Fusion-Discontinuity Disposition in a D17.1 Repair
A fabrication shop is welding a 0.125 in (3.2 mm) thick 321 stainless steel fuel-line bracket per a D17.1 drawing note. The welder completes a single-pass autogenous GTAW butt joint and the inspector finds a 0.060 in (1.5 mm) linear indication on the radiograph, oriented transverse to the weld. The joint is a Category B weld per the drawing, and the applicable acceptance class is Class A. The shop's quality manager wants to know whether the part must be scrapped, repaired, or accepted as-is, and whether a repair weld would require re-qualification. The part is not flight-critical but is in a fuel-wetted zone.
1. Determine the disposition of the indication and justify it against D17.1 acceptance criteria logic.
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The key move is to classify the indication before judging it. A 0.060 in transverse linear indication in 0.125 in material is a crack-like or incomplete-fusion-type flaw, not porosity. D17.1 Class A acceptance for fusion discontinuities is far tighter than for porosity; a 0.060 in indication in 0.125 in section is roughly 48% of the thickness and generally exceeds Class A linear-discontinuity limits regardless of length. Disposition should be reject and repair, not accept-as-is. Scrapping is premature because the flaw is accessible and the part is not flight-critical. The reasoning chain: (1) identify flaw type from orientation and morphology, (2) apply the Class A linear criterion, (3) confirm section thickness so the percentage-based limit is computed correctly. A common wrong answer is to accept because 0.060 in is small in absolute terms; D17.1 limits are thickness-relative, so absolute size alone is not the test.
2. The shop proposes a repair weld. What re-qualification and documentation questions must be answered before the repair is performed?
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A repair weld on a qualified joint is not automatically covered by the original WPS/PQR. The shop must confirm: (1) the repair WPS is supported by a PQR covering the repair conditions (same base metal group, thickness range, and process), (2) whether D17.1 requires a separate repair procedure or a repair-classification note on the drawing, (3) whether the repair introduces a second thermal cycle that could sensitize the 321 stainless steel, which is a real metallurgical concern in a fuel-wetted zone, and (4) whether post-repair inspection (radiography again, plus penetrant for surface) is required by the drawing or contract. Documentation must capture the flaw location, the repair method, the welder/operator identification, and the NDE results. The trap is treating a repair as a routine rework; D17.1 ties repair to the same qualification chain as original welding.