Optimization Research Of Stress Model In Processing Inside Taper Thread Of Oil Well Pipe Joint

With increasing of internal and overseas oil production day by day, the demand for oil well pipes is becoming more and more which is causing the increasing of oil extraction more difficulty. And the operational environment and specificity of oil well pipe are mainly depending on the material and the forms of thread. So thread processing of oil well pipe becomes the key technology of oil well pipe production. But the most difficult is the processing of inside taper thread of oil well pipe. So oil well pipe joint had the high requirement of thread roundness. But oil well pipe joint is one typical thin-wall barrel workpiece which causes the difficulty of inside taper thread processing. Baosteel is the main factory of producing inside taper thread of special oil well pipe joint in domestic. But the inside roundness overproof caused by oversize clamp force often happen during the processing of joint inside taper thread, which seriously effected the production efficiency and cost. This article is talking about the stress model during the production of inside taper thread of oil well pipe joint in Baosteel. And the main researches are as following points:1. Analyze the production process of oil well pipe joint. According to the structure forms of joint jig and quality inspection data of inside oil well pipe joint taper thread, to analysis the main reasons of faults in the present production of inside joint taper thread.2. Analyze the relation between clamp force and main cutting force to get the balance model of clamp force and cutting force in the producing process; measure the intensity of main cutting force in the producing process by experimentation, and to forecast the main cutting force by creating the mapping relation between cutting output and main cutting force by BP artificial neural net, and to create model simulation of turning process by using finite element software and to test the balance model of cutting force and clamp force.3. Analyze the cross section deformation during the producing process of inside taper thread of oil well pipe joint depending on energy conservation law, and to make a deduction on the relation of clamp force and joint deformation error, then to get mathematic model of the roundness deformation error of inside joint taper thread.4. Analyze clamp force optimization model basing on the standard of cutting force and deformation error which is on the basis of model of clamp force, processing cutting force of joint inside taper thread and clamp deformation, then to get the numeric area of clamp force of oil well pipe joint inside taper thread in the producing process. And to test the correctness and veracity of theory model by the practical experiment of clamp processing finite element model, joint clamp and producing process.Through the research of above points, we get the clamp force optimization control model of inside oil well pipe joint taper thread processing basing on the safety of processing technology and quality guarantee, and to make an optimization modification of present processing technology of inside oil well pipe joint taper thread and relevant structure.And we got the following innovation achievements:1. The new multipoint floating inside joint taper thread jig: the stress on every point will be smaller which provide the clamp force concentration causing the processing deformation.2. The control technology of controlled clamp force of oil well pipe inside taper thread production: to guarantee the most optimization of clamp force during the whole production process which guarantee the quality of products.