AISI 409Cb (S40940) Stainless Steel
AISI 409Cb stainless steel is a ferritic stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 409Cb is the AISI designation for this material. S40940 is the UNS number.
It has a fairly low tensile strength among the wrought ferritic stainless steels in the database.
The graph bars on the material properties cards below compare AISI 409Cb 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 60 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
440 °C 820 °F
Maximum Temperature: Mechanical
710 °C 1300 °F
Melting Completion (Liquidus)
1450 °C 2640 °F
Melting Onset (Solidus)
1410 °C 2570 °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
10 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
8.5 % relative
Density
7.8 g/cm3 480 lb/ft3
Embodied Carbon
2.2 kg CO2/kg material
Embodied Energy
31 MJ/kg 13 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 409Cb stainless steel is notable for including niobium (Nb). Niobium is primarily used to improve yield strength, particularly at elevated temperatures.
| Fe | 84.9 to 89.5 | |
| Cr | 10.5 to 11.7 | |
| Mn | 0 to 1.0 | |
| Si | 0 to 1.0 | |
| Nb | 0 to 0.75 | |
| Ni | 0 to 0.5 | |
| C | 0 to 0.060 | |
| P | 0 to 0.045 | |
| S | 0 to 0.040 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
ASTM A493: Standard Specification for Stainless Steel Wire and Wire Rods for Cold Heading and Cold Forging
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
CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015