Can I use my existing solid-wire GMAW WPS for metal-cored electrodes?

No. Changing from solid wire (ER70S-X) to metal-cored wire (E70C-X) changes the filler metal classification designation, which is an essential variable under AWS D1.1:2025 Table 6.6. A separate qualified or prequalified WPS that lists the metal-cored classification is required.

Are metal-cored electrodes permitted on a prequalified AWS D1.1 WPS?

Yes. Metal-cored electrodes classified per AWS A5.18 (E70C-X series) for carbon steel and AWS A5.28 for low-alloy steel appear on the approved filler metal lists for prequalified WPS under AWS D1.1. However, short-circuit transfer with metal-cored wire is generally not permitted for structural prequalified applications; spray or globular transfer is required.

What shielding gas parameters must appear on a metal-cored GMAW WPS?

The WPS must identify the exact gas blend and composition, such as 90% Ar/10% CO2 (C10) or 75% Ar/25% CO2 (C25). Shielding gas composition is an essential variable under Table 6.6—any change beyond the documented range triggers requalification.

Does the higher deposition rate of metal-cored wire affect heat input limits on the WPS?

Yes. Higher wire feed speeds with metal-cored wire increase current draw and heat input (kJ/in). The WPS must document the heat input range established during qualification, and production welding must stay within that range per Table 6.6 requirements.

Sep 4, 20267 min read

Metal-Cored Wire GMAW-C WPS Documentation Under AWS D1.1

Metal-cored electrodes deliver higher deposition than solid wire, but their WPS documentation and essential variables under AWS D1.1:2025 Table 6.6 differ from standard GMAW.

WPS GMAW Filler Metal AWS D1.1 Essential Variables

Metal-cored wire electrodes have been standard equipment in high-production fabrication shops for two decades, yet WPS documentation for GMAW-C still generates more shop-floor confusion than almost any other process variant. The appeal is clear: deposition rates 20–40% above comparable solid wire, better sidewall fusion on groove joints, and a wider usable parameter window than solid wire in spray transfer. The complication is equally clear — metal-cored wire is not simply "solid wire with a coating," and AWS D1.1 treats the two as distinct filler metal classifications requiring separate WPS coverage.

This article walks through the WPS documentation requirements under AWS D1.1:2025, focusing on the essential variables that differ from solid-wire GMAW and the production inspection checkpoints that matter.

What Metal-Cored Wire Actually Is

Metal-cored wire (process designation GMAW-C) consists of a mild steel or low-alloy outer sheath filled with a metallic powder blend — iron powder, alloying agents, and arc stabilizers — rather than the slag-forming minerals used in flux-cored wire. The result is a gas-shielded process that produces a full-coverage weld bead with minimal post-weld cleanup, unlike flux-cored wire which leaves a slag blanket.

AWS classifies metal-cored carbon-steel electrodes under A5.18 using an "EC" prefix: E70C-6M is the most commonly specified grade, where "70" = 70 ksi minimum tensile strength, "C" = composite (metal-cored), "6" = chemistry group, and "M" = mixed gas shielding. Low-alloy grades fall under A5.28 with an EC designation and chemistry suffix.

The key distinction for WPS purposes: E70C-6M and ER70S-6 are both A5.18 electrodes, but they carry different classification designations. Under AWS D1.1:2025 Table 6.6, the filler metal classification designation is an essential variable for all GMAW and FCAW procedures. A WPS qualified or written with ER70S-6 does not cover E70C-6M production welding.

Why a Separate WPS Is Required

The essential variable logic in Table 6.6 is straightforward: any change to the filler metal classification that moves outside the range qualified in the PQR — or outside the prequalified filler metal list for Clause 5 WPS — requires a new WPS with its own qualification basis. Solid wire and metal-cored wire, despite sharing a base AWS specification (A5.18 for carbon steel), have different "C" vs. "R" designation characters that represent materially different electrode constructions.

There is also a process behavior reason. Metal-cored wire carries higher current density at a given wire feed speed than solid wire, because the metal powder in the core conducts current to a smaller effective cross section. This changes the arc characteristics, penetration profile, and bead geometry — factors that matter when the PQR mechanical test results are the qualification basis for a structural connection.

For shops running both solid and metal-cored wire, the practical solution is to maintain separate WPS documents for each filler type. Many shops use the same joint detail and process parameters but maintain two parallel WPS files — one listing ER70S-6 (or ER70S-3), one listing E70C-6M — so welders can pull the correct document based on the wire loaded on the feeder.

Essential Variables Specific to GMAW-C

Beyond the filler metal classification, these Table 6.6 parameters require particular attention when writing a metal-cored WPS:

Shielding gas composition. Metal-cored wire performs best with higher argon content blends — typically 75–95% Ar with CO2 balance. The WPS must state the exact blend (e.g., "75% Ar / 25% CO2") or reference a specific AWS shielding gas classification. Changing to a blend outside the qualified range is an essential variable change. Some shops use the same C25 blend for both solid and metal-cored wire; documenting this consistently allows a single shielding gas qualification to support both WPS documents.

Transfer mode. AWS D1.1 recognizes that transfer mode significantly affects weld quality and mechanical properties. Metal-cored wire is not designed for true short-circuit transfer — the tubular construction resists the controlled pinching needed for short-circuit. Prequalified WPS (Clause 5) and most tested WPS for structural applications specify spray or globular transfer. Attempting short-circuit transfer with metal-cored wire at low voltage produces erratic arc behavior and inconsistent fusion; documenting this on the WPS protects both quality and WPS coverage.

