SMAW A5.5 Low-Alloy Electrodes: E8018, E9018 in Structural WPS

Most structural fab shops carry a single SMAW electrode: E7018. It qualifies the full range of common A36 and A572 Grade 50 structural steel, and its low-hydrogen coating satisfies the preheat and hydrogen-cracking requirements of AWS D1.1:2025 for typical structural work. But when the base metal steps up to A572 Grade 65, A514, A709 HPS 70W or HPS 100W, or any other steel with a specified minimum yield strength above 70 ksi, E7018 is no longer adequate — the weld metal yield strength is below the base metal, creating an undermatching condition that AWS D1.1 permits only in specific fillet weld situations.

AWS A5.5 low-alloy SMAW electrodes fill this gap. Understanding when they are required, how they are classified, and what the WPS and PQR must record is practical knowledge for any CWI, welding engineer, or QC manager working with higher-strength structural steel.

AWS A5.5 classification system

The AWS A5.5 electrode designation follows the same basic structure as A5.1 but adds a suffix that identifies the alloy system:

E8018-C3 means:

• E: electrode (SMAW)
• 80: minimum tensile strength of deposited weld metal = 80,000 psi (80 ksi)
• 1: positions qualified (1 = all positions, including vertical up and overhead)
• 8: covering type and current (low-hydrogen, DC reverse polarity, same as 8 in E7018)
• C3: alloy designation — C3 indicates a nickel-alloyed deposit (nominally 1% Ni)

Common AWS A5.5 electrode designations used in structural work:

The minimum yield strength of the electrode is approximately the UTS value minus about 12 ksi for most A5.5 electrodes. When matching or slightly overmatching base metal yield strength is the design intent, select the electrode grade accordingly.

The -G suffix designates "general low-alloy" — the only requirement is that the weld metal have one alloying element (Mn, Si, Ni, Cr, Mo, or V) above a minimum level. -G electrodes are used when the designer wants some alloy addition but not a specific chemistry. Because -G electrodes have no defined alloy chemistry beyond the one-element requirement, they cannot be substituted freely for a classified alloy like -C3 or -M; the WPS must specify the electrode by its full classification, and the PQR must be run with the same classification.

When A5.5 electrodes are required by AWS D1.1

AWS D1.1:2025 does not enumerate a list of base metals that require A5.5 filler — instead, the rule is implicit in the matching filler metal concept for groove welds in tension: the filler metal must produce weld metal with a tensile strength equal to or greater than the specified minimum tensile strength of the base metal.

For A572 Grade 50 (65 ksi UTS), E7018 (80 ksi UTS deposited) already overmatch in tensile strength. For A572 Grade 65 (80 ksi UTS), E7018 at 80 ksi UTS is exactly matching. AWS D1.1 permits this, but the yield strength may not match — E7018 deposits at ~68–72 ksi yield, while A572 Grade 65 is 65 ksi yield. The match is close.

For A514 (100–130 ksi UTS depending on thickness), E7018 clearly falls short for groove welds. AWS D1.1 requires that CJP groove welds in primary tension members use matching or overmatching filler — for A514, that means E9018-M or E10018-M depending on thickness and yield requirement. AWS D1.1:2025 Clause 3 and the base metal / filler metal matching tables govern this selection.

For fillet welds and PJP groove welds, undermatching is permitted under certain conditions because the weld geometry provides redundancy and the fillet weld leg size can be adjusted to compensate for lower-strength filler. An engineer can design a larger fillet using E7018 on A572 Grade 65 rather than specifying a smaller fillet with E8018, provided the connection geometry allows it. The choice is the structural engineer's, but it must be reflected in the WPS.

For information on undermatching filler strategies, see undermatching filler metal WPS under AWS D1.1.

PQR requirements for A5.5 electrodes

A PQR supports a WPS. When the WPS specifies an A5.5 electrode, the PQR must have been run with the same electrode classification. The mechanical tests from the PQR — tensile, bend, and CVN if required — reflect the actual weld metal deposited with that electrode. You cannot use a PQR run with E7018 to support a WPS that specifies E8018-C3.

