4130 HT
4130 heat treat is an aircraft quality chromium-molybdenum alloy steel primarily melted in an electric air furnace.
Aircraft Alloy 4340 is a high-strength, medium-carbon, low-alloy steel engineered for exceptional toughness, fatigue resistance, and structural reliability in demanding aerospace and industrial applications. Through controlled heat treatment and normalization, 4340 develops superior mechanical properties, deep hardenability, and improved impact resistance, making it ideal for critical, load-bearing components. This aircraft-quality alloy is commonly used in aerospace hardware, landing gear components, shafts, and other parts subjected to high stress and dynamic loading conditions.
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Key Benefits:
| Element | Min | Max |
|---|---|---|
| Carbon, C | 0.4 | 0.43 |
| Manganese, Mn | 0.65 | 0.9 |
| Silicon, Si | 1.45 | 1.8 |
| Phosphorus, P | - | 0.01 |
| Sulfur, S | - | 0.008 |
| Chromium, Cr | 0.7 | 0.95 |
| Molybdenum, Mo | 0.35 | 0.45 |
| Nickel, Ni | 1.65 | 2 |
| Copper, Cu | - | 0.35 |
| Vanadium, V | 0.05 | 0.1 |
Fry Steel has an ISO 9001 certification specific to aerospace SAE standards AS9100D & AS9120B, so we meet the global industry quality standard. Our suppliers are held to the same standard, and the stock is traceable. We’re audited every year by International Standards Authority, Inc. to ensure our quality program meets all current requirements.
We’ve had a really positive experience working with their team. The sales department is always responsive and turns around material quotes quickly. The quality department has also been incredibly helpful and is always ready to answer any questions we have about material certifications.
Fry Steel Company is a leading raw material supplier globally. Fry Steel’s ISO 13485/9001/AS9120/AS9100D certification is your assurance that we meet the global industry standard for quality. We hold our suppliers to the same standard, so all of our metal stock is completely traceable. Our ISO 13485/9001/AS9120/AS9100 program is audited annually by accredited third parties.
Yes — and that’s one of its biggest advantages.
4340 responds extremely well to:
Oil quenching
Tempering
Through-hardening
It offers deep hardenability, meaning even thick sections can achieve consistent mechanical properties throughout.
While both are chromium-molybdenum steels:
4340 contains nickel, which improves toughness and fatigue resistance.
4140 does not contain nickel and generally has slightly lower toughness at similar strength levels.
4340 is preferred for more demanding aerospace and high-stress applications.
If impact resistance and fatigue life matter, 4340 is often the better choice.
4340 can be welded, but:
It requires preheat and post-weld heat treatment.
It has higher hardenability, so improper welding can cause cracking.
It is generally not chosen when heavy welding is required.
Proper procedures are critical.
Yes — excellent fatigue strength is one of its key advantages.
Because of its:
High toughness
Strength after heat treatment
Resistance to crack propagation
It is commonly used in cyclic load applications like landing gear and rotating shafts.
No — 4340 is not stainless steel and does not offer corrosion resistance.
It typically requires:
Coating
Plating
Painting
Or controlled environments
For corrosion resistance, stainless alloys like 15-5 or 17-4 are better options.