Which filler metal classification is commonly used for 304 stainless in MIG welding?

• A. ER308L
• B. ER316L
• C. ER347
• D. ER309L

Answer: (A)

When welding 304 stainless steel with MIG, you want a filler metal that closely matches the base metal’s alloying elements to preserve corrosion resistance and ductility. ER308L is the go-to for 304 because its nickel-chromium balance aligns well with 304, creating a weld that behaves similarly to the base metal and resists corrosion effectively. The “L” indicates low carbon, which reduces carbide precipitation in the heat-affected zone during welding, lowering the risk of sensitization and intergranular corrosion.

ER316L would be chosen if you needed extra corrosion resistance in chloride-containing environments due to its molybdenum, but that isn’t the typical default for standard 304 joints. ER347 is stabilized with niobium for high-temperature stability in specific service conditions, not the general weld for 304. ER309L is used for dissimilar joints or particular high-temperature scenarios, so it isn’t the standard filler for welding 304 to itself.

So, ER308L is the common MIG filler for 304 stainless.