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AISI 4140
Category Steel
Class Alloy steel
Type Standard
Common Names Chromium-molybdenum steel
Designations  France: AFNOR 40 CD 4 , AFNOR 42 CD 4
Germany: DIN 1.7225
Italy: UNI 38 CrMo 4 KB , UNI 40 CrMo 4 , UNI G 4O CrMo 4
Japan: JIS SCM 4 , JIS SCM 4 H
Sweden: SS 2244
United Kingdom: B.S. 708 A 42 , B.S. 708 M 40 , B.S. 709 M 40
United States: AMS 6378 , AMS 6379 , AMS 6381B , AMS 6382 , AMS 6382G , AMS 6390 , AMS 6390A , AMS 6395 , ASTM A322 , ASTM A331 , ASTM A505 , ASTM A519 , ASTM A547 , ASTM A646 , MIL SPEC MIL-S-16974 , SAE J404 , SAE J412 , SAE J770 , UNS G41400

Composition

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  0.80-1.10 
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) 655.0  25  annealed at 815°C  more
Yield Strength (Mpa) 417.1 
Elongation (%) 25.7 
Reduction in Area (%) 56.9 
Hardness (HB) 197  25  annealed at 815°C more
Impact Strength (J)
(Izod)
54.5  25  annealed at 815°C  more

Thermal Properties

Properties Conditions 
T (°C)Treatment
Thermal Expansion (10-6/ºC) 12.3  20-100 more oil hardened, tempered 600°C 
Thermal Conductivity (W/m-K) 42.7  100 more  
Specific Heat (J/kg-K) 473  150-200 more  

Electric Properties

Properties Conditions 
T (°C)Treatment
Electric Resistivity (10-9W-m) 222  20 more  
Glossary