4340 Metal High Strength Alloy Steel Bar Properties

4340 Metal: The Ultimate High-Strength Alloy Steel

When your project demands a material that won’t fail under extreme stress, 4340 metal is the industry standard. As a premier supplier of high-strength structural steels, we provide AISI 4340 in various forms, including round bars, plates, and custom-cut blocks. This nickel-chromium-molybdenum alloy is engineered for components that require a superior combination of strength, toughness, and wear resistance.

Why 4340 Steel Dominates Tough Applications

In the world of heavy machinery and aerospace, “tough” isn’t just a buzzword—it’s a requirement. AISI 4340 steel stands out because it maintains its mechanical integrity in environments where carbon steels or lesser alloys would fracture.

• Superior Toughness: It resists brittle fracture even at low temperatures.
• High Ductility: Unlike many high-strength metals, 4340 can be formed and machined effectively when annealed.
• Deep Hardening: The inclusion of nickel and molybdenum ensures that the material achieves uniform properties throughout the entire cross-section.

Deep Hardenability and Fatigue Resistance

One of the primary reasons we recommend 4340 alloy steel for critical parts is its exceptional hardenability. While other alloys might only harden on the surface, 4340 develops high strength deep into the core of large diameter sections.

Key Performance Factors:

• Resistenza alla fatica: Excellent resistance to cyclic loading, making it the go-to for crankshafts and transmission gears.
• Heat Treatment Versatility: We supply this material in Quenched and Tempered (Q+T) or Annealed states, depending on your specific machining and strength requirements.
• Impact Strength: It absorbs energy efficiently, protecting high-value assemblies from sudden shocks or impact loads.

By choosing our high-quality nickel chromium molybdenum steel, you are investing in a material that has been rigorously tested and verified with full Material Test Certificates (MTC). Whether you are manufacturing aircraft landing gear or heavy-duty power transmission shafts, our 4340 metal provides the reliability your reputation depends on.

Key Features and Performance of 4340 Metal

When your project demands a material that won’t fail under pressure, 4340 metal is the industry standard. This nickel-chromium-molybdenum steel is engineered for high-stress environments where ordinary alloys fall short. We supply this grade to industries that require a perfect balance of ductility, toughness, and extreme strength.

Superior Performance in Heavy Sections

One of the biggest reasons engineers choose AISI 4340 steel over other grades is its deep hardenability. While many steels lose their properties as the section size increases, 4340 maintains high strength throughout the entire cross-section.

• Uniform Hardness: Unlike 4140, which may only harden on the surface in large diameters, 4340 ensures consistent mechanical properties even in massive forged blocks or large round bars.
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• AMS 6414 / AMS 6415: Critical for aerospace applications, often referred to as aircraft quality 4340.
• MIL-S-5000: Military-grade requirements for high-performance structural components.
• DIN EN 10083-3: European standard for quenching and tempering steels.

We provide full Material Test Certificates (MTC) with every order to verify that the chemical composition and mechanical properties align perfectly with these international standards. Whether your project calls for EN24 steel or 1.6511 steel, our stock provides a seamless substitute that meets the rigorous demands of your local or international specifications.

4340 Chemical Composition Breakdown

 

Forniamo 4340 alloy steel with a precise chemical balance that sets it apart from standard carbon steels. As a high-strength nickel chromium molybdenum steel, its performance is dictated by the specific ratios of these alloying elements. This unique combination ensures the material maintains its integrity under extreme stress and temperature fluctuations.

The Role of Nickel, Chromium, and Molybdenum

Each element in the 4340 metal matrix serves a specific structural purpose:

• Nickel (1.65% – 2.00%): This is the key to the material’s superior toughness. It increases impact resistance, especially in low-temperature environments, making it more reliable than 4140. For specialized needs, we also offer high-performance nickel alloy machining services to handle extreme industrial demands.
• Chromium (0.70% – 0.90%): Improves the depth of hardening and provides a baseline for wear and corrosion resistance.
• Molybdenum (0.20% – 0.30%): Prevents brittleness after tempering and ensures the steel retains its strength at higher operating temperatures.

