Study on filling shape and speed of lost foam casting

The research on filling shape and filling speed not only has an important impact on the establishment of numerical simulation calculation of filling process, but also has an important impact on the guidance of process design of lost foam casting and the reduction of defects caused by lost foam casting. The main research contents include: the shape of liquid metal front, the moving speed of interface front, filling ability and so on.

Among the factors affecting the filling shape of Al Si alloy lost foam casting, katashima et al studied the effect of vacuum on it. The results show that the extrusion of the decomposition products of the pattern to the mold wall is caused by the convex forward movement of the end of the liquid metal, which occurs under normal pressure. The generation of pores is due to the involvement of decomposition products and pattern fragments into the liquid metal. At this time, the liquid metal is preferentially filled forward along the mold wall. This situation is generated under negative pressure.

The filling ability and filling speed of liquid metal are reduced because of the obstruction of molten metal caused by the molten metal. Such as pouring temperature, pattern density, gate size and coating permeability, various process parameters have varying degrees of influence on the filling speed. For example, for aluminum alloy, the filling speed of 80 ~ 100cm · S-1 is ordinary casting, and the filling speed is generally 10 cm · s-1, which is a steady state.

Among the factors affecting the filling process of gray cast iron, various process parameters have a great influence on it. Wang et al. Found through a large number of experiments that the most important factor affecting the filling time of liquid metal is the pattern material. Due to the different decomposition characteristics of different pattern materials, the filling time of polymethylmethacrylate (PMMA) pattern is much slower than that of polystyrene (EPS) pattern under certain conditions. The effects of mold modulus, inner gate area, metal static head, coating thickness, pouring temperature and coating permeability on mold filling time and speed increase in turn.

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