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AISI 8640
Category Steel
Class Alloy steel
Type Standard
Common Names Nickel-chromium-molybdenum steel
Designations  Germany: DIN 1.6546
Italy: UNI 40 NiCrMo 2 KB
United Kingdom: B.S. Type 7
United States: ASTM A322 , ASTM A331 , ASTM A506 , ASTM A519 , MIL SPEC MIL-S-16974 , SAE J404 , SAE J412 , SAE J770 , UNS G86400


ElementWeight %
C  0.38-0.43 
Mn  0.75-1.00 
P  0.035 (max) 
S  0.04 (max) 
Si  0.15-0.30 
Cr  0.40-0.60 
Ni  0.40-0.70 
Mo  0.15-0.25 

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) 1862  25  oil quenched, fine grained, tempered at 205°C  more
Yield Strength (Mpa) 1669 
Elongation (%) 10 
Reduction in Area (%) 40 
Hardness (HB) 505  25  oil quenched, fine grained, tempered at 205°C more