In the process, the asbestos is wrapped on the mold shell for treatment (as shown in Figure 5), that is, the asbestos is pasted on the bottom plate position (leaving the hot joint position), the casting is poured out, and the hot joint position is

No looseness was found, and no looseness was found on the bottom plate. The under cast defect was also increased by 80%.

Analysis of process improvement effect

When casting is melted and poured, in the process of vacuumizing, the temperature of the mold shell will drop in the smelting furnace. After the base plate is wrapped with asbestos, the asbestos will keep the mold shell warm, slow down the cooling speed of the base plate, and prolong the solidification time of the base plate, so as to ensure that the alloy liquid can effectively supplement the hot spot through the base plate, and also effectively ensure the base plate filling.

Asbestos is a kind of soft material. After wrapped with asbestos, asbestos can slow down the extrusion of sand on the mold shell, reduce the deformation of the mold shell, indirectly increase the wall thickness of the bottom plate and prolong the filling time of the bottom plate.

After wrapping the asbestos, the solidification time of the bottom plate is prolonged, the inclusions in the alloy liquid can fully float or sink, and the tendency of slag inclusion in the casting is reduced invisibly.

By using the method of covering asbestos in the mold shell, the extrusion of sand on the mold shell can be prevented, the cooling rate of the mold shell can be reduced, the filling and solidification time of the bottom plate can be prolonged, so as to effectively supplement the hot joint at the edge of the casting and improve the tendency of looseness.