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SAE-AISI 8740 (G87400) Ni-Cr-Mo Steel

SAE-AISI 8740 steel is an alloy steel formulated for primary forming into wrought products. 8740 is the designation in both the SAE and AISI systems for this material. G87400 is the UNS number.

The properties of SAE-AISI 8740 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 SAE-AISI 8740 steel to: SAE-AISI wrought steels (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

170 to 200

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

11 to 23 %

Fatigue Strength

270 to 350 MPa 40 to 51 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

370 to 400 MPa 53 to 58 x 103 psi

Tensile Strength: Ultimate (UTS)

580 to 670 MPa 84 to 97 x 103 psi

Tensile Strength: Yield (Proof)

380 to 570 MPa 55 to 82 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

410 °C 780 °F

Melting Completion (Liquidus)

1460 °C 2660 °F

Melting Onset (Solidus)

1420 °C 2580 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

39 W/m-K 22 BTU/h-ft-°F

Thermal Expansion

13 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.3 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.4 % IACS

Otherwise Unclassified Properties

Base Metal Price

2.6 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.5 kg CO2/kg material

Embodied Energy

20 MJ/kg 8.8 x 103 BTU/lb

Embodied Water

50 L/kg 6.0 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

71 to 120 MJ/m3

Resilience: Unit (Modulus of Resilience)

390 to 850 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

20 to 24 points

Strength to Weight: Bending

20 to 22 points

Thermal Diffusivity

10 mm2/s

Thermal Shock Resistance

17 to 20 points

Alloy Composition

Among alloy steels, the composition of SAE-AISI 8740 steel is notable for including nickel (Ni). Nickel is used to improve mechanical properties, and to make the alloy easier to heat treat.

Iron (Fe) 96.5 to 97.7
Manganese (Mn) 0.75 to 1.0
Nickel (Ni) 0.4 to 0.7
Chromium (Cr) 0.4 to 0.6
Carbon (C) 0.38 to 0.43
Silicon (Si) 0.15 to 0.35
Molybdenum (Mo) 0.2 to 0.3
Sulfur (S) 0 to 0.040
Phosphorus (P) 0 to 0.035

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM A752: Standard Specification for General Requirements for Wire Rods and Coarse Round Wire, Alloy Steel

ASTM A322: Standard Specification for Steel Bars, Alloy, Standard Grades

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