AISI - 4340 Round Bar

AISI - 4340 Round Bar Specification

Grade
4340

Standard
ASTM A29 / A29M, AMS 6415, DIN 1.6511, JIS SNCM439

Application
Automotive, Aerospace, Forging, Machine Components, Gears, Shafts, Bolts, Fasteners

Diameter
10 mm to 500 mm

Material
AISI 4340 Alloy Steel

Specific Use
High strength and toughness applications, heavy-duty components

Finish
Bright, Black, Polished, Peeled

Type
Round Bar

Length
Customizable, typically up to 6000 mm

Technique
Hot Rolled, Cold Drawn

Tolerance
H9, H10, or as per customer requirement

Processing
Heat Treated, Annealed, Quenched and Tempered

Elongation
12 - 16% (in 50 mm)

Packing
Standard Export Packing, Bundles or as required

Hardness
24 - 28 HRC (annealed), 36 - 45 HRC (quenched/tempered)

Melting Point
1427C - 1460C

Machinability
Good, particularly in annealed condition

Surface Condition
Peeled, Turned, or Ground

Tensile Strength
930 - 1080 MPa

Density
7.85 g/cm3

Yield Strength
850 - 1000 MPa (depending on heat treatment)

Weldability
Limited-preheating and post-weld heat treatment recommended

Corrosion Resistance
Moderate; improved with protective coating

About AISI - 4340 Round Bar

AISI - 4340 Round Bar

A 4340 round bar isan alloy steel conforming to various standards like AISI/SAE J404, ASTM A29, and AMS 6415, offering high tensile strength, toughness, and fatigue resistance.Key components include Nickel, Chromium, and Molybdenum, which contribute to its hardenability and strength.Mechanical properties like tensile strength, yield strength, and Brinell hardness vary significantly based on its heat treatment condition, with options including annealed, normalized, hardened, and tempered.It is available in various finishes such as hot rolled, cold drawn, and bright polished.

Key Specifications and Properties

Chemical Composition:

Contains Nickel, Chromium, and Molybdenum, along with Carbon, Manganese, Silicon, and Phosphorus.
Mechanical Properties:

High tensile strength, high hardness, and good fatigue resistance are characteristic, but properties are highly dependent on the heat treatment.
Heat Treatment:
Can be supplied in various conditions, such as:

Annealed:Softer condition for machining.

Normalized:An intermediate step before hardening.

Hardened and Tempered:To achieve very high strength levels.

Flame or Induction Hardened:For increased surface hardness after pre-hardening.
Standard Specifications:
Conforms to standards including:

SAE (Society of Automotive Engineers):J404.

ASTM (American Society for Testing and Materials):A29.

AMS (Aerospace Material Specifications):AMS 6415 is a common sub-specification for 4340.

European Standards:Equivalent toEN24/817M40(British) and1.6511/36CrNiMo4(European).

Japanese Standards:Equivalent to SNCM439.

Applications

Heavy Industry:Found in applications requiring high strength and toughness, such as in heavy machinery.
Automotive:Used for various components in the automotive sector.
Aerospace:Utilized in demanding applications like aircraft landing gear.
Ordnance:Applied in hardware for military and defense applications.

Versatile Engineering Performance

AISI 4340 Round Bar delivers outstanding performance for critical components in automotive, aerospace, and general engineering. With excellent strength, impact resistance, and ductility, these bars are ideal for gears, shafts, bolts, and fasteners. Their adaptability to various processing techniques makes them a go-to solution for heavy-duty applications requiring high mechanical properties.

Customizable Options for Your Needs

Available in diameters from 10 mm to 500 mm and lengths up to 6000 mm, AISI 4340 Round Bars offer flexibility tailored to your specifications. Choose from surface conditions such as peeled, turned, or ground, and finishes including bright, black, or polished. Your required tolerance (H9, H10, or as per request) and packing preferences are accommodated, ensuring a fit-for-purpose product.

FAQs of AISI - 4340 Round Bar:

Q: How can AISI 4340 Round Bars be processed and finished?

A: AISI 4340 Round Bars can be hot rolled, cold drawn, heat treated, annealed, or quenched and tempered to achieve specific mechanical properties. Surface finishes available include bright, black, polished, peeled, turned, or ground, ensuring suitability for various applications.

Q: What are the primary benefits of using AISI 4340 Round Bar in heavy-duty applications?

A: These bars offer a combination of high yield and tensile strength, excellent toughness, and good machinability, especially in the annealed condition. They are well suited for high-stress and impact environments, making them ideal for gears, shafts, bolts, and other heavily loaded components.

Q: When should preheating and post-weld heat treatment be used during welding?

A: AISI 4340 alloy steel has limited weldability due to its high hardenability. Preheating before welding and post-weld heat treatment are recommended to reduce the risk of cracking and maintain desired mechanical properties. This is especially important for critical, high-strength applications.

Q: Where are AISI 4340 Round Bars typically utilized?

A: These round bars are widely used in industries like automotive, aerospace, machine building, and forging, specifically in components such as gears, shafts, fasteners, and bolts that require high strength and toughness.

Q: What is the corrosion resistance of AISI 4340 Round Bar and how can it be improved?

A: AISI 4340 provides moderate resistance to corrosion, which may not be sufficient for highly corrosive environments. Applying protective coatings or surface treatments can significantly enhance its corrosion resistance.

Q: How does the machinability of AISI 4340 compare in annealed versus hardened conditions?

A: Machinability is generally good in the annealed state, making it easier to cut and shape. After hardening, the material becomes more challenging to machine, so machining is usually performed prior to heat treatment when possible.

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