AISI 4340 steel stockholders and suppliers from china. Otai special steel have more 16 years experience in 4340 steel plate, round bar, flat bar, square bar, hexagonal bar, sheet, pipe and worm gear supply.
Aisi 4340 Steel is a high quality Quenched and Tempered Alloy Structural steel, Oil Quenched & Tempered Hardness is 28-34 HRc.4340 Annealing delivery hardness less than 250HB.
4340 Alloy structural steel properties is very simliar 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 DIN EN 10083/3 JIS G4053 GB GB/T 3077
1.Form of Supply
ASTM 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.Chemical composition
| C(％) | 0.38～0.43 | Si(％) | 0.15～0.35 | Mn(％) | 0.60～0.80 | P(％) | ≤0.035 |
| S(％) | ≤0.040 | Cr(％) | 0.70～0.90 | Mo(％) | 0.20～0.30 | Ni(%) | 1.65～2.00 |
Equivalent Of aisi 4340 steel- alloy Structure Steel material garde
| USA | Germany | China | Japan | France | England | Italy | Poland | ISO | Austria | Sweden | Spain |
| ASTM/AISI/UNS/SAE | DIN,WNr | GB | JIS | AFNOR | BS | UNI | PN | ISO | ONORM | SS | UNE |
| 4340/ G43400 | 34CRNIMO6/1.6582/DIN17200 | 40CrNiMoA / 45CrNiMoVA | SNCM439 | 40NCD3 | 817M40/BS970-3 | 35NICRMO6(KB) | 2547 | ||||
3.Heat treatment of AIS 4140 steel grade
- Annealing
Heat to 844°C (1550°F), then cooling in the furnace.
- Welding
AISI 4340 alloy steel can be welded using fusion or resistance welding methods. But need Preheat and post heat weld procedures ,
while welding this steel by established methods.
- Heat Treatment
Heat to 830°C (1525°F) then quenching in oil.
- Forging
Forging the AISI 4340 alloy steel at 427 to 1233°C (1800 to 2250°F).
- Cold Working
normal cold worked using all conventional methods in the annealed condition. It have high ductility.
- Annealing
AISI 4340 alloy steel is annealed at 844°C (1550°F) followed by cooling the furnace.
- Tempering
AISI 4340 alloy steel 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.
4.Mechanical Properties
The mechanical properties of annealed aisi 4340 alloy steel are outlined in the table below
| Tensile | Yield | Bulk modulus | Shear modulus | Poisson’s ratio | Izod Impact |
| MPa | MPa | GPa | GPa | ft.lb | |
| 745 | 470 | 140 | 80 | 0.27-0.30 | 84.8 |
5.Applications of aisi 4340 steel material
ASTM aisi 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
6.Regular size and Tolerance of aisi 4340 steel plate
AISI 4340 Steel round bar: Diameter Ø 5mm – 3000mm
ASTM 4340 Steel plate: Thickness 5mm – 3000mm x Width 100mm – 3500mm
SAE 4340 Steel Hexagonal bar: Hex 5mm – 105mm
| 1) Hot Rolled round bar | |||
| Diameter (mm) |
Diameter Tolerance (mm) |
Diameter (mm) |
Diameter Tolerance (mm) |
| ≤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 (mm) |
Thickness Tolerance (mm) |
Thickness (mm) |
Thickness Tolerance (mm) |
| ≤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.
ASTM 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.SAE 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 AISI 4340 Tool steel questionsadn enquiry by Email or Telphone. The questions will be reply in 24 hours.
OTAI SPECIAL STEEL CO., LTD
Email: jack@otaisteel.com TEL: 0086-769-33232622 FAX: 0086-769-88705839
