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SAE-AISI 4340M Steel vs. SAE-AISI 9255 Steel

Both SAE-AISI 4340M steel and SAE-AISI 9255 steel are iron alloys. Both are furnished in the annealed condition. 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 9255 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 710
200
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 6.0
21
Fatigue Strength, MPa 690
270
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 72
72
Shear Strength, MPa 1360
430
Tensile Strength: Ultimate (UTS), MPa 2340
680
Tensile Strength: Yield (Proof), MPa 1240
390

Thermal Properties

Latent Heat of Fusion, J/g 280
280
Maximum Temperature: Mechanical, °C 430
400
Melting Completion (Liquidus), °C 1440
1430
Melting Onset (Solidus), °C 1400
1390
Specific Heat Capacity, J/kg-K 480
480
Thermal Conductivity, W/m-K 38
46
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.8
7.4
Electrical Conductivity: Equal Weight (Specific), % IACS 9.1
8.6

Otherwise Unclassified Properties

Base Metal Price, % relative 3.9
2.0
Density, g/cm3 7.8
7.7
Embodied Carbon, kg CO2/kg material 1.9
1.5
Embodied Energy, MJ/kg 26
20
Embodied Water, L/kg 55
46

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 120
120
Resilience: Unit (Modulus of Resilience), kJ/m3 4120
400
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 25
25
Strength to Weight: Axial, points 84
24
Strength to Weight: Bending, points 51
22
Thermal Diffusivity, mm2/s 10
13
Thermal Shock Resistance, points 70
21

Alloy Composition

Carbon (C), % 0.38 to 0.43
0.51 to 0.59
Chromium (Cr), % 0.7 to 1.0
0
Iron (Fe), % 93.3 to 94.8
96.2 to 97
Manganese (Mn), % 0.65 to 0.9
0.7 to 1.0
Molybdenum (Mo), % 0.35 to 0.45
0
Nickel (Ni), % 1.7 to 2.0
0
Phosphorus (P), % 0 to 0.012
0 to 0.035
Silicon (Si), % 1.5 to 1.8
1.8 to 2.2
Sulfur (S), % 0 to 0.012
0 to 0.040
Vanadium (V), % 0.050 to 0.1
0