AISI 4340 Alloy steel forged round bar is very popular steel bar by customer, it will choose excellent alloy steel raw material and be forged.

Its main chemical specification :

C:0.38-0.43%     Si:0.15-0.35%   Mn:0.60-0.90% 

Cr:0.70-0.90 %   Ni:1.65-2.0%    Mo:0.20-0.30% 

P:max 0.035% , S:max 0.04%

Its property :

4340 steel can achieve excellent properties of tensile strength ≥ 980MPa and yield strength ≥ 835MPa 

through quenching and tempering heat treatment (quenching+tempering), and is widely used in 

aerospace, deep-sea tools, high load mechanical components and other fields. Its high nickel content 

design allows it to maintain stability even in extreme environments

Core mechanical performance parameters

Tensile strength (σ b): ≥ 980 MPa

Yield strength (σ s): ≥ 835 MPa

Elongation rate (δ 5): ≥ 12% (after heat treatment and tempering)

Shrinkage rate of cross-section (ψ): ≥ 55% (reflecting the material's plastic deformation ability)

Impact energy (A kv): ≥ 78 J (reflecting the material's impact toughness)

Impact toughness value (α kv): ≥ 98 J/cm ² (applicable for dynamic load assessment)

Characteristic Description

Balance between high strength and toughness: 4340 steel can achieve high strength while 

maintaining good toughness through appropriate heat treatment (such as quenching+tempering),

 making it suitable for mechanical components that can withstand high loads (such as gears and shafts).

Wear resistance and fatigue resistance: This material exhibits excellent wear resistance and fatigue resistance in complex stress environments, making it suitable for manufacturing long-term operating mechanical parts.

According to shape

1. Round bar

2. Square bar

3. Flat bar

4. Hollow bar

Its size range following :

1. Round bar diameter: max 800mm, max length 15meters

2. Squre: 800*800mm

3. Flat bar: max width 2000mm

4. Hollow bar: max diameter 600mm

Delivery condition:

1. Forged + annealing + black surface

2. Forged + annealing + polish

3. Forged + quenching /tempering + black surface

4. Forged + quenching /tempering + polish