Abstract: The invention discloses a method to determine the weld joint penetration from arc voltage measurements in gas tungsten arc welding (GTAW). It is based on an observation on the dynamic weld pool surface in GTAW—the surface tends to first expand toward the electrode and then be pushed away from the electrode after full penetration is established. For the pool surface in GTAW, localized partial keyholes around the arc axis as in plasma arc welding are not significant. The pool surface is relatively smooth. The arc voltage that reflects changes in the arc length thus first tends to reduce and then increases after full penetration is established. This invention thus tracks the arc voltage until the decrease slope becomes insignificant. Once full penetration is established, the current is reduced to decrease the weld penetration or first decrease the penetration growth for a certain period and then decrease the weld penetration.

Abstract: For fillet welding, sufficient amounts of metal must be deposited in order to make welds with sufficient sizes. In conventional submerged arc welding (SAW), the heat input is proportional to the amount of metal melted and is thus determined by the required weld size. In order to reduce the needed heat input, Double-Electrode SAW (DE-SAW) method is used for fillet joints. To minimize the heat input required to produce the welds with required geometry and sizes, a gap is introduced between the panel and the tee forming a modified fillet joint design. The use of the gap improves the ability of DE-SAW to produce the required weld beads at reduced heat input and penetration capability. Major parameters including the gap, travel speed and heat input level have been selected/optimized/minimized to produce required fillet weld beads with a minimized heat input based on qualitative and quantitative analyses.

Abstract: The invention discloses a method to determine the weld joint penetration from arc voltage measurements in gas tungsten arc welding (GTAW). It is based on an observation on the dynamic weld pool surface in GTAW—the surface tends to first expand toward the electrode and then be pushed away from the electrode after full penetration is established. For the pool surface in GTAW, localized partial keyholes around the arc axis as in plasma are welding are not significant. The pool surface is relatively smooth. The arc voltage that reflects changes in the arc length thus first tends to reduce and then increases after full penetration is established. This invention thus tracks the arc voltage until the decrease slope becomes insignificant. Once full penetration is established, the current is reduced to decrease the weld penetration or first decrease the penetration growth for a certain period and then decrease the weld penetration.

Abstract: This invention is to plasma arc weld using a keyhole mode to build a partially-penetrated keyhole and then a melt-in mode to finally reach the full penetration before switching to the base period. The full penetration is thus established during the peak period in two stages: keyhole stage and then melt-in stage. While the keyhole stage helps reduce the heat inputs and weld puddles, the melt-in stage finishes the full penetration at reduced impacts from the plasma jets producing the desired weld bead geometry and regularity. The duration of the melt-in stage is automatically determined using arc signals to assure the full penetration. In comparison with keyhole PAW, bead geometry and regularity are significantly improved with slightly increased net heat inputs. In comparison with melt-in PAW and GTAW, the net heat input is reduced approximately forty percent.