FCAW flux core welding parameters
Operating Parameters
Section titled “Operating Parameters”Flux-cored arc welding (FCAW) uses a continuous tubular electrode and key parameters such as arc voltage, wire feed speed, amperage, electrode extension (stickout), travel speed, polarity, and, when applicable, shielding gas composition. Representative operating values for different materials and process variants are given below.
Typical Parameters for Gas-Shielded FCAW (Dual Shield)
Section titled “Typical Parameters for Gas-Shielded FCAW (Dual Shield)”| Material | Wire Diameter | Voltage (V) | Wire Feed Speed | Amperage (A) | Electrode Extension (stickout) | Travel Speed | Shielding Gas |
|---|---|---|---|---|---|---|---|
| Carbon Steel (e.g., ASTM A36) | 1,2 mm / 0.045 in | 24–28 V | 5,3–8,5 m/min / 210–335 in/min | 180–280 A | 16–19 mm / 5/8–3/4 in | 350–500 mm/min / 14–20 in/min | 75% Ar / 25% CO₂ or pure CO₂ |
| Carbon Steel (thickness > 12 mm / 0.47 in) | 1,6 mm / 1/16 in | 26–32 V | 3,2–5,6 m/min / 125–220 in/min | 280–380 A | 20–25 mm / 3/4–1 in | 300–450 mm/min / 12–18 in/min | Pure CO₂ |
| Stainless Steel (AISI 304L) | 1,2 mm / 0.045 in | 23–27 V | 5,0–7,5 m/min / 200–295 in/min | 160–240 A | 13–16 mm / 1/2–5/8 in | 380–530 mm/min / 15–21 in/min | 90% He / 7,5% Ar / 2,5% CO₂ |
| Duplex Stainless Steel | 1,2 mm / 0.045 in | 25–29 V | 5,5–8,0 m/min / 215–315 in/min | 190–260 A | 16–19 mm / 5/8–3/4 in | 350–450 mm/min / 14–18 in/min | 98% Ar / 2% CO₂ |
| Nickel Alloy (Inconel 625) | 1,2 mm / 0.045 in | 24–26 V | 4,8–6,8 m/min / 190–270 in/min | 160–220 A | 14–17 mm / 9/16–11/16 in | 300–400 mm/min / 12–16 in/min | 75% Ar / 25% He |
Typical Parameters for Self-Shielded FCAW (No Gas)
Section titled “Typical Parameters for Self-Shielded FCAW (No Gas)”| Material | Wire Diameter | Voltage (V) | Wire Feed Speed | Amperage (A) | Electrode Extension (stickout) | Travel Speed | Polarity |
|---|---|---|---|---|---|---|---|
| Carbon Steel (thickness < 6 mm / 0.24 in) | 0,9 mm / 0.035 in | 16–21 V | 2,5–4,3 m/min / 100–170 in/min | 70–140 A | 13–19 mm / 1/2–3/4 in | 200–350 mm/min / 8–14 in/min | Electrode Negative (DCEN) |
| Carbon Steel (thickness 6–12 mm / 0,24–0,47 in) | 1,6 mm / 1/16 in | 18–24 V | 1,9–3,2 m/min / 75–125 in/min | 140–220 A | 19–25 mm / 3/4–1 in | 150–300 mm/min / 6–12 in/min | Electrode Negative (DCEN) |
| Low-Alloy Steel (HSLA) | 1,2 mm / 0.045 in | 18–22 V | 3,0–5,1 m/min / 120–200 in/min | 110–180 A | 15–20 mm / 5/8–3/4 in | 180–320 mm/min / 7–13 in/min | Electrode Negative (DCEN) |
Note: Ranges are approximate and depend on welding position, joint design, and the type of internal flux in the wire.
Typical Tolerances
Section titled “Typical Tolerances”Assembly and finishing tolerances in FCAW follow quality criteria similar to other arc processes, with emphasis on root gap and alignment.
| Parameter | Typical Tolerance |
|---|---|
| Root gap in butt joint (thickness ≤ 10 mm / 0.39 in) | 1,5 mm ± 0,5 mm / 0.06 in ± 0.02 in |
| Root gap in butt joint (thickness > 10 mm / 0.39 in) | 3,0 mm ± 1,0 mm / 0.12 in ± 0.04 in |
| Edge misalignment (thickness ≤ 12 mm / 0.47 in) | ≤ 1,5 mm / 0.06 in |
| Edge misalignment (thickness > 12 mm / 0.47 in) | ≤ 3,0 mm / 0.12 in or 10% of thickness, whichever is less |
| Bevel angle in V-groove joint | 60° ± 5° |
| Root face (land) for full penetration | 1,5–2,5 mm / 0.06–0.10 in |
| Maximum allowable reinforcement (general structural steels) | ≤ 3 mm / 0.12 in above base surface |
Applicable Materials
Section titled “Applicable Materials”FCAW is suitable for welding the following material groups:
- Carbon and low-alloy steels: from structural grades such as ASTM A36 and A572 Gr. 50 to API 5L X42-X80 pipe. Both self-shielded and dual-shield gas-shielded variants are widely used.
- Stainless steels: austenitic (304, 304L, 316L), ferritic (409, 430), and duplex (2205). A shielding gas atmosphere (typically argon, helium, and CO₂ mixtures) is required to maintain corrosion resistance.
