Research On The Forming Process Simulation And Die Wear Of Semi-Hot Temperature Range

Accompany with the upsurge of the economy development and the manufacturing globalization, and to make the product have more market competition abilities, the advanced manufacturing technique having low cost and high quality has becoming the manufacturing industry development trend. Precision plasticity forming is the process which can get net shape or near net shape part with a low cost. The semi-hot precision forming process is one of the precision plasticity forming whose forming temperature range is between warm forming and hot forming. The semi-hot precision forming has some advantages: saving energy consumption, lower the forming resistance, reducing the equipments input and acquiring good property products. Although this advanced process has been gotten widely using, its mechanism has not been system researched. In order to investigate the forming property, takes 40Cr and Cf53 steel as the subjects, systematic experimental and theoretical studies on the forming behavior and microstructure evolvement of the semi-hot precision forming was carried out, then conducts numerical simulation and experimental verification of the process , and has also applied for the invention patent.Using the ring compressing test, process parameters on the impact of friction factor has been studied. Results show high temperature and low velocity decrease friction factor.Plastic deformation resistance is an important factor which can affect process developing, die life and equipment selection etc. Based on the thermal-simulation test, the flow behavior of 40Cr and Cf53 steel was analyzed. The results show that flow stress curve represent different types with the deformation process parameters changing. Strain rate and temperature is the most sensitive factors.Based on the thermal simulation results and the evaluation of the existing flow stress models, the forming activation energies of 40Cr and Cf53 has been calculated using a hyperbolic sine expression. They are 270.321 KJ·mol-1 and 290.782 KJ·mol-1 respectively.Based on the Zener-Hollomon parameters, semi-hot activation energy has been associated with the strain. A new creep model has been constituted. The calculated results using this new model showed that all the values are in line with the experiment, so this flow stress model can be applied to the follow-up numerical simulation analysis.The simulation of semi-hot extrusion of 40Cr and Cf53 steel was conducted out by the thermo- mechanical coupled finite element method and the new creep model was used in the simulation to calculate the flow stress. The simulation predicts the distribution of strain, stress and temperature in extrusion test. The deformation temperature, the forming velocity, deformation extent and friction factor on the semi-hot extrusion process has been analyzed. The results may provide the scientific guidance to determine reasonable forming process parameters.On the basis of the analysis of existing wear models, a new wear model has been applied to the finite element simulation of die. Comparing the actual contours with the simulated wear contour, we find that the two contours are match which prove that this model can be used to the research of mould. Then forming parameters on the wear of die has been studied using this model. The results show that forming velocity and friction factor is the most sensitive factors, which should be controlled in the process design.Physical simulation has been conducted to verify the accuracy of the flow stress model and the die wear model. The results show that the flow stress model and numerical simulation system in the semi-hot forming process of 40Cr and Cf53 steel have a high stability and reliability.Semi-hot controlling precise forging simulation system was adopted to analyze the semi-hot forming property of an automobile outer race, and the process scheme has been determined. The semi-hot controlling precise forming of Cf53 steel was realized for the first time, and metallographic analysis for the outer race forging was preceded. The results show that the semi-hot controlling precise forging process in this study can decrease the material forming resistance, and the single normalizing treatment procedure can be omitted. The cooling can be controlled by the residual thermal. Then the finer internal structure and the higher overall mechanical property are obtained. This method has good characteristics of simplifying working process, conserving energy and making final products have better internal and surface quality.