{"id":4126,"date":"2025-06-27T16:07:26","date_gmt":"2025-06-27T13:07:26","guid":{"rendered":"https:\/\/www.defencemetal.com\/?p=4126"},"modified":"2026-09-17T23:07:22","modified_gmt":"2026-09-17T20:07:22","slug":"aisi-8740-uns-g87400-1-6546-40nicrmo2-2-ams-6322-ams-6325-alloy-steel","status":"publish","type":"post","link":"https:\/\/www.defencemetal.com\/index.php\/2025\/06\/27\/aisi-8740-uns-g87400-1-6546-40nicrmo2-2-ams-6322-ams-6325-alloy-steel\/","title":{"rendered":"AISI 8740 (UNS G87400 \/ 1.6546 \/ 40NiCrMo2-2) \u2014 AMS 6322 \/ AMS 6325 Alloy Steel"},"content":{"rendered":"

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We supply AISI 8740.<\/strong> For dimensions, standard equivalents, stock and quotations, take a look at the AISI 8740 product page<\/strong><\/a>.<\/div>\n

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AISI 8740 Alloy Steel: Technical Properties, Industrial Applications and a Standardisation Perspective<\/b><\/b><\/h3>\n

AISI 8740 is a nickel-chromium-molybdenum alloy steel that stands out with its high strength, excellent ductility<\/a> and good machinability properties. This alloy group is preferred especially in critical engineering applications such as aerospace, automotive, defence and highly stressed fasteners. Although AISI 8740 steel is of lower hardness compared with popular alloys such as 4140 and 4340, it has a broad area of application thanks to its improved formability and welding capability.<\/p>\n

AISI 8740 <\/b>Chemical Composition and Mechanical Properties<\/b><\/h3>\n

AISI 8740 steel has a chemical composition balanced so as to contain 0.38\u20130.43% carbon (C), 0.75\u20131.00% manganese (Mn), 0.15\u20130.35% silicon (Si), 0.40\u20130.60% chromium (Cr), 0.20\u20130.30% molybdenum (Mo), 0.40\u20130.70% nickel (Ni) and the remainder iron (Fe). This composition gives the alloy both tensile strength and ductility while at the same time increasing dimensional stability after tempering.<\/p>\n

Its typical mechanical properties are defined, in a heat treated condition, by a tensile strength varying between 930\u20131080 MPa, a yield strength of approximately 760 MPa and an elongation value between 18\u201322%. The high tensile and yield strength make it suitable for systems operating under high load. In addition, the resistance it shows to crack propagation is also a parameter that increases the fatigue life.<\/p>\n

AISI 8740 <\/b>Heat Treatment and Microstructure<\/b><\/h3>\n

AISI 8740 steel is generally used after passing through heat treatments such as annealing, normalising, quenching and tempering (quench & temper). The annealing operation is carried out in the 830\u2013860\u00b0C temperature range, and the microstructure is then made homogeneous with a controlled cooling. The quenching operation, on the other hand, is applied at 850\u2013880\u00b0C, and oil cooling is generally preferred. The subsequent tempering operation is carried out in the 480\u2013650\u00b0C range and the final hardness is set.<\/p>\n

The microstructure formed after heat treatment contains martensite + tempered ferrite phases. This structure is critical in terms of providing sufficient toughness together with high strength. In AISI 8740 steels obtained by special production methods such as vacuum melting (VAR) or electroslag refining (ESR) in particular, the microstructural purity is at the highest level.<\/p>\n

AISI 8740 <\/b>Application Areas<\/b><\/h3>\n

AISI 8740 steel is used in a very wide variety of industries thanks both to its mechanical properties and to its formability advantages:<\/p>\n