Stainless Steel 409 is a Ferritic steel that offers good mechanical properties and high-temperature corrosion resistance. It is generally considered a chromium stainless steel, with applications in exhaust systems of automobiles and applications that demand weldability.
Grade 409 steel is also available in highly stabilized forms, the stability of these grades is provided by the presence of niobium, titanium, or both, in the composition of steels.
Corrosion Resistance of Stainless Steel 409 Pipes
Stainless Steel 409 Pipes have excellent resistance to exhaust gas and atmospheric corrosion, superior to that of 410 martensitic grades with 12 percent chromium and 3CR12. However, the corrosion resistance is lower than that of grade 430 steel containing 17 percent chromium. Stainless Steel 409 Pipes are liable to mild corrosion, which limits the usage of steel for decorative purposes.
Heat Resistance of Stainless Steel 409 Pipes
Stainless Steel 409 Tubes offer to scale resistance at temperatures up to 675 degrees C during continuous operation, and up to 815 degrees C under intermittent conditions. These temperatures pertain to specific service environments.
Heat Treatment Stainless Steel 409 Pipes
Annealing of Stainless Steel 409 Pipes is carried out at temperatures ranging from 790 to 900 degrees C, followed by air-cooling. Thermal treatment does not harden grade 409 steel.
Welding Stainless Steel 409 Pipes
Stainless Steel 409 Pipes must be pre-heated to temperatures of 150 to 260 degrees C before welding. Although grade 430 and 409 filler rods or electrodes can be used during welding of grade 409 steel, grade 309 electrodes or filler rods are strongly recommended by AS 1554.6. Care should be taken to weld Stainless Steel 409 Pipes with minimum heat, in order to mitigate grain growth.
Ductility of the Stainless Steel 409 Welded Pipes can be improved by annealing post-welding at temperatures of 760 to 815 degrees C. However, this is not required for thin welded Pipes. Welding of exhaust tubing of automobiles is carried out without filler rods.
Applications of Stainless Steel 409 Pipes
The typical applications of Stainless Steel 409 Pipes are listed below:
- Catalytic converter systems
- Automotive and truck exhaust systems
- Tubular manifolds
- Agricultural spreaders
- Gas turbine exhaust silencers
- Heat exchangers
- Fuel filters.
