Flat and Horizontal Fillet Welds (1F and 2F)

Flat and Horizontal Fillet Welds (1F and 2F) with FCAW

Flux-cored arc welding (FCAW) is one of the most productive processes used in structural steel fabrication and construction. In this lab you will produce fillet welds on tee joints in the 1F (flat) and 2F (horizontal) positions using E71T-1C wire and a 75% Ar / 25% CO₂ shielding gas mix. Every weld you submit must meet the visual acceptance criteria in AWS D1.1 Table 6.1.

Joint Setup and Fit-Up

A tee joint is formed by standing one plate on edge at 90° to a base plate. Tack-weld both ends to hold that square angle before welding. Poor fit-up — gaps larger than 1/16 in. at the root — forces you to compensate with travel speed and can produce undersized or convex beads. Check fit-up with a square before you strike an arc.

For the 1F position, rotate the tee joint so the weld axis is flat and the joint bisector points straight up — you are welding into the valley at roughly 45° to both plate faces. For the 2F position, one plate is vertical and one is horizontal; gravity pulls the puddle toward the horizontal plate, which is the main challenge of this position.

Gun Angles

Correct gun angles are critical to weld quality and are tested in every structural welding credential.

• Work angle (1F): Hold the gun at 45° to each plate face so the arc is aimed equally at both members. Tilting toward one plate deposits more metal there and starves the other leg.
• Work angle (2F): Again target 45° between the vertical and horizontal plates. Many beginners drop the gun toward the horizontal plate — watch that angle.
• Travel angle (both positions): Use a 5–15° drag angle (gun tilted back, opposite the direction of travel). This keeps the arc ahead of the slag and gives you a clear view of the puddle.

Travel Speed and Bead Technique

Travel speed controls leg size and bead profile. Move too fast and you get an undersized, convex bead; too slow and you get an oversized, flat bead with potential overlap at the toes. For a 5/16 in. fillet weld on 3/8 in. A36 plate, maintain a steady pace that keeps the puddle about 3/8 in. behind the arc. Watch the trailing edge of the puddle — that is where leg size is set.

Stringer beads are narrow passes made without side-to-side motion. They penetrate well and are preferred for root passes and single-pass fillets on thinner material. Weave beads use a controlled side-to-side motion to fill a wider groove in fewer passes; pause slightly at each toe to avoid undercut. For multi-pass 5/16 in. fillets, a single stringer is often sufficient; heavier welds may use a root stringer followed by one or more cover passes.

E71T-1C Wire and Shielding Gas

The E71T-1C classification tells you the electrode is flux-cored (E), rated at 70 ksi minimum tensile strength (7), all-position capable (1), flux-cored tubular (T), designed for 75%Ar/25%CO₂ shielding gas (C suffix). Always verify the shielding gas on the wire's data sheet. Check the cylinder label before connecting. Set gas flow per the manufacturer — typically in the range of 35–45 CFH for this wire diameter in a shop environment. Protect the arc from drafts; wind can strip shielding gas and introduce porosity.

Slag Removal Between Passes

FCAW produces a slag layer that must be completely removed before depositing the next pass. Slag inclusions trapped between passes are a rejectable discontinuity under D1.1. Use your chipping hammer to crack the slag, then clean with a wire brush. Wear your safety glasses — flying slag chips cause eye injuries. If the slag is hard to remove, the interpass area may be too cold or the bead is too convex; adjust technique.

AWS D1.1 Table 6.1 Visual Acceptance Criteria

For each coupon you submit, the instructor will check four criteria:

1. Weld size: The fillet must be at least the specified size (no undersize allowed; up to +1/4 in. over is acceptable).

2. Undercut: Maximum depth at the weld toe is 1/32 in. Undercut weakens the base metal and is a stress riser.

3. Overlap: The weld face must not roll over onto the base metal without fusion. Any visible overlap is rejectable — zero tolerance.

4. Uniform ripple: The bead surface must show reasonably consistent ripple pattern, indicating steady travel speed and arc control.

Measure fillet leg size with a fillet weld gauge (convex gauge). Place both legs of the gauge against the plate faces; the scale reads the theoretical throat and leg size simultaneously.

Peer Inspection Protocol

During the peer inspection session, treat your partner's coupon as if it were a real production weld. Record actual measured values — not just pass/fail — on the inspection form, and sign it with your name as inspector. This mirrors industry quality-control practice and is a skill assessed in the AWS SENSE and NCCER programs.

Safety in the FCAW Lab

• Auto-darkening helmet, minimum shade 10: E71T-1C at typical parameters produces a bright arc; never look at it with bare eyes.
• Leather gloves, jacket or sleeves, and leather boots: Spatter from FCAW is heavier than from GMAW solid wire. Synthetic fabrics melt onto skin.
• Ventilation: FCAW fumes include iron oxides, manganese, and fluorides. Use local exhaust ventilation at the weld point. Do not weld in confined spaces without engineering controls.
• Hot metal awareness: Mark hot work pieces with chalk ("HOT") and allow cooling before handling. Use pliers or tongs.
• Angle grinder PPE: When using a flap disc to remove tacks or grind beads, add a face shield over your safety glasses and secure loose clothing.
• Cylinder security: Gas cylinders must be chained or strapped upright at all times. Check connections for leaks with approved leak-check solution before striking an arc.