The PQR must record the complete electrode classification (including the suffix), the heat/lot number if traceability is needed for CVN testing, the actual preheat and interpass temperatures used, and the welding parameters (amperage, voltage, travel speed). All of these become the basis for the WPS operating ranges.

For CVN (Charpy V-notch) applications — common on bridge structures (AASHTO/D1.5) and seismic structures requiring supplementary essential variables under AWS D1.1:2025 Table 6.8 — the filler metal classification is a supplementary essential variable. Any change in AWS classification (including from -C3 to -M or from one manufacturer's -G to another's -G with different chemistry) requires a new PQR with CVN testing at the required temperature. For more on CVN supplementary essential variables, see CVN supplementary essential variables under AWS D1.1:2025 Table 6.8.

Preheat requirements with A5.5 electrodes on higher-strength base metals

Higher-strength base metals generally have higher carbon equivalent values, which means higher susceptibility to hydrogen cracking and higher required preheat. AWS D1.1:2025 preheat tables (or the Annex I calculation method) must be applied to the specific base metal, process, and heat input.

For A572 Grade 65 with SMAW in the over-1.5-inch thickness range, preheat of 225°F (107°C) or higher is typical. For A514 and A517, preheating to 400°F (204°C) is common, and AWS D1.1 restricts interpass temperature on A514 to a maximum of 400°F (204°C) as well — overheating A514 can degrade its as-quenched microstructure.

The WPS must record the preheat minimum and interpass maximum. For A514 with both a minimum preheat and a maximum interpass, the welding procedure becomes a thermal management exercise in production: the joint must stay above preheat and below maximum interpass throughout the entire welding sequence. This is an area where CWI hold points and actual temperature measurement logs — not just pyrometer spot checks — are critical for auditability.

Low-hydrogen requirements and electrode handling

Like E7018, all A5.5 electrodes with the "8" in the third digit are low-hydrogen coverings. They are subject to the same moisture sensitivity as E7018 and must be stored in a heated oven at 250–300°F (121–149°C) or come from a hermetically sealed container. E8018 and E9018 electrodes carry the same H-suffix options as A5.1 electrodes: H4, H8, H16, and the R (moisture-resistant) designator.

For high-strength steel applications like A514, many engineers specify E10018-M-H4R — meaning the electrode must meet the H4 hydrogen limit and carry the R moisture-resistance designation. This is the most conservative available combination for hydrogen control in SMAW and is appropriate for heavy, restrained, high-strength joints.

For overall electrode storage and handling practices, see FCAW electrode storage and moisture control and diffusible hydrogen and filler metal selection under AWS D1.1.

WPS documentation checklist for A5.5 electrodes

When writing or reviewing a WPS that specifies an A5.5 electrode, confirm:

1. Complete electrode classification is recorded. The WPS must list the full AWS designation including alloy suffix (E8018-C3, not just E8018). Specifying "E8018" without a suffix is ambiguous — it doesn't define the alloy chemistry.
2. Supporting PQR used the same classification. Verify the PQR records the same electrode designation used in production.
3. Preheat is based on the actual base metal, not the electrode. Preheat tables in AWS D1.1 are organized by base metal group, not by filler metal. The preheat minimum applies to the base metal being welded.
4. H-designator is specified if required. If the application requires an H4 or H8 maximum, it must appear in the WPS electrode specification.
5. Base metal qualification range covers the production steel. The PQR base metal must support the base metal in the WPS. A PQR on A572 Grade 65 (Group II base metal) supports welding of Group I and Group II base metals per the qualification range rules in AWS D1.1:2025. For more on base metal groups and WPS qualification ranges, see AWS D1.1 Table 6.9 base metal groups.

Shops moving into higher-strength structural work — AISC-certified bridge or seismic work, for instance — often discover that their entire WPS library was written for A36 and A572 Grade 50, with no A5.5 procedures on file. Auditing your procedure library against the actual base metals you are welding is a fundamental step in quality system readiness. For a software-based approach to managing WPS libraries across multiple base metal groups, see our pricing page.

Rule library based on AWS D1.1:2025; verify against your governing edition. The authority having jurisdiction (AHJ) or contract may specify AWS D1.1:2020 or an earlier edition.