Flat-rolled electrical steels are produced to meet magnetic property specifications rather than specific chemical composition. Magnetic characteristics are of first importance and are dependent on processing as well as on chemical composition. However, to indicate the varieties of core materials and show how they are generally classed according to composition, the typical chemical analyses of a few of these materials are listed.

Silicon is the primary alloying element in electrical steels. It is added because it increases the volume resistivity of the steel and thereby reduces the eddy current component of core loss. Silicon is more effective in this respect than any other element which may be conveniently added. Silicon has an added benefit in that it affects the grain structure of the steel and thus gives somewhat improved core loss by its reduction of the hysteresis component in nonoriented electrical steels.  Additionally, certain levels of silicon must be maintained to avoid a phase change and thus aid the crystal orientation process in oriented electrical steels.

Depending upon the type of product, the other main alloying elements added to electrical steel are aluminum and manganese. Each of these usually is added in amounts less than 1.0% and more often between 0.1 and 0.5%. These elements are added mainly for their metallurgical effect rather than for any physical effect such as volume resistivity. They also favorably affect grain structure of the steel, thereby contributing to the lowering of the hysteresis component of the core loss.

Other elements are present in electrical steels but are essentially impurities and are found only in residual amounts. Carbon is one element that changes in content from that present in the melt to that in the final product. Special heat treatments are given during mill processing to lower carbon content of the fully processed material to very low values. This removal of carbon occurs during annealing of the semi-processed grades by the customer.

In the case of grain oriented steels, impurities such as sulphur and nitrogen are required initially to help develop the final crystal orientation, but these elements are then removed in the final anneal. Since the magnetic quality of electrical steel is a function of chemical analysis and of mill processing, there may be some overlapping of the grades as shown in Table 2. However, core loss will generally vary with silicon content, with increasing silicon producing an improved core loss grade but resulting in lowering of high induction permeability.