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Stainless Filler Selection Chart

A base metal to filler cross-reference for common stainless steels and stainless-to-carbon-steel joints, using AWS A5.9 wire and rod designations.

Ref WG-0212AWS A5.9

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

AWS A5.9 classifies bare stainless steel wires and rods for GMAW, GTAW and submerged arc (ER prefix), and composite metal-cored wires (EC prefix). Stick electrodes for stainless are covered by AWS A5.4 (for example E308L-16). The basic rule is to match the filler to the base metal grade, but dissimilar joints and some grades use a different, over-alloyed filler. The WPS governs on code and corrosion-critical work.

How to read it

L = low carbon (0.03% maximum carbon), which limits carbide precipitation and the loss of corrosion resistance next to the weld.
Si (as in ER308LSi) = higher silicon for better wetting and bead shape in GMAW.
H (as in ER308H) = controlled higher carbon for high-temperature strength.

Cross-reference

Base metal	Common filler	Notes
304, 304L	ER308L or ER308LSi	Most common stainless combination
304H (high temperature)	ER308H	For elevated temperature service
316, 316L	ER316L or ER316LSi	Molybdenum for pitting resistance
317L	ER317L	Higher molybdenum
321	ER347	Columbium (niobium) stabilized filler; titanium does not transfer well across the arc
347	ER347	Stabilized
309, 309S	ER309L	Also used for clad and overlay buffer layers
310	ER310	High-temperature service
Stainless to carbon steel	ER309L	Over-alloyed to absorb dilution from the carbon steel
410	ER410	Preheat and postweld heat treatment usually needed
430	ER430	Ferritic; low toughness in heat-affected zone
2205 duplex	ER2209	Nickel-enriched to balance ferrite and austenite

Key points

Never weld stainless with carbon steel filler. It will rust and may crack.
Back purging with argon protects the root side of tube and pipe welds.
Keep stainless separate from carbon steel tools, brushes and grinding discs to prevent contamination.
Heat tint (discoloration) reduces corrosion resistance. Pickling or passivation may be needed.

Common mistakes

Using ER308L on 316 parts in corrosive service.
Using ER308L to join stainless to mild steel.
Using plain ER308L in GMAW where the LSi version would give better bead shape.
Running a straight 75/25 gas on stainless GMAW.

Governing standards: AWS A5.9; AWS A5.4 (stick electrodes).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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