刘章健Heat transfer characteristics of lost foam casting process of magnesium alloy.pdf

Heat transfer characteristics of lost foam casting process of magnesium alloy 1, 2 2 LIU Zi-li() , PAN Qing-lin() , CHEN Zhao-feng()1 1 1 , LIU Xi-qin() , TAO Jie( ) 1. College of Materials Science and Engineering , Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; 2. School of Materials Science and Engineering, Central South University, Changsha 410083, China Received 14 June 2005; accepted 20 March 2006 Abstract: Effects of vacuum, pouring temperature and pattern thickness on the heat transfer of magnesium alloy lost foam casting(LFC) process were explored. The results indicate that without vacuum a positive thermal gradient from the gate to the end of the casting was formed immediately after the mold filling. The average temperature of the casting, the temperature gradient and solidification times increase significantly with pouring temperature and pattern thickness. Vacuum plays a quite different role in the heat transfer during mould filling and solidification periods: it significantly increases the cooling rate of the filling melt, but decreases the cooling rate of the casting during solidification period. The temperature of the liquid metal drops sharply and varies greatly with no apparent mode in the casting after the mold filling. The amplitude of temperature fluctuations in the casting increases with vacuum, pouring temperature and pattern thickness. The average te