Welding Austenitic, Ferritic, Martensitic, Duplex, and Precipitation-Hardenable Stainless Steel
Welding stainless steel requires the user to know a little bit about their material before welding. An important property about the stainless steel that a welder needs to know is whether the stainless steel is austenitic, ferritic, martenistic, a duplex, or precipitation-hardenable. Each type of stainless steel require different welding system setups and different welding components and techniques.
Austenitic – Austenitic stainless steel is usually placed in the 300 series of stainless steel. 304, 308, and 316 austenitic stainless steel are commonly used in the manufacturing industry. Austenitic stainless steel contains between 16 and 30% chromium and 10 and 24% nickel. Austenitic stainless steel is easier to weld than other stainless steels because it is more pliable and takes heat better.
Ferritic – Ferritic stainless steel contains between 16 and 31% chromium and 1 and 7% nickel. Ferritic stainless steel is tougher than austenitic and has reduced corrosion resistance.
Martensitic – Martensitic stainless steel is very strong and highly machinable. This type of stainless steel can be hardened by heat treatments but is not as easy to weld as ferritic or austenitic stainless steel. Because of its molecular structure and rigidity, cracks are more likely to form when welding martensitic stainless steel. Martensitic stainless steel is generally classified in the 400 series.
Duplex – Duplex stainless steel is typically a 50/50 mix of austenitic and ferritic stainless steel, but can also be 40/60. Duplex stainless steel is also about twice as strong as austenitic stainless steel.
Precipitation-Hardenable – This type of stainless steel is similar in stucture to austenitic stainless steel but can be precipitation-hardened to become stronger than even martensitic stainless steel.
Each type of stainless steel requires different filler metals and gas combinations for arc shielding.