection
- Shipbuilding and barge construction
- Heavy equipment manufacture and repair
- Outdoor field welding with self-shielded wire
- Hobby and farm welding on small gasless machines
Filler metals for flux-cored welding
E71T-1
AWS A5.20/A5.20M · Flux-Cored
E71T-1 is gas-shielded flux-cored wire — the high-deposition, all-position production workhorse for structural steel…
E71T-11
AWS A5.20/A5.20M · Flux-Cored
E71T-11 is self-shielded flux-cored wire — no gas bottle, runs DCEN, and works in wind, which makes it the standard…
Flux-Cored Welding — common questions
What is the difference between gas-shielded and self-shielded flux core?
Gas-shielded wire (FCAW-G, such as E71T-1) uses external shielding gas on top of the flux, runs DCEP, and produces tougher, higher-quality welds suited to code work. Self-shielded wire (FCAW-S, such as E71T-11) needs no gas, runs DCEN, and works outdoors, but has lower toughness and is usually thickness limited.
Is flux core DCEP or DCEN?
It depends on the wire. Gas-shielded wires such as E71T-1 run DCEP. Most self-shielded wires including E71T-11 run DCEN. Getting this backwards is the most common flux-core setup mistake.
Is flux core stronger than MIG?
Both deposit 70 ksi class weld metal on carbon steel. Flux core penetrates deeper at a given current and fills faster, which makes it better suited to thick plate — but on a properly designed joint neither is inherently stronger.
Why does my flux core weld look so rough?
Check polarity first, then stickout, then gun angle. Self-shielded wire needs DCEN, a long stickout of 1/2 to 3/4 in, and a drag angle. Pushing the gun rolls slag ahead of the puddle and traps it.
Can you use flux core wire without gas?
Only if it is self-shielded wire such as E71T-11. Gas-shielded wire like E71T-1 will go porous without its gas. The wire's classification, not the machine, decides.