What does the '-1' suffix mean on an E71T-1 electrode?

The '-1' is a Charpy V-notch impact designation. An E71T-1C-H8 or E71T-1M-H8 with a '-1' suffix meets a 20 ft-lbf minimum at 0°F (–18°C). Without '-1', no impact requirement applies. If your WPS covers CVN supplementary essential variables under AWS D1.1:2025 Table 6.8, you must use an electrode that was tested at the required temperature — the -1 designation tells you the lot meets 0°F.

Is an E71T-9 electrode the same as E71T-1 for WPS purposes?

No. They are different A5.20 classifications and therefore different essential variables under Table 6.6 of AWS D1.1:2025. E71T-9 is specifically formulated for multi-pass operation with more consistent slag removal than T-1. You cannot substitute one for the other without requalifying your WPS, even though both produce 70 ksi weld metal.

Can I run E71T-11 on a prequalified WPS under AWS D1.1?

Yes. E71T-11 is an A5.20 self-shielded classification that is acceptable for prequalified WPS under Clause 5, but only on specific base metal groups and joint configurations. Check the prequalified WPS requirements for your joint type. E71T-11 is single-pass to a limited extent on thinner material — multi-pass on structural plate requires careful position and pass sequence documentation.

What does the H-suffix (H4, H8, H16) mean on FCAW electrodes?

The H-suffix indicates maximum diffusible hydrogen in the deposited weld metal: H4 ≤4 mL/100g, H8 ≤8 mL/100g, H16 ≤16 mL/100g. Under AWS D1.1:2025, when hydrogen-controlled filler metals are required (typically on higher-strength steels or higher preheat applications), the H-suffix classification on the electrode must match or exceed the WPS requirement. An electrode without an H-suffix has no diffusible hydrogen guarantee.

AWS A5.20 FCAW Electrode Designators Explained for WPS

Decode AWS A5.20 FCAW electrode classification suffixes (-1, -4, -8, -9, -11, -12) and how each affects your WPS essential variables and PQR requirements under AWS D1.1:2025.

When a CWI or QC manager reviews a GMAW or FCAW WPS, the filler metal section often reads something like "AWS A5.20, E71T-1C-H8" and stops there. If you don't know how to decode that string, you can't verify the procedure is correct for the application — or catch a substitution that violates the WPS. AWS A5.20 is the specification for carbon steel electrodes for flux-cored arc welding, and its classification system carries real engineering information that directly affects your WPS essential variables under AWS D1.1:2025.

How the A5.20 Classification String Is Built

Take a full example: E71T-9C-J-H4

E — Electrode
7 — Minimum tensile strength in units of 10 ksi (70 ksi minimum)
1 — Usability position: 1 = all positions; 2 = flat and horizontal only
T — Tubular (flux-cored) construction
9 — Usability and performance suffix (the key variable — see below)
C — Shielding gas: C = 100% CO₂; M = mixed gas (Ar/CO₂); no letter = self-shielded (FCAW-S)
-J — Charpy impact designation at a specific temperature (J = 20 ft-lbf at –40°F)
H4 — Maximum diffusible hydrogen 4 mL/100g

The numeric suffix after the T is where most confusion lives.

The Usability Suffix: What -1, -4, -8, -9, -11, -12 Mean

E71T-1 (Gas-Shielded, Multi-Pass)

The original workhorse FCAW-G classification. E71T-1 electrodes are designed for multi-pass welding with CO₂ or mixed-gas shielding. They produce a fluid slag that ties over the bead and peels relatively easily. The T-1 suffix alone (without a -1 Charpy designation) has no specified impact requirement — suitable for applications where CVN testing is not required by the contract or code.

E71T-1C vs E71T-1M

The "C" and "M" suffix was added to A5.20 to clarify which shielding gas the electrode was classified with. E71T-1C = classified using 100% CO₂. E71T-1M = classified using mixed gas (Ar/CO₂ blend). Under AWS D1.1:2025, the shielding gas type is its own essential variable, and the electrode classification must match the gas you're running. Running an E71T-1C wire with 90/10 Ar/CO₂ is a classification mismatch — the electrode was not tested with that gas.

E71T-4 (Self-Shielded, High Deposition, Single or Multi-Pass)

T-4 is self-shielded (FCAW-S), optimized for high-deposition flat and horizontal welding. It is primarily a semi-flat operation wire used in shop fabrication for heavy groove welds where deposition rate matters more than position flexibility. Not suitable for overhead or vertical-up in most applications. The slag system is different from T-1 — expect a more voluminous slag that requires thorough interpass removal.

E71T-8 (Self-Shielded, Low Hydrogen, All Position)

E71T-8 is self-shielded and carries a specified CVN impact requirement even without a Charpy designator: the A5.20 classification itself specifies minimum 20 ft-lbf at 0°F. This makes T-8 the most commonly required self-shielded wire for seismic and demand-critical weld applications under AWS D1.8. It runs all-position and was specifically developed to meet low-hydrogen and impact requirements without external shielding gas.

For a comparison of T-8 versus T-11 in specific structural applications, see FCAW-S E71T-8 vs E71T-11 electrode selection under AWS D1.1.

