Optimization Of Process Parameters Of TC4 Thick-walled Tube On Cone-type Piercing

TC4 alloy is widely used in ships,automotive and energy industries with excellent comprehensive performance,at the same time in the aerospace and other fields,the need for a large number of titanium thick-tube as a ring and other complex shape parts secondary processing blank.Titanium alloy seamless pipe production is difficult,because of its deformation resistance is large,prone to a strong work hardening phenomenon,easy to crack in the processing process.Titanium alloy pipe processing methods are mainly mechanical processing,pressure perforation(extrusion method),punching and rotary piercing.However,the diameter ratio of titanium alloy(outer diameter D to wall thickness S)produced by rotary piercing method is generally greater than 10,and the resulting tissue is widmanstatten structure.In this paper,the TC4 thick-walled pipe with diameter-to-thickness ratio less than 5 is processed by rotary piercing,and the optimized process parameters are used to obtain the duplex microstructure.The main research contents and analysis are as follows:Based on the principle of skew rolling,UG software was used to establish the geometrical model of TC4 thick-walled pipe rotary piercing.The finite element software was used to establish the thermal-mechanical coupling finite element model and the simulation calculation.By analyzing the influence of the feed angle,reduction rate of diameter and the top reduction rate on the piercing process of the rotary piercing,it can be seen that the small feeding angle is prone to the phenomenon of the rotary piercing,and the feeding angle is conducive to the establishment of the perforation process.With the reduction rate of diameter is increased,the length of the deformation zone is increased which is easy tomeet the bite condition and the internal expansion is achieved.The strain field and the temperature field are evenly distributed.With the increase of the top reduction rate,the piercing process is easy to be realized,and strain field and temperature field distribution evenly.The orthogonal test is designed to analyze whether the rolling process is established,the dimensional accuracy of the finished pipe after smooth rolling and the equivalent strain and temperature field are obtained by the feed angle,reduction rate of diameter and the top reduction rate.TC4 thick-walled tube is obtained,and the optimum process parameters of the perforation are: the feed angle is 18 °,the reduction rate of diameter is 10%,and the top reduction rate is 7%.The tapering test of TC4 thick-walled pipe was completed by using Ф50mm×10mm full parameter control perforation testing machine.Billet specifications for theФ45mm TC4 bar,after rolling through the hole after the finished product specificationsФ48.9mm× 11.5mm,the diameter ratio is about 4.25.The rotary piercing of the thick-walled tube was realized,and the resulting structure was duplex microstructure.