Research On Microstructure And Thermoplastic Flow Stress Of Retaining Ring Steel

As China's economic development,the market demand and internal quality requirement of retaining ring which is a basic part for power have become more sophisticated.The hot forming process of retaining ring in China is multi-heating and multi-deformation process,which is less controllable,and leads to serious forging surface cracks and large grain size.So the hot forging technology seriously cannot meet the current requirements of the development.Therefore,microstructure evolution rule during the hot deformation process of retaining ring steel has been thoroughly studied.These results could provide significant theoretical basis during the practical forging technology of retaining ring steel for the heavy forging.In addition,it has important practical meaning and theoretical value for the development of microstructure evolution simulation of the finite element simulation technology.In order to improve the uniformity and stability of the retaining ring material's austenitic organization,prevent carbide precipitation and improve the cold deformation strengthening performance,it is necessary to study the solution treatment process.Paper's main work and achievements are shown as follows:(1)There are some experiments about the solution treatment of the retaining ring steel.By the analysis of the mechanical properties and the tensile fracture,we explore the influence of the solution treatment process parameters about the retaining ring steel's room temperature mechanical and we get that the best solution treatment temperature is 1100?,the best solution treatment time is 1.5h.With the increase of the solution treatment temperature,the elongation steel and the reduction of area of the test increase.The solution temperature has little effect on the yield strength and tensile strength of the specimen.(2)By the hot compression simulation test,the high temperature plasticity behavior of retaining ring steel has been investigated in the different conditions.The relationship among flow stress,strain rate and deformation temperature under high temperature deformation has been described by hyperbolic sine function by the analysis.According to the strain hardening rate,the critical strain value of dynamic recrystallization,dynamic recrystallization model and grain size model of test steel have been established.(3)Using double pass hot compression test,the static softening behavior of retaining ring steel has been studied.The softening curves of static recrystallization are in accord with the Avrami equation.And the corresponding recrystallization kinetics model and grain size model have been obtained by analysis the effect of different deformation parameters.(4)Based on the simulation software DEFORM-3D,in order to have the function to simulate microstructure evolution,the mathematic models of microstructure evolution and grain growing during hot forging process have been embedded in user subroutines.The microstructure simulation of the hot compression process of the retaining ring steel is carried out by the finite element simulation system.