A3 Tool Steel (UNS T30103) - Air-Hardening, Medium-Alloy, Cold-Work Steels

Topics Covered

Chemical Composition
Physical Properties
Mechanical Properties
Other Designations


Air-hardening, medium alloy, cold work steels comprise several types that include A2, A3, A4, A6, A7, A8, A9, and A10. These steels also known as group A steels contain sufficient amounts of manganese, molybdenum and chromium. The presence of manganese, molybdenum and chromium in these steels provide full hardness in sections comprising thickness of at least 100 mm (4 in.) in diameter when air cooled.

Group A steels have a carbon content ranging from 0.5 to 2% and are provided with air hardening characteristics that permit minimum distortion and cracking on quenching.

The data below will provide an overview of A3 air-hardening, medium-alloy, cold-work tool steels.

Chemical Composition

The chemical composition of A3 tool steels is predominantly Iron (Fe) with the following elements outlined in the table also present:

Element Content (%)
C 1.20-1.30
Mn 0.40-0.60
Si 0.50
Cr 4.75-5.50
Ni 0.30
Mo 0.90-1.40
V 0.80-1.40
Cu 0.25
P 0.03
S 0.03

Physical Properties

The following table shows the physical properties of A3 tool steels.

Properties Metric Imperial
Density 7.86 g/cm3 0.284 lb/in3

Mechanical Properties

The mechanical properties of A3 tool steels are displayed in the following table.

Properties Metric Imperial
Machinability (based on carbon tool steel) 65% 65%
Shear modulus (typical for steels) 80.0 GPa 11600 ksi
Poisson's ratio 0.27-0.30 0.27-0.30
Elastic modulus 190-210 GPa 27557-30457 ksi

Other Designations

Equivalent materials to A3 tool steels are:

  • ASTM A681
  • FED QQ-T-570
  • UNS T30103

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