Research On Precise Sizing Technology Of TC4Titanium Alloy Cylindrical Workpiece

Titanium and its alloys are widely used in various engineering fields for their high specificstrength and high-temperature strength within a broad temperature range, and also a high corrosionresistance in most aggressive media，However dur to the poor forming characteristic feature of TC4,it’s difficult to manufacture high accuracy part at room temperature. So hot sizing is usually used toimprove the precision of sheet metal forming.In this paper, the thermal elastic deformation behavior of the mould and the behaviors ofthermal elastic-plastic deformation, creep, high-temperature and short-term stress relaxation throughthe hot sizing process were theoretically, numerically and experimentally studied for cylindrical partof TC4.The main contents are as follows：(1) The theoretical calculation of the process of hot sizing was conducted based on thetheories of thermal elastic-plastic bending and stress relaxation, and the accuracy formula of hotsizing was deduced.(2) The2D finite element model for heat conduction of the furnace was set up. The heatingprocesses of parts of ZGCr25Ni20stainless steel and RQTSieMo cast iron materials weresimulated respectively and the simulation results were verified by experiments, which lays a goodfoundation for the temperature simulation of the hot sizing process.(3) Based on the finite element model of the furnace, the simulations of thermal expansion ofring-shaped moulds of ZGCr25Ni20stainless steel and RQTSieMo cast iron materials were carriedout to analyse the relations between the mould geometric dimension and temperature for a givedTC4cylindrical parts. Then the formula used to design the hot sizing mould was summarized; Thecylindrical finite element model of sequence thermal coupling for the hot sizing was built toanalyze the effects of temperature, time and initial deformation on the residual stress anddimension precision. The results show that the reasonable processing parameters for the hot sizingof cylindrical part is heating to650℃and keeping for half an hour.(4) Stress relaxation experiments under different temperatures and initial deformations werecarried out to analysis the effects of various factors on relaxing residual stress. The result was ingood conformity with the simulation conclusion. (5) Hot sizing experiments of TC4cylindrical part were carried out with the application of theparameters optimized by simulations. The sizing results were in good agreement with theengineering standard.