The Casting Process Optimization Of The Main Pump Support Of CPR1000 Project And The Numerical Simulation Of The Microstructure Of Castings

The nuclear main pump bearing support is the casting studied in this dissertation.The wall thickness is beyond 200 mm and the weight of this casting is nearly 2.5t, thus making it a thick and large piece. Its material is 12MDV6, which is called ZG12 MnMo V interiorly. In production the defects such as bonded sand, shrinkage cavity and porosity are found. The severe working conditions give a strict requirement for casting quality, so this paper offers solutions by studying.The cause of defects is found by simulating and analyzing previous process scheme, and defects like shrinkage cavity and porosity are eliminated by process improvement. Bonded sand is eliminated by improving coating. Resulting in shrinkage cavity and Niyama porosity, the effects of mold initial temperature, pouring temperature and time on casting quality is confirmed by uniform design and regression analysis in use of software Minitab. And the optimal solution is acquired.Secondary dendrite arm spacing module of software Procast is used to analyze the effects of pouring temperature on microsegregation, thus finding that lowering pouring temperature is conductive to decrease microsegregation, improve casting quality and fining structure.The dissertation successfully eliminates the defects like bonded sand, shrinkage cavity and porosity, thus solving those problems the enterprise met with. And the cost-saving process scheme becomes much more reasonable, which bringing more profits to enterprise. The study provides the theoretical basis to related research.