# ASTM A369 Grade FP21 Cr-Mo Steel

ASTM A369 grade FP21 is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition.

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

The graph bars on the material properties cards below compare ASTM A369 grade FP21 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

140

Elastic (Young's, Tensile) Modulus

190 *GPa* 28 *x 10 ^{6} psi*

Elongation at Break

20 *%*

Fatigue Strength

160 *MPa* 24 *x 10 ^{3} psi*

Poisson's Ratio

0.29

Shear Modulus

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

Shear Strength

300 *MPa* 43 *x 10 ^{3} psi*

Tensile Strength: Ultimate (UTS)

470 *MPa* 69 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

240 *MPa* 34 *x 10 ^{3} psi*

## Thermal Properties

Latent Heat of Fusion

260 *J/g*

Maximum Temperature: Mechanical

470 *°C* 890 *°F*

Melting Completion (Liquidus)

1470 *°C* 2670 *°F*

Melting Onset (Solidus)

1430 *°C* 2600 *°F*

Specific Heat Capacity

470 *J/kg-K* 0.11 *BTU/lb-°F*

Thermal Conductivity

41 *W/m-K* 24 *BTU/h-ft-°F*

Thermal Expansion

13 *µm/m-K*

## Electrical Properties

Electrical Conductivity: Equal Volume

7.7 *% IACS*

Electrical Conductivity: Equal Weight (Specific)

8.8 *% IACS*

## Otherwise Unclassified Properties

Base Metal Price

4.0 *% relative*

Density

7.8 *g/cm ^{3}* 490

*lb/ft*

^{3}Embodied Carbon

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

Embodied Energy

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

Embodied Water

61 *L/kg* 7.3 *gal/lb*

## Common Calculations

PREN (Pitting Resistance)

6.2

Resilience: Ultimate (Unit Rupture Work)

80 *MJ/m ^{3}*

Resilience: Unit (Modulus of Resilience)

150 *kJ/m ^{3}*

Stiffness to Weight: Axial

13 *points*

Stiffness to Weight: Bending

24 *points*

Strength to Weight: Axial

17 *points*

Strength to Weight: Bending

17 *points*

Thermal Diffusivity

11 *mm ^{2}/s*

Thermal Shock Resistance

14 *points*

## Alloy Composition

Among alloy steels, the composition of ASTM A369 grade FP21 is notable for containing a comparatively high amount of chromium (Cr). Chromium is used to improve corrosion resistance and most mechanical properties (particularly at higher temperatures).

Fe | 94.3 to 96.2 | |

Cr | 2.7 to 3.4 | |

Mo | 0.8 to 1.1 | |

Mn | 0.3 to 0.6 | |

Si | 0 to 0.5 | |

C | 0.050 to 0.15 | |

P | 0 to 0.025 | |

S | 0 to 0.025 |

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

## Followup Questions

## Similar Alloys

## Further Reading

ASTM A369: Standard Specification for Carbon and Ferritic Alloy Steel Forged and Bored Pipe for High-Temperature Service