Does E7018 meet demand-critical CVN requirements?

E7018 does not guarantee CVN at -20°F. E7018-1 does — the '-1' designator in AWS A5.1 is specifically the low-temperature CVN supplement (20 ft-lbf at -20°F). For AISC 341 demand-critical welds, you must specify E7018-1, not plain E7018.

How do I verify that a FCAW electrode meets CVN requirements?

The AWS A5.20 or A5.36 classification alone is usually not enough. Get a manufacturer's certificate of conformance (MCC) for the specific heat lot showing CVN test results at -20°F. AISC 341 Section A3.4b requires the MCC; the electrode classification is a necessary but insufficient condition.

Why doesn't ER70S-6 solid wire have a CVN requirement in its AWS classification?

AWS A5.18 (solid wire) does not include mandatory CVN test requirements in its classification system. Most ER70S-6 wire shows acceptable toughness in manufacturer testing, but there is no AWS-required minimum. For demand-critical GMAW, request a supplemental data sheet from the manufacturer showing CVN at the specified temperature.

What changes on the WPS or PQR when CVN is part of the qualification?

Per AWS D1.1:2025, when CVN testing is included in the PQR, Table 6.8 supplementary essential variables apply on top of Table 6.6. A change to a different filler metal classification becomes a supplementary essential variable that triggers requalification. The PQR must record CVN results as part of the test record.

CVN filler metal selection for demand-critical structural welds

AISC 341 demand-critical welds require filler metals with tested Charpy toughness, not just tensile strength. Here is how to read AWS filler classifications and get the right certificate.

When AISC 341 (Seismic Provisions for Structural Steel Buildings) applies to a project, a subset of welds are designated demand-critical: the welds in moment connections and other fracture-critical locations where brittle fracture could be catastrophic during a seismic event. These welds have an additional requirement that catches many fabricators off-guard — the filler metal must have demonstrated Charpy V-Notch (CVN) impact toughness at a specified low temperature, and the proof must come from a manufacturer's certificate, not just the AWS electrode classification.

Understanding how CVN toughness is encoded in — and often absent from — AWS filler metal classification designators is essential for any QC manager running a seismic project.

Why CVN matters more than tensile strength

Tensile strength is a measure of how hard you have to pull to break a weld under a slow, steady load. CVN impact toughness measures how much energy a weld absorbs when the load is sudden — a shock, an impact, the inertial loads of an earthquake. A filler metal with excellent tensile strength can still be brittle: it will crack in a fracture-critical application before the parent steel yields.

AWS D1.1 invokes CVN testing through supplementary essential variables in Table 6.8. When CVN testing is required by the project specification — typically because AISC 341 applies, the engineer of record specifies it, or the contract documents require it — Table 6.8 supplementary essential variables add to, not replace, the baseline Table 6.6 essential variables. A filler metal change that would otherwise be minor under Table 6.6 becomes a full requalification trigger under Table 6.8.

AISC 341 Section A3.4a requires filler metals used for demand-critical welds to demonstrate CVN ≥ 20 ft-lbf (27 J) at −20°F (−29°C). This requirement applies to the deposited weld metal, tested in accordance with AWS A5 classification test methods.

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

How the AWS classification system encodes CVN — and when it doesn't

The AWS A5 filler metal classification standards use letters, numbers, and suffixes to describe the electrode's characteristics. CVN performance is sometimes built into the classification and sometimes an optional add-on that requires separate documentation.

SMAW: AWS A5.1 and A5.5

For covered electrodes, the low-temperature CVN designation is a suffix after the main classification:

E7018: No guaranteed CVN at −20°F. This is the standard E7018 most shops stock. It likely passes CVN testing, but the AWS classification does not require it.
E7018-1: The "-1" suffix designates 20 ft-lbf CVN at −20°F, tested in accordance with AWS A5.1. This is the designation AISC 341 demand-critical applications require.
E7018-H4R: This adds low hydrogen (H4 = max 4 mL/100g) and absorbed moisture resistance (R suffix). Adding "-1" to this gives E7018-1 H4R — the most common specification for demand-critical SMAW in seismic applications.

Do not substitute E7018 for E7018-1 on a demand-critical weld. They are different products with different AWS classifications. Ordering the wrong electrode is a QA nonconformance, not a clerical error — it will trigger a Stop-Work if an inspector checks the packing.

For low-alloy SMAW (AWS A5.5), the suffix system is similar. E8018-C3 includes CVN at −40°F in its classification; E8018-B2 does not include CVN. Know your suffix.

FCAW: AWS A5.20 and A5.36

Flux-cored arc welding electrodes are the most common cause of demand-critical CVN mistakes because the classification structure is more complex and the CVN guarantee is often optional.

