Contents
AerMet 340 Alloy Steel Guide: Properties, Products, Processes
- John
AerMet® 340 steel defies conventional trade-offs in high-performance alloys. This guide covers everything you need to know about AerMet 340 alloy steel, from its chemical composition and mechanical properties to heat treatment processes and product specifications.
If you’re looking for high-strength steel that outperforms traditional alloys, SteelPro Group will help you make an informed decision.
What Is AerMet 340 Steel?
AerMet® 310 is an ultra-high-strength, cobalt-containing alloy designed for extreme performance. It offers high strength, toughness, and ductility, making it superior to many high-strength steels. It also offers outstanding shock absorption and durability, making it perfect for aviation, military, and industrial uses.
This alloy is commonly used in landing gear, drive shafts, armor, and structural components that require a strong yet lightweight material. While not stainless steel, it resists corrosion better than most high-strength alloys and is often plated or coated for protection.
AerMet 340 Steel Chemical Composition
| Element | Content (%) |
| Carbon (C) | 0.33% |
| Silicon (Si) | ≤12%* |
| Chromium (Cr) | 2.25% |
| Cobalt (Co) | 15.60% |
| Molybdenum (Mo) | 1.85% |
| Iron (Fe) | Balance |
AerMet 340 Steel Mechanical Properties (Longitudinal)
| Property | Aged Condition | Annealed Condition |
| 0.2% Yield Strength (ksi / MPa) | 300 / 2068 | 155 / 1068 |
| Ultimate Tensile Strength (ksi / MPa) | 345 / 2379 | 202 / 1393 |
| Elongation (%) | 11 | 18 |
| Reduction of Area (%) | 53 | 57 |
| Charpy V-notch (Ft.-lbs. / J) | 11 / 15 | 25 / 34 |
| Hardness (HRC) | 56.5 | 42 |
| Fracture Toughness (ksi√in / MPa√m) | 34 / 37 | N/A |
Heat Treatment Process for Aged Condition:
- 1775°F (968°C) for 1 hour, air cool.
- -100°F (-73°C) for 1 hour, air warm.
- 900°F (482°C) for 2.5 hours, air cool.
- -100°F (-73°C) for 1 hour, air warm.
Heat Treatment Process for Annealed Condition:
- 1250°F (677°C) for 16 hours, air cool.
AerMet 340 Steel Physical Properties
| Property | Value | Metric Value |
| Density | 0.2900 lb/in³ | 8.03 g/cm³ |
AerMet 340 Steel Thermal Properties
| Mean Coefficient of Thermal Expansion (CTE) | |||||
| Temperature Range | Annealed | Heat Treated | |||
| 75°F to (°F) | 25°C to (°C) | × 10⁻⁶/°F | × 10⁻⁶/°C | × 10⁻⁶/°F | × 10⁻⁶/°C |
| 200°F | 93°C | 5.60 | 10.08 | 5.56 | 10.00 |
| 300°F | 149°C | 5.74 | 10.33 | 5.76 | 10.36 |
| 400°F | 204°C | 5.88 | 10.58 | 5.87 | 10.56 |
| 500°F | 260°C | 6.01 | 10.82 | 5.97 | 10.75 |
| 600°F | 316°C | 6.13 | 11.07 | 6.05 | 10.89 |
| 700°F | 371°C | 6.23 | 11.23 | 6.16 | 11.08 |
| 800°F | 427°C | 6.35 | 11.43 | 6.26 | 11.26 |
| 900°F | 482°C | 6.44 | 11.59 | 6.36 | 11.44 |
| 1000°F | 538°C | 6.34 | 11.41 | 6.44 | 11.59 |
AerMet 340 Steel Products Specification
At SteelPro Group, we supply ultra-high-strength steel for industries that require durability, strength, and precision machining. Our materials are available in multiple dimensions and shapes to accommodate various requirements. Below is a detailed specification sheet outlining available options.
| Product Forms | Available Dimensions |
| Round Bar | Diameter: 0.5” – 12” (12.7 mm – 304.8 mm) |
| Hollow Bar | Outer Diameter: 1” – 8” (25.4 mm – 203.2 mm) |
| Wall Thickness: 0.2” – 1.5” (5 mm – 38.1 mm) | |
| Plate | Thickness: 0.25” – 2” (6.35 mm – 50.8 mm) |
| Width: Up to 96” (Up to 2,438 mm) | |
| Sheet | Thickness: 0.04” – 0.5” (1 mm – 12.7 mm) |
| Width: Up to 72” (Up to 1,829 mm) | |
| Strip | Thickness: 0.01” – 0.1” (0.25 mm – 2.54 mm) |
| Width: Custom sizes available | |
| Wire | Diameter: 0.01” – 0.5” (0.25 mm – 12.7 mm) |
| Form: Supplied in coils or cut lengths |
AerMet 340 Steel Applications
AerMet® 310 is used in high-stress industries requiring exceptional strength and durability:
- Aerospace: Landing gear, drive shafts, structural parts.
