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SAE-AISI 4720 Steel vs. ASTM A369 Grade FPA

Both SAE-AISI 4720 steel and ASTM A369 grade FPA are iron alloys. They have a very high 98% of their average alloy composition in common.

For each property being compared, the top bar is SAE-AISI 4720 steel and the bottom bar is ASTM A369 grade FPA.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 150
110
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 25
27
Fatigue Strength, MPa 260
180
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 73
73
Shear Strength, MPa 310
240
Tensile Strength: Ultimate (UTS), MPa 490
380
Tensile Strength: Yield (Proof), MPa 350
240

Thermal Properties

Latent Heat of Fusion, J/g 250
250
Maximum Temperature: Mechanical, °C 410
400
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 39
52
Thermal Expansion, µm/m-K 13
12

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.3
7.1
Electrical Conductivity: Equal Weight (Specific), % IACS 8.4
8.1

Otherwise Unclassified Properties

Base Metal Price, % relative 2.9
1.8
Density, g/cm3 7.9
7.8
Embodied Carbon, kg CO2/kg material 1.6
1.4
Embodied Energy, MJ/kg 21
18
Embodied Water, L/kg 50
46

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 110
89
Resilience: Unit (Modulus of Resilience), kJ/m3 330
150
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 17
13
Strength to Weight: Bending, points 18
15
Thermal Diffusivity, mm2/s 10
14
Thermal Shock Resistance, points 14
12

Alloy Composition

Carbon (C), % 0.17 to 0.22
0 to 0.25
Chromium (Cr), % 0.35 to 0.55
0
Iron (Fe), % 96.7 to 97.8
98.3 to 99.63
Manganese (Mn), % 0.5 to 0.7
0.27 to 0.93
Molybdenum (Mo), % 0.15 to 0.25
0
Nickel (Ni), % 0.9 to 1.2
0
Phosphorus (P), % 0 to 0.035
0 to 0.035
Silicon (Si), % 0.15 to 0.35
0.1 to 0.5
Sulfur (S), % 0 to 0.040
0 to 0.035