AISI 4720 Alloy Steel (UNS G47200)

Topics Covered

Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations


Alloy steels are of many types where each steel type comprises compositions that exceed the limitations of Si, Va, Cr, Ni, Mo, Mn, B and C allocated for carbon steels. Alloy steels have elements such as chromium, cobalt, nickel, etc.

Alloy steels are capable of using unique melting and deoxidization processes for specific kind of applications. When compared with to carbon steels, the alloy steels seem to be a lot more responsive to mechanical and heat treatments.

The following datasheet provides an overview of AISI 4720 alloy steel.

Chemical Composition

The chemical composition of AISI 4720 alloy steel is outlined in the following table.

Element Content (%)
Iron, Fe 96.705-97.78
Nickel, Ni 0.900-1.20
Manganese, Mn 0.500-0.700
Chromium, Cr 0.350-0.550
Carbon, C 0.170-0.220
Silicon, Si 0.150-0.300
Molybdenum, Mo 0.150-0.250
Sulfur, S ≤ 0.0400
Phosphorous, P ≤ 0.0350

Physical Properties

The following table shows the physical properties of AISI 4720 alloy steel.

Properties Metric Imperial
Density 7.85 g/cm3 0.284 lb/in³

Mechanical Properties

The mechanical properties of AISI 4720 alloy steel are displayed in the following table.

Properties Metric Imperial
Bulk modulus (typical for steel) 140 GPa 20300 ksi
Shear modulus (typical for steel) 80.0 GPa 11600 ksi
Elastic modulus 190-210 GPa 27557-30458 ksi
Poisson's ratio 0.27-0.30 0.27-0.30
Hardness, Brinell 187-229 187-229
Hardness, Knoop (converted from Brinell hardness) 230 230
Hardness, Rockwell B (converted from Brinell hardness) 94 94
Hardness, Rockwell C (converted from Brinell hardness, value below normal HRC range, for comparison purposes only) 15 15
Hardness, Vickers (converted from Brinell hardness) 218 218
Machinability (hot rolled and cold drawn, based on 100 machinability for AISI 1212 steel) 65 65

Thermal Properties

The thermal properties of AISI 4720 alloy steel are given in the following table.

Properties Metric Imperial
Thermal conductivity (typical steel) 44.5 W/mK 309 BTU in/hr.ft².°F

Other Designations

Equivalent materials to AISI 4720 alloy steel are:

  • ASTM A322
  • ASTM A331
  • ASTM A519
  • ASTM A535
  • ASTM A711
  • SAE J404
  • SAE J412
  • SAE J770

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