ASTM A387 Grade 91 Class 2 (K90901) 9Cr-1Mo Steel
Alloy Steels
Property Overview
Density7.8g/cm³
Elastic Modulus190GPa
Tensile Strength670MPa
Yield Strength470MPa
Brinell Hardness200HB
Maximum Service Temperature600°C
Chemical Composition
C
0.080 to 0.12%
CR
8.0 to 9.5%
NI
0 to 0.4%
MO
0.85 to 1.1%
MN
0.3 to 0.6%
SI
0.2 to 0.5%
N
0.030 to 0.070%
P
0 to 0.020%
S
0 to 0.010%
NB
0.060 to 0.1%
TI
0 to 0.010%
V
0.18 to 0.25%
AL
0 to 0.020%
ZR
0 to 0.010%
FE
87.3 to 90.3%
Mechanical
Elastic (Young's, Tensile) Modulus
190 GPa
Elongation at Break
20 %
Fatigue Strength
330 MPa
Poisson's Ratio
0.28
Shear Modulus
75 GPa
Shear Strength
420 MPa
Tensile Strength: Ultimate (UTS)
670 MPa
Tensile Strength: Yield (Proof)
470 MPa
Hardness
Brinell Hardness
200
Physical
Density
7.8 g/cm 3
Thermal
Latent Heat of Fusion
270 J/g
Maximum Temperature: Mechanical
600 °C
Melting Completion (Liquidus)
1460 °C
Melting Onset (Solidus)
1420 °C
Specific Heat Capacity
470 J/kg-K
Thermal Conductivity
26 W/m-K
Thermal Diffusivity
6.9 mm 2 /s
Thermal Expansion
13 µm/m-K
Thermal Shock Resistance
19 points
Electrical
Electrical Conductivity: Equal Volume
8.9 % IACS
Electrical Conductivity: Equal Weight (Specific)
10 % IACS
Calculated
PREN (Pitting Resistance)
13
Resilience: Ultimate (Unit Rupture Work)
120 MJ/m 3
Resilience: Unit (Modulus of Resilience)
580 kJ/m 3
Stiffness to Weight: Axial
14 points
Stiffness to Weight: Bending
25 points
Strength to Weight: Axial
24 points
Strength to Weight: Bending
22 points
Environmental
Base Metal Price
7.0 % relative
Embodied Carbon
2.6 kg CO 2 /kg material
Embodied Energy
37 MJ/kg
Embodied Energy
37 MJ/kg 16 x 10 3 BTU/lb
Embodied Water
88 L/kg
Embodied Water
88 L/kg 10 gal/lb
Registered Designations & Aliases
ASTM A387 Grade 91 Class 2 (K90901) 9Cr-1Mo SteelK90901
Standards
ASTM A182 ASTM A182: Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service
ASTM A387 ASTM A387: Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum
ASTM A387 ASTM A387: Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum ASTM A182: Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service Pressure Vessels: External Pressure Technology, 2nd ed., Carl T. F. Ross, 2011