SAE-AISI 81B45 (G81451) Boron Steel
SAE-AISI 81B45 steel is an alloy steel formulated for primary forming into wrought products. 81B45 is the designation in both the SAE and AISI systems for this material. G81451 is the UNS number.
The properties of SAE-AISI 81B45 steel include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare SAE-AISI 81B45 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
160 to 200
Elastic (Young's, Tensile) Modulus
190 GPa 27 x 106 psi
Elongation at Break
12 to 24 %
Fatigue Strength
250 to 350 MPa 36 to 51 x 103 psi
Poisson's Ratio
0.29
Shear Modulus
73 GPa 11 x 106 psi
Shear Strength
340 to 400 MPa 50 to 58 x 103 psi
Tensile Strength: Ultimate (UTS)
540 to 670 MPa 79 to 97 x 103 psi
Tensile Strength: Yield (Proof)
350 to 560 MPa 50 to 81 x 103 psi
Thermal Properties
Latent Heat of Fusion
250 J/g
Maximum Temperature: Mechanical
410 °C 770 °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
40 W/m-K 23 BTU/h-ft-°F
Thermal Expansion
12 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
7.2 % IACS
Electrical Conductivity: Equal Weight (Specific)
8.3 % IACS
Otherwise Unclassified Properties
Base Metal Price
2.3 % 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
49 L/kg 5.8 gal/lb
Common Calculations
Resilience: Ultimate (Unit Rupture Work)
77 to 110 MJ/m3
Resilience: Unit (Modulus of Resilience)
320 to 840 kJ/m3
Stiffness to Weight: Axial
13 points
Stiffness to Weight: Bending
24 points
Strength to Weight: Axial
19 to 24 points
Strength to Weight: Bending
19 to 22 points
Thermal Diffusivity
11 mm2/s
Thermal Shock Resistance
17 to 21 points
Alloy Composition
Among alloy steels, the composition of SAE-AISI 81B45 steel is notable for including boron (B). Boron is used to improve hardenability. It has a substantial effect when added in even tiny amounts.
| Fe | 97 to 98 | |
| Mn | 0.75 to 1.0 | |
| C | 0.43 to 0.48 | |
| Cr | 0.35 to 0.55 | |
| Ni | 0.2 to 0.4 | |
| Si | 0.15 to 0.35 | |
| Mo | 0.080 to 0.15 | |
| S | 0 to 0.040 | |
| P | 0 to 0.035 | |
| B | 0.00050 to 0.0030 |
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
Boron in Steel, S. K. Banerji and J. E. Morral (editors), 1980
ASTM A29: Standard Specification for Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements for
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