Lincoln Electric Blue Max ER309LSi is the standard stainless MIG wire for dissimilar metal welding — joining austenitic stainless steel to carbon or low-alloy steel — and for cladding carbon steel with corrosion-resistant stainless overlays. Classified AWS A5.9/A5.9M ER309LSi, this 0.035 in (0.9 mm) wire on a 33 lb spool (ED037291) contains higher chromium (23–25% Cr) and higher nickel (12–14% Ni) than ER308LSi, providing the compositional buffer needed to dilute iron from the carbon steel side without pushing the weld metal out of the austenitic range. The elevated silicon (0.65–1.00% Si) promotes excellent puddle wetting and bead shape in spray arc transfer, and the low carbon (≤ 0.03%) reduces sensitization risk. WeldingMart ships as an authorized Lincoln Electric distributor. Browse the full welding wire catalog.
| Property | Value |
|---|---|
| AWS Classification | ER309LSi per AWS A5.9/A5.9M |
| Lincoln Part Number | ED037291 |
| Wire Diameter | 0.035 in (0.9 mm) |
| Spool Weight | 33 lb (15 kg) |
| Carbon Content | ≤ 0.03% C |
| Silicon Content | 0.65–1.00% Si |
| Chromium Content | 23.0–25.0% Cr |
| Nickel Content | 12.0–14.0% Ni |
| Manganese Content | 1.0–2.5% Mn |
| Polarity | DCEP (electrode positive) |
| Shielding Gas | Tri-mix (90% He / 7.5% Ar / 2.5% CO₂) or 98% Ar / 2% O₂ |
| Tensile Strength (as-welded) | ≥ 515 MPa (75,000 psi) |
| Yield Strength (as-welded) | ≥ 310 MPa (45,000 psi) |
| Elongation | ≥ 30% |
| Welding Process | GMAW (MIG), spray arc transfer, pulsed MIG |
| Conformances | AWS A5.9/A5.9M, ASME SFA-5.9 |
- Stainless-to-carbon steel dissimilar joints: Piping transitions, equipment nozzles, and structural attachments where a 304 stainless pipe or vessel connects to carbon steel flanges or supports — the standard application for ER309LSi.
- Stainless cladding on carbon steel: Corrosion-resistant overlay on carbon steel base plates, valve bodies, and pressure vessel internals exposed to acidic or chloride environments.
- Automotive exhaust dissimilar joints: Welding 409 ferritic stainless steel (heat shields, mufflers) to 304 austenitic stainless (intermediate pipes, manifolds) — ER309LSi accommodates the compositional difference.
- Chemical plant maintenance: Repair welding on equipment where the exact base metal chemistry is unknown or mixed (field repair of stainless/carbon steel assemblies).
- Transition piping: Boiler connections, heat exchanger inlets, and steam system piping transitions from carbon steel headers to 304 or 316 stainless outlets.
- Nuclear and power generation: Stainless cladding and weld overlay on carbon steel reactor support structures and containment vessel attachments (per ASME and AWS D1.6 procedures).
When welding stainless to carbon steel, base metal dilution alters weld chemistry. ER309LSi's high Cr and Ni content accommodates this dilution while maintaining an austenitic microstructure:
| Property | ER308LSi | ER309LSi (this product) |
|---|---|---|
| Chromium Content | 19.5–22.0% Cr | 23.0–25.0% Cr |
| Nickel Content | 9.0–11.0% Ni | 12.0–14.0% Ni |
| Carbon Content | ≤ 0.03% C | ≤ 0.03% C |
| Dilution Tolerance | Low — for SS-to-SS only | High — handles Fe dilution from carbon steel |
| Primary Application | 304-to-304 stainless | Stainless-to-carbon steel dissimilar joints |
When welding stainless to carbon steel in a butt joint, dilution from the carbon steel side can be 30–50%, depending on joint geometry and technique. At that dilution level, ER308LSi weld metal would drop into the ferritic/martensitic range, causing brittle welds. ER309LSi's higher alloy content keeps the weld metal austenitic even with high carbon steel dilution. Source: Lincoln Electric Blue Max Stainless Wire Technical Data.
| Material Thickness | WFS (in/min) | Voltage (V) | Amperage | Gas / Flow |
|---|---|---|---|---|
| 12 ga (0.104 in) | 270–340 | 23–25 | 120–160 A | 98/2 Ar/O₂, 25 CFH |
| 1/8 in (3.2 mm) | 330–410 | 24–26 | 150–195 A | 98/2 Ar/O₂, 28 CFH |
| 3/16 in (4.8 mm) | 390–470 | 25–27 | 185–230 A | Tri-mix, 30 CFH |
| 1/4 in (6.4 mm) | 450–530 | 26–28 | 215–265 A | Tri-mix, 35 CFH |
- What is ER309LSi used for in stainless MIG welding?
- Primarily for welding stainless to carbon/low-alloy steel (dissimilar joints), stainless cladding on carbon steel, joining 409 to 304 stainless exhaust, and field repair of mixed stainless/carbon assemblies.
- What is the difference between ER308LSi and ER309LSi?
- ER309LSi has higher Cr (23–25%) and Ni (12–14%) to compensate for iron dilution from carbon steel. Use ER308LSi for 304-to-304 joints; use ER309LSi for 304-to-carbon-steel dissimilar joints.
- Can ER309LSi be used to weld 316L stainless?
- It can be used in some scenarios but lacks molybdenum, so it does not provide the same chloride resistance as ER316LSi. For 316L-to-carbon steel dissimilar joints in corrosive service, consult AWS D1.6 or ASME Section IX.
- Do I need different shielding gas for ER309LSi versus ER308LSi?
- No — both use tri-mix or 98/2 Ar/O₂. Never use C25 on any stainless wire.
- Can ER309LSi be used for stainless cladding on carbon steel pressure vessels?
- Yes — ER309LSi is the standard buttering layer wire for stainless clad vessels. Subsequent layers use ER308LSi or ER316LSi. ASME Section IX procedure qualification required for pressure service.
Related products: Blue Max ER309LSi MIG Wire (family hub, ED037293) | Blue Max ER308LSi 0.035 in, 33 lb (ED037250) | All Welding Wire