AISI 8645 Alloy Steel (UNS G86450)

Topics Covered

Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations


Alloy steels consist of alloying elements such as manganese, silicon, nickel, titanium, copper, chromium and aluminum in varying amounts to enhance the properties of steel such as corrosion resistance, hardenability, formability, strength and weldability.

AISI 8645 alloy steel is a nickel-chromium-molybdenum steel. The following section will discuss about AISI 8645 alloy steel.

Chemical Composition

The chemical composition AISI 8645 alloy steels is outlined in the following table.

Element Content (%)
Iron, Fe 96.595 - 97.72
Manganese, Mn 0.75 - 1
Carbon, C 0.43 - 0.48
Nickel, Ni 0.40 - 0.70
Chromium, Cr 0.40 - 0.60
Silicon, Si 0.15 - 0.30
Molybdenum, Mo 0.15 - 0.25
Sulfur, S ≤0.040
Phosphorous, P ≤0.035

Physical Properties

The following table shows the physical properties of AISI 8645 alloy steels.

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

Mechanical Properties

The mechanical properties of AISI 8645 alloy steels are displayed in the following table.

Properties Metric Imperial
Tensile strength 1158 MPa 167953 psi
Yield strength 1034 MPa 149969 psi
Elongation 15% 15%
Bulk modulus 140 GPa 20300 ksi
Shear modulus 80 GPa 11600 ksi
Hardness, Brinell 184 - 235 184 - 235
Hardness, Vickers 220 220
Hardness, Knoop 239 239

Thermal Properties

The thermal properties of AISI 8645 alloy steels are given in the following table.

Properties Metric Imperial
Thermal expansion co-efficient (@0-100°C/32-212°F) 16-17 µm/m°C 8.8-9.4 µin/in°F
Thermal conductivity 16 W/mK 110.94².°F

Other Designations

Other designations that are equivalent to AISI 8645 alloy steels include the following:

  • SAE J404
  • SAE J412
  • SAE J770
  • ASTM A322
  • ASTM A331
  • ASTM A505
  • ASTM A519
  • MIL-SPEC MIL-S-16974

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