Wire diameter. Diameter is a separate essential variable. A WPS qualified with 0.045 in. (1.2 mm) E70C-6M does not cover 1/16 in. (1.6 mm) E70C-6M without a separate qualification. Metal-cored wire is most commonly specified at 0.045 in. for short-to-medium travel speed applications and 1/16 in. for high-deposition flat and horizontal passes on heavy plate.

Electrode extension (CTWD). Contact-tip-to-work distance influences resistive preheating of the wire stub and therefore the arc voltage and penetration profile. Metal-cored wire is more sensitive to CTWD variation than solid wire because current flows through a smaller effective conductor. Document the CTWD range on the WPS and train welders and inspectors to check this during setup.

Heat input range. Higher deposition at comparable voltages means metal-cored wire operates at higher heat input per pass than solid wire under the same joint size. The PQR records heat input for each pass; the qualified WPS sets the allowable range. Verify that heat input during CVN-qualified applications stays within the Table 6.8 supplementary essential variable limits. Rule library based on AWS D1.1:2025; verify against your governing edition.

Prequalified WPS for GMAW-C: What Clause 5 Allows

AWS D1.1 Clause 5 lists approved filler metals for prequalified WPS. Metal-cored electrodes classified to A5.18 (E70C series) and A5.28 (low-alloy EC series) are included, which means a shop can write a prequalified WPS for metal-cored wire without running a PQR — provided all other Clause 5 constraints are satisfied.

The critical Clause 5 constraints most often violated on metal-cored WPS:

Joint geometry must match a prequalified joint type from Annex B.
Base metals must be from the approved prequalified base metal list.
Preheat and interpass temperature must meet Clause 5 minimums for the base metal grade and thickness.
Minimum fillet size and maximum effective throat must be within the prequalified range.
The WPS must document all required parameters — preheat, interpass max, shielding gas, voltage/amperage range, wire feed speed range, travel speed range — with enough specificity that a welder can set up without interpretation.

A prequalified WPS does not require witnessed production test plates, but it requires complete and accurate parameter documentation. A WPS that lists only "spray transfer, 90% Ar/10% CO2, E70C-6M, 0.045 in." without current range, wire feed speed, and travel speed is not compliant with Clause 5 documentation requirements.

What the CWI Checks on Metal-Cored Production Welds

During in-process inspection of GMAW-C welds, the CWI should verify:

Wire spool label matches the WPS. E70C-6M and ER70S-6 spools look identical; confirm the classification is printed on the spool hub or label, not just the outer packaging that may have been discarded.
Shielding gas cylinder and blend. Check the regulator label and cylinder contents. Many shops use shared manifold systems — confirm the gas blend feeding the station matches the WPS.
Contact tip to work distance. Use a ruler or CTWD gauge during setup and at weld start. Document the measured value on the inspection record.
Voltage and wire feed speed. Spot-check machine settings against the WPS range. Shops running digital feeders can often print parameter logs; shops running analog machines require physical verification at the feeder.
Transfer mode observation. A brief arc observation (with proper shade filter) confirms whether the arc is in spray (fine, uniform droplet transfer, smooth hiss) or globular/short-circuit (larger droplets, irregular sound, more spatter). Document observed transfer mode on the inspection record.

Practical Notes for Shops Transitioning to Metal-Cored Wire

If your shop is evaluating metal-cored wire for the first time, plan the WPS update before the wire arrives on the floor. Ordering wire without updating WPS documentation creates production stops when an inspector or AHJ asks for the WPS covering the electrode on the feeder.

The fastest path for most structural shops: write a prequalified GMAW WPS per Clause 5 listing the metal-cored classification, complete with parameter ranges drawn from the manufacturer's recommended operating parameters for the joint configuration. Run a sample pass on scrap to verify the parameters before production starts, and document those verified parameters on the WPS rather than copying manufacturer data directly.

For shops already running a tested WPS (Clause 6 qualification), a separate PQR coupon with metal-cored wire is the compliant path. The test is straightforward — use the same joint design and thickness as the existing GMAW PQR — and can often be witnessed and processed in a single day at an independent test lab.

For guidance on selecting the right qualification path for your specific base metal and joint combination, the WPS and PQR walkthrough for A36 SMAW and multiple WPS from a single PQR articles cover the general qualification logic. See the pricing page for qualification tracking tools built into the platform.

FAQ

Frequently asked.

Can I use my existing solid-wire GMAW WPS for metal-cored electrodes?: No. Changing from solid wire (ER70S-X) to metal-cored wire (E70C-X) changes the filler metal classification designation, which is an essential variable under AWS D1.1:2025 Table 6.6. A separate qualified or prequalified WPS that lists the metal-cored classification is required.
Are metal-cored electrodes permitted on a prequalified AWS D1.1 WPS?: Yes. Metal-cored electrodes classified per AWS A5.18 (E70C-X series) for carbon steel and AWS A5.28 for low-alloy steel appear on the approved filler metal lists for prequalified WPS under AWS D1.1. However, short-circuit transfer with metal-cored wire is generally not permitted for structural prequalified applications; spray or globular transfer is required.
What shielding gas parameters must appear on a metal-cored GMAW WPS?: The WPS must identify the exact gas blend and composition, such as 90% Ar/10% CO2 (C10) or 75% Ar/25% CO2 (C25). Shielding gas composition is an essential variable under Table 6.6—any change beyond the documented range triggers requalification.
Does the higher deposition rate of metal-cored wire affect heat input limits on the WPS?: Yes. Higher wire feed speeds with metal-cored wire increase current draw and heat input (kJ/in). The WPS must document the heat input range established during qualification, and production welding must stay within that range per Table 6.6 requirements.