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ASTM A372 Grade K Steel vs. ASTM A387 Grade 9 Steel

Both ASTM A372 grade K steel and ASTM A387 grade 9 steel are iron alloys. They have a moderately high 91% of their average alloy composition in common.

For each property being compared, the top bar is ASTM A372 grade K steel and the bottom bar is ASTM A387 grade 9 steel.

Metric UnitsUS Customary Units

Mechanical Properties

Brinell Hardness 230
150 to 180
Elastic (Young's, Tensile) Modulus, GPa 190
190
Elongation at Break, % 23
20 to 21
Fatigue Strength, MPa 440
160 to 240
Poisson's Ratio 0.29
0.28
Shear Modulus, GPa 73
75
Shear Strength, MPa 490
310 to 380
Tensile Strength: Ultimate (UTS), MPa 780
500 to 600
Tensile Strength: Yield (Proof), MPa 620
230 to 350

Thermal Properties

Latent Heat of Fusion, J/g 250
270
Maximum Temperature: Mechanical, °C 440
600
Melting Completion (Liquidus), °C 1460
1460
Melting Onset (Solidus), °C 1420
1410
Specific Heat Capacity, J/kg-K 470
470
Thermal Conductivity, W/m-K 48
26
Thermal Expansion, µm/m-K 13
13

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.8
9.0
Electrical Conductivity: Equal Weight (Specific), % IACS 8.9
10

Otherwise Unclassified Properties

Base Metal Price, % relative 4.4
6.5
Density, g/cm3 7.9
7.8
Embodied Carbon, kg CO2/kg material 1.8
2.1
Embodied Energy, MJ/kg 24
28
Embodied Water, L/kg 57
87

Common Calculations

PREN (Pitting Resistance) 2.7
12
Resilience: Ultimate (Unit Rupture Work), MJ/m3 160
83 to 110
Resilience: Unit (Modulus of Resilience), kJ/m3 1010
140 to 310
Stiffness to Weight: Axial, points 13
14
Stiffness to Weight: Bending, points 24
25
Strength to Weight: Axial, points 27
18 to 21
Strength to Weight: Bending, points 24
18 to 20
Thermal Diffusivity, mm2/s 13
6.9
Thermal Shock Resistance, points 23
14 to 17

Alloy Composition

Carbon (C), % 0 to 0.18
0 to 0.15
Chromium (Cr), % 1.0 to 1.8
8.0 to 10
Iron (Fe), % 93.4 to 96.6
87.1 to 90.8
Manganese (Mn), % 0.1 to 0.4
0.3 to 0.6
Molybdenum (Mo), % 0.2 to 0.6
0.9 to 1.1
Nickel (Ni), % 2.0 to 3.3
0
Phosphorus (P), % 0 to 0.015
0 to 0.025
Silicon (Si), % 0.15 to 0.35
0 to 1.0
Sulfur (S), % 0 to 0.010
0 to 0.025
Vanadium (V), % 0
0 to 0.040