Alloy steel AISI 4028 (UNS G40280)


Updated by Reginald Davey on 9/19/22

Topics Covered

Chemical composition
Physical properties
Mechanical properties
Thermal properties
Other designations

Image Credit: ruhmal/


Alloy steels are designated by four-digit AISI numbers. They contain different types of steels whose compositions exceed the limits of Mn, C, Mo, Si, Ni, Va and B set for carbon steels. They are more reactive to mechanical and thermal treatments.

This article will provide an overview of the composition, properties, processing routes and applications of ASI 4028 alloy steel. The USN number for ASI 4028 steel is G40280.

The following data sheet provides an overview of the chemical composition, mechanical, physical and thermal properties of AISI 4028 alloy steel. ASI 2048 steel is a carbon steel.

Chemical composition

The following table shows the chemical composition of AISI 4028 alloy steel.

Element Contents (%)
Iron, Fe 98.07 – 98.67
Manganese, Mn 0.70 – 0.90
Carbon, C 0.25 – 0.30
Molybdenum, Mo 0.20 – 0.30
Silicon, Si 0.15 – 0.35
Sulphur, S 0.035 – 0.050
Phosphorus, P 0.035

Physical properties

The physical properties of AISI 4028 alloy steel are listed in the following table.

Properties Metric Imperial
Density 7.85gsm3 0.284 lb/in³

Mechanical properties

The mechanical properties of AISI 4028 alloy steel are described in the following table.

Properties Metric Imperial
Modulus of compressibility (typical for steel) 140GPa 20300 ksi
Shear modulus (typical for steel) 80GPa 11600 ksi
Elasticity module 190-210GPa 27557-30458 ksi
Poisson coefficient 0.27-0.30 0.27-0.30
Hardness, Brinell 167 – 212 167 – 212
Hardness, Knoop (converted from Brinell hardness) 212 212
Hardness, Rockwell B (converted from Brinell hardness) 91 91
Hardness, Rockwell C (converted from Brinell hardness. Value below normal HRC range, for comparison purposes only) 11 11
Hardness, Vickers (converted from Brinell hardness) 199 199
Machinability (annealed and cold drawn. Based on a machinability of 100 for AISI 1212 steel) 75 75

Thermal properties

The thermal properties of AISI 4028 alloy steel are given in the following table.

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

Processing and manufacturing

AISI 4028 steel alloys are made using different melting processes. These include vacuum induction melting, EF, LF, VD, IFF and electroslag remelting processes. Some processes can be used in tandem, such as vacuum induction melting and electroslag remelting. These steels can be cold rolled or hot rolled.

Several processes are commonly used to provide forged alloys. Annealing, stress relieving, normalizing and tempering processes, quenching and tempering methods and solution treatment.

The heat treatment of ASI 4028 alloy steel is carried out between 1368 and 1997ohC. Final product surface finishes are either smooth, plated or brushed. Steels are typically supplied to end users in thicknesses of 3-150mm, widths of 1000-4500mm and lengths of 1000-1800mm.


ASI 4028 steels are formed into wrought products, and these alloy steels are used in several critical industrial applications. They are used as structural steels in aircraft, vehicles, ships, bridges, missiles, railways and bridges. Additionally, they are used in machine tools, pressure vessels, and mechanical components that have large cross-sectional areas.

Power generation applications include boiler support rods and turbine mounts. ASI 4028 alloy steels are also used as fasteners in processing plants. Mechanical gears, valve stems, gear shafts, connecting rods, multi-diameter shafts, bolts and nuts all commonly use ASI 4028 steels as materials.

Additionally, these steel alloys are used in the construction of shipping containers, warehouses, and pipeline components for several critical industries.

Other designations

Other designations equivalent to AISI 4028 alloy steel include:

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

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