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    +44(0)1767 604555
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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 often ship goods to our MRO customers on the same day.

4140 Bar (AMS 6349)

Aerospace Steel Bar

4140 steel bars are aircraft grade material supplied to AMS 6349.

Our 4140 steel alloy bars promote high fatigue strength and good ductility, performing well in elevated temperatures.

The aerospace-grade material has a slightly higher carbon content when compared to 4130 steel and finds use in aircraft components due to the higher strength that, the higher carbon content provides, especially in the production of critical stressed components. Crankshafts, gears and couplings are manufactured using 4140 steel. Our product also finds extensive use in the production of forgings.


This chromium-molybdenum deep hardening steel combines good impact toughness with overall strength. Greater strength and hardness are achieved due to the introduction of molybdenum in the alloying process. Wear resistance is also a positive feature of the alloy, and the material offers good machinability, particularly after annealing. Note that the weldability of the alloy is only rated as fair.

Specifications & Sizes

Round bars are certified to AMS 6349 (normalised condition), AMS 6382 (annealed condition) and also MIL/AMS-S-5626 (various states). AMS 6349 and AMS 6382 round bars are available from Smiths MRO in sizes ranging from 0.25” diameter to 6” diameter.

Processing & Supply

We supply 4130 steel bars to the aerospace MRO sector in standard lengths or cut to size via our in-house processing services. Our bulk warehouse in Biggleswade processes more than 2 million cut billets every year.

We combine our stock range, processing services and systems power to deliver raw material supply services which will improve your supply chain. Speed of response in the MRO sector means everything, and we support you with rapid response times on all stocked products.

Product Features:

    AMS 6349 (normalised condition)
    AMS 6382 (annealed condition)
    MIL/AMS-S-5626 (various states)


    High fatigue strength
    Wear resistance
    Good ductility
    Good elevated temperature performance

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4140 Steel Bar?

Smiths MRO

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