| 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. Semi-hot controlling precise forming is the process whose forming temperature range is between warming forming and hot forming. The semi-hot forming process have some advantages: save energy consumption, lower the forming resistance, reduce the equipments input and make the products acquire good internal overall properties as well as good external dimensional accuracy. In this thesis, takes 40Cr and Cf53 steel as the subjects to investigate, systematic experimental and theoretical studies on the forming behavior and microstructure evolvement of the semi-hot precise forming was carries out, then conducts numerical simulation and experimental verification of the process, and has also applied for the invention patent.A new flow stress model, which consisted of the steady state term and the modified term is established based on the study of Zener-hollomon parameter. The steady state term is the steady flow stress model of metal materials in the semi-hot forming process, and it is a model related to the Z parameter; while the modified term refers to the part of flow stress which varies with the changes of strain. And the values of specific parameters in the new flow stress model of 40Cr steel and Cf53 steel are calculated by applying the model into these steels. The semi-hot forming activation energies of 40Cr and Cf53 steel are calculated, they are 318.759 kJ/mol and 274.803 kJ/mol respectively.Taking the Zener-hollomon parameter as a bridge between the macroscopic flow stress and the microscopic grain size in the semi-hot forming process, the...
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