Low thickness NGO FeSi electrical steel for high frequency automotive applications

Electrical steels account for approximately 1% of the world’s steel production and are a key requirement of our industrial society, vital in most electromagnetic components used in generation, distribution and utilisation of electrical energy. Electrical steels are all around us in our daily lives and they are usually taken for granted. Electrical steels are produced in two main families, Grain Oriented (GO) and Non Oriented (NO) with a range of demands and market pressures that call for improvements in magnetic and physical properties, reduction in environmental impact and price reduction usually in parallel. This presentation will cover NO steel developments in particular thin gauge products for higher frequency automotive applications.
In NO electrical steels the magnetic properties are essentially the same in all directions making such grades particularly suitable for rotating machines including motors and generators. Non oriented electrical steels are produced in two types, fully processed where the magnetic properties are fully developed by the steel manufacturer and semi-processed where the final magnetic properties are only achieved after the lamination producer or motor manufacturer heat treats the laminations, cores or packs of laminations after forming. For fully processed non oriented grades the magnetic properties are largely unchanged through the final customer manufacturing process. To improve the performance of the final component, understanding the interactions between steel mechanical properties magnetic properties, surface coating, stamping characteristics, joining methods etc. are key to delivering improvements.
The best quality NO grades require very thin strip, high resistivity controlled primarily by large Si and Al alloying additions, excellent orientation, controlled grain size and very low impurity levels. Further improvements will require non-traditional production methods to achieve extremely high Si levels for increased resistivity or even thinner material although there would need to be a balance between increased costs and benefits in specific applications. Growth in the use of NO electrical steels in electric motors many employing high frequencies means mechanical properties particularly tensile strength and fatigue performance, are becoming increasingly important necessitating a compromise between mechanical and magnetic properties.