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SAE-AISI 81B45 Steel vs. SAE-AISI 4718 Steel

Both SAE-AISI 81B45 steel and SAE-AISI 4718 steel are iron alloys. They have a very high 99% of their average alloy composition in common.

For each property being compared, the top bar is SAE-AISI 81B45 steel and the bottom bar is SAE-AISI 4718 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 160 to 200
150
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 12 to 24
24
Fatigue Strength, MPa 250 to 350
270
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 73
73
Shear Strength, MPa 340 to 400
330
Tensile Strength: Ultimate (UTS), MPa 540 to 670
510
Tensile Strength: Yield (Proof), MPa 350 to 560
370

Thermal Properties

Latent Heat of Fusion, J/g 250
250
Maximum Temperature: Mechanical, °C 410
420
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 40
39
Thermal Expansion, µm/m-K 12
11

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.2
7.3
Electrical Conductivity: Equal Weight (Specific), % IACS 8.3
8.4

Otherwise Unclassified Properties

Base Metal Price, % relative 2.3
3.0
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
51

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 77 to 110
110
Resilience: Unit (Modulus of Resilience), kJ/m3 320 to 840
360
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 19 to 24
18
Strength to Weight: Bending, points 19 to 22
18
Thermal Diffusivity, mm2/s 11
10
Thermal Shock Resistance, points 17 to 21
17

Alloy Composition

Boron (B), % 0.00050 to 0.0030
0
Carbon (C), % 0.43 to 0.48
0.16 to 0.21
Chromium (Cr), % 0.35 to 0.55
0.35 to 0.55
Iron (Fe), % 97 to 98
96.3 to 97.4
Manganese (Mn), % 0.75 to 1.0
0.7 to 0.9
Molybdenum (Mo), % 0.080 to 0.15
0.3 to 0.4
Nickel (Ni), % 0.2 to 0.4
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