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UNS S21900 (XM-10) Stainless Steel

S21900 stainless steel is an austenitic stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. XM-10 is the ASTM designation for this material. S21900 is the UNS number. Additionally, the common industry name is 21-6-9.

It has a moderately high electrical conductivity among wrought austenitic stainless steels. In addition, it has a fairly high ductility and a moderately high tensile strength.

The graph bars on the material properties cards below compare S21900 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

220

Elastic (Young's, Tensile) Modulus

200 GPa 29 x 106 psi

Elongation at Break

50 %

Fatigue Strength

380 MPa 55 x 103 psi

Poisson's Ratio

0.28

Reduction in Area

57 %

Shear Modulus

78 GPa 11 x 106 psi

Shear Strength

510 MPa 73 x 103 psi

Tensile Strength: Ultimate (UTS)

710 MPa 100 x 103 psi

Tensile Strength: Yield (Proof)

390 MPa 56 x 103 psi

Thermal Properties

Latent Heat of Fusion

290 J/g

Maximum Temperature: Corrosion

420 °C 800 °F

Maximum Temperature: Mechanical

980 °C 1800 °F

Melting Completion (Liquidus)

1400 °C 2550 °F

Melting Onset (Solidus)

1350 °C 2470 °F

Specific Heat Capacity

480 J/kg-K 0.12 BTU/lb-°F

Thermal Conductivity

14 W/m-K 8.1 BTU/h-ft-°F

Thermal Expansion

17 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

2.5 % IACS

Electrical Conductivity: Equal Weight (Specific)

2.9 % IACS

Otherwise Unclassified Properties

Base Metal Price

15 % relative

Density

7.7 g/cm3 480 lb/ft3

Embodied Carbon

3.0 kg CO2/kg material

Embodied Energy

43 MJ/kg 19 x 103 BTU/lb

Embodied Water

160 L/kg 19 gal/lb

Common Calculations

PREN (Pitting Resistance)

25

Resilience: Ultimate (Unit Rupture Work)

300 MJ/m3

Resilience: Unit (Modulus of Resilience)

380 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

25 points

Strength to Weight: Axial

26 points

Strength to Weight: Bending

23 points

Thermal Diffusivity

3.8 mm2/s

Thermal Shock Resistance

15 points

Alloy Composition

Among wrought stainless steels, the composition of S21900 stainless steel is notable for containing a comparatively high amount of manganese (Mn). Manganese is used to improve ductility at elevated temperatures. It also permits a higher nitrogen content than would otherwise be possible.

Iron (Fe) 59.4 to 67.4
Chromium (Cr) 19 to 21.5
Manganese (Mn) 8.0 to 10
Nickel (Ni) 5.5 to 7.5
Silicon (Si) 0 to 1.0
Nitrogen (N) 0.15 to 0.4
Carbon (C) 0 to 0.080
Phosphorus (P) 0 to 0.045
Sulfur (S) 0 to 0.030

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM A473: Standard Specification for Stainless Steel Forgings

Machining of Stainless Steels and Super Alloys: Traditional and Nontraditional Techniques, Helmi A. Youssef, 2016

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

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