4340

AISI/SAE 4340 (UNS G 43400) & E04340 (UNS G43406) a Nickel-Chromium-Molybdenum Alloy Machinery Steel
Typical Analysis
C Mn P S Si Ni Cr Mo
.40 .70 .020 .020 .25 1.80 .80 .25
Characteristics
  • Richly alloyed heavy-duty steel, this nickel-chromium- molybdenum alloy possesses much deeper hardenability than the 4100 series, with increased ductility and toughness. These advantages are realized principally where high strength is required in heavy sections.
  • Also the high fatigue strength of 4340 makes it ideal for all highly stressed parts in the most severe conditions. It may be used in both elevated and low temperature environments; and has good wear resistance.
  • For special service conditions or where material may be subject to magnetic particle inspection we stock Aircraft Quality E-4340 to MIL-S- 5000 and AMS 2301 in condition E.I (Hot rolled Normalized and Tempered) to HB 235 max. AISI 4340 is stocked in the heat treated and stress-relieved condition at approximately 150,000 psi (1034 N/mm2) and in the annealed condition at HB 235 max.
Typical Applications
  • High strength machine parts, heavy-duty shafting, high tensile bolts and studs, gears, axle shafts, crankshafts, boring bars and down-hole drilling components
Typical Heat Treatment
  • Forging
    • Commence 1200℃ max.
    • Finish 950℃
  • Normalizing
    • 900℃ Air cool
  • Hardened & Tempered: (Owing to the air-hardening properties of AISI 4340, normalizing is not recommended except when followed by tempering.) 810℃/860℃. Oil quench.
Mechanical Properties
  • Annealed Typical
  • Tensile Strength - 80,000 psi
  • Yield Strength - 80,000 psi
  • Elongation - 28%
  • Reduction of Area - 57%
  • Hardness - 22 Rc Max, surface
AISI/SAE 4340 (UNS G 43400) & E04340 (UNS G43406) Mechanical Properties
  • Annealed - Typical
Size - inches 1" Dia 2" Dia 4" Dia 8" Dia
Size - mm 25.4 mm 50.8 mm 101.6 mm 203.2 mm
Tensile Strength, psi 114,000 110,000 106,000 104,000
Tensile Strength, N/mm² 786 758 731 717
Yield Strength, psi 91,000 86,000 85,500 81,500
Yield Strength, N/mm² 627 593 590 562
Elongation (%) 20 23 21 22
Reduction of Area (%) 46 49 50 48
HB 229 223 217 217
Machinability 55 55 55 55
AISI/SAE 4340 (UNS G 43400) & E04340 (UNS G43406) Mechanical Properties
  • Heat Treated and Stress Relieved to ASTM A 434 - Typical
Size - inches 2" Dia 3¾" Dia 7" Dia 10" Dia
Size - mm 50.8 mm 95.25 mm 177.8 mm 254 mm
Tensile Strength, psi 162,000 155,904 145,152 144,256
Tensile Strength, N/mm² 1117 1075 1000 995
Yield Strength, psi 145,000 141,568 111,104 124,544
Yield Strength, N/mm² 1000 976 766 858
Elongation (%) 16 19 17 18
Reduction of Area (%) 50 55 47 45
HB 331 321 302 302
AISI/SAE 4340 (UNS G 43400) & E04340 (UNS G43406) Mechanical Properties
  • Normalized and Tempered - Typical. E-4340 AQ MIL-S-5000
Size - inches 2" Dia 4" Dia
Tensile Strength, psi 116,000 112,000
Yield Strength, psi 94,000 87,500
Elongation (%) 20 21
Reduction of Area (%) 53 52
HB 235 229

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