4340 steel has outstanding harden-ability and high-strength characteristics. Ideal for highly stressed parts operating under severe conditions, aircraft quality AISI 4340 steel alloy material is excellent for shafts and valves that are subject to extreme conditions. The term Aircraft Quality (or AQ steel) which all of our steel carries means it is suitable for the production of aircraft parts which are subject to magnetic particle inspection after machining.


4340 Alloy Steel Grade Chemistry
Fe Ni Cr Mn C Mo Si S P
MIN 95.195 1.65 0.70 0.60 0.370 0.200 0.150
MAX 96.33 2.0 0.90 0.80 0.430 0.300 0.300 0.04 0.035



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