ALLOY & CARBON STEEL 4340

4340 alloy steel is a warmth treatable and low compound steel containing chromium, nickel and molybdenum. It has high durability and quality in the warmth treated condition.


4340 alloy steel is mainly used in power transmission gears and shafts, aircraft landing gear, and other structural parts.




Chemical Composition


Element
Min
Max
Carbon, C
0.35 0.45
Manganese, Mn
0.45 0.70
Silicon, Si
0.10 0.35
Nickel, Ni
1.3 1.8
Molybdenum, Mo
0.20 0.35
Chromium,Cr
0.90 1.40
Sulfur, S
-.--0.5
Phosphorous, P
-.--0.5

Mechanical Properties


Properties
Metric
Imperial
Tensile strength745 MPa108000 psi
Yield strength470 MPa68200 psi
Bulk modulus (typical for steel)140 GPa20300 ksi
Shear modulus (typical for steel)80 GPa11600 ksi
Elastic modulus190-210 GPa27557-30458 ksi
Poisson's ratio0.27-0.300.27-0.30
Elongation at break0.220.22
Reduction of area0.50.5
Hardness, Brinell217217
Hardness, Knoop (converted from Brinell hardness)240240
Hardness, Rockwell B (converted from Brinell hardness)9595
Hardness, Rockwell C (converted from Brinell hardness. Value below normal HRC range, for comparison purposes only)1717
Hardness, Vickers (converted from Brinell hardness)228228
Machinability (annealed and cold drawn. Based on 100 machinability for AISI 1212 steel.)5050

Thermal Properties


Properties
Metric
Imperial
Thermal expansion co-efficient (20°C/68°F, specimen oil hardened, 600°C (1110°F) temper12.3 µm/m°C6.83 µin/in°F
Thermal conductivity (typical steel)44.5 W/mK309 BTU in/hr.ft².°F

Features


Heat Treatment

Tempering

Hardening

Normalizing

Soft Annealing

Forging

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