Choosing filler metal for stainless steels: 308LSi, 316LSi, 318Si, 2209 and more

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

For stainless steels, a matching or similar filler metal is normally used, i.e. a wire with about the same composition as the base material. It is balanced so that the weld metal contains some delta ferrite and is just as corrosion-resistant as the sheet.

Over-alloyed fillers are special cases: when the weld is to be more resistant than the base material, when different materials are joined, or to simplify stockholding. A molybdenum-alloyed wire such as 316LSi is also suitable for molybdenum-free steels such as 1.4301 and 1.4541. The reverse does not work: 308LSi on 1.4404 produces a weld without molybdenum that is weaker against chlorides than the sheet.

Besides the composition, required approvals, service temperature, wall thickness and welding position also play a part. For pressure equipment or construction, an approval of the wire may be mandatory.

The assignment of common steels according to DVS 0931. For the standard grades 1.4301 and 1.4404, 308LSi and 316LSi are the wires most frequently needed.

According to DVS 0931, Tables 1a to 1d, simplified; “(Si)” means with or without increased silicon content. For 1.4539 under increased corrosive load, clarify the molybdenum content of the weld metal. For duplex steels, see also DVS 0946.

All wires: stainless steel welding wire and nickel welding wire.

A stainless steel wire usually has three names: according to ISO 14343 system A (European, by composition), according to system B (by alloy type, as in the American standards) and according to AWS A5.9. Often they all stand for the same alloy.

System A, for example ISO 14343-A – G 19 12 3 L Si:

• G = wire electrode for gas metal arc welding. For other processes, the letter is W (TIG), P (plasma), S (submerged arc), B (strip electrode) or L (laser).
• 19 12 3 = nominal contents: around 19 % chromium, 12 % nickel, 3 % molybdenum.
• L = low carbon, a maximum of 0.03 %.
• Si = increased silicon content of 0.65 to 1.2 % instead of a maximum of 0.65 %.
• Other symbols: Nb = niobium-stabilised, N = with nitrogen, Mn = with increased manganese, H = higher carbon for high temperatures, Z = alloy not listed in the standard table.

System B, for example ISO 14343-B – SS316LSi: the first S stands for solid wire, the second for stainless steel. There is no letter for the process; the same name applies to MIG/MAG wire and TIG rod. According to AWS A5.9, the wire is called ER316LSi.

The ranges of the two systems do not match exactly. A wire may carry both designations if its analysis falls within both sets of limits. Covered electrodes are standardised in ISO 3581 (e.g. E 19 12 3 L R), tubular cored electrodes in ISO 17633 (e.g. T 19 12 3 L P M).

Both protect against intergranular corrosion, and according to DVS 0931 both may also be used crosswise: an L wire for a stabilised steel and vice versa. A 1.4571 therefore does not have to be welded with 318; 316LSi is common.

• L grades (maximum 0.03 % C) are the standard today. They are generally approved up to a service temperature of about 350 °C.
• Stabilised fillers contain niobium instead of titanium, because most of the titanium burns off in the arc. Molybdenum-alloyed and stabilised steels can be used up to about 400 °C. Above that, the steel manufacturer's specifications apply.
• For electropolished components, DVS 0931 specifies unstabilised fillers.

Why carbon matters so much is explained in What makes stainless steel stainless.

For MIG/MAG welding, the Si variants such as 308LSi and 316LSi are common. The higher silicon content makes the weld pool more fluid; it wets better and the weld blends in more smoothly.

The variants without Si, such as 19 12 3 L, are used when a low silicon content is required. For TIG welding, rods are available with and without increased silicon content. Silicon is a ferrite former and slightly increases the delta ferrite, see Microstructure, delta ferrite and hot cracking.

Ferritic chromium steels such as 1.4016 or 1.4512 are usually welded with an austenitic filler such as 19 9 L Si, 19 12 3 L Si, 18 8 Mn or 23 12 L. The austenitic weld metal is considerably tougher than a ferritic one.

A ferritic filler is needed when the weld must match the colour, when sulphur-containing gases attack (nickel forms low-melting sulphides with sulphur) or when weld and sheet are to expand equally, for example in exhaust systems. With thicker parts, the fill and cap passes can also be combined: fill with austenitic filler and weld the passes facing the medium with ferritic filler.

The martensitic steel 1.4313 is an exception. It is welded with the matching filler 13 4.

In these cases, the filler is deliberately composed differently from the base material.

• Duplex: 2209 (22 9 3 N L) contains more nickel than the steel 1.4462, so that enough austenite forms during rapid cooling. For super duplex such as 1.4410, 25 9 4 N L is used. More in Duplex and super duplex.
• Stainless steel with carbon steel: over-alloyed fillers such as 309LSi (23 12 L Si), 307 (18 8 Mn) or 312 (29 9). They absorb the dilution with the carbon steel without martensite forming. This can be checked with the Schaeffler calculator; background in Joining stainless to carbon steel.
• Fully austenitic grades such as 1.4539 or 1.4529: fillers such as 20 25 5 Cu L or nickel-base alloys. They solidify without ferrite and need particularly low heat input and great cleanliness. The higher manganese content of some grades counteracts hot cracking.
• Heat-resistant steels: 22 12 H or 25 20, depending on the base material.

Solid wire for MAG welding of stainless steels is common in 0.8, 1.0, 1.2 and 1.6 mm, metal-cored wire in 1.2 and 1.6 mm, flux-cored wire in 0.9, 1.2 and 1.6 mm.

Besides spools of 1 kg, 5 kg and 15 to 18 kg, there are bulk packs such as drums and large spools. They pay off on robots and in series production because fewer spool changes are needed.

Diameters and packaging according to DVS 0931, Table 3.

Can I use 316LSi for 1.4301?

Yes. The weld metal is then slightly higher alloyed than the sheet, which does no harm to corrosion resistance and simplifies stockholding.

Can I use 308LSi for 1.4404 or 1.4571?

No. The weld then lacks molybdenum and is less resistant to chlorides than the sheet.

Does 1.4571 have to be welded with a stabilised wire?

No. According to DVS 0931, there is nothing against 316LSi. A stabilised filler such as 318Si is used when it is specified or at higher service temperatures.

What is the difference between 308LSi and 19 9 L Si?

None in practice. 19 9 L Si is the designation according to ISO 14343 system A, 308LSi that according to system B and AWS A5.9. The permitted analyses differ in detail.

Does the same assignment apply to TIG rods?

Yes. The alloy is the same, only the letter changes: W 19 12 3 L instead of G 19 12 3 L Si.

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. Processes at a glance
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