Computer Optimization Design On Casting Process Of Marine Propeller Hub Body

Marine propeller hub is one of the core components of adjustable pitch propeller device. It is one of the most stressed parts of propelling power as well as the final executive component of pitch control. Owing to its large dimension, thin wall and complicated shape, it’s difficult to determine the casting process only by experimental method. To eliminate conventionally trial-and-error approach for getting the optimum design of casting processes, numerical simulation techniques have become a powerful tool. In this work, gravity casting, centrifugal casting, and low pressure casting methods used for casting the marine propeller hub are compared and studied by simulating their mold filling and solidification processes. A proper method selected via the comparisons is finally applied to cast the marine propeller hub.Based on the mathematical description of mould filling and solidification process, ProCAST(?) software is used to simulate the mould filling and solidification process of the three casting processes. In the present study, the pouring temperature of the three casting processes is1110℃. The pre-heated mould temperature for gravity casting, centrifugal casting, and low pressure casting process is100℃,300℃, and600℃, respectively. The pressure exerting in low pressure casting is based on Pascal’s principle and practical experience. In centrifugal casting process, the rotating speed is150r/min.All the cast parameters used in experiments are corresponding to those in simulation. The actual temperature curves during pouring and solidification processes are obtained. An inverse method is used to determine the value of interface heat transfer coefficient (IHTC) for the three casting methods. The simulated cooling curve is compared with the experimental one, and the IHTC is adjusted according to the comparison. The optimized IHTCs values are800,1000, and3500W-m-2K-1for gravity, centrifugal and low pressure casting processes, respectively.The simulation results show that no obvious turbulence or gas entrapment is detected in the three mould filling processes, which is benefit for the preparation of sound casting. The propeller hub does not experience sequential solidification and the feeding paths are restricted by gravity casting. The feeding path from the bottom gate into the upper zone is blocked during the low pressure casting process. The centrifugal casting process fits the propeller hub body best with a well-sequenced solidification from bottom to top and the melt in the riser can feed the dendritic structure of the lower part of the casting.The defects of propeller hub body by centrifugal casting process is analyzed to determine the optimal parameters for preparing the propeller hub body. The effect of pouring temperature, mold preheat temperature and centrifugal speed on the shrinkage defects in the castings is studied. The optimum process parameters of the propeller hub body are:the superheat50℃, mold preheat temperature300℃, and centrifugal speed150r/min.