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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
Mechanical Engineers Outlook

Guide for those interested in becoming a mechanical engineer. Includes qualifications, pay, and job duties.

Salary Expectation

8 things to know about the interview question "What's your salary expectation"?

Metal 3D Printing Design Guide

Direct Metal Laser Sintering (DMLS) 3D printing for parts with reduced cost and little waste.

Selecting the Right 3D Printer

Discover how to choose the right 3D printer for your needs and the key performance attributes to consider.