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SAE-AISI A9 (T30109) Air-Hardening Steel

SAE-AISI A9 steel is a tool steel. A9 is the designation in both the SAE and AISI systems for this material. T30109 is the UNS number.

The properties of SAE-AISI A9 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 A9 steel to: tool 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

Elastic (Young's, Tensile) Modulus

190 GPa 28 x 106 psi

Poisson's Ratio


Shear Modulus

74 GPa 11 x 106 psi

Tensile Strength: Ultimate (UTS)

770 to 2030 MPa 110 to 290 x 103 psi

Thermal Properties

Latent Heat of Fusion

280 J/g

Melting Completion (Liquidus)

1460 °C 2650 °F

Melting Onset (Solidus)

1410 °C 2580 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

35 W/m-K 20 BTU/h-ft-°F

Thermal Expansion

12 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.9 % IACS

Electrical Conductivity: Equal Weight (Specific)

9.2 % IACS

Otherwise Unclassified Properties

Base Metal Price

7.0 % relative


7.8 g/cm3 480 lb/ft3

Embodied Carbon

4.7 kg CO2/kg material

Embodied Energy

70 MJ/kg 30 x 103 BTU/lb

Embodied Water

82 L/kg 9.7 gal/lb

Common Calculations

PREN (Pitting Resistance)


Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

25 points

Strength to Weight: Axial

28 to 73 points

Strength to Weight: Bending

24 to 46 points

Thermal Diffusivity

9.6 mm2/s

Thermal Shock Resistance

25 to 66 points

Alloy Composition

Iron (Fe)Fe 87 to 90.5
Chromium (Cr)Cr 4.8 to 5.5
Molybdenum (Mo)Mo 1.3 to 1.8
Nickel (Ni)Ni 1.3 to 1.8
Vanadium (V)V 0.8 to 1.4
Silicon (Si)Si 1.0 to 1.2
Carbon (C)C 0.45 to 0.55
Manganese (Mn)Mn 0 to 0.5
Copper (Cu)Cu 0 to 0.25
Phosphorus (P)P 0 to 0.030
Sulfur (S)S 0 to 0.030

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM A681: Standard Specification for Tool Steels Alloy

Tool Steels, 5th ed., George Roberts et al., 1998

Tool Steels: Properties and Performance, Rafael A. Mesquita (editor), 2016

ASM Specialty Handbook: Carbon and Alloy Steels, J. R. Davis (editor), 1996