ASTM A372 Grade G Class 55 Steel
ASTM A372 grade G class 55 is ASTM A372 grade G steel in the normalized condition. ASTM A372 Grade G Class 55 is the ASTM designation for this material. Older literature may refer to this material as Type V Grade 3 Class 55, but this is now discouraged.
It has the lowest strength and highest ductility compared to the other variants of ASTM A372 grade G steel.
The graph bars on the material properties cards below compare ASTM A372 grade G 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 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
7.2 % IACS
Electrical Conductivity: Equal Weight (Specific)
8.3 % IACS
Otherwise Unclassified Properties
Base Metal Price
2.2 % 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 5.8 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
13 mm2/s
Thermal Shock Resistance
19 points
Alloy Composition
| Fe | 97.4 to 98.4 | |
| Mn | 0.7 to 1.0 | |
| Cr | 0.4 to 0.65 | |
| C | 0.25 to 0.35 | |
| Si | 0.15 to 0.35 | |
| Mo | 0.15 to 0.25 | |
| 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
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
Steels: Processing, Structure, and Performance, 2nd ed., George Krauss, 2015