The Research On Continuous Steel Tube Rolling With Two-Roll Grooves Using Backing Mandrel

At present,the continuous rolling has become the main type of seamless steel tube production in our country.How to maximize the role of the continuous rolling mill becomes an important issue for seamless steel pipe workers.The backing mandrel is according to predetermined differential reverse movement,and after the completion of the rolling out of the steel pipe.In two roller rolling process,the common mode of operation are full floating mandrel,semi floating mandrel and retained mandrel,no backing mandrel are used in industrial production.It has been proposed that using the backing mandrel in steel pipe two roll rolling mills that the mandrel operation mode is helpful to improve the quality of steel products,but this is only the idea,there is no experimental data support.In this paper the numerical simulation of the two roll tube rolling using backing mandrel process by finite element software MSC.SuperForm,the same pass system is used,only change the mode of the mandrel.By comparing the different operation mode of steel rolling mandrel metal deformation,mechanical parameters and Wall-thickness accuracy,so as to reveal the characteristics of backing mandrel,is aimed to provide reference to the backing mandrel used in two rollers rolling steel tube technology.The main conclusions are as follows:(1)The metal lateral flow is limited and over-fill tendency of metal in roll gap is decreased with the backing mandrel compared to continuous rolling process with the full floating mandrel.So it can reduce the rolling pass in the opening to form a "handle" defect trend and the possibility of tube defects in crease edge profile.(2)The average wall thickness of the steel pipe is thin,which is advantageous to the reduction of the wall of the steel tube.However,compared with the full floating mandrel,wall thickness accuracy is poor,in particular,thin wall tubes and medium thick wall tubes.(3)According to the distribution of the thickness of the workpiece,it is found that the thickness of the tube wall of the backing mandrel mill is a little thin in 90°,and the wall thickness of the medium thick wall tube and the thick wall tube in the direction of 75 degrees is thinner.Therefore,in the design of the pass,we should pay attention to reduce the volume of the workpiece in the 90 and 75 degrees of reduction,in order to obtain higher wall thickness accuracy(uniformity).(4)Rolling force in continuous rolling process with the backing mandrel is reduced and the rolling force decreases with the increase of friction.(5)Compared to the retained mandrel process,the axial force on the mandrel is large and the mandrel is easy to be held by the steel pipe,especially for the thin wall tubes.So,the electrical loads will be large,we can reduce the friction mandrel to alleviate the problem of excessive mandrel axial force.