Paper

Effect of Temper rolling on texture formation in a Low Loss CRML Steel

S.W. Cheong*, E.J. Hilinski** and A.D. Rollett*

*Department of Material Science & Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 **U.S. Steel Research and Technology Center, 4000 Tech Center Drive, Monroeville, Pennsylvania 15146

Abstract The dependence of magnetic properties such as core loss and peak permeability on the temper rolling process has been studied in a semi-processed, cold rolled magnetic lamination (CRML) steel. The results indicate that temper rolling parameters such as temper mill extension and roll roughness have a significant influence on the magnetic properties. Material processed with high temper mill extension and smooth work rolls shows a sharper texture, which results in highly anisotropic peak permeability values between the rolling direction and the transverse direction. Texture analysis suggests that temper rolling with both high extension and smooth work rolls may concentrate strain at the surface, which would explain the development of the rolling texture at the surface. 1. Introduction. Semi-processed, cold rolled magnetic lamination steel (CRML) is used as the core material for electrical machinery, particularly for rotating electrical machines and small transformers that require weak in-plane anisotropy.1 An optimum texture for these applications is obtained by minimizing {111} planes but maximizing {100} planes parallel to the plane of the sheet since the magnetic induction is highest for the fiber and smallest for the fiber.2,3 Temper rolling or skin pass rolling followed by annealing is widely used to obtain the optimum microstructure by the customer. This processing step introduces a critical strain into the materials in order to develop a coarse grained microstructure during the CRML lamination anneal. The extensions required for grain growth are typically greater than 3 percent and less than 20 percent. Since the temper...