- Nickel alloys: Inconel 625, 718, Hastelloy C-276, among others, welded with specific tubular wires and argon-helium shielding gas.
- Hardfacing and part repair: cobalt-based (Stellite) or high-carbon iron-based alloys, using self-shielded or gas-shielded wires per manufacturer recommendations.
Advantages and Limitations
Section titled “Advantages and Limitations”Advantages
Section titled “Advantages”- Deposition rates in flat position (1G/1F) of 5 to 15 kg/h / 11 to 33 lb/h, approximately 30-50% higher than solid GMAW under comparable conditions.
- Self-shielded wires withstand winds up to 13 m/s / 30 mph without loss of quality, eliminating the need for tents outdoors.
- Lower operator skill requirement compared to SMAW or GTAW.
- Tolerance to light rust and mill scale on the workpiece surface, reducing pre-cleaning time.
- The slag formed protects the newly solidified metal and usually removes easily.
- Very low risk of porosity when stickout and ventilation parameters are respected.
- Portable equipment without the need for a gas cylinder in the self-shielded variant.
Limitations
Section titled “Limitations”- Smoke generation can be 2 to 3 times higher than in GMAW or SMAW, requiring local exhaust systems in enclosed spaces.
- Cost of tubular wire is 2 to 3 times that of solid GMAW wire of the same diameter.
- Some wires are not suitable for all positions; only specific classifications (e.g., E71T-1 for vertical up welding) allow out-of-position work.
- Changing filler material requires replacing the entire spool, which takes 3 to 5 minutes on standard industrial equipment.
- The contact tip can melt if stickout is reduced below 10 mm / 0.39 in.
- Travel speed must be controlled to avoid slag entrapment in multipass welds.
Selection Guide
Section titled “Selection Guide”The decision between gas-shielded and self-shielded FCAW is based on the environment and the mechanical requirements of the joint.
| Criterion | Gas-Shielded FCAW | Self-Shielded FCAW |
|---|---|---|
| Work environment | Indoor workshop, no drafts > 5 km/h / 3 mph | Outdoor, construction site, windy conditions; valid up to 13 m/s / 30 mph |
| Material thickness | ≥ 3 mm / 0.12 in; ideal > 6 mm / 0.24 in | ≥ 1,5 mm / 0.06 in for thin sheet, up to 25 mm / 1 in with multipass |
| Quality requirements | High-toughness structural welds, low porosity, radiographic testing | General applications, repair, field assembly |
| Welding position | All positions with designed wires (E71T-1, E71T-9), best in flat and horizontal | All positions with classifications such as E71T-11 (multipurpose self-shielded) |
| Typical shielding gas | 100% CO₂ (deep penetration, more spatter) or 75% Ar / 25% CO₂ (more stable arc, less spatter) | None |
| Recommended polarity | Electrode Positive (DCEP) | Electrode Negative (DCEN) |
For thicknesses greater than 20 mm / 0.79 in in structural steels, FCAW with pure CO₂ is preferred to maximize penetration. On sheets of ≤ 3 mm / 0.12 in outdoors, self-shielded FCAW with 0,9 mm / 0.035 in wire offers greater ease of handling.
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the maximum deposition rate that can be achieved in FCAW?
Section titled “What is the maximum deposition rate that can be achieved in FCAW?”The deposition rate in flat position can reach up to 15 kg/h / 33 lb/h with 2.4 mm / 3/32 in wires and high currents, exceeding solid GMAW rates by more than 40% under equivalent conditions.
What sheet thickness can be welded without bevel using self-shielded FCAW?
Section titled “What sheet thickness can be welded without bevel using self-shielded FCAW?”With self-shielded wire of 0,9 mm / 0.035 in and a single pass, it is feasible to join sheets up to 4 mm / 0.16 in thick in a butt joint, provided voltage and electrode extension are kept within the recommended ranges.
What is the typical travel speed for a horizontal fillet weld in carbon steel with gas-shielded FCAW?
Section titled “What is the typical travel speed for a horizontal fillet weld in carbon steel with gas-shielded FCAW?”For a 6 mm / 0.24 in throat fillet weld, speeds of 400 to 550 mm/min / 16 to 22 in/min are used with 1,2 mm / 0.045 in wire and controlled heat input.
What stickout length is recommended to ensure a stable arc?
Section titled “What stickout length is recommended to ensure a stable arc?”Electrode extension should be maintained between 13 and 25 mm / 1/2 and 1 in; values below 12 mm / 0.47 in can damage the contact tip, while values above 30 mm / 1.2 in increase the risk of lack of penetration.
At what wind speed is the use of gas-shielded FCAW discouraged?
Section titled “At what wind speed is the use of gas-shielded FCAW discouraged?”Breezes above 8 km/h / 5 mph start to disperse the shielding gas and cause porosity; above 13 km/h / 8 mph, it is recommended to switch to self-shielded wire.
How much can a local exhaust system reduce smoke?
Section titled “How much can a local exhaust system reduce smoke?”A local exhaust system with a capacity of 150 to 300 m³/h / 5300 to 10600 ft³/h per torch can reduce the concentration of fumes in the environment by more than 80% compared to general ventilation.