In the process of solidification and cooling of sand-clad iron mold casting for pump valve castings, there are many cores under the mold cavity, so the heat transfer of sand-clad iron mold casting for pump valve castings is the coexistence of sand casting and sand-clad iron mold casting, involving a variety of boundary conditions, namely: mold / air boundary, casting / sand-clad boundary, casting / core boundary, core / mold boundary, etc.
The three-dimensional solid modeling of different pump valve castings, sand coating layer, iron mold, clay core and other structures is carried out by CAD three-dimensional modeling software. After saved as STL file, it is imported into the iron mold sand coating solidification simulation software developed by ZHY casting for the second time. All simulation parameters including thermal physical parameters, initial conditions, boundary conditions, etc. of the involved materials are set, and then loaded for solution. Through the simulation results of casting filling and solidification process, we can directly see the status of casting filling process, solidification process temperature field, casting defects and so on. Based on this, we can optimize the sand-clad casting process of pump valve castings, so that it can make correct selection and decision in the early stage of the design and manufacturing process of the mold and tooling, so as to optimize the casting process and improve the tooling design.
Taking td32-32 pump body casting as an example, through numerical simulation of filling and solidification process, particle tracing diagram (Figure 1) and temperature distribution diagram (Figure 2) of filling process of pump body casting can be obtained. It can be seen from Fig. 1 and Fig. 2 that there is no obvious splashing of molten iron during the whole filling process. The molten metal rises slowly from the bottom of the pump body to fill the whole cavity, and the flow is very stable, so the casting defects caused by filling are not easy to occur. Figure 3 is the distribution diagram of shrinkage cavity and porosity of the pump body. It can be seen from the figure that there is no shrinkage cavity and porosity defect on the pump body casting, and only the shrinkage cavity and porosity defect can be seen in the pouring system, which shows that we have reasonable design on the iron mold, sand coating layer, pouring system, core sand and so on in the process design of the iron mold sand covering casting of the pump body casting, which can be applied to the actual casting production. It has been verified in the production of td32-32 pump body casting with sand coated iron mold. Compared with the common sand casting, the size accuracy and surface roughness of the castings are improved by one grade, and the production cost is reduced by about 15%.
