Powder metallurgical materials and processes for soft magnetic applications

Abstract

For many designers of electrical machines, the term “soft magnetic materials” automatically means laminated electrical sheet. This is unfortunate, since for many applications, particularly at low frequencies, laminated sheet is rarely the best material choice. Soft magnetic powder materials are available to satisfy the needs of virtually any application imaginable, from plain iron, giving good induction for DC applications, to ultra-high permeability nickel irons. The use of these materials brings with it all the attendant advantages of powder metallurgical (PM) production: low cost, tight tolerances, complicated forms, and minimal material waste. For high frequency applications, a range of soft magnetic composite materials or SMCs are available which can provide magnetic performance comparable to or surpassing that of laminated sheets, while at the same time allowing much greater freedom to the designer due to their isotropic nature, which permits the implementation of complicated 3D flux paths. This paper presents a review of the available powder-based soft magnetic materials, together with typical applications and a consideration of some of the factors which must be taken into account when producing powder-based components for magnetic applications.