SAE-AISI 4340M (300M, K44220) Silicon-Vanadium Steel
SAE-AISI 4340M steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 4340M is the designation in both the SAE and AISI systems for this material. K44220 is the UNS number.
It has the lowest ductility among SAE-AISI wrought steels. In addition, it has the highest tensile strength and a moderately low thermal conductivity.
The graph bars on the material properties cards below compare SAE-AISI 4340M 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
710
Elastic (Young's, Tensile) Modulus
190 GPa 27 x 106 psi
Elongation at Break
6.0 %
Fatigue Strength
690 MPa 100 x 103 psi
Fracture Toughness
60 MPa-m1/2 55 x 103 psi-in1/2
Impact Strength: V-Notched Charpy
18 J 13 ft-lb
Poisson's Ratio
0.29
Rockwell C Hardness
55
Shear Modulus
72 GPa 10 x 106 psi
Shear Strength
1360 MPa 200 x 103 psi
Tensile Strength: Ultimate (UTS)
2340 MPa 340 x 103 psi
Tensile Strength: Yield (Proof)
1240 MPa 180 x 103 psi
Thermal Properties
Latent Heat of Fusion
280 J/g
Maximum Temperature: Mechanical
430 °C 800 °F
Melting Completion (Liquidus)
1440 °C 2620 °F
Melting Onset (Solidus)
1400 °C 2550 °F
Specific Heat Capacity
480 J/kg-K 0.11 BTU/lb-°F
Thermal Conductivity
38 W/m-K 22 BTU/h-ft-°F
Thermal Expansion
13 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
7.8 % IACS
Electrical Conductivity: Equal Weight (Specific)
9.1 % IACS
Otherwise Unclassified Properties
Base Metal Price
3.9 % relative
Density
7.8 g/cm3 480 lb/ft3
Embodied Carbon
1.9 kg CO2/kg material
Embodied Energy
26 MJ/kg 11 x 103 BTU/lb
Embodied Water
55 L/kg 6.5 gal/lb
Common Calculations
PREN (Pitting Resistance)
2.2
Resilience: Ultimate (Unit Rupture Work)
120 MJ/m3
Resilience: Unit (Modulus of Resilience)
4120 kJ/m3
Stiffness to Weight: Axial
13 points
Stiffness to Weight: Bending
25 points
Strength to Weight: Axial
84 points
Strength to Weight: Bending
51 points
Thermal Diffusivity
10 mm2/s
Thermal Shock Resistance
70 points
Alloy Composition
Among alloy steels, the composition of SAE-AISI 4340M steel is notable for containing a comparatively high amount of silicon (Si). Silicon content is typically governed by metallurgical processing concerns, and not its effects on final material properties. However, it does have a modest strengthening effect.
| Fe | 93.3 to 94.8 | |
| Ni | 1.7 to 2.0 | |
| Si | 1.5 to 1.8 | |
| Cr | 0.7 to 1.0 | |
| Mn | 0.65 to 0.9 | |
| C | 0.38 to 0.43 | |
| Mo | 0.35 to 0.45 | |
| V | 0.050 to 0.1 | |
| P | 0 to 0.012 | |
| S | 0 to 0.012 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
ASTM A646: Standard Specification for Premium Quality Alloy Steel Blooms and Billets for Aircraft and Aerospace Forgings
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