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ASTM A387 Grade 21 Steel vs. SAE-AISI 4340 Steel

Both ASTM A387 grade 21 steel and SAE-AISI 4340 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 (1, in this case) are not shown.

For each property being compared, the top bar is ASTM A387 grade 21 steel and the bottom bar is SAE-AISI 4340 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 150 to 180
210 to 360
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 21
12 to 22
Fatigue Strength, MPa 160 to 250
330 to 740
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 74
73
Shear Strength, MPa 310 to 370
430 to 770
Tensile Strength: Ultimate (UTS), MPa 500 to 590
690 to 1280
Tensile Strength: Yield (Proof), MPa 230 to 350
470 to 1150

Thermal Properties

Latent Heat of Fusion, J/g 260
250
Maximum Temperature: Mechanical, °C 480
430
Melting Completion (Liquidus), °C 1470
1460
Melting Onset (Solidus), °C 1430
1420
Specific Heat Capacity, J/kg-K 470
470
Thermal Conductivity, W/m-K 41
44
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.6
7.5
Electrical Conductivity: Equal Weight (Specific), % IACS 8.8
8.6

Otherwise Unclassified Properties

Base Metal Price, % relative 4.1
3.5
Density, g/cm3 7.9
7.8
Embodied Carbon, kg CO2/kg material 1.8
1.7
Embodied Energy, MJ/kg 23
22
Embodied Water, L/kg 62
53

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 84 to 110
79 to 170
Resilience: Unit (Modulus of Resilience), kJ/m3 140 to 320
590 to 3490
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 18 to 21
24 to 45
Strength to Weight: Bending, points 18 to 20
22 to 33
Thermal Diffusivity, mm2/s 11
12
Thermal Shock Resistance, points 14 to 17
20 to 38

Alloy Composition

Carbon (C), % 0.050 to 0.15
0.38 to 0.43
Chromium (Cr), % 2.8 to 3.3
0.7 to 0.9
Iron (Fe), % 94.4 to 96
95.1 to 96.3
Manganese (Mn), % 0.3 to 0.6
0.6 to 0.8
Molybdenum (Mo), % 0.9 to 1.1
0.2 to 0.3
Nickel (Ni), % 0
1.7 to 2.0
Phosphorus (P), % 0 to 0.025
0 to 0.035
Silicon (Si), % 0 to 0.5
0.15 to 0.35
Sulfur (S), % 0 to 0.025
0 to 0.040

Comparable Variants