Study On Critical Process Parameters In Cold Rolling Process Of AZ31 Magnesium Alloy Tube

As the lightest metal structural material in practical applications,magnesium alloy has the advantages of light specific gravity,specific strength and high specific stiffness.However,due to the close-packed hexagonal crystal structure of the magnesium alloy,the magnesium alloy has poor plasticity and high temperature sensitivity,which leads to cracks and uneven structure of the magnesium alloy during the rolling process,which affects the quality of the tube.The pilger cold rolling has the characteristics of single pass small deformation and multi-pass cumulative deformation effect,and is suitable for forming difficult-to-deformed metal,and further realizes the advantages of refining crystal grains,improving grain orientation,etc.,and obtaining high-performance magnesium alloy tube.Affecting the forming of tubes during the whole process of deformation,mechanical deformation characteristics and process parameters are one of the key factors affecting the forming of tubes.Therefore,It is necessary to conduct research on the above key problems and obtain the corresponding influencing laws and organizational evolution behaviors,Which have certain behind significance for the processing and preparation of magnesium alloy tubes.Based on this,combined with the working principle of the pilger cold rolling mill and the deformation mechanism of the metal tube forming process,the paper studies the relationship between the stress and strain of each deformation section in the cold rolling forming process,and finds that the wall thickness increases in the reducing section.The plastic deformation of the diameter reduction and the length elongation;the plastic deformation of the wall thickness reduction,the outer diameter decrease and the length elongation occur in the reduced wall section;the plastic deformation of the finishing section in the wall thickness and length direction tends to be uniform.The numerical simulation of the forming process of AZ31 magnesium alloy tube was carried out by using finite element software.The comprehensive mechanical laws of tube metal flow and tube deformation zone were obtained and verified.Several controllable rolling process parameters that have great influence on the cold rolling process include feed amount,rotating angle and rolling speed.Through numerical simulation,the influence of key rolling process parameters on cold rolling forming process is analyzed.During the cold rolling process,the equivalent stress,equivalent plastic strain and joint temperature increase with the increase of the feed amount,the rotating angle and the rolling speed.Combined with the principle of pilgering cold rolled tube deformation and actual production conditions,the most reasonable rolling process parameters were selected.Through the rolling experiment with the AZ31 magnesium alloy tube corresponding to the finite element numerical simulation,the outer diameter of the finished tube and the average temperature of the characteristic deformation section were obtained.The results verified the accuracy of the numerical simulation model of the rolling process parameters.The microscopic metallographic experiment was carried out on the characteristic deformation section of the finished tube obtained by the rolling experiment.The preliminary microstructure evolution of the deformation zone of the pilgering cold rolled AZ31 magnesium alloy tube was obtained,and the cellular automaton was verified.The accuracy of the microstructure prediction model of AZ31 magnesium alloy tube.