E71T-9 (Gas-Shielded, Multi-Pass, Improved Slag Removal)

T-9 is very similar to T-1 but specifically formulated for consistent slag release and multi-pass performance. It is often the preferred choice for shops doing high-volume multi-pass groove welds where consistent slag removal without chipping or grinding between passes is critical. The mechanical minimums match T-1; the difference is in the slag system and usability. A WPS qualified with T-1 does not automatically cover T-9 — they are different classifications under the essential variable rules.

For a closer look at T-1, T-9, and T-12 gas-shielded electrodes, see FCAW-G electrode classification: E71T-1, E71T-9, and E71T-12.

E71T-11 (Self-Shielded, Single-Pass or Limited Multi-Pass)

T-11 is a general-purpose self-shielded wire designed primarily for single-pass or limited multi-pass work. It is listed as acceptable for prequalified WPS under AWS D1.1 Clause 5 for certain base metals and joint configurations. However, it has no CVN impact requirement, and AWS D1.1:2025 restricts its use for seismic or demand-critical joints. Fab shops using T-11 need to confirm that the application does not require supplementary CVN testing.

E71T-12 (Gas-Shielded, Improved CVN Performance vs T-1)

T-12 was developed specifically to meet improved CVN requirements while maintaining the usability characteristics of T-1. It is classified with a 20 ft-lbf minimum at –20°F as part of the standard classification (without requiring the separate -1 Charpy suffix). For work where intermediate impact temperature requirements apply, T-12 can be a cleaner solution than sourcing a T-1 wire with a -1 suffix and confirming the heat number meets the Charpy threshold.

Charpy Designators and Table 6.8 CVN Requirements

Under AWS D1.1:2025, if your WPS covers welds subject to CVN supplementary essential variables (Table 6.8), the filler metal heat number that produces the CVN data must be documented. The A5.20 Charpy suffix tells you what temperature the classification requires:

Suffix	Minimum CVN	Temperature
(none)	Not required	—
-1	20 ft-lbf	0°F (–18°C)
-J	20 ft-lbf	–40°F (–40°C)

This matters because under a CVN supplementary essential variable program, you are not just checking that the classification has a Charpy designator — you must verify that the actual heat or lot number used during production was tested and met the minimum. The CMTR (Certified Mill Test Report) from the wire manufacturer is the documentation instrument. See CVN supplementary essential variables under AWS D1.1:2025 Table 6.8 for the full documentation chain.

H-Suffix and Diffusible Hydrogen Control

The H-suffix on an A5.20 classification is not cosmetic. When the WPS or project spec calls for a low-hydrogen filler, the H-suffix must be present on the electrode classification AND the electrode must be stored and handled per the H-designation requirements:

H4 — Maximum 4 mL/100g; requires hermetically sealed packaging or special storage conditions
H8 — Maximum 8 mL/100g; standard moisture-resistant packaging
H16 — Maximum 16 mL/100g; basic packaging

An electrode with no H-suffix provides no hydrogen guarantee. On higher-carbon-equivalent base metals or on thick plate where hydrogen-induced cracking risk is elevated, specifying a minimum H8 or H4 on the WPS is a risk-management measure, not just paperwork.

Proper storage and conditioning of FCAW electrodes is covered in FCAW electrode storage and moisture control.

Essential Variable Impact Under AWS D1.1:2025

Under Table 6.6 of AWS D1.1:2025, the following changes each require WPS requalification (or a new PQR):

A change in filler metal specification (e.g., A5.20 to A5.29)
A change in filler metal classification (e.g., E71T-1C to E71T-9C)
A change in shielding gas type or composition percentage (e.g., C25 to 100% CO₂)

This means that even though T-1 and T-9 are both 70-ksi multi-pass FCAW-G wires that look nearly identical in production, they are distinct essential variables. A shop that runs T-9 in production but lists T-1 on the WPS — or vice versa — has a documentation nonconformance. The fix is to ensure the WPS lists the exact classification, the PQR was run with that classification, and production controls verify the wire spool matches what is specified.

Rule library based on AWS D1.1:2025; verify against your governing edition — the AHJ or contract may specify 2020 or earlier.

What to List on the WPS

The WPS must identify:

Filler metal specification: AWS A5.20
Filler metal classification: E71T-1C-H8 (or the specific designation used in the PQR)
Shielding gas type and composition: 75% Ar / 25% CO₂ (C25) or 100% CO₂
Wire diameter: separate essential variable

If you are writing a WPS for self-shielded FCAW (FCAW-S), there is no shielding gas entry, but you still list the specific A5.20 classification (e.g., E71T-8) and wire diameter. The FCAW wire diameter is an independent essential variable — see FCAW wire diameter as an essential variable under AWS D1.1.

Building a WPS That Covers Your Production Reality

The most common A5.20-related audit finding is a mismatch between what is listed on the WPS and what is actually run in the shop — different T-suffix, different gas code letter, or no H-suffix when a low-hydrogen requirement applies. Prevent this by auditing your filler metal procurement list against your active WPS documents at least once per project. Each WPS should reference the specific classification it was qualified with, and production controls should prevent any wire substitution without QC review and, if required, requalification.

If you're managing a WPS library across multiple processes and need a platform that tracks filler metal classifications, links WPS to PQR data, and flags essential variable mismatches, see how WPS software handles filler metal documentation.