Flux-cored arc welding 136 and 138
Cored wire is the same machine and the same feeder with a different wire in it — and roughly twice the deposition at the same settings. The price is equally concrete: more fume and a dearer metre of wire.
Short answer
"Cored wire" covers four different processes in ISO 4063, and confusing them costs later in the paperwork:
| No. | Wire | Gas | Slag | Where |
|---|---|---|---|---|
| 135 | Solid | Active | None | The baseline everything is compared with |
| 136 | Cored, flux core | Active | Yes | Heavier sections, positional work |
| 138 | Cored, metal core | Active | Traces | Long runs where a clean cap matters |
| 114 | Self-shielded cored | None | Yes | Site work and wind, where a gas shield will not stay |
The full table of process numbers — ISO 4063.
Where the deposition comes from
Cored wire is a tube filled with powder. Current runs through the tube alone, not through the whole cross-section, so current density in the metal is higher than in solid wire of the same diameter. The tip heats faster, melts faster, and deposition rises without touching the machine.
The second gain is in bead shape. Slag from a flux core supports the pool from underneath and from the sides, which is why 136 will weld positionally at currents where solid wire would simply run out of the joint. That is the usual reason a site fabrication shop switches to cored wire.
Gas and settings
136 and 138 run under active gas, most often argon with carbon dioxide. Straight CO₂ works too, but gives more spatter and a harsher toe. Choosing the mixture and the flow — the shielding gas calculator.
Stick-out is longer than with solid wire — typically 15–25 mm rather than 10–15. That follows from the same tube: a longer extension preheats the wire resistively, which here is wanted. Too short a stick-out gives an unstable arc and burnt contact tips.
Polarity depends on the wire, not on the process. Most 136 and 138 wires run electrode positive, but a good share of self-shielded 114 wires run the other way. The maker states it on the spool, and getting it wrong produces an arc that "will not settle" for reasons nobody can find in the settings.
What you pay
Fume. This is the main hidden cost. Cored wire produces several times more of it than solid — and on stainless the flux additionally stabilises hexavalent chromium. Extraction at source stops being a recommendation and becomes a condition of working; details in respiratory protection.
The wire itself. A kilogram of cored wire costs markedly more than solid. The arithmetic works out only when the time saved outweighs the material — that is, on heavier sections and long welds, not on small parts.
Chipping the slag on 136 is an extra operation and an extra place to go wrong: slag left between runs comes out as an inclusion (301).
When it does not pay
On sheet up to 3 mm — the deposition you are paying for is not wanted there and burn-through is easier. On short, numerous welds — the time goes into handling, not into melting. And anywhere without extraction: cored wire in an unventilated bay is the worst choice in this whole section.
What next
The baseline it is measured against — MIG/MAG. How much filler a joint will take — deposit and run count. Process numbers in documentation — the ISO 4063 table.
Frequently asked questions
What is the difference between 136 and 138?
The core of the wire. In 136 it is flux: it leaves slag, which shields and shapes the bead but has to be chipped off. In 138 the core is metal powder: there is next to no slag and the surface comes out cleaner, but bead shaping is weaker and the demands on the gas higher. Both run under active gas.
Is self-shielded 114 wire worse?
Not worse, just for something else. 114 needs no cylinder, so it wins outdoors and in wind, where a gas shield would blow away anyway. You pay in fume and usually in impact toughness. In a still workshop, 136 with gas gives the better result.
Why does cored wire melt faster than solid?
Because current flows only through the thin sheath, not through the whole section. Current density in that sheath is higher than in solid wire of the same diameter, so the tip heats faster and the deposition rate rises — at the same machine settings.
Updated: