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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).

Iron (Fe)Fe 94.4 to 96.1
Chromium (Cr)Cr 2.8 to 3.3
Molybdenum (Mo)Mo 0.9 to 1.1
Manganese (Mn)Mn 0.3 to 0.6
Silicon (Si)Si 0 to 0.5
Carbon (C)C 0 to 0.1
Phosphorus (P)P 0 to 0.025
Sulfur (S)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