Numerical Simulation And Experimental Research On Interference Hot Assembling Connection Of Aluminium Alloy Drill Pipe Body With Steel Tool Joint

With the rapid development of oil, gas and geological prospecting industry, thetechnical requirements for drilling become higher and higher. The total drillingworkload increases, so vastly does the depth of census wells and exploration wells. Atthe same time the requirements are more complicated as the drilling depth increasing.The drilling device and tools need to be comprehensively improved, and it is moreimportant to improve the working performance of drill pipes. Compared with steeldrill pipes, the aluminium alloy drill pipes has lower proportion, higher corrosionresistance, no magnetism and steady mechanical properties in many harshenvironments. And it can greatly reduce the transportation cost of equipment andmaterials in the sea and the area with poor road infrastructure. It can also save thepower and time and increase the ability of drill rig, which make it get wide attentionin drilling industry.While the increasing drilling depth and bit changing will cause pipe tripping andjoint screwing more often. And the aluminium alloy drill pipes has the disadvantageof low wear resistance, so it is usually assembled with steel tool joint to againstscrewing and unscrewing operations. And there is always unreliable connectionbetween drill pipes and tool joints, due to the difference of two materials at elasticmodulus, thermal expansion coefficient, elongation, yield strength and others.In this paper, assembling test is finished on the basic of hot assembling techniqueon interference connection of aluminium alloy drill pipe body-steel tool joint.Interference connection means that the limit maximum size of the inside of steel tooljoint is smaller than the limit minimum size of the outside diameter of drill pipes.Normally these two parts can’t be screwed close to the desired location, it need to get pre-tightening force and enough connection strength through the two parts tightenafter thermal expansion and contraction. The hot assembling working routine is firstlyheating the steel tool joint to set temperature to get enough expansion, then fast screwthe aluminium alloy drill pipe, and at the same time cooling the inside part of the drillpipe to prevent aluminum alloy material strength decline caused by high temperature.After assembling, the connection will be forced cooling to get the hold tight force andreliable connection, to meet the assembly requirements.Although in the process of assembling, the high temperature could change thetemperature of aluminium alloy drill pipe so that to impact its intensity. The numericalsimulation and experimental research are finished to verify that: as long as the coolingsystem inside the drill pipe works well and pump output is appropriate, thetemperature of aluminium alloy drill pipe will not exceed the allowed temperaturelimit so that it will not impact the performance of aluminium alloy materials.In this paper, the theoretical calculation and numerical simulation are focused onthe interference connection between the aluminium alloy drill pipes and steel tooljoint to get the theory reference value of Interference with good mechanical property.The smaller aluminium alloy drill pipes testing samples are manufactured at thediameter of50mm and thickness of5mm. The samples are assembled according tothe required temperature, and then destructive tensile tested to get the tensileperformance difference under different magnitude of interference. And at the sametime to the micro-hardness test and scanning electron microscopy (SEM) test are doneafter assembling in order to analysis of the practicability of this process and optimizethe process parameters. At last the full size drill pipes are manufactured by hotassembling and tensile test are carried out to provide a reference for the design andmanufacture of aluminium alloy drill pipes.