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SAE-AISI 4140 (SCM440, G41400) Cr-Mo Steel

SAE-AISI 4140 steel is an alloy steel formulated for primary forming into wrought products. 4140 is the designation in both the SAE and AISI systems for this material. G41400 is the UNS number. It can have a moderately high tensile strength among the SAE-AISI wrought steels in the database.

The properties of SAE-AISI 4140 steel include four common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare SAE-AISI 4140 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

200 to 310

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

11 to 26 %

Fatigue Strength

360 to 650 MPa 53 to 94 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

410 to 660 MPa 60 to 96 x 103 psi

Tensile Strength: Ultimate (UTS)

690 to 1080 MPa 100 to 160 x 103 psi

Tensile Strength: Yield (Proof)

590 to 990 MPa 85 to 140 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

420 °C 790 °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

43 W/m-K 25 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

2.4 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.5 kg CO2/kg material

Embodied Energy

20 MJ/kg 8.5 x 103 BTU/lb

Embodied Water

51 L/kg 6.1 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

74 to 180 MJ/m3

Resilience: Unit (Modulus of Resilience)

920 to 2590 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

25 to 38 points

Strength to Weight: Bending

22 to 30 points

Thermal Diffusivity

12 mm2/s

Thermal Shock Resistance

20 to 32 points

Alloy Composition

Among alloy steels, the composition of SAE-AISI 4140 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) 96.8 to 97.8
Chromium (Cr) 0.8 to 1.1
Manganese (Mn) 0.75 to 1.0
Carbon (C) 0.38 to 0.43
Silicon (Si) 0.15 to 0.35
Molybdenum (Mo) 0.15 to 0.25
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

Sintering of Advanced Materials: Fundamentals and Processes, Zhigang Zak Fang (editor), 2010

Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993

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