Why does AWS D1.1 have a separate essential variable table for ESW and EGW?

Electroslag and electrogas welding deposit in a fundamentally different thermal regime than arc processes. The single-pass, very high heat input characteristic of ESW/EGW produces a wide HAZ with grain growth unlike anything in SMAW or FCAW, so the code restricts their qualification range more tightly and identifies process-specific triggers that don't exist in Table 6.6.

Does qualifying an ESW WPS under Table 6.7 also qualify FCAW or SMAW connections?

No. A PQR run under the ESW or EGW process qualifies that process only. It does not extend qualification to arc processes governed by Table 6.6. Each process family requires its own PQR.

What thickness range does a typical ESW PQR qualify?

Thickness qualification for ESW is narrower than for arc processes. The qualified range is restricted based on the test plate thickness per Table 6.7 provisions. Unlike the generous multiplier-based thickness ranges common in Table 6.6, ESW often ties qualification to a limited window around the tested thickness.

When does CVN testing become mandatory for ESW and EGW welds?

When the contract, governing code edition, or project specification invokes supplementary CVN requirements. At that point, AWS D1.1:2025 Table 6.8 supplementary essential variables apply on top of Table 6.7 for ESW/EGW — just as Table 6.8 layers over Table 6.6 for arc processes.

ESW and EGW Under AWS D1.1: Table 6.7 Essential Variables

AWS D1.1:2025 Table 6.7 governs ESW and EGW essential variables separately from Table 6.6. Learn what changes force requalification and when thick-plate structural work justifies these processes.

ESW and EGW Under AWS D1.1:2025: Table 6.7 Essential Variables

Electroslag welding (ESW) and electrogas welding (EGW) are high-deposition processes built for thick plate. A single pass of ESW can fill a joint that would require dozens of SMAW or FCAW passes. That thermal efficiency comes with a trade-off: the process deposits enormous heat into a narrow weld joint over an extended time, producing a heat-affected zone (HAZ) unlike anything generated by arc welding. AWS D1.1:2025 recognizes this distinction by placing ESW and EGW essential variables in Table 6.7 — separate from Table 6.6, which governs SMAW, SAW, GMAW, FCAW, and GTAW.

Understanding why the tables are split, what Table 6.7 actually requires, and where ESW/EGW are genuinely useful in structural work helps CWIs and QC managers avoid both qualification gaps and unnecessary PQR costs.

Why Two Separate Essential Variable Tables

AWS D1.1 groups welding processes by their qualification requirements, not by their industrial popularity. Arc processes — SMAW, SAW, GMAW, FCAW, GTAW — share enough thermal and metallurgical behavior that a single essential variable table (Table 6.6) can govern them with process-specific exceptions. ESW and EGW share neither the arc physics nor the thermal profile of those processes.

In ESW, the weld pool is kept molten by electrical resistance heating through a liquid flux bath — not an arc. The electrode feeds into a slag pool that acts as both the heating medium and the shielding. A single vertical pass can fill a butt joint in 4 in [100 mm] thick plate in one continuous operation. The heat input values are orders of magnitude higher than arc welding: multiple thousands of kJ/in are common in heavy ESW, compared to typical structural FCAW values of 30–80 kJ/in.

That extreme heat input produces HAZ grain coarsening, potential toughness degradation, and a solidification structure that responds differently to post-weld treatment than arc weld HAZs. The code accounts for this by making the Table 6.7 essential variable triggers narrower and more process-specific than Table 6.6.

Rule library based on AWS D1.1:2025; verify against your governing edition — table numbers and content differ from the 2020 and earlier editions.

What Table 6.7 Governs: ESW/EGW-Specific Essential Variables

Table 6.7 in AWS D1.1:2025 covers essential variables for electroslag and electrogas welding specifically. A change in any Table 6.7 variable requires requalification of the WPS — producing a new PQR or demonstrating coverage from an existing PQR that addressed the new condition.

The essential variable categories unique to ESW/EGW — and absent from Table 6.6 for arc processes — include:

Electrode and guide configuration changes. ESW uses a consumable guide tube that becomes part of the weld deposit, or a non-consumable oscillating guide. Changing the type of guide, the cross-sectional geometry of the electrode wire, or the number of electrodes changes the deposition pattern and heat distribution in ways that directly affect the weld profile and HAZ width. Table 6.7 treats these as essential variables; Table 6.6 has no equivalent because arc processes don't use slag-bath guides.

Oscillation parameters. Many ESW setups oscillate the electrode across the joint to promote uniform fusion across thick butt joints. Oscillation frequency, amplitude, and dwell time at the edges determine how heat distributes across the joint width. A change in any of these parameters constitutes an essential variable under Table 6.7.

Flux type and manufacturer. The flux in ESW is the heating medium, not just a shielding agent. Flux composition controls the electrical resistance of the slag pool, the melting temperature, and the chemical interaction with the weld metal. Table 6.7 restricts flux changes more tightly than Table 6.6 restricts SAW flux changes.

