Research On Numerical Simulation Of Temperature Field Of Cold-Rolled Pure Titanium Strip Coil During Annealing Process

With the development of large aircraft project, desalination and coastal power stations in China, the demand for titanium coil is significantly increasing. However, the domestic industrial production of titanium coil is still a blank. To meet the market demand for titanium strip, Baosteel Co., Ltd. established the nation's largest production base of titanium coil. The implementation of this project will make the quality and output of our titanium strip significantly improved. For the vacuum annealing of large titanium strip coil, there is no related experience in domestic. It is an urgent task for us to develop the vacuum annealing technology for titanium strip coil as soon as possible. To determine the optimal annealing process parameters, optimize process system, in order to improve production efficiency, it is a must for us to have a more accurate grasp of the temperature distribution of titanium strip coil during annealing process in the vacuum furnace.In this paper, radial thermal conductivity of titanium coil was determined through solving inverse problem of heat conduction. On the basis of the analysis of heat transfer process in the vacuum furnace, using Haute Rama-line method to determine the radiation angle coefficient between the two titanium coils placed side by side, the temperature model of titanium coil was established. ANSYS software was used to carry out the simulation calculation, and the calculated results were verified by experimental results. Finally, the influences of structure parameters and annealing process parameters on the heating time of titanium coil during annealing process were analyzed. The study not only provides theory basis for making the annealing process, but also has practical meaning for reducing the time of annealing process.Main tasks of this paper are as follows:(1) Using the sample block of superimposed titanium plate to simulate titanium coil, the heating process was measured in the test furnace. Through solving the inverse heat conduction problem, the coefficient of thermal conductivity between titanium plates was determined.(2) The heat transfer conditions during the annealing process were analyzed, and the two-dimensional model, which based on the hypothesis that there was no radiation influence between adjacent titanium coils, was established. The key parameters of boundary conditions were determined. Numerical simulation of temperature field of titanium coil by using ANSYS software. The comparison between the experimental data and calculated results show that, the two-dimensional calculated results can only predict the temperature distribution of the side of titanium coil, which is away from another coil.(3) On the basis of two-dimensional simulation, considering the effects of radiation between the adjacent titanium coils, using Haute Rama-line method to determine the radiation angle coefficient between the two coils, the there-dimensional model was established. The three-dimensional simulation results agree well with the experimental data, and the relative error meets the accuracy requirement of engineering application. According to the 3D simulation results, after 25.7 h, temperature "cold spot" has reached the minimum annealing temperature (670℃).(4) From the two aspects, structure parameters and the annealing process parameters, the impact factors on annealing heating time of titanium coil were analyzed. The results show that the heating time will be extended by increasing the outer diameter of titanium coil, but this effect will be smaller and smaller as the diameter increasing; When the radial equivalent coefficient of thermal conductivity is relatively small, It is more effective to shorten the heating time by increasing its value; The influence of the height of titanium coil on the heating time is more significant than the influence of radial equivalent coefficient of thermal conductivity and titanium coil diameter. In fact, they are highly almost in a linear relationship. Cycle gas flow has little effect on annealing temperature field of titanium coil.