ER309L Dissimilar Metal Stainless MIG & TIG Wire
ER309L Amperage by Diameter
| Diameter | Amperage Range |
|---|---|
| 0.030" (0.8 mm) | 40 - 150A |
| 0.035" (0.9 mm) | 60 - 200A |
| 0.045" (1.2 mm) | 100 - 300A |
| 1/16" (TIG) (1.6 mm) | 60 - 130A |
| 3/32" (TIG) (2.4 mm) | 100 - 200A |
ER309L is a low-carbon stainless steel wire classified under AWS A5.9 for MIG (GMAW) and TIG (GTAW) welding. It deposits approximately 23% chromium and 13% nickel, providing a weld chemistry that bridges the gap between stainless and carbon steel. The higher chromium and nickel content compared to ER308L compensates for dilution when one side of the joint is carbon steel. ER309L is the standard filler metal for dissimilar metal joints between austenitic stainless and carbon or low-alloy steel. It is also widely used for the first layer of stainless cladding on carbon steel vessels and piping. For MIG welding, use with tri-mix (90He/7.5Ar/2.5CO2) or 98Ar/2CO2 shielding gas. For TIG welding, use 100% argon.
What This Means in Practice
ER309L is the wire version of E309L-16. It serves the same purpose: joining stainless steel to carbon steel by providing a buffer chemistry that handles the dilution from both base metals. Use it with MIG or TIG equipment when you need a wire-feed or precision process instead of stick welding.
ER309L Suitability Scores
How well this electrode matches common applications. Not a quality rating. all AWS-certified electrodes meet their specification.
When to Use ER309L
Use ER309L whenever joining stainless steel to carbon steel with MIG or TIG.
Required for the first layer of stainless overlay or cladding on carbon steel.
Also suitable for welding 309 or 309S stainless base metal to itself.
ER309L Limitations
Not for joining carbon steel to carbon steel.
More expensive than ER308L.
Not the correct choice for 304-to-304 joints where ER308L is sufficient.
Service temperature limited to approximately 800F for dissimilar joints due to differential thermal expansion stress.
ER309L Storage Requirements
Store in original packaging. Keep dry. Stainless wire is less sensitive to moisture than carbon steel but should be kept clean and free of oil.
ER309L Technical Specifications
| Property | Value |
|---|---|
| AWS Classification | ER309L |
| Process | stainless-wire () |
| Polarity | DCEP |
| Positions | flat, horizontal, vertical up, overhead |
| Penetration | medium |
| Coating Type | bare wire |
| Tensile Strength | 80,000 psi |
| Yield Strength | 55,000 psi |
| Elongation | 35% |
| Base Metals | Stainless to carbon steel joints, 309/309S stainless, Cladding/overlay base layers |
| Shielding Gas | 98/2 Ar/CO2 (MIG), 100% Ar (TIG) |
| AWS Specification | A5.9 |
Frequently Asked Questions
What is ER309L used for?
ER309L is the standard filler wire for joining stainless steel to carbon steel using MIG or TIG welding. Its 23Cr-13Ni chemistry compensates for dilution from the carbon steel side of the joint. It is also used for the first layer of stainless cladding or overlay on carbon steel vessels and piping.
Can I use ER309L to weld 304 stainless to itself?
Technically yes, but it is not the correct choice. ER309L has higher alloy content than needed for 304-to-304 joints, making it more expensive. ER308L is the correct filler for 304-to-304 stainless welds. Use ER309L only when one side of the joint is carbon steel or when you are applying the first layer of stainless overlay.
What shielding gas does ER309L require?
For MIG welding, use a tri-mix gas (90He/7.5Ar/2.5CO2) or 98Ar/2CO2. Do not use 75/25 Ar/CO2 as the high CO2 content causes excessive carbon pickup, which defeats the low-carbon L designation. For TIG welding, use 100% argon with a back purge of argon on the root side to prevent sugaring.
External Resources
Manufacturer data sheets and standards for ER309L.
Data sourced from AWS A5.9/A5.9M. Amperage ranges are approximate starting points. adjust based on position, fit-up, and material thickness. Always follow manufacturer recommendations and applicable codes.