Standard Chemical Ranges for UNS G43400

To ensure our customers receive consistent, high-quality cURL Too many subrequests., we adhere strictly to the UNS G43400 and ASTM standards. The typical chemical makeup includes:

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• cURL Too many subrequests. 0.60% – 0.80%
• Silicio (Si): 0.15% – 0.35%
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• Sulfur (S): ≤ 0.040%

By maintaining these tight tolerances, we guarantee that every batch of AISI 4340 steel we export meets the rigorous safety and performance requirements of the aerospace and defense industries.

4340 Mechanical Properties and Performance

L' 4340 mechanical properties are what make this grade a staple in heavy engineering and high-stress manufacturing. We supply cURL Too many subrequests. cURL Too many subrequests. nickel chromium molybdenum steel, cURL Too many subrequests.

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• Uniform Hardness: cURL Too many subrequests.

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• Annealing: For parts requiring extensive tornitura CNC or milling, we perform a full anneal at 1525°F (830°C) followed by a slow furnace cool. This creates the softest possible state for easier metal removal.

The Quenching and Tempering (QT) Process

Most of our clients require cURL Too many subrequests. because it offers the best balance of strength and ductility. As a nickel chromium molybdenum steel, it has excellent deep-hardening properties, meaning the mechanical properties remain consistent even in large sections.

• Austenitizing: We heat the steel to 1500°F – 1550°F (815°C – 845°C).
• cURL Too many subrequests. An oil quench is mandatory for 4340 metal to prevent cracking while ensuring the material reaches its maximum potential hardness.
• Tempering: After quenching, we temper the steel between 400°F and 1200°F. Lower temperatures maintain high hardness and tensile strength, while higher tempering temperatures increase toughness for parts subject to heavy shock loads.

By controlling these variables, we deliver material that is perfectly optimized for your specific engineering requirements, ensuring every block or bar performs reliably under pressure.

Machining and Welding Tips for 4340 Metal

Working with 4340 alloy steel requires a specific approach due to its high alloy content. Whether you are turning, milling, or joining parts, following these shop floor tips ensures the integrity of the final component and prevents tool breakage or material failure.

Achieving the Best Machinability

In the annealed condition, 4340 metal is rated at approximately 57% machinability compared to 1212 carbon steel. However, most industrial projects require it in a heat-treated state, which makes it significantly tougher on cutting tools.

• Tooling: Always use carbide inserts for high-speed operations to handle the toughness of this nickel chromium molybdenum steel.
• Raffreddamento: Heavy sulfurized oil or chlorinated soluble oil is recommended to manage heat and improve surface finish.
• Rigidity: Maintain high setup rigidity. Because 4340 is prone to work hardening, any vibration or chatter will quickly dull your bits and ruins the tolerances.

Welding Procedures and Crack Prevention

cURL Too many subrequests. 4340 alloy steel is possible, but it is not as straightforward as welding mild steel. Because of its deep-hardening characteristics, it is highly susceptible to hydrogen-induced cracking if the proper thermal cycle isn’t followed.

cURL Too many subrequests. 4340 metal is already in a quenched and tempered state, welding will create a soft zone around the weld. To restore the high-strength properties of the material, the entire part must be re-heat treated after the welding process is complete. Always use low-hydrogen electrodes to minimize the risk of embrittlement.

Common 4340 Metal Applications in High-Stress Industries

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• cURL Too many subrequests. cURL Too many subrequests. cURL Too many subrequests. is free from internal inclusions or cracks, making it safe for critical, high-stress applications.

Certified Quality Standards

Reliability is our baseline. Every shipment of AISI 4340 steel is backed by a Material Test Certificate (MTC) according to EN 10204 3.1, providing full traceability of chemical heat analysis and mechanical performance. Our operations follow strict ISO certification standards, and we implement comprehensive test e controllo qualità measures throughout the supply chain. We guarantee that the material you receive matches your technical specifications exactly, ensuring total confidence in your finished components.