- Defense: Armor, ballistic protection, fasteners.
- Industry: Shafts, springs, structural supports.
- Motorsports: Suspension, drivetrain components.
AerMet 340 Steel Forging
During forging, the starting temperature should not exceed 2250°F (1232°C), ensuring the material remains within an optimal workability zone. As forging progresses, the material should be worked down to a finishing temperature between 1800°F (982°C) and below 1650°F (899°C) to retain its refined microstructure.
After forging, proper post-forging treatment is essential to restore mechanical integrity:
- Air cooling is required to bring the material back to room temperature gradually.
- A 1250°F (677°C) anneal for 16 hours helps to soften the alloy for subsequent machining.
- Normalization at 1775°F (968°C) ensures uniformity in hardness and strength before further processing.
AerMet 340 Steel Heat Treatment
Although its heat treatment process is intricate and expensive, AerMet® 340 achieves outstanding strength and longevity, making it perfect for aerospace, defense, and industrial uses.
Solution Treatment
- Heat the alloy to 1775°F (968°C) for 1 hour.
- Ensure uniform temperature distribution by using a thermocouple to monitor the load.
- Air cool the material.
Quenching
- Water quenching is not recommended due to the risk of cracking.
- To retain optimal properties, cool the material to 150°F (66°C) within 1-2 hours.
- Large sections (>2 inches (5 cm) in diameter or >1 inch (2.5 cm) thick) require oil quenching.
- A controlled cooling rate must be maintained using a thermocouple in the hottest spot of the load.
Cold Treatment
- After quenching, cool to -100°F (-73°C) and hold for 1 hour.
- This step enhances toughness and improves microstructural stability.
- After cold treatment, air warm to room temperature before proceeding to aging.
If the cold treatment step is omitted, a double aging process is required to achieve comparable strength and toughness:
- First aging cycle: 900°F (482°C) for 3-8 hours, air cool.
- Second aging cycle: Repeat the first cycle after an intermediate refrigeration step.
Aging
- Heat the alloy to 900°F (482°C) for 3-8 hours.
- Air cool to room temperature after aging.
- Important: Aging must never be performed below 875°F (468°C), as it can negatively affect mechanical properties.
Alternative Heat Treatment Process (When Skipping Cold Treatment)
Decarburization Prevention
Like other high-carbon, high-strength alloys, AerMet 340 is susceptible to surface decarburization during heat treatment. To avoid carbon loss, the alloy must be processed in a:
- Neutral atmosphere furnace
- Salt bath
- Vacuum furnace
Post-Heat Treatment Considerations
- Straightening: Some mechanical straightening may be required to correct slight distortions.
- Stress Relief: If stress relief is necessary, heat the material to 350-400°F (177-204°C) for 5 hours before mechanical straightening.
- Final Hardness Achieved: 56-57 HRC after proper aging.
AerMet 340 Steel Machinability
Due to its high hardness and strength, AerMet 340 is more challenging to machine than 4340 steel at HRC 38. Carbide tooling is strongly advised to enhance machining performance and extend tool life.
- Optimal cutting speeds range between 280-350 SFM, depending on the machining setup.
- To minimize internal stresses after rough machining, stress relief at 800°F (427°C) for 1-3 hours is advisable.
AerMet 340 Steel Unlock Superior Strength
At SteelPro Group, we are committed to delivering exceptional material solutions for your high-performance applications. We offer:
- Wide Range of Custom & Standard Sizes – Ensuring flexibility for various manufacturing processes.
- Precision Processing Available – Cut-to-length, heat-treated, and pre-machined options for easy integration.
- Reliable Supply Chain – Strategic stock availability and on-time delivery for critical applications.
- Expert Technical Support – Our specialists provide guidance on material selection and processing.
Contact us today to explore our high-strength alloy options and find the best solution for your project.
