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ASTM A231 Spring Steel vs. R30021 Cobalt

ASTM A231 spring steel belongs to the iron alloys classification, while R30021 cobalt belongs to the cobalt alloys. There are 26 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 ASTM A231 spring steel and the bottom bar is R30021 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 190
220
Elongation at Break, % 14
9.0
Fatigue Strength, MPa 1000
250
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 73
86
Tensile Strength: Ultimate (UTS), MPa 1790
700
Tensile Strength: Yield (Proof), MPa 1570
500

Thermal Properties

Latent Heat of Fusion, J/g 250
330
Melting Completion (Liquidus), °C 1460
1350
Melting Onset (Solidus), °C 1410
1190
Specific Heat Capacity, J/kg-K 470
450
Thermal Conductivity, W/m-K 52
15
Thermal Expansion, µm/m-K 13
11

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.3
1.9
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
8.0
Embodied Energy, MJ/kg 28
110
Embodied Water, L/kg 51
520

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 230
57
Stiffness to Weight: Axial, points 13
15
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 64
23
Strength to Weight: Bending, points 42
21
Thermal Diffusivity, mm2/s 14
3.8
Thermal Shock Resistance, points 53
21

Alloy Composition

Carbon (C), % 0.48 to 0.53
0.2 to 0.35
Chromium (Cr), % 0.8 to 1.1
26 to 29
Cobalt (Co), % 0
61.7 to 67.3
Iron (Fe), % 96.7 to 97.7
0 to 3.0
Manganese (Mn), % 0.7 to 0.9
0
Molybdenum (Mo), % 0
4.5 to 6.0
Nickel (Ni), % 0
2.0 to 3.0
Phosphorus (P), % 0 to 0.040
0
Silicon (Si), % 0.15 to 0.35
0 to 1.5
Sulfur (S), % 0 to 0.040
0
Vanadium (V), % 0.15 to 0.3
0