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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.

Iron (Fe) 35.5 to 46.2
Nickel (Ni) 26 to 28
Chromium (Cr) 20.5 to 23
Molybdenum (Mo) 6.5 to 8.0
Manganese (Mn) 0 to 3.0
Copper (Cu) 0.5 to 1.5
Nitrogen (N) 0.3 to 0.4
Silicon (Si) 0 to 0.5
Phosphorus (P) 0 to 0.030
Carbon (C) 0 to 0.020
Sulfur (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