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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 15    No. 3    June 2005

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Numerical simulation for permanent mold centrifugal cast TiAl exhaust valve
SHENG Wen-bin(盛文斌)1, 2, LI Dong(李 东)2

1. Department of Mechanical Engineering, Shandong University of Technology, Zibo 255049, China; 
2. Titanium Alloy Laboratory, Institute of Metal Research, 
The Chinese Academay of Sciences, Shenyang 110016, China

Abstract:The filling and solidification in centrifugal field, as well as the forming mechanism of off-center porosities were summarized, based on the mathematical model established for the centrifugal cast TiAl exhaust valves.  The calculated results show that the centrifugal field results in the phenomenon that the flow in the valve cavity consists of forward flow and backward flow. The unsymmetrical initial temperature field causes continuous unsymmetrical variation in the following solidification, which makes the final solidified region depart from the cavity axis and then leads to the occurrence of off-center porosity.  A series of optimized parameters, including the entrance velocity of 0.6-1.3m/s, the rotation speed higher than 300r/min, 80mm or longer entrance length and 400℃ or higher preheated temperature of the mold, are suggested for the manufacture of permanent mold centrifugal cast TiAl exhaust valves.

 

Key words: TiAl alloy; exhaust valve; permanent mold; mathematical model; off-center porosity

ISSN 1672-7029
CN 43-1423/U

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