Design Of New Gating System For Supercritical C12A Valve Body And Optimization Casting Process By Computer Simulation

Supercritical steam power plant is a highly efficient and green power technology. The large C12 A valve body casting is an important part in the supercritical steam power plants, and it works long time in the environment under high temperature and high pressure. So it is a serious challenge for the properties of the valve body castings. In industrial production, casting defects as pores, slags and others often be found in the large valve body castings. And this phenomenon is inextricably linked to the rational gating system design. Recently research shows that it is a great effect on the qualities of castings when filling disorders during casting process or filling velocity value which is much greater than the critical velocity. Obviously, if the production of the castings are great, gating system design is critical.In this paper, for the production of the supercritical large C12 A valve body castings, based on the new concept for gating system design, and then optimized the design plan in the combination of computer simulation. By the results of computer simulation, reasonable parameters have been determined. C12 A valve body castings were produced in the factory, there are no slag entrapment and gas defects were found in the castings. Good valve body castings were obtained by the proper gating system designing and well degassing. Main contents in this paper include:(1) Design of new type gating system for supercritical C12 A valve body casting.Based on new concept of gating system design, three methods of improving gating system C12 A valve body castings were put forward. First program, no gas gap with flow type, is to reduce velocity speed through increasing cross cut area according to equal flow principles; second program based on the first program added a horizontal lu-type slot design and set slag package design at the end, and this program was named a new block slag type pouring system design program; third program which chose filling the mould at the end instead of traditional types, can makes filling type process more smooth, and therefore the third improvement was called antes-smooth filling designs.(2) Optimization casting process with computer simulation for supercritical C12 A valve body.The Experto Viewcast software was used to simulate the mold filling and solidification process for C12 A valve casting in original technical solution and three improvement programs. Several results should be paid more attention: whether the filling process is stable, splashing or disorders phenomenon occurs or not; monitor the filling speed at the internal gate and whether the filling speed is below the critical speed or not; observe the variation of temperature in solidification process to verify the feasibility of riser and chill process, and predict possible location of shrinkage and porosity. Analyses simulation results and verify the reasonableness of three improved schemes providing suitable parameters for production.(3) Trial manufacture for supercritical C12 A valve body.Mid-experimental tests were conducted in the enterprise based on three improvement plans. Casting results showed that the casting profile was intact, and inclusions, voids, cracks and other defects were not observed on the surface. It could be concluded from the x-ray results that ante-smooth filling solution is the best option, and no internal defects were detected in the casting. Skimming effect of new type skimmer gating system was analyzed, and the experimental results showed that the horizontal u-type slot design did have some skimming effect.