Can a groove weld PQR substitute for a fillet weld procedure test?

Yes. AWS D1.1:2025 Clause 4 allows a qualified groove weld PQR to qualify fillet welding for the same process and base metal group without a separate fillet weld test. Most shops leverage this to avoid running a dedicated fillet weld test plate.

What acceptance criteria apply to macro cross-sections?

The macro section must show complete fusion to the root of the joint, weld leg size meeting the WPS minimum, no visible cracks at 10× magnification, and profile within the limits of AWS D1.1:2025 Clause 5. Porosity visible in the section is evaluated against the same limits as the visual acceptance criteria.

How many cross-sections are required from a fillet weld test assembly?

AWS D1.1 requires transverse cross-sections cut from specific locations on the test assembly — not at weld starts or stops. Typically two or more sections at different locations are required to capture root condition across the test weld length.

What etchant is used for macro preparation?

Carbon and low-alloy steel sections are etched with either a 10% ammonium persulfate solution at room temperature, or a nital solution (2–5% nitric acid in ethanol). The etchant reveals fusion boundaries, the HAZ, and any subsurface discontinuities.

Fillet weld PQR macro examination under AWS D1.1:2025

When a fillet weld procedure is qualified by test, macro cross-sections are the primary method. Here's what to cut, etch, and accept under AWS D1.1:2025.

Fillet welds appear in nearly every structural steel project — beam-to-column connections, shear tabs, stiffener plates, and base plates all rely on them. When a groove weld PQR is on file for the same process and base metal group, that record usually extends coverage to fillet welds. But when shops need to qualify a new process without a groove weld test, or when a specific joint configuration warrants its own documentation, a dedicated fillet weld test assembly is run — and the test method is macro examination, not tensile or bend testing.

When a dedicated fillet weld test is necessary

AWS D1.1:2025 Clause 4 is explicit: a groove weld PQR qualifies fillet welding for the same process, electrode classification, and base metal group. The groove weld qualification covering fillet welds article covers the specific boundaries of that coverage and when a separate fillet weld PQR becomes necessary.

The scenarios that drive a dedicated fillet weld procedure test:

A new process or consumable combination for which no groove weld PQR exists in the shop's library
Owner or contract requirements for a process-specific fillet weld qualification record independent of groove weld tests
SAW (Submerged Arc Welding) configurations where thermal conditions and joint geometry in fillet welds differ materially from the groove weld test
Multi-wire or high-deposition configurations where running a groove weld test first is not practical

In these cases, Clause 4 permits procedure qualification through a fillet weld test assembly. The result is a macro examination — there are no reduced-section tensile specimens or guided bend coupons. The cross-section is the test, and the PQR stands or falls on what the etch reveals.

The test assembly

A standard fillet weld test plate uses a T-joint configuration: a web plate standing at approximately 90° on a flange plate. The welder runs a fillet weld along one or both sides of the web, following the WPS parameters exactly — preheat (confirmed by contact thermometer or temp sticks before and during the run), amperage, voltage, wire feed speed, travel speed, and pass sequence all matching what the WPS documents.

The assembly should be long enough to produce multiple cross-section specimens after the non-representative end sections are discarded. Weld starts and stops are trimmed off; the middle portion of the run is where the test specimens come from.

WPS parameters must be recorded in real time during the test weld. This data populates the PQR. A QC witness or CWI — or at minimum a calibrated data acquisition logger — should capture arc voltage and amperage while the test weld is running. Travel speed can be timed with a stopwatch. If the welder drifted outside the parameter ranges the WPS records, the PQR cannot support the WPS. Discover that at the test stage, not when an auditor reviews the PQR later.

Cutting and preparing the macro specimen

Specimens are cut transverse (across) the weld by band saw or abrasive cutoff saw. Cuts must be located per the test configuration requirements — away from starts, stops, and tack welds. The cut face is then prepared through a series of steps:

Grinding. Remove saw marks and level the face. Coarse grinding establishes a representative plane. Avoid overheating the specimen during grinding — excessive heat can blur the HAZ boundary or, in extreme cases, alter the microstructure.

Polishing. Progress through successively finer abrasive papers — typically 120, 240, 320, and 400 grit — to remove the scratches from each prior stage. The goal is a surface smooth enough to etch uniformly. Each polishing stage runs perpendicular to the previous to make scratch removal visible.

Etching. Apply the etchant to the polished face. For shop use, a 10% ammonium persulfate solution is common — it is effective on carbon and low-alloy steel and is safer to handle than acid solutions. Nital (2–5% nitric acid in ethanol) works faster and reveals finer detail but requires proper ventilation and acid handling procedures. The etchant dissolves the surface selectively based on microstructural differences, making weld metal, heat-affected zone, and base metal distinguishable.

What the etch reveals

After etching, the following features become readable under a 10× loupe or stereo microscope:

Fusion boundary. The transition from weld metal to HAZ is visible as a distinct line. The examination confirms that the weld metal actually joined to the base metal at the root — lack of fusion at the root shows up as a bright, unfused seam at the apex of the fillet.

HAZ width and character. A wide HAZ relative to weld size indicates high heat input. A very narrow HAZ combined with cracking at the toes or root suggests a heat input or preheat problem. The HAZ appearance is not itself a pass/fail criterion under Clause 4, but it is diagnostic.

Subsurface porosity. Gas pockets that did not break the weld surface show up in cross-section. Cluster porosity, pipe porosity, or wormholes that were invisible to visual inspection appear in the macro.

Weld profile geometry. The macro section shows the actual geometry — leg length, effective throat, convexity or concavity — in a way that a surface measurement can't. The weld may pass a toe-to-toe measurement but have a deeply concave profile that reduces the effective throat below the required minimum.

Acceptance criteria

For the fillet weld PQR macro examination to pass, all of the following must be satisfied:

No cracks. Zero cracks are acceptable — in the weld metal, in the HAZ, or in the base metal near the weld toes. Cracks of any length visible at 10× magnification are rejectable. Cold cracking (hydrogen-assisted) typically shows up at the toes or in the HAZ. Hot cracking (solidification cracking) tends to run along the weld centerline.

Complete fusion at the root. The weld metal must fuse continuously to the theoretical root of the joint with no visible unfused gap. Root fusion is the criterion that matters most, because lack of fusion at the root is invisible to visual inspection and radiography on a T-joint fillet weld, and is only reliably detected by macro section or angle-beam UT.

Weld size meets the WPS minimum. Leg length measured on the cross-section must equal or exceed the minimum fillet weld size the WPS specifies. For convex fillets, the effective throat is calculated from the measured legs. The PQR records what the test actually produced; the WPS then specifies the minimum production size supported by that PQR.

Profile within Clause 5 limits. Fillet profile requirements — maximum convexity, limits on concavity, and undercut limits at the toes — apply at the PQR stage just as they do in production. A weld that produces a deeply convex or irregularly profiled fillet under the WPS parameters is telling you the parameters need adjustment before they go into production.

Connecting the macro to the WPS

When the macro passes, the PQR is complete for the fillet weld qualification. The PQR records the measured weld parameters, the macro result (pass), and any measured weld dimensions. The WPS then cites the PQR as its qualification basis. From that point, every production fillet weld made under that WPS is supported by documented evidence that those parameters produce compliant welds.

If the macro fails — lack of root fusion is the most common finding — the failure points back to the parameters. Too-low amperage, excessive travel speed, or a joint fitup that was out of tolerance during the test are the usual suspects. The parameters are adjusted and a new test weld is run. The failed test plate and its documentation are retained as part of the qualification record, per PQR record retention requirements.

For a practical overview of how fillet weld size requirements flow from drawing to WPS to production, see fillet weld size and WPS requirements. Shops managing multiple PQRs across processes and base metals — and needing macro results linked to a searchable procedure library — can see how a dedicated WPS platform handles that at wpswelding.com/pricing.

Rule library based on AWS D1.1:2025; verify against your governing edition.