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ASTM A231 Spring Steel vs. R31538 Cobalt

ASTM A231 spring steel belongs to the iron alloys classification, while R31538 cobalt belongs to the cobalt alloys. There are 27 material properties with values for both materials. Properties with values for just one material (6, in this case) are not shown.

For each property being compared, the top bar is ASTM A231 spring steel and the bottom bar is R31538 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 190
220
Elongation at Break, % 14
13 to 23
Fatigue Strength, MPa 1000
310 to 480
Poisson's Ratio 0.29
0.29
Reduction in Area, % 46
13 to 22
Shear Modulus, GPa 73
86
Tensile Strength: Ultimate (UTS), MPa 1790
1020 to 1360
Tensile Strength: Yield (Proof), MPa 1570
580 to 930

Thermal Properties

Latent Heat of Fusion, J/g 250
320
Melting Completion (Liquidus), °C 1460
1360
Melting Onset (Solidus), °C 1410
1290
Specific Heat Capacity, J/kg-K 470
450
Thermal Conductivity, W/m-K 52
13
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.3
2.0
Electrical Conductivity: Equal Weight (Specific), % IACS 8.4
2.1

Otherwise Unclassified Properties

Density, g/cm3 7.8
8.4
Embodied Carbon, kg CO2/kg material 2.0
8.1
Embodied Energy, MJ/kg 28
110
Embodied Water, L/kg 51
530

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 230
140 to 200
Stiffness to Weight: Axial, points 13
15
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 64
34 to 45
Strength to Weight: Bending, points 42
27 to 32
Thermal Diffusivity, mm2/s 14
3.5
Thermal Shock Resistance, points 53
25 to 33

Alloy Composition

Carbon (C), % 0.48 to 0.53
0.15 to 0.35
Chromium (Cr), % 0.8 to 1.1
26 to 30
Cobalt (Co), % 0
58.7 to 68.9
Iron (Fe), % 96.7 to 97.7
0 to 0.75
Manganese (Mn), % 0.7 to 0.9
0 to 1.0
Molybdenum (Mo), % 0
5.0 to 7.0
Nickel (Ni), % 0
0 to 1.0
Nitrogen (N), % 0
0 to 0.25
Phosphorus (P), % 0 to 0.040
0
Silicon (Si), % 0.15 to 0.35
0 to 1.0
Sulfur (S), % 0 to 0.040
0
Vanadium (V), % 0.15 to 0.3
0