AISI 4118 Alloy Steel (UNS G41180)

Topics Covered

Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations


Alloy steels contain elements such as chromium, cobalt, nickel. They comprise a wide range of steels with compositions that exceed the limitations of Si, Va, Cr, Ni, Mo, Mn, B and C allocated for carbon steels.

Alloy steels are used in specific melting and deoxidization processes for particular kind of applications. When compared to carbon steels, alloy steels are a lot more responsive to mechanical and heat treatments.

The following datasheet provides an overview of AISI 4118 alloy steel.

Chemical Composition

The chemical composition of AISI 4118 alloy steel is outlined in the following table.

Element Content (%)
Iron, Fe 97.7-98.49
Manganese, Mn 0.70-0.90
Chromium, Cr 0.40-0.60
Carbon, C 0.18-0.230
Silicon, Si 0.15-0.35
Molybdenum, Mo 0.080-0.15
Sulfur, S 0.040
Phosphorous, P 0.035

Physical Properties

The following table shows the physical properties of AISI 4118 alloy steel.

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

Mechanical Properties

The mechanical properties of annealed AISI 4118 alloy steel are displayed in the following table.

Properties Metric Imperial
Tensile strength 517 MPa 75000 psi
Yield strength 365 MPa 52900 psi
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
Elongation at break (in 50 mm) 33.00% 33.00%
Reduction of area 63.70% 63.70%
Hardness, Brinell 137 137
Hardness, Knoop (converted from Brinell hardness) 156 156
Hardness, Rockwell B (converted from Brinell hardness) 75 75
Hardness, Vickers (converted from Brinell hardness) 143 143
Machinability (hot rolled and cold drawn, based on 100 machinability for AISI 1212 steel) 60 60

Thermal Properties

The thermal properties of AISI 4118 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 4118 alloy steel are as follows:.

ASTM A513 ASTM A519 ASTM A752 ASTM A829 SAE J404
SAE J1397 SAE J412 ASTM A505 SAE J770  

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Your comment type