This WPS covers self-shielded FCAW (FCAW-S) on 1-1/2" A572 Gr 50 heavy plate for outdoor structural field work. Self-shielded flux core is the go-to process when wind makes gas-shielded welding impractical — the flux in the wire generates its own shielding atmosphere, eliminating the need for external gas bottles and regulators. IronKit generated this for a bridge and highway contractor who does field splice welding on structural steel in exposed conditions. The procedure uses E71T-8 wire (the most common self-shielded classification for structural steel) and includes a 225°F preheat for the 1-1/2" thickness — a detail that gets missed in the field more than any other parameter. The WPS also notes the vertical-up technique requirement, since self-shielded FCAW is particularly sensitive to travel angle in the vertical position.
Frequently Asked Questions
What is self-shielded FCAW?
Self-shielded flux-core arc welding (FCAW-S) uses a tubular wire with flux compounds that decompose during welding to create a protective gas shield around the arc. No external gas bottle is needed. This makes it the ideal process for field work in windy conditions where MIG or dual-shield FCAW shielding gas would blow away.
Why does E71T-8 require DCEN polarity?
E71T-8 is formulated for DCEN (electrode negative) operation. Running it on DCEP reverses the arc characteristics — causing excessive spatter, porosity, and poor slag detachment. Polarity is the most common weld defect source when shops switch between gas-shielded (DCEP) and self-shielded (DCEN) processes.
Can I use self-shielded FCAW for code structural work?
Yes. E71T-8 is prequalified under AWS D1.1 and widely used for bridge work under AWS D1.5. It meets the same mechanical property requirements as gas-shielded E71T-1. The key requirement is proper technique — longer stickout, drag angle, and thorough slag removal between passes.
Why is the preheat 225°F for 1-1/2" plate?
AWS D1.1 Table 3.3 requires 225°F minimum preheat for Group 2 steels (A572 Gr 50) at thicknesses above 1-1/2". Preheat slows the cooling rate in the HAZ, reducing the risk of hydrogen cracking. This is the most commonly missed parameter on field splice work.