ER309 is a stainless steel filler metal (wire/rod) used for welding similar alloys (like 24%Cr-13%Ni steels) and dissimilar metals, especially joining stainless steel (like Type 304) to carbon or low-alloy steels, providing excellent corrosion/oxidation resistance and forming a critical buffer layer, often with higher chromium/nickel content than the base metal. It's used in MIG, TIG, and SAW processes for high-dilution applications, offering good mechanical properties and scaling resistance, with the 'L' version (ER309L) having lower carbon for better ductility.
Key Characteristics & Applications:
Composition: High Chromium (around 24%) and Nickel (around 13%) content.
Primary Use: Welding dissimilar metals, such as 18/8 stainless steel to mild/carbon steel.
Buffer Layer: Applied as an intermediate layer on clad steels or carbon steel before final stainless overlay.
Corrosion Resistance: Provides good resistance, even under severe conditions, and is resistant to scaling up to high temperatures.
Processes: Suitable for GMAW (MIG), GTAW (TIG), and SAW (Submerged Arc Welding).
ER309L: The 'L' variant (low carbon) offers improved ductility and is used where cracking is a concern, while standard ER309 provides higher strength.