Research Of The Method And Mechanism Of Honing Magnetorheological Polishing On The Inner Wall Of Titanium Alloy Tube

Titanium alloy is a kind of structural metal developed from the 20th century.It has high thermal strength,good corrosion resistance,and good mechanical properties.Therefore,it is widely used in aerospace as a structural part of metal materials,or as a pipe material in oil and gas transmission pipeline.In the process of fuel delivery in oil and gas pipeline,the requirements for flow are particularly strict,so the inner wall of the pipeline needs to have high smoothness.Traditional machining methods are mostly applicable to plane and open surface,and as a flexible polishing method,magnetorheological polishing is achieved with"flexible polishing layer" formed by magnetorheological fluid under the magnetic field.Material removal is realized through the relative movement between the "polishing layer"and the inner wall,and finally the inner wall with glassy surface is obtained.In view of the low polishing quality and efficiency of the original inner wall polishing,based on the existing horizontal MRF polishing device,this paper carried out a thorough study,the main research contents are as follows:(1)By changing the excitation mode of the magnetic field in the original horizontal polishing device,the peripheral layout of the permanent magnet is realized through the design of the excitation core bracket,so as to increase the size of the polishing area,resulting in two magnetic field layout schemes.Using Ansoft Maxwell software to simulate the static magnetic field,the magnetic induction intensity and the distribution rule of magnetic field in two kinds of magnetic field layout schemes under different polishing gaps are studied;In order to improve the magnetic field intensity of polishing area,the magnetic field distribution and magnetic induction intensity of polishing area under non-conducting polishing head are further studied.(2)Using the designed excitation device under the permanent magnetic field,the polishing test was carried out on the horizontal magnetorheological polishing device about the rotating speed and polishing time,and the surface roughness was compared with that under the electromagnetic permanent magnetic field to analyse the effects of different parameters.(3)Based on the shear movement law of carbonyl iron powder chain in the MRF,the initial roughness of the inner wall surface of the tube will affect the actual polishing effect.The inner wall surface of the titanium alloy tube was pre-treated to reduce the surface roughness.After the pretreating,the test was carried out under same rotating speed and polishing time to study the influence of initial surface roughness on polishing effect.(4)Design and build a vertical MRF polishing device,and in order to improve polishing quality and polishing efficiency,under permanent magnetic field,the combination of different size of polishing particles and the combination of different rotating speed were used to carry out the combined gradient MRF polishing test.