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SAE-AISI 4042 (G40420) Molybdenum Steel

SAE-AISI 4042 steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the cold worked (strain hardened) condition. 4042 is the designation in both the SAE and AISI systems for this material. G40420 is the UNS number.

It has a moderately high tensile strength and a moderately low ductility among SAE-AISI wrought steels.

The graph bars on the material properties cards below compare SAE-AISI 4042 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

200

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

13 %

Fatigue Strength

360 MPa 52 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

410 MPa 59 x 103 psi

Tensile Strength: Ultimate (UTS)

680 MPa 98 x 103 psi

Tensile Strength: Yield (Proof)

570 MPa 82 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

400 °C 760 °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

49 W/m-K 28 BTU/h-ft-°F

Thermal Expansion

12 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.1 % 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

1.5 kg CO2/kg material

Embodied Energy

19 MJ/kg 8.3 x 103 BTU/lb

Embodied Water

47 L/kg 5.6 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

81 MJ/m3

Resilience: Unit (Modulus of Resilience)

860 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

24 points

Strength to Weight: Bending

22 points

Thermal Diffusivity

13 mm2/s

Thermal Shock Resistance

22 points

Alloy Composition

Among alloy steels, the composition of SAE-AISI 4042 steel is notable for containing comparatively high amounts of manganese (Mn) and carbon (C). Manganese is used to improve hardenability, hot workability, and surface quality. There is some loss of ductility and weldability, however. Carbon is used to increase strength at the cost of a decrease in formability.

Iron (Fe) 97.9 to 98.6
Manganese (Mn) 0.7 to 0.9
Carbon (C) 0.4 to 0.45
Silicon (Si) 0.15 to 0.35
Molybdenum (Mo) 0.2 to 0.3
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

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