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AISI 4340 Alloy Steel (UNS G43400)

AISI 4340 Alloy Steel (UNS G43400) Image

Alloy steels are designated by AISI four-digit numbers. They comprise different kinds of steels having composition exceeding the limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va set for carbon steels.

AISI 4340 alloy steel is a heat treatable and low alloy steel containing chromium, nickel and molybdenum. It has high toughness and strength in the heat treated condition.

Category::
Alloy Steel Grades
Chemical Composition:
Chemical Composition The following table shows the chemical composition of AISI 4340 alloy steel.
Element Content (%)
Iron, Fe 95.195 - 96.33
Nickel, Ni 1.65 - 2.00
Chromium, Cr 0.700 - 0.900
Manganese, Mn 0.600 - 0.800
Carbon, C 0.370 - 0.430
Molybdenum, Mo 0.200 - 0.300
Silicon, Si 0.150 - 0.300
Sulfur, S  0.0400
Phosphorous, P  0.0350

Other Designations:
BAR/WIRE:  SHEET/STRIP: PLATE:
AMS-6414 AMS-6415 ASTM-A 304 ASTM-A 320 ASTM-A 322 ASTM-A 331 MIL-S-5000 MIL-S-8844 AMS-6359 ASTM-A 505 AMS-6359
TUBE: PIPE: FORGINGS:
AMS-6414 AMS-6415 ASTM-A 519 COMMERCIAL AMS-6414 AMS-6415 ASTM-A 646

Inventory:
In Stock
Mechanical Properties:
Mechanical Properties The mechanical properties of annealed AISI 4340 alloy steel are displayed in the following table.
Properties Imperial
Tensile strength 108000 psi
Yield strength 68200 psi
Bulk modulus (typical for steel) 20300 ksi
Shear modulus (typical for steel) 11600 ksi
Elastic modulus 27557-30458 ksi
Poisson's ratio 0.27-0.30
Elongation at break 22%
Reduction of area 50%
Hardness, Brinell 217
Hardness, Knoop (converted from Brinell hardness) 240
Hardness, Rockwell B (converted from Brinell hardness) 95
Hardness, Rockwell C (converted from Brinell hardness. Value below normal HRC range, for comparison purposes only) 17
Hardness, Vickers (converted from Brinell hardness) 228
Machinability (annealed and cold drawn. Based on 100 machinability for AISI 1212 steel.) 50

Density:
0.284 lb/in³
Thermal Properties:
Thermal Properties The following table outlines the thermal properties of AISI 4340 alloy steel.
Properties Imperial
Thermal expansion co-efficient (20°C/68°F, specimen oil hardened, 600°C (1110°F) temper 6.83 µin/in°F
Thermal conductivity (typical steel) 309 BTU in/hr.ft².°F

Forming:
AISI 4340 alloy steel has good ductility and formability in the annealed condition. It can be bent or formed by pressing or spinning in the annealed state.
Welding:
AISI 4340 alloy steel can be welded using fusion or resistance welding methods. Preheat and post heat weld procedures are followed while welding this steel by established methods.
Heat Treatment:
AISI 4340 alloy steel is heat treated at 830°C (1525°F) followed by quenching in oil.
Forging:
AISI 4340 alloy steel is forged at 427 to 1233°C (1800 to 2250°F).
Hot Working:

Cold Working:
AISI 4340 alloy steel can be cold worked using all conventional methods in the annealed condition. It has high ductility.
Annealing:
AISI 4340 alloy steel is annealed at 844°C (1550°F) followed by cooling the furnace.
Tempering:
AISI 4340 alloy steel should be in the heat treated or normalized and heat treated condition before tempering. Tempering temperatures depend upon the desired strength level.
Hardening:
AISI 4340 alloy steel can be hardened by cold working or heat treatment.
Melting Point:
2600°F
Applications:
AISI 4340 alloy steel is mainly used in power transmission gears and shafts, aircraft landing gear, and other structural parts.
Machinability:
AISI 4340 alloy steel can be machined using all conventional techniques. Machining process can be performed in the annealed or normalized and tempered conditions.

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AISI 4340 Alloy Steel (UNS G43400)

AISI 4340 Alloy Steel (UNS G43400) Image

Alloy steels are designated by AISI four-digit numbers. They comprise different kinds of steels having composition exceeding the limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va set for carbon steels.

AISI 4340 alloy steel is a heat treatable and low alloy steel containing chromium, nickel and molybdenum. It has high toughness and strength in the heat treated condition.