Machined Graphite Mold Casting And Its Numerical Simulation Of Titanium Alloy Casing For Centrifugal Pump

With the vigorous development of the petrochemical industry,the demand for petrochemical pumps has grown tremendously.Titanium alloy pumps have excellent corrosion resistance,and are especially suitable for alkali production,salt production and petrochemical industries in corrosive environments.This thesis aims at the gravity graphite casting of TA2 titanium alloy pump casing of centrifugal pump for petrochemical industry.Through the analysis of the casting process,the casting process parameters of the pump casing were determined,and three casting process schemes were designed.Through numerical simulation using software-ProCAST,the filling law,solidification characteristics and the casting defects(including location,size,number)of the pump casing under different casting process schemes were analyzed.and the feasible gravity graphite casting process scheme of the TA2 titanium alloy pump casing was optimized.According the casting scheme,loose pieces of molds and cores for the casting were designed and pruduced by machinable graphite.Small batches of TA2 titanium alloy pump casings were trial-produced through core(mold)assembly molding,vacuum melting and vacuum pouring.The mechanical properties of TA2 titanium alloy pump casing were tested,and the casting defects in the casing were also measure by X-ray radio graphic tests.The conclusions of this thesis are as follows:Titanium alloy pump casing is large in size and complex in structure.It is suitable for machined graphite mold casting in small batch production.The surface roughness of the machined graphite molds is low.As a result,the casing castings have a smooth surface.Furthermorc.the machined graphite molds can be rc-used.For the top gating system and the side gating system,the simulation results show that there are many dcfects on the volute runner and flange in the titanium alloy pump casing.The reason is that the velocity of molten metal entering the cavity is high in the top gating system,and resulting in the turbulence in the volute runner.For the side-cast gating system,sprue is too thinner,and the height of the static pressure head is not enough.The step gating system of the titanium alloy pump casing has the advantages of both the top gating system and the side gating system.The simulation results show that the defects in the flow passage of the volute disappear after the stepped non-pressurized gating system is adopted in the casting of titanium alloy pump casing.Titanium alloy pump casing can be produced by core(mold)assembly molding.The mold is first separated into loose pieces,and then a total of 12 loose piece(i.e.bottom plate,upper type,lower type,3 of positioning pins,2 of bottom corner cover plates,outlet flange cover plate risers,riser rings,2 of combined cores)are designed and produced by machinable graphite,and finally they are assembled into a total mold.Small batches of TA2 titanium alloy pump casings are trial-produced by vacuum melting and vacuum pouring.The X-ray inspection test results of the pump casing are basically consistent with the simulation results.The trial-produced titanium alloy pump casing meets the technical requirements.