Analysis of the filling process of the open casting system for sand casting bridge shell

Figures (a) and (b) show the flow of the liquid metal in the bridge shell when the metal liquid fills the front half of the cavity; the figure (a) shows the immediate screenshot of the liquid metal just filling the runner when the metal liquid enters the bridge shell at the beginning of pouring; the filling ratio of the cavity is 25%, and the solidification fraction is 0.0%, and figure (b) shows the flow start of the liquid metal in the bridge shell when the metal liquid is filled with the cavity. The filling ratio of the cavity is 30.3%, the solidification fraction is 0.1%; figure (c) and figure (d) are the screenshots of the middle and later stage of the filling of the metal liquid; figure (c) is the screenshot of the middle filling period of the metal liquid, with the filling ratio of the cavity being 64%, the solidification fraction being 0.1% The results showed that the filling ratio of the cavity was 96.4%, and the solidification fraction was 18.8%. During pouring, under the action of gravity, the liquid metal enters the cavity through the direct runner, enters the transverse and internal pouring channels, and finally enters the whole process of filling the bridge shell.

It can be seen from the velocity field shown in the figure that the flow of the runner is not stable in the whole filling process of the cavity, and there are many isolated metal fluids in Fig. (b), which are easy to produce defects such as cold separation and cold beans. The liquid metal is in unsaturated state in the casting channel, and the filtration effect of molding sand is small, so that the casting defects such as sand holes may occur in the bridge shell. The filling rate of each bridge shell varies greatly during the whole filling process of the liquid metal, and the flow of the melt is turbulent. In figure (c) and (d), the solidification fraction is very large, which results in the temperature difference of 150 โ„ƒ at the final solidification position of bridge shell, which causes the incompletely coincidence and cold insulation defect, and the disadvantages are obvious.

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