When strength, toughness, and fatigue resistance are critical, 4340 steel alloy stands out as a top-performing material. Known for its excellent mechanical properties and versatility, 4340 is widely used in aerospace, automotive, and heavy machinery sectors. In this article, we explore what makes 4340 steel alloy unique, its key properties, applications, and why it remains a favorite among engineers and manufacturers.
As a trusted supplier of high-performance alloys, sasaalloy provides top-quality 4340 steel products to meet the toughest industrial standards.
What Is 4340 Steel Alloy?
4340 steel is a nickel-chromium-molybdenum alloy steel, known for its combination of high strength, toughness, and wear resistance. It falls under the AISI (American Iron and Steel Institute) classification and is often used where components are subjected to extreme stress and impact.
Key Composition:
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Carbon: 0.38 – 0.43 percent
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Nickel: 1.65 – 2.00 percent
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Chromium: 0.70 – 0.90 percent
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Molybdenum: 0.20 – 0.30 percent
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Manganese: 0.60 – 0.80 percent
This unique chemical balance enhances hardenability and tensile strength, making 4340 a superior material for high-load components.
Mechanical Properties of 4340 Steel
4340 steel exhibits excellent mechanical performance after proper heat treatment such as quenching and tempering.
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Tensile strength: up to 1080 MPa (157 ksi)
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Yield strength: 745 MPa (108 ksi)
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Hardness: up to 50 HRC after heat treatment
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Good impact resistance
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Excellent fatigue and torsional strength
These properties make 4340 ideal for parts that need to withstand repeated stress over time without failure.
Heat Treatment and Machinability
4340 steel alloy responds well to various heat treatment processes:
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Annealing: For improved machinability
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Quenching and tempering: To achieve maximum strength
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Normalizing: For uniform grain structure
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Nitriding: To enhance surface hardness and wear resistance
Machinability of 4340 is rated fair to good when compared to carbon steels. It is commonly used in a hardened and tempered condition for maximum performance.
sasaalloy offers 4340 steel in multiple heat-treated conditions and formats, including round bars, flat bars, and forged blocks.
Applications of 4340 Steel Alloy
4340 is used in demanding applications across multiple industries due to its ability to resist failure under stress and load. Common uses include:
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Aircraft landing gear and engine components
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Automotive crankshafts, axles, and connecting rods
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Oil and gas drilling tools
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High-strength machine parts and shafts
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Heavy-duty gear systems
It is especially useful in applications that require both toughness and high fatigue strength under cyclic loading.
4340 Steel vs Other Alloy Steels
Compared to other alloy steels like 4140 or 4130:
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4340 has higher nickel content, offering better toughness and deeper hardening capability
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Stronger performance in impact resistance
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More durable in high-stress environments
While 4140 is more economical and commonly used, 4340 is preferred when critical strength is essential.
Why Choose sasaalloy for 4340 Steel?
At sasaalloy, we understand that quality and consistency matter. Our 4340 steel products are manufactured according to international standards such as ASTM A29, AMS 6415, and EN equivalents. We provide:
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Custom-cut dimensions
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Certification with every batch
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Technical support for heat treatment and machining
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Fast delivery and global logistics service
sasaalloy is your reliable partner for high-performance alloy solutions.
Conclusion
4340 steel alloy remains a benchmark material for engineers who demand strength, toughness, and reliability. Its excellent fatigue resistance, high tensile strength, and adaptability through heat treatment make it ideal for the most demanding applications.
Whether you are designing aircraft components, industrial machinery, or high-stress tools, 4340 steel from sasaalloy will deliver the performance you need.
Post time: Jun-23-2025