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SAE-AISI 4340M Steel vs. SAE-AISI 8645 Steel

Both SAE-AISI 4340M steel and SAE-AISI 8645 steel are iron alloys. They have a very high 97% of their average alloy composition in common. There are 31 material properties with values for both materials. Properties with values for just one material (4, in this case) are not shown.

For each property being compared, the top bar is SAE-AISI 4340M steel and the bottom bar is SAE-AISI 8645 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 710
180 to 200
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 6.0
12 to 23
Fatigue Strength, MPa 690
280 to 350
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 72
73
Shear Strength, MPa 1360
380 to 400
Tensile Strength: Ultimate (UTS), MPa 2340
600 to 670
Tensile Strength: Yield (Proof), MPa 1240
390 to 560

Thermal Properties

Latent Heat of Fusion, J/g 280
250
Maximum Temperature: Mechanical, °C 430
410
Melting Completion (Liquidus), °C 1440
1460
Melting Onset (Solidus), °C 1400
1420
Specific Heat Capacity, J/kg-K 480
470
Thermal Conductivity, W/m-K 38
39
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.8
7.3
Electrical Conductivity: Equal Weight (Specific), % IACS 9.1
8.4

Otherwise Unclassified Properties

Base Metal Price, % relative 3.9
2.6
Density, g/cm3 7.8
7.8
Embodied Carbon, kg CO2/kg material 1.9
1.5
Embodied Energy, MJ/kg 26
20
Embodied Water, L/kg 55
50

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 120
77 to 120
Resilience: Unit (Modulus of Resilience), kJ/m3 4120
420 to 840
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 25
24
Strength to Weight: Axial, points 84
21 to 24
Strength to Weight: Bending, points 51
20 to 22
Thermal Diffusivity, mm2/s 10
10
Thermal Shock Resistance, points 70
18 to 20

Alloy Composition

Carbon (C), % 0.38 to 0.43
0.43 to 0.48
Chromium (Cr), % 0.7 to 1.0
0.4 to 0.6
Iron (Fe), % 93.3 to 94.8
96.5 to 97.7
Manganese (Mn), % 0.65 to 0.9
0.75 to 1.0
Molybdenum (Mo), % 0.35 to 0.45
0.15 to 0.25
Nickel (Ni), % 1.7 to 2.0
0.4 to 0.7
Phosphorus (P), % 0 to 0.012
0 to 0.035
Silicon (Si), % 1.5 to 1.8
0.15 to 0.35
Sulfur (S), % 0 to 0.012
0 to 0.040
Vanadium (V), % 0.050 to 0.1
0