Numerical Simulation Of Isothermal Forging Process And Microstructure Of Aluminum Alloy Control Arm

Control arm is one of the main parts of automobile suspension system, which needs superior stiffness,strength and service life. In order to achieve automobile lightening, the 6082 aluminum alloy is widely used in the production of control arm now. The structure and forming process of control arm are very complex,and the aluminum alloy has narrow forging temperature range, high viscous force and strong crack sensitivity. So the forming of aluminum alloy is very difficult and easy to generate variety of defects in the forming process such as short shot, folding, fracture, over burnt, coarse grain, streamline disorder and so on.Coarse grain defect is one of the common defects in aluminum alloy forging production, especially for the aluminum alloy control arm with complex structure, coarse grain defects are easy generate in the surface,web center and the junction between rod and web of forging. The coarse grain defect will seriously reduce the strength and fatigue life of forging, so must be improved or eliminated. Researchs show that the uneven deformation of different parts and surface heat dissipation too fast of forging are the main reasons for the coarse grain defects production. In this paper, the isothermal forging process was researched in the forging forming of 6082 aluminum alloy control arm. The FEM software DEFORM-3D was used in the simulation of the forging process. The main research contents and results are as follows:1.According to the structure characteristics of the control arm, designed the forming technological processes. The simulation results show that the optimum forging temperature of aluminum alloy control arm is 450℃.2.Reasonable design and calculation of the roll forging process was carried out, and four passes roll forging process and ellipse- square- ellipse- circular grooves system were adopted. Reasonable roll forging process help to get the quality forging, reduce the die forging flash, and improve the utilization of the material.3.The structure of cold roll forging billet and roll forging dies were optimized by numerical simulation.By increasing the length of transition section of cold roll forging billet and optimizing roll forging and bending die eliminated the folding of the pre-forging process.4.The velocity, temperature, stress and strain multi field simulation and analysis were carried out.Pre-forging is the most complicated working procedure, so the section fields analysis on the key area of the pre-forging should be carried out. The results show that there are no over burnt, fold and fracture defects in the entire forging process, and the streamline of forging is good. The dies load are predicted, and the results show that the equipments selection is reasonable.5.The microstructure simulation model of aluminum alloy 6082 was studied. The grain size evolution of aluminum alloy control arm was simulated and analyzed. The results show that the average grain size of forgings decrease continuously, forgings microstructure become uniform and refinement in the process of roll forging. The average grain size of forging reduced from 100 μm to 17.7 μm after bending process. In the pre-forging process, the average grain size of the forging is increased and reached 28.7 μm at the end.After finish forging, the average grain size was 23.3 μm, which reached the first grain size level. The dynamic recrystallization evolution process of finish forging process was simulated and analyzed.6.The coarse grain defects of aluminum alloy control arm were studied, and found that the center of web and the junction between web and rod are the most serious coarse grain defect area. The coarse grain defects nearby branch and the large end are also very serious and difficult to eliminate. The grain size of nonisothermal forging control arm was simulated, and the grain size distribution of the finish forgings of isothermal forging and nonisothermal forging were compared. The results show that the isothermal forging can significantly improved the coarse grain defects of aluminum alloy control arm.