ThePipingMart Blog Grades AISI E4340 Alloy Steel (UNS G43406) – Composition, Properties and Uses

AISI E4340 Alloy Steel (UNS G43406) – Composition, Properties and Uses

AISI E4340

If you’re in the market for a steel alloy that provides excellent strength, wear resistance, and fatigue resistance, then you need to take a look at UNS G43406. AISI E4340 high-strength steel alloy is used for a variety of applications due to its versatility and durability. Let’s take a closer look at some of the uses and properties of E4340 Alloy Steel.

AISI E4340 Composition

Element Content (%)
Iron, Fe 95.175-96.27
Nickel, Ni 1.65-2.00
Chromium, Cr 0.700-0.900
Manganese, Mn 0.650-0.850
Carbon, C 0.380-0.430
Molybdenum, Mo 0.200-0.300
Silicon, Si 0.150-0.300
Phosphorous, P ≤ 0.0250
Sulfur, S ≤ 0.0200

AISI E4340 Physical Properties

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

AISI E4340 Mechanical Properties

Properties Metric Imperial
Tensile strength 745 MPa 108000 psi
Yield strength 470 MPa 68200 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) 22.00% 22.00%
Reduction of area 50.00% 50.00%
Hardness, Brinell 217 217
Hardness, Knoop (converted from Brinell hardness) 240 240
Hardness, Rockwell B (converted from Brinell hardness) 95 95
Hardness, Rockwell C (converted from Brinell hardness, value below normal HRC range, for comparison purposes only) 17 17
Hardness, Vickers (converted from Brinell hardness) 228 228
Machinability (annealed and cold drawn. Based on 100 machinability for AISI 1212 steel) 50 50

AISI E4340 Thermal Properties

Properties Metric Imperial
Thermal expansion co-efficient (austenitized 870°C (1600°F), 545°C (1010°F) temper for 2 hrs/@ -70-20°C/-94- 68°F) 11.3 µm/m°C 6.28 µin/in°F
Thermal conductivity (typical steel) 44.5 W/mK 309 BTU in/hr.ft².°F

AISI E4340 Equivalent

AMS 6415 ASTM A331 ASTM A519 ASTM A752 ASTM A829
MIL S-5000 MIL S-83135 SAE J1397 SAE J404 ASTM A304

AISI E4340 Uses

AISI E4340 can be used in a wide range of applications due to its versatility. It is commonly used in automotive components, aerospace components, shafts and gears, as well as fasteners. It has also been used in military applications such as tanks and armoured personnel carriers due to its strength and durability.

Corrosion Resistance

AISI E4340 has excellent corrosion resistance due to its high chromium content. Chromium helps protect against oxidation and pitting caused by acidic environments or other corrosive materials. Additionally, it offers good stress corrosion cracking resistance when exposed to chloride ions or other water-soluble salts. This makes it an ideal choice for parts that are likely to be exposed to harsh environments or chemicals.

Heat Resistance

AISI E4340 is capable of withstanding very high temperatures without losing its strength or becoming brittle. This makes it suitable for use in applications where parts may be exposed to extreme heat, such as aircraft engines or turbines. Additionally, it is relatively easy to work with at elevated temperatures, so it can be formed into complex shapes without too much difficulty.

Heat Treatment

The heat treatment process for AISI E4340 involves heating it up to a specific temperature before rapidly cooling it down via quenching in oil or water, depending on the desired properties being sought after by the user. The combination of temperature cycles and rapid cooling allows the steel alloy to form grain structures that offer superior strength and other desirable properties, such as wear resistance and fatigue resistance, compared to other steel alloys that have not undergone heat treatment processes.


AISI 4340 can be machined fairly easily with standard machining techniques, although care must be taken at higher speeds because this material can become quite hard during machining operations if not cooled properly during cutting operations. High-speed tools may also be necessary for greater accuracy while maintaining reasonable machining times.


Welding AISI 4340 requires preheating prior to welding, which helps reduce distortion while ensuring superior weld integrity when compared with welding without preheating prior to welding operations. Additionally, special attention must be taken when selecting filler materials because some filler materials may lead to poor weld integrity, which could result in catastrophic failure under certain conditions if not addressed properly before welding operations begin.


Overall, AISI 4340 is an ideal choice for those looking for an all-around steel solution due to its excellent strength, wear resistance, fatigue resistance, corrosion resistance, heat resistance and ease of machining & welding, making it one of the most versatile steels available today! Whether you’re looking for automotive components, aerospace components, shafts & gears, fasteners, military applications tanks & APCs or anything else – you won’t go wrong with this versatile steel alloy!

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