Development And Optimization Of Warm Roll Hot Rolling Process For TiAl Alloy

Due to TiAl alloys itself has the characteristics of low density,high specific stiffness and high specific strength,in addition,and excellent mechanical properties at high temperature,so it can be replaced to some Ti based and Ni based superalloys in the aerospace field.However,the engineering application of TiAl alloy is limited by its own shortcomings,such as poor plastic properties at room temperature,narrow processing window and harsh conditions in the process of heat treatment.Under this background,we based on the theory of electromagnetic thermal field coupling,and to explore a new warm roll hot rolling technology.After the roller surface is induction heated,the non clad hot rolling of TiAl alloy is carried out.It is aimed to improve the forming quality of sheet metal by reducing the temperature loss during the rolling process.This paper is intended to study the induction heating of roller and the hot rolling of TiAl alloy,the main research work is as follows:(1)Based on the research of electromagnetic induction theory,in order to meet the needs of electromagnetic induction heating process,the special coil for the roll of two high mill roll was designed.The geometric model of the roller and the special induction coil were completed by using Solid Works software.(2)By using the finite element software of DEFORM,the temperature field distribution of the roller in the static and dynamic induction heating process under the special induction coil was calculated and then analyzed.The skin effect of induced current makes the surface temperature of roller rise rapidly,while the core is still at a low temperature.The special induction coil was made and the electromagnetic induction heating experiment was carried out with the roller.When the power frequency is 1000Hz and exert a current density for 10e~5A/m~2,the maximum surface temperature of roller can achieve 681?at 75s.The temperature change process of roll during electromagnetic induction heating was recorded meanwhile.The calculation results did tally well with the experimental results.(3)The cooling way of roller in the process of induction heating was studied and analyzed,and the cooling and heating process of roller under different cooling modes was simulated by finite element software.When the average surface temperature of the roll is 800?and the center temperature is 200?,the surface temperature of the roller can be reduced to 200?and the center temperature can be reduced to about 50?in 1 min through the cooling mode of end water cooling+roller surface air cooling.Besides,the cooling mode of cooling water in the roller is simulated,which can meet the cooling requirements of rolling mill equipment.(4)The geometric rolling model of TiAl alloy sheet was established by using ABAQUS.and the finite element simulation of warm roll hot rolling process of TiAl alloy was carried out under the rolling conditions of 20?,200?,400?,600?and 800?with roll temperature and reduction rate of 10%,20%and 30%respectively.In the post-processing of the software,the data of temperature field change and the distribution of stress and strain field were got.The results show that the increase of roll temperature in the rolling process can effectively reduce the temperature drop of the plate in the rolling process,and it is also very beneficial to improve the shape of the plate and the uniformity of the surface deformation degree of the plate.When the reduction rate is controlled between 10%and 20%,the deformation of the plate is relatively uniform,and no obvious strain concentration occurs.With the increase of roller temperature,the surface deformation uniformity and flatness can be improved obviously.