QW – Welding Qualification: Procedures, Variables, and Performance
Architecture of Article II
QW-200 governs welding procedure qualification, QW-300 governs welder and welding operator performance qualification, and QW-400 holds the variable tables feeding both. First decide whether a scenario is a procedure problem or a person problem.
Procedure qualification
A WPS is qualified by welding a test coupon to the variables recorded on a PQR, then testing per QW-150 (tension), QW-160 (guided bend), and QW-170 (notch toughness) when toughness is specified. Tension specimens must reach at least the minimum specified tensile strength of the base metal - for dissimilar joints, the lower of the two minimums. Bend specimens pass when no crack or open defect exceeds 1/8 in. (3 mm) in any direction in the weld or heat-affected zone; small corner cracks are not rejectable.
Grouping is where marks are lost. Base metals are grouped by P-number (QW-420 series); filler metals by F-number and A-number. Qualification with one P-number usually covers others in the same group, subject to the substitution rules of QW-423/QW-424, but a change of P-number not permitted by those rules is essential.
Performance qualification
Welders and welding operators are qualified under QW-301 through QW-305. Performance essentials resemble procedure essentials but include items such as whether backing was used. Two traps: a welder qualified on a groove weld is qualified for fillet welds, but a fillet-only qualification never covers groove welds; and a welder's qualification expires after six months without welding with that process (QW-322).
Rule of thumb
If the question asks how to keep making the same joint, think WPS and PQR. If it asks who may make it, think WPQ, position, thickness limits, and continuity.