UNS R30556 (Alloy 556) Fe-Cr-Ni-Co Alloy
R30556 alloy is a superaustenitic (highly alloyed) stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. R30556 is the UNS number for this material. Alloy 556 is the common industry name.
It has a very high base cost among wrought superaustenitic stainless steels. In addition, it has a fairly low thermal conductivity and a very high embodied energy.
The graph bars on the material properties cards below compare R30556 alloy 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
320 MPa 47 x 103 psi
Poisson's Ratio
0.28
Shear Modulus
81 GPa 12 x 106 psi
Shear Strength
550 MPa 79 x 103 psi
Tensile Strength: Ultimate (UTS)
780 MPa 110 x 103 psi
Tensile Strength: Yield (Proof)
350 MPa 51 x 103 psi
Thermal Properties
Latent Heat of Fusion
300 J/g
Maximum Temperature: Corrosion
450 °C 850 °F
Maximum Temperature: Mechanical
1100 °C 2010 °F
Melting Completion (Liquidus)
1420 °C 2580 °F
Melting Onset (Solidus)
1330 °C 2430 °F
Specific Heat Capacity
450 J/kg-K 0.11 BTU/lb-°F
Thermal Conductivity
11 W/m-K 6.4 BTU/h-ft-°F
Thermal Expansion
15 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
1.8 % IACS
Electrical Conductivity: Equal Weight (Specific)
1.9 % IACS
Otherwise Unclassified Properties
Base Metal Price
70 % relative
Density
8.4 g/cm3 530 lb/ft3
Embodied Carbon
8.7 kg CO2/kg material
Embodied Energy
130 MJ/kg 55 x 103 BTU/lb
Embodied Water
300 L/kg 36 gal/lb
Common Calculations
PREN (Pitting Resistance)
40
Resilience: Ultimate (Unit Rupture Work)
290 MJ/m3
Resilience: Unit (Modulus of Resilience)
290 kJ/m3
Stiffness to Weight: Axial
14 points
Stiffness to Weight: Bending
23 points
Strength to Weight: Axial
26 points
Strength to Weight: Bending
22 points
Thermal Diffusivity
2.9 mm2/s
Thermal Shock Resistance
18 points
Alloy Composition
Among wrought stainless steels, the composition of R30556 alloy is notable for including zinc (Zn) and tantalum (Ta). The literature is unclear on the metallurgical role of zinc in stainless steel. Tantalum is used to improve pitting corrosion resistance.
| Fe | 20.4 to 38.2 | |
| Cr | 21 to 23 | |
| Ni | 19 to 22.5 | |
| Co | 16 to 21 | |
| Mo | 2.5 to 4.0 | |
| W | 2.0 to 3.5 | |
| Mn | 0.5 to 2.0 | |
| Ta | 0.3 to 1.3 | |
| Si | 0.2 to 0.8 | |
| Al | 0.1 to 0.5 | |
| N | 0.1 to 0.3 | |
| Nb | 0 to 0.3 | |
| C | 0.050 to 0.15 | |
| La | 0.0050 to 0.1 | |
| Zn | 0.0010 to 0.1 | |
| P | 0 to 0.040 | |
| B | 0 to 0.020 | |
| S | 0 to 0.015 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
ASTM B435: Standard Specification for UNS N06002, UNS N06230, UNS N12160, and UNS R30556 Plate, Sheet, and Strip
ASTM B572: Standard Specification for UNS N06002, UNS N06230, UNS N12160, and UNS R30556 Rod
ASTM B619: Standard Specification for Welded Nickel and Nickel-Cobalt Alloy Pipe
ASTM B626: Standard Specification for Welded Nickel and Nickel-Cobalt Alloy Tube
ASTM B622: Standard Specification for Seamless Nickel and Nickel-Cobalt Alloy Pipe and Tube
Welding Metallurgy and Weldability of Stainless Steels, John C. Lippold and Damian J. Kotecki, 2005
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
Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993
ASM Specialty Handbook: Stainless Steels, J. R. Davis (editor), 1994