UNS S21904 (XM-11) Stainless Steel
S21904 stainless steel is an austenitic stainless steel formulated for primary forming into wrought products. XM-11 is the ASTM designation for this material. S21904 is the UNS number.
This material is well established: the Further Reading section below cites a number of published standards, and that list is not necessarily exhaustive.
It has a moderately high electrical conductivity and can have a moderately high tensile strength among wrought austenitic stainless steels.
The properties of S21904 stainless steel include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare S21904 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
210 to 300
Elastic (Young's, Tensile) Modulus
200 GPa 29 x 106 psi
Elongation at Break
17 to 51 %
Fatigue Strength
380 to 550 MPa 55 to 80 x 103 psi
Poisson's Ratio
0.28
Shear Modulus
78 GPa 11 x 106 psi
Shear Strength
510 to 620 MPa 73 to 89 x 103 psi
Tensile Strength: Ultimate (UTS)
700 to 1000 MPa 100 to 150 x 103 psi
Tensile Strength: Yield (Proof)
390 to 910 MPa 56 to 130 x 103 psi
Thermal Properties
Latent Heat of Fusion
290 J/g
Maximum Temperature: Corrosion
430 °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)
160 to 310 MJ/m3
Resilience: Unit (Modulus of Resilience)
380 to 2070 kJ/m3
Stiffness to Weight: Axial
14 points
Stiffness to Weight: Bending
25 points
Strength to Weight: Axial
25 to 36 points
Strength to Weight: Bending
23 to 29 points
Thermal Diffusivity
3.8 mm2/s
Thermal Shock Resistance
15 to 21 points
Alloy Composition
Among wrought stainless steels, the composition of S21904 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.
| Fe | 59.5 to 67.4 | |
| Cr | 19 to 21.5 | |
| Mn | 8.0 to 10 | |
| Ni | 5.5 to 7.5 | |
| Si | 0 to 1.0 | |
| N | 0.15 to 0.4 | |
| P | 0 to 0.045 | |
| C | 0 to 0.040 | |
| 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
ASTM A479: Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels
ASTM A666: Standard Specification for Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate, and Flat Bar
ASTM A182: Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service
ASTM A240: Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications
Welding Metallurgy of Stainless Steels, Erich Folkhard et al., 2012
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