Wire welder: with gas or with flux-cored wire?

"I bought a wire welder that runs without gas because I didn't want the cylinder, but everything comes out dirty and full of holes." When you show me the part, the problem usually isn't the flux-cored wire itself: it's that the machine was set up as if it were going to run with gas.

Flux-cored wire or solid wire with gas

Flux-cored wire carries its protection inside: no cylinder, and outdoors in a bit of wind it copes better. In return it makes more smoke, leaves slag to chip off and the bead is less clean. Solid wire with gas gives a cleaner, more even bead, but the first draught blows the gas away: on an open site that is a real limit.

The standards treat them as two separate processes: in EN ISO 4063, which numbers the welding processes, MIG is 131, MAG with solid wire is 135 and self-shielded flux-cored wire, the one without gas, is 114. If a specification or a welding procedure calls for one of them, the other does not qualify.

Not every machine does both. The Awelco EASYMIG 120 works without gas only: the Awelco catalogue lists it as "NO GAS ONLY", with flux-cored wire from 0.8 to 1.0 mm on 100 mm spools (up to 1 kg). From the Easymig 130 upwards the same catalogue shows both gas and no gas. The Telwin Bimax 150i Synergic does both, with flux-cored wire from 0.8 to 0.9 mm. The Panther 132 is a gas machine that also accepts 0.9 mm flux-cored wire. But switching from one mode to the other is not just a matter of changing the spool.

Polarity: the mistake I see most often

Flux-cored wire and solid wire almost always run with reversed polarity relative to each other. Solid wire with gas usually runs with the torch on the positive pole; self-shielded flux-cored wire, the one without gas, usually runs with the torch on the negative pole. If you fit flux-cored wire and leave the cables as they were for gas, you get exactly what you described: spatter, porosity, an ugly bead.

There is one exception: flux-cored wires made to run with gas are normally connected like solid wire. That is why what is written on the spool or on the wire's data sheet counts for more than what I write here. Then look at the machine's manual and check how the torch and the earth are connected.

The change is made in two ways. On many machines you swap the cables in the wire-feeder compartment, near the rollers. On others the reversal is external: Telwin states it on the Bimax 150i Synergic for both MIG-MAG and flux-cored wire.

One habit from gas welding that should not be carried over to flux-cored wire is the wire stick-out. With flux-cored wire it must be kept longer: manufacturers indicate about 19 mm (3/4 inch), twice that of MIG with gas.

Rollers, liner and tip: the three parts nobody changes

• Rollers: the groove must match the wire diameter. A two-groove roller fitted the wrong way round puts too much pressure on the wire. The type of groove matters too: V for solid steel wire, knurled V for flux-cored wire, U for aluminium and soft wires. With flux-cored wire on a plain V roller the wire slips, and if you tighten to compensate you crush it.
• Contact tip: the same diameter as the wire, and it must be changed when the hole wears oval. A tip that is too wide lets the wire wander, a worn tip makes the arc jump. The contact tips we stock come in 0.6, 0.8 and 1 mm: tell me which torch you have, because each tip goes with its own thread.
• Liner: if the wire comes out in jerks and the torch is full of dust, cleaning or replacing the liner is often enough. Wire shavings, dust and dirt build up inside. A liner with a hole in it can also let gas escape and cause porosity.

How to tell whether the liner needs changing. Loosen the rollers and pull the wire out with pliers: it should come out without effort. If you have to pull, the liner needs replacing. Torch manufacturers suggest changing it about once a year in normal use, a couple of times a year in a very busy workshop.

Meanwhile, spatter sticks to the nozzle and chokes the gas flow: the bead turns porous. Clean the nozzle often; an anti-spatter spray helps.

Roller pressure, step by step

Too little and the wire slips, tangles on the rollers (the "bird's nest") and the arc stutters. Too much and the wire deforms: flux-cored wire, which is a tube with flux inside, crushes more easily than solid wire and then jams in the tip. Set it like this:

1. Cold torch, about 50 mm of wire sticking out of the tip, gloves on.
2. Loosen the knob until the rollers turn but the wire stays still when you pull the trigger.
3. Tighten by half a turn, then hold the wire lightly between thumb and forefinger and pull the trigger: if you can stop it, the rollers are slipping and you need another half turn.
4. Stop when your fingers can no longer stop the wire and it feeds without slipping. Beyond that it is not needed.

