Study On Multi-pass Temperature Controlled Rolling Process Of TC4 Titanium Alloy Plate

High specific strength,strong corrosion resistance,non-magnetism,and good mechanical properties of the titanium alloy make it to be a high-quality lightweight structural material,a new functional materials and an important biological engineering materials.And the current market demand of the titanium alloy plate and accounting for about 1/3 of titanium processed materials,is relatively large.However,the rolling process of titanium plate is complicated,the rolling temperature window is narrow,and the thermal conductivity is poor.If the rolling temperature is too high or the rolling deformation is too large,the temperature of the central area of the rolled product will rise sharply,and the plate temperature distribution will be uneven.There are structural differences in the thickness direction,which in turn causes problems such as poor plasticity of the strip,uneven rolling deformation,and edge cracking,making it difficult to control the quality of the strip.The low rolling temperature causes severe work hardening,which leads to excessive hot rolling force and heavy rolling mill load,increasing the difficulty of rolling titanium alloy plates.Therefore,it is extremely critical to control the strip temperature during the titanium plate rolling process.Based on the hot rolling process of typical titanium alloy TC4,this paper carried out experimental research and finite element simulation analysis on the plate rolling of TC4 titanium alloy from the perspective of temperature-controlled rolling and combined with the on-site rolling process of titanium alloy plate in a factory,providing theoretical basis for the development of hot rolling process of titanium alloy plate.The Gleeble-3800 thermal simulator was used to measure the high-temperature flow stress of the TC4 titanium alloy material,and the influence of temperature and deformation rate on the flow stress was analyzed.The hot working range of the TC4 titanium alloy was studied using the hot working chart.Through the hot rolling experiment,the effect of the rolling reduction ratio of the transverse and longitudinal rolling passes on the anisotropy of the TC4 titanium alloy plate was studied,the study shows that when the rolling reduction ratio of the horizontal and vertical rolling passes is 1: 1,the material anisotropy is basically eliminated.Carry out heat transfer experiment and rolling experiment of TC4 titanium alloy plate,measure the multi-point temperature change at the designated position of the sample,and a finite element model consistent with the experimental conditions is established.Through reverse heat transfer calculation and forward simulation verification,the comprehensive heat transfer coefficient between TC4 titanium alloy plate and air,and contact heat transfer coefficient with the roll are determined.The hot-rolling finite element model of TC4 titanium alloy strip was established,and the reliability of the finite element model was verified through industrial field data investigation.Then,the rolling conditions of different rolling process parameters and multi-parameter coupling were simulated and analyzed.Results it is shown that the main factors affecting the temperature distribution of hot-rolled strip are rolling speed and pass reduction.A three-dimensional full-process rolling simulation model was established combined with a typical rolling production procedure of TC4 titanium alloy in a certain plant,to study the temperature distribution,plate widening deformation law and the temperature uniformity in the width direction after rolling of the titanium alloy plate.The results show that the temperature drop of the rolled strip is about 50 mm inward along the width direction,and the maximum temperature difference between the rolled strip and the inside of the rolled strip exceeds 50?,and the main cause of the uneven deformation and cracking of the rolled strip is the uneven temperature distribution.When the rolled piece is thicker,the lateral deformation along the thickness direction is approximately “double drum” shape,it becomes “convex” shape with the progress of the rolling pass,and the width extension decreases as the thickness of the plate decreases.Based on the finite element simulation,the rolling temperature window of hot-rolled TC4 titanium alloy was determined,giving the guiding principles of the rolling process system of titanium alloy plate.The hot rolling process specification software for titanium alloy was developed in combination with the actual rolling process on site.By controlling the rolling process parameters,the entire process control of the temperature of the titanium alloy plate is achieved.