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ASTM A372 Grade H Class 55 Steel

ASTM A372 grade H class 55 is ASTM A372 grade H steel in the normalized condition. ASTM A372 Grade H Class 55 is the ASTM designation for this material. Older literature may refer to this material as Type V Grade 4 Class 55, but this is now discouraged.

It has the lowest strength and highest ductility compared to the other variants of ASTM A372 grade H steel.

The graph bars on the material properties cards below compare ASTM A372 grade H class 55 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

200

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

22 %

Fatigue Strength

310 MPa 45 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

410 MPa 60 x 103 psi

Tensile Strength: Ultimate (UTS)

650 MPa 95 x 103 psi

Tensile Strength: Yield (Proof)

430 MPa 63 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

410 °C 780 °F

Melting Completion (Liquidus)

1460 °C 2660 °F

Melting Onset (Solidus)

1420 °C 2580 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

45 W/m-K 26 BTU/h-ft-°F

Thermal Expansion

13 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.2 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.3 % IACS

Otherwise Unclassified Properties

Base Metal Price

2.3 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.5 kg CO2/kg material

Embodied Energy

20 MJ/kg 8.4 x 103 BTU/lb

Embodied Water

49 L/kg 5.9 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

130 MJ/m3

Resilience: Unit (Modulus of Resilience)

500 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

23 points

Strength to Weight: Bending

21 points

Thermal Diffusivity

12 mm2/s

Thermal Shock Resistance

19 points

Alloy Composition

Iron (Fe)Fe 97.3 to 98.3
Manganese (Mn)Mn 0.75 to 1.1
Chromium (Cr)Cr 0.4 to 0.65
Carbon (C)C 0.3 to 0.4
Silicon (Si)Si 0.15 to 0.35
Molybdenum (Mo)Mo 0.15 to 0.25
Phosphorus (P)P 0 to 0.015
Sulfur (S)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

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