Electroslag Welding Procedure Qualification for Thick Flange
A fabricator proposes electroslag welding (ESW) to join 2-1/2 in. thick flange plates on a plate girder, citing productivity. The ESW procedure was qualified on 2 in. material with a Charpy test at the weld centerline only. The EOR's special provisions require notch toughness testing at the weld metal and at the fusion line plus 1 mm, and require that the qualification thickness bracket the production thickness. The fabricator's PQR shows absorbed energy of 20 ft-lb at the centerline at -10 F. Production will be at -20 F service. The inspector must determine whether the PQR supports production welding.
1. Does the qualification on 2 in. material support welding 2-1/2 in. production?
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No. Qualification thickness brackets are defined by the code, and ESW is particularly sensitive to thickness because heat input, cooling rate, and the resulting microstructure vary strongly with section size. A PQR on 2 in. material does not automatically bracket 2-1/2 in. unless the qualified range explicitly extends to it. The fabricator must either qualify at a thickness that brackets 2-1/2 in. or demonstrate that the qualified essential variable range covers it. The inspector should reject the PQR as a basis for production at 2-1/2 in. until the bracket is confirmed.
2. The PQR tested only weld centerline. Evaluate against the EOR requirement for fusion-line testing.
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The EOR requires toughness at both weld metal and fusion line plus 1 mm. Testing only the centerline leaves the fusion line - often the weakest location in ESW because of coarse grain and possible lack of fusion - unevaluated. A centerline-only PQR does not satisfy the special provision and cannot support acceptance. The fabricator must supplement the qualification with fusion-line testing at the specified location, and the results must meet the required energy at the specified test temperature. The inspector should treat the PQR as incomplete rather than as a failed qualification, and require supplemental testing before production.
3. PQR toughness is 20 ft-lb at -10 F; production service is -20 F. What is the problem and the required action?
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The qualification test temperature (-10 F) is warmer than the service temperature (-20 F), so the PQR does not demonstrate toughness at the service condition. Toughness testing must be conducted at a temperature at or below the service temperature as specified, and the acceptance energy must be met at that temperature. The fabricator must re-qualify or supplement testing at -20 F, with test locations per the EOR, and meet the required energy. The 20 ft-lb value at -10 F cannot be extrapolated to -20 F. Production welding should not proceed until the qualification supports the service temperature.