SAE-AISI 4012 (G40120) Molybdenum Steel
SAE-AISI 4012 steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 4012 is the designation in both the SAE and AISI systems for this material. G40120 is the UNS number.
It has the lowest tensile strength and a moderately high thermal conductivity among SAE-AISI wrought steels.
The graph bars on the material properties cards below compare SAE-AISI 4012 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
130
Elastic (Young's, Tensile) Modulus
190 GPa 27 x 106 psi
Elongation at Break
23 %
Fatigue Strength
160 MPa 23 x 103 psi
Poisson's Ratio
0.29
Shear Modulus
73 GPa 11 x 106 psi
Shear Strength
270 MPa 39 x 103 psi
Tensile Strength: Ultimate (UTS)
420 MPa 61 x 103 psi
Tensile Strength: Yield (Proof)
220 MPa 32 x 103 psi
Thermal Properties
Latent Heat of Fusion
250 J/g
Maximum Temperature: Mechanical
400 °C 760 °F
Melting Completion (Liquidus)
1460 °C 2670 °F
Melting Onset (Solidus)
1420 °C 2590 °F
Specific Heat Capacity
470 J/kg-K 0.11 BTU/lb-°F
Thermal Conductivity
51 W/m-K 30 BTU/h-ft-°F
Thermal Expansion
13 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
7.1 % IACS
Electrical Conductivity: Equal Weight (Specific)
8.1 % 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 8.2 x 103 BTU/lb
Embodied Water
47 L/kg 5.6 gal/lb
Common Calculations
Resilience: Ultimate (Unit Rupture Work)
82 MJ/m3
Resilience: Unit (Modulus of Resilience)
130 kJ/m3
Stiffness to Weight: Axial
13 points
Stiffness to Weight: Bending
24 points
Strength to Weight: Axial
15 points
Strength to Weight: Bending
16 points
Thermal Diffusivity
14 mm2/s
Thermal Shock Resistance
12 points
Alloy Composition
Among alloy steels, the composition of SAE-AISI 4012 steel is notable for containing comparatively high amounts of manganese (Mn) and silicon (Si). Manganese is used to improve hardenability, hot workability, and surface quality. There is some loss of ductility and weldability, however. Silicon content is typically governed by metallurgical processing concerns, and not its effects on final material properties. However, it does have a modest strengthening effect.
| Fe | 98.2 to 98.9 | |
| Mn | 0.75 to 1.0 | |
| Si | 0.15 to 0.35 | |
| Mo | 0.15 to 0.25 | |
| C | 0.090 to 0.14 | |
| 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
Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993
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