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AISI 4340
Category Steel
Class Alloy steel
Type Standard
Common Names Nickel-chromium-molybdenum steel
Designations  Germany: DIN 1.6565
Japan: JIS SNCM 8
United Kingdom: B.S. 2 S 119 , B.S. 3 S 95 , B.S. 3111 Type 6 , B.S. 817 M 40
United States: AMS 5331 , AMS 6359 , AMS 6359B , AMS 6414 , AMS 6414A , AMS 6415 , AMS 6415G , ASTM A322 , ASTM A331 , ASTM A505 , ASTM A519 , ASTM A547 , ASTM A646 , MIL SPEC MIL-S-16974 , SAE J404 , SAE J412 , SAE J770 , UNS G43400

Composition

ElementWeight %
C  0.38-0.43 
Mn  0.60-0.80 
P  0.035 (max) 
S  0.04 (max) 
Si  0.15-0.30 
Cr  0.70-0.90 
Ni  1.65-2.00 
Mo  0.20-0.30 

Mechanical Properties

Properties Conditions 
T (°C)Treatment
Density (×1000 kg/m3) 7.7-8.03 25  
Poisson's Ratio 0.27-0.30 25  
Elastic Modulus (GPa) 190-210 25  
Tensile Strength (Mpa) 744.6  25  annealed at 810°C  more
Yield Strength (Mpa) 472.3 
Elongation (%) 22.0 
Reduction in Area (%) 49.9 
Hardness (HB) 217  25  annealed at 810°C more
Impact Strength (J)
(Izod)
51.1  25  annealed at 810°C  more

Thermal Properties

Properties Conditions 
T (°C)Treatment
Thermal Expansion (10-6/ºC) 11.5  20-100 more oil hardened, tempered 630°C 

Electric Properties

Properties Conditions 
T (°C)Treatment
Electric Resistivity (10-9W-m) 248  20 more  
Glossary