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ACI-ASTM CN7MS Steel vs. R31538 Cobalt

ACI-ASTM CN7MS steel belongs to the iron alloys classification, while R31538 cobalt belongs to the cobalt alloys. They have a modest 24% of their average alloy composition in common, which, by itself, doesn't mean much. There are 25 material properties with values for both materials. Properties with values for just one material (9, in this case) are not shown.

For each property being compared, the top bar is ACI-ASTM CN7MS steel and the bottom bar is R31538 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 200
220
Elongation at Break, % 39
13 to 23
Fatigue Strength, MPa 200
310 to 480
Poisson's Ratio 0.28
0.29
Shear Modulus, GPa 77
86
Tensile Strength: Ultimate (UTS), MPa 540
1020 to 1360
Tensile Strength: Yield (Proof), MPa 230
580 to 930

Thermal Properties

Latent Heat of Fusion, J/g 340
320
Melting Completion (Liquidus), °C 1400
1360
Melting Onset (Solidus), °C 1350
1290
Specific Heat Capacity, J/kg-K 480
450
Thermal Conductivity, W/m-K 12
13
Thermal Expansion, µm/m-K 16
13

Otherwise Unclassified Properties

Density, g/cm3 7.9
8.4
Embodied Carbon, kg CO2/kg material 5.1
8.1
Embodied Energy, MJ/kg 71
110
Embodied Water, L/kg 180
530

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 170
140 to 200
Resilience: Unit (Modulus of Resilience), kJ/m3 140
750 to 1920
Stiffness to Weight: Axial, points 14
15
Stiffness to Weight: Bending, points 25
24
Strength to Weight: Axial, points 19
34 to 45
Strength to Weight: Bending, points 19
27 to 32
Thermal Diffusivity, mm2/s 3.2
3.5
Thermal Shock Resistance, points 13
25 to 33

Alloy Composition

Carbon (C), % 0 to 0.070
0.15 to 0.35
Chromium (Cr), % 18 to 20
26 to 30
Cobalt (Co), % 0
58.7 to 68.9
Copper (Cu), % 1.5 to 2.0
0
Iron (Fe), % 45.4 to 53.5
0 to 0.75
Manganese (Mn), % 0 to 1.0
0 to 1.0
Molybdenum (Mo), % 2.5 to 3.0
5.0 to 7.0
Nickel (Ni), % 22 to 25
0 to 1.0
Nitrogen (N), % 0
0 to 0.25
Phosphorus (P), % 0 to 0.040
0
Silicon (Si), % 2.5 to 3.5
0 to 1.0
Sulfur (S), % 0 to 0.030
0