The Research Of Die-casting Process And Numerical Simulation Of Automotive Steering Gear Servo Housing

The automotive steering gear servo housing is a key component in the steering gear assembly,which requires high reliability of the part.Aiming at the problem that there were more defects of blowholes,shrinkage and porosity in the casting of steering gear servo housing produced by some company,the casting simulation software-Anycasting was used to simulate the filling process and the solidification process of steering gear servo housing casting,which can provide the data support for the improvement of mold structure and the optimization of die-casting process parameters,thus achieving the purpose of improving casting quality.By means of simulating the filling and solidification process of the casting of original scheme,it was found that the filling process of the casting of original scheme was unstable,there were more phenomenon of air entrapment and eddy current in the filling process,and the distribution of temperature field in solidification process was inhomogeneous,there were more isolated liquid phase regions in the solidification process,which resulted in more defects of shrinkage and porosity in the final solidification position.According to the simulation results of flow field in the filling process of original scheme,the eddy current phenomenon in the filling process was reduced by improving the feeding modes of mold,and the air entrapment phenomenon was reduced by improving the size of runner and increasing the thickness of inner gate.According to the simulation results of temperature field in the solidification process of original scheme,the heat balance and temperature field distribution in the mold were improved by optimizating the cooling system.In this paper,we selected three die-casting process parameters which can have an important influence on the quality of casting: injection speed,pouring temperature of alloy liquid and initial preheating temperature of mold,and the orthogonal test of three factors and three levels was designed on the basis of three process parameters of die casting,then according to the numerical simulation results,the total score of defects area(i.e.the product of defects area and corresponding defect probability in the cloud picture)on the section of casting was calculated,and the total score of defects area was used as objective function to investigate and analyze the test,it was concluded that the optimal parameters of die-casting process were injection speed of 1.6m/s,the mold initial preheating temperature of 180°C and the pouring temperature of 630°C.By analyzing the extreme difference of the total score of defects area,it was found that the influence degree of three die-casting process parameters on the quality of castings from the order of main to secondary is injection speed,pouring temperature and initial preheating temperature of mold,and according to the data of orthogonal test,the influence of three die-casting parameters on the casting defects was analyzed.Finally,the optimized mold and the optimal parameters of die-casting process were used for test production of die-casting,after cutting the obtained casting,the section of casting was observed by using the metallographic microscope,it was found that the blowholes,shrinkage and porosity defects in the casting were reduced significantly,and the quality of casting had been improved obviously.The research results of paper show that combining the analysis of numerical simulation and the verification of orthogonal test and applying it to solve the problems of casting defects in the automobile steering gear servo housing can provide the technology and data support to improve the casting quality of steering gear servo housing,moreover,the research results can also provide inspiration and reference for the production of other similar aluminum alloy die-casting housing parts,therefore,the research results have higher practical value of engineering.