About Smiths Advanced

We are a leading stockholder and global supplier of metals and plastics into Aerospace & Space, Chemical, Defence, Medical, MRO, Naval, Nuclear, Oil & Gas and Power industries.

We make high quality materials available in a fast, cost-effective and convenient package and provide a consistent supply path for all our customers.

Processing Services

BS S106 Steel Bar (4S106D)

Chromium-Molybdenum Nitriding Steel

BS S106 is ideal for applications including gears and crankshafts due to the alloys hardness and wear characteristics.

Classed as nitriding steel, BS S106 is a British Aerospace Standard aerospace steel alloy grade which contains 3% chromium molybdenum.

Engineering steel EN40B (744M24) is a direct equivalent. The alloy is typically supplied in the hardened, tempered and stress-relieved condition as bright bar, and the material develops a hard casing after heat treatment. Performance characteristics of the alloy include medium tensile strength, high fatigue strength and excellent wear/abrasion resistance. The material may also be supplied under the Rolls Royce specification (MSRR 6001).


BS S106 is produced using the air melt or VAR method (vacuum arc remelting). Excellent transverse properties are present after the VAR production process, and the alloy also finds suitability in elevated temperature applications. The product is suitable for applications requiring a combination of wear resistance, fatigue resistance and moderate strength. We stock BS S106 in various sizes to suit your engineering requirements and process materials in-house. We also supply the alloy in standard and pre-cut lengths.

BS S106 Steel Bar Datasheet

Commercial Engineering

Although BS S106 is an aerospace grade, the alloy is not exclusively used for aerospace applications. The material also finds use in markets such as motorsport and automotive components. Shafts, spindles, crankshafts and gears are produced utilising this alloy due to the product's performance capabilities which lends itself to numerous engineering applications.

Product Features:

    BS S106
    MSRR 6001
    EN40B (744M24)


    Excellent wear/abrasion resistance
    High hardness after heat treatment
    High fatigue strength
    Suitable for use in elevated temperatures

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