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SAE-AISI 4145 (SCM445, G41450) Cr-Mo Steel

SAE-AISI 4145 steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 4145 is the designation in both the SAE and AISI systems for this material. G41450 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 4145 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

310

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

16 %

Fatigue Strength

240 MPa 34 x 103 psi

Poisson's Ratio

0.29

Reduction in Area

46 %

Rockwell C Hardness

33

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

360 MPa 52 x 103 psi

Tensile Strength: Ultimate (UTS)

580 MPa 85 x 103 psi

Tensile Strength: Yield (Proof)

360 MPa 53 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

420 °C 790 °F

Melting Completion (Liquidus)

1460 °C 2650 °F

Melting Onset (Solidus)

1420 °C 2580 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

42 W/m-K 24 BTU/h-ft-°F

Thermal Expansion

13 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.3 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.4 % IACS

Otherwise Unclassified Properties

Base Metal Price

2.4 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.5 kg CO2/kg material

Embodied Energy

20 MJ/kg 8.5 x 103 BTU/lb

Embodied Water

51 L/kg 6.1 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

80 MJ/m3

Resilience: Unit (Modulus of Resilience)

350 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

21 points

Strength to Weight: Bending

20 points

Thermal Diffusivity

11 mm2/s

Thermal Shock Resistance

17 points

Alloy Composition

Among alloy steels, the composition of SAE-AISI 4145 steel is notable for containing comparatively high amounts of chromium (Cr) and manganese (Mn). Chromium is used to improve corrosion resistance and most mechanical properties (particularly at higher temperatures). Manganese is used to improve hardenability, hot workability, and surface quality. There is some loss of ductility and weldability, however.

Iron (Fe) 96.7 to 97.7
Chromium (Cr) 0.8 to 1.1
Manganese (Mn) 0.75 to 1.0
Carbon (C) 0.43 to 0.48
Silicon (Si) 0.15 to 0.35
Molybdenum (Mo) 0.15 to 0.25
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

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