# ASTM A372 Grade M Class 85 Steel

ASTM A372 grade M class 85 is ASTM A372 grade M steel in the quenched and tempered condition. ASTM A372 Grade M Class 85 is the ASTM designation for this material. Older literature may refer to this material as Type IX Class A, but this is now discouraged.

The graph bars on the material properties cards below compare ASTM A372 grade M class 85 to: wrought alloy steels in the same category (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

240

Elastic (Young's, Tensile) Modulus

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

Elongation at Break

21 *%*

Fatigue Strength

450 *MPa* 66 *x 10 ^{3} psi*

Poisson's Ratio

0.29

Shear Modulus

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

Shear Strength

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

Tensile Strength: Ultimate (UTS)

810 *MPa* 120 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

660 *MPa* 95 *x 10 ^{3} psi*

## Thermal Properties

Latent Heat of Fusion

250 *J/g*

Maximum Temperature: Mechanical

450 *°C* 850 *°F*

Melting Completion (Liquidus)

1460 *°C* 2670 *°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

13 *µm/m-K*

## Electrical Properties

Electrical Conductivity: Equal Volume

8.0 *% IACS*

Electrical Conductivity: Equal Weight (Specific)

9.1 *% IACS*

## Otherwise Unclassified Properties

Base Metal Price

5.0 *% relative*

Density

7.9 *g/cm ^{3}* 490

*lb/ft*

^{3}Embodied Carbon

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

Embodied Energy

27 *MJ/kg* 11 *x 10 ^{3} BTU/lb*

Embodied Water

61 *L/kg* 7.2 *gal/lb*

## Common Calculations

PREN (Pitting Resistance)

3.4

Resilience: Ultimate (Unit Rupture Work)

160 *MJ/m ^{3}*

Resilience: Unit (Modulus of Resilience)

1140 *kJ/m ^{3}*

Stiffness to Weight: Axial

13 *points*

Stiffness to Weight: Bending

24 *points*

Strength to Weight: Axial

29 *points*

Strength to Weight: Bending

24 *points*

Thermal Diffusivity

12 *mm ^{2}/s*

Thermal Shock Resistance

24 *points*

## Alloy Composition

Fe | 92.5 to 95.1 | |

Ni | 2.8 to 3.9 | |

Cr | 1.5 to 2.0 | |

Mo | 0.4 to 0.6 | |

Mn | 0.2 to 0.4 | |

Si | 0 to 0.3 | |

C | 0 to 0.23 | |

V | 0 to 0.080 | |

P | 0 to 0.015 | |

S | 0 to 0.010 |

All values are % weight. Ranges represent what is permitted under applicable standards.

## Followup Questions

## Further Reading

ASTM A372: Standard Specification for Carbon and Alloy Steel Forgings for Thin-Walled Pressure Vessels

Pressure Vessels: External Pressure Technology, 2nd ed., Carl T. F. Ross, 2011

Manufacture and Uses of Alloy Steels, Henry D. Hibbard, 2005

Steels: Processing, Structure, and Performance, 2nd ed., George Krauss, 2015