ASTM A387 Grade 21L Class 1 3Cr-1Mo Steel
ASTM A387 grade 21L class 1 is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. It has a moderately low tensile strength and a moderately high base cost among wrought alloy steels in the same category.
The graph bars on the material properties cards below compare ASTM A387 grade 21L class 1 to: wrought alloy steels in the same category (top), all iron alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.
Mechanical Properties
Brinell Hardness
150
Elastic (Young's, Tensile) Modulus
190 GPa 28 x 106 psi
Elongation at Break
21 %
Fatigue Strength
160 MPa 23 x 103 psi
Poisson's Ratio
0.29
Shear Modulus
74 GPa 11 x 106 psi
Shear Strength
310 MPa 45 x 103 psi
Tensile Strength: Ultimate (UTS)
500 MPa 73 x 103 psi
Tensile Strength: Yield (Proof)
230 MPa 33 x 103 psi
Thermal Properties
Latent Heat of Fusion
260 J/g
Maximum Temperature: Mechanical
480 °C 890 °F
Melting Completion (Liquidus)
1470 °C 2670 °F
Melting Onset (Solidus)
1430 °C 2600 °F
Specific Heat Capacity
470 J/kg-K 0.11 BTU/lb-°F
Thermal Conductivity
41 W/m-K 24 BTU/h-ft-°F
Thermal Expansion
13 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
7.6 % IACS
Electrical Conductivity: Equal Weight (Specific)
8.8 % IACS
Otherwise Unclassified Properties
Base Metal Price
4.1 % relative
Density
7.9 g/cm3 490 lb/ft3
Embodied Carbon
1.8 kg CO2/kg material
Embodied Energy
23 MJ/kg 10 x 103 BTU/lb
Embodied Water
62 L/kg 7.4 gal/lb
Common Calculations
PREN (Pitting Resistance)
6.4
Resilience: Ultimate (Unit Rupture Work)
84 MJ/m3
Resilience: Unit (Modulus of Resilience)
140 kJ/m3
Stiffness to Weight: Axial
13 points
Stiffness to Weight: Bending
24 points
Strength to Weight: Axial
18 points
Strength to Weight: Bending
18 points
Thermal Diffusivity
11 mm2/s
Thermal Shock Resistance
14 points
Alloy Composition
Among alloy steels, the composition of ASTM A387 grade 21L class 1 is notable for containing a comparatively high amount of chromium (Cr). Chromium is used to improve corrosion resistance and most mechanical properties (particularly at higher temperatures).
| Fe | 94.4 to 96.1 | |
| Cr | 2.8 to 3.3 | |
| Mo | 0.9 to 1.1 | |
| Mn | 0.3 to 0.6 | |
| Si | 0 to 0.5 | |
| C | 0 to 0.1 | |
| P | 0 to 0.025 | |
| S | 0 to 0.025 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
ASTM A387: Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum
Pressure Vessels: External Pressure Technology, 2nd ed., Carl T. F. Ross, 2011
Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993
Manufacture and Uses of Alloy Steels, Henry D. Hibbard, 2005
CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015
Steels: Processing, Structure, and Performance, 2nd ed., George Krauss, 2015