AISI 309Cb (S30940) Stainless Steel
AISI 309Cb stainless steel is an austenitic stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 309Cb is the AISI designation for this material. S30940 is the UNS number.
It has a moderately low tensile strength among wrought austenitic stainless steels. In addition, it has a moderately high base cost and a moderately low ductility.
The graph bars on the material properties cards below compare AISI 309Cb stainless steel to: wrought austenitic 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
Brinell Hardness
190
Elastic (Young's, Tensile) Modulus
200 GPa 29 x 106 psi
Elongation at Break
39 %
Fatigue Strength
200 MPa 29 x 103 psi
Poisson's Ratio
0.28
Reduction in Area
46 %
Rockwell B Hardness
84
Shear Modulus
78 GPa 11 x 106 psi
Shear Strength
390 MPa 57 x 103 psi
Tensile Strength: Ultimate (UTS)
580 MPa 84 x 103 psi
Tensile Strength: Yield (Proof)
230 MPa 34 x 103 psi
Thermal Properties
Latent Heat of Fusion
300 J/g
Maximum Temperature: Corrosion
510 °C 950 °F
Maximum Temperature: Mechanical
1090 °C 1990 °F
Melting Completion (Liquidus)
1420 °C 2590 °F
Melting Onset (Solidus)
1380 °C 2510 °F
Specific Heat Capacity
480 J/kg-K 0.11 BTU/lb-°F
Thermal Conductivity
15 W/m-K 8.7 BTU/h-ft-°F
Thermal Expansion
16 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
2.2 % IACS
Electrical Conductivity: Equal Weight (Specific)
2.5 % IACS
Otherwise Unclassified Properties
Base Metal Price
23 % relative
Density
7.8 g/cm3 490 lb/ft3
Embodied Carbon
4.1 kg CO2/kg material
Embodied Energy
59 MJ/kg 26 x 103 BTU/lb
Embodied Water
170 L/kg 21 gal/lb
Common Calculations
PREN (Pitting Resistance)
23
Resilience: Ultimate (Unit Rupture Work)
180 MJ/m3
Resilience: Unit (Modulus of Resilience)
140 kJ/m3
Stiffness to Weight: Axial
14 points
Stiffness to Weight: Bending
25 points
Strength to Weight: Axial
20 points
Strength to Weight: Bending
20 points
Thermal Diffusivity
4.0 mm2/s
Thermal Shock Resistance
13 points
Alloy Composition
Among wrought stainless steels, the composition of AISI 309Cb stainless steel is notable for including niobium (Nb) and containing a comparatively high amount of chromium (Cr). Niobium is primarily used to improve yield strength, particularly at elevated temperatures. Chromium is the defining alloying element of stainless steel. Higher chromium content imparts additional corrosion resistance.
| Fe | 56 to 66 | |
| Cr | 22 to 24 | |
| Ni | 12 to 16 | |
| Mn | 0 to 2.0 | |
| Nb | 0 to 1.1 | |
| Si | 0 to 0.75 | |
| 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 A479: Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels
ASTM A276: Standard Specification for Stainless Steel Bars and Shapes
ASTM A240: Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications
ASTM A959: Standard Guide for Specifying Harmonized Standard Grade Compositions for Wrought Stainless Steels
Corrosion of Austenitic Stainless Steels: Mechanism, Mitigation and Monitoring, H. S. Khatak and B. Raj (editors), 2002
Pressure Vessels: External Pressure Technology, 2nd ed., Carl T. F. Ross, 2011
Austenitic Stainless Steels: Microstructure and Mechanical Properties, P. Marshall, 1984
ASM Specialty Handbook: Stainless Steels, J. R. Davis (editor), 1994
Advances in Stainless Steels, Baldev Raj et al. (editors), 2010