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ASTM A387 Grade 11 (K11789) 1.25Cr-0.5Mo Steel

ASTM A387 grade 11 steel is an alloy steel formulated for primary forming into wrought products. ASTM A387 Grade 11 is the ASTM designation for this material. K11789 is the UNS number.

It has a fairly high ductility and a moderately low thermal conductivity among wrought alloy steels in the same category.

The properties of ASTM A387 grade 11 steel include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare ASTM A387 grade 11 steel 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 to 180

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

25 %

Fatigue Strength

200 to 250 MPa 29 to 37 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

320 to 390 MPa 46 to 56 x 103 psi

Tensile Strength: Ultimate (UTS)

500 to 600 MPa 73 to 87 x 103 psi

Tensile Strength: Yield (Proof)

270 to 350 MPa 40 to 50 x 103 psi

Thermal Properties

Latent Heat of Fusion

260 J/g

Maximum Temperature: Mechanical

430 °C 810 °F

Melting Completion (Liquidus)

1460 °C 2660 °F

Melting Onset (Solidus)

1420 °C 2590 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

39 W/m-K 23 BTU/h-ft-°F

Thermal Expansion

13 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.4 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.5 % IACS

Otherwise Unclassified Properties

Base Metal Price

2.9 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.6 kg CO2/kg material

Embodied Energy

21 MJ/kg 9.1 x 103 BTU/lb

Embodied Water

53 L/kg 6.3 gal/lb

Common Calculations

PREN (Pitting Resistance)

3.1

Resilience: Ultimate (Unit Rupture Work)

100 to 130 MJ/m3

Resilience: Unit (Modulus of Resilience)

200 to 320 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

18 to 21 points

Strength to Weight: Bending

18 to 20 points

Thermal Diffusivity

11 mm2/s

Thermal Shock Resistance

15 to 18 points

Alloy Composition

Among alloy steels, the composition of ASTM A387 grade 11 steel 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) 96.2 to 97.6
Chromium (Cr) 1.0 to 1.5
Silicon (Si) 0.5 to 0.8
Molybdenum (Mo) 0.45 to 0.65
Manganese (Mn) 0.4 to 0.65
Carbon (C) 0.050 to 0.17
Phosphorus (P) 0 to 0.025
Sulfur (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

ASM Specialty Handbook: Carbon and Alloy Steels, J. R. Davis (editor), 1996

Manufacture and Uses of Alloy Steels, Henry D. Hibbard, 2005

Steels: Processing, Structure, and Performance, 2nd ed., George Krauss, 2015