Complete Technical Write-Up: 4F Welding Position 1. Definition and Basic Concept The 4F welding position is a classification defined by the American Welding Society (AWS) and international standards (ISO 6947 – PD position). It refers to welding a fillet weld with the weld face oriented downwards, while the welder works from underneath the joint.
"4" = Overhead position (axis of the weld is roughly horizontal, but the welding is done from the underside). "F" = Fillet weld (welding on a corner joint, T-joint, or lap joint).
In the 4F position, gravity works directly against the molten weld pool, pulling it downward toward the welder. This makes it one of the most difficult manual welding positions to master. 2. Joint Configurations for 4F The 4F position applies to the following joint types where the weld is a fillet:
T-joint – Vertical member on a horizontal base. Lap joint – Two overlapping plates. Corner joint – Two plates meeting at an angle (usually 90°). 4f welding position full
In all cases, the weld axis is horizontal , but the weld face is below the welder (overhead). 3. Visual Representation (Text Diagram) Top View (from above the joint): | (Vertical plate) | |_______ (Horizontal plate – underside is where weld is made) From the welder's perspective (looking up):
| | | Vertical plate | | | | (Weld here – overhead) | |_________________________________| Horizontal plate (overhead, above welder)
4. Welding Processes Commonly Used in 4F Not all processes are equally suited to 4F due to gravity's effect on molten metal. | Process | Suitability | Notes | |---------|-------------|-------| | SMAW (Stick) | Good | Requires careful rod angle and manipulation; use E7018 or E6010. | | GMAW (MIG) | Moderate to Good | Short-circuit transfer only (avoid globular/spray). Use smaller wire diameter. | | FCAW (Flux-Core) | Excellent (self-shielded) | Self-shielded flux-core (E71T-GS, E71T-11) works well; gas-shielded requires skill. | | GTAW (TIG) | Difficult | Not common for production 4F fillets due to low deposition and puddle control issues. | 5. Key Technical Challenges Complete Technical Write-Up: 4F Welding Position 1
Gravity-induced drooping – Molten metal sags or drips if the puddle is too large or heat too high. Reduced visibility – Sparks, slag, and spatter fall downward toward the welder’s hood and body. Ergonomic strain – Arms raised overhead for extended periods; awkward body positioning. Slag control (SMAW/FCAW) – Slag tends to drip or run ahead of the puddle, causing inclusions. Penetration consistency – Ensuring fusion into the vertical and horizontal members is difficult.
6. Recommended Techniques for 4F Welding 6.1 Electrode/Wire Angle (SMAW as example)
Work angle : 45° between the two plates (bisecting the 90° joint). Travel angle : 10–15° drag (backhand) for stick; 0–5° push for MIG short-circuit. Aim : Direct arc slightly more into the vertical plate to counteract sagging. "4" = Overhead position (axis of the weld
6.2 Travel Speed and Puddle Control
Use stringer beads , not wide weaves – wide weaves increase droop risk. Keep the puddle small and frozen behind the arc. For multipass welds, use small-diameter electrodes (e.g., 1/8" or 3/32" for SMAW).