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
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Outer Diameter (OD): 10 mm – 200 mm
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Wall Thickness (WT): 1 mm – 20 mm
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Lengths: Cut to customer requirements (up to 6 m)
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Tolerance: ±0.1 mm OD, ±0.05 mm WT per ASTM A519 precise tubing tolerance
Chemical Composition Comparison
| Grade |
C (wt %) |
Si (wt %) |
Mn (wt %) |
P (max %) |
S (max %) |
Cr (wt %) |
Mo (wt %) |
Ni (wt %) |
| 4340 |
0.38 – 0.43 |
0.15 – 0.35 |
0.65 – 0.90 |
≤ 0.010 |
≤ 0.010 |
0.70 – 0.90 |
0.20 – 0.30 |
1.65 – 2.00 |
| 4140 |
0.38 – 0.43 |
0.15 – 0.30 |
0.75 – 1.00 |
≤ 0.035 |
≤ 0.040 |
0.80 – 1.10 |
0.15 – 0.25 |
– |
| 4130 |
0.28 – 0.33 |
0.15 – 0.35 |
0.40 – 0.60 |
≤ 0.035 |
≤ 0.040 |
0.80 – 1.10 |
0.15 – 0.25 |
– |
| 4145 |
0.43 – 0.48 |
0.15 – 0.35 |
0.75 – 1.00 |
≤ 0.035 |
≤ 0.040 |
0.80 – 1.10 |
0.15 – 0.25 |
– |
| 42CrMo4 |
0.38 – 0.45 |
≤ 0.40 |
0.60 – 0.90 |
≤ 0.025 |
≤ 0.035 |
0.90 – 1.20 |
0.15 – 0.30 |
– |
Mechanical Properties Comparison
| Grade |
Tensile Strength (MPa) |
Yield Strength (MPa) |
Elongation (%) |
Hardness |
| 4340 |
860 – 1980 |
740 – 1860 |
11 – 23 |
24 – 53 HRC |
| 4140 |
655 – 950 |
415 |
25.7 |
B 92 (197 HB) |
| 4130 |
586 – 690 |
480 |
20 – 30 |
HRB 90 – 96 |
| 4145 |
880 – 1020 |
620 |
15 – 25 |
– |
| 42CrMo4 |
900 – 1200 |
650 – 750 |
11 – 12 |
270 – 350 HB |
Key Features
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High Strength & Toughness: Exceptional tensile and yield strengths with good ductility for safety under dynamic loading.
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Elevated-Temperature Performance: Maintains mechanical integrity up to 600 °C in tempered conditions.
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Fatigue & Creep Resistance: Ideal for cyclic and sustained-load service in hydraulic, aerospace, and pressure-vessel components.
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Wear & Impact Resistance: Hardenable surface layer provides abrasion resistance while core retains toughness.
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Precision & Finish: Cold-drawn surface finish with concentricity and roundness tolerances suited for high-precision assemblies.
Applicable Standards
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ASTM A519: Seamless carbon and alloy steel mechanical tubing
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EN 10216-2: Seamless steel tubes for pressure purposes – alloy steels with specified elevated-temperature properties
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JIS G3445 / G4105: Alloy steel tubes for general structural and mechanical purposes
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GB/T 8162: Seamless carbon and alloy steel tubes for general structural purpose
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GOST 8732-78: Seamless steel pipes for general purposes
Application Fields
General Sectors
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Aerospace & Defense
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Oil & Gas Exploration
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Automotive & Heavy Machinery
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Hydraulic & Pneumatic Systems
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Power Generation & Pressure Vessels
Specific Uses
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Hydraulic Cylinder Rods & Shafts: High fatigue life under cycling loads.
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Aircraft Landing Gear & Fasteners: Demanding toughness at sub-zero and elevated temperatures.
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Crankshafts & Gears: Superior wear resistance and surface hardenability.
-
Oilfield Drill Collars & Tubing: Sustained load capacity and corrosion resistance in downhole environments.
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Pressure Vessel Components: Reliable performance under pressure and thermal cycling.
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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,
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A: Yes, we could offer the sample for free charge but need pay the cost of freight.
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A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.
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