The spool brake is another adjustment. Too tight, and the rollers struggle to pull the wire; too loose, and the spool keeps turning when you release the trigger and the wire goes slack on the rollers.

Aluminium is a different world

Aluminium wire is soft and in a long torch it tends to bend and jam. That is why you use a spool gun, the torch with the small spool mounted on top. The Awelco SPOOL GUN (code 90101) has a Euro connection, takes 0.8 or 0.9 mm wire, has 20 mm rollers and a rated current of 130 A; the Awelco catalogue gives it as 130 A at 35%. You need a machine with a Euro connection that is set up for the spool gun. The Easymig machines, for example, have a direct torch connection (that is what the catalogue calls it): tell me your model and I will tell you whether it fits.

With a standard torch, aluminium can only be tried on a limited basis, the manufacturers say: a U roller, a PTFE (Teflon) liner, the right roller pressure and a torch cable as straight as possible. And before welding, the oxide has to be removed with a stainless steel brush, which does not contaminate the part.

Gas, cylinder and MIG or MAG

With solid wire the gas depends on the material. On steel you weld in MAG, with an active gas: CO2 or an argon and CO2 mixture (with CO2 between 5 and 25% it is M21 in EN ISO 14175). On aluminium you weld in MIG, with pure argon, and the steel gas will not do. Flux-cored wire without gas, on the other hand, does not need a cylinder.

The non-refillable argon cylinder, 13.6 L (code 92493, Awelco) holds 780 litres of gas, with a tolerance of ±10%. To do the sums: with the flowmeter at 10 l/min that is about 78 minutes of gas flowing. If you weld every day, a non-refillable one runs out quickly.

Synergic and pulsed: do you really need them?

The synergic function suggests wire speed and voltage once you have chosen material, diameter and thickness: for someone who doesn't weld every day it is a big help. Pulsed and double pulsed make sense on stainless steel and aluminium and on thin sections, where you control the heat better. On steel fabrication done now and then, it is money you can save.

For heavy, continuous work, look instead at machines with a water-cooled torch: over long hours an air-cooled torch gets hot.

Amps, duty cycle and the power socket

The adjustment range tells you how far the machine goes, not how long it stays there. That is what the duty cycle is for: according to EN 60974-1 it is measured over 10 minutes and says for how many minutes the machine can weld at a given current before it has to cool down. Three examples from the data sheets:

• EASYMIG 120: in MIG from 25 to 120 A, duty cycle 15% at 120 A. That is a minute and a half of welding every 10 minutes.
• Panther 132: from 30 to 120 A, duty cycle 60% at 52 A. That is 6 minutes in every 10 at 52 A.
• Bimax 150i Synergic: from 20 to 150 A; according to Telwin 115 A at 20%, 85 A at 35% and 65 A at 60%. The higher the current, the less time you get.

For long jobs look at the values at 60% and above, not at the top of the range. Then there is the socket: the EASYMIG 120 runs on 230 V single-phase and in MIG draws 4.1 kVA (3.0 kW). The more powerful machines run on 400 V three-phase and will not work on a single-phase socket, so check your electrical installation before ordering. If you move the machine around, weight matters too: the Bimax 150i weighs 7.1 kg, the Panther 132 weighs 25 kg.

What I need to know

• Materials (steel, stainless steel, aluminium) and thicknesses;
• whether you weld indoors or outdoors;
• whether you already have a cylinder and gas or are starting from zero;
• the model of the machine you already have, if any: from that I pick the right rollers, tips and torches;
• how many hours a day and whether you need spare torches, wires and consumables.

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We have these in the shop

A few items from the range we stock. If you can't find the size or the model you need, ask: what you see online is only part of what we can get for you.

See the whole category: Saldatrici e Accessori per Saldatura a Filo MIG/MAG