Research Rapid Sand Casting Process Of Cylinder Head Based On Numerical Simulation

Rapid sand casting is a foundry technology combined with conventional crafts of casting, which directly utilizes CAD system to designing casting process and uses prototypes instead of steel molds or wood molds in the production. Some process steps are slap designed by borrowing the CAD system,for example gating system. Model and core box are caked using photosensitive resin. Difficulty of production can be reduced and quality of casting can be improved by applying this technology. So rapid sand casting process is particularly suitable for some products which have complex shapes and need sand core such as cylinder head, cylinder block, intake manifold of the automotive. With the application and development of numerical simulation technology in the casting, macro-forming of casting can be observed, casting defects can be predicted, or parameters can be optimized.Unigraphics NX 8.0 was utilized to design three-dimensional model in this paper, independently developed rapid sand casting process CAD system by laboratory was applied to completing the casting technological design. France ESI’s simulation software PROCAST was used to simulate the filling and solidification of three different gating systems. The pouring temperature, pouring speed, and interfacial heat transfer coefficient(IHTC) were analyzed for the influences of filling and solidification, casting defects were predicted in each case. Finally, considering the characteristics of casting process and the production requirements of the SLA prototypes, its mold of rapid sand casting was designed, and then trial production of low-rate was carried out to get qualified products.The main results are as followed:1. According to the structural characteristics of cylinder head, an appropriate gating system was chosen. By analyzing the mold-filling and solidification process in different gating system, using unilateral bottom structure can fill smoothly, avoid the impact of metal to sand, produce fewer defects, sequence solidification principles are followed during solidification.2. For guaranteeing the accuracy of numerical simulation, interfacial heat transfer coefficient between ZL105 aluminum alloy and resin sand was obtained by experiment. Analog of IHTC has been established, based on theexperimentally measured temperature, the value of a function between the interfacial heat transfer and the temperature was figured out by the method of inverse computing.3. Filling and solidification process of cylinder head was simulated by software PROCAST, and gating system was optimized. Pouring temperature is690℃, pouring speed is 0.22 m/s. Liquid metal could flow smoothly without turbulence and drying in the cavity. We could forecast the defects of shrinkage by the temperature field and flow field.4. The Unigraphics NX8.0 software was used to design the rapid sand casting mold. The visualization from casting was achieved, which was propitious to modify or optimal design. By above method, the design’s flexibility and efficiency were improved.5. The best ratio of modeling materials was determined. According to actual production requirements, the tensile strength tests were performed for ratio of the various ingredients for phenolic urethane resin sand. The ideal ration of component I relative to component II is 1:1, and mass of component I is 0.8%-1% in all original sand.