4340 Alloy Steel

A bar of 4340 Alloy Steel in Dongguan, China
M35- high speed steels

OTAI SPECIAL STEEL is ASTM 4340 alloy steel stockholders and suppliers from china. we have more 16 years experience in 4340 steel round bar, plate, steel flat bar, square supply.

4340 alloy steel is a?high?quality Quenched and Tempered Alloy Structural steel, It?belong to the high quality medium carbon, Oil Quenched & Tempered Hardenss is 28-34 HRc.4340 Annealing delivery hardenss less than 250HB.

4340 steel?properties is very similar with GB 40CrNiMo steel, JIS SNCM439 and DIN 1.6511 36CrNiMo4 Alloy structural steel. At most work environment,4340 is?equivalent with 40CrNiMo, 1.6511 36CrNiMo4, SNCM439 steel.

Related Specifications?ASTM A29/A29M ASTM AISI SAE 4340 UNS G43400 DIN EN 10083/3 JIS G4053 GB/T 3077

4340 steel PDF Data Down

1.Form of Supply

ASTM aisi 4340 Alloy structural steel, we can supply the 4340?round bar, steel flat bar, plate, hexagonal steel bar and steel square block. 4340?steel Round bar?can be sawn to your required lengths as one offs or multiple cut pieces. 4340 Rectangular pieces can be sawn from flat bar or plate to your specific sizes. Ground tool steel bar can be supplied, providing a quality precision finished bar to tight tolerances.

2.4340 Alloy Steel Supply Range

AISI 4340 Steel Round Bar: ?Diameter ?5mm – 1700mm x Length 20000mm Max

SAE?4340 Steel Plate: ? ? Thickness 10mm – 1400mm x Width 210mm-2300mm X Length

ASTM 4340 Steel Flat Bar: ?5mm-210mm x 5mm-210mm x Length

We can make the biggest Steel product 380 tons a piece.

3.Chemical composition

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


ASTM 4340 steel is a alloy structural steel, 4340 is used for engineering structural, Used as require good toughness, high strength, as well as the important conditioning of large size, heavy machinery such as high load of axial, turbine shaft, larger than 250 mm in diameter of helicopter rotor shaft, turbojet engine turbine shaft, blade, high load of transmission parts, fasteners of the crankshaft. Gear, etc.; Can also be used for operating temperature over 400 ℃ of rotor shaft and blade, etc.; And after nitriding processing can also be used to make special performance requirements of the important parts, after low temperature tempering or can be used for ultra-high strength steel after isothermal quenching

5.Regular size and Tolerance

1) Hot Rolled round bar
Diameter Tolerance
Diameter Tolerance
≤12.70 -0.13 ~0.30 >50.80~63.5 -0.25~0.76
12.7~25.40 -0.13~0.41 >63.50~76.20 -0.25~1.02
>25.4~38.10 -0.15~0.51 >76.20~101.60 -0.30~+1.27
>38.1~50.80 -0.20~0.64 >101.60~203.20 -0.38~3.81
2) Hot Rolled steel plate
Thickness Tolerance
Thickness Tolerance
≤25.4 -0.41~0.79 >127~152 -1.60~2.39
>25.4~76 -0.79~1.19 >178~254 -1.98~3.18
>76~127 -1.19~1.60 >254~305 -2.39~3.96

Others 4340 have not specified size, pls contact our?experienced sales team.

AISI 4340 alloy steel can be machined using all conventional techniques. Machining process can be performed in the annealed or normalized and tempered conditions.

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.

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.

AISI 4340 alloy steel is forged at 427 to 1233°C (1800 to 2250°F).

10.Cold Working
AISI 4340 alloy steel can be cold worked using all conventional methods in the annealed condition. It has high ductility.

AISI 4340 alloy steel is annealed at 844°C (1550°F) followed by cooling the furnace.

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.

AISI 4340 alloy steel can be hardened by cold working or heat treatment.


SAE 4340?tool steel round bar and flat sections can be cut to your required sizes. AISI 4340?tool steel ground bar can also be supplied, providing a high quality tool steel precision ground tool steel bar to your required tolerances. ASTM 4340?steel is also available as Ground Flat Stock / Gauge Plate, in standard and nonstandard sizes.

Contact our experienced sales team to help you with your 4340 alloy steel questionsadn enquiry?by?Email or Telphone.?The questions will be reply in 24 hours.

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