Research On The Large Pipe Three-roller Whole Type Setting Roundness Process

With oil,natural gas and other energy pipelines were constructed to the polar region,ocean,desert and other remote areas,It proposed more stringent requirements on the quality and performance of pipe fittings.Among them,ovality is one of the indexes that must be checked when the steel pipe is manufactured and installed,according to the American Petroleum Institute API standard,stipulate pipelines ovality should not exceed1% of its nominal diameter.However,because of the forming methods and material properties fluctuations in pipe fittings production,and after sizing due to remanent stress release,creep and other factors influenced,it will also cause the ovality does not meet the standards.The diameter of the tube blank will be changed by the traditional expanding and shrinking process,over-bending setting round process is only applied to the pipe end reshaped,however,roll bending setting round process can be rectify of the whole pipe’s ovality without changing the circumferential size.Based on springback theory of small curvature plane bending and uniform curvature theorem by reciprocating bending,presents a new method of roll bending setting round that is three-roller whole type setting round process.That is,the tube is to be placed among the three rollers,by controlling each roller relative position and rotating motion,the tube blank will through the reciprocating bending during the rolling process,resulting in plastic deformation,can realize curvature uniform after unloading springback,reduce the ellipse error of the whole tube blank.The three-roller whole type setting round process does not need to turning hydraulic cylinder device,can be set for each of the roller supporting roller,Especially suitable for tube that larger ratio of length to diameter and lesser ratio of diameter to thickness.Firstly,the deformation characteristics of the tube during the setting round process are analyzed,the tube has three positive bending zones and three anti-bending zones.According to the theory of three-point circle,two kinds of roller outside type are determined.The structure of the main body of the three-roller whole type setting round machine was designed,introduced its working principle and the characteristics of equipment.The setting round process was simulated by ABAQUS,during the tube blank deformation,obtained the stress and strain distribution and trends in the positive and negative bending zone,as well as setting round forming force versus time curve of each roller,the influence of the relative thickness of the tube on the optima pressing down of rolll reduction was analyzed,the best three-roller whole type setting round process parameters of two kinds of materials tube are determined,as well as Initial ellipticity of tube and friction coefficient influence rule of setting round result.Finally,using simulation parameters in designed three-roller whole type setting round test machine verify it,found that the change trend of the setting round result was consistent under the influence of each parameter,which proved the feasibility of this setting round process method.