Welding Processes, Procedures, and Welder Qualification
Procedure and performance qualification
A welding procedure specification (WPS) is the controlled instruction used in production. It is supported by a procedure qualification record (PQR) produced by welding a test coupon and testing it to the code. Welder performance qualification (WPQ) demonstrates that an individual can deposit sound weld metal using a qualified procedure. These are separate: a PQR does not qualify a welder, and a WPQ does not qualify a procedure.
Know the common arc processes - SMAW, GTAW, GMAW, FCAW, and SAW - and their essential variables: base-metal group (P-number), filler classification (F-number and A-number), thickness, joint design, position, preheat, post-weld heat treatment, current type and polarity, shielding gas, and transfer mode. A change outside the code's qualification range requires a new PQR, a new WPS, or both. Welder qualification has its own essential variables and range, including position, thickness, and process.
Traps
- Treating a WPS as qualification evidence; the PQR is the supporting test record.
- Assuming a procedure qualification qualifies every welder.
- Overlooking supplementary essential variables when notch toughness is required.
- Confusing a change in a nonessential variable with a change requiring requalification.
- Applying a welder's previous qualification without checking continuity and position range.
Worked rule
Use the phrase 'procedure qualifies the process, performance qualifies the person.' For a P-number change from P-1 to P-4, assume a new PQR is needed unless the code's grouping permits the change. For a welder, verify the qualified position and thickness range on the WPQ before production.