AWS A5.20 (carbon steel FCAW-G and FCAW-S): The main classification designators (T-1, T-5, T-8, T-9, etc.) describe the slag system, polarity, and position — not CVN. There is an optional supplemental impact designator. Without a supplemental impact designator in the classification, there is no CVN guarantee from the manufacturer.

AWS A5.36 (introduced to consolidate and update FCAW classifications): This standard adds an optional impact toughness designator as part of the classification. A "J" suffix indicates 20 ft-lbf at −20°F. For example, an E71T-1C-J H8 electrode carries the optional CVN designation and is an acceptable choice for demand-critical FCAW work — but only if the manufacturer's certificate of conformance confirms the current heat lot was tested and passed.

The practical takeaway: for FCAW demand-critical welds, do not buy based on AWS classification alone. Get the MCC before the electrode goes into production.

GMAW: AWS A5.18 and A5.28

Solid wire (GMAW) classifications under A5.18 do not include mandatory CVN test requirements. ER70S-6 and ER70S-3 are classified by tensile, yield, and elongation. CVN is not in the classification.

Most ER70S-6 wire will produce welds with acceptable CVN at −20°F in manufacturer testing — the chemistry and heat input that produce good ductile fracture morphology tend to also produce good CVN. But "tends to" is not "requires." For demand-critical GMAW applications, request the manufacturer's supplemental test data showing CVN results for the specific wire product and heat lot. Major filler metal manufacturers (Lincoln Electric, ESAB, Hobart, Illinois Tool Works) publish this data or will provide it on request.

SAW: AWS A5.17 and A5.23

Submerged arc welding CVN is a function of both the wire and the flux — the combination produces the weld deposit properties. AWS A5.17 (carbon steel SAW) includes optional supplemental testing with CVN results when a "-P" designation is added to the classification. AWS A5.23 (low-alloy SAW) has a similar structure.

For demand-critical SAW work, the flux-wire combination must be tested together. Changing either the wire classification or the flux brand or lot is a change in the filler metal combination — and under Table 6.8 supplementary essential variables, that change triggers PQR requalification when CVN is part of the qualification. Never substitute a different lot of flux on a demand-critical seismic application without verifying the CVN data for the new combination.

The manufacturer's certificate of conformance requirement

AWS filler metal classification is a product-type requirement. A heat lot of E7018-1 is manufactured to the A5.1 requirement, but it is tested at the production batch level — not every coil or every box. AISC 341 Section A3.4b goes further: it requires the fabricator to maintain a manufacturer's certificate of conformance (MCC) showing that the specific heat lot being used was tested and achieved the required CVN values.

This is a document control requirement, not just a procurement requirement. The MCC must:

Identify the specific heat or lot number
Show CVN test results at the required temperature (−20°F for AISC 341)
Be traceable to the material used in production

Maintain the MCCs in the project quality file alongside the WPS and PQR. An NDE audit package for a seismic project that cannot produce MCCs for the filler metal used in demand-critical welds is incomplete, and some inspectors will require all affected welds to be re-examined or removed.

What your WPS and PQR must record

When CVN is a project requirement, the WPS and PQR need to reflect it:

WPS: List the filler metal by full AWS classification including all suffixes (e.g., E7018-1 H4R, not just E7018). List the acceptable make and model if the project QC plan requires it. Note that a change in filler metal classification is a Table 6.8 essential variable trigger when CVN testing was part of the PQR.

PQR: If CVN testing was conducted, record the test results in the PQR document. Include test temperature, specimen size, and individual specimen results — not just the average. The AWS D1.1 supplementary essential variable framework under Table 6.8 applies once you conduct CVN testing as part of qualification.

For demand-critical weld procedures that have already been qualified with CVN test data, see our guide to CVN supplementary essential variables under AWS D1.1:2025 Table 6.8. For the seismic supplement requirements that trigger these filler metal controls, see AWS D1.8 seismic WPS demand-critical requirements.

Procurement checklist for demand-critical filler metals

Before production welding begins:

Confirm the electrode AWS classification includes the CVN designator (E7018-1, not E7018)
Confirm the flux-wire combination for SAW has been tested together, not just the wire
Request MCC from the manufacturer for the specific heat/lot being delivered
Verify MCC shows CVN ≥ 20 ft-lbf at −20°F (or the project-specified temperature)
File the MCC in the project quality record alongside the WPS and PQR
Verify the filler metal classification on the WPS matches the electrode in the storage room
If a lot substitution is necessary mid-project, get a new MCC before using the new lot

Tracking filler metal certifications across multiple procedures, multiple projects, and multiple heat lots is the kind of work that gets missed in spreadsheet-based QC programs. WPS and qualification management software that ties filler metal lot numbers to procedures and welder job logs provides the audit trail AISC 341 projects require without the manual chasing.

For a related discussion of how filler metal is treated as an essential variable in the broader PQR system, see WPS essential variables vs non-essential variables.