409 Stainless Steel Data Sheet

GENERAL PROPERTIES

Grade 409 stainless steel is a Ferritic steel that offers good mechanical properties and high-temperature corrosion resistance. It is commonly considered as a chromium stainless steel, with applications in exhaust systems of automobiles and applications that demand weldability.

Grade 409 steels are also available in highly stabilized forms, such as grades S40930, S40920 and S40910. The stability of these grades is provided by the presence of niobium, titanium, or both, in the composition of steels.

RESISTANCE TO CORROSION

Grade 409 stainless steels have excellent resistance to exhaust gas and atmospheric corrosion, superior to that of 410 martensitic grades with 12% chromium and 3CR12. However, the corrosion resistance is lower than that of grade 430 steels containing 17% chromium. The surface of grade 409 steels is liable to mild corrosion, which limits the usage of steels for decorative purposes.

PHYSICAL PROPERTIES

MECHANICAL PROPERTIES

CHEMICAL PROPERTIES

WELDING

Grade 409 steels must be pre-heated to temperatures of 150 to 260°C before welding. Although grade 430 and 409 filler rods or electrodes can be used during welding of grade 409 steels, grade 309 electrodes or filler rods are strongly recommended by AS 1554.6. Care should be taken to weld grade 409 steels with minimum heat, in order to mitigate grain growth.

Ductility of the welded products can be improved by annealing post-welding at temperatures of 760 to 815°C. However, this is not required for thin welded products. Welding of exhaust tubing of automobiles is carried out without filler rods.

HEAT TREATMENT

Annealing of grade 409 steels is carried out at temperatures ranging from 790 to 900°C, followed by air-cooling. Thermal treatment does not harden grade 409 steels.