Numerical Simulation Study On Deformation Pattern And Forming Quality Of Mo Alloy Nuclear Fu-El Clad Tube Under Pilger Warm Rolling

As the primary forming technology for the preparation of Mo alloy nuclear fuel casing tubes,pilger warm rolling is a multi-stroke,non-stationary and triple non-linear complex physical process.It is important to study the doformation mechanism and forming rule of this process to optimize the pilger rolling process and further improve the tube forming quality.Therefore,based on the finite element simulation software ABAQUS/Explicit and 3D modeling software Solidwork,this paper establishes a 3D finite element model of Mo alloy tube single pass multistroke pilger rolling.And on this basis,the deformation characteristics and deformation mechanism of Mo alloy tubes under pilger rolling are discussed,analyzes the influence of process parameters and die parameters on roll,mandrel and tube forces in the rolling process.To explore the influence of these parameters on the final tube circuler degree and thickness,to provide a theoretical basis for the practical production of pilger warm-rolled Mo alloy tubes.The main results of this paper are as follows:(1)Mo alloy tube mainly goes through three stages of deformation process during the rolling process,and the tube strain variable is small in the early stage of deformation in the reduction zone.The diameter reduction and wall reduction zone is in the middle of deformation,the plastic deformation of the tube is obvious,and the strain variable is large.The sizing zone is at the end of deformation,and the tube strain reaches the maximum to achieve finishing.(2)The influence of the change of internal and external friction coefficient on the axial force is more obvious,and the increase of the axial force accelerates the aging of the mandrel and the rotary feeding mechanism.The friction coefficient inside and outside the tube is different,which increases the average wall thickness and Mean Square Error(MSE)of the tube,which is not conducive to the forming quality of the tube.With the increase of the feeding amount,the rolling force,mandrel and axial force of the tube increase,and the thickness and circuler degree of the tube also increase,shortening the service life of the mold and reducing the forming quality of the tube.The rolling temperature increases,the rolling force and axial force decrease,the damage to the mold is reduced but the requirements for heating equipment are increased,the average tube thickness is reduced,the MSE of the wall thickness increases,the circuler degree is reduced,as well as the increase in MSE of the wall thickness and the increase in circumference will reduce the quality of the tube forming.When the internal and external friction coefficient is 0.05,the feeding amount is 4 mm/feed and the rolling temperature is 300℃,the wall thickness of the final tube is better.When the internal and external friction coefficient is 0.02,the feeding amount is 2 mm/feed and the rolling temperature is 1000℃,the circuler degree of the final tube is better.(3)The increase of rolling opening angle,the influence of rolling force and axial force is small,the thickness and circuler degree of the tube increase,the MSE of the wall thickness first decreases and then increases,and the forming performance of the tube is best in the MSE of the wall thickness and the circuler degree are small.The roll gap increases,the rolling force fluctuation increases,the axial force increases,the tube thickness,MSE and circuler degree also increase,increasing the mold damage and reducing the forming quality of the tube.When the opening angle is 25° and the roll gap is 0 mm,the wall thickness of the final tube is better.When the opening angle is 20° and the roll gap is 0 mm,the circuler degree of the final tube is better.