Fixing of impeller shell in investment casting

If the coating tooling is removed immediately after the coating of partial mold shell of investment casting impeller blade, due to the large volume of partial mold shell of impeller blade, deformation will occur in the process of handling, dewaxing and roasting. In serious cases, the mold shell can also be scrapped. At the same time, in order to ensure the convenience of lifting during mold shell transfer and the accuracy of positioning during mold closing, the mold shell fixing process of making sodium silicate sand sleeve on the periphery of the mold shell and pre placing cast iron stiffeners with two lifting rings in the sand sleeve is formulated in the design process.

1. Sodium silicate sand sleeve process

(1) As shown in the figure below, the lower half of the ring-shaped sand cover plate is designed to match with the lower half of the 973mm ring-shaped sand cover plate.

(2) Make a cast iron stiffener ring with two lifting rings that can be placed in the sand ferrule.

(3) The formula of sodium silicate sand is the same as that of molding sodium silicate sand.

(4) After coating, open the nut on the fastening shaft, remove the upper cover plate, place the cast iron stiffener, install the annular sand ring (two half rings) for making sodium silicate sand sleeve, and connect and fasten it with bolts after matching with the positioning step on the lower cover plate; Fill in the mixed sodium silicate sand and blow CO2 gas for hardening. The thickness of sodium silicate sand sleeve is about 100mm.

2. Effect analysis

Remove the shell shape of the locating ring and the lower cover plate, as shown in Figure 1. The mold shell after removing the annular sand ferrule (two half rings) is shown in Figure 2.

The impeller shell with ring-like granulated substance ferrule
The shell with silicate granulated substance set of lamina

It can be seen from Figure 1 and Figure 2 that the mold shell coated with ethyl silicate water glass composite coating, after being fixed by the peripheral water glass sand sleeve, not only ensures the solid and durable shape of the investment casting impeller blade, but also solves the positioning problem of the mold shell in the sand mold during the composite mold, and meets the requirements of the investment casting impeller blade process.