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SAE-AISI 5120 (SCr420, G51200) Chromium Steel

SAE-AISI 5120 steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 5120 is the designation in both the SAE and AISI systems for this material. G51200 is the UNS number.

It has a moderately low ductility among the SAE-AISI wrought steels in the database.

The graph bars on the material properties cards below compare SAE-AISI 5120 steel to: SAE-AISI wrought steels (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

150

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

16 %

Fatigue Strength

210 MPa 31 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

310 MPa 45 x 103 psi

Tensile Strength: Ultimate (UTS)

500 MPa 73 x 103 psi

Tensile Strength: Yield (Proof)

320 MPa 47 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

420 °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

47 W/m-K 27 BTU/h-ft-°F

Thermal Expansion

12 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.2 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.2 % IACS

Otherwise Unclassified Properties

Base Metal Price

2.1 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.4 kg CO2/kg material

Embodied Energy

19 MJ/kg 8.2 x 103 BTU/lb

Embodied Water

49 L/kg 5.9 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

71 MJ/m3

Resilience: Unit (Modulus of Resilience)

280 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

18 points

Strength to Weight: Bending

18 points

Thermal Diffusivity

13 mm2/s

Thermal Shock Resistance

16 points

Alloy Composition

Among alloy steels, the composition of SAE-AISI 5120 steel is notable for containing comparatively high amounts of manganese (Mn) and chromium (Cr). Manganese is used to improve hardenability, hot workability, and surface quality. There is some loss of ductility and weldability, however. Chromium is used to improve corrosion resistance and most mechanical properties (particularly at higher temperatures).

Iron (Fe) 97.6 to 98.3
Manganese (Mn) 0.7 to 0.9
Chromium (Cr) 0.7 to 0.9
Silicon (Si) 0.15 to 0.35
Carbon (C) 0.17 to 0.22
Sulfur (S) 0 to 0.040
Phosphorus (P) 0 to 0.035

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

Followup Questions

Similar Alloys

Further Reading

ASTM A752: Standard Specification for General Requirements for Wire Rods and Coarse Round Wire, Alloy Steel

ASTM A322: Standard Specification for Steel Bars, Alloy, Standard Grades

ASM Specialty Handbook: Carbon and Alloy Steels, J. R. Davis (editor), 1996

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

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