Oriented and Non-Oriented Silicon Steel: Which One Your Core Needs

Two families, one material

Silicon steel for transformers divides into oriented and non-oriented. The difference is grain orientation, and it changes where in the sheet the good magnetic behaviour lives.

Oriented grades

The magnetic properties of oriented silicon steel are strongly directional. Iron loss is lowest in the rolling direction, permeability is highest, and magnetic susceptibility is high under a given magnetising field. Silicon content is around 3%, the steel needs a low content of oxide inclusions, and it relies on inhibitors such as MnS and AlN. Because it is used mainly for transformer cores, it is also called cold-rolled transformer steel.

Non-oriented grades

Non-oriented silicon steel has very low carbon and silicon between 0.8% and 4.8%. Adding silicon raises resistivity and maximum permeability while reducing coercive force, core loss and magnetic ageing. Through deformation and annealing the grains end up irregularly oriented, and the sheet is rolled to 1 mm or less.

Low silicon against high silicon

Sheet with less than 2.8% silicon keeps a certain mechanical strength. Sheet from 2.8% to 4.8% silicon has better magnetic properties but is more brittle, which matters when the laminations are sheared and stacked.

Cold rolled has replaced hot rolled

By use, silicon steel splits into hot rolled, cold rolled electrical steel and special purpose grades. Cold rolled sheet has uniform thickness, good surface quality and higher magnetic performance, and has gradually replaced hot rolled sheet.

What to send when you ask for a quotation

Thickness from the 0.23 to 0.5 mm range, slit width from the 40 to 1290 mm range, the standard you work to, and the quantity.