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ASTM A387 Grade 21 Steel vs. AISI 309 Stainless Steel

Both ASTM A387 grade 21 steel and AISI 309 stainless steel are iron alloys. They have 66% of their average alloy composition in common. There are 32 material properties with values for both materials. Properties with values for just one material (2, 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 AISI 309 stainless steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 150 to 180
180 to 210
Elastic (Young's, Tensile) Modulus, GPa 190
200
Elongation at Break, % 21
34 to 47
Fatigue Strength, MPa 160 to 250
250 to 280
Poisson's Ratio 0.29
0.27
Shear Modulus, GPa 74
78
Shear Strength, MPa 310 to 370
420 to 470
Tensile Strength: Ultimate (UTS), MPa 500 to 590
600 to 710
Tensile Strength: Yield (Proof), MPa 230 to 350
260 to 350

Thermal Properties

Latent Heat of Fusion, J/g 260
290
Maximum Temperature: Mechanical, °C 480
980
Melting Completion (Liquidus), °C 1470
1450
Melting Onset (Solidus), °C 1430
1400
Specific Heat Capacity, J/kg-K 470
480
Thermal Conductivity, W/m-K 41
16
Thermal Expansion, µm/m-K 13
15

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.6
2.2
Electrical Conductivity: Equal Weight (Specific), % IACS 8.8
2.5

Otherwise Unclassified Properties

Base Metal Price, % relative 4.1
19
Density, g/cm3 7.9
7.8
Embodied Carbon, kg CO2/kg material 1.8
3.6
Embodied Energy, MJ/kg 23
51
Embodied Water, L/kg 62
170

Common Calculations

PREN (Pitting Resistance) 6.4
23
Resilience: Ultimate (Unit Rupture Work), MJ/m3 84 to 110
200 to 230
Resilience: Unit (Modulus of Resilience), kJ/m3 140 to 320
170 to 310
Stiffness to Weight: Axial, points 13
14
Stiffness to Weight: Bending, points 24
25
Strength to Weight: Axial, points 18 to 21
21 to 25
Strength to Weight: Bending, points 18 to 20
20 to 23
Thermal Diffusivity, mm2/s 11
4.3
Thermal Shock Resistance, points 14 to 17
14 to 16

Alloy Composition

Carbon (C), % 0.050 to 0.15
0 to 0.2
Chromium (Cr), % 2.8 to 3.3
22 to 24
Iron (Fe), % 94.4 to 96
58 to 66
Manganese (Mn), % 0.3 to 0.6
0 to 2.0
Molybdenum (Mo), % 0.9 to 1.1
0
Nickel (Ni), % 0
12 to 15
Phosphorus (P), % 0 to 0.025
0 to 0.045
Silicon (Si), % 0 to 0.5
0 to 0.75
Sulfur (S), % 0 to 0.025
0 to 0.030