Complete specifications for AISI 4340, a premium nickel-chromium-molybdenum steel with exceptional hardenability and strength for aerospace and critical applications.
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 yield may be achieved by suitable heat treatment. Often used in preference to AISI 4140 at higher strength levels because of its better hardenability and improved CVN impact toughness.
Generally used in applications for subsea components such as running tools, seals and hangers. The hardenability limitations must be taken into account when designing equipment. With targeted cast analysis and controlled heat treatment, 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 | Balance | Balance |
| Strength Level | Tensile Strength | Yield Strength | Hardness | Applications |
|---|---|---|---|---|
| Standard Strength | 150 ksi (1034 MPa) | 130 ksi (896 MPa) | 32-38 HRC | General engineering, automotive |
| High Strength | 180 ksi (1241 MPa) | 160 ksi (1103 MPa) | 38-42 HRC | Aerospace, high-stress components |
| Ultra High Strength | 220 ksi (1517 MPa) | 200 ksi (1379 MPa) | 45-50 HRC | Critical aerospace, specialized tools |
Exceptional strength-to-weight ratio with superior hardenability for large sections
Outstanding hardenability and toughness for critical subsea applications
Deep hardening capability for large cross-sections with consistent properties
Lower alloy content, reduced hardenability but better weldability than 4340
Lower carbon and strength but excellent weldability compared to 4340
Similar nickel content but different chemistry with good low-temp properties
Vacuum melted version with vanadium addition for improved cleanliness
Complete chemical composition, mechanical properties, and heat treatment specifications
Jominy hardenability data and section size recommendations for AISI 4340
AMS and aerospace specifications for AISI 4340 in aircraft applications
Get competitive pricing on high-quality AISI 4340 steel with complete material certifications, heat treatment services, and aerospace-grade quality documentation.