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ACI-ASTM CG8M Steel vs. R31537 Cobalt

ACI-ASTM CG8M steel belongs to the iron alloys classification, while R31537 cobalt belongs to the cobalt alloys. They have a modest 25% of their average alloy composition in common, which, by itself, doesn't mean much. There are 27 material properties with values for both materials. Properties with values for just one material (8, in this case) are not shown.

For each property being compared, the top bar is ACI-ASTM CG8M steel and the bottom bar is R31537 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 200
220
Elongation at Break, % 45
14 to 23
Fatigue Strength, MPa 280
310 to 480
Poisson's Ratio 0.28
0.29
Shear Modulus, GPa 79
87
Tensile Strength: Ultimate (UTS), MPa 550
1000 to 1340
Tensile Strength: Yield (Proof), MPa 300
590 to 940

Thermal Properties

Latent Heat of Fusion, J/g 300
320
Melting Completion (Liquidus), °C 1450
1360
Melting Onset (Solidus), °C 1400
1290
Specific Heat Capacity, J/kg-K 470
450
Thermal Conductivity, W/m-K 16
13
Thermal Expansion, µm/m-K 16
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 2.0
2.0
Electrical Conductivity: Equal Weight (Specific), % IACS 2.3
2.1

Otherwise Unclassified Properties

Density, g/cm3 7.9
8.4
Embodied Carbon, kg CO2/kg material 4.1
8.1
Embodied Energy, MJ/kg 56
110
Embodied Water, L/kg 160
530

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 210
140 to 200
Resilience: Unit (Modulus of Resilience), kJ/m3 220
780 to 1990
Stiffness to Weight: Axial, points 14
15
Stiffness to Weight: Bending, points 25
24
Strength to Weight: Axial, points 19
33 to 44
Strength to Weight: Bending, points 19
26 to 32
Thermal Diffusivity, mm2/s 4.3
3.4
Thermal Shock Resistance, points 12
24 to 32

Alloy Composition

Carbon (C), % 0 to 0.080
0 to 0.14
Chromium (Cr), % 18 to 21
26 to 30
Cobalt (Co), % 0
58.9 to 69
Iron (Fe), % 58.8 to 70
0 to 0.75
Manganese (Mn), % 0 to 1.5
0 to 1.0
Molybdenum (Mo), % 3.0 to 4.0
5.0 to 7.0
Nickel (Ni), % 9.0 to 13
0 to 1.0
Nitrogen (N), % 0
0 to 0.25
Phosphorus (P), % 0 to 0.040
0
Silicon (Si), % 0 to 1.5
0 to 1.0
Sulfur (S), % 0 to 0.040
0