# 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 10 ^{6} psi*

Elongation at Break

6.0 *%*

Fatigue Strength

690 *MPa* 100 *x 10 ^{3} psi*

Fracture Toughness

60 *MPa-m ^{1/2}* 55

*x 10*

^{3}psi-in^{1/2}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 10 ^{6} psi*

Shear Strength

1360 *MPa* 200 *x 10 ^{3} psi*

Tensile Strength: Ultimate (UTS)

2340 *MPa* 340 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

1240 *MPa* 180 *x 10 ^{3} 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/cm ^{3}* 480

*lb/ft*

^{3}Embodied Carbon

1.9 *kg CO _{2}/kg material*

Embodied Energy

26 *MJ/kg* 11 *x 10 ^{3} 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/m ^{3}*

Resilience: Unit (Modulus of Resilience)

4120 *kJ/m ^{3}*

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 *mm ^{2}/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