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.
| Fe | 95.8 to 97 | |
| Ni | 1.7 to 2.0 | |
| Mn | 0.45 to 0.65 | |
| Cr | 0.4 to 0.6 | |
| Si | 0.15 to 0.35 | |
| Mo | 0.2 to 0.3 | |
| C | 0.17 to 0.22 | |
| S | 0 to 0.040 | |
| 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