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AISI 409 (S40900) Stainless Steel

AISI 409 stainless steel is a ferritic stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 409 is the AISI designation for this material. S40900 is the UNS number. Additionally, the British Standard (BS) designation is 409S17.

It has a fairly low base cost among wrought ferritic stainless steels. In addition, it has a fairly low tensile strength and a moderately low embodied energy.

The graph bars on the material properties cards below compare AISI 409 stainless steel to: wrought ferritic stainless steels (top), all iron alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

190 GPa 28 x 106 psi

Elongation at Break

24 %

Fatigue Strength

140 MPa 20 x 103 psi

Poisson's Ratio

0.28

Shear Modulus

75 GPa 11 x 106 psi

Shear Strength

270 MPa 39 x 103 psi

Tensile Strength: Ultimate (UTS)

420 MPa 61 x 103 psi

Tensile Strength: Yield (Proof)

200 MPa 29 x 103 psi

Thermal Properties

Latent Heat of Fusion

270 J/g

Maximum Temperature: Corrosion

450 °C 840 °F

Maximum Temperature: Mechanical

710 °C 1300 °F

Melting Completion (Liquidus)

1450 °C 2640 °F

Melting Onset (Solidus)

1400 °C 2560 °F

Specific Heat Capacity

480 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

25 W/m-K 14 BTU/h-ft-°F

Thermal Expansion

11 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

2.9 % IACS

Electrical Conductivity: Equal Weight (Specific)

3.3 % IACS

Otherwise Unclassified Properties

Base Metal Price

6.5 % relative

Density

7.7 g/cm3 480 lb/ft3

Embodied Carbon

2.0 kg CO2/kg material

Embodied Energy

28 MJ/kg 12 x 103 BTU/lb

Embodied Water

94 L/kg 11 gal/lb

Common Calculations

PREN (Pitting Resistance)

11

Resilience: Ultimate (Unit Rupture Work)

83 MJ/m3

Resilience: Unit (Modulus of Resilience)

100 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

25 points

Strength to Weight: Axial

15 points

Strength to Weight: Bending

16 points

Thermal Diffusivity

6.7 mm2/s

Thermal Shock Resistance

15 points

Alloy Composition

Among wrought stainless steels, the composition of AISI 409 stainless steel is notable for including titanium (Ti). Titanium is used to broadly improve mechanical properties.

Iron (Fe) 84.9 to 89.5
Chromium (Cr) 10.5 to 11.7
Manganese (Mn) 0 to 1.0
Silicon (Si) 0 to 1.0
Titanium (Ti) 0 to 0.75
Nickel (Ni) 0 to 0.5
Carbon (C) 0 to 0.080
Phosphorus (P) 0 to 0.045
Sulfur (S) 0 to 0.030

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM A276: Standard Specification for Stainless Steel Bars and Shapes

Creep-Resistant Steels, Fujio Abe et al. (editors), 2008

ASTM A240: Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications

Welding Metallurgy and Weldability of Stainless Steels, John C. Lippold and Damian J. Kotecki, 2005

Advanced Materials in Automotive Engineering, Jason Rowe (editor), 2012

ASTM A959: Standard Guide for Specifying Harmonized Standard Grade Compositions for Wrought Stainless Steels

Corrosion of Stainless Steels, A. John Sedriks, 1996

ASM Specialty Handbook: Stainless Steels, J. R. Davis (editor), 1994

Advances in Stainless Steels, Baldev Raj et al. (editors), 2010