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AISI 4340 Alloy Steel | 34CrNiMo6 | 1.6582 | SNCM439
Ningshing Special-Steel is the leading stockist of AISI 4340 alloy steel rounds. We have running stock of solid round bars dia.16-300mm. Annealed or Q+T condition. We can also do furthur machining as per customers' requirement.
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. It is mainly used in power transmission gears and shafts, aircraft landing gear, and other structural parts.
Dimensions
Hot Rolled Round: dia.16-300 mm
Forged Round: dia.150-1200 mm
Cold Drawn Round: dia.6-30 mm
Delivery Condition
EAF+LF+VD, Hot Rolled or Forged or Cold Drawn, Annealed or Q+T, Black or Machined surface, UT SEP1921 Class3 C/c or D/d
Equivalence
| AISI / SAE | DIN / W.Nr | JIS | GB | |
| 4340 | 34CrNiMo6 1.6582 | SNCM439 | 40CrNiMoA | |
| Other designations that are equivalent to AISI 4340 alloy steel include the following: | ||||
| AMS 6359 | AMS 6454 | ASTM A331 (4340) | ASTM A711 | SAE J1397 (4340) |
| AMS 6409 | ASTM A29 (4340) | ASTM A506 (4340) | ASTM A752 (4340) | SAE J404 (4340) |
| AMS 6414 | ASTM A320 (L43) | ASTM A519 (4340) | ASTM A829 | SAE J412 (4340) |
| AMS 6415 | ASTM A322 (4340) | ASTM A646 (4340-7) | MIL S-5000 | |
Chemical Composition (%)
| Steel Grade | C | Si | Mn | P | S | Cr | Mo | Ni |
| 34CrNiMo6 | 0.30-0.38 | ≤ 0.40 | 0.50-0.80 | ≤ 0.035 | ≤ 0.035 | 1.30-1.70 | 0.15-0.30 | 1.30-1.70 |
| 1.6582 | ||||||||
| 4340 | 0.38-0.43 | 0.15-0.35 | 0.60-0.80 | ≤ 0.035 | ≤ 0.040 | 0.70-0.90 | 0.20-0.30 | 1.65-2.00 |
| SNCM439 | 0.36-0.43 | 0.15-0.35 | 0.60-0.90 | ≤ 0.030 | ≤ 0.030 | 0.60-1.00 | 0.15-0.30 | 1.60-2.00 |
| 40CrNiMoA | 0.37-0.44 | 0.17-0.37 | 0.50-0.80 | ≤ 0.030 | ≤ 0.030 | 0.60-0.90 | 0.15-0.25 | 1.25-1.65 |
Applications
This low-alloy steel finds many applications where high strength, plasticity required such as large and important parts requiring hardening and tempering as heavy load axle for heavy machinery, axle with diameter over 250mm for steam turbine, axle of rotor wing for helicopter, axle of turbo and turbine blade and heavy load transmission part for jet engine, fasteners and gear for crank axle. It's also used for rotor spindle and blade where temperature over 400ºC. It can be used as important part with special properties after nitriding and ultrahigh strength steel after low tempering isothermal quenching.
Mechanical Properties
| Properties | Metric | Imperial |
| Tensile strength | 745 MPa | 108000 psi |
| Yield strength | 470 MPa | 68200 psi |
| Bulk modulus (typical for steel) | 140 GPa | 20300 ksi |
| Shear modulus (typical for steel) | 80 GPa | 11600 ksi |
| Elastic modulus | 190-210 GPa | 27557-30458 ksi |
| Poisson's ratio | 0.27-0.30 | 0.27-0.30 |
| Elongation at break | 22% | 22% |
| Reduction of area | 50% | 50% |
| Hardness, Brinell | 217 | 217 |
| Hardness, Knoop (converted from Brinell hardness) | 240 | 240 |
| Hardness, Rockwell B (converted from Brinell hardness) | 95 | 95 |
| Hardness, Rockwell C (converted from Brinell hardness. Value below normal HRC range, for comparison purposes only) | 17 | 17 |
| Hardness, Vickers (converted from Brinell hardness) | 228 | 228 |
| Machinability (annealed and cold drawn. Based on 100 machinability for AISI 1212 steel.) | 50 | 50 |
Thermal Properties
| Properties | Metric | Imperial |
| Thermal expansion co-efficient (20°C/68°F, specimen oil hardened, 600°C (1110°F) temper | 12.3 µm/m°C | 6.83 µin/in°F |
| Thermal conductivity (typical steel) | 44.5 W/mK | 309 BTU in/hr.ft².°F |
Fabrication & Heat Treatment
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.
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).
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.
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