Influences of Cold Rolling Reductions and Strain Mode Changes on the through-thickness Texture Evolutions of a Hot-Rolled Non-oriented Electrical Steel

• Main Authors: Tsai-Chun Lee, 李采錞
• Other Authors: Pei-Ling Sun
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/v3jsd2

碩士 === 國立中山大學 === 材料與光電科學學系研究所 === 106 === In this study, non-oriented electrical steel (NOES) which was hot-rolled and APL (annealing and pickling line) treated was used as the starting material. Two types of hot band annealed specimens were prepared and they were either ground on one side of the normal plane to remove half of the original thickness (Type Ⅰ) or on both sides of the normal plane to remove quarters of the original thickness (Type Ⅱ). These two materials were then cold rolled to different rolling reductions (50% and 78%). Depending on the different locations of the specimens, different deformation modes dominate. Therefore, five different types of specimens were obtained (S-S, SS-S, C-S, SS-C, C-C), where S stands for the surface layer of the specimen, SS stands for the sub-surface layer of the specimen, and C stands for the center layer of the specimen. The specimens were then heat treated at different annealing temperatures to obtain the early, middle and late stages of RX process, according to the measured micro-hardness value variations as a function of annealing temperature. Macrotextures were obtained by using X-ray diffractometer (XRD) to measure the pole figures. The results of the macrotexture show that α-fiber and γ-fiber intensities are observed in the CR state in the five specimens. It is also observed that α-fiber intensity increases with rolling reduction. The specimen underwent plane strain deformation is found to have the highest {111} <110> intensity. The effect of deformation mode changes is observed to be affected by rolling reductions. After the specimens were annealed at different temperatures, it is observed that the one deformed by shear deformation results in the highest intensity of Goss texture in the 78% CR specimen. Electron backscatter diffraction (EBSD) was used to observe the microstructures and microtextures. It is observed that different microstructures exist at the hot band annealed specimens and therefore Type Ⅰ and Type Ⅱ CR microstructures are compared carefully. There are more shear bands in Type Ⅰ specimen, while smooth grains with laminar morphology dominates in Type Ⅱ specimen for the 50% CR condition. Moreover, the deformed grains in C-S specimen are more elongated than those in S-S specimen. On the contrary, the microstructure difference is not obvious in the 78% CR specimens. By observing the results of the microtexture in different cold rolling reduction specimens, there are higher fractions of Goss texture in Type Ⅰ specimens, while Type Ⅱ specimens have a higher fractions of Rotated cube, {112} <110>, and Cube textures. After annealing treatments, it is observed that the 78% CR specimens are more favorable to the development of Goss texture.