456A FCAW — Questions and Answers
Question 1: What are the two types of FCAW (Flux-Cored Arc Welding)?
- Gas-shielded FCAW and manual FCAW
- Gas-shielded FCAW (FCAW-G) using external shielding gas and self-shielded FCAW (FCAW-S) where the flux core provides all shielding (Correct answer)
- Single-pass FCAW and multi-pass FCAW
- AC FCAW and DC FCAW
Correct answer: Gas-shielded FCAW (FCAW-G) using external shielding gas and self-shielded FCAW (FCAW-S) where the flux core provides all shielding
FCAW has two variants: gas-shielded (FCAW-G or dual-shield) uses flux-cored wire plus external shielding gas (typically CO₂ or argon-CO₂ mix) for dual protection. Self-shielded (FCAW-S or inner-shield) relies entirely on the flux core to produce shielding gas and slag — no external gas is needed, making it ideal for outdoor and windy conditions.
Question 2: What is the main advantage of self-shielded FCAW over GMAW for outdoor structural welding in Canada?
- It produces a more attractive weld bead
- The self-generated shielding is not affected by wind, making it reliable for outdoor and field welding in Canadian weather conditions (Correct answer)
- It requires less skill to operate
- It uses less electricity
Correct answer: The self-generated shielding is not affected by wind, making it reliable for outdoor and field welding in Canadian weather conditions
Self-shielded FCAW generates its own protective atmosphere from the decomposing flux core, so wind cannot blow away the shielding as it can with GMAW's external gas. This makes FCAW-S the preferred process for outdoor structural steel erection, bridge work, and field welding across Canada's varied weather conditions.
Question 3: What type of polarity is typically used for self-shielded FCAW?
- DCEP (Reverse Polarity)
- DCEN (DC Electrode Negative / Straight Polarity) for most self-shielded wires (Correct answer)
- AC only
- No polarity preference
Correct answer: DCEN (DC Electrode Negative / Straight Polarity) for most self-shielded wires
Most self-shielded FCAW wires are designed for DCEN (straight polarity), which concentrates heat in the workpiece and produces shallower penetration suited to the process. Gas-shielded FCAW wires typically use DCEP. Always verify the wire manufacturer's specifications, as using the wrong polarity can cause severe porosity and poor weld quality.
Question 4: What is the purpose of the flux core inside an FCAW wire?
- To make the wire cheaper to manufacture
- To produce shielding gas, form protective slag, add deoxidizers and alloying elements, and stabilize the arc — similar functions to SMAW flux coating (Correct answer)
- To increase the wire's electrical resistance
- To make the wire more flexible
Correct answer: To produce shielding gas, form protective slag, add deoxidizers and alloying elements, and stabilize the arc — similar functions to SMAW flux coating
The flux core serves multiple functions similar to a SMAW electrode coating: it produces shielding gases (for self-shielded wires), creates a slag blanket that protects the cooling weld, adds deoxidizers to clean the weld metal, contributes alloying elements, and stabilizes the arc. Different flux formulations are designed for specific applications.
Question 5: What is the typical wire stick-out (contact-tip-to-work distance) for FCAW?
- 6 to 10 mm (1/4 to 3/8 in.)
- 19 to 38 mm (3/4 to 1-1/2 in.) — longer than GMAW (Correct answer)
- 50 to 75 mm (2 to 3 in.)
- The same as GMAW — 10 to 19 mm
Correct answer: 19 to 38 mm (3/4 to 1-1/2 in.) — longer than GMAW
FCAW typically uses a longer stick-out (19 to 38 mm / 3/4 to 1-1/2 inches) compared to GMAW. Self-shielded FCAW often uses even longer stick-out (up to 50 mm). The longer stick-out preheats the wire through resistance heating and is part of the designed operating characteristics of flux-cored wires.
Question 6: What is worm tracking (gas marks) on an FCAW weld surface?
- A decorative weld pattern
- Small surface marks or trails on the weld bead caused by gas escaping through the slag as it solidifies; usually cosmetic but can indicate improper technique or excessive voltage (Correct answer)
- A type of internal porosity visible only on X-ray
- Marks left by the wire feed mechanism
Correct answer: Small surface marks or trails on the weld bead caused by gas escaping through the slag as it solidifies; usually cosmetic but can indicate improper technique or excessive voltage
Worm tracking appears as small herringbone or track-like marks on the surface of FCAW welds. They are caused by gas escaping through the solidifying slag. While primarily cosmetic (not typically a structural concern), excessive worm tracking may indicate voltage is too high, excessive stick-out, or contaminated base metal.
456A FCAW
What are the two types of FCAW (Flux-Cored Arc Welding)?