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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.

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
Niobium (Nb) 0 to 0.75
Nickel (Ni) 0 to 0.5
Carbon (C) 0 to 0.060
Phosphorus (P) 0 to 0.045
Sulfur (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