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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.

Our stock range is selected to support aerospace repair applications.

Type 431 Bar (AMS 5628)

Stainless Steel

Type 431 stainless steel bars offer good strength and toughness.

431 stainless is a martensitic stainless steel alloy that offers high strength and toughness with good corrosion resistance.

The product is highly suitable in engineering situations where good corrosion resistance, toughness and tensile strength are essential.

Type 431 stainless bars find use in specific aircraft components, including valves, propellor shafts, fasteners and studs. Note that suitability in specific aerospace applications is limited due to reduced ductility at low temperatures and loss of strength at high temperatures.


431 stainless represents the most corrosion-resistant of all martensitic products, although resistance is lower than most austenitic alloys. The alloy may be pre-heated to improve welding performance, but the annealed condition is best when considering machining. The alloy offers excellent hardenability and combines high yield and tensile strength.

After heat-treatment, 431 stainless steel bar responds well to nitriding, but this is at the expense of overall corrosion resistance.

Sizes & Specifications

Smiths MRO offers the material according to AMS 5628 and other specifications, including 1.4057, MIL-S-18732 and British BS S80. Our 431 stainless round bars are available in stock from 0.25 inches to 6 inches in diameter.

Market Support

We support the aerospace MRO sector with a broad range of alloys, including Type 431 stainless steel. We stock our products in much closer incremental sizes, which means you will purchase products from us that may not require machining, saving you time and money.

We offer unrivalled services too, by combining our stock portfolio with in-house processing operations and rapid product turnaround on an international basis.

Product Features:

    AMS 5628
    BS S80


    Good corrosion resistance
    High yield & tensile strength
    Excellent hardenability
    Good toughness

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