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SAE-AISI 4142 Steel vs. SAE-AISI 8645 Steel

Both SAE-AISI 4142 steel and SAE-AISI 8645 steel are iron alloys. Their average alloy composition is basically identical.

For each property being compared, the top bar is SAE-AISI 4142 steel and the bottom bar is SAE-AISI 8645 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 180
180 to 200
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 20
12 to 23
Fatigue Strength, MPa 250
280 to 350
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 73
73
Shear Strength, MPa 370
380 to 400
Tensile Strength: Ultimate (UTS), MPa 590
600 to 670
Tensile Strength: Yield (Proof), MPa 370
390 to 560

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 44
39
Thermal Expansion, µm/m-K 12
13

Electrical Properties

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

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 100
77 to 120
Resilience: Unit (Modulus of Resilience), kJ/m3 360
420 to 840
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 21
21 to 24
Strength to Weight: Bending, points 20
20 to 22
Thermal Diffusivity, mm2/s 12
10
Thermal Shock Resistance, points 19
18 to 20

Alloy Composition

Carbon (C), % 0.4 to 0.45
0.43 to 0.48
Chromium (Cr), % 0.8 to 1.1
0.4 to 0.6
Iron (Fe), % 96.8 to 97.8
96.5 to 97.7
Manganese (Mn), % 0.75 to 1.0
0.75 to 1.0
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