Observation of the Mold-Filling Process of a Large Hydro-Turbine Guide Vane Casting
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ng process of the melt into the mold cavity is the first step to make castings, which has a significant effect on the quality of castings. Improper filling may cause turbulence, mold wall erosion, cold shut, inclusions, misrun, etc. The research on mold filling has been a focus for a half century. Physical measurement and numerical simulation are the two methods typically used. Numerical simulation has been widely used in the research on mold filling and the design of gating systems.[1–7] However, the simulated filling results have always been doubted due to a lack of pervasive validation. Physical methods are rooted in the mind of researchers; so, many kinds of methods have been managed to investigate the filling process. Among them, water analog was used to investigate the mold filling for casting specimens and to optimize the gating system design,[7–12] but it is not suitable for castings because the mold model making for complicated castings was difficult. To directly observe the molten metal flow, a heat-resistant transparent window was mounted in the front side of the mold cavity.[13,14] Zhao et al.[13] observed the filling of aluminum melt by using a transparent pyrex window. Khodai and Parvin[14] adopted this method to investigate the filling of aluminum, cast iron, and steel melts during lost foam casting. However, this
JINWU KANG, Associate Professor, HAIMIN LONG, XIAOKUN HAO, RUI YOU, GANG NIE, and TIANJIAO WANG, Master Graduates, are with the School of Materials Science and Engineering, Key Laboratory for Advanced Materials Processing Technology, Tsinghua University, Haidian District, Beijing 100084, P.R. China. Contact e-mail: [email protected] YONGJIE LI, Master Graduate, is with the Department of Mechanical Engineering, Tsinghua University, Beijing 100084, P.R. China. CHENGCHUN ZHANG, Senior Engineer, is with the Harbin Electric Machinery Co., LTD, Harbin 150040, P.R. China. Manuscript submitted March 19, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
method is still limited to experimental study and only is good for two-dimensional shapes. In recent years, the development of high-powered X-ray provides a new way to research mold filling for specimens and small and simple castings. By using the in situ X-ray method, Kashiwai et al.[15] and Zhao et al.[16] examined the fluid flow during the pouring of aluminum castings. Li et al.[17] studied the filling process of a cast iron test casting with the shape of turbine blade. It is also difficult for the application of X-ray radiography method into production because of its critical restriction in size and thickness, complex equipment, and expense. Jong and Hwang[18] proposed a contact time method, created a set of circuits with wires exposed to the mold cavity to detect the melt flow, and applied it to aluminum castings successfully. Li et al.[19] applied the same method to study the filing process of an iron plate in lost foam casting and estimated the filling speed by the filling time and distance. However, this method is not suitable for casting production because wire
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