AISI 4340 alloy steel is a medium carbon nickel-chromium-molybdenum alloy steel that develops an excellent combination of ductility, toughness, and strength after heat treatment. It offers high hardenability, allowing for consistent strength through section thickness, along with good resistance to shock, impact, wear, and abrasion in the hardened condition. These properties make it well-suited for components subjected to heavy loads and demanding service environments.
Due to its superior hardenability and mechanical performance, AISI 4340 is often utilized in applications where other alloy steels may not achieve the required strength levels. Its ability to withstand high pressures, cyclic stresses, and abrasive conditions makes it a reliable choice for heavy-duty components such as pump shafts, axle shafts, trunnion shafts, and machine tool arbors. In more severe environments, including fluid handling and high-pressure systems, 4340 provides the durability and toughness needed to maintain performance and extend component life.
Choosing the right material for frac pumps and fluid ends?
Read a comparison of 4340 vs 4140.
Available Products
AISI 4340 Chemical Composition
Chemical Composition (wt%) limits of AISI 4340 per ASTM A29*
| Carbon | 0.38-0.43 | Chromium | 0.70-0.90 |
| Manganese | 0.60-0.80 | Molybdenum | 0.20-0.30 |
| Silicon | 0.15-0.35 | Phosphorus | 0.035 |
| Nickel | 1.65-2.00 | Sulfur | 0.040 |
*Maximum, unless range is indicated
AISI 4340 Physical Properties
| Density, lb/in3 | 0.284 |
| Modulus of Elasticity, psi | 29 x 106 |
| Coefficient of Thermal Expansion, 68-212˚F, /˚F | 6.83 x 10-6 |
| Thermal Conductivity, Btu/ft hr ˚F | 30.0 |
| Specific Heat, Btu/lb ˚F | 0.114 |
| Electrical Resistivity, Microhm-in | 6.42 |
AISI 4340 Standards
| ASTM A29 |
| ASTM A322 |
Your Source for AISI 4340 Alloy Steel
At Double Eagle Alloys, we supply 4340 alloy steel in long bar engineered for these demanding services. Contact our team to learn how 4340 alloy steel can support long-term performance and reliability.
Questions? We’d love to help. Contact us today to discuss your needs or to check current availability.
Contact Us
Data shown are typical and provided for informational purposes only. Values should not be considered minimums or maximums for specification or final design. Actual product data may vary, and information may be revised without notice.