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ASTM A387 Grade 21 Steel vs. R30035 Cobalt

ASTM A387 grade 21 steel belongs to the iron alloys classification, while R30035 cobalt belongs to the cobalt alloys. There are 28 material properties with values for both materials. Properties with values for just one material (5, in this case) are not shown.

For each property being compared, the top bar is ASTM A387 grade 21 steel and the bottom bar is R30035 cobalt.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 190
220 to 230
Elongation at Break, % 21
9.0 to 46
Fatigue Strength, MPa 160 to 250
170 to 740
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 74
84 to 89
Tensile Strength: Ultimate (UTS), MPa 500 to 590
900 to 1900
Tensile Strength: Yield (Proof), MPa 230 to 350
300 to 1650

Thermal Properties

Latent Heat of Fusion, J/g 260
320
Melting Completion (Liquidus), °C 1470
1440
Melting Onset (Solidus), °C 1430
1320
Specific Heat Capacity, J/kg-K 470
440
Thermal Conductivity, W/m-K 41
11
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.6
1.7
Electrical Conductivity: Equal Weight (Specific), % IACS 8.8
1.8

Otherwise Unclassified Properties

Base Metal Price, % relative 4.1
100
Density, g/cm3 7.9
8.7
Embodied Carbon, kg CO2/kg material 1.8
10
Embodied Energy, MJ/kg 23
140
Embodied Water, L/kg 62
410

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 84 to 110
160 to 320
Resilience: Unit (Modulus of Resilience), kJ/m3 140 to 320
210 to 5920
Stiffness to Weight: Axial, points 13
14 to 15
Stiffness to Weight: Bending, points 24
23 to 24
Strength to Weight: Axial, points 18 to 21
29 to 61
Strength to Weight: Bending, points 18 to 20
24 to 39
Thermal Diffusivity, mm2/s 11
3.0
Thermal Shock Resistance, points 14 to 17
23 to 46

Alloy Composition

Boron (B), % 0
0 to 0.015
Carbon (C), % 0.050 to 0.15
0 to 0.025
Chromium (Cr), % 2.8 to 3.3
19 to 21
Cobalt (Co), % 0
29.1 to 39
Iron (Fe), % 94.4 to 96
0 to 1.0
Manganese (Mn), % 0.3 to 0.6
0 to 0.15
Molybdenum (Mo), % 0.9 to 1.1
9.0 to 10.5
Nickel (Ni), % 0
33 to 37
Phosphorus (P), % 0 to 0.025
0 to 0.015
Silicon (Si), % 0 to 0.5
0 to 0.15
Sulfur (S), % 0 to 0.025
0 to 0.010
Titanium (Ti), % 0
0 to 1.0

Comparable Variants