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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


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


Rockwell C Hardness


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


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)


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.

Iron (Fe)Fe 93.3 to 94.8
Nickel (Ni)Ni 1.7 to 2.0
Silicon (Si)Si 1.5 to 1.8
Chromium (Cr)Cr 0.7 to 1.0
Manganese (Mn)Mn 0.65 to 0.9
Carbon (C)C 0.38 to 0.43
Molybdenum (Mo)Mo 0.35 to 0.45
Vanadium (V)V 0.050 to 0.1
Phosphorus (P)P 0 to 0.012
Sulfur (S)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