Flux Core Welding

Understanding flux-cored arc welding:

Process Basics:

Equipment:
- Power source (CV, DC)
- Wire feeder
- Gun/torch
- Gas supply (FCAW-G only)

Electrode:
- Tubular wire with flux core
- Flux provides shielding/deoxidation
- Various diameters (0.035" to 5/64")
- Matched to application

Two Varieties:

Self-Shielded (FCAW-S):
- No external gas required
- Flux generates all shielding
- Good for outdoor/windy conditions
- More spatter, typically rougher appearance
- E71T-8, E71T-11 common

Gas-Shielded (FCAW-G):
- External gas (CO2 or 75/25)
- Cleaner weld, less spatter
- Higher quality appearance
- Sensitive to wind
- E71T-1, E70T-1 common

Electrode Classifications:

Example: E71T-1C:
- E = Electrode
- 7 = 70,000 PSI tensile
- 1 = All position
- T = Tubular (flux-cored)
- 1 = Usability/characteristics
- C = CO2 shielding gas

Position Designations:
- 0 = Flat and horizontal only
- 1 = All position

Operating Principles:

Arc:
- Constant voltage power source
- Wire feed speed controls amperage
- Voltage controls arc length/penetration

Flux Function:
- Shielding gas generation
- Slag for protection and contour
- Deoxidizers for clean weld
- Alloying elements for properties

Deposition Rate:
- Higher than GMAW
- 12-25 lb/hour possible
- Efficiency advantage
- Production welding suitable

Optimizing FCAW performance:

Key Parameters:

Wire Feed Speed:
- Controls amperage
- Match to material thickness
- Higher = more deposition
- Typical range 200-600 IPM

Voltage:
- Controls arc length
- Affects penetration and profile
- Too low: stubbing, poor wetting
- Too high: excessive spatter, porosity

Travel Speed:
- Affects bead size and penetration
- Too slow: excess buildup, cold lap
- Too fast: insufficient fusion

Electrical Stickout:
- Distance from contact tip to work
- Affects preheat of wire
- Typical 3/4" to 1"
- Longer = lower amperage

Gas Flow (FCAW-G):
- 35-50 CFH typical
- Adequate coverage without turbulence
- Too high wastes gas, causes turbulence

Technique:

Gun Angle:
- 10-15 degrees drag angle (push for aluminum)
- Work angle varies with joint
- Consistency important

Travel Pattern:
- Straight for thin material
- Weave for wider beads/buildup
- Stringer preferred for structural

Starts and Stops:
- Start ahead, backtrack to fill crater
- Fill crater before stopping
- Avoid stops in critical areas

Position Considerations:

Flat/Horizontal:
- Highest deposition rates
- More forgiving
- Slag easily controlled

Vertical:
- Up for deep penetration, heavy plate
- Down (with special wires) for speed
- All-position wires required

Overhead:
- Lower parameters
- Control puddle size
- Slag falls, careful of spatter

Common Issues:

Porosity:
- Contamination
- Insufficient shielding
- Moisture in flux
- Wrong polarity

Worm Tracking:
- Gas trapped under slag
- Too fast travel
- Excessive voltage
- Contamination

Spatter:
- Wrong voltage
- Wrong polarity
- Excessive stickout
- Contamination

FCAW applications across industries:

Structural Steel:

Advantages:
- High deposition rates
- Deep penetration
- All position capability
- Code acceptance

Applications:
- Buildings
- Bridges
- Heavy equipment
- Storage tanks

Shipbuilding:

Why FCAW:
- High productivity
- Large welds
- Varied positions
- Outdoor conditions (FCAW-S)

Materials:
- Structural steel
- High-strength low-alloy
- Special alloys

Heavy Equipment:

Applications:
- Construction equipment
- Mining equipment
- Agricultural machinery
- Pressure vessels

Advantages:
- Thick material capability
- Production welding
- Field repair

Material Considerations:

Carbon Steel:
- Most common FCAW application
- Wide wire selection
- Matching filler easy

Low-Alloy Steel:
- Match wire to base metal
- Preheat often required
- Controlled interpass temperature

Stainless Steel:
- Special wires available
- Gas-shielded typically
- Heat input control important

Comparison to Other Processes:

vs. SMAW:
- Higher productivity
- Less welder fatigue
- Continuous welding
- Equipment cost higher

vs. GMAW:
- Better penetration
- Better for thick material
- More tolerance of mill scale
- More spatter/cleanup

vs. SAW:
- More portable
- All position
- Lower deposition rate
- More manual skill needed

Building FCAW expertise:

Career Paths:

Entry Level Welder:
Beginning FCAW:
- Basic positions
- Supervised work
- Learning procedures
- $35,000-$50,000

Structural Welder:
Construction/fabrication:
- All positions
- Code work
- Reading drawings
- $45,000-$70,000

Pipe Welder:
Pipe and pressure:
- Specialized techniques
- Certifications required
- Higher demands
- $55,000-$90,000

Welding Supervisor:
Lead and manage:
- Team supervision
- Quality responsibility
- Procedure knowledge
- $60,000-$90,000

Certifications:

AWS Certifications:
- D1.1 Structural Steel
- D1.5 Bridge Welding
- D1.8 Seismic

ASME Certifications:
- Section IX qualified
- Pressure vessel work
- Procedure specific

Other:
- API 1104 (pipeline)
- Company specific

Skill Development:

Fundamentals:
- Equipment setup
- Basic positions
- Parameter selection
- Safety practices

Intermediate:
- All positions
- Multiple materials
- Code work
- Troubleshooting

Advanced:
- Procedure development
- Multiple processes
- Inspection/testing
- Training capability

Training Paths:

Formal:
- Trade school programs
- Apprenticeships
- Union training
- AWS courses

On-the-Job:
- Supervised practice
- Progressive responsibility
- Mentorship
- Certification testing

Industries:
- Construction
- Shipbuilding
- Heavy equipment
- Fabrication shops
- Field construction

FCAW skills are highly marketable for welders seeking productive, versatile work.