# SAE-AISI 4718 (G47180) Ni-Cr-Mo Steel

SAE-AISI 4718 steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 4718 is the designation in both the SAE and AISI systems for this material. G47180 is the UNS number.

The graph bars on the material properties cards below compare SAE-AISI 4718 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

150

Elastic (Young's, Tensile) Modulus

190 *GPa* 27 *x 10 ^{6} psi*

Elongation at Break

24 *%*

Fatigue Strength

270 *MPa* 39 *x 10 ^{3} psi*

Poisson's Ratio

0.29

Shear Modulus

73 *GPa* 11 *x 10 ^{6} psi*

Shear Strength

330 *MPa* 47 *x 10 ^{3} psi*

Tensile Strength: Ultimate (UTS)

510 *MPa* 74 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

370 *MPa* 53 *x 10 ^{3} psi*

## Thermal Properties

Latent Heat of Fusion

250 *J/g*

Maximum Temperature: Mechanical

420 *°C* 780 *°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

39 *W/m-K* 22 *BTU/h-ft-°F*

Thermal Expansion

11 *µm/m-K*

## Electrical Properties

Electrical Conductivity: Equal Volume

7.3 *% IACS*

Electrical Conductivity: Equal Weight (Specific)

8.4 *% IACS*

## Otherwise Unclassified Properties

Base Metal Price

3.0 *% relative*

Density

7.9 *g/cm ^{3}* 490

*lb/ft*

^{3}Embodied Carbon

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

Embodied Energy

21 *MJ/kg* 9.1 *x 10 ^{3} BTU/lb*

Embodied Water

51 *L/kg* 6.1 *gal/lb*

## Common Calculations

Resilience: Ultimate (Unit Rupture Work)

110 *MJ/m ^{3}*

Resilience: Unit (Modulus of Resilience)

360 *kJ/m ^{3}*

Stiffness to Weight: Axial

13 *points*

Stiffness to Weight: Bending

24 *points*

Strength to Weight: Axial

18 *points*

Strength to Weight: Bending

18 *points*

Thermal Diffusivity

10 *mm ^{2}/s*

Thermal Shock Resistance

17 *points*

## Alloy Composition

Among alloy steels, the composition of SAE-AISI 4718 steel is notable for including nickel (Ni). Nickel is used to improve mechanical properties, and to make the alloy easier to heat treat.

Fe | 96.3 to 97.4 | |

Ni | 0.9 to 1.2 | |

Mn | 0.7 to 0.9 | |

Cr | 0.35 to 0.55 | |

Mo | 0.3 to 0.4 | |

Si | 0.15 to 0.35 | |

C | 0.16 to 0.21 | |

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