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.
| Fe | 96.7 to 97.7 | |
| Cr | 0.8 to 1.1 | |
| Mn | 0.75 to 1.0 | |
| C | 0.43 to 0.48 | |
| Si | 0.15 to 0.35 | |
| Mo | 0.15 to 0.25 | |
| S | 0 to 0.040 | |
| 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