AISI 8740 Alloy Steel (UNS G87400)

Topics Covered

Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations


Alloy steels contain a broad range of steels whose compositions exceed the limitations of C, Mo, Cr, Va, Mn, Ni, Si, and B associated with carbon steels. These steels are more responsive to mechanical and heat treatments than carbon steels.

The following datasheet provides further details about AISI 8740 alloy steel.

Chemical Composition

The following table shows the chemical composition of AISI 8740 alloy steel.

Element Content (%)
Iron, Fe 96.595-97.72
Manganese, Mn 0.750-1.00
Nickel, Ni 0.400-0.700
Chromium, Cr 0.400-0.600
Carbon, C 0.380-0.430
Molybdenum, Mo 0.200-0.300
Silicon, Si 0.150-0.300
Sulfur, S 0.0400
Phosphorous, P 0.0350

Physical Properties

The physical properties of AISI 8740 alloy steel are outlined in the following table.

Properties Metric Imperial
Density 7.85 g/cm3 0.284 lb/in³

Mechanical Properties

The mechanical properties of annealed AISI 8740 alloy steel are outlined in the table below.

Properties Metric Imperial
Tensile strength 695 MPa 101000 psi
Yield strength 415 MPa 60200 psi
Elastic modulus 190-210 GPa 27557-30458 ksi
Bulk modulus (typical for steel) 140 GPa 20300 ksi
Shear modulus (typical for steel) 80 GPa 11600 ksi
Poisson’s ratio 0.27-0.30 0.27-0.30
Elongation at break (50mm) 22.20% 22.20%
Izod Impact 41 J 30.2
Hardness, Brinell 201 201
Hardness, Knoop (converted from Brinell hardness) 223 223
Hardness, Rockwell B (converted from Brinell hardness) 93 93
Hardness, Rockwell B (converted from Brinell hardness, value below normal HRC range, for comparison only) 13 13
Hardness, Vickers (converted from Brinell hardness) 211 211
Machinability (hot rolled and cold drawn, based on 100 machinability for AISI 1212 steel) 65 65

Thermal Properties

The thermal properties of AISI 8740 alloy steel are highlighted below.

Properties Metric Imperial
Thermal conductivity 46.6 W/mK 323 BTU in/hr.ft².°F

Other Designations

Equivalent materials to AISI 8740 alloy steel are outlined in the table below.

DIN 1.6546 UNI 40 NiCrMo 2 KB B.S. Type 7 AMS 6322 AMS 6322F AMS 6323
AMS 6323D AMS 6325 AMS 6325D AMS 6327D AMS 6358 AMS 6358B
ASTM A322 ASTM A331 ASTM A505 ASTM A519 SAE J770 SAE J412
AMS 6327 MIL SPEC MIL-S-6049 AMS 7496 ASTM A29 ASTM A752 MIL S-6049
SAE J1397 ASTM A320 (L7C, L73) SAE J404      

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