Numerical Simulation And Process Optimization Of Casting Molding Of Automobile Steering Knuckle

As an important part of the automobile steering bridge,the steering knuckle has a very hostile working environment,it not only has to withstand the load of the vehicle body and the impact of the road,but also withstand the torsion of braking and steering.Therefore,the steering knuckle is required to have high standards for structure,strength,plastic toughness and shock absorption performance,and its performance directly determines the safety of the automobile.Ductile iron QT400-15 and QT450-10 are typical material for steering knuckles due to their low cost and good comprehensive mechanical performance.However,with the gradual improvement of automobile performance,its insufficient strength will reduce the service life of the steering knuckle.At the same time,the unique paste solidification method of ductile iron easily leads to defects,such as shrinkage porosity and cavity in the castings,and the quality is unsteady.So,the development of high strength and toughness ductile iron automotive steering knuckle products that suit for high safety automobiles has received extensive attention from the industry.In this paper,ductile iron steering knuckle is taken as the research object,a kind of high strength and toughness ductile iron material that meets the performance requirements of automobile steering knuckles was prepared by designing and controlling the chemical composition.The effects of C and Si elements on the graphite spheres,matrix microstructure and mechanical properties of the Cu alloying-ductile iron were studied and analyzed.In addition,the casting process and structure of the steering knuckle were analyzed,and a casting process scheme was designed.The filling and solidification process of steering knuckle casting was simulated by Magmasoft simulation software,the defects produced in the casting process were analyzed,the program was improved by proposing rationalization,and it can provide technical support for the actual production of high strength and toughness ductile iron automotive steering knuckle products.The main results are as follows:1.The effects of C and Si elements on the graphite spheres,matrix microstructure and mechanical properties of the prepared ductile iron were studied and analyzed.The results showed that: on the basis of adding 0.36% Cu,the increase of Si content can improve the number of the graphite nodules and reduce the diameter.The increase of C and Si content can improve the content of pearlite in the matrix of ductile cast iron,and reduce the spacing of pearlite.Both Cu element and Si element have the function of strengthening the matrix of ductile iron.The increase of the pearlite content in the ductile iron matrix and the refinement of the pearlite lamella structure can improve the tensile properties of the materials.2.A high strength and high toughness ductile iron with a tensile strength of 765 MPa and an elongation of 10.2% was prepared by designing and controlling the chemical composition of ductile iron,the strength and toughness of this material fully meet the performance requirements of automobile steering knuckle.3.A process scheme of steering knuckle casting was designed.Including the selection of moulding scheme,casting position and parting surface,the design of sand core,gating system and feeding system: the production mode of steering knuckle casting is quartz sand green sand casting with four pieces in a box(two pieces for each left and right knuckles),stepped curved surface parting method was used,horizontal pouring,the left and right knuckle forming holes share one sand core.The gating system is unchocked gating system,the combination of a flat ingate and a pressure control risering as the design of the gating-feeder system was adopted.4.Magmasoft numerical simulation software was used to simulate the filling and solidification process of the steering knuckle under the pouring temperature of 1375?,1400? and 1425? and the pouring time of 10s.The simulation results show that,there are molten iron splashing and gas entrainment in the upper trailing arm,and there is gas trap at the axle neck and the highest point of castings,there are many defects of shrinkage porosity and cavity in the thick wall position of the casting.And with the increase of the pouring temperature,the flow speed of the molten iron in the mold cavity increases,the pressure in the mold cavity increases,and the probability of gas trap at the highest point of the casting increases.The number of shrinkage porosity and cavity produced by the steering knuckle casting decreases first and then increases.The best pouring temperature is 1400?.5.The molten iron splashing and gas entrainment in the casting process of the steering knuckle castings can be solved by adding a new ingate on the side of the upper trailing arm close to the runner gate,the gas trap phenomenon of the casting can be solved by adding vent needle at the four positions where the gas trap in the casting,shrinkage porosity and cavity defects can be solved by placing graphite external chills at the location where shrinkage porosity and cavity defects in the casting.Finally,good casting quality of automobile steering knuckle products and the optimal process scheme were obtained.