IMPROVED LOW-LOSS HIGH PERMEABILITY GRADES, PROCESSING AND PROPERTIES

Non-oriented electrical steels are sub-divided into 'fully processed' and semi-processed' types. The history of loss reduction has generally been associated with silicon additions for both types of steel which unfortunately is detrimental to high field permeability. More recently the availability of ultra low carbon and ultra low sulphur steels has permitted a shift in the loss/permeability compromise associated with silicon addition by adopting a 'lean and clean' approach in which los ses are lowered by improved purity and. perhaps. thickness selection w hilst good high field permeability is maintained by a restriction on s ilicon additions. This paper deals with recently developed steels of t his type, particularly 'Polycor' aimed at the high efficiency inductio n motor marker. The changing role of insulative coatings on new materi als is also considered. Potential further development of low loss high permeability grades is discussed.