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SAE-AISI 4340M Steel vs. ASTM A387 Grade 91 Class 2

Both SAE-AISI 4340M steel and ASTM A387 grade 91 class 2 are iron alloys. They have a moderately high 91% of their average alloy composition in common. There are 32 material properties with values for both materials. Properties with values for just one material (3, in this case) are not shown.

For each property being compared, the top bar is SAE-AISI 4340M steel and the bottom bar is ASTM A387 grade 91 class 2.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 710
200
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 6.0
20
Fatigue Strength, MPa 690
330
Poisson's Ratio 0.29
0.28
Shear Modulus, GPa 72
75
Shear Strength, MPa 1360
420
Tensile Strength: Ultimate (UTS), MPa 2340
670
Tensile Strength: Yield (Proof), MPa 1240
470

Thermal Properties

Latent Heat of Fusion, J/g 280
270
Maximum Temperature: Mechanical, °C 430
600
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
26
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.8
8.9
Electrical Conductivity: Equal Weight (Specific), % IACS 9.1
10

Otherwise Unclassified Properties

Base Metal Price, % relative 3.9
7.0
Density, g/cm3 7.8
7.8
Embodied Carbon, kg CO2/kg material 1.9
2.6
Embodied Energy, MJ/kg 26
37
Embodied Water, L/kg 55
88

Common Calculations

PREN (Pitting Resistance) 2.2
13
Resilience: Ultimate (Unit Rupture Work), MJ/m3 120
120
Resilience: Unit (Modulus of Resilience), kJ/m3 4120
580
Stiffness to Weight: Axial, points 13
14
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
6.9
Thermal Shock Resistance, points 70
19

Alloy Composition

Aluminum (Al), % 0
0 to 0.020
Carbon (C), % 0.38 to 0.43
0.080 to 0.12
Chromium (Cr), % 0.7 to 1.0
8.0 to 9.5
Iron (Fe), % 93.3 to 94.8
87.3 to 90.3
Manganese (Mn), % 0.65 to 0.9
0.3 to 0.6
Molybdenum (Mo), % 0.35 to 0.45
0.85 to 1.1
Nickel (Ni), % 1.7 to 2.0
0 to 0.4
Niobium (Nb), % 0
0.060 to 0.1
Nitrogen (N), % 0
0.030 to 0.070
Phosphorus (P), % 0 to 0.012
0 to 0.020
Silicon (Si), % 1.5 to 1.8
0.2 to 0.5
Sulfur (S), % 0 to 0.012
0 to 0.010
Titanium (Ti), % 0
0 to 0.010
Vanadium (V), % 0.050 to 0.1
0.18 to 0.25
Zirconium (Zr), % 0
0 to 0.010