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SAE-AISI 4720 Steel vs. S81921 Stainless Steel

Both SAE-AISI 4720 steel and S81921 stainless steel are iron alloys. Both are furnished in the annealed condition. They have 74% of their average alloy composition in common. There are 31 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 4720 steel and the bottom bar is S81921 stainless steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 150
260
Elastic (Young's, Tensile) Modulus, GPa 190
200
Elongation at Break, % 25
29
Fatigue Strength, MPa 260
370
Poisson's Ratio 0.29
0.28
Shear Modulus, GPa 73
79
Shear Strength, MPa 310
460
Tensile Strength: Ultimate (UTS), MPa 490
710
Tensile Strength: Yield (Proof), MPa 350
500

Thermal Properties

Latent Heat of Fusion, J/g 250
290
Maximum Temperature: Mechanical, °C 410
990
Melting Completion (Liquidus), °C 1460
1430
Melting Onset (Solidus), °C 1420
1390
Specific Heat Capacity, J/kg-K 470
480
Thermal Conductivity, W/m-K 39
15
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.3
2.2
Electrical Conductivity: Equal Weight (Specific), % IACS 8.4
2.5

Otherwise Unclassified Properties

Base Metal Price, % relative 2.9
14
Density, g/cm3 7.9
7.7
Embodied Carbon, kg CO2/kg material 1.6
2.9
Embodied Energy, MJ/kg 21
41
Embodied Water, L/kg 50
150

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 110
180
Resilience: Unit (Modulus of Resilience), kJ/m3 330
630
Stiffness to Weight: Axial, points 13
14
Stiffness to Weight: Bending, points 24
25
Strength to Weight: Axial, points 17
25
Strength to Weight: Bending, points 18
23
Thermal Diffusivity, mm2/s 10
4.0
Thermal Shock Resistance, points 14
20

Alloy Composition

Carbon (C), % 0.17 to 0.22
0 to 0.030
Chromium (Cr), % 0.35 to 0.55
19 to 22
Iron (Fe), % 96.7 to 97.8
66.7 to 75.9
Manganese (Mn), % 0.5 to 0.7
2.0 to 4.0
Molybdenum (Mo), % 0.15 to 0.25
1.0 to 2.0
Nickel (Ni), % 0.9 to 1.2
2.0 to 4.0
Nitrogen (N), % 0
0.14 to 0.2
Phosphorus (P), % 0 to 0.035
0 to 0.040
Silicon (Si), % 0.15 to 0.35
0 to 1.0
Sulfur (S), % 0 to 0.040
0 to 0.030