AWS D1.1 Table 6.7 ESW and EGW Essential Variables

Electroslag welding (ESW) and electrogas welding (EGW) occupy a specialized corner of the AWS D1.1 world. They're single-pass, high-deposition vertical processes used on thick plate joints — common in heavy fabrication, shipbuilding, bridge plate girder webs, and storage tank construction. Because their physics and failure modes differ so sharply from conventional arc processes, AWS D1.1:2025 assigns them their own essential variable table: Table 6.7.

If you're working with ESW or EGW and treating the variables the same as a SMAW or FCAW requalification trigger, you're using the wrong table. Here's what Table 6.7 actually governs.

Why ESW and EGW Get Their Own Table

Conventional arc welding (SMAW, GMAW, FCAW, GTAW, SAW) deposits weld metal in multiple passes with a relatively small molten pool. Heat input is high compared to base metal conduction in a small zone. Table 6.6 essential variables for those processes focus on things like filler metal classification, shielding gas, base metal group, preheat, and heat input — variables that a multi-pass arc weld is sensitive to.

ESW and EGW work entirely differently. In ESW, the arc is extinguished after startup; the electrode melts through resistive heating of the molten slag pool. In EGW, a single continuous arc operates in a gas-shielded environment, progressing vertically upward in a single pass with water-cooled copper shoes or ceramic backup confining the weld pool.

Both processes expose the entire through-thickness joint cross-section to a single massive heat input event. This creates a coarse grain heat-affected zone (HAZ) unlike anything seen in multi-pass welding, and makes the process extremely sensitive to geometric variables — electrode configuration, oscillation, and the dam or shoe type — that simply don't exist in arc welding.

The essential variables in Table 6.7 capture those process-specific sensitivities. For background on how SMAW/GMAW/FCAW/GTAW essential variables are structured, see AWS D1.1 Table 6.6 explained.

Table 6.7 Variables: What Triggers Requalification

Table 6.7 lists the essential variables specific to ESW and EGW. The following covers the major categories; always verify against the published AWS D1.1:2025 text since the authoritative requirements are in the code, not in secondary summaries.

Number and configuration of electrodes. Whether the electrode is a single wire, multiple wires, or a consumable guide affects the geometry and thermal distribution of the weld. Adding or removing an electrode, or changing from parallel to tandem configuration, is an essential variable requiring requalification. This has no analog in Table 6.6 processes.

Electrode oscillation. ESW and EGW procedures frequently specify oscillation — a controlled back-and-forth electrode movement across the joint width. A change from oscillation to no oscillation, or a significant change in dwell time, travel speed, or oscillation width, triggers requalification. Oscillation directly affects fusion at the side walls, so it's not a parameter to vary without testing.

Type of dam or shoe. Copper shoes (water-cooled) versus ceramic backup dams are not interchangeable. The thermal properties of the retention device affect the cooling rate at the fusion boundary, the surface profile of the deposited weld, and the soundness of the root and face. A change in dam or shoe material or design is an essential variable under Table 6.7.

Addition or deletion of supplemental filler metal. Some ESW procedures use supplemental filler (iron powder or additional wire) to increase deposition rate. Adding or removing supplemental filler changes the weld metal chemistry and heat balance — requalification is required.

Base metal group. As with other processes, a change outside the qualified base metal grouping requires requalification. ESW and EGW are commonly used on high-strength structural steels, where the coarse-grained HAZ produced by these processes is a particular concern for toughness. Qualifying a new base metal group isn't just a paperwork exercise — it reflects genuinely different HAZ behavior.

Shielding gas (EGW). For electrogas welding, the shielding gas composition is an essential variable. A change in gas mixture or flow rate affects arc stability and weld metal composition.

Electrode classification or specification. A change in filler metal classification — even within the same diameter — triggers requalification. The weld metal composition produced by ESW and EGW has a dominant influence on toughness in the HAZ-affected zone, and the filler is the primary lever the engineer has to control weld metal chemistry.

The Renumbering Issue: 2020 vs. 2025

Engineers and QC managers working from older PQRs need to be aware that the 2025 edition renumbered these tables:

If your WPS references "Table 6.6 essential variables for ESW," it was written against the 2020 edition. If the governing contract or AHJ cites AWS D1.1:2025, verify that your procedure still satisfies the 2025 Table 6.7 requirements — and update the table reference in your WPS documentation.

This is the kind of edition-transition issue that surfaces in third-party audits. For a full summary of 2025 vs. 2020 changes, see AWS D1.1:2025 vs. 2020 key changes.

CVN Requirements for ESW and EGW Joints

ESW and EGW produce notoriously coarse-grained HAZs with reduced toughness compared to multi-pass welds. When the application requires supplemental CVN testing — demand-critical connections, low-temperature service, or owner-specified toughness requirements — Table 6.8 supplementary essential variables apply.

A change in any Table 6.8 variable requires requalification of CVN performance, independent of whether Table 6.7 requires requalification. In practice, this means an ESW or EGW WPS used on CVN-designated connections may face dual requalification triggers — one set from Table 6.7 (process variables) and a second set from Table 6.8 (CVN supplementary variables).

For the CVN supplementary essential variables and how they interact with process qualification, see CVN supplementary essential variables AWS D1.1 Table 6.8.

Practical PQR Scope for ESW/EGW

When qualifying an ESW or EGW WPS, the PQR test coupon must be welded using the same electrode configuration, oscillation pattern, dam type, and supplemental filler arrangement that the production WPS will specify. There is very limited room to treat these as non-essential variables and adjust in production without triggering requalification.

The test assembly dimensions must reflect the production joint — including joint width, since oscillation parameters are joint-width-dependent. A PQR welded on a narrow coupon to save material cost, then applied to a wider production joint with different oscillation settings, is not supported by the PQR.

Mechanical testing for ESW and EGW PQRs follows the same ASME IX / AWS D1.1 framework as other processes — tensile testing, bend testing, macro examination, and CVN testing if required. Given the coarse HAZ, Charpy sampling location is particularly important; specimens must sample the weld metal and the fusion zone rather than base metal only.

Managing ESW/EGW WPS in a Multi-Process Shop

Shops that use ESW or EGW alongside conventional arc processes need a WPS management system that correctly tags Table 6.7 as the governing essential variable table for those WPS documents — not Table 6.6. Misfiling an ESW WPS under the conventional arc table structure leads to incorrect requalification assessments when production variables change.

A WPS that mixes ESW and GMAW in the same joint (GMAW root pass, ESW fill for thick plate) needs to address essential variables from both Table 6.6 (for the GMAW pass) and Table 6.7 (for the ESW passes). The qualifying PQR must demonstrate both process segments.

If your shop is tracking multiple WPS documents across processes and base metal groups, see WPS library management for multi-project fab shops, or review our WPS management platform for tooling that maps essential variable tables to each process automatically.

Rule library based on AWS D1.1:2025; verify against your governing edition. The authoritative essential variable requirements for ESW and EGW are in AWS D1.1:2025 Table 6.7. The renumbering versus the 2020 edition (where these were Table 6.6) is confirmed in the cheat sheet above — always verify the edition of the code referenced in your contract.