What Do You Know About These Welding Methods?

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  Key takeaways
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  What separates these welding methods
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  SMAW and FCAW: flux does the protecting
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  GMAW and GTAW: gas-shielded work
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  SAW, resistance and beam welding
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  Matching the process to the drawing
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  How to set up and run a weld, step by step
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  These welding methods at a glance

Every fusion weld does the same job: melt the parent metal and a filler, then let it freeze into one piece. The difference between these welding methods is how the heat gets there and how the molten pool is protected. Stick and flux-cored wire generate their own shielding gas from a flux coating or a flux core. MIG and TIG carry separate shielding gas through the torch. Submerged arc buries the arc under a layer of granular flux, so you never see the arc itself.

That single difference drives everything else. A flux-based process tolerates wind and dirty plate, because the slag covers the pool. A gas-shielded process gives a cleaner bead but stalls when the draught blows the shielding away. Resistance and laser processes do not use filler at all in many cases, so joint fit has to be tight before you start.

The practical question is not which process is best. It is which one matches the thickness, position, material and inspection level of the part in front of you. A 1.5 mm stainless sensor housing and a 20 mm excavator arm have almost nothing in common, even though both are 'welded'.

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  Heat sourceConsumable electrode, non-consumable electrode, resistance, or a beam
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  ShieldingFlux, gas, slag, or vacuum
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  Position toleranceFlat only for SAW; all positions for stick, MIG and TIG

Shielded metal arc welding (SMAW, or stick) runs a flux-coated electrode against the work. The coating burns off and forms both a gas shield and a slag layer. It is the most forgiving process for outdoor work and for rusty or painted plate, which is why it still dominates site repair. Current range for a 3.2 mm electrode sits around 90–130 A; for 4.0 mm, roughly 130–180 A.

The trade-off is speed and cleanup. You stop every 300–450 mm to change the electrode, and each restart leaves a crater unless you back-step into the previous bead. Slag must be chipped before the next pass, or you trap it as slag inclusion. Stick also struggles below about 2 mm thickness, where the arc burns through before you can move.

Flux-cored arc welding (FCAW) solves the stopping problem. The flux sits inside a continuous tubular wire, so you weld without breaking the arc. Self-shielded wire works outdoors; gas-shielded wire needs a CO₂ or mixed-gas feed but runs smoother. Deposition on 6–25 mm structural steel is where FCAW earns its place, typically 2–4 kg per hour against roughly 1–2 kg per hour for stick.

Both processes leave slag, so both need the same discipline: chip, brush, inspect, then lay the next bead. If your drawing calls for a clean, paint-ready surface with no slag lines, plan a finishing step or choose a gas-shielded process instead.

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  Best fitSite repair, thick plate, windy or dirty conditions
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  Watch forSlag inclusion, arc strikes, crater cracks at restarts
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  Not ideal forSheet under 2 mm, thin-wall tube, cosmetic beads

Gas metal arc welding (GMAW, or MIG) feeds a solid wire through a gun that also delivers shielding gas. It is the default for production work on 1–12 mm steel, stainless and aluminium. Short-circuit transfer suits thin sheet and out-of-position work at lower voltage; spray transfer gives a hot, smooth bead on thicker plate but must be run flat or near-flat.

MIG is fast and easy to automate, and the wire feed removes the restrike problem. It is less tolerant of contamination. Oil, mill scale and moisture all produce porosity, because there is no flux to absorb them. Gas flow is a common failure point: too low and the pool oxidises, too high and the flow turns turbulent and pulls air in. A typical setting is 12–18 L/min at the regulator, checked at the nozzle with a flow meter.

Gas tungsten arc welding (GTAW, or TIG) uses a non-consumable tungsten electrode and a separate filler rod. The arc is stable at low current, so it handles 0.5–3 mm sheet, root passes on pipe, and any joint where appearance or cleanliness matters. Stainless and titanium welds come out bright when the gas coverage is right and the part is purged from behind.

TIG is slow and demands more skill. Travel speed is roughly a third of MIG on the same joint, and the operator controls the filler by hand. On a 10 mm plate, TIG is usually the wrong economic choice unless the joint needs a specific root quality that MIG cannot deliver.

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  MIG strengthSpeed, all-position capability, easy automation
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  TIG strengthThin material, clean root, no spatter
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  Shared failure modeShielding gas disturbed by draught or set too high

Submerged arc welding (SAW) drops a continuous electrode into a bed of granular flux. The arc burns beneath the flux, so there is no visible arc, no spatter, and almost no fume. It runs at high current, often 400–1,000 A, and deposits several kilograms of metal per hour. It only works in the flat or horizontal position, because the flux bed has to stay put.

Resistance welding passes current through overlapping sheets and relies on the resistance at the interface to generate heat. No filler is added. Spot and seam welding of 0.5–3 mm sheet is the classic use, and it is fast enough for automotive body assembly. Electrode force, current and cycle time all have to be set together, and the electrodes wear, so the schedule drifts unless it is monitored.

Laser and electron beam welding focus energy into a very small spot, producing a narrow, deep weld with a small heat-affected zone. Setup cost and joint fit tolerance are both high. They suit precision assemblies where distortion must stay minimal, such as sealed sensor packages or thin-walled battery components.

Brazing sits at the edge of this list. It melts a filler above 450 °C but below the parent metal's melting point, so the base metal never fuses. It joins dissimilar metals and thin sections well, and it lets you keep a tight tolerance, but the joint strength is lower than a true fusion weld.

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  SAWFlat position, thick plate, high deposition
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  ResistanceOverlapping sheet, no filler, high cycle rate
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  BeamPrecision, low distortion, tight fit required

Start with thickness. Under 3 mm, TIG or short-circuit MIG gives the most control. Between 3 and 12 mm, MIG and FCAW cover most work. Above 12 mm, FCAW and SAW take over because they can carry enough current to fuse the root without a huge number of passes.

Next, read the position. If the joint is flat and can stay flat through the whole pass, SAW becomes viable. If the part has to be turned or welded overhead, SAW drops out and you are choosing between stick, MIG and FCAW. Position also changes the transfer mode: spray transfer is off the table for overhead work.

Then check the material. Carbon and low-alloy steel tolerate all the arc processes. Stainless needs low heat input and good gas coverage to keep the chromium from oxidising. Aluminium needs AC TIG or MIG with a push technique and clean, oxide-free edges. Dissimilar joints often point to brazing or a transition insert rather than a fusion weld.

Finally, ask what happens after welding. If a hole, a bearing seat or a sealing face sits near the weld, distortion will move it. Welding heat can pull a 500 mm steel frame out of flat by a millimetre or more. On parts that must hold ±0.005 mm after welding, leave a machining allowance and cut the critical features after the weld cools, not before.

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  Thickness firstIt eliminates half the process list immediately
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  Position secondFlat-only processes rarely survive a fixture change
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  Finishing lastWeld, then machine, then inspect the datums