Flux core wire: which gasless wire your machine needs, and what GS and -11 mean
E71T-GS and E71T-11 are gasless; E71T-1 and dual shield need gas. Single pass versus multi pass, DC negative polarity, and makers' published thickness limits.
Flux core wire listings mix two families that look alike on the spool: wire that makes its own shielding and wire that needs a gas cylinder. A gasless machine can only use the first.
A gasless machine needs self-shielded wire: E71T-GS or E71T-11, in .030 or .035 inch, run on DC electrode negative. Avoid E71T-1 and anything called dual shield, which need gas. GS means single pass only; -11 allows several passes, within each maker’s thickness limit.
Which classes need no gas
From Lincoln’s guide to flux cored designators:
| Suffix | Gas | Passes |
|---|---|---|
| -GS | None when sold as self-shielded, which is what gasless listings are | Single pass only |
| -11 | None | Single or multiple (Hobart); multiple (Lincoln NR-211-MP) |
| -1, -12 | Needs external gas (dual shield) | Not for a gasless machine |
GS is the one to read carefully. Lincoln says the G stands for general and the S for single pass only. One seller’s page says GS means gasless; Lincoln’s definition is the one the classification uses.
Why a pass limit? Lincoln explains that single-pass wires rely on mixing with the base metal, and weld cracking could result if they are used for multiple passes. Its guide adds that plate thickness limits apply whether you make single or multiple passes.
Source: Lincoln, flux cored usability designators.
Check the polarity
Lincoln: most self-shielded Innershield wires operate best on DC electrode negative, the opposite of solid mig wire, which runs DC electrode positive. Hobart’s Handler 140 chart marks its E71T-11 setting DCEN with no shielding gas. A flux-core-only machine is usually wired for this already. A machine that also runs gas has a polarity change for flux core, and its manual shows where.
Five gasless wires compared
Each maker’s published data, checked 2026-09-27:
| Wire | Class | Passes as published | Thickness as published | Coated steel | Listing |
|---|---|---|---|---|---|
| Lincoln Innershield NR-211-MP | E71T-11 | Multiple | 5/16 in maximum for .045 and smaller | Lists galvanized sheet metal | .035, 10 lb |
| Hobart E71T-11 (Fabshield 21B) | E71T-11 | Single or multiple | Applications include light structural under 3/4 in | Works well on coated steels | .030, 10 lb, .035, 10 lb |
| Blue Demon E71T-11 | E71T-11 | Limited multi-pass | 16 gauge through 1/2 in | Not published | .030, 2 lb |
| Forney E71T-GS | E71T-GS | Single pass | Not published | Not published | .030, 10 lb |
| ARCCAPTAIN E71T-GS | E71T-GS | Page says both single pass and single or multi pass | 1.2 to 5 mm on its 10 lb page | Not published | .030, 2 lb |
Lincoln’s 5/16 inch is the only true thickness ceiling in the table; Hobart’s 3/4 inch is an application description, not a limit. Where a maker is silent, treat GS wire as single pass on thin material, as its classification says.
Also sold: YesWelder E71T-GS, which its maker describes as all-position, single-pass. Its Amazon listings did not show the diameter in the title, so we could not match one to a size.
Sources: NR-211-MP, Fabshield 21B data sheet, Blue Demon, Forney 42301, ARCCAPTAIN 10 lb.
.030 or .035
Small machines list both. Hobart’s Handler 140 and Miller’s Millermatic 141 list flux core at .030 to .035, and Lincoln’s POWER MIG 140 MP at .030 and .035 NR-211-MP. Wires sold only in .045 and up, such as Lincoln NR-212, are beyond these machines. Match the contact tip, and use the knurled drive roll your manual names for flux core. Spool sizes and hub adapters work as for solid wire; see will the spool fit.
Keeping it dry
Lincoln’s Innershield guide says opened wire should be used within about a week, kept in a poly bag of at least 4 mil when not in use, and discarded if rusty. Hobart says tubular wire should not be stored in a drying oven.
Fume
Self-shielded wire makes its shielding by burning its core, so it smokes more than gas mig. OSHA warns that prolonged exposure to manganese fume can cause Parkinson’s-like symptoms, and that welding outdoors does not guarantee adequate ventilation. Respirators are compared in welding respirators.
What the process suits and where it struggles is in flux core welders. Structural work, trailers and anything holding pressure belong to a certified welder.
Frequently asked questions
Can I use dual shield flux core wire without gas?
No. Lincoln lists T-1 and T-12 among the gas-shielded designators, and says gas-shielded flux cored wires use an external shielding gas, which is why they are called double or dual shielded. ESAB's Dual Shield wires are for CO2 or argon and CO2.
Why does my flux core weld look bad?
Check polarity first. Lincoln says most self-shielded wires run best on DC electrode negative, the opposite of solid mig wire. If your machine was last set up for gas mig, the leads are probably reversed. Then check the wire is dry and rust free.
What is the best flux core wire for galvanized steel?
Lincoln lists galvanized sheet metal for NR-211-MP, and Hobart says its E71T-11 works well on coated steels. Welding galvanized releases zinc fume, so ventilation matters more than the wire.