Welded Connections: Processes, Qualification, and Weld Inspection
Welding questions center on AWS D1.1 and AISC 360 Chapter N. Know the common processes: SMAW (shielded metal arc, stick), GMAW (gas metal arc, short-circuit or spray), FCAW (flux cored), SAW (submerged arc), and the electroslag/electrogas processes for vertical groove welds. Each has position limits and consumable rules.
The qualification chain
A WPS (welding procedure specification) is the recipe. It may be prequalified under D1.1 Clause 3 only if joint geometry, process, position, thickness, and consumables fall within the prequalified limits; otherwise it must be supported by a PQR (procedure qualification record) from tested coupons. Separately, each welder must be performance-qualified for the process, position, and thickness being welded. A welder qualification does not qualify a procedure, and a qualified procedure does not qualify a welder.
Inspection
Visual inspection (VT) applies to 100 percent of welds and catches most defects: cracks, undercut, overlap, incomplete fusion at the surface, crater pits, and profile problems. Non-destructive testing - ultrasonic (UT), radiographic (RT), magnetic particle (MT), and penetrant (PT) - is added where the contract documents, AISC 360 Chapter N tables, or a demand-critical designation require it. NDT personnel must be qualified to a recognized standard such as ASNT SNT-TC-1A.
Traps: "100 percent NDT is required on all welds" (false); "prequalified means no WPS needed" (false - the prequalified WPS still must be written and followed); accepting a welder card without matching the process and position; ignoring preheat and interpass temperature on thick or restrained joints.
Rule of thumb: no WPS on site, no arc struck - and match the WPS to the joint, the process, and the position before the first pass.