overhead fillet weld

The 4F welding position refers to an on a plate or pipe. In this position, the joint is located above the welder, and the weld is deposited from the underside of the workpiece, where gravity tends to pull the molten puddle down. 1. Technical Definition and Identification

To master the 4F welding position, welders must develop specific techniques and strategies. Here are some tips:

To pass, the welder must demonstrate:

The Full and Standard Terms for Welding Positions Are:

• Break long welds into shorter segments with intermittent stops to let metal cool slightly and prevent sagging.
• For joints requiring continuous welds, weld in back-step or stitch patterns: short welds (2–6 inches / 50–150 mm) placed in sequence to distribute heat.
• Preheat (or interpass temperature) per material specification to avoid cracking in thick or high-carbon steels; avoid excessive heat that increases sag.
• Use chill bars/clamps to help control heat and reduce distortion where needed.

• Keep the electrode tip very close to the puddle (almost touching the plate).
• A tight arc focuses the heat and allows the electromagnetic forces to help push the metal into the joint, overcoming gravity.

6.1 Electrode/Wire Angle (SMAW as example)

• The Root Pass: This is the most critical part. You are welding upside down, looking up at a gap. The key is a "keyhole" effect. You must keep the arc force pushing into the root to ensure you burn through the back side, but you must travel fast enough so the liquid metal doesn't fall through the keyhole.
• Suck Back: A common defect in overhead full pen welds is "suck back," where the root pass looks concave (dipped inward) from the back side. This happens because the welder didn't keep enough pressure in the puddle or let it get too hot.