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SAE-AISI 4320 (SNCM420, G43200) Ni-Cr-Mo Steel

SAE-AISI 4320 steel is an alloy steel formulated for primary forming into wrought products. 4320 is the designation in both the SAE and AISI systems for this material. G43200 is the UNS number. It has a moderately high base cost among the SAE-AISI wrought steels in the database.

The properties of SAE-AISI 4320 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 4320 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

160 to 240

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

21 to 29 %

Fatigue Strength

320 MPa 47 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

370 to 500 MPa 54 to 72 x 103 psi

Tensile Strength: Ultimate (UTS)

570 to 790 MPa 83 to 110 x 103 psi

Tensile Strength: Yield (Proof)

430 to 460 MPa 62 to 67 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 2590 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

46 W/m-K 27 BTU/h-ft-°F

Thermal Expansion

11 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

3.4 % relative

Density

7.9 g/cm3 490 lb/ft3

Embodied Carbon

1.7 kg CO2/kg material

Embodied Energy

22 MJ/kg 9.4 x 103 BTU/lb

Embodied Water

52 L/kg 6.2 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

140 to 150 MJ/m3

Resilience: Unit (Modulus of Resilience)

480 to 560 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

20 to 28 points

Strength to Weight: Bending

19 to 24 points

Thermal Diffusivity

13 mm2/s

Thermal Shock Resistance

19 to 27 points

Alloy Composition

Among alloy steels, the composition of SAE-AISI 4320 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) 95.8 to 97
Nickel (Ni) 1.7 to 2.0
Manganese (Mn) 0.45 to 0.65
Chromium (Cr) 0.4 to 0.6
Silicon (Si) 0.15 to 0.35
Molybdenum (Mo) 0.2 to 0.3
Carbon (C) 0.17 to 0.22
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

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

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