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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.

We provide in-house processing services to cut your material to size.

4130 Bar (AMS 6346)

Aerospace Steel Bar

4130 aircraft steel bars from Smiths MRO.

Our 4130 steel bars represent one of the most commonly used aircraft-grade steels due to the alloy's good weldability and workability.

Our chromium-molybdenum steel bars benefit from improved hardness and strength compared to standard steels. Smaller sizes may be hardened to achieve higher strength, but it is still used for parts where hardness is less critical in the normalised condition. The fabrication characteristics of the alloy are good, although general corrosion resistance is low. High ductility is another attractive characteristic of the alloy

4130 steel finds typical use in component manufacture that requires fusion welding.

Specifications available

  • AMS6348 – for normalised or hardened and tempered condition
  • AMS6346 – for hardened and tempered condition
  • AMS/MIL-S-6758 – available in multiple conditions and finishes
  • AMS6370 – for normalised condition

We stock 0.5” diameter bars up to large 8” diameter bars according to AMS 6348 or another of the above-listed specifications.

Abrasion Resistance

4130 steel also offers improved abrasion and wear characteristics once nitrided, increasing the scope of applications where the material finds use. Specific wear-resistant features are present before nitriding due to the alloy's molybdenum content, although nitriding enhances performance further.

Typical applications include aircraft structural parts, bearings, gears and general aeronautic engineering. Market sector support includes commercial jets, military aircraft and helicopters.


We offer unrivalled engineering raw material support for the aerospace MRO sector, and our 4130 steel bars are no exception. We offer fast dispatch times from stock which ensures that you receive materials to effect repairs as quickly as possible.

Product Features:

    AMS 6348 (normalised or hardened & tempered condition)
    AMS 6346 (hardened & tempered condition)
    AMS 6370 (for normalised condition)

    Aircraft structural parts
    General aeronautic engineering

    Good weldability
    Good fabricality
    High ductility
    Abrasion resistant

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