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SAE-AISI 4118 Steel vs. SAE-AISI 4720 Steel

Both SAE-AISI 4118 steel and SAE-AISI 4720 steel are iron alloys. Both are furnished in the annealed condition. They have a very high 99% of their average alloy composition in common.

For each property being compared, the top bar is SAE-AISI 4118 steel and the bottom bar is SAE-AISI 4720 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 150
150
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 23
25
Fatigue Strength, MPa 230
260
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 73
73
Shear Strength, MPa 320
310
Tensile Strength: Ultimate (UTS), MPa 500
490
Tensile Strength: Yield (Proof), MPa 320
350

Thermal Properties

Latent Heat of Fusion, J/g 250
250
Maximum Temperature: Mechanical, °C 410
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 46
39
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.2
7.3
Electrical Conductivity: Equal Weight (Specific), % IACS 8.2
8.4

Otherwise Unclassified Properties

Base Metal Price, % relative 2.3
2.9
Density, g/cm3 7.8
7.9
Embodied Carbon, kg CO2/kg material 1.5
1.6
Embodied Energy, MJ/kg 20
21
Embodied Water, L/kg 49
50

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 100
110
Resilience: Unit (Modulus of Resilience), kJ/m3 280
330
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 18
17
Strength to Weight: Bending, points 18
18
Thermal Diffusivity, mm2/s 13
10
Thermal Shock Resistance, points 15
14

Alloy Composition

Carbon (C), % 0.18 to 0.23
0.17 to 0.22
Chromium (Cr), % 0.4 to 0.6
0.35 to 0.55
Iron (Fe), % 97.5 to 98.4
96.7 to 97.8
Manganese (Mn), % 0.7 to 0.9
0.5 to 0.7
Molybdenum (Mo), % 0.2 to 0.3
0.15 to 0.25
Nickel (Ni), % 0
0.9 to 1.2
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