What the Macro Suggests From the image: Fusion is occurring on the upper groove walls. Root area shows an unfused triangular gap / cold lap zone . Weld metal is flowing around the joint rather than penetrating fully to the root. This is typical when the arc cannot adequately reach the root face or root land. Likely Causes 1. Amperage Too Low for Root Pass 82 A for first pass on a restrained joint with 50 mm thick tubesheet may be too low, especially if heat is rapidly absorbed by the heavy SA-516 tubesheet. The tubesheet acts as a heat sink , pulling heat away from the root. 2. Groove Design / Root Land Too Heavy If the groove has: narrow included angle excessive land/root face insufficient tube projection or mismatch then penetration becomes difficult at lower amps. 3. Arc Position / Torch Angle If arc is focused too much on filler or upper bevel edges rather than root corner, fusion at the bottom will be poor. 4. Travel Speed Too F...
Dear Sirs, As per my below mail history and your recommendation for low Amps to avoid high heat input, After performing the new MOCKUPs for 15.85, & 19.05 OD SS304L tubes to CS SA-516-70N tubesheet of 50mm with GTAW ER309LMO 1.6 Dia only of 3 passes for 19.05 ID tube, 82 A for 1st pass, 95A for 2nd, 100A for 3rd pass. Only 2 passes given for 15.85 OD tube. We got incomplete penetration aa per the attached macro photo., almost for all the tube welds for both sized tube welds. Please see the groove design for your reference. Also, please give me suggestions to make sound complete penetration on root pass and to avoid cracks too. Thanks and regards, Saravanan Sornam, Ansan city, S.Korea On Thu, 16 Apr 2026, 2:51 pm 'Ahmed Osman' via Materials & Welding, < materials-welding@googlegroups.com > wrote: ...