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ASTM A387 Grade 21L Class 1 vs. ASTM A372 Grade K Steel

Both ASTM A387 grade 21L class 1 and ASTM A372 grade K steel are iron alloys. They have a very high 97% of their average alloy composition in common.

For each property being compared, the top bar is ASTM A387 grade 21L class 1 and the bottom bar is ASTM A372 grade K steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 150
230
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 21
23
Fatigue Strength, MPa 160
440
Poisson's Ratio 0.29
0.29
Shear Modulus, GPa 74
73
Shear Strength, MPa 310
490
Tensile Strength: Ultimate (UTS), MPa 500
780
Tensile Strength: Yield (Proof), MPa 230
620

Thermal Properties

Latent Heat of Fusion, J/g 260
250
Maximum Temperature: Mechanical, °C 480
440
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
48
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.6
7.8
Electrical Conductivity: Equal Weight (Specific), % IACS 8.8
8.9

Otherwise Unclassified Properties

Base Metal Price, % relative 4.1
4.4
Density, g/cm3 7.9
7.9
Embodied Carbon, kg CO2/kg material 1.8
1.8
Embodied Energy, MJ/kg 23
24
Embodied Water, L/kg 62
57

Common Calculations

PREN (Pitting Resistance) 6.4
2.7
Resilience: Ultimate (Unit Rupture Work), MJ/m3 84
160
Resilience: Unit (Modulus of Resilience), kJ/m3 140
1010
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 24
24
Strength to Weight: Axial, points 18
27
Strength to Weight: Bending, points 18
24
Thermal Diffusivity, mm2/s 11
13
Thermal Shock Resistance, points 14
23

Alloy Composition

Carbon (C), % 0 to 0.1
0 to 0.18
Chromium (Cr), % 2.8 to 3.3
1.0 to 1.8
Iron (Fe), % 94.4 to 96.1
93.4 to 96.6
Manganese (Mn), % 0.3 to 0.6
0.1 to 0.4
Molybdenum (Mo), % 0.9 to 1.1
0.2 to 0.6
Nickel (Ni), % 0
2.0 to 3.3
Phosphorus (P), % 0 to 0.025
0 to 0.015
Silicon (Si), % 0 to 0.5
0.15 to 0.35
Sulfur (S), % 0 to 0.025
0 to 0.010