Processes for welding stainless steel: MAG, TIG, plasma, MMA and laser compared

By Robert Lahnsteiner, International Welding Engineer (IWE) · Updated: November 2026

Almost all of those known from carbon steel. Austenitic and ferritic stainless steels can be joined with the same fusion and pressure welding processes and the same equipment as unalloyed steels. Only oxy-fuel gas welding is out of the question.

In production, MAG welding with solid or flux-cored wire and TIG welding dominate. Plasma and laser beam welding are the mechanised processes for high volumes, manual metal arc welding has its place on site, and submerged arc welding for thick plate.

Guide values according to ISER information sheet 823 (2019) and DVS 0931. The limits depend on material, joint shape and equipment.

In gas metal arc welding of stainless steels, almost exclusively MAG is used, with an argon-rich gas containing only a little oxygen or CO₂. More CO₂ brings carbon into the weld metal and reduces the resistance to intergranular corrosion.

Welding is done with direct current, wire electrode positive, with wires from 0.8 to 1.6 mm. The type of arc is chosen according to the task:

• Spray arc for the flat and horizontal positions: fine droplets, no short circuits, hardly any spatter, high output.
• Short arc for thin sheet, root passes and positional welding when little heat is required. Drawbacks: firmly adhering spatter and an excessively convex bead.
• Pulsed arc: little heat with a calm, low-spatter metal transfer. It can be used to weld thin sheet as well as thick plate, also in positional welding. For stainless steels it is often the best choice.

For torch guidance, DVS 0931 recommends:

• Keep the arc as short as possible. A long arc burns off more chromium and picks up nitrogen from the air, which lowers the ferrite content.
• Guide solid wire slightly pushing to neutral, with the shortest possible wire stick-out. This improves wetting and penetration.
• Weld metal-cored wire with up to 5 mm longer stick-out, slag-forming flux-cored wire slightly dragging and in the spray arc.

The suitable gases are shown in Shielding gases, the choice of wire in Choosing the filler metal.

Flux-cored wires weld with little spatter, and the beads flow out flat and without notches. They can be used on any standard GMAW machine.

• Slag-forming, rutile (136): soft arc, shallow penetration, easily removable slag. With fast-freezing slag for all positions, with slow-freezing slag for the flat and horizontal positions. Welded in the spray or short arc, not pulsed, under argon with O₂ or CO₂.
• Metal-cored (138): no slag, high deposition rate and deep penetration. Good for fully mechanised multi-pass welding, gases as for solid wire.

Flux-cored wire is softer than solid wire and can deform under the pressure of the feed rolls. A 4-roll drive and low contact pressure are therefore needed as a minimum.

TIG is the process for the highest weld quality: thin sheet, pipelines, root passes and all positions. Welding is done with direct current, tungsten electrode negative, under argon.

For austenitic steels, argon with a little hydrogen can be used in mechanised welding to weld faster. This does not apply to ferritic and duplex steels, see Shielding gases.

Up to about 3 mm sheet thickness, the standard austenitic grades 1.4301, 1.4307, 1.4541, 1.4401, 1.4404 and 1.4571 can also be joined without filler metal (process 142). The higher-alloyed grades such as 1.4435, 1.4439, 1.4539 and the duplex steel 1.4462, on the other hand, are welded with filler metal. With duplex, too much ferrite would remain in the weld metal without filler.

The plasma arc is strongly constricted by a nozzle and has a much higher energy density than the TIG arc. It is used almost exclusively in mechanised form.

• Microplasma for foils and sheet up to about 1 mm, with currents from a few amperes.
• Keyhole welding: the plasma jet pierces the sheet, and the weld pool closes behind it. Sheets up to about 10 mm are welded through in one pass as a square butt joint. Thicker plates are given a Y groove with a root face of about 5 mm, and the rest is filled with other processes.

Welding is mostly done without filler metal. If the gap is wider than 0.08 times the sheet thickness, wire is needed. Argon serves as the plasma gas, with a little hydrogen for austenitic grades, and the outer shielding gas is usually argon-hydrogen.

In the workshop, the stick electrode has lost importance; on site it is indispensable: simple equipment, insensitive to wind, all positions, little heat per bead.

• Rutile-coated electrodes weld with fine droplets, a smooth, flat seam and easily removable slag, on direct and alternating current. They are the most widely used.
• Basic-coated electrodes run on direct current only (electrode positive), are easy to weld in positional welding and bridge gaps well, which is why they are often used for roots.
• Because the high-alloy core wire has a higher electrical resistance, welding is done with a lower current than with carbon steel electrodes and with a short arc.
• Damp coatings cause pores and, in ferritic and duplex steels, cold cracks. Re-dry electrodes according to the manufacturer’s instructions and use them from a quiver, for duplex also the rutile-coated ones.

The laser melts the metal in a narrowly confined area and creates a vapour capillary that reaches deep into the sheet. The seams are very narrow, as is the heat-affected zone, and distortion is low.

• Fibre lasers with about 100 W to 10 kW for sheets from 0.2 to about 4 mm, robot-guided via optical fibre. CO₂ lasers up to about 25 kW for 1 to around 15 mm, guided by mirrors.
• Without filler metal, the gap may be at most one tenth of the sheet thickness, and with thicker sheets no more than half the focus diameter. With filler wire, a larger gap is possible, but the speed drops by about a third.
• With higher-alloyed steels, centreline cracks are a risk. A suitable filler wire and utmost cleanliness help; even a little sulphur is enough to cause hot cracks.
• With duplex, little austenite forms because of the rapid cooling. With the standard duplex 1.4462, sufficient impact values were nevertheless achieved in 10 mm thick plates without heat treatment.

Why the constitution diagrams no longer apply with the laser is explained in Microstructure, delta ferrite and hot cracking.

Submerged arc welding pays off with thick plate and long seams, for example in vessel and apparatus construction. Welding is done only in the flat and horizontal positions, with wires from 1.2 to 4 mm, electrode positive.

The current is about 10 to 20 % below that for unalloyed steels. Wires are standardised in ISO 14345, fluxes in ISO 14174. For duplex steels, basic fluxes of type AF have proven themselves.

The choice follows from sheet thickness, quantity, position and surface requirements.

Solid wires for MAG: 308LSi, 316LSi and all others under Stainless steel welding wire.

Can I weld stainless steel with the usual 82/18 mixed gas?

Not with solid wire. 18 % CO₂ brings too much carbon into the weld metal and impairs corrosion resistance. For solid wire, argon with 1 to 3 % O₂ or at most 2.5 % CO₂ is used. Slag-forming flux-cored wires, on the other hand, are designed for argon-CO₂ mixtures.

Do you need a different welding machine for stainless steel?

No. The equipment is the same as for carbon steel. A machine with pulsed arc makes MAG welding of thin sheet considerably easier, though.

Can stainless steel be TIG welded without filler metal?

For standard austenitic grades up to about 3 mm, yes. Higher-alloyed grades and duplex steels need filler metal; duplex without filler only with subsequent solution annealing.

Alternating or direct current in TIG welding?

Direct current, electrode negative. Alternating current is only needed in TIG welding for aluminium and magnesium.

The series from the material via process, gas and root protection to the tested weld. For an overview, see Welding of stainless steel.

1. What makes stainless steel stainless
2. Microstructure, delta ferrite and hot cracking
3. Choosing the filler metal
4. Shielding gases
5. Heat input and interpass temperature
6. Joint preparation and tack welding
7. Root protection and purging
8. Temper colours, pickling, passivation
9. Duplex and super duplex
10. Joining stainless to carbon steel
11. Weld defects and corrosion damage
12. Testing, health and safety