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.
| Fe | 84.9 to 89.5 | |
| Cr | 10.5 to 11.7 | |
| Mn | 0 to 1.0 | |
| Si | 0 to 1.0 | |
| Ti | 0 to 0.75 | |
| Ni | 0 to 0.5 | |
| C | 0 to 0.080 | |
| P | 0 to 0.045 | |
| 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