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SAE-AISI 4140 Steel vs. SAE-AISI 8620 Steel

Both SAE-AISI 4140 steel and SAE-AISI 8620 steel are iron alloys. Their average alloy composition is basically identical.

For each property being compared, the top bar is SAE-AISI 4140 steel and the bottom bar is SAE-AISI 8620 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 200 to 310
150 to 210
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 11 to 26
13 to 31
Fatigue Strength, MPa 360 to 650
270 to 360
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 73
73
Shear Strength, MPa 410 to 660
340 to 420
Tensile Strength: Ultimate (UTS), MPa 690 to 1080
520 to 690
Tensile Strength: Yield (Proof), MPa 590 to 990
360 to 570

Thermal Properties

Latent Heat of Fusion, J/g 250
250
Maximum Temperature: Mechanical, °C 420
410
Melting Completion (Liquidus), °C 1460
1460
Melting Onset (Solidus), °C 1420
1420
Specific Heat Capacity, J/kg-K 470
470
Thermal Conductivity, W/m-K 43
39
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.3
7.3
Electrical Conductivity: Equal Weight (Specific), % IACS 8.4
8.3

Otherwise Unclassified Properties

Base Metal Price, % relative 2.4
2.6
Density, g/cm3 7.8
7.8
Embodied Carbon, kg CO2/kg material 1.5
1.5
Embodied Energy, MJ/kg 20
20
Embodied Water, L/kg 51
50

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 74 to 180
86 to 150
Resilience: Unit (Modulus of Resilience), kJ/m3 920 to 2590
340 to 880
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 25 to 38
18 to 24
Strength to Weight: Bending, points 22 to 30
18 to 22
Thermal Diffusivity, mm2/s 12
10
Thermal Shock Resistance, points 20 to 32
15 to 20

Alloy Composition

Carbon (C), % 0.38 to 0.43
0.18 to 0.23
Chromium (Cr), % 0.8 to 1.1
0.4 to 0.6
Iron (Fe), % 96.8 to 97.8
96.9 to 98
Manganese (Mn), % 0.75 to 1.0
0.7 to 0.9
Molybdenum (Mo), % 0.15 to 0.25
0.15 to 0.25
Nickel (Ni), % 0
0.4 to 0.7
Phosphorus (P), % 0 to 0.035
0 to 0.035
Silicon (Si), % 0.15 to 0.35
0.15 to 0.35
Sulfur (S), % 0 to 0.040
0 to 0.040

Comparable Variants