# ASTM A231 Chromium-Vanadium Spring Steel

ASTM A231 spring steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the quenched and tempered condition.

It has a very high tensile strength among wrought alloy steels in the same category. In addition, it has a very low ductility and a fairly high thermal conductivity.

The graph bars on the material properties cards below compare ASTM A231 spring steel 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

540

Elastic (Young's, Tensile) Modulus

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

Elongation at Break

14 *%*

Fatigue Strength

1000 *MPa* 150 *x 10 ^{3} psi*

Poisson's Ratio

0.29

Reduction in Area

46 *%*

Shear Modulus

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

Shear Strength

1080 *MPa* 160 *x 10 ^{3} psi*

Tensile Strength: Ultimate (UTS)

1790 *MPa* 260 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

1570 *MPa* 230 *x 10 ^{3} psi*

## Thermal Properties

Latent Heat of Fusion

250 *J/g*

Maximum Temperature: Mechanical

420 *°C* 790 *°F*

Melting Completion (Liquidus)

1460 *°C* 2650 *°F*

Melting Onset (Solidus)

1410 *°C* 2580 *°F*

Specific Heat Capacity

470 *J/kg-K* 0.11 *BTU/lb-°F*

Thermal Conductivity

52 *W/m-K* 30 *BTU/h-ft-°F*

Thermal Expansion

13 *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

2.3 *% relative*

Density

7.8 *g/cm ^{3}* 490

*lb/ft*

^{3}Embodied Carbon

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

Embodied Energy

28 *MJ/kg* 12 *x 10 ^{3} BTU/lb*

Embodied Water

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

## Common Calculations

Resilience: Ultimate (Unit Rupture Work)

230 *MJ/m ^{3}*

Stiffness to Weight: Axial

13 *points*

Stiffness to Weight: Bending

24 *points*

Strength to Weight: Axial

64 *points*

Strength to Weight: Bending

42 *points*

Thermal Diffusivity

14 *mm ^{2}/s*

Thermal Shock Resistance

53 *points*

## Alloy Composition

Among alloy steels, the composition of ASTM A231 spring steel is notable for including vanadium (V). Vanadium has a strong hardening effect, but this effect is particularly sensitive to the type of tempering.

Fe | 96.7 to 97.7 | |

Cr | 0.8 to 1.1 | |

Mn | 0.7 to 0.9 | |

C | 0.48 to 0.53 | |

Si | 0.15 to 0.35 | |

V | 0.15 to 0.3 | |

P | 0 to 0.040 | |

S | 0 to 0.040 |

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

## Followup Questions

## Similar Alloys

## Further Reading

ASTM A231: Standard Specification for Chromium-Vanadium Alloy Steel Spring Wire

Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993

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

Ferrous Materials: Steel and Cast Iron, Hans Berns and Werner Theisen, 2008

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