Which filler metal is commonly used for welding stainless steel 304/304L?

• A. ER308L
• B. ER70S-6
• C. ER4043
• D. ER5356

Answer: (A)

When welding stainless steel in the 300-series, you want a filler that matches the austenitic stainless chemistry to preserve corrosion resistance and the weld’s microstructure. ER308L fits this need for 304/304L because it is a nickel-chromium-iron alloy with very low carbon. The low carbon reduces carbide precipitation at the heat-affected zone, minimizing sensitization and preserving corrosion resistance, while still providing good compatibility with 304/304L base metal in terms of strength and ductility.

The other options aren’t suitable here: ER70S-6 is a carbon steel filler, which would create a mismatched joint. ER4043 and ER5356 are aluminum fillers, not stainless, which would not weld stainless properly and would lead to poor properties and corrosion performance.