UNS S31277 (27-7Mo) Stainless Steel
S31277 stainless steel is a superaustenitic (highly alloyed) stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. S31277 is the UNS number for this material. 27-7Mo is the common industry name.
It has a fairly high tensile strength among wrought superaustenitic stainless steels. In addition, it has a moderately high ductility and a fairly high embodied energy.
The graph bars on the material properties cards below compare S31277 stainless steel to: wrought superaustenitic 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
210 GPa 30 x 106 psi
Elongation at Break
45 %
Fatigue Strength
380 MPa 54 x 103 psi
Poisson's Ratio
0.28
Shear Modulus
80 GPa 12 x 106 psi
Shear Strength
600 MPa 87 x 103 psi
Tensile Strength: Ultimate (UTS)
860 MPa 130 x 103 psi
Tensile Strength: Yield (Proof)
410 MPa 60 x 103 psi
Thermal Properties
Latent Heat of Fusion
310 J/g
Maximum Temperature: Corrosion
430 °C 810 °F
Maximum Temperature: Mechanical
1100 °C 2010 °F
Melting Completion (Liquidus)
1460 °C 2650 °F
Melting Onset (Solidus)
1410 °C 2560 °F
Specific Heat Capacity
460 J/kg-K 0.11 BTU/lb-°F
Thermal Expansion
16 µm/m-K
Otherwise Unclassified Properties
Base Metal Price
36 % relative
Density
8.1 g/cm3 510 lb/ft3
Embodied Carbon
6.7 kg CO2/kg material
Embodied Energy
90 MJ/kg 39 x 103 BTU/lb
Embodied Water
220 L/kg 26 gal/lb
Common Calculations
PREN (Pitting Resistance)
51
Resilience: Ultimate (Unit Rupture Work)
320 MJ/m3
Resilience: Unit (Modulus of Resilience)
410 kJ/m3
Stiffness to Weight: Axial
14 points
Stiffness to Weight: Bending
24 points
Strength to Weight: Axial
29 points
Strength to Weight: Bending
25 points
Thermal Shock Resistance
19 points
Alloy Composition
Among wrought stainless steels, the composition of S31277 stainless steel is notable for containing comparatively high amounts of manganese (Mn) and nickel (Ni). Manganese is used to improve ductility at elevated temperatures. It also permits a higher nitrogen content than would otherwise be possible. Nickel is primarily used to achieve a specific microstructure. In addition, it has a beneficial effect on mechanical properties and certain types of corrosion.
| Fe | 35.5 to 46.2 | |
| Ni | 26 to 28 | |
| Cr | 20.5 to 23 | |
| Mo | 6.5 to 8.0 | |
| Mn | 0 to 3.0 | |
| Cu | 0.5 to 1.5 | |
| N | 0.3 to 0.4 | |
| Si | 0 to 0.5 | |
| P | 0 to 0.030 | |
| C | 0 to 0.020 | |
| S | 0 to 0.010 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
ASTM A240: Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications
Corrosion of Austenitic Stainless Steels: Mechanism, Mitigation and Monitoring, H. S. Khatak and B. Raj (editors), 2002
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