Research On Optimal Design Method Of Gating And Riser Process And CAD/CAE Integrated System For Steel Castings

With the advantages of high strength and good toughness,steel castings have been widely used in industries,such as ships and vehicles,construction machinery,power station equipment and so on.Steel casting is a very important metal part in the national economy.However,the casting defects such as misrun,air entrapment,shrinkage are easy to appear in the forming process of steel castings,which seriously affect the mechanical properties and service life of steel castings.Reasonable process design of gating and riser is an important method to solve the above casting defects problem.At present,the process design of gating and riser system is usually carried out with CAD as the design platform and CAE as the analysis tool in an iterative trial and error manner.The "passive" process design method which highly depends on engineer experience has subjectivity and randomness,which makes the final process yield low and resource consumption large.In this paper,an optimization design method of gating and riser system for steel castings based on intelligent optimization algorithm is proposed,and the integrated CAD/CAE system of gating and riser process optimization is constructed.The "passive" mode of traditional artificial experience is changed to the "active" mode of system intelligent optimization,which provides new ideas and key technology for intelligent process design of steel castings.The main research work is as follows.Firstly,a process optimization design method of the gating system based on the fruit fly optimization algorithm is proposed.Considering the flow characteristics of molten metal and taking the minimum filling time as the optimization objective,Reynolds number and runner modulus as constraints,a process optimization design model of gating system for steel castings is established,and is solved by an improved fruit fly optimization algorithm.Ihe above method is applied to the geometric dimension optimization of the gating system for the upper center plate casting to obtain optimum size of each runner of gating system.The results of numerical simulation and pouring experiment show that the proposed method can achieve the shortest filling time under the steady state,reduce the energy loss during the filling process,and greatly reduce the probability of defects.Secondly,a hybrid numerical simulation and geometric reasoning hot spots calculation method for riser system process optimization is proposed.A hot spots calculation model considering the influence of flow in casting forming process on feed paths is established by numerical simulation to accurate calculation of feed paths and hot spots.The influence law of the flow in the filling process and solidification process on feed paths and hot spots is explored by using T-shaped part.The results show that if only considering the flow of solidification process,it will cause a larger temperature difference and form asymmetric feed paths and multiple hot spots.If the filling and solidification process flow are considered simultaneously,the effect of initial temperature inhomogeneity on feed paths and hot spots will be further strengthened.The number and location of hot spots will be increased,and the feed paths will be more asymmetric.The application results of plate part show that the feed paths and hot spots results are in good agreement with the experimental results.Based on geometric reasoning method,a hot spots calculation model based on distance field representation of complex geometric entities is bulit and verified by the application of standard typical castings.Based on the riser feeding criterion,taking the minimum riser volume as the optimization objective and modulus and volume as the constraint conditions,a process optimization design model of riser system for steel castings is established.Taking cylinder sleeve casting as an example,the optimization model of riser system is solved by using fruit fly optimization algorithm,and the geometric size optimization results of riser system are obtained.The numerical simulation results show that the method realizes the minimization of riser volume and reduces resource consumption,which provides a new idea for process design of riser system.Thirdly,the framework of CAD/CAE integrated system for gating and riser process optimization based on multi-source data fusion and data intelligent analysis technology is constructed,which realizes the integration of casting CAD,process optimization and casting CAE.The casting process three dimensional geometry data,casting process optimization data and casting CAE numerical simulation data of steel castings are constructed,and the multi-source data are fused to form data stream.Taking Open CASCADE kernel as the core of geometric modeling and the geometric modeling of cylindrical open riser as an example,the modeling process of parametric casting process primitives is studied and integrated modeling is realized.Through the intelligent analysis of flow field data,hot spots data and shrinkage defects data,the intelligent process optimization and data feedback of the gating and riser system are realized.The basic modules of CAD/CAE integrated system are constructed,and the integrated CAD/CAE system of gating and riser process optimization is successfully developed.The process optimization process of gating system and riser system is given in detail by two cases.Finally,the practicability and reliability of the CAD/CAE integrated system for gating/riser process optimization are verified by the application of base steel casting.The optimization design process of gating and riser system of the base steel casting is analyzed in detail and verified by numerical simulation method.The pouring experiment is carried out with the integrated system design process.The casting is detected by penetrant inspection and ultrasonic inspection.The results show that shrinkage defect of 1.6mm equivalent size appeares in the middle section of the casting without chill,while no defects occurred in the casting with chill.The numerical simulation results are consistent with the experimental pouring results.Through the comparative analysis of the original process design and the optimized process design,it can be seen that the process yield of the casting is increased by nearly 10% under the condition of ensuring no defects in the casting.The results effectively present the practicability and reliability of the CAD/CAE integrated system for the gating and riser process optimization of the steel castings.