AISI 4640 Alloy Steel (UNS G46400)

Topics Covered

Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties


The alloying elements in all types of alloy steels tend to form carbides or compounds, rather than being uniformly mixed with carbon and iron. Silicon, nickel and aluminum are some of the elements that form compounds in the steel. Tungsten and vanadium also form carbides to increase the stability and hardness of the finished product.

AISI 4640 alloy steels are characterized by high toughness, strength and corrosion resistance. The following section will discuss in detail about AISI 4640 alloy steel.

Chemical Composition

The chemical composition AISI 4640 alloy steels is outlined in the following table.

Element Content (%)
Nickel, Ni 1.65-2
Manganese, Mn ≤0.6-0.8
Carbon, C ≤0.38-0.43
Silicon, Si ≤0.2-0.35
Molybdenum, Mo 0.2-0.3
Phosphorus, P ≤0.04
Sulfur, S ≤0.04

Physical Properties

The following table shows the physical properties of AISI 4640 alloy steels.

Properties Metric Imperial
Density 7.75 g/cm3 0.280 lb/in3

Mechanical Properties

The mechanical properties of AISI 4640 alloy steels are displayed in the following table.

Properties Metric Imperial
Tensile strength 1276 MPa 185100 psi
Yield strength 1103 MPa 160000 psi
Modulus of elasticity 201-209 GPa 29200-30300 ksi
Bulk modulus 160-170 GPa 23200-24700 ksi
Shear modulus 81-82 GPa 11700-11900 ksi
Poisson’s ratio 0.27-030 0.27-030
Elongation at break 14% 14%
Hardness, Brinell 390 390

Thermal Properties

The thermal properties of AISI 4640 alloy steels are given in the following table

Properties Metric Imperial
Thermal expansion co-efficient (@0-100°C/32-212°F) 10 µm/m°C 5.5 µin/in°F
Thermal conductivity 25 W/mK 173².°F


The following are the applications of AISI 4640 alloy steels:

  • Aircraft engine mounts
  • Welded tubing applications

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