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AISI 4340 / EN 24

AISI 4340, also known as EN 24, is a high-strength, low-alloy steel that is widely used for manufacturing critical parts requiring a combination of high tensile strength, toughness, and fatigue resistance. It is often used in aerospace, automotive, and heavy-duty engineering applications. This steel grade is known for its excellent hardenability, good machinability, and ability to retain strength and toughness at elevated temperatures. AISI 4340 is commonly supplied in various conditions, including quenched and tempered states.

Steel Properties

AISI 4340 steel exhibits exceptional tensile strength and toughness, which makes it suitable for components that experience heavy loads or are subjected to impact. It also offers good fatigue resistance and has the ability to perform in both high and low-temperature environments. When properly heat-treated, it can achieve hardness levels of 28-32 HRC. The steel’s high nickel content ensures good toughness, while its chromium content improves strength and wear resistance. Due to its alloying elements, AISI 4340 provides excellent hardenability and can be heat-treated to achieve high strength in thick sections.

Application

AISI 4340 is widely used in the manufacture of critical parts such as shafts, gears, axles, crankshafts, turbine blades, and structural components in the aerospace, automotive, and oil & gas industries. It is particularly favored for components that require both strength and toughness, such as aircraft landing gear, high-performance machine components, and heavy-duty gears. Additionally, AISI 4340 is used in applications that require resistance to shock and impact loads, making it suitable for use in heavy machinery, vehicle components, and high-stress environments.