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4340
Qilu
Product Description
ASTM A29 AISI 4340 Alloy Steel Bar
1: AISI 4340 Steel Introduction
AISI 4340 steel is a Ni-Cr-Mo series alloy structural steel with medium carbon. It is an American steel grade from ASTM A29. Known for its exceptional strength, high hardenability, excellent toughness, and good fatigue resistance, AISI 4340 is widely used in critical high-stress components such as aircraft landing gear, crankshafts, connecting rods, heavy-duty gears, and high-strength fasteners. SAE 4340 is typically supplied in a quenched and tempered condition with a hardness range of 28-34 HRC, though it can be further heat-treated to achieve higher strength levels (e.g., for aerospace applications).
4340 Steel Stock in Warehouse
2: AISI 4340 Quality Standard
AISI 4340 steel according to ASTM A29-05.
3: Chemical Composition
Grade | C | Si | Mn | P | S | Cr | Mo | Ni |
4340 | 0.38-0.43 | 0.15-0.35 | 0.60-0.80 | 0.035 | 0.040 | 0.70-090 | 0.20-0.30 | 1.65-2.00 |
4: Mechanical Properties
Grade | H+T | Tensile strength | Yield strength | Elongation | Reduction | Impact Value | Hardness/HB |
| 4340 | +A | / | / | / | / | / | 182 |
4340 | +QT | 920 | 725 | 25 | 50 | 85/91/96 | 300/291/287 |
5: AISI 4340 Steel Equivalent
Country | Japan | Germany | Britain | USA |
Standard | JIS G4103 | EN10250 | BS970 | ASTM A29 |
Grade | SNCM439 | 36CrNiMo4/1.6511 | EN24/817M40 | 4340 |
6: Goods available in China
If you want to purchase AISI 4340 steel from China—whether hot-rolled bars, plates, or forged materials—you can find some stock in the market, but the available quantity is usually limited because the domestic market prefers 40CrNiMoA for similar applications. If you can accept 40CrNiMoA instead of AISI 4340, it may reduce cost and lead time, as it is more commonly produced in China. However, for critical applications requiring exact 4340 specifications, custom production is the best option.
