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ASTM A387 Grade 12 (K11757) 1Cr-0.5Mo Steel

ASTM A387 grade 12 steel is an alloy steel formulated for primary forming into wrought products. ASTM A387 Grade 12 is the ASTM designation for this material. K11757 is the UNS number.

It has a moderately low electrical conductivity among wrought alloy steels in the same category. In addition, it can have a moderately low tensile strength and has a fairly high ductility.

The properties of ASTM A387 grade 12 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 12 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

140 to 160

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

25 %

Fatigue Strength

190 to 230 MPa 28 to 33 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

300 to 330 MPa 43 to 48 x 103 psi

Tensile Strength: Ultimate (UTS)

470 to 520 MPa 67 to 75 x 103 psi

Tensile Strength: Yield (Proof)

260 to 310 MPa 38 to 45 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

430 °C 800 °F

Melting Completion (Liquidus)

1470 °C 2670 °F

Melting Onset (Solidus)

1420 °C 2600 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

44 W/m-K 26 BTU/h-ft-°F

Thermal Expansion

13 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.2 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.3 % IACS

Otherwise Unclassified Properties

Base Metal Price

2.8 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.6 kg CO2/kg material

Embodied Energy

21 MJ/kg 8.9 x 103 BTU/lb

Embodied Water

51 L/kg 6.1 gal/lb

Common Calculations

PREN (Pitting Resistance)

2.7

Resilience: Ultimate (Unit Rupture Work)

98 to 110 MJ/m3

Resilience: Unit (Modulus of Resilience)

180 to 250 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

16 to 18 points

Strength to Weight: Bending

17 to 18 points

Thermal Diffusivity

12 mm2/s

Thermal Shock Resistance

14 to 15 points

Alloy Composition

Among alloy steels, the composition of ASTM A387 grade 12 steel is notable for containing comparatively high amounts of chromium (Cr) and manganese (Mn). Chromium is used to improve corrosion resistance and most mechanical properties (particularly at higher temperatures). Manganese is used to improve hardenability, hot workability, and surface quality. There is some loss of ductility and weldability, however.

Iron (Fe) 97 to 98.2
Chromium (Cr) 0.8 to 1.2
Manganese (Mn) 0.4 to 0.65
Molybdenum (Mo) 0.45 to 0.6
Silicon (Si) 0.15 to 0.4
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