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Flux-Cored and Metal-Cored Wire Classifications

Flux-cored and metal-cored wires are tubular wires classified under AWS A5.20, A5.36 and A5.29. This sheet explains how to read E71T-1C/M and E70C-6M designations and how to tell gas-shielded from self-shielded wire.

Ref WG-0104AWS A5.20AWS A5.36AWS A5.29

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

A flux-cored wire is a metal tube filled with flux and alloying powders. Some need external shielding gas (gas-shielded, FCAW-G). Others make their own shielding from the flux (self-shielded, FCAW-S). A metal-cored wire is a tube filled mostly with metal powders and very little flux. It runs like a solid MIG wire with higher deposition and needs shielding gas. Carbon steel flux-cored wires were classified under AWS A5.20 and metal-cored wires under A5.18. AWS A5.36 now covers both in an open format. Low-alloy flux-cored wires are under AWS A5.29.

How to read it

E71T-1C: E = electrode, 7 = 70 ksi minimum tensile strength, 1 = all-position (0 = flat and horizontal only), T = tubular, 1 = usability type, C = 100% CO2 gas. An M in place of C means an argon-CO2 mixed gas. Labels showing both, such as E71T-1C/M or E71T-1C-JH8 and E71T-1M-JH8, are classified for both gases. E70C-6M: E = electrode, 70 = 70 ksi, C = composite (metal-cored), 6 = chemistry, M = mixed gas. Suffixes such as J show extra impact testing, and H4, H8 or H16 show the diffusible hydrogen limit. See the wire decoder chart for the A5.36 open format.

Common usability types

Designation	Shielding	Positions	Typical use
E71T-1C, E71T-1M	Gas	All position	Structural and general fabrication; smooth arc, easy slag removal
E70T-1C, E70T-1M	Gas	Flat and horizontal	Higher deposition on heavy fillets
E71T-5 types	Gas	Varies by product	Basic flux, good toughness and crack resistance; harder to run
E71T-8	Self-shielded	All position	Structural field work, often where impact toughness is required
E71T-11	Self-shielded	All position	General purpose multipass work on lighter sections; check thickness limits
E71T-GS	Self-shielded	All position	Single pass only, light gauge, hobby and farm welders
E70C-6M	Gas, mixed	Flat and horizontal for most; some all-position	Production welding with low spatter and little slag

Key points

Self-shielded wire usually runs DCEN (electrode negative). Gas-shielded and metal-cored wire usually runs DCEP. Check the label and set polarity to match.
Use knurled or cored-wire drive rolls. V-groove rolls for solid wire can crush tubular wire.
Gas designator must match the gas used. Running an M wire on CO2, or a C wire on a mix, changes the weld metal.
Structural codes may require specific classifications, J suffixes and hydrogen limits. Follow the WPS.
Store flux-cored wire dry. Moisture in the core can raise hydrogen and cause porosity.

Common mistakes

Using E71T-GS for multipass work.
Forgetting to switch polarity between self-shielded and gas-shielded wire.
Assuming metal-cored wire works without gas.
Treating the 1 after 7 as a usability number. It is the position code.

Governing standards: AWS A5.20 (carbon steel flux-cored electrodes); AWS A5.36 (carbon and low-alloy steel flux-cored and metal-cored electrodes); AWS A5.29 (low-alloy steel flux-cored electrodes); AWS A5.18 (metal-cored under the older format).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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