Thickness range. Qualification thickness range for ESW is generally tighter than for arc processes. The generous multiplier-based upper thickness limits in Table 6.6 — which allow a PQR on 1 in plate to qualify joints up to 2× the test plate thickness — do not apply the same way to ESW. Confirm the specific provisions in Table 6.7 for the edition you're working under.

Change in the groove type configuration. ESW and EGW are used almost exclusively in vertical groove joints. The groove opening, which functions more as a retaining dam for the slag pool than as a fusion bevel geometry, is an essential variable because the weld pool size and circulation directly depend on it.

Table 6.7 vs. Table 6.6: Practical Differences for the QC Manager

For a CWI managing a WPS library that includes both arc processes and ESW, the key operational difference is that ESW PQRs are not interchangeable with arc process PQRs. A PQR run on an ESW WPS using 4 in [100 mm] A36 plate qualifies that ESW process within the Table 6.7 range. It does not extend qualification to FCAW-G or SMAW connections, even on the same base metal group.

Conversely, a FCAW-G PQR does not cover ESW. If your shop adds ESW capability for a heavy plate project — column splices, heavy box girder corner seams, or bridge pier base connections — a new ESW-specific PQR is required, and it must address Table 6.7 essential variables in full.

The other practical difference is that Table 6.7 has no prequalified option under Clause 5. ESW and EGW are not among the processes for which AWS D1.1 allows prequalified WPS. Every ESW or EGW procedure is a tested WPS backed by a PQR, full stop.

For arc process essential variables and how Table 6.6 handles changes in position, filler metal, and base metal group, see AWS D1.1 Table 6.6 explained for structural welding.

When ESW and EGW Make Sense in Structural Fabrication

Given the qualification overhead, ESW earns its place only on specific geometry and thickness scenarios:

Heavy box column corner seams. Box columns fabricated from four plates with full-penetration corner welds are a classic ESW application. The joint is vertical, the thickness is typically 1-1/2 in to 4 in [38 mm to 100 mm], and the groove geometry is compatible with slag-bath welding. A single ESW pass per corner seam can replace 20–40 FCAW passes, dramatically reducing labor hours and distortion on a tight column.

Column splices in heavy industrial frames. Butt splices on 3–5 in [75–125 mm] thick flanges — common in power plant, petrochemical, and heavy machinery foundation structures — are candidates for ESW where access allows. The single-pass nature minimizes distortion in a highly restrained joint.

Web-to-flange joints on heavily built-up plate girders. Wide-flange plate girders with flange plates exceeding 3 in [75 mm] thick can use ESW for the longitudinal flange-to-web groove welds in some configurations, though the fit-up requirements and backup bar arrangements must be addressed in the WPS.

Where ESW is not appropriate: connections requiring CVN toughness without post-weld normalization, thin plate (under 1 in [25 mm]), horizontal groove welds, and any situation where the slag bath cannot be retained vertically.

CVN Toughness and Table 6.8 Interaction

ESW and EGW are under particular scrutiny for CVN toughness applications because the high heat input produces HAZ coarsening that can significantly reduce notch toughness. When a project or owner specification invokes CVN requirements — seismic applications, fracture-critical members, cold-service connections — the supplementary essential variables in AWS D1.1:2025 Table 6.8 layer over Table 6.7 requirements.

This means the PQR must include CVN impact testing of the weld metal and HAZ, and any subsequent change listed in Table 6.8 (such as an increase in heat input, a change in interpass temperature maximum, or a change in PWHT condition) forces re-examination of CVN qualification. For ESW applications where toughness is contractually required, the qualification program is substantially more involved than for the same base metal welded by arc processes.

For the Table 6.8 supplementary essential variable framework and how it interacts with PQR test requirements, see CVN supplementary essential variables under AWS D1.1 Table 6.8.

WPS Documentation Requirements for ESW

The written WPS for an ESW procedure must specify the Table 6.7 variables in detail:

Electrode wire specification, diameter, and number of electrodes
Guide type (consumable vs. non-consumable) and dimensions
Oscillation parameters: frequency, amplitude, and dwell time if applicable
Flux classification, manufacturer, and brand name
Starting and run-off tab configuration and dimensions
Groove opening (width) and joint assembly tolerances
Applicable thickness range consistent with the PQR
Backing type (copper shoe dimensions, retaining bar specifications)

Omitting any of these from the written WPS creates a compliance gap — the WPS can't be used to govern production welding if the essential variable values aren't recorded. A CWI reviewing the WPS for the first time needs to find every Table 6.7 variable in the document to confirm it governs the joint.

For complete WPS documentation requirements and how to structure a weld procedure package for a project submittal, WPS library management for multi-project shops covers the organizational side, and the complete WPS submittal package review checklist covers what the engineer of record will verify on the receiving end.

If your shop is qualifying ESW for the first time or expanding an existing WPS library to cover new processes and thicknesses, a WPS management platform purpose-built for structural welding — like the tools available at wpswelding.com/pricing — keeps Table 6.7 variables, PQR test records, and qualification ranges organized in one place, so your CWI's review starts from accurate data rather than hunting through binders.