Papers by Author: Jiong Hui Mao

Abstract: A kind of environment-friendly Cr-free insulating coating for grain-oriented electrical steel is exhibited in this paper. The tensile stress and the magnetic properties for both Cr-free and Cr-containing insulating coating were measured. The results showed that the more the coating on the metal, the bigger the tensile stress produced. The contribution of the Cr-free insulating coating to the reduction in P_1.7/50 varies from 0.092 to 0.192 W/kg, while the reduction in P_1.7/50 by the Cr-containing insulating coating is from 0.066 to 0.177 W/kg, with the weight of the coating varies from 4 to 6.5 g/m². In comparison with the traditional Cr-containing insulating coating, the Cr-free coating produces larger tensile stresses in the metal, thus leads to better magnetic properties, especially in the magnetic losses. Keywords: grain-oriented electrical steel, insulating coating, Chromium-free, magnetic property, tensile stress

Abstract: Hot bands of Fe-3%Si steel containing 0.24%Cu were characterized to examine the precipitation of copper sulfides following different heat treatment schedules. It was found that copper sulfides were dominantly in a sphere shape. From 950°C to 1050°C, the precipitates were the complex of copper sulfides and aluminum nitrides. The size of the precipitates decreased and the distribution increased as the temperature increased. However, from 1050°C to 1150°C, the precipitates size increased and the distribution decreased with the rise of temperature. The precipitates were mainly complex copper-manganese sulfides. When the sample was annealed at 1050°C, air cooled to 900°C and boiling water quenched, the most fine and disperse precipitates were obtained. The average size and distribution of the precipitates was 37nm and 2.72μm-2, respectively.

Abstract: Low energy grain boundaries were considered to be important in abnormal grain growth by theoretical deduction. The disorientation angles and coincidence site lattice grain boundaries distribution of more than 20 Goss grains and their neighboring matrix grains in primary recrystallized Fe-3%Si alloy were investigated using an electron backscatter diffraction method. It was found that the frequency of low energy grain boundaries of Goss grains which are more likely to abnormally grow are higher than their neighboring matrix grains, which indicated that low energy grain boundaries play a dominant role in the abnormal grain growth of Fe-3%Si alloy. The result meets well with the abnormal grain growth theory.