Lost Foam Casting Process Optimization Of Cast Steel Valve Body

LFC has the advantages of agility design,high accuracy,lower production cost and been widely used in small and medium enterprises.For steel casting,casting steel often forms shrinkage cavity?shrinkage porosity and carburization defect in LFC,this defect form is related to the filling solidification process.So it's need to numerical simulation analysis of steel temperature field and flow field in the process of lost foam casting and analysis the formation mechanism of defect,and it has a certain guiding significance for the production practice of steel.In this paper,using the Unigraphics NX.8.0 as 3D modeling software,the ProCAST as numerical simulation software,the lost foam casting process of cast steel valve body produced by a foundry are analyzed and improved.A factory production of cast steel valve body,ZG25,is used to adjust the flow of fluid,and have high requirement on casting compactibility.But the casting have the leakage phenomenon,and its air tightness can not meet the technical requirements,its rejection rate as high as 60%.Analysis of casting anatomy that shrinkage defects appear on the casting internal,the casting internal shrinkage defects is to make the products can not meet the requirements of the main causes of air-tightness.Using ProCAST numerical simulation software as a tool,then the filling and solidification process of actual technological process are simulated,and adopted solid method,the direct analysis method to predict the shrinkage cavity,shrinkage defects.Simulation results show that the production of the original casting defects of shrinkage porosity,the defect position and the actual production of casting defects distribution is similar,to verify the simulation accuracy.Design the top gating system and bottom gating system two kinds.Simulation results show that the shrinkage cavity of the top gating system ismore than the bottom gating system,and the top gating system have wrapped gas phenomenon in the filling process,so the bottom gating system is more reasonable.By the orthogonal experiment,studying the pouring temperature,pattern density and vacuum degree effect the shrinkage porosity forming.The results show that when the pouring temperature is 1620?,the pattern density is18kg/cm3,the negative pressure is 0.05 MPa,the shrinkage porosity of valve body is the smallest.In the end,changed the riser process on the basis of the above process optimization,result show that it is no shrinkage defects in the casting and obtained a qualified casting process.