| Summary: | 碩士 === 國立雲林科技大學 === 機械工程技術研究所 === 88 === Grain oriented electrical steel is an important function materials used as laminated cores of transformers. Its magnetic properties influence the efficiency of transformers. This study investigate the effects of carbon contents and various process variables on the magnetic properties of oriented electrical steels added with MnS and AlN inhibitors. The carbon content in the steels is 0.034 and 0.004wt% respectively. The process variables studied are slab reheating temperature, hot band annealing temperature, intermediate annealing temperature, heating rate and secondary recrystallization temperature. Meanwhile, the microstructure, inclusion, texture and magnetic properties at various stages are studied.
It is found that the intensity of (110)<001> component exists at the surface and quarter thickness and is weak at the center during the stages of hot rolling, hot band annealing and intermediate cold-roll annealing in the electrical steel containing 0.004wt% carbon. However, strong Goss texture develop after secondary recrystallization annealing in certain process conditions. It is better to get lower core loss for the specimens reheated to 1100℃ than 1300℃. Core loss decreases with increasing secondary recrystallization temperature. Low slab reheating temperature is also benefit to magnetic flux density and permeability. Maximum magnetic flux density and permeability exists at certain optimum process condition.
Slab reheating temperature affects the solubility of MnS and AlN inclusions in steels. At 1300℃, MnS and AlN almost dissolve in the steel matrix. After hot band annealing, fine inclusion comes out uniformly and impedes the primary recrystallization. It also increases the start temperature of secondary recrystallization. Therefore, specimen that reheated to 1300℃ has less completely secondary recrystallization and develop weak Goss texture. On the other hand, specimens that reheated to 1100℃ has coarse inclusion and lower secondary recrystallization start temperature. After secondary recrystallization, it develops strong Goss texture and gets better magnetic properties.
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