As shown in the figure, the filling process diagram of lost foam casting after the improved process is shown. The whole filling process takes 27.9s. It can be seen from figure a that the filling speed is fast at the beginning of pouring, mainly because the sprue adopts hollow ceramic tube, so the initial filling process of lost foam casting is the same as that of general gravity casting. The hollow ceramic tube can not only reduce the filling time, but also avoid the combustion of foam material in the runner, reduce the volume of gas and effectively prevent the phenomenon of backspray.
It can be seen from Fig. B that the filling speed of lost foam casting is obviously reduced, because the gaseous products generated by the combustion of foam pattern are slower in the mold, less than the rate at which the gaseous products are generated, so that some of the gaseous products accumulate at the front of the molten metal filling and produce gas gap pressure, which hinders the filling of liquid metal. At the same time, it can be found that the temperature of the molten metal and the molten metal in the filling part of the lost foam casting mold has been reduced. On the one hand, because of the contact between the molten metal and the mold, some of the heat is transmitted to the mold, and on the other hand, the combustion process of the foam pattern is an endothermic process, which requires absorbing a lot of heat from the molten metal. Moreover, this process is the main reason for the decrease of liquid metal temperature, so it can be found that the temperature drop of liquid metal at the front of lost foam casting filling is much greater than that at the filled part. For this reason, the pouring temperature of lost foam casting is 30 ~ 50 ℃ higher than that of traditional sand casting.
There is foam burning in the process of figure B to figure D. From figure B to figure C, the filling rate of lost foam casting increased by 25%, and the filling time increased by 4.3s. During the process of figure C to map D, the filling rate of lost foam casting increased by about 25%, and the filling time increased by 4.3s. Combined with figures B, C and D, it can be found that the whole lost foam casting filling process is relatively stable.