Non-oriented electrical steel sheets are sheets tailored to produce specific properties and are produced from Fe-Si or Fe-Si-Al alloys. Non-oriented electrical steel sheets are incorporated into a wide range of equipment, from the simplest domestic appliances to hybrid and pure electric vehicles.
Non-oriented electrical steel sheets are sheets tailored to produce specific properties and are produced from Fe-Si or Fe-Si-Al alloys. Non-oriented electrical steel sheets are incorporated into a wide range of equipment, from the simplest domestic appliances to hybrid and pure electric vehicles. Future efforts will be focused on controlling the residual elements in the steel, optimizing the hot and cold rolling, and optimizing the crystallographic texture development, with the aim to enhance the performance of the finished product.
INTRODUCTION
Soft magnetic materials are ubiquitous in the current electronics-based economy. Silicon steel was developed at the beginning of the 20th century and soon became the preferred core material for large transformers, motors, and generators. Silicon-bearing steels are used as soft magnetic materials in electrical appliances and devices and are rated in terms of power loss when magnetized in an alternating electric field. The total amount of these steels is around 1 % of the world production of steel1. The Worldsteel Committee on Economic Studies, Brussels, reports that the worldwide production of strip in 2008 was 10.291.000 metric tons, and in the EU it was 1.498.000 metric tons. The production of electrical steel sheet and strip in the last 10 years has almost doubled. The production of non-oriented electrical steel in Slovenia is approximately 100.000 metric tons per year.2
Texture is one of the most important parameters determining the magnetic properties of steel sheets. The ideal texture of non-oriented silicon steel sheets would be a cubic texture with grains with their (001) or (110) planes parallel to the plane of the sheet and a uniform distribution of the [100] direction, whereas the Goss texture with a (110)[100] crystallographic orientation of the grains is the typical grain structure of grain-oriented silicon steel.
Silicon steels are fundamental for the economy of electrical appliances, and offer the best combination for transmitting and distributing electrical energy. The properties required of these steels are a high permeability and induction, low magnetic losses, and low magneto- striction. A high permeability and induction reduce the size and weight of the parts; low magnetic losses diminish the the generation of Joule heat and energy consumption; and a low magnetostriction reduces the noise (which appears as humming) in transformers and high-capacity machines3.
The basic technology of production for non-oriented, fully processed electrical steels has not changed signifi- cantly in recent decades: the basic chemistry is similar in terms of the main alloying elements and the processing steps are basically unchanged. Nevertheless, the losses in a steel with a given Si and Al content are today much lower compared to previous decades. Accordingly, electrical steel producers have made only very small changes to the basic chemistry used for most commercial standard grades. International and national standards only specify the maximum loss (and often also a minimization of polarization/permeability), but have in principle no lower limit to the losses. Consequently, for a given standardized grade the difference between the guaranteed maximum loss and the actual loss of the material produced has increased significantly over time. An electrical steel is a commodity product with a market price very much determined by its grade designation. From the steel user’s point of view, this development has brought advantages, but it has also increased the variability in the market and it is uncertain as to what a standardized grade really is.
