Dissimilar metal welding is a specialty within a specialty. Choose the wrong filler and the joint fails - sometimes months after leaving the shop. So what is actually the best filler for the job? The honest answer is: it depends on which two metals you are joining and what the joint has to do.
The Two Most Common Choices
ER309L - the workhorse
- 23 Cr / 13 Ni austenitic-ferritic deposit
- Handles routine stainless ↔ carbon steel joints
- Good corrosion resistance
- Widely stocked, cost-effective
ER312 - the specialist
- 29 Cr / 9 Ni high-ferrite deposit
- Handles high-dilution, high-restraint, or unknown base metals
- Superior crack resistance
- Ideal for repair and tool steel buttering
Other Common Dissimilar Fillers
- ERNiCr-3 (Inconel 82) - dissimilar joints involving nickel alloys, high temperature service
- ERNiCrMo-3 (Inconel 625) - for corrosion-service dissimilar joints
- ENiFe-CI / ENi-CI - for cast iron dissimilar joints (AWS A5.15)
Decision Framework
| Scenario | Recommended Filler |
|---|---|
| Standard 304/316 to mild steel | ER309L |
| Stainless to carbon steel with high restraint | ER312 |
| Unknown base metal | ER312 |
| Tool steel / spring steel repair | ER312 (buttering) |
| Cast iron to steel | ENiFe-CI or ENi-CI |
| Nickel alloy to steel, high temp | ERNiCr-3 |
| Nickel alloy to steel, corrosion service | ERNiCrMo-3 |
Common Mistakes to Avoid
- Using ER308L for stainless-to-carbon steel - deposit dilutes below the safe ferrite range
- Using carbon steel filler on stainless-to-carbon steel joints - corrosion and cracking follow
- Preheating austenitic joints unnecessarily - can promote sigma phase
- Skipping post-weld cleanup - carbon steel contamination causes surface rust on stainless side
Best Practice
Match the filler to the worse of the two base metals plus dilution. When in doubt on a high-value or safety-critical joint, default to ER312 - its overalloyed chemistry provides the largest safety margin against cracking.
Dayang Welding supplies ER309L, ER312, ERNiCr-3, ERNiCrMo-3, and ENi-family dissimilar fillers as part of one integrated stainless / nickel alloy line.
