AISI 4340 is a low alloy steel containing nominally 0.4% C, 0.8% Cr, 0.25% Mo and 1.8% Ni. Higher strength levels up to 150 KSI 0.2% PS may be achieved by suitable heat treatment. Often used in preference to AISI 4140 at the higher strength levels because of its better hardenability and improved CVN impact toughness. Generally, the material is used in applications for subsea components such as running tools, seals and hangers.
The hardenability limitations of this grade (depth to which it will harden / obtain the specified mechanical properties after heat treatment) must always be taken into account when designing and selecting equipment.
With targeted cast analysis and Howco’s heat treatment control, high strength levels can be achieved while maintaining good ductility.
| Element | Min | Max |
|---|---|---|
| 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 |
| Ni | 1.65 | 2.00 |
| Mo | 0.20 | 0.30 |
| Fe | 0.00 | - |
| Property | Value |
|---|---|
| U.T.S | 150 KSI Min (1034 N/mm2) |
| 0.2% Proof Stress | 130 KSI Min (896 N/mm2) |
| Elongation | 13% |
| Red of Area | 40% |