Charpy V-Notch Testing Under AWS D1.1: Table 6.8 Explained

Charpy V-notch impact testing sits at an intersection that confuses even experienced welding personnel: it's not required for every WPS qualification under AWS D1.1, but when it is required, a missed variable or a test result below the minimum voids the qualification entirely.

This article walks through when CVN testing applies under AWS D1.1:2025, what Table 6.8 governs, what changed from the 2020 edition, and what the CWI must confirm during audit.

The Two-Tier Qualification Framework

AWS D1.1:2025 separates welding procedure qualification into two tiers:

Tier 1 — Standard essential variables (Table 6.6): These govern all WPS qualification. A change to a standard essential variable requires requalification with a new PQR and mechanical testing (bend tests, tensile test). CVN testing is NOT part of the Tier 1 requirement.

Tier 2 — Supplementary essential variables (Table 6.8): These apply only when CVN impact testing is specifically invoked—by the contract documents, the EOR, or the applicable design standard. When invoked, the supplementary variables layer on top of Table 6.6, not in place of it.

If the project doesn't invoke CVN requirements, Table 6.8 is irrelevant. If it does, both Table 6.6 and Table 6.8 apply simultaneously.

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

When Do Projects Invoke CVN Requirements?

The most common scenarios where CVN impact testing lands in the WPS package:

Bridge fabrication (AASHTO/FHWA): Fracture-critical member welding under AASHTO requirements typically mandates CVN testing. The AWS D1.5 bridge welding code has its own CVN provisions, but many projects reference D1.1 with D1.5 CVN overlay.

Seismic demand-critical welds (AISC 341): Demand-critical weld designations—common in Special Moment Frames and other seismic force-resisting systems—require filler metal with documented CVN properties. The AISC 358 prequalified connection standard also has CVN filler metal requirements for certain connection types.

Low-temperature or dynamic-load service: Structures subject to low operating temperatures, impact loading, or fracture-critical classification may have contract-specified CVN minimums. This is common in crane runways, press frames, and heavy industrial structures.

Owner- or EOR-specified: Some sophisticated owners (utilities, DOD, offshore) include CVN requirements as standard purchase conditions regardless of the applicable code's default.

AWS D1.1:2025 Table 6.8: The Supplementary Essential Variables

Table 6.8 lists the supplementary essential variables for the five primary processes (SMAW, SAW, GMAW, FCAW, GTAW). A change to any of these, when CVN requirements are invoked, requires a new PQR with CVN testing.

Key supplementary essential variables include:

Filler metal classification change: Changing to a filler metal with a different AWS A5 classification (e.g., from E7018 to E7016) triggers requalification. This reflects real differences in weld metal toughness between electrode types.

Heat input increase beyond the qualified range: This is the most operationally significant variable for most shops. High heat input reduces weld metal toughness. Table 6.8 limits how much heat input can increase above the PQR without requalification. The heat input formula is: HI = (V × A × 60) / (S × 1000), where V = voltage, A = amperage, S = travel speed in inches per minute.

Base metal thickness reduction (row 2a): The qualified base metal thickness range has a lower floor. The 2025 edition lowered this minimum from 5/8 in [16 mm] to 1/2 in [12 mm]—meaning more moderate-thickness applications now fall under the supplementary essential variable framework.

Post-weld heat treatment (PWHT) change: Adding or eliminating PWHT, or changing the PWHT temperature range, triggers requalification because PWHT significantly affects weld metal CVN properties.

Shielding gas change: For GMAW and FCAW, a change in shielding gas type or composition is a supplementary essential variable. Gas mixture affects penetration profile and bead morphology, which influence toughness.

Interpass temperature maximum increase (row 8): This is where the 2025 edition diverged from 2020. The old D1.1:2020 included preheat changes in the supplementary scope. The 2025 edition removed preheat from Table 6.8—only interpass temperature maximum increase now triggers supplementary requalification. If your WPS was qualified under 2020 and you're working under a 2025 contract, this distinction matters for what's still valid.

The CVN Test Itself: What the PQR Needs

When CVN testing is invoked, the PQR must document:

Test specimen location: CVN specimens are taken from the weld metal or heat-affected zone (HAZ), or both, depending on what the specification requires. WELD METAL specimens test the deposited filler; HAZ specimens test how the base metal responds to the thermal cycle. The spec should state which is required.

Test temperature: AWS D1.1:2025 does not prescribe a default CVN test temperature. The contract or referenced standard sets the temperature. Common values are 0°F (–18°C), –20°F (–29°C), and –40°F (–40°C) for structural applications. The test lab must be told the temperature, and the PQR must document it.

Acceptance criterion: The minimum absorbed energy (ft-lb or joules) and percent shear area are specified by the contract. A typical value might be 20 ft-lb at –20°F. The PQR records the actual absorbed energy for each specimen; the average of the set must meet the minimum, with no single specimen below a lower bound (typically two-thirds of the required average).

Number of specimens: AWS D1.1 requires three specimens per test set for CVN qualification.

What the CWI Reviews in the Audit Package

For any WPS package where CVN requirements apply, the CWI's document review should confirm:

PQR CVN data matches the contract specification: Test temperature and acceptance criterion on the PQR must be equal to or more demanding than the contract requires. If the contract says 20 ft-lb at –20°F and the PQR test was run at 0°F, that PQR doesn't qualify the welds for –20°F service.

Qualified heat input range is respected on the floor: The WPS must list heat input as a range, and the maximum must not exceed the PQR-qualified maximum. If production welders are running higher amperage or slower travel speed, the heat input can exceed the qualified range—which voids the CVN qualification even if the welder is otherwise within WPS parameters.

No unrecorded essential variable changes: If the shop changed electrode lots and the new lot has a different classification, a supplementary variable was changed without requalification. This is harder to catch in an audit but will show up in filler metal certs vs. WPS documentation.

PWHT records match WPS: If PWHT is specified in the WPS (and was part of the CVN qualification), the time-temperature cycle on the heat treat records must fall within the qualified range.

Connection to Seismic and High-Performance Applications

For seismic work under AISC 341, CVN requirements on demand-critical welds go beyond D1.1's supplementary essential variables. AISC 341 requires documented CVN properties from the filler metal manufacturer—typically 20 ft-lb at –20°F from a standard classification test, certified for each lot. This is a filler metal qualification, not a WPS qualification.

The intersection can confuse shops: D1.1 Table 6.8 governs whether your WPS/PQR is valid for CVN applications; AISC 341 governs whether the specific filler metal lot you're using is certified to the toughness requirement. Both apply simultaneously.

For more on seismic WPS requirements, see AISC 341 Seismic Provisions WPS and PQR Requirements. For the broader context of essential variable categories, see WPS Essential Variables vs. Nonessential Variables. The 2020 vs 2025 essential variable changes also covers the Table 6.8 updates in detail.

Practical Guidance for Shops

If your work regularly involves CVN-qualified WPS procedures, set up a heat-input tracking log. The supplementary essential variables are largely about heat input, and a welder who dials up amperage by 15% to fight a cold plate may inadvertently exceed the qualified heat input range—invalidating the CVN qualification mid-project.

The cleaner solution is building the qualified heat input range into the WPS as explicit parameter windows, not just approximate guidelines. When the welder knows the specific voltage/amperage/travel-speed envelope that keeps heat input within range, compliance is predictable.

For shops building out a WPS library that handles CVN-qualified applications, wpswelding.com/pricing covers what documentation support looks like.