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ASTM F15 (1.3981, K94610) Fe-Ni-Co Sealing Alloy

ASTM F15 Fe-Ni-Co is an iron alloy formulated for controlled thermal expansion. ASTM F15 is the defining standard for this material. K94610 is the UNS number. Additionally, the EN chemical designation is FeNi28Co18Mn. And the AFNOR (French) designation is A54-301.

It has the highest base cost among low-expansion iron alloys. In addition, it has the highest electrical conductivity and can have the highest tensile strength.

The properties of ASTM F15 Fe-Ni-Co include five common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare ASTM F15 Fe-Ni-Co to: low-expansion iron alloys (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

190 GPa 28 x 106 psi

Poisson's Ratio


Shear Modulus

73 GPa 11 x 106 psi

Tensile Strength: Ultimate (UTS)

520 to 880 MPa 75 to 130 x 103 psi

Thermal Properties

Curie Temperature

430 °C 810 °F

Latent Heat of Fusion

270 J/g

Melting Completion (Liquidus)

1410 °C 2570 °F

Melting Onset (Solidus)

1450 °C 2640 °F

Specific Heat Capacity

460 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

17 W/m-K 9.8 BTU/h-ft-°F

Thermal Expansion

6.0 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

3.7 % IACS

Electrical Conductivity: Equal Weight (Specific)

4.0 % IACS

Otherwise Unclassified Properties

Base Metal Price

49 % relative


8.3 g/cm3 520 lb/ft3

Embodied Carbon

5.2 kg CO2/kg material

Embodied Energy

71 MJ/kg 30 x 103 BTU/lb

Embodied Water

190 L/kg 23 gal/lb

Common Calculations

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

23 points

Strength to Weight: Axial

17 to 29 points

Strength to Weight: Bending

17 to 24 points

Thermal Diffusivity

4.5 mm2/s

Thermal Shock Resistance

32 to 55 points

Alloy Composition

Iron (Fe)Fe 50.3 to 56
Nickel (Ni)Ni 28 to 30
Cobalt (Co)Co 16 to 18
Manganese (Mn)Mn 0 to 0.5
Silicon (Si)Si 0 to 0.2
Chromium (Cr)Cr 0 to 0.2
Molybdenum (Mo)Mo 0 to 0.2
Copper (Cu)Cu 0 to 0.2
Aluminum (Al)Al 0 to 0.1
Titanium (Ti)Ti 0 to 0.1
Zirconium (Zr)Zr 0 to 0.1
Magnesium (Mg)Mg 0 to 0.1
Carbon (C)C 0 to 0.040

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

Followup Questions

Similar Alloys

Further Reading

ASTM F15: Standard Specification for Iron-Nickel-Cobalt Sealing Alloy

Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993

Manufacture and Uses of Alloy Steels, Henry D. Hibbard, 2005