Welding
Dissimilar metal welding: which filler metal
In short
For dissimilar metal welding, the filler metal depends on the pair: 309L between carbon steel and 304(L) stainless, 309LMo with 316(L) stainless, E2209 or E2594 between duplex grades. The calculation only keeps pairs quoted by a source (IMOA, ASSDA, Hobart, TWI, Materials 2025) and refuses the others.
Calculation
Example calculated with the tool’s default values.
Inputs
- Metal A
- Carbon or low-alloy steel
- Metal B
- Stainless 304 / 304L
Results
- Filler metal
- 309LCarbon or low-alloy steel + Stainless 304 / 304L
Worked example
Every value in this section belongs to the example, calculated with the tool’s default values.
- No welding without an over-alloyed filler: dilution would give martensite that cracks (ASSDA).
- Preheat 150 °C if the steel has more than 0.2 % carbon or is over 30 mm thick and restrained; gas without oxygen, low CO2 (ASSDA).
- Galvanised steel: remove the zinc from the heated zone (zinc embrittlement).
- AWS designations: E = covered electrode, ER = wire or rod; use the same grade for the process used.
Step-by-step calculation
Source table
ASSDA Technical FAQ 9: welding dissimilar metals: Carbon steel ↔ austenitic stainless (AS/NZS 1554.6)
309L
How to use it
- Pick metal A: carbon or low-alloy steel, 304 or 316 stainless, lean duplex, 2205 or super duplex, nickel alloy type 600, aluminium.
- Pick metal B from the same list.
- Read the recommended filler metal.
Frequently asked questions
Which filler wire for dissimilar metal welding of steel to stainless?
An over-alloyed filler: 309L for 304 or 304L stainless, 309LMo for 316 or 316L stainless (ASSDA, AS/NZS 1554.6). Without an over-alloyed filler, dilution would give martensite that cracks (ASSDA). Hobart also quotes 309 for carbon steel to austenitic stainless.
What precautions for welding stainless to carbon steel?
According to ASSDA: preheat to 150 °C if the steel has more than 0.2 % carbon or is over 30 mm thick and restrained; shielding gas without oxygen and with low CO2. On galvanised steel, remove the zinc from the heated zone to avoid zinc embrittlement.
How do I select the electrode for dissimilar metal welding?
The grade stays the same, only the form changes: in AWS designations, E is a covered electrode and ER a wire or rod. Use the same grade for the process used, for example E309L electrode or ER309L wire between carbon steel and 304L stainless.
Which filler metal for duplex dissimilar welds?
From table 1 of IMOA shop sheet 104: 2205 duplex to itself, E2209; 2205 to super duplex, E2594; 304 or 316 stainless to 2205 duplex, E309LMo or E2209; carbon steel to duplex, E309L, E309LMo or E2209. With a nickel-base filler, use a niobium-free one; heat input and interpass per the WPS.
Can aluminium be welded to steel?
Not by arc welding: according to TWI, the two metals are almost insoluble in each other and form brittle intermetallic compounds. Join them by adhesive bonding, mechanical fastening or brazing. For a type 600 nickel alloy to steel or stainless, the source quotes ENiCrFe-2 (electrode) and ERNiCr-3 (wire).
Limits
Indicative results: only pairs found in a cited public source (IMOA, ASSDA, Hobart, TWI, Materials 2025) are offered; for the others, refer to the filler manufacturer and the WPS. The choice does not replace the qualified WPS.
Sources
- ASSDA Technical FAQ 9 : soudage de métaux différents : Acier au carbone ↔ inox austénitique (AS/NZS 1554.6) (link)