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We are specialists in engineering materials support to improve the aerospace MRO supply chain.

Smiths MRO is a sub-divsion of a larger business - Smiths Advanced Metals.

Smiths MRO focuses on raw material support for the global aircraft maintenance, repair and overhaul market. Our business is supported by a broad and diverse stock range with a dedicated team that provides outstanding service levels required for our industry.

Discover more about Smiths MRO.

4340 Bar (AMS 6414, AMS 6415, AMS 6419)

Aerospace Steel Bar

Our 4340 aircraft steel bars offer outstanding ductility and toughness.

4340 is a nickel and chromium molybdenum steel alloy which finds particular suitability in oil and gas applications.

As a high tensile steel alloy, 4340 steel finds extensive use in commercial engineering applications, which is not exclusive to the oil and gas sector. Aerospace, for example, utilises the alloy in producing aerostructures and landing gear. Most structural applications may benefit from the performance characteristics of 4340, and the material finds widespread use in other markets such as automotive and power generation.


The alloy comes under the category of heat-treatable, low-alloy steels and benefits from ultra-high tensile strength and toughness. Subsequent heat-treatment of the alloy increases the hardenability of the material considerably. Case hardening is particularly suitable. The product also offers superior ductility, creep resistance and fatigue resistance compared to other steel products. The material may be bent or formed due to the material's good ductile characteristics.

The alloy finds favour over 4140 steel in higher strength applications due to the inclusion of nickel in the alloying process, which improves overall hardenability and toughness.

Corrosion Resistance

The material offers good corrosion resistance and maintains good atmospheric corrosion resistance when exposed to the elements. The alloy also provides resistance in marine and freshwater environments. The oil and gas sector utilises this alloy in applications such as downhole tools due to the product's excellent strength and impact toughness.


4340 offers good machinability and excellent weldability. The alloy is also readily formed and therefore lends well to various commercial engineering and fabrication applications.

Product Features:

    AMS 6414
    AMS 6415
    AMS 6419

    Landing gears
    Downhole tooling

    Ultra-high strength
    Excellent hardenability
    Good ductility
    Superior toughness

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