Vertical Fillet and Groove Welds (3F and 3G)

Why Vertical Welding Is Different

When you move from flat (1F/1G) to vertical (3F/3G) position, gravity becomes your biggest challenge. In the flat position the molten puddle sits in a pocket and surface tension does most of the work. In the vertical position the puddle wants to roll downhill. If your travel speed is too slow or your heat is too high, you get overlap (cold lap) at the toes and sagging beads. If your heat is too low or travel is too fast, you get cold lap and lack of fusion. Mastering uphill vertical FCAW means learning to read the puddle and constantly balance heat input against puddle behavior.

Uphill vs. Downhill Progression

For structural work governed by AWS D1.1, uphill (vertical-up) progression is the standard for FCAW on material 3/16 in. and thicker. Uphill travel allows deeper penetration and a larger, more controllable puddle. Downhill is faster but produces a shallower fusion zone and is restricted by code for thicker structural members. All work in this lesson uses uphill progression.

Parameter Adjustments for Vertical Position

Start with your flat-position settings as a baseline, then make the following adjustments:

• Wire feed speed (WFS): Reduce by roughly 10–15 % from your flat settings. Lower WFS reduces heat input and slows puddle formation so gravity has less melt to pull.
• Voltage: Reduce slightly to shorten the arc and stiffen the puddle. A short, tight arc transfers metal more directly and reduces spatter.
• Wire extension (stick-out): Hold 3/4 in. to 1 in. for .045 in. E71T-1C wire. Longer extension increases resistance heating and can make the puddle too fluid.
• Gun angle: Use a 5°–15° push (drag) angle pointed upward into the direction of travel. This directs shielding gas over the puddle and helps support it against gravity.
• Work angle: 45° into the joint for a tee joint (3F); bisect the groove angle for a groove joint (3G).

Always document the WFS, voltage, and shielding gas flow rate (typically 35–50 CFH for 75/25 Ar/CO2 mix) on your weld data card before striking an arc.

The Triangular Weave with Toe Pause

The triangular weave is the most effective motion for vertical fillet and groove welds with FCAW:

1. Start at one toe of the joint.

2. Weave across the puddle to the opposite toe, moving slightly upward as you cross.

3. Pause briefly at each toe — one to two seconds — to allow fusion and fill the undercut-prone zone.

4. Move back across and slightly upward to the first toe, then pause again.

5. The overall path traces a series of overlapping triangles climbing the joint.

The pause at the toes is critical. That is where the base metal is coolest and where undercut forms if you rush. Watch for a bright, fluid keyhole at the toe; when you see it wet in cleanly, begin your cross-travel.

Reading the Puddle

A healthy vertical puddle is slightly elongated, roughly oval, with a bright, fluid leading edge. Warning signs:

• Sagging or drooping puddle: Heat too high or travel too slow — increase travel speed or reduce WFS.
• Dark, sluggish puddle: Heat too low — increase WFS or voltage slightly.
• Undercut at toes: Insufficient pause at toes, or gun angle directed away from the toe — correct motion and angle.
• Overlap (cold lap): Travel speed too slow combined with low voltage — increase voltage slightly and keep moving.

AWS D1.1 Visual Acceptance Criteria

Your completed coupons must meet AWS D1.1 visual acceptance criteria. Key limits include:

• Cracks: None permitted of any size.
• Weld face porosity: Individual pore diameter and cluster limits apply per the code table — no porosity visible to the naked eye above the specified maximum.
• Undercut: Shall not exceed 1/32 in. depth for primary members (check Table 6.1 on your criteria card for the applicable limit).
• Overlap: Not acceptable.
• Fillet weld size: Must meet the specified leg size within the tolerance shown on the drawing or procedure; use your fillet gauge to verify.
• Groove weld reinforcement: Must be within the limits in D1.1 Table 6.1; excessive crown that is too high or too flat both fail.

Use your fillet gauge on every 3F coupon. Measure the minimum leg size at three locations along the weld. Use your groove gauge to check crown height on every 3G coupon.

Safety in the Vertical Position

• Spatter falls. Wear leather welding gloves, a leather apron or jacket, and ensure your collar and cuffs are buttoned. Hot spatter that falls into a boot or glove cuff causes burn injuries.
• Fumes rise toward your face. Ensure local exhaust ventilation (LEV) is positioned above and to the side of the weld zone. In confined or low-ventilation areas use supplied-air respiratory protection per OSHA requirements.
• Chipping slag from a vertical weld. Wear your welding helmet or safety glasses — slag chips fly outward and downward unpredictably. Allow the weld to cool to a safe handling temperature before chipping.
• Positioner or fixture pinch points. Before adjusting a vertical weld fixture, follow lockout/tagout (LOTO) procedures if the positioner is powered. Verify zero-energy state before reaching into the fixture.
• Fire watch. Spatter from vertical welds travels farther horizontally than from flat welds. Clear combustibles from a 35-ft radius and maintain a fire watch for at least 30 minutes after welding stops.