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FeSi4- Iron Silicon Alloys

Steel data sheets

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Valbruna Grade


Steel type

Iron Silicon Alloys

Description of material

FeSi4 is a carbon alloy steel with highest resistivity of the alloys included in ASTM A867. This characteristic, together with highest magnetic permeability and low coercitivity, reduces the eddy currents effects in AC circuits. FeSi4 is normally supplied in mill annealed + cold finished condition. In this case, the level of magnetic permeability and the coercive force, could be not sufficient for optimum magnetic purposes. A soft magnetic annealing in a protective atmosphere should be carried out to obtain the best magnetic properties. See Soft Magnetic Steels brochure for more information about magnetic, mechanical and physical properties.


Relays, pole pieces, solenoid switches, fuel injectors and any kind of magnetic device where higher values of magnetic properties are required.

Melting practices

Argon Oxygen Decarburization

Corrosion resistance

FeSi4 is not a stainless steel and rusts more quickly than Carbon and alloy steel grades if not immediately protected by a coating after machining and/or soft magnetic annealing of finished parts.

Cold working

FeSi4 has very poor cold deformability and is not suitable for upsetting. It should be pointed out that this grade is designed for parts/pieces that have to be machined.


FeSi4 is not a micro-re-sulphurised grade and has the typical poor machinability of a soft ferritic structure .Productivity gain depends on types of machines, the kind of tools used and their geometry, cutting fluids and the kind of machine operations on the pieces being produced. However, the harder structure of annealing+ cold finishing (as cold drawing) offers advantages in some machine operations and a better surface roughness. Obviously, a vacuum, or protective atmosphere annealing, of machined parts should be done if an improvement of magnetic properties were required. The Norm ASTM A867 suggests temperatures, soaking times, cooling rate and furnace atmospheres for the soft magnetic annealing.


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