4340 Chromoly Alloy Steel Seameless Round Tube for High Temperature Service

AISI 4340 seamless chromoly tubing is a medium-carbon, low-alloy steel tube engineered for elevated-temperature applications, offering exceptional strength, toughness, fatigue resistance, and wear properties. It is manufactured by cold drawing or hot pilgering processes to tight tolerances, yielding a smooth surface finish and uniform mechanical properties. Typical dimensions range from 10 mm to 200 mm outer diameter with wall thicknesses of 1 mm to 20 mm, accommodating a broad spectrum of hydraulic, aerospace, oil-and-gas, and mechanical applications. The tubing meets key delivery conditions under ASTM A519, EN 10216-2, JIS G3445, GB/T 8162, and GOST 8732-78 standards, ensuring compatibility with global engineering specifications.

Material Description

AISI 4340 is an ultra-high strength chromoly alloy steel containing nickel, chromium, molybdenum, manganese, and silicon, with a carbon content of 0.38 – 0.43 wt %. Its alloying promotes a fine martensitic microstructure upon quenching and tempering, resulting in yield strengths from 740 MPa up to 1860 MPa and tensile strengths of 860 – 1980 MPa, depending on heat treatment. This composition delivers a hardness range of HRC 24 – 53, excellent creep resistance, and superior crack-arrest toughness at elevated temperatures.

Specifications

• Outer Diameter (OD): 10 mm – 200 mm

• Wall Thickness (WT): 1 mm – 20 mm

• Lengths: Cut to customer requirements (up to 6 m)

• Tolerance: ±0.1 mm OD, ±0.05 mm WT per ASTM A519 precise tubing tolerance

Chemical Composition Comparison

Mechanical Properties Comparison

Key Features

• High Strength & Toughness: Exceptional tensile and yield strengths with good ductility for safety under dynamic loading.

• Elevated-Temperature Performance: Maintains mechanical integrity up to 600 °C in tempered conditions.

• Fatigue & Creep Resistance: Ideal for cyclic and sustained-load service in hydraulic, aerospace, and pressure-vessel components.

• Wear & Impact Resistance: Hardenable surface layer provides abrasion resistance while core retains toughness.

• Precision & Finish: Cold-drawn surface finish with concentricity and roundness tolerances suited for high-precision assemblies.

Applicable Standards

• ASTM A519: Seamless carbon and alloy steel mechanical tubing

• EN 10216-2: Seamless steel tubes for pressure purposes – alloy steels with specified elevated-temperature properties

• JIS G3445 / G4105: Alloy steel tubes for general structural and mechanical purposes

• GB/T 8162: Seamless carbon and alloy steel tubes for general structural purpose

• GOST 8732-78: Seamless steel pipes for general purposes

Application Fields

General Sectors

• Aerospace & Defense

• Oil & Gas Exploration

• Automotive & Heavy Machinery

• Hydraulic & Pneumatic Systems

• Power Generation & Pressure Vessels

Specific Uses

• Hydraulic Cylinder Rods & Shafts: High fatigue life under cycling loads.

• Aircraft Landing Gear & Fasteners: Demanding toughness at sub-zero and elevated temperatures.

• Crankshafts & Gears: Superior wear resistance and surface hardenability.

• Oilfield Drill Collars & Tubing: Sustained load capacity and corrosion resistance in downhole environments.

• Pressure Vessel Components: Reliable performance under pressure and thermal cycling.

Q: Are you trading company or manufacturer ?

A: manufacturer,also can do trading.

Q: How long is your delivery time?

A: Generally speaking,it is 10-15 days if the goods are in stock,or it is 30-40 days if the goods are not in stock,

it is according to quantity.

Q: Do you provide samples? is it free or extra ?

A: Yes, we could offer the sample for free charge but need pay the cost of freight.

Q: What is your terms of payment ?

A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.

If you have another question, pls feel free to contact with me.