Crystalline Soft Magnetics Materials. Grain Oriented Electrical Steel

Until now, NF EN 10107 was known as "grain-oriented electrical steel strip and sheet delivered in the finished state"; in a resolution dated December 23, 2013, AFNOR Commission UF68 – système français de normalisation – UTE adopted the name "grain-oriented electrical steel strip and sheet delivered in the finished state". This steel is commonly called GO, or grain-oriented silicon steel.

Grain-oriented steel belongs to the family of soft magnetic materials that offer high permeability to the magnetic field, and magnetize and demagnetize easily. It is a silicon-alloyed steel, containing around 3% silicon by weight, marketed as a flat product and electrically insulated on both sides by a layer formed from magnesium silicates supplemented by an inorganic phosphate film.

The manufacturing process includes multiple steps from steelmaking, hot rolling and thermomechanical transformation operations, aimed at obtaining a specific crystallographic texture called "Goss texture". This texture is the reason for their good magnetic performance in the rolling direction of the sheet. They feature high magnetic polarization at saturation and very low specific losses.

Grain-oriented laminations are well suited to unidirectional field applications, such as in static machines like transformers, where the electrical efficiencies targeted are very high. On the other hand, they are less efficient in the case of traditional rotating machines, but are so in large generators and alternators. Their characteristics are specified in the standard, which distinguishes two classes of material in thicknesses of 0.23, 0.27, 0.30 and 0.35 mm:

• conventional grain-oriented material, known as CGO ;

• high-permeability grain-oriented material, known as HGO, with improved properties for power transformers.