Research On Extrusion Forming Of Variable Cross Section Pipe And Thread Optimization Of Aluminum Drill Pipe

Traditionally, the oil drilling mainly use steel drill pipe. However, with thedrilling depth increases, the weight of the drill pipe also increases accordingly.Therefore, for deep and ultra-deep drilling, it is necessary to use light-weight drillpipe, among the light-weight drill pipe the aluminum drill pipe is most economical.At present, the research of aluminum drill pipe used for deep oil and gas drillinginteriorly is seldom, in this paper, applied the variable cross section once extrusionforming technology to the processing of internal upset aluminum drill pipe, andextruded the internal upset aluminum pipe successfully. Then carried out the test forthe dimension of the extruded aluminum pipe and the macrostructure、microstructure、chemical composition and mechanical properties of material sample, and evaluatedthe test result, the dimension of the extruded aluminum pipe basically meet the designdimensions, mechanical properties of material sample meet the require of aluminumdrill pipe.Considered the functional mode、force and characteristic of aluminum drill pipeto research the failure cause of aluminum drill pipe, the failure of steel joint wear andfatigue failure of aluminum drill pipe is the main cause of aluminum drill pipe failure.Researched the fatigue analysis model, and found the fatigue analysis model which ismost suitable for the aluminum pipe is, firstly carried out a test to obtain theconventional S-N curves, and then analysis the thread that aluminum pipe connectedwith steel joint using the multi-axis model. Designed the small-scale fatigue test ofaluminum pipe material sample. Researched the proposal of full-scale fatigue testequipment, the test equipment should be selected according to the actual test. Whentesting the small diameter aluminum drill pipe or only research the fatigue failure ofthread part of drill pipe, three kinds of conventional fatigue test equipment can bechoosed, while carrying out full-scale fatigue test of large diameter aluminum drillpipe, the best selection should be the resonant fatigue test equipment. Based on the theory of nonlinear finite element analysis, adopted finite elementanalysis software ANSYS Workbench, and used of static structural analysis module toanalyze connection model, found the key position of the connection betweenaluminum pipe and tool joint is the place of the engaged threads，especially the lastengaged three threads and first engaged thread. And then optimized the parameters ofaluminum drill pipe thread connection structure by applying the simplifiedtwo-dimensional model, improved the parameters of pitch and height of thread.