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SAE-AISI A4 (T30104) Air-Hardening Steel

SAE-AISI A4 steel is a tool steel. A4 is the designation in both the SAE and AISI systems for this material. T30104 is the UNS number.

The properties of SAE-AISI A4 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 A4 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 27 x 106 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Tensile Strength: Ultimate (UTS)

710 to 2050 MPa 100 to 300 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Melting Completion (Liquidus)

1450 °C 2640 °F

Melting Onset (Solidus)

1410 °C 2570 °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

7.4 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.6 % IACS

Otherwise Unclassified Properties

Base Metal Price

3.9 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.8 kg CO2/kg material

Embodied Energy

24 MJ/kg 10 x 103 BTU/lb

Embodied Water

59 L/kg 7.0 gal/lb

Common Calculations

PREN (Pitting Resistance)

5.3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

25 to 73 points

Strength to Weight: Bending

23 to 46 points

Thermal Diffusivity

11 mm2/s

Thermal Shock Resistance

23 to 67 points

Alloy Composition

Iron (Fe) 92 to 95.5
Manganese (Mn) 1.8 to 2.2
Chromium (Cr) 0.9 to 2.2
Molybdenum (Mo) 0.9 to 1.4
Carbon (C) 1.0 to 1.1
Silicon (Si) 0 to 0.5
Nickel (Ni) 0 to 0.3
Copper (Cu) 0 to 0.25
Phosphorus (P) 0 to 0.030
Sulfur (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