Prequalified Joints and WPS/PQR Documentation
AWS D1.1 (Structural Welding Code — Steel) is the dominant welding code for structural steel fabrication in the United States. It is used for buildings, bridges, offshore structures, and structural steel fabrication of all types. The code defines joint geometry, prequalified welding procedures, inspection requirements, and welder qualification. Prequalified joint designations are joint configurations (groove and fillet welds in specific geometries) that AWS has determined, through extensive testing, will produce adequate strength when welded with code-compliant parameters. Using a prequalified joint eliminates the need for procedure qualification testing (PQR). Prequalified joint requirements must be met exactly — deviating from the geometry (root opening, groove angle, land/root face) takes the joint outside prequalified status and requires qualification testing. Common prequalified groove joints: the single-bevel groove (B-L1a) with 45° bevel angle, 1/4" root opening, and 1/16" land; the double-V groove; and the single-U groove for thicker materials (the curved U-groove requires less weld metal fill than a V-groove at the same depth). For a weld that does not use a prequalified joint or procedure, the fabricator must develop a Welding Procedure Specification (WPS) — a document defining every parameter of the welding procedure: base metal type and thickness range, filler metal classification, current and polarity, travel speed range, preheat and interpass temperature, joint geometry, and position. The WPS is supported by a Procedure Qualification Record (PQR), which documents the actual welding parameters used on a test coupon and the results of mechanical testing (tensile test, bend tests, and impact tests if required) demonstrating the procedure produces welds meeting code mechanical property requirements. Preheat requirements: D1.1 requires preheat for steel above certain carbon equivalents (CE) to prevent hydrogen-induced cracking (a delayed cold cracking mechanism caused by hydrogen in the HAZ diffusing to regions of high triaxial stress). Minimum preheat temperatures are specified in D1.1 Table 4.5 based on base metal minimum specified yield strength and thickness.