Effect of Inclusions on the Magnetic Properties of High-Grade Cold-Rolled Non-Oriented Silicon Steel

摘要

High-grade cold-rolled non-oriented electrical steel is an important soft ferromagnetic material that is used in power, electronic and military industries. It is mainly employed for manufacturing a variety of large motors and generators using steel grades 50W350 and above. The power loss in non-oriented electrical steel is strongly influenced by steel composition, cleanliness and microstructural features'. In particular, the existence of nonmetallic inclusions can depress the grain size of the steel sheets, distort the crystal lattice, block the motion of magnetic domains, and hence produce low quality magnetic properties in the finished steel sheets. Generally, in this study, inclusions in steel can be divided into three categories, large inclusions (particle size>50pm), micro inclusions (1～50μm) and ultrafine inclusions (<1 μm). The large and micro inclusions mainly affect the surface quality and service performance of the silicon steel sheet, while the ultrafine inclusions do great harm to the magnetic properties of the finished product. The study by Boca et al. indicated that the effect of inclusions in the size range 0.05 to 0. 5μm on the electromagnetic properties is greater than that of inclusions that are >0.5μm or <0.05μm. Wang et al. reported that in low-grade non-oriented electrical steel, 50W1300, the inclusions with sizes from 100 to 500nm have the greatest adverse effect on iron loss, while inclusions with sizes from 100 to 200nm have the most deleterious effect on the magnetic induction property. With respect to the production of non-oriented electrical steel, numerous studies have focused on purifying the molten steel and reducing the number of inclusions. On the other hand, there have been relatively few reports on the effect of inclusion character on the magnetic properties of the steel. The aim of this study is to investigate the effects of inclusion morphology and inclusion characteristics on magnetic properties of high-grade cold-rolled non-oriented silicon steel.