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MIG and Flux-Core Wire Decoder Chart

How to read solid and metal-cored wire (ER70S-6, E70C-6M) and flux-cored wire (E71T-1C) classifications, including the newer AWS A5.36 open format.

Ref WG-0203AWS A5.18AWS A5.20AWS A5.36

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

What it is

Carbon steel solid and composite (metal-cored) wires for GMAW are classified under AWS A5.18. Carbon steel flux-cored wires were classified under AWS A5.20. AWS A5.36 introduced an "open" format for flux-cored and metal-cored wires that spells out shielding gas, heat treatment and impact properties in the designation. Both formats appear on spools today.

How to read it

Solid wire, ER70S-6: E = electrode, R = can also be used as a rod (TIG filler), 70 = minimum tensile strength in ksi, S = solid, 6 = chemistry.

Flux-cored, E71T-1C (A5.20 style): E = electrode, 7 = 70 ksi, 1 = position, T = tubular, 1 = usability, C = CO2 gas.

A5.36 open style, E71T1-M21A4-CS1-H8: tensile, position, T, usability, shielding gas, condition and impact designator, composition, optional hydrogen.

Decoder

Part	Example	Meaning
ER	ER70S-6	Electrode or rod
70 or 7	ER70S, E71T	Minimum tensile strength, 70 ksi
S	ER70S-6	Solid wire
C	E70C-6M	Composite (metal-cored) wire
Position digit (flux-cored)	E71T, E70T	0 = flat and horizontal; 1 = all positions
T	E71T-1	Tubular (flux-cored)
Usability number	T-1, T-8, T-11, T-GS	Process type and characteristics, including self-shielded types
C	E71T-1C	100% CO2 shielding (A5.20)
M	E71T-1M, E70C-6M	Argon/CO2 mixed shielding (A5.20, A5.18)
C1	E71T1-C1	100% CO2 (A5.36, ISO 14175 code)
M21	E71T1-M21	Argon with about 15–25% CO2 (A5.36, ISO 14175 code)
A or P	M21A4	Tested as-welded (A) or after postweld heat treatment (P)
Digit after A or P	A4	Impact test temperature designator; look up in A5.36
Suffix such as -2, -3, -6 (solid)	ER70S-3, ER70S-6	Deoxidizer chemistry; -6 has higher Mn and Si
H4, H8, H16	-H8	Diffusible hydrogen limit

Key points

Self-shielded wires (for example T-8, T-11, T-GS) carry no gas designator.
"GS" means single-pass use only.
The gas designator must match the gas used. Mixed-gas wire on CO2 changes weld chemistry.

Common mistakes

Treating ER70S-3 and ER70S-6 as identical on rusty or mill-scale steel.
Running a C-designated wire on 75/25 without checking the classification.
Using a single-pass (GS) wire for multipass welds.

Governing standards: AWS A5.18; AWS A5.20; AWS A5.36; ISO 14175 (gas codes).

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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