Analysis of Inclusions in Horizontal Continuous Casting Large-diameter Ductile Iron Bars
Author of the article:LIU Caiyan;ZHANG Yunpeng;YAN Shuncai;XU Haoran;LIU Yonghui
Author's Workplace：School of Materials Science and Engineering, Xi'an University of Technology, Xi'an 710048, China;Shaanxi Huaan Cast Iron Bars Co., Ltd., Xi 'an 710062, China
Key Words：horizontal continuous casting large-diameter ductile iron bars inclusions degradation graphite
Abstract：
The distribution, size and composition of inclusions in large diameter ductile iron bars were studied. The results show that the main inclusions are clustered around 3/4R above the center line of the bar, and most of them are distributed in a filamentous manner with large size. SEM results show that almost all filamentous, massive and scattered inclusions are distributed in ferrite, and there is usually degenerate graphite around. Granular inclusions are distributed in both ferrite and pearlite. EDS and EPMA results indicate that magnesium deficiency caused by the reaction of RE-Mg spheroidizing agent with other elements in the iron solution is the main reason for the formation of most inclusions, especially filament-like,lump-like and scattered-like inclusions. The presence of inclusions and degraded graphite is unfavorable to the mechanical properties of the ductile iron bars. Therefore, the selection of appropriate spheroidizing process and parameters is of great significance to prevent inclusion and ensure the microstructure and properties of large diameter